C-Peptide Ameliorates Particulate Matter 2.5-Induced Skin Cell Apoptosis by Inhibiting NADPH Oxidation.

Connecting peptide (C-peptide), a byproduct of insulin biosynthesis, has diverse cellular and biological functions. Particulate matter 2.5 (PM) adversely affects human skin, leading to skin thickening, wrinkle formation, skin aging, and inflammation. This study aimed to investigate the protective effects of C-peptide against PM-induced damage to skin cells, focusing on oxidative stress as a key mechanism. C-peptide mitigated NADPH oxidation and intracellular reactive oxygen species (ROS) production induced by PM. It also suppressed PM-induced NADPH oxidase (NOX) activity and alleviated PM-induced NOX1 and NOX4 expression. C-peptide protected against PM-induced DNA damage, lipid peroxidation, and protein carbonylation. Additionally, C-peptide mitigated PM-induced apoptosis by inhibiting intracellular ROS production. In summary, our findings suggest that C-peptide mitigates PM-induced apoptosis in human HaCaT keratinocytes by inhibiting intracellular ROS production and NOX activity.