Study On The Mechanism Of Iridoid Glycosides From Corni Fructus And Radix Rehmanniae On Podocyte Injury In Diabetic Nephropathy

Aims:With the increasing number of diabetic patients in the world,as one of the most common micro vascular complications in diabetes,diabetic nephropathy has become the leading cause of high morbidity and high mortality and finally develop to end-stage renal disease.Podocytes are terminally differentiated cells which play a pivotal role in maintain the structure and function of glomerular filtrating barrier.So we probe into the protective effect of iridoid glycosides from Radix Rehmanniae(RI)and Corni Fructus(CI)on podocyte injury induced by advanced glycation end products(AGEs)in vivo and in vitro.Methods:In vivo:The wistar rats were used to establish a diabetic nephropathy model by intraperitoneal injection of streptozotocin and high fats feeding.The fasting blood glucose,food intake,water intake,urine volume,weight,24h urine protein,24h urine creatinine were measured every 3 weeks.After administration of 12 weeks,the ultrastructure of podocytes were observed by transmission electron microscope,the expression of WT-1 in podocytes was determined by immunofluorescence and the expression of nephrin and desmin was evaluated by immunohistochemical.In vitro:Part one:Podocytes injury model was induced by AGEs with different concentration at different time.The cell viability and morphology was observed.The expression of desmin,ILK,bax/bcl-2 and cleaved caspase-3 was determined by western blot.The cell apoptosis was measured by Hoechst staining.Part two:Based on the podocyte injury model,we explored the protective mechanism of iridoid glycosides from Radix Rehmanniae and Corni Fructus by MTT,ELISA,AO/EB staining and western blot.Results:In vivo the DN rats exhibited the symptoms of polydipsia,polyphagia,polyuria and loss of weight.The iridoid glycosides from Radix Rehmanniae and Corni Fructus could ameliorate these changes.In addition,RI and Cl could also decrease the 24h urine protein and AGEs in kidney,upregulate the expression of WT-1 and nephrin.In vitro,AGEs 100mg/L at 18h was thought to be the appropriate stimulation.Loganin,morroniside from CI and verbascoside,catalpol from RI could ameliorate the podocyte injury by enhancing the cell viability,increasing the secretion of extra matrix like fibronectin,laminin and Col-IV and down-regulating the expression of ILK,bax,and cleaved caspase-3.Conclusion:According to the results,CI and RI could improve podocyte injury,the protective mechanism might be associated with promoting cell survival,increasing the adhesiveness of podocyte and the inhibition of apoptosis.