SHUEI-LIONG LINChen R.-H.YUNG-MING CHENWEN-CHIH CHIANGCHUN-FU LAIKWAN-DUN WUTUN-JUN TSAI2021-05-022021-05-0220051046-6673https://www.scopus.com/inward/record.uri?eid=2-s2.0-31744440775&doi=10.1681%2fASN.2005040435&partnerID=40&md5=46eb45f44950d0ba61c1abd08d9574cchttps://scholars.lib.ntu.edu.tw/handle/123456789/558493Pentoxifylline (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-β1-induced CTGF expression but also CTGF-induced collagen I (α1) [Col I (α1)] expression in normal rat kidney fibroblasts (NRK-49F) and α-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 (α1) 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-β1-induced CTGF transcription, but PTX did not interfere with TGF-β1 signaling to Smad2/3 activation and association with Smad4 and their nuclear translocation. However, PTX was capable of blocking activation of TGF-β1-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. Copyright ? 2005 by the American Society of Nephrology.[SDGs]SDG3alpha smooth muscle actin; bucladesine; cancer growth factor; collagen type 1; collagen type 1 alpha; connective tissue growth factor; cyclic AMP; cyclic AMP dependent protein kinase inhibitor; forskolin; pentoxifylline; Smad3 protein; Smad4 protein; unclassified drug; actin; angiotensin II; immediate early protein; Madh3 protein, rat; Madh4 protein, rat; signal peptide; Smad3 protein; Smad4 protein; Tgfb1 protein, rat; transforming growth factor beta; transforming growth factor beta1; animal cell; animal experiment; article; drug antagonism; drug inhibition; drug mechanism; gene expression; kidney artery stenosis; kidney epithelium; kidney fibrosis; male; myofibroblast; nonhuman; priority journal; protein binding; protein phosphorylation; rat; animal; biological model; biosynthesis; cell line; drug effect; fibrosis; genetics; kidney; metabolism; pathology; signal transduction; transactivation; ureter obstruction; Wistar rat; Actins; Angiotensin II; Animals; Cell Line; Collagen Type I; Fibrosis; Gene Expression; Immediate-Early Proteins; Intercellular Signaling Peptides and Proteins; Kidney; Male; Models, Biological; Pentoxifylline; Rats; Rats, Wistar; Signal Transduction; Smad3 Protein; Smad4 Protein; Trans-Activation (Genetics); Transforming Growth Factor beta; Transforming Growth Factor beta1; Ureteral Obstructionjournal article10.1681/ASN.2005040435159877462-s2.0-31744440775