A combination of Chinese herbs, Astragalus membranaceus var. mongholicus and Angelica sinensis, improved renal microvascular insufficiency in 5/6 nephrectomized rats

Abstract

Chronic renal ischemia and hypoxia in the tubulointerstitium are involved in the mechanisms of progressive chronic kidney disease. Previous studies showed that the decoction of a combination of two Chinese herbs, Astragalus membranaceus var . mongholicus and Angelica sinensis (A & A) has antifibrotic effects through multiple pathways in different animal models. In this study, remnant kidney model was employed to investigate whether A & A affect the expression of VEGF, the density of the renal microvasculature and thus alleviate the renal injury. Rats were divided randomly into four groups: sham group ( N = 31), 5/6 Nx group (5/6 nephrectomy, N = 43), A & A treated group (A & A group, N = 40, A & A 12 g/kg/d po), enalapril treated group (Ena group, N = 56, enalapril 4 mg/kg/d po). Rats from each group were sacrificed at the 2th, 4th, 8th and 12th weeks respectively after surgery and treatment. The 24 h urinary protein excretion, serum creatinine (Scr) and urea were measured. The collagen IV (COL-IV), fibronectin (FN), aminopeptidase P (APP) and VEGF were stained using immunohistochemistry. The COL-IV, FN and APP were semi-quantitatively analyzed. Peritubular capillary density in the cortical interstitial area was quantified. The level of VEGF was assayed by ELISA. The results revealed that Scr, urea and urinary protein excretion remained constant at each time point in sham group. Compared to sham group, 5/6 Nx group was shown severe glomerulosclerosis, tubulointerstitial lesions and vascular damage, as well as higher level of Scr from the 2nd week (72.3 ± 5.2 vs. 48.6 ± 2.6 μmol/L, P < 0.05) to the 12th week (71.9 ± 8.0 vs. 55.7 ± 4.5 μmol/L, P < 0.05). Although there was no significant difference in Scr level after treatment of enalapril or A & A ( P > 0.05), kidney damage was alleviated at the 8th and the 12th week in the two treatment groups ( P < 0.05, vs. 5/6 Nx group). The urinary protein excretion of 5/6 Nx group was significantly increased from the 4th week, it was 1.5, 2.4 and 3.8 fold of that of sham group at the 4th, 8th and 12th week, respectively. Compared to 5/6 Nx group, proteinuria was decreased by enalapril to 59%, 33% at 8th and 12th week. After A & A administration, urinary protein excretion decreased to 66%, 56%, 75%, 55% of 5/6 Nx group at the 2nd, 4th, 8th and 12th, respectively ( P < 0.05). Compared with sham group, there was increased expression of FN and COL-IV in rats with 5/6 Nx. After A & A or enalapril administration, the expression of FN and COL-IV was significantly decreased compared with that in the 5/6 Nx group at 8th and 12th week ( P < 0.05). On the other hand, the capillary density was decreased at the 8th and 12th week in 5/6 Nx rats ( P < 0.01). In A & A-treated group, similarly with enalapril group, the amount of APP-positive glomerular capillary increased by 36% ( P < 0.01), and the peritubular capillary density was increased 94% at 8th week and 52% at 12th week compared with 5/6 Nx group ( P < 0.05). The renal level of VEGF was decreased in 5/6 Nx rats, but increased at the 8th and 12th week in A & A group ( P < 0.05, vs. 5/6 Nx group). In conclusion, A & A has renoprotective effects by suppression of extra cellular matrix deposition in 5/6 Nx rat. The renoprotective effects may be associated with reduction of proteinuria, up-regulation of VEGF which may reduce the loss of capillaries and improve microstructure dysfunction.