Protective Mechanism of Danggui Shaoyaosan on Podocytes of Nephrotic Syndrome Rats Based on AngⅡ-TRPC6 Pathway / 中国实验方剂学杂志

ABSTRACT

Objective:To explore the protective effect and the mechanism of Danggui Shaoyaosan（DSS） on angiotensin Ⅱ （AngⅡ）/transient receptor potential cation channel 6 （TRPC6） pathway in nephrotic syndrome （NS） rats. Method:In animal experiments， doxorubicin （4 mg·kg^-1 for the 1^st week and 2 mg·kg^-1 for the 2^nd week） was injected twice to the tail vein of rats to induce NS model in 160 rats， which were then randomly divided into model group （normal saline）， losartan group （30 mg·kg^-1·d^-1）， and low-（4.3 g·kg^-1·d^-1）， medium-（8.6 g·kg^-1·d^-1）， and high-dose （17.2 g·kg^-1·d^-1） DSS groups. Besides， a normal group was also set. After intervention for four weeks， ultrastructure changes of the kidney were identified by transmission electron microscopy （TEM）. The 24-hour urine protein was detected by kits. Radioimmunoassay was used to detect the content of AngⅡ and Calcineurin （CaN） in plasma. Western blot was used to detect the protein expression of TRPC6， angiotensin Ⅱ type 1 receptor （AT1R）， podocyte slit diaphragm-specific protein （Nephrin）， and cysteine-aspartic acid protease-3 （Caspase-3） in the renal cortex. Immunohistochemistry was used to detect the expression of TRPC6 and AT1R in the slit diaphragm. In cell experiments， AngⅡ stimulated MPC5 podocytes. The cells were randomly divided into a normal group， an AngⅡ group， an AngⅡ+SAR7334 （TRPC6-specific inhibitor） group， an AngⅡ+5%DSS group， an AngⅡ+10%DSS group， and an AngⅡ+15%DSS group. Western blot was used to detect the protein expression of TRPC6， AT1R， Nephrin， and Caspase-3 in podocytes. Result:Compared with the normal group， the model group showed increased 24-hour urine protein content （<italic>P</italic><0.01） and AngⅡ and CaN in plasma （<italic>P</italic><0.01）， incomplete glomerular structure， the extensive fusion of podocyte process with elevated fusion rate （<italic>P</italic><0.01）， increased expression distribution of AT1R and TRPC6 in the renal cortex， and up-regulated protein expression of AT1R， TRPC6， and Caspase-3 in renal tissues （<italic>P</italic><0.01）， and reduced Nephrin protein expression （<italic>P</italic><0.01）. Compared with model group， the losartan group and the high-dose DSS group exhibited decreased 24-hour urine protein content （<italic>P</italic><0.01） and the content of AngⅡ and CaN in plasma （<italic>P</italic><0.01）， improved glomerular structure， reduced fusion rate of podocyte process （<italic>P</italic><0.01）， diminished expression distribution of TRPC6 and AT1R in the renal cortex， declining protein expression of AT1R， TRPC6 and Caspase-3 in renal tissues （<italic>P</italic><0.01）， and elevated Nephrin protein expression （<italic>P</italic><0.01）. Additionally， compared with the normal podocytes， AngⅡ-stimulated podocytes showed increased protein expression of AT1R， TRPC6 and Caspase-3 （<italic>P</italic><0.01）， and decreased expression of Nephrin （<italic>P</italic><0.01）. Compared with the AngⅡ group， the AngⅡ+SAR7334 group displayed reduced protein expression of AT1R， TRPC6， and Caspase-3 （<italic>P</italic><0.01） and increased protein expression of Nephrin （<italic>P</italic><0.01）. Conclusion:DSS can improve the pathological characteristics of NS presumedly by inhibiting the interaction between AngⅡ and TRPC6 in podocytes and improving the structural integrity of podocytes to repair the damage of glomerular molecular barrier and slow down the progression of NS-induced proteinuria.