Photoprotective potential of Cordyceps polysaccharides against ultraviolet B radiation-induced DNA damage to human skin cells

Abstract

Ultraviolet (UV) radiation causes DNA damage resulting in photoageing and skin cancer. UVB (290-320 nm) interacts directly with DNA, inducing two major photoproducts: cyclobutane-pyrimidine dimers (CPDs) and (6-4) pyrimidine-pyrimidone photoproducts. Cordyceps sinensis (Berk.) Sacc. is a medicinal fungus with reported anticancer and cytoprotective effects. To investigate genoprotective effects of polysaccharide-rich Cordyceps mycelial components against UVB-induced damage in normal human fibroblast cells. Cultured human fibroblasts (BJ cells) were treated for 30 min and, separately, for 24 h with hot water extract of Cordyceps fungal mycelia or exopolysaccharides. Cells were washed, irradiated with UVB (302 nm), and immediately lysed, after which DNA damage, as strand breaks, was measured using an enzyme-assisted comet assay that detects CPDs. DNA damage in UVB-irradiated cells was significantly lowered (P < 0·01) with Cordyceps pretreatment. Similar results were seen with 30 min and 24 h pretreatment. Specifically, and in comparison with irradiated cells with no Cordyceps pretreatment, there was a 27% reduction in CPDs in irradiated cells with 24 h pretreatment with 200 μg mL(-1) of the hot water Cordyceps extract, and a 34% reduction with 24 h pretreatment with 200 μg mL(-1) of the exopolysaccharide extract. Clear evidence of protection against UVB-induced CPDs was seen with Cordyceps mycelial extracts. Results indicate that Cordyceps may offer photoprotection and lower the risk of basal cell carcinoma, the main skin cancer caused by CPDs. Further study is needed to identify protective mechanisms.