Chronic Cerebral Ischemia Induces Downregulation of A1 Adenosine Receptors During White Matter Damage in Adult Mice

Potential Protective Effect of Dl-3-n-butylphthalide on Chronic Cerebral Ischemia Brain Injury

Chronic cerebral ischemia is one of the common ischemic cerebrovascular diseases. Chronic cerebral ischemia can lead to brain dysfunction, and its pathophysiological mechanism involves inflammation, blood-brain barrier destruction, oxidative stress, and other factors. As it is difficult to detect, it is easily overlooked, and it is often only observed following the onset of cognitive dysfunction. At present, there are only a few drugs for its treatment. Dl-3-n-butylphthalide (NBP), a compound extracted from celery seed, may play an important role in protecting against brain damage caused by chronic cerebral ischemia. Therefore, here, we have paid attention to the prevention and treatment of chronic cerebral ischemia with NBP.

Berberine Ameliorates Cognitive Impairment by Regulating Microglial Polarization and Increasing Expression of Anti-inflammatory Factors following Permanent Bilateral Common Carotid Artery Occlusion in Rats

BACKGROUND

Chronic cerebral hypoperfusion is associated with vascular cognitive impairment, and there are no specific therapeutic agents for use in clinical practice. Berberine has demonstrated good neuroprotective effects in models of acute cerebral ischemia; however, whether it can alleviate cognitive impairment caused by chronic cerebral hypoperfusion has rarely been investigated.

OBJECTIVE

The present study aimed to explore the mechanism by which berberine alleviates cognitive impairment resulting from chronic cerebral hypoperfusion.

METHODS

Forty-two male Sprague-Dawley rats were randomly divided into three groups: sham, model, and berberine. The models of chronic cerebral hypoperfusion were established via permanent bilateral common carotid artery occlusion (BCCAO). Cognitive function was evaluated using the Morris water maze, while neuronal damage and microglial activation and polarization were evaluated using western blotting and immunofluorescence, respectively. Enzyme-linked immunosorbent assays were used to detect the expression of anti-inflammatory factors including interleukin- 4 (IL-4) and interleukin-10 (IL-10).

RESULTS

Rats exhibited cognitive dysfunction after BCCAO, which was significantly attenuated following the berberine intervention. Levels of synaptophysin and NeuN were decreased in states of chronic cerebral hypoperfusion, during which microglial activation and a transition from the M2 to M1 phenotype were observed. Berberine treatment also significantly reversed these features. Moreover, levels of IL-4 and IL-10 expression increased significantly after berberine treatment.

CONCLUSION

Berberine may mitigate vascular cognitive dysfunction by promoting neuronal plasticity, inhibiting microglial activation, promoting transformation from an M1 to an M2 phenotype, and increasing levels of IL-4 and IL-10 expression.

High-fat diet exacerbates cognitive decline in mouse models of Alzheimer's disease and mixed dementia in a sex-dependent manner

BACKGROUND

Approximately 70% of Alzheimer's disease (AD) patients have co-morbid vascular contributions to cognitive impairment and dementia (VCID); this highly prevalent overlap of dementia subtypes is known as mixed dementia (MxD). AD is more prevalent in women, while VCID is slightly more prevalent in men. Sex differences in risk factors may contribute to sex differences in dementia subtypes. Unlike metabolically healthy women, diabetic women are more likely to develop VCID than diabetic men. Prediabetes is 3× more prevalent than diabetes and is linked to earlier onset of dementia in women, but not men. How prediabetes influences underlying pathology and cognitive outcomes across different dementia subtypes is unknown. To fill this gap in knowledge, we investigated the impact of diet-induced prediabetes and biological sex on cognitive function and neuropathology in mouse models of AD and MxD.

METHODS

Male and female 3xTg-AD mice received a sham (AD model) or unilateral common carotid artery occlusion surgery to induce chronic cerebral hypoperfusion (MxD model). Mice were fed a control or high fat (HF; 60% fat) diet from 3 to 7 months of age. In both sexes, HF diet elicited a prediabetic phenotype (impaired glucose tolerance) and weight gain.

RESULTS

In females, but not males, metabolic consequences of a HF diet were more severe in AD or MxD mice compared to WT. In both sexes, HF-fed AD or MxD mice displayed deficits in spatial memory in the Morris water maze (MWM). In females, but not males, HF-fed AD and MxD mice also displayed impaired spatial learning in the MWM. In females, but not males, AD or MxD caused deficits in activities of daily living, regardless of diet. Astrogliosis was more severe in AD and MxD females compared to males. Further, AD/MxD females had more amyloid beta plaques and hippocampal levels of insoluble amyloid beta 40 and 42 than AD/MxD males. In females, but not males, more severe glucose intolerance (prediabetes) was correlated with increased hippocampal microgliosis.

CONCLUSIONS

High-fat diet had a wider array of metabolic, cognitive, and neuropathological consequences in AD and MxD females compared to males. These findings shed light on potential underlying mechanisms by which prediabetes may lead to earlier dementia onset in women.

Tectorigenin attenuates cognitive impairments in mice with chronic cerebral ischemia by inhibiting the TLR4/NF-κB signaling pathway

This study aims to explore the effect of Tectorigenin in chronic cerebral ischemia (CCI)-induced cognitive impairment mice model. Cognitive impairment, hippocampal tissue histopathology, and myelin density in CCI mice were detected. HT22 cells were used to induce oxygen-glucose deprivation/reperfusion (OGD/R) injury. Cell viability and apoptosis of transfected HT22 cells and toll-like receptor-4 (TLR4)/nuclear factor-kappaB (NF-κB) pathway-related factor levels in hippocampal tissue and OGD/R models were detected. CCI caused cognitive impairment, hippocampal damage, and decreased myelin density in mice while promoting interleukin-1β, tumor necrosis factor-alpha, TLR4, myeloid differentiation primary response gene 88, p-p65, NLRP3, and ASC levels. Tectorigenin reversed the effects of CCI in mice and reversed the promoting effects of OGD/R on apoptosis and TLR4/NF-κB pathway-related factors levels, while overexpressed TLR4 reversed the effects of Tectorigenin in OGD/R-induced HT-22 cells. Tectorigenin alleviated cognitive impairment in CCI mice by inhibiting the TLR4/NF-κB signaling pathway.

Encephalopathy in Preterm Infants: Advances in Neuroprotection With Caffeine

With the improvement in neonatal rescue technology, the survival rate of critically ill preterm infants has substantially increased; however, the incidence of brain injury and sequelae in surviving preterm infants has concomitantly increased. Although the etiology and pathogenesis of preterm brain injury, and its prevention and treatment have been investigated in recent years, powerful and effective neuroprotective strategies are lacking. Caffeine is an emerging neuroprotective drug, and its benefits have been widely recognized; however, its effects depend on the dose of caffeine administered, the neurodevelopmental stage at the time of administration, and the duration of exposure. The main mechanisms of caffeine involve adenosine receptor antagonism, phosphodiesterase inhibition, calcium ion activation, and γ-aminobutyric acid receptor antagonism. Studies have shown that there are both direct and indirect beneficial effects of caffeine on the immature brain. Accordingly, this article briefly reviews the pharmacological characteristics of caffeine, its mechanism of action in the context of encephalopathy in premature infants, and its use in the neuroprotection of encephalopathy in this patient population.

Perturbation of Ephrin Receptor Signaling and Glutamatergic Transmission in the Hypothalamus in Depression Using Proteomics Integrated With Metabolomics

Hypothalamic dysfunction is a key pathological factor in inflammation-associated depression. In the present study, isobaric tags for relative-absolute quantitation (iTRAQ) combined with mass spectrometry and gas chromatography-mass spectrometry (GC-MS) were employed to detect the proteomes and metabolomes in the hypothalamus of the lipopolysaccharide (LPS)-induced depression mouse, respectively. A total of 187 proteins and 27 metabolites were differentially expressed compared with the control group. Following the integration of bi-omics data, pertinent pathways and molecular interaction networks were further identified. The results indicated altered molecules were clustered into Ephrin receptor signaling, glutamatergic transmission, and inflammation-related signaling included the LXR/RXR activation, FXR/RXR activation, and acute phase response signaling. First discovered in the hypothalamus, Ephrin receptor signaling regulates N-methyl-D-aspartate receptor (NMDAR)-predominant glutamatergic transmission, and further acted on AKT signaling that contributed to changes in hypothalamic neuroplasticity. Ephrin type-B receptor 2 (EPHB2), a transmembrane receptor protein in Ephrin receptor signaling, was significantly elevated and interacted with the accumulated NMDAR subunit GluN2A in the hypothalamus. Additionally, molecules involved in synaptic plasticity regulation, such as hypothalamic postsynaptic density protein-95 (PSD-95), p-AKT and brain-derived neurotrophic factor (BDNF), were significantly altered in the LPS-induced depressed group. It might be an underlying pathogenesis that the EPHB2-GluN2A-AKT cascade regulates synaptic plasticity in depression. EPHB2 can be a potential therapeutic target in the correction of glutamatergic transmission dysfunction. In summary, our findings point to the previously undiscovered molecular underpinnings of the pathophysiology in the hypothalamus of inflammation-associated depression and offer potential targets to develop antidepressants.

Effect of low-dose Levamlodipine Besylate in the treatment of vascular dementia

Vascular dementia (VaD) is a complex disorder caused by reduced blood flow in the brain. However, there is no effective pharmacological treatment option available until now. Here, we reported that low-dose levamlodipine besylate could reverse the cognitive impairment in VaD mice model of right unilateral common carotid arteries occlusion (rUCCAO). Oral administration of levamlodipine besylate (0.1 mg/kg) could reduce the latency to find the hidden platform in the MWM test as compared to the vehicle group. Furthermore, vehicle-treated mice revealed reduced phospho-CaMKII (Thr286) levels in the hippocampus, which can be partially restored by levamlodipine besylate (0.1 mg/kg and 0.5 mg/kg) treatment. No significant outcome on microglia and astrocytes were observed following levamlodipine besylate treatment. This data reveal novel findings of the therapeutic potential of low-dose levamlodipine besylate that could considerably enhance the cognitive function in VaD mice.

Caffeine Treatment Promotes Differentiation and Maturation of Hypoxic Oligodendrocytes via Counterbalancing Adenosine 1 Adenosine Receptor-Induced Calcium Overload

Background

We aimed to explore the involvement of adenosine 1 adenosine receptor (A1AR) in hypoxia-induced poor differentiation of oligodendrocytes (OLs), and the underlying mechanism of caffeine treatment in hypoxic injuries.

Material/Methods

Real-time polymerase chain reaction (RT-PCR) was used to assess the alterations of AR expression in cultured hypoxic OLs with or without caffeine treatment. Then, intracellular alterations of Ca²⁺ concentrations ([Ca²⁺]) were detected by confocal Fluo-3 imaging. The subsequent changes of myelin related protein expression were determined by western blot and immunofluorescence.

Results

Three hours after hypoxia, significantly upregulated expression of A1AR was observed, accompanied with significantly decreased expression of oligodendrocyte transcription factor (Olig2). In addition, either hypoxia stimulation or 100 μM adenosine induced apparent elevation of resting [Ca²⁺] in cultured OLs. However, pretreatment with DPCPX (A1AR selective antagonist) or caffeine abolished the [Ca²⁺] increase, and the subsequent adenosine of high dose induced Ca²⁺ activity in developing OLs. Furthermore, caffeine or DPCPX improved the expression MBP and CNPase proteins after hypoxia stimulation, which resulted in the morphological maturation of OLs.

Conclusions

Caffeine treatment exerted protective effects on neonatal hypoxia injuries. It prevented Ca²⁺ overload injury, kept Ca²⁺ homeostasis in hypoxic developing OLs, and facilitated optimal expression of myelin related proteins by inhibiting A1AR in vitro. This study also provided experimental evidence for clinical application of caffeine in early treatment of neonatal hypoxia, and highlighted the potential significance of A1AR in anti-hypoxic drug discovery.

Persistent therapeutic effect of a novel α5-GABAA receptor antagonist in rodent preclinical models of vascular cognitive impairment

This study examined the potential of the selective extra-synaptic α5-GABA_A receptor inhibitor S44819 (Egis-13529) to improve cognitive performance in preclinical models of vascular cognitive impairment (VCI). Chronic hypoperfusion of the brain in mice was induced by permanent occlusion of the right common carotid artery (rUCO). rUCO induced impairments of cognitive function in the object recognition test (OR) and the rewarded T-maze (RTM). In both tests, a single oral treatment with S44819 (OR - 0.1-3 mg/kg, RTM - 1-3 mg/kg p.o.) significantly reduced the effect of rUCO. Long-term treatment with S44819 (1-10 mg/kg twice daily p.o. for 14 days), that was initiated 24 h after surgery and was followed by a 10- or 13-day wash-out period, fully prevented the decline of cognitive performance of rUCO mice. In rats, occlusion of the middle cerebral artery (MCA) for 30 min caused a significantly diminished performance in the OR. This was prevented by S44819 given p.o. 15 mg/kg twice daily for 8 days, starting 7 days after surgery and tested following a 7-day wash-out period. Taken together, S44819 markedly and stably improved reference and working memory impaired by rUCO in mice. In rats, the compound effectively suppressed the development of cognitive impairment after mild stroke. In conclusion, as longer-term administration led to a persistent reversal of the cognitive deficits, it appears that S44819 may have symptomatic, as well as disease-modifying effects in models of VCI. Proof of concept is therefore provided for testing S44819 in the therapy of VCI and post-stroke dementia in humans.

Neurological Changes in Vulnerable Brain Areas of Chronic Cerebral Hypoperfusion Mice

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is associated with neurological changes and cognitive decline. It is a major cause of vascular dementia and a contributing factor in Alzheimer disease. Animal models are useful in helping to elucidate the mechanisms of these diseases while demonstrating differences in pathological onset and severity. Furthermore, different mouse strains show differences in their susceptibility to neurological damage resulting in different cognitive outcomes.

PURPOSE

This study investigated the effect of CCH induced by permanent unilateral common carotid artery occlusion (UCO) on neurological damage in vulnerable brain regions such as hippocampus, striatum, and white matter areas from 2 to 8 weeks following CCH induction.

METHODS

Thirty-six male Institute of Cancer Research (ICR) mice were randomly divided into 2 main experimental groups, Sham and UCO. These 2 main groups were further divided into 3 observation periods of 2, 4, and 8 weeks following CCH. Histological study was then employed using 0.1% cresyl violet and luxol fast blue staining to assess neurological damage.

RESULTS

We found equal levels of neurological damage induced by CCH between ipsi- and contralateral hemispheres. Hippocampus and striatum damage were slightly increased from 2 to 8 weeks rising to significance at 8 weeks in both areas, while the white matter densities of the corpus callosum, internal capsule, optic tract and striatum fiber did not change.

CONCLUSION

CCH induced by UCO in ICR mice induces hippocampal and striatal damage at 8 weeks while leaving white matter undamaged.

Adenosine A1-Receptors Modulate mTOR Signaling to Regulate White Matter Inflammatory Lesions Induced by Chronic Cerebral Hypoperfusion

We sought to investigate the role of the adenosine A1 receptors (A1ARs) in white matter lesions under chronic cerebral hypoperfusion (CCH) and explore the potential repair mechanisms by activation of the receptors. A right unilateral common carotid artery occlusion (rUCCAO) method was used to construct a CCH model. 2-chloro-N6-cyclopentyladenosine (CCPA), a specific agonist of A1ARs, was used to explore the biological mechanisms of repair in white matter lesions under CCH. The expression of mammalian target of rapamycin (mTOR), phosphorylation of mTOR (P-mTOR), myelin basic protein (MBP, a marker of white matter myelination) were detected by Western-blot. Pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) and anti-inflammatory cytokine interleukin-10 (IL-10) levels were determined by ELISA. Compared with the control groups on week 2, 4 and 6, in CCPA-treated groups, the ratio of P-mTOR/mTOR, expression of MBP and IL-10 increased markedly, while the expression of TNF-α reduced at week 6. In conclusion, A1ARs appears to reduce inflammation in white matter via the mTOR signaling pathway in the rUCCAO mice. Therefore, A1ARs may serve as a therapeutic target during the repair of white matter lesions under CCH.

Recombinant Tissue Plasminogen Activator Induces Neurological Side Effects Independent on Thrombolysis in Mechanical Animal Models of Focal Cerebral Infarction: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Recombinant tissue plasminogen activator (rtPA) is the only effective drug approved by US FDA to treat ischemic stroke, and it contains pleiotropic effects besides thrombolysis. We performed a meta-analysis to clarify effect of tissue plasminogen activator (tPA) on cerebral infarction besides its thrombolysis property in mechanical animal stroke.

METHODS

Relevant studies were identified by two reviewers after searching online databases, including Pubmed, Embase, and ScienceDirect, from 1979 to 2016. We identified 6, 65, 17, 12, 16, 12 and 13 comparisons reporting effect of endogenous tPA on infarction volume and effects of rtPA on infarction volume, blood-brain barrier, brain edema, intracerebral hemorrhage, neurological function and mortality rate in all 47 included studies. Standardized mean differences for continuous measures and risk ratio for dichotomous measures were calculated to assess the effects of endogenous tPA and rtPA on cerebral infarction in animals. The quality of included studies was assessed using the Stroke Therapy Academic Industry Roundtable score. Subgroup analysis, meta-regression and sensitivity analysis were performed to explore sources of heterogeneity. Funnel plot, Trim and Fill method and Egger's test were obtained to detect publication bias.

RESULTS

We found that both endogenous tPA and rtPA had not enlarged infarction volume, or deteriorated neurological function. However, rtPA would disrupt blood-brain barrier, aggravate brain edema, induce intracerebral hemorrhage and increase mortality rate.

CONCLUSIONS

This meta-analysis reveals rtPA can lead to neurological side effects besides thrombolysis in mechanical animal stroke, which may account for clinical exacerbation for stroke patients that do not achieve vascular recanalization with rtPA.

Molecular Mechanisms of Vascular Dementia: What Can Be Learned from Animal Models of Chronic Cerebral Hypoperfusion?

Vascular dementia (VD) is defined as a progressive neurodegenerative disease of cognitive decline, attributable to cerebrovascular factors. Numerous studies have demonstrated that chronic cerebral hypoperfusion (CCH) is associated with the initiation and progression of VD and Alzheimer's disease (AD). Suitable animal models were established to replicate such pathological condition in experimental research, which contributes largely to comprehending causal relationships between CCH and cognitive impairment. The most widely used experimental model of VD and CCH is permanent bilateral common carotid artery occlusion in rats. In CCH models, changes of learning and memory, cerebral blood flow (CBF), energy metabolism, and neuropathology initiated by ischemia were revealed. However, in order to achieve potential therapeutic targets, particular mechanisms in cognitive and neuropathological changes from CCH to dementia should be investigated. Recent studies have shown that hypoperfusion resulted in a chain of disruption of homeostatic interactions, including oxidative stress, neuroinflammation, neurotransmitter system dysfunction, mitochondrial dysfunction, disturbance of lipid metabolism, and alterations of growth factors. Evidence from experimental studies that elucidate the damaging effects of such imbalances suggests their critical roles in the pathogenesis of VD. The present review provides a summary of the achievements in mechanisms made with the CCH models, permits an understanding of the causative role played by CCH in VD, and highlights preventative and therapeutic prospects.

Protective effects of carnosine on white matter damage induced by chronic cerebral hypoperfusion

Carnosine is a dipeptide that scavenges free radicals, inhibits inflammation in the central nervous system, and protects against ischemic and hypoxic brain damage through its anti-oxidative and anti-apoptotic actions. Therefore, we hypothesized that carnosine would also protect against white matter damage caused by subcortical ischemic injury. White matter damage was induced by right unilateral common carotid artery occlusion in mice. The animals were treated with 200, 500 or 750 mg/kg carnosine by intraperitoneal injection 30 minutes before injury and every other day after injury. Then, 37 days later, Klüver-Barrera staining, toluidine blue staining and immunofluorescence staining were performed. Carnosine (200, 500 mg/kg) substantially reduced damage to the white matter in the corpus callosum, internal capsule and optic tract, and it rescued expression of myelin basic protein, and alleviated the loss of oligodendrocytes. However, carnosine at the higher dose of 750 mg/kg did not have the same effects as the 200 and 500 mg/kg doses. These findings show that carnosine, at a particular dose range, protects against white matter damage caused by chronic cerebral ischemia in mice, likely by reducing oligodendroglial cell loss.