| BACKGROUND: The ardor for nitric oxide (NO) has persisted for more than 10 years. In the meantime, the studies of nitric oxide in diabetic nephropathy (DN) have been reported more and more. But until now, the role of NO in DN hasn't been fully understood. Studies have shown that NO has important effects on DN. NO has displayed its beneficial effects on DN's prevention through interrupting the deleterious effects of several potential therapeutic targets of DN, including that of transforming growth factor- B (TGF- B ), accumulation of extra-cellular matrix, reactive oxygen intermediates (ROI), and protein kinase C (PKC), et al. The main problems encountered by NO researchers nowadays are how to overcome the "double-edged knife" effects of NO on DN and how NO behaves itself exactly at different stages of DN. Based on the aim to make up the impercipience of NO in DN, the role of NO in DN was studied in some depth here through three different ways, i.e. in vitro, in vivo, and the Mendel's genetic means. METHODS: (1) The in vitro part of this study focused on the effects of NO regulators on the high-glucose induced changes of cultured glomerular mesangial cells (GMC). The following indices were investigated: cellular proliferation, apoptosis, expression of iNOS and TGF- B i mRNA, and TGF- B ] concentration in the culture supernatant. In addition, the effects and the research value of iNOS gene knock-down by antisense oligodeoxynucleotides (AS-ODN) on GMC were also investigated. (2) The effects of NO regulators on renal changes at the early-stage of diabetic mellitus (DM) in streptozotocin-induced rat models were investigated in the in vivo part of this study. The NO and ROI metabolism, serum TGF- B i and CRP concentration, immunostaining of iNOS, ecNOS and TGF- B , in the renal cortex, together with metabolic disorders, renal functional and morphological changes, were investigated to probe into the mechanism of NO in DN in vivo. (3) To reflect NO's role in DN from the position of Mendel's genetics, the association be tween the deletion/ insertion polymorphism in intron 4 of ecNOS gene (ecNOS4a/b) and DN in the Han people of Tianjin, China, was examined. How to use the methods of meta-analysis, which were summarized from our long-period research work in evidence-based medicine, in solving the problems encountered by Mendel's genetics study, were also presented. RESULTS: (1) The results of cultured GMC research showed that the changes induced by high glucose couldn't be countered sufficiently by either NO donor or NO inhibitor, while the changes could be reversed by NO and ROI scavenger. These findings have important science count for interpreting the double-edged effects of NO, i.e. the latter, comes mainly from the mingled effects of ROI. The iNOS gene knock-down research showed that AS-ODN technique was an effective way to achieve the specific regulation of iNOS expression, while it was also been confirmed that the inhibiting of inducible NO production did promote the expression of TGF- B , by GMC in vitro. (2) The rese arch of diabetic ratshowed that NO over-production, especially that from ecNOS, was the main cause of renal changes at the early stage of DM. Inhibiting NO production could reverse the renal functional and morphological changes, which was independent of the correction of metabolic disorders of DM. In addition, serum TGF- P i and CRP were found to behave as two ideal markers of DN. Nevertheless, the experimental data implied the long-dated effects of NO inhibitor on DN might not allow too much optimism. (3) The data from Mendel's genetics study showed that there was no association between ecNOS4a/b and DN, whereas there was one between ecNOS4a/b and non-DN CRF. Allele a was associated with the increased risk of non-DN CRF. In addition, it was found that the role of the mutation of ecNOS gene in DN CRF was different from that in non-DN CRF. These findings also implied that it was NO over-production, not the contrary, that had increased the risk of DN. Besides that, it was found that th...
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