Inhibiting the phosphatase activity of soluble epoxide hydrolase reduces arterial calcification and prevents the cardiovascular complications of chronic kidney disease

Abstract

Increasing evidence suggests that the bifunctional soluble epoxide hydrolase (sEH) regulates vascular calcification. This study addressed the hypothesis that the phosphatase activity of soluble epoxide hydrolase (sEH-P) is involved in this regulation. We carefully assessed the impact of sEH-P inhibition on aortic calcification using genetic and pharmacological approaches and explored the putative mechanism involved. Pharmacological and genetic inhibition of sEH-P reduced the increase in calcium deposition in rat aortic rings cultured in high-phosphate conditions. This was associated with a decreased mRNA expression of the osteochondrogenic marker Msx2 and Sox9. The deendothelialization of aortic rings abolished this anti-calcifying effect and the calcification of human aortic smooth muscle cells was not affected by sEH-P inhibition, suggesting a major role of the endothelium. Endothelial NO release appeared not involved since the level of its metabolite nitrite was not increased during sEH-P inhibition and the inhibition of NO-synthase did not prevent the anti-calcifying effect of sEH-P inhibition. However, an increased level of the calcification inhibitor pyrophosphate anions (PPi) was observed in the culture supernatant of aortic rings when sEH-P is inhibited and in vitro experiments demonstrated that PPi is released by human aortic endothelial cells and can be metabolized by sEH-P. In addition, the blockade of PPARγ, which mediate the intracellular effect of the sEH metabolites lysophosphatidic acids, prevented the anti-calcifying effect of sEH-P inhibition. Finally, the aortic calcification associated with chronic kidney disease induced by subtotal nephrectomy was reduced in sEH-P-deficient rats compared with wild-type rats. This was associated with a prevention of the development of hypertension, vascular dysfunction, cardiac hypertrophy and dysfunction. These results show that the inhibition of sEH-P prevents the development of vascular calcification by reducing the degradation of PPi and represents a promising therapeutic approach to limit the development of the cardiovascular complications of patients with chronic kidney disease.