Pial Arterioles Research Articles

Genetic and Environmental Contributions to Variation in the Posterior Communicating Collaterals of the Circle of Willis.

Variation in blood flow mediated by the posterior communicating collateral arteries (PComs) contributes to variation in the severity of tissue injury in obstructive disease. Evidence in animals and humans indicates that differences in the extent of PComs, i.e., their anatomic lumen diameter and whether they are present bilaterally, unilaterally, or absent, are a major factor. These differences arise during development since they are present at birth. However, the causal mechanisms are unknown. We used angiography after maximal dilation to examine involvement of genetic, environmental, and stochastic factors. The extent of PComs varied widely among seven genetically diverse strains of mice. Like pial collaterals in the microcirculation, aging and hypertension reduced PCom diameter, while in contrast, obesity, hyperlipidemia, metabolic syndrome, and diabetes mellitus had no effect. Naturally occurring intrauterine growth restriction had no effect on extent of PCom or pial collaterals in the adult. The number and diameter of PComs evidenced much larger apparent stochastic-dependent variation than pial collaterals. In addition, both PComs underwent flow-mediated outward remodeling after unilateral permanent MCA occlusion that varied with genetic background and was greater on the ipsilesional side. These findings indicate that variation in the number and diameter of PCom collateral arteries arises from stochastic factors and naturally occurring genetic variants that differ from those that cause variation in pial collateral arterioles. Environmental factors also contribute: aging and hypertension reduce PCom diameter. Our resultssuggest possible sources of variation of PComs in humans and provide information relevant when studying mouse models of occlusive cerebrovascular disease.

Thrombosis and systemic and cardiac oxidative stress and DNA damage induced by pulmonary exposure to diesel exhaust particles and the effect of nootkatone thereon.

Adverse cardiovascular effects of particulate air pollution persist even at lower concentrations than those of the current air quality limit. Therefore, identification of safe and effective measures against particle-induced cardiovascular toxicity is needed. Nootkatone is a sesquiterpenoid in grapefruit with diverse bioactivities including anti-inflammatory and antioxidant effects. However, its protective effect on the cardiovascular injury induced by diesel exhaust particles (DEPs) has not been studied before. We assessed the possible protective effect of nootkatone (90 mg/kg) administered by gavage 1 h before intratracheal instillation of DEPs (30 μg/mouse). Twenty-four hours after the intratracheal administration of DEPs, various thrombotic and cardiac parameters were assessed. Nootkatone inhibited the prothrombotic effect induced by DEPs in pial arterioles and venules in vivo and platelet aggregation in whole blood in vitro. Also, nootkatone prevented the shortening of activated partial thromboplastin time and prothrombin time induced by DEPs. Nootkatone inhibited the increase of plasma concentration of fibrinogen, plasminogen activator inhibitor-1, interleukin-6, and lipid peroxidation induced by DEPs. Immunohistochemically, hearts showed an analogous increase in glutathione and nuclear factor erythroid-derived 2-like 2 expression by cardiac myocytes and endothelial cells after DEP exposure, and these effects were enhanced in mice treated with nootkatone + DEPs. Likewise, heme oxygenase-1 was increased in mice treated with nootkatone + DEPs compared with those treated with DEPs or nootkatone + saline. The DNA damage caused by DEPs was prevented by nootkatoone pretreatment. In conclusion, nootkatoone alleviates DEP-induced thrombogenicity and systemic and cardiac oxidative stress and DNA damage, at least partly, through nuclear factor erythroid-derived 2-like 2 and heme oxygenase-1 activation. NEW & NOTEWORTHY Nootkatoone, a sesquiterpenoid found in grapefruit, alleviates the thrombogenicity and systemic and cardiac oxidative stress and DNA damage in mice exposed to diesel exhaust particles. Nootkatone-induced boosting of nuclear factor erythroid-derived 2-like 2 and heme oxygenase-1 levels in the heart of mice exposed to diesel exhaust particles suggests that its protective effect is, at least partly, mediated through nuclear factor erythroid-derived 2-like 2 and heme oxygenase-1 activation.

РЕАКЦИИ ЦЕРЕБРАЛЬНЫХ МИКРОСОСУДОВ НА ОСТРОЕ ГИПОКСИЧЕСКОЕ ВОЗДЕЙСТВИЕ ПРИ ЭКЗОГЕННОМ ПОВЫШЕНИИ УРОВНЯ ИНТЕРЛЕЙКИНА-1? В КРОВИ, "Российский физиологический журнал им. И.М. Сеченова"

Были изучены особенности влияния повышенного системного уровня провоспалительного цитокина интерлейкина-1-бета ( -1 ) на вазомоторные реакции пиальных артериол теменной области коры головного мозга наркотизированных крыс при прогрессивно развивающейся острой нормобарической гипоксии, приводящей к остановке дыхания животных, при апноэ и в постгипоксический период. Показано, что вазодилатирующее влияние гипоксии на микроциркуляторное русло коры головного мозга крыс происходит лишь при значительном уменьшении содержания кислорода во вдыхаемой газовой смеси. В экспериментальной группе животных, которым предварительно производилось внутривенное введение 500 нг -1 , достоверное увеличение диаметра пиальных артериол на 45-55 % наблюдалось при снижении содержания кислорода в дыхательной смеси до 10 %, тогда как в контрольной группе диаметр артериол при данной степени гипоксии не изменялся. При углублении гипоксии до 4-6 %, вызывающей остановку дыхания, вазодилатация пиальных артериол отмечалась и в контрольной группе, достигая 26 %. После перехода на дыхание воздухом у всех животных в контроле наблюдалось самопроизвольное восстановление дыхания. В экспериментальной группе у 50 % животных дыхание не восстанавливалось. Вазодилатация при этом была более выраженной у всех животных экспериментальной группы: диаметр артериол увеличивался на 70 % у животных с последующим полным восстановлением дыхания и на 135 % у животных без его восстановления. Таким образом, установлено, что экзогенное повышение системного уровня -1 усиливает чувствительность микрососудов мозга к гипоксии и увеличивает их дилатацию в ответ на прогрессивно нарастающее гипоксическое воздействие, снижая при этом возможность спонтанного возобновления дыхания после апноэ.

In vivo observation of cerebral microcirculation after experimental subarachnoid hemorrhage in mice

Acute brain injury caused by subarachnoid hemorrhage is the major cause of poor prognosis. The pathology of subarachnoid hemorrhage likely involves major morphological changes in the microcirculation. However, previous studies primarily used fixed tissue or delayed injury models. Therefore, in the present study, we used in vivo imaging to observe the dynamic changes in cerebral microcirculation after subarachnoid hemorrhage. Subarachnoid hemorrhage was induced by perforation of the bifurcation of the middle cerebral and anterior cerebral arteries in male C57/BL6 mice. The diameter of pial arterioles and venules was measured by in vivo fluorescence microscopy at different time points within 180 minutes after subarachnoid hemorrhage. Cerebral blood flow was examined and leukocyte adhesion/albumin extravasation was determined at different time points before and after subarachnoid hemorrhage. Cerebral pial microcirculation was abnormal and cerebral blood flow was reduced after subarachnoid hemorrhage. Acute vasoconstriction occurred predominantly in the arterioles instead of the venules. A progressive increase in the number of adherent leukocytes in venules and substantial albumin extravasation were observed between 10 and 180 minutes after subarachnoid hemorrhage. These results show that major changes in microcirculation occur in the early stage of subarachnoid hemorrhage. Our findings may promote the development of novel therapeutic strategies for the early treatment of subarachnoid hemorrhage.

Vasodilator dysfunction and oligodendrocyte dysmaturation in aging white matter.

Microvascular brain injury (mVBI) is a common pathological correlate of vascular contributions to cognitive impairment and dementia (VCID) that leads to white matter (WM) injury (WMI). VCID appears to arise from chronic recurrent white matter ischemia that triggers oxidative stress and an increase in total oligodendrocyte lineage cells. We hypothesized that mVBI involves vasodilator dysfunction of white matter penetrating arterioles and aberrant oligodendrocyte progenitor cell (OPC) responses to WMI. We analyzed cases of mVBI with low Alzheimer's disease neuropathological change in prefrontal cortex WM from rapid autopsies in a population-based cohort where VCID frequently occurs. Arteriolar vasodilator function was quantified by videomicroscopy. OPC maturation was quantified using lineage specific markers. Acetylcholine-mediated arteriolar dilation in mVBI was significantly reduced in WM penetrators relative to pial arterioles. Astrogliosis-defined WMI was positively associated with increased OPCs and was negatively associated with decreased mature oligodendrocytes. Selectively impaired vasodilator function of WM penetrating arterioles in mVBI occurs in association with aberrant differentiation of OPCs in WMI, which supports that myelination disturbances in VCID are related to disrupted maturation of myelinating oligodendrocytes. Ann Neurol 2018;83:142-152.

Microvascular insulin resistance in skeletal muscle and brain occurs early in the development of juvenile obesity in pigs.

Impaired microvascular insulin signaling may develop before overt indices of microvascular endothelial dysfunction and represent an early pathological feature of adolescent obesity. Using a translational porcine model of juvenile obesity, we tested the hypotheses that in the early stages of obesity development, impaired insulin signaling manifests in skeletal muscle (triceps), brain (prefrontal cortex), and corresponding vasculatures, and that depressed insulin-induced vasodilation is reversible with acute inhibition of protein kinase Cβ (PKCβ). Juvenile Ossabaw miniature swine (3.5 mo of age) were divided into two groups: lean control ( n = 6) and obese ( n = 6). Obesity was induced by feeding the animals a high-fat/high-fructose corn syrup/high-cholesterol diet for 10 wk. Juvenile obesity was characterized by excess body mass, hyperglycemia, physical inactivity (accelerometer), and marked lipid accumulation in the skeletal muscle, with no evidence of overt atherosclerotic lesions in athero-prone regions, such as the abdominal aorta. Endothelium-dependent (bradykinin) and -independent (sodium nitroprusside) vasomotor responses in the brachial and carotid arteries (wire myography), as well as in the skeletal muscle resistance and 2A pial arterioles (pressure myography) were unaltered, but insulin-induced microvascular vasodilation was impaired in the obese group. Blunted insulin-stimulated vasodilation, which was reversed with acute PKCβ inhibition (LY333-531), occurred alongside decreased tissue perfusion, as well as reduced insulin-stimulated Akt signaling in the prefrontal cortex, but not the triceps. In the early stages of juvenile obesity development, the microvasculature and prefrontal cortex exhibit impaired insulin signaling. Such adaptations may underscore vascular and neurological derangements associated with juvenile obesity.

Effects of Transient Cerebral Ischemia on the Adrenoreactivity of the Pial Vessels in Rats

Ischemia is known to affect endothelium-dependent reactions of cerebral vessels and to change the metabolic and myogenic mechanisms regulating brain blood flow. The role of local neurogenic regulatory mechanisms in changes in the reactions of cerebral vessels after ischemia remains incompletely understood. The aim of the present work was to study the reactions of pial arterial and venous vessels in rats to noradrenaline before and 2, 7, 14, and 21 days after ischemia induced by occlusion of both carotid arteries for 12 min with simultaneous control of hypotension at level of 45 ± 3 mmHg. Ischemia was found to increase the constrictor reaction to noradrenaline of mainly small pial arteries and arterioles and third-degree venules. Increases in the number of constrictor reactions in rats subjected to ischemia, persisting to post-reinfusion day 21, were most marked at post-ischemia day 14. The post-ischemic increase in adrenoreactivity may be linked with an increase in the reactivity and sensitivity of adrenoreceptors of cerebral vessels.

Low-Frequency Components in Rat Pial Arteriolar Rhythmic Diameter Changes

This study aimed to analyze the frequency components present in spontaneous rhythmic diameter changes in rat pial arterioles. Pial microcirculation was visualized by fluorescence microscopy. Rhythmic luminal variations were evaluated via computer-assisted methods. Spectral analysis was carried out on 30-min recordings under baseline conditions and after administration of acetylcholine (Ach), papaverine (Pap), Nω-nitro-<smlcap>L</smlcap>-arginine (<smlcap>L</smlcap>-NNA) prior to Ach, indomethacin (INDO), INDO prior to Ach, charybdotoxin and apamin, and charybdotoxin and apamin prior to Ach. Under baseline conditions all arteriolar orders showed 3 frequency components in the ranges of 0.0095-0.02, 0.02-0.06, and 0.06-0.2 Hz, another 2 in the ranges of 0.2-2.0 and 2.5-4.5 Hz, and another ultra-low-frequency component in the range of 0.001-0.0095 Hz. Ach caused a significant increase in the spectral density of the frequency components in the range of 0.001-0.2 Hz. Pap was able to slightly increase spectral density in the ranges of 0.001-0.0095 and 0.0095-0.02 Hz. <smlcap>L</smlcap>-NNA mainly attenuated arteriolar responses to Ach. INDO prior to Ach did not affect the endothelial response to Ach. Charybdotoxin and apamin, suggested as endothelium-derived hyperpolarizing factor inhibitors, reduced spectral density in the range of 0.001-0.0095 Hz before and after Ach administration. In conclusion, regulation of the blood flow distribution is due to several mechanisms, one of which is affected by charibdotoxin and apamin, modulating the vascular tone.

Temporal remodeling of pial collaterals and functional deficits in a murine model of ischemic stroke

BackgroundLeptomeningeal anastomoses play a critical role in regulating reperfusion following cerebrovascular obstruction; however, methods to evaluate their temporospatial remodeling remains under investigation. New methodWe combined arteriole-specific vessel painting with histological evaluation to assess the density and diameter of inter-collateral vessels between the middle cerebral artery and anterior cerebral artery (MCA-ACA) or posterior cerebral artery (MCA-PCA) in a murine model of permanent middle cerebral artery occlusion (pMCAO). ResultsWhile the overall density was not influenced by pMCAO, the size of MCA-ACA and MCA-PCA vessels had significantly increased 2days post-pMCAO and peaked by 4days compared to the un-injured hemisphere. Using a combination of vessel painting and immunofluorescence, we uniquely observed an induction of cellular division and a remodeling of the smooth muscle cells within the collateral niche following post-pMCAO on whole mount tissue sections. Vessel painting was also applied to pMCAO-injured Cx3cr1GFP mice, in order to identify the spatial relationship between Cx3cr1-positive peripheral-derived monocyte/macrophages and the vessel painted collaterals. Our histological findings were supplemented with analysis of cerebral blood flow using laser Doppler imaging and behavioral changes following pMCAO. Comparison with existing methodsCompared to polyurethane and latex methods for collateral labeling, this new method provides detailed cell-type specific analysis within the collateral niche at the microscopic level, which has previously been unavailable. ConclusionsThis simple and reproducible combination of techniques is the first to dissect the temporospatial remodeling of pial collateral arterioles. The method will advance investigations into the underlying mechanisms governing the intricate processes of arteriogenesis.

Repeated Mandibular Extension in Rat: A Procedure to Modulate the Cerebral Arteriolar Tone.

Previous data have shown both in the rat and in the human that a single mandibular extension lasting 10 min induces a significant important and prolonged reduction in blood pressure and heart rate, affecting also rat pial microcirculation by the release of endothelial factors. In the present work, we assessed whether repeated mandibular extension could further prolong these effects. We performed two mandibular extensions, the second mandibular extension being applied 10 min after the first one. The second mandibular extension produced a reduction in blood pressure and heart rate for at least 240 min. As in the case of a single mandibular extension, pial arterioles dilated persisting up to 140 min after the second extension. Spectral analysis on 30 min recordings under baseline conditions and after repetitive mandibular extensions showed that the pial arterioles dilation was associated with rhythmic diameter changes sustained by an increase in the frequency components related to endothelial, neurogenic, and myogenic activity while a single mandibular extension caused, conversely, an increase only in the endothelial activity. In conclusion, repetitive mandibular extension prolonged the effects of a single mandibular extension on blood pressure, heart rate and vasodilation and induced a modulation of different frequency components responsible of the pial arteriolar tone, in particular increasing the endothelial activity.

Cerebral Vasoactivity and Oxygenation with Oxygen Carrier M101 in Rats.

The severity of traumatic brain injury (TBI) may be reduced if oxygen can be rapidly provided to the injured brain. This study evaluated if the oxygen-carrier M101 causes vasoconstricton of pial vasculature in healthy rats (Experiment 1) and if M101 improves brain tissue oxygen (PbtO2) in rats with controlled cortical impact (CCI)-TBI (Experiment 2). M101 (12.5 mL/kg intravenous [IV] over 2 h) caused a mild (9 mm Hg) increase in the mean arterial blood pressure (MAP) of healthy rats without constriction of cerebral pial arterioles. M101 (12 mL/kg IV over 1 h) caused a modest (27 mm Hg) increase in MAP (peak, 123 ± 5 mm Hg [mean ± standard error of the mean]) of CCI-TBI rats and restored PbtO2 to near pre-injury levels. In both M101 and untreated control (NON) groups, PbtO2 was ∼30 ± 2 mm Hg pre-injury and decreased (p ≤ 0.05) to ∼16 ± 2 mm Hg 15 min after CCI. In NON, PbtO2 remained ∼50% of baseline but M101 administration resulted in a sustained increase in PbtO2 (peak, 25 ± 5 mm Hg), which was not significantly different from pre-injury until the end of the study, when it decreased again below pre-injury (but was still higher than NON). Histopathology showed no differences between groups. In conclusion, M101 increased systemic blood pressures without concurrent cerebral pial vasoconstriction (in healthy rats) and restored PbtO2 to 86% of pre-injury for at least 80 min when given soon after CCI-TBI. M101 should be evaluated in a clinically-relevant large animal model for pre-hospital treatment of TBI.

Immunolocation of Heme Oxygenases in the Walls of Cerebral Arteries of Various Diameters in Rats.

The distribution of two enzymes involved in the formation of carbon monoxide, heme oxygenases 1 and 2, in the pial branches of orders I-V of the middle cerebral artery basin and in intracerebral vessels was studied in adult Wistar rats. Immunohistochemical studies detected hemeoxygenase-2 in the endothelium of the small pial and intracerebral arterioles and in myocytes of pial branches I-III. Heme oxygenase 1, an inducible form of the enzyme, is normally not expressed in the cerebral vessels, but the enzyme is expressed in response to sodium metaarsenite. In this case, heme oxygenase markers are detected in myocytes of pial arteries I-II and in the endothelium of small pial and intracerebral vessels. Sodium meta-arsenite is inessential for immunolocation and quantitative distribution of heme oxygenase 2 in the vessels.

Correlation between reduction in microvascular transit time after superficial temporal artery-middle cerebral artery bypass surgery for moyamoya disease and the development of postoperative hyperperfusion syndrome.

OBJECTIVE Hyperperfusion syndrome (HPS) is a notable complication that causes various neurological symptoms after superficial temporal artery (STA)-middle cerebral artery (MCA) bypass surgery for moyamoya disease (MMD). The authors used intraoperative indocyanine green (ICG) videoangiography to measure the change in microvascular transit time (MVTT) after bypass surgery. An analysis was then conducted to identify the correlation between change in MVTT and presence of postoperative HPS. METHODS This study included 105 hemispheres of 81 patients with MMD who underwent STA-MCA single bypass surgery between January 2010 and January 2015. Intraoperative ICG videoangiography was performed before and after bypass surgery. The MVTT was calculated from the ICG time intensity curve recorded in the pial arterioles and venules. Multivariate logistic regression analysis was conducted to test the effect of multiple variables, including the change in MVTT after bypass surgery, on postoperative HPS. RESULTS Postoperative HPS developed in 28 (26.7%) of the 105 hemispheres operated on. MVTT was reduced significantly after bypass surgery (prebypass 5.34 ± 2.00 sec vs postbypass 4.12 ± 1.60 sec; p < 0.001). The difference between prebypass and postbypass MVTT values, defined as ΔMVTT, was significantly greater in the HPS group than in the non-HPS group (2.55 ± 2.66 sec vs 0.75 ± 1.78 sec; p < 0.001). Receiver operating characteristic curve analysis revealed that the optimal cutoff point of ΔMVTT was 2.6 seconds (sensitivity 46.4% and specificity 85.7% as a predictor of postoperative HPS). A ΔMVTT > 2.6 seconds was an independent predictor of HPS in multivariate analysis (hazard ratio 4.88, 95% CI 1.76-13.57; p = 0.002). CONCLUSIONS MVTT in patients with MMD was reduced significantly after bypass surgery. Patients with a ΔMVTT > 2.6 seconds tended to develop postoperative HPS. Because ΔMVTT can be easily measured during surgery, it is a useful diagnostic tool for identifying patients at high risk for HPS after STA-MCA bypass surgery for MMD.

Harmful Effects of Neonatal Epileptic Seizures on Cerebrovascular Functions: Does Sex Matter?

There is a growing interest in the potential contribution of sex‐related variables to cerebrovascular functions in healthy and sick neonates. Epileptic seizures, the most common adverse neurological event in human newborns, may lead to cerebrovascular injury and abnormalities in cerebral blood flow regulation. Clinical studies suggest that male neonates are more susceptible to seizures, with a higher incidence of neurological complications. Cerebral vascular health is an important contributing factor to brain homeostasis and neuronal health. Newborn piglets provide a valuable and translationally relevant animal model for studying the cerebrovascular effects of epileptic seizures in the neonatal brain. This study in newborn pigs (2–5 days old) was designed to investigate whether sex‐related differences contribute to systemic parameters and cerebrovascular functions in: 1) control healthy animals and 2) piglets subjected to bicuculline‐induced epileptic seizures leading to prolonged cerebral vascular dysfunction during the delayed postictal period. After a 48‐h recovery period from epileptic seizures, postictal cerebrovascular functions were tested using intravital microscopy via the closed cranial window technique. We recorded the responses of small‐ and medium‐sized pial cerebral arterioles (50–100 μm) to a battery of vasodilator stimuli including: A) endothelium‐dependent hypercapnia and bradykinin; B) dual endothelium/astrocyte‐dependent stimuli glutamate, ionotropic glutamate receptor agonist quisqualic acid, and hemin; C) astrocyte‐dependent vasodilator adenosine diphosphate, and D) endothelium/astrocyte‐independent vasodilator sodium nitroprusside (SNP). We found no sex‐related differences in cardiovascular parameters (mean arterial blood pressure, heart rate), arterial blood gases, or core body temperature in either control or postictal groups of newborn piglets. A significant reduction (50–70%) in responses of pial arterioles to endothelium‐ and/or astrocyte‐dependent vasodilators was observed 48 h after seizures (delayed postictal period) in both male and female piglets. In piglets of both sexes, vasodilation to SNP was preserved during the delayed postictal period, suggesting that vascular smooth muscle contractility was not affected by seizures. An antioxidant and cytoprotective compound, the carbon‐monoxide (CO)‐releasing molecule CORM‐A1 (3 mg/kg i.p.) that was administered shortly before and/or during seizures, prevented postictal loss of cerebrovascular functions in both male and female piglets. Overall, we observed no sex‐specific differences in selected systemic cardiovascular parameters and cerebrovascular dilator functions in control and epileptic newborn pigs. In both male and female piglets, epileptic seizures lead to severe cerebral vascular dysfunction during the delayed postictal period. Antioxidant therapy with CORM‐A1 is neuroprotective in both male and female newborn pigs because it effectively prevents deleterious effects of epileptic seizures on cerebral blood flow regulation in a sex‐independent manner.Support or Funding InformationThe study was supported by NIH/NHLBI/NINDS.

The acute pulmonary and thrombotic effects of cerium oxide nanoparticles after intratracheal instillation in mice.

Cerium oxide nanoparticles (CeO2 NPs), used as a diesel fuel catalyst, can be emitted into the ambient air, resulting in exposure to humans by inhalation. Recent studies have reported the development of lung toxicity after pulmonary exposure to CeO2 NPs. However, little is known about the possible thrombotic effects of these NPs. The present study investigated the acute (24 hours) effect of intratracheal (IT) instillation of either CeO2 NPs (0.1 or 0.5 mg/kg) or saline (control) on pulmonary and systemic inflammation and oxidative stress and thrombosis in mice. CeO2 NPs induced a significant increase of neutrophils into the bronchoalveolar lavage (BAL) fluid with an elevation of tumor necrosis factor α (TNFα) and a decrease in the activity of the antioxidant catalase. Lung sections of mice exposed to CeO2 NPs showed a dose-dependent infiltration of inflammatory cells consisting of macrophages and neutrophils. Similarly, the plasma levels of C-reactive protein and TNFα were significantly increased, whereas the activities of catalase and total antioxidant were significantly decreased. Interestingly, CeO2 NPs significantly and dose dependently induced a shortening of the thrombotic occlusion time in pial arterioles and venules. Moreover, the plasma concentrations of fibrinogen and plasminogen activator inhibitor-1 were significantly elevated by CeO2 NPs. The direct addition of CeO2 NPs (1, 5, or 25 μg/mL) to mouse whole blood, collected from the inferior vena cava, in vitro neither caused significant platelet aggregation nor affected prothrombin time or partial thromboplastin time, suggesting that the thrombotic events observed in vivo may have resulted from systemic inflammation and/or oxidative stress induced by CeO2 NPs. This study concludes that acute pulmonary exposure to CeO2 NPs induces pulmonary and systemic inflammation and oxidative stress and promotes thrombosis in vivo.

Collateral blood flow in different cerebrovascular hierarchy provides endogenous protection in cerebral ischemia.

Collateral blood flow as vascular adaptions to focal cerebral ischemia is well recognized. However, few studies directly investigate the dynamics of collateral vessel recruitment in vivo and little is known about the effect of collateral blood flow in different cerebrovascular hierarchy on the neuropathology after focal ischemic stroke. Here, we report that collateral blood flow is critically involved in blood vessel compensations following regional ischemia. We occluded a pial arteriole using femtosecond laser ablating under the intact thinned skull and documented the changes of collateral flow around the surface communication network and between the surface communication network and subsurface microcirculation network using in vivo two photon microscopy imaging. Occlusion of the pial arteriole apparently increased the diameter and collateral blood flow of its leptomeningeal anastomoses, which significantly reduced the cortical infarction size. This result suggests that the collateral flow via surface communicating network connected with leptomeningeal anastomoses could greatly impact on the extent of infarction. We then further occluded the target pial arteriole and all of its leptomeningeal anastomoses. Notably, this type of occlusion led to reversals of blood flow in the penetrating arterioles mainly proximal to the occluded pial arteriole in a direction from the subsurface microcirculation network to surface arterioles. Interesting, the cell death in the area of ischemic penumbra was accelerated when we performed occlusion to cease the reversed blood flow in those penetrating arterioles, suggesting that the collateral blood flow from subsurface microcirculation network exerts protective roles in delaying cell death in the ischemic penumbra. In conclusion, we provide the first experimental evidence that collateral blood vessels at different cerebrovascular hierarchy are endogenously compensatory mechanisms in brain ischemia.

The effects of Y-27632 on pial microvessels during global brain ischemia and reperfusion in rabbits

BackgroundGlobal brain ischemia-reperfusion during propofol anesthesia provokes persistent cerebral pial constriction. Constriction is likely mediated by Rho-kinase. Cerebral vasoconstriction possibly exacerbates ischemic brain injury. Because Y-27632 is a potent Rho-kinase inhibitor, it should be necessary to evaluate its effects on cerebral pial vessels during ischemia—reperfusion period. We therefore tested the hypotheses that Y-27632 dilates cerebral pial arterioles after the ischemia-reperfusion injury, and evaluated the time-course of cerebral pial arteriolar status after the ischemia-reperfusion.MethodsJapanese white rabbits were anesthetized with propofol, and a closed cranial window inserted over the left hemisphere. Global brain ischemia was produced by clamping the brachiocephalic, left common carotid, and left subclavian arteries for 15 min. Rabbits were assigned to cranial window perfusion with: (1) artificial cerebrospinal fluid (Control group, n = 7); (2) topical infusion of Y-27632 10−6 mol · L−1 for 30 min before the initiation of global brain ischemia (Pre group, n = 7); (3) topical infusion of Y-27632 10−6 mol · L−1 starting 30 min before ischemia and continuing throughout the study period (Continuous group, n = 7); and, (4) topical infusion of Y-27632 10−6 mol · L−1 starting 10 min after the ischemia and continuing until the end of the study (Post group, n = 7). Cerebral pial arterial and venule diameters were recorded 30 min before ischemia, just before arterial clamping, 10 min after clamping, and 5, 10, 20, 40, 60, 80, 100, and 120 min after unclamping.ResultsMean arterial blood pressure and blood glucose concentration increased significantly after global brain ischemia except in the Continuous group. In the Pre and Continuous groups, topical application of Y-27632 produced dilation of large (mean 18–19%) and small (mean; 25–29%) pial arteries, without apparent effect on venules. Compared with the Control and Pre groups, arterioles were significantly dilated during the reperfusion period in the Continuous and Post groups (mean at 120 min: 5–8% in large arterioles and 11–12% in small arterioles).ConclusionsY-27632 dilated cerebral pial arterioles during reperfusion. Y-27632 may enhance recovery from ischemia by preventing arteriolar vasoconstriction during reperfusion.

Abstract TMP120: Genetic, Environmental and Stochastic Factors Contribute to Variation in the Posterior Communicating Collaterals of the Circle of Willis

Variation in blood flow mediated by the posterior communicating collateral arteries (PComs) contributes to variation in severity of tissue injury in obstructive disease. The “extent” of PCom collaterals (lumen diameter &amp;/or number—ie, presence bilaterally, unilaterally or absent) varies widely in humans and other species due in part to developmental differences, since well-known patterns of variation are present at birth. However, mechanisms underlying this variation have not been examined. Herein we used angiography to probe involvement of genetic, environmental and stochastic factors. PCom extent varied widely among 7 mouse strains with different genetic backgrounds that was unrelated to differences in PCA diameter or brain weight. The pattern differed strongly from that previously reported by us for differences in extent of pial collateral arterioles. Like pial collaterals, PCom diameter was reduced by advanced aging (-28±3%, n=11-16, p&lt;0.01; opposite seen for PCA diameter) and hypertension (-14±8%, n=7-9, p&lt;0.05; -18% for PCA diameter). In contrast to pial collaterals, obesity, hyperlipidemia, metabolic syndrome and diabetes had no effect on PCom extent (or PCA diameter). Intrauterine growth restriction reduced PCom diameter 55±4% (n=6-17, p&lt;0.05; -24% for PCA) in the adult despite catch-up growth of brain after birth, while pial collaterals were unaffected. Compared to pial collaterals (and PCA), PCom extent evidenced &gt;8-fold larger stochastic variation (n=16, p&lt;0.01). In addition, PComs underwent outward remodeling after MCA occlusion that varied with genetic background (12-133% lumen enlargement among 5 strains; n=5-14, p&lt;0.05-0.001) and was greater on the side of occlusion in most strains. In conclusion, variation in number and diameter of PCom collateral arteries arises from genetic, environmental and stochastic factors. The responsible genetic polymorphisms appear to differ from those that contribute to variation in extent of pial collateral arterioles. Extent of PComs is also adversely affected by intrauterine growth restriction, aging and hypertension. These findings suggest possible sources of PCom variation in humans and provide information relevant when studying mouse models of occlusive cerebrovascular disease.

Water-Pipe Smoke Exposure-Induced Circulatory Disturbances in Mice, and the Influence of Betaine Supplementation Thereon

Background/Aims: It has been shown, both experimentally and clinically, that water-pipe smoke (WPS) exposure adversely affects the cardiovascular system (CVS) through the generation of oxidative stress and inflammation. Betaine, a naturally occurring compound in common foods, has antioxidant and anti-inflammatory actions. However, its potential to mitigate the adverse effect of WPS on the CVS has never been reported before. This is the subject of this study in mice. Methods: Mice were exposed daily for 30 min to either normal air (control), or to WPS for two consecutive weeks. Betaine was administered daily by gavage at a dose of 10mg/kg, 1h before either air or WPS exposure. Results: Betaine mitigated the in vivo prothrombotic effect of WPS in pial arterioles and venules. Moreover, it reversed the WPS-induced decrease in circulating platelets. Likewise, betaine alleviated platelet aggregation in vitro, and the shortening of activated partial thromboplastin time and prothrombin time induced by WPS. Betaine reduced the increase of plasminogen activator inhibitor-1 and fibrinogen concentrations in plasma induced by WPS. Betaine also diminished the WPS-induced increase of plasma concentrations of interleukin 6 and tumor necrosis factor α, and attenuated the increase of lipid peroxidation and superoxide dismutase. Immunohistochemical analysis of the heart revealed an increase in the expression of inducible nitric oxide synthase and cytochrome C by cardiomyocytes of the WPS-exposed mice. These effects were averted by betaine. Conclusion: Our findings suggest that betaine treatment significantly mitigated WPS-induced hypercoagulability, and inflammation, as well as systemic and cardiac oxidative stress.

Photothrombotic Induction of Capillary Ischemia in the Mouse Cortex during in vivo Two-photon Imaging.

Photothrombosis of blood vessels refers to the activation of a circulating photosensitive dye with a green light to induce clotting in vivo (Watson et al., 1985). Previous studies have described how a focused green laser could be used to noninvasively occlude pial arterioles and venules at the brain surface (Schaffer et al., 2006; Nishimura et al., 2007; Shih et al., 2013). Here we show that small regions of the capillary bed can similarly be occluded to study the ischemic response within the capillary system of the mouse cerebral cortex. The advantage of this approach is that the ischemic zone is restricted to a diameter of approximately 150-250 μm. This permits higher quality two-photon imaging of degenerative processes that would be otherwise difficult to visualize with models of large-scale stroke, due to excessive photon scattering. A consequence of capillary occlusion is leakage of the blood-brain barrier (BBB). Here, through the use of two-photon imaging data sets, we show how to quantify capillary leakage by determining the spatial extent and localization of intravenous dye extravasation.