Korean J Nephrol.  2005 Sep;24(5):729-738.

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

• Lee YK
• Kim EJ
• Kim YO
• Kim HJ
• Lee JE
• Huh WS
• Kim DJ
• Noh JW
• Oh HY
• Kim YG

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.

Keyword

Hypoxia; Connective tissue growth factor; TGF-beta; MAP kinase; Fibrosis

MeSH Terms

Animals
Anoxia*
Blotting, Northern
Cell Proliferation
Connective Tissue Growth Factor*
Connective Tissue*
Culture Media, Conditioned
Enzyme-Linked Immunosorbent Assay
Fibrosis
Gene Expression
Mice
p38 Mitogen-Activated Protein Kinases
Phosphotransferases
Polymerase Chain Reaction
RNA, Messenger
Transforming Growth Factor beta
Transforming Growth Factor beta1
Connective Tissue Growth Factor
Culture Media, Conditioned
Phosphotransferases
RNA, Messenger
Transforming Growth Factor beta
Transforming Growth Factor beta1
p38 Mitogen-Activated Protein Kinases