| Objective: Diabetes mellitus (DM) is a metabolic syndrome characterized by hyperglycemia due either to an absolute deficiency in insulin secretion or to a reduction in the biologic effectiveness of insulin. The majority of DM patient undergoes a cascade of pathogenesis of the disease at the various periods of time in which many organs may be involved such as vascular, nervous system, muscular system and the skin, etc. The mechanism of these chronic complications still remains unclear while recent studies have implied that the immune responses and the biological effects of lymphokine could play an important role in the pathogenesis of DM. Our previous work also demonstrated the deposition of immunological complexes of various kinds, such as IgG, IgA, IgM, Clq, C3 and FRA, on the various organs, such as kidneys, muscle, skin and pituitary gland. Thus, it is very interesting to study if it is by immunosuppressive therapy that these chronic complications could be prevented. In the present study, our investigation aimed at the abnormal deposition of immunoglobulins in the aorta, heart and kidney of STZ-induced diabetic rats and evaluated the protective effects of cyclosporine A against these immunological complexes.Materials and methods: The DM rat models were made by intravenous administration of STZ. Then, they were randomly divided into 6 CsA treated groups, 1 insulin-treated group and 1 diabetic group without any treatment. The 6 CsA treated groups differed only in the time of CsA treatment (1 week before or post modeling) and the dose they received (1mg/kg/d, 4mg/kg/d and 8mg/kg/d,respectively). The insulin-treated group initiated 6U/kg/d insulin from 1 week post modeling. Another group of normal rats was also monitored simultaneously. Hepatic function, renal function, serum insulin, C-reactive protein and urine albumin were also investigated by routine test each month. The deposition of immunoglobulins was detected in the aorta, heart and retina by immunohistochemistry and immunofluorescence.Results: CsA seemed to fail to prevent the onset of diabetes induced by STZ since all the rats treated with STZ fully demonstrated the clinical manifestations of DM eventually. On the other hand, all the doses of CsA we adopted had not shown any impairment on the hepatic and renal function. Even though the serum CRP was remarkably elevated in the STZ-induced diabetic rats, this elevation was fortunately reversed by the intervention of CsA however. At 8-week, interstitial fibrosis was clearly demonstrated along with obvious lymphocyte infiltration in diabetic aortas and hearts. Compared with the control group, it is quite obvious that the deposition of IgG, IgA and IgM was remarkably increased in diabetic aortas, hearts and retina. In contrast, by CsA intervention, fibrosis on the aorta was prevented and the immunoglobulins deposition on these organs was being vanished while the serum CRP was declined also in our study. A significant positive correlation was found between the fibrosis of aorta and the deposition of immunoglobulin in the diabetic rats. In our study, it could be concluded that the earlier the intervention was initiated, the better the outcomes of the intervention would be.Conclusions: The presence of lymphocytes or/and immunoglobulins in the aorta, heart and retina of STZ-induced diabetic rats suggests that the autoimmune injuries play a critical role in the pathogenesis of the chronic diabetic complications. Immunosuppressive treatment with CsA has demonstrated protective effects on a variety of organs by inhibiting the abnormal deposition of immunoglobulins on them. Our conclusion may challenge the traditional theory of the pathogenesis ofatherosclerosis in diabetes.Part II: The effect of CsAon the expression of MMP-2 and MMP-9 in the vascular complications of STZ-induced diabetic rats.Objective: Diabetic vascular complications can be conveniently divided into two main categories, macrovascular disease and microvascular disease. Macrovascular disease is the accelerated atherosclerosis of aorta, coronary artery, cerebral artery, renal artery and peripheral artery. It accounts for the high risk of myocardial infarction, stroke and peripheral gangrene. Microvascular disease includes diabetic nephropathy, diabetic retinopathy and diabetic cardiomyopathy. It manifests an abnormal thickening of the capillary basement membrane.Matrix metalloproteinases (MMPs) are members of Zn2+-dependent endopeptidases family, which exhibit a high affinity to extracellular matrix components. Since these enzymes are able to breakdown many kinds of effective molecules, they are essential for cellular migration and tissue remodeling in both physiological and pathological conditions. Several studies have demonstrated the alterations of the expression levels and activities of certain MMPs in diabetes and suggested a potential role of these abnormalities in the pathogenesis of diabetic vascular disease. We wonder whether immunosuppressive therapy could correct these molecular disorders and relief the vascular complications. So in the present study, we investigated the effects of CsA, an immunosuppressive reagent, on the expression of MMP-2 and MMP-9 in diabetic aorta, heart and kidney.Material and methods: The modeling and grouping of the experimental animals are described as above. The expression of MMP-2 and -9 in diabetic aortas, hearts and kidneys was detected by immunohistochemistry and semi-quantified by RT-PCRon the transcriptional level and Western blotting on the translation level.Results: Even normal myocardium, nephritic tubule epithelium and smooth muscle from aorta expressed a certain level of both MMP-2 and -9. However, both the mRNA and protein levels of MMP-2 and -9 elevated significantly in diabetic rats. These proteins were also found depositing in the mesenterium of glomerulus. CsA treatment resulted in decreased mRNA and protein levels of these molecules in the above organs. As for MMP-2, significant correlations were found between the mRNA and the protein levels in all of these organs. But for MMP-9, corresponding correlation was only found in aorta.Conclusions: The upregulation of MMP-2 and -9 in the smooth muscle, myocardium and nephritic tubule epithelium may contribute to the atherosclerosis, heart failure and renal failure by facilitating smooth muscle migration, ventricular rebuilding and modulating apoptotic process. Decreasing cytokine release, CsA could inhibit the expression of MMP-2 and -9, and further attenuate the diabetic vascular complications.
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