Prenatal exposure to alcohol impairs responses of cerebral arterioles to activation of potassium channels: Role of oxidative stress.

BACKGROUND: Potassium channels play an important role in the basal tone and dilation of cerebral resistance arterioles in response to many stimuli. However, the effect of prenatal alcohol exposure (PAE) on specific potassium channel function remains unknown. The first goal of this study was to determine the influence of PAE on the reactivity of cerebral arterioles to activation of ATP-sensitive potassium (KATP ) and BK channels. Our second goal was to determine whether oxidative stress contributed to potassium channel dysfunction of cerebral arterioles following PAE. METHODS: We fed Sprague-Dawley dams a liquid diet with or without alcohol (3% EtOH) for the duration of their pregnancy (21 to 23 days). We examined in vivo responses of cerebral arterioles in control and PAE male and female offspring (14 to 16 weeks after birth) to activators of potassium channels (Iloprost [BK channels] and pinacidil [KATP channels]), before and following inhibition of oxidative stress with apocynin. RESULTS: We found that PAE impaired dilation of cerebral arterioles in response to activation of potassium channels with iloprost and pinacidil, and this impairment was similar in male and female rats. In addition, treatment with apocynin reversed the impaired vasodilation to iloprost and pinacidil in PAE rats to levels observed in control rats. This effect of apocynin also was similar in male and female rats. CONCLUSIONS: PAE induces dysfunction in the ability of specific potassium channels to dilate cerebral arterioles which appears to be mediated by an increase in oxidative stress. We suggest that these alterations in potassium channel function may contribute to the pathogenesis of cerebral vascular abnormalities and/or behavioral/cognitive deficits observed in fetal alcohol spectrum disorders.

Prenatal exposure to alcohol: mechanisms of cerebral vascular damage and lifelong consequences.

Alcohol is a well-known teratogen, and prenatal alcohol exposure (PAE) leads to a greater incidence of many cardiovascular-related pathologies. Alcohol negatively impacts vasculogenesis and angiogenesis in the developing fetal brain, resulting in fetal alcohol spectrum disorders (FASD). Ample preclinical evidence indicates that the normal reactivity of cerebral resistance arterioles, which regulate blood flow distribution in response to metabolic demand (neurovascular coupling), is impaired by PAE. This impairment of dilation of cerebral arteries may carry implications for the susceptibility of the brain to cerebral ischemic damage well into adulthood. The focus of this review is to consolidate findings from studies examining the influence of PAE on vascular development, give insights into relevant pathological mechanisms at the vascular level, evaluate the risks of ethanol-driven alterations of cerebrovascular reactivity, and revisit different preventive interventions that may have promise in reversing vascular changes in preclinical FASD models.

Constrictor responses of cerebral resistance arterioles in male and female rats exposed to prenatal alcohol.

While it is known that dilation of cerebral arterioles to NOS-dependent agonists is impaired in rats exposed to prenatal alcohol, no studies have examined the influence of prenatal alcohol on constrictor response of cerebral arterioles. Our goal was to determine whether constrictor responses of cerebral resistance arterioles are altered by prenatal exposure to alcohol and if any changes differed as a function of age or sex. We fed Sprague-Dawley rat dams a liquid diet with or without alcohol (3% ethanol) for the duration of their pregnancy. We then examined reactivity of cerebral arterioles to thromboxane (U-46619; 0.01 and 0.1 µM), arginine vasopressin (0.1 and 1 nM), and angiotensin II (1 and 10 µM) in four groups of offspring: control male and female, and prenatal alcohol male and female at two different ages (adolescent: 4-6 weeks old and adult: 14-16 weeks old). Constriction of cerebral arterioles to U-46619 and AVP were similar in male and female rats regardless of exposure to prenatal alcohol and age. Similarly, adolescent male and female rats showed no difference to angiotensin II following prenatal exposure to alcohol. However, alcohol-exposed females exhibited an unexpected dilation to the high concentration of angiotensin II in adulthood, which was absent in males. We suggest that the findings from these studies may have implications regarding the susceptibility of the brain to cerebral ischemic damage. We speculate that impaired vasodilation, coupled with preserved vasoconstriction, can lead to a scenario favoring a decrease in cerebral blood flow during times of increased metabolic demand.

Rosiglitazone restores nitric oxide synthase-dependent reactivity of cerebral arterioles in rats exposed to prenatal alcohol.

BACKGROUND: Prenatal exposure to alcohol leads to a greater incidence of many cardiovascular-related diseases, presumably via a mechanism that may involve increased oxidative stress. An agonist of peroxisome proliferator-activated receptor gamma (PPARγ; rosiglitazone) has been shown to suppress alcohol-induced neuroinflammation and oxidative stress. The goal of this study was to determine whether acute and chronic treatment with rosiglitazone could restore or prevent impaired nitric oxide synthase (NOS)-dependent responses of cerebral arterioles in male and female adult (14-16 weeks old) rats exposed to alcohol in utero. METHODS: We fed Sprague-Dawley dams a liquid diet with or without 3% ethanol for the duration of their pregnancy (21-23 days). In the first series of studies, we examined the reactivity of cerebral arterioles to eNOS- (ADP), nNOS-dependent (NMDA), and NOS-independent agonists in male and female adult rats before and during acute (1 hour) topical application of rosiglitazone (1 µM). In a second series of studies, we examined the influence of chronic treatment with rosiglitazone (3 mg/kg/day in drinking water for 2-3 weeks) on the responses of cerebral arterioles in male and female adult rats exposed to alcohol in utero. RESULTS: We found that in utero exposure to alcohol similarly reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in male and female adult rats. In addition, acute treatment of the male and female adult rats with rosiglitazone similarly restored this impairment in cerebral vascular function to that observed in controls. We also found that chronic treatment with rosiglitazone prevented impaired vascular function in male and female adult rats that were exposed to alcohol in utero. CONCLUSIONS: PPARγ activation may be an effective and relevant treatment to reverse or prevent cerebral vascular abnormalities associated with prenatal exposure to alcohol.

A cannabinoid type 2 (CB2) receptor agonist augments NOS-dependent responses of cerebral arterioles during type 1 diabetes.

While activation of cannabinoid (CB2) receptors has been shown to be neuroprotective, no studies have examined whether this neuroprotection is directed at cerebral arterioles and no studies have examined whether activation of CB2 receptors can rescue cerebrovascular dysfunction during a chronic disease state such as type 1 diabetes (T1D). Our goal was to test the hypothesis that administration of a CB2 agonist (JWH-133) would improve impaired endothelial (eNOS)- and neuronal (nNOS)-dependent dilation of cerebral arterioles during T1D. In vivo diameter of cerebral arterioles in nondiabetic and T1D rats was measured in response to an eNOS-dependent agonist (adenosine 5'-diphosphate; ADP), an nNOS-dependent agonist (N-methyl-d-aspartate; NMDA), and an NOS-independent agonist (nitroglycerin) before and 1 h following JWH-133 (1 mg/kg IP). Dilation of cerebral arterioles to ADP and NMDA was greater in nondiabetic than in T1D rats. Treatment with JWH-133 increased responses of cerebral arterioles to ADP and NMDA in both nondiabetic and T1D rats. Responses of cerebral arterioles to nitroglycerin were similar between nondiabetic and T1D rats, and JWH-133 did not influence responses to nitroglycerin in either group. The restoration in responses to the agonists by JWH-133 could be inhibited by treatment with a specific inhibitor of CB2 receptors (AM-630; 3 mg/kg IP). Thus, activation of CB2 receptors can potentiate reactivity of cerebral arterioles during physiologic and pathophysiologic states. We speculate that treatment with CB2 receptor agonists may have potential therapeutic benefits for the treatment of cerebral vascular diseases via a mechanism that can increase cerebral blood flow.

Author Correction: Effect of Low-Dose Alcohol Consumption on Inflammation Following Transient Focal Cerebral Ischemia in Rats.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Dose-Dependent Influences of Ethanol on Ischemic Stroke: Role of Inflammation.

Chronic ethanol consumption dose-dependently affects both incidence and prognosis of ischemic stroke. Our goal was to determine whether the influence of chronic ethanol consumption on ischemic stroke is related to an altered inflammatory profile in the brain. Male C57BL/6J mice were divided into six groups and gavage fed with 0.175, 0.35, 0.7, 1.4, 2.8 g/kg/day ethanol or volume-matched water once a day for 8 weeks. Adhesion molecules, microglial activation, neutrophil infiltration, pro- and anti-inflammatory cytokines/chemokines, blood-brain barrier (BBB) permeability, and matrix metallopeptidases (MMPs) in the cerebral cortex before and following a 90-min unilateral middle cerebral artery occlusion (MCAO)/24-h reperfusion were evaluated. Brain ischemia/reperfusion (I/R) injury was significantly reduced in 0.7 g/kg/day ethanol group (peak blood ethanol concentration: 9 mM) and worsened in 2.8 g/kg/day ethanol group (peak blood ethanol concentration: 37 mM). Baseline E-selectin was downregulated in all ethanol groups, whereas baseline intercellular adhesion molecule-1 (ICAM-1) was only downregulated in 0.35 and 0.7 g/kg/day ethanol groups. Interestingly, baseline vascular cell adhesion molecule-1 (VCAM-1) was upregulated in 0.35, 0.7, and 1.4 g/kg/day ethanol groups. Post-ischemic upregulation of ICAM-1 and E-selectin were suppressed in all ethanol groups. Post-ischemic neutrophil infiltration and microglial activation were significantly less in the low-moderate (0.175-1.4 g/kg/day) ethanol groups but greater in the 2.8 g/kg/day ethanol group compared to the vehicle group. At basal conditions, ethanol increased one pro- and two anti-inflammatory cytokines/chemokines at the 0.7 g/kg/day dose, and 13 pro- and eight anti-inflammatory cytokines/chemokines at the 2.8 g/kg/day dose. After ischemia, 0.7 g/kg/day ethanol suppressed post-ischemic pro-inflammatory cytokines/chemokines and enhanced post-ischemic anti-inflammatory cytokines/chemokines. Moreover, 0.7 g/kg/day ethanol significantly reduced baseline MMP-9 activity and alleviated post-ischemic BBB breakdown. On the other hand, 2.8 g/kg/day ethanol worsened post-ischemic BBB breakdown. Our findings suggest that low-moderate ethanol consumption may prevent ischemic stroke and reduce brain I/R injury by suppressing inflammation, whereas heavy alcohol consumption may induce ischemic stroke and worsen brain I/R injury by aggravating inflammation.

In Utero Exposure to Alcohol Impairs Reactivity of Cerebral Arterioles and Increases Susceptibility of the Brain to Damage Following Ischemia/Reperfusion in Adulthood.

BACKGROUND: Maternal consumption of alcohol produces abnormalities in the developing fetus and can contribute to an increased incidence of many cardiovascular-related diseases. The first goal of this study was to determine whether in utero exposure to alcohol influences reactivity of cerebral arterioles in adult (12 to 15 weeks old) rats. The second goal of this study was to examine whether in utero exposure to alcohol increased the susceptibility of the brain to damage following an ischemic event in adult rats. METHODS: We fed Sprague Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of their pregnancy (21 to 23 days). In the first series of studies, we examined reactivity of cerebral arterioles to endothelial nitric oxide synthase (eNOS)- (adenosine diphosphate [ADP]) and neuronal nitric oxide synthase (nNOS)-dependent N-methyl-D-aspartate (NMDA, and NOS-independent agonists in adult rats before and during application of l-NMMA. In another series of studies, we examined infarct volume following middle cerebral artery occlusion in adult offspring exposed to alcohol in utero. In both series of studies, we also determined the role for an increase in oxidative stress by feeding dams apocynin for the duration of their pregnancy. RESULTS: We found that in utero exposure to alcohol reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in adult rats. In addition, treatment of the dams with apocynin prevented this impairment in cerebral vascular function. We also found that in utero exposure to alcohol worsened brain damage following ischemia/reperfusion in adult rats and that treatment of dams with apocynin prevented this increase in brain damage following ischemia/reperfusion. CONCLUSIONS: We suggest that our findings may have important implications for the pathogenesis of brain abnormalities associated with fetal alcohol exposure.

In utero exposure to alcohol alters reactivity of cerebral arterioles.

Our goal was to examine whether in utero exposure to alcohol impaired reactivity of cerebral arterioles during development. We fed Sprague-Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of pregnancy (21-23 days). Around 4-6 weeks after birth, we examined reactivity of cerebral arterioles to eNOS- (ADP) and nNOS-dependent (NMDA) agonists in the offspring. We found that in utero exposure to alcohol attenuated responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in rats exposed to alcohol in utero. L-NMMA reduced responses to agonists in control rats, but not in rats exposed to alcohol in utero. Treatment of dams with apocynin for the duration of pregnancy rescued the impairment in reactivity to ADP and NMDA in the offspring. Protein expression of NOX-2 and NOX-4 was increased in alcohol rats compared to control rats. We also found an increase in superoxide levels in the cortex of rats exposed to alcohol in utero. Our findings suggest that in utero exposure to alcohol impairs eNOS and nNOS reactivity of cerebral arterioles via a chronic increase in oxidative stress.

Mito-Tempo prevents nicotine-induced exacerbation of ischemic brain damage.

Nicotine may contribute to the pathogenesis of cerebrovascular disease via the generation of reactive oxygen species (ROS). Overproduction of ROS leads to brain damage by intensifying postischemic inflammation. Our goal was to determine the effect of Mito-Tempo, a mitochondria-targeted antioxidant, on ischemic brain damage and postischemic inflammation during chronic exposure to nicotine. Male Sprague-Dawley rats were divided into four groups: control, nicotine, Mito-Tempo-treated control, and Mito-Tempo-treated nicotine. Nicotine (2 mg·kg-1·day-1) was administered via an osmotic minipump for 4 wk. Mito-Tempo (0.7 mg·kg-1·day-1 ip) was given for 7 days before cerebral ischemia. Transient focal cerebral ischemia was induced by occlusion of the middle cerebral artery for 2 h. Brain damage and inflammation were evaluated after 24 h of reperfusion by measuring infarct volume, expression of adhesion molecules, activity of matrix metalloproteinase, brain edema, microglial activation, and neutrophil infiltration. Nicotine exacerbated infarct volume and worsened neurological deficits. Nicotine did not alter baseline ICAM-1 expression, matrix metallopeptidase-2 activity, microglia activation, or neutrophil infiltration but increased these parameters after cerebral ischemia. Mito-Tempo did not have an effect in control rats but prevented the chronic nicotine-induced augmentation of ischemic brain damage and postischemic inflammation. We suggest that nicotine increases brain damage following cerebral ischemia via an increase in mitochondrial oxidative stress, which, in turn, contributes to postischemic inflammation. NEW & NOTEWORTHY Our findings have important implications for the understanding of mechanisms contributing to increased susceptibility of the brain to damage in smokers and users of nicotine-containing tobacco products.

Effect of Low-Dose Alcohol Consumption on Inflammation Following Transient Focal Cerebral Ischemia in Rats.

Increasing evidence suggest that low-dose alcohol consumption (LAC) reduces the incidence and improves the functional outcome of ischemic stroke. We determined the influence of LAC on post-ischemic inflammation. Male Sprague-Dawley rats were divided into 3 groups, an ethanol (13.5% alcohol) group, a red wine (Castle Rock Pinot Noir, 13.5% alcohol) group, and a control group. The amount of alcohol given to red wine and ethanol groups was 1.4 g/kg/day. After 8 weeks, the animals were subjected to a 2-hour middle cerebral artery occlusion (MCAO) and sacrificed at 24 hours of reperfusion. Cerebral ischemia/reperfusion (I/R) injury, expression of adhesion molecules and pro- and anti-inflammatory cytokines/chemokines, microglial activation and neutrophil infiltration were evaluated. The total infarct volume and neurological deficits were significantly reduced in red wine- and ethanol-fed rats compared to control rats. Both red wine and ethanol suppressed post-ischemic expression of adhesion molecules and microglial activation. In addition, both red wine and ethanol upregulated expression of tissue inhibitor of metalloproteinases 1 (TIMP-1), downregulated expression of proinflammatory cytokines/chemokines, and significantly alleviated post-ischemic expression of inflammatory mediators. Furthermore, red wine significantly reduced post-ischemic neutrophil infiltration. Our findings suggest that LAC may protect the brain against its I/R injury by suppressing post-ischemic inflammation.

Tetrahydrobiopterin rescues impaired responses of cerebral resistance arterioles during type 1 diabetes.

Our goal was to test the hypothesis that administration of tetrahydrobiopterin (BH4) would improve impaired endothelial nitric oxide synthase-dependent dilation of cerebral arterioles during type 1 diabetes. In addition, we examined the influence of BH4 on levels of superoxide in brain tissue. In vivo diameter of cerebral arterioles in nondiabetic and diabetic rats was measured in response to endothelial nitric oxide synthase-dependent agonists (acetylcholine and adenosine 5'-diphosphate) and an endothelial nitric oxide synthase-independent agonist (nitroglycerine) before and during application of BH4 (1.0 µM). We also measured levels of superoxide from cortex tissue in nondiabetic and diabetic rats under basal states and during BH4 Acetylcholine and adenosine 5'-diphosphate dilated cerebral arterioles in nondiabetic rats, but this vasodilation was significantly impaired in diabetic rats. In contrast, nitroglycerine produced similar vasodilation in nondiabetic and diabetic rats. Application of BH4 did not enhance vasodilation in nondiabetic rats but improved impaired cerebral vasodilation in diabetic rats. Basal superoxide levels were increased in cortex tissue from diabetic rats, and BH4 reduced these levels to that found in nondiabetic rats. Thus, BH4 is an important mediator of endothelial nitric oxide synthase-dependent responses of cerebral arterioles in diabetes and may have therapeutic potential for the treatment of cerebral vascular disease.

Severe respiratory changes at end stage in a FUS-induced disease state in adult rats.

BACKGROUND: Fused in sarcoma (FUS) is an RNA-binding protein associated with the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration. ALS manifests in patients as a progressive paralysis which leads to respiratory dysfunction and failure, the primary cause of death in ALS. We expressed human FUS in rats to determine if FUS would induce ALS relevant respiratory changes to serve as an early stage disease indicator. The FUS expression was initiated in adult rats by way of an intravenously administered adeno-associated virus vector serotype 9 (AAV9) providing an adult onset model. RESULTS: The rats developed progressive motor impairments observed as early as 2-3 weeks post gene transfer. Respiratory abnormalities manifested 4-7 weeks post gene transfer including increased respiratory frequency and decreased tidal volume. Rats with breathing abnormalities also had arterial blood acidosis. Similar detailed plethysmographic changes were found in adult rats injected with AAV9 TDP-43. FUS gene transfer to adult rats yielded a consistent pre-clinical model with relevant motor paralysis in the early to middle stages and respiratory dysfunction at the end stage. Both FUS and TDP-43 yielded a similar consistent disease state. CONCLUSIONS: This modeling method yields disease relevant motor and respiratory changes in adult rats. The reproducibility of the data supports the use of this method to study other disease related genes and their combinations as well as a platform for disease modifying interventional strategies.

Smooth muscle-generated methylglyoxal impairs endothelial cell-mediated vasodilatation of cerebral microvessels in type 1 diabetic rats.

BACKGROUND AND PURPOSE: Endothelial cell-mediated vasodilatation of cerebral arterioles is impaired in individuals with Type 1 diabetes (T1D). This defect compromises haemodynamics and can lead to hypoxia, microbleeds, inflammation and exaggerated ischaemia-reperfusion injuries. The molecular causes for dysregulation of cerebral microvascular endothelial cells (cECs) in T1D remains poorly defined. This study tests the hypothesis that cECs dysregulation in T1D is triggered by increased generation of the mitochondrial toxin, methylglyoxal, by smooth muscle cells in cerebral arterioles (cSMCs). EXPERIMENTAL APPROACH: Endothelial cell-mediated vasodilatation, vascular transcytosis inflammation, hypoxia and ischaemia-reperfusion injury were assessed in brains of male Sprague-Dawley rats with streptozotocin-induced diabetes and compared with those in diabetic rats with increased expression of methylglyoxal-degrading enzyme glyoxalase-I (Glo-I) in cSMCs. KEY RESULTS: After 7-8 weeks of T1D, endothelial cell-mediated vasodilatation of cerebral arterioles was impaired. Microvascular leakage, gliosis, macrophage/neutrophil infiltration, NF-κB activity and TNF-α levels were increased, and density of perfused microvessels was reduced. Transient occlusion of a mid-cerebral artery exacerbated ischaemia-reperfusion injury. In cSMCs, Glo-I protein was decreased, and the methylglyoxal-synthesizing enzyme, vascular adhesion protein 1 (VAP-1) and methylglyoxal were increased. Restoring Glo-I protein in cSMCs of diabetic rats to control levels via gene transfer, blunted VAP-1 and methylglyoxal increases, cECs dysfunction, microvascular leakage, inflammation, ischaemia-reperfusion injury and increased microvessel perfusion. CONCLUSIONS AND IMPLICATIONS: Methylglyoxal generated by cSMCs induced cECs dysfunction, inflammation, hypoxia and exaggerated ischaemia-reperfusion injury in diabetic rats. Lowering methylglyoxal produced by cSMCs may be a viable therapeutic strategy to preserve cECs function and blunt deleterious downstream consequences in T1D.

Sex-related differences in reactivity of cerebral arterioles during moderate exercise training.

OBJECTIVE: Our goals were to determine the influence of sex on reactivity of cerebral arterioles and whether MExT could influence sex-related differences in reactivity of cerebral arterioles. MATERIALS AND METHODS: Responses of cerebral arterioles were measured in Sed and MExT adult male and female Sprague-Dawley rats to eNOS-dependent (ADP), nNOS-dependent (NMDA), and NOS-independent (nitroglycerin) agonists before and following L-NMMA. In addition, protein expression for eNOS and nNOS was determined. RESULTS: NOS-dependent vasodilation was enhanced in Sed and MExT female rats compared to their male counterparts. L-NMMA produced a greater decrease in baseline diameter of arterioles in females compared to males, and produced less inhibition of NOS-dependent vasodilation in females. Expression of eNOS protein was significantly increased in Sed female when compared to Sed male rats; nNOS protein was similar in Sed males and females, but increased in MExT females. CONCLUSIONS: The findings from this study indicate that while NOS-dependent vascular reactivity is increased in females, MExT does not alter vasodilation in males or females. These studies provide insights into the influence of sex and MExT on the cerebral microcirculation and may have implications regarding mechanisms that protect the brain in females compared to males.

Chronic nicotine exposure exacerbates transient focal cerebral ischemia-induced brain injury.

Tobacco smoking is a risk factor contributing to the development and progression of ischemic stroke. Among many chemicals in tobacco, nicotine may be a key contributor. We hypothesized that nicotine alters the balance between oxidant and antioxidant networks leading to an increase in brain injury following transient focal cerebral ischemia. Male Sprague-Dawley were treated with nicotine (2 or 4 mg·kg(-1)·day(-1)) for 4 wk via an implanted subcutaneous osmotic minipump and subjected to a 2-h middle cerebral artery occlusion (MCAO). Infarct size and neurological deficits were evaluated at 24 h of reperfusion. Superoxide levels were determined by lucigenin-enhanced chemiluminescence. Expression of oxidant and antioxidant proteins was measured using Western blot analysis. We found that chronic nicotine exposure significantly increased infarct size and worsened neurological deficits. In addition, nicotine significantly elevated superoxide levels of cerebral cortex under basal conditions. Transient focal cerebral ischemia produced an increase in superoxide levels of cerebral cortex in control group, but no further increase was found in the nicotine group. Furthermore, chronic nicotine exposure did not alter protein expression of NADPH oxidase but significantly decreased MnSOD and uncoupling protein-2 (UCP-2) in the cerebral cortex and cerebral arteries. Our findings suggest that nicotine-induced exacerbation in brain damage following transient focal cerebral ischemia may be related to a preexisting oxidative stress via decreasing of MnSOD and UCP-2.

Influence of type 1 diabetes on basal and agonist-induced permeability of the blood-brain barrier.

Type 1 diabetes mellitus (T1D) impairs endothelial nitric oxide synthase (eNOS)-dependent responses of cerebral arterioles. However, the influence of T1D on another critical aspect of endothelial cell function in the cerebral microcirculation, i.e., regulation of permeability of the blood-brain barrier (BBB), remains largely unknown. Our goal was to examine basal and agonist-induced changes in permeability of the BBB in nondiabetic and type 1 diabetic (streptozotocin; 50 mg/kg IP) rats. On the day of the experiment (2-3 months after streptozotocin), a craniotomy was made over the parietal cortex in nondiabetic and diabetic rats. We measured the permeability of the BBB (FITC-dextran-10K) under basal conditions and during application of histamine. We also measured diameter of cerebral arterioles in response to histamine in the absence and presence of NG-monomethyl-L-arginine (L-NMMA). We found that basal permeability of the BBB was elevated in T1D and application of histamine did not produce a further increase in permeability. In contrast, basal permeability of the BBB was minimal in nondiabetics and histamine produced an increase in permeability. In addition, histamine-induced arteriolar dilation was less in diabetics than in nondiabetics, and vasodilation to histamine was inhibited by L-NMMA. Our findings suggest that T1D-induced endothelial dysfunction leads to an increase in basal permeability of the BBB, but decreases the ability of the endothelium of the BBB to respond to an important inflammatory mediator. Thus, T1D impairs two critical aspects of endothelial cell function in the cerebral microcirculation, i.e., basal and agonist-induced changes in permeability of the BBB and arteriolar dilation.

Vigorous exercise training improves reactivity of cerebral arterioles and reduces brain injury following transient focal ischemia.

OBJECTIVE: Our objective was to examine whether vigorous exercise training (VExT) could influence nitric oxide synthase (NOS)-dependent vasodilation and transient focal ischemia-induced brain injury. Rats were divided into sedentary (SED) or VExT groups. MATERIALS AND METHODS: Exercise was carried out 5 days/week for a period of 8-10 weeks. First, we measured responses of pial arterioles to an eNOS-dependent (ADP), an nNOS-dependent (NMDA) and a NOS-independent (nitroglycerin) agonist in SED and VExT rats. Second, we measured infarct volume in SED and VExT rats following middle cerebral artery occlusion (MCAO). Third, we measured superoxide levels in brain tissue of SED and VExT rats under basal and stimulated conditions. RESULTS: We found that eNOS- and nNOS-dependent, but not NOS-independent vasodilation, was increased in VExT compared to SED rats, and this could be inhibited with L-NMMA in both groups. In addition, we found that VExT reduced infarct volume following MCAO when compared to SED rats. Further, superoxide levels were similar in brain tissue from SED and VExT rats under basal and stimulated conditions. CONCLUSIONS: We suggest that VExT potentiates NOS-dependent vascular reactivity and reduces infarct volume following MCAO via a mechanism that appears to be independent of oxidative stress, but presumably related to an increase in the contribution of nitric oxide.

Influence of exercise training on ischemic brain injury in type 1 diabetic rats.

While exercise training (ExT) appears to influence cerebrovascular function during type 1 diabetes (T1D), it is not clear whether this beneficial effect extends to protecting the brain from ischemia-induced brain injury. Thus our goal was to examine whether modest ExT could influence transient focal ischemia-induced brain injury along with nitric oxide synthase (NOS)-dependent dilation of cerebral (pial) arterioles during T1D. Sprague-Dawley rats were divided into four groups: nondiabetic sedentary, nondiabetic ExT, diabetic (streptozotocin; 50 mg/kg ip) sedentary, and diabetic ExT. In the first series of studies, we measured infarct volume in all groups of rats following right MCA occlusion for 2 h, followed by 24 h of reperfusion. In a second series of studies, a craniotomy was performed over the parietal cortex, and we measured responses of pial arterioles to an endothelial NOS (eNOS)-dependent, a neuronal NOS (nNOS)-dependent, and a NOS-independent agonist in all groups of rats. We found that sedentary diabetic rats had significantly larger total, cortical, and subcortical infarct volumes following ischemia-reperfusion than sedentary nondiabetic, nondiabetic ExT, and diabetic ExT rats. Infarct volumes were similar in sedentary nondiabetic, ExT nondiabetic, and ExT diabetic rats. In contrast, ExT did not alter infarct size in nondiabetic compared with sedentary nondiabetic rats. In addition, ExT diabetic rats had impaired eNOS- and nNOS-dependent, but not NOS-independent, vasodilation that was restored by ExT. Thus ExT of T1D rats lessened ischemic brain injury following middle cerebral artery occlusion and restored impaired eNOS- and nNOS-dependent vascular function. Since the incidence of ischemic stroke is increased during T1D, we suggest that our finding are significant in that modest ExT may be a viable preventative therapeutic approach to lessen ischemia-induced brain injury that may occur in T1D subjects.

Low-dose alcohol consumption protects against transient focal cerebral ischemia in mice: possible role of PPARγ.

BACKGROUND: We examined the influence of low-dose alcohol consumption on cerebral ischemia/reperfusion (I/R) injury in mice and a potential mechanism underlying the neuroprotective effect of low-dose alcohol consumption. METHODOLOGY/PRINCIPAL FINDINGS: C57BL/6 J mice were fed a liquid diet without or with 1% alcohol for 8 weeks, orally treated with rosiglitazone (20 mg/kg/day), a peroxisome proliferator-activated receptor gamma (PPARγ)-selective agonist, or GW9662 (3 mg/kg/day), a selective PPARγ antagonist, for 2 weeks. The mice were subjected to unilateral middle cerebral artery occlusion (MCAO) for 90 minutes. Brain injury, DNA fragmentation and nuclear PPARγ protein/activity were evaluated at 24 hours of reperfusion. We found that the brain injury and DNA fragmentation were reduced in 1% alcohol-fed mice compared to nonalcohol-fed mice. Rosiglitazone suppressed the brain injury in nonalcohol-fed mice, but didn't alter the brain injury in alcohol-fed mice. In contrast, GW9662 worsened the brain injury in alcohol-fed mice, but didn't alter the brain injury in nonalcohol-fed mice. Nuclear PPARγ protein/activity at peri-infarct and the contralateral corresponding areas of the parietal cortex was greater in alcohol-fed mice compared to nonalcohol-fed mice. Using differentiated catecholaminergic (CATH.a) neurons, we measured dose-related influences of chronic alcohol exposure on nuclear PPARγ protein/activity and the influence of low-dose alcohol exposure on 2-hour oxygen-glucose deprivation (OGD)/24-hour reoxygenation-induced apoptosis. We found that low-dose alcohol exposure increased nuclear PPARγ protein/activity and protected against the OGD/reoxygenation-induced apoptosis. The beneficial effect of low-dose alcohol exposure on OGD/reoxygenation-induced apoptosis was abolished by GW9662. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that chronic consumption of low-dose alcohol protects the brain against I/R injury. The neuroprotective effect of low-dose alcohol consumption may be related to an upregulated PPARγ.