1.NO is a broadly acting and uniquely characterized signaling molecule, whose diverse effects are primarily determined by its concentration and target binding sites.

2.Skin cells express all three types of nitric oxide synthase (NOS): neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS). nNOS and eNOS are calcium-dependent and constitutively expressed, whereas iNOS is calcium-independent and inducible.

3.Skin problems associated with aging may result from cellular damage caused by excessive NO, while low, physiological levels of NO can actually be beneficial to the skin.

4.At physiological concentrations, NO participates in the regulation of cutaneous blood circulation, supports skin barrier repair, accelerates wound healing, promotes the expression of collagen and fibronectin, and inhibits the degradation of the extracellular matrix (ECM).