Study On Intervention Mechanisms Of Tea Polyphenol In The Renal Vascular Lesions Of A Hyperuricemic Rat Model

Background and objective:Hyperuricemia (HUA) is a common observation in patients with chronic kidney disease (CKD). Meanwhile, elevated uric acid levels are closely associated with increased risk of cardiovascular disease (CVD) motality. Therefore, uric acid may serve as a bridge to link CKD and CVD. HUA induces renal vascular lesions, which further accelerate the progress of CKD. However, the specific regulatory mechanisms on renal vascular lesions induced by HUA are not yet fully elucidated. The Notch signaling pathway is a critical component of vascular formation and morphogenesis in both development and disease. Accumulating evidence indicates that Notch signaling plays a key role in determinating the fate of blood vessels and its cells. Abnormal Notch signaling pathway is also associated with various vascular diseases in human. However, under the context of hyperuricemic CKD whether Notch signaling participate in regulating renal vascular lesions is not yet reported in the literature. In this article, we first observed expression of Notch ligand Jagged-1in the renal arteries of a remnant kidney rat model with hyperuricemia induced by oxonic acid (OA), and then we further analyzed the possible regulatory mechanism in renal arterial lesions mediated by Notch signaling pathway. We considered the regulatory mechanism as a entry point to explore the therapeutic efficacy of tea polyphenol (TP) in the renal arterial lesions of a hyperuricemic remnant rat model. Furthermore, we sought to provide a theoretical basis for clinical treatment.Materials and Methods:The RK model was established with5/6subtotal nephrectomy by two-step operation, and then the RK rats were fed with2%OA for4wk to induce HUA. Female SD rat (32total) were randomly divided into four groups:SO (sham operation, n=8), RK (remnant kidney, n=8), RK+OA (remant kidney rat fed2%OA, n=8) and RK+OA+TP (remant kidney rat fed2%OA with TP, n=8).24-h urinary protein excretion rate, biochemical parameters and pathological changes were evaluated. The morphological changes of preglomerular arteries (including arcuate artery, interlobular artery and afferent artery) were analyzed by Motic Med6.0digital image analysis system. The expression of Jagged-1mRNA in the preglomerular arteries was detected by in situ hybridization. The expression of Jagged-1, Notch1intracellular domain (Notch1-ICD), hairy and enhancer of split5(Hes5), phosphorylated signal transducers and activators of transcription3(P-STAT3), manganese superoxide dismutase (MnSOD2) and xanthine oxidase (XO) in the preglomerular arteries among the different groups were detected by immunohistochemistry. Serum levels of reactive oxygen species (ROS) in different groups were detected by enzyme-linked immunosorbent assay (ELISA).Results:1. Compared with the SO group, the serum concentration of uric acid in the RK group (86.50±13.81μmol.L-1vs98.51±17.75μmol.L-1, P>0.05) and the RK+OA group (86.50±13.81μmol.L-1vs207.23±29.82μmol.L-1, P<0.01) were elevated. Furthermore, the serum uric acid increased more in the RK+OA group than that in the RK group (98.51±17.75μmol.L-1vs207.23±29.82μmol.L-1, P<0.01).2. Both biochemical parameters and pathological score that reflected the renal functional and structural changes increased significantly in the RK+OA and RK groups as compare to that in the SO group (P<0.05). In terms of thses indices, there was a significant difference between the RK+OA and RK groups (P<0.05). With the serum concentration of uric acid icreasing, these indices also increased (P<0.05).3. Compared to the SO group, the media/lumen ration of preglomerular arteries increased siginificantly in the RK and RK+OA groups (P<0.01). The RK+OA group showed higher media/lumen ration in the arcuate artery (5.71±0.68vs3.44+-0.56, P<0.01), in the interlobular artery (5.18±0.91vs3.77±1.04, P<0.01), and in the afferent artery (8.21±0.78vs5.05±0.97, P<0.01) as compared to the RK group. With the serum concentration of uric acid icreasing, the media/lumen ration of preglomerular arteries among the different groups increased siginificantly (P<0.05). With the media/lumen ration of preglomerular arteries icreasing, both biochemical parameters and pathological score that reflected the renal functional and structural changes significantly increased (P<0.05).4. Compared to the SO group, both Jagged-1and Jagged-1mRNA expression in the preglomerular arteries were markedly down-regulated (P<0.01). In addition, the expression of Jagged-1and Jagged-1mRNA were negatively correlated with media/lumen ration of preglomerular arteries. Both Jagged-1and Jagged-lmRNA expression in preglomerular arteries were lower in the RK+OA group than that in the RK group (P<0.01).5. The expression of Notch1-ICD, Hes5, P-STAT3and MnSOD2were all significantly down-regulated in preglomerular arteries in the RK and RK+OA groups, compared with that in the SO group (P<0.01). Down-regulation of the expression of these proteins were most obvious in the RK+OA group, and there was significant difference between the RK and RK+OA groups (P<0.05).6. The expression of XO was significantly up-regulated in preglomerular arteries in the RK and RK+OA groups than that in the SO group (P<0.01). Up-regulation of the XO expression was most obvious in the RK+OA group, and there was significant difference between the RK and RK+OA groups (P<0.01).7. With the degree of the preglomerular arteries lesions worsing, the expression levels of Jagged-1、Notch1-ICD、Hes5、STAT3and MnsOD2were all significantly down-regulated gradually (P<0.01).8. With the expression of Jagged-1down-regulating, the expression levels of Notchl-ICD、Hes5、STAT3and MnsOD2were all significantly down-regulated gradually (P<0.01); However, the expression of XO was significantly up-regulated gradually (P<0.01).9. With the degree of the preglomerular arteries lesions worsing, the level of ROS detected by ELISA was significantly elevated (P<0.01), which accompanied by the up-regulated expression of XO (P<0.01).10. Compared to the RK and RK+OA groups, the the TP treated group showed the significantly reduced media/lumen ration (P<0.01) and expression of XO (P<0.01) in the preglomerular arteries. The serum level of ROS in the TP treated group were lower that in the model control groups. Both Jagged-1and Jagged-1mRNA expression in the preglomerular arteries were markedly up-regulated in the TP treated group as compared to that in the model control groups (P<0.01).11. The expression of Notch1ICD、Hes5、P-STAT3and MnSOD2were also significantly up-regulated in the TP treated group than that in the model control groups (P<0.05).12. The correlational analysis confirmed that with the expression of Jagged-1up-regulating, the level of the expression of Notch1-ICD, Hes5, STAT3and MnsOD2were all significantly up-regulated gradually (P<0.01).Conclusions:1. HUA aggravate the preglomerular arteries lesions which accelerated the progression of kidney disease.2. The increased XO expression, resulting in the elevated level of ROS in the preglomerular arteries, could lead to the vascular lesions in hyeruricemic RK rats. The reduced expression of MnSOD2, resulting in the declined scavening of ROS in the preglomerular arteries, could lead to the vascular lesions in hyeruricemic RK rats. Under the context of hyperuricemic RK rat, the reduced activity of Notch signaling pathway which coordinated JAK-STAT pathway resulting in the down-regulated expression of MnSOD2, thus participated in the regulation of vascular lesions.3. TP improved the preglomerular arteries lesions, at least in part, through up-regulating the activity of Notch signaling pathway to reduce ROS production in the hyperuricemic RK rat model. Objective:To evaluate the impact of hyperuricemia (HUA) induced by oxonic acid (OA) on the progressive renal disease and preglomerular arterial lesions of a remnant kidney (RK) rat model and detect the expression of Jagged-1in the preglomerular arteries.Methods:The RK model was established with5/6subtotal nephrectomy by two-step operation, and then the RK rats were fed with2%OA for4wk to induce HUA. Rat (24total) were randomly divided into three groups: SO (sham operation, n=8), RK (remnant kidney, n=8) and RK+OA (remant kidney rat fed2%OA, n=8).24-h urinary protein excretion rate, biochemical parameters and pathological changes were evaluated. The morphological changes of preglomerular arteries (including arcuate artery, interlobular artery and afferent artery) were analyzed by Motic Med6.0digital image analysis system. The expression of Jagged-1mRNA in the preglomerular arteries was detected by in situ hybridization. The expression of Jagged-1in the preglomerular arteries among the different groups were detected by immunohistochemistry.Results:1. Compared with the SO group, the serum level of uric acid in the RK group (86.50±13.81μmol.L-1vs98.51±17.75μmol.L-1, P>0.05) and the RK+OA group (86.50±13.81μmol.L-1vs207.23±29.82μmol.L-1, P<0.01) were elevated. Furthermore, the serum level of uric acid increased more in the RK+OA group than that in the RK group (207.23±29.82μmol.L-1vs98.51±17.75μmol.L-1, P<0.01). Similarly, both biochemical parameters and pathological score that reflected the renal functional and structural changes increased significantly in the RK+OA and RK groups as compare to that in the SO group (P<0.05). In terms of thses indices, there was a significant difference between the RK+OA and RK groups (P<0.05). Compare with the SO group,24-h urinary protein excretion rate in the RK group (3.05±0.99mg/24h vs5.32±1.25mg/24h, P<0.05) and the RK+OA group (3.05±0.99mg/24h vs8.41±2.10mg/24h, P<0.01) were significantly elevated.24-h urinary protein excretion rate increased more in the RK+OA group than that in the RK group (8.41±2.10mg/24h vs5.32±1.25mg/24h, P <0.01). With the serum level of uric acid icreasing, these indices also significantly increased (P<0.01).2. Compared to the SO group, the media/lumen ration of preglomerular arteries increased siginificantly in other two groups (P<0.01). The RK+OA group showed higher media/lumen ration in arcuate artery (5.71±0.68vs3.44±0.56, P<0.01), in interlobular artery (5.18±0.91vs3.77±1.04, P<0.01), and in afferent artery (8.21±0.78vs5.05±0.97, P<0.01) as compared to the RK group. With the serum level of uric acid icreasing, the media/lumen ration of preglomerular arteries among the different groups increased siginificantly. With the media/lumen ration of preglomerular arteries icreasing, both biochemical parameters and pathological score that reflected the renal functional and structural changes significantly increased.3. Compared to the SO group, both Jagged-1and Jagged-1mRNA expression in the preglomerular arteries were markedly down-regulated (P<0.01). In addition, the expression of Jagged-1or Jagged-1mRNA were negatively correlated with media/lumen ration of preglomerular arteries(P<0.01). Both Jagged-1and Jagged-1mRNA expression in the preglomerular arteries were lower in the RK+OA group than that in the RK group (P<0.01).Conclusions:1. HUA aggravate the preglomerular arteries lesions which accelerated the progression of kidney disease.2. With the aggravation of preglomerular arterial lseions, expression of Jagged-1reduced gradually. Therefore, Jagged1-dependent Notch signaling pathway may be involved in the regulation of renal arterial lesions. Objective:To explore possible regulatory mechanisms of Notch signaling pathway in the preglomerular arterial lesions of a remnant kidney (RK) rat model with hyperuricemia induced by oxonic acid (OA).Methods:The RK model with hyperuricemia was developed by feeding2%OA for4wk after5/6RK surgery. Rats (24total) were randomly divided into three groups:SO (sham operation, n=8), RK (remnant kidney, n=8) and RK+OA (remant kidney rat fed2%OA, n=8). The expression of Jagged-1、Notch1-ICD. Hes5、P-STAT3、MnSOD2and XO in the preglomerular arteries among the different groups were detected by immunohistochemistry. Semi-quantitative immunohistochemical analysis were performed by Motic Med6.0digital medical image analysis system. Serum level of ROS in different groups were detected by enzyme-linked immunosorbent assay (ELISA).Results:1. Jagged-1、Notch1-ICD、Hes5、P-STAT3、MnSOD2and XO were all expressed by the immunohistochemical staining in rat preglomerular arteries among the different groups.2. The expression of Jagged-1、Notch1-ICD、Hes5、P-STAT3and MnSOD2were all significantly down-regulated in the preglomerular arteries between the RK and RK+OA groups, compared with that in the SO group (P<0.01). Down-regulation of the expression of these proteins was most obvious in the RK+OA group, and there was significant difference between the RK and RK+OA groups (P<0.05).3. The expression of XO was significantly up-regulated in the preglomerular arteries between the RK and RK+OA groups than that in the SO group (P<0.01). Up-regulation of the XO expression was most obvious in the RK+OA group, and there was significant difference between the RK and RK+OA groups (P<0.01).4. With the degree of the preglomerular arteries lesions worsing, the level of the expression of Jagged-1、Notchl-ICD、Hes5、STAT3and MnsOD2were all significantly down-regulated gradually (P<0.01).5. With the expression of Jagged-1down-regulating, the level of the expression of Notch1ICD、Hes5、STAT3and MnsOD2were all significantly down-regulated gradually (P<0.01);6. The serum ELISA study show with the degree of the preglomerular arteries lesions worsing, the level of ROS was significantly elevated (P<0.01), which accompanied by the up-regulated expression ofXO(P<0.01).Conclusions:1. The increased XO expression resulting in the elevated level of ROS in the preglomerular arteries, could lead to the vascular lesions in hyeruricemic RK rats.2. The reduced expression of MnSOD2, resulting in the declined scavening of ROS in the preglomerular arteries, could lead to the vascular lesions in hyeruricemic RK rats.3. Under the context of hyperuricemic RK rat, the reduced activity of Notch signaling pathway which coordinated JAK-STAT pathway resulting in the down-regulated expression of MnSOD2, thus participated in the regulation of vascular lesions. Objective:To evaluate the intervention efficacy and mechanisms of tea polyphenol (TP) in the preglomerular arteries lesions of a remnant kidney (RK) rat model with hyperuricemia induced by oxonic acid (OA).Methods:The RK model with hyperuricemia was developed by feeding2%OA for4wk after5/6RK surgery. Rats (32total) were randomly divided into four groups:SO (sham operation, n=8), RK (remnant kidney, n=8), RK+OA (remant kidney rat fed2%OA, n=8) and RK+OA+TP (remant kidney rat fed2%OA with TP, n=8). Pathological lesions in the preglomerular arteries (including arcuate artery, interlobular artery and afferent artery) were evaluated. The expression of Jagged-lmRNA in the preglomerular arteries was detected by in situ hybridization. The expression of Jagged-1、Notch1-ICD、Hes5、P-STAT3. MnSOD2and XO in the preglomerular arteries among the different groups were detected by immunohistochemistry. Serum level of ROS in different groups were detected by enzyme-linked immunosorbent assay (ELISA).Results:Compared to the model control groups, the RK+OA+TP group showed the significantly reduced media/lumen ration (P<0.01) and expression of XO (P<0.01) in the preglomerular arteries. The serum level of ROS in RK+OA+TP group were lower that in the model control groups. Both Jagged-1and Jagged-1mRNA expression in the preglomerular arteries were markedly up-regulated in the RK+OA+TP group as compared to that in the model control groups (P<0.01). The expression of Notchl-ICD、Hes5、P-STAT3and MnSOD2were also significantly up-regulated in the RK+OA+TP group than that in the model control groups (P<0.05). The correlational analysis confirmed that with the expression of Jagged-1up-regulating, the level of the expression of Notchl-ICD、Hes5、STAT3and MnsOD2were all significantly up-regulated gradually (P<0.01).Conclusions:TP improved the preglomerular arteries lesions, at least in part, through up-regulating the activity of Notch signaling pathway to reduce ROS production in the hyperuricemic RK rat model.