Soluble guanylyl cyclase modulates redox-dependent regulation of the cardiac sodium potassium pump

Abstract

Modulation of redox-dependent regulation of the Na+-K+ pump is a potential therapeutic strategy in heart failure. This Thesis examined if stimulation of soluble guanylyl cyclase (sGC) can modulate oxidative signalling to the Na+-K+ pump in rabbit cardiomyocytes and the mechanisms by which this may occur. sGC stimulation with 3-(5’-hydroxymethyl-2’-furyl)-1-benzylindazole (YC-1) attenuated the Angiotensin (Ang) II-induced 1) inhibition of the electrogenic Na+-K+ pump current (Ip), 2) O2•-sensitive fluorescence, 3) serine phosphorylation of p47phox (necessary for NADPH oxidase activation) and 4) co-localisation of p47phox with the Na+-K+ pump (α1 subunit). It decreased both baseline and Ang II-induced glutathionylation of the β1 subunit, while increasing the α1/β1 subunits’ interaction, necessary for Na+-K+ pump function. YC-1 had similar effects when forskolin was used as the oxidant stimulus. Okadaic acid and C6 ceramide effects implicate protein phosphatase 2A’s (PP2A) role in the effects of YC-1. We conclude that stimulation of sGC attenuates receptor-coupled oxidative inhibition of the cardiac Na+-K+ pump by attenuation of NADPH oxidase activation, cellular O2• levels and glutathionylation of the β1 subunit of the pump. This allows for increased α1/β1 subunit interaction and hence Na+-K+ pump activity. The signalling pathway from sGC is via PP2A which attenuated NADPH oxidase activity.