Aldosterone stimulating PDGF-B expression in HSC via activation of EGR-1 / 中华肝脏病杂志

<p><b>OBJECTIVE</b>It is known that intrahepatic renin-angiotensin-aldosterone system (RAAS) plays a key role in liver fibrogenesis. Aldosterone (Aldo), the principal effector molecule of the RAAS, exerts local effects on cell growth and fibrogenesis. However, the signal transduction mechanisms underlying the effects of Aldo on hepatic fibrogenesis remain to be fully elucidated. The present study aims to investigate the signal transduction mechanism underlying the effects of Aldo on extracellular signal-regulated kinase 1/2 (ERK1/2), early growth response-1 (EGR-1) and on the platelet-derived growth factor-B (PDGF-B).</p><p><b>METHODS</b>In vitro, hepatic stellate cell (HSC)-T6 cell line was treated with Aldo for 10 min, 0.5 h, 1 h, 2 h and 3 h. Protein expression of phospho-p42/44 was detected by Western blot. In addition, HSC-T6 were preincubated for 1 h or not at all with U0126 (an inhibitor of the MAPK/ERK kinase), and antioxidant-N-acetylcysteine (NAC) prior to exposure to Aldo for the indicated times. Protein expressions of phospho-p42/44 and PDGF-B were measured by Western blot. DNA biding activity of EGR-1 was analyzed by electrophoretic gel mobility shift assay (EMSA). By means of immunohistochemistry, expression of PDGF-B was detected.</p><p><b>RESULTS</b>Aldo induced phospho-p42/44 expression could be abrogated by U0126; NAC did not inhibit phospho-p42/44 expression. Gel shift study showed that stimulation of HSC by Aldo markedly increased the EGR-1 DNA binding activity, which was abrogated by U0126, reaching a maximum at 60 minutes, and then declined progressively. NAC did not reduce the EGR-1 activity. Aldo increased the PDGF-B protein level in HSC, which was not attenuated by NAC and U0126.</p><p><b>CONCLUSIONS</b>Stimulation of HSC by Aldo results in activation of EGR-1 via ERK1/2 pathway, leading to up-regulation of PDGF-B expression.</p>

Aldosterone stimulates alpha1-(1) procollagen mRNA expression in HSC via activation of ERK1/2 and AP-1 / 中华肝脏病杂志

<p><b>OBJECTIVE</b>It has been known that the intrahepatic renin-angiotensin-aldosterone system (RAAS) plays a key role in the fibrogenesis in livers. Aldosterone (Aldo), the principal effector molecule of the RAAS, exerts local effects on cell growth and fibrogenesis. However, the signal transduction mechanisms underlying the effects of Aldo on hepatic fibrogenesis remain to be fully elucidated. The present study aims to investigate the signal transduction mechanism underlying the effects of Aldo on the signal passageway of active protein-1 (AP-1).</p><p><b>METHODS</b>In vitro, HSCs-T6 cell line was treated with Aldo for 10 min, 30 min, 60 min, 120 min and 180 min, and protein expression of Phospho-P42/44 was detected by Western blot. In addition, HSCs-T6 cell line was preincubated for 60 min or not with U0126 (an inhibitor of the MAPK/ERK kinase), and also with antioxidant-N-acetylcysteine (NAC) prior to exposure to Aldo for the indicated times. Protein expression of Phospho-P42/44 was measured by Western blot. DNA biding activity of AP-1 was analyzed by electrophoretic gel mobility shift assay (EMSA). By means of RT-PCR, expression of alpha1(1) procollagen mRNA was detected.</p><p><b>RESULTS</b>Aldo stimulated HSC via extracellular signal-regulated kinase (ERK1/2) pathway. Time course experiments showed that Aldo induced Phospho-P42/44 expression, which was abrogated by U0126, reaching a maximum at 10 minutes, and then declined progressively. NAC inhibited the Phospho-P42/44 expression. EMSA showed that stimulation of HSC by Aldo markedly increased AP-1 DNA binding activity. U0126 markedly reduced AP-1 DNA binding activity induced by Aldo; NAC partly decreased AP-1 activity induced by Aldo. Aldo up-regulated expression of alpha1(1) procollagen mRNA, which was attenuated by U0126 and NAC.</p><p><b>CONCLUSION</b>Stimulation of HSC by Aldo results in activation of AP-1 via ERK1/2 pathway, leading to up-regulation of AP-1 target gene alpha1(1) procollagen mRNA expression.</p>

Perindopril attenuates the progression of CCl4-inducing rat hepatic fibrosis / 中华肝脏病杂志

<p><b>OBJECTIVES</b>The aim of the present study was to determine the effects of angiotensin-converting enzyme inhibitor, perindopril, on the progression of rat hepatic fibrosis induced by CCl4.</p><p><b>METHODS</b>Male wistar rats weighting about 250g were treated with perindopril (2mg/kg, daily gavage), except for model group and control group. After 4, 6 weeks, morphological examination was based on microscopy. RT-PCR was utilized to detect gene expression of angiotensin II type 1 receptor (AT1 receptor) in the liver. Meanwhile, the protein expressions of AT1 receptor, transforming growth factor beta 1 (TGF-beta1) and platelet-derived growth factor-BB (PDGF-BB) in liver tissue were examined by Western blot. The activity of matrix metalloproteinase-2 (MMP-2) was assessed by zymography. Serum laminin (LN) and hyaluronic acid (HA) were measured using radio-immunity technique.</p><p><b>RESULTS</b>RT-PCR and Western blot revealed that there was a up-regulation in AT1 receptor expression in model group compared with control group. Perindopril treatment significantly reduced mean fibrosis score, messenger RNA and protein levels of AT1 receptor, protein levels of TGF-beta1 and PDGF-BB, Serum levels of HA and LN, and MMP-2 activity.</p><p><b>CONCLUSION</b>These results suggest that angiotensin II may play an important role in fibrosis of liver. Perindopril may have a inhibiting effect on CCl4-induced hepatic fibrogenesis of rat.</p>