RESUMO
OBJECTIVE: To investigate the effects of cAMP-response element binding protein-1 (CREB-1) on transforming growth factor-b3 (TGF b3) mRNA expression and promoter activity in hepatic stellate cells (HSCs). METHODS: Freshly isolated HSCs from rats were divided into six groups: CREB-1 expression plasmid transfected group (C), siRNA-CREB-1 plasmid transfected group (S), negative control group (N), forskolin treated group (F), H-89 treated group (H), and blank group (B). Rats in each group were further sub-divided according to whether (+) or not (-) they were exposed to exogenous TGF b3. TGF b3 mRNA expression was measured by real time quantitative PCR. HSCs of the C, S, N, F, H and B groups were transfected with the TGF b3 promoter luciferase reporter plasmid (PGL3-TGF b3-P; W group), the TGF b3 promoter luciferase reporter plasmid with CRE mutation (PGL3-basic-TGF b3P-mCRE; M group) and the renilla luciferase control plasmid (pRL-SV40; control group). TGF b3 promoter activity was assessed by luciferase reporter assays. RESULTS: Compared to N(-), the TGF b3 mRNA expression was reduced to 0.69+/-0.15 in S(-) (P less than 0.05) and increased to 4.68+/-2.76 in C(-) (P more than 0.05). Compared to B(-), the TGF b3 mRNA expression was reduced to 0.57+/-0.08 in H(-) (P less than 0.05). The differences between N(+) and N(-), S(+) and S(-), B(+) and B(-), and H(+) and H(-) were all significant (P less than 0.05). The values of TGF b3 promoter activity in S(W), N(W), and C(W) were 0.062+/-0.013, 0.122+/-0.011, and 0.165+/-0.016 (P less than 0.05), but the changes of TGF b3 promoter activity in S(M), N(M), and C(M) were not significant (P more than 0.05). The values of TGF b3 promoter activity in H(W), B(W), and F(W) were 0.154+/-0.010, 0.188+/-0.016, and 0.276+/-0.031 (P less than 0.05), but the changes of TGF b3 promoter activity in H(M), B(M), and F(M) were not significant (P more than 0.05). CONCLUSION: Increased levels of CREB-1 mRNA or p-CREB-1 up-regulate the TGF b3 mRNA expression and promoter activity in rat HSCs. The CRE site in the TGF b3 promoter is critical for this effect, and the gene's activity becomes significantly decreased when the site is missing. Exogenous TGF b3 enhances expression of endogenous TGF b3 in rat HSCs.