Cilostazol reduces blood brain barrier dysfunction, white matter lesion formation and motor deficits following chronic cerebral hypoperfusion

MYPT1SMKO Mice Function as a Novel Spontaneous Age- and Hypertension-Dependent Animal Model of CSVD

Cerebral small vessel disease (CSVD) is the most common progressive vascular disease that causes vascular dementia. Aging and hypertension are major contributors to CSVD, but the pathophysiological mechanism remains unclear, mainly due to the lack of an ideal animal model. Our previous study revealed that vascular smooth muscle cell (VSMC)-specific myosin phosphatase target subunit 1 (MYPT1) knockout (MYPT1SMKO) leads to constant hypertension, prompting us to explore whether hypertensive MYPT1SMKO mice can be considered a novel CSVD animal model. Here, we found that MYPT1SMKO mice displayed age-dependent CSVD-like neurobehaviors, including decreased motion speed, anxiety, and cognitive decline. MYPT1SMKO mice exhibited remarkable white matter injury compared with control mice, as shown by the more prominent loss of myelin at 12 months of age. Additionally, MYPT1SMKO mice were found to exhibit CSVD-like small vessel impairment, including intravascular hyalinization, perivascular space enlargement, and microbleed and blood-brain barrier (BBB) disruption. Last, our results revealed that the brain of MYPT1SMKO mice was characterized by an exacerbated inflammatory microenvironment, which is similar to patients with CSVD. In light of the above structural and functional phenotypes that closely mimic the conditions of human CSVD, we suggest that MYPT1SMKO mice are a novel age- and hypertension-dependent animal model of CSVD.

Sex, Endothelial Cell Functions, and Peripheral Artery Disease

Peripheral artery disease (PAD) is caused by blocked arteries due to atherosclerosis and/or thrombosis which reduce blood flow to the lower limbs. It results in major morbidity, including ischemic limb, claudication, and amputation, with patients also suffering a heightened risk of heart attack, stroke, and death. Recent studies suggest women have a higher prevalence of PAD than men, and with worse outcomes after intervention. In addition to a potential unconscious bias faced by women with PAD in the health system, with underdiagnosis, and lower rates of guideline-based therapy, fundamental biological differences between men and women may be important. In this review, we highlight sexual dimorphisms in endothelial cell functions and how they may impact PAD pathophysiology in women. Understanding sex-specific mechanisms in PAD is essential for the development of new therapies and personalized care for patients with PAD.

Amorphous selenium inhibits oxidative stress injury of neurons in vascular dementia rats by activating NMDAR pathway

Vascular dementia (VD) is one of the most common causes of dementia, taking account for about 20% of all cases. Although studies have found that selenium supplementation can improve the cognitive ability of Alzheimer's patients, there is currently no research on the cognitive impairment caused by VD. This study aimed to investigate the role and mechanism of Amorphous selenium nanodots (A SeNDs) in the prevention of VD. The bilateral common carotid artery occlusion (BCCAO) method was used to establish a VD model. The neuroprotective effect of A SeNDs was evaluated by Morris water maze, Transcranial Doppler TCD, hematoxylin-eosin (HE) staining, Neuron-specific nuclear protein (Neu N) staining and Golgi staining. Detect the expression levels of oxidative stress and Calcium-calmodulin dependent protein kinase II (CaMK II), N-methyl-D-aspartate receptor subunit NR2A, and postsynaptic dense protein 95 (PSD95). Finally, measure the concentration of calcium ions in neuronal cells. The results showed that A SeNDs could significantly improve the learning and memory ability of VD rats, restore the posterior arterial blood flow of the brain, improve the neuronal morphology and dendritic remodeling of pyramidal cells in hippocampal CA1 area, reduce the level of oxidative stress in VD rats, increase the expression of NR2A, PSD95, CaMK II proteins and reduce intracellular calcium ion concentration, but the addition of selective NR2A antagonist NVP-AAMO77 eliminated these benefits. It suggests that A SeNDs may improve cognitive dysfunction in vascular dementia rats by regulating the NMDAR pathway.

Long-Term Effectiveness of Cilostazol in Patients with Hemodialysis with Peripheral Artery Disease

AIM

The aim of this study was to investigate the effects of continuous cilostazol use on emergency department (ED) visits, hospitalizations, and vascular outcomes in patients with hemodialysis (HD) with peripheral artery disease (PAD).

METHODS

This retrospective cohort study recruited 558 adult patients, who had received chronic HD for at least 90 days between January 1, 2008 and December 31, 2012, from the National Health Insurance Research Database. Eligible patients were divided into two groups based on continuing or discontinuing cilostazol treatment. Outcome measures were ED visits, hospitalizations, mortality, and vascular outcomes such as percutaneous transluminal angioplasty, surgical bypass, lower leg amputation, ischemic stroke, hemorrhagic stroke, and cardiovascular events.

RESULTS

Patients with continuous cilostazol use had significantly higher prevalence of stroke, cancer, vintage, and the use of angiotensin receptor blocker and β-blocker, but significantly lower incidence of ischemic stroke and cardiovascular events, as well as lower mortality, than those without continuous cilostazol use (all p＜.05). Continuous cilostazol use was independently associated with lower risk of ED visits, hemorrhagic stroke, and cardiovascular events (adjusted hazard ratios: 0.79, 0.29, and 0.67; 95% confidence intervals: 0.62-0.98, 0.10-0.84, and 0.48-0.96, respectively; all p＜.05). Continuous cilostazol use was significantly associated with higher ED visit-free and cardiovascular event-free rates (log-rank test; p＜.05).

CONCLUSION

Continuous treatment of cilostazol in patients with HD with PAD significantly decreases the risk of ED visits, hemorrhagic stroke, and cardiovascular events and improves ED visit-free and cardiovascular event-free rates during long-term follow-up.

Reversal of spatial memory impairment by phosphodiesterase 3 inhibitor cilostazol is associated with reduced neuroinflammation and increased cerebral glucose uptake in aged male mice

The nucleotide second messenger 3', 5'-cyclic adenosine monophosphate (cAMP) and 3', 5'-cyclic guanosine monophosphate (cGMP) mediate fundamental functions of the brain, including learning and memory. Phosphodiesterase 3 (PDE3) can hydrolyze both cAMP and cGMP and appears to be involved in the regulation of their contents in cells. We previously demonstrated that long-term administration of cilostazol, a PDE3 inhibitor, maintained good memory performance in aging mice. Here, we report on studies aimed at determining whether cilostazol also reverses already-impaired memory in aged male mice. One month of oral 1.5% cilostazol administration in 22-month-old mice reversed age-related declines in hippocampus-dependent memory tasks, including the object recognition and the Morris water maze. Furthermore, cilostazol reduced neuroinflammation, as evidenced by immunohistochemical staining, and increased glucose uptake in the brain, as evidence by positron emission tomography (PET) with 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG). These results suggest that already-expressed memory impairment in aged male mice that depend on cyclic nucleotide signaling can be reversed by inhibition of PDE3. The reversal of age-related memory impairments may occur in the central nervous system, either through cilostazol-enhanced recall or strengthening of weak memories that otherwise may be resistant to recall.

A Study on the Pathogenesis of Vascular Cognitive Impairment and Dementia: The Chronic Cerebral Hypoperfusion Hypothesis

The pathogenic mechanisms underlying vascular cognitive impairment and dementia (VCID) remain controversial due to the heterogeneity of vascular causes and complexity of disease neuropathology. However, one common feature shared among all these vascular causes is cerebral blood flow (CBF) dysregulation, and chronic cerebral hypoperfusion (CCH) is the universal consequence of CBF dysregulation, which subsequently results in an insufficient blood supply to the brain, ultimately contributing to VCID. The purpose of this comprehensive review is to emphasize the important contributions of CCH to VCID and illustrate the current findings about the mechanisms involved in CCH-induced VCID pathological changes. Specifically, evidence is mainly provided to support the molecular mechanisms, including Aβ accumulation, inflammation, oxidative stress, blood-brain barrier (BBB) disruption, trophic uncoupling and white matter lesions (WMLs). Notably, there are close interactions among these multiple mechanisms, and further research is necessary to elucidate the hitherto unsolved questions regarding these interactions. An enhanced understanding of the pathological features in preclinical models could provide a theoretical basis, ultimately achieving the shift from treatment to prevention.

Post-stroke treatment with K-134, a phosphodiesterase 3 inhibitor, improves stroke outcomes in the stroke-prone spontaneously hypertensive rat model-A comparative evaluation of antiplatelet drugs

Post-stroke antiplatelet therapy has been proved to reduce the risk of recurrent stroke; however, it may also increase the incidence of intracranial hemorrhage that could offset any benefits. Therefore, the balance between the benefits and risks of antiplatelet drugs is a critical issue to consider. In the present study, we have compared the effects of post-stroke administration of antiplatelet agents on functional outcomes in the stroke-prone spontaneously hypertensive rat (SHRSP), an established animal model that mimics human lacunar stroke and cerebral small vessel disease. We confirmed that a potent phosphodiesterase 3 (PDE3) inhibitor, K-134, significantly improved post-stroke survival rate and survival time, attenuated stroke-induced neurological deficits, and decreased the incidence of cerebral lesion caused by intracerebral hemorrhage and softening. Similarly, cilostazol showed beneficial effects, though to a lower extent with respect to the survival outcome and neurological symptoms. On the other hand, a P2Y12 inhibitor, clopidogrel significantly improved survival outcomes at the higher dose but caused massive bleeding in the brain at both low and high doses. In contrast, no hemorrhagic lesion was observed in K-134-treated SHRSPs despite its antiplatelet activity. Our findings indicate that K-134 may have a superior post-stroke therapeutic outcome in comparison to other antiplatelet drugs.

Salvianolic acid A relieves cognitive disorder after chronic cerebral ischemia: Involvement of Drd2/Cryab/NF-κB pathway

Chronic cerebral ischemia (CCI) refers to long-term hypoperfusion of cerebral blood flow with the main clinical manifestations of progressive cognitive impairment. The pathological mechanism of CCI is complex, and there is a lack of effective treatments. Salvianolic acid A (SalA) is a neuroprotective extract of Salvia miltiorrhiza with the effects of anti-inflammation and anti-apoptosis. In this study, the effect of SalA on cognitive function and Drd2/Cryab/NF-κB signaling pathway in rats with CCI was investigated. Morris water maze and open field test were used to observe the effects of SalA on the cognitive function of CCI rats. The pathological changes in the brain were observed by HE, Nissl, and LFB staining. TUNEL staining, enzyme-linked immunosorbent assay, and western blot analysis were used to detect the inflammatory and apoptosis in the cortex and hippocampus. The expression of Drd2/Cryab/NF-κB pathway-related molecules and Drd2 localization were detected by western blotting and dual immunofluorescence, respectively. SH-SY5Y cells were exposed to chronic hypoglycemic and hypoxic injury in vitro, and Drd2 inhibitor haloperidol was used to verify the involved pathway. The results showed that SalA could improve the cognitive function of CCI rats, reduce pathological damage of cortex and hippocampus, inhibit neuroinflammation and apoptosis, and suppress the activation of NF-κB by regulating Drd2/Cryab pathway. And SalA inhibited NF-κB activation and nuclear translocation in SH-SY5Y cells by upregulating Drd2/Cryab pathway, which was reversed by haloperidol interference. In conclusion, SalA could relieve CCI-induced cognitive impairment in rats, at least partly through the Drd2/Cryab/NF-κB pathway.

Prevention of vascular dementia via immunotherapeutic blockade of renin-angiotensin system in a rat model

INTRODUCTION

As several clinical trials have revealed that angiotensin-converting enzyme inhibitors and angiotensin II (Ang II) receptor blockers may be efficient in treating vascular dementia (VaD), the long-acting blockade of the renin-angiotensin system (RAS) would be useful considering the poor adherence of antihypertensive drugs. Accordingly, we continuously blocked RAS via vaccination and examined the effectiveness of the VaD model in rats.

METHODS

Male Wistar rats were exposed to two-vessel occlusions (2VO) after three injections of Ang II peptide vaccine. The effects of the vaccine were evaluated in the novel object recognition test, brain RAS components, and markers for oligodendrocytes.

RESULTS

In the vaccinated rats, anti-Ang II antibody titer level was increased in serum until Day 168, but not in cerebral parenchyma. Vaccinated rats showed better object recognition memory with inhibited demyelination in the corpus callosum and activation of astrocytes and microglia. Also, levels of BrdU/GSTπ-positive cells and the phosphorylation of cAMP response element binding protein was increased in vaccinated rats, indicating that the differentiation of oligodendrocyte progenitor cells to mature oligodendrocytes was accelerated. Vaccinated rats showed increased expression of fibroblast growth factor-2 (FGF2), which was observed in endothelial cells. Angiotensinogen mRNA was decreased at 7 days after 2VO but increased at 14 and 28 days.

CONCLUSION

Ang II vaccine might have promoted oligodendrocyte differentiation and inhibited astrocytic and microglial activation by stimulating FGF2 signaling in the endothelial cells-oligodendrocyte/astrocyte/microglia coupling. These data indicate the feasibility of Ang II vaccine for preventing progression of vascular dementia.

MTT and Blood-Brain Barrier Disruption within Asymptomatic Vascular WM Lesions

BACKGROUND AND PURPOSE

White matter lesions of presumed ischemic origin are associated with progressive cognitive impairment and impaired BBB function. Studying the longitudinal effects of white matter lesion biomarkers that measure changes in perfusion and BBB patency within white matter lesions is required for long-term studies of lesion progression. We studied perfusion and BBB disruption within white matter lesions in asymptomatic subjects.

MATERIALS AND METHODS

Anatomic imaging was followed by consecutive dynamic contrast-enhanced and DSC imaging. White matter lesions in 21 asymptomatic individuals were determined using a Subject-Specific Sparse Dictionary Learning algorithm with manual correction. Perfusion-related parameters including CBF, MTT, the BBB leakage parameter, and volume transfer constant were determined.

RESULTS

MTT was significantly prolonged (7.88 [SD, 1.03] seconds) within white matter lesions compared with normal-appearing white (7.29 [SD, 1.14] seconds) and gray matter (6.67 [SD, 1.35] seconds). The volume transfer constant, measured by dynamic contrast-enhanced imaging, was significantly elevated (0.013 [SD, 0.017] minutes-1) in white matter lesions compared with normal-appearing white matter (0.007 [SD, 0.011] minutes-1). BBB disruption within white matter lesions was detected relative to normal white and gray matter using the DSC-BBB leakage parameter method so that increasing BBB disruption correlated with increasing white matter lesion volume (Spearman correlation coefficient = 0.44; P < .046).

CONCLUSIONS

A dual-contrast-injection MR imaging protocol combined with a 3D automated segmentation analysis pipeline was used to assess BBB disruption in white matter lesions on the basis of quantitative perfusion measures including the volume transfer constant (dynamic contrast-enhanced imaging), the BBB leakage parameter (DSC), and MTT (DSC). This protocol was able to detect early pathologic changes in otherwise healthy individuals.

Acupuncture Can Regulate the Peripheral Immune Cell Spectrum and Inflammatory Environment of the Vascular Dementia Rat, and Improve the Cognitive Dysfunction of the Rats

Objective

The aim of this study is to analyze the effects of acupuncture on peripheral immune function, inflammation, and cognitive impairment in vascular dementia (VD) rats.

Methods

In this study, 2-month-old healthy male Wistar rats (260-280 g) were assigned to the groups as follows: normal group (Gn, n = 10), sham-operated group (Gs, n = 10), and operated group (Go, n = 45). The Go group was established by permanent, bilateral common carotid artery occlusion (BCCAO). Two months after operation, the operated rats were screened by hidden platform trial and the rats with cognitive dysfunction were further randomly divided into impaired group (Gi), acupoint group (Ga), and non-acupoint group (Gna) with 10 rats in each group. The Ga group was given acupuncture treatment for 14 days with a rest for every 7 days. After treatment, the Morris water maze (MWM) test was performed to evaluate the spatial learning and memory abilities of rats. The lymphocyte subsets in peripheral blood and spleen of rats were measured by flow cytometry. The levels of cytokines [i.e., interleukin (IL)-1β, IL-2, IL-4, IL-10, tumor necrosis factor-α (TNF-α), and interferon-γ (INF-γ)], chemokines (i.e., macrophage inflammatory protein-2 (MIP-2)), and other inflammatory mediators (i.e., cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS)) in peripheral blood and hippocampus were measured by enzyme linked immunosorbent assay (ELISA).

Results

Compared with the Gn group, the Gi rats presented long escape latencies to find the platform. After acupuncture treatment, the escape latencies of the Ga group were rescued markedly when compared with the Gi group (P < 0.05). The proportion of CD4 + T lymphocytes in both spleen and peripheral blood in the Ga group increased (P < 0.05) in comparison with the Gi group. There is an obvious reduction in IL-1β (P < 0.05), IL-2 (P < 0.05), TNF-α (P < 0.01), INF-γ (P < 0.01), MIP-2 (P < 0.05), and iNOS (P < 0.01), coming along with the increased levels of IL-4 and IL-10 (P < 0.01) in the Ga group when compared with the Gi group. In addition, the hippocampus proinflammatory factors IL-1β (P < 0.01), IL-2 (P < 0.01), TNF-α (P < 0.05), INF-γ (P < 0.05), MIP-2 (P < 0.05), iNOS (P < 0.01), and COX-2 decreased in the Ga group, whereas the anti-inflammatory factors IL-4 and IL-10 (P < 0.01) increased.

Conclusion

There are abnormal immune function and peripheral inflammation in VD rats. Acupuncture can regulate the peripheral immune function and inflammation of the VD rats and can improve the cognitive dysfunction of the rats.

The Effect of High Fat Diet on Cerebrovascular Health and Pathology: A Species Comparative Review

In both humans and animal models, consumption of a high-saturated-fat diet has been linked to vascular dysfunction and cognitive impairments. Laboratory animals provide excellent models for more invasive high-fat-diet-related research. However, the physiological differences between humans and common animal models in terms of how they react metabolically to high-fat diets need to be considered. Here, we review the factors that may affect the translatability of mechanistic research in animal models, paying special attention to the effects of a high-fat diet on vascular outcomes. We draw attention to the dissociation between metabolic syndrome and dyslipidemia in rodents, unlike the state in humans, where the two commonly occur. We also discuss the differential vulnerability between species to the metabolic and vascular effects of macronutrients in the diet. Findings from animal studies are better interpreted as modeling specific aspects of dysfunction. We conclude that the differences between species provide an opportunity to explore why some species are protected from the detrimental aspects of high-fat-diet-induced dysfunction, and to translate these findings into benefits for human health.

Association of White Matter Hyperintensities and Cardiovascular Disease: The Importance of Microcirculatory Disease

Cardiac and cerebrovascular diseases are currently the leading causes of mortality and disability worldwide. Both the heart and brain display similar vascular anatomy, with large conduit arteries running on the surface of the organ providing tissue perfusion through an intricate network of penetrating small vessels. Both organs rely on fine tuning of local blood flow to match metabolic demand. Blood flow regulation requires adequate functioning of the microcirculation in both organs, with loss of microvascular function, termed small vessel disease (SVD) underlying different potential clinical manifestations. SVD in the heart, known as coronary microvascular dysfunction, can cause chronic or acute myocardial ischemia and may lead to development of heart failure. In the brain, cerebral SVD can cause an acute stroke syndrome known as lacunar stroke or more subtle pathological alterations of the brain parenchyma, which may eventually lead to neurological deficits or cognitive decline in the long term. Coronary microcirculation cannot be visualized in vivo in humans, and functional information can be deduced by measuring the coronary flow reserve. The diagnosis of cerebral SVD is largely based on brain magnetic resonance imaging, with white matter hyperintensities, microbleeds, and brain atrophy reflecting key structural changes. There is evidence that such structural changes reflect underlying cerebral SVD. Here, we review interactions between SVD and cardiovascular risk factors, and we discuss the evidence linking cerebral SVD with large vessel atheroma, atrial fibrillation, heart failure, and heart valve disease.

Mfsd2a Reverses Spatial Learning and Memory Impairment Caused by Chronic Cerebral Hypoperfusion via Protection of the Blood-Brain Barrier

Disruption of the blood–brain barrier (BBB) can lead to cognitive impairment. Major facilitator superfamily domain-containing protein 2a (Mfsd2a) is a newly discovered protein that is essential for maintaining BBB integrity. However, the role of Mfsd2a in vascular cognitive impairment has not been explored yet. In this study, a rat model of chronic cerebral hypoperfusion (CCH) was established by producing permanent bilateral common carotid artery occlusion (2VO) in rats. We found that after the 2VO procedure, the rats exhibited cognitive impairment, showed increased BBB leakage within the hippocampus, and had reduced expression of the Mfsd2a protein. The overexpression of Mfsd2a in the rat hippocampus reversed these changes. Further investigations using transmission electron microscopy revealed a significantly increased rate of vesicular transcytosis in the BBB of the hippocampus of the CCH rats; the rate reduced after overexpression of Mfsd2a. Moreover, Mfsd2a overexpression did not cause changes in the expression of tight junction-associated proteins and in the ultrastructures of the tight junctions. In conclusion, Mfsd2a attenuated BBB damage and ameliorated cognitive impairment in CCH rats, and its protective effect on the BBB was achieved via inhibition of vesicular transcytosis.

Epimedium flavonoids improve cognitive impairment and white matter lesions induced by chronic cerebral hypoperfusion through inhibiting the Lingo-1/Fyn/ROCK pathway and activating the BDNF/NRG1/PI3K pathway in rats

Chronic cerebral hypoperfusion is a common cause of cerebral small vascular disease (CSVD). White matter (WM) lesions are the typical pathological manifestation of CSVD and contribute to cognitive decline. Epimedium flavonoids (EF) are the main component in Epimedium brevicornu Maxim., which is commonly used in traditional Chinese medicine. The purpose of this study was to investigate the effects of EF on cognitive impairment and the underlying mechanisms in a CSVD rat model induced with chronic cerebral hypoperfusion. The model was established by permanent bilateral common carotid artery occlusion (2VO) in rats. EF (50, 100, and 200 mg/kg) was intragastrically administered once a day for 12 weeks starting 2 weeks after 2VO surgery. The learning and memory capacity of the rats were measured using the Morris water maze and step-through tests. WM lesions were observed by MRI-diffusion tensor imaging, transmission electron microscopy, and LFB staining. Oligodendrocytes were detected by immunohistochemistry. Western blotting assay was used to determine the level of protein expression. The results showed that EF significantly improved learning and memory impairment, alleviated WM nerve fiber injuries and demyelination, and increased the number of mature oligodendrocytes in the corpus callosum, subcortical WM, and periventricular WM in 2VO rats. Mechanistically, EF reduced the expression of Lingo-1 and ROCK2 and increased the levels of phosphorylated (p-) Fyn, brain-derived neurotrophic factor (BDNF), TrkB, neuregulin-1 (NRG-1), p-ErbB4, PI3K p85 and p110α, p-Akt, and p-CREB in the corpus callosum of 2VO rats. These results suggest that EF may improve cognitive impairment and WM lesions induced by chronic cerebral hypoperfusion through inhibiting the Lingo-1/Fyn/ROCK pathway and activating the BDNF/TrkB, NRG-1/ErbB4, and the downstream PI3K/Akt/CREB pathways in WM. Thus, EF can be used as a potential neuroprotective agent in CSVD therapy.

Cilostazol use is associated with FIM cognitive improvement during convalescent rehabilitation in patients with ischemic stroke: a retrospective study

Cilostazol is a phosphodiesterase III-inhibiting antiplatelet agent that is often used to prevent stroke and peripheral artery disease, and its administration has shown significant improvements for cognitive impairment. We investigate the potential of cilostazol for reducing or restoring cognitive decline during convalescent rehabilitation in patients with non-cardioembolic ischemic stroke. The study sample included 371 consecutive patients with lacunar (n = 44) and atherothrombosis (n = 327) subtypes of non-cardioembolic ischemic stroke (224 men and 147 women; mean age, 72.9 ± 8.1 years) who were required for inpatient convalescent rehabilitation. Their medical records were retrospectively surveyed to identify those who had received cilostazol (n = 101). Patients were grouped based on cilostazol condition, and Functional Independence Measure (FIM) scores (total and motor or cognitive subtest scores) were assessed both at admission and discharge. The gain and efficiency in FIM cognitive scores from admission to discharge were significantly higher in patients who received cilostazol than those who did not (p = 0.047 and p = 0.035, respectively); we found no significant differences in other clinical factors or scores. Multiple linear regression analysis confirmed that cilostazol was a significant factor in FIM cognitive scores at discharge (β = 0.041, B = 0.682, p = 0.045); the two tested dosages were not significantly different (100 mg/day, n = 43; 200 mg/day, n = 58). Cilostazol can potentially improve cognitive function during convalescent rehabilitation of patients with non-cardioembolic ischemic stroke, although another research must be needed to confirm this potential.

[White matter hyperintensities in ageing: Pathophysiology, associated cognitive disorders and prevention]

White matter hyperintensities (WMH), also known as leukoaraïosis are very common neuroradiological manifestations in the elderly. The main risk factors for WMH are age and high blood pressure. The vascular origin of these lesions is classically accepted and WMH are considered as one feature of the small vessel disease. WMH may be associated with clinical symptoms, depending notably on their importance according to age. They are associated with increased mortality, strokes and changes in cognition with a higher risk of dementia (vascular dementia or Alzheimer's disease). Modification of vascular risk factors could have a beneficial effect, but few evidences from controlled trials are available.

A Comparison Study of Cilostazol and Aspirin on Changes in Volume of Cerebral Small Vessel Disease White Matter Changes: Protocol of a Multicenter, Randomized Controlled Trial

Background and Purpose

Cerebral small vessel disease (CSVD) is the most common cause of vascular dementia and a major contributor to mixed dementia. CSVD is characterized by progressive cerebral white matter changes (WMC) due to chronic low perfusion and loss of autoregulation. In addition to its antiplatelet effect, cilostazol exerts a vasodilating effect and improves endothelial function. This study aims to compare the effects of cilostazol and aspirin on changes in WMC volume in CSVD.

Methods

The comparison study of Cilostazol and aspirin on cHAnges in volume of cerebral smaLL vEssel disease white matter chaNGEs (CHALLENGE) is a double blind, randomized trial involving 19 hospitals across South Korea. Patients with moderate or severe WMC and ≥ 1 lacunar infarction detected on brain magnetic resonance imaging (MRI) are eligible; the projected sample size is 254. Participants are randomly assigned to a cilostazol or aspirin group at a 1:1 ratio. Cilostazol slow release 200 mg or aspirin 100 mg are taken once daily for 2 years. The primary outcome measure is the change in WMC volume on MRI from baseline to 104 weeks. Secondary imaging outcomes include changes in the number of lacunes and cerebral microbleeds, fractional anisotropy and mean diffusivity on diffusion tensor imaging, and brain atrophy. Secondary clinical outcomes include all ischemic strokes, all vascular events, and changes in cognition, motor function, mood, urinary symptoms, and disability.

Conclusions

CHALLENGE will provide evidence to support the selection of long-term antiplatelet therapy in CSVD.

Trial Registration

ClinicalTrials.gov Identifier: NCT01932203.

Animal Models of Chronic Cerebral Hypoperfusion: From Mouse to Primate

Vascular cognitive impairment (VCI) or vascular dementia occurs as a result of brain ischemia and represents the second most common type of dementia after Alzheimer’s disease. To explore the underlying mechanisms of VCI, several animal models of chronic cerebral hypoperfusion have been developed in rats, mice, and primates. We established a mouse model of chronic cerebral hypoperfusion by narrowing the bilateral common carotid arteries with microcoils, eventually resulting in hippocampal atrophy. In addition, a mouse model of white matter infarct-related damage with cognitive and motor dysfunction has also been established by asymmetric common carotid artery surgery. Although most experiments studying chronic cerebral hypoperfusion have been performed in rodents because of the ease of handling and greater ethical acceptability, non-human primates appear to represent the best model for the study of VCI, due to their similarities in much larger white matter volume and amyloid β depositions like humans. Therefore, we also recently developed a baboon model of VCI through three-vessel occlusion (both the internal carotid arteries and the left vertebral artery). In this review, several animal models of chronic cerebral hypoperfusion, from mouse to primate, are extensively discussed to aid in better understanding of pathophysiology of VCI.

Protection of blood-brain barrier as a potential mechanism for enriched environments to improve cognitive impairment caused by chronic cerebral hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is a common pathophysiological basis for Alzheimer's Disease and vascular dementia in the early stages. It has been confirmed that blood-brain barrier (BBB) destruction is a key factor in CCH-related cognitive impairment. Here we explored the effects of an enriched environment (EE) intervention on CCH-induced BBB destruction and cognitive impairment, and the underlying mechanism.

METHODS

Rats in the EE group were exposed to an EE, while the standard environment (SE) group was maintained in a standard cage with bedding but no other objects. On day 14, CCH was induced via permanent bilateral common carotid artery occlusion (2VO). Next, Evans blue (EB) leakage in the hippocampus was measured by chemical colorimetry to dynamically evaluate BBB permeability. On day 28, the BBB ultrastructure was observed using transmission electron microscopy. The expression levels of BBB integrity-related proteins, matrix metalloproteinases-2/-9 (MMP-2/-9), and the classical Wnt/β-catenin signaling pathway-related proteins were detected using western-blotting techniques. On day 43, cognitive function was assessed using the Morris water maze.

RESULTS

After 2VO, CCH rats exposed to the SE developed obvious cognitive impairment and BBB destruction. BBB damage was manifested through increased EB leakage, ultrastructural destruction, degradation of BBB integrity-related proteins, and up-regulation of MMP-2/-9. These changes were significantly alleviated after the EE intervention. In addition, EEs activated the Wnt/β-catenin signaling pathway in the hippocampus of rats.

CONCLUSIONS

These results suggest that protection of the BBB may be a novel mechanism by which EEs ameliorate CCH-induced cognitive impairment, and this effect may be related to the activation of the Wnt/β-catenin pathway.

Cerebral Small Vessel Disease (CSVD) - Lessons From the Animal Models

Cerebral small vessel disease (CSVD) refers to a spectrum of clinical and imaging findings resulting from pathological processes of various etiologies affecting cerebral arterioles, perforating arteries, capillaries, and venules. Unlike large vessels, it is a challenge to visualize small vessels in vivo, hence the difficulty to directly monitor the natural progression of the disease. CSVD might progress for many years during the early stage of the disease as it remains asymptomatic. Prevalent among elderly individuals, CSVD has been alarmingly reported as an important precursor of full-blown stroke and vascular dementia. Growing evidence has also shown a significant association between CSVD's radiological manifestation with dementia and Alzheimer's disease (AD) pathology. Although it remains contentious as to whether CSVD is a cause or sequelae of AD, it is not far-fetched to posit that effective therapeutic measures of CSVD would mitigate the overall burden of dementia. Nevertheless, the unifying theory on the pathomechanism of the disease remains elusive, hence the lack of effective therapeutic approaches. Thus, this chapter consolidates the contemporary insights from numerous experimental animal models of CSVD, to date: from the available experimental animal models of CSVD and its translational research value; the pathomechanical aspects of the disease; relevant aspects on systems biology; opportunities for early disease biomarkers; and finally, converging approaches for future therapeutic directions of CSVD.

High-Mobility Group Box 1 Neutralization Prevents Chronic Cerebral Hypoperfusion-Induced Optic Tract Injuries in the White Matter Associated with Down-regulation of Inflammatory Responses

Chronic cerebral hypoperfusion (CCH)-induced white matter lesions (WMLs) are region-specific with the optic tract (OT) displaying the most severe damages and leading to visual-based behavioral impairment. Previously we have demonstrated that anti-high-mobility group box 1 (HMGB1) neutralizing antibody (Ab) prevents CCH-induced hippocampal damages via inhibition of neuroinflammation. Here we tested the protective role of the Ab on CCH-induced OT injuries. Rats were treated with permanent occlusion of common carotid arteries (2-VO) or a sham surgery, and then administered with PBS, anti-HMGB1 Ab, or paired control Ab. Pupillary light reflex examination, visual water maze, and tapered beam-walking were performed 28 days post-surgery to investigate the behavioral deficits. Meanwhile, WMLs were measured by Klüver-Barrera (KB) and H&E staining, and glial activation was further assessed to evaluate inflammatory responses in OT. Results revealed that anti-HMGB1 Ab ameliorated the morphological damages (grade scores, vacuoles, and thickness) in OT area and preserved visual abilities. Additionally, the increased levels of inflammatory responses and expressions of TLR4 and NF-κB p65 and phosphorylated NF-κB p65 (p-p65) in OT area were partly down-regulated after anti-HMGB1 treatment. Taken together, these findings suggested that HMGB1 neutralization could ease OT injuries and visual-guided behavioral deficits via suppressing inflammatory responses.

Changes in blood-brain barrier permeability and ultrastructure, and protein expression in a rat model of cerebral hypoperfusion

Cerebral hypoperfusion involved a reduction in cerebral blood flow, leading to neuronal dysfunction, microglial activation and white matter degeneration. The effects on the blood-brain barrier (BBB) however, have not been well-documented. Here, two-vessel occlusion model was adopted to mimic the condition of cerebral hypoperfusion in Sprague-Dawley rats. The BBB permeability to high and low molecular weight exogenous tracers i.e. Evans blue dye and sodium fluorescein respectively, showed marked extravasation of the Evans blue dye in the frontal cortex, posterior cortex and thalamus-midbrain at day 1 following induction of cerebral hypoperfusion. Transmission electron microscopy revealed brain endothelial cell and astrocyte damages including increased pinocytotic vesicles and formation of membrane invaginations in the endothelial cells, and swelling of the astrocytes' end-feet. Investigation on brain microvessel protein expressions using two-dimensional (2D) gel electrophoresis coupled with LC-MS/MS showed that proteins involved in mitochondrial energy metabolism, transcription regulation, cytoskeleton maintenance and signaling pathways were differently expressed. The expression of aconitate hydratase, heterogeneous nuclear ribonucleoprotein, enoyl Co-A hydratase and beta-synuclein were downregulated, while the opposite observed for calreticulin and enhancer of rudimentary homolog. These findings provide insights into the BBB molecular responses to cerebral hypoperfusion, which may assist development of future therapeutic strategies.

PDE3 Inhibitors Repurposed as Treatments for Age-Related Cognitive Impairment

As the population of older individuals grows worldwide, researchers have increasingly focused their attention on identifying key molecular targets of age-related cognitive impairments, with the aim of developing possible therapeutic interventions. Two such molecules are the intracellular cyclic nucleotides, cAMP and cGMP. These second messengers mediate fundamental aspects of brain function relevant to memory, learning, and cognitive function. Consequently, phosphodiesterases (PDEs), which hydrolyze cAMP and cGMP, are promising targets for the development of cognition-enhancing drugs. Inhibitors that target PDEs work by elevating intracellular cAMP. In this review, we provide an overview of different PDE inhibitors, and then we focus on pharmacological and physiological effects of PDE3 inhibitors in the CNS and peripheral tissues. Finally, we discuss findings from experimental and preliminary clinical studies and the potential beneficial effects of the PDE3 inhibitor cilostazol on age-related cognitive impairments. In the innovation pipeline of pharmaceutical development, the antiplatelet agent cilostazol has come into the spotlight as a novel treatment for mild cognitive impairment. Overall, the repurposing of cilostazol may represent a potentially promising way to treat mild cognitive impairment, Alzheimer's disease, and vascular dementia. In this review, we present a brief summary of cAMP signaling and different PDE inhibitors, followed by a discussion of the pharmacological and physiological role of PDE3 inhibitors. In this context, we discuss the repurposing of a PDE3 inhibitor, cilostazol, as a potential treatment for age-related cognitive impairment based on recent research.

Sigma-1 receptor activation alleviates blood-brain barrier dysfunction in vascular dementia mice

Sigma-1 receptor (Sig-1R) activation has been shown to decrease infarct volume and enhance neuronal survival after brain ischemia-reperfusion (IR) in rodent models. The present study aims to investigate first the effect of Sig-1R activation on blood-brain barrier (BBB) disruption during experimental stroke. Male C57BL/6 mice were subjected to bilateral common carotid artery occlusion (BCCAO) for 15 min, and the worst BBB leakage was observed on the 7th day after brain IR. To confirm the BBB protective role of Sig-1R, mice were divided into five groups (sham group, BCCAO group, PRE084 group, BD1047 group, PRE084 and BD1047 group; 29-35 mice for each group), and treated with agonist PRE084 (1 mg/kg) and/or antagonist BD1047 (1 mg/kg) for 7 days intraperitoneally once a day after BCCAO. Interestingly, PRE084 administration significantly improved neurobehavioral performance as well as healing of neuron damage and white matter lesions. PRE084 also reduced the leakage of Evans blue and IgG and attenuated the disassembly of BBB structural proteins, while the neuroprotective and BBB protective functions of PRE084 were blocked by BD1047. Furthermore, in Sig-1R knockout (Sig-1R KO) mice, brain IR produced more serious IgG leakage and degradation of BBB structural proteins than in wild-type model mice. In addition, the protective effect of PRE084 against the BBB was lost in Sig-1R KO mice after brain IR. Finally, treatment with PRE084 significantly increased the expression of Sig-1R in brain microvascular endothelial cells of mice that were subjected to brain IR and increased translocation of Sig-1R to the cell plasmalemma. Thus, we identified a previously unexplored role of Sig-1R in alleviating BBB disruption in stroke processes and have demonstrated that reversing BBB rupture through Sig-1R activation may be another promising method for cerebral protection against IR injury.

Cilostazol for treatment of cerebral infarction

INTRODUCTION

Stroke not only causes critical disability and death but is also a cause of anxiety with the possibility of secondary cardiovascular events including secondary ischemic stroke. Indeed, patients with a history of previous stroke have a high rate of stroke recurrence, indicating the clinical importance of secondary stroke prevention. Area of covered: This review provides an overview of the pooled evidence for cilostazol's use in the management of secondary stroke prevention. Among the various antiplatelet agents that are available, aspirin is the most frequently used agent worldwide for the prevention of secondary stroke. Cilostazol, a selective phosphodiesterase (PDE) 3A inhibitor, is used worldwide for the treatment of patients with intermittent claudication. However, in Asia, cilostazol is recommended and used in practice for secondary stroke prevention. Expert opinion: The authors believe that cilostazol could be used for secondary stroke prevention not only in Asia but worldwide. However, further randomized trials on cilostazol are needed, especially in the US and Europe to better support its case.

Oxidation-induced C-H amination leads to a new avenue to build C-N bonds

In this work, we develop an oxidation-induced C-H functionalization strategy, which not only leads to a new avenue to build C-N bonds, but also leads to different site-selectivity compared with "classic directing-groups". The high selectivity of our new catalytic system originates from the heterogeneous electron-density distribution of the radical cation species which are induced by single electron transfer between the aromatics and oxidant-Cu(ii) species.

The degree of leukoaraiosis predicts clinical outcomes and prognosis in patients with middle cerebral artery occlusion after intravenous thrombolysis

Leukoaraiosis (LA) is common in elderly patients with ischemic stroke on magnetic resonance imaging. In this study, we investigate whether the degree of LA is associated with clinical outcomes and prognosis of patients with middle cerebral artery occlusion following intravenous thrombolytic. Ninety-seven patients were recruited and divided into three groups based on the degree of LA (no, mild and moderate to severe LA) by the Fazekas scale. Clinical outcomes, recurrent stroke, Fugl-Meyer rating scale (FMS) and complications of intravenous thrombolysis were assessed. The association between the degree of LA and functional outcomes was analyzed by multivariable logistic regression model. Patients enrolled were divided into three groups: 26 patients with no LA, 43 patients with mild LA and 28 patients with moderate to severe LA. Impressively, the patients with mild LA were better in early neurological recovery and 90-day FMS score than patients in the other two groups. Multivariate logistic analysis revealed that moderate to severe LA was an independent predictor of poor functional outcome (OR: 10.482; 95% CI: 1.442-76.181; P = .020). Moreover, the patients with moderate to severe LA have a higher rate of hemorrhagic transformation and recurrent stroke as compared with two other groups during 90-day follow-up. Different degrees of LA differentially affect clinical outcome and prognosis in patients with middle cerebral artery occlusion following intravenous thrombolytic. Moderate to severe LA is a risk factor of poor prognosis. Mild LA is associated with early neurological recovery and good motor functional outcome.

Cilostazol alleviates white matter degeneration caused by chronic cerebral hypoperfusion in mice: Implication of its mechanism from gene expression analysis

Cilostazol is known to alleviate white matter demyelination due to chronic cerebral hypoperfusion in rodent models, although their pharmacological mechanisms remain unclear. In this study, we investigated the protective effect of cilostazol in relation to gene expression profile. Bilateral common carotid artery stenosis (BCAS) mice were treated with oral administration of cilostazol or placebo starting from a week after the surgery. Demyelination of the cingulum was compared between the 2 groups 2, 6, and 10 weeks after initial drug administration. Also, to examine temporal gene expression change during demyelination, DNA microarray analysis was conducted using samples from the corpus callosum of 2nd and 6th week BCAS mice. For genes that showed more than 2-fold up-regulation, their increase was validated by qPCR. Finally, to determine the effect of cilostazol towards those genes, their expression in the corpus callosum of 6-week placebo-treated and cilostazol-treated BCAS mice was compared by qPCR. Amelioration of myelin loss was observed in cilostazol-treated group, showing significant difference with those observed in placebo group after 10-week treatment. Gene ontology analysis of the 17 up-regulated (FDR<0.01) genes showed that majority of the genes were related to cell development processes. Among the validated genes, expression of Btg2 was significantly promoted in the corpus callosum of BCAS mice by administration of cilostazol. Results of this study suggest that activation of Btg2 may be one of the key pharmacological effects of cilostazol towards the white matter during chronic ischemia.

Cilostazol for Secondary Prevention of Stroke: Should the Guidelines Perhaps Be Extended?

Cilostazol belongs to the new generation antiplatelet agents that have been introduced and studied regarding a potential role in cardiovascular disease prevention or treatment. Although data on peripheral artery disease are sufficient, and the drug has been recommended as first line treatment for intermittent claudication, it has not been approved nor recommended as far as cerebrovascular events are concerned. However, a great volume of randomized as well as pooled data has been published during the last years. Therefore, this review aims to describe the basic mechanisms of cilostazol’s action as well as to present all recent clinical data in order to conclude on whether official guidelines should be extended.

Effects of phosphodiesterase 3A modulation on murine cerebral microhemorrhages

BACKGROUND

Cerebral microbleeds (CMB) are MRI-demonstrable cerebral microhemorrhages (CMH) which commonly coexist with ischemic stroke. This creates a challenging therapeutic milieu, and a strategy that simultaneously protects the vessel wall and provides anti-thrombotic activity is an attractive potential approach. Phosphodiesterase 3A (PDE3A) inhibition is known to provide cerebral vessel wall protection combined with anti-thrombotic effects. As an initial step in the development of a therapy that simultaneously treats CMB and ischemic stroke, we hypothesized that inhibition of the PDE3A pathway is protective against CMH development.

METHODS

The effect of PDE3A pathway inhibition was studied in the inflammation-induced and cerebral amyloid angiopathy (CAA)-associated mouse models of CMH. The PDE3A pathway was modulated using two approaches: genetic deletion of PDE3A and pharmacological inhibition of PDE3A by cilostazol. The effects of PDE3A pathway modulation on H&E- and Prussian blue (PB)-positive CMH development, BBB function (IgG, claudin-5, and fibrinogen), and neuroinflammation (ICAM-1, Iba-1, and GFAP) were investigated.

RESULTS

Robust development of CMH in the inflammation-induced and CAA-associated spontaneous mouse models was observed. Inflammation-induced CMH were associated with markers of BBB dysfunction and inflammation, and CAA-associated spontaneous CMH were associated primarily with markers of neuroinflammation. Genetic deletion of the PDE3A gene did not alter BBB function, microglial activation, or CMH development, but significantly reduced endothelial and astrocyte activation in the inflammation-induced CMH mouse model. In the CAA-associated CMH mouse model, PDE3A modulation via pharmacological inhibition by cilostazol did not alter BBB function, neuroinflammation, or CMH development.

CONCLUSIONS

Modulation of the PDE3A pathway, either by genetic deletion or pharmacological inhibition, does not alter CMH development in an inflammation-induced or in a CAA-associated mouse model of CMH. The role of microglial activation and BBB injury in CMH development warrants further investigation.

Inhibition of SENP3 by URB597 ameliorates neurovascular unit dysfunction in rats with chronic cerebral hypoperfusion

Disruption of the neurovascular unit (NVU), induced by chronic cerebral hypoperfusion (CCH), has been broadly found in various neurological disorders. SUMO-specific protease 3 (SENP3) is expressed in neurons, astrocytes, and microglia, and regulates a variety of cell events. However, whether SENP3 is involved in neurovascular injury under the condition of CCH is still elusive. To address this issue, we investigated the effect of the fatty acid amide hydrolase (FAAH) inhibitor URB597 on NVU and the role of SENP3 in this process, as well as the underling mechanisms. The expression of SENP3 was detected by immunochemistry. The function and structure of the NVU was assessed by Western blot analysis and transmission electron microscopy. CCH caused the upregulation of SENP3, the disruption of cell and non-cell components at the protein level within the NVU, and ultrastructural deterioration. The NVU impairment as well as overexpression of SENP3 were reversed by treatment with URB597. These results reveal a novel neuroprotective role in URB597, which implicates URB597 in the amelioration of CCH-induced NVU impairment by inhibiting SENP3.