Calpain 1 cleaves and inactivates prostacyclin synthase in mesenteric arteries from diabetic mice

Diabetes is associated with a number of co-morbidities including an increased risk of developing cardiovascular diseases. The activation of Ca²⁺-activated proteases of the calpain family has been implicated in platelet activation associated with diabetes and this study aimed to determine the role of calpain activation in the development of endothelial dysfunction. Diabetes induction in mice attenuated acetylcholine-induced relaxation of mesenteric artery rings, an effect prevented in mice receiving a calpain inhibitor. A nitric oxide-independent but diclofenac-sensitive component of the relaxation–response was altered and correlated with a loss of prostacyclin (PGI₂) generation and reduced vascular levels of PGI₂ synthase. Calpain inhibition was also able to restore PGI₂ synthase levels and PGI₂ generation in arteries from diabetic animals. The effects of diabetes were reproduced in vitro by a combination of high glucose and palmitate, which elicited calpain activation, PGI₂ synthase cleavage and inactivation as well as endothelial dysfunction in mesenteric arteries from wild-type mice. PGI₂ cleavage was not observed in arteries from calpain 1^−/− mice or mice overexpressing the endogenous calpain inhibitor calpastatin. Finally, proteomic analyses revealed that calpain 1 cleaved the C-terminal domain of PGI₂ synthase close to the catalytic site of the enzyme. These data demonstrate that diabetes leads to the activation of calpain 1 in mesenteric arteries and can initiate endothelial dysfunction by cleaving and inactivating the PGI₂ synthase. Given that calpain inhibition prevented diabetes-induced endothelial dysfunction in mesenteric arteries, calpains represent an interesting therapeutic target for the prevention of cardiovascular complication of diabetes.