title: Both Ca2+ -dependent and -independent pathways are involved in rat hepatic stellate cell contraction and intrahepatic hyperresponsiveness to methoxamine.
abstract: In chronic liver injury, hepatic stellate cells (HSCs) have been implicated as regulators of sinusoidal vascular tone. We studied the relative role of Ca(2+)-dependent and Ca(2+)-independent contraction pathways in rat HSCs and correlated these findings to in situ perfused cirrhotic rat livers. Contraction of primary rat HSCs was studied by a stress-relaxed collagen lattice model. Dose-response curves to the Ca(2+) ionophore A-23187 and to the calmodulin/myosin light chain kinase inhibitor W-7 served to study Ca(2+)-dependent pathways. Y-27632, staurosporin, and calyculin (inhibitors of Rho kinase, protein kinase C, and myosin light chain phosphatase, respectively) were used to investigate Ca(2+)-independent pathways. The actomyosin interaction, the common end target, was inhibited by 2,3-butanedione monoxime. Additionally, the effects of W-7, Y-27632, and staurosporin on intrahepatic vascular resistance were evaluated by in situ perfusion of normal and thioacetamide-treated cirrhotic rat livers stimulated with methoxamine (n = 25 each). In vitro, HSC contraction was shown to be actomyosin based with a regulating role for both Ca(2+)-dependent and -independent pathways. Although the former seem important, an important auxiliary role for the latter was illustrated through their involvement in the phenomenon of "Ca(2+) sensitization." In vivo, preincubation of cirrhotic livers with Y-27632 (10(-4) M) and staurosporin (25 nM), more than with W-7 (10(-4) M), significantly reduced the hyperresponsiveness to methoxamine (10(-4) M) by -66.8 +/- 1.3%, -52.4 +/- 2.7%, and -28.7 +/- 2.8%, respectively, whereas in normal livers this was significantly less: -43.1 +/- 4.2%, -40.2 +/- 4.2%, and -3.8 +/- 6.3%, respectively. Taken together, these results suggest that HSC contraction is based on both Ca(2+)-dependent and -independent pathways, which were shown to be upregulated in the perfused cirrhotic liver, with a predominance of Ca(2+)-independent pathways.
authors.affiliation: Dept of Hepatology, Univ Hospital Gasthuisberg, K U Leuven, Leuven, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Laleman
authors.forename: Lien
authors.initials: L
authors.lastname: Van Landeghem
authors.forename: Tamara
authors.initials: T
authors.lastname: Severi
authors.forename: Ingrid
authors.initials: I
authors.lastname: Vander Elst
authors.forename: Marcel
authors.initials: M
authors.lastname: Zeegers
authors.forename: Raf
authors.initials: R
authors.lastname: Bisschops
authors.forename: Jos
authors.initials: J
authors.lastname: Van Pelt
authors.forename: Tania
authors.initials: T
authors.lastname: Roskams
authors.forename: David
authors.initials: D
authors.lastname: Cassiman
authors.forename: Johan
authors.initials: J
authors.lastname: Fevery
authors.forename: Frederik
authors.initials: F
authors.lastname: Nevens
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D048430:Cell Shape / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D008297:Male; D008387:Marine Toxins; D008729:Methoxamine / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010080:Oxazoles / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D013449:Sulfonamides; D014662:Vasoconstrictor Agents; C108830:Y 27632; C004717:diacetylmonoxime; D000001:Calcimycin; C017967:W 7; C059041:calyculin A; D000205:Actomyosin; D009219:Myosin-Light-Chain Kinase; D019311:Staurosporine; D008729:Methoxamine; D003931:Diacetyl; D002118:Calcium