Pentoxifylline attenuates tubulointerstitial fibrosis by blocking Smad3/4-activated transcription and profibrogenic effects of connective tissue growth factor
Pentoxifylline attenuates tubulointerstitial fibrosis by blocking Smad3/4-activated transcription and profibrogenic effects of connective tissue growth factor
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DOI：
10.1681/asn.2005040435
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发表时间：
2005-09-01
影响因子：
13.6
通讯作者：
Tsai, TJ
中科院分区：
文献类型：
--
作者：
Lin, SL;Chen, RH;Tsai, TJ
戊茶碱（PTX）是一种有效的结缔组织生长因子（CTGF）抑制剂，但其潜在的机制知之甚少。在此，证明PTX不仅抑制TGF-β 1诱导的CTGF表达，而且抑制CTGF诱导的正常大鼠肾成纤维细胞（NRK-49 F）中的胶原I（α 1）[Col I（α 1）]表达和正常大鼠肾近端小管上皮细胞（NRK-52 E）中的α-平滑肌肌动蛋白表达。此外，PTX减弱了单侧输尿管梗阻肾中的肾小管间质纤维化、肌成纤维细胞积聚以及CTGF和Col I（α 1）的表达。研究了PTX减少NRK-49 F和NRK-52 E中CTGF的机制。Smad 3/4的激活是TGF-β 1诱导CTGF转录所必需的，但PTX并不干扰TGF-β 1信号传导至Smad 2/3的激活以及与Smad 4的关联及其核转位。然而，PTX能够阻断TGF-β 1诱导的Smad 3/4依赖性报告基因以及CTGF启动子的激活，表明PTX影响与Smad 3/4协同作用以执行转录激活的因子。结果发现，PTX增加细胞内cAMP，并引起cAMP反应元件结合蛋白磷酸化。蛋白激酶A拮抗剂H89可阻断PTX对Smad 3/4依赖性CTGF转录的抑制作用，而双丁酰cAMP和forskolin则可阻断PTX对Smad 3/4依赖性CTGF转录的抑制作用。总之，这些结果表明，PTX抑制CTGF的表达，通过干扰Smad 3/4依赖性CTGF转录通过蛋白激酶A和阻断CTGF对肾细胞的促纤维化作用。由于双重阻断，PTX可有效减轻单侧输尿管梗阻肾的肾小管间质纤维化。
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-beta 1-induced CTGF expression but also CTGF-induced collagen I (alpha 1) [Col I (alpha 1)] 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 (alpha 1) 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-beta 1-induced CTGF transcription, but PTX did not interfere with TGF-beta 1 signaling to Smad2/3 activation and association with Smad4 and their nuclear translocation. However, PTX was capable of blocking activation of TGF-beta 1-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.