Corneal Antifibrotic Switch Identified in Genetic and Pharmacological Deficiency of Vimentin

• Published in: The Journal of biological chemistry Vol. 287; no. 2; pp. 989 - 1006
• Main Authors: Bargagna-Mohan, Paola, Paranthan, Riya R., Hamza, Adel, Zhan, Chang-Guo, Lee, Do-Min, Kim, Kyung Bo, Lau, Daniel L., Srinivasan, Cidambi, Nakayama, Keiko, Nakayama, Keiichi I., Herrmann, Harald, Mohan, Royce
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 06.01.2012; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Cell Cycle; Cell Differentiation - drug effects; Cell Differentiation - genetics; Cell Proliferation - drug effects; Cornea - metabolism; Cornea - pathology; Corneal Diseases - drug therapy; Corneal Diseases - genetics; Corneal Diseases - metabolism; Corneal Diseases - pathology; Cytoskeleton; Desmin; Desmin - genetics; Desmin - metabolism; Drug Discovery; Fibrosis; Gene Expression Regulation - drug effects; Gene Expression Regulation - genetics; Humans; Mice; Mice, Knockout; Molecular Bases of Disease; Pharmacogenetics; S-Phase Kinase-Associated Proteins - genetics; S-Phase Kinase-Associated Proteins - metabolism; Skp2; Tissue Repair; Vimentin; Vimentin - antagonists & inhibitors; Vimentin - genetics; Vimentin - metabolism; Withaferin A; Withanolides - pharmacology; Wound Healing - drug effects; Wound Healing - genetics; Vimentin; Withaferin A; Pharmacogenetics; Tissue Repair; Cell Cycle; Fibrosis; Cytoskeleton; Drug Discovery; Skp2; Desmin
• DOI: 10.1074/jbc.M111.297150
• ISSN: 0021-9258

The type III intermediate filaments (IFs) are essential cytoskeletal elements of mechanosignal transduction and serve critical roles in tissue repair. Mice genetically deficient for the IF protein vimentin (Vim−/−) have impaired wound healing from deficits in myofibroblast development. We report a surprising finding made in Vim−/− mice that corneas are protected from fibrosis and instead promote regenerative healing after traumatic alkali injury. This reparative phenotype in Vim−/− corneas is strikingly recapitulated by the pharmacological agent withaferin A (WFA), a small molecule that binds to vimentin and down-regulates its injury-induced expression. Attenuation of corneal fibrosis by WFA is mediated by down-regulation of ubiquitin-conjugating E3 ligase Skp2 and up-regulation of cyclin-dependent kinase inhibitors p27Kip1 and p21Cip1. In cell culture models, WFA exerts G2/M cell cycle arrest in a p27Kip1- and Skp2-dependent manner. Finally, by developing a highly sensitive imaging method to measure corneal opacity, we identify a novel role for desmin overexpression in corneal haze. We demonstrate that desmin down-regulation by WFA via targeting the conserved WFA-ligand binding site shared among type III IFs promotes further improvement of corneal transparency without affecting cyclin-dependent kinase inhibitor levels in Vim−/− mice. This dissociates a direct role for desmin in corneal cell proliferation. Taken together, our findings illuminate a previously unappreciated pathogenic role for type III IF overexpression in corneal fibrotic conditions and also validate WFA as a powerful drug lead toward anti-fibrosis therapeutic development. Background: Withaferin A (WFA) is a vimentin-targeting inhibitor that has potent anti-proliferative activity. Results: WFA protects against corneal fibrosis by down-regulating injury-induced vimentin to exert epithelial cell cycle arrest and inhibit myofibroblast expression, which is a mechanism closely mimicked in vimentin-deficient mice during injury healing. Conclusion: Vimentin is a novel fibrosis target. Significance: Ocular fibrotic conditions that overexpress vimentin could be treatable with WFA.