Stress-induced arrhythmic disease of the heart--Part I

Detection of heat shock protein 27, 70, 90 expressions in primary parenchymatous organs of goats after transport stress by real-time PCR and ELISA

Transport stress causes a series of problems to goat production, such as tissue injury and immunity damage. As a pro‐survival pathway, the heat shock response protects healthy cells of goat from stressors. To evaluate the effects of transport stress on heat shock protein (HSPs) expression on goat primary parenchymatous organs, a total of three batches of goats were treated in this study. For each batch, 12 healthy adult male goats were randomly and averagely divided into three groups: Control group (non‐transported group), 2 hr transported group and 6 hr transported group. Real‐time PCR results indicated that the mRNA expression level of heat shock protein 27 (HSP27) in all examined organs of 2 hr transport‐treated goats were upregulated (p < .05) except lung, and heat shock protein 70 (HSP70; except spleen) and heat shock protein 90 (HSP90; except liver and lung) were also increased (p < .05). In 6 hr transported group, the transcription levels of HSP27 (except heart and kidney), HSP70 (except heart, liver and lymph nodes) and HSP90 (except heart and spleen) were all backed to the original levels or even reduced (p < .05). Enzyme‐linked immunosorbent assay (ELISA) results showed that the protein levels of HSP27 (except lymph nodes), HSP70 (except spleen) and HSP90 (except liver and lung) were all increased after 2 hr transport (p < .05). After 6 hr transport, HSP27 only in kidney and HSP70 only in heart and liver were upregulated (p < .05), while HSP90 in all the examined organs except liver and lung were also maintained in relatively high levels (p < .05). Taken together, these results suggested that the expression of HSPs in goat primary parenchymatous organs may be regulated by transport stress time. Moreover, this study also provides some new data to advocate reducing transport stress of goats and improving animal welfare.

The Dorsomedial Hypothalamus Is Involved in the Mediation of Autonomic and Neuroendocrine Responses to Restraint Stress

We hypothesized that dorsomedial hypothalamus (DMH) modulates autonomic and neuroendocrine responses in rats at rest and when subjected to restraint stress (RS). Male Wistar rats were used, and guide cannulas were bilaterally implanted in the DMH for microinjection of vehicle or the nonspecific synaptic blocker CoCl₂ (1 mM/100 nl). A polyethylene catheter was inserted into the femoral artery for the recording of arterial pressure and heart rate (HR). Tail temperature was measured using a thermal camera. The session of RS started 10 min after DMH treatment with vehicle or CoCl2. Under home-cage condition, the pretreatment of DMH with CoCl₂ increased baseline blood pressure (BP), and heart rate (HR) without affecting the tail temperature. In addition, it decreased plasma vasopressin levels without affecting plasma corticosterone and oxytocin contents. When rats pretreated with CoCl₂ were exposed to RS, the RS-evoked cardiovascular were similar to those observed in vehicle-treated animals; however, because cobalt pretreatment of the DMH increased baseline BP and HR values, and the RS-evoked cardiovascular responses did not exceed those observed in vehicle-treated animals, suggesting a possible celling limit, the possibility that DMH is involved in the modulation of RS-evoked cardiovascular responses cannot be certainly excluded. Nonetheless, the pretreatment of DMH with CoCl₂ blocked the reduction in tail temperature caused by RS. The DMH pretreatment with CoCl₂ did not modify the RS-evoked increase in plasma corticosterone and oxytocin contents. In conclusion, the present data suggest the involvement of DMH in the maintenance of BP, HR, and vasopressin release under the rest conditions at the home-cage. Furthermore, indicate that DMH is an important thermoregulatory center during exposure to RS, regulating tail artery vasoconstriction.

Acute Stress Decreases but Chronic Stress Increases Myocardial Sensitivity to Ischemic Injury in Rodents

Cardiovascular disease (CVD) is the largest cause of mortality worldwide, and stress is a significant contributor to the development of CVD. The relationship between acute and chronic stress and CVD is well evidenced. Acute stress can lead to arrhythmias and ischemic injury. However, recent evidence in rodent models suggests that acute stress can decrease sensitivity to myocardial ischemia-reperfusion injury (IRI). Conversely, chronic stress is arrhythmogenic and increases sensitivity to myocardial IRI. Few studies have examined the impact of validated animal models of stress-related psychological disorders on the ischemic heart. This review examines the work that has been completed using rat models to study the effects of stress on myocardial sensitivity to ischemic injury. Utilization of animal models of stress-related psychological disorders is critical in the prevention and treatment of cardiovascular disorders in patients experiencing stress-related psychiatric conditions.

Cortisol response to stress is associated with myocardial remodeling in salmonid fishes

Cardiac disease is frequently reported in farmed animals, and stress has been implicated as a factor for myocardial dysfunction in commercial fish rearing. Cortisol is a major stress hormone in teleosts, and this hormone has adverse effects on the myocardium. Strains of rainbow trout (Oncorhynchus mykiss) selected for divergent post-stress cortisol levels [high responsive (HR) and low responsive (LR)] have been established as a comparative model to examine how fish with contrasting stress-coping styles differ in their physiological and behavioral profiles. We show that the mean cardiosomatic index (CSI) of adult HR fish was 34% higher than in LR fish, mainly because of hypertrophy of the compact myocardium. To characterize the hypertrophy as physiological or pathological, we investigated specific cardiac markers at the transcriptional level. HR hearts had higher mRNA levels of cortisol receptors (MR, GR1 and GR2), increased RCAN1 levels [suggesting enhanced pro-hypertrophic nuclear factor of activated T-cell (NFAT) signaling] and increased VEGF gene expression (reflecting increased angiogenesis). Elevated collagen (Col1a2) expression and deposition in HR hearts supported enhanced fibrosis, whereas the heart failure markers ANP and BNP were not upregulated in HR hearts. To confirm our results outside the selection model, we investigated the effect of acute confinement stress in wild-type European brown trout, Salmo trutta. A positive correlation between post-stress cortisol levels and CSI was observed, supporting an association between enhanced cortisol response and myocardial remodeling. In conclusion, post-stress cortisol production correlates with myocardial remodeling, and coincides with several indicators of heart pathology, well-known from mammalian cardiology.

Markers of autonomic tone on a standard ECG are predictive of mortality in old age

BACKGROUND

To investigate markers of autonomic tone on a standard electrocardiogram in relation to mortality in old age.

METHODS

A total of 599 inhabitants of Leiden, the Netherlands, were enrolled in a population-based follow-up study at their 85th birthday. Electrocardiograms (ECGs) were taken on entry and annually thereafter. ECGs were analysed automatically to determine four markers of autonomic tone, i.e. heart rate, the occurrence of ventricular extrasystoles and two time domain measures of heart rate variability. All participants were followed up for mortality.

RESULTS

Participants with a heart rate in the highest quartile had a 1.8-fold increased total mortality risk (95% confidence interval (CI) 1.0-3.4), but not an increased cardiovascular mortality risk. The occurrence of at least one ventricular extrasystole was related with a 2.3-fold increased total mortality risk (95% CI 1.3-3.9) and a 3.6-fold increased cardiovascular mortality (95% CI 1.6-8.2). In stratified analyses, the prognostic effect was confined to males. Both measures of heart rate variability were not related to mortality.

CONCLUSION

High heart rate and the occurrence of a ventricular extrasystole, both markers of sympathetic dominance, were predictive of mortality in old age. Two short-term measures of heart rate variability as measured on a standard 10-s ECG were not related to mortality, and hence may not reflect autonomic tone in old age.

The dorsomedial hypothalamus and the response to stress: part renaissance, part revolution

Emotional stress provokes a stereotyped pattern of autonomic and endocrine changes that is highly conserved across diverse mammalian species. Nearly 50 years ago, a specific region of the hypothalamus, the hypothalamic defense area, was defined by the discovery that electrical stimulation in this area evoked changes that replicated this pattern. Attention later shifted to the hypothalamic paraventricular nucleus (PVN) owing to (1) elucidation of its role as the final common pathway mediating activation of the hypothalamic-pituitary-adrenal (HPA) axis, a defining feature of the stress response and (2) the finding that the PVN was the principal location of hypothalamic neurons that project directly to spinal autonomic regions. Consequently, a primary role for the PVN as the hypothalamic center integrating the autonomic and endocrine response to stress was inferred. However, our findings indicate that neurons in the nearby dorsomedial hypothalamus (DMH)--a region originally included in the hypothalamic defense area--and not in the PVN play a key role in the cardiovascular changes associated with emotional or exteroceptive stress. Indeed, excitation of neurons in the parvocellular PVN and consequent recruitment of the HPA axis that occurs in exteroceptive stress is also signaled from the DMH. Thus, the DMH may represent a higher order hypothalamic center responsible for integrating autonomic, endocrine and even behavioral responses to emotional stress.

Repeated intermittent stress exacerbates myocardial ischemia-reperfusion injury

Chronic stress in humans has been correlated with increased risk for ischemic heart disease. Thus experiments were conducted to determine if repeated intermittent restraint stress increased infarct size in a rat model of myocardial ischemia-reperfusion injury. Male Sprague-Dawley rats were subjected to no stress (control) or to daily restraint stress for 1-1.5 h for 8-14 days (stress protocol A) or for 2 h daily for 11 or 12 days (stress protocol B). Myocardial ischemia-reperfusion (30-min ischemia, 3-h reperfusion) was performed in anesthetized rats. Average baseline arterial pressures were 111 +/- 4, 120 +/- 10, and 125 +/- 7 mmHg in the control, stress protocol A, and stress protocol B groups, respectively. Infarct size (%area at risk) was significantly larger in both groups of stressed rats compared with control rats (58 +/- 5, 78 +/- 2, and 79 +/- 3% in the control, stress protocol A, and stress protocol B groups, respectively). During ischemia or early reperfusion, zero of eight control, two of six protocol A stress, and two of five protocol B stress rats had at least one period of severe arrhythmia. Therefore, these results provide experimental evidence corroborating correlative studies in humans that link chronic stress with increased morbidity and mortality from ischemic heart disease.

Immobilization stress induces c-fos and c-jun immediate early genes expression in the heart

Emotional stress is considered to be one of the etiological factors in ischemic heart disease (IHD) and sudden cardiac death (SCD), mechanisms of which are poorly understood. Immediate early genes (IEGs), such as c-fos and c-jun are used as tools for detection of cellular activation. Male Wistar rats were exposed to acute immobilization (IMO). IMO stress for 30 min induced c-fos and c-jun mRNAs expression in the myocardium and the smooth muscle layer of the coronary arteries. IMO stress for 2 h also induced Fos and Jun like-immunoreactivities in the same regions. Distribution of IEG mRNAs and their protein products in the myocardium was not uniform but rather localized. These data provided histological evidence for an early cellular event in the stress response whose consequences could result in activation of tissues in the myocardium and coronary arterial smooth muscle cells which play a role in the pathophysiological changes in IHD and SCD.

Ionic mechanisms of ischemia-related ventricular arrhythmias

The aim of this review is the utmost simplification of the cellular electrophysiologic background of ischemia-related arrhythmias. In the acute and subacute phase of myocardial infarction, arrhythmias can be caused by an abnormal impulse generation, abnormal automaticity or triggered activity caused by early or delayed afterdepolarizations (EAD and DAD), or by abnormalities of impulse conduction (i.e., reentry). This paper addresses therapeutic intervention aimed at preventing the depolarization of "pathologic" slow fibers, counteracting the inward calcium (Ca) influx that takes place through the L-type channels (Ca antagonists), or hyperpolarizing the diastolic membrane action potential, increasing potassium (K) efflux (K-channel openers) in arrhythmias generated by an abnormal automaticity (ectopic tachycardias or accelerated idioventricular rhythms). If the cause enhanced impulse generation is related to triggered activity, and since both EAD and DAD are dependent on calcium currents that can appear during a delayed repolarization, the therapeutic options are to shorten the repolarization phase through K-channel openers or Ca antagonists, or to suppress the inward currents directly responsible for the afterdepolarization with Ca blockers. Magnesium seems to represent a reasonable choice, as it is able to shorten the action potential duration and to function as a Ca antagonist. Abnormalities of impulse conduction (re-entry) account for the remainder of arrhythmias that occur in the acute and subacute phase of ischemia and for most dysrhythmias that develop during the chronic phase. Reentrant circuits due to ischemia are usually Na channel-dependent. Drug choice will depend on the length of the excitable gap: in case of a short gap (ventricular fibrillation, polymorphic ventricular tachycardia, etc.), the refractory period has been identified as the most vulnerable parameter, and therefore a correct therapeutic approach will be based on drugs able to prolong the effective refractory period (K-channel blockers, such as class III antiarrhythmic drugs); on the other hand, for those arrhythmias characterized by a long excitable gap (most of the monomorphic ventricular tachycardias), the most appropriate therapeutic intervention consists of depressing ventricular excit-ability and conduction by use of sodium-channel blockers such as mexiletine and lidocaine. Compared with other class I antiarrhythmic agents, these drugs minimally affect refractoriness and exhibit a use-dependent effect and a voltage dependent action (i.e., more pronounced on the ischemic tissue because of its partial depolarization).

Mind-body medicine in primary care. Implications and applications

A growing body of research in basic and clinical science confirms that psychological states and interventions affect physiologic and pathophysiologic processes and the outcome of clinical illness. This evidence is reviewed in detail, with special attention paid to those findings that have particular relevance for primary care physicians. Specific guidelines are offered for incorporating mind-body principles and techniques into primary care practice.