SMAD2 and pulmonary fibrosis: Moreover, trichocarboline A, a β-carboline alkaloid from the deep-sea fungus Trichoderma MCCC 3A01244 (Hao et al., 2022), was further tested to found to reduce pulmonary fibrosis by downregulating Smad2 and Smad3 phosphorylation, thereby directly inhibiting TGF-β/Smad signal transduction in human lung fibroblast cell lines (HFL1).