Recombinant human activated protein C improves endotoxemia-induced endothelial dysfunction: a blood-free model in isolated mouse arteries

Abstract

Recombinant human activated protein C (rhAPC) is one of the treatment panels for improving vascular dysfunction in septic patients. In a previous study, we reported that rhAPC treatment in rat endotoxemia improved vascular reactivity, although the mechanisms involved are still under debate. In the present study, we hypothesized that rhAPC may improve arterial dysfunction through its nonanticoagulant properties. Ten hours after injection of LPS in mice (50 mg/kg ip), aortic rings and mesenteric arteries were isolated and incubated with or without rhAPC for 12 h. Aortic rings were mounted in a myograph, after which arterial contractility and endothelium-dependent relaxation were measured in the presence or absence of nitric oxide synthase or cyclooxygenase inhibitors. Flow (shear stress)-mediated dilation with or without the above inhibitors was also measured in mesenteric resistance arteries. Protein expression was assessed by Western blotting. Lipopolysaccharide (LPS) reduced aortic contractility to KCl and phenylephrine as well as dilation to acetylcholine. LPS also reduced flow-mediated dilation in mesenteric arteries. In rhAPC-treated aorta and mesenteric arteries, contractility and endothelial responsiveness to vasodilator drug and shear stress were improved. rhAPC treatment also improved LPS-induced endothelial dysfunction; this effect was associated with an increase in the phosphorylated form of endothelial nitric oxide synthase and protein kinase B as well as cyclooxygenase vasodilatory pathways, thus suggesting that these pathways, together with the decrease in nuclear factor-κB activation and inducible nitric oxide synthase expression in the vascular wall, are implicated in the endothelial effect of rhAPC. In conclusion, ex vivo application of rhAPC improves arterial contractility and endothelial dysfunction resulting from endotoxemia in mice. This finding provides important insights into the mechanism underlying rhAPC-induced improvements on arterial dysfunction during septic shock.

Endothelial Dysfunction in Sepsis

“…But in rodent models of endotoxemia, rhAPC also demonstrated a protective effect on microcirculation through the inhibition of leukocyte-endothelial interaction, inhibition of subsequent leukocytes adherence to the endothelium and suppression of inflammatory cytokine production [115][116][117]. Moreover, Sennoun et al [69] reported that rhAPC improved both endothelial dysfunction and arterial contractility induced by bacterial LPS in isolated mouse arteries, through an increase in eNOS activation, a reduction of LPS-induced upregulation of NF-B and iNOS expression. At last, De Backer et al [118] used OPS to visualize sublingual microcirculation and investigate the effects of rhAPC on septic patients; they showed an early increase of perfused capillaries.…”

Bench-to-bedside review: Circulating microparticles - a new player in sepsis?

“…During sepsis, the endothelial function is altered and the endothelial surface becomes proadhesive, procoagulant and antifibrinolytic [42]. The endothelium is one of the primary targets of circulating MPs, as demonstrated by Barry and colleagues [43] in vitro .…”

Comparative effects of recombinant human activated protein C and dexamethasone in experimental septic shock

“…Vascular reactivity of aortic rings was studied on a wire myograph (Danish Myo Technology, Aarhus, Denmark) as described previously [22] and in the ESM.…”

“…Interestingly, APC and Dexa overcome the deleterious endothelial effect of CLP. Indeed, the beneficial effect of APC and Dexa on ACh-induced relaxation could be explained by eNOS activation and COX vasorelaxant metabolites [22]. NO is one of the major endothelial relaxant factors produced by eNOS, allowing the endothelium to regulate smooth muscle tone and proliferation, leukocyte recruitment, and platelet aggregation.…”