Expression Changes Of VEGF、NOS In The Hippocampus Of Diabetic Rats Induced By STZ

[Objective] To investigate the localization and expression of VEGF and NOS in the hippocampus of the early diabetic rats, approach their effect on the pathogenesis of cognitive impairment in diabetes, thus provide a new theoretical basis for the further exploration of the early cognitive impairment in diabetes.[Methods] Eighty male SD rats, were randomly divided into the study group and the normal control group (NC). Rats of the study group were injected with large-dose (65mg/kg) of STZ by intraperitoneal injection to induce the type1diabetic rats model. Meanwhile the control group rats were given equal volume lemonacid buffer liquid. After model was succeeded, the diabetic rats were divided into the third week (DM3), the sixth week (DM6), the ninth week (DM9) diabetic group on average(20per group). Rats were anesthetized, their brain tissue were fixed, embedded in paraffin and sliced. Hippocampus sections were stained by HE and the change of hippocampus tissue structure were observed by the light microscope. Immunohistochemistry, computer image analysis and western blotting were used to investigate the expression and distribution of VEGF and NOS protein on the hippocampus of diabetic rats.[Results] HE staining showed that there is no significant change in hippocampus structure of DM3group, the pathological changes aggravate with the prolonged course of disease, including hippocampal pyramidal neurons sparse, disordered arrangement and a large number of cells degeneration and necrosis. The results of immunohistochemistry showed that VEGF-positive cells and NOS-positive cells mainly distributed in the hippocampal pyramidal neurons. With the progression of diabetes, VEGF protein expression increased gradually, there was significant difference in the positive expression of VEGF among NC, DM3, DM6and DM9groups (P<0.05); nNOS-positive cells significantly increased in DM groups than in NC group (P<0.05), there was no difference in the positive expression of nNOS between DM3group and DM6group (P>0.05), there was significant difference in the positive expression of nNOS among the remaining DM groups (P<0.05); with the progression of diabetes, iNOS and eNOS protein expression increased gradually, there was significant difference in the positive expression among NC, DM3, DM6and DM9groups (P<0.05). The result of western blotting showed that VEGF protein band was very weak in NC group, the relative optical density of VEGF protein band increased gradually in the DM3, DM6and DM9groups, the level of VEGF protein expression markedly increased than those in NC group (P<0.05); the relative optical density of nNOS protein band were gradually higher in DM groups than in NC group (P <0.05), there was no evident difference in the relative optical density of nNOS protein band between DM6group and DM9group (P>0.05), there was significant difference in the expression of nNOS protein among the remaining DM groups (P<0.01); the relative optical density of iNOS and eNOS protein band were increased gradually in the DM3, DM6and DM9groups, there was significant difference in the relative optical density among NC, DM3, DM6and DM9groups (P<0.05).[Conclusions]1. The type1diabetic rat model induced successfully by STZ may represent early CID.2. In the early CID, cerebral ischemia caused by diabetes induces expression of VEGF protein increased gradually, which may be one of the mechanisms of vascular protection.3. In the early CID, the expression of nNOS、iNOS、eNOS protein increased gradually with the progression of diabetes, we speculated it may be related to microvascular lesion and neuron dysfunction of hippocampus.