Dexamethasone Alleviates Diabetes Induced Cognitive Impairment By Inhibiting IFN-γ/Caspase-1 Pyroptosis

Objective: Diabetic Encephalopathy(DE)refers to cognitive impairment and neurophysiological and structural changes of the brain caused by diabetes.It is characterized by cognitive and motor dysfunction and even dementia.Current studies on the mechanism of DE mainly involve oxidative stress injury,abnormal insulin signaling pathway,and Alzheimer’s disease,etc.The mechanism is complex and there is crosstalk among various mechanisms.As a chronic metabolic disease,the role of inflammatory response caused by diabetes in its complications has been paid more and more attention,but its role in diabetic brain complications has been less studied.This study focuses on the changes of proinflammatory cytokine Interferon-gamma(IFN-γ)in diabetic brain and its possible role in the process of DE generation,and further explores whether anti-inflammatory therapy can improve the cognitive function of diabetic rats through the intervention of anti-inflammatory drug dexamethasone.In this study,a model of SD diabetic rats was constructed to detect the changes of IFN-γ in the brain.The results showed that the expression of IFN-γ was increased in the cerebral cortex and hippocampus of diabetic patients.Immunofluorescence co-labeling assay confirmed that the overexpression of IFN-γ in diabetic patients was mainly from activated microglia cells.At the same time,the expression of Caspase-1and GSDMD-N was also increased in the performers of the typical scorched death pathway in the diabetic brain,suggesting that this pathway may be involved in the process of diabetic encephalopathy.Then,in order to further verify the relationship between INF-γ expression and classical pyrodeath pathway,dexamethasone intervention experiment was designed based on literature reports.The results showed that oral dexamethasone inhibited the activation of microglia and the expression of IFN-γ in the brain,and the classical pyrodeath mediated by Caspase-1 was also relieved after the inhibition of IFN-γ.Finally,behavioral experiments also confirmed the improvement of diabetes-related cognitive function and anxiety in diabetic rats after dexamethasone intervention.These results indicate that the pro-inflammatory factor IFN-γ is the initial factor promoting the pathogenesis of diabetic encephalopathy,which provides a new way to understand the pathological mechanism of diabetic brain,and also proves that dexamethasone anti-inflammatory therapy can improve the brain dysfunction caused by diabetes.Methods: SD rats were fed a high-fat and high-sugar diet and injected with STZ intraperitoneum to construct a rat diabetes model.The model was successfully determined by blood glucose,intake,water intake,urine volume,body weight and behavioral experiments.The changes of IFN-γ,Caspase-1 and GSDMD-N in the cerebral cortex and hippocampus of normal and diabetic rats were compared by Western blot analysis.Immunofluorescence co-labeling was used to locate the source of IFN-γ.The effect of oral anti-inflammatory drug dexamethasone on the damage related indexes of inflammatory factors in diabetic rats after in vivo inhibition of IFN-γ expression;Behavioral experiments to explore changes in cognitive function in rats.Results:1.Establishment of rat diabetes model and detection of related indexesSD rats were fed a high-fat and high-sugar diet combined with low-dose STZ intraperitoneal injection to construct a rat diabetes model.The model was successfully determined by blood glucose,feeding,water intake,urine volume,body weight,liver fat infiltration,etc.2.The expression of inflammatory factor IFN-γ protein in rat brain was detectedDetection of IFN-γ : The content of IFN-γ in cerebral cortex and hippocampus of DM group was significantly higher than that of Ctrl group(P<0.05);Immunofluorescence results showed that the content of IFN-γ in the brain of DM group was significantly higher than that of Ctrl group(P<0.05),and IFN-γ was more co-marked than IBA-1,suggesting that activation of microglia cells is the main source of IFN-γ in diabetic brain.3.Detection of scorch death signaling pathway proteins GSDMD-N and Caspase-1 in the brain of diabetic rats(1)Detection of GSDMD-N content in the brain of rats: the content of GSDMD-N in the cortex and hippocampus of rats in DM group was significantly higher than that in Ctrl group(P < 0.05);(2)Detection of Caspase-1 in rat brain: the content of Caspase-1 in DM group was significantly higher than that in Ctrl group(P < 0.05),and the Caspase-1 in hippocampus was higher than that in Ctrl group(P < 0.05);(3)Immunofluorescence showed that Caspase-1(positive cell count)in DM group was significantly higher than that in Ctrl group(P < 0.05);4.Effect of anti-inflammatory drug dexamethasone on classical pyrogenic pathway after intervention of IFN-γ4.1 IFN-γ inhibition experiment and effect verification:The experimental group was given dexamethasone 5 mg orally.After 7consecutive days,the levels of IFN-γ in the cerebral cortex and hippocampus of diabetic rats were significantly decreased(P < 0.05);4.2 In vivo intervention of IFN-γ expression regulates metabolism of pyrogenic signaling protein in brain:The expressions of GSDMD-N and Caspase-1 in the brain of rats in diabetic group were significantly decreased compared with those in normal group.5.Effects of dexamethasone intervention on cognitive function in diabetic ratsThrough the experiment to explore the cognitive function of diabetic rats through the Y-word maze and the elevated cross maze,it was found that compared with the normal group,diabetic rats showed obvious cognitive dysfunction and depression tendency,and the learning activity behavior of learning ability to explore the unknown region was also weakened with statistical significance.The cognitive dysfunction of diabetic rats was significantly improved after dexamethasone intervention(P < 0.05).Conclusions:SD rats were fed with HDF and injected with STZ.The results of behavioral experiments confirm that SD rats have obvious cognitive dysfunction.The scorched signaling proteins GSDMD-N and Caspase-1 were increased in the brain of diabetic rats.The content of IFN-γ in cognition-related brain regions(cortex and hippocampus)of diabetic rats increased significantly,and microglia cells were activated.After dexamethasone treatment,the level of IFN-γ protein in diabetic brain and the expression of classical pyrogenic signaling protein also decreased significantly,and the animal behavior was improved significantly.In conclusion,we suggest that the increase of IFN-γ induced by diabetes-related factors can activate the scorched signaling pathway in the brain of diabetic rats.The anti-inflammatory drug dexamethasone can improve the cognitive function caused by diabetes by inhibiting the above pathway...