Photoprotective effects of <i>Caulerpa lentillifera</i> extract against UV-induced cellular damage via Nrf2 activation and MMP inhibition

Caulerpa lentillifera is an edible green seaweed widely consumed in Southeast Asia and has been recognized for its nutritional and antioxidant properties. Previous studies demonstrated that its ethyl acetate extract (CLEA) exhibits strong free radical-scavenging and metabolic regulatory activities; however, its potential protective role against ultraviolet (UV)-induced oxidative stress has not yet been elucidated. Therefore, this study aimed to evaluate the photoprotective effects of CLEA on UV-induced cellular damage in keratinocytes (HaCaT) and fibroblasts (L929), and explore its underlying mechanisms. The results revealed that CLEA significantly improved cell viability following UV irradiation and attenuated intracellular reactive oxygen species (ROS) accumulation in both keratinocytes and fibroblasts. Mechanistically, CLEA enhanced nuclear translocation of nuclear factor erythroid 2–related factor 2 (Nrf2) and upregulated the mRNA expression of downstream antioxidant enzymes, particularly heme oxygenase-1 (HMOX1). In addition, CLEA suppressed UV-induced expression of matrix metalloproteinases, MMP1 and MMP3, while promoting procollagen synthesis, suggesting its role in preserving skin integrity. Collectively, these findings suggest that CLEA confers photoprotective effects against UV-induced oxidative stress and extracellular matrix degradation through activation of the Nrf2/HMOX1 pathway and inhibition of MMPs. This study highlights the potential of C. lentillifera extract as a natural photoprotective agent, warranting further in vivo and clinical investigations to validate its efficacy and safety.