Enhanced antioxidant properties of sericin-cecropin fusion protein against oxidative stress in human adult dermal fibroblasts

Chronic exposure to UVB radiation causes photoaging, immunosuppression, and ultimately photocarcinogenisis through the generation of reactive oxygen species (ROS). The ability of natural compounds in neutralizing the effects of oxidative stress is being explored with increased interest. Silk sericin, a biopolymer is reported to have diverse biological properties. In an effort to make the silk sericin pure, more effective and multifunctional, we have recombinantly expressed both functional sericin as well as sericin-cecropin B fusion proteins. Herein, we studied the antioxidant and anti-UVB potential of recombinant sericin and sericin-cecropin B proteins against oxidative stress using human primary dermal fibroblast cells. Treating the cells with recombinant sericin (RS) or sericin-cecropin B (RSC) prior to exposure to UVB and H₂O₂, effectively increased the cell viability by approximately 30% and 50%, respectively, in comparison to non-treated control. The protective effects were further evident in terms of significant reduction of LDH in oxidatively challenged cells treated with RS and RSC. A reduction in LDH release of at least 16 and 33% was observed with RS and RSC treatments, respectively, in comparison to exposed control. Further, elevated levels of catalase and superoxide dismutase (SOD) activity were observed. Importantly, the RSC fusion protein exhibited enhanced protective effects than cells treated with RS alone. Our results demonstrate that the functional attributes of cecropin B along with sericin activity in the fusion protein conferred enhanced protection against UVB- and H₂O₂-induced oxidative damage in human dermal fibroblasts. The improved antioxidant activity of recombinant sericin fusion biopolymer has great potential as a promising therapeutic agent for ROS-induced skin diseases.