Autophagy regulates endothelial dysfunction and hepatic fibrosis development

Background: Endothelial dysfunction (ED), one of the first changes occurring after liver injury, precedes hepatic fibrosis and regulates hepatic stellate cell (HSC) activation. The regulatory pathways of ED are still not fully... [ view full abstract ]

Background: Endothelial dysfunction (ED), one of the first changes occurring after liver injury, precedes hepatic fibrosis and regulates hepatic stellate cell (HSC) activation. The regulatory pathways of ED are still not fully understood. Autophagy is essential for cellular homeostasis and efficient response to stress, but its role in ED is not known. We investigated whether defects in LSEC autophagy contribute to amplify hepatic injury. Methods: autophagy (LC3, P62, flow) and endothelial phenotype markers (eNOS, iNOS, CD31, VEGFR2, endothelin-1) were evaluated in primary LSEC from control, fibrotic (CCl₄ip 4w) and early- cirrhotic (CCl₄ ip 6w) rats. Autophagy was induced (rapamycin) and inhibited (3MA&cloroquine) in control LSEC and impact on LSEC phenotype was evaluated. HSC were cultivated with LSEC-conditioned medium where autophagy was manipulated and fibrogenic markers (alpha-sma, collagen-alphaI, pdgfr-beta) were assessed. Results: LSEC culture induced autophagy levels that declined after 48h, overlapping LSEC phenotype greatest change. Fibrotic LSEC showed increased autophagy. However if injury persists, autophagy decreases coinciding with the onset of cirrhosis, suggesting inability of dysfunctional LSEC to increase autophagy and restrict fibrosis progression. These results suggest that autophagy regulates ED in vitro and in vivo. Autophagy-deficient LSEC exhibited accelerated ED, whereas autophagy-overexpression ameliorated LSEC phenotype. LSEC-conditioned media with autophagy inhibition promoted HSC activation whereas HSC cultivated with LSEC media with autophagy upregulation were more quiescent. This suggests that manipulating endothelial autophagy impacts on ED and liver fibrosis. Conclusion: Autophagy regulates ED and could contribute to development of fibrosis. Induction of endothelial autophagy could be used for antifibrotic therapy.