Protection effects of rice protein hydrolysate on UVB-irradiated photodamage in Hartley guinea pigs skin and human skin fibroblasts

Abstract This study examined the ameliorative effects of rice protein hydrolysate (RPH) on UVB irradiation-induced photodamage in Hartley guinea pigs, particularly its influence on antioxidant indicators, moisture content, hydroxyproline (HYP) content and skin histopathology. The molecular mechanisms of RPH characteristic peptides Leu-Leu-Lys (LLK), Leu-Pro-Lys (LPK), and pyroGlu-Lys (pEK) were explored, and the results showed that RPH improved antioxidant capacity, prevented the loss of both water and HYP, and provided effective protection to the skin tissue. LPK and pEK increased the expression of type I collagen by regulating the AP-1/MMP-1 (pEK) and TGF-β/Smad (LPK) signaling pathways, with the LPK exhibiting the most significant effect. These findings indicate that RPH and its characteristic peptides can play vital roles in skin protection and, thus, this study provides a theoretical basis for RPH to become a novel, functional cosmetic ingredient.