Renal Expression Of P38MAPK In Type1Diabetic Rats And The Effect Of Candesartan Intervention

Objective: This study observed the expression of p38mitogen-activatedprotein kinases(P38MAPK) and transforming growth factor-β (TGF-β) in thekidney of streptozotocin-induced type1diabetic rats, and explored therelationship of P38MAPK and TGF-β with diabetic nephropath（yDN）, as wellas the protection mechanism of candesartan for diabetic kidney damage.Methods：1.36male Wistar rats were randomized divided into3groups afteradaptive feeding one week: normal control group (NC group, n=12), diabeticgroup (DM group, n=12) and candesartan intervention group (DM-C group,n=12). After fasting for12hours, DM and DM-C group were given a singleintraperitoneal injection of streptozotocin (STZ,50mg/kg) to induce type1diabetic rat modes. After3days, random blood glucose levels higher than16.7mmol/L were considered as diabetes modeling successful, NC group wereintraperitoneal injected with the same volume of citrate buffer.2. The DM-C group were treated with candesartan5mg·kg-1·d-1, NC andDM groups were treated with the same volume of normal saline. After12weeks, all rats were placed into the metabolic cages to collect24hours urinesamples, then we recorded the urine volume, and determined urinary albuminexcretion(UAE) and urinary creatinine. All the rats were weighted and theplasma samples were collected to assay fasting blood glucose(FBG), serumcreatinine(Scr), blood urea nitrogen(BUN), total cholesterol (TC),triglycerides(TG) and calculate creatinineclearance rate(Ccr). We cut the rightkidney, removed capsule and weighed, calculated the kidney weight index(KW/BW). The histopathology changes of glomeruli were observed bymicroscope and transmission electron microscope. The expression ofp-P38MAPK and TGF-β in glomeruli and renal tubules were determined by immunohistochemistry. The results of immunohistochemistry were analysedby Cell medical image analysis system（CMIAS-2011）, the grayscale value ofp-P38MAPK and TGF-β of3groups were calculated. The rest of the renaltissue was quickly stored in-70°C refrigerator. Reverse transcriptionpolymerase chain reaction (RT-PCR) was used to detect the mRNA expressionof P38MAPK and TGF-β in kidney.Results: At the end of the study,12rats in NC group,10rats in DMgroup and9rats in DM-C group survived.1. FBG, Ccr, BUN, UAE and KW/BW: Compared with NC group, FBG,Ccr, BUN, UAE and KW/BW were significantly increased in both DM groupand DM-C group (both P＜0.01); compared with DM group, UAE, KW/BWwas significantly lower in DM-C group (P <0.01，P <0.05).2. TG, TC: Compared with NC group, TG and TC were significantlyincreased in both DM group and DM-C group (P<0.01, P<0.01); comparedwith DM group, TG and TC was significantly lower in DM-C group (P <0.01,P <0.05).3. The histopathology changes of glomeruli: Compared with NC group,light microscopy showed glomerular mesangial, mesangial expansion,extracellular matrix accumulation, more PAS-positive materials and part ofrenal tubular structural disorder in DM group and DM-C group. Comparedwith DM group, these lesions in DM-C group were alleviated, but not yetreturn to normal. Transmission electron microscope showed that glomerrularbasement membrane were thickened unevenly and foot process of podocytefractured and confluenced in DM group; whereas these were partly relieved inDM-C group.4. The immunohistochemical results: NC group showed a small amountexpression of p-P38MAPK and TGF-βin both glomeruli and renal tubules.The expression of p-P38MAPK and TGF-βin DM group had greater increasethan NC group(P＜0.01, P＜0.01); and the expression of p-P38MAPK andTGF-βin DM-C group had greater decrease than DM group(P＜0.01, P＜0.01), whereas still higher than NC group(P＜0.01, P＜0.01). 5. The RT-PCR results: the NC group showed a small amount expressionof P38MAPK and TGF-β mRNA in renal cortex. The expression ofP38MAPK and TGF-βmRNA in DM group had greater increase than NCgroup(P＜0.01, P＜0.01); and the expression of P38MAPK and TGF-βmRNA in DM-C group had greater decrease than DM group(P＜0.01, P＜0.05), whereas still higher than NC group(P＜0.01, P＜0.05).Conclusion:1. In rats with diabetes, the expression of P38MAPK and TGF-βincreased significantly in kidney tissues.2. Candesartan had a renoprotective effect through relieveing the renalhistopathological damage and reducing the24-hour UAE, which may beassociated with the down-regulating expression of P38MAPK and TGF-β inkidney tissues.