Hypoxia induces connective tissue growth factor mRNA expression.
Connective tissue growth factor (CTGF) is known to be a profibrotic growth factor, which mediate the fibrotic effect of transforming growth factor-beta (TGF-beta) and to stimulate cell proliferation and matrix production. CTGF has been shown to be hypoxia-inducible in several cell types. Here we investigated the effect of hypoxia on CTGF gene expression in cultured mouse renal tubular cells (MTC). Quiescent cultures of MTC were exposed to hypoxia (1% O(2)) or normoxia in serum-free medium. The effects on hypoxia-induced CTGF expression were evaluated by Northern blot and real-time PCR. The roles of mitogen-activated protein kinase (MAPK) and TGF-beta were also determined using specific biochemical inhibitors. Exposure of quiescent tubular cells to hypoxia for 24 hr in a conditioned medium resulted in a significant increase TGF-beta. Hypoxia caused a significant increase in CTGF mRNA expression in MTC. Either JNK or ERK inhibitor did not block the hypoxia-induced stimulation of CTGF, whereas an inhibitor of p38 MAPK reduced the hypoxia-induced changes of CTGF. Although hypoxia stimulated TGF-beta production, neutralizing anti-TGF-beta1 antibody did not abolish the hypoxia-induced CTGF mRNA expression. The data suggest that hypoxia up-regulates CTGF gene expression, and that p38 MAPK plays a role in hypoxic-stimulation of CTGF. We also demonstrated that hypoxia induces CTGF mRNA expression via a TGF-beta1-independent mechanism.
Lee
Young Ki
YK
Department of Internal Medicine, Hallym University, Seoul, Korea.
Kim
Eun-Ji
EJ
Lee
Jung Eun
JE
Noh
Jung Woo
JW
Kim
Yoon-Goo
YG
D000818:Animals; D055513:Connective Tissue Growth Factor / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation; D000860:Hypoxia; D007668:Kidney / Q000378:metabolism; D007684:Kidney Tubules / Q000166:cytology; D020935:MAP Kinase Signaling System; D051379:Mice; D008954:Models, Biological; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism
D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor