Neuropilin-1 Aggravates Liver Cirrhosis by Promoting Angiogenesis Via VEGFR2-Dependent PI3K/Akt Pathway in Hepatic Sinusoidal Endothelial Cells

Abstract

Liver fibrosis is a common liver injury characterized by excessive extracellular matrix deposition and increased intrahepatic angiogenesis. We have revealed that neuropilin-1(NRP-1) promoted hepatic stellate cell activation and liver fibrosis through its profibrogenic signaling pathways, PDGF/TGF-β. However, the role of NRP-1 in intrahepatic angiogenesis in hepatic sinusoidal endothelial cells (HSECs) during liver cirrhosis remains unclear. In this study, higher expression of NRP-1 in HSECs was detected in both human and murine cirrhotic liver tissues by immunohistochemical staining, quantitative real-time PCR and western blot assays. Interestingly, we found that the expression of NRP-1 was positively correlated with the expression of VEGFR2 and CD31 in liver cirrhosis. In vitro, the role of NRP-1 in regulating VEGFR2-dependent intrahepatic angiogenesis was identified in endothelial cells (ECs). NRP-1 knockdown suppressed the expression and activation of VEGFR2, accompanied by reduced ability of angiogenesis and migration of ECs. On the contrary, NRP-1 over-expression in ECs upregulated VEGFR2 expression and activation, promoted tube formation and migration of ECs. Mechanistically, NRP-1 modulated the expression of VEGFR2 by regulating FAK and its kinase activity. Furthermore, NRP-1 promoted VEGFR2-dependent angiogenesis via PI3K/Akt pathway in HSECs. Blocking NRP-1 function suppressed neoangiogenesis in HSECs, and reduced intrahepatic angiogenesis and fibrosis associated factors in vitro liver histoculture. In conclusion, NRP-1 promotes intrahepatic angiogenesis by upregulating the expression and activation of VEGFR2 through PI3K/Akt signaling pathway in liver cirrhosis. This study highlights the possibility of therapeutically targeting NRP-1 for the treatment of cirrhosis. Funding: This work was supported by funds from National Natural Science Foundation of China (No. 81570551; 81770607; 81600469; 81401868), Key Research project of Shandong Province (No. 2016GSF201008; 2017GSF218053), Natural Science Foundation of Shandong Province (No. ZR2017MH102), National Science and Technology Major Project of China (No. 2018ZX10302206-001-006) Declaration of Interest: The authors do not have a commercial or other association with pharmaceutical companies or other parties that might pose a conflict of interest. Ethical Approval: All procedures were approved by the Ethics Committee of Shandong Provincial Hospital Affiliated to Shandong University (Jinan, China).