Modulation of Heme Biosynthesis by Ferrochelatase Inhibition Controls Soluble Guanylate Cyclase Expression and Superoxide Production in Bovine Coronary Arteries

Abstract

Nitric oxide interacts with the Fe2+ heme prosthetic group in soluble guanylate cyclase (sGC) stimulating the conversion of guanosine 5′‐triphosphate to cyclic guanosine 3′,5′‐monophosphate (cGMP). Adequate cGMP production is associated with protective mechanisms against multiple cardiovascular disease processes. Thus, disturbances in this signaling pathway can lead to many pathological consequences. Since there has been minimal investigation on the consequences of altering heme biosynthesis on the cardiovascular system, we investigated if mitochondrial heme biosynthesis is an important factor in controlling the expression and function of sGC and systems influencing superoxide generation and actions. For the purpose of this study, we induced a heme deficiency by inhibiting ferrochelatase (FECH) with N‐methyl protoporphyrin IX (NMPP), potent FECH inhibitor. Bovine coronary arteries (BCA) were treated for 24 hours with 10 μM NMPP. Chemiluminescence (5μM lucigenin) was used to measure superoxide production; western blot analysis was used to measure expression of FECH, sGC and other heme‐containing proteins; and a QuantiChrom heme assay kit was used to measure heme levels. NMPP treatment promoted sGC depletion and attenuation of its activity based on it decreasing protein kinase G‐mediated phosphorylation of VASP and attenuation of relaxation to a nitric oxide donor. NMPP also decreased the expression of heme proteins including cytochrome oxidase subunit 4 and catalase. In addition, superoxide production was significantly elevated in NMPP treated coronary arteries when compared to that in control samples, and scavenging extra mitochondrial superoxide with Tempol and mitochondrial matrix superoxide with MitoTempol attenuated the increase in superoxide. NMPP stimulated increases in superoxide were associated with a decrease expression of mitochondrial FECH expression. Thus, inhibition of FECH increased extra mitochondrial and mitochondrial superoxide and depleted sGC. Our studies suggest that disruption of heme biosynthesis resulting in a loss of cGMP production may serve as a contributing mechanism to the progression of cardiovascular disease.Support or Funding InformationFunded by NIH grants R01HL115124 & R01HL129797