Endothelin‐1 and COMP Regulate Heme Biosynthesis and Guanylate Cyclase Expression in Smooth Muscle of Pulmonary Arteries

Abstract

The objective of this study is to examine if heme biosynthesis is regulated in smooth muscle of pulmonary arteries by endothelin‐1 (ET1) and/or conditions modulating the availability of Cartilage Oligomeric Matrix Protein (COMP). Our recent studies in endothelium‐rubbed bovine pulmonary arteries (BPA) organoid cultured for up to 48 hours observed ET1 (10nM) increases superoxide in the mitochondrial matrix and extra mitochondrial regions associated with COMP depletion. While incubation with COMP (0.5μM) attenuated ET1‐induced superoxide increases. We hypothesize that increased superoxide in the mitochondrial matrix could impair heme biosynthesis from protoporphyrin IX (PpIX) by decreasing the availability of Fe2+ and/or ferrochelatase (FECH). To examine this hypothesis, we studied the effects of ET1, COMP and siRNA depletion of COMP on the expression of FECH, transferrin receptor‐1 (TfR1, an indicator of iron availability) and soluble guanylate cyclase (sGC, a key heme‐dependent protein), and on measurements of PpIX (HPLC) and heme content. ET1 decreased FECH, heme and sGC, and increased PpIX and TfR1. COMP reversed these effects of ET1, and COMP also decreased PpIX and increased heme in the absence of ET1. The depletion of COMP by siRNA increased detection of mitochondrial Matrix (MitoSOX‐HPLC) and extramitochondrial (DHE‐HPLC) superoxide, PpIX and TfR1 expression, and decreased the expression of FECH, sGC and the phosphorylation of VASP on the site mediated by cGMP protein kinase. In vascular reactivity studies, it was observed that relaxation of BPA to the nitric oxide donor spermine NONOate was inhibited by organoid culture with ET1, and this effect of ET1 was attenuated in the presence of COMP during the exposure to ET1. Collectively, ET1 and COMP depletion appears to impair the biosynthesis of heme in pulmonary arteries potentially associated with the loss of protective sGC and cGMP vasodilator and remodeling‐inhibitory mechanisms.Support or Funding InformationSupported by NIH Grants HL115124 & HL129797; The Natural Science Foundation of the P. R. China (31400989); The Natural Science Foundation of Heilongjiang Province (C2015069) ; Postdoctoral Science Foundation of Heilongjiang Province (LBHQ15087)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.