Nitric oxide (NO) and hydrogen peroxide (H2O2) play key roles in physiological and pathological responses in cardiac myocytes. The mechanisms whereby H2O2-modulated phosphorylation pathways regulate the endothelial isoform of nitric oxide synthase (eNOS) in these cells are incompletely understood. We show here that H2O2 treatment of adult mouse cardiac myocytes leads to increases in intracellular Ca2+ ([Ca2+]i), and document that activity of the L-type Ca2+ channel is necessary for the H2O2-promoted increase in sarcomere shortening and of [Ca2+]i. Using the chemical NO sensor Cu2(FL2E), we discovered that the H2O2-promoted increase in cardiac myocyte NO synthesis requires activation of the L-type Ca2+ channel, as well as phosphorylation of the AMP-activated protein kinase (AMPK), and mitogen-activated protein kinase kinase 1/2 (MEK1/2). Moreover, H2O2-stimulated phosphorylations of eNOS, AMPK, MEK1/2, and ERK1/2 all depend on both an increase in [Ca2+]i as well as the activation of protein kinase C (PKC). We also found that H2O2-promoted cardiac myocyte eNOS translocation from peripheral membranes to internal sites is abrogated by the L-type Ca2+ channel blocker nifedipine. We have previously shown that kinase Akt is also involved in H2O2-promoted eNOS phosphorylation. Here we present evidence documenting that H2O2-promoted Akt phosphorylation is dependent on activation of the L-type Ca2+ channel, but is independent of PKC. These studies establish key roles for Ca2+- and PKC-dependent signaling pathways in the modulation of cardiac myocyte eNOS activation by H2O2.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)