[Effect of ERK/AP-1 signaling pathway on proliferation of hepatoma cells induced by PAR-2 agonists].
OBJECTIVE
To investigate the expression of protease activated receptor-2 (PAR-2) in human HepG2 hepatoma cells and elucidate the effects of trypsin and PAR-2 agonist peptide SLIGKV-NH(2) upon the proliferation of hepatoma cells and its intracellular signaling mechanism.


METHODS
PAR-2 protein and mRNA expression were detected by immunofluorescence and RT-PCR. The cells were treated with SLIGKV-NH(2), trypsin, reverse PAR-2 agonist peptide VKGILS-NH(2) or PD98059. The changes of cell cycle distribution were evaluated by flow cytometry. The proliferative potential of HepG2 cells was estimated by MTT. The changes of PAR-2, c-fos and PCNA mRNA expression were detected by RT-PCR. The changes of c-fos and PCNA protein expression were detected by Western blotting.


RESULTS
PAR-2 protein and mRNA were expressed in HepG2 cells. PAR-2 mRNA expression (PAR-2/beta-actin) were 0.70 +/- 0.04 and 0.99 +/- 0.05 respectively in cells treated with trypsin and SLIGKV-NH(2). They were both significantly higher than that in the control group (0.35 +/- 0.05, F = 135.534, P < 0.01). Percent G(0)/G(1) phase of HepG2 cells treated with trypsin or SLIGKV-NH(2) were significantly lower than those in the control group [(56.11 +/- 0.85)%, (57.85 +/- 0.46)% vs (79.12 +/- 0.67)%, both P < 0.01] Percent S phase, G(2)/M phase and proliferation index (PI) of HepG2 cells treated with trypsin or SLIGKV-NH(2) were significantly elevated (P < 0.01). The proliferation-enhancing effects and the up-regulation of mRNA and protein of c-fos and PCNA induced by trypsin or SLIGKV-NH(2) were significantly blocked by pretreatment with PD98059 (P < 0.01). There was no statistical significance in proliferation of HepG2 cells between the reverse PAR-2 agonist peptide VKGILS-NH(2) and control group (P > 0.05).


CONCLUSIONS
PAR-2 is expressed in HepG2 hepatoma cells. PAR-2 activation induced by trypsin or SLIGKV-NH(2) promotes the proliferation of HepG2 cells partially via the ERK/AP-1 pathway.
Zheng
Yan-min
YM
Department of Gastroenterology, Affiliated Hospital, Medical College of Chinese People's Armed Police Forces, Tianjin 300162, China.
Xie
Li-qun
LQ
Li
Xuan
X
Zhao
Jun-yan
JY
Chen
Xiao-yi
XY
Chen
Li
L
Zhou
Jing
J
Li
Fei
F
D049109:Cell Proliferation; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D044464:Receptor, PAR-2 / Q000819:agonists / Q000378:metabolism*; D044462:Receptors, Proteinase-Activated / Q000378:metabolism; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism
D044464:Receptor, PAR-2; D044462:Receptors, Proteinase-Activated; D018808:Transcription Factor AP-1; D014357:Trypsin