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.
Lin
Shuei-Liong
SL
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Chen
Ruey-Hwa
RH
Chen
Yung-Ming
YM
Chiang
Wen-Chih
WC
Lai
Chun-Fu
CF
Wu
Kwan-Dun
KD
Tsai
Tun-Jun
TJ
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