This study was designed to evaluate the protective effect of CPD1, a novel phosphodiesterase 5 inhibitor, on renal interstitial fibrosis after unilateral renal ischemia-reperfusion injury (UIRI). Male BALB/c mice were subjected to UIRI, and treated with CPD1 once daily (i.g, 5 mg/kg). Contralateral nephrectomy was performed on day 10 after UIRI, and the UIRI kidneys were harvested on day 11. Hematoxylin-eosin (HE), Masson trichrome and Sirius Red staining methods were used to observe the renal tissue structural lesions and fibrosis. Immunohistochemical staining and Western blot were used to detect the expression of proteins related to fibrosis. HE, Sirius Red and Masson trichrome staining showed that CPD1-treated UIRI mice had lower extent of tubular epithelial cell injury and deposition of extracellular matrix (ECM) in renal interstitium compared with those in the fibrotic mouse kidneys. The results from immunohistochemistry and Western blot assay indicated significantly decreased protein expressions of type I collagen, fibronectin, plasminogen activator inhibitor-1 (PAI-1) and α-smooth muscle actin (α-SMA) after CPD1 treatment. In addition, CPD1 dose-dependently inhibited the expression of ECM-related proteins induced by transforming growth factor β1 (TGF-β1) in normal rat kidney interstitial fibroblasts (NRK-49F) and human renal tubular epithelial cell line (HK-2). In summary, the novel PDE inhibitor, CPD1, displays strong protective effects against UIRI and fibrosis by suppressing TGF-β signaling pathway and regulating the balance between ECM synthesis and degradation through PAI-1.

中文翻译：

---

[新型磷酸二酯酶 5 抑制剂 CPD1 对单侧肾缺血再灌注损伤后肾间质纤维化的影响]。

本研究旨在评估新型磷酸二酯酶 5 抑制剂 CPD1 对单侧肾缺血再灌注损伤 (UIRI) 后肾间质纤维化的保护作用。对雄性 BALB/c 小鼠进行 UIRI，并每天用 CPD1 治疗一次（ig，5 mg/kg）。UIRI后第10天行对侧肾切除术，第11天取UIRI肾脏。采用苏木精-伊红（HE）、马松三色和天狼星红染色法观察肾组织结构病变及纤维化情况。采用免疫组化染色和Western blot检测纤维化相关蛋白的表达。他，天狼星红和马森三色染色显示，与纤维化小鼠肾脏相比，CPD1 处理的 UIRI 小鼠肾间质中肾小管上皮细胞损伤和细胞外基质 (ECM) 沉积程度较低。免疫组织化学和蛋白质印迹试验的结果表明，在 CPD1 处理后，I 型胶原蛋白、纤连蛋白、纤溶酶原激活物抑制剂-1 (PAI-1) 和 α-平滑肌肌动蛋白 (α-SMA) 的蛋白表达显着降低。此外，CPD1 剂量依赖性地抑制正常大鼠肾间质成纤维细胞 (NRK-49F) 和人肾小管上皮细胞系 (HK-2) 中转化生长因子 β1 (TGF-β1) 诱导的 ECM 相关蛋白的表达。总之，新型 PDE 抑制剂 CPD1，