Genoprotective effects of Chaga mushroom (Inonotus obliquus) polysaccharides in UVB-exposed embryonic zebrafish (Danio rerio) through coordinated expression of DNA repair genes

Background Chaga mushroom (Inonotus obliquus) is one of the most promising antioxidants with incredible health-promoting effects. Chaga polysaccharides (IOP) have been reported to enhance immune response and alleviate oxidative stress during development. However, the effects of IOP on the genotoxicity in model organisms are yet to be clarified. Methods Zebrafish embryos (12 hours post fertilization, hpf) were exposed to transient UVB (12 J/m 2 /s, 310 nm) for 10 secs using a UV hybridisation chamber, followed by IOP treatment (2.5 mg/mL) at 24 hpf for up to 7 days post fertilization (dpf). The genotoxic effects were assessed using acridine orange staining, alkaline comet assay, and qRT-PCR for screening DNA repair genes. Results We found significant reduction in DNA damage and amelioration of the deformed structures in the IOP-treated zebrafish exposed to UVB (p < 0.05) at 5 dpf and thereafter. In addition, the relative mRNA expressions of XRCC-5, XRCC-6, RAD51, P53, and GADD45 were significantly upregulated in the IOP-treated UVB-exposed zebrafish. Pathway analysis demonstrated coordinated regulation of DNA repair genes, suggesting collective response during UVB exposure. Conclusions Overall, IOP treatment ameliorated the genotoxic effects in UVB-exposed zebrafish embryos, which eventually assisted in normal development. The study suggested the efficacy of Chaga mushroom polysaccharides in mitigating UV-induced DNA damage.