Effects Of Spironolactone On Podocyte Injury In Diabetic Rats

Objective:Diabetic nephropathy(DN)is one of the greatest harmful capillary complications of diabetes mellitus.The exact pathogenesy is uncertained.Recent research indicates that the structural change of podocyte,glomerular visceral epithelial cell,is very important to the formation and development of albuminuria in DN.Podocyte injury is appeared in early stage of DN and then albuminuria which accelerate progression of DN.Integrin is one of crucial adhesion molecules which attach podocytes to glomerular basement membrane(GBM),maintenance normal morphous of podocyte and permeability of GBM,mediates signals from GBM to cells or from cells to GBM.Podocytes express integrin ofα3/β1.Animal studies confirm that aldosterone receptor is expressed at renal tubule and partial glomerular cells including podocyte.Aldosterone receptor has consistent expression of mRNA and protein in cultured podocytes.So podocyte is one of target cells of aldosterone. Aldosterone may have effects on podocyte injury through alteration of hemodynamics, up-regulation of ROS and induction of podocyte apoptosis.We hypothesize that spironolactone is playing a major role to protect podocyte structure and delay progression of DN by antagonistic action to aldosterone.In the present study,we observe the expression of integrinα3 and urinary podocyte excretion to evaluate the effects of spironolactone to the podocyte injury and approach its protective mechanism to DN.Materials and methods:Fifty-seven male Wistar rats,weighing 180-220g,were randomly divided into three groups as follows according to weight:(1)control group(group C,n=18);(2)dibetic model group(group D,n=21);(3)group treated with spironolactone(group S,n=18).After receiving the vena caudalis injection of STZ, animals were considered diabetic if blood glucose concentrations increased to over 16.7 mmol/L within 24 hours.The rats in the group S were given spironolactone 40mg/kg/day.On study day of week 4,8,12,individual rats were placed in metabolic cages to obtain 24-hour urine collection for measurement of urine albumin concentration.Urinary podocyte excretion and expression of integrinα3 were detected by immunofluorescence and immunohistochemistry.Glomerular pathematological injury is also evaluated through light microscope and electron microscope.Results:(1)On study day of week 4-12,24-hour urine albumin and urinary podocyte excretion were significantly increased in group D and group S as compared to those in group C.24-hour urine albumin and urinary podocyte excretion were significantly decreased in group S than in group D after treatment with spironolactone.(2)In group C,light microscope has no pathological alteration.Widening of the mesangial regions, increased mesangial matrix,thickened GBM were found in STZ-rats.After administration of spironolactone,the pathological alteration above improved.In group C,electron microscope has no pathological injury.On study day of week 4, segmental foot process effacement,slightly thickened GBM can be detected in diabetic rats.In week 12,foot process effacement is increased and GBM appeared obviously thickened.In group S,the pathological alteration above improved.(3)The expression ofα3 was mainly expressed at glomeruli in line.On study day of week 4,8,12,the deposition is decreased in STZ-rats compared to those in group C.Theα3 expression of group S is significantly increased than group D from week 4 to 12.Conclusions:Podocyte injury is appeared at early stage of DN in STZ-rats.24-hour urine albumin and urinary podocyte excretion are significantly increased.Widening of the mesangial regions,increased mesangial matrix,thickened GBM are found in STZ-rats through light microscope.Segmental foot process effacement,thickened GBM can be detected through electron microscope.Expression of integrinα3 is significantly decreased;After administration of spironolactone the mentioned above improved.So we can concluded that spironolactone can prevent podocyte injury by means of decreasing urine albumin and podcyte excretion,attenuating pathological alteration without affecting blood glucose level.