Showing papers by "Garret A. FitzGerald published in 2012"

Obesity in mice with adipocyte-specific deletion of clock component Arntl

Abstract: Adipocytes store excess energy in the form of triglycerides and signal the levels of stored energy to the brain. Here we show that adipocyte-specific deletion of Arntl (also known as Bmal1), a gene encoding a core molecular clock component, results in obesity in mice with a shift in the diurnal rhythm of food intake, a result that is not seen when the gene is disrupted in hepatocytes or pancreatic islets. Changes in the expression of hypothalamic neuropeptides that regulate appetite are consistent with feedback from the adipocyte to the central nervous system to time feeding behavior. Ablation of the adipocyte clock is associated with a reduced number of polyunsaturated fatty acids in adipocyte triglycerides. This difference between mutant and wild-type mice is reflected in the circulating concentrations of polyunsaturated fatty acids and nonesterified polyunsaturated fatty acids in hypothalamic neurons that regulate food intake. Thus, this study reveals a role for the adipocyte clock in the temporal organization of energy regulation, highlights timing as a modulator of the adipocyte-hypothalamic axis and shows the impact of timing of food intake on body weight.

Large-Scale Gene-Centric Meta-Analysis across 39 Studies Identifies Type 2 Diabetes Loci

Abstract: To identify genetic factors contributing to type 2 diabetes (T2D), we performed large-scale meta-analyses by using a custom similar to 50,000 SNP genotyping array (the ITMAT-Broad-CARe array) with similar to 2000 candidate genes in 39 multiethnic population-based studies, case-control studies, and clinical trials totaling 17,418 cases and 70,298 controls. First, meta-analysis of 25 studies comprising 14,073 cases and 57,489 controls of European descent confirmed eight established T2D loci at genome-wide significance. In silico follow-up analysis of putative association signals found in independent genome-wide association studies (including 8,130 cases and 38,987 controls) performed by the DIAGRAM consortium identified a T2D locus at genome-wide significance (GATAD2A/CILP2/PBX4; p = 5.7 x 10(-9)) and two loci exceeding study-wide significance (SREBF1, and TH/INS; p < 2.4 x 10(-6)). Second, meta-analyses of 1,986 cases and 7,695 controls from eight African-American studies identified study-wide-significant (p = 2.4 x 10(-7)) variants in HMGA2 and replicated variants in TCF7L2 (p = 5.1 x 10(-15)). Third, conditional analysis revealed multiple known and novel independent signals within five T2D-associated genes in samples of European ancestry and within HMGA2 in African-American samples. Fourth, a multiethnic meta-analysis of all 39 studies identified T2D-associated variants in BCL2 (p = 2.1 x 10(-8)). Finally, a composite genetic score of SNPs from new and established T2D signals was significantly associated with increased risk of diabetes in African-American, Hispanic, and Asian populations. In summary, large-scale meta-analysis involving a dense gene-centric approach has uncovered additional loci and variants that contribute to T2D risk and suggests substantial overlap of T2D association signals across multiple ethnic groups.

Prostaglandin D2 inhibits hair growth and is elevated in bald scalp of men with androgenetic alopecia

Abstract: Testosterone is necessary for the development of male pattern baldness, known as androgenetic alopecia (AGA); yet, the mechanisms for decreased hair growth in this disorder are unclear. We show that prostaglandin D2 synthase (PTGDS) is elevated at the mRNA and protein levels in bald scalp compared to haired scalp of men with AGA. The product of PTGDS enzyme activity, prostaglandin D2 (PGD2), is similarly elevated in bald scalp. During normal follicle cycling in mice, Ptgds and PGD2 levels increase immediately preceding the regression phase, suggesting an inhibitory effect on hair growth. We show that PGD2 inhibits hair growth in explanted human hair follicles and when applied topically to mice. Hair growth inhibition requires the PGD2 receptor G protein (heterotrimeric guanine nucleotide)–coupled receptor 44 (GPR44), but not the PGD2 receptor 1 (PTGDR). Furthermore, we find that a transgenic mouse, K14-Ptgs2, which targets prostaglandin-endoperoxide synthase 2 expression to the skin, demonstrates elevated levels of PGD2 in the skin and develops alopecia, follicular miniaturization, and sebaceous gland hyperplasia, which are all hallmarks of human AGA. These results define PGD2 as an inhibitor of hair growth in AGA and suggest the PGD2-GPR44 pathway as a potential target for treatment.

Vascular COX-2 modulates blood pressure and thrombosis in mice.

Abstract: Prostacyclin (PGI2) is a vasodilator and platelet inhibitor, properties consistent with cardioprotection. More than a decade ago, inhibition of cyclooxygenase-2 (COX-2) by the nonsteroidal anti-inflammatory drugs (NSAIDs) rofecoxib and celecoxib was found to reduce the amount of the major metabolite of PGI2 (PGI-M) in the urine of healthy volunteers. This suggested that NSAIDs might cause adverse cardiovascular events by reducing production of cardioprotective PGI2. This prediction was based on the assumption that the concentration of PGI-M in urine likely reflected vascular production of PGI2 and that other cardioprotective mediators, especially nitric oxide (NO), were not able to compensate for the loss of PGI2. Subsequently, eight placebo-controlled clinical trials showed that NSAIDs that block COX-2 increase adverse cardiovascular events. We connect tissue-specific effects of NSAID action and functional correlates in mice with clinical outcomes in humans by showing that deletion of COX-2 in the mouse vasculature reduces excretion of PGI-M in urine and predisposes the animals to both hypertension and thrombosis. Furthermore, vascular disruption of COX-2 depressed expression of endothelial NO synthase and the consequent release and function of NO. Thus, suppression of PGI2 formation resulting from deletion of vascular COX-2 is sufficient to explain the cardiovascular hazard from NSAIDs, which is likely to be augmented by secondary mechanisms such as suppression of NO production.

Niacin and biosynthesis of PGD2 by platelet COX-1 in mice and humans

Abstract: The clinical use of niacin to treat dyslipidemic conditions is limited by noxious side effects, most commonly facial flushing. In mice, niacin-induced flushing results from COX-1–dependent formation of PGD2 and PGE2 followed by COX-2–dependent production of PGE2. Consistent with this, niacin-induced flushing in humans is attenuated when niacin is combined with an antagonist of the PGD2 receptor DP1. NSAID-mediated suppression of COX-2–derived PGI2 has negative cardiovascular consequences, yet little is known about the cardiovascular biology of PGD2. Here, we show that PGD2 biosynthesis is augmented during platelet activation in humans and, although vascular expression of DP1 is conserved between humans and mice, platelet DP1 is not present in mice. Despite this, DP1 deletion in mice augmented aneurysm formation and the hypertensive response to Ang II and accelerated atherogenesis and thrombogenesis. Furthermore, COX inhibitors in humans, as well as platelet depletion, COX-1 knockdown, and COX-2 deletion in mice, revealed that niacin evoked platelet COX-1–derived PGD2 biosynthesis. Finally, ADP-induced spreading on fibrinogen was augmented by niacin in washed human platelets, coincident with increased thromboxane (Tx) formation. However, in platelet-rich plasma, where formation of both Tx and PGD2 was increased, spreading was not as pronounced and was inhibited by DP1 activation. Thus, PGD2, like PGI2, may function as a homeostatic response to thrombogenic and hypertensive stimuli and may have particular relevance as a constraint on platelets during niacin therapy.

Disruption of the 5-lipoxygenase pathway attenuates atherogenesis consequent to COX-2 deletion in mice

Abstract: Suppression of cyclooxygenase 2 (COX-2)–derived prostacyclin (PGI2) is sufficient to explain most elements of the cardiovascular hazard from nonsteroidal antinflammatory drugs (NSAIDs). However, randomized trials are consistent with the emergence of cardiovascular risk during chronic dosing with NSAIDs. Although deletion of the PGI2 receptor fosters atherogenesis, the importance of COX-2 during development has constrained the use of conventional knockout (KO) mice to address this question. We developed mice in which COX-2 was deleted postnatally, bypassing cardiorenal defects exhibited by conventional KOs. When crossed into ApoE-deficient hyperlipidemic mice, COX-2 deletion accelerated atherogenesis in both genders, with lesions exhibiting leukocyte infiltration and phenotypic modulation of vascular smooth muscle cells, as reflected by loss of α-smooth muscle cell actin and up-regulation of vascular cell adhesion molecule-1. Stimulated peritoneal macrophages revealed suppression of COX-2–derived prostanoids and augmented 5-lipoxygenase product formation, consistent with COX-2 substrate rediversion. Although deletion of the 5-lipoxygenase activating protein (FLAP) did not influence atherogenesis, it attenuated the proatherogeneic impact of COX-2 deletion in hyperlipidemic mice. Chronic administration of NSAIDs may increasingly confer a cardiovascular hazard on patients at low initial risk. Promotion of atherogenesis by postnatal COX-2 deletion affords a mechanistic explanation for this observation. Coincident inhibition of FLAP may offer an approach to attenuating such a risk from NSAIDs.

Recalibrating Intellectual Property Rights to Enhance Translational Research Collaborations

Abstract: Multisectoral collaborative models for drug and therapeutic research and development (R&D) are emerging, requiring a recalibration of how intellectual property rights (IPRs) are used. Although these models appear promising, little study has been conducted on the optimal blend of sharing and exclusion as mediated through the proactive use or nonuse of IPRs. This Commentary is a call for a combination of theoretical and empirical analyses to build a comprehensive understanding of the interplay between formal IP laws, institutions that administer and manage IPRs, and the use of IPRs in practice to better construct and manage collaborations. Such analyses require outcome metrics formulated to measure the success of therapeutic outcomes and to capture the complexity of a highly networked R&D environment.

Effects of celecoxib on prostanoid biosynthesis and circulating angiogenesis proteins in familial adenomatous polyposis

Abstract: Vascular cyclooxygenase (COX)-2-dependent prostacyclin (PGI2) may affect angiogenesis by preventing endothelial activation and platelet release of angiogenic factors present in platelet α-granules. Thus, a profound inhibition of COX-2-dependent PGI2 might be associated with changes in circulating markers of angiogenesis. We aimed to address this issue by performing a clinical study with celecoxib in familial adenomatous polyposis (FAP). In nine patients with FAP and healthy controls, pair-matched for gender and age, we compared systemic biosynthesis of PGI2, thromboxane (TX) A2, and prostaglandin (PG) E2, assessing their urinary enzymatic metabolites, 2,3-dinor-6-keto PGF1α (PGI-M), 11-dehydro-TXB2 (TX-M), and 11-α-hydroxy-9,15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M), respectively. The impact of celecoxib (400 mg b.i.d. for 7 days) on prostanoid biosynthesis and 14 circulating biomarkers of angiogenesis was evaluated in FAP. Intestinal tumorigenesis was associated with enhanced urinary TX-M levels, but unaffected by celecoxib, suggesting the involvement of a COX-1-dependent pathway, presumably from platelets. This was supported by the finding that in cocultures of a human colon adenocarcinoma cell line (HT-29) and platelets enhanced TXA2 generation was almost completely inhibited by pretreatment of platelets with aspirin, a preferential inhibitor of COX-1. In FAP, celecoxib profoundly suppressed PGE2 and PGI2 biosynthesis that was associated with a significant increase in circulating levels of most proangiogenesis proteins but also the antiangiogenic tissue inhibitor of metalloproteinase 2. Urinary PGI-M, but not PGE-M, was negatively correlated with circulating levels of fibroblast growth factor 2 and angiogenin. In conclusion, inhibition of tumor COX-2-dependent PGE2 by celecoxib may reduce tumor progression. However, the coincident depression of vascular PGI2, in a context of enhanced TXA2 biosynthesis, may modulate the attendant angiogenesis, contributing to variability in the chemopreventive efficacy of COX-2 inhibitors such as celecoxib.

Prostaglandin I2 signaling drives Th17 differentiation and exacerbates experimental autoimmune encephalomyelitis.

Abstract: Background Prostaglandin I2 (PGI2), a lipid mediator currently used in treatment of human disease, is a critical regulator of adaptive immune responses. Although PGI2 signaling suppressed Th1 and Th2 immune responses, the role of PGI2 in Th17 differentiation is not known.

Comparative Impact on Prostanoid Biosynthesis of Celecoxib and the Novel Nonsteroidal Anti-Inflammatory Drug CG100649

Abstract: Nonsteroidal anti-inflammatory drugs (NSAIDs) elevate cardiovascular risk by disrupting cyclooxygenase-2 (COX-2)-dependent biosynthesis of prostacyclin (PGI2). CG100649 is a novel NSAID proposed to inhibit both COX-2 and carbonic anhydrase (CA)-I/-II. We compared its impact on prostanoid biosynthesis with that of celecoxib, an NSAID purposefully designed to selectively inhibit COX-2. In a controlled, double-blind randomized trial, single oral doses of 2 or 8 mg CG100649, 200 mg celecoxib, or placebo were well tolerated by healthy volunteers (n = 23). Both CG100649 and celecoxib had the effect of depressing urinary excretion of 2,3-dinor-6-keto-PGF1α (PGI-M); the effect of CG100649 was dose-dependent and more sustained (up to 240 h after the dose) than that of celecoxib. Neither CG100649 nor celecoxib significantly inhibited COX-1-dependent prostanoid formation. CA inhibition was not detected after administration of CG100649, despite its partitioning asymmetrically into erythrocytes. CG100649 and celecoxib are both relatively selective inhibitors of COX-2, but they differ in duration of action. Whether they have similar impact on cardiovascular events remains to be determined. Clinical Pharmacology & Therapeutics (2012); 91 6, 986–993. doi:10.1038/clpt.2012.3

Role of Thromboxane Receptor in C-Reactive Protein–Induced Thrombosis

Abstract: Objective— Thromboxane A 2 and prostacyclin are thromboregulatory prostaglandins. The inflammatory C-reactive protein (CRP) promotes thrombosis after vascular injury, presumably via potentiation of thromboxane activity. Using a genetic approach, we investigated the role of thromboxane receptor (TP) pathway in CRP-induced thrombosis. Methods and Results— Four genetically engineered mice strains were used: C57BL / 6 wild-type, human CRP transgenic ( CRPtg ), thromboxane receptor–deficient ( Tp −/− ), and CRPtgTp −/− mice. CRP and TP expression were correlated, and suppression of CRP expression using small interfering RNA/CRP led to reduction in TP expression. Platelet–endothelial adherence was increased in CRPtg and suppressed in CRPtgTP −/− and CRPtg cells that were suppressed with TP small interfering RNA. TP deficiency in both platelets and endothelial cells was synergistic in affecting platelet–endothelial interactions. Time until arterial occlusion, measured after photochemical injury, was significantly shorter in CRPtg and prolonged in CRPtgTp −/− compared with controls (n=10–15, 35±3.4, 136±13.8, and 67±8.9 minutes, respectively; P Conclusion— TP pathway is of major importance in CRP-induced thrombosis. The expression of TP is increased in CRPtg endothelial cells, and its blockade significantly suppresses the prothrombotic effect of CRP.

Can Intellectual Property Save Drug Development

Abstract: The imbalance between the roughly constant rate of new drug approvals and the exploding cost estimates of drug development—mostly the cost of failure—has raised concern about the declining productivity of the pharmaceutical industry. Efforts to address the situation have included an investment in human capital—particularly those individuals who can project science across the translational divide (bench to clinic)—and investment in infrastructure, as exemplified by Clinical and Translational Science Awards in the United States and Biomedical Research Centers in the United Kingdom, and an increase in partnerships between academia and industry ( 1 ). However, radical reform of the iron rules of intellectual property (IP) worldwide will be necessary if we are to harvest and integrate the efforts of scientists and clinicians scattered across companies, universities, and countries, best qualified to generate new therapies.

Almost) Everything is Illuminated Adenosine Shines a Light on Cardioprotection

Abstract: In a recent issue of Nature Medicine , Eckle et al1 demonstrated that activation of an adenosine receptor (Adora2b) acts via the circadian clock protein, period2 (Per2), to induce a metabolic switch from fatty acid to glucose in cardiomyocytes, which is protective against ischemic injury. Indeed, stabilization of Per2 expression by exposure of mice to intense light has a similar cardioprotective effect as Adora2b activation. Timing is everything, and it has long been known that there is a temporal variation in the incidence of clinical cardiovascular events—myocardial infarction, stroke, and perhaps even the response to angioplasty.2 Recently, genetic manipulations in mice have linked proteins relevant to the core molecular clock with regulation of blood pressure homeostasis3 and thrombogenesis,4 as well as the size of cardiac infarcts consequent to ischemia-reperfusion.5 Now, a report by Eckle et al1 in Nature Medicine implicates Per2, an important regulator of the negative limb of the molecular clock, in cardioprotection from ischemia in mice by inducing a metabolic switch away from fatty acid metabolism to anaerobic glycolysis. Adenosine has long …

What Great Creation

Abstract: In this case study, an early-career mechanical engineer interviews an established translational bioscientist about mechanisms for merging engineering and biomedicine to pursue clinically informed research questions.