Adenoviral transfer of human aquaporin -1 gene to rat liver improves bile flow in estrogen-induced cholestasis

Abstract

Estrogens can cause liver cholestatic disease. As downregulation of hepatocyte canalicular aquaporin-8 (AQP8) water channels has been involved in estrogen-induced bile secretory failure, we tested whether the archetypal water channel AQP1 improves 17α-ethinylestradiol (EE)-induced cholestasis. EE administration to rats reduced bile flow by 50%. A recombinant adenoviral (Ad) vector encoding human AQP1 (hAQP1), AdhAQP1, or a control vector was administered by retrograde bile ductal infusion. Hepatocyte canalicular hAQP1 expression was confirmed by liver immunostaining and immunoblotting in purified membrane fractions. Accordingly, canalicular osmotic water permeability was markedly increased. Bile flow, either basal or bile salt-stimulated was significantly augmented by over 50%. The choleretic efficiency of endogenous bile salts (that is, volume of bile per μmol of excreted bile salt) was significantly increased by 45% without changes in the biliary bile salt composition. Our data suggest that the adenoviral transfer of hAQP1 gene to the livers of EE-induced cholestatic rats improves bile flow by enhancing the AQP-mediated bile salt-induced canalicular water secretion. This novel finding might have potential therapeutic implications for cholestatic diseases.

Hepatic gene transfer of human aquaporin‐1 improves bile salt secretory failure in rats with estrogen‐induced cholestasis

“…After the procedure was completed, the catheter was gently removed, the duodenal puncture and abdominal wall were sutured, and the animal was allowed to recover. Initial experiments indicated that the protein expression of hAQP1 in hepatocytes takes 72 hours . Thus, the experiments were performed 72 hours after adenoviral infusion (i.e., on the sixth day after starting EE treatment).…”

“…The gene transfer of the archetypal human aquaporin‐1 (hAQP1) water channel through the adenoviral vector encoding hAQP1 (AdhAQP1) has been successfully used to restore normal salivary flow to irradiated hypofunctional salivary glands in experimental animals and humans . We have recently provided evidence suggesting that the adenoviral transfer of hAQP1 gene to livers of EE‐induced cholestatic rats improves bile flow, at least in part by enhancing the canalicular hAQP1‐mediated osmotic water secretion . In an effort to fully understand the mechanisms involved in the hAQP1‐induced improvement of estrogen‐induced cholestasis, we further studied the biliary output of BS and the functional expression of BSEP.…”

Aquaporin gene therapy for cholestasis

“…(1) We thank the authors for their comments in our recent studies. (2,3) Nevertheless, we believe that an analysis of the role of aquaporins (AQPs) in hepatocyte canalicular water transport and bile secretion should take into account several published contributions that were not cited in the editorial.…”

“…Nevertheless, the retrograde biliary vector administration allowed that most of the periportal hepatocytes were transduced with AQP1. (2,3) This is relevant because periportal hepatocytes are exposed to the highest blood concentrations of bile salts and thus are the primary cells involved in bile-salt-dependent bile secretion.…”

“…Nevertheless, the retrograde biliary vector administration allowed that most of the periportal hepatocytes were transduced with AQP1. (2,3) This is relevant because periportal hepatocytes are exposed to the highest blood concentrations of bile salts and thus are the primary cells involved in bile-salt-dependent bile secretion.We think it may be premature to judge whether the hepatic gene transfer of AQPs is a credible approach for treatment of cholestasis. We anticipate that further studies will clarify its impact as a novel therapeutic strategy.…”