Sanglifehrin A mitigates multiorgan fibrosis by targeting the collagen chaperone cyclophilin B.

Pathological deposition and crosslinking of collagen type I by activated myofibroblasts drives progressive tissue fibrosis. Therapies that inhibit collagen synthesis have potential as antifibrotic agents. We identify the collagen chaperone cyclophilin B as a major cellular target of the natural product sanglifehrin A (SfA) using photoaffinity labeling and chemical proteomics. Mechanistically, SfA inhibits and induces the secretion of cyclophilin B from the endoplasmic reticulum (ER) and prevents TGF-ß1-activated myofibroblasts from synthesizing and secreting collagen type I in vitro, without inducing ER stress or affecting collagen type I mRNA transcription, myofibroblast migration, contractility, or TGF-ß1 signaling. In vivo, SfA induced cyclophilin B secretion in preclinical models of fibrosis, thereby inhibiting collagen synthesis from fibrotic fibroblasts and mitigating the development of lung and skin fibrosis in mice. Ex vivo, SfA induces cyclophilin B secretion and inhibits collagen type I secretion from fibrotic human lung fibroblasts and samples from patients with idiopathic pulmonary fibrosis (IPF). Taken together, we provide chemical, molecular, functional, and translational evidence for demonstrating direct antifibrotic activities of SfA in preclinical and human ex vivo fibrotic models. Our results identify the cellular target of SfA, the collagen chaperone cyclophilin B, as a mechanistic target for the treatment of organ fibrosis.

Sanglifehrin A mitigates multi-organ fibrosis in vivo by inducing secretion of the collagen chaperone cyclophilin B.

Pathological deposition and crosslinking of collagen type I by activated myofibroblasts drives progressive tissue fibrosis. Therapies that inhibit collagen synthesis by myofibroblasts have clinical potential as anti-fibrotic agents. Lysine hydroxylation by the prolyl-3-hydroxylase complex, comprised of cartilage associated protein, prolyl 3-hydroxylase 1, and cyclophilin B, is essential for collagen type I crosslinking and formation of stable fibers. Here, we identify the collagen chaperone cyclophilin B as a major cellular target of the macrocyclic natural product sanglifehrin A (SfA) using photo-affinity labeling and chemical proteomics. Our studies reveal a unique mechanism of action in which SfA binding to cyclophilin B in the endoplasmic reticulum (ER) induces the secretion of cyclophilin B to the extracellular space, preventing TGF-ß1-activated myofibroblasts from synthesizing collagen type I in vitro without inhibiting collagen type I mRNA transcription or inducing ER stress. In addition, SfA prevents collagen type I secretion without affecting myofibroblast contractility or TGF-ß1 signaling. In vivo, we provide chemical, molecular, functional, and translational evidence that SfA mitigates the development of lung and skin fibrosis in mouse models by inducing cyclophilin B secretion, thereby inhibiting collagen synthesis from fibrotic fibroblasts in vivo . Consistent with these findings in preclinical models, SfA reduces collagen type I secretion from fibrotic human lung fibroblasts and precision cut lung slices from patients with idiopathic pulmonary fibrosis, a fatal fibrotic lung disease with limited therapeutic options. Our results identify the primary liganded target of SfA in cells, the collagen chaperone cyclophilin B, as a new mechanistic target for the treatment of organ fibrosis.