Isoliquiritigenin attenuates acute renal injury through suppressing oxidative stress, fibrosis and JAK2/STAT3 pathway in streptozotocin-induced diabetic rats

Abstract

The aim of the current study was to evaluate the protective effects and mechanisms of isoliquiritigenin (ISO) on acute renal injury. CCK-8 assays were applied to assess the effects of ISO at different doses (20, 40, and 80 μg/mL) on oxidative damage in human renal HK-2 cells incubated with high glucose. After the diabetic nephropathy (DN) rat model was established, the model animals were randomly assigned to saline-treated control, three model groups received the 10, 20 and 40 mg/kg ISO, respectively, using the healthy Sprague-Dawley (SD) rats as normal control. The blood biochemical indexes, renal functions, oxidative stress, morphological changes, fibrosis- and JAK2/STAT3-related factors in DN model rats were all assessed. The cellular viability of the renal HK-2 cells with oxidative damages were all markedly ameliorated via the incubation of ISO between 10 and 80 μg/mL compared with negative control. In addition, the significantly down-regulated ROS content and up-regulated expression levels of GSH, SOD2, and GPX1 were all observed in ISO-treated groups. Long-term administration of ISO at different doses in DN rats effectively improved general diabetic characteristics and renal morphology. Furthermore, long-term administration of ISO could ameliorate excessive oxidation stress, down-regulate the expression levels of renal fibrosis- and inflammation-related factors, as well as inhibit the JAK2/STAT3 signaling pathway. In conclusion, ISO at all three dosages could efficiently improve the renal injury induced by STZ via ameliorating renal fibrosis, oxidative stress, and inhibiting JAK2/STAT3 signaling pathways in the DN rats.

Keywords: Isoliquiritigenin; TGF-β/Smad signaling pathway; diabetic nephropathy; fibrosis; oxidative damage.

Figure 1.

The protective effects of ISO on cellular viabilities of human renal HK-2 cells (a) without or (b) with treatment of high glucose. *p < 0.05, **p < 0.01, ***p < 0.001 compared with saline-treated HK-2 cells without high glucose in Figure 1(a) and with high glucose in Figure 1(b), respectively. All data were presented as mean ± SD (n = 5)

Figure 2.

Effects of treatment of ISO at different concentrations on the antioxidant ability of the HK-2 cell. The content of (a) ROS and (b) SOD2 and (c) GPX1 in HK-2 cell with the oxidative injury induced by high glucose. *p < 0.05, **p < 0.01, ***p < 0.001 compared with high glucose only treated HK-2 cells. All data were presented as mean ± SD (n = 5)

Figure 3.

Effect of long-term administration of ISO at three dosages on the general factors and renal function-related disorders of DN model rats. The changes of (a) body weight, (b) kidney/body ratio, (c) fasting BGL, and the serum levels of (d) TC, (e) TG, (f) Crea, (g) BUN, (h) UA, (i) β2-MG, and (j) UP/24 h in DN model rats after chronic treatment of ISO. *p < 0.05, **p < 0.01, ***p < 0.001 compared with saline only treated DN model animals. All data were presented as mean ± SD (n = 8)

Figure 4.

Effect of long-term administration of ISO at three dosages on the renal tissue changes, oxidative injury-related and apoptosis-related indicators of DN model rat. (a) H&E-staining images (Scale bar: 50 μm), the expression levels of (b) BCL2 and (d) BAX, and the contents of (D) SOD, (e) MDA and in renal tissues of DN model rat. *p < 0.05, **p < 0.01, ***p < 0.001 compared with saline only treated DN model animals. All data were presented as mean ± SD (n = 8)

Figure 5.

Effects of 8-week treatment of ISO at three doses on the renal tissue change, the apoptosis and fibrosis-related factors in DKD rats. (a) The WB analysis of the protein expression levels of (b) TGF-β1, (c) Collagen-1, and (d) Fibronectin protein levels. ***p < 0.001, **p < 0.01 vs. saline-treated DKD model ones. All the above results were showed as Mean ± SD (n = 8)

Figure 6.

Chronic effects of ISO treatment on the protein expression levels of JAK/STAT signaling pathway-related indicators in renal tissues of acute DN model rats. (a) Western blotting gel of the protein expression levels and analysis of (b) IL-6, (c) ICAM-1, (d) JAK2, (e) p-JAK2, (f) STAT-3, and (g) p-STAT-3. *p < 0.05, **p < 0.01, ***p < 0.001 vs. saline-treated DN model rats. All the results were shown as mean ± SD (n = 8)