Noriko Hagiwara

Role of NHE1 in calcium signaling and cell proliferation in human CNS pericytes

The central nervous system (CNS) pericytes play an important role in brain microcirculation. Na(+)/H(+) exchanger isoform 1 (NHE1) has been suggested to regulate the proliferation of nonvascular cells through the regulation of intracellular pH, Na(+), and cell volume; however, the relationship between NHE1 and intracellular Ca(2+), an essential signal of cell growth, is still not known. The aim of the present study was to elucidate the role of NHE1 in Ca(2+) signaling and the proliferation of human CNS pericytes. The intracellular Ca(2+) concentration was measured by fura 2 in cultured human CNS pericytes. The cells showed spontaneous Ca(2+) oscillation under quasi-physiological ionic conditions. A decrease in extracellular pH or Na(+) evoked a transient Ca(2+) rise followed by Ca(2+) oscillation, whereas an increase in pH or Na(+) did not induce the Ca(2+) responses. The Ca(2+) oscillation was inhibited by an inhibitor of NHE in a dose-dependent manner and by knockdown of NHE1 by using RNA interference. The Ca(2+) oscillation was completely abolished by thapsigargin. The proliferation of pericytes was attenuated by inhibition of NHE1. These results demonstrate that NHE1 regulates Ca(2+) signaling via the modulation of Ca(2+) release from the endoplasmic reticulum, thus contributing to the regulation of proliferation in CNS pericytes.

Blood Pressure Changes During the Initial Week After Different Subtypes of Ischemic Stroke

Background and Purpose— The purpose of this study was to clarify the differences in the acute blood pressure course among different ischemic stroke subtypes. Methods— We divided 588 consecutive patients with acute brain infarction into four clinical subgroups to study the blood pressure levels during the initial 6 hospital days. Results— During the 6 days, systolic blood pressure of lacunar and atherothrombotic patients was higher (P=0.0001) and diastolic blood pressure of lacunar patients was higher (P=0.0371) than of patients with the other subtypes. Preexisting hypertension was associated with elevated acute systolic blood pressure in all patients and in each subtype and with elevated acute diastolic blood pressure in all patients, cardioembolic patients, and patients with stroke of other etiology. After adjustment by preexisting hypertension, diabetes mellitus with a hemoglobin A1c >7.0% was associated with elevated systolic blood pressure in all, lacunar, and cardioembolic patients and with diastolic blood pressure in all patients. Conclusions— Blood pressure course of patients sustaining acute stroke varied widely according to stroke subtypes. Poorly controlled diabetes mellitus, as well as preexisting hypertension, appeared to influence blood pressure during the initial week of stroke.

NAD(P)H oxidase p22phox C242T polymorphism and ischemic stroke in Japan: the Fukuoka Stroke Registry and the Hisayama study.

The C242T polymorphism of p22phox, a component of NAD(P)H oxidase, may have an impact on cardiovascular diseases; however, the association between this polymorphism and brain infarction is not fully understood. Here, we investigate the relationship between the C242T polymorphism and brain infarction in Japan. We recruited 1055 patients with brain infarction and 1055 control subjects. A chi‐squared test revealed that the T‐allele frequency was lower in patients with cardioembolic infarction (5.6%) than in control subjects (11.0%, P < 0.001); however, allele frequencies in patients with lacunar and atherothrombotic infarction (11.2%) were not significantly different from those in control subjects (11.0%). A multivariate‐adjusted conditional logistic regression analysis also revealed no association between CT + TT genotype, and lacunar and atherothrombotic infarction (odds ratio = 0.97, 95% confidence interval: 0.72–1.32). To investigate the functional effects of the C242T polymorphism, we examined superoxide production in COS‐7 cells cotransfected with Nox4 and p22phox of each genotype. The superoxide‐producing activity in those cells expressing p22phox with the T allele was not significantly different from that in cells expressing p22phox with the C allele. The present results suggest that the p22phox C242T polymorphism may have a protective effect against cardioembolic infarction, but is not related to lacunar and atherothrombotic infarction in Japan.

Hydrogen peroxide-induced Ca2+ responses in CNS pericytes

OBJECTIVE The aims of the present study were to elucidate the interaction of reactive oxygen species (ROS) and Ca(2+) response in central nervous system (CNS) pericytes. METHODS The intracellular Ca(2+) concentration was measured using fluorescent Ca(2+) indicator, fura-2, in cultured CNS pericytes. RESULTS Hydrogen peroxide evoked a dose-dependent increase in cytosolic Ca(2+), which was completely inhibited by catalase. Removal of external Ca(2+) or addition of nicardipine (1 microM) during application of hydrogen peroxide did not affect Ca(2+) response. Incubation of the cells in Ca(2+) free solution did not abolish but slightly reduced Ca(2+) response by hydrogen peroxide. Ca(2+) response to hydrogen peroxide was not altered by the depletion of intracellular Ca(2+) by thapsigargin (1 microM). Pretreatment of the cells with tyrosine kinase inhibitor genistein (100 microM) or tyrphostin A47 (30 microM) significantly reduced Ca(2+) increase by hydrogen peroxide. CONCLUSIONS These results indicate that hydrogen peroxide evokes Ca(2+) increase predominantly by release from intracellular Ca(2+) store, which may be regulated by tyrosine kinases.

Primary intraventricular hemorrhage from dural arteriovenous fistula

Dural arteriovenous fistulas (AVFs) cause several types of intracranial hemorrhage, but rarely cause primary intraventricular hemorrhage (IVH). We report a 67-year-old man with sudden headache and a long history of a pulsatile bruit who developed intraventricular hemorrhage without any parenchymal hemorrhage. Cerebral angiogram revealed dural arteriovenous fistulas in transverse and sigmoid sinuses. Severe retrograde venous drainage seemed to have caused backward flow into the subependymal veins with their consequential rupture. Transvenous embolization was successful.

Renal cholesterol embolism in patients with carotid stenosis: a severe and underdiagnosed complication following cerebrovascular procedures

Here, we report two cases with rapidly progressive renal failure, caused by cholesterol crystal embolism (CCE), after an angiography for carotid artery stenosis. The diagnosis was determined by histological examination and from clinical symptoms, including livedo reticularis and eosinophilia. Neurologists and neuroradiologists tend to underdiagnose CCE, which results from the same atherosclerotic risk factors as cerebrovascular disease. We need to understand more about CCE and identify its unique clinical symptoms to enable an early diagnosis and treatment.

Amiloride inhibits hydrogen peroxide-induced Ca2+ responses in human CNS pericytes

The aims of the present study were to investigate the mechanisms of Ca(2+) signaling caused by hydrogen peroxide in CNS pericytes. In cultured human brain microvascular pericytes, cytosolic Ca(2+) concentration was measured by means of fura-2 fluorescence. Reverse transcription and polymerase chain reaction was performed to examine the expression of mRNA. Knockdown of Na(+)/H(+) exchanger (NHE) was done by transfecting the cells with specific double-strand siRNAs for NHE. Externally applied hydrogen peroxide dose-dependently (100 microM-10 mM) increased cytosolic Ca(2+) in human CNS pericytes. Cytosolic Ca(2+) remained high after wash-out of hydrogen peroxide. However, the addition of dithiothreitol rapidly reversed cytosolic Ca(2+) to the resting level. The hydrogen peroxide-induced Ca(2+) increase was not inhibited by nicardipine, Gd(3+), La(3+), or omission of external Ca(2+). Neither thapsigargin nor carbonyl cyanide 4-trifluoromethoxyphenylhydrazone attenuated the hydrogen peroxide-induced Ca(2+) rise. Amiloride and its derivatives, benzamil and hexamethylene amiloride reversed the hydrogen peroxide-induced Ca(2+) increase. Human CNS pericytes expressed acid sensing ion channel (ASIC) 1a, Na(+)/Ca(2+) exchanger (NCX) 1, Na(+)/H(+) exchanger (NHE) 1, and NHE7. However, the removal of external Na(+), treatment with KB-R 7943 and mibefradil, or knockdown of NHE1 and NHE7 did not affect the hydrogen peroxide-induced Ca(2+) increase. Hydrogen peroxide releases Ca(2+) from intracellular Ca(2+) pool via an amiloride-sensitive protein, which is controlled by oxidation of thiol group in human CNS pericytes.

Elevated cerebrospinal fluid lactate levels and the pathomechanism of calcification in Fahr's disease.

In this study, we report the case of a 68‐year‐old man complaining of involuntary movement of his left shoulder and lower jaw plus dyspnea. On cranial computed tomography and magnetic resonance imaging, marked and symmetrical calcification at the basal ganglia and dentate nuclei was documented. An elevated cerebrospinal fluid (CSF) lactate level was confirmed by spinal tap examination and magnetic resonance spectroscopy. The raised CSF lactate level, clinical characteristics such as diabetes, bilateral hearing loss and symmetrical cerebral calcification strongly suggested some kinds of mitochondrial disease. However, gene analysis of peripheral blood leukocytes revealed no typical or known mutations. Under the diagnosis of Fahrs disease, we treated him with haloperidol, which completely abolished his symptoms. In Ellsworth–Howard test, he showed markedly decreased phosphaturic response to parathyroid hormone with same pattern as type 2 pseudohypoparathyroidism. This abnormal response in our patient, probably due to respiratory alkalosis reflecting chronic hyperventilation, might in part explain similar mechanism of ectopic calcification underlying these two diseases.

Polymorphisms in the Lymphotoxin Alpha Gene and the Risk of Ischemic Stroke in the Japanese Population

Background and Purpose: Lymphotoxin α (LTA), one of the tumor necrosis factor family proteins, is an important proinflammatory cytokine and appears to play a putative role in the inflammatory process of atherosclerosis. Recent genetic studies have suggested that variations in the gene encoding LTA, which affect its expression and biological function, may contribute to the development of vascular diseases. We conducted a case-control study to clarify the association of LTA gene polymorphisms with ischemic stroke in a large Japanese population. Methods: Genotyping for LTA A252G and C804A polymorphisms was achieved by a rapid-cycle polymerase chain reaction and melting curve analysis using fluorescent probes in 1,044 incident cases of ischemic stroke recruited from the Fukuoka Stroke Registry and 1,044 age- and sex-matched control subjects recruited from the Hisayama Study. Results: The overall distribution of allele and genotype for each polymorphism was similar between stroke patients and control subjects. The allele frequencies of 252G and 804A were slightly lower in stroke patients than in control subjects; however, conditional logistic regression analysis adjusted for potential risk factors found no association between the risk of ischemic stroke and either polymorphism. In terms of stroke subtype, we also found no association of these polymorphisms with any subtypes of ischemic stroke. Conclusions: Neither the A252G nor C804A polymorphism of the LTA gene was associated with stroke overall and any subtypes of ischemic stroke in the Japanese population.

Polymorphism in the sorbin and SH3-domain-containing-1 (SORBS1) gene and the risk of brain infarction in the Japanese population: the Fukuoka Stroke Registry and the Hisayama study

Background and purpose:  Sorbin and SH3‐domain‐containing‐1 (SORBS1) is an important adaptor protein in insulin‐signalling pathway, and its genetic polymorphism may regulate the activity of insulin resistance. We investigated the association between the SORBS1 T228A polymorphism and ischaemic stroke.