Joanne L. Hart

Impairment of both nitric oxide-mediated and EDHF-type relaxation in small mesenteric arteries from rats with streptozotocin-induced diabetes.

BACKGROUND AND PURPOSE To investigate whether diabetes affects either or both nitric oxide (NO)‐mediated and endothelium‐derived hyperpolarizing factor (EDHF)‐type relaxation in endothelium‐dependent relaxation of mesenteric arteries from streptozotocin‐induced diabetic rats.

Hydrogen sulfide treatment reduces blood pressure and oxidative stress in angiotensin II-induced hypertensive mice.

Hydrogen sulfide (H2S) is increasingly recognized as a gasotransmitter with protective effects in the cardiovascular system. The aim of the study was to examine the effects of chronic NaHS treatment on blood pressure, vascular function and oxidative stress in an in vivo model of hypertension and oxidative stress. Male C57Bl6/J mice were rendered hypertensive with 0.7 mg kg−1 per day angiotensin II (AngII) for 14 days administered via implanted mini-pumps. The mice were treated with NaHS (10 μmol kg−1 per day) to deliver H2S or an inhibitor of cystathionine-γ-lyase, DL-propargylglycine (PPG 30 mg kg−1 per day) via intraperitoneal (i.p.) injection. Systolic blood pressure was measured and vascular function examined by myography. Vascular superoxide production was measured by lucigenin-enhanced chemiluminescence. AngII infusion significantly increased systolic blood pressure (P<0.001). This increase was significantly attenuated by treatment with NaHS (P<0.001). Both aortic endothelial function and NO bioavailability were significantly attenuated in the AngII group (P<0.01) but this attenuation was reversed by NaHS treatment. Similarly, aortic superoxide anion production was significantly enhanced by AngII (P<0.01), and this was reversed by NaHS treatment, and also exacerbated by PPG treatment (P<0.001). These data show that in a mouse model of hypertension and oxidative stress induced by AngII, exogenous H2S treatment in vivo reduces blood pressure, endothelial dysfunction and vascular oxidative stress, while inhibiting endogenous H2S production in vivo is deleterious. This furthers the evidence that H2S is a vasoprotective molecule that may be a useful treatment target in cardiovascular disease.

Hydrogen sulfide as a vasculoprotective factor

Hydrogen sulfide is a novel mediator with the unique properties of a gasotransmitter and many and varied physiological effects. Included in these effects are a number of cardiovascular effects that are proving beneficial to vascular health. Specifically, H2S can elicit vasorelaxation, prevention of inflammation and leukocyte adhesion, anti-proliferative effects and anti-thrombotic effects. Additionally, H2S is a chemical reductant and nucleophile that is capable of inhibiting the production of reactive oxygen species, scavenging and neutralising reactive oxygen species and boosting the efficacy of endogenous anti-oxidant molecules. These result in resistance to oxidative stress, protection of vascular endothelial function and maintenance of blood flow and organ perfusion. H2S has been shown to be protective in hypertension, atherosclerosis and under conditions of vascular oxidative stress, and deficiency of endogenous H2S production is linked to cardiovascular disease states. Taken together, these effects suggest that H2S has a physiological role as a vasculoprotective factor and that exogenous H2S donors may be useful therapeutic agents. This review article will discuss the vascular effects and anti-oxidant properties of H2S as well as examine the protective role of H2S in some important vascular disease states.

Endothelium-dependent nitroxyl-mediated relaxation is resistant to superoxide anion scavenging and preserved in diabetic rat aorta

The aim of the study was to investigate whether diabetes-induced oxidant stress affects the contribution of nitroxyl (HNO) to endothelium-dependent relaxation in the rat aorta. Organ bath techniques were employed to determine vascular function of rat aorta. Pharmacological tools (3mM l-cysteine, 5mM 4-aminopyridine (4-AP), 200μM carboxy-PTIO and 100μM hydroxocobalamin, HXC) were used to distinguish between NO and HNO-mediated relaxation. Superoxide anion levels were determined by lucigenin-enhanced chemiluminescence. In the diabetic aorta, where there is increased superoxide anion production, responses to the endothelium-dependent relaxant ACh were not affected when the contribution of NO to relaxation was abolished by either HXC or carboxy-PTIO, indicating a preserved HNO-mediated relaxation. Conversely, when the contribution of HNO was inhibited with l-cysteine or 4-AP, the sensitivity and maximum relaxation to ACh was significantly decreased, suggesting that the contribution of NO was impaired by diabetes. Furthermore, whereas HNO appears to be derived from eNOS in normal aorta, in the diabetic aorta it may also arise from an eNOS-independent source, perhaps derived from nitrosothiol stores. Similarly, exposure to the superoxide anion generator, pyrogallol (100μM) significantly reduced the sensitivity to the NO donor, DEANONOate and ACh-induced NO-mediated relaxation but had no effect on responses to the HNO donor, Angelis salt and ACh-induced HNO-mediated relaxation in the rat aorta. These findings demonstrate that NO-mediated relaxation is impaired during oxidative stress but the HNO component of relaxation is preserved under those conditions.

Effect of type 1 diabetes on the production and vasoactivity of hydrogen sulfide in rat middle cerebral arteries.

Hydrogen sulfide (H2S) is produced endogenously in vascular tissue and has both vasoregulation and antioxidant effects. This study examines the effect of diabetes‐induced oxidative stress on H2S production and function in rat middle cerebral arteries. Diabetes was induced in rats with streptozotocin (50 mg/kg, i.v.). Middle cerebral artery function was examined using a small vessel myograph and superoxide anion generation measured using nicotinamide adenine dinucleotide phosphate (NADPH)‐dependent lucigenin‐enhanced chemiluminescence. Cystathionine‐γ‐lyase (CSE) mRNA expression was measured via RT‐PCR. Diabetic rats had elevated blood glucose and significantly reduced cerebral artery endothelial function. Maximum vasorelaxation to the H2S donor NaHS was unaffected in diabetic cerebral arteries and was elicited via a combination of K+, Cl−, and Ca2+ channel modulation, although the contribution of Cl− channels was significantly less in the diabetic cerebral arteries. Vasorelaxation to the H2S precursor l‐cysteine and CSE mRNA were significantly increased in diabetic cerebral arteries. Cerebral artery superoxide production was significantly increased in diabetes, but this increase was attenuated ex vivo by incubation with the H2S donor NaHS. These data confirm that cerebral artery endothelial dysfunction and oxidative stress occurs in diabetes. Endogenous H2S production and activity is upregulated in cerebral arteries in this model of diabetes. Vasorelaxation responses to exogenous H2S are preserved and exogenous H2S attenuates the enhanced cerebral artery generated superoxide observed in the diabetic group. These data suggest that upregulation of endogenous H2S in diabetes may play an antioxidant and vasoprotective role.

Chronic NaHS Treatment Is Vasoprotective in High-Fat-Fed ApoE−/− Mice

Hydrogen sulfide is emerging as an important mediator of vascular function that has antioxidant and cytoprotective effects. The aim of this study was to investigate the role of endogenous H2S and the effect of chronic exogenous H2S treatment on vascular function during the progression of atherosclerotic disease. ApoE−/− mice were fed a high-fat diet for 16 weeks and treated with the H2S donor NaHS or the cystathionine-γ-lyase (CSE) inhibitor D,L-propargylglycine (PPG), to inhibit endogenous H2S production for the final 4 weeks. Fat-fed ApoE−/− mice displayed significant aortic atherosclerotic lesions and significantly impaired endothelial function compared to wild-type mice. Importantly, 4 weeks of NaHS treatment significantly reduced vascular dysfunction and inhibited vascular superoxide generation. NaHS treatment significantly reduced the area of aortic atherosclerotic lesions and attenuated systolic blood pressure. Interestingly, inhibiting endogenous, CSE-dependent H2S production with PPG did not exacerbate the deleterious vascular changes seen in the untreated fat-fed ApoE−/− mice. The results indicate NaHS can improve vascular function by reducing vascular superoxide generation and impairing atherosclerotic lesion development. Endogenous H2S production via CSE is insufficient to counter the atherogenic effects seen in this model; however exogenous H2S treatment has a significant vasoprotective effect.

Hydrogen Sulfide in the RVLM and PVN has No Effect on Cardiovascular Regulation

Hydrogen sulfide (H2S) is now recognized as an important signaling molecule and has been shown to have vasodilator and cardio-protectant effects. More recently it has been suggested that H2S may also act within the brain to reduce blood pressure (BP). In the present study we have demonstrated the presence of the H2S-producing enzyme, cystathionine-β-synthase (CBS) in the rostral ventrolateral medulla (RVLM), and the hypothalamic paraventricular nucleus (PVN), brain regions with key cardiovascular regulatory functions. The cardiovascular role of H2S was investigated by determining the BP, heart rate (HR), and lumbar sympathetic nerve activity (LSNA) responses elicited by a H2S donor sodium hydrogen sulfide (NaHS) or inhibitors of CBS, microinjected into the RVLM and PVN. In anesthetized Wistar Kyoto rats bilateral microinjections of NaHS (0.2–2000 pmol/side) into the RVLM did not significantly affect BP, HR, or LSNA, compared to vehicle. Similarly, when the CBS inhibitors, amino-oxyacetate (AOA; 0.1–1.0 nmol/side) or hydroxylamine (HA; 0.2–2.0 nmol/side), were administered into the RVLM, there were no significant effects on the cardiovascular variables compared to vehicle. Microinjections into the PVN of NaHS, HA, and AOA had no consistent significant effects on BP, HR, or LSNA compared to vehicle. We also investigated the cardiovascular responses to NaHS microinjected into the RVLM and PVN in spontaneously hypertensive rats. Again, there were no significant effects on BP, HR, and LSNA. Together, these results suggest that H2S in the RVLM and PVN does not have a major role in cardiovascular regulation.

An evaluation of pharmacology curricula in Australian science and health-related degree programs

BackgroundPharmacology is a biomedical discipline taught in basic science and professional degree programs. In order to provide information that would facilitate pharmacology curricula to be refined and developed, and approaches to teaching to be updated, a national survey was undertaken in Australia that investigated pharmacology course content, teaching and summative assessment methods.MethodsTwenty-two institutions participated in a purpose-built online questionnaire, which enabled an evaluation of 147 courses taught in 10 different degrees. To enable comparison, degrees were grouped into four major degree programs, namely science, pharmacy, medicine and nursing. The pharmacology content was then classified into 16 lecture themes, with 2-21 lecture topics identified per theme. The resultant data were analysed for similarities and differences in pharmacology curricula across the degree programs.ResultsWhile all lecture themes were taught across degree programs, curriculum content differed with respect to the breadth and hours of coverage. Overall, lecture themes were taught most broadly in medicine and with greatest coverage in pharmacy. Reflecting a more traditional approach, lectures were a dominant teaching method (at least 90% of courses). Sixty-three percent of science courses provided practical classes but such sessions occurred much less frequently in other degree programs, while tutorials were much more common in pharmacy degree programs (70%). Notably, problem-based learning was common across medical programs. Considerable diversity was found in the types of summative assessment tasks employed. In science courses the most common form of in-semester assessment was practical reports, whereas in other programs pen-and-paper quizzes predominated. End-of-semester assessment contributed 50-80% to overall assessment across degree programs.ConclusionThe similarity in lecture themes taught across the four different degree programs shows that common knowledge- and competency-based learning outcomes can be defined for pharmacology. The authors contend that it is the differences in breadth and coverage of material for each lecture theme, and the differing teaching modes and assessment that characterise particular degree programs. Adoption of pharmacology knowledge-based learning outcomes that could be tailored to suit individual degree programs would better facilitate the sharing of expertise and teaching practice than the current model where pharmacology curricula are degree-specific.

H2S causes contraction and relaxation of major arteries of the rabbit

OBJECTIVE Cardiovascular disease (CVD) caused by atherosclerosis remains a worldwide burden. Hydrogen sulfide is a promising new therapeutic avenue for the treatment of CVD, however reports show exogenous H2S has both vasodilator and vasoconstrictor effects depending on organ examined, and in vitro studies in animal models which are not resistant to developing atherosclerosis are limited. We sought to determine if rabbit arteries constricted or dilated to hydrogen sulfide. MATERIAL AND METHODS The aorta, carotid, renal and iliac arteries were harvested from New Zealand White rabbits (n=4) and subjected to a concentration response curve to the fast H2S releaser NaHS. In addition, a bolus dose of NaHS was used to determine if further dilation was achievable after maximum dilation to acetylcholine similar to nitric oxide donors. Further, NaHS was used to determine if H2S could impair homocysteine induced endothelial dysfunction. RESULTS Blood vessels relaxed poorly to NaHS and contracted at higher doses. A bolus dose of NaHS relaxed then contracted the aorta, however a bolus dose of NaHS after maximal relaxation to acetylcholine caused marked contraction. NaHS did not prevent homocysteine induced vascular dysfunction. CONCLUSION NaHS at low doses caused minor relaxation of rabbit blood vessels, indicating a possible therapeutic benefit for low dose H2S in the cellular milieu.

Chronic NaHS treatment decreases oxidative stress and improves endothelial function in diabetic mice

Hydrogen sulphide (H2S) is endogenously produced in vascular tissue and has anti-oxidant and vasoprotective properties. This study investigates whether chronic treatment using the fast H2S donor NaHS could elicit a vasoprotective effect in diabetes. Diabetes was induced in male C57BL6/J mice with streptozotocin (60 mg/kg daily, ip for 2 weeks) and confirmed by elevated blood glucose and glycated haemoglobin levels. Diabetic mice were then treated with NaHS (100 µmol/kg/day) for 4 weeks, and aortae collected for functional and biochemical analyses. In the diabetic group, both endothelium-dependent vasorelaxation and basal nitric oxide (NO•) bioactivity were significantly reduced (p < 0.05), and maximal vasorelaxation to the NO• donor sodium nitroprusside was impaired (p < 0.05) in aorta compared to control mice. Vascular superoxide generation via nicotine adenine dinucleotide phosphate (NADPH) oxidase (p < 0.05) was elevated in aorta from diabetic mice which was associated with increased expression of NOX2 (p < 0.05). NaHS treatment of diabetic mice restored endothelial function and exogenous NO• efficacy back to control levels. NaHS treatment also reduced the diabetes-induced increase in NADPH oxidase activity, but did not affect NOX2 protein expression. These data show that chronic NaHS treatment reverses diabetes-induced vascular dysfunction by restoring NO• efficacy and reducing superoxide production in the mouse aorta.