Tomoaki Tomiya

Functional diversity between Rho-kinase- and MLCK-mediated cytoskeletal actions in a myofibroblast-like hepatic stellate cell line.

Using a rat myofibroblast-like hepatic stellate cell line, we studied the actomyosin-based cytoskeletal actions mediated by Rho-kinase and/or myosin light chain kinase (MLCK). Calmodulin/MLCK inhibitors W-7 and ML-7 attenuated cell migration dose-relatedly at concentrations from 10(-6) to 10(-4)M and collagen gel-contraction by the cells at 10(-4)M, respectively. Rho-kinase inhibitors Y-27632 and HA1077 attenuated the gel-contraction at concentrations from 10(-6) to 10(-4) M, respectively. These Rho-kinase inhibitors attenuated cell migration at 10(-7)M but enhanced the migration at 10(-4)M, respectively. They altered cell morphology showing prominent peripheral actin bundles and sparse central stress fibers, in comparison with the calmodulin/MLCK inhibitors. Both ML-7 and Y-27632 attenuated phosphorylation of myosin regulatory light chain and cell attachment to extracellular substrate. ML-7 attenuated the activation of GTP-binding protein Rac, while Y-27632 did not. These findings suggest that the actomyosin-based cytoskeletal actions can be functionally diverse depending on the Rho-kinase-mediated pathway and the MLCK-mediated pathway.

Leucine stimulates the secretion of hepatocyte growth factor by hepatic stellate cells

Branched-chain amino acids (BCAAs) modulate various cellular functions, in addition to providing substrates for the production of proteins. In this study, we examined the effect of BCAAs on the secretion of hepatocyte growth factor (HGF) by hepatic stellate cells. A hepatic stellate cell clone was cultured in medium supplemented with various concentrations of valine, leucine, or isoleucine. Of these BCAAs, leucine markedly induced an increase in the levels of HGF in the medium in a dose-dependent manner. The addition of valine or isoleucine had no significant effect on HGF levels in the medium. The difference in levels of HGF in the medium between leucine-treated and non-treated cells was enhanced by the incubation period. These results demonstrate that, among BCAAs, leucine stimulates the secretion of HGF by cultured hepatic stellate cells.

Activation of hepatic macrophage contributes to hepatic necrosis after post-ischemic reperfusion in alcoholic fatty liver

Fatty livers are vulnerable to ischemia/reperfusion (I/R) injury. We investigated the role of hepatic macrophages in the I/R injury in the fatty liver. Rats with alcoholic or nonalcoholic fatty liver were subjected to hepatic warm ischemia for 30 min. A bolus of gadolinium chloride (GdCl(3)) was injected intravenously twice before I/R to block hepatic macrophage activity. Alcoholic fatty liver developed more extensive hepatic necrosis with neutrophil infiltration in association with a higher production of cytokine-induced neutrophil chemoattractant (CINC)-1, a potent neutrophil chemokine in rat, after I/R than the nonalcoholic fatty liver or control liver without steatosis. Hepatic apoptosis after I/R increased to a similar degree (3-fold) in each of the two fatty liver models, compared with the control liver. Alcoholic fatty liver exposed to I/R showed a rapid increase in nuclear factor-kappa B (NF-kappaB) binding activity. The GdCl(3) pretreatment significantly reduced NF-kappaB binding activity, CINC-1 level and necrosis in alcoholic fatty liver, despite no significant decrease in the extent of apoptosis. Our results suggest that the activation of hepatic macrophages in alcoholic fatty liver may contribute to hepatic necrosis after I/R, and that the apoptosis might be less dependent on the macrophage activity.

HMG-COA reductase inhibitor modulates collagen GEL-contraction by hepatic myofibroblast-like stellate cell line: involvement of geranylgeranylated proteins

Department of Internal Medicine, Kawakita General Hospital, Tokyo, JapanEmail: Mikio Yanase* - yanase-1IM@h.u-tokyo.ac.jp; Hitoshi Ikeda- ikeda-1IM@h.u-tokyo.ac.jp; Atsushi Matsui - atsushim@saitama-med.ac.jp; Eisei Noiri - noiri-1IM@h.u-tokyo.ac.jp; Tomoaki Tomiya -tomiya-1IM@h.u-tokyo.ac.jp; Masahiro Arai - arai-1IM@h.u-tokyo.ac.jp; Yukiko Inoue - yanase-1IM@h.u-tokyo.ac.jp; Kazuaki Tejima - yanase-1I M@h.u-tokyo.ac.jp; Kayo Nagashima- yanase-1IM@h.u-tokyo.ac.jp; Takako Nishikawa - yanase-1IM@h.u-tokyo.ac.jp; Satoshi Kimura - yanase-1IM@h.u-tokyo.ac.jp; Kenji Fujiwara - yanase-1IM@h.u-tokyo.ac.jp; Marcos Rojkind - marcos.rojkind@na.amedd.army.mil; Itsuro Ogata - itsuro@viola.ocn.ne.jp* Corresponding author