Aquaporin-1 promotes angiogenesis, fibrosis, and portal hypertension through mechanisms dependent on osmotically sensitive microRNAs.

Publication Type:

Journal Article

Source:

The American journal of pathology, Volume 179, Issue 4, p.1851-60 (2011)

Keywords:

Animalsdigestive disease, digestive deseases Aquaporin 1digestive disease, digestive deseases Base Sequencedigestive disease, digestive deseases Bile Ductsdigestive disease, digestive deseases Down-Regulationdigestive disease, digestive deseases Endothelial Cellsdigestive disease, digestive deseases Hypertension, Portaldigestive disease, digestive deseases Hypertonic Solutionsdigestive disease, digestive deseases Ligationdigestive disease, digestive deseases Liver Cirrhosisdigestive disease, digestive deseases Micedigestive disease, digestive deseases Mice, Knockoutdigestive disease, digestive deseases MicroRNAsdigestive disease, digestive deseases Molecular Sequence Datadigestive disease, digestive deseases Neovascularization, Pathologicdigestive disease, digestive deseases Osmosisdigestive disease, digestive deseases Protein Binding

Abstract:

Changes in hepatic vasculature accompany fibrogenesis, and targeting angiogenic molecules often attenuates fibrosis in animals. Aquaporin-1 (AQP1) is a water channel, overexpressed in cirrhosis, that promotes angiogenesis by enhancing endothelial invasion. The effect of AQP1 on fibrogenesis in vivo and the mechanisms driving AQP1 expression during cirrhosis remain unclear. The purpose of this study was to test the effect of AQP1 deletion in cirrhosis and explore mechanisms regulating AQP1. After bile duct ligation, wild-type mice overexpress AQP1 that colocalizes with vascular markers and sites of robust angiogenesis. AQP1 knockout mice demonstrated reduced angiogenesis compared with wild-type mice, as evidenced by immunostaining and endothelial invasion/proliferation in vitro. Fibrosis and portal hypertension were attenuated based on immunostaining, portal pressure, and spleen/body weight ratio. AQP1 protein, but not mRNA, was induced by hyperosmolality in vitro, suggesting post-transcriptional regulation. Endothelial cells from normal or cirrhotic mice were screened for microRNA (miR) expression using an array and a quantitative PCR. miR-666 and miR-708 targeted AQP1 mRNA and were decreased in cirrhosis and in cells exposed to hyperosmolality, suggesting that these miRs mediate osmolar changes via AQP1. Binding of the miRs to the untranslated region of AQP1 was assessed using luciferase assays. In conclusion, AQP1 promotes angiogenesis, fibrosis, and portal hypertension after bile duct ligation and is regulated by osmotically sensitive miRs.