Anti-inflammatory effects of Ganoderma lucidum sterols via attenuation of the p38 MAPK and NF-κB pathways in LPS-induced RAW 264.7 macrophages

Ganoderma lucidum exhibits pronounced anti-inflammatory effects, polysaccharides and triterpenoids are regarded as major constituents displaying the anti-inflammatory activities, whether sterols contribute to this activity remains unclear. Herein Ganoderma lucidum sterols (GLS) were innovatively isolated by a single-step procedure, the profile of GLS was characterized by HPLC-ELSD and shown similar to that of sterols separated by a traditional method, but much higher in content. Furthermore, GLS inhibited inflammation in macrophages by significantly attenuating LPS-induced cell polarization as well as releases and mRNA expressions of pro-inflammatory mediators NO, TNF-α, IL-1β and IL-6. Moreover, the anti-inflammatory activity of GLS was mediated by MAPK and NF-κB pathways, GLS suppressed MAPK pathways by blocking phosphorylation of p38 but not ERK and JNK, which is complementary with inhibitory effects of Ganoderma polysaccharides and triterpenes on JNK and ERK, indicating Ganoderma sterols may exert synergistic anti-inflammatory effect with polysaccharides and triterpenes. GLS also inhibited NF-κB pathways by restraining phosphorylation and degradation of IκB-α and blocking phosphorylation of NF-κB p65. Molecular docking confirmed that sterols of GLS were directly bound to active sites of p38 and p65 to suppress their activation. Therefore, our findings suggest GLS as natural and safe anti-inflammatory agents to prevent and treat inflammatory diseases.