Prostaglandin E2 induces contraction of liver myofibroblasts by activating EP3 and FP prostanoid receptors.
OBJECTIVE
Increased portal pressure in liver injury results from hypercontraction of perivascular non-parenchymal cells including liver myofibroblasts (MFs). Prostaglandin E2 (PGE2) is the major eicosanoid which is released around the venous system during liver injury, but little is known about their contractile effect on MFs.


METHODS
Contraction of primary rat liver MFs was measured by a collagen gel contraction assay. Expression of E prostanoid (EP) receptor subtypes was assessed by reverse transcription-polymerase chain reaction. Fura-2 fluorescence was used to determine intracellular Ca2+ concentration ([Ca2+](i)). Phosphorylation of protein kinase C (PKC) was detected by Western blot analysis.


RESULTS
Liver MFs expressed mRNAs for all four EP receptors. PGE2 induced contraction in a dose- and time-dependent manner, and slightly increased [Ca2+](i) only at high concentrations (10 micromol.L(-1)). An agonist selective for EP(3) receptors, ONO-AE-248, dose-dependently induced MF contraction but did not increase [Ca2+](i). Pretreatment with rottlerin (a specific novel PKC inhibitor) and Ro 31-8425 (a general PKC inhibitor) significantly reduced 1 micromol.L(-1) PGE(2)- or ONO-AE-248-induced contractions. Furthermore, 1 micromol.L(-1) PGE(2) stimulated phosphorylation of PKC isoforms PKCdelta and PKCepsilon. The F prostanoid (FP) receptor antagonist AL8810 abolished the [Ca(2+)](i) elevation and the rapid contraction induced by 10 micromol.L(-1) PGE2.


CONCLUSIONS
Lower concentrations up to 1 micromol.L(-1) of PGE2 induce liver MF contraction via a [Ca2+](i)-independent PKC-mediated pathway through the EP(3) receptor, while higher concentrations have an additional pathway leading to Ca(2+)-dependent contraction through activating the FP receptor.
Ayabe
S
S
Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan.
Murata
T
T
Maruyama
T
T
Hori
M
M
Ozaki
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism; D048429:Cell Size; D002470:Cell Survival; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology / Q000502:physiology*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008099:Liver / Q000166:cytology*; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011982:Receptors, Prostaglandin / Q000819:agonists* / Q000096:biosynthesis; D018078:Receptors, Prostaglandin E / Q000819:agonists* / Q000096:biosynthesis; D058308:Receptors, Prostaglandin E, EP3 Subtype
D007527:Isoenzymes; C545649:Ptger3 protein, rat; D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D058308:Receptors, Prostaglandin E, EP3 Subtype; C034671:prostaglandin F2alpha receptor; D011493:Protein Kinase C; D015232:Dinoprostone; D002118:Calcium