Masayoshi Hashimoto

Modulation of Endothelium-Dependent Flow-Mediated Dilatation of the Brachial Artery by Sex and Menstrual Cycle

BACKGROUND Estrogen has been reported to augment endothelium-dependent vasodilatation. The role of endogenous ovarian hormones in modulating endothelium-dependent vasodilatation, however, remains to be determined. The purpose of the present study was to investigate the effects of sex and menstrual cycle on endothelium-dependent flow-mediated vasodilatation. METHODS AND RESULTS Seventeen female volunteers 25.1 +/- 0.8 years old and 17 age-matched male volunteers were examined. We measured brachial artery diameters noninvasively using a 7.5-MHz ultrasound machine at rest, during reactive hyperemia, and after sublingual nitroglycerin administration. All female subjects were studied three times each, in three different phases of one menstrual cycle (M, menstrual phase; F, follicular phase; and L, luteal phase). Flow-mediated diameter (D) increase (%FMD; delta D/D x 100) in M, when serum estradiol level was low (121.9 +/- 12.5 pmol/L), was 11.22 +/- 0.58%, and the value was comparable to that in male subjects (10.60 +/- 0.75%). %FMD increased in F (18.20 +/- 0.81%, P < .01 versus M) and L (17.53 +/- 0.74%, P < .01 versus M), when serum estradiol level was high (F, 632.0 +/- 74.5 and L, 533.8 +/- 33.4 pmol/L, P < .01 versus M). Endothelium-independent vasodilatation by nitroglycerin increased in both F and L. However, the increment was smaller than that of %FMD. CONCLUSIONS Endothelium-dependent vasodilatation varies during the menstrual cycle. The endogenous estradiol may be involved in this menstrual cycle-related vasodilatation.

The impairment of flow-mediated vasodilatation in obese men with visceral fat accumulation.

BACKGROUND: Obesity has been reported to be associated with coronary artery disease and other atherosclerotic diseases. Recently, evidence has accumulated indicating that intra-abdominal visceral fat accumulation contributes to atherogenesis; however, the mechanism underlying this remains to be determined. This study was undertaken to elucidate whether intra-abdominal visceral fat accumulation impairs vascular endothelial function in obese men.METHODS AND RESULTS: Thirty-eight obese men (body mass index (BMI)≥26.0), aged 19–64 y (mean age 37.6±1.8 y) and 23 age-matched non-obese subjects were examined. According to the ratio of the maximum thickness of preperitoneal fat to the minimum thickness of subcutaneous fat (Pmax/Smin) obtained by longitudinal ultrasound scanning in the subxiphoid region in obese men, we divided obese subjects into two categories; visceral (Pmax/Smin≥1; n=23) and subcutaneous type (Pmax/Smin<1; n=15). To investigate endothelial function, we performed ultrasound measurement of the brachial artery diameter non-invasively both at rest and during reactive hyperaemia in the muscle distal to the brachial artery which causes endothelium-dependent vasodilatation. The brachial diameter change was also measured after sublingual administration of nitroglycerin, which causes endothelium-independent vasodilatation. Flow-mediated diameter (D) increase (%FMD; ΔD/D×100), in the subjects with visceral type obesity (3.09±0.43%) was significantly lower than those of the subjects with subcutaneous type obesity and non-obese subjects (7.90±0.51%, 8.91±0.44%, respectively, P<0.01). The magnitude of endothelium-independent vasodilatation by nitroglycerin was similar in all groups. On multiple regression analysis, the Pmax/Smin showed a significant inverse correlation with %FMD.CONCLUSIONS: The subjects with visceral type obesity, rather than those with the subcutaneous type, are associated with impaired flow-mediated endothelium-dependent vasodilatation of the brachial artery.

Correlation Between Flow-Mediated Vasodilatation of the Brachial Artery and Intima-Media Thickness in the Carotid Artery in Men

Endothelial dysfunction has been reported to be the initial step in atherosclerosis. A noninvasive technique that uses ultrasound to measure the intima-media thickness of the carotid artery has been applied to evaluate localized atherosclerosis. This study was undertaken to elucidate whether endothelial dysfunction in the brachial artery is related to the intima-media thickness of the carotid artery. Thirty-four men with atherosclerosis (mean+/-SE age 61+/-2 years) and 33 age-matched men without clinical atherosclerosis were examined. The intima-media thickness and plaque formation of the common carotid artery were assessed by B-mode ultrasonography. We also noninvasively measured brachial artery diameter by the same ultrasound machine when the subjects were at rest, during reactive hyperemia, which causes endothelium-dependent vasodilatation, and after sublingual administration of nitroglycerin, which causes endothelium-independent vasodilatation. The atherosclerosis group had a significantly greater intima-media thickness of the common carotid artery than did the control group (1. 02+/-0.04 versus 0.91+/-0.03 mm, P<0.05). The flow-mediated diameter (FMD) increase (percent FMD=DeltaD/D x 100) in the atherosclerosis group was significantly smaller than that in the control group (2. 8+/-0.4% versus 5.1+/-0.6%, P<0.01). A significant negative correlation between the intima-media thickness of the carotid artery and percent FMD was found in all of the subjects. On multiple regression analysis, percent FMD showed a significant negative correlation with the intima-media thickness of the common carotid artery. These findings support the concept that endothelial dysfunction is significantly related to atherogenesis.

Estrogen receptor ß is involved in the anorectic action of estrogen

OBJECTIVE: Estrogen has been implicated in feeding behavior and adiposity. This study was undertaken to elucidate the mechanism underlying the anti-obesity and anorectic action of estrogen and the role of estrogen receptor (ER) in the central nervous system.METHODS AND RESULTS: Ovariectomy in 8-week-old female Wistar rats induced hyperphagia along with an increase in body weight and abdominal fat accumulation compared to control sham-operated rats. These changes were fully reversed by subcutaneous replacement of estradiol and were abrogated by pair-feeding. Then, the effects of intracerebroventricular infusion of estradiol, alone or in combination with antisense oligodeoxynucleotides (ODN), for ER in ovariectomized rats were examined. The estradiol group showed 10–20% lower daily food intake, and after the 2-week infusion period a 14% reduction in body weight with a similar reduction in abdominal fat compared to the vehicle group. The inhibitory effect of estradiol on food intake and body weight was blocked by co-administration of ER-ß antisense ODN, whereas ER-α antisense ODN did not show any influence.CONCLUSION: These results indicate that ER-ß in the central nervous system is involved in the anorectic action of estrogen.

Estrogen Prevents Oxidative Stress–Induced Endothelial Cell Apoptosis in Rats

Background —Estrogen replacement attenuates the increased risk of cardiovascular disease in postmenopausal women. Recent studies using an in vitro culture system have shown that estrogen inhibits endothelial cell (EC) apoptosis. The in vivo relevance of this finding, however, is not defined. To do so, we have developed a rat vascular injury model in which EC apoptosis induced by hydrogen peroxide plays a role. Methods and Results —Intracarotid arterial administration of 0.01 mmol/L hydrogen peroxide for 5 minutes evoked EC apoptosis after 6 to 24 hours, determined by nuclear staining with Hoechst 33342, terminal deoxynucleotidyl transferase–mediated dUTP nick end-labeling, and electron microscopy. Apoptosis was associated with EC loss and was followed by EC regeneration at 72 hours and neointima formation at 1 to 2 weeks. Estradiol replacement in ovariectomized female Wistar rats decreased the rate of apoptotic ECs by ≈50%, assayed by nuclear morphology of en face specimens, resulting in increased remaining ECs and decreased neointima formation. Progesterone did not influence the effects of estradiol on EC apoptosis. Conclusions —These results provide new insight into the cardioprotective action of estrogen as well as a paradigm of the response-to-injury hypothesis.

Impact of Blood Pressure Variability on Cardiovascular Events in Elderly Patients with Hypertension

Blood pressure variability is one of the characteristic features of hypertension in the elderly. However, its clinical significance remains to be determined. We therefore examined the impact of blood pressure variability on the development of cardiovascular events in elderly hypertensive patients. A total of 106 consecutive hypertensive patients aged more than 60 years old (mean age, 73.9±8.1 years old; male, 54%), all of whom underwent 24-h ambulatory blood pressure monitoring, were followed up (median, 34 months; range, 3−60 months). During the follow-up period, 39 cardiovascular events were observed, including 14 cases of cerebral infarction and 7 cases of acute myocardial infarction. The coefficient of variation (CV) of 24-h systolic blood pressure (SBP) values was used as an index of blood pressure variability. The patients showed a mean CV value of 10.6%, and were divided into two groups according to this mean value as a cut-off point: a high CV group (n=46) and a low CV group (n=60). Although baseline clinical characteristics were similar in the two groups, Kaplan-Meier plots for event-free survival revealed that the rate of cardiovascular events was significantly higher in high CV group than in low CV group (p<0.05). Coxs proportional hazards analysis showed that increased blood pressure variability (a high CV value of 24-h SBP) was an independent predictive variable for cardiovascular events. The CV value of daytime SBP and the SD value of both 24-h SBP and daytime SBP also had positive correlations with the onset of cardiovascular events. These results suggest that increased blood pressure variability may be an independent risk factor for cardiovascular events in elderly hypertensive patients.

Viral-induced systemic necrosis in plants involves both programmed cell death and the inhibition of viral multiplication, which are regulated by independent pathways.

Resistant plants respond rapidly to invading avirulent plant viruses by triggering a hypersensitive response (HR). An HR is accompanied by a restraint of virus multiplication and programmed cell death (PCD), both of which have been observed in systemic necrosis triggered by a successful viral infection. Here, we analyzed signaling pathways underlying the HR in resistance genotype plants and those leading to systemic necrosis. We show that systemic necrosis in Nicotiana benthamiana, induced by Plantago asiatica mosaic virus (PlAMV) infection, was associated with PCD, biochemical features, and gene expression patterns that are characteristic of HR. The induction of necrosis caused by PlAMV infection was dependent on SGT1, RAR1, and the downstream mitogen-activated protein kinase (MAPK) cascade involving MAPKKKalpha and MEK2. However, although SGT1 and RAR1 silencing led to an increased accumulation of PlAMV, silencing of the MAPKKKalpha-MEK2 cascade did not. This observation indicates that viral multiplication is partly restrained even in systemic necrosis induced by viral infection, and that this restraint requires SGT1 and RAR1 but not the MAPKKKalpha-MEK2 cascade. Similarly, although both SGT1 and MAPKKKalpha were essential for the Rx-mediated HR to Potato virus X (PVX), SGT1 but not MAPKKKalpha was involved in the restraint of PVX multiplication. These results suggest that systemic necrosis and HR consist of PCD and a restraint of virus multiplication, and that the latter is induced through unknown pathways independent from the former.

Lectin-Mediated Resistance Impairs Plant Virus Infection at the Cellular Level

This work identifies jacalin-type lectin that is responsible for resistance to multiple plant viruses belonging to the genus Potexvirus. The isolation and characterization of this lectin sheds light on a novel resistance machinery to plant viruses. Plants possess a multilayered defense response, known as plant innate immunity, to infection by a wide variety of pathogens. Lectins, sugar binding proteins, play essential roles in the innate immunity of animal cells, but the role of lectins in plant defense is not clear. This study analyzed the resistance of certain Arabidopsis thaliana ecotypes to a potexvirus, plantago asiatica mosaic virus (PlAMV). Map-based positional cloning revealed that the lectin gene JACALIN-TYPE LECTIN REQUIRED FOR POTEXVIRUS RESISTANCE1 (JAX1) is responsible for the resistance. JAX1-mediated resistance did not show the properties of conventional resistance (R) protein–mediated resistance and was independent of plant defense hormone signaling. Heterologous expression of JAX1 in Nicotiana benthamiana showed that JAX1 interferes with infection by other tested potexviruses but not with plant viruses from different genera, indicating the broad but specific resistance to potexviruses conferred by JAX1. In contrast with the lectin gene RESTRICTED TEV MOVEMENT1, which inhibits the systemic movement of potyviruses, which are distantly related to potexviruses, JAX1 impairs the accumulation of PlAMV RNA at the cellular level. The existence of lectin genes that show a variety of levels of virus resistance, their targets, and their properties, which are distinct from those of known R genes, suggests the generality of lectin-mediated resistance in plant innate immunity.

A Dual Strategy for the Suppression of Host Antiviral Silencing: Two Distinct Suppressors for Viral Replication and Viral Movement Encoded by Potato Virus M

ABSTRACT Viruses encode RNA silencing suppressors to counteract host antiviral silencing. In this study, we analyzed the suppressors encoded by potato virus M (PVM), a member of the genus Carlavirus. In the conventional green fluorescent protein transient coexpression assay, the cysteine-rich protein (CRP) of PVM inhibited both local and systemic silencing, whereas the triple gene block protein 1 (TGBp1) showed suppressor activity only on systemic silencing. Furthermore, to elucidate the roles of these two suppressors during an active viral infection, we performed PVX vector-based assays and viral movement complementation assays. CRP increased the accumulation of viral RNA at the single-cell level and also enhanced viral cell-to-cell movement by inhibiting RNA silencing. However, TGBp1 facilitated viral movement but did not affect viral accumulation in protoplasts. These data suggest that CRP inhibits RNA silencing primarily at the viral replication step, whereas TGBp1 is a suppressor that acts at the viral movement step. Thus, our findings demonstrate a sophisticated viral infection strategy that suppresses host antiviral silencing at two different steps via two mechanistically distinct suppressors. This study is also the first report of the RNA silencing suppressor in the genus Carlavirus.

Association of low testosterone with metabolic syndrome and its components in middle-aged Japanese men.

Epidemiological studies have shown that low testosterone is associated with metabolic syndrome (MetS) in Caucasian men. We investigated whether testosterone level is related to the prevalence of MetS in middle-aged Japanese men. A cross-sectional survey was conducted in 194 men aged 30–64 years (49±9). Blood sampling was performed in the morning after a 12-h fast, and the relationship between plasma hormone and MetS was analyzed. Low total testosterone was associated with MetS according to the Japanese criteria (HRs of 2.02 by quartile of testosterone; 95% CI=1.43–2.87) and the International Diabetes Federation criteria (HRs of 1.68 by quartile of testosterone; 95% CI=1.25–2.25). Age-adjusted regression analyses revealed that testosterone was significantly related to the MetS parameters of obesity (β=−0.365 and −0.343 for waist circumference and body mass index, respectively), hypertension (β=−0.278 and −0.157 for systolic and diastolic blood pressure, respectively), dyslipidemia (β=−0.242 and 0.228 for triglycerides and high-density lipoprotein cholesterol, respectively), insulin resistance (β=−0.253 and −0.333 for fasting plasma glucose and homeostasis model assessment of insulin resistance, respectively) and adiponectin (β=0.216). Inclusion of waist circumference into the model largely weakened the association of testosterone with other metabolic risk factors. In contrast, high estradiol was associated with MetS and its parameters, mostly attributing to the positive correlation between estradiol and obesity. Dehydroepiandrosterone sulfate was not associated with MetS or its parameters. These results suggest that low testosterone is associated with MetS and its parameters in middle-aged Japanese men. The association between estradiol and MetS needs further investigation.