Corneal blindness is the second leading cause of vision loss in the world. The exposed cornea is first to also become involved in ocular infections, chemical or blast injuries, and rapidly develops angiogenesis and fibrosis, which ultimately leads to scarring and corneal blindness. In the US alone, work-related eye injuries account for over 50,000 cases per year, while on the battlefield, US soldiers in Iraq and Afghanistan succumb to eye and face injuries at four times the rate of torso injuries. To tackle the prevailing enigma for angio-fibrotic drugs, we developed a high throughput screening platform for drug discovery, from which was borne out the pluripotent inhibitor withaferin A (WFA). A second innovative discovery, afforded by the chemical genetic approach, illuminated vimentin, a type III intermediate filament (IF) protein, as the binding target of WFA. Molecular modeling studies have unraveled the WFA-binding site in tetrameric vimentin and showed, for the first time, a highly conserved druggable site that is retained in members of type III IFs. This unprecedented molecular insight into IF-protein pharmacology combined with studies on target deficient (Vim KO) mice yielded vimentin as a critical regulator of the fibrotic switch. In this current proposed study, we will investigate the hypothesis that type III IF proteins are druggable targets for corneal anti- fibrosis. We will test three specific aims: (1) Activated corneal resident cells engage the corneal fibrotic switch cells by overexpressing vimentin. We will then validate the molecular mechanism of anti-fibrosis exerted by genetic and pharmacological downregulation of vimentin. Additionally, we plan to rescue mice from the ocular disease Aniridia, by inducing vimentin deficiency in these mice. (2) Investigate the role of desmin expression in corneal tissue repair, and demonstrate that desmin combines with vimentin to exacerbate corneal fibrosis and their coordinate downregulation by genetic or pharmacological means can improve corneal recovery after traumatic injury. (3) Develop WFA analogs with improved solubility for topical ocular treatment. Use of these novel WFA analogs will enhance our understanding of therapeutic modalities for WFA-based drug development and the rational to target type III IFs in corneal fibrosis.
There are no available FDA-approved drugs to inhibit scarring. We recently identified the first chemical inhibitor of type III IFs that downregulates these targets in ocular fibrosis and gliosis, which are the central pathogenic mechanisms that cause scarring and blindness in humans. The goal of this project is to advance the clinical development of WFA by validating its molecular targets in pre-clinical animal studies. PUBLIC HEALTH RELEVANCE: We have discovered a small molecule that targets vimentin and desmin, two critical type III intermediate filament proteins implicated in corneal fibrosis. Here we will validate that vimentin and desmin are novel druggable targets for fibrosis and we will develop novel drug analogs for corneal traumatic injuries.
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|Bargagna-Mohan, Paola; Lei, Ling; Thompson, Alexis et al. (2015) Vimentin Phosphorylation Underlies Myofibroblast Sensitivity to Withaferin A In Vitro and during Corneal Fibrosis. PLoS One 10:e0133399|
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