Neuropilin-1 promotes cirrhosis of the rodent and human liver by enhancing PDGF/TGF-β signaling in hepatic stellate cells
Sheng Cao, … , Debabrata Mukhopadhyay, Vijay H. Shah
Sheng Cao, … , Debabrata Mukhopadhyay, Vijay H. Shah
Published June 23, 2010
Citation Information: J Clin Invest. 2010;120(7):2379-2394. https://doi.org/10.1172/JCI41203.
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Neuropilin-1 promotes cirrhosis of the rodent and human liver by enhancing PDGF/TGF-β signaling in hepatic stellate cells

Abstract

PDGF-dependent hepatic stellate cell (HSC) recruitment is an essential step in liver fibrosis and the sinusoidal vascular changes that accompany this process. However, the mechanisms that regulate PDGF signaling remain incompletely defined. Here, we found that in two rat models of liver fibrosis, the axonal guidance molecule neuropilin-1 (NRP-1) was upregulated in activated HSCs, which exhibit the highly motile myofibroblast phenotype. Additionally, NRP-1 colocalized with PDGF-receptor β (PDGFRβ) in HSCs both in the injury models and in human and rat HSC cell lines. In human HSCs, siRNA-mediated knockdown of NRP-1 attenuated PDGF-induced chemotaxis, while NRP-1 overexpression increased cell motility and TGF-β–dependent collagen production. Similarly, mouse HSCs genetically modified to lack NRP-1 displayed reduced motility in response to PDGF treatment. Immunoprecipitation and biochemical binding studies revealed that NRP-1 increased PDGF binding affinity for PDGFRβ-expressing cells and promoted downstream signaling. An NRP-1 neutralizing Ab ameliorated recruitment of HSCs, blocked liver fibrosis in a rat model of liver injury, and also attenuated VEGF responses in cultured liver endothelial cells. In addition, NRP-1 overexpression was observed in human specimens of liver cirrhosis caused by both hepatitis C and steatohepatitis. These studies reveal a role for NRP-1 as a modulator of multiple growth factor targets that regulate liver fibrosis and the vascular changes that accompany it and may have broad implications for liver cirrhosis and myofibroblast biology in a variety of other organ systems and disease conditions.

Authors

Sheng Cao, Usman Yaqoob, Amitava Das, Uday Shergill, Kumaravelu Jagavelu, Robert C. Huebert, Chittaranjan Routray, Soha Abdelmoneim, Meher Vasdev, Edward Leof, Michael Charlton, Ryan J. Watts, Debabrata Mukhopadhyay, Vijay H. Shah

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Figure 6

NRP-1 enhances PDGFRβ autophosphorylation and Rac1 activity.

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NRP-1 enhances PDGFRβ autophosphorylation and Rac1 activity. (A) hHSCs t...
(A) hHSCs transduced with NRP-1–RFP or RFP alone were stimulated with PDGF-BB (10 ng/ml) for various durations of time from 0 to 180 minutes. Cell lysates were subjected to Western blot analyses with indicated Abs. NRP-1 overexpression enhanced the duration and intensity of PDGFRβ autophosphorylation at Tyr857. (B) Rac1 activity assay was performed with LX2 cells transduced with NRP-1–RFP and RFP and treated with PDGF-BB in a time series of 0, 3, 10, and 60 minutes. Rac1 activation levels are increased in LX2 cells transduced with NRP-1–RFP treated with PDGF-BB compared with HSCs transduced with RFP alone in the absence of changes in total Rac1 protein levels (representative autoradiographs or Western blots are from 3 independent experiments). (C) Rac1 inhibition blocks NRP-1–induced increase in cell migration. Ad–NRP-1 or Ad-GFP was cotransduced with a retroviral dominant negative Rac1 (Rac1DN) or LacZ in HSCs. Cell migration was analyzed in the presence of either vehicle or PDGF. The boxed Western blot shows the overexpression of Rac1DN in the experimental compared with the control group. *P < 0.05.