Inhibition of the Na+/H+ exchanger reduces rat hepatic stellate cell activity and liver fibrosis: An in vitro and in vivo study

Background & Aims: The Na+/H+ exchanger is the main intracellular pH (pH(i) ) regulator in hepatic stellate cells (HSCs) and plays a key role in regula ting proliferation and gene expression. We evaluated the effect of specific inhibition of this exchanger on HSC proliferation and collagen synthesis i n vivo and in vitro. Methods: Rat HSCs were incubated in the presence of pl atelet-derived growth factor (PDGF), transforming growth factor (TGF)-beta1 iron ascorbate (FeAsc), and ferric nitrilotriacetate solution (FeNTA) with or without the Na+/H+ exchanger inhibitor 5-N-ethyl-N-isopropyl-amiloride (EIPA). pH(i) and Na+/H+ exchanger activity, cell proliferation, and type I collagen accumulation were measured by using the fluorescent dye 2',7'-bis -(carboxyethyl)-5(6)-carboxyfluorescein, by immunohistochemistry for bromod eoxyuridine, and by enzyme-linked immunosorbent assay, respectively. In viv o liver fibrosis was induced by dimethylnitrosamine administration and bile duct ligation (BDL) in vats treated or not treated with amiloride. Results : PDGF, FeAsc, and FeNTA increased Na+/H+ exchange activity and induced HSC proliferation. TGF-beta1 had no effect on the Na+/H+ exchanger and was abl e, as for FeAsc and FeNTA, to induce type I collagen accumulation. EIPA inh ibited all the effects determined by PDGF, FeAsc, and FeNTA and had no effe ct on TGF-beta1-induced collagen accumulation. In vivo, amiloride reduced H SC proliferation, activation, collagen deposition, and collagen synthesis. Conclusions: The Na+/H+ exchanger can play a key role in the development of liver fibrosis and in HSC activation in vivo.