Aquaporin-1 Promotes Angiogenesis, Fibrosis, and Portal Hypertension Through Mechanisms Dependent on Osmotically Sensitive MicroRNAs

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.

Regulation of miR-101/miR-199a-3p by the epithelial sodium channel during embryo implantation: involvement of CREB phosphorylation

“…However, despite their recognized roles in embryo implantation, how the dynamic expression of miRNAs is controlled during implantation remains elusive. Although it has been reported that miRNAs are sensitive to environmental/extracellular cues, such as osmolality (Huebert et al 2011), pH (Lu et al 2012), and mechanical forces (Mohamed & Boriek 2010, Qin et al 2010, the exact mechanisms responsible for linking extracellular signals to changes in miRNAs are largely unexplored. Interestingly, as membrane proteins with signal transduction capacity, ion channels have been proposed to be candidate epigenetic regulators in linking extracellular signals to miRNA alterations in the cell .…”

Mechanisms and therapeutic potential of microRNAs in hypertension

“…In addition, Guo et al confirmed that miR-126 might be used in reducing intrahepatic vascular resistance and in improving hepatic microcirculation [143]. miR-666 and miR-708 influenced the post-transcriptional of aquaporin-1 and subsequently mediated osmolar changes to reverse angiogenesis, fibrosis and portal hypertension [144]. Nevertheless, the research and application of miRNAs directly on relieving portal hypertension have been rarely reported.…”

New Role for Kruppel-like Factor 14 as a Transcriptional Activator Involved in the Generation of Signaling Lipids

“…Human HEK 293 cells were grown in Dulbecco's modified Eagle's medium with 10% serum. Primary liver endothelial cells were obtained from C57Bl/6J and Klf14 Ϫ/Ϫ mice as previously described (19). Klf14 Ϫ/Ϫ mice were generated at the Mayo Transgenic and Gene Targeted Mouse Shared Resource facility using ES cells engineered by University of CA Davis Knock-out project to carry a 1035-bp deletion encompassing the complete, intronless, coding region of this gene.…”