Takashi Ueyama

Takotsubo Cardiomyopathy A New Form of Acute, Reversible Heart Failure

Several relatively recent case reports and series have described a condition featuring symptoms and signs of acute myocardial infarction without demonstrable coronary artery stenosis or spasm in which the heart takes on the appearance of a Japanese octopus fishing pot called a takotsubo (Figure 1). In takotsubo cardiomyopathy (also called transient apical ballooning and stress cardiomyopathy), left ventricular dysfunction, which can be remarkably depressed, recovers within a few weeks.1–4 Figure 1 Left ventriculogram (A, end-diastolic phase; B, end-systolic phase) in the right anterior oblique projection. The extensive area around the apex shows akinesis, and the basal segments display hypercontraction, especially in the end-diastolic phase. C, ... Takotsubo cardiomyopathy occurs predominantly in post-menopausal women soon after exposure to sudden, unexpected emotional or physical stress. For instance, the incidence of takotsubo cardiomyopathy increased substantially in elderly women living near the epicenter of the Niigata earthquake.4 Although the left ventricular dysfunction is transient and there is no evidence of obstructive epicardial coronary disease, an increasing number of angioplasty procedures have been performed for presumed acute coronary syndromes. Concepts about the demographics, clinical features, prognosis, and management of this reversible form of left ventricular failure are still evolving. In this brief review, we summarize recent clinical reports and discuss an animal model that may clarify the pathogenesis of this condition.

Emotional Stress‐Induced Tako‐tsubo Cardiomyopathy: Animal Model and Molecular Mechanism

Abstract: Emotional or physical stress triggers Tako‐tsubo cardiomyopathy in postmenopausal females, which is characterized by an elevation of the ST segment in the electrocardiogram (ECG) and left ventricular apical ballooning in the left ventriculogram (LVG). Immobilization stress (IMO) of rats can reproduce these ECG and LVG changes, both of which are normalized by combined blockade of α‐ and β‐adrenoceptors. An increase of serum estrogen partially attenuated these cardiac changes. IMO induced a rapid activation of p44/p42 mitogen‐activated protein kinase, followed by a transient upregulation of immediate early genes (IEG) in the coronary artery and myocardium. Blocking of both α‐ and β‐adrenoceptors eliminated the upregulation of IEG induced by stress, while α‐ or β‐agonists upregulated IEG in the perfused heart. Heat shock protein 70 was induced in the aorta, coronary artery, and the myocardium. Natriuretic peptide genes (ANP and BNP) were also upregulated in the myocardium. Sequential gene expression can be considered as an adaptive response to stress. Activation of α‐ or β‐adrenoceptors is the primary trigger of emotional stress‐induced cardiac changes.

Nitric oxide synthase-containing magnocellular neurons of the rat hypothalamus synthesize oxytocin and vasopressin and express Fos following stress stimuli.

We investigated the chemical and anatomical features of nitric oxide synthase (NOS)-containing neurons in the paraventricular and supraoptic nuclei in the rat hypothalamus using combinations of enzyme histochemistry, in situ hybridization and immuno-histochemistry. Neurons expressing NOS mRNA completely overlapped with NADPH-diaphorase-positive neurons. Topographical distribution of NOS was segregated from that of CRF-containing parvicellular neurons in the posterior paraventricular nucleus but overlapped with that of magnocellular neurons. In the paraventricular nucleus, 70% of oxytocin neurons contained NOS, which corresponded to one half of NOS neurons. About one third of vasopressin-immunoreactive neurons were NADPH-diaphorase-positive and the same proportion of NADPH-diaphorase-positive neurons were vasopressin-immunoreactive. In the supraoptic nucleus, 50% of oxytocin neurons were NADPH-diaphorase-positive, which corresponded to 40% of NOS neurons. About 25% of vasopressin neurons were NADPH-diaphorase-positive, and 30% of NADPH-diaphorase-positive neurons were vasopressin-immunoreactive. When NADPH-diaphorase histochemistry was performed first, subsequent immunostaining was markedly perturbed. Using fluoro-gold as a retrograde tracer, 4% of NADPH-diaphorase-positive neurons were shown to contribute to the descending projection to the spinal cord. About 40%-50% of NADPH-diaphorase-positive neurons exhibited Fos immunoreactivity after injection of lipopolysaccharide or hypertonic saline, while only 10%-15% of these neurons expressed Fos in response to immobilization or pain. Endogenous NO may be involved in the regulation of magnocellular functions, especially when the internal environment is disturbed.

Catecholamines and estrogen are involved in the pathogenesis of emotional stress-induced acute heart attack.

Emotional stress triggers takotsubo cardiomyopathy in postmenopausal women. Clinical analysis of autonomic nervous function has revealed a transient increase of sympathetic nervous activity and decrease of vagal nervous activity. Immobilization (IMO) stress of rats can reproduce the electrocardiographic and left ventriculographic changes that occur in takotsubo cardiomyopathy, both of which are prevented by combined blockade of α‐ and β‐adrenoceptors. Estrogen supplementation partially attenuated these cardiac changes. It also attenuated the IMO‐induced increase of c‐Fos immunoreactivity, or c‐fos mRNA expression in the lateral septum, medial amygdaloid nucleus, paraventricular hypothalamic nucleus, dorsomedial hypothalamic nucleus, laterodorsal tegmental nucleus, and locus ceruleus; these regions contain central sympathetic neurons and neurons with immunoreactive estrogen receptors. It also downregulated c‐fos mRNA expression in the adrenal gland and the heart, suggesting an increase of estrogen attenuated the stress‐induced hypothalamo‐sympathoadrenal outflow from the central nervous system to the target organs. Estrogen treatment also upregulated the levels of cardioprotective substances, such as atrial natriuretic peptide and heat shock protein 70, in the heart. These data suggest that reduction of estrogen levels following menopause might be involved in the primary cause of takotsubo cardiomyopathy both by indirect action on the nervous system and by direct action on the heart.

Adaptive HNE-Nrf2-HO-1 pathway against oxidative stress is associated with acute gastric mucosal lesions

Disturbance of the microcirculation and generation of reactive oxygen species are crucial in producing acute gastric mucosal lesions (AGML). To understand the protective mechanism against mucosal injury and oxidative stress in the stomach, we investigated sequential expression and localization of a product of lipid peroxidation and a chemical mediator of the oxidative response array, 4-hydroxynonenal (HNE), transcriptional factor, NF-E2-related factor (Nrf2), and the inducible heme oxygenase (HO-1) in the injured stomach. AGML was produced by intragastric administration of 0.6 N HCl in male rats. Expression and localization of HNE, Nrf2, and HO-1 were investigated by Western blotting, immunohistochemistry, real-time RT-PCR, and in situ hybridization histochemistry. Mucosal lesions and expression of HNE and HO-1 were assessed by prior treatment with the PGI2 analog beraprast or after sensory denervation by pretreatment with capsaicin. Mucosal lesions were assessed by prior treatment with a HO-1 inhibitor, zinc protoporphyrin (ZnPP). After AGML, increased generation of HNE was observed in the injured mucosa and the surrounding submucosa, followed by nuclear translocation of Nrf2 and upregulation of HO-1 in the macrophages located in the margin of the injured mucosa and in the submucosa. Pretreatment with beraprost attenuated AGML and downregulated the expression of HNE and HO-1, while sensory denervation aggravated AGML and upregulated the expression of HNE and HO-1. Pretreatment with ZnPP also aggravated AGML. The sequential HNE-Nrf2-HO-1 pathway in the gastric mucosal cells and the macrophages is involved in an adaptive mechanism against oxidative stress after AGML.

Estrogen alters c-Fos response to immobilization stress in the brain of ovariectomized rats

Estrogen receptors are widely expressed in the brain, where estrogen modulates central nervous function. In this study, we investigated the effect of estrogen on the emotional stress response in the brain by comparing the CNS patterns of c-Fos expression in response to immobilization stress (IMO) in ovariectomized rats with placebo treatment (OVX + Pla) vs. ovariectomized rats supplemented with 17beta-estradiol (OVX + E2). Increased c-Fos immunoreactive neurons in response to IMO were observed in cerebral cortex, septum, thalamus, hypothalamus, midbrain, pons and medulla oblongata in accordance with previous findings. When OVX + E2/Stress were compared with OVX + Pla/Stress, the numbers of c-Fos immunoreactive cells were significantly lower in the lateral septum, paraventricular hypothalamic nucleus, dorsomedial hypothalamic nucleus, medial amygdaloid nucleus, lateral periaqueductal gray, laterodorsal tegmental nucleus and locus coeruleus, while they were significantly higher in paraventricular thalamic nucleus and nucleus of the solitary tract. These data suggest that neuronal activities in these areas are influenced bidirectionally by systemic estrogen level.

Brain Regions Responsible for Tinnitus Distress and Loudness: A Resting-State fMRI Study

Subjective tinnitus is characterized by the perception of phantom sound without an external auditory stimulus. We hypothesized that abnormal functionally connected regions in the central nervous system might underlie the pathophysiology of chronic subjective tinnitus. Statistical significance of functional connectivity (FC) strength is affected by the regional autocorrelation coefficient (AC). In this study, we used resting-state functional MRI (fMRI) and measured regional mean FC strength (mean cross-correlation coefficient between a region and all other regions without taking into account the effect of AC (rGC) and with taking into account the effect of AC (rGCa) to elucidate brain regions related to tinnitus symptoms such as distress, depression and loudness. Consistent with previous studies, tinnitus loudness was not related to tinnitus-related distress and depressive state. Although both rGC and rGCa revealed similar brain regions where the values showed a statistically significant relationship with tinnitus-related symptoms, the regions for rGCa were more localized and more clearly delineated the regions related specifically to each symptom. The rGCa values in the bilateral rectus gyri were positively correlated and those in the bilateral anterior and middle cingulate gyri were negatively correlated with distress and depressive state. The rGCa values in the bilateral thalamus, the bilateral hippocampus, and the left caudate were positively correlated and those in the left medial superior frontal gyrus and the left posterior cingulate gyrus were negatively correlated with tinnitus loudness. These results suggest that distinct brain regions are responsible for tinnitus symptoms. The regions for distress and depressive state are known to be related to depression, while the regions for tinnitus loudness are known to be related to the default mode network and integration of multi-sensory information.

Increased nerve growth factor levels in spontaneously hypertensive rats

Objective: Increased sympathetic innervation has been reported in spontaneously hypertensive rats (SHR); however, the precise mechanisms involved are not yet clear. Nerve growth factor (NGF), a neurotrophic peptide in peripheral sympathetic neurons, is believed to contribute to this phenomenon. Methods: We measured the content of NGF in SHR and control Wistar–Kyoto (WKY) rats during development. Mesenteric artery, spleen, heart and sciatic nerve were isolated and homogenized. NGF content in the supernatant fractions was measured using a highly sensitive and specific two-site enzyme immunoassay. Results: At 3 weeks of age, SHR had a greater NGF content in the spleen, the sciatic nerve and the mesenteric artery than WKY rats. However, these differences disappeared completely at 12 weeks of age. Cardiac NGF content was slightly lower in 3-week-old SHR and, conversely, higher in 12-week-old SHR than in age-matched WKY rats. Conclusions: These findings suggest that, except for the heart, the SHR tissues observed overproduce NGF at a young age, leading to enhancement of peripheral sympathetic nervous system activity and the production of vasoconstrictive catecholamines.

Emotional stress induces immediate-early gene expression in rat heart via activation of α- and β-adrenoceptors

We have studied the adrenergic mechanisms of immediate-early gene (IEG) induction in the discrete types of cardiac cells with the use of in situ hybridization histochemistry in an immobilization-stress model in conscious rats. Expression of c- fos, fos B, c- jun, jun B, NGFI-A, and NGFI-B mRNA was rapidly upregulated in the endothelial, myocardial, and smooth muscle cells of coronary vessels by 15-45 min after the onset of immobilization. Simultaneous blockade of both α- and β-adrenoceptors completely abolished expression of IEGs in these cardiac cells. Application of an α-agonist or β-agonist alone to the perfused rat heart under constant pressure elicited the upregulation of IEGs in a fashion similar to that of emotional stress. These data suggest that activation of either α- or β-adrenoceptor is sufficient to evoke expression of these genes and that there may be cross talk in signal transduction downstream from α- and β-adrenoceptors in cardiac cells.

Expression of c-fos, Heat Shock Protein 70, Neurotrophins, and Cyclooxygenase-2 mRNA in Response to Focal Cerebral Ischemia/Reperfusion in Rats and Their Modification by Magnesium Sulfate

The marginal area surrounding a region of ischemic brain tissue, designated as the penumbra, is of interest as a potential area for the rescue of neurons from cell death. Despite its clinical importance, relatively little is known about the molecular events leading to changes in brain cells in the penumbra following ischemia. In the first part of this study, we used in situ hybridization to investigate the temporal and spatial expression of c-fos, heat shock protein 70 (HSP70), neurotrophins and inducible cyclooxygenase-2 (COX-2) in the rat brain following a 2-h occlusion of the middle cerebral artery (MCA) with reperfusion. In the penumbra and surrounding cortex, upregulation of c-fos, brain-derived neurotrophic factor (BDNF), and COX-2 mRNAs was observed, while expression of HSP70 mRNA was restricted to the penumbra. This spatial discrepancy of mRNA expression suggests that different mechanisms are involved in the regulation of c-fos/BDNF/COX-2 and HSP70 expression. Intravenous infusion of magnesium sulfate (25 mg/kg) decreased both the infarct volume and upregulation of these mRNAs, suggesting its therapeutic potential.