Vascular ATP-sensitive potassium channels are over-expressed and partially regulated by nitric oxide in experimental septic shock

International audiencePurpose To study the activation and expression of vascular (aorta and small mesenteric arteries) potassium channels during septic shock with or without modulation of the NO pathway. Methods Septic shock was induced in rats by peritonitis. Selective inhibitors of vascular KATP (PNU-37883A) or BKCa [iberiotoxin (IbTX)] channels were used to demonstrate their involvement in vascular hyporeactivity. Vascular response to phenylephrine was measured on aorta and small mesenteric arteries mounted on a wire myograph. Vascular expression of potassium channels was studied by PCR and Western blot, in the presence or absence of 1400W, an inducible NO synthase (iNOS) inhibitor. Aortic activation of the transcriptional factor nuclear factor-kappaB (NF-κB) was assessed by electrophoretic mobility shift assay. Results Arterial pressure as well as in vivo and ex vivo vascular reactivity were reduced by sepsis and improved by PNU-37883A but not by IbTX. Sepsis was associated with an up-regulation of mRNA and protein expression of vascular KATP channels, while expression of vascular BKCa channels remained unchanged. Selective iNOS inhibition blunted the sepsis-induced increase in aortic NO, decreased NF-κB activation, and down-regulated vascular KATP channel expression. Conclusions Vascular KATP but not BKCa channels are activated, over-expressed, and partially regulated by NO via NF-κB activation during septic shock. Their selective inhibition restores arterial pressure and vascular reactivity and decreases lactate concentration. The present data suggest that selective vascular KATP channel inhibitors offer potential therapeutic perspectives for septic shock.</p

Activated protein C improves LPS-induced cardiovascular dysfunction by decreasing tissular inflammation and oxidative stress.

International audienceBACKGROUND:: Recombinant human activated Protein C (APC) is used as an adjunctive therapeutic treatment in septic shock. APC seemingly acts on coagulation-inflammation interaction but also by decreasing proinflammatory gene activity, thus inhibiting subsequent production of proinflammatory cytokines, NO and NO-induced mediators, reactive oxygen species production and leukocyte-endothelium interaction. The hemodynamic effects of APC on arterial pressure and cardiac function are now well established in animal models. However, the specific effects of APC on heart and vessels have never been studied. OBJECTIVES:: To investigate the potential protective properties of therapeutic ranges of APC on a rat endotoxic shock model in terms of anti-inflammatory and cytoprotective pathways. DESIGN:: Laboratory investigation. SETTING:: University medical center research laboratory. INTERVENTIONS:: Rats were exposed to lipopolysaccharide (LPS) (10 mg/Kg iv.). Endotoxic shock was treated with infusion of saline with or without APC (33 mug/kg/h) during 4 hrs. Hemodynamic parameters were continuously assessed and measurements of muscle oxygen partial pressures, NO and superoxide anion (O2) by spin trapping, of NF-kappaB, metalloproteinase-9 (MMP-9) and inducible NO synthase (iNOS) by Western blotting, as well as leukocyte infiltration and MMP-9 activity were performed at both the heart and aorta level (tissue). MAIN RESULTS:: APC partially prevented the reduction of blood pressure induced by LPS and improved both vascular hyporeactivity and myocardial performance. This was associated with a decreased up-regulation of NF-kappaB, iNOS and MMP-9. LPS-induced tissue increases in NO and O2 production were decreased by APC. Furthermore, APC decreased tissue leukocyte infiltration/activation as assessed by a decrease in myeloperoxydase and matrix metalloproteinase 9 activity. CONCLUSIONS:: These data suggest that APC improves cardiovascular function i) by modulating the endotoxin induced-proinflammatory/prooxydant state, ii) by decreasing endothelial/leukocyte interaction and iii) by favoring stabilization of the extracellular matrix.</p