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

Recurrent Takotsubo syndrome: case report and literature review

Abstract Introduction: Takotsubo syndrome is a cardiomyopathy that can lead to severe myocardial involvement. It is characterized by the presence of signs and symptoms suggestive of ventricular dysfunction associated with an adrenergic discharge during a stressful event. This case report presents a literature review, as well as a comparison with other similar cases. Case presentation. A 56-year-old female with a previous episode of Takotsubo was admitted to the emergency department due to symptoms of acute coronary syndrome and a history of Takotsubo syndrome. Her electrocardiogram showed T-wave inversion in leads V1-V4 and a raise in troponins. Percutaneous coronary angiography revealed no coronary lesions, and an echocardiogram revealed segmental alterations compatible with Takotsubo syndrome, requiring medical therapy with beta-blockers and angiotensin-converting enzyme (ACE) inhibitors, with subsequent improvement in ventricular function. Conclusions. Recurrence in Takotsubo cardiomyopathy is a rare complication that should be suspected. The risk factors associated with recurrence are not known. Although therapy with ACE inhibitors and beta-blockers seems to have an impact on the recovery of ventricular function in patients with this condition, further studies are necessary to establish the best pharmacological treatment.

Molecular Mechanisms of Takotsubo Syndrome

Takotsubo syndrome (TTS) is a severe but reversible acute heart failure syndrome that occurs following high catecholaminergic stress. TTS patients are similar to those with acute coronary syndrome, with chest pain, dyspnoea and ST segment changes on electrocardiogram, but are characterised by apical akinesia of the left ventricle, with basal hyperkinesia in the absence of culprit coronary artery stenosis. The pathophysiology of TTS is not completely understood and there is a paucity of evidence to guide treatment. The mechanisms of TTS are thought to involve catecholaminergic myocardial stunning, microvascular dysfunction, increased inflammation and changes in cardiomyocyte metabolism. Here, we summarise the available literature to focus on the molecular basis for the pathophysiology of TTS to advance the understanding of the condition.

Takotsubo Syndrome: Translational Implications and Pathomechanisms

Takotsubo syndrome (TTS) is identified as an acute severe ventricular systolic dysfunction, which is usually characterized by reversible and transient akinesia of walls of the ventricle in the absence of a significant obstructive coronary artery disease (CAD). Patients present with chest pain, ST-segment elevation or ischemia signs on ECG and increased troponin, similar to myocardial infarction. Currently, the known mechanisms associated with the development of TTS include elevated levels of circulating plasma catecholamines and their metabolites, coronary microvascular dysfunction, sympathetic hyperexcitability, inflammation, estrogen deficiency, spasm of the epicardial coronary vessels, genetic predisposition and thyroidal dysfunction. However, the real etiologic link remains unclear and seems to be multifactorial. Currently, the elusive pathogenesis of TTS and the lack of optimal treatment leads to the necessity of the application of experimental models or platforms for studying TTS. Excessive catecholamines can cause weakened ventricular wall motion at the apex and increased basal motion due to the apicobasal adrenoceptor gradient. The use of beta-blockers does not seem to impact the outcome of TTS patients, suggesting that signaling other than the beta-adrenoceptor-associated pathway is also involved and that the pathogenesis may be more complex than it was expected. Herein, we review the pathophysiological mechanisms related to TTS; preclinical TTS models and platforms such as animal models, human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) models and their usefulness for TTS studies, including exploring and improving the understanding of the pathomechanism of the disease. This might be helpful to provide novel insights on the exact pathophysiological mechanisms and may offer more information for experimental and clinical research on TTS.

Takotsubo cardiomyopathy: do the genetics matter?

Takotsubo cardiomyopathy (TTC) is an enigmatic disease with a multifactorial and still unresolved pathogenesis. Recent experimental and clinical observation has suggested a role for genetics in the pathogenesis of TTC. Ethnic as well as seasonal variation in the prevalence of TTC is well described, but it is only recently that familial cases of TTC have been reported. In recent years technological advances in exome capture and DNA sequencing have offered clinicians a new opportunity to discover genetics-related disease. This article explores the role of genetic mechanisms that might explain or modulate the pathogenesis of TTC.

Amlodipine has a preventive effect on temporal left ventricular hypokinesia after emotional stress compared with an angiotensin II receptor blocker

PURPOSE

We previously reported that α- and β-blockers protected against emotional stress-induced cardiac dysfunction, but the protective effects of other antihypertensive drugs is unknown. The purpose of this study is to evaluate the ability of a calcium channel blocker, amlodipine, to prevent temporal left ventricular hypokinesia after emotional stress compared with an angiotensin II receptor blocker, olmesartan medoxomil.

METHODS

Rats premedicated with amlodipine (0.2 mg/kg), olmesartan (0.8 mg/kg), or vehicle were restrained for 30 min (immobilization stress: IMO) to reproduce emotional stress and then anesthetized to release stress. We measured the fractional area change (FAC) using echocardiography (SONOS5500) with a s12 probe (frequency 5-12 MHz, frame rate 120 Hz) and blood pressure and heart rate at the end of IMO and every 10 for 60 min after IMO.

RESULTS

During IMO, FAC in the amlodipine or the olmesartan group was as high as that in the vehicle group. At 20 min after IMO, FAC in the amlodipine group was significantly higher than in the other two groups (84 ± 8 vs. 60 ± 7 or 68 ± 15 %, p < 0.05). During IMO, blood pressure in the amlodipine or the olmesartan group was significantly lower than with vehicle (119 ± 6 and 110 ± 7 vs. 124 ± 5 mmHg, p < 0.05). After IMO, blood pressure in the olmesartan group was significantly lower than in the other two groups.

CONCLUSION

Acute administration of amlodipine could prevent a sudden drop in cardiac function after acute stress like IMO, but olmesartan did not. Amlodipine might have a protective effect on temporal left ventricular hypokinesia after emotional stress, which might not be related to decreased blood pressure.

Cardiac and vascular gene profiles in an animal model of takotsubo cardiomyopathy

We investigated cardiac and vascular gene profiles in response to immobilization stress (IMO) in rats, an animal model of emotional stress-induced takotsubo cardiomyopathy using microarray analysis, followed by re-confirmation with real-time reverse transcription-polymerase chain reaction. Expression levels of the identified genes were further estimated by pretreatment with an α1-adrenoceptor blocker and/or a β1-adrenoceptor blocker. In response to IMO, expression of 46 genes was significantly altered in the heart and that of 49 genes was significantly altered in the aorta. Pathway analysis with DAVID Bioinformatics Resources indicated that regulation of transcription and response to endogenous stimulation were the top two scoring pathways. Altered expression of cardiac genes was blunted by pretreatment with a β1-adrenoceptor blocker or α1 + β1-adrenoceptor blockers. In contrast, that of aortic genes was blunted by pretreatment with an α1-adrenoceptor blocker or α1 + β1-adrenoceptor blockers. Activation of α1-adrenoceptor in the blood vessels or activation of β1-adrenoceptors in the heart were mainly responsible for emotional stress-induced alteration of cardiac and vascular gene profiles.

Restraint stress induces connexin-43 translocation via α-adrenoceptors in rat heart

BACKGROUND

Immobilization (IMO) confers emotional stress in animals and humans. It was recently reported that IMO in rats induced translocation of connexin-43 (Cx43) to gap junctions (GJs) and attenuated arrhythmogenesis with GJ inhibition, and Cx43 translocation in the ischemic heart was also shown. Few reports show the contribution of adrenoceptors to Cx43 upregulation in cardiomyocytes, but the involvement of adrenoceptors and ischemia in Cx43 translocation in IMO remains elusive.

METHODS AND RESULTS

Male Sprague-Dawley rats underwent IMO and the ventricular distribution of Cx43 was examined by western blotting. IMO induced translocation of Cx43 to the GJ-enriched membrane fraction, with a peak at 60min. The IMO-induced Cx43 translocation was inhibited by pretreatment with the α(1)-adrenoceptor blockers, prazosin (1mg/kg, PO) and bunazosin (4mg/kg, PO), but not with either the β(1)-blocker, metoprolol (10mg/kg, IP), or the β(1+2)-blocker, propranolol (1mg/kg, PO). The translocation was inhibited by the nitric oxide, donor isosorbide dinitrate (100µg·kg(-1)·min(-1), IV), possibly through sympathetic inhibition. Hypoxia inducible factor-1α was not redistributed by IMO. The β-blockers, but not the α-blockers, inhibited the premature ventricular contractions (PVCs) induced by IMO.

CONCLUSIONS

Translocation of Cx43 to the GJ-enriched fraction occurs via the α(1)-adrenoceptor pathway, independently of ischemia. The β-adrenoceptor pathway contributes to the inducing of PVCs in IMO.

Norepinephrine mediates the transcriptional effects of heterotypic chronic stress on colonic motor function

Chronic stress precipitates or exacerbates the symptoms of functional bowel disorders, including motility dysfunction. The cellular mechanisms of these effects are not understood. We tested the hypothesis that heterotypic chronic stress (HeCS) elevates the release of norepinephrine from the adrenal medulla, which enhances transcription of the gene-regulating expression of Ca(v)1.2 (L-type) channels in colonic circular smooth muscle cells, resulting in enhanced colonic motor function. The experiments were performed in rats using a 9-day heterotypic chronic stress (HeCS) protocol. We found that HeCS, but not acute stress, time dependently enhances the contractile response to ACh in colonic circular smooth muscle strips and in single dissociated smooth muscle cells, the plasma levels of norepinephrine and the mRNA and protein expressions of the alpha(1C) subunit of Ca(v)1.2 channels. These effects result in faster colonic transit and increase in defecation rate. The effects of HeCS are blocked by adrenalectomy but not by depletion of norepinephrine in sympathetic neurons. The inhibition of receptors for glucocortocoids, corticotropin-releasing hormone or nicotine also does not block the effects of heterotypic chronic stress. Norepinephrine acts on alpha- and beta(3)-adrenergic receptors to induce the transcription of alpha(1C) subunit. We conclude that HeCS alters colonic motor function by elevating the plasma levels of norepinephrine. Colonic motor dysfunction is associated with enhanced gene transcription of Ca(v)1.2 channels in circular smooth muscle cells. These findings suggest the potential cellular mechanisms by which heterotypic chronic stress may exacerbate motility dysfunction in patients with irritable bowel syndrome.

Upregulation of heme oxygenase-1 in an animal model of Takotsubo cardiomyopathy

BACKGROUND

Disturbance of the coronary microcirculation and catecholamine intoxication, which may be responsible for the pathogenesis of takotsubo cardiomyopathy, could trigger an oxidative stress response in the heart.

METHODS AND RESULTS

Expression and localization of inducible heme oxygenase-1 (HO-1), which is an oxidative stress-related factor in the heart of immobilization stressed (IMO) rats, an animal model of takotsubo cardiomyopathy, were investigated by real-time reverse transcriptase-polymerase chain reaction and in situ hybridization histochemistry and immunohistochemistry. In response to IMO, the levels of HO-1 mRNA in the heart and in the aorta were slightly increased at 90 min, and increased 3-fold at 3 h compared with control levels. The signals for HO-1 mRNA were expressed on scatted cells in the myocardium and aortic adventitia. Double fluorescence immunohistochemistry showed that HO-1 immunoreactive cells were also ED1 and ED2 positive, indicating that they were macrophages. The numbers of ED1 and ED2 positive cells were constant, whereas the number of HO-1 positive cells was increased 5-fold at 6 h compared with control levels. Blocking of alpha- and beta-adrenoceptors attenuated IMO-induced upregulation of HO-1 mRNA levels in the heart.

CONCLUSIONS

Emotional stress and a surge of catecholamine upregulate HO-1 in the cardiac and aortic macrophages.

p38 MAP kinase inhibitor reverses stress-induced myocardial dysfunction in vivo

Recent clinical reports strongly support the intriguing possibility that emotional stress alone is sufficient to cause reversible myocardial dysfunction in patients. We previously reported that a combination of prenatal stress followed by restraint stress (PS+R) results in echocardiographic evidence of myocardial dysfunction in anesthetized rats compared with control rats subjected to the same restraint stress (Control+R). We now report results of our catheter-based hemodynamic studies in both anesthetized and freely ambulatory awake rats, comparing PS+R vs. Control+R. Systolic function [positive rate of change in left ventricular pressure over time (+dP/dt)] was significantly depressed (P < 0.01) in PS+R vs. Control+R both under anesthesia (6,287 +/- 252 vs. 7,837 +/- 453 mmHg/s) and awake (10,438 +/- 741 vs. 12,111 +/- 652 mmHg/s). Diastolic function (-dP/dt) was also significantly depressed (P < 0.05) in PS+R vs. Control+R both under anesthesia (-5,686 +/- 340 vs. -7,058 +/- 458 mmHg/s) and awake (-8,287 +/- 444 vs. 10,440 +/- 364 mmHg/s). PS+R also demonstrated a significantly attenuated (P < 0.05) hemodynamic response to increasing doses of the beta-adrenergic agonist isoproterenol. Intraperitoneal injection of the p38 MAP kinase inhibitor SB-203580 reversed the baseline reduction in +dP/dt and -dP/dt as well as the blunted isoproterenol response. Intraperitoneal injection of SB-203580 also reversed p38 MAP kinase and troponin I phosphorylation in cardiac myocytes isolated from PS+R. Thus the combination of prenatal stress followed by restraint stress results in reversible depression in both systolic and diastolic function as well as defective beta-adrenergic receptor signaling. Future studies in this animal model may provide insights into the basic mechanisms contributing to reversible myocardial dysfunction in patients with ischemic and nonischemic cardiomyopathies.

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 alpha- and beta-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.

Reaction of rat brain capillaries to immobilization stress

The calcium adenosine triphosphate method of Chilingaryan was used to study the morphofunctional state of the capillary component of the microcirculatory bed of the brain in rats at different time points after experimental immobilization stress (fixation of the animal on its back for 2 h). Analysis of morphometric data showed that in comparison with intact animals, stress was immediately followed by constriction of capillaries by 17.2%, with compensatory dilation by 2.5% occurring at two days, and subsequent minor constriction by 5.6%. Morphometric measures in placid and aggressive animals showed that the behavioral stereotype of placid animals produced a more sparing physiological response to stress. It is suggested that the difference in capillary dysfunction is largely dependent on impairment of neuronal systems involved in regulating the microcirculation.

Chronic Estrogen Supplementation Following Ovariectomy Improves the Emotional Stress-Induced Cardiovascular Responses by Indirect Action on the Nervous System and by Direct Action on the Heart

BACKGROUND

Takotsubo cardiomyopathy is triggered by emotional or physical stress especially in post-menopausal women. A reduction in estrogen levels following menopause might underlie the high incidence of takotsubo cardiomyopathy.

METHODS AND RESULTS

The left ventricular contraction between ovariectomized rats (OVX) and OVX with estrogen supplementation (OVX + E) while subjected to immobilization stress (IMO) was compared. The IMO in combination with general anesthesia impaired the left ventricular contraction in both OVX and OVX + E. Estrogen supplementation tended to improve the IMO-induced cardiac dysfunction and significantly attenuated the increase of blood pressure and heart rate. To understand the protective mechanism of estrogen, the expression of c-fos mRNA, a marker of cellular activation was compared. The mRNA expression of cardioprotective substances in the heart was also investigated. In the OVX + E, the levels of c-fos mRNA were significantly decreased in the paraventricular hypothalamic nucleus, adrenal gland and left ventricle, suggesting that an increase of estrogen attenuates the emotional stress-induced hypothalamo-sympatho-adrenal outflow from the central nervous system to the target organs. An expression of heat shock protein 70 and atrial natriuretic peptide was significantly augmented in the OVX + E.

CONCLUSIONS

These data suggest that estrogen supplementation partially prevents emotional stress-induced cardiovascular responses both by indirect action on the nervous system and by direct action on the heart.

Evidence for Nr4a1 as a cold-induced effector of brown fat thermogenesis

Acute cold exposure leads to norepinephrine release in brown adipose tissue (BAT) and activates uncoupling protein (UCP)1-mediated nonshivering thermogenesis. Chronic sympathetic stimulation is known to initiate mitochondrial biogenesis, UCP1 expression, hyperplasia of BAT, and recruitment of brown adipocytes in white adipose tissue (WAT) depots. Despite distinct functions of BAT and WAT in energy balance, only a few genes are exclusively expressed in either tissue. We identified NUR77 (Nr4a1), an orphan receptor, to be induced transiently in brown adipocytes in response to beta-adrenergic stimulation and in BAT of cold-exposed mice. Subsequent reporter gene assays demonstrated an inhibitory action of NUR77 on basal and peroxisome proliferator-activated receptor (PPAR)gamma/retinoid X receptor (RXR)alpha-mediated transactivation of the Ucp1 enhancer in heterologous cotransfection experiments. Despite this function of NUR77 in the control of Ucp1 gene expression, nonshivering thermogenesis was not affected in Nur77 knockout mice. However, we observed a superinduction of Nor1 in BAT of cold-exposed knockout mice. We conclude that NUR77 is a cold-induced negative regulator of Ucp1, but phenotypic consequences in knockout mice are compensated by functional redundancy of Nor1.

Estrogen Attenuates the Emotional Stress-induced Cardiac Responses in the Animal Model of Tako-Tsubo (Ampulla) Cardiomyopathy

Reduction of estrogen levels may underlie the high incidence of 'Tako-tsubo (Ampulla) cardiomyopathy in postmenopausal females. Ovariectomized (OVX) and estradiol-supplemented ovariectomized female rats (OVX + E) were subjected to immobilization stress, an animal model of Tako-tsubo cardiomyopathy. In order to evaluate cardiac changes, left ventriculography and electrocardiography were performed under anesthesia (control). Next day, the conscious rats were exposed to immobilization stress, and left ventriculography was performed (stress). In OVX rats, percentage contraction in left ventriculography was significantly reduced in response to stress, while it was not significantly changed in OVX + E rats. In both groups, heart rate was significantly increased in response to stress. However, heart rate in stress was significantly higher in OVX than in OVX + E rats. In summary, these data suggest that increase of serum estradiol levels can diminish the pathological changes in the heart induced by emotional stress.

Activation of c-fos expression in the heart after morphine but not U-50,488H withdrawal

1. In the present work we have studied in the heart the expression of Fos, the protein product of the c-fos proto-oncogene and the adaptive changes in noradrenergic neurons after naloxone or nor-binaltorphimine (nor-BNI) administration to morphine or U-50,488H pretreated rats. 2. Male rats were implanted with placebo (naïve) or morphine (tolerant/dependent) pellets for 7 days. On day 8 rats received saline s.c., naloxone (5 mg kg(-1) s.c.) or nor-BNI (5 mg kg(-1) i.p.). Other groups of rats were rendered tolerant/dependent on U-50,488H by injecting the drug twice daily (15 mg kg(-1) i.p.) for 4 days. Control animals received saline. On day 5 the animals were injected with vehicle i.p. or nor-BNI (5 mg kg(-1) i.p.). 3. Using immunohistochemical staining of Fos, present results indicate that morphine withdrawal induced marked Fos immunoreactivity (Fos-IR) within the cardiomyocyte nuclei. Moreover, Western blots analysis revealed a peak expression of c-fos in right and left ventricle after naloxone induced withdrawal in parallel with an increase in noradrenaline (NA) turnover. 4. However, after nor-BNI administration to rats chronically treated with U-50,488H, we found a decrease in the NA turnover. In addition, the administration of nor-BNI to rats chronically treated with U-50,488H or morphine did not induce modifications in the Fos-IR, in the heart. 5. These results demonstrated that morphine withdrawal induces the expression of Fos protein, as well as an enhancement of noradrenergic activity in the heart. In contrast to morphine U-50,488 withdrawal produces no changes in Fos-IR in parallel with a decrease in NA turnover, indicating that the kappa-opioid receptors are not involved in the molecular adaptive mechanisms responsible for the development of opioid dependence in the heart.