Human hepatic stellate cells secrete adrenomedullin: potential autocrine factor in the regulation of cell contractility.
OBJECTIVE
Hepatic stellate cells (HSCs) are perisinusoidal pericytes which have receptors for vasoactive factors, such as endothelin-1, which can regulate cell contractility in an autocrine manner. It is unknown whether human HSCs have receptors for and are able to synthesize the vasodilator peptide adrenomedullin (ADM), a peptide produced by most contractile cells.


RESULTS
Stimulation of HSCs with ADM resulted in a dose-dependent raise in cAMP concentration (radioimmunoassay) and markedly blunted the endothelin-induced increase in [Ca2+]i and cell contraction, as assessed in cells loaded with fura-2 using a morphometric method. The existence of the receptor CRLR for ADM and their associated proteins RAMP-1 and RAMP-2 was demonstrated by reverse transcriptase-polymerase chain reaction (RT-PCR). Moreover, activated human HSCs spontaneously secreted ADM in the culture medium in a time-dependent manner. ADM secretion was markedly enhanced by tumour necrosis factor-alpha and interleukin-1beta. Specific mRNA for ADM (RT-PCR and Northern blot) was detected in HSCs and increased after incubation of cells with cytokines.


CONCLUSIONS
Human HSCs have functional receptors for ADM, the stimulation of which blunts the contractile effect of endothelin-1. Cultured human HSCs secrete ADM in baseline conditions. This secretion is markedly increased by cytokines. These results suggest that ADM can regulate HSCs' contractility in an autocrine manner.
Institute of Digestive Diseases, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi-Sunyer, University of Barcelona School of Medicine, Catalonia, Spain.
M N
MN
Görbig
P
P
Ginès
R
R
Bataller
J M
JM
Nicolás
E
E
Garcia-Ramallo
P
P
Cejudo
P
P
Sancho-Bru
W
W
Jiménez
V
V
Arroyo
J
J
Rodés
D053607:Adrenomedullin; D058286:Calcitonin Receptor-Like Protein; D020013:Calcium Signaling / Q000187:drug effects; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D019332:Endothelin-1 / Q000494:pharmacology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D010455:Peptides / Q000378:metabolism* / Q000494:pharmacology; D058265:Receptors, Adrenomedullin; D018003:Receptors, Calcitonin / Q000378:metabolism; D018000:Receptors, Peptide / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
C545578:CALCRL protein, human; D058286:Calcitonin Receptor-Like Protein; D019332:Endothelin-1; D007375:Interleukin-1; D010455:Peptides; D058265:Receptors, Adrenomedullin; D018003:Receptors, Calcitonin; D018000:Receptors, Peptide; D014409:Tumor Necrosis Factor-alpha; D053607:Adrenomedullin; D000242:Cyclic AMP