Inhibition Of Prolyl-tRNA Synthetase As A Novel Mediator Of Cardiac Fibrosis

Introduction: Prolyl-tRNA synthetase (PRS), a member of aminoacyl tRNA synthetases (ARS), is an enzyme that conjugates amino acid proline to its cognate tRNA to generate prolyl-tRNA to be used in protein synthesis. Since ARS are essential for protein synthesis and viability, dysregulation of ARS has been proposed to many human diseases. Cardiac fibrosis is characterized by excess production and deposition of ECM proteins by activated fibroblast. Although proline is a main component of collagen and ECM proteins, the exact mechanism and involvement of PRS in cardiac fibrosis has not yet been elucidated. Hypothesis: We hypothesized that suppression of PRS would down-regulate collagen synthesis, which could be beneficial in cardiac fibrosis. Results: To validate our hypothesis, we investigated the expression levels of pro-fibrotic markers by overexpression or knockdown of PRS in vitro. We showed that PRS is closely related to the expression of collagen I and α-SMA. Then, we showed that treatment of DWN12088, a novel small molecular selective inhibitor of PRS, reduced expression levels of pro-fibrotic markers in TGFβ-induced fibrotic environments using various cell-lines and primary fibroblasts. Interestingly, we showed that down-regulation of pro-fibrotic markers by DWN12088 is independent of TGFβ signaling pathway, although TGFβ is required for induction of pro-fibrotic markers. In vivo study, we performed transverse aortic constriction in C57BL/6 mice to evaluate the effect of DWN12088 in cardiac fibrosis. TAC results in pressure overload-induced left ventricular hypertrophy and fibrosis, and it is one of the most widely used models to study cardiovascular diseases. 2-week oral treatment of DWN12088 markedly reduced cardiac fibrosis with ED 50 of 0.4 mg/kg, based on histological examinations. In addition, we demonstrated that 2-week oral treatment of DWN12088 showed reduction in infiltration of inflammatory cells, left ventricle thickness and accumulation of collagen fiber. Conclusion: These results suggest that inhibition of PRS attenuates pressure-overloaded cardiac fibrosis and a selective inhibitor of PRS, DWN12088, could serve as a potent anti-fibrotic agent without affecting critical cellular signaling cascade.