Pentoxifylline attenuates tubulointerstitial fibrosis by blocking Smad3/4-activated transcription and profibrogenic effects of connective tissue growth factor.
Pentoxifylline (PTX) is a potent inhibitor of connective tissue growth factor (CTGF), but its underlying mechanism is poorly understood. Here, it was demonstrated that PTX inhibited not only TGF-beta1-induced CTGF expression but also CTGF-induced collagen I (alpha1) [Col I (alpha1)] expression in normal rat kidney fibroblasts (NRK-49F) and alpha-smooth muscle actin expression in normal rat kidney proximal tubular epithelial cells (NRK-52E). Furthermore, PTX attenuated tubulointerstitial fibrosis, myofibroblasts accumulation, and expression of CTGF and Col I (alpha1) in unilateral ureteral obstruction kidneys. The mechanism by which PTX reduced CTGF in NRK-49F and NRK-52E was investigated. Activation of Smad3/4 was essential for TGF-beta1-induced CTGF transcription, but PTX did not interfere with TGF-beta1 signaling to Smad2/3 activation and association with Smad4 and their nuclear translocation. However, PTX was capable of blocking activation of TGF-beta1-induced Smad3/4-dependent reporter as well as CTGF promoter, suggesting that PTX affects a factor that acts cooperatively with Smad3/4 to execute transcriptional activation. It was found that PTX increased intracellular cAMP and caused cAMP response element binding protein phosphorylation. The protein kinase A antagonist H89 abolished the inhibitory effect of PTX on Smad3/4-dependent CTGF transcription, whereas dibutyryl cAMP and forskolin recapitulated the inhibitory effect. In conclusion, these results indicate that PTX inhibits CTGF expression by interfering with Smad3/4-dependent CTGF transcription through protein kinase A and blocks the profibrogenic effects of CTGF on renal cells. Because of the dual blockade, PTX potently attenuates the tubulointerstitial fibrosis in unilateral ureteral obstruction kidneys.
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Shuei-Liong
SL
Lin
Ruey-Hwa
RH
Chen
Yung-Ming
YM
Chen
Wen-Chih
WC
Chiang
Chun-Fu
CF
Lai
Kwan-Dun
KD
Wu
Tun-Jun
TJ
Tsai
D000199:Actins / Q000096:biosynthesis; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D024042:Collagen Type I / Q000096:biosynthesis; D055513:Connective Tissue Growth Factor; D005355:Fibrosis; D015870:Gene Expression / Q000187:drug effects; D017874:Immediate-Early Proteins / Q000235:genetics*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008954:Models, Biological; D010431:Pentoxifylline / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein / Q000378:metabolism*; D051901:Smad4 Protein / Q000378:metabolism*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D014517:Ureteral Obstruction / Q000473:pathology / Q000517:prevention & control
D000199:Actins; C526316:CCN2 protein, rat; D024042:Collagen Type I; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D051901:Smad4 Protein; C490811:Smad4 protein, rat; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D000804:Angiotensin II; D055513:Connective Tissue Growth Factor; D010431:Pentoxifylline