Effect Of Tripterygium Wilfordii Polyglycoside On Salt-sensitive Hypertension-induced Renal Injury

Background:Inflammation plays a key role in the development of cardiovascular diseases including hypertension. Hypertension, especially salt-sensitive hypertension, is one of major diseases leading to end-stage renal disease. There is evidence showing that monocyte/macrophage-induced inflammation plays an important role in salt-sensitive hypertension-induced renal injury. Tripterygium wilfordii polyglycoside (TWP) derived from Tripterygium wilfordii has anti-inflammation and immunosuppression. Based on TWP-induced anti-inflammation, we speculate that TWP leads to protection against salt-sensitive hypertension-induced renal injury possibly via attenuating monocyte/macrophage.Purpose:To clarify the mechanisms for TWP-mediated renal protection during salt-sensitive hypertension, we determined the effect of TWP on monocyte/macrophage and its action on renal injury in deoxycorticosterone acetate (DOCA)-salt hypertensive animal model.Methods:Male C57BL/6 mice (8-9 weeks old) were acclimated for 1 week, and then randomly assigned to sham group, DOCA-salt hypertensive group, and TWP-treated DOCA-salt hypertensive group. The detailed experimental method was described below. The mice were anesthetized with ketamine and xylazine (80 and 4 mg/kg SC, respectively), and the left kidney was removed. The DOCA pellet (24 mg/10 g of body weight) was implanted subcutaneously in the neck area. In addition to tap water, the sham group underwent uninephrectomy without receiving DOCA and saline. The DOCA-salt hypertensive group was given distilled water (2 ml/kg) via oral gavage per a day, and the TWP-treated DOCA-salt hypertensive group was given TWP (12 mg/kg/day) via oral gavage every time a day. TWP was dissolved in distilled water. After surgery, all rats were intramuscularly injected penicillin for 3 days. The treatment continued for 5 weeks. The tail-cuff systolic blood pressure was measured in conscious mice before surgery and at the end of each week after surgery. At the end of 5 week of treatment, urine, plasma and kidney were harvested for the next experiment as described below.1. Determination of urinary output, kidney weight, creatinine clearance and urinary albumin; 2. Measurement of urinary 8-isoprostane using a specific ELISA kit; 3. Determination of renal collagen level by the use of hydroxyproline assay;4. Analysis of glomerulosclerosis and renal tubulointerstitial injury in sections stained with periodic acid-Schiff (PAS) and Masson's trichrome stain; 5. Determination of monocyte/macrophage infiltration using F4/80 immunohistochemical staining.Results:1. Changes in systolic blood pressure in every groupThere was no significant difference in baseline blood pressure among 3 groups (P>0.05). Systolic blood pressure did not increase in sham group during the experiment. One week after treatment with DOCA and salt, systolic blood pressure increased remarkably compared with the baseline, and reached the peak after 3 and 4 week treatment in DOCA-salt treated mice with and without TWP treatment, but there was no significant difference in systolic blood pressure between two groups (P>0.05).2. Changes in body weight and renal parameters in every groupThere was no significant difference in body weight among 3 groups (P>0.05). Compared with sham group, kidney.body weight ratio and urinary albumin excretion significantly increased and creatinine clearance markedly decreased in DOCA-salt hypertensive group (P<0.05). TWP inhibited the changes occurring in DOCA-salt hypertensive group (P<0.05).3. Changes in urinary 8-isoprostane excretion in every groupCompared with sham group, urinary 8-isoprostane excretion obviously increased in DOCA-salt hypertensive group (P<0.05), and TWP significantly attenuated the increase in urinary 8-isoprostane excretion (P<0.05).4. Changes in renal collagen in every groupRenal collagen level was significantly increased in DOCA-salt hypertensive group compared with sham group (P<0.05). The increase in renal collagen level was inhibited by the treatment of TWP (P<0.05).5. Changes in renal pathology in every groupCompared with sham group, glomerulosclerosis and tubulointerstitial injury were obviously seen in DOCA-salt hypertensive group (P<0.05), which were associated with the increases in glomerulosclerosis index and tubulointerstitial injury score (P<0.05). Treatment with TWP significantly inhibited the changes in glomerulosclerosis and tubulointerstitial injury (P<0.05).6. Analysis of renal monocyte/macrophage infiltration in every groupThe number of F4/80-positive monocyte/macrophage obviously increased in DOCA-salt hypertensive group compared with sham group (P<0.05). Treatment with TWP significantly reduced F4/80-positive monocyte/macrophage infiltration found in DOCA-salt hypertensive group (P<0.05). The results suggest that TWP reduced salt-sensitive hypertension-induced renal injury possibly via inhibiting monocyte/macrophage.Conclusions:1. Treatment with TWP obviously attenuated DOCA-salt hypertension-induced renal injury, indicating that TWP provides protection against salt-sensitive hypertension-induced renal injury.2. TWP treatment significantly reduced renal monocyte/macrophage infiltration in DOCA-salt hypertensive mice, suggesting that TWP provides protection against salt-sensitive hypertension-induced renal injury possibly via inhibition of monocyte/macrophage-induced inflammation.