Role of Angiotensin II‐associated Mitochondrial Superoxide in Inhibiting Ferrochelatase Activity and Disrupting Heme Biosynthesis Regulation of Coronary Artery Soluble Guanylate Cyclase Expression

Abstract

Oxidation of the soluble guanylate cyclase (sGC) heme promotes loss of regulation by nitric oxide (NO) and the proteolytic degradation of sGC. Due to the mitochondrial heme generating enzyme ferrochelatase (FECH) having an iron‐sulfur cluster which could potentially be disrupted by superoxide, and Angiotensin II (AngII) promoting increased mitochondrial superoxide and a loss of NO‐stimulated sGC/cGMP‐mediated vasodilation, we hypothesized that AngII may influence the regulation of sGC through a superoxide‐mediated inhibition of the conversion of protoporphyrin IX (PpIX) into heme by FECH.In addition, since we previously reported that 24‐hour organoid culture of bovine arteries with δ‐aminolevulinic acid (ALA) caused an increase in sGC activity by generating PpIX, we investigated if ALA attenuates actions of AngII. Organoid culture of bovine coronary arteries (BCAs) with 0.1 µM AngII for 24‐hours caused increases in mitochondrial (MitoSox/HPLC) and extra‐mitochondrial/cytosolic superoxide (DHE/HPLC), but ALA only reversed the increase in mitochondrial superoxide. AngII also decreased FECH activity, and this was attenuated by ALA or the mitochondrial superoxide scavenger mitoTempol. Treatment of BCAs with AngII also decreased FECH and sGC expression, and ALA prevented these actions of AngII suggesting a role of increased mitochondrial superoxide in regulating the loss of FECH and sGC. These observations suggest that AngII stimulated mitochondrial superoxide generation plays an important role in inhibiting FECH activity and its influence on maintaining the expression of sGC.