Background:Postmenopausal females who carry an APOEε4 allele are at higher risk of late-onset Alzheimer's Disease compared to age-matched APOEε4 males. Estrogen deficiency predisposes females to an increased risk of vascular, cognitive, and metabolic impairments. While estrogen and APOE genotype are known to impact metabolic and mitochondrial function in the brain, their cerebrovascular effects are less understood. Thus, the purpose of this study was to determine the interaction between APOE genotype and estrogen on cerebrovascular endothelial and mitochondrial function. Methods:Young female homozygous APOEε3 and APOEε4 mice (n=19-20/group; ~6 months old) fed a high-fat diet were ovariectomized (OVX), OVX and supplemented with 17β-estradiol, or left intact. Results:In APOEε3 mice, OVX was associated with impaired posterior cerebral artery endothelium-dependent dilation, which was rescued by 17β-estradiol. However, in APOEε4 mice, there was no effect of OVX or 17β-estradiol on cerebral artery endothelial function. Carotid artery passive stiffness was greater with OVX and lower with 17β-estradiol treatment in APOEε3 mice, but there was no impact of OVX or 17β-estradiol in the APOEε4 mice. In cerebral arteries and arterioles, mitochondrial complexes I and I+II respiration were lower in APOEε4 mice compared with APOEε3 mice. 17β-estradiol led to higher mitochondrial complex I respiration in APOEε3 but not APOEε4 mice. These functional differences were concomitant with group differences in mitochondrial DNA copy number, antioxidant enzymes, and pro-inflammatory factors. In contrast to other outcomes, we found that 17β-estradiol treatment was associated with lower cerebral artery stiffness in APOEε4 but not APOEε3 mice. Conclusions:Overall, these results indicate that the APOE genotype modulates the impact of estrogen on the cerebral vasculature. We found that 17β-estradiol enhances cerebrovascular endothelial and mitochondrial function in APOEε3 mice but not in APOEε4 mice. The results suggest that 17β-estradiol supplementation has more cerebrovascular benefit for APOEε4 non-carriers. Novelty & Significance:What is known?: Females have twice the risk of Alzheimer's disease compared with males, and the APOE4 genetic variant is associated with a greater risk for Alzheimer's disease compared with the APOE3 variant. The risk for Alzheimer's disease increases after menopause in females, suggesting that the loss of female sex hormones may play a role. There are highly inconsistent results among past studies examining the interaction of APOE genotype and estrogens on cognitive function and other brain outcomes. What new information does this article contribute?: Vascular outcomes were not measured in previous studies examining the interaction between APOE genotype and estrogens. As such, we aimed to determine the impact of APOE4 genotype on the cerebrovascular response to estradiol. We found that estradiol improved cerebral artery endothelial function and mitochondrial respiration in APOE3 mice following ovariectomy. In contrast, APOE4 mice were refractory to the beneficial effects of estradiol on cerebrovascular endothelial and mitochondrial function. The broader implication of this research is that APOE genotype may be a consideration when prescribing hormone replacement therapy to menopausal females due to the impact on vascular outcomes.

Artery structural properties and Alzheimer's disease (AD) pathology are individually associated with impaired cerebrovascular function; however, the interaction of these factors is unclear. Furthermore, while elastin haploinsufficient (Eln +/- ) mice are known to have impaired cerebrovascular function, sex differences for this effect have not been previously studied. To answer these questions, we crossed middle-aged and old Eln +/- mice with 3xTg-AD mice. We measured cerebral blood flow (CBF) using arterial spin labeling MRI at rest and during hypercapnia to calculate cerebrovascular reactivity (CVR). We also assessed neuroinflammation by microglia and astrocyte cell counts. We found that Eln +/- mice had lower resting blood flow rate in the cerebral cortex compared with Eln +/+ mice, but Eln +/- mice had an intact hypercapnic response, resulting in better CVR compared with Eln +/+ in hippocampus. Sex did not impact resting blood flow or CVR. 3xTg-AD mice had a lower resting CBF than non-AD mice, and there was an interaction between Eln genotype and AD mutations on CVR, such that Eln +/- x 3xTg-AD mice had the poorest hippocampal CVR of all groups. Glia cell counts were highly dependent on brain region, with Eln +/- having more microglia but fewer astrocytes, while 3xTg-AD having higher both microglia and astrocytes. While sex also impacted glial cell counts, we found no interactions between sex and Eln genotype. Our results demonstrate that elastin haploinsufficiency and AD mutations individually result in lower resting CBF, and the combination of these leads to impaired CVR.

Therapeutic angiogenesis is essential for regenerating brain tissue damaged by stroke, yet it remains an unmet clinical challenge. During brain development, pro-angiogenic genes drive the formation of vascular networks, with their expression tightly regulated in later stages. We found that in adult CNS endothelial cells (ECs), angiogenesis-related genes are epigenetically silenced through histone deacetylase 2 (HDAC2) and the polycomb repressive complex 2 (PRC2). Conditional deletion of Hdac2 in ECs reactivated pro-angiogenic signaling, including Wnt/β-catenin target genes, leading to functional neovascularization with preserved blood-brain barrier (BBB) integrity in the adult brain. In contrast, Ezh2 (PRC2 subunit) deletion reduced vessel density and compromised BBB function. Deletion of Hdac2 and Ezh2 immediately after transient ischemic stroke conferred vascular protection by modulating stroke-induced transcriptional programs in CNS ECs. In contrast, delayed deletion, initiated seven days post-stroke, after significant neuronal loss in the infarct region, induced robust revascularization and promoted post-stroke neurogenesis, with differentiation into both excitatory and inhibitory neurons. These findings highlight CNS EC HDAC2 as a promising therapeutic target for inducing adult brain angiogenesis, facilitating revascularization, and supporting neuronal regeneration following stroke.

Background/Aims: The Stroke Preclinical Assessment Network (SPAN) is a randomized, placebo-controlled, blinded, multi-laboratory preclinical study using a Multi-Arm Multi-Stage statistical design to select one or more putative stroke treatments with an implied high likelihood of success in future human clinical stroke trials. Methods: Through a rigorous NIH-managed peer review process, six independent research laboratories were selected for testing five promising cerebrovascular interventions. A Coordinating Center at the University of Southern California leads the trial. The Interventions, also selected through an NIH peer review process, included NanO2 (NuvOx) an oxygen delivery emulsion, tatCN19o (Neurexis) a CaM-kinase II inhibitor, GSK2256098 (GlaxoSmithKline/ETSU) a focal adhesion kinase inhibitor, GSK2256294 (GlaxoSmithKline/OHSU) a soluble epoxide hydrolase inhibitor, and BPN-27332 (Loxagen/MGH) a lipoxygenase inhibitor. After a pilot trial to evaluate several behavioral measures, we designated the primary endpoint for SPAN 2 to be a multi-item functional test battery, the Simplified SPAN Score. All other procedures, including behavior tests and magnetic resonance imaging were performed as they were in SPAN 1. Per the SPAN 2 pre-specified protocol, an interim analysis was performed after Stage 1, aka, SPAN 2.1. Results: SPAN 2.1 enrolled 774 subjects, divided among 4 animal co-morbid models in whom a transient filament MCAo was performed: young healthy mice (n=193), diet-induced obese mice (n=197), aged mice (n=192), and spontaneously hypertensive rats (192). Nine subjects were found ineligible, leaving an ITT population of 765, of whom 13 were dropped during the stroke procedure—the primary analysis population (mITT) included 751 subjects. Protocol compliance was evaluated: over 99% of subjects received the correct assigned intervention, but dose timing was protocol adherent in only 61%. Animals who did not receive all assigned doses (n=100) were excluded, leaving a Full Treatment population of 651. Mortality after treatment included 158 subjects, 21% of the mITT group. Among the animal comorbid models, mortality was greatest (40%) in aged mice. Conclusions: The feasibility and protocol compliance seen in SPAN 1 have been replicated in stage 1 of the second trial, SPAN 2.1. Mortality resembles previous experience, with an improved survival in aged mice. SPAN 2 has advanced to Stage 2 where improved dose timing is implemented.

Postmenopausal females who carry an APOE4 allele are at higher risk of late-onset Alzheimer’s Disease (LOAD) compared to age-matched APOE4 males. Estrogen deficiency predisposes females to an increased risk of vascular, cognitive and metabolic impairments. Estrogen and APOE genotype are known to impact metabolic and mitochondrial function in the brain, but their effects on cerebral vessels are unknown. Thus, the purpose of this study was to determine the interaction between APOE genotype and estrogen deficiency in relation to cerebrovascular mitochondrial function. Young female homozygous APOE3 and APOE4 mice (n = 6-8 per group; 6 months old) fed a high-fat diet were ovariectomized (“ovx”), ovariectomized and supplemented with 17β-estradiol (0.36 mg, 60-day release, “estradiol”), or left intact (“sham”). At 2 months after ovariectomy, a glucose tolerance test (GTT) was performed, then cerebral arteries and arterioles were dissected, incubated in saponin, then assessed for mitochondrial respiration in response to substrates probing carbohydrate metabolism (Oroboros). Data are presented as mean±SEM. There was an interaction between APOE genotype and ovx/estradiol status in relation to cerebrovascular complex I (CI)- (p = 0.04) and complex II (CII)-coupled respiration (p = 0.04). Additionally, there was a significant effect of genotype, such that vessels from APOE3 mice had greater CI-coupled respiration than vessels from APOE4 mice (p = 0.02). When examining differences between APOE3 groups, APOE3 -estradiol mice had a 53% greater CI-coupled respiration than APOE3 -sham mice (15.4±3.4 vs. 7.2±1.2 pmol/(s*mg), p = 0.03) and a 60% greater CI-coupled respiration than APOE3 -ovx mice (6.2±1.6 pmol/(s*mg), p = 0.007). The APOE3 -estradiol group also had greater CI+CII-coupled respiration compared to both APOE3 -sham (50.8±7.1 vs. 27.3±1.7 pmol/(s*mg), p = 0.006) and ovx groups (28.0±5.7 pmol/(s*mg), p = 0.009). Interestingly, CI and CI+CII coupled respiration did not differ between sham, ovx, and estradiol in APOE4 mice (p>0.05). Maximal uncoupled respiration was greater in the APOE3 mice than APOE4 mice (p = 0.01). Whole-body glucose tolerance did not differ between groups (all p>0.05). Overall, these results indicate that APOE genotype modulates the impact of estrogen on the cerebrovasculature. We found that 17β-estradiol enhances cerebrovascular mitochondrial function in APOE3 mice but not APOE4 mice. The results suggest that estradiol supplementation may have more therapeutic benefit for APOE4 non-carriers.

Signal Transducer and Activator of Transcription 3 (STAT3) activation is increased in the brain following cerebral ischemia. STAT3, a transcription factor, is a positive regulator of cell survival and is implicated in cytoprotection following ischemia in multiple cell types, including neurons and endothelial cells. We hypothesized that pharmacological inhibition of STAT3 activation in mice during the reperfusion phase after middle cerebral artery occlusion (MCAO) will lead to increased infarct size. We subjected mice to 1-hour MCAO, following which they received STAT3 inhibitor Stattic (20 mg/kg), or vehicle, for 24 hours delivered subcutaneously via osmotic pump. Twenty-four hours later, infarct was measured by TTC and inflammatory cells were measured by flow cytometry. For experiments involving splenectomy, spleens were surgically removed 14 days prior to MCAO surgery. Surprisingly, we found that STAT3 inhibition reduces infarct after MCAO, with infarct in the hemisphere reducing from 49.90 ± 2.44 % in vehicle to 32.86 ± 1.55 % in Stattic-treated mice. Since STAT3 is involved in inflammatory processes, as well as cytoprotection, this led us to hypothesize that the reduction in infarct we observe may be due to decreased inflammation. We carried out FACS analysis and observed that Stattic inhibits MCAO-induced infiltration of B-, T- and dendritic cells into the brain. Neutrophil and monocyte infiltration into the brain were unaffected by Stattic. Since MCAO is known to induce splenic atrophy, with spleen size being inversely proportional to infarct volume, we measured spleen weights. Interestingly Stattic-treated mice had larger spleens (66.31 ± 5.40 g) compared to vehicle-treated mice (46.43 ± 4.60 g), indicating a dampened peripheral immune response upon inhibition of STAT3. Furthermore, Stattic was no longer effective in reducing infarct size in splenectomized mice. We conclude that pharmacological inhibition of STAT3 reduces infarct following MCAO, with the mechanism of protection involving differential regulation of the peripheral immune response.

Midlife metabolic syndrome (MetS) is associated with cognitive impairment in late life. The mechanism of delayed MetS-related cognitive dysfunction (MetSCD) is not clear, but it has been linked to systemic inflammation and chronic cerebral microangiopathy. Currently there is no treatment for late life MetSCD other than early risk factor modification. We investigated the effect of soluble epoxide hydrolase (sEH) inhibitor 4-[[trans-4-[[(tricyclo[3.3.1.13,7]dec-1-ylamino)carbonyl]amino]cyclohexyl]oxy]-benzoic acid (t-AUCB) on cognitive performance, cerebral blood flow (CBF), and central and peripheral inflammation in the high-fat diet (HFD) model of MetS in mice. At 6 weeks of age, male mice were randomly assigned to receive either HFD or standard chow (STD) for 6 months. Mice received either t-AUCB or vehicle for 4 weeks. Cognitive performance was evaluated, followed by CBF measurement using magnetic resonance imaging (MRI). At the end of the study, blood was collected for measurement of eicosanoids and inflammatory cytokines. The brains were then analyzed by immunohistochemistry for glial activation markers. The HFD caused a significant impairment in novel object recognition. Treatment with t-AUCB increased plasma levels of 14,15-EET, prevented this cognitive impairment and modified hippocampal glial activation and plasma cytokine levels, without affecting CBF in mice on HFD. In conclusion, sEH inhibition for four weeks prevents cognitive deficits in mice on chronic HFD by modulating inflammatory processes without affecting CBF.

Chronic coronary artery stenosis can lead to regional myocardial dysfunction in the absence of myocardial infarction by repetitive stunning, hibernation or both. The molecular mechanisms underlying repetitive stunning-associated myocardial dysfunction are not clear. We used non-targeted metabolomics to elucidate responses to chronically stunned myocardium in a canine model with and without β-adrenergic blockade treatment. After development of left ventricular systolic dysfunction induced by ameroid constrictors on the coronary arteries, animals were randomized to 3 months of placebo, metoprolol or carvedilol. We compared these two β-blockers with their different β-adrenergic selectivities on myocardial function, perfusion and metabolic pathways involved in tissue undergoing chronic stunning. Control animals underwent sham surgery. Dysfunction in stunned myocardium was associated with reduced fatty acid oxidation and enhanced ketogenic amino acid metabolism, together with alterations in mitochondrial membrane phospholipid composition. These changes were consistent with impaired mitochondrial function and were linked to reduced nitric oxide and peroxisome proliferator-activated receptor signalling, resulting in a decline in adenosine monophosphate-activated protein kinase. Mitochondrial changes were ameliorated by carvedilol more than metoprolol, and improvement was linked to nitric oxide and possibly hydrogen sulphide signalling. In summary, repetitive myocardial stunning commonly seen in chronic multivessel coronary artery disease is associated with adverse metabolic remodelling linked to mitochondrial dysfunction and specific signalling pathways. These changes are reversed by β-blockers, with the non-selective inhibitor having a more favourable impact. This is the first investigation to demonstrate that β-blockade-associated improvement of ventricular function in chronic myocardial stunning is associated with restoration of mitochondrial function. KEY POINTS: The mechanisms responsible for the metabolic changes associated with repetitive myocardial stunning seen in chronic multivessel coronary artery disease have not been fully investigated. In a canine model of repetitive myocardial stunning, we showed that carvedilol, a non-selective β-receptor blocker, ameliorated adverse metabolic remodelling compared to metoprolol, a selective β1-receptor blocker, by improving nitric oxide synthase and adenosine monophosphate protein kinase function, enhancing calcium/calmodulin-dependent protein kinase, probably increasing hydrogen sulphide, and suppressing cyclic-adenosine monophosphate signalling. Mitochondrial fatty acid oxidation alterations were ameliorated by carvedilol to a larger extent than metoprolol; this improvement was linked to nitric oxide and possibly hydrogen sulphide signalling. Both β-blockers improved the cardiac energy imbalance by reducing metabolites in ketogenic amino acid and nucleotide metabolism. These results elucidated why metabolic remodelling with carvedilol is preferable to metoprolol when treating chronic ischaemic left ventricular systolic dysfunction caused by repetitive myocardial stunning.

OBJECTIVE:There have been attempts to use therapeutic ultrasound (US) for the treatment of both experimental and clinical stroke. We hypothesized that low-intensity US has direct beneficial effects on the brain independent of cerebral blood flow (CBF) during middle cerebral artery occlusion (MCAO).METHODS:Three groups of mice were studied. Group I included 84 mice with MCAO undergoing US treatment/no treatment at two US frequencies (0.25 and 1.05 MHz) with three different acoustic pressures at each frequency in which infarct size (IS) was measured 24 h later. Group II included 11 mice undergoing treatment based on best US results from group I animals in which the IS/risk area (RA) ratio was measured 24 h later. Group III included 38 normal mice undergoing US treatment/no treatment for assessment of CBF, tissue metabolite and protein expression and histopathology.DISCUSSION:Ultrasound at both frequencies and most acoustic pressures resulted in reduction in IS in group I animals, with the best results obtained with 0.25 MHz at 2.0 MPa: IS was reduced 4-fold in the cerebral cortex, 1.5-fold in the caudate putamen and 3.5-fold in the cerebral hemisphere compared with control. US application in group III animals elicited only a marginal increase in CBF despite a 2.6-fold increase in phosphorylated endothelial nitric oxide synthase (p-eNOS)-S1177 and a corresponding decrease in p-eNOS-T494. Histopathology revealed no evidence of hemorrhage, inflammation or necrosis.CONCLUSION:Low-intensity US at specific frequencies and acoustic pressures results in marked neuroprotection in a mouse model of stroke by modulation of p-eNOS independent of its effect on CBF.

HomeStrokeAhead of PrintThe Ever-Evolving Concept of the Neurovascular Unit No AccessArticle CommentaryRequest AccessAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toNo AccessArticle CommentaryRequest AccessThe Ever-Evolving Concept of the Neurovascular Unit Nabil J. Alkayed and Marilyn J. Cipolla Nabil J. AlkayedNabil J. Alkayed Correspondence to: Nabil J. Alkayed, MD, PhD, Department of Anesthesiology and Perioperative Medicine, Knight Cardiovascular Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239. Email E-mail Address: [email protected] https://orcid.org/0000-0002-3489-4730 Department of Anesthesiology and Perioperative Medicine, Knight Cardiovascular Institute, Portland, OR (N.J.A.). Search for more papers by this author and Marilyn J. CipollaMarilyn J. Cipolla https://orcid.org/0000-0002-9172-5941 Department of Neurological Sciences, Larner College of Medicine at The University of Vermont, Burlington (M.J.C.). Department of Electrical and Biomedical Engineering, College of Engineering and Mathematical Sciences, Burlington, VT (M.J.C.). Search for more papers by this author Originally published3 Jul 2023https://doi.org/10.1161/STROKEAHA.123.042705Stroke. 2023;0FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.For Sources of Funding and Disclosures, see page XXX.Correspondence to: Nabil J. Alkayed, MD, PhD, Department of Anesthesiology and Perioperative Medicine, Knight Cardiovascular Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239. Email [email protected]edu eLetters(0)eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.Sign In to Submit a Response to This Article Previous Back to top Next FiguresReferencesRelatedDetails Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/STROKEAHA.123.042705PMID: 37395105 Originally publishedJuly 3, 2023 Keywordsneurovascular couplingstrokeblood-brain barrierPDF download Advertisement SubjectsBasic Science ResearchMechanisms

HomeStrokeVol. 54, No. 3Vascular Biology of Dementia No AccessReview ArticleRequest AccessFull TextAboutView Full TextView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toNo AccessReview ArticleRequest AccessFull TextVascular Biology of Dementia Marilyn J. Cipolla and Nabil J. Alkayed Marilyn J. CipollaMarilyn J. Cipolla Correspondence to: Marilyn J. Cipolla, PhD, Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, VT 05405. Email E-mail Address: [email protected] https://orcid.org/0000-0002-9172-5941 Department of Neurological Sciences, University of Vermont Larner College of Medicine, Burlington (M.J.C.). Department of Electrical and Biomedical Engineering, College of Engineering and Mathematical Sciences, University of Vermont, Burlington (M.J.C.). and Nabil J. AlkayedNabil J. Alkayed https://orcid.org/0000-0002-3489-4730 Department of Anesthesiology & Perioperative Medicine and Knight Cardiovascular Institute, Portland, OR (N.J.A.). Originally published27 Feb 2023https://doi.org/10.1161/STROKEAHA.123.042298Stroke. 2023;54:646–647is accompanied byDetection of Cardioembolic Sources With Nongated Cardiac Computed Tomography Angiography in Acute Stroke: Results From the ENCLOSE StudyCerebral Small Vessel Disease–Related Dementia: More Questions Than AnswersHippocampal Vascular Supply and Its Role in Vascular Cognitive ImpairmentBlood-Brain Barrier Dysfunction in Normal Aging and Neurodegeneration: Mechanisms, Impact, and Treatments"Vascular Biology of Dementia." Stroke, 54(3), pp. 646–647FootnotesFor Sources of Funding and Disclosures, see page 646.Correspondence to: Marilyn J. Cipolla, PhD, Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, VT 05405. Email marilyn.cipolla@uvm.eduReferences1. Sachdev P, Kalaria R, O'Brien J, Skoog I, Alladi S, Black SE, Blacker D, Blazer DG, Chen C, Chui H, et al. International society for vascular behavioral and cognitive disorders. diagnostic criteria for vascular cognitive disorders: a VASCOG statement.Alzheimer Dis Assoc Disord. 2014; 28:206–218. doi: 10.1097/wad.0000000000000034CrossrefMedlineGoogle Scholar2. Rundek T, Tolea M, Ariko T, Fagerli EA, Camargo CJ. Vascular Cognitive Impairment (VCI).Neurotherapeutics. 2022; 19:68–88. doi: 10.1007/s13311-021-01170-yCrossrefMedlineGoogle Scholar3. Elahi FM, Wang MM, Meschia JF. Cerebral small vessel disease (CSVD)-related dementia: more questions than answers.Stroke. 2023; 54:648–660. doi: 10.1161/STROKEAHA.122.038265LinkGoogle Scholar4. Silbert LC, Dodge HH, Perkins LG, Sherbakov L, Lahna D, Erten-Lyons D, Woltjer R, Shinto L, Kaye JA. Trajectory of white matter hyperintensity burden preceding mild cognitive impairment.Neurology. 2012; 79:741–747. doi: 10.1212/WNL.0b013e3182661f2bCrossrefMedlineGoogle Scholar5. Andjelkovic A, Situ M, Citalan-Madrid AF, Stamatovic S, Xiang J, Keep R. Blood-brain barrier dysfunction in normal aging and neurodegeneration: mechanisms, impact and treatments.Stroke. 2023; 54:661–672. doi: 10.1161/STROKEAHA.122.040578LinkGoogle Scholar6. Iadecola C, Duering M, Hachinski V, Joutel A, Pendlebury ST, Schneider JA, Dichgans M. Vascular cognitive impairment and dementia: JACC scientific expert panel.J Am Coll Cardiol. 2019; 73:3326–3344. doi: 10.1016/j.jacc.2019.04.034CrossrefMedlineGoogle Scholar7. Johnson AC. The hippocampal vascular supply and its role in vascular cognitive impairment and dementia.Stroke. 2023; 54:673–685. doi: 10.1161/STROKEAHA.122.038263LinkGoogle Scholar8. Lovick TA, Brown LA, Key BJ. Neurovascular relationships in hippocampal slices: physiological and anatomical studies of mechanisms underlying flow-metabolism coupling in intraparenchymal microvessels.Neuroscience. 1999; 92:47–60. doi: 10.1016/s0306-4522(98)00737-4CrossrefGoogle Scholar9. Longden TA, Dabertrand F, Koide M, Gonzales AL, Tykocki NR, Brayden JE, Hill-Eubanks D, Nelson MT. Capillary K+-sensing initiates retrograde hyperpolarization to increase local cerebral blood flow.Nat Neurosci. 2017; 20:717–726. doi: 10.1038/nn.4533CrossrefMedlineGoogle Scholar10. Lourenco CF, Santos RM, Barbosa RM, Cadenas E, Radi R, Laranjinha J. Neurovascular coupling in hippocampus is mediated via diffusion by neuronal-derived nitric oxide.Free Radic Biol Med. 2014; 73:421–429. doi: 10.1016/j.freeradbiomed.2014.05.021CrossrefGoogle Scholar11. Iadecola C. The pathobiology of vascular dementia.Neuron. 2013; 80:844–866. doi: 10.1016/j.neuron.2013.10.008CrossrefMedlineGoogle Scholar12. Katusic Z, d'Uscio L, He T. The emerging roles of endothelial nitric oxide in preservation of cognitive health.Stroke. 2023; 54:686–696. doi: 10.1161/STROKEAHA.122.041444LinkGoogle Scholar13. Austin SA, Santhanam AV, Katusic ZS. Endothelial nitric oxide modulates expression and processing of amyloid precursor protein.Circ Res. 2010; 107:1498–1502. doi: 10.1161/circresaha.110.233080LinkGoogle Scholar14. Correia SS, Liu G, Jacobson S, Bernier SG, Tobin JV, Schwartzkopf CD, Atwater E, Lonie E, Rivers S, Carvalho A, et al. The CNS-penetrant soluble guanylate cyclase stimulator CYR119 attenuates markers of inflammation in the central nervous system.J Neuroinflammation. 2021; 18:213. Doi: 10.1186/s12974-021-02275-zGoogle Scholar15. Selkoe DJ. The molecular pathology of Alzheimer's disease.Neuron. 1991; 6:487–498. doi: 10.1016/0896-6273(91)90052-2CrossrefGoogle Scholar eLetters(0)eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.Sign In to Submit a Response to This Article Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesDetection of Cardioembolic Sources With Nongated Cardiac Computed Tomography Angiography in Acute Stroke: Results From the ENCLOSE StudyFrans Kauw, et al. Stroke. 2023;54:821-830Cerebral Small Vessel Disease–Related Dementia: More Questions Than AnswersFanny M. Elahi, et al. Stroke. 2023;54:648-660Hippocampal Vascular Supply and Its Role in Vascular Cognitive ImpairmentAbbie C. Johnson,Stroke. 2023;54:673-685Blood-Brain Barrier Dysfunction in Normal Aging and Neurodegeneration: Mechanisms, Impact, and TreatmentsAnuska V. Andjelkovic, et al. Stroke. 2023;54:661-672 March 2023Vol 54, Issue 3 Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/STROKEAHA.123.042298PMID: 36848429 Originally publishedFebruary 27, 2023 Keywordscarotid stenosisblood-brain barrierheart diseasedementiacognitive disordersPDF download Advertisement

INTRODUCTION: Aneurysmal subarachnoid hemorrhage (SAH) is a devastating stroke with high morbidity and mortality. It causes an early brain injury (EBI), the severity of which can predict delayed cerebral ischemia (DCI). Neuroinflammation is a key component of EBI. The G protein-coupled receptor 39 (GPR39) is expressed in brain, and it has been shown to modulate neuroinflammation. METHODS: Endovascular perforation technique induced SAH in GPR39 knockout (KO) and wild-type (WT) littermate mice. Laser-Doppler was used to monitor cortical perfusion before, during, and right after SAH. Body mass and neurological deficit (neuroscore) were assessed daily after SAH. T2-weighted MRI was used to measure ventricular volumes, and T2*-weighted gradient recalled echo (GRE) MRI was used to assess cortical vein engorgement at 24 hours after SAH. Behavioral deficit was assessed using the accelerating rotarod at baseline and on days 2, 3 and 4 after SAH and balance beam on days 2, 3 and 4 after SAH. RESULTS: SAH caused an acute, communicating hydrocephalus with engorged cortical veins. WT and KO mice exhibited significant weight loss and deficits in neuroscore after SAH compared to sham mice. GPR39 KO mice had a significantly worse neuroscore than WT mice 3 days after SAH (mean 20.7 vs. 22.3; n = 12 vs. 15, respectively; p = 0.01). Additionally, GPR39 KO mice exhibited worse scores on rotarod 2 days after SAH (mean latency to fall 138.9 vs. 108.8; n=12 vs 15, respectively, p = 0.07) and balance beam 1 day after SAH (mean time to traverse 24.8 vs. 31.8; n = 8 vs. 11, respectively, p = 0.1). CONCLUSIONS: Our findings indicate that mice with GPR39 deletion exhibit worse outcomes in neuroscore and sensorimotor domains. These results suggest that GPR39 plays a protective role and may serve as a therapeutic target in SAH.

The major risk factors for late-onset Alzheimer’s Disease (LOAD) include old age, female sex and the APOE4 allele. Post-menopausal females with an APOE4 allele have higher rates of LOAD compared with age-matched males with an APOE4 allele, suggesting an interaction between APOE genotype and estrogen deficiency. Importantly, cerebrovascular dysfunction is a contributor to LOAD risk. However, it is unknown if APOE genotype and estrogen deficiency interact to impact cerebrovascular function.Young female homozygous APOE3 and APOE4 mice (n=4-6 per group; ~6 months old) fed a high-fat, high-cholesterol diet were intact (sham) or ovariectomized (OVX). We assessed endothelium-dependent dilation to increasing doses of acetylcholine (ACh) in pressurized posterior cerebral arteries (PCAs). There was an interaction effect of APOE genotype and OVX status for endothelium-dependent dilation (p=0.03), such that APOE3 -Sham mice had a greater endothelium-dependent dilation compared to the APOE3 -OVX group (70±9.1% vs. 39±7.6%, p=0.003). These differences were mediated by nitric oxide as indicated by the absence of dilation in the presence of N omega-Nitro-L-arginine methyl ester hydrocholoride (L-NAME, Sham: 3.7±3.3% vs OVX: 4.1±4.0%, p= 0.99). In contrast, APOE4 -OVX had preserved endothelium-dependent dilation compared with APOE4 -Sham (49.9±14.8% vs 56.1±9.2%, p=0.8). Endothelium-independent dilation was assessed by the response to increasing doses of sodium nitroprusside and did not differ among groups (all p>0.05). Passive stiffness was measured in isolated PCAs after incubation in a calcium-free solution. For the elastic modulus at low pressures, there was an interaction effect of APOE genotype and OVX status (p=0.03), with APOE4 -OVX having a higher elastic modulus compared to APOE4 -Sham (0.93±0.3 vs. 0.47±0.1, p=0.03). The elastic modulus was similar in APOE3 groups (sham: 0.64±0.01, OVX: 0.62±0.09, p=0.99). Overall, we found that estrogen deficiency impacts cerebral artery endothelial function in APOE3 , but not APO E4 mice, while estrogen deficiency impacts cerebral artery stiffness in APOE4 , but not APOE3 mice. These results shed light on the impact of APOE genotype on the cerebral vasculature, suggesting a potential mechanism for LOAD.

Cytochrome P450 metabolism of arachidonic acid produces epoxyeicosatrienoates (EETs) and hydroxyeicosatetraenoates (HETEs). Both classes of eicosanoids play important and opposing roles in brain function and disease. EETs promote vasodilation and exhibit antiinflammatory and cytoprotective properties; their biological action is blunted by metabolism to less active diols by the enzyme soluble epoxide hydrolase (sEH). EETs levels are dysregulated in disease states, primarily due to increased activity of sEH. Inhibition of sEH is a promising therapeutic approach for multiple brain disorders including stroke, dementia, subarachnoid hemorrhage and epilepsy. In this chapter, we summarize evidence implicating P450 eicosanoids and their synthetic and metabolizing enzymes in brain health and disease, and experimental and clinical studies targeting these pathways for brain disorders. We also discuss the diagnostic utility of quantifying P450 eicosanoids and their enzymes as disease biomarkers. Remarkable progress has been achieved in translating basic science discoveries in this field clinically.

Recent human and animal model experimental studies revealed novel pathways for fluid movement, immune cell trafficking and metabolic waste clearance in CNS. These studies raise the intriguing possibility that the newly discovered pathways, including the glymphatic system, lymphatic meningeal vessels and skull-brain communication channels, are impaired in aging and neurovascular and neurodegenerative diseases associated with dementia, including Alzheimer's disease (AD) and AD-related dementia. We provide an overview of the glymphatic and dural meningeal lymphatic systems, review current methods and approaches used to study glymphatic flow in humans and animals, and discuss current evidence and controversies related to its role in CNS flow homeostasis under physiological and pathophysiological conditions. Non-invasive imaging approaches are needed to fully understand the mechanisms and pathways driving fluid movement in CNS and their roles across lifespan including healthy aging and aging-related dementia.

Background: Type 2 diabetes (DM2) exacerbates stroke injury, reduces efficacy of endovascular therapy, and worsens long-term functional outcome. Sex differences exist in stroke incidence, response to therapy, poststroke microvascular dysfunction, and functional recovery. In this study, we tested the hypotheses that poor outcome after stroke in the setting of DM2 is linked to impaired microvascular tissue reperfusion and that male and female DM2 mice exhibit different microvascular reperfusion response after transient middle cerebral artery occlusion (MCAO). Methods: Transient MCAO was induced for 60 minutes using an intraluminal filament in young adult DM2 and nondiabetic control male and female mice. Capillary flux in deep cortical layers was assessed using optical coherence tomography–based optical microangiography (OMAG), and associated regional brain infarct size was evaluated by hematoxylin and eosin staining. Results: Compared to baseline, MCAO reduced absolute capillary red blood cell flux by 84% at 24 hours post-MCAO in male DM2 ( P <0.001) but not male control mice. When normalized to pre-MCAO baseline, red blood cell flux 24 hours after stroke was 64% lower in male DM2 mice than male nondiabetic controls ( P <0.01). In females, MCAO decreased capillary flux by 48% at 24 hours post-MCAO compared with baseline in DM2 ( P <0.05) but not in control mice. Red blood cell flux of female DM2 mice did not differ from that of nondiabetic controls either before or 24 hours after MCAO. Furthermore, normalized capillary flux 24 hours after MCAO failed to differ between female DM2 mice and nondiabetic controls. Concomitantly, male but not female DM2 mice experienced 25% larger infarct in caudate-putamen versus respective nondiabetic controls ( P <0.05). Conclusions: DM2 impairs capillary perfusion and exacerbates ischemic deep brain injury in male but not female young adult mice. Premenopausal females appear to be protected against DM2-related capillary dysfunction and brain injury.

Hemorrhagic stroke is the deadliest form of stroke and includes the subtypes of intracerebral hemorrhage and subarachnoid hemorrhage. A common cause of hemorrhagic stroke in older individuals is cerebral amyloid angiopathy. Intracerebral hemorrhage and subarachnoid hemorrhage both lead to the rapid collection of blood in the central nervous system and generate inflammatory immune responses that involve both brain resident and infiltrating immune cells. These responses are complex and can contribute to both tissue recovery and tissue injury. Despite the interconnectedness of these major subtypes of hemorrhagic stroke, few reviews have discussed them collectively. The present review provides an update on inflammatory processes that occur in response to intracerebral hemorrhage and subarachnoid hemorrhage, and the role of inflammation in the pathophysiology of cerebral amyloid angiopathy-related hemorrhage. The goal is to highlight inflammatory processes that underlie disease pathology and recovery. We aim to discuss recent advances in our understanding of these conditions and identify gaps in knowledge with the potential to develop effective therapeutic strategies.

Arachidonic acid metabolites epoxyeicosatrienoates (EETs) and hydroxyeicosatetraenoates (HETEs) are important regulators of myocardial blood flow and coronary vascular resistance (CVR), but their mechanisms of action are not fully understood. We applied a chemoproteomics strategy using a clickable photoaffinity probe to identify G protein-coupled receptor 39 (GPR39) as a microvascular smooth muscle cell (mVSMC) receptor selective for two endogenous eicosanoids, 15-HETE and 14,15-EET, which act on the receptor to oppose each other's activity. The former increases mVSMC intracellular calcium via GPR39 and augments coronary microvascular resistance, and the latter inhibits these actions. Furthermore, we find that the efficacy of both ligands is potentiated by zinc acting as an allosteric modulator. Measurements of coronary perfusion pressure (CPP) in GPR39-null hearts using the Langendorff preparation indicate the receptor senses these eicosanoids to regulate microvascular tone. These results implicate GPR39 as an eicosanoid receptor and key regulator of myocardial tissue perfusion. Our findings will have a major impact on understanding the roles of eicosanoids in cardiovascular physiology and disease and provide an opportunity for the development of novel GPR39-targeting therapies for cardiovascular disease.