Differential expression of the C5a receptor on the main cell types of rat liver as demonstrated with a novel monoclonal antibody and by C5a anaphylatoxin-induced Ca2+ release.
The C5-anaphylatoxin (C5a) is a protein of 74 (human) or 77 (rat) amino acid residues, respectively, which is generated by limited proteolysis upon activation of the fifth component of complement. Its generation may be induced by both the classical and alternative pathways. C5a has been shown to indirectly increase glucose output from hepatocytes (HC) in perfused rat liver by inducing prostanoid release from Kupffer cells (KC) and hepatic stellate cells (HSC). A direct action of C5a on hepatocytes would require their expression of the specific C5a receptor (C5aR). In former studies using quantitative reverse transcription polymerase chain reaction (RT-PCR) it was shown that HC lack this receptor in contrast to KC, HSC and, probably, sinusoidal endothelial cells (SEC), all of which contained mRNA for the C5aR in decreasing amounts. Using a novel monoclonal antibody (mAb R63) against the rat receptor, expression of the rat receptor on the four cell types was investigated by FACS analysis, immunohistochemistry, and immunocytochemistry. The data obtained were confirmed by functional studies in which the Ca2+ response after stimulation of the isolated cells with recombinant rat C5a (rrC5a), the ligand for the receptor was recorded. The FACS and the immunocytochemical data presented here clearly indicate that rat HC do not express the C5aR, whereas KC have the highest expression level followed by HSC. SEC expressed the receptor only weakly. In line with these findings, a strong Ca2+ response was observed after stimulation of KC and HSC, and a weak one with SEC. However, no signal was obtained upon stimulation of HC. The results of this study support the indirect stimulation of glucose output from HC via prostanoid release from nonparenchymal liver cells and contradict the formerly proposed hypothesis of a direct action of C5 anaphylatoxin on hepatocytes.
Schlaf
G
G
Abteilung für Immunologie, Georg-August-Universität Göttingen, Germany.
Schieferdecker
H L
HL
Rothermel
E
E
Jungermann
K
K
Götze
O
O
D000706:Anaphylatoxins / Q000494:pharmacology*; D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002469:Cell Separation; D015936:Complement C5a; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005434:Flow Cytometry; D007150:Immunohistochemistry; D007728:Kupffer Cells / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical
D000706:Anaphylatoxins; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement; D015936:Complement C5a; D002118:Calcium