Hydrogen peroxide differentially modulates cardiac myocyte nitric oxide synthesis

Area of Science:

• Cardiovascular Physiology
• Cellular Signaling
• Biochemistry

Background:

• Nitric oxide (NO) and hydrogen peroxide (H2O2) are crucial signaling molecules in cardiac myocytes.
• The specific roles of endothelial (eNOS) and neuronal (nNOS) nitric oxide synthases and their interaction with reactive oxygen and nitrogen species are not fully understood.
• Understanding these pathways is vital for comprehending cardiac function and dysfunction.

Purpose of the Study:

• To investigate the differential roles of NOS isoforms in cardiac signaling.
• To elucidate the interplay between H2O2 and NO signaling in cardiac myocytes.
• To determine the mechanisms of H2O2-mediated eNOS activation and its impact on cardiac contractility.

Main Methods:

• Utilized a novel NO chemical sensor [Cu(2)(FL2E)] to measure NO production in cardiac myocytes from wild-type, eNOS-null, and nNOS-null mice.
• Employed a H2O2 biosensor (HyPer2) to quantify H2O2 synthesis in response to various stimuli.
• Assessed cardiac myocyte contractility under different signaling conditions.

Main Results:

• Physiological H2O2 concentrations selectively activate eNOS, not nNOS, in cardiac myocytes.
• H2O2-induced eNOS activation is dependent on AMP-activated protein kinase and Akt phosphorylation.
• Angiotensin II stimulation leads to H2O2 synthesis and enhances cardiac myocyte contractility, while beta-adrenergic stimulation does not involve H2O2 signaling.

Conclusions:

• H2O2 plays distinct roles in regulating cardiac contractility and receptor-dependent NOS activation.
• Oxidative stress can modulate NO signaling pathways in the heart.
• Identified novel targets for modulating NO signaling in response to oxidant stress in the cardiovascular system.