Cholera toxin-sensitive GTP-binding protein-coupled activation of augmenter of liver regeneration (ALR) receptor and its function in rat kupffer cells.
Mitogenic effect of augmenter of liver regeneration (ALR), a protein produced and released by hepatocytes, on hepatocytes in vivo but not in vitro suggests that the effect is mediated by nonparenchymal cells. Since mediators produced by Kupffer cells are implicated in hepatic regeneration, we investigated receptor for ALR and its functions in rat Kupffer cells. Kupffer cells were isolated from rat liver by enzymatic digestion and centrifugal elutriation. Radioligand ([(125)I] ALR) receptor binding, ALR-induced GTP/G-protein association, and nitric oxide (NO), tumor necrosis factor (TNF)-alpha, and interleukin-6 (IL-6) synthesis were determined. High-affinity receptor for ALR, belonging to the G-protein family, with K(d) of 1.25 +/- 0.18 nM and B(max) of 0.26 +/- 0.02 fmol/microg DNA was identified. ALR stimulated NO, TNF-alpha, and IL-6 synthesis via cholera toxin-sensitive G-protein, as well as p38-MAPK activity and nuclear translocation of NFkappaB. While inhibitor of NFkappaB (MG132) inhibited ALR-induced NO synthesis, MG132 and p38-MAPK inhibitor (SB203580) abrogated ALR-induced TNF-alpha and IL-6 synthesis. ALR also prevented the release of mediator(s) from Kupffer cells that cause inhibition of DNA synthesis in hepatocytes. Administration of ALR to 40% partially hepatectomized rats increased expression of TNF-alpha, IL-6, and inducible nitric oxide synthase (iNOS) and caused augmentation of hepatic regeneration. These results demonstrate specific G-protein coupled binding of ALR and its function in Kupffer cells and suggest that mediators produced by ALR-stimulated Kupffer cells may elicit physiologically important effects on hepatocytes.
VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, USA. gandhics@msx.upmc.edu
Chandrashekhar R
CR
Gandhi
Noriko
N
Murase
Thomas E
TE
Starzl
D000818:Animals; D049109:Cell Proliferation; D002772:Cholera Toxin / Q000494:pharmacology*; D006498:Hepatectomy; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism; D007728:Kupffer Cells / Q000187:drug effects / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000601:surgery; D008115:Liver Regeneration / Q000187:drug effects; D008297:Male; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D019899:Paracrine Communication; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011917:Rats, Inbred Lew; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D050862:Oxidoreductases Acting on Sulfur Group Donors
D002772:Cholera Toxin; D007093:Imidazoles; D015850:Interleukin-6; D007976:Leupeptins; D016328:NF-kappa B; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D047428:Protein Kinase Inhibitors; D011506:Proteins; D011725:Pyridines; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; C088825:GFER protein, rat; D050862:Oxidoreductases Acting on Sulfur Group Donors; C496318:Nos2 protein, rat; C093642:SB 203580; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde