Hydrogen peroxide enhances vasodilatation by increasing dimerization of cGMP-dependent protein kinase type Iα

Abstract

Background: cGMP-dependent protein kinase type I (PKG I) plays a key role in vasodilatation caused by cGMPelevating agents. It is a homodimer in mammalian cells, existing as 2 isoforms, Iα and Iβ. The aim of the present study was both to determine whether PKG I dimerization and activity are modulated by hydrogen peroxide (H 2O 2) and its influence on vasodilatation. Methods and Results: The dimers and monomers of total PKG I and PKG Iβ were analyzed by Western blotting. PKG I activity was assayed by measuring the incorporation of 32P into BPDEtide. Changes in vessels tension were determined by organ chamber technique. In isolated porcine coronary arteries, H 2O 2 increased the dimers of total PKG I in a concentration-dependent manner, but had no effect on dimerization of PKG Iβ. The dimerization of PKG I caused by H 2O 2 was prevented by catalase but not by deferoxamine and tiron. H 2O 2 promoted the translocation of PKG I from cytoplasm to membrane. H 2O 2 enhanced the activity of PKG I and relaxations of porcine coronary arteries to the nitric oxide donor and 8-Br-cGMP. Inhibition of catalase under in vivo conditions significantly decreased rat mean arterial pressure, which was associated with increased dimerization of PKG I. Conclusions: The present study suggests that H 2O 2 may enhance the activity of PKG Iα- and PKG I-dependent vasodilatation via increased dimerization of the enzyme.