Cerebral vascular dysfunction during hypercholesterolemia

Association between Brain-Derived Neurotrophic Factor and Lipid Profiles in Acute Ischemic Stroke Patients

Ischemic stroke, the most prevalent form of stroke, leads to neurological impairment due to cerebral ischemia and affects 55-90% of the population. Brain-derived neurotrophic factor (BDNF) plays a crucial role in the central nervous system and regulates cardiometabolic risk factors, including lipids. This single-center study aimed to explore the relationship between lipid profiles and BDNF levels in 90 patients who had experienced AIS for the first time. The results show that the high BDNF group (≥3.227 ng/mL) had significantly higher HbA1C and TG levels; ratios of TC/HDL-C, LDL-C/HDL-C, and TG/HDL-C; and percentage of hyperlipidemia (60%) as well as lower levels of HDL-C, with an OR of 1.903 (95% CI: 1.187-3.051) for TG/HDL-C, 1.975 (95% CI: 1.188-3.284) for TC/HDL-C, and 2.032 (95% CI: 1.113-3.711) for LDL-C/HDL-C. Plasma BDNF levels were found to be significantly positively correlated with TG and negatively with HDL-C, with OR values of 1.017 (95% CI: 1.003-1.030) and 0.926 (95% CI: 0.876-0.978), respectively. TC/HDL-C, TG/HDL-C, and LDL-C/HDL-C ratios are associated with BDNF levels in AIS patients. The results also indicate that, in AIS patients, higher BDNF levels are associated with lower HDL and higher TG concentrations.

Studies on the Effects of Hypercholesterolemia on Mouse Ophthalmic Artery Reactivity

Atherogenic lipoproteins may impair vascular reactivity, leading to tissue damage in various organs, including the eye. This study aimed to investigate whether ophthalmic artery reactivity is affected in mice lacking the apolipoprotein E gene (ApoE-/-), a model for hypercholesterolemia and atherosclerosis. Twelve-month-old male ApoE-/- mice and age-matched wild-type controls were used to assess vascular reactivity using videomicroscopy. Moreover, the vascular mechanics, lipid content, levels of reactive oxygen species (ROS), and expression of pro-oxidant redox enzymes and the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) were determined in vascular tissue. Unlike the aorta, the ophthalmic artery of ApoE-/- mice developed no signs of endothelial dysfunction and no signs of excessive lipid deposition. Remarkably, the levels of ROS, nicotinamide adenine dinucleotide phosphate oxidase 1 (NOX1), NOX2, NOX4, and LOX-1 were increased in the aorta but not in the ophthalmic artery of ApoE-/- mice. Our findings suggest that ApoE-/- mice develop endothelial dysfunction in the aorta by increased oxidative stress via the involvement of LOX-1, NOX1, and NOX2, whereas NOX4 may participate in media remodeling. In contrast, the ophthalmic artery appears to be resistant to chronic apolipoprotein E deficiency. A lack of LOX-1 expression/overexpression in response to increased oxidized low-density lipoprotein levels may be a possible mechanism of action.

The relationship between serum lipid and sudden sensorineural hearing loss

BACKGROUND

Hyperlipidemia may be part of the important mechanisms for the development of idiopathic sudden sensorineural hearing loss (ISSNHL).

AIMS

So the purpose of this study was to evaluate the relationship between changes in blood lipid levels and ISSNHL.

MATERIALS AND METHODS

We enrolled 90 ISSNHL patients in our hospital using a retrospective study design from 2019.1 to 2021.12. Blood levels of total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL-C). Hearing recovery was analyzed using the chi-square test and one-way analysis of variance (ANONA). Univariate and multifactorial Logstic retrospective analyses to establish the relationship between LDL-C/HDL-C ratio and hearing recovery after adjustment for potential confounding factors.

RESULTS

In our study, 65 (72.2%) patients had their hearing recovered. All group analyses and three group analyses (i.e. Excluding the no-recovery group) found that LDL/HDL was on an upward trend from complete recovery to a slight recovery group and strongly associated with hearing recovery. Univariate and multivariate logistic regression analysis found high levels of LDL and LDL/HDL in the partial hearing recovery group, relative to the full hearing recovery group. Curve fitting intuitively demonstrates the influence of blood lipids on prognosis.

CONCLUSIONS

Our findings suggest that LDL. TC, TC/HDL, and LDL/HDL concentrations may be closely related to the pathogenesis of ISSNHL.

SIGNIFICANCE

Improving the relevant lipid test at the time of admission to the hospital has good clinical significance for improving the prognosis of ISSNHL.

Association between Cerebrovascular Risk Factors and Collateral Compensation in Chronic Symptomatic Intracranial Vertebrobasilar Stenosis

INTRODUCTION

The level of collateral compensation plays a pivotal role in chronic symptomatic intracranial vertebrobasilar stenosis (IVBS). This study aimed to evaluate the association between cerebrovascular risk factors and collateral compensation in chronic symptomatic IVBS.

METHODS

This single-center cross-sectional study retrospectively reviewed 238 patients with angiographically demonstrated IVBS and divided them into good collateral compensation (GCC) group (collateral grade: 3-4, n = 110) and poor collateral compensation (PCC) group (collateral grade: 0-2, n = 128). The demographic information, laboratory tests, and clinical data of the two groups were compared and assessed using univariate logistic regression. Multivariate logistic regression was employed to analyze the independent related factors of collateral compensation.

RESULTS

Hyperlipidemia, high-density lipoprotein (HDL), and fasting blood glucose (FBG) were significantly different between the two groups. Multivariate logistic regression analysis revealed that HDL (odds ratio [OR]: 1.134, 95% confidence interval [CI]: 1.081-1.190), FBG (OR: 0.945, 95% CI: 0.925-0.964), and hyperlipidemia (OR: 0.261, 95% CI: 0.129-0.527) were statistically independent related factors of collateral compensation. The receiver-operating characteristic (ROC) analysis provided cutoff values of 34 mg/dL and 135 mg/dL for HDL and FBG associated with GCC and PCC.

CONCLUSION

Higher HDL levels are associated with higher incidence of GCC, whereas higher FBG levels and hyperlipidemia are associated with higher incidence of PCC.

Vascular pathology and pathogenesis of cognitive impairment and dementia in older adults

It is well recognized that brains of older people often harbor cerebrovascular disease pathology including vessel disease and vascular-related tissue injuries and that this is associated with vascular cognitive impairment and contributes to dementia. Here we review vascular pathologies, cognitive impairment, and dementia. We highlight the importance of mixed co-morbid AD/non-AD neurodegenerative and vascular pathology that has been collected in multiple clinical pathologic studies, especially in community-based studies. We also provide an update of vascular pathologies from the Rush Memory and Aging Project and Religious Orders Study cohorts with special emphasis on the differences across age in persons with and without dementia. Finally, we discuss neuropathological perspectives on the interpretation of clinical-pathological studies and emerging data in community-based studies.

Understanding the Connection Between Common Stroke Comorbidities, Their Associated Inflammation, and the Course of the Cerebral Ischemia/Reperfusion Cascade

Despite the enormous progress in the understanding of the course of the ischemic stroke over the last few decades, a therapy that effectively protects neurovascular units (NVUs) and significantly improves neurological functions in stroke patients has still not been achieved. The reasons for this state are unclear, but it is obvious that the cerebral ischemia and reperfusion cascade is a highly complex phenomenon, which includes the intense neuroinflammatory processes, and comorbid stroke risk factors strongly worsen stroke outcomes and likely make a substantial contribution to the pathophysiology of the ischemia/reperfusion, enhancing difficulties in searching of successful treatment. Common concomitant stroke risk factors (arterial hypertension, diabetes mellitus and hyperlipidemia) strongly drive inflammatory processes during cerebral ischemia/reperfusion; because these factors are often present for a long time before a stroke, causing low-grade background inflammation in the brain, and already initially disrupting the proper functions of NVUs. Broad consideration of this situation in basic research may prove to be crucial for the success of future clinical trials of neuroprotection, vasculoprotection and immunomodulation in stroke. This review focuses on the mechanism by which coexisting common risk factors for stroke intertwine in cerebral ischemic/reperfusion cascade and the dysfunction and disintegration of NVUs through inflammatory processes, principally activation of pattern recognition receptors, alterations in the expression of adhesion molecules and the subsequent pathophysiological consequences.

Early Cerebrovascular Ultrasonography as a Predictor of Hemorrhagic Transformation After Thrombectomy

OBJECTIVES

To determine the predictive value of early transcranial color-coded sonography (TCCS) for intracranial hemorrhage (ICH) in patients with large artery occlusion (LAO) stroke of carotid circulation, who were submitted to endovascular therapy (EVT) with successful reperfusion.

MATERIALS AND METHODS

Retrospective study evaluating a cohort of consecutive stroke patients with LAO of the carotid circulation that were recanalyzed with EVT. We measured angle-corrected peak systolic velocities, end-diastolic velocities and mean flow velocities (PSV, EDV and MFV) of the symptomatic and asymptomatic middle cerebral artery (MCA). The ratio between MFV of the symptomatic MCA and MFV of the asymptomatic MCA (MCA-Ra) was calculated. Parenchymal hematoma in the 24 hours control CT was considered as ICH. Univariate associations and multivariate analyses were used to identify early independent predictors for ICH among TCCS findings.

RESULTS

We included 234 patients, mean age 72.5 (SD 12.6) years, 52.1% male. The mean time between recanalization and TCCS was 12.3 hours (range 3-22). Patients who developed postinterventional ICH showed a higher MCA-Ra (1.02 ± 0.26 vs 1.16 ± 0,21, p = 0.036). In multivariate analysis, only higher MCA-Ra remained independently associated with postinterventional ICH (OR: 6.778, 95%CI: 1.152-39.892, p = 0.034). A value of MCA-Ra ≥ 1,05 was associated with ICH, showing a sensitivity of 81.3% and a specificity of 65.9%; the AUC based of the ROC analysis was 0.688 (95% CI 0.570-0.806).

CONCLUSION

TCCS performed within the first 24 hours after stroke onset can help to predict hemorrhagic transformation in patients with LAO.

Cholesterol antagonism of alcohol inhibition of smooth muscle BK channel requires cell integrity and involves a protein kinase C-dependent mechanism(s)

Alcohol constricts cerebral arteries via inhibition of voltage/calcium-gated, large conductance potassium (BK) channels in vascular myocytes. Using a rat model of high-cholesterol (high-CLR) diet and CLR enrichment of cerebral arteries in vitro, we recently showed that CLR protected against alcohol-induced constriction of cerebral arteries. The subcellular mechanism(s) underlying CLR protection against alcohol-induced constriction of the artery is unclear. Here we use a rat model of high-CLR diet and patch-clamp recording of BK channels in inside-out patches from cerebral artery myocytes to demonstrate that this diet antagonizes inhibition of BK currents by 50 mM ethanol. High-CLR-driven protection against alcohol inhibition of BK currents is reversed following CLR depletion in vitro. Similar to CLR accumulation in vivo, pre-incubation of arterial myocytes from normocholesterolemic rats in CLR-enriching media in vitro protects against alcohol-induced inhibition of BK current. However, application of CLR-enriching media to cell-free membrane patches does not protect against the alcohol effect. These different outcomes point to the involvement of cell signaling in CLR-alcohol interaction on BK channels. Incubation of myocytes with the PKC activators phorbol 12-myristate 13-acetate or 1,2-dioctanoyl-sn-glycerol, but not with the PKC inhibitor Gouml 6983, prior to patch excision precludes CLR enrichment from antagonizing alcohol action. Thus, PKC activation either disables the CLR target(s) or competes with elevated CLR. Favoring the latter possibility, 1,2-dioctanoyl-sn-glycerol protects against alcohol-induced inhibition of BK currents in patches from myocytes with naïve CLR. Our findings document that CLR antagonism of alcohol-induced BK channel inhibition requires cell integrity and is enabled by a PKC-dependent mechanism(s).

Apolipoprotein E Deficiency Causes Endothelial Dysfunction in the Mouse Retina

Objective

Atherogenic lipoproteins may impair vascular reactivity consecutively causing tissue damage in multiple organs via abnormal perfusion and excessive reactive oxygen species generation. We tested the hypothesis that chronic hypercholesterolemia causes endothelial dysfunction and cell loss in the retina.

Methods

Twelve-month-old apolipoprotein E-deficient (ApoE-/-) mice and age-matched wild-type controls were used in this study (n = 8 per genotype for each experiment). Intraocular pressure, blood pressure, and ocular perfusion pressure were determined. Retinal arteriole responses were studied in vitro, and reactive oxygen and nitrogen species were quantified in the retinal and optic nerve cryosections. The expression of the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) and the NADPH oxidase isoforms, NOX1, NOX2, and NOX4, were determined in retinal cryosections by immunofluorescence microscopy. Pro- and antioxidant redox genes were quantified in retinal explants by PCR. Moreover, cell number in the retinal ganglion cell layer and axon number in the optic nerve was calculated.

Results

Responses to the endothelium-dependent vasodilator, acetylcholine, were markedly impaired in retinal arterioles of ApoE-/- mice (P < 0.01). LOX-1 (P = 0.0007) and NOX2 (P = 0.0027) expressions as well as levels of reactive oxygen species (P = 0.0022) were increased in blood vessels but not in other retinal structures. In contrast, reactive nitrogen species were barely detectable in both mouse genotypes. Messenger RNA for HIF-1α, VEGF-A, NOX1, and NOX2, but also for various antioxidant redox genes was elevated in the retina of ApoE-/- mice. Total cell number in the retinal ganglion cell layer did not differ between ApoE-/- and wild-type mice (P = 0.2171). Also, axon number in the optic nerve did not differ between ApoE-/- and wild-type mice (P = 0.6435).

Conclusion

Apolipoprotein E deficiency induces oxidative stress and endothelial dysfunction in retinal arterioles, which may trigger hypoxia in the retinal tissue. Oxidative stress in nonvascular retinal tissue appears to be prevented by the upregulation of antioxidant redox enzymes, resulting in neuron preservation.

Comparative benefits of simvastatin and exercise in a mouse model of vascular cognitive impairment and dementia

Aerobic physical exercise (EX) and controlling cardiovascular risk factors in midlife can improve and protect cognitive function in healthy individuals and are considered to be effective at reducing late-onset dementia incidence. By investigating commonalities between these preventative approaches, we sought to identify possible targets for effective interventions. We compared the efficacy of EX and simvastatin (SV) pharmacotherapy to counteract cognitive deficits induced by a high-cholesterol diet (2%, HCD) in mice overexpressing TGF-β1 (TGF mice), a model of vascular cognitive impairment and dementia. Cognitive deficits were found in hypercholesterolemic mice for object recognition memory, and both SV and EX prevented this decline. EX improved stimulus-evoked cerebral blood flow responses and was as effective as SV in normalizing endothelium-dependent vasodilatory responses in cerebral arteries. The up-regulation of galectin-3-positive microglial cells in white matter (WM) of HCD-fed TGF mice with cognitive deficits was significantly reduced by both SV and EX concurrently with cognitive recovery. Altered hippocampal neurogenesis, gray matter astrogliosis, or microgliosis did not correlate with cognitive deficits or benefits. Overall, results indicate that SV and EX prevented cognitive decline in hypercholesterolemic mice and that they share common sites of action in preventing endothelial cell dysfunction and reducing WM inflammation.-Trigiani, L. J., Royea, J., Tong, X.-K., Hamel, E. Comparative benefits of simvastatin and exercise in a mouse model of vascular cognitive impairment and dementia.

Oxidative stress in cerebral small vessel disease. Role of reactive species

Cerebral small vessel disease (CSVD) is a wide term describing the condition affecting perforating arterial branches as well as arterioles, venules, and capillaries. Cerebral vascular net is one of the main targets of localised oxidative stress processes causing damage to vasculature, changes in the blood flow and blood-brain barrier and, in consequence, promoting neurodegenerative alterations in the brain tissue. Numerous studies report the fact of oxidation to proteins, sugars, lipids and nucleic acids, occurring in most neurodegenerative diseases mainly in the earliest stages and correlations with the development of cognitive and motor disturbances. The dysfunction of endothelium can be caused by oxidative stress and inflammatory mechanisms as a result of reactions and processes generating extensive reactive oxygen species (ROS) production such as high blood pressure, oxidised low density lipoproteins (oxLDL), very low density lipoproteins (vLDL), diabetes, homocysteinaemia, smoking, and infections. Several animal studies show positive aspects of ROS, especially within cerebral vasculature.

Rho-associated protein kinases as therapeutic targets for both vascular and parenchymal pathologies in Alzheimer's disease

The causes of late-onset Alzheimer's disease are unclear and likely multifactorial. Rho-associated protein kinases (ROCKs) are ubiquitously expressed signaling messengers that mediate a wide array of cellular processes. Interestingly, they play an important role in several vascular and brain pathologies implicated in Alzheimer's etiology, including hypertension, hypercholesterolemia, blood-brain barrier disruption, oxidative stress, deposition of vascular and parenchymal amyloid-beta peptides, tau hyperphosphorylation, and cognitive decline. The current review summarizes the functions of ROCKs with respect to the various risk factors and pathologies on both sides of the blood-brain barrier and present support for targeting ROCK signaling as a multifactorial and multi-effect approach for the prevention and amelioration of late-onset Alzheimer's disease. This article is part of the Special Issue "Vascular Dementia".

COPD and stroke: are systemic inflammation and oxidative stress the missing links?

Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow limitation and loss of lung function, and is currently the third largest cause of death in the world. It is now well established that cardiovascular-related comorbidities such as stroke contribute to morbidity and mortality in COPD. The mechanisms linking COPD and stroke remain to be fully defined but are likely to be interconnected. The association between COPD and stroke may be largely dependent on shared risk factors such as aging and smoking, or the association of COPD with traditional stroke risk factors. In addition, we propose that COPD-related systemic inflammation and oxidative stress may play important roles by promoting cerebral vascular dysfunction and platelet hyperactivity. In this review, we briefly discuss the pathogenesis of COPD, acute exacerbations of COPD (AECOPD) and cardiovascular comorbidities associated with COPD, in particular stroke. We also highlight and discuss the potential mechanisms underpinning the link between COPD and stroke, with a particular focus on the roles of systemic inflammation and oxidative stress.

Direct activation of Ca2+ and voltage-gated potassium channels of large conductance by anandamide in endothelial cells does not support the presence of endothelial atypical cannabinoid receptor

Endocannabinoid anandamide induces endothelium-dependent relaxation commonly attributed to stimulation of the G-protein coupled endothelial anandamide receptor. The study addressed the receptor-independent effect of anandamide on large conductance Ca²⁺-dependent K⁺ channels expressed in endothelial cell line EA.hy926. Under resting conditions, 10µM anandamide did not significantly influence the resting membrane potential. In a Ca²⁺-free solution the cells were depolarized by ~10mV. Further administration of 10µM anandamide hyperpolarized the cells by ~8mV. In voltage-clamp mode, anandamide elicited the outwardly rectifying whole-cell current sensitive to paxilline but insensitive to GDPβS, a G-protein inhibitor. Administration of 70µM Mn²⁺, an agent used to promote integrin clustering, reversibly stimulated whole-cell current, but failed to further facilitate the anandamide-stimulated current. In an inside-out configuration, anandamide (0.1-30µM) facilitated single BK_Ca channel activity in a concentration-dependent manner within a physiological Ca²⁺ range and a wide range of voltages, mainly by reducing mean closed time. The effect is essentially eliminated following chelation of Ca²⁺ from the cytosolic face and pre-exposure to cholesterol-reducing agent methyl-β-cyclodextrin. O-1918 (3µM), a cannabidiol analog used as a selective antagonist of endothelial anandamide receptor, reduced BK_Ca channel activity in inside-out patches. These results do not support the existence of endothelial cannabinoid receptor and indicate that anandamide acts as a direct BK_Ca opener. The action does not require cell integrity or integrins and is caused by direct modification of BK_Ca channel activity.

Cerebral Vascular Disease and Neurovascular Injury in Ischemic Stroke

The consequences of cerebrovascular disease are among the leading health issues worldwide. Large and small cerebral vessel disease can trigger stroke and contribute to the vascular component of other forms of neurological dysfunction and degeneration. Both forms of vascular disease are driven by diverse risk factors, with hypertension as the leading contributor. Despite the importance of neurovascular disease and subsequent injury after ischemic events, fundamental knowledge in these areas lag behind our current understanding of neuroprotection and vascular biology in general. The goal of this review is to address select key structural and functional changes in the vasculature that promote hypoperfusion and ischemia, while also affecting the extent of injury and effectiveness of therapy. In addition, as damage to the blood-brain barrier is one of the major consequences of ischemia, we discuss cellular and molecular mechanisms underlying ischemia-induced changes in blood-brain barrier integrity and function, including alterations in endothelial cells and the contribution of pericytes, immune cells, and matrix metalloproteinases. Identification of cell types, pathways, and molecules that control vascular changes before and after ischemia may result in novel approaches to slow the progression of cerebrovascular disease and lessen both the frequency and impact of ischemic events.

Cerebrovascular Disease: Consequences of Obesity-Induced Endothelial Dysfunction

Despite the well-known global impact of overweight and obesity in the incidence of cerebrovascular disease, many aspects of this association are still inconsistently defined. In this chapter we aim to present a critical review on the links between obesity and both ischemic and hemorrhagic stroke and discuss its influence on functional outcomes, survival, and current treatments to acute and chronic stroke. The role of cerebrovascular endothelial function and respective modulation is also described as well as its laboratory and clinical assessment. In this context, the major contributing mechanisms underlying obesity-induced cerebral endothelial function (adipokine secretion, insulin resistance, inflammation, and hypertension) are discussed. A special emphasis is given to the participation of adipokines in the pathophysiology of stroke, namely adiponectin, leptin, resistin, apelin, and visfatin.

Cerebral blood flow autoregulation in ischemic heart failure

Patients with ischemic heart failure (iHF) have a high risk of neurological complications such as cognitive impairment and stroke. We hypothesized that iHF patients have a higher incidence of impaired dynamic cerebral autoregulation (dCA). Adult patients with iHF and healthy volunteers were included. Cerebral blood flow velocity (CBFV, transcranial Doppler, middle cerebral artery), end-tidal CO₂ (capnography), and arterial blood pressure (Finometer) were continuously recorded supine for 5 min at rest. Autoregulation index (ARI) was estimated from the CBFV step response derived by transfer function analysis using standard template curves. Fifty-two iHF patients and 54 age-, gender-, and BP-matched healthy volunteers were studied. Echocardiogram ejection fraction was 40 (20-45) % in iHF group. iHF patients compared with control subjects had reduced end-tidal CO₂ (34.1 ± 3.7 vs. 38.3 ± 4.0 mmHg, P < 0.001) and lower ARI values (5.1 ± 1.6 vs. 5.9 ± 1.0, P = 0.012). ARI <4, suggestive of impaired CA, was more common in iHF patients (28.8 vs. 7.4%, P = 0.004). These results confirm that iHF patients are more likely to have impaired dCA compared with age-matched controls. The relationship between impaired dCA and neurological complications in iHF patients deserves further investigation.

Role of GPx4 in human vascular endothelial cells, and the compensatory activity of brown rice on GPx4 ablation condition

Oxidative stress is implicated in the pathologies of vascular endothelial cells. However, the importance of specific antioxidant enzymes in vascular endothelial cells is not fully understood. The purpose of this study was to elucidate the importance of Glutathione peroxidase 4 (GPx4), and the involvement of ferroptosis on cell death induced by GPx4 loss in human vascular endothelial cells. In addition, we examined the compensatory activity of brown rice on GPx4 ablation condition. Human umbilical vein endothelial cells were transfected with GPx4 or scramble control siRNA. GPx4 knockdown caused the increase in the levels of lipid oxidation, and induced cytotoxicity. On the other hand, α-tocopherol (vitamin E) and extract of brown rice, ameliorated lipid peroxidation, cytotoxicity, and delay of proliferation induced by GPx4 knockdown. Furthermore, ferrostatin-1, inhibitor of ferroptosis, also prevented cytotoxicity and delay of proliferation. In conclusion, our data demonstrated that GPx4 is an essential antioxidant enzyme for protecting lipid peroxidation, and is a regulator of ferroptosis in vascular endothelial cells. Furthermore, vitamin E rich food, such as brown rice, can compensate for GPx4 loss by protecting cells against lipid peroxidation.

Sex Difference in Coronary Endothelial Dysfunction in Apolipoprotein E Knockout Mouse: Role of NO and A2A Adenosine Receptor

OBJECTIVE

Sex plays an important role in the pathophysiology of cardiovascular diseases. This study aims to investigate how sex impacts on the coronary flow regulation during atherosclerosis.

METHODS

ApoE KO mouse fed with western diet were used for atherosclerosis model. Coronary RH and flow response were measured using Langendorff-perfused isolated hearts.

RESULTS

Coronary RH and A23187-induced NO-dependent flow increases were significantly reduced in female (by ~28% and 48%, respectively), but not in male atherosclerotic mice. However, SNP-induced coronary vasodilation remains intact in both sexes of ApoE KO mice. L-NAME (NOS inhibitor) reduced baseline flow and RH to a lesser extent in ApoE KO (by ~19% and 31%) vs. WT (~30% and 59%, respectively), and abolished the sex difference in RH. In contrast, SCH58261 (a selective A2A AR antagonist) reduced the baseline flow and RH to a greater extent in atherosclerotic mice, but did not affect the sex difference. Immunofluorescent staining of coronary arteries showed a similar A2A AR upregulation in both sexes of ApoE KO mice.

CONCLUSIONS

Our results suggest that during atherosclerosis, female mice are more susceptible to NO-dependent endothelial dysfunction and the upregulation of A2A AR may serve as a compensatory mechanism to counteract the compromised endothelial function.

Association between Serum Lipid Profiles and Early Neurological Deterioration in Acute Ischemic Stroke

BACKGROUND

Dyslipidemia is associated with chronic cardiovascular disease. However, the effect of dyslipidemia on acute ischemic stroke is unclear. We hypothesized that dyslipidemia could contribute to early neurological deterioration (END) after ischemic stroke.

METHODS

A total of 410 acute ischemic stroke patients who were admitted to our stroke center within 24 hours after ictus were consecutively included in this study. END was defined as any new neurological symptoms/signs or any neurological worsening occurring during the admission and/or within 3 weeks after the index stroke. Multivariable logistic regression was used to examine the independent association between lipid indices and END.

RESULTS

Mean age was 68.2 ± 13.3 years, 241 (58.8%) were male, and 78 (19.0%) experienced END. Almost END occurred within 3 days after admission (n = 70, 89.7%), and the majority of END was stroke progression (n = 68, 87.1%). In univariate analysis, high-density lipoprotein (HDL)-cholesterol levels (per 1 mmol/L; odds ratio [OR] .37; 95% CI .17-.80; P = .012) and apolipoprotein B (apoB)/apoA-I ratio (per 1 increase; OR 3.71; 95% CI 1.48-9.29; P = .005) were associated with END. In the multivariable analysis, adjusted ORs of END for the highest quartile of HDL-cholesterol and apoB/apoA-I ratio were .42 (95% CI .19-.94; P = .034) and 2.37 (95% CI 1.02-5.53; P = .045), respectively. The ratio of apoB/apoA-I was associated with END in large artery atherosclerosis stroke but not in other stroke subtypes.

CONCLUSIONS

Independent association of low HDL-cholesterol and high apoB/apoA-I ratio with END warrants further research to investigate if correction of the lipid profile during the acute period of ischemic stroke could reduce the risk of END.

Cerebral Small Vessel Disease: Targeting Oxidative Stress as a Novel Therapeutic Strategy?

Cerebral small vessel disease (SVD) is a major contributor to stroke, and a leading cause of cognitive impairment and dementia. Despite the devastating effects of cerebral SVD, the pathogenesis of cerebral SVD is still not completely understood. Moreover, there are no specific pharmacological strategies for its prevention or treatment. Cerebral SVD is characterized by marked functional and structural abnormalities of the cerebral microcirculation. The clinical manifestations of these pathological changes include lacunar infarcts, white matter hyperintensities, and cerebral microbleeds. The main purpose of this review is to discuss evidence implicating oxidative stress in the arteriopathy of both non-amyloid and amyloid (cerebral amyloid angiopathy) forms of cerebral SVD and its most important risk factors (hypertension and aging), as well as its contribution to cerebral SVD-related brain injury and cognitive impairment. We also highlight current evidence of the involvement of the NADPH oxidases in the development of oxidative stress, enzymes that are a major source of reactive oxygen species in the cerebral vasculature. Lastly, we discuss potential pharmacological strategies for oxidative stress in cerebral SVD, including some of the historical and emerging NADPH oxidase inhibitors.

Microvascular Dysfunction and Cognitive Impairment

The impact of vascular risk factors on cognitive function has garnered much interest in recent years. The appropriate distribution of oxygen, glucose, and other nutrients by the cerebral vasculature is critical for proper cognitive performance. The cerebral microvasculature is a key site of vascular resistance and a preferential target for small vessel disease. While deleterious effects of vascular risk factors on microvascular function are known, the contribution of this dysfunction to cognitive deficits is less clear. In this review, we summarize current evidence for microvascular dysfunction in brain. We highlight effects of select vascular risk factors (hypertension, diabetes, and hyperhomocysteinemia) on the pial and parenchymal circulation. Lastly, we discuss potential links between microvascular disease and cognitive function, highlighting current gaps in our understanding.

High-fat diet increases O-GlcNAc levels in cerebral arteries: a link to vascular dysfunction associated with hyperlipidaemia/obesity?

Obesity and high fat intake induce alterations in vascular function and structure. Aberrant O-GlcNAcylation (O-GlcNAc) of vascular proteins has been implicated in vascular dysfunction associated with cardiovascular and metabolic diseases. In the present study, we tested the hypothesis that high-fat diet (HFD)-mediated increases in O-GlcNAc-modified proteins contribute to cerebrovascular dysfunction. O-GlcNAc-protein content was increased in arteries from male Wistar rats treated with a HFD (45% fat) for 12 weeks compared with arteries from rats on control diet (CD). HFD augmented body weight [(g) 550±10 compared with 502±10 CD], increased plasma triacylglycerols [(mg/dl) 160±20 compared with 95±15 CD] and increased contractile responses of basilar arteries to serotonin [5-hydroxytryptamine (5-HT)] [(pD2) 7.0±0.1 compared with 6.7±0.09 CD] and the thromboxane analogue 9,11-dideoxy-9α,11α-methanoepoxy prostaglandin F2α (U-46619) [(pD2) 7.2±0.1 compared with 6.8±0.09 CD]. Of importance, increased levels of O-GlcNAc [induced by 24 h-incubation of vessels with a potent inhibitor of O-GlcNAcase (OGA), O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PugNAc)] increased basilar artery contractions in response to U-46619 [(pD2) 7.4±0.07 compared with 6.8±0.08 CD] and 5-HT [(pD2) 7.5±0.06 compared with 7.1±0.1 CD]. Vessels from rats on the HFD for 12 weeks and vessels treated with PugNAc displayed increased phosphorylation of p38 (Thr(180/182)) and extracellular signal-regulated kinase 1/2 (Erk1/2) (Ser(180/221)). Increased 5HT-induced contractions in arteries from rats on the HFD or in arteries incubated with PugNAc were abrogated by mitogen-activated protein kinase (MAPK) inhibitors. Our data show that HFD augments cerebrovascular O-GlcNAc and this modification contributes to increased contractile responses and to the activation of the MAPK pathway in the rat basilar artery.

Differential Effects of Pioglitazone in the Hippocampal CA1 Region Following Transient Forebrain Ischemia in Low- and High-Fat Diet-Fed Gerbils

In the present study, we investigated the effects of pioglitazone (PGZ) in the hippocampal CA1 region of low- or high-fat diet (LFD or HFD) fed gerbils after transient forebrain ischemia. After 8 weeks of LFD or HFD feeding, PGZ (30 mg/kg) was intraperitoneally administered to the gerbils, following which ischemia was induced by occlusion of the bilateral common carotid arteries for 5 min. Administration of PGZ significantly reduced the ischemia-induced hyperactivity 1 day after ischemia/reperfusion in both LFD- and HFD-fed gerbils. At 4 days after ischemia/reperfusion, the neurons were significantly reduced and microglial activation was observed in the hippocampal CA1 region in LFD- and HFD-fed gerbils. The microglial activation was more prominent in the HFD-fed gerbils compared to the LFD-fed gerbils. Administration of PGZ ameliorated ischemia-induced neuronal death and microglial activation in the hippocampal CA1 region 4 days after ischemia/reperfusion in the LFD-fed gerbils, but not in the HFD-gerbils. At 6 h after ischemia/reperfusion, tumor necrosis factor-α (TNF-α) and interlukin-1β (IL-1β) levels were significantly increased in the hippocampal homogenates of LFD-fed group compared to control group, and HFD feeding further increased TNF-α and IL-1β levels. PGZ treatment significantly ameliorated the increase of TNF-α and IL-1β levels in LFD-fed gerbils, not in the HFD-fed gerbils. At 12 h after ischemia/reperfusion, superoxide dismutase (SOD) and malondialdehyde (MDA) levels in hippocampal homogenates were significantly increased in the LFD-fed group compared to the control group, and HFD feeding significantly showed relatively reduction in SOD activity and increase in MDA level. PGZ administration significantly reduced the increase in MDA levels 12 h after ischemia/reperfusion in the LFD-fed gerbils, but not in the HFD-fed gerbils. These results suggest that PGZ ameliorates the neuronal damage induced by ischemia by maintaining the TNF-α, IL-1β, SOD and MDA levels in LFD-fed gerbils. In addition, HFD feeding affects the modulation of these parameters in the hippocampus after transient forebrain ischemia.

Endothelial dysfunction abrogates the efficacy of normobaric hyperoxia in stroke

Hyperoxia has been uniformly efficacious in experimental focal cerebral ischemia. However, pilot clinical trials have showed mixed results slowing its translation in patient care. To explain the discordance between experimental and clinical outcomes, we tested the impact of endothelial dysfunction, exceedingly common in stroke patients but under-represented in experimental studies, on the neuroprotective efficacy of normobaric hyperoxia. We used hyperlipidemic apolipoprotein E knock-out and endothelial nitric oxide synthase knock-out mice as models of endothelial dysfunction, and examined the effects of normobaric hyperoxia on tissue perfusion and oxygenation using high-resolution combined laser speckle and multispectral reflectance imaging during distal middle cerebral artery occlusion. In normal wild-type mice, normobaric hyperoxia rapidly and significantly improved tissue perfusion and oxygenation, suppressed peri-infarct depolarizations, reduced infarct volumes, and improved neurological function. In contrast, normobaric hyperoxia worsened perfusion in ischemic brain and failed to reduce infarct volumes or improve neurological function in mice with endothelial dysfunction. These data suggest that the beneficial effects of hyperoxia on ischemic tissue oxygenation, perfusion, and outcome are critically dependent on endothelial nitric oxide synthase function. Therefore, vascular risk factors associated with endothelial dysfunction may predict normobaric hyperoxia nonresponders in ischemic stroke. These data may have implications for myocardial and systemic circulation as well.

Impact of fatty acids on brain circulation, structure and function

The use of dietary intervention has evolved into a promising approach to prevent the onset and progression of brain diseases. The positive relationship between intake of omega-3 long chain polyunsaturated fatty acids (ω3-LCPUFAs) and decreased onset of disease- and aging-related deterioration of brain health is increasingly endorsed across epidemiological and diet-interventional studies. Promising results are found regarding to the protection of proper brain circulation, structure and functionality in healthy and diseased humans and animal models. These include enhanced cerebral blood flow (CBF), white and gray matter integrity, and improved cognitive functioning, and are possibly mediated through increased neurovascular coupling, neuroprotection and neuronal plasticity, respectively. Contrary, studies investigating diets high in saturated fats provide opposite results, which may eventually lead to irreversible damage. Studies like these are of great importance given the high incidence of obesity caused by the increased and decreased consumption of respectively saturated fats and ω3-LCPUFAs in the Western civilization. This paper will review in vivo research conducted on the effects of ω3-LCPUFAs and saturated fatty acids on integrity (circulation, structure and function) of the young, aging and diseased brain.

Resveratrol attenuates high-fat diet-induced disruption of the blood-brain barrier and protects brain neurons from apoptotic insults

The blood-brain barrier (BBB) maintains brain microenvironment. Our previous study showed that oxidized low-density lipoprotein (oxLDL) can damage the BBB by inducing apoptosis of cerebrovascular endothelial cells. This study was aimed at evaluating the effects of resveratrol on high-fat diet-induced insults to the BBB and brain neurons. Exposure of mice to a high-fat diet for 8 weeks increased levels of serum total cholesterol (146 ± 13) and LDL (68 ± 8), but resveratrol decreased such augmentations (119 ± 6; 45 ± 8). Permeability assays showed that a high-fat diet induced breakage of the BBB (88 ± 21). Meanwhile, resveratrol alleviated this interruption (16 ± 6). Neither resveratrol nor a high-fat diet caused the death of cerebrovascular endothelial cells. Instead, exposure to a high-fat diet disrupted the polymerization of occludin and zonula occludens (ZO)-1, but resveratrol significantly attenuated those injuries. Neither a high-fat diet nor resveratrol changed the levels of occludin or ZO-1 in brain tissues. Resveratrol protected brain neurons against high-fat diet-induced caspase-3 activation and genomic DNA fragmentation. This study shows that resveratrol can attenuate the high-fat diet-induced disruption of the BBB via interfering with occludin and ZO-1 tight junctions, and protects against apoptotic insults to brain neurons.

Dietary cholesterol protects against alcohol-induced cerebral artery constriction

BACKGROUND

Binge drinking represents the major form of excessive alcohol (ethanol [EtOH]) consumption in the United States. Episodic (such as binge) drinking results in blood alcohol levels (BAL) of 18 to 80 mM and leads to alcohol-induced cerebral artery constriction (AICAC). AICAC was shown to arise from EtOH-induced inhibition of large-conductance, calcium/voltage-gated potassium (BK) channels in the vascular smooth muscle. Factors that modulate BK channel-mediated AICAC remain largely unknown.

METHODS

Male Sprague Dawley rats were placed on high-cholesterol (2% of cholesterol) diet for 18 to 23 weeks. Their littermates were placed on control iso-caloric diet. AICAC was evaluated both in vivo and in vitro, by means of pial arteriole diameter monitoring through a closed cranial window and diameter measurements of isolated, pressurized cerebral arteries. Cholesterol level in the cerebral artery tissue was manipulated by methyl-β-cyclodextrin to reverse dietary-induced accumulation of cholesterol. BK channel surface presence on the plasma membrane of cerebral artery myocytes was evaluated by immunofluorescence staining. BK channel function in pressurized cerebral artery was assessed using selective BK channel blocker paxilline.

RESULTS

Within 5 minutes of 50 mM EtOH injection into carotid artery in vivo, arteriole diameter decreased by 20% in control group. Pial arteriole constriction was significantly reduced in rats on high-cholesterol diet, resulting in only 10% reduction in diameter. BAL in both groups, however, remained the same. Significant reduction in AICAC in group on high-cholesterol diet compared to control was also observed after middle cerebral artery dissection and in vitro pressurization at 60 mmHg, this reduction remaining after endothelium removal. Cholesterol level in de-endothelialized cerebral arteries was significantly increased in rats on high-cholesterol diet. Removal of excessive cholesterol content restored AICAC to the level observed in cerebral arteries of rats on normal diet. Immunofluorescence staining of BK channel-forming and accessory, smooth muscle-specific β1 subunit in freshly isolated cerebral artery myocyte showed that high-cholesterol diet did not down-regulate surface presence of BK protein. However, paxilline-induced cerebral artery constriction was diminished in arteries from rats on high-cholesterol diet.

CONCLUSIONS

Our data indicate that dietary cholesterol protects against AICAC. This protection is caused by cholesterol buildup in the arterial tissue and diminished function (but not surface presence) of EtOH target-BK channel.

Rho-kinase inhibition improves ischemic perfusion deficit in hyperlipidemic mice

Hyperlipidemia is a major cardiovascular risk factor associated with progressive cerebrovascular dysfunction and diminished collateral perfusion in stroke. Rho-associated kinase (ROCK) may be an important mediator of hyperlipidemic vascular dysfunction. We tested the efficacy of acute or chronic ROCK inhibition on the size of dynamic perfusion defect using laser speckle flowmetry in hyperlipidemic apolipoprotein E knockout mice fed on a high-fat diet for 8 weeks. Mice were studied at an age before the development of flow-limiting atherosclerotic stenoses in aorta and major cervical arteries. Focal ischemia was induced by distal middle cerebral artery occlusion (dMCAO) during optical imaging. The ROCK inhibitor fasudil (10 mg/kg) was administered either as a single dose 1 hour before ischemia onset, or daily for 4 weeks. Fasudil decreased both baseline arterial blood pressure and cerebrovascular resistance (CVR) by ∼15%, and significantly improved tissue perfusion during dMCAO. Interestingly, peri-infarct depolarizations were also reduced. Chronic treatment did not further enhance these benefits compared with acute treatment with a single dose. These data show that ROCK inhibition improves CVR and ischemic tissue perfusion in hyperlipidemic mice.

Mouse models to study the effect of cardiovascular risk factors on brain structure and cognition

Recent clinical data indicates that hemodynamic changes caused by cardiovascular diseases such as atherosclerosis, heart failure, and hypertension affect cognition. Yet, the underlying mechanisms of the resulting vascular cognitive impairment (VCI) are poorly understood. One reason for the lack of mechanistic insights in VCI is that research in dementia primarily focused on Alzheimer's disease models. To fill in this gap, we critically reviewed the published data and various models of VCI. Typical findings in VCI include reduced cerebral perfusion, blood-brain barrier alterations, white matter lesions, and cognitive deficits, which have also been reported in different cardiovascular mouse models. However, the tests performed are incomplete and differ between models, hampering a direct comparison between models and studies. Nevertheless, from the currently available data we conclude that a few existing surgical animal models show the key features of vascular cognitive decline, with the bilateral common carotid artery stenosis hypoperfusion mouse model as the most promising model. The transverse aortic constriction and myocardial infarction models may be good alternatives, but these models are as yet less characterized regarding the possible cerebral changes. Mixed models could be used to study the combined effects of different cardiovascular diseases on the deterioration of cognition during aging.

A clinical study of serum lipid disturbance in Chinese patients with sudden deafness

Background

Pathological levels of blood lipids could be one of the causes of sudden sensorineural hearing loss (SSNHL). The objective of this manuscript is therefore to evaluate the relationship between blood lipid content and sudden sensorineural hearing loss (SSNHL).

Methods

The correlation between serum lipid parameters, including total cholesterol (TC), triglycerides, high-density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), apolipoprotein AI (apo AI), apolipoprotein B (apo B), and lipoprotein A (Lp(a)), and the onset of SSNHL was analyzed from a data set of 250 patients and an age, gender and weight matched control group of 250 subjects.

Results

The result of single factor logistic regression shows that TC (p<0.01), LDL-C (p<0.01), and apo B (p=0.03) of SSNHL group were significantly higher than those of the control group. The odds ratio of TC, LDL, and apo B are higher than 1, while the confidence intervals of the odds rations do not include 1. No significant difference was found with the prevalence of hypertension (P=0.818), diabetes (P=0.869) and smoking habits (P=0.653) between SSNHL group and control group.

Conclusion

Total cholesterol, low density lipoprotein cholesterol and apolipoprotein B concentrations may be important factors in the pathogenesis of sudden sensorineural hearing loss, and should be assessed during the investigation of patients with this condition.

Hyperlipidemia disrupts cerebrovascular reflexes and worsens ischemic perfusion defect

Hyperlipidemia is a highly prevalent risk factor for coronary and cervical atherosclerosis and stroke. However, even in the absence of overt atherosclerosis, hyperlipidemia disrupts endothelial and smooth muscle function. We investigated the impact of hyperlipidemia on resting-brain perfusion, fundamental cerebrovascular reflexes, and dynamic perfusion defect during acute focal ischemia in hyperlipidemic apolipoprotein E knockout mice before the development of flow-limiting atherosclerotic stenoses. Despite elevated blood pressures, absolute resting cerebral blood flow was reduced by 20% in apolipoprotein E knockout compared with wild type when measured by [(14)C]-iodoamphetamine technique. Noninvasive, high spatiotemporal resolution laser speckle flow imaging revealed that the lower autoregulatory limit was elevated in apolipoprotein E knockout mice (60 vs. 40 mm Hg), and cortical hyperemic responses to hypercapnia and functional activation were attenuated by 30% and 64%, respectively. Distal middle cerebral artery occlusion caused significantly larger perfusion defects and infarct volumes in apolipoprotein E knockout compared with wild type. Cerebrovascular dysfunction showed a direct relationship to the duration of high-fat diet. These data suggest that hyperlipidemia disrupts cerebral blood flow regulation and diminishes collateral perfusion in acute stroke in the absence of hemodynamically significant atherosclerosis.

Early effects of high-fat diet on neurovascular function and focal ischemic brain injury

Obesity is a risk factor for stroke, but the early effects of high-fat diet (HFD) on neurovascular function and ischemic stroke outcomes remain unclear. The goal of this study was to test the hypotheses that HFD beginning early in life 1) impairs neurovascular coupling, 2) causes cerebrovascular dysfunction, and 3) worsens short-term outcomes after cerebral ischemia. Functional hyperemia and parenchymal arteriole (PA) reactivity were measured in rats after 8 wk of HFD. The effect of HFD on basilar artery function after middle cerebral artery occlusion (MCAO) and associated O-GlcNAcylation were assessed. Neuronal cell death, infarct size, hemorrhagic transformation (HT) frequency/severity, and neurological deficit were evaluated after global ischemia and transient MCAO. HFD caused a 10% increase in body weight and doubled adiposity without a change in lipid profile, blood glucose, and blood pressure. Functional hyperemia and PA relaxation were decreased with HFD. Basilar arteries from stroked HFD rats were more sensitive to contractile factors, and acetylcholine-mediated relaxation was impaired. Vascular O-GlcNAcylated protein content was increased with HFD. This group also showed greater mortality rate, infarct volume, HT occurrence rate, and HT severity and poor functional outcome compared with the control diet group. These results indicate that HFD negatively affects neurovascular coupling and cerebrovascular function even in the absence of dyslipidemia. These early cerebrovascular changes may be the cause of greater cerebral injury and poor outcomes of stroke in these animals.

Treatment with Evasin-3 reduces atherosclerotic vulnerability for ischemic stroke, but not brain injury in mice

Neutrophilic inflammation might have a pathophysiological role in both carotid plaque rupture and ischemic stroke injury. Here, we investigated the potential benefits of the CXC chemokine-binding protein Evasin-3, which potently inhibits chemokine bioactivity and related neutrophilic inflammation in two mouse models of carotid atherosclerosis and ischemic stroke, respectively. In the first model, the chronic treatment with Evasin-3 as compared with Vehicle (phosphate-buffered saline (PBS)) was investigated in apolipoprotein E-deficient mice implanted of a 'cast' carotid device. In the second model, acute Evasin-3 treatment (5 minutes after cerebral ischemia onset) was assessed in mice subjected to transient left middle cerebral artery occlusion. Although CXCL1 and CXCL2 were upregulated in both atherosclerotic plaques and infarcted brain, only CXCL1 was detectable in serum. In carotid atherosclerosis, treatment with Evasin-3 was associated with reduction in intraplaque neutrophil and matrix metalloproteinase-9 content and weak increase in collagen as compared with Vehicle. In ischemic stroke, treatment with Evasin-3 was associated with reduction in ischemic brain neutrophil infiltration and protective oxidants. No other effects in clinical and histological outcomes were observed. We concluded that Evasin-3 treatment was associated with reduction in neutrophilic inflammation in both mouse models. However, Evasin-3 administration after cerebral ischemia onset failed to improve poststroke outcomes.

Effects of angiotensin II on the cerebral circulation: role of oxidative stress

Oxidative stress has emerged as a key component of many diseases that affect the vasculature. Oxidative stress is characterized as a cellular environment where the generation of oxidant molecules overwhelms endogenous anti-oxidant defense mechanisms. NADPH oxidases are a family of enzymes whose primary purpose is generation of reactive oxygen species (oxidant molecules) and therefore are likely to be key contributors to oxidative stress. Hypertension is associated with oxidative stress in the vasculature and is a major risk factor for stroke and cognitive abnormalities. Angiotensin II (Ang II) is the main effector peptide of the renin-angiotensin system (RAS) and plays a critical role in promoting oxidative stress in the vasculature. In the cerebral circulation, Ang II has been implicated in reactive oxygen species generation, alterations to vasomotor function, impaired neurovascular coupling, inflammation, and vascular remodeling. Furthermore, studies in humans have shown that cerebral blood flow is altered during hypertension and therapeutically targeting the RAS improves cerebral blood flow. Importantly, many of the aforementioned effects have been shown to be dependent on NADPH oxidases. Thus, Ang II, NADPH oxidases and oxidative stress are likely to play key roles in the pathogenesis of hypertension and associated cerebrovascular disease. This review will focus on our current understanding of the contribution of Ang II and NADPH oxidases to oxidative stress in the cerebral circulation.

Pregnancy enhances the effects of hypercholesterolemia on posterior cerebral arteries

In preeclampsia, hyperlipidemia is enhanced compared to normal pregnancy that could adversely affect vascular function. In the cerebral vasculature, this could lead to dysregulation of cerebral blood flow and neurological complications. Here, we examined the effect of excessive hyperlipidemia, as seen in preeclampsia, on cerebral artery function and expression of inflammatory markers in pregnancy. Pregnant and nonpregnant rats received a 14-day high-cholesterol diet or normal chow and posterior cerebral artery function was compared. High cholesterol significantly increased sensitivity of posterior cerebral arteries to the nitric oxide donor sodium nitroprusside that was accompanied by a ~12-fold increased messenger RNA (mRNA) expression of inducible nitric oxide synthase in late-pregnant rats only. Further, high cholesterol significantly increased peroxynitrite-induced dilation and decreased myogenic tone in cerebral arteries from late pregnant compared to nonpregnant animals. These results suggest that pathologically high levels of cholesterol in pregnancy enhance inflammatory responses and peroxynitrite generation in cerebral arteries.

Impact of ACE2 deficiency and oxidative stress on cerebrovascular function with aging

BACKGROUND AND PURPOSE

Angiotensin II produces oxidative stress and endothelial dysfunction in cerebral arteries, and angiotensin II type I receptors may play a role in longevity and vascular aging. Angiotensin-converting enzyme type 2 (ACE2) converts angiotensin II to angiotensin (1-7) and thus, may protect against effects of angiotensin II. We hypothesized that ACE2 deficiency increases oxidative stress and endothelial dysfunction in cerebral arteries and examined the role of ACE2 in age-related cerebrovascular dysfunction.

METHODS

Endothelial function, expression of angiotensin system components, NADPH oxidase subunits, and proinflammatory cytokines were examined in cerebral arteries from adult (12 months old) and old (24 months old) ACE2 knockout (KO) and wild-type (WT) mice. The superoxide scavenger tempol was used to examine the role of oxidative stress on endothelial function.

RESULTS

Vasodilatation to acetylcholine was impaired in adult ACE2 KO (24±6% [mean±SE]) compared with WT mice (52±7%; P<0.05). In old mice, vasodilatation to acetylcholine was impaired in WT mice (29±6%) and severely impaired in ACE2 KO mice (7±5%). Tempol improved endothelial function in adult and old ACE2 KO and WT mice. Aging increased mRNA for tumor necrosis factor-α in WT mice, and significantly increased mRNA levels of NAPDH oxidase 2, p47(phox), and Regulator of calcineurin 1 in both ACE2 KO and WT mice. mRNA levels of angiotensin system components did not change during aging.

CONCLUSIONS

ACE2 deficiency impaired endothelial function in cerebral arteries from adult mice and augmented endothelial dysfunction during aging. Oxidative stress plays a critical role in cerebrovascular dysfunction induced by ACE2 deficiency and aging.

Serum triglyceride level is an important predictor of early prognosis in patients with acute ischemic stroke

BACKGROUND

Some recent studies have shown that poor outcomes after acute ischemic stroke (AIS) were closely related to lower serum triglyceride (TG) levels, not hypertriglyceridemia. However, hypertriglyceridemia has been shown to be an independent predictor for poor outcome in patients with coronary artery disease. This study attempted to evaluate the association between serum TG levels and early prognosis of AIS.

METHODS

We enrolled 736 consecutive patients with AIS. Based on the TG level, patients were divided into 5 groups based on the guidelines of the National Cholesterol Education Program (NCEP). We defined early neurological deterioration (END) as a 4-point or greater deterioration of the NIH stroke scale (NIHSS) score and early clinical improvement (ECI) as a 4-point reduction of NIHSS within a week after symptom onset. We compared patients with END, ECI, and neither END nor ECI.

RESULTS

The risk of END was significantly higher in the hyperTG and hypoTG groups compared with the normal group. The percentages of ECI were significantly lower in the hypoTG, borderline, and hyperTG groups compared with the normal group. For END, the multivariable adjusted odds ratios were significantly higher in the hypoTG, borderline, and hyperTG groups compared with the low normal group (50 to 100mg/dl).

CONCLUSIONS

TG had a nonlinear, J-shaped association with poor outcome and a reverse J-shaped association with good outcome in AIS. This study suggests that both hyperTG and hypoTG can be risk factors for poor early outcome in AIS.

Cardiac and vascular phenotypes in the apolipoprotein E-deficient mouse

Cardiovascular death is frequently associated with atherosclerosis, a chronic multifactorial disease and a leading cause of death worldwide. Genetically engineered mouse models have proven useful for the study of the mechanisms underlying cardiovascular diseases. The apolipoprotein E-deficient mouse has been the most widely used animal model of atherosclerosis because it rapidly develops severe hypercholesterolemia and spontaneous atherosclerotic lesions similar to those observed in humans. In this review, we provide an overview of the cardiac and vascular phenotypes and discuss the interplay among nitric oxide, reactive oxygen species, aging and diet in the impairment of cardiovascular function in this mouse model.

Endothelial dysfunction in the apolipoprotein E-deficient mouse: insights into the influence of diet, gender and aging

Since the early 1990s, several strains of genetically modified mice have been developed as models for experimental atherosclerosis. Among the available models, the apolipoprotein E-deficient (apoE⁻/⁻) mouse is of particular relevance because of its propensity to spontaneously develop hypercholesterolemia and atherosclerotic lesions that are similar to those found in humans, even when the mice are fed a chow diet. The main purpose of this review is to highlight the key achievements that have contributed to elucidating the mechanisms pertaining to vascular dysfunction in the apoE⁻/⁻ mouse. First, we summarize lipoproteins and atherosclerosis phenotypes in the apoE⁻/⁻ mouse, and then we briefly discuss controversial evidence relative to the influence of gender on the development of atherosclerosis in this murine model. Second, we discuss the main mechanisms underlying the endothelial dysfunction of conducting vessels and resistance vessels and examine how this vascular defect can be influenced by diet, aging and gender in the apoE⁻/⁻ mouse.

Modest effect on plaque progression and vasodilatory function in atherosclerosis-prone mice exposed to nanosized TiO(2)

Background

There is growing evidence that exposure to small size particulate matter increases the risk of developing cardiovascular disease.

Methods

We investigated plaque progression and vasodilatory function in apolipoprotein E knockout (ApoE^-/-) mice exposed to TiO₂. ApoE^-/- mice were intratracheally instilled (0.5 mg/kg bodyweight) with rutile fine TiO₂ (fTiO₂, 288 nm), photocatalytic 92/8 anatase/rutile TiO₂ (pTiO₂, 12 nm), or rutile nano TiO₂ (nTiO₂, 21.6 nm) at 26 and 2 hours before measurement of vasodilatory function in aorta segments mounted in myographs. The progression of atherosclerotic plaques in aorta was assessed in mice exposed to nanosized TiO₂ (0.5 mg/kg bodyweight) once a week for 4 weeks. We measured mRNA levels of Mcp-1, Mip-2, Vcam-1, Icam-1 and Vegf in lung tissue to assess pulmonary inflammation and vascular function. TiO₂-induced alterations in nitric oxide (NO) production were assessed in human umbilical vein endothelial cells (HUVECs).

Results

The exposure to nTiO₂ was associated with a modest increase in plaque progression in aorta, whereas there were unaltered vasodilatory function and expression levels of Mcp-1, Mip-2, Vcam-1, Icam-1 and Vegf in lung tissue. The ApoE^-/- mice exposed to fine and photocatalytic TiO₂ had unaltered vasodilatory function and lung tissue inflammatory gene expression. The unaltered NO-dependent vasodilatory function was supported by observations in HUVECs where the NO production was only increased by exposure to nTiO₂.

Conclusion

Repeated exposure to nanosized TiO₂ particles was associated with modest plaque progression in ApoE^-/- mice. There were no associations between the pulmonary TiO₂ exposure and inflammation or vasodilatory dysfunction.

Chronic renal failure alters endothelial function in cerebral circulation in mice

We examined structure, composition, and endothelial function in cerebral arterioles after 4 wk of chronic renal failure (CRF) in a well-defined murine model (C57BL/6J and apolipoprotein E knockout female mice). We also determined quantitative expression of endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (on serine 1177 and threonine 495), and caveolin-1; quantitative expression of markers of vascular inflammation or oxidative stress [Rock-1, Rock-2, VCAM-1, and peroxisome proliferator-activated receptor-γ (PPARγ)]; and the plasma concentration of l-arginine and asymmetric dimethylarginine (ADMA). Our hypothesis was that endothelial function would be impaired in cerebral arterioles during CRF following either a decrease in NO production (through alteration of eNOS expression or regulation) or an increase in NO degradation (due to oxidative stress or vascular inflammation). Endothelium-dependent relaxation was impaired during CRF, but endothelium-independent relaxation was not. CRF had no effect on cerebral arteriolar structure and composition. Quantitative expressions of eNOS, eNOS phosphorylated on serine 1177, caveolin-1, Rock-1, Rock-2, and VCAM-1 were similar in CRF and non-CRF mice. In contrast, quantitative expression of PPARγ (which exercises a protective role on blood vessels) was significantly lower in CRF mice, whereas quantitative expression of eNOS phosphorylated on the threonine 495 (the inactive form of eNOS) was significantly higher. Lastly, the plasma concentration of ADMA (a uremic toxin and an endogenous inhibitor of eNOS) was elevated and plasma concentration of l-arginine was low in CRF. In conclusion, endothelial function is impaired in a mouse model of early stage CRF. These alterations may be related (at least in part) to a decrease in NO production.

Vascular contributions to cognitive impairment and dementia: a statement for healthcare professionals from the american heart association/american stroke association

BACKGROUND AND PURPOSE

This scientific statement provides an overview of the evidence on vascular contributions to cognitive impairment and dementia. Vascular contributions to cognitive impairment and dementia of later life are common. Definitions of vascular cognitive impairment (VCI), neuropathology, basic science and pathophysiological aspects, role of neuroimaging and vascular and other associated risk factors, and potential opportunities for prevention and treatment are reviewed. This statement serves as an overall guide for practitioners to gain a better understanding of VCI and dementia, prevention, and treatment.

METHODS

Writing group members were nominated by the writing group co-chairs on the basis of their previous work in relevant topic areas and were approved by the American Heart Association Stroke Council Scientific Statement Oversight Committee, the Council on Epidemiology and Prevention, and the Manuscript Oversight Committee. The writing group used systematic literature reviews (primarily covering publications from 1990 to May 1, 2010), previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and, when appropriate, formulate recommendations using standard American Heart Association criteria. All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. After peer review by the American Heart Association, as well as review by the Stroke Council leadership, Council on Epidemiology and Prevention Council, and Scientific Statements Oversight Committee, the statement was approved by the American Heart Association Science Advisory and Coordinating Committee.

RESULTS

The construct of VCI has been introduced to capture the entire spectrum of cognitive disorders associated with all forms of cerebral vascular brain injury-not solely stroke-ranging from mild cognitive impairment through fully developed dementia. Dysfunction of the neurovascular unit and mechanisms regulating cerebral blood flow are likely to be important components of the pathophysiological processes underlying VCI. Cerebral amyloid angiopathy is emerging as an important marker of risk for Alzheimer disease, microinfarction, microhemorrhage and macrohemorrhage of the brain, and VCI. The neuropathology of cognitive impairment in later life is often a mixture of Alzheimer disease and microvascular brain damage, which may overlap and synergize to heighten the risk of cognitive impairment. In this regard, magnetic resonance imaging and other neuroimaging techniques play an important role in the definition and detection of VCI and provide evidence that subcortical forms of VCI with white matter hyperintensities and small deep infarcts are common. In many cases, risk markers for VCI are the same as traditional risk factors for stroke. These risks may include but are not limited to atrial fibrillation, hypertension, diabetes mellitus, and hypercholesterolemia. Furthermore, these same vascular risk factors may be risk markers for Alzheimer disease. Carotid intimal-medial thickness and arterial stiffness are emerging as markers of arterial aging and may serve as risk markers for VCI. Currently, no specific treatments for VCI have been approved by the US Food and Drug Administration. However, detection and control of the traditional risk factors for stroke and cardiovascular disease may be effective in the prevention of VCI, even in older people.

CONCLUSIONS

Vascular contributions to cognitive impairment and dementia are important. Understanding of VCI has evolved substantially in recent years, based on preclinical, neuropathologic, neuroimaging, physiological, and epidemiological studies. Transdisciplinary, translational, and transactional approaches are recommended to further our understanding of this entity and to better characterize its neuropsychological profile. There is a need for prospective, quantitative, clinical-pathological-neuroimaging studies to improve knowledge of the pathological basis of neuroimaging change and the complex interplay between vascular and Alzheimer disease pathologies in the evolution of clinical VCI and Alzheimer disease. Long-term vascular risk marker interventional studies beginning as early as midlife may be required to prevent or postpone the onset of VCI and Alzheimer disease. Studies of intensive reduction of vascular risk factors in high-risk groups are another important avenue of research.

Brain inflammation is induced by co-morbidities and risk factors for stroke

Chronic systemic inflammatory conditions, such as atherosclerosis, diabetes and obesity are associated with increased risk of stroke, which suggests that systemic inflammation may contribute to the development of stroke in humans. The hypothesis that systemic inflammation may induce brain pathology can be tested in animals, and this was the key objective of the present study. First, we assessed inflammatory changes in the brain in rodent models of chronic, systemic inflammation. PET imaging revealed increased microglia activation in the brain of JCR-LA (corpulent) rats, which develop atherosclerosis and obesity, compared to the control lean strain. Immunostaining against Iba1 confirmed reactive microgliosis in these animals. An atherogenic diet in apolipoprotein E knock-out (ApoE(-/-)) mice induced microglial activation in the brain parenchyma within 8 weeks and increased expression of vascular adhesion molecules. Focal lipid deposition and neuroinflammation in periventricular and cortical areas and profound recruitment of activated myeloid phagocytes, T cells and granulocytes into the choroid plexus were also observed. In a small, preliminary study, patients at risk of stroke (multiple risk factors for stroke, with chronically elevated C-reactive protein, but negative MRI for brain pathology) exhibited increased inflammation in the brain, as indicated by PET imaging. These findings show that brain inflammation occurs in animals, and tentatively in humans, harbouring risk factors for stroke associated with elevated systemic inflammation. Thus a "primed" inflammatory environment in the brain may exist in individuals at risk of stroke and this can be adequately recapitulated in appropriate co-morbid animal models.

Vasorelaxant and antiaggregatory actions of the nitroxyl donor isopropylamine NONOate are maintained in hypercholesterolemia

Nitroxyl (HNO) displays pharmacological and therapeutic actions distinct from those of its redox sibling nitric oxide (NO(•)). It remains unclear, however, whether the vasoprotective actions of HNO are preserved in disease. The ability of the HNO donor isopropylamine NONOate (IPA/NO) to induce vasorelaxation, its susceptibility to tolerance development, and antiaggregatory actions were compared with those of a clinically used NO(•) donor, glyceryl trinitrate (GTN), in hypercholesterolemic mice. The vasorelaxant and antiaggregatory properties of IPA/NO and GTN were examined in isolated carotid arteries and washed platelets, respectively, from male C57BL/6J mice [wild-type (WT)] maintained on either a normal diet (WT-ND) or high fat diet (WT-HFD; 7 wk) as well as apolipoprotein E-deficient mice maintained on a HFD (ApoE(-/-)-HFD; 7 wk). In WT-ND mice, IPA/NO (0.1-30 μmol/l) induced concentration-dependent vasorelaxation and inhibition of collagen (30 μg/ml)-stimulated platelet aggregation, which was predominantly soluble guanylyl cyclase/cGMP dependent. Compared with WT-HFD mice, ApoE(-/-)-HFD mice displayed an increase in total plasma cholesterol levels (P < 0.001), vascular (P < 0.05) and platelet (P < 0.05) superoxide (O(2)(·-)) production, and reduced endogenous NO(•) bioavailability (P < 0.001). Vasorelaxant responses to both IPA/NO and GTN were preserved in hypercholesterolemia, whereas vascular tolerance developed to GTN (P < 0.001) but not to IPA/NO. The ability of IPA/NO (3 μmol/l) to inhibit platelet aggregation was preserved in hypercholesterolemia, whereas the actions of GTN (100 μmol/l) were abolished. In conclusion, the vasoprotective effects of IPA/NO were maintained in hypercholesterolemia and, thus, HNO donors may represent future novel treatments for vascular diseases.