Hydrogen sulfide (H2S) has been shown to have powerful antioxidative and anti-inflammatory properties that can regulate multiple cardiovascular functions. However, its precise role in diabetes-accelerated atherosclerosis remains unclear. We report here that H2S reduced aortic atherosclerotic plaque formation with reduction in superoxide (O2−) generation and the adhesion molecules in streptozotocin (STZ)-induced LDLr−/− mice but not in LDLr−/−Nrf2−/− mice. In vitro, H2S inhibited foam cell formation, decreased O2− generation, and increased nuclear factor erythroid 2–related factor 2 (Nrf2) nuclear translocation and consequently heme oxygenase 1 (HO-1) expression upregulation in high glucose (HG) plus oxidized LDL (ox-LDL)–treated primary peritoneal macrophages from wild-type but not Nrf2−/− mice. H2S also decreased O2− and adhesion molecule levels and increased Nrf2 nuclear translocation and HO-1 expression, which were suppressed by Nrf2 knockdown in HG/ox-LDL–treated endothelial cells. H2S increased S-sulfhydration of Keap1, induced Nrf2 dissociation from Keap1, enhanced Nrf2 nuclear translocation, and inhibited O2− generation, which were abrogated after Keap1 mutated at Cys151, but not Cys273, in endothelial cells. Collectively, H2S attenuates diabetes-accelerated atherosclerosis, which may be related to inhibition of oxidative stress via Keap1 sulfhydrylation at Cys151 to activate Nrf2 signaling. This may provide a novel therapeutic target to prevent atherosclerosis in the context of diabetes.

BackgroundActivated platelets exert a pro-inflammatory action that can be largely ascribed to their ability to interact with leukocytes and modulate their activity. We hypothesized that platelet activation and consequent formation of monocyte-platelet aggregates (MPA) induces a pro-inflammatory phenotype in circulating monocytes.Methodology/Principal FindingsCD62P+ platelets and MPA were measured, and monocytes characterized, by whole blood flow cytometry in healthy subjects, before and two days after receiving influenza immunization. Three monocytic subsets were identified: CD14+CD16−, CD14highCD16+and CD14lowCD16+. The increase in high sensitivity C-reactive protein post-immunization was accompanied by increased platelet activation and MPA formation (25.02±12.57 vs 41.48±16.81; p = 0.01), along with enhancement of circulating CD14highCD16+ cells (4.7±3.6 vs 10.4±4.8; p = 0.003), their percentage being linearly related to levels of CD62P+-platelets (r2 = 0.4347; p = 0.0008). In separate in vitro experiments, co-incubation of CD14+CD16− cells, isolated from healthy donor subjects, with autologous platelets gave rise to up-regulation of CD16 on monocytes as compared with those maintained in medium alone (% change in CD14+CD16+ cells following 48 h co-incubation of monocytes with platelets was +106±51% vs monocytes in medium alone; p<0.001). This effect correlated directly with degree of MPA formation (r2 = 0.7731; p<0.0001) and was associated with increased monocyte adhesion to endothelial cells. P-selectin glycoprotein ligand-1 (PSGL-1) blocking antibody, which abrogates MPA formation, abolished these effects, as did the cyclooxygenase (COX)-2 selective inhibitor NS-398, aspirin and the EP1/EP2-selective antagonist AH6809.Conclusions/SignificanceThese data suggest that MPA formation, as occurs in the blood under pro-inflammatory conditions, expands the pool of circulating CD14highCD16+ monocytes in a COX-2 dependent manner, and these monocytes exhibit increased adhesion to endothelium. Our findings delineate a novel mechanism underlying the pro-inflammatory effect of platelet activation.

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1 Some animal studies suggest that b-adrenoceptor-mediated vasorelaxation is in part mediated through nitric oxide (NO) release. Furthermore, in humans, we have recently shown that forearm blood¯ow is increased by infusion of b 2 -adrenergic agonists into the brachial artery, and the nitric oxide synthase (NOS) inhibitor N G -monomethyl-L-arginine (L-NMMA) inhibits this response. 2 The purpose of the present study was to determine whether stimulation of human umbilical vein endothelial b-adrenoceptors causes vasorelaxation and nitric oxide generation, and whether this might be mediated by cyclic adenosine-3',5'-monophosphate (cyclic AMP). 5 Isoprenaline relaxed umbilical vein rings, and this vasorelaxation was abolished by b 2 -(but not b 1 -) adrenergic blockage, and by endothelium removal or 1 mM L-NMMA. In addition, vasorelaxant responses to dibutyryl cyclic AMP were inhibited by 1 mM L-NMMA, with a reduction in E max from 90.0+9.3% to 50.5+9.9% (P50.05). 6 Isoprenaline 1 mM increased NOS activity in HUVEC (34.0+5.9% above basal, P50.001). Furthermore, isoprenaline increased adenylyl cyclase activity in a concentration-dependent manner; this response was inhibited by b 2 (but not b 1 -) adrenergic blockade. Forskolin 1 mM and dibutyryl cyclic AMP 1 mM each increased NOS activity in HUVEC, to a degree similar to isoprenaline 1 mM. The increase in L-arginine to L-citrulline conversion observed with each agent was abolished by coincubation with NOS inhibitors. 7 These results indicate that endothelial b 2 -adrenergic stimulation and cyclic AMP elevation activate the L-arginine/NO system, and give rise to vasorelaxation, in human umbilical vein.

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WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • A genetic basis for aspirin resistance has been postulated to exist. • The individual studies published have been too small to allow reliable conclusions to be drawn. • In order to clarify what, if any, genetic basis exists for aspirin resistance, we have undertaken, to our knowledge, the largest and most comprehensive systematic review conducted to‐date in this field. WHAT THIS STUDY ADDS • There is a significant association between the PlA1/A2 molecular variant and aspirin resistance in healthy subjects, with the effect diminishing in the presence of cardiovascular disease. • However further studies are needed to confirm this. • We argue that investigators now need to agree on a standard technique to measure and define aspirin resistance. AIMS The aim was to perform a systematic review of all candidate gene association studies in aspirin resistance. METHODS Electronic databases were searched up until 1 December 2007 for all studies investigating any candidate gene for aspirin resistance in humans. Aspirin resistance was required to have been measured by a standardized laboratory technique to be included in the analysis. RESULTS Within 31 studies, 50 polymorphisms in 11 genes were investigated in 2834 subjects. The PlA1/A2 polymorphism in the GPIIIa platelet receptor was the most frequently investigated, with 19 studies in 1389 subjects. The PlA1/A2 variant was significantly associated with aspirin resistance when measured in healthy subjects [odds ratio (OR) 2.36, 95% confidence interval (CI) 1.24, 4.49; P = 0.009]. Combining genetic data from all studies (comprising both healthy subjects and those with cardiovascular disease) reduced the observed effect size (OR 1.14, 95% CI 0.84, 1.54; P = 0.40). Moreover, the observed effect of PlA1/A2 genotype varied depending on the methodology used for determining aspirin sensitivity/resistance. No significant association was found with aspirin resistance in four other investigated polymorphisms in the COX‐1, GPla, P2Y1 or P2Y12 genes. CONCLUSIONS Our data support a genetic association between the PlA1/A2 molecular variant and aspirin resistance in healthy subjects, with the effect diminishing in the presence of cardiovascular disease. The laboratory methodology used influences the detection of aspirin resistance. However, as heterogeneity was significant and our results are based on a limited number of studies, further studies are required to confirm our findings.

Abstract-Nitric oxide (NO) exerts important vasodilatory, antiplatelet, antioxidant, antiadhesive, and antiproliferative effects. Although endothelium derived NO has been shown to be of prime importance in cardio-and vasculoprotection, until recently little was known about the role of platelet-derived NO. New evidence suggests that NO synthesized by platelets regulates platelet functions, in particular suppressing platelet activation and intravascular thrombosis. Moreover, platelet NO biosynthesis may be decreased in patients with cardiovascular risk factors or with coronary heart disease, and this may contribute to arterial thrombotic disease in these patients. Here, we review the current state of knowledge as regards the role of platelet-derived NO, both in normal physiology and in cardiovascular disease states, and compare platelet NO signaling and regulation with that in endothelial cells. (Circ Res. 2007;101:654-662.)

Nitric oxide (NO) was originally described as the principal endothelium-derived relaxing factor, but it is now known to subserve a variety of functions throughout the body, both physiological and pathophysiological. NO-donor drugs decompose in the body, by a variety of mechanisms, to generate NO. Such drugs have been used for many years in cardiovascular therapeutics, in particular the organic nitrates for the prevention and treatment of angina pectoris and sodium nitroprusside for the treatment of hypertensive emergencies. However, patients taking long-term nitrates often develop tolerance, and prolonged nitroprusside administration can give rise to cyanide accumulation in the body. Newer NO-donor drugs, in particular the S-nitrosothiols, offer advantages over the existing drugs, since they do not share these drawbacks, and initial small clinical studies suggest that they may be of benefit in a variety of cardiovascular disorders. Here we briefly review the chemistry and physiology of NO, and discuss the chemistry and clinical possibilities of the S-nitrosothiols.