Rhodojaponin II attenuates kidney injury by regulating TGF-β1/Smad pathway in mice with adriamycin nephropathy

Rhododendron molle G. Don (Ericaceae) (RM) is a natural medicinal plant. Its root extracts have been applied in clinic and proved to be effective in chronic glomerulonephritis and rheumatoid arthritis in China. Surprising, little is understood about the key compound of RM and the exact mechanisms underlying its treatment on kidney diseases. In this study, we will explore whether rhodojaponin II (R–II), as the important compound of RM, also exerts the major effect. Mouse model of focal segmental glomerulosclerosis was induced by single dose of adriamycin injection. Induced adriamycin nephropathy (ADRN) mice were treated individually with RM root extract (5 mg/kg, n = 5), RM root extract (60 mg/kg, n = 5), R–II (0.04 mg/kg, n = 6) or captopril (30 mg/kg, n = 5) for five weeks. Podocyte marker (nephrin and podocin) expressions were examined by immunohistochemical staining and Western Blot analysis. Fibronectin level was evaluated by immunohistochemical staining and Western Blot analysis. Interstitial infiltrated inflammatory cells (CD4+ T cells, CD8+ T cells, and CD68+ macrophages) were examined with immunohistochemical staining. The expressions of NF-ĸB p-p65 and TGF-β1/Smad pathway associated key proteins, such as TGF-β1, Smad3, phosphorylated-Smad3 (p-Smad3), and Smad7, were analyzed respectively by Western Blot analysis. RM root extract (5 mg/kg) and its important compound R–II (0.04 mg/kg) significantly ameliorated proteinuria, podocyte injury, and glomerulosclerosis, meanwhile, they hampered interstitial fibrosis in mice with ADRN. R–II significantly reduced NF-ĸB p65 phosphorylation, interstitial infiltrated CD4+ T cells, CD8+ T cells, and CD68+ macrophages, at the same time, down-regulated TGF-β1 and p-Smad3 protein expressions in mice with ADRN. RM root extract, R–II, could effectively ameliorate proteinuria and kidney injury in ADRN, related to its anti-inflammatory effects, as well as suppression of TGF-β1/Smad signaling pathway.