Effect of astragaloside IV on indoxyl sulfate-induced kidney injury in mice via attenuation of oxidative stress

Abstract

Background: Astragalus membranaceus, a traditional Chinese medicine (TCM), has been widely used in the treatment of chronic kidney disease (CKD) in China. Astragaloside IV is one of the major compounds of Astragalus membranaceus. Recent research has shown that astragaloside IV demonstrates pharmacological effects, such as anti-inflammatory, anti-fibrotic and anti-oxidative stress activities. Our aim was to investigate the effects of astragaloside IV on indoxyl sulfate (IS)-induced kidney injury in vivo, and to study the underlying mechanism.

Methods: Forty C57BL/6 mice with ½ nephrectomy were divided into four groups: control group (n = 10), IS group (n = 10), IS plus 10 mg/kg of astragaloside IV group (n = 10) and IS plus 20 mg/kg of astragaloside IV group (n = 10). IS intraperitoneal injection and astragaloside IV treatment were administered continuously for 1 month. Next, the blood urea nitrogen (BUN) level, serum IS level, tubulointerstitial injury, renal oxidative stress and inflammatory injury were assessed.

Results: The IS intraperitoneal injection mouse group showed increasing levels of serum IS, BUN, tubulointerstitial injury, renal oxidative stress and inflammatory injury. Astragaloside IV treatment couldn't reduce the serum IS level or renal nuclear factor-κB and interleukin-1β levels. However, 20 mg/kg astragaloside IV treatment reduced the BUN level and significantly attenuated IS-induced tubulointerstitial injury. Renal oxidative stress was decreased by the administration of astragaloside IV.

Conclusions: These results suggest that astragaloside IV prevents IS-induced tubulointerstitial injury by ameliorating oxidative stress and may be a promising agent for the treatment of uremia toxin-induced injury.

Keywords: Astragaloside IV; IS; Oxidative stress; Tubulointerstitial injury.

Fig. 1

Serum levels of indoxyl sulfate. The serum indoxyl sulfate concentration of mice was detected by high-performance liquid chromatography (HPLC) tandem mass spectrometry. Data were presented as means ± SE. **P < 0.001 vs. control group. IS: indoxyl sulfate. ASIV: astragaloside IV

Fig. 2

Serum levels of blood urea nitrogen (BUN). IS: indoxyl sulfate. ASIV: astragaloside IV. **P < 0.001 vs. control group. ^#P = 0.048 vs. IS group

Fig. 3

Representative histopathology in IS intraperitoneal injection mice treated with or without astragaloside IV (HE staining). IS intraperitoneal injection mice showed partial tubular epithelial cell degeneration, loss of the brush border, enlargement of the tubular lumen and interstitial expansion. a: control group; b: IS group; c: IS plus 10 mg/kg astragaloside IV treatment group; d: IS plus 20 mg/kg astragaloside IV treatment group

Fig. 4

Expression levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and nuclear factor (NF)-κB in frozen sections of kidney. Localization of 8-OHdG and NF-κB in frozen sections was determined by immunofluorescence (IF) (× 200) with 8-OHdG antibody (green) and NF-κB ant (red)

Fig. 5

Expression of NF-κB and cytochrome C in kidney tissue. Western blot analysis of the NF-κB and cytochrome C protein levels. a Representative western blot of NF-κB and cytochrome C in control and IS mice treated with or without astragaloside IV. b The data was shown as ratio of NF-κB or cytochrome C density to β-actin density. The values were expressed as mean ± SE and were compared by analysis of variance. *P = 0.003 vs. control group, **P < 0.001 vs. control group. ^#P = 0.011 vs. IS group

Fig. 6

Expression of IL-1β and IL-6 in kidney tissue. Expression of IL-1β and IL-6 protein in the kidney determined with Enzyme-linked immunosorbent assay (ELISA) in IS mice treated with or without astragaloside IV. a ELISA analysis of IL-1β in kidney tissues. b ELISA analysis of IL-6 in kidney tissues. *P = 0.016 vs. control group

Fig. 7

Malondialdehyde (MDA) and superoxide dismutase (SOD) activity assays. Kidney oxidative stress was determined with MDA and SOD activity assays. a MDA levels of kidney tissues. b SOD activity of kidney tissues. IS group mice showed higher MDA and lower SOD values than control group mice. *P < 0.001 vs. the control group. The MDA value was significantly lower, and SOD activity was significantly higher, after treatment with 20 mg/kg of astragaloside IV. ^#P = 0.036 vs IS group, ^&P = 0.068 vs IS group, ^&&P = 0.043 vs IS group, ^##P = 0.031 vs IS group