Coronary endothelial dysfunction induced by nucleotide oligomerization domain-like receptor protein with pyrin domain containing 3 inflammasome activation during hypercholesterolemia: beyond inflammation.

aimsThis study hypothesized that activation of endothelial nucleotide oligomerization domain-like receptor protein with pyrin domain containing 3 (Nlrp3) inflammasomes directly produces endothelial dysfunction during hypercholesterolemia, which is distinct from its canonical roles in inflammation.

resultsAcute hypercholesterolemia in mice was induced by intraperitoneal administration of poloxamer 407 (0.5 g/kg) for 24 h. Endothelial dysfunction was assessed by evaluating endothelium-dependent vasodilation in isolated, perfused, and pressurized coronary arteries in response to bradykinin (10(-10)-10(-6) M) and acetylcholine (10(-9)-10(-5) M). Impaired endothelium-dependent vasodilation was observed in Nlrp3(+/+) mice with acute hypercholesterolemia, which was markedly ameliorated in Nlrp3(-/-) mice. Treatment of mice with inhibitors for caspase-1 or high mobility group box 1 (HMGB1) significantly restored endothelium-dependent vasodilation in Nlrp3(+/+) mice with acute hypercholesterolemia. Confocal microscopic analysis demonstrated that hypercholesterolemia markedly increased caspase-1 activity and HMGB1 expression in coronary arterial endothelium of Nlrp3(+/+) mice, which was absent in Nlrp3-deficient mice. Further, recombinant HMGB1 directly induced endothelial dysfunction in normal Nlrp3(+/+) coronary arteries. In vitro, Nlrp3 inflammasome formation and its activity were instigated in cultured endothelial cells by cholesterol crystal, a danger factor associated with hypercholesterolemia. Moreover, cholesterol crystals directly induced endothelial dysfunction in coronary arteries from Nlrp3(+/+) mice, which was attenuated in Nlrp3(-/-) arteries. Such cholesterol crystal-induced impairment was associated with enhanced superoxide production, downregulation of endothelial nitric oxide synthase activity, and pyroptosis. INNOVATION AND

conclusionOur data provide the first evidence that activation of endothelial Nlrp3 inflammasome directly impairs endothelial function beyond its canonical inflammatory actions. This novel non-canonical action of Nlrp3 inflammasomes may initiate or exacerbate vascular injury during hypercholesterolemia.