| Objectives:IgA nephropathy(IgAN), a chronic and prosessive Glomerular disease, is one of the major reasons of glomerulosclerosis and end-stage renal disease(ESRD), which induces a series of clinical and pathophysiological changes. IgAN is histologically characterized by overaccumulation of mensangial cell and extracellular matrix. With the development of renal tissue biopsy, diognosis ratio of children IgAN is increasing gradually. However, there is still no specific treatment. Empirical therapy is the main procedure for the IgAN patients in clinical practice. It was thought that IgAN is a benign disease and have a good prognosis. But long-term follow-up results found that about 20%~50% of adult patients will develop into the eventual development of renal failure. Prognosis of patients with children is better than adults. 5%, 6% and 11% children patients in 5 years, 10 years and 15 years after onset have chronic renal failure. Therefore, the active prevention of IgAN has a pivotal position in study of kidney disease. A lot of research shown Renin-Angiotensin System has important influence in the chronic renal disease, especially for angiotensinⅡ. RAS also play an important role in the pathogenesis of IgAN. Application of RAS blockers is effective in improving clinical symptoms of IgAN patients. AngiotensinⅡreceptor blockers is RAS blockers and has been effectively used for the treatment of IgAN in recent years. Losartan is a kind of angiotensinⅡI type receptor antagonist. The study shows that for patients with IgAN, especially in the merger or urinary protein in patients with hypertension, losartan can protect renal function and delay the occurrence of renal failure. The results show that p38 mitogen-activated protein kinase(p38MAPK) signal transduction pathway can be activated by many kinds of inflammatory factors, such as angiotensinⅡ. p38MAPK play a important role in inflammatory response and promote renal fibrosis by multiple channels. The block of p38MAPK signal transduction pathway can improve renal fibrosis and delay glomerulosclerosis. There is no definite conclusion about the renal protective effect of angiotensinⅡI type receptor antagonist whether by block of p38MAPK signal transduction pathway or not. We observe the effect of losartan on expression of p38MAPK in IgAN rats renal tissue by IgA nephropathy rats model and preliminary study the mechanism of the renal protective effect of AngiotensinⅡreceptor blockers.Methods:30 male Wistar rats (provided by animal experiment center of Hebei Medical University) with 100~120g of weight were randomly divided into three groups: control group(n=10), IgAN group(n=10) and losartan group(n=10). The rats of IgAN group and losartan group had been administered with bovine serum albumin by gavage at a dose of 400mg·kg-1·d-1 every other day for 6 weeks and injected 0.4ml castor oil plus 0.1ml CCl4 once a week for 9 weeks. Lipoplysaccharides were injected at 6th and 8th week. These rats were observrd until 10th week. The rats of control group were free of eating and drinking. Afte 10 weeks, renal tissue was cut into 3μm frozen secion. IgA accumulation in glomerular mensangial areas was examined under the microscope after stained with flurorescein-conjugated affinipure goat anti-rabbit IgG and rabbit anti-rat IgA by immunofluorescence. Proliferation of mensangial cell and overaccumulation of extracellular matrix were observed by PASM and Masson stains. These results indicated that the successful ratio of the IgA nephropathy model was 90%. The rats of losartan group had been administered with losartan by gavage at a dose of 20mg·kg-1·d-1 everyday for 6 weeks. The total experimental period was 14 weeks. Rats in each group were collected 24-hour urine for 24 hour urine protein. Blood was drawn from femoral to separate serum for determination renal function. Partial renal tissue was fixed in 4% formaldehydum and embeded with paraffin. Partial renal cortices were used to abstract total RNA and protein. The protein localization of p-p38MAPK was evaluated by immunohistochemistry. The protein levels of p38MAPK and p-p38MAPK was evaluated by Western blot; The mRNA levels of p38MAPK was measured by reverse transcription and polymerase chain reaction(RT-PCR). All data were expressed as x±s. F and T test was separately used to analyse the difference between two groups and within one group, which was finished with SPSS11.5 software.Results:1 Biochemical indexes: 24 hour urine protein, BUN and SCr in the rat of IgAN group were obviously higher than the rat of control group(P<0.01). ALB in the rat of IgAN group was obviously lower than the rat of control group(P<0.01). The biochemical indexes in the rat of losartan group was significantly improve.2 Immunohistochemically: p-p38MAPK has weak expression in the control group of rats kidney. Compared with those of control rats, the expressions of p-p38MAPK was obviously higher in IgAN group(P<0.01). Compared with those of IgAN group, the expressions of p-p38MAPK was obviously lower in losartan group(P<0.01).3 Western blot: Compared with those of control rats, the expressions of p38MAPK have no significant difference in IgAN group(P>0.05); Compared with those of control rats, the expressions of p-p38MAPK was obviously higher in IgAN group(P<0.01); Compared with those of IgAN group, the expressions of p-p38MAPK was obviously lower in losartan group(P<0.01).4 Real-time quantitative polymerase chain reaction(RT-PCR): p38MAPK mRNA has weak expression in the control group of rats kidney. Compared with those of control rats, the expressions of p38MAPK mRNA was obviously higher in IgAN group(P<0.01). Compared with those of IgAN group, the expressions of p38MAPK mRNA was obviously down-regulated in losartan group(P<0.01).Conclusion:1 Losartan can obviously decrease 24-hour urine protein of IgA nephropathy rats and improve the renal function of IgA nephropathy rats.2 P38MAPK signal transduction pathway was activated in renal tissue of IgAN rats. The activation of p38MAPK signal transduction pathway may play an important role in the pathogenesis of IgA nephropathy.3 Losartan can obviously inhibit expression of p38MAPK in renal tissue of IgA nephropathy rats.4 The renal protective effect of Losartan may be by regulating the expression of p38MAPK to improve renal fibrosis and delay glomerular sclerosis.5 Inhibitor of p38MAPK signaling pathway may be a new routin for treating IgA nephropathy. |
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