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Background: Vascular fibrosis directly causes vascular thickening in Takayasu arteritis (TAK), in which sustained transforming growth factor beta (TGF-β) activation is critical. Understanding TGF-β activation regulation and blocking it might yield a therapeutic effect in TAK. Proprotein convertase subtilisin/kexin type 5 (PCSK5) rs6560480 (T/C) is associated with TAK development. In this study, we assessed the association between the PCSK5 rs6560480 genotype and PCSK5 expression in TAK and explored its molecular role in TGF-β activation and vascular fibrosis development., Methods: In TAK patients, PCSK5 and TGF-β expression in plasma and aortic tissue was examined by ELISA and immunohistochemical staining, and PCSK5 rs6560480 was genotyped. The correlation between PCSK5 and extracellular matrix (ECM) expression was examined by Western blotting (WB) and immunohistochemistry staining. Detection by co-immunoprecipitation was performed to detect the interaction between PCSK5 and TGF-β in adventitial fibroblasts (AAFs). Downstream signaling pathways were detected by WB and validated with appropriate inhibitors. Potential immunosuppressive agents to inhibit the effects of PCSK5 were explored in cell culture and TAK patients., Results: Patients with PCSK5 rs6560480 TT patients had significantly higher PCSK5 levels and more thickened vascular lesions than patients with PCSK5 rs6560480 CT. PCSK5 expression was significantly increased in alpha smooth muscle actin (α-SMA)-positive myofibroblasts in TAK vascular lesions. Overexpressing PCSK5 facilitated TGF-β and downstream SMAD2/3 activation and ECM expression in AAFs and aorta in in-vitro culture. The mechanistic study supported that PCSK5 activated precursor TGF-β (pro-TGF-β) to the mature form by binding the pro-TGF-β cleavage site. Leflunomide inhibited PCSK5 and pro-TGF-β binding, decreasing TGF-β activation and ECM expression, which was also partially validated in leflunomide-treated patients., Conclusion: The findings revealed a novel pro-fibrotic mechanism of PCSK5 in TAK vascular fibrosis via TGF-β and downstream SMAD2/3 pathway activation. Leflunomide might be anti-fibrotic by disrupting PCSK5 and pro-TGF-β binding, presenting a new TAK treatment approach., Competing Interests: Declaration of competing interest None., (Copyright © 2024. Published by Elsevier Ltd.)

Background: Autophagy is a ubiquitous and evolutionarily conserved self-rescue process. Studies have shown that autophagy is involved in the pathogenesis of multiple diseases; however, whether autophagy is associated with the pathogenesis of Takayasu's arteritis (TA), a large vessel idiopathic inflammatory disease characterized by vascular fibrosis, remains unclear. Moreover, although IL-6 is believed to be a direct target for TA treatment, anti-IL-6 treatment could not block TA-associated fibrosis in some cases, which impairs the aortic function of patients and can result in death. Thus, identify the mechanisms associated with TA is extremely important. Based on the relationship between autophagy and IL-6, we investigated the role of autophagy in the vascular fibrosis of TA induced by IL-6., Methods: Autophagy proteins (LC3 and Atg3), IL-6, and markers of fibrosis (collagen 1 and α-SMA) were detected in tissues with TA lesions via immunochemistry, immunofluorescence, and Western blot, respectively. Different stages of autophagy were analyzed by the specific inhibitors, 3-methyladenosine (early stage), hydroxychloroquine sulfate (late stage), and bafilomycin A1 (late stage). Autophagosomes were detected using electron microscopy and a viral-vector transfection assay. The fibrosis profiles induced by IL-6-dependent autophagy was assessed with an ELISA., Results: The expression of autophagy, IL-6, and fibrosis markers were elevated and correlated with each other in the adventitia tissues of TA patients. Furthermore, exogenous IL-6/IL-6Rα could significantly increase autophagy and fibrosis in vitro. An autophagy inhibitor was found to significantly block both autophagy and fibrosis induced by IL-6. Finally, IL-6 was found to significantly promote autophagy-induced fibrosis through the activation of the Jak1 pathway., Conclusions: IL-6-induced autophagy plays an important role in vascular fibrosis of TA. Targeting autophagy pathways might represent a novel therapeutic option for the treatment of TA., (Copyright © 2019 Elsevier Ltd. All rights reserved.)