Background: Ganoderma lucidum  (G. lucidum ) is one of China’s traditional medicinal materials. G. lucidum  polysaccharide has a wide range of promising pharmacological applications. However, there are many kinds of G. lucidum  and they contain different kinds of polysaccharides. The biological mechanism through which Ganoderma lucidum  polysaccharides (GLP) is able to protect human skin fibroblasts (HSFs) from H₂O₂-induced oxidative damage is still unclear.
Methods: Six polysaccharides were obtained from G. lucidum  to evaluate their free radical scavenging ability (DPPH free radical, ABTS free radical, hydroxyl-free radical, superoxide anion-free radical) in vitro, and their protective and reparative effects on oxidative damage induced by H₂O₂ in human skin fibroblasts. One polysaccharide was selected to detect oxidative damage markers and gene expression in the Keap1-Nrf2/ARE signaling pathway in HSFs.
Results: All six polysaccharides showed the ability to scavenge free radicals and enhance the tolerance of human skin fibroblasts to H2O2 damage. Among them, GLP1 was selected and separated into two components (GLP1I and GLP1II). The results showed that GLP1, GLP1I and GLPII could significantly reduce the levels of reactive oxygen species (ROS) and malondialdehyde (MDA). The protective effect of GLP1II was stronger than that of positive control vitamin C. In addition, GLP1, GLP1I and GLP1II could significantly increase the levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). And GLP1I works best in both ways. Meanwhile, Nrf2, a key regulator of keAP1-NRF2/ARE signaling pathway, was activated, while Keap1, a negative regulator, was inhibited, thus promoting the expression of downstream antioxidant enzyme genes (GSTs, GCLs, Nqo1, and Ho-1).
Conclusion: The results showed that GLP could protect human skin fibroblasts from oxidative damage caused by H₂O₂ peroxide by enhancing enzyme activity and activating Keap1-Nrf2/ARE signaling pathway. GLP will act as a natural antioxidant to protect the skin from oxidative stress damage.
Keywords: Ganoderma lucidum , polysaccharide, oxidative stress, Keap1-Nrf2/ARE signaling pathway