Intestinal dysbiosis mediates cognitive impairment via the intestine and brain NLRP3 inflammasome activation in chronic sleep deprivation.

Growing evidence suggests the involvement of the microbiota-gut-brain axis in cognitive impairment induced by sleep deprivation (SD), however how the microbiota-gut-brain axis work remains elusive. Here, we discovered that chronic SD induced intestinal dysbiosis, activated NLRP3 inflammasome in the colon and brain, destructed intestinal/blood-brain barrier, and impaired cognitive function in mice. Transplantation of "SD microbiota" could almost mimic the pathological and behavioral changes caused by chronic SD. Furthermore, all the behavioral and pathological abnormalities were practically reversed in chronic sleep-deprived NLRP3-/- mice. Regional knockdown NLRP3 expression in the gut and hippocampus, respectively. We observed that down-regulation of NLRP3 in the hippocampus inhibited neuroinflammation, and ameliorated synaptic dysfunction and cognitive impairment induced by chronic SD. More intriguingly, the down-regulation of NLRP3 in the gut protected the intestinal barrier, attenuated the levels of peripheral inflammatory factors, down-regulated the expression of NLRP3 in the brain, and improved cognitive function in chronic SD mice. Our results identified gut microbiota as a driver in chronic SD and highlighted the NLRP3 inflammasome as a key regulator within the microbiota-gut-brain axis.

Construction of circRNA-Mediated Immune-Related ceRNA Network and Identification of Circulating circRNAs as Diagnostic Biomarkers in Acute Ischemic Stroke.

Background and Purpose: Accumulating evidence suggests that circular RNAs (circRNAs) are involved in immune and inflammatory processes after acute ischemic stroke (AIS). However, the roles of circRNA-mediated competing endogenous RNA (ceRNA) in modulating immune inflammation of AIS have not yet been determined. This study aimed to construct a circRNA-mediated immune-related ceRNA network and identify novel circRNAs in AIS. Methods: Microarray data were downloaded from the GEO database and further analysed by R software. Then, we constructed a circRNA-mediated ceRNA network based on interaction information from the bioinformatics database. A topological property analysis of the ceRNA network was conducted to screen novel circRNAs. Finally, we further applied quantitative real-time polymerase chain reaction (qRT-PCR) to two independent sets. Results: We constructed an AIS immune-related ceRNA (AISIRC) network containing immune-related genes (IRGs), miRNAs, and circRNAs. Additionally, we extracted the subnetwork from the AISIRC network and screened six immune-related circRNAs. After identification and validation, we finally confirmed that plasma levels of circPTP4A2 and circTLK2 were significantly increased in AIS patients compared with both healthy control subjects (HCs) and transient ischemic attack (TIA) patients. Logistic regression and receiver-operating characteristic (ROC) curve analyses demonstrated that these two circRNAs may function as predictive and discriminative biomarkers for AIS. We also confirmed that plasma levels of circPTP4A2 were elevated in TIA patients compared with HCs and might be an independent risk factor for predicting TIA. Longitudinal analysis of circRNA expression up to 90 days after AIS indicated that the ability of circPTP4A2 and circTLK2 to monitor AIS dynamics was highly desirable. Conclusion: In summary, the circRNA-mediated immune-related ceRNA network was successfully constructed, and two circulating circRNAs (circPTP4A2 and circTLK2) improved sensitivity for the diagnosis of AIS and could be considered diagnostic biomarkers.

Endovascular Treatment With and Without Intravenous Thrombolysis in Large Vessel Occlusions Stroke: A Systematic Review and Meta-Analysis.

Background: Previous studies have shown conflicting results about the benefits of pretreatment with intravenous thrombolysis before endovascular treatment (EVT) in patients with acute ischemic stroke (AIS) with large vessel occlusions (LVOs). This study aimed to investigate the clinical efficacy and safety of EVT alone vs. bridging therapy (BT) in patients with AIS with LVOs. Methods: A systematic review with meta-analysis of all available studies comparing clinical outcomes between BT and EVT alone was conducted by searching the National Center for Biotechnology Information/National Library of Medicine PubMed and Web of Science databases for relevant literature from database inception to October 20, 2020. Results: A total of 93 studies enrolling 45,190 patients were included in the present analysis. In both unadjusted and adjusted analyses, BT was associated with a higher likelihood of 90-day good outcome (crude odds ratio [cOR] 1.361, 95% confidence interval [CI] 1.234-1.502 and adjusted OR [aOR] 1.369, 95% CI 1.217-1.540) and successful reperfusion (cOR 1.271, 95% CI 1.149-1.406 and aOR 1.267, 95% CI 1.095-1.465) and lower odds of 90-day mortality (cOR 0.619, 95% CI 0.560-0.684 and aOR 0.718, 95% CI 0.594-0.868) than EVT alone. The two groups did not differ in the occurrence of symptomatic intracranial hemorrhage (sICH) (cOR 1.062, 95% CI 0.915-1.232 and aOR 1.20, 95% CI 0.95-1.47), 24-h early recovery (cOR 1.306, 95% CI 0.906-1.881 and aOR 1.46, 95% CI 0.46-2.19), and number of thrombectomy device passes ≤ 2 (aOR 1.466, 95% CI 0.983-2.185) after sensitivity analyses and adjustment for publication bias. Conclusions: BT provides more benefits than EVT alone in terms of clinical functional outcomes without compromising safety in AIS patients with LVOs.

Unhealthy Lifestyle Is an Important Risk Factor of Idiopathic BPPV.

Background: Benign paroxysmal positional vertigo (BPPV) is a self-limiting and recurrent disease but the cost is considerable. The number of patients with BPPV increased significantly under the quarantine policy in Hangzhou. The unhealthy lifestyle risk factors of BPPV have not yet been investigated. Thus, the objective is to analyze whether an unhealthy lifestyle is a risk factor of BPPV. Methods: One hundred and sixty three patients with idiopathic BPPV aged 22-87 years (BPPV group), and 89 aged 23-92 years sex-matched control subjects (non-BPPV group) were enrolled in this study. All BPPV patients received a definitive diagnosis which excluded secondary BPPV. Non-BPPV cases excluded BPPV, sudden deafness, Meniere's disease, ear or craniofacial surgery, vestibular neuritis, and head trauma history. We obtained a blood lipids profile, serum uric acid, total bilirubin, and related diagnostic information through the electronic medical record system. To get the time of physical activities and recumbent positions, we asked the patient or their family from February 2020 to June 2020, and the rest of the patient's information was acquired by phone or WeChat. Data Analyses: The t-test or chi-squared test, univariate, and multiple logistic regression analyses were performed for the two groups. For each factor, odds ratios were calculated with 95% confidence intervals (CIs). Moreover, test equality of two or more receiver operating characteristic (ROC) analyses were applied to the physical activities, and recumbent position time; area under curve (AUC) measures were calculated with 95% CIs and compared with each other. Results: The BPPV group had unhealthy lifestyles such as poor physical activities, prolonged recumbent position time, and low rate of calcium or VD supplementation in univariate logistic regression analyses (P < 0.05). Poor physical activities and prolonged recumbent position time were independently associated with BPPV in multiple logistic regression models (OR = 18.92, 95% CI: 6.34-56.43, p = 0.00 and OR = 1.15, 95% CI: 1.01-1.33, p < 0.04). In the comparison of ROC curves of recumbent position time and physical activities in identifying BPPV, AUCs were 0.68 (0.61-0.74), and 0.68 (0.63-0.73), respectively. Conclusion: We conclude that poor physical activities and prolonged recumbent position time may be independent risk factors for BPPV patients, but hypertension, hyperuricemia, hyperlipidemia, hemoglobin, diabetes, serum bilirubin, CHD, and CI, may not be.

Differential long noncoding RNA expressions in peripheral blood mononuclear cells for detection of acute ischemic stroke.

Long noncoding RNAs (lncRNAs) have been highlighted to be involved in the pathological process of ischemic stroke (IS). The purpose of the present study was to investigate the expression profile of lncRNAs in peripheral blood mononuclear cells (PBMCs) of acute IS patients and to explore their utility as biomarkers of IS. Distinctive expression patterns of PBMC lncRNAs were identified by an lncRNA microarray and individual quantitative real-time PCR (qRT-PCR) in four independent sets for 206 IS, 179 healthy controls (HCs), and 55 patients with transient ischemic attack (TIA). A biomarker panel (lncRNA-based combination index) was established using logistic regression. LncRNA microarray analysis showed 70 up-regulated and 128 down-regulated lncRNAs in IS patients. Individual qRT-PCR validation demonstrated that three lncRNAs (linc-DHFRL1-4, SNHG15, and linc-FAM98A-3) were significantly up-regulated in IS patients compared with HCs and TIA patients. Longitudinal analysis of lncRNA expression up to 90 days after IS showed that linc-FAM98A-3 normalized to control levels by day 7, while SNHG15 remained increased, indicating the ability of lncRNAs to monitor IS dynamics. Receiver-operating characteristic (ROC) curve analysis showed that the lncRNA-based combination index outperformed serum brain-derived neurotrophic factor (BDNF) and neurone-specific enolase (NSE) in distinguishing IS patients from TIA patients and HCs with areas under ROC curve of more than 0.84. Furthermore, the combination index increased significantly after treatment and was correlated with neurological deficit severity of IS. The panel of these altered lncRNAs was associated with acute IS and could serve as a novel diagnostic method.

The Short-term Prognostic Value of the Triglyceride-to-high-density Lipoprotein Cholesterol Ratio in Acute Ischemic Stroke.

The triglyceride (TG)-to-high-density lipoprotein cholesterol (HDL-C) ratio (TG/HDL-C) is a simple approach to predicting unfavorable outcomes in cardiovascular disease. The influence of TG/HDL-C on acute ischemic stroke remains elusive. The purpose of this study was to investigate the precise effect of TG/HDL-C on 3-month mortality after acute ischemic stroke (AIS). Patients with AIS were enrolled in the present study from 2011 to 2017. A total of 1459 participants from a single city in China were divided into retrospective training and prospective test cohorts. Medical records were collected periodically to determine the incidence of fatal events. All participants were followed for 3 months. Optimal cutoff values were determined using X-tile software to separate the training cohort patients into higher and lower survival groups based on their lipid levels. A survival analysis was conducted using Kaplan-Meier curves and a Cox proportional hazards regression model. A total of 1459 patients with AIS (median age 68.5 years, 58.5% male) were analyzed. Univariate Cox regression analysis confirmed that TG/HDL-C was a significant prognostic factor for 3-month survival. X-tile identified 0.9 as an optimal cutoff for TG/HDL-C. In the univariate analysis, the prognosis of the TG/HDL-C >0.9 group was markedly superior to that of TG/HDL-C ≤0.9 group (P<0.001). A multivariate Cox regression analysis showed that TG/HDL-C was independently correlated with a reduced risk of mortality (hazard ratio [HR], 0.39; 95% confidence interval [CI], 0.24-0.62; P<0.001). These results were confirmed in the 453 patients in the test cohort. A nomogram was constructed to predict 3-month case-fatality, and the c-indexes of predictive accuracy were 0.684 and 0.670 in the training and test cohorts, respectively (P<0.01). The serum TG/HDL-C ratio may be useful for predicting short-term mortality after AIS.

ß-arrestin2 functions as a key regulator in the sympathetic-triggered immunodepression after stroke.

BACKGROUND: Stroke-induced immunodeficiency syndrome (SIDS) is regarded as a protective mechanism for secondary inflammatory injury as well as a contributor to infection complications. Although stroke-induced hyperactivation of the sympathetic system is proved to facilitate SIDS, the involved endogenous factors and pathways are largely elusive. In this study, we aim to investigate the function of beta-arrestin-2 (ARRB2) in the sympathetic-mediated SIDS. METHODS: Splenic ARRB2 expression and the sympathetic system activity were detected after establishing transient models of middle cerebral artery occlusion (MCAO). In addition, a correlation between ARRB2 expression and the sympathetic system activity was analyzed using a linear correlation analysis. Any SIDS reflected in monocyte dysfunction was investigated by measuring inflammatory cytokine secretion and neurological deficit scores and infarct volume were tested to assess neurological outcome. Further, ARRB2 expression in the monocytes was knocked down in vitro by siRNAs. Following the stimulation of noradrenaline and lipopolysaccharide, cytokine secretion and the nuclear factor-κB (NF-κB) pathway were evaluated to gain insight into the mechanisms related to the contribution of ARRB2 to adrenergic-induced monocyte dysfunction. RESULTS: Splenic ARRB2 expression was significantly increased after stroke and also showed a significant positive correlation with the sympathetic system activity. Stroke-induced monocyte dysfunction resulted in an increase of the interleukin-10 (IL-10) level as well as a decrease of the interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) levels. Also, blockade of adrenergic-activity significantly reversed these cytokine levels, and blockade of adrenergic-activity improved stroke-induced neurological results. However, the improved neurological results had no significant correlation with ARRB2 expression. Furthermore, the in vitro results showed that the deficiency of ARRB2 dramatically repealed adrenergic-induced monocyte dysfunction and the inhibition of NF-κB signaling phosphorylation activity. CONCLUSIONS: ARRB2 is implicated in the sympathetic-triggered SIDS, in particular, monocyte dysfunction after stroke. Accordingly, ARRB2 may be a promising therapeutic target for the immunological management of stroke in a clinic.

Potential specific immunological indicators for stroke associated infection are partly modulated by sympathetic pathway activation.

BACKGROUND: Evidence has led to the consideration of immunodepression after stroke as an important contributor to stroke associated infection (SAI). However, so far no specific immunological indicator has been identified for SAI, and the underlying mechanism remains poorly understood. RESULTS: SAI patients had significantly higher IL-6 and IL-10 levels and lower HLA-DR levels than no-infection patients within 48h after stroke onset. NA significantly increased IL-10 levels, reduced HLA-DR expression, and decreased IL-6 expression by increasing ß-arrestin2 expression which reduced the activation of the NF-κB pathway. Propranolol reversed this effect of NA by reducing ß-arrestin2 expression. MATERIALS AND METHODS: A systematic search for eligible clinical studies was applied to pool the differences in peripheral cytokine levels between infection and no-infection stroke patients. The underlying mechanism behind these differences was investigated in vitro by applying norepinephrine (NA) and lipopolysaccharide (LPS) to simulate sympathetic pathway activation and sepsis respectively in THP-1 cells. Propranolol was applied to determine the effect of reversing the activation of the sympathetic pathway. Immunological indicators were also detected to assess the immune activation of THP-1 cells and measurements of the expression of ß-arrestin2, NF-κB, IκBα and phosphor-IκBα were performed to assess the activation of the sympathetic pathway. CONCLUSION: IL-6, IL-10 and HLA-DR are good candidate biomarkers for SAI. The activation of the sympathetic pathway could partly account for the specific immunological alterations found in SAI patients including HLA-DR decrease and IL-10 increase, which both could be reversed by propranolol. However, the mechanism underlying IL-6 increase still needs further exploration.

Splenectomy following MCAO inhibits the TLR4-NF-κB signaling pathway and protects the brain from neurodegeneration in rats.

BACKGROUND AND PURPOSE: The Toll-like receptor 4(TLR4)/nuclear factor kappa B NF-κB inflammatory pathway contributes to secondary inflammation in many diseases including stroke. Moreover, the neuroprotective effect of splenectomy in stroke is supported by a vast body of experimental evidence. Nevertheless, the underlying mechanism(s) by which splenectomy enhance neuroprotection in stroke is still poorly understood. Our study aimed to investigate whether post-ischemic splenectomy modulate the TLR4/NF-κB inflammatory pathway in stroke. METHODS: Immunohistochemistry was used to evaluate the levels of TLR4 and NF-κB expression in brain areas (parietal lobe, hippocampus and striatum) of rats that underwent: MCAO-splenectomy surgery (MS ); MCAO surgery without splenectomy (MCAO control or MC); Sham MCAO and splenectomy surgery (sham control group or SC group respectively. Apoptosis in these areas was assessed by TUNEL detection technique. RESULTS: The levels of TLR4 and NF-κB expression were significantly reduced in splenectomized rats relative to the MS group (P<0.01). Additionally, the number of apoptotic cells in the ischemic hemisphere were significantly higher in both MCAO groups compared to the Sham group (P<0.05), between day 1 and day 7. An exception was observed in the striatum where the difference in apoptotic rate between the MS and sham group was not statistically significant at the same time points. Moreover, the variation apoptotic rate in different cerebral zone correlated to variation in TLR4 and NF-κB expression. CONCLUSION: In summary, our study provides further evidence of neuroprotective effect of splenectomy in ischemic stroke. Our results suggest that such an effect might be due to the inhibition of theTLR4/NF-κB inflammatory pathway.

Blocking Sympathetic Nervous System Reverses Partially Stroke-Induced Immunosuppression but does not Aggravate Functional Outcome After Experimental Stroke in Rats.

Stoke results in activation of the sympathetic nervous system (SNS), inducing systemic immunosuppression. However, the potential mechanisms underlying stroke-induced immunosuppression remain unclear. Here, we determined the SNS effects on functional outcome and explored the interactions among SNS, ß-arrestin2 and nuclear factor-κB (NF-κB) after experimental stroke in rats. In the current study, stroke was induced by a transient middle cerebral artery occlusion (MCAO) in rats, and SNS activity was inhibited by intraperitoneal injection of 6-hydroxydopamine HBr (6-OHDA). 7.0 T Micro-MRI and Longa score were employed to assess the functional outcome after stroke. Flow cytometry and ELISA assay were used to measure the expression of MHC class II, tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). Western blot was conducted to analyze ß-arrestin2 and NF-κB protein expression levels after experimental stroke. We found significantly increased infarct volumes and functional impairment after MCAO at different post-surgery time points, which were not aggravated by 6-OHDA treatment. SNS blockade partially reversed the expression of MHC class II after stroke over time, as well as TNF-α and IFN-γ levels in lipopolysaccharide-stimulated macrophages in vitro. Treatment of MCAO rats with SNS-inhibitor significantly diminished NF-κB activation and enhanced ß-arrestin2 expression after stroke. This study suggests that pharmacological SNS inhibition dose not aggravate functional outcome after stroke. Stroke-induced immunosuppression may be involved in the SNS-ß-arrestin2-NF-κB pathway.

Role of the sympathetic nervous system and spleen in experimental stroke-induced immunodepression.

BACKGROUND: The mechanism of stroke-induced immunodepression syndrome (SIDS) remains uncertain. Some studies suggest that hyperactivation of the sympathetic nervous system (SNS) may be the key factor underlying SIDS. Catecholamines impair early lymphocyte response, which can increase the risk of stroke-associated infection (SAI). MATERIAL/METHODS: Our study focused on dynamic changes of metanephrine (MN), normetanephrine (NMN), cytokines, and spleen volume in the rat middle cerebral artery occlusion (MCAO) model. RESULTS: After MCAO, there is hyperactivation of SNS and pro-/anti-inflammatory imbalance, indicating systemic immunodepression. In addition, rat spleen size was reduced. Correlation analysis indicated that MCAO-induced spleen size reduction correlated with the changes in MN, NMN, and cytokines. Blocking SNS with propranolol can partly reverse the immunodepression and the reduction in spleen volume. CONCLUSIONS: Taken together, these findings suggest that acute ischemic stroke induces over-activation of the SNS, which lowers the threshold of infection and increases the risk of infection.

[Male sexual dysfunction and Parkinson's disease: a preliminary investigation].

OBJECTIVE: To investigate the prevalence of male sexual dysfunction in males with Parkinson's disease and the pathogenesis and related factors of the problem. METHODS: We evaluated the sexual function of 140 men with Parkinson's disease using Mini-mental State Examination (MMSE), Unified Parkinson's Disease Rating Scale (Part III) (UPDRS III), Hoenhn-Yahr Staging (HYS), Hamilton Depression Scale (HAMD) and Sexual Dysfunction Standard of ICD-10. We calculated the Levodopa equivalent doses (LED) for all the patients. RESULTS: Sexual dysfunction was found in 58 (41.43%) of the patients with Parkinson's disease. There were no significant differences in age, education, age of onset, course of disease and scores on UPDRS III, HYS and LED between the sexual dysfunction and normal sexual function groups. The HAMD score was 14.95 +/- 9.12 in the sexual dysfunction group, significantly higher than 10.96 +/- 9.82 in the normal sexual function group (P < 0.05), and it was positively correlated with the inci- dence of male sexual dysfunction (P < 0.05). CONCLUSION: Sexual dysfunction is a common symptom in males with Parkinson's disease, and is correlated with the high HAMD score of Parkinson's disease patients.

Cytotoxic role of advanced glycation end-products in PC12 cells treated with ß­amyloid peptide.

Alzheimer's disease (AD) is the most common type of dementia afflicting the elderly. Recent studies have increasingly suggested that a high concentration of advanced glycation end products (AGEs) may be important in AD pathogenesis. However, the mechanisms and pathways involved remain unknown. The aim of this study was to explore whether the mechanism of the effect of AGEs on Aß­PC12 cells [PC12 cells treated with ß­amyloid (Aß) peptide] was associated with oxidative stress; and to study whether inhibiting the activity of the receptor for AGE (RAGE) attenuated the toxic effect of AGEs and Aß on PC12 cells. Several PC12 cells were pretreated with Aß, and were then treated with different concentrations of AGEs. Other PC12 cells were treated with trypsin, a pancreatic protein enzyme and an inhibitor of RAGE, and were then treated with Aß and AGEs. Apoptosis was measured by flow cytometry (FCM) and cell viability was measured by MTT assay. RAGE and nuclear factor­κB (NF­κB) were measured by reverse transcription-polymerase chain reaction (RT­PCR) assay. With an increase in AGE concentration, the viability of Aß­PC12 cells treated with AGEs decreased. However, the Aß­PC12 cell viability was greater in the trypsin group than in the non­trypsin group. Cell apoptosis rates and mRNA expression of RAGE and NF­κB in Aß­PC12 cells treated with AGEs were significantly higher than in the Aß­PC12 cells. AGEs and Aß were neurotoxic, and RAGE triggered the neural cytotoxic role of AGEs in Aß­PC12 cells. The molecular mechanisms may be connected with the expression of NF­κB and apoptosis mediated by RAGE. Inhibiting the activity of RAGE may mitigate the toxic effect of AGEs and Aß on neural cells.

Effects of ginkgo biloba extract EGb761 on expression of RAGE and LRP-1 in cerebral microvascular endothelial cells under chronic hypoxia and hypoglycemia.

Alzheimer's disease (AD), characterized by accumulation of amyloid-beta protein (Abeta) in brain parenchyma, is closely associated with brain ischemia. Decreased clearance of Abeta from brain is the main cause of Abeta accumulation in sporadic AD. However, the mechanisms underlying ischemia-mediated AD pathogenesis remain unclear. The receptor for advanced end glycation products (RAGE) and low-density lipoprotein receptor-related protein-1 (LRP-1) expressed at blood brain barrier (BBB) are actively involved in Abeta clearance. RAGE is thought to be a primary transporter of Abeta across BBB into the brain from the systemic circulation, while LRP-1 mediates the transport of Abeta out of the brain. Ginkgo biloba extract EGb761, a traditional Chinese medicine, has been widely used in the treatment of AD. To investigate the effects of EGb761 on the expression of RAGE and LRP-1 in endothelial cells in response to ischemic injury, we cultured bEnd.3 cells, an immortalized mouse cerebral microvessel endothelial cell line, under a chronic hypoxic and hypoglycemic condition (CHH) to mimic ischemic injury of BBB, and then treated with EGb 761. We found that EGb 761 markedly ameliorated the damage (evaluated by MTT assay) from CHH. Moreover, we demonstrated that CHH led to a significant increase in the expression of RAGE both at the mRNA and protein levels at all times (24, 36, and 48 h), conversely; CHH induced a dramatic decrease in LRP-1 mRNA and protein expression at both 36 and 48 h. The results indicated that CHH has differential effects on the expression of RAGE and LRP-1. Furthermore, EGb761 significantly reversed CHH-induced upregulation of RAGE expression and downregulation of LRP-1 expression. Our findings suggest that EGb761 favor clearance of Abeta via regulating the expression of RAGE and LRP-1 during brain ischemia. This may provide a new insight into a possible molecular mechanism underlying brain ischemia-mediated AD pathogenesis, and potential therapeutic application of EGb 761 in treatment of AD.

[mRNA expression and activity of ADAM17 in hippocampus after chronic cerebral hypoperfusion: experiment with aged rats].

OBJECTIVE: To explore the effect of alpha-secretase on the pathogenesis of cognitive impairment following cerebral ischemia. METHODS: Forty-eight 12~16-months-old Wistar rats were randomly divided into 2 equal groups: hypoperfusion group, undergoing permanent occlusion of bilateral common carotid arteries to mimic cerebral hypoperfusion, and sham-operation group. Each group was further divided into 1, 2, 4, and 16 week subgroups. Y-maze test was conducted before operation and at different time points as mentioned above to examine the spatial learning and memory ability. The rats tested by Y-maze were killed with their hippoccampi taken out. Realtime PCR was used to assay the mRNA expression of a disintegrin and metalloproteinase (ADAM)-17 representing alpha-secretase in the hippocampus, and fluorescence spectrometry was applied to measure activity thereof. RESULTS: The numbers of electric stroke since 2 weeks after hypoperfusion were significantly higher than that before hypoperfusion in the same group and those of the sham-operation group (P < 0.05 or P < 0.01). The mRNA expressions of hippocampal ADAM17 of the hypoperfusion subgroup 2, 4, and 16 weeks after operation were 0.78 +/- 0.03, 0.78 +/- 0.02, and 0.54 +/- 0.03 respectively, all significantly lower than those of the sham-operation group (1.12 +/- 0.05, 0.99 +/- 0.04, and 1.01 +/- 0.04 respectively, all P < 0.01). The average fluorescence values of hippocampal alpha-secretase 1, 2, 4, and 16 weeks after hypoperfusion of the hypoperfusion group were 33,880 +/- 1086, 37,496 +/- 817, 32,295 +/- 864 and 30,069 +/- 1111, respectively, all significantly lower than those of the sham-operation group (39 497 +/- 838, 39 802 +/- 1052, 40,137 +/- 776, and 39,894 +/- 1076 respectively, all P < 0.01). CONCLUSION: The mRNA expression of ADAM17 that represents alpha-secretase in the hippocampus is down-regulated and the activity of alpha-secretase is decreased after chronic cerebral hypoperfusion. That may subsequently result in accumulation of beta amyloid precursor protein, substrate of alpha-secretase, (APP), and then activate the other pathway cleaving APP, i.e., the pathway by beta secretase. At last, the production of beta amyloid protein in brain after chronic cerebral hypoperfusion increases and impairs the memory.