Hypoxia Induces Connective Tissue Growth Factor (CTGF) in Cultured Tubular Cells / 대한신장학회잡지

ABSTRACT

BACKGROUND: Connective tissue growth factor (CTGF) is demonstrated to mediate the fibrotic effect of TGF-beta1 and to stimulate cell proliferation and matrix production. In the present study, we examined the effect of hypoxia on CTGF gene expression in cultured mouse tubular cell (MTC). METHODS: Quiescent cultures of MTC were exposed to hypoxia (1% O2) or normoxia in serum-free medium. The effects on hypoxia-induced CTGF expression were evaluated by Northern blot and real- time PCR. The role of MAP kinase was assessed using specific biochemical inhibitors. RESULTS: ELISA revealed that TGF-beta in conditioned medium by MTC exposed to hypoxia was maximally greater at 24 hours (41.16+/-6.31 ng/mL) than medium from normoxic cultures (15.742.92 ng/mL). Hypoxia caused a significant increase in CTGF mRNA expression in MTC (p<0.05). The steady-state level of CTGF mRNA was maximally up regulated by 3-fold within 4 hours as compared with the cells cultured under the normoxic condition. The induction of CTGF was not blocked by either JNK or ERK inhibitor, whereas an inhibitor of p38 MAP kinase reduced the hypoxia-induced stimulation of CTGF (p<0.05). Although hypoxia stimulated TGF-beta production, neutralizing anti-TGF-beta1 antibody did not abolish the hypoxia-induced CTGF mRNA expression. CONCLUSION: These data indicate that hypoxia up-regulates CTGF gene expression, and that p38 MAP kinase plays a role in hypoxic-stimulation of CTGF in cultured renal tubular cells. In addition, hypoxia induces CTGF mRNA expression via a TGF-beta1-independent mechanism.