Hydrogen sulfide preconditioning or neutrophil depletion attenuates ischemia-reperfusion-induced mitochondrial dysfunction in rat small intestine.

The objectives of this study were to determine whether neutrophil depletion with anti-neutrophil serum (ANS) or preconditioning with the hydrogen sulfide (H(2)S) donor NaHS (NaHS-PC) 24 h prior to ischemia-reperfusion (I/R) would prevent postischemic mitochondrial dysfunction in rat intestinal mucosa and, if so, whether calcium-activated, large conductance potassium (BK(Ca)) channels were involved in this protective effect. I/R was induced by 45-min occlusion of the superior mesenteric artery followed by 60-min reperfusion in rats preconditioned with NaHS (NaHS-PC) or a BK(Ca) channel activator (NS-1619-PC) 24 h earlier or treated with ANS. Mitochondrial function was assessed by measuring mitochondrial membrane potential, mitochondrial dehydrogenase function, and cytochrome c release. Mucosal myeloperoxidase (MPO) and TNF-α levels were also determined, as measures of postischemic inflammation. BK(Ca) expression in intestinal mucosa was detected by immunohistochemistry and Western blotting. I/R induced mitochondrial dysfunction and increased tissue MPO and TNF-α levels. Although mitochondrial dysfunction was attenuated by NaHS-PC or NS-1619-PC, the postischemic increases in mucosal MPO and TNF-α levels were not. The protective effect of NaHS-PC or NS-1619-PC on postischemic mitochondrial function was abolished by coincident treatment with BK(Ca) channel inhibitors. ANS prevented the I/R-induced increase in tissue MPO levels and reversed mitochondrial dysfunction. These data indicate that neutrophils play an essential role in I/R-induced mucosal mitochondrial dysfunction. In addition, NaHS-PC prevents postischemic mitochondrial dysfunction (but not inflammation) by a BK(Ca) channel-dependent mechanism.

Effects of interventions on oxidative stress and inflammation of cardiovascular diseases.

Excessive oxidative stress and low-grade chronic inflammation are major pathophysiological factors contributing to the development of cardiovascular diseases (CVD) such as hypertension, diabetes and atherosclerosis. Accumulating evidence suggests that a compromised anti-oxidant system can lead to excessive oxidative stress in cardiovascular related organs, resulting in cell damage and death. In addition, increased circulating levels of pro-inflammatory cytokines, such as tumor necrosis factor α, interleukin-6 and C-reactive protein, are closely related to morbidity and mortality of cardiovascular complications. Emerging evidence suggests that interventions including nutrition, pharmacology and exercise may activate expression of cellular anti-oxidant systems via the nuclear factor erythroid 2-related factor 2-Kelch-like ECH-associated protein 1 signaling pathway and play a role in preventing inflammatory processes in CVD. The focus of the present review is to summarize recent evidence showing the role of these anti-oxidant and anti-inflammatory interventions in cardiovascular disease. We believe that these findings may prompt new effective pathogenesis-oriented interventions, based on the exercise-induced protection from disease in the cardiovascular system, aimed at targeting oxidant stress and inflammation.

Isoform-selective 5'-AMP-activated protein kinase-dependent preconditioning mechanisms to prevent postischemic leukocyte-endothelial cell adhesive interactions.

We previously demonstrated that preconditioning induced by ethanol consumption at low levels [ethanol preconditioning (EPC)] or with 5-aminoimidazole-4-carboxamide 1-ß-d-ribofuranoside (AICAR-PC) 24 h before ischemia-reperfusion prevents postischemic leukocyte-endothelial cell adhesive interactions (LEI) by a mechanism that is initiated by nitric oxide formed by endothelial nitric oxide synthase. Recent work indicates that 1) ethanol increases the activity of AMP-activated protein kinase (AMPK) and 2) AMPK phosphorylates endothelial nitric oxide synthase at the same activation site seen following EPC (Ser1177). In light of these observations, we postulated that the heterotrimeric serine/threonine kinase, AMPK, may play a role in triggering the development of the anti-inflammatory phenotype induced by EPC. Ethanol was administered to C57BL/6J mice by gavage in the presence or absence of AMPK inhibition. Twenty-four hours later, the numbers of rolling and adherent leukocytes in postcapillary venules of the small intestine were recorded using an intravital microscopic approach. Following 45 min of ischemia, LEI were recorded after 30 and 60 min of reperfusion or at equivalent time points in control animals. Ischemia-reperfusion induced a marked increase in LEI relative to sham-operated control mice. The increase in LEI was prevented by EPC, an effect that was lost with AMPK inhibition during the period of ethanol exposure. Studies conducted in AMPK α(1)- and α(2)-knockout mice suggest that the anti-inflammatory effects of AICAR are not dependent on which isoform of the catalytic α-subunit is present because a deficiency of either isoform results in a loss of protection. In sharp contrast, EPC appears to be triggered by an AMPK α(2)-isoform-dependent mechanism.