A novel dibenzofuran from endophytic fungus Mycosphaerella nawae preferentially inhibits CD4+ T cell activation and proliferation

Abstract

Abstract Aim To obtain promising immunosuppressants from endophytic fungus. Methods and Results The endophytic fungus Mycosphaerella nawae (ZJLQ129) was isolated from the plant Smilax china L. and its secondary metabolites extracted and fractionated through column chromatography. The metabolites were further modified by a derivatization reaction with ammonium hydroxide. After isolation and derivatization, a new dibenzofuran named as (+)isomycousnine enamine (iME) was obtained. The structures of the derivatives were determined based on chemical evidences and extensive spectroscopic methods including 2D-NMR, DEPT and HRESI-MS spectra. The immune activities of iME were first evaluated on the proliferation and cytokines (IL-2 and IFN-γ) production of T and B cells by using MTT and ELISA methods respectively. Then, its effects on the proliferation of T-cell subsets (CD4+ and CD8+ T cells), as well as CD25 and CD69 expressions were also determined by flow cytometry. Finally, by using Cytometric Bead Array (CBA), the impacts of iME on the secretion of Th1/Th2/Th17 cytokines from purified CD4+ T cells were assayed. The results showed that iME not only selectively suppressed the immune responses of T cells, but also preferentially inhibited the activation and proliferation of CD4+ T cells. Conclusion A novel dibenzofuran derived from endophytic fungus Mycosphaerella nawae preferentially inhibits CD4+ T-cell activation and proliferation. Significance and Impact of the Study This work obtained iME, a new dibenzofuran derived from endophytic fungus. iME has the capacity to inhibit CD4+ T-cell activation and therefore is a novel potential immunosuppressant for development in the future.