| Diabetic nephropathy is the most serious and major complication and is the most common cause of end-stage renal insufficiency. Glomeralar enlargement due to accumulation of extracellular matrix (ECM) accompanied by renal tubular basement membrane thickening and glomerular capillary ultrafiltration are very early characteristics of pathophysiology of diabetic nephropathy. In the end it lead to irreversible damage to renal structure. Glomerular mesangial cells play a central role in maintaining structure and function of glomerular capillary ultrafiltration apparatus.Numerous hypotheses have been put forward over the last decade to explain the pathogenesis of diabetic nephropathy, but scientists now focused on oxidative stress. But data indicate that despite long-term near-normoglycemia achieved by intensive insulin treatment or pancreatic transplantation, characteristic features of microvascular disease such as renal basement membrane thickening progress , persist, or show a remarkably inertial slowing of deterioration . These observations suggest that events occurring during a finite period of metabolic derangement can leave long-lasting sequelae in the system. Processes that could conceivably propagate a "memory" of the diabetic state at these early stages are called "hyperglycaemia memory". So our study focus on oxidative stress and the role of it on the pathogenesis of diabetic nephropathy and hyperglycaemia memory. In the end, we studied the therapeutical effect of Picrorhiza rhizome on diabetic nephropathy and hyperglycaemia memory.In the first part, the role of oxidative stress on the pathogenesis of diabetic nephropathy is introduced, we put forward the hypothesis that the "memory" should clue to glycation and oxidative stress(glycoxidation). In the second part, we studied the proliferation of bovine mesangial cells induced by high glucose (25mM) and AGEs(250ug/ml) measured by MTT assay and flow cytometry. It was found that the proliferation of mesangial cells were inhibited after incubated with high glucose and AGEs for 4 days, and the cell cycle was arrested at G phase. Meanwhile the level ofcollagen secreted by mesangial cells cultured in high glucose and AGEs medium increased vs normal group. These data suggested that AGEs play the same important role as hyperglycemia do in the pathogenesis of diabetic nephropathy, and perhaps related with hyperglycemia memory.In the third part, in order to investigate the role of glycoxidative in the pathogenesis of diabetic nephropathy, The bovine mesangial cells were cultured in high glucose for 3 weeks. It was found that aminoguanidin(AG), DMSO and CAT could inhibited cells hypertrophy and the increased level of collagen. The studies of polyol pathway and AGEs in mesangial cells had been conducted. The results shown that the polyol pathway was actived (the level of sorbitol increased), and the AGEs increased too, cultured in high glucose for 3 weeks, antioxidant and AG could correct it. These results suggested that the disorder of glycometabolism has relationship with oxidative stress. We also found that in mesangial cells exposed to prolonged hyperglycaemia the level of reactive oxygen species(ROS) and Ca2+ increased, mitochondrial membrane potential(MMP, m) decreased, suggested that oxidative stress caused cellular damage, indicated that glycoxidative play a key role in diabetic nephropathy. Glycated proteins had been shown to have close relationship with oxidative stress, because AG and antioxidant can reduce the cellular damage.In the forth part, in order to support the hypothesis thathyperglycaemia-glycation and glycoxidation-mesangial cell hypertrophy/matrix accumulation is the cytopathological chain, which is the main cause of diabetic nephropathy and the basis of hyperglycemia memory phenomenon. The mesangial cells maintained for 4 weeks.in high glucose, substituted normal glucose for high glucose for 3 more weeks incubation. The morphology of mesangial cell, matrix and ROS were observed. The effects of AG, DMSO and CAT on the cell cycling phase... |
PDF Full Text Request