Showing papers in "British Journal of Pharmacology in 2005"

Nanoparticle-induced platelet aggregation and vascular thrombosis

Abstract: Ever increasing use of engineered carbon nanoparticles in nanopharmacology for selective imaging, sensor or drug delivery systems has increased the potential for blood platelet-nanoparticle interactions. We studied the effects of engineered and combustion-derived carbon nanoparticles on human platelet aggregation in vitro and rat vascular thrombosis in vivo. Multiplewall (MWNT), singlewall (SWNT) nanotubes, C60 fullerenes (C60CS) and mixed carbon nanoparticles (MCN) (0.2-300 microg ml(-1)) were investigated. Nanoparticles were compared with standard urban particulate matter (SRM1648, average size 1.4 microm). Platelet function was studied using lumi aggregometry, phase-contrast, immunofluorescence and transmission electron microscopy, flow cytometry, zymography and pharmacological inhibitors of platelet aggregation. Vascular thrombosis was induced by ferric chloride and the rate of thrombosis was measured, in the presence of carbon particles, with an ultrasonic flow probe. Carbon particles, except C60CS, stimulated platelet aggregation (MCN>or=SWNT>MWNT>SRM1648) and accelerated the rate of vascular thrombosis in rat carotid arteries with a similar rank order of efficacy. All particles resulted in upregulation of GPIIb/IIIa in platelets. In contrast, particles differentially affected the release of platelet granules, as well as the activity of thromboxane-, ADP, matrix metalloproteinase- and protein kinase C-dependent pathways of aggregation. Furthermore, particle-induced aggregation was inhibited by prostacyclin and S-nitroso-glutathione, but not by aspirin. Thus, some carbon nanoparticles and microparticles have the ability to activate platelets and enhance vascular thrombosis. These observations are of importance for the pharmacological use of carbon nanoparticles and pathology of urban particulate matter.

The selectivity of β-adrenoceptor antagonists at the human β1, β2 and β3 adrenoceptors

Abstract: 1β-Adrenoceptor antagonists (‘β-blockers’) are one of the most widely used classes of drugs in cardiovascular medicine (hypertension, ischaemic heart disease and increasingly in heart failure) as well as in the management of anxiety, migraine and glaucoma. Where known, the mode of action in cardiovascular disease is from antagonism of endogenous catecholamine responses in the heart (mainly at β1-adrenoceptors), while the worrisome side effects of bronchospasm result from airway β2-adrenoceptor blockade. The aim of this study was to determine the selectivity of β-antagonists for the human β-adrenoceptor subtypes. 23H-CGP 12177 whole cell-binding studies were undertaken in CHO cell lines stably expressing either the human β1-, β2- or the β3-adrenoceptor in order to determine the affinity of ligands for each receptor subtype in the same cell background. 3In this study, the selectivity of well-known subtype-selective ligands was clearly demonstrated: thus, the selective β1 antagonist CGP 20712A was 501-fold selective over β2 and 4169-fold selective over β3; the β2-selective antagonist ICI 118551 was 550- and 661-fold selective over β1 and β3, respectively, and the selective β3 compound CL 316243 was 10-fold selective over β2 and more than 129-fold selective over β1. 4Those β2-adrenoceptor agonists used clinically for the treatment of asthma and COPD were β2 selective: 29-, 61- and 2818-fold for salbutamol, terbutaline and salmeterol over β1, respectively. There was little difference in the affinity of these ligands between β1 and β3 adrenoceptors. 5The clinically used β-antagonists studied ranged from bisoprolol (14-fold β1-selective) to timolol (26-fold β2-selective). However, the majority showed little selectivity for the β1- over the β2-adrenoceptor, with many actually being more β2-selective. 6This study shows that the β1/β2 selectivity of most clinically used β-blockers is poor in intact cells, and that some compounds that are traditionally classed as ‘β1-selective’ actually have higher affinity for the β2-adrenoceptor. There is therefore considerable potential for developing more selective β-antagonists for clinical use and thereby reducing the side-effect profile of β-blockers. British Journal of Pharmacology (2005) 144, 317–322. doi:10.1038/sj.bjp.0706048

Potential of ketamine and midazolam, individually or in combination, to induce apoptotic neurodegeneration in the infant mouse brain.

Abstract: Recently, it was reported that anesthetizing infant rats for 6 h with a combination of anesthetic drugs (midazolam, nitrous oxide, isoflurane) caused widespread apoptotic neurodegeneration in the developing brain, followed by lifelong cognitive deficits. It has also been reported that ketamine triggers neuroapoptosis in the infant rat brain if administered repeatedly over a period of 9 h. The question arises whether less extreme exposure to anesthetic drugs can also trigger neuroapoptosis in the developing brain. To address this question we administered ketamine, midazolam or ketamine plus midazolam subcutaneously at various doses to infant mice and evaluated the rate of neuroapoptosis in various brain regions following either saline or these various drug treatments. Each drug was administered as a single one-time injection in a dose range that would be considered subanesthetic, and the brains were evaluated by unbiased stereology methods 5 h following drug treatment. Neuroapoptosis was detected by immunohistochemical staining for activated caspase-3. It was found that either ketamine or midazolam caused a dose-dependent, statistically significant increase in the rate of neuroapoptosis, and the two drugs combined caused a greater increase than either drug alone. The apoptotic nature of the neurodegenerative reaction was confirmed by electron microscopy. We conclude that relatively mild exposure to ketamine, midazolam or a combination of these drugs can trigger apoptotic neurodegeneration in the developing mouse brain.

Characterisation of cell-penetrating peptide-mediated peptide delivery

Abstract: Cell-penetrating peptides such as antennapedia, TAT, transportan and polyarginine have been extensively employed for in vitro and in vivo delivery of biologically active peptides. However, little is known of the relative efficacy, toxicity and uptake mechanism of individual protein transduction domain-peptide conjugates, factors that will be critical in determining the most effective sequence. In the present study, we show by FACS analysis that unconjugated antennapedia, TAT, transportan and polyarginine demonstrate similar kinetic uptake profiles, being maximal at 1-3 h and independent of cell type (HeLa, A549 and CHO cell lines). A comparison of the magnitude of uptake of cell-penetrating peptide conjugates demonstrated that polyarginine=transportan>antennapedia>TAT. However, examination of cellular toxicity showed that antennapedia

Heat shock proteins as emerging therapeutic targets.

Abstract: Chaperones (stress proteins) are essential proteins to help the formation and maintenance of the proper conformation of other proteins and to promote cell survival after a large variety of environmental stresses. Therefore, normal chaperone function is a key factor for endogenous stress adaptation of several tissues. However, altered chaperone function has been associated with the development of several diseases; therefore, modulators of chaperone activities became a new and emerging field of drug development. Inhibition of the 90 kDa heat shock protein (Hsp)90 recently emerged as a very promising tool to combat various forms of cancer. On the other hand, the induction of the 70 kDa Hsp70 has been proved to be an efficient help in the recovery from a large number of diseases, such as, for example, ischemic heart disease, diabetes and neurodegeneration. Development of membrane-interacting drugs to modify specific membrane domains, thereby modulating heat shock response, may be of considerable therapeutic benefit as well. In this review, we give an overview of the therapeutic approaches and list some of the key questions of drug development in this novel and promising therapeutic approach.

The crucial role of metal ions in neurodegeneration: the basis for a promising therapeutic strategy

Abstract: The variety of factors and events involved in neurodegeneration renders the subject a major challenge. Neurodegenerative disorders include a number of different pathological conditions, which share similar critical metabolic processes, such as protein aggregation and oxidative stress, both of which are associated with the involvement of metal ions. In this review, Alzheimer's disease, Parkinson's disease and prion disease are discussed, with the aim of identifying common trends underlying these devastating neurological conditions. Chelation therapy could be a valuable therapeutic approach, since metals are considered to be a pharmacological target for the rationale design of new therapeutic agents directed towards the treatment of neurodegeneration.

Carbon monoxide-releasing molecules (CO-RMs) attenuate the inflammatory response elicited by lipopolysaccharide in RAW264.7 murine macrophages

Abstract: The enzyme heme oxygenase-1 (HO-1) is a cytoprotective and anti-inflammatory protein that degrades heme to produce biliverdin/bilirubin, ferrous iron and carbon monoxide (CO). The anti-inflammatory properties of HO-1 are related to inhibition of adhesion molecule expression and reduction of oxidative stress, while exogenous CO gas treatment decreases the production of inflammatory mediators such as cytokines and nitric oxide (NO). CO-releasing molecules (CO-RMs) are a novel group of substances identified by our group that are capable of modulating physiological functions via the liberation of CO. We aimed in this study to examine the potential anti-inflammatory characteristics of CORM-2 and CORM-3 in an in vitro model of lipopolysaccharide (LPS)-stimulated murine macrophages. Stimulation of RAW264.7 macrophages with LPS resulted in increased expression of inducible NO synthase (iNOS) and production of nitrite. CORM-2 or CORM-3 (10-100 microM) reduced nitrite generation in a concentration-dependent manner but did not affect the protein levels of iNOS. CORM-3 also decreased nitrite levels when added 3 or 6 h after LPS exposure. CORM-2 or CORM-3 did not cause any evident cytotoxicity and produced an increase in HO-1 expression and heme oxygenase activity; this effect was completely prevented by the thiol donor N-acetylcysteine. CORM-3 also considerably reduced the levels of tumor necrosis factor-alpha, another mediator of the inflammatory response. The inhibitory effects of CORM-2 and CORM-3 were not observed when the inactive compounds, which do not release CO, were coincubated with LPS. These results indicate that CO liberated by CORM-2 and CORM-3 significantly suppresses the inflammatory response elicited by LPS in cultured macrophages and suggest that CO carriers can be used as an effective strategy to modulate inflammation.

Flavonols inhibit proinflammatory mediator release, intracellular calcium ion levels and protein kinase C theta phosphorylation in human mast cells

Abstract: Mast cells participate in allergies, and also in immunity and inflammation by secreting proinflammatory cytokines. Flavonoids are naturally occurring polyphenolic plant compounds, one group of which -- the flavonols, inhibits histamine and some cytokine release from rodent basophils and mast cells. However, the effect of flavonols on proinflammatory mediator release and their possible mechanism of action in human mast cells is not well defined. Human umbilical cord blood-derived cultured mast cells (hCBMCs) grown in the presence of stem cell factor (SCF) and interleukin (IL)-6 were preincubated for 15 min with the flavonols quercetin, kaempferol, myricetin and morin (0.01, 0.1, 1, 10 or 100 microM), followed by activation with anti-IgE. Secretion was quantitated for IL-6, IL-8, tumor necrosis factor-alpha (TNF-alpha), histamine and tryptase levels. Release of IL-6, IL-8 and TNF-alpha was inhibited by 82-93% at 100 microM quercetin and kaempferol, and 31-70% by myricetin and morin. Tryptase release was inhibited by 79-96% at 100 microM quercetin, kampferol and myricetin, but only 39% by morin; histamine release was inhibited 52-77% by the first three flavonols, but only 28% by morin. These flavonols suppressed intracellular calcium ion elevations in a dose-response manner, with morin being the weakest; they also inhibited phosphorylation of the calcium-insensitive protein kinase C theta (PKC theta). Flavonol inhibition of IgE-mediated proinflammatory mediator release from hCBMCs may be due to inhibition of intracellular calcium influx and PKC theta signaling. Flavonols may therefore be suitable for the treatment of allergic and inflammatory diseases.

Endothelium-Dependent Contractions in Hypertension

Abstract: 1. Endothelial cells, under given circumstances, can initiate contraction (constriction) of the vascular smooth muscle cells that surround them. Such endothelium-dependent, acute increases in contractile tone can be due to the withdrawal of the production of nitric oxide, to the production of vasoconstrictor peptides (angiotensin II, endothelin-1), to the formation of oxygen-derived free radicals (superoxide anions) and/or the release of vasoconstrictor metabolites of arachidonic acid. The latter have been termed endothelium-derived contracting factor (EDCF) as they can contribute to moment-to-moment changes in contractile activity of the underlying vascular smooth muscle cells. 2. To judge from animal experiments, EDCF-mediated responses are exacerbated by aging, spontaneous hypertension and diabetes. 3. To judge from human studies, they contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients. 4. Since EDCF causes vasoconstriction by activation of the TP-receptors on the vascular smooth muscle cells, selective antagonists at these receptors prevent endothelium-dependent contractions, and curtail the endothelial dysfunction in hypertension and diabetes.

Effects of piperine, the pungent component of black pepper, at the human vanilloid receptor (TRPV1)

Abstract: 1. We have characterised the effects of piperine, a pungent alkaloid found in black pepper, on the human vanilloid receptor TRPV1 using whole-cell patch-clamp electrophysiology. 2. Piperine produced a clear agonist activity at the human TRPV1 receptor yielding rapidly activating whole-cell currents that were antagonised by the competitive TRPV1 antagonist capsazepine and the non-competitive TRPV1 blocker ruthenium red. 3. The current-voltage relationship of piperine-activated currents showed pronounced outward rectification (25+/-4-fold between -70 and +70 mV) and a reversal potential of 0.0+/-0.4 mV, which was indistinguishable from that of the prototypical TRPV1 agonist capsaicin. 4. Although piperine was a less potent agonist (EC50=37.9+/-1.9 microM) than capsaicin (EC50=0.29+/-0.05 microM), it demonstrated a much greater efficacy (approximately two-fold) at TRPV1. 5. This difference in efficacy did not appear to be related to the proton-mediated regulation of the receptor since a similar degree of potentiation was observed for responses evoked by piperine (230+/-20%, n=11) or capsaicin (284+/-32%, n=8) upon acidification to pH 6.5. 6. The effects of piperine upon receptor desensitisation were also unable to explain this effect since piperine resulted in more pronounced macroscopic desensitisation (t(1/2)=9.9+/-0.7 s) than capsaicin (t(1/2)>20 s) and also caused greater tachyphylaxis in response to repetitive agonist applications. 7. Overall, our data suggest that the effects of piperine at human TRPV1 are similar to those of capsaicin except for its propensity to induce greater receptor desensitisation and, rather remarkably, exhibit a greater efficacy than capsaicin itself. These results may provide insight into the TRPV1-mediated effects of piperine on gastrointestinal function.

Neuritic regeneration and synaptic reconstruction induced by withanolide A.

Abstract: We investigated whether withanolide A (WL-A), isolated from the Indian herbal drug Ashwagandha (root of Withania somnifera), could regenerate neurites and reconstruct synapses in severely damaged neurons. We also investigated the effect of WL-A on memory-deficient mice showing neuronal atrophy and synaptic loss in the brain. Axons, dendrites, presynapses, and postsynapses were visualized by immunostaining for phosphorylated neurofilament-H (NF-H), microtubule-associated protein 2 (MAP2), synaptophysin, and postsynaptic density-95 (PSD-95), respectively. Treatment with A beta(25-35) (10 microM) induced axonal and dendritic atrophy, and pre- and postsynaptic loss in cultured rat cortical neurons. Subsequent treatment with WL-A (1 microM) induced significant regeneration of both axons and dendrites, in addition to the reconstruction of pre- and postsynapses in the neurons. WL-A (10 micromol kg(-1) day(-1), for 13 days, p.o.) recovered A beta(25-35)-induced memory deficit in mice. At that time, the decline of axons, dendrites, and synapses in the cerebral cortex and hippocampus was almost recovered. WL-A is therefore an important candidate for the therapeutic treatment of neurodegenerative diseases, as it is able to reconstruct neuronal networks.

Block of TRPC5 channels by 2-aminoethoxydiphenyl borate : a differential, extracellular and voltage-dependent effect

Abstract: 1 2-aminoethoxydiphenyl borate (2-APB) has been widely used to examine the roles of inositol 1,4,5-trisphosphate receptors (IP3Rs) and store-operated Ca2+ entry and is an emerging modulator of cationic channels encoded by transient receptor potential (TRP) genes. 2 Using Ca2+-indicator dye and patch-clamp recording we first examined the blocking effect of 2-APB on human TRPC5 channels expressed in HEK-293 cells. 3 The concentration-response curve has an IC50 of 20 microM and slope close to 1.0, suggesting one 2-APB molecule binds per channel. The blocking effect is not shared by other Ca2+ channel blockers including methoxyverapamil, nifedipine, N-propargylnitrendipine, or berberine. 4 In whole-cell and excised membrane patch recordings, 2-APB acts from the extracellular but not intracellular face of the membrane. 5 Block of TRPC5 by 2-APB is less at positive voltages, suggesting that it enters the electric field or acts by modulating channel gating. 6 2-APB also blocks TRPC6 and TRPM3 expressed in HEK-293 cells, but not TRPM2. 7 Block of TRP channels by 2-APB may be relevant to cell proliferation because 2-APB has a greater inhibitory effect on proliferation in cells overexpressing TRPC5. 8 Our data indicate a specific and functionally important binding site on TRPC5 that enables block by 2-APB. The site is only available via an extracellular route and the block shows mild voltage-dependence.

Acetylcholine-induced endothelium-dependent contractions in the SHR aorta: the Janus face of prostacyclin.

Abstract: In the spontaneously hypertensive rat (SHR) and aging Wistar-Kyoto rats (WKY), acetylcholine releases an endothelium-derived contracting factor (EDCF) produced by endothelial cyclooxygenase-1, which stimulates thromboxane A2 receptors (TP receptors) on vascular smooth muscle. The purpose of the present study was to identify this EDCF by measuring changes in isometric tension and the release of various prostaglandins by acetylcholine. In isolated aortic rings of SHR, U 46619, prostaglandin (PG) H2, PGF2alpha, PGE2, PGD2, prostacyclin (PGI2) and 8-isoprostane, all activate TP receptors of the vascular smooth muscle to produce a contraction (U 46619>>8-isoprostane=PGF2alpha=PGH2>PGE2=PGD2>PGI2). The contractions produced by PGH2 and PGI2 were fast and transient, mimicking endothelium-dependent contractions. PGI2 did not relax isolated aortic rings of WKY and SHR. Acetylcholine evoked the endothelium-dependent release of thromboxane A2, PGF2alpha, PGE2, PGI2 and most likely PGH2 (PGI2>>PGF2alpha>or=PGE2>TXA2>8-isoprostane, PGD2). Dazoxiben abolished the production of thromboxane A2, but did not influence the endothelium-dependent contractions to acetylcholine. The release of PGI2 was significantly larger in the aorta of SHR than in WKY, and the former was more sensitive to the contractile effect of PGI2 than the latter. The inhibition of PGI-synthase was associated with an increase in PGH2 spillover and the enhancement of acetylcholine-induced endothelium-dependent contractions. Thus, in the aorta of SHR and aging WKY, the endothelium-dependent contractions elicited by acetylcholine most likely involve the release of PGI2 with a concomitant contribution of PGH2.

Pharmacodynamics and pharmacokinetics of SQ109, a new diamine-based antitubercular drug

Abstract: SQ109 is a novel [1,2]-diamine-based ethambutol (EMB) analog developed from high-throughput combinatorial screening. The present study aimed at characterizing its pharmacodynamics and pharmacokinetics. The antimicrobial activity of SQ109 was confirmed in vitro (Mycobacterium tuberculosis-infected murine macrophages) and in vivo (M. tuberculosis-infected C57BL/6 mice) and compared to isoniazid (INH) and EMB. SQ109 showed potency and efficacy in inhibiting intracellular M. tuberculosis that was similar to INH, but superior to EMB. In vivo oral administration of SQ109 (0.1-25 mg kg(-1) day(-1)) to the mice for 28 days resulted in dose-dependent reductions of mycobacterial load in both spleen and lung comparable to that of EMB administered at 100 mg kg(-1) day(-1), but was less potent than INH at 25 mg kg(-1) day(-1). Monitoring of SQ109 levels in mouse tissues on days 1, 14 and 28 following 28-day oral administration (10 mg kg(-1) day(-1)) revealed that lungs and spleen contained the highest concentration of SQ109, at least 10 times above its MIC. Pharmacokinetic profiles of SQ109 in mice following a single administration showed its C(max) as 1038 (intravenous (i.v.)) and 135 ng ml(-1) (p.o.), with an oral T(max) of 0.31 h. The elimination t(1/2) of SQ109 was 3.5 (i.v.) and 5.2 h (p.o.). The oral bioavailability was 4%. However, SQ109 displayed a large volume of distribution into various tissues. The highest concentration of SQ109 was present in lung (>MIC), which was at least 120-fold (p.o.) and 180-fold (i.v.) higher than that in plasma. The next ranked tissues were spleen and kidney. SQ109 levels in most tissues after a single administration were significantly higher than that in blood. High tissue concentrations of SQ109 persisted for the observation period (10 h). This study demonstrated that SQ109 displays promising in vitro and in vivo antitubercular activity with favorable targeted tissue distribution properties.

Endothelin-1 enhances oxidative stress, cell proliferation and reduces apoptosis in human umbilical vein endothelial cells: role of ETB receptor, NADPH oxidase and caveolin-1.

Abstract: 1 Endothelin-1 (ET-1), an endothelium-derived vasoactive peptide, participates in the regulation of endothelial function through mechanisms that are not fully elucidated. This study examined the impact of ET-1 on oxidative stress, apoptosis and cell proliferation in human umbilical vein endothelial cells (HUVEC). HUVECs were challenged for 24 h with ET-1 (10 pM-10 nM) in the absence or presence of the ET(B) receptor antagonist BQ788 (1 microM) or the NADPH oxidase inhibitor apocynin (1 microM). Reactive oxygen species (ROS) were detected using chloromethyl-2',7'-dichlorodihydrofluorescein diacetate. Apoptosis was evaluated with 4',6'-diamidino-2'-phenylindoladihydrochloride staining and by the caspase-3 assay. Cell proliferation was measured by a colorimetric assay. Expression of NADPH oxidase, Akt, pAkt, Bcl-2, Bax, IkappaB, caveolin-1 and eNOS was evaluated by Western blot analysis. 2 ET-1 significantly enhanced ROS generation and cell proliferation following 24-h incubation, both of which were prevented by BQ788 or apocynin, consistent with the ability of ET-1 to directly upregulate NADPH oxidase. ET-1 itself did not affect apoptosis but attenuated homocysteine-induced apoptosis through an ET(B) receptor-mediated mechanism. Western blot analysis indicated that ET-1 alleviated homocysteine (Hcy)-induced apoptosis, likely acting by antagonizing the Hcy-induced decreases in Akt, pAkt, pAkt-to-Akt, Bcl-2-to-Bax ratios and increases in Bax and caveolin-1 expression. Furthermore, ET-1 downregulated expression of caveolin-1 and eNOS, which was attenuated by BQ788 or apocynin. 3 In summary, our results suggest that ET-1 affects oxidative stress, proliferation and apoptosis possibly through ET(B), NADPH oxidase, Akt, Bax and caveolin-1-mediated mechanisms.

Muscarinic receptor subtypes in human bladder detrusor and mucosa, studied by radioligand binding and quantitative competitive RT-PCR : changes in ageing

Abstract: 1. We investigated muscarinic receptors in the detrusor and mucosa of the human bladder body. Radioligand-binding studies with [(3)H]QNB were conducted using specimens collected from patients (36-77 years) with normal bladder function, undergoing surgery. For RT-PCR, biopsies of normal bladder were obtained from patients (30-88 years) undergoing check cystoscopy. 2. Binding of [(3)H]QNB in detrusor (n=20) was of high affinity (K(D) 77.1 (55.2-99.0) pM) and capacity (B(max) 181+/-7 fmol mg protein(-1)). Similar values were obtained in mucosa (n=6) (K(D) 100.5 (41.2-159.9) pM; B(max) 145+/-9 fmol mg protein(-1)). 3. Competition-binding experiments in detrusor membranes with muscarinic receptor antagonists including trospium, darifenacin, 4-DAMP, methoctramine, AQ-RA 741, AF-DX 116 and pirenzepine indicated a receptor population of 71% M(2), 22% M(3) and 7% M(1). In the mucosa, 75% of sites were M(2) receptors, with 25% M(3)/M(5). 4. Using RT-PCR, expression of M(1), M(2), M(3) and M(5) mRNA was demonstrated in both detrusor and mucosa. 5. The presence of a high density of mainly M(2) muscarinic receptors in the mucosa appears to be a novel finding and raises the question of their physiological significance and the source of their endogenous ligand. 6. There was a negative correlation of receptor number (B(max)) with age in detrusor muscle from male patients (P=0.02). Quantitative competitive RT-PCR demonstrated a selective age-related decrease in mRNA for muscarinic M(3) but not M(2) receptors, in both male (P<0.0001) and female (P=0.019) detrusor. These findings correspond with reports of decreased detrusor contractility with ageing.

CB1 cannabinoid receptor-mediated modulation of food intake in mice

Abstract: 1 Marijuana's appetite-increasing effects have long been known. Recent research suggests that the CB(1) cannabinoid receptor antagonist SR141716A may suppress appetite. This study represents a further, systematic investigation of the role of CB(1) cannabinoid receptors in the pharmacological effects of cannabinoids on food intake. 2 Mice were food-restricted for 24 h and then allowed access to their regular rodent chow for 1 h. Whereas the CB(1) antagonist SR141716A dose-dependently decreased food consumption at doses that did not affect motor activity, Delta(9)-tetrahydrocannabinol (Delta(9)-THC) increased food consumption at doses that had no effect on motor activity. O-3259 and O-3257, structural analogs of SR141716A, produced effects similar to those of the parent compound. 3 Amphetamine (a known anorectic) and diazepam (a benzodiazepine and CNS depressant) decreased food consumption, but only at doses that also increased or decreased motor activity, respectively. The CB(2) cannabinoid receptor antagonist SR144528 and the nonpsychoactive cannabinoid cannabidiol did not affect food intake nor activity. 4 SR141716A decreased feeding in wild-type mice, but lacked pharmacological activity in CB(1) knockout mice; however, basal food intake was lower in CB(1) knockout mice. Amphetamine decreased feeding in both mouse genotypes. 5 These results suggest that SR141716A may affect the actions of endogenous cannabinoids in regulating appetite or that it may have effects of its own aside from antagonism of cannabinoid effects (e.g., decreased feeding behavior and locomotor stimulation). In either case, these results strongly suggest that CB(1) receptors may play a role in regulation of feeding behavior.

Inhibitors of fatty acid amide hydrolase reduce carrageenan-induced hind paw inflammation in pentobarbital-treated mice: comparison with indomethacin and possible involvement of cannabinoid receptors

Abstract: The in vivo effect of inhibitors of fatty acid amide hydrolase (FAAH) upon oedema volume and FAAH activity was evaluated in the carrageenan induced hind paw inflammation model in the mouse. Oedema was measured at two time points, 2 and 4 h, after intraplantar injection of carrageenan to anaesthetised mice. Intraperitoneal (i.p.) injections of the FAAH inhibitor URB597 (0.1, 0.3, 1 and 3 mg kg(-1)) 30 min prior to carrageenan administration, dose-dependently reduced oedema formation. At the 4 h time point, the ED(50) for URB597 was approximately 0.3 mg kg(-1). Indomethacin (5 mg kg(-1) i.p.) completely prevented the oedema response to carrageenan. The antioedema effects of indomethacin and URB597 were blocked by 3 mg kg(-1) i.p. of the CB(2) receptor antagonist SR144528. The effect of URB597 was not affected by pretreatment with the peroxisome proliferator-activated receptor gamma antagonist bisphenol A diglycidyl ether (30 mg kg(-1) i.p.) or the TRPV1 antagonist capsazepine (10 mg kg(-1) i.p.), when oedema was assessed 4 h after carrageenan administration. The CB(1) receptor antagonists AM251 (3 mg kg(-1) i.p.) and rimonabant (0.5 mg kg(-1) i.p.) gave inconsistent effects upon the antioedema effect of URB597. FAAH measurements were conducted ex vivo in the paws, spinal cords and brains of the mice. The activities of FAAH in the paws and spinal cords of the inflamed vehicle-treated mice were significantly lower than the corresponding activities in the noninflamed mice. PMSF treatment almost completely inhibited the FAAH activity in all three tissues, as did the highest dose of URB597 (3 mg kg(-1)) in spinal cord samples, whereas no obvious changes were seen ex vivo for the other treatments. In conclusion, the results show that in mice, treatment with indomethacin and URB597 produce SR144528-sensitive anti-inflammatory effects in the carrageenan model of acute inflammation.

Inhibition of endogenous hydrogen sulfide formation reduces the organ injury caused by endotoxemia

Abstract: Hydrogen sulfide (H2S) is a naturally occurring gaseous transmitter, which may play important roles in normal physiology and disease. Here, we investigated the role of H2S in the organ injury caused by severe endotoxemia in the rat. Male Wistar rats were subjected to acute endotoxemia (Escherichia coli lipopolysaccharide (LPS) 6 mg kg(-1) intravenously (i.v.) for 6 h) and treated with vehicle (saline, 1 ml kg(-1) i.v.) or DL-propargylglycine (PAG, 10-100 mg kg(-1) i.v.), an inhibitor of the H2S-synthesizing enzyme cystathionine-gamma-lyase (CSE). PAG was administered either 30 min prior to or 60 min after the induction of endotoxemia. Endotoxemia resulted in circulatory failure (hypotension and tachycardia) and an increase in serum levels of alanine aminotransferase and aspartate aminotransferase (markers for hepatic injury), lipase (indicator of pancreatic injury) and creatine kinase (indicator of neuromuscular injury). In the liver, endotoxemia induced a significant increase in the myeloperoxidase (MPO) activity, and in the expression and activity of the H2S-synthesizing enzymes CSE and cystathionine-beta-synthase. Administration of PAG either prior to or after the injection of LPS dose-dependently reduced the hepatocellular, pancreatic and neuromuscular injury caused by endotoxemia, but not the circulatory failure. Pretreatment of rats with PAG abolished the LPS-induced increase in the MPO activity and in the formation of H2S and in the liver. These findings support the view that an enhanced formation of H2S contributes to the pathophysiology of the organ injury in endotoxemia. We propose that inhibition of H2S synthesis may be a useful therapeutic strategy against the organ injury associated with sepsis and shock.

Vasomotion: cellular background for the oscillator and for the synchronization of smooth muscle cells

Abstract: 1. Vasomotion is the oscillation of vascular tone with frequencies in the range from 1 to 20 min(-1) seen in most vascular beds. The oscillation originates in the vessel wall and is seen both in vivo and in vitro. 2. Recently, our ideas on the cellular mechanisms responsible for vasomotion have improved. Three different types of cellular oscillations have been suggested. One model has suggested that oscillatory release of Ca2+ from intracellular stores is important (the oscillation is based on a cytosolic oscillator). A second proposed mechanism is an oscillation originating in the sarcolemma (a membrane oscillator). A third mechanism is based on an oscillation of glycolysis (metabolic oscillator). For the two latter mechanisms, only limited experimental evidence is available. 3. To understand vasomotion, it is important to understand how the cells synchronize. For the cytosolic oscillators synchronization may occur via activation of Ca2+-sensitive ion channels by oscillatory Ca2+ release. The ensuing membrane potential oscillation feeds back on the intracellular Ca2+ stores and causes synchronization of the Ca2+ release. While membrane oscillators in adjacent smooth muscle cells could be synchronized through the same mechanism that sets up the oscillation in the individual cells, a mechanism to synchronize the metabolic-based oscillators has not been suggested. 4. The interpretation of the experimental observations is supported by theoretical modelling of smooth muscle cells behaviour, and the new insight into the mechanisms of vasomotion has the potential to provide tools to investigate the physiological role of vasomotion.

Inhibition of the human two-pore domain potassium channel, TREK-1, by fluoxetine and its metabolite norfluoxetine.

Abstract: 1. Block of the human two-pore domain potassium (2-PK) channel TREK-1 by fluoxetine (Prozac) and its active metabolite, norfluoxetine, was investigated using whole-cell patch-clamp recording of currents through recombinant channels in tsA 201 cells. 2. Fluoxetine produced a concentration-dependent inhibition of TREK-1 current that was reversible on wash. The IC50 for block was 19 microM. Block by fluoxetine was voltage-independent. Fluoxetine (100 microM) produced an 84% inhibition of TREK-1 currents, but only a 31% block of currents through a related 2-PK channel, TASK-3. 3. Norfluoxetine was a more potent inhibitor of TREK-1 currents with an IC50 of 9 microM. Block by norfluoxetine was also voltage-independent. 4. Truncation of the C-terminus of TREK-1 (delta89) resulted in a loss of channel function, which could be restored by intracellular acidification or the mutation E306A. The mutation E306A alone increased basal TREK-1 current and resulted in a loss of the slow phase of TREK-1 activation. 5. Progressive deletion of the C-terminus of TREK-1 had no effect on the inhibition of the channel by fluoxetine. The E306A mutation, on the other hand, reduced the magnitude of fluoxetine inhibition, with 100 microM producing only a 40% inhibition. 6. It is concluded that fluoxetine and norfluoxetine are potent inhibitors of TREK-1. Block of TREK-1 by fluoxetine may have important consequences when the drug is used clinically in the treatment of depression.

Evidence that the plant cannabinoid Δ9-tetrahydrocannabivarin is a cannabinoid CB1 and CB2 receptor antagonist

Abstract: Δ9-tetrahydrocannabivarin (THCV) displaced [3H]CP55940 from specific binding sites on mouse brain and CHO-hCB2 cell membranes (Ki=75.4 and 62.8 nM, respectively). THCV (1 μM) also antagonized CP55940-induced stimulation of [35S]GTPγS binding to these membranes (apparent KB=93.1 and 10.1 nM, respectively). In the mouse vas deferens, the ability of Δ9-tetrahydrocannabinol (THC) to inhibit electrically evoked contractions was antagonized by THCV, its apparent KB-value (96.7 nM) approximating the apparent KB-values for its antagonism of CP55940- and R-(+)-WIN55212-induced stimulation of [35S]GTPγS binding to mouse brain membranes. THCV also antagonized R-(+)-WIN55212, anandamide, methanandamide and CP55940 in the vas deferens, but with lower apparent KB-values (1.5, 1.2, 4.6 and 10.3 nM, respectively). THCV (100 nM) did not oppose clonidine, capsaicin or (−)-7-hydroxy-cannabidiol-dimethylheptyl-induced inhibition of electrically evoked contractions of the vas deferens. Contractile responses of the vas deferens to phenylephrine hydrochloride or β,γ-methylene-ATP were not reduced by 1 μM THCV or R-(+)-WIN55212, suggesting that THCV interacts with R-(+)-WIN55212 at prejunctional sites. At 32 μM, THCV did reduce contractile responses to phenylephrine hydrochloride and β,γ-methylene-ATP, and above 3 μM it inhibited electrically evoked contractions of the vas deferens in an SR141716A-independent manner. In conclusion, THCV behaves as a competitive CB1 and CB2 receptor antagonist. In the vas deferens, it antagonized several cannabinoids more potently than THC and was also more potent against CP55940 and R-(+)-WIN55212 in this tissue than in brain membranes. The bases of these agonist- and tissue-dependent effects remain to be established. Keywords: Δ9-Tetrahydrocannabivarin, Δ9-tetrahydrocannabinol, R-(+)-WIN55212, anandamide, methanandamide, CP55940, cannabinoids, mouse vas deferens, CB1 receptor antagonist, CB2 receptor antagonist Introduction Cannabis sativa is the natural source of a set of at least 66 oxygen-containing aromatic hydrocarbon compounds that are known collectively as phytocannabinoids (reviewed in ElSohly, 2002). This study focused on a little-investigated phytocannabinoid, the n-propyl analogue of Δ9-tetrahydrocannabinol (THC) (Figure 1), which was first detected in cannabis by Gill et al. (1970) and named Δ9-tetrahydrocannabivarin (THCV) by Merkus (1971). The initial objective of this research was to establish whether THCV can activate or block cannabinoid CB1 or CB2 receptors. Some of our experiments were performed with membranes prepared from healthy brain tissue, which is densely populated with CB1 but not CB2 receptors (reviewed in Howlett et al., 2002), or from Chinese hamster ovary (CHO) cells transfected with hCB2 receptors. These membranes were used to investigate the ability of THCV to displace [3H]CP55940 from CB1- and CB2-binding sites and to determine whether it behaves as a CB1 or CB2 receptor agonist or antagonist. Experiments were also carried out with the mouse isolated vas deferens, a tissue in which cannabinoid receptor agonists such as R-(+)-WIN55212, CP55940, THC and 2-arachidonoyl ethanolamide (anandamide) can inhibit electrically evoked contractions (Devane et al., 1992; Pertwee et al., 1995b). This they are thought to do by acting on prejunctional neuronal cannabinoid CB1 receptors to inhibit release of the contractile neurotransmitters, ATP, acting on postjunctional P2X purinoceptors, and noradrenaline, acting on postjunctional α1-adrenoceptors (von Kugelgen & Starke, 1991; Trendelenburg et al., 2000; see also Pertwee, 1997; Schlicker & Kathman, 2001). Experiments were also performed with (−)-7-hydroxy-cannabidiol-dimethylheptyl, a synthetic analogue of the phytocannabinoid, (−)-cannabidiol, that inhibits electrically evoked contractions of the mouse vas deferens through a mechanism that appears to operate prejunctionally and to be at least partly CB1 receptor-independent (Pertwee et al., 2005). Some of the results described in this paper have been presented to the British Pharmacological Society (Pertwee et al., 2004). Figure 1 Structures of THC and THCV. Methods The methods used comply with the U.K. Animals (Scientific Procedures) Act, 1986 and Associated Guidelines for the Use of Experimental Animals. Drugs and chemicals THCV was supplied by GW Pharmaceuticals (Porton Down, Wiltshire, U.K.), THC by the National Institute on Drug Abuse (Bethesda, MD, U.S.A.) and (−)-7-hydroxy-cannabidiol-dimethylheptyl by Professor R. Mechoulam (Hebrew University of Jerusalem, Israel). SR141716A and SR144528 were obtained from Sanofi-Aventis (Montpellier, France). Phenylephrine hydrochloride, β,γ-methyleneadenosine 5′-triphosphate (β,γ-methylene-ATP), anandamide and clonidine hydrochloride were purchased from Sigma-Aldrich (Poole, Dorset, U.K.), R-(+)-WIN55212 and CP55940 from Tocris (Bristol, U.K.) and capsaicin from Research Biochemicals International (Natick, MA, U.S.A.). Phenylephrine hydrochloride, β,γ-methylene-ATP and clonidine were dissolved in a 0.9% aqueous solution of NaCl (saline). R-(+)-WIN55212 was dissolved in a 50% (v v−1) solution of dimethyl sulphoxide (DMSO) in saline and all other drugs were dissolved in pure DMSO. Drugs were added to organ baths in a volume of 10 μl. For the binding experiments, [3H]CP55940 (168 Ci mmol−1), [3H]R-(+)-WIN55212 (40 Ci mmol−1) and [35S]GTPγS (1250 Ci mmol−1) were obtained from Perkin-Elmer Life Sciences Inc. (Boston, MA, U.S.A.). [3H]SR141716A (44 Ci mmol−1) was obtained from Amersham Biosciences U.K. Ltd (Little Chalfont, Buckinghamshire, U.K.), GTPγS and adenosine deaminase from Roche Diagnostic (Indianapolis, IN, U.S.A.) and GDP from Sigma-Aldrich.

Ethyl caffeate suppresses NF-kappaB activation and its downstream inflammatory mediators, iNOS, COX-2, and PGE2 in vitro or in mouse skin.

Abstract: Ethyl caffeate, a natural phenolic compound, was isolated from Bidens pilosa, a medicinal plant popularly used for treating certain inflammatory syndromes. The purpose of this study was to investigate the structural activity, and the anti-inflammatory functions and mechanism(s) of ethyl caffeate. Ethyl caffeate was found to markedly suppress the lipopolysaccharide (LPS)-induced nitric oxide (NO) production (IC50=5.5 μg ml−1), mRNA and protein expressions of inducible nitric oxide synthase (iNOS), and prostaglandin E2 (PGE2) production in RAW 264.7 macrophages. Transient gene expression assays using human cox-2 promoter construct revealed that ethyl caffeate exerted an inhibitory effect on cox-2 transcriptional activity in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 cells. Immunohistochemical studies of mouse skin demonstrated that TPA-induced COX-2 expression was significantly inhibited by ethyl caffeate with a superior effect to that of celecoxib, a nonsteroidal anti-inflammatory drug. The phosphorylation and degradation of inhibitor κB (IκB) and the translocation of nuclear transcription factor-κB (NF-κB) into the nucleus, as well as the activation of mitogen-activated protein kinases (MAPKs) induced by LPS in macrophages, were not affected by ethyl caffeate. Ethyl caffeate, however, could inhibit NF-κB activation by impairing the binding of NF-κB to its cis-acting element. These results suggest that ethyl caffeate suppresses iNOS and COX-2 expressions partly through the inhibition of the NF-κB·DNA complex formation. Structure–activity relationship analyses suggested that the catechol moiety and α,β-unsaturated ester group in ethyl caffeate are important and essential structural features for preventing NF-κB·DNA complex formation. This study provides an insight into the probable mechanism(s) underlying the anti-inflammatory and therapeutic properties of ethyl caffeate. Keywords: Ethyl caffeate, Bidens pilosa, NF-κB, COX-2, iNOS, PGE2 Introduction The nuclear factor-κB (NF-κB) is essential for host defense and inflammatory responses to microbial and viral infections (Li & Verma, 2002). In response to extracellular stimuli, such as bacterial lipopolysaccharide (LPS), tumor-necrosis factor-α (TNF-α), or other inflammatory mediators, the transcription factor NF-κB is often activated and subsequently facilitates the transcription of a number of genes involved in inflammation, such as cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and specific cytokines (Bayon et al., 2003). The inhibitor of κB (IκB) kinase (IKK) complex is a central element of NF-κB-related signaling. IKK phosphorylates NF-κB-bound IκB complexes at two conserved serine residues within the IκB N-terminal regulatory domain. This targets IκB for ubiquitin-dependent degradation and allows the liberated NF-κB dimers to be translocated to the nucleus and bind to cognate DNA enhancer sequences that lead to the transcription of various genes (Karin et al., 2002). The other major extracellular signal transduction pathway stimulated by inflammatory mediators is the mitogen-activated protein kinase (MAPK) pathway (Guha & Mackman, 2001). MAPKs are a family of serine/threonine protein kinases composed of the p44 and p42 isoforms (also known as extracellular signal receptor-activated kinase ERK1 and ERK2), p38, and c-Jun NH2-terminal kinase (JNK) (Nishida & Gotoh, 1993; Han et al., 1994). It has been found that LPS, the key mediator in the inflammation response, can induce activation of these MAPK proteins in macrophage and other cell types (Hambleton et al., 1996; Chen & Wang, 1999; Guha & Mackman, 2001). Activation of p38, but not p44/p42 MAPK, by LPS resulted in the stimulation of NF-κB-specific DNA–protein binding and the subsequent expression of iNOS and nitric oxide (NO) release in RAW 264.7 macrophages (Chen & Wang, 1999). NF-κB and MAPKs are therefore known as important targets for anti-inflammatory molecules. Improper activation or upregulation of iNOS or COX-2 has been shown to be associated with the pathophysiologies of certain types of human cancers as well as inflammatory disorders (Beyaert, 2003). Therefore, the identification of naturally occurring phytocompounds that can suppress or downregulate the functions of iNOS or COX-2, or the activation of their upstream transcriptional factor NF-κB, may lead to the discovery of important anti-inflammatory therapeutics. Since inflammation is closely linked to the promotion of certain tumors, substances with potent anti-inflammatory activities are anticipated to exert chemopreventive effects on carcinogenesis (Surh et al., 2001). For instance, phenolic compounds, particularly those present in edible and medicinal plants, have been reported to possess substantial anticancer or cancer chemopreventive properties (Park & Pezzuto, 2002). Bidens pilosa (Asteraceae), commonly known as ‘hairy beggar-ticks' or ‘Spanish needles', is widely distributed in tropical and subtropical regions, and has been reported to possess antihyperglycemic (Ubillas et al., 2000), antihypertensive (Dimo et al., 2001; 2002), antiulcerogenic (Tan et al., 2000), hepatoprotective (Chin et al., 1996), immunosuppressive and anti-inflammatory (Pereira et al., 1999), antileukemic (Chang et al., 2001), antimalarial (Brandao et al., 1997), and antimicrobial (Khan et al., 2001) properties. B. pilosa has traditionally or anecdotally been used for the management of inflammatory diseases, and stomach and liver disorders. However, the cellular and molecular mechanisms underlying the anti-inflammatory properties of B. pilosa extract and its derived active compound are currently not well defined. In our previous study, we identified an ethyl acetate (EA) fraction partitioned from the ethanolic extract of fresh whole B. pilosa plants that significantly inhibited the LPS-induced NO production in RAW 264.7 cells (IC50=36 μg ml−1) (Chiang et al., 2004). In the present study, a bioactive phytocompound, ethyl caffeate that exhibits potent inhibitory effects on NO production in macrophages was identified from the bioactive EA fraction using bioactivity-guided fractionation. Ethyl caffeate was then investigated for its anti-inflammatory mechanisms in vitro in LPS-stimulated macrophages, and in vivo using TPA-treated mouse skin system. The effects of ethyl caffeate on the activation of NF-κB, MAPKs, as well as on the downstream mediators of inflammation, such as iNOS, COX-2 and prostogladin E2 (PGE2), were investigated.

Andrographolide interferes with binding of nuclear factor-κB to DNA in HL-60-derived neutrophilic cells

Abstract: 1 Andrographolide, the major active component from Andrographis paniculata, has shown to possess anti-inflammatory activity. Andrographolide inhibits the expression of several proinflammatory proteins that exhibit a nuclear factor kappa B (NF-κB) binding site in their gene. 2 In the present study, we analyzed the effect of andrographolide on the activation of NF-κB induced by platelet-activating factor (PAF) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) in HL-60 cells differentiated to neutrophils. 3 PAF (100 nM) and fMLP (100 nM) induced activation of NF-κB as determined by degradation of inhibitory factor B α (IκBα) using Western blotting in cytosolic extracts and by binding to DNA using electrophoretic mobility shift assay (EMSA) in nuclear extracts. 4 Andrographolide (5 and 50 μM) inhibited the NF-κB-luciferase activity induced by PAF. However, andrographolide did not reduce phosphorylation of p38 MAPK or ERK1/2 and did not change IκBα degradation induced by PAF and fMLP. 5 Andrographolide reduced the DNA binding of NF-κB in whole cells and in nuclear extracts induced by PAF and fMLP. 6 Andrographolide reduced cyclooxygenase-2 (COX-2) expression induced by PAF and fMLP in HL-60/neutrophils. 7 It is concluded that andrographolide exerts its anti-inflammatory effects by inhibiting NF-κB binding to DNA, and thus reducing the expression of proinflammatory proteins, such as COX-2. British Journal of Pharmacology (2005) 144, 680–686. doi:10.1038/sj.bjp.0706105

Inhibition of RhoA/Rho kinase pathway is involved in the beneficial effect of sildenafil on pulmonary hypertension.

Abstract: Inhibition of the type 5 phosphodiesterase and inhibition of Rho kinase are both effective in reducing pulmonary hypertension (PH). Here we investigate whether Rho kinase inhibition is involved in the beneficial effect of the type 5 phosphodiesterase inhibitor sildenafil on PH. Chronic hypoxia-induced PH in rats is associated with an increase in RhoA activity in pulmonary artery that was maximal after 2 days (10.7±0.9-fold increase, n=6, P<0.001). The activity of Rho kinase assessed by measuring the level of myosin phosphatase target subunit 1 (MYPT1) phosphorylation was also increased (5.7±0.8-fold over control, n=8). Chronic fasudil (30 mg kg−1 day−1; 14 days) and sildenafil (25 mg kg−1 day−1; 14 days) treatments reduced PH and pulmonary cardiovascular remodelling, and inhibited the MYPT1 phosphorylation in pulmonary artery from hypoxic rats by 82.3±3% (n=4) and by 76.6±2% (n=4), respectively. The inhibitory effect of sildenafil (10 μM) on MYPT1 phosphorylation was demonstrated by the loss of actin stress fibres in vascular smooth muscle cells. However, in vitro kinase assays indicated that sildenafil had no direct inhibitory action on Rho kinase activity. Sildenafil treatment induced increased RhoA phosphorylation and association to its cytosolic inhibitory protein, guanine dissociation inhibitor (GDI) in pulmonary artery. We propose that sildenafil inhibits RhoA/Rho kinase-dependent functions in pulmonary artery through enhanced RhoA phosphorylation and cytosolic sequestration by GDI. The inhibition of intracellular events downstream of RhoA thus participates in the beneficial effect of sildenafil on PH. British Journal of Pharmacology (2005) 146, 1010–1018. doi:10.1038/sj.bjp.0706408

The hypoglycaemic activity of fenugreek seed extract is mediated through the stimulation of an insulin signalling pathway.

Abstract: The in vivo hypoglycaemic activity of a dialysed fenugreek seed extract (FSE) was studied in alloxan (AXN)-induced diabetic mice and found to be comparable to that of insulin (1.5 U kg(-1)). FSE also improved intraperitoneal glucose tolerance in normal mice. The mechanism by which FSE attenuated hyperglycaemia was investigated in vitro. FSE stimulated glucose uptake in CHO-HIRc-mycGLUT4eGFP cells in a dose-dependent manner. This effect was shown to be mediated by the translocation of glucose transporter 4 (GLUT4) from the intracellular space to the plasma membrane. These effects of FSE on GLUT4 translocation and glucose uptake were inhibited by wortmannin, a phosphatidylinositol 3-kinase (PI3-K) inhibitor, and bisindolylmaleimide 1, a protein kinase C (PKC)-specific inhibitor. In vitro phosphorylation analysis revealed that, like insulin, FSE also induces tyrosine phosphorylation of a number of proteins including the insulin receptor, insulin receptor substrate 1 and p85 subunit of PI3-K, in both 3T3-L1 adipocytes and human hepatoma cells, HepG2. However, unlike insulin, FSE had no effect on protein kinase B (Akt) activation. These results suggest that in vivo the hypoglycaemic effect of FSE is mediated, at least in part, by the activation of an insulin signalling pathway in adipocytes and liver cells.

Hydrogen sulfide causes vanilloid receptor 1-mediated neurogenic inflammation in the airways.

Abstract: 1 Hydrogen sulfide (H2S) is described as a mediator of diverse biological effects, and is known to produce irritation and injury in the lung following inhalation. Recently, H2S has been found to cause contraction in the rat urinary bladder via a neurogenic mechanism. Here, we studied whether sodium hydrogen sulfide (NaHS), used as donor of H2S, produces responses mediated by sensory nerve activation in the guinea-pig airways. 2 NaHS evoked an increase in neuropeptide release in the airways that was significantly attenuated by capsaicin desensitization and by the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine. In addition, NaHS caused an atropine-resistant contraction of isolated airways, which was completely prevented by capsaicin desensitization. Furthermore, NaHS-induced contraction was reduced by TRPV1 antagonism (ruthenium red, capsazepine and SB366791), and was abolished by pretreatment with the combination of tachykinin NK1 (SR140333) and NK2 (SR48968) receptor antagonists. 3 In anesthetized guinea-pigs, intratracheal instillation of NaHS increased the total lung resistance and airway plasma protein extravasation. These two effects were reduced by TRPV1 antagonism (capsazepine) and tachykinin receptors (SR140333 and SR48968) blockade. 4 Our results provide the first pharmacological evidence that H2S provokes tachykinin-mediated neurogenic inflammatory responses in guinea-pig airways, and that this effect is mediated by stimulation of TRPV1 receptors on sensory nerves endings. This novel mechanism may contribute to the irritative action of H2S in the respiratory system. British Journal of Pharmacology (2005) 145, 1123–1131. doi:10.1038/sj.bjp.0706277; published online 6 June 2005

Cannabidiol inhibits human glioma cell migration through a cannabinoid receptor-independent mechanism.

Abstract: We evaluated the ability of cannabidiol (CBD) to impair the migration of tumor cells stimulated by conditioned medium. CBD caused concentration-dependent inhibition of the migration of U87 glioma cells, quantified in a Boyden chamber. Since these cells express both cannabinoid CB1 and CB2 receptors in the membrane, we also evaluated their engagement in the antimigratory effect of CBD. The inhibition of cell was not antagonized either by the selective cannabinoid receptor antagonists SR141716 (CB1) and SR144528 (CB2) or by pretreatment with pertussis toxin, indicating no involvement of classical cannabinoid receptors and/or receptors coupled to Gi/o proteins. These results reinforce the evidence of antitumoral properties of CBD, demonstrating its ability to limit tumor invasion, although the mechanism of its pharmacological effects remains to be clarified.

Hydrogen sulphide is a mediator of carrageenan-induced hindpaw oedema in the rat

Abstract: Hydrogen sulphide (H2S) is a naturally occurring gas, with potent vasodilator activity. In this report, we identify a role for H2S in carrageenan-induced hindpaw oedema in the rat. Intraplantar injection of carrageenan (150 μl, 2% (w v−1)) resulted in an increase in hindpaw H2S synthesising enzyme activity and increased myeloperoxidase (MPO) activity. Pretreatment (i.p. 60 min before carrageenan) with DL-propargylglycine (PAG, 25–75 mg kg−1), an inhibitor of the H2S synthesising enzyme cystathionine-γ-lyase (CSE), significantly reduced carrageenan-induced hindpaw oedema in a dose-dependent manner (e.g. increase in hindpaw weight at 3 h, saline: 0.12±0.017 g; carrageenan, 1.39±0.037 g; PAG, 50 mg kg−1, 1.11±0.06 g, n=10) and MPO activity (fold increase) in the hindpaw (saline: 1.0±0.12; carrageenan, 2.92±0.45 g; PAG, 50 mg kg−1, 1.1±0.22, n=10); PAG (50 mg kg−1) also inhibited H2S synthesising enzyme activity (nmol μg DNA−1) in the hindpaw in a dose-dependent manner (saline, 0.46±0.05; carrageenan, 0.71±0.08 g; PAG, 50 mg kg−1, 0.17±0.05, n=10). British Journal of Pharmacology (2005) 145, 141–144. doi:10.1038/sj.bjp.0706186

Emerging roles for cyclooxygenase-2 in gastrointestinal mucosal defense.

Abstract: The development of selective inhibitors of cyclooxygenase-2 (COX-2) was based on the concept that this enzyme played little, if any, role in modulating the ability of the gastrointestinal (GI) tract to resist and respond to injury. There is now overwhelming evidence that this is far from true. Indeed, COX-2 mediates several of the most important components of 'mucosal defense', contributes significantly to the resolution of GI inflammation and plays a crucial role in regulating ulcer healing. COX-2 also contributes to long-term changes in GI function after bouts of inflammation.