Involvement of Nuclear Receptors PPAR-α, PPAR-γ, and the Transcription Factor Nrf2 in Cellular Protection Against Oxidative Stress Regulated by HS and Induced by Hypoxia-Reoxygenation and High Glucose in Primary Cardiomyocyte Cultures.

Myocardial oxidative stress increases under conditions of hyperglycemia and ischemia/reperfusion (I/R) injury, leading to cellular damage. Inhibition of oxidative stress is involved in the cardioprotective effects of hydrogen sulfide (HS) during I/R and diabetes, and HS has the potential to protect the heart. However, the mechanism by which HS regulates the level of cardiac reactive oxygen species (ROS) during I/R and hyperglycemic conditions remains unclear. Therefore, the objective of this study was to evaluate the cytoprotective effect of HS in primary cardiomyocyte cultures subjected to hyperglycemia, hypoxia-reoxygenation (HR), or both conditions, by assessing the PPAR-α/Keap1/Nrf2/p47phox/NOX4/p-eNOS/CAT/SOD and the PPAR-γ/PGC-1α/AMPK/GLUT4 signaling pathways. Treatment with NaHS (100 μM) as an HS donor in cardiomyocytes subjected to hyperglycemia, HR, or a combination of both increased cell viability, total antioxidant capacity, and tetrahydrobiopterin (BH) concentrations, while reducing ROS production, malondialdehyde concentrations, 8-hydroxy-2'-deoxyguanosine, and dihydrobiopterin (BH) concentrations. Additionally, the HS donor treatment increased the expression and activity of PPAR-α, reversed the reduction in the expression of PPAR-γ, PGC-1α, AMPK, GLUT4, Nrf2, p-eNOS, SOD, and CAT, and decreased the expression of Keap1, p47phox and NOX4. Therefore, the treatment with the HS donor protects cardiomyocytes from damage caused by hyperglycemia, HR, or both conditions by reducing oxidative stress markers and improving antioxidant mechanisms, thereby increasing cell viability and "cardiomyocyte ultrastructure".