Jiro Kitayama

Proteinuria and clinical outcomes after ischemic stroke

Objectives: The impact of chronic kidney disease (CKD) on clinical outcomes after acute ischemic stroke is still not fully understood. The aim of the present study was to elucidate how CKD and its components, proteinuria and low estimated glomerular filtration rate (eGFR), affect the clinical outcomes after ischemic stroke. Methods: The study subjects consisted of 3,778 patients with first-ever ischemic stroke within 24 hours of onset from the Fukuoka Stroke Registry. CKD was defined as proteinuria or low eGFR (<60 mL/min/m2) or both. The study outcomes were neurologic deterioration (≥2-point increase in the NIH Stroke Scale during hospitalization), in-hospital mortality, and poor functional outcome (modified Rankin Scale score at discharge of 2 to 6). The effects of CKD, proteinuria, and eGFR on these outcomes were evaluated using a multiple logistic regression analysis. Results: CKD was diagnosed in 1,320 patients (34.9%). In the multivariate analyses after adjusting for confounding factors, patients with CKD had significantly higher risks of neurologic deterioration, in-hospital mortality, and poor functional outcome (p <0.001 for all). Among the CKD components, a higher urinary protein level was associated with an elevated risk of each outcome (p for trend < 0.001 for all), but no clear relationship between the eGFR level and each outcome was found. Conclusions: CKD is an important predictor of poor clinical outcomes after acute ischemic stroke. Proteinuria independently contributes to the increased risks of neurologic deterioration, mortality, and poor functional outcome, but the eGFR may not be relevant to these outcomes.

Inhibition of Na+/H+ exchanger reduces infarct volume of focal cerebral ischemia in rats

Activation of Na+/H+ exchanger (NHE) may have an important role in ischemic cell death by means of intracellular overload of Na(+) and Ca(2+). Recent evidence has suggested that inhibitors of NHE have protective effects on myocardial ischemia both in vivo and in vitro. In this study, we tested the hypothesis that FR183998, an inhibitor of NHE, reduces infarct volume produced by focal cerebral ischemia in rats. We used 20 male spontaneously hypertensive rats. Either FR183998 (1 mg/kg; n=10), or vehicle (n=10) was given intravenously to the rats and the distal middle cerebral artery of each animal was occluded using a photothrombotic technique. We measured regional cerebral blood flow using laser-Doppler flowmetry throughout the experiments. After 3 days, infarct volume was measured in each animal group. To estimate the brain edema, we also calculated the cortical volume in both hemispheres. The infarct volume in the FR183998-treated group (82+/-8 mm(3), mean+/-S.E.M.) was significantly smaller than that in the control group (115+/-12 mm(3)) (P=0.034). The cortical volume of the occluded side in the FR183998-treated group (359+/-7 mm(3)) tended to be smaller than that in the control group (378+/-9 mm(3)) (P=0.116). The regional cerebral blood flow and physiological variables during ischemia were not significantly different between the two groups throughout the experiments. These results suggest that inhibition of NHE by FR183998 may have beneficial effects in reducing infarct volume and brain edema during cerebral ischemia. Thus, NHE may play an important role in the development of neuronal damage during acute cerebral ischemia.

Impairment of Dilator Responses of Cerebral Arterioles During Diabetes Mellitus Role of Inducible NO Synthase

Background and Purpose— During diabetes, expression of inducible nitric oxide synthase (iNOS) plays an important role in the development of endothelial dysfunction in extracranial blood vessels. Progression of vascular dysfunction after the onset of diabetes differs among vascular beds. In this study, the effects of hyperglycemia/diabetes on vasomotor function were examined in cerebral arterioles at 2 different times in control and iNOS-deficient mice and compared with the effects on carotid arteries. Methods— Streptozotocin (150 mg/kg IP) was given to induce diabetes. The diameter of cerebral arterioles was measured through a cranial window in diabetic and nondiabetic mice in vivo. Vasomotor function of the carotid artery was examined in vitro. Results— In diabetic mice, responses of the cerebral arterioles to acetylcholine (1 &mgr;mol/L) were normal after 3 weeks of diabetes but were significantly impaired after 5 to 6 weeks of diabetes (4±1% [mean±SEM] increase in diameter) compared with control mice (14±1; P=0.0002). Responses to sodium nitroprusside were similar in diabetic and nondiabetic mice at both time points. In contrast, the vasomotor function of the carotid artery was not affected after 5 to 6 weeks of diabetes. In diabetic iNOS-deficient mice, cerebral arteriolar vasomotor function was not impaired, even after 4 months of diabetes. Conclusions— During diabetes, endothelial dysfunction of cerebral arterioles requires expression of iNOS and develops earlier than in carotid arteries.

Role of Phosphatidylinositol 3-Kinase in Acetylcholine-Induced Dilatation of Rat Basilar Artery

Background and Purpose We tested the hypothesis that activation of phosphatidylinositol (PI) 3-kinase is involved in dilator responses of the basilar artery to acetylcholine in vivo. Methods Responses of the basilar artery were measured by the cranial window technique in anesthetized rats. To examine the role of PI 3-kinase in acetylcholine-induced calcium signaling, we measured intracellular free calcium concentration ([Ca2+]i) of cultured rat basilar arterial endothelial cells using a fluorescent calcium indicator, indo 1. Results Topical application of acetylcholine (10−6, 10−5.5, and 10−5 mol/L) increased the diameter of the basilar artery by 8±1%, 14±2%, and 24±3%, respectively. An inhibitor of PI 3-kinase, wortmannin (10−8 mol/L), did not change the baseline diameter of the artery. In the presence of wortmannin, acetylcholine (10−6, 10−5.5, and 10−5 mol/L) dilated the artery only by 3±2%, 6±2%, and 12±2%, respectively. Thus, wortmannin attenuated acetylcholine-induced dilatation of the basilar artery (P <0.05 versus control). Wortmannin had no effect on dilatation of the artery in response to a nitric oxide donor, sodium nitroprusside. LY294002, another inhibitor of PI 3-kinase, also inhibited dilator response of the basilar artery to acetylcholine. Acetylcholine produced an increase in [Ca2+]i of the endothelial cells. Genistein, an inhibitor of tyrosine kinase, markedly attenuated acetylcholine-induced calcium influx to the cells; however, wortmannin had no effect on acetylcholine-induced calcium changes. Conclusions These results suggest that acetylcholine-induced dilatation of the basilar artery is mediated, at least in part, by activation of PI 3-kinase in vivo. Acetylcholine-induced [Ca2+]i changes of the endothelial cells may not be mediated by activation of the kinase. PI 3-kinase as well as [Ca2+]i may play an important role in the acetylcholine-induced nitric oxide production of the basilar arterial endothelial cells.

Role of Tyrosine Kinase in Serotonin-Induced Constriction of the Basilar Artery In Vivo

BACKGROUND AND PURPOSE Serotonin is one of the most potent constrictors of cerebral blood vessels and is implicated in several pathological conditions, including migraine and cerebral ischemia. Recent evidence has suggested that tyrosine kinase is involved in vasocontractile responses. The objective of this study was to test the hypothesis that activation of tyrosine kinase contributes to serotonin-induced constriction of the basilar artery in vivo. METHODS Using a cranial window in anesthetized Sprague-Dawley rats, we examined effects of inhibitors of tyrosine kinase and tyrosine phosphatase on constrictor responses of the basilar artery to serotonin in vivo. RESULTS Serotonin (10(-8), 10(-7), and 10(-6) mol/L) produced constriction of the basilar artery by 12+/-2%, 27+/-2%, and 37+/-3%, respectively. Genistein (3 x 10(-6) mol/L), an inhibitor of tyrosine kinase, did not affect baseline diameter of the basilar artery but attenuated serotonin-induced vasoconstriction (P<.05 versus control responses). Daidzein, an inactive analogue of genistein, did not affect serotonin-induced constriction of the basilar artery. Tyrphostin 47 (10(-5) mol/L), another inhibitor of tyrosine kinase, also attenuated serotonin-induced vasoconstriction, and tyrphostin 63, an inactive analogue of tyrphostin 47, did not affect the vasoconstriction. Sodium orthovanadate (10(-5) mol/L), an inhibitor of tyrosine phosphatase, enhanced serotonin-induced vasoconstriction. Phorbol 12,13-dibutyrate, a direct activator of protein kinase C, also caused constriction of the basilar artery, which was not affected by genistein or sodium orthovanadate. CONCLUSIONS These results suggest that serotonin-induced constriction of the basilar artery is mediated, at least in part, by activation of tyrosine kinase in vivo.

Chronic administration of a tyrosine kinase inhibitor restores functional and morphological changes of the basilar artery during chronic hypertension.

Objective Activation of tyrosine kinase appears to play an important role in pathogenesis of cardiovascular disease during chronic hypertension. In the present study, we tested the hypothesis that long-term treatment with an inhibitor of tyrosine kinase would have beneficial effects on hypertension-induced morphological and functional changes of the cerebral artery. Methods Male spontaneously hypertensive rats (SHR; 4 months old) were fed normal rat chow, or that containing an inhibitor of tyrosine kinase, genistein (1 mg/kg chow). Normotensive Wistar–Kyoto (WKY) rats were also fed either of the chows. After feeding the rats for 2 months, we measured wall thickness, diameter of the basilar artery and its dilator responses to acetylcholine (ACh); Y-26763, an opener of ATP-sensitive potassium channels; and Y-27632, an inhibitor of Rho-associated kinase. Results Treatment with genistein did not cause significant changes in physiological variables, including mean arterial pressure in either strain. In control SHR, the wall thickness of the basilar artery was greater than that of WKY rats. Genistein treatment reduced the wall thickness significantly in SHR. Vasodilator responses induced by ACh and Y-26763 were markedly attenuated in SHR compared to WKY rats, and treatment of SHR with genistein significantly improved the vasodilatation. Dilatation of the artery in response to Y-27632 was enhanced in SHR compared to WKY rats and treatment of SHR with genistein did not affect the enhanced vasodilator responses to Y-27632. Conclusions Chronic treatment with genistein may be a novel approach to prevent cerebrovascular disorders.

Long-term effects of benidipine on cerebral vasoreactivity in hypertensive rats.

We tested the hypothesis that long-term application of a Ca2+ channel blocker would ameliorate the functional and morphological deterioration of the cerebral arteries during hypertension. Male spontaneously hypertensive rats (SHR) were fed a standard rat chow, containing a low (3 mg/kg/day) or high dose (6 mg/kg/day) of benidipine, a Ca2+ channel blocker, for 2 months. Using a cranial window, we examined responses of the basilar artery to acetylcholine, sodium nitroprusside, (-)-(3S,4R)-4-(N-acetyl-N-hydroxyamino)-6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ol (Y-26763; an opener of ATP-sensitive K+ channels), and (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632; an inhibitor of Rho-associated kinase). Mean arterial pressure of the control group was 193+/-5 mm Hg (mean+/-S.E.M.), while that of the low-dose benidipine group was 183+/-5 mm Hg and that of the high-dose group was 159+/-4 mm Hg. Dilator responses of the basilar artery to acetylcholine and Y-26763 were impaired in SHR compared with those of normotensive Wistar-Kyoto (WKY) rats and treatment with benidipine enhanced the vasodilator responses to acetylcholine and Y-26763 in SHR. Y-27632-induced dilatation of the basilar artery was enhanced in SHR compared to that in WKY rats and the vasodilatation was reduced by benidipine in SHR. Sodium nitroprusside caused similar dilatation of the basilar artery, in both WKY rats and the SHR control group, and benidipine did not affect nitroprusside-induced dilatation of the artery in SHR. The wall of the basilar artery was significantly thicker in SHR than in WKY rats and benidipine treatment reduced the wall thickness of the artery in SHR. These findings suggest that chronic treatment with a Ca2+ channel blocker may enhance the dilator capacity and reduce contractility of the basilar artery during hypertension. Benidipine may also ameliorate the morphological changes of the basilar artery in hypertension.

Ischemic Brain Metabolism in Patients With Chronic Cerebrovascular Disease : Increased Oxygen Extraction Fraction and Cerebrospinal Fluid Lactate

The aim of the present study is to elucidate the existence of chronically ischemic metabolism concomitant with misery perfusion of the brain in patients with chronic cerebrovascular disease. For this purpose, we measured cerebral blood flow (CBF) and oxygen metabolism by positron emission tomography (PET) and also determined cerebrospinal fluid (CSF) lactate as an indicator of the ischemic brain metabolism. Twenty-eight patients with chronic ischemic stroke and transient ischemic attack (TIA), who had angiographically occlusive (n = 11), stenotic (n = 10), and nonstenotic changes (n = 7) of the carotid artery and/or the intracranial major artery, were selected for this study. CBF, oxygen extraction fraction (OEF), cerebral metabolic rate for oxygen (CMRO2), and cerebral blood volume (CBV) were determined by PET, and CSF lactate and pyruvate were determined by enzymatic method in the patients with various grades of stenotic changes of the carotid artery. There were no significant differences in PET parameters and CSF variables among the groups of the occlusive, stenotic, and nonstenotic carotid artery. However, CSF lactate was correlated negatively with mean bilateral hemispheric (m)CBF (R(2) = 0.229, P<.01), positively with mOEF (R(2) = 0.278, P<.005) and more highly with mCMRO2/CBF (absolute extraction of oxygen content to the brain) (R(2) = 0.473, P<.0001) in all patients. There was no correlation between CSF lactate and mCMRO2 or mCBV. None of the cases in the nonstenotic group showed mOEF greater than 0.45, or mCMRO2/CBF greater than 7.9 vol%, while 80% of the cases in the stenotic group and 82% of the cases in the occlusive group showed mOEF and mCMRO2/CBF exceeding the above-mentioned values, respectively. The present findings, that increased mOEF and mCMRO2/CBF were significantly correlated with increased CSF lactate, indicate the brain to be in a metabolically ischemic state or increased anaerobic glycolysis with oxygen metabolism maintained in patients with chronic ischemic stroke.

Influence of Statin Pretreatment on Initial Neurological Severity and Short-Term Functional Outcome in Acute Ischemic Stroke Patients: The Fukuoka Stroke Registry

Background: Statins have neuroprotective effects against ischemic stroke. However, associations between pre-stroke statin treatment and initial stroke severity and between the treatment and functional outcome remain controversial. This study aimed at determining these associations in ischemic stroke patients. Methods: Among patients registered in the Fukuoka Stroke Registry from June 2007 to October 2014, 3,848 patients with ischemic stroke within 24 h of onset, who had been functionally independent before onset, were enrolled in this study. Ischemic stroke was classified as cardioembolic or non-cardioembolic infarction. Primary and secondary study outcomes were mild neurological symptoms defined as a National Institutes of Health Stroke Scale score of ≤4 on admission and favorable functional outcome defined as a modified Rankin Scale score of ≤2 at discharge, respectively. Multivariable logistic regression models were used to quantify associations between pre-stroke statin treatment and study outcomes. Results: Of all 3,848 participants, 697 (18.1%) were taking statins prior to the stroke. The frequency of mild neurological symptoms was significantly higher in patients with pre-stroke statin treatment (64.1%) than in those without the treatment (58.3%, p < 0.01). Multivariable analysis showed that pre-stroke statin treatment was significantly associated with mild neurological symptoms (OR 1.31; 95% CI 1.04-1.65; p < 0.01). Sensitivity analysis in patients with dyslipidemia (n = 1,998) also showed the same trend between pre-stroke statin treatment and mild neurological symptoms (multivariable-adjusted OR 1.26; 95% CI 0.99-1.62; p = 0.06). In contrast, the frequency of favorable functional outcome was not different between patients with (67.0%) and without (65.3%) the treatment (p = 0.40). Multivariable analysis also showed no significant association between pre-stroke statin treatment and favorable functional outcome (OR 1.21; 95% CI 0.91-1.60; p = 0.19). Continuation of statin treatment, however, was significantly associated with favorable functional outcome among patients with pre-stroke statin treatment (multivariable-adjusted OR 2.17; 95% CI 1.16-4.00; p = 0.02). Conclusions: Pre-stroke statin treatment in ischemic stroke patients was significantly associated with mild neurological symptoms within 24 h of onset. Pre-stroke statin treatment per se did not significantly influence the short-term functional outcome; however, continuation of statin treatment during the acute stage of stroke seems to relate with favorable functional outcome for patients with pre-stroke statin treatment.

Calcium Antagonist Isradipine Reduces Metabolic Alterations in Acute Cerebral Ischemia in Spontaneously Hypertensive Rats

The present study was designed to examine the effect of a calcium antagonist isradipine (PN200-110: PN) on local cerebral blood flow and brain tissue metabolism after 1-hour supratentorial ischemia induced by bilateral carotid artery ligation (BCL) in spontaneously hypertensive rats (SHR). PN, dissolved in ethanol plus polyethylene glycol 400, diluted with saline to make the final concentration of 0.25mg/ml and 2.5mg/ml, was administered subcutaneously either 30 min prior to BCL or just after the induction of incomplete cerebral ischemia (n = 7 in each group). Vehicle injection was served as a control group (n = 7). Cerebral blood flow in the parietal cortex (CBF) and the cerebellar cortex (CeBF) was measured by hydrogen clearance technique, and the supra- and infratentorial metabolites of the brain frozen in situ were determined by the enzymatic method. Blood pressure was lowered, but CBF was increased by PN administration in pre-BCL treatment study. After 1 hour of BCL, CBF decreased to around 10% or less of the resting value, being insignificant among the groups. Brain adenosine triphosphate was better preserved in PN-administered groups. The increase in lactate level tended to reduce dose dependently by PN treatment. PN also reduced the metabolic alterations in brain tissue with significance, even when administered just after the induction of forebrain ischemia. It is considered that pre- as well as post-BCL administration of PN is beneficial to attenuate the metabolic alterations in incomplete forebrain ischemia in SHR.