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Showing papers in "Naunyn-schmiedebergs Archives of Pharmacology in 2010"


Journal ArticleDOI
TL;DR: An improved understanding of the involvement of the adrenergic system and its control in basic mechanisms of AF under differing cardiac pathologies might lead to better treatments.
Abstract: Atrial fibrillation (AF) is the most common cardiac arrhythmia, and it causes substantial mortality. The autonomic nervous system, and particularly the adrenergic/cholinergic balance, has a profound influence on the occurrence of AF. Adrenergic stimulation from catecholamines can cause AF in patients. In human atrium, catecholamines can affect each of the electrophysiological mechanisms of AF initiation and/or maintenance. Catecholamines may produce membrane potential oscillations characteristic of afterdepolarisations, by increasing Ca2+ current, [Ca2+]i and consequent Na+–Ca2+ exchange, and may also enhance automaticity. Catecholamines might affect reentry, by altering excitability or conduction, rather than action potential terminal repolarisation or refractory period. However, which arrhythmia mechanisms predominate is unclear, and likely depends on cardiac pathology and adrenergic tone. Heart failure (HF), a major cause of AF, causes adrenergic activation and adaptational changes, remodelling, of atrial electrophysiology, Ca2+ homeostasis, and adrenergic responses. Chronic AF also remodels these, but differently to HF. Myocardial infarction and AF cause neural remodelling that also may promote AF. β-Adrenoceptor antagonists (β-blockers) are used in the treatment of AF, mainly to control the ventricular rate, by slowing atrioventricular conduction. β-Blockers also reduce the incidence of AF, particularly in HF or after cardiac surgery, when adrenergic tone is high. Furthermore, the chronic treatment of patients with β-blockers remodels the atria, with a potentially antiarrhythmic increase in the refractory period. Therefore, the suppression of AF by β-blocker treatment may involve an attenuation of arrhythmic activity that is caused by increased [Ca2+]i, coupled with effects of adaptation to the treatment. An improved understanding of the involvement of the adrenergic system and its control in basic mechanisms of AF under differing cardiac pathologies might lead to better treatments.

115 citations


Journal ArticleDOI
TL;DR: A contemporary evidence-based insight is provided into the possible preventative and reverse remodeling role of statins and polyunsaturated fatty acids in AF.
Abstract: Atrial fibrillation (AF) is an increasingly common arrhythmia that now stands at epidemic proportion, with more than 2.3 million people affected in the USA and over 4.5 million people affected in Western Europe. AF is an expression of underlying heart disease and is increasingly associated with hypertension, congestive heart failure, and ischemic heart disease. It is also a progressive disease secondary to continuous structural remodeling of the atria, which relates to AF itself, to changes associated with aging and to progression of the underlying heart disease. Traditionally, AF has been addressed only after it has already presented with pharmacological and nonpharmacological therapies designed for rhythm or rate control (secondary prevention). Although secondary prevention is the most feasible approach at present, the concept of primary prevention of AF with therapies aimed at preventing the development of substrate and correcting the risk factors for AF has emerged as a strategy, which is likely to produce a larger effect in the general population. Recent experiments provided new insights into AF pathophysiology, which generated background for new mechanism-based therapies. Agents targeting inflammation, oxidative injury, atrial myocyte metabolism, extracellular matrix remodeling, and fibrosis have theoretical advantages as novel therapeutic strategies. In this respect, drugs that are not traditionally antiarrhythmic such as angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, aldosterone antagonists, statins, and omega-3 polyunsaturated fatty acids have shown an antiarrhythmic potential in addition to any treatment effect on the underlying disease. These agents are thought to have an advantage of targeting both the occurrence and progression of the substrate for AF, thus, providing primary and secondary prevention of the arrhythmia. Although first experimental and hypothesis-generating small clinical studies or retrospective analyses have been encouraging, several larger, properly designed, prospective trials have not confirmed earlier observations. This review provides a contemporary evidence-based insight into the possible preventative and reverse remodeling role of statins and polyunsaturated fatty acids in AF.

89 citations


Journal ArticleDOI
TL;DR: The results showed that at a dose of 50 mg/kg, these compounds reduced the percentage of ulcer by around 71.26 ± 9.26%, which may be attributed, at least in part, to the antiulcerogenic activity of P. cyparissias.
Abstract: The present study evaluates the gastroprotective properties of acetone extract, chloroform, and methanol fractions, α-spinasterol (1); 1,3-dihydroxy-7-methoxyxan- thone (2); and 1,7-dihydroxy-2,3-methylenedioxyxanthone (3) obtained from Polygala cyparissias (Polygalaceae). Gastroprotective assays were performed in mice using ethanol/HCl and nonsteroidal anti-inflammatory drug (NSAID)/bethanechol-induced ulcer models. Chloroformic fraction showed no interesting results. On the other hand, in the ethanol/HCl-induced ulcer model, the treatment using doses of 50, 125, and 250 mg/kg promoted ulcer inhibition of 45.19±12.93%, 62.99±3.49%, and 67.40±4.75% for acetone extract and 43.70±5.12%, 64.56±5.64%, and 74.49±6.13% for methanol fraction. In the model of NSAID/bethanechol-induced ulcer, the ulcer inhibitions in the same doses were 28.12±12.45%, 60.16±6.58%, and 77.86±7.18% for the acetone extract and 46.09±6.92%, 67.45±4.36%, and 75.00±2.92% for the methanol fraction. In view of the antiulcer potential of the acetone extract and its high yield and xanthone content, it was submitted to chromatographic procedures, giving compounds 1-3, which were also evaluated in the ethanol-induced ulcer model. The results showed that at a dose of 50 mg/kg, these compounds reduced the percentage of ulcer by around 71.26±9.40%, 81.10±5.75%, and 86.22±3.42%, for compounds 1, 2, and 3, respectively. The antiulcerogenic activity of P. cyparissias may be attributed, at least in part, to these compounds.

86 citations


Journal ArticleDOI
TL;DR: Antiarrhythmic peptides are effective against ventricular tachyarrhythmias, such as late ischaemic ventricular fibrillation, CaCl2 or aconitine-induced arrhythmia, and it is still a matter of debate whether these drugs also act against atrialfibrillation.
Abstract: Co-ordinated electrical activation of the heart is maintained by intercellular coupling of cardiomyocytes via gap junctional channels located in the intercalated disks. These channels consist of two hexameric hemichannels, docked to each other, provided by either of the adjacent cells. Thus, a complete gap junction channel is made from 12 protein subunits, the connexins. While 21 isoforms of connexins are presently known, cardiomyocytes typically are coupled by Cx43 (most abundant), Cx40 or Cx45. Some years ago, antiarrhythmic peptides were discovered and synthesised, which were shown to increase macroscopic gap junction conductance (electrical coupling) and enhance dye transfer (metabolic coupling). The lead substance of these peptides is AAP10 (H-Gly-Ala-Gly-Hyp-Pro-Tyr-CONH2), a peptide with a horseshoe-like spatial structure as became evident from two-dimensional nuclear magnetic resonance studies. A stable d-amino-acid derivative of AAP10, rotigaptide, as well as a non-peptide analogue, gap-134, has been developed in recent years. Antiarrhythmic peptides act on Cx43 and Cx45 gap junctions but not on Cx40 channels. AAP10 has been shown to enhance intercellular communication in rat, rabbit and human cardiomyocytes. Antiarrhythmic peptides are effective against ventricular tachyarrhythmias, such as late ischaemic (type IB) ventricular fibrillation, CaCl2 or aconitine-induced arrhythmia. Interestingly, the effect of antiarrhythmic peptides is higher in partially uncoupled cells and was shown to be related to maintained Cx43 phosphorylation, while arrhythmogenic conditions like ischaemia result in Cx43 dephosphorylation and intercellular decoupling. It is still a matter of debate whether these drugs also act against atrial fibrillation. The present review outlines the development of this group of peptides and derivatives, their mode of action and molecular mechanisms, and discusses their possible therapeutic potential.

79 citations


Journal ArticleDOI
TL;DR: Investigation of in vitro effects of cannabinoids on the activity of monoamine oxidase found decrease of MAO activity may play a role in some effects of cannabinoid on serotonergic, noradrenergic, and dopaminergic neurotransmission.
Abstract: Brain monoamines are involved in many of the same processes affected by neuropsychiatric disorders and psychotropic drugs, including cannabinoids. This study investigated in vitro effects of cannabinoids on the activity of monoamine oxidase (MAO), the enzyme responsible for metabolism of monoamine neurotransmitters and affecting brain development and function. The effects of the phytocannabinoid Δ9-tetrahydrocannabinol (THC), the endocannabinoid anandamide (N-arachidonoylethanolamide [AEA]), and the synthetic cannabinoid receptor agonist WIN 55,212-2 (WIN) on the activity of MAO were measured in a crude mitochondrial fraction isolated from pig brain cortex. Monoamine oxidase activity was inhibited by the cannabinoids; however, higher half maximal inhibitory concentrations (IC50) of cannabinoids were required compared to the known MAO inhibitor iproniazid. The IC50 was 24.7 μmol/l for THC, 751 μmol/l for AEA, and 17.9 μmol/l for WIN when serotonin was used as substrate (MAO-A), and 22.6 μmol/l for THC, 1,668 μmol/l for AEA, and 21.2 μmol/l for WIN when phenylethylamine was used as substrate (MAO-B). The inhibition of MAOs by THC was noncompetitive. N-Arachidonoylethanolamide was a competitive inhibitor of MAO-A and a noncompetitive inhibitor of MAO-B. WIN was a noncompetitive inhibitor of MAO-A and an uncompetitive inhibitor of MAO-B. Monoamine oxidase activity is affected by cannabinoids at relatively high drug concentrations, and this effect is inhibitory. Decrease of MAO activity may play a role in some effects of cannabinoids on serotonergic, noradrenergic, and dopaminergic neurotransmission.

79 citations


Journal ArticleDOI
TL;DR: Inductions of lipid and cholesterol synthesis observed with clozapine and olanzapine were also associated with up-regulation of the transcription factors sterol regulatory element-binding protein (SREBP)-1 and/or SREBP-2 and their associated target genes.
Abstract: The use of some of antipsychotic drugs (APDs) in humans has been hampered by the induction of metabolic disorders such as weight gain, dyslipidemia, and diabetes. In primary rat hepatocytes, we investigated the actions of several APDs on lipid and cholesterol metabolism using [14C]acetate incorporation, quantitative reverse transcription-polymerase chain reaction, and western blotting. Clozapine and olanzapine, known to have significant metabolic side effects in man, strongly increased de novo lipid and cholesterol synthesis in rat hepatocytes. Haloperidol, which has less impact in metabolic disorders, enhanced lipogenesis without altering cholesterol production. By contrast, quetiapine, which exhibits few metabolic side effects in man, did not affect lipid and cholesterol synthesis. Interestingly, aripiprazole, which has not yet been reported to induce metabolic disorders in humans, strongly decreases cholesterol synthesis. Furthermore, these inductions of lipid and cholesterol synthesis observed with clozapine and olanzapine were also associated with up-regulation of the transcription factors sterol regulatory element-binding protein (SREBP)-1 and/or SREBP-2 and their associated target genes. Part of the APD-induced metabolic disorders in humans may be due to direct effects on liver metabolism. Our model may also be of interest to assess the action of future drugs on metabolic parameters.

74 citations


Journal ArticleDOI
TL;DR: The mechanism of action of the anticonvulsant effect of the EOs studied is, at least in part, dependent upon the GABAergic neurotransmission and their effects on inflammatory biomarkers can also contribute to their central nervous system activity.
Abstract: The fresh leaves of Cymbopogon citratus are a good source of an essential oil (EO) rich in citral, and its tea is largely used in the Brazilian folk medicine as a sedative. A similar source of EO is Cymbopogon winterianus, rich in citronellal. The literature presents more studies on the EO of C. citratus and their isolated bioactive components, but only a few are found on the EO of C. winterianus. The objective of the present study was then to study, in a comparative way, the effects of both EOs on three models of convulsions (pentylenetetrazol, pilocarpine, and strychnine) and on the barbiturate-induced sleeping time on male Swiss mice. The animals (20-30 g) were acutely treated with 50, 100, and 200 mg kg(-1), intraperitoneally, of each EO, and 30 min later, the test was initiated. The observed parameters were: latency to the first convulsion and latency to death in seconds. Furthermore, the in vitro effects of the EOs were also studied on myeloperoxidase (MPO; a biomarker for inflammation) and lactate dehydrogenase (LDH; an index of cytotoxicity) releases from human neutrophils. The EOs radical-scavenging activities were also evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The results showed that both EOs were more active on the pentylenetetrazol-induced convulsion model, and C. citratus was even more efficient in increasing latency to the first convulsion and latency to death. Both parameters were potentiated in the presence of a lower dose of diazepam (reference drug) when associated to a lower dose of each EO (25 mg kg(-1)). Besides, their anticonvulsant effects were blocked by flumazenil, a known benzodiazepine antagonist. This effect was somewhat lower on the pilocarpine-induced convulsion, and better effects were seen only with the EOs' higher doses (200 mg kg(-1)). A similar result was observed on the strychnine-induced convulsion model. Both EOs potentiated the barbiturate-induced sleeping time. However, C. citratus was more efficient. Interestingly, both EOs completely blocked the MPO release from human neutrophils and showed no cytotoxic effect on the LDH release from human neutrophils. On the other hand, only a very low or no effect on the DPPH assay was observed with C. winterianus and C. citratus, respectively, indicating that the radical scavenging activity did not play a role on the EOs' effects. We conclude that the mechanism of action of the anticonvulsant effect of the EOs studied is, at least in part, dependent upon the GABAergic neurotransmission. In addition, their effects on inflammatory biomarkers can also contribute to their central nervous system activity.

67 citations


Journal ArticleDOI
TL;DR: The results of the present study show that 4-CD has the potential to attenuate cognitive dysfunction and oxidative stress induced by toxicants like propoxur in the brain.
Abstract: Carbamate pesticides like propoxur have been shown to adversely affect memory and induce oxidative stress on both acute and chronic exposure. The present study was designed to explore the modulation of the effects of propoxur over cognitive function by progesterone (PROG) and 4′-chlorodiazepam (4CD). Cognitive function was assessed using step-down latency (SDL) on a passive avoidance apparatus, transfer latency (TL) on a plus maze and spatial navigation test on Morris water maze. Oxidative stress was assessed by examining brain malondialdehyde (MDA) and reduced glutathione (GSH) levels and catalase (CAT) activity. A significant reduction in SDL and prolongation of TL and spatial navigation test was found for the propoxur (10 mg/kg/d; p.o.) treated group at weeks 6 and 7 as compared with control. One-week treatment with 4CD (0.5 mg/kg/d; i.p.) antagonized the effect of propoxur on SDL, spatial navigation test as well as TL; whereas, PROG failed to modulate this effect at a dose of 15 mg/kg/d, i.p. Propoxur produced a statistically significant increase in the brain MDA levels and decrease in the brain GSH levels and CAT activity. Treatment with 4CD at the above dose attenuated the effect of propoxur on oxidative stress whereas PROG (15 mg/kg/d; i.p.) failed to influence the same. The results of the present study thus show that 4-CD has the potential to attenuate cognitive dysfunction and oxidative stress induced by toxicants like propoxur in the brain.

62 citations


Journal ArticleDOI
TL;DR: In the I/R plus atorvastatin groups, although minimal vascular dilation in the ovary stoma and some degenerative cell clusters were seen, most of the cellular structures showed no pathological changes.
Abstract: The aim of this study was to evaluate the effects of atorvastatin as an antioxidant and tissue protective agent and study the biochemical and histopathological changes in experimental ischemia and ischemia/reperfusion (I/R) injury in rat ovaries. The experiment used 48 adult female rats, and the experimental groups can be summarized as: group I, a sham operation; group II, a sham operation +10 mg/kg atorvastatin; group III, bilateral ovarian ischemia; and groups IV and V, bilateral ovarian ischemia +5 and 10 mg/kg atorvastatin before 30 min of ischemia, respectively (after a 3-h period of ischemia, the bilateral ovaries were surgically removed); group VI, 3-h period of ischemia followed by 3-h reperfusion; groups VII and VIII received 5 and 10 mg/kg atorvastatin, respectively, 2.5 h after the induction of ischemia, and at the end of a 3-h period of ischemia, bilateral vascular clips were removed and 3-h reperfusion continued. After the experiments, superoxide dismutase (SOD) and myeloperoxidase (MPO) activity and levels of glutathione (GSH) and lipid peroxidation (LPO) were determined, and histopathological changes were examined in all rat ovarian tissue. Ischemia and I/R increased the LPO level and MPO activity while decreasing the SOD activity and GSH level significantly in comparison to the sham group. The 5- and 10-mg/kg doses of atorvastatin before ischemia and I/R reversed the trend in LPO level and MPO activity. The levels of SOD and GSH were decreased by ischemia and I/R. The administration of atorvastatin before ischemia and I/R treatments also reversed the trend in the SOD and GSH levels. In the I/R plus atorvastatin groups, although minimal vascular dilation in the ovary stoma and some degenerative cell clusters were seen, most of the cellular structures showed no pathological changes. Administration of atorvastatin is effective in reversing tissue damage induced by ischemia and/or I/R in ovaries.

60 citations


Journal ArticleDOI
TL;DR: It may be suggested that tramadol exerts a seizurogenic effect on mice via an H1 receptor activation-linked pathway possibly through an opioid receptor-dependent release of histamine from the mast cells.
Abstract: The present study has been designed to investigate the role of opioid receptors, mast cells, and histamine receptors (H(1) subtype) in the seizurogenic effect of tramadol on pentylenetetrazole-treated mice. A single injection of pentylenetetrazole (80 mg kg(-1)) was used to elicit seizure activity in mice. Seizures were assessed in terms of the time latency of the onset of Straub-like tail, onset of jerky movements of whole body, convulsions, and death. Tramadol administration (50 mg kg (-1)) caused a marked increase in seizurogenic activity of pentylenetetrazole as measured in terms of a significant decrease in the time latency of the onset of Straub-like tail, jerky movements of whole body, convulsions, and death. Moreover, prior administration of naloxone (2 mg kg(-1)), fexofenadine (100 mg kg(-1)), cetrizine, sodium cromoglycate, and ketotifen (10 mg kg(-1)), respectively, attenuated the seizurogenic activity that tramadol exerted on pentylenetetrazole-treated mice. Therefore, it may be suggested that tramadol exerts a seizurogenic effect on mice via an H(1) receptor activation-linked pathway possibly through an opioid receptor-dependent release of histamine from the mast cells.

59 citations


Journal ArticleDOI
TL;DR: It is concluded that in cAF, flecainide and AVE0118 reduce receptor-independent, constitutively active IK,ACh, suggesting that they may block IK-ACh channels, whereas propafenone and dofetilide likely inhibit M-receptors.
Abstract: Inward rectifier potassium currents I(K1) and acetylcholine activated I(K,ACh) are implicated in atrial fibrillation (AF) pathophysiology. In chronic AF (cAF), I(K,ACh) develops a receptor-independent, constitutively active component that together with increased I(K1) is considered to support maintenance of AF. Here, we tested whether class I (propafenone, flecainide) and class III (dofetilide, AVE0118) antiarrhythmic drugs inhibit atrial I(K1) and I(K,ACh) in patients with and without cAF. I(K1) and I(K,ACh) were measured with voltage clamp technique in atrial myocytes from 58 sinus rhythm (SR) and 35 cAF patients. The M-receptor agonist carbachol (CCh; 2 microM) was employed to activate I(K,ACh). In SR, basal current was not affected by either drug indicating no effect of these compounds on I(K1). In contrast, all tested drugs inhibited CCh-activated I(K,ACh) in a concentration-dependent manner. In cAF, basal current was confirmed to be larger than in SR (at -80 mV, -15.2 +/- 1.2 pA/pF, n = 88/35 vs. -6.5 +/- 0.4 pA/pF, n = 194/58 [myocytes/patients]; P < 0.05), whereas CCh-activated I(K,ACh) was smaller (-4.1 +/- 0.5 pA/pF vs. -9.5 +/- 0.6 pA/pF; P < 0.05). In cAF, receptor-independent constitutive I(K,ACh) contributes to increased basal current, which was reduced by flecainide and AVE0118 only. This may be due to inhibition of constitutively active I(K,ACh) channels. In cAF, all tested drugs reduced CCh-activated I(K,ACh). We conclude that in cAF, flecainide and AVE0118 reduce receptor-independent, constitutively active I(K,ACh), suggesting that they may block I(K,ACh) channels, whereas propafenone and dofetilide likely inhibit M-receptors. The efficacy of flecainide to terminate AF may in part result from blockade of I(K,ACh).

Journal ArticleDOI
TL;DR: The results indicate similar cholinergic mechanisms, probably through the a4b2 receptors involved in the rewarding effects of nicotine and morphine in rats and may suggest that nicotinic receptors could be a potential target for developing pharmacotherapeutic strategies to treat and prevent nicotine and/or opioid addiction and relapse.
Abstract: Nicotine addiction is a chronic disorder characterized by a relatively high rate of relapse even after long period of abstinence. In the present study, we used the conditioned place preference (CPP) paradigm to investigate the establishment, extinction, reinstatement, and cross-reinstatement of nicotine-induced place conditioning in rats. First, we revealed that nicotine produced a place preference to the initially less-preferred compartment paired with its injections during conditioning (0.175 mg/kg, base, intraperitoneally (i.p.)). Once established, nicotine CPP was extinguished by repeated testing. Following this extinction phase, nicotine-experienced rats were challenged with nicotine (0.175 mg/kg, i.p.) or morphine (10 mg/kg, i.p.). These priming injections of both drugs induced a marked preference for the compartment previously paired with nicotine. Furthermore, given the important role of alpha4beta2 (a4b2) nicotinic receptor subtype in the acquisition and maintenance of nicotine dependence, we evaluated and compared the efficacy of varenicline, a partial a4b2 nicotinic receptor agonist (0.5, 1, and 2 mg/kg, subcutaneously (s.c.)), and mecamylamine (0.5, 1, and 2 mg/kg, s.c.), a non-selective nicotinic receptor antagonist, in blocking nicotine-induced CPP as well as reinstatement of nicotine CPP provoked by nicotine and morphine. It was shown that both nicotinic receptor ligands attenuated the acquisition and expression of nicotine CPP as well as the expression of reinstatement of nicotine CPP provoked by both drugs. Our results indicate similar cholinergic mechanisms, probably through the a4b2 receptors involved in the rewarding effects of nicotine and morphine in rats and may suggest that nicotinic receptors could be a potential target for developing pharmacotherapeutic strategies to treat and prevent nicotine and/or opioid addiction and relapse.

Journal ArticleDOI
TL;DR: Amiodarone blockade of hK2P3.1 channels may cause prolongation of cardiac repolarization and action potential duration in patients with high individual plasma concentrations, possibly contributing to the antiarrhythmic efficacy of the class III drug.
Abstract: Two-pore-domain (K2P) potassium channels mediate background potassium currents, stabilizing resting membrane potential and expediting action potential repolarization. In the heart, K2P3.1 (TASK-1) channels are implicated in the cardiac plateau current, I KP . Class III antiarrhythmic drugs target cardiac K+ currents, resulting in action potential prolongation and suppression of atrial and ventricular arrhythmias. The objective of this study was to investigate acute effects of the class III antiarrhythmic drug amiodarone on human K2P3.1 channels. Potassium currents were recorded from Xenopus oocytes using the two-microelectrode voltage clamp technique. Amiodarone produced concentration-dependent inhibition of hK2P3.1 currents (IC50 = 0.40 µM) with maximum current reduction of 58.1%. Open rectification properties that are characteristic to hK2P3.1 currents were not altered by amiodarone. Channels were blocked in open and closed states in reverse frequency-dependent manner. hK2P3.1 channel inhibition was voltage-independent at voltages between −40 and +60 mV. Modulation of protein kinase C activity by amiodarone does not contribute to hK2P3.1 current reduction, as pre-treatment with the protein kinase C inhibitor, staurosporine, did not affect amiodarone block. Amiodarone is an inhibitor of cardiac hK2P3.1 background channels. Amiodarone blockade of hK2P3.1 may cause prolongation of cardiac repolarization and action potential duration in patients with high individual plasma concentrations, possibly contributing to the antiarrhythmic efficacy of the class III drug.

Journal ArticleDOI
TL;DR: Investigation of in vivo and in vitro experiments showed that berberine suppresses disaccharidase activities and SI complex mRNA expression with beneficial metabolic effects in diabetic states, and the inhibitory effect, at least partly, involves the PKA-dependent pathway.
Abstract: Clinical reports have demonstrated that berberine is a potential antidiabetic agent, but the underlying mechanism is unclear. The purpose of this study was to investigate if berberine exerts its hypoglycemic action via inhibiting intestinal disaccharidases using in vivo and in vitro experiments. Streptozotocin-induced diabetic rats received berberine (100 or 200 mg/kg) orally once daily or acarbose (40 mg/kg) orally twice daily for 5 weeks. Disaccharidase activities and sucrase-isomaltase (SI) complex messenger RNA (mRNA) expression in intestinal regions were assessed. The same treatment was operated in normal rats. Sucrose and maltose loading tests were also documented. In addition, Caco-2 cells were cultured in medium containing berberine or berberine plus chelerythrine. Compound C or H-89 for 5 days, disaccharidase activities, and SI complex mRNA levels were measured. The animal experiments showed that berberine significantly decreased the disaccharidase activities and SI complex mRNA expression both in diabetic rats and normal rats. Berberine can also significantly lower postprandial blood glucose levels induced by sucrose or maltose loading in normal rats. The cellular results showed that berberine may suppress disaccharidase activities and downregulate SI complex mRNA expression in a concentration-dependent manner. Only H-89, an inhibitor of protein kinase A (PKA), may reverse the decrease in disaccharidase activities and SI complex mRNA expression induced by berberine. In conclusion, berberine suppresses disaccharidase activities and SI complex mRNA expression with beneficial metabolic effects in diabetic states. The inhibitory effect, at least partly, involves the PKA-dependent pathway.

Journal ArticleDOI
TL;DR: It is suggested that selaginellin has a neuroprotective effect against l-glutamate-induced neurotoxicity through mechanisms related to anti-oxidation and anti-apoptosis via scavenging reactive oxygen species and up-regulating the expression of klotho gene.
Abstract: l-glutamate plays a key role in neuronal cell death associated with many neurodegenerative conditions such as cerebral ischemia, hypoxia, Alzheimer's, Huntington’s, and Parkinson’s diseases. Selaginellin, a component extracted from Saussurea pulvinata (Hook.et Grev.) Maximo, was assessed for its ability to protect rat pheochromocytoma (PC12) cells against oxidative toxicity induced by glutamate. The differentiated PC12 cells were pretreated with various concentrations (10−7, 3 × 10−7, or 10−6 M) of selaginellin for 1 h prior to exposure to l-glutamate. Selaginellin was shown to protect PC12 cells against glutamate toxicity, as determined by characteristic morphological features, lactate dehydrogenase release and cell viability, and apoptosis as evaluated by Hoechst 33342 staining assay and caspase-3 activity. In addition, the increase in levels of reactive oxygen species and decrease in klotho gene expression induced by glutamate were significantly reversed by selaginellin. Our study suggests that selaginellin has a neuroprotective effect against l-glutamate-induced neurotoxicity through mechanisms related to anti-oxidation and anti-apoptosis via scavenging reactive oxygen species and up-regulating the expression of klotho gene.

Journal ArticleDOI
TL;DR: It is shown that metformin increased AMPK activity in microglial cells and that all observed effects are AMPK-dependent because the pretreatment of microglia with compound C reversed the effects of the drug.
Abstract: Recent evidence suggests that metformin shows beneficial effects in experimental models of neuroinflammatory diseases. The aim of the present study was to determine the effect of metformin on phagocytosis and acidification of lysosomal/endosomal compartments in rat primary microglia in the presence of lipopolysaccharide (LPS) and/or beta-peptides (25–35), (1–40), and (1–42). Metformin increased the phagocytosis of fluorescent microspheres in the presence or absence of all the beta-peptides. However, the drug had no effect on the phagocytosis in LPS-stimulated microglia regardless of the presence of all the beta-peptides. Metformin acidified the lysosomal/endosomal compartments in the presence or absence of the beta-peptide 1–40 in both resting and activated microglia. To elucidate the mechanism of metformin action, we used 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside as an activator of adenosine monophosphate-activated protein kinase (AMPK) and compound C as a confirmed pharmacological inhibitor of AMPK. We have shown that metformin increased AMPK activity in microglial cells and that all observed effects are AMPK-dependent because the pretreatment of microglia with compound C reversed the effects of the drug. Since degradation of proteins in lysosomal/endosomal compartments depends largely on their phagocytosis and acidification, metformin may be beneficial in proteinopathies affecting the brain.

Journal ArticleDOI
Asami Mori1, Tomoyo Miwa1, Kenji Sakamoto1, Tsutomu Nakahara1, Kunio Ishii1 
TL;DR: It is suggested that stimulation of β3-adrenoceptors causes the vasodilation of retinal arterioles in vivo and the Vasodilator responses are unaffected at the early stage of diabetes.
Abstract: The aim of this study was to examine whether stimulation of β3-adrenoceptors dilates rat retinal blood vessels and how diabetes affects the vasodilator responses. Images of ocular fundus were captured with an original high-resolution digital fundus camera in vivo. The retinal vascular responses were evaluated by measuring diameter of retinal blood vessels contained in the digital images. Both systemic blood pressure and heart rate (HR) were continuously recorded. The β3-adrenoceptor agonist CL316243 (0.3–10 μg/kg/min, i.v.) increased diameter of retinal arterioles (at 10 μg/kg/min, a 31% increase) and decreased mean blood pressure (at 10 μg/kg/min, a 21% decrease) in a dose-dependent manner. CL316243 produced a small but significant increase in HR (at 10 μg/kg/min, a 9% increase). Both SR59230A (1 mg/kg, i.v.) and L-748337 (50 μg/kg, i.v.), β3-adrenoceptor antagonists, significantly prevented CL316243-induced retinal vasodilator responses. Similar observations were made with another β3-adrenoceptor agonist, BRL37344. The β2-adrenoceptor agonist salbutamol also increased diameter of retinal arterioles (at 10 μg/kg/min, a 43% increase), whereas the drug produced greater decrease in blood pressure (at 10 μg/kg/min, a 46% decrease) and increase in HR (at 10 μg/kg/min, a 16% increase), compared with β3-adrenoceptor agonists. The retinal vasodilator responses to CL316243 and BRL37344 observed under blockade of β1/β2-adrenoceptors with propranolol (2 mg/kg, i.v. bolus followed by 100 μg/kg/min infusion) were unaffected 2 weeks after induction of diabetes by the combination of streptozotocin treatment and d-glucose feeding. On the other hand, the vasodilator responses to salbutamol of retinal arterioles were significantly reduced in diabetic rats. These results suggest that stimulation of β3-adrenoceptors causes the vasodilation of retinal arterioles in vivo and the vasodilator responses are unaffected at the early stage of diabetes.

Journal ArticleDOI
TL;DR: The pharmacological potential of proteins from the latex of C. procera to control sarcoma cell proliferation and the 5-FU-induced depletion of leukocytes in mice even when given orally is confirmed.
Abstract: Latex of Calotropis procera has been described as a relevant source of pharmacologically active proteins, including proteins with anticancer activity. A previous in vitro study of laticifer proteins (LP) from C. procera reported that they had selective cytotoxic effects on human cancer cell lines. The aim of this study was to determine the effects of LP in vivo using mice transplanted with sarcoma 180. Biochemical, hematological, histopathological, and morphological analyses were performed in animals given LP by oral or intraperitoneal routes. LP significantly reduced tumor growth (51.83%) and augmented the survival time of animals for up to 4 days. Tumor growth inhibitory activity was lost when LP fraction was submitted to proteolysis, acidic treatment, or pretreated with iodoacetamide. However, LP retained its inhibitory activities on sarcoma 180 growth after heat treatment. Thus, it seems that heat-stable proteins are involved in tumor suppression. Biochemical parameters, such as the enzymatic activity of aspartate aminotransferase and alanine aminotransferase and urea content in serum were not affected in treated mice. It is worth noting that LP completely eliminated the 5-FU-induced depletion of leukocytes in mice even when given orally. The active proteins were recovered in a single fraction by ion exchange chromatography and still exhibited anticancer activity. This study confirms the pharmacological potential of proteins from the latex of C. procera to control sarcoma cell proliferation.

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TL;DR: Results indicate that SMTP-7 shows potential thrombolytic and anti-inflammatory effects as well as a wide therapeutic time window and little hemorrhagic region compared with that of t-PA, and this novel low-molecular-weight compound may represent a novel approach for the treatment of cerebral infarction.
Abstract: Tissue plasminogen activator (t-PA) has a short therapeutic time window for administration (3 h) and carries a risk of promoting intracerebral hemorrhage. The aim of the present study was to investigate a therapeutic time window and frequency of hemorrhagic region by treatment with Stachybotrys microspora triprenyl phenol-7 (SMTP-7). Thrombotic occlusion was induced by transfer of acetic acid-induced thrombus at the right common carotid artery into the brain of mice. Infarction area, neurological score, edema percentage, and regional cerebral blood flow (CBF) were determined as the index of the efficacy of SMTP-7. In order to evaluate the mechanism of SMTP-7, plasmin activities and the expressions of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-6 mRNA were examined. SMTP-7 (0.1, 1, 10 mg/kg) dose dependently reduced infarction area, neurological score, and edema percentage. Additionally, its therapeutic time window was longer than that of t-PA, a high-molecular-weight compound. In addition, little hemorrhagic region was induced by treatment with SMTP-7. SMTP-7 showed plasmin activity in vivo and caused a decreased CBF to recover. Furthermore, the expressions of inflammatory cytokine mRNA (IL-1β, TNF-α, IL-6) were increased by t-PA treatment 3 h after ischemia but were not induced by SMTP-7 treatment. These results indicate that SMTP-7 shows potential thrombolytic and anti-inflammatory effects as well as a wide therapeutic time window and little hemorrhagic region compared with that of t-PA. Therefore, this novel low-molecular-weight compound may represent a novel approach for the treatment of cerebral infarction.

Journal ArticleDOI
TL;DR: Ivabradine appears effective and safe in patients with symptomatic inappropriate sinus tachycardia, approved for angina pectoris, and three patients reported transient phosphene-like phenomena without discontinuation of ivABradine while on therapy.
Abstract: Inappropriate sinus tachycardia (IST) is characterized by paroxysmal tachycardia originating in the sinus nodal area. IST predominately affects young, female patients. Current antiarrhythmic drug treatment (s-blockers, calcium antagonists), frequently complicated by side effects, is often not successful. Ivabradine, approved for angina pectoris, selectively reduces heart rate by blocking the “funny current” in the sinus node. We therefore evaluated the effect of ivabradine in patients with symptomatic IST. Ten female patients (median age 32.5 years, range 12–57) suffering from symptomatic IST who had either failed (n = 8) or refused (n = 2) conventional therapy were analyzed. Symptoms included palpitations, pre-syncope, syncope, dyspnea, and exercise intolerance. After obtaining informed consent for individual off-label therapy, patients were treated with ivabradine (5–7.5 mg bid) in addition to beta-blocker therapy (n = 3) or as mono- therapy (n = 7). Therapy was monitored by 72-h Holter ECG and a symptoms questionnaire. Ivabradine significantly reduced maximum and mean heart rate (baseline, maximal heart rate 176 ± 45/min, mean heart rate 84 ± 11/min; ivabradine, maximal heart rate 137 ± 36/min, mean HR 74 ± 8/min, both p < 0.05, all values as mean ± SD). Minimum heart rate was not significantly changed. Three patients reported transient phosphene-like phenomena without discontinuation of ivabradine while on therapy. IST-associated symptoms were ameliorated (3 pts) or suppressed (5 pts) in all eight patients who could be contacted after a mean follow-up of 16 ± 9 months. Ivabradine appears effective and safe in patients with symptomatic inappropriate sinus tachycardia.

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TL;DR: It is concluded that the beneficial effects of curcumin are mediated through the activation of PPAR-γ receptors in memory deficits associated with experimental dementia in Swiss albino mice.
Abstract: The present study was undertaken to investigate the possible mechanism of curcumin-mediated beneficial effects in memory deficits associated with experimental dementia. Dementia was induced in Swiss albino mice by administrating streptozotocin (3 mg kg−1) intracerebroventricularly on first and third day. Morris water maze test was employed to assess learning and memory of the animals. Biochemical analysis of brain homogenate was performed to assess brain acetyl cholinesterase (AChE) activity and total oxidative stress. Streptozotocin (STZ) produced a significant decrease in water maze performance of mice indicative of impairment in spatial reference memory. Curcumin (20 mg/kg p.o. daily for 14 days) successfully attenuated STZ-induced memory deficits. Higher levels of brain AChE activity and oxidative stress were observed in STZ-treated animals, which were significantly attenuated by curcumin. Furthermore, the noted beneficial effect of curcumin on STZ-induced dementia was significantly abolished by pretreatment with PPAR-γ receptor antagonist bisphenol-A-diglycidyl ether, i.e., BADGE (30 mg/kg intraperitoneally (i.p.)). It may be concluded that the beneficial effects of curcumin are mediated through the activation of PPAR-γ receptors.

Journal ArticleDOI
TL;DR: The findings suggest the antidepressant-like effect of bupropion to be related to levels of dopamine in the rat nucleus accumbens, specifically in relation to the site of action through the use of microinjections into the medial prefrontal cortex and nucleus Accumbens.
Abstract: The dopamine reuptake inhibitor bupropion has clinically been proven to improve depression and treatment-resistant depression. We examined its influence on the duration of immobility during the forced swim test in adrenocorticotropic hormone (ACTH)-treated rats and further analyzed the possible role of dopamine receptors in this effect. Additionally, the mechanism by which bupropion acts in this model was explored specifically in relation to the site of action through the use of microinjections into the medial prefrontal cortex and nucleus accumbens. Bupropion significantly decreased the duration of immobility in normal and ACTH-treated rats. This effect was blocked by D2 and D3 receptor antagonists in normal rats. Furthermore, infusions of bupropion into the nucleus accumbens, but not medial prefrontal cortex, decreased the immobility of normal and ACTH-treated rats during the forced swim test. Bupropion treatment plus repeated ACTH treatment significantly increased the extracellular dopamine concentration. These findings suggest the antidepressant-like effect of bupropion to be related to levels of dopamine in the rat nucleus accumbens.

Journal ArticleDOI
TL;DR: The molecular mechanisms of altered Ca2+ signaling in AF are reviewed and the potential value of novel approaches targeting atrial Ca2+, including dronedarone and possibly vernakalant, are discussed.
Abstract: Atrial fibrillation (AF) is the most frequent arrhythmia and is associated with increased morbidity and mortality. Current drugs for AF treatment have moderate efficacy and increase the risk of life-threatening antiarrhythmias, making novel drug development crucial. Newer antiarrhythmic drugs like dronedarone and possibly vernakalant are efficient and may have less proarrhythmic potential. Emerging evidence suggests that abnormal intracellular Ca2+ signaling is the key contributor to focal firing, substrate evolution, and atrial remodeling during AF. Accordingly, identification of the underlying atrial Ca2+-handling abnormalities is expected to discover novel mechanistically based therapeutic targets. This article reviews the molecular mechanisms of altered Ca2+ signaling in AF and discusses the potential value of novel approaches targeting atrial Ca2+-handling abnormalities.

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TL;DR: It is proposed that many responses attributed to β3-adrenoceptor stimulation may need re-evaluation in the light of the development of more selective tools and findings in experimental animals need to be extended to humans in order to better understand the potential additional indications and side effects of the α3- adrenoceptors that are beginning to enter clinical medicine.
Abstract: As β3-adrenoceptor agonists metamorphose from experimental tools into therapeutic drugs, it is vital to obtain a comprehensive picture of the cell and tissue functions mediated by this receptor subtype in humans. Human tissues with proven functions and/or a high expression of β3-adrenoceptors include the urinary bladder, the gall bladder, and other parts of the gastrointestinal tract. While several other β3-adrenoceptor functions have been proposed based on results obtained in animals, their relevance to humans remains uncertain. For instance, β3-adrenoceptors perform an important role in thermogenesis and lipolysis in rodent brown and white adipose tissue, respectively, but their role in humans appears less significant. Moreover, the use of tools such as the agonist BRL 37344 and the antagonist SR59230A to demonstrate functional involvement of β3-adrenoceptors may lead in many cases to misleading conclusions as they can also interact with other β-adrenoceptor subtypes or even non-adrenoceptor targets. In conclusion, we propose that many responses attributed to β3-adrenoceptor stimulation may need re-evaluation in the light of the development of more selective tools. Moreover, findings in experimental animals need to be extended to humans in order to better understand the potential additional indications and side effects of the β3-adrenoceptor agonists that are beginning to enter clinical medicine.

Journal ArticleDOI
TL;DR: The results suggest that the antihypertensive effects of quercetin were associated with increased NO formation and improved endothelial function, which probably result from its antioxidant effects.
Abstract: Quercetin has antioxidants properties which may increase nitric oxide (NO) bioavailability. However, the effects of quercetin on NO status have been poorly studied. We evaluated whether quercetin improves the plasma levels of NO metabolites in two-kidney one-clip (2K1C) hypertensive rats and assessed its effect on endothelial function. Sham-operated and 2K1C rats were treated with quercetin (10 mg−1 kg−1 day−1 by gavage) or vehicle for 3 weeks. Systolic blood pressure (SBP) was monitored weekly. Vascular responses to acetylcholine (Ach) and sodium nitroprusside (SNP) were assessed in hindquarter vascular bed. Plasma nitrate levels were assessed by Griess reagent and plasma nitrite and nitroso species (S, N-nitroso species) were assessed by ozone- based chemiluminescence. Aortic NADPH oxidase activity and superoxide production were evaluated. While quercetin had no effects in control normotensive rats (P > 0.05), it significantly reduced SBP in 2K1C rats (P 0.05). However, plasma nitrite and the nitroso species levels were significantly lower in 2K1C rats when compared with controls (P 0.05), it restored the vascular responses to Ach. Quercetin significantly attenuated 2K1C-hypertension-induced increases in NADPH oxidase activity and vascular superoxide production (P < 0.05). These results suggest that the antihypertensive effects of quercetin were associated with increased NO formation and improved endothelial function, which probably result from its antioxidant effects.

Journal ArticleDOI
TL;DR: The mechanisms underlying in vitro the neuroprotective properties of VB involve modulation of transcription factors and consequent altered gene expression, resulting in downregulation of inflammation, providing support that VB may provide a promising approach for the treatment of oxidative-stress-related neurodegenerative diseases.
Abstract: The glycosylated phenylpropanoid verbascoside (VB), isolated from cultured cells of the medicinal plant Syringa vulgaris (Oleaceae), has previously been characterized as an effective scavenger of biologically active free radicals and an inhibitor of lipid peroxidation. The aim of the present study was to evaluate in a rat glioma cell line (C6) the effect of VB biotechnologically produced by S. vulgaris plant cell cultures in the regulation of the inflammatory response. We used a model of central nervous system inflammation induced by bacterial endotoxin/cytokine (lipopolysaccharide (LPS)/interferon (IFN)-gamma, 1 microg/ml and 100 U/ml, respectively). Our results show that the treatment with LPS/IFN-gamma for 24 h elicited the induction of inducible nitric oxide synthase (iNOS) activity as determined by NO(x) accumulation in the culture medium. Preincubation with VB (10-100 microg/ml) abrogated the mixed cytokine-mediated induction of iNOS. The effect was concentration-dependent. Our studies also showed an inhibitory effect of VB on neuronal nitric oxide synthase expression. Moreover, Western blot analysis showed that this glycoside prevents specifically the activation of the proinflammatory enzyme cyclooxygenase (COX)-2 in glioma cells without simultaneous inhibition of COX-1 enzyme. Moreover, we found that VB reduced the expression of proinflammatory enzymes in LPS/IFN-gamma through the inhibition of the activation of nuclear factor kappa B and mitogen-activated protein kinase signaling pathway. The mechanisms underlying in vitro the neuroprotective properties of VB involve modulation of transcription factors and consequent altered gene expression, resulting in downregulation of inflammation. These findings provide support that VB may provide a promising approach for the treatment of oxidative-stress-related neurodegenerative diseases.

Journal ArticleDOI
TL;DR: The presence of TAar-1 suggests that vasoconstriction may be via these receptors; however, the potency order differed from that reported for transfected cells expressing rat TAAR-1.
Abstract: Trace amines including tyramine and β-phenylethylamine (β-PEA) increase blood pressure and cause vasoconstriction which is attributed to indirect sympathomimetic actions. However, there is evidence that they may also have non-sympathomimetic mechanisms. This study examined whether β-PEA causes vasoconstriction of rat aorta by a sympathomimetic action or through the recently described trace-amine-associated receptors (TAAR). Concentration–response curves (CRCs) for β-PEA were constructed either cumulatively or non-cumulatively in rat isolated aortic rings. TAAR-1 and TAAR-4 protein expression was determined in rat aorta by Western blotting and TAAR-1 mRNA by reverse transcriptase polymerase chain reaction (RT-PCR). β-PEA caused concentration-related constriction of rat aorta. The contractions were unaffected by endothelium removal or the nitric oxide synthase inhibitor, $$ {N_\omega } $$ -nitro-l-arginine methyl ester (l-NAME, 100 μM) or the cyclooxygenase inhibitor, indomethacin (10 μM). Non-cumulative CRCs showed greater contractions and sensitivity to β-PEA than cumulative. The α1-adrenoceptor antagonist, prazosin, failed to inhibit either curve. The β-adrenoceptor antagonist, propranolol, the adrenergic neuronal transport inhibitor, cocaine, and the monoamine oxidase inhibitor, pargyline, also failed to alter the CRC. In the combined presence of prazosin, cocaine, pargyline, and the selective β2-adrenoceptor antagonist, ICI-118,551, the trace amine contractile potency order was tryptamine > β-PEA > octopamine > d-amphetamine > tyramine. Western blotting and RT-PCR revealed the presence of TAAR-1 in rat aorta, but TAAR-4 was poorly expressed. Vasoconstriction of rat aorta by β-PEA appears not to be an indirect sympathomimetic action. The presence of TAAR-1 suggests that vasoconstriction may be via these receptors; however, the potency order differed from that reported for transfected cells expressing rat TAAR-1.

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TL;DR: Concentration of TM in the lung of foals was significantly lowered by comedication of rifampicin most likely caused by extrapulmonary mechanisms leading to lower plasma concentrations.
Abstract: Macrolide antibiotics penetrate in the lung against steep concentration gradients into the epithelial lining fluid (ELF) and broncho-alveolar cells (BAC). Since they interact with ABCB1, ABCC2, and organic anion transporting proteins (OATPs), which are localized to lung tissue, pulmonary concentration may be influenced by rifampicin (RIF), an inducer and modulator of efflux and uptake transporters. We measured concentrations of tulathromycin (TM) in plasma, ELF and BAC in 21 warm-blooded foals 24 and 192 h after first and last intramuscular injection of 2.5 mg/kg TM once weekly for 6 weeks. In 11 foals, TM was combined with RIF (10 mg/kg twice daily), and mRNA expression of ABCB1 and ABCC2 in BAC was assessed before and after RIF. Affinity of TM to ABCB1 and ABCC2 was measured by transport assays using cell monolayers and membrane vesicles of MDCKII and 2008 cells transfected with ABCB1 and ABCC2, respectively. At steady state, TM concentrated manifold in ELF and BAC. Comedication of RIF significantly decreased the AUC of TM (18.5 +/- 4.0 versus 24.4 +/- 3.7 microg x h/ml, p < 0.05) and lowered its concentrations in plasma (24 h, 0.17 +/- 0.05 versus 0.24 +/- 0.05 microg/ml; 192 h, 0.05 +/- 0.01 versus 0.06 +/- 0.01 microg/ml) and BAC (24 h, 0.84 +/- 0.36 versus 1.56 +/- 1.02 microg/ml; 192 h, 0.60 +/- 0.23 versus 1.23 +/- 0.90 microg/ml, all p < 0.05). Treatment with rifampicin did not markedly induce ABCB1 and ABCC2 expression. TM had no affinity to ABCB1 and ABCC2 in vitro. Concentration of TM in the lung of foals was significantly lowered by comedication of rifampicin most likely caused by extrapulmonary mechanisms leading to lower plasma concentrations.

Journal ArticleDOI
TL;DR: It is demonstrated that the rate of cAMP accumulation is influenced by agonist efficacy and that this, in combination with lipophilicity, may explain why β2 AR agonists demonstrate differences in their onset of action.
Abstract: Inhaled β2 adrenoceptor (β2 AR) agonists are widely used as bronchodilator therapies for asthma and COPD. Different agonists have varying rates of onset of action, e.g. indacaterol and salbutamol are effective bronchodilators within 5 min whereas salmeterol takes 15 min to achieve significant bronchodilation over baseline (Brookman et al., Curr Med Res Opin 23:3113–3122, 2007). This has been attributed to differences in the lipophilicity of the agonists such that hydrophobic ligands take longer to diffuse into tissue and may even access the receptor via the membrane compartment (Anderson et al., Eur Respir J 7:569-578, 1994). While this holds true for salmeterol and salbutamol, the relatively high lipophilicity of indacaterol should result in a slower onset of action. Here we have explored the possibility that the efficacy of these ligands may also contribute to their onset of action. We have characterised efficacy and rate of cyclic adenosine monophosphate (cAMP) accumulation in primary human bronchial smooth muscle cells using a competition assay (AlphaScreen, Perkin Elmer) and in HEK 293-GloSensor™ cells endogenously expressing the β2 AR using a luminescence readout. For all agonists tested, cAMP was generated in a concentration-dependent manner. For both assay formats, the relative efficacies were unchanged, with isoprenaline > formoterol > indacaterol > salbutamol > salmeterol. The rate of cAMP generation varied for each agonist and correlated well with intrinsic efficacy in that the high-efficacy agonists promoted the most rapid rise in cAMP levels. We have demonstrated that the rate of cAMP accumulation is influenced by agonist efficacy and that this, in combination with lipophilicity, may explain why β2 AR agonists demonstrate differences in their onset of action.

Journal ArticleDOI
TL;DR: It is demonstrated that the resistance to LPS in DPP4-deficient rats seems to be derived from the higher GLP-1 production, and exendin-4 prevents cardiac dysfunction in wild-type rats with endotoxemia.
Abstract: Glucagon-like peptide-1 (GLP-1) is rapidly cleaved by widely expressed dipeptidyl peptidase-4 (DPP4) enzyme. Both DPP4 inhibitors and GLP-1 analogue are being developed as a novel class of oral antihyperglycemic agent in the treatment of diabetes. However, the benefits of both agents on the cardiovascular function of endotoxemic animals remains poorly understood. In this study, the cardiac function of wild-type and DPP4-deficient rats was evaluated by pressure–volume loops in control and 4 h after lipopolysaccharide (LPS, 10 mg/kg, i.v.) treatment. LPS-induced suppression of cardiovascular function in wild-type rats was associated with a significant reduction in cardiac cAMP level, phosphorylation of phospholamban, and attenuation of aortic contractile response to phenylephrine. DPP4-deficient rats had better preservation of cardiovascular function than wild-type rats during endotoxemia, which was correlated with a more prominent elevation of GLP-1 signaling. These findings coincided with the pretreatment of GLP-1 analogue, exendin-4, where the deterioration of cardiovascular function during endotoxemia was significantly reversed in wild-type rats. Furthermore, the benefit of DPP4 deficiency or GLP-1 analogue not only preserved cardiovascular function but also alleviated multiple organ injury and improved survival rate during endotoxemia. In summary, this study demonstrated that the resistance to LPS in DPP4-deficient rats seems to be derived from the higher GLP-1 production, and exendin-4 prevents cardiac dysfunction in wild-type rats with endotoxemia. This study proves that GLP-1 agonists or DPP4 inhibitor may possibly be used as a preventive or even as a novel therapeutic agent in septic shock.