Changes in the concentration of oxidants in cells can regulate biochemical signaling mechanisms that control cell function. We have found that guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase (PKG) functions directly as a redox sensor. The Ialpha isoform, PKGIalpha, formed an interprotein disulfide linking its two subunits in cells exposed to exogenous hydrogen peroxide. This oxidation directly activated the kinase in vitro, and in rat cells and tissues. The affinity of the kinase for substrates it phosphorylates was enhanced by disulfide formation. This oxidation-induced activation represents an alternate mechanism for regulation along with the classical activation involving nitric oxide and cGMP. This mechanism underlies cGMP-independent vasorelaxation in response to oxidants in the cardiovascular system and provides a molecular explantion for how hydrogen peroxide can operate as an endothelium-derived hyperpolarizing factor.

There was an error published in J. Cell Sci. 120, 929-942. We apologise for the incorrect publication of a reference, for which the wrong year, title and journal details were given. The correct reference is shown below.

The expression of inducible nitric-oxide synthase (iNOS) and subsequent "high-output" nitric oxide (NO) production underlies the systemic hypotension, inadequate tissue perfusion, and organ failure associated with septic shock. Therefore, modulators of iNOS expression and activity, both endogenous and exogenous, are important in determining the magnitude and time course of this condition. We have shown previously that NO from the constitutive endothelial NOS (eNOS) is necessary to obtain maximal iNOS expression and activity following exposure of murine macrophages to lipopolysaccharide (LPS). Thus, eNOS represents an important regulator of iNOS expression in vitro. Herein, we validate this hypothesis in vivo using a murine model of sepsis. A temporal reduction in iNOS expression and activity was observed in LPS-treated eNOS knock-out (KO) mice as compared with wild-type animals; this was reflected in a more stable hemodynamic profile in eNOS KO mice during endotoxaemia. Furthermore, in human umbilical vein endothelial cells, LPS leads to the activation of eNOS through phosphoinositide 3-kinase-and Akt/protein kinase B-dependent enzyme phosphorylation. These data indicate that the pathogenesis of sepsis is characterized by an initial eNOS activation, with the resultant NO acting as a co-stimulus for the expression of iNOS, and therefore highlight a novel pro-inflammatory role for eNOS.The systemic hypotension, organ failure, and morbidity that occur during bacterial sepsis are associated with the expression of inducible nitric-oxide synthase (iNOS) 1 and excessive production of nitric oxide (NO). This is evidenced by the increased levels of nitrite (NO 2 Ϫ ) and nitrate (NO 3 Ϫ ; stable metabolites of NO) measured in the plasma of septic patients (1, 2), inflammation-induced iNOS expression (3, 4), and by the ability of selective iNOS inhibitors to restore blood pressure in experimental models of sepsis and reverse hypotension in human endotoxaemia (5-10).Inducible NOS is effectively absent under physiological conditions but is expressed in many cell types in response to pro-inflammatory cytokines and lipopolysaccharides (LPS); in accord, induction of this NOS isoform is necessary for "high output" NO production and cytostatic and cytotoxic effects that facilitate host defense (11). While iNOS expression is essential to combat bacterial infection, the sustained overproduction of NO is deleterious to the host, as exemplified by the cardiovascular dysfunction during sepsis. Since iNOS is regulated primarily at a transcriptional level (12-14), a better understanding of the mechanisms involved in iNOS mRNA and protein expression should lead to improved treatment for endotoxaemia and other inflammatory cardiovascular disorders.In contrast to iNOS, a potential role for endothelial NOS (eNOS) in the pathogenesis of sepsis is unsubstantiated. Initial studies suggested that eNOS knock-out (KO) animals respond to endotoxin in an identical manner to wild-type (WT) littermates (15), and more recently, mice overexpressing eNO...

AimDespite prompt revascularization of acute myocardial infarction (AMI), substantial myocardial injury may occur, in part a consequence of ischaemia reperfusion injury (IRI). There has been considerable interest in therapies that may reduce IRI. In experimental models of AMI, sodium nitrite substantially reduces IRI. In this doubleblind randomized placebo controlled parallel-group trial, we investigated the effects of sodium nitrite administered immediately prior to reperfusion in patients with acute ST-elevation myocardial infarction (STEMI).Methods and resultsA total of 229 patients presenting with acute STEMI were randomized to receive either an i.v. infusion of 70 μmol sodium nitrite (n = 118) or matching placebo (n = 111) over 5 min immediately before primary percutaneous intervention (PPCI). Patients underwent cardiac magnetic resonance imaging (CMR) at 6–8 days and at 6 months and serial blood sampling was performed over 72 h for the measurement of plasma creatine kinase (CK) and Troponin I. Myocardial infarct size (extent of late gadolinium enhancement at 6–8 days by CMR-the primary endpoint) did not differ between nitrite and placebo groups after adjustment for area at risk, diabetes status, and centre (effect size −0.7% 95% CI: −2.2%, +0.7%; P = 0.34). There were no significant differences in any of the secondary endpoints, including plasma troponin I and CK area under the curve, left ventricular volumes (LV), and ejection fraction (EF) measured at 6–8 days and at 6 months and final infarct size (FIS) measured at 6 months.ConclusionsSodium nitrite administered intravenously immediately prior to reperfusion in patients with acute STEMI does not reduce infarct size.

Background-Endothelium-dependent dilatation is mediated by 3 principal vasodilators: nitric oxide (NO), prostacyclin (PGI 2 ), and endothelium-derived hyperpolarizing factor (EDHF). To determine the relative contribution of these factors in endothelium-dependent relaxation, we have generated mice in which the enzymes required for endothelial NO and PGI 2 production, endothelial NO synthase (eNOS) and cyclooxygenase-1 (COX-1), respectively, have been disrupted (eNOS Ϫ/Ϫ and COX-1 Ϫ/Ϫ mice). Methods and Results-In female mice, the absence of eNOS and COX-1 had no effect on mean arterial blood pressure (BP), whereas BP was significantly elevated in eNOS Ϫ/Ϫ /COX-1 Ϫ/Ϫ males compared with wild-type controls. Additionally, endothelium-dependent relaxation remained intact in the resistance vessels of female mice and was associated with vascular smooth muscle hyperpolarization; however, these responses were profoundly suppressed in arteries of male eNOS Ϫ/Ϫ /COX-1 Ϫ/Ϫ animals. Similarly, the endothelium-dependent vasodilator bradykinin produced dose-dependent hypotension in female eNOS Ϫ/Ϫ /COX-1 Ϫ/Ϫ animals in vivo but had no effect on BP in male mice. Conclusions-These studies indicate that EDHF is the predominant endothelium-derived relaxing factor in female mice, whereas NO and PGI 2 are the predominant mediators in male mice. Moreover, the gender-specific prevalence of EDHF appears to underlie the protection of female eNOS

These data substantiate CNP/NPR-C signalling as a fundamental pathway underlying EDHF-dependent regulation of vascular tone in the rat mesenteric resistance vasculature. An increased understanding of the physiological roles of CNP/NPR-C signalling in the vasculature (now facilitated by the identification of a selective NPR-C antagonist) should aid determination of the (patho)physiological importance of EDHF and might provide the rationale for the design of novel therapeutics.

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Both heart failure with reduced ejection fraction (HFrEF) and with preserved ejection fraction (HFpEF) are associated with high morbidity and mortality. Although many established pharmacological interventions exist for HFrEF, hospitalization and death rates remain high, and for those with HFpEF (approximately half of all heart failure patients), there are no effective therapies. Recently, the role of impaired cardiac energetic status in heart failure has gained increasing recognition with the identification of reduced capacity for both fatty acid and carbohydrate oxidation, impaired function of the electron transport chain, reduced capacity to transfer ATP to the cytosol, and inefficient utilization of the energy produced. These nodes in the genesis of cardiac energetic impairment provide potential therapeutic targets, and there is promising data from recent experimental and early-phase clinical studies evaluating modulators such as carnitine palmitoyltransferase 1 inhibitors, partial fatty acid oxidation inhibitors and mitochondrial-targeted antioxidants.Metabolic modulation may provide significant symptomatic and prognostic benefit for patients suffering from heart failure above and beyond guideline-directed therapy, but further clinical trials are needed.