Hypoxia Stimulates The Expression Of Connective Tissue Growth Factor Through P38 Signaling Pathway In Human Renal Interstitial Fibroblasts

Renal fibrosis is the final common way for almost all renal disease to progress into end-stage kidney disease (ESKD) , and tubulointerstitial fibrosis is an important factor to determine the outcome of renal function. Our previous studies and other documents had showed that the increased expression of CTGF in renal interstitium may play an important role in renal fibrogenesis, but the mechanisms by which enhance CTGF expression remains unclear. Recently some literatures indicated that chronic hypoxia in renal tubulointerstitium may be one of the important causes of renal interstitial fibrosis. We used HIF-1α as a marker of hypoxia, and to assess the expression of connective tissue growth factor(CTGF),and relevant signaling pathway for the regulation of CTGF by hypoxia in human renal interstitial fibroblast. Methods:A human renal interstitial fibroblast cell line TK173 was treated under hypoxia (l%02) or nomoxia (21%O2) condition. The expression of a hypoxia marker protein, HIFl-oc and CTGF protein was analysized by Western blotting. PT-PCR was carried out assess the level of CTGF mRNA. The activation of MAPKs (ERK, JNK, p38) signaling pathways were assessed in different time(30min, lh, 6h, 12h ) , and the changes of CTGF expression were detected after the inhibitors were applied, respectively. Results:1 The expression of HIF-loc protein was seen in hypoxic cells by 6h. The expressions of CTGF protein were up-regulated at 12h in TK173 cells by hypoxia, markedly increased at 24h compared with control group (normoxia) cells (2.09±0.14 vs control), kept increase until 48h.2 The levels of CTGF mRNA were elevated at lh, significantly increased at 6h ( 8.27+0.18 vs control). Activition of ERK1/2, JNK and p38 were seen in hypoxic cells. Activition of ERK 1/2 and JNK were occurred as early as lOmin, to the peak level at lh, while the peak level of activated JNK were seen at 30 min, then declined at 6h, back to baseline level at 12h.3 Blockade of ERK activation with PD98059, and blockade of JNK activation with SP600125 did not suppress hypoxia-induced expression of CTGF protein, whereas blockade of p38 MARK with SB203580 can abolished hypoxia-induced expression ofCTGF protein and mRNA. Conclusions:1 Hypoxia could stimulate the expression of CTGF in human renal interstitial fibroblast2 The increase in CTGF expression induced by hypoxia was through activation of p38 MARK signaling pathway, which CTGF may in turn contribute to renal interstitial fibrosis.