Abstract: Decreased dilation of cerebral arterioles via an increase in oxidative stress may be a contributing factor in the pathogenesis of diabetes-induced complications leading to cognitive dysfunction and/or stroke. Our goal was to determine whether resveratrol, a polyphenolic compound present in red wine, has a protective effect on cerebral arterioles during type 1 diabetes (T1D). We measured the responses of cerebral arterioles in untreated and resveratrol-treated (10 mg·kg(-1)·day(-1)) nondiabetic and diabetic rats to endothelial (eNOS) and neuronal (nNOS) nitric oxide synthase (NOS)-dependent agonists and to a NOS-independent agonist. In addition, we harvested brain tissue from nondiabetic and diabetic rats to measure levels of superoxide under basal conditions. Furthermore, we used Western blot analysis to determine the protein expression of eNOS, nNOS, SOD-1, and SOD-2 in cerebral arterioles and/or brain tissue from untreated and resveratrol-treated nondiabetic and diabetic rats. We found that T1D impaired eNOS- and nNOS-dependent reactivity of cerebral arterioles but did not alter NOS-independent vasodilation. While resveratrol did not alter responses in nondiabetic rats, resveratrol prevented T1D-induced impairment in eNOS- and nNOS-dependent vasodilation. In addition, superoxide levels were higher in brain tissue from diabetic rats and resveratrol reversed this increase. Furthermore, eNOS and nNOS protein were increased in diabetic rats and resveratrol produced a further increased eNOS and nNOS proteins. SOD-1 and SOD-2 proteins were not altered by T1D, but resveratrol treatment produced a decrease in SOD-2 protein. Our findings suggest that resveratrol restores vascular function and oxidative stress in T1D. We suggest that our findings may implicate an important therapeutic potential for resveratrol in treating T1D-induced cerebrovascular dysfunction.
Abstract: Our goal was to examine whether exercise training (ExT) could normalize impaired nitric oxide synthase (NOS)-dependent dilation of cerebral (pial) arterioles during type 1 diabetes (T1D). We measured the in vivo diameter of pial arterioles in sedentary and exercised nondiabetic and diabetic rats in response to an endothelial NOS (eNOS)-dependent (ADP), an neuronal NOS (nNOS)-dependent [N-methyl-D-aspartate (NMDA)], and a NOS-independent (nitroglycerin) agonist. In addition, we measured superoxide anion levels in brain tissue under basal conditions in sedentary and exercised nondiabetic and diabetic rats. Furthermore, we used Western blot analysis to determine eNOS and nNOS protein levels in cerebral vessels/brain tissue in sedentary and exercised nondiabetic and diabetic rats. We found that ADP and NMDA produced a dilation of pial arterioles that was similar in sedentary and exercised nondiabetic rats. In contrast, ADP and NMDA produced only minimal vasodilation in sedentary diabetic rats. ExT restored impaired ADP- and NMDA-induced vasodilation observed in diabetic rats to that observed in nondiabetics. Nitroglycerin produced a dilation of pial arterioles that was similar in sedentary and exercised nondiabetic and diabetic rats. Superoxide levels in cortex tissue were similar in sedentary and exercised nondiabetic rats, were increased in sedentary diabetic rats, and were normalized by ExT in diabetic rats. Finally, we found that eNOS protein was increased in diabetic rats and further increased by ExT and that nNOS protein was not influenced by T1D but was increased by ExT. We conclude that ExT can alleviate impaired eNOS- and nNOS-dependent responses of pial arterioles during T1D.
Abstract: We examined the dose-related influence of alcohol consumption on cerebral ischemia/reperfusion (I/R) injury and the potential mechanism that accounts for the disparate effects of high-dose and low-dose alcohol consumption on cerebral I/R injury.
Abstract:  Chronic alcohol consumption increases ischemic stroke and exacerbates ischemic brain injury. We determined the role of NAD(P)H oxidase in exacerbated ischemic brain injury during chronic alcohol consumption.
Abstract: Our goal was to determine whether exercise training (ExT) alleviates impaired nitric oxide synthase (NOS)-dependent dilation of pial arterioles during chronic exposure to nicotine. We measured dilation of cerebral (pial) arterioles in sedentary and exercised control and nicotine-treated (2 mg·kg(-1)·day(-1) for 4 wk via an osmotic minipump) rats to an endothelial NOS (eNOS)-dependent (ADP), a neuronal NOS (nNOS)-dependent [N-methyl-D-aspartic acid (NMDA)], and a NOS-independent (nitroglycerin) agonist. In addition, we harvested brain tissue from sedentary and exercised control and nicotine-treated rats to measure the production of superoxide anion and measured superoxide dismutase-1 (SOD-1) protein in cerebral microvessels using Western blot. We found that eNOS-and nNOS-dependent, but not NOS-independent, vasodilation was impaired in nicotine-treated compared with control rats. In addition, the production of superoxide anion (lucigenin chemiluminescence) was increased, and SOD-1 protein decreased, in rats treated with nicotine compared with control rats. Further, although ExT did not significantly affect eNOS- or nNOS-dependent vasodilation in control rats, ExT restored impaired eNOS- and nNOS-dependent responses in nicotine-treated rats. In addition, the increase in superoxide anion production observed in nicotine-treated rats was reduced by ExT, and SOD-1 protein was increased in nicotine-treated rats by ExT. We suggest that ExT restores impaired NOS-dependent dilation of pial arterioles during chronic exposure to nicotine by a mechanism related to the formation of superoxide anion.
Abstract: Our goals were to determine whether acute exposure to nicotine alters nitric oxide synthase (NOS)-dependent responses of the basilar artery and to identify a potential role for activation of NAD(P)H oxidase in nicotine-induced impairment in NOS-dependent responses of the basilar artery.
Abstract: Inward rectifier potassium (K(IR)) channels appear to play an important role in the regulation of cerebral blood flow. Our goal was to examine the influence of chronic alcohol exposure on K(IR) channels in cerebral arterioles. Sprague-Dawley rats were fed liquid diets with or without alcohol for 8-12 weeks. Using intravital microscope, we measured diameter of pial arterioles in response to an inhibitor, BaCl(2), and an activator, KCl, of K(IR) channels in the absence and presence of a scavenger of reactive oxygen species, tempol, or an inhibitor of NAD(P)H oxidase, apocynin. Application of BaCl(2) (30 and 100 microM) produced dose-related vasoconstriction in non-alcohol-fed, but not in alcohol-fed rats. In addition, application of KCl (3, 10, and 30 mM) produced dose-related dilation in non-alcohol-fed and alcohol-fed rats, but the magnitude of vasodilatation was less in alcohol-fed rats. In contrast, nitroglycerin-induced vasodilation was similar in non-alcohol-fed and alcohol-fed rats. Superfusion of cranial window with tempol (0.1 mM) or apocynin (1 mM) did not alter baseline diameter and nitroglycerin-induced dilation of pial arterioles in non-alcohol-fed and alcohol-fed rats but significantly improved impaired KCl-induced dilation in alcohol-fed rats. Our findings suggest that chronic alcohol consumption impairs the role of K(IR) channels in basal tone and KCl-induced dilation of cerebral arterioles. In addition, impaired KCl-induced dilation of cerebral arterioles during alcohol consumption may be related to enhanced release of oxygen-derived free radicals via NAD(P)H oxidase.
Abstract: Chronic alcohol consumption impairs cerebral vasoreactivity, and thus, may result in an increase in ischemic brain damage. The goal of this study is to examine the influence of chronic alcohol consumption on transient focal ischemia-induced brain damage. Sprague-Dawley rats were divided into two groups, a control group and an alcohol group. Eight weeks after being fed a liquid diet with or without alcohol, responses of parietal pial arterioles to systemic hypoxia and hypercapnia were measured using a cranial window technique. In separate experiments, rats were subjected to right middle cerebral artery occlusion (MCAO) for 2 h under ketamine/xylazine or isoflurane anesthesia. Regional cerebral blood flow (rCBF) was monitored through a Laser-Doppler flow probe attached to the lateral aspect of the skull. Neurological evaluation and ischemic lesion were assessed 24 h after reperfusion. Dilation of pial arterioles in response to hypoxia and hypercapnia was significantly reduced in alcohol-fed rats. Alcohol-fed rats had significantly larger infarct volumes and worse neurological outcomes than non-alcohol-fed rats under ketamine/xylazine or isoflurane anesthesia. In addition, rCBF measurement indicated that alcohol-fed rats had less regulatory rebound increase in rCBF after the initial drop in rCBF at the onset of MCAO. Our findings suggest that chronic alcohol consumption exacerbates transient focal ischemia-induced brain damage. Increased ischemic brain damage during alcohol consumption may be related to an impaired cerebral vasoreactivity.
Abstract: Intraluminal occlusion of the middle cerebral artery (MCA) is used extensively in cerebral ischemia research. We tested a modified nylon suture in a rat model of middle cerebral artery occlusion (MCAO) under two anesthesia regimens. Sprague-Dawley rats were divided into six groups (Group 1, Poly-L-lysine-coated suture under ketamine/xylazine anesthesia; Group 2, modified suture under ketamine/xylazine anesthesia; Group 3, Poly-L-lysine-coated suture under ketamine/xylazine anesthesia with mechanical ventilation; Group 4, modified suture under ketamine/xylazine anesthesia with mechanical ventilation; Group 5, Poly-L-lysine-coated suture under isoflurane anesthesia; Group 6, modified suture under isoflurane anesthesia) and subjected to 2-hour MCAO. Regional cerebral blood flow (rCBF) was monitored by Laser-Doppler flowmetry. Neurological evaluation and ischemic lesion (TTC stain) were assessed at 24 hours of reperfusion. The total ischemic lesion (sum of areas with lacking and intermediate TTC staining) was similar among all six groups. Compared with a Poly-L-lysine-coated suture technique, the modified suture technique produced a lower rCBF, larger infarct size, smaller variance of infarct size, and greater neurological deficit. In addition, isoflurane significantly reduced infarct size. We conclude that the use of this modified suture technique with ketamine/xylazine anesthesia and mechanical ventilation produces a more consistent change in cerebral ischemic damage following MCAO in rats.
Abstract: We examined whether activation of angiotensin-1 receptors (AT1R) could account for impaired responses of cerebral arterioles during type 1 diabetes (T1D). First, we measured responses of cerebral arterioles in nondiabetic rats to eNOS-dependent (acetylcholine and adenosine diphosphate (ADP)) and -independent (nitroglycerin) agonists before and during application of angiotensin II. Next, we examined whether losartan could improve impaired responses of cerebral arterioles during T1D. In addition, we harvested cerebral microvessels for Western blot analysis of AT1R protein and measured production of superoxide anion by brain tissue under basal conditions and in response to angiotensin II in the absence or presence of losartan. We found that angiotensin II specifically impaired eNOS-dependent reactivity of cerebral arterioles. In addition, while losartan did not alter responses in nondiabetics, losartan restored impaired eNOS-dependent vasodilatation in diabetics. Further, AT1R protein was higher in diabetics compared to nondiabetics. Finally, superoxide production was higher in brain tissue from diabetics compared to nondiabetics under basal conditions, angiotensin II increased superoxide production in nondiabetics and diabetics, and losartan decreased basal (diabetics) and angiotensin II-induced production of superoxide (nondiabetics and diabetics). We suggest that activation of AT1R during T1D plays a critical role in impaired eNOS-dependent dilatation of cerebral arterioles.
Abstract: Our goal was to identify the role of poly(ADP-ribose) polymerase (PARP) in cerebrovascular dysfunction in Type 1 diabetes mellitus (T1D). In a first series of studies, rats were assigned to nondiabetic and diabetic (streptozotocin; 50 mg/kg IP) groups. Two to three months after injection of streptozotocin, we examine in vivo responses of pial arterioles to nitric oxide synthase (NOS)-dependent (adenosine diphosphate (ADP), acetylcholine and histamine) and -independent (nitroglycerin) agonists. After the initial examination of reactivity to the agonists, we treated pial arterioles acutely with an inhibitor of PARP (PJ-34; 1 microM), and then we again examined responses to the agonists. In a second series of studies, we examine superoxide production (lucigenin chemiluminescence) by parietal cortex tissue in nondiabetic and diabetic rats. We found that dilation of pial arterioles in response to ADP, acetylcholine and histamine, but not to nitroglycerin, was impaired in diabetic compared to nondiabetic rats. In addition, although PJ-34 did not alter responses in nondiabetic rats, PJ-34 alleviated T1D-induced impairment of NOS-dependent vasodilation. We also found that basal production of superoxide was increased in diabetic compared to nondiabetic rats and that PJ-34 decreased this basal production of superoxide. Our findings suggest that T1D impairs NOS-dependent reactivity of cerebral arterioles by a mechanism that appears to be related to the formation of superoxide via activation of PARP.
Abstract: Our goals were to determine whether Type 1 diabetes (T1D) alters neuronal nitric oxide synthase (nNOS)-dependent reactivity of cerebral arterioles and to identify a potential role for oxidative stress in T1D-induced impairment in nNOS-dependent responses of cerebral arterioles. Rats were injected with vehicle (sodium citrate buffer) or streptozotocin (50 mg/kg IP) to induce T1D. Two to three months later, we measured functional responses of cerebral arterioles to nNOS-dependent (NMDA and kainate) and -independent (nitroglycerin) agonists in nondiabetic and diabetic rats before and during inhibition of oxidative stress using tempol (100 microM). In addition, we measured superoxide anion production under basal conditions, during stimulation with NMDA and kainate, and during treatment with tempol. We found that nNOS-dependent, but -independent, vasodilatation was impaired in diabetic compared to nondiabetic rats. In addition, treatment of the cerebral microcirculation with tempol restored impaired nNOS-dependent vasodilatation in diabetic rats toward that observed in nondiabetic rats. Furthermore, the production of superoxide anion (lucigenin chemiluminescence) was increased in parietal cortical tissue of diabetic rats under basal conditions. Application of NMDA and kainate did not increase superoxide anion production in nondiabetic or diabetic rats. However, tempol decreased basal production of superoxide anion in diabetic rats. Our findings suggest that T1D impairs nNOS-dependent dilatation of cerebral arterioles by a mechanism that appears to be related to the formation of superoxide anion.
Abstract: Our goals were to determine whether chronic exposure to nicotine alters nitric oxide synthase (NOS)-dependent reactivity of cerebral (pial) arterioles and to identify a potential role for NADPH oxidase in impaired NOS-dependent responses during chronic exposure to nicotine. We measured in vivo diameter of pial arterioles to NOS-dependent (acetylcholine and ADP) and -independent (nitroglycerin) agonists in saline-treated rats and rats chronically treated with nicotine (2 mg.kg(-1).day(-1) for 2 wk via an osmotic minipump). We found that NOS-dependent, but not -independent, vasodilatation was impaired in nicotine-treated compared with saline-treated rats. In addition, the production of superoxide anion (lucigenin chemiluminescence) was increased in rats treated with nicotine compared with saline-treated rats. Furthermore, using Western blot analysis, we found that chronic exposure to nicotine increased p47phox protein in the parietal cortex. Finally, we found that apocynin (40 mg.kg(-1).day(-1)) in the drinking water to inhibit NADPH oxidase alleviated impaired NOS-dependent cerebral vasodilatation in nicotine treated rats but did not alter NOS-dependent responses in saline treated rats and did not alter NOS-independent reactivity in saline- or nicotine-treated rats. These findings suggest that chronic exposure to nicotine impairs NOS-dependent dilatation of pial arterioles by a mechanism that appears to be related to the formation of superoxide anion via activation of NADPH oxidase.
Abstract: Our goal was to determine whether NAD(P)H oxidase is involved in impaired endothelial nitric oxide synthase (eNOS)-dependent reactivity of cerebral arterioles during chronic alcohol consumption.
Abstract: The goal of the present study was to determine the role of NAD(P)H oxidase in alcohol consumption-induced impairment of nNOS-dependent reactivity in cerebral arterioles. Sprague-Dawley rats were fed an alcohol diet for 2-3 months. We measured the effects of acute (1 hour) and chronic (1 month) treatment with a NAD(P)H oxidase inhibitor, apocynin, on responses of parietal pial arterioles to nNOS-dependent agonists (NMDA and kainate) and an nitric oxide synthase (NOS)-independent agonist (nitroglycerin). In addition, we measured the expression of NAD(P)H oxidase subunits and superoxide production in parietal cortex. Topical application of NMDA and kainate produced dose-related dilation of pial arterioles. However, the magnitude of vasodilation to these agonists was significantly less in alcohol-fed rats. Treatment with apocynin (acute and chronic) did not alter vasodilation in nonalcohol-fed rats, but significantly improved vasodilation in alcohol-fed rats. Response of pial arterioles to nitroglycerin was similar in nonalcohol-fed and alcohol-fed rats, and was not affected by apocynin. In addition, we found an up-regulation of gp91phox and p47phox in parietal cortex of alcohol-fed rats. Finally, alcohol consumption produced an increase in superoxide production under basal conditions and in the presence of NADPH. Acute treatment with apocynin suppressed alcohol consumption-induced superoxide generation. Our findings suggest that NAD(P)H oxidase plays an important role in chronic alcohol consumption-induced impairment of nNOS-dependent dilation of cerebral arterioles.
Abstract: Although long-term alcohol consumption impairs both endothelial nitric oxide synthase (NOS) (eNOS)-dependent and neuronal NOS (nNOS)-dependent reactivity of cerebral arterioles in male rats, the influence of sex on alcohol consumption-induced impairment of NOS-dependent cerebral vasodilation has not been examined. Therefore, the authors' first goal was to determine whether long-term alcohol consumption alters eNOS-dependent and nNOS-dependent reactivity of pial arterioles in female rats. Their second goal was to examine potential mechanisms for impaired responses of pial arterioles during long-term alcohol consumption.
Abstract: Our goal was to examine whether exercise training alleviates impaired nitric oxide synthase (NOS)-dependent dilatation of the basilar artery in Type 1 diabetic rats. To test this hypothesis, we measured in vivo diameter of the basilar artery in sedentary and exercised nondiabetic and diabetic rats in response to NOS-dependent (acetylcholine) and -independent (nitroglycerin) agonists. To determine the potential role for nitric oxide in vasodilatation in sedentary and exercised nondiabetic and diabetic rats, we examined responses after NG-monomethyl-l-arginine (l-NMMA). We found that acetylcholine produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic rats. Acetylcholine produced only minimal vasodilatation in sedentary diabetic rats. However, exercise alleviated impaired acetylcholine-induced vasodilatation in diabetic rats. Nitroglycerin produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic and diabetic rats. l-NMMA produced similar inhibition of acetylcholine-induced dilatation of the basilar artery in sedentary and exercised nondiabetic and diabetic rats. Finally, we found that endothelial NOS (eNOS) protein in the basilar artery was higher in diabetic compared with nondiabetic rats and that exercise increased eNOS protein in the basilar artery of nondiabetic and diabetic rats. We conclude that 1) exercise can alleviate impaired NOS-dependent dilatation of the basilar artery during diabetes mellitus, 2) the synthesis and release of nitric oxide accounts for dilatation of the basilar artery to acetylcholine in sedentary and exercised nondiabetic and diabetic rats, and 3) exercise may exert its affect on cerebrovascular reactivity during diabetes by altering levels of eNOS protein in the basilar artery.
Abstract: While potassium (K+) channels are important in basal tone and dilatation of large and small cerebral vessels, the effect of diabetes mellitus on K+ channels remains unclear. The goal of this study was to identify the influence of diabetes on responses of cerebral vessels to inhibition/activation of K+ channels.
Abstract: Exogenous treatment with L-arginine has been shown to restore impaired nitric oxide synthase (NOS)-dependent dilatation of peripheral blood vessels during disease states. We have shown that nicotine impairs NOS-dependent arteriolar dilatation in the cerebral circulation. However, the role of L-arginine in impaired responses of cerebral arterioles during infusion of nicotine has not been examined. Thus the goal of the present study was to examine the role of L-arginine in nicotine-induced impairment of cerebral arteriolar reactivity. We measured the diameter of pial arterioles in response to NOS-dependent (5'-adenosine diphosphate [ADP] and acetylcholine) and NOS-independent (nitroglycerin) agonists before and after infusion of vehicle or nicotine (2 microg/kg/min intravenously for 30 min followed by a maintenance dose of 0.35 microg/kg/min) in the absence or presence of L-arginine (10(-3) M). We found that topical application of L-arginine to cerebral microvessels during infusion of nicotine could prevent impaired NOS-dependent vasodilatation. We suggest that exogenous L-arginine may have a beneficial role in preventing cerebral microvascular dysfunction during exposure to nicotine.
Abstract: The goals of this study were to determine whether chronic alcohol consumption alters potassium channel-mediated reactivity in the basilar artery and to determine a potential mechanism that might account for the effects of alcohol on the basilar artery.
Abstract: Our goal was to identify the effects of chronic treatment with enalapril on cerebrovascular dysfunction and endothelial nitric oxide synthase (eNOS) protein in diabetic rats.
Abstract: The effects of nicotine on nitric oxide synthase (NOS)-dependent reactivity of cerebral arterioles remain uncertain. Our first goal was to examine whether infusion of nicotine alters NOS-dependent reactivity of cerebral arterioles. Our second goal was to examine the mechanisms that may account for the effects of nicotine on cerebral arterioles. We measured the diameter of pial arterioles to NOS-dependent (ADP and acetylcholine) and NOS-independent (nitroglycerin) agonists before and after the infusion of nicotine (2 microg x kg(-1) x min(-1) iv for 30 min, followed by a maintenance dose of 0.35 microg x kg(-1) x min(-1)). ADP- and acetylcholine-induced vasodilatation was impaired after the infusion of nicotine. In contrast, nicotine did not alter vasodilatation to nitroglycerin. Next, we examined whether the impaired responses of pial arterioles during infusion of nicotine may be related to oxygen radicals. We found that application of superoxide dismutase or tetrahydrobiopterin during infusion of nicotine could prevent impaired NOS-dependent vasodilatation. Thus acute exposure of cerebral vessels to nicotine specifically impairs NOS-dependent dilatation via the production of oxygen radicals possibly related to an alteration in the utilization of tetrahydrobiopterin.
Abstract: The goals of this study were to determine the effects of type II diabetes mellitus on nitric oxide synthase-dependent responses of cerebral arterioles and on endothelial nitric oxide synthase (eNOS) protein in cerebral arterioles. We examined dilatation of cerebral (pial) arterioles in 13-15 week old male lean and diabetic obese Zucker rats in response to nitric oxide synthase-dependent agonists (acetylcholine and adenosine diphosphate (ADP)) and a nitric oxide synthase-independent agonist (nitroglycerin). We found that acetylcholine (10 microM) increased cerebral arteriolar diameter by 10 +/- 3% (mean +/- SE) in lean Zucker rats, but by only 2 +/- 2% in diabetic obese Zucker rats (p<0.05). In addition, ADP (100 microM) increased cerebral arteriolar diameter by 20 +/- 2% in lean Zucker rats, but by only 8 +/- 2% in diabetic obese Zucker rats (p<0.05). In contrast, nitroglycerin produced similar vasodilatation in lean and diabetic obese Zucker rats. Thus, impaired dilatation of cerebral arterioles in diabetic obese Zucker rats is not related to non-specific impairment of vasodilatation. Following these functional studies, we harvested cerebral microvessels for Western blot analysis of eNOS protein. We found that eNOS protein was significantly higher in diabetic obese Zucker rats than in lean Zucker rats (p<0.05). Thus, type II diabetes mellitus impairs nitric oxide synthase-dependent responses of cerebral arterioles. In addition, eNOS protein from cerebral blood vessels is increased in diabetic obese Zucker rats.
Abstract: The first goal of the present study was to examine the influence of gender on reactivity of the basilar artery. The second goal of this study was to examine the effect of diabetes mellitus on reactivity of the basilar artery in male and female rats. We examined in vivo responses of the basilar artery in male and female nondiabetic and diabetic rats in response to a nitric oxide synthase (NOS)-dependent (acetylcholine) and -independent (nitroglycerin) agonist. In nondiabetic male and female rats, acetylcholine and nitroglycerin produced dose-related dilatation of the basilar artery. However, the magnitude of vasodilatation in response to acetylcholine and a high concentration of nitroglycerin was significantly greater in female than in male rats. Acetylcholine (1.0 microM) dilated the basilar artery by 11 +/- 2% in nondiabetic males versus 25 +/- 4% in nondiabetic females (P<0.05). Nitroglycerin (1.0 microM) dilated the basilar artery by 37 +/- 8% in nondiabetic males versus 62 +/- 5% in nondiabetic females (P<0.05). Thus, there is a significant effect of gender on reactivity of the basilar artery during physiologic conditions. Dilatation of the basilar artery in response to acetylcholine, but not nitroglycerin, was impaired in diabetic male and female rats compared to their nondiabetic counterparts. Acetylcholine (1.0 microM) dilated the basilar artery by only 5 +/- 1% in diabetic males and by only 4 +/- 1% in diabetic females. In summary, dilatation of the basilar artery in response to NOS-dependent agonist was significantly greater in nondiabetic female than in nondiabetic male rats. In addition, diabetes mellitus impaired NOS-dependent dilatation of the basilar artery not only in male rats, but also in female rats. We suggest that the results of these studies provide insight into the pathogenesis of cerebrovascular abnormalities observed in postmenopausal women.
Abstract: Although chronic alcohol consumption impairs endothelial nitric oxide synthase-dependent reactivity of cerebral arterioles, the effect of alcohol consumption on vasodilation in response to activation of neuronal nitric oxide synthase (nNOS) has not been examined. Thus, our first goal was to determine whether chronic alcohol consumption impairs nNOS-dependent reactivity of pial arterioles. Our second goal was to examine potential mechanisms for impaired responses of pial arterioles during chronic alcohol consumption.
Abstract: The goals of this study were to determine whether chronic alcohol consumption impairs nitric oxide synthase-dependent reactivity of the basilar artery and to determine a potential mechanism which might account for the effects of alcohol on the basilar artery. Sprague-Dawley rats were fed liquid diets with or without alcohol for 8 weeks. Using intravital microscopy, we measured the diameter of basilar artery in response to nitric oxide synthase-dependent agonists (acetylcholine and bradykinin) and a nitric oxide synthase-independent agonist (nitroglycerin). Topical application of acetylcholine (0.1 and 1 microM) and bradykinin (1 and 10 nM) produced dose-related dilatation of the basilar artery in non-alcohol-fed and alcohol-fed rats. However, the magnitude of vasodilatation in response to acetylcholine and bradykinin was significantly less in alcohol-fed rats compared to non-alcohol-fed rats. Dilatation of the basilar artery in response to nitroglycerin was similar in non-alcohol-fed and alcohol-fed rats. Next, we examined whether impaired responses of the basilar artery in alcohol-fed rats in response to acetylcholine and bradykinin may be related to the production of oxygen radicals. We found that topical application of superoxide dismutase (150 U/ml) significantly improved impaired receptor-mediated nitric oxide synthase-dependent dilatation of basilar artery in alcohol-fed rats. However, superoxide dismutase did not alter responses of the basilar artery to nitroglycerin in alcohol-fed rats, and did not alter responses of the basilar artery to nitric oxide synthase-dependent or -independent agonists in non-alcohol-fed rats. Our findings suggest that chronic consumption of alcohol impairs nitric oxide synthase-dependent dilatation of a large cerebral artery which may be related to the receptor-mediated release of oxygen radicals to inactivate nitric oxide.
Abstract: We sought to investigate mechanisms that may account for impaired nitric oxide synthase (NOS)-dependent dilatation of cerebral arterioles during alcohol consumption. Our goals were to examine 1) the effect of exogenous application of a cofactor for NOS, i.e., tetrahydrobiopterin (BH4) on the reactivity of pial arterioles during alcohol consumption; and 2) endothelial NOS (eNOS) protein in nonalcohol-fed and alcohol-fed rats. Sprague-Dawley rats were fed liquid diets with or without alcohol for 2-3 mo. We measured in vivo diameter of pial arterioles in response to NOS-dependent agonists (ACh and ADP) and a NOS-independent agonist (nitroglycerin) before and during application of BH4. Blood vessels were then harvested for Western blot analysis of eNOS protein. In nonalcohol-fed rats, ACh and ADP produced vasodilatation, which was impaired in alcohol-fed rats. Vasodilatation to nitroglycerin was similar in both groups of rats. Application of BH4 did not alter vasodilatation in nonalcohol-fed rats but improved impaired vasodilatation in alcohol-fed rats. Also, eNOS protein in cerebral cortex microvessels, the basilar artery, and aorta was not different between nonalcohol-fed and alcohol-fed rats. Thus impaired NOS-dependent vasodilatation during alcohol consumption does not appear to be related to an alteration in eNOS protein but may be related to a deficiency and/or alteration in the utilization of BH4.
Abstract: Chronic alcohol consumption reduces nitric oxide synthase-dependent responses of pial arterioles via mechanisms that remain uncertain. In addition, the temporal effects of alcohol on pial arterioles is unclear. Thus our goals were to examine the role of oxygen-derived free radicals in alcohol-induced impairment of cerebrovascular reactivity and the temporal effect of alcohol on reactivity of pial arterioles. Sprague-Dawley rats were pair-fed a liquid diet with or without alcohol for 2-3 wk, 2-3 mo, or 5-6 mo. We measured the in vivo diameter of pial arterioles in response to nitric oxide synthase-dependent dilators acetylcholine and ADP and the nitric oxide synthase-independent dilator nitroglycerin. In nonalcohol-fed rats, acetylcholine (1.0 and 10 microM) and ADP (10 and 100 microM) produced dose-related dilatation of pial arterioles. Whereas there was no difference in reactivity of arterioles to the agonists in rats fed the nonalcohol and alcohol diets for a period of 2-3 wk, there was a significant impairment in reactivity of arterioles to acetylcholine and ADP, but not nitroglycerin, in rats fed the alcohol diet for longer durations. We then found that treatment with superoxide dismutase did not alter baseline diameter of pial arterioles in nonalcohol-fed or alcohol-fed rats, but significantly improved impaired nitric oxide synthase-dependent dilatation of pial arterioles in alcohol-fed rats. Thus our findings suggest a temporal relationship in the effects of alcohol on reactivity of pial arterioles and that impaired nitric oxide synthase-dependent cerebral vasodilatation during chronic alcohol consumption may be related, in part, to enhanced release of oxygen-derived free radicals.
Abstract: Tirilazad mesylate has been used in the attempt to prevent cerebral vasospasm after subarachnoid hemorrhage (SAH), although the actual targets of this agent in vivo have thus far been controversial. Chemiluminescence/high-performance liquid chromatography provided a new method for direct measurements of phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH) in vivo and showed that phosphatidylcholine is the lipid class most susceptible to lipid peroxidation. In the present study we measured those levels in a primate model of SAH for determination of the effects of tirilazad on vasospasm.
Abstract: Delayed cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) causes cerebral ischemia and infarction. To date, the pathogenesis and gene expression associated with vasospasm remain poorly understood. The present study used fluorescent differential display to identify differentially expressed genes in a rat model of SAH. By using quantitative RT-PCR, we found that heme oxygenase-1 (HO-1) mRNA was prominently induced in the basilar artery and modestly in brain tissue in a rat vasospasm model. A significant correlation was observed between the degree of vasospasm and HO-1 mRNA levels in the basilar arteries exhibiting vasospasm. Intracisternal injection of antisense HO-1 oligodeoxynucleotide (ODN) significantly delayed the clearance of oxyhemoglobin and deoxyhemoglobin from the subarachnoid space and aggravated angiographic vasospasm. Antisense HO-1 ODN inhibited HO-1 induction in the basilar arteries but not in the whole brain tissue. This phenomenon was not observed in the nontreated, sense HO-1 ODN-treated, or scrambled ODN-treated arteries. We report the protective effects of HO-1 gene induction in cerebral vasospasm after SAH, a finding that should provide a novel therapeutic approach for cerebral vasospasm.
Abstract: In order to clarify the effect of clot lysis by recombinant tissue-type plasminogen activator (tPA) on the brain lipid peroxidation, we measured phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH) levels in a primate model of subarachnoid hemorrhage (SAH). Monkeys were assigned into two groups; a tPA-treated group receiving intrathecal injections of 0.02 mg tPA, and a placebo-treated group receiving saline. The tPA or placebo was injected into the right side of the basal cistern every 8 h for 6 days following bilateral SAH induction. The tPA cleared the right side clots (p < 0.0001), but not the left side clots. The degree of vasospasm in the right middle cerebral artery and the rCBF decrease in the right parietal cortex were significantly attenuated in the tPA group (p < 0.05). In the placebo group, more severe vasospasm and marked rCBF reduction were noted in comparison with those in the tPA group. PCOOH levels in the parietal cortex were significantly higher in the placebo group than in the tPA group (p < 0.05). There were no significant changes in brain PEOOH levels. These results may explain the limitations for clinical application of unilateral intrathecal administration of tPA.
