Effect and mechanism of astragaloside Ⅳ on Toll-like receptor pathway in fibrotic mice after renal ischemia-reperfusion

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The aim of this paper is to study the effect of astragaloside Ⅳ on renal fibrosis mice with ischemia-reperfusion injury (IRI) and discuss the mechanism. Male C57BL/6 50 mice were randomly divided into four groups, namely Sham-operated group, model group, AS-Ⅳ prevention group and AS-Ⅳ treatment group. Since the day of surgery, the mice in astragaloside Ⅳ prevention group were treated with astragaloside Ⅳ by gavage for 30 days at the dose of 30 mg·kg⁻¹·d⁻¹. At the 60th day after surgery, the mice in astragaloside Ⅳ treatment group were treated with astragaloside Ⅳ 100 by gavage for 30 days at the dose of 30 mg·kg⁻¹·d⁻¹. The mice in Sham-operated group and model group were treated with double distilled water containing 0.1% ethanol instead of astragaloside Ⅳ. Serum creatinine and blood urea nitrogen were detected by chemical methods. Histopathological changes and collagen deposition of affected kidneys were observed under optical microscope by HE and Masson staining. The expression levels of Toll like receptor pathway related molecules (TLR4,MyD88,TRAF6,TRAM,TRIF,NF-κB,TNF-α,IL-6, IFN-γ) in affected kidneys were observed by immunohistochemistry, Western blot methods and reverse transcription-PCR atprotein and mRNA levels in each group. The results showed that the degrees of fibrosis and histopathological damage of affected kidneys of mice in model group were the most obvious. And the expression levels of TLR4/MyD88 dependent signaling pathway-related molecules (TLR4 and MyD88, TRAF6 and NF-κB) in affected kidneys of mice in model group were the highest. At the same time, there was no difference in the expression levels of TLR4/MyD88 independent signaling pathway-related molecules（TRAM, TRIF）among sham-operated group, model group, astragaloside IV prevention group and astragaloside Ⅳ treatment group. In astragaloside Ⅳ prevention group and astragaloside Ⅳ treatment group, the injury of affected kidney was obviously reduced, and the protein expression levels of TLR4/MyD88 dependent signaling pathway-related molecules were also correspondingly reduced; at the same time, the expressions of terminal inflammatory cytokines (TNF-α,IL-6, IFN-γ) were suppressed. Therefore, astragaloside Ⅳ may improve renal interstitial fibrosis in mice after IRI by inhibiting the expression of TLR4/MyD88 dependent signaling pathway and the release of inflammatory cytokines (TNF-α,IL-6, IFN-γ), while the TLR4/MyD88 independent signaling pathway may not be involved in the process of renal fibrosis after ischemia-reperfusion injury.