Opioid peptides in response to mental stress in asymptomatic dilated cardiomyopathy

The Role of Endogenous Opioids in Cardioprotection

The opioid system involves opioid receptors (OPRs) and endogenous opioid peptides.This chapter will focus on the distribution of OPRs in the cardiovascular system, the expression pattern in the heart, the activation by opioid peptides, and the effects of OPRs activation with potential relevance in cardiovascular performance. In the heart, OPRs are co-expressed with beta adrenergic receptors (β-ARs) in the G-protein-coupled receptor (GPCR) superfamily, functionally cross-talk with β-Ars and modify catecholamine-induced effects. They are involved in cardiac contractility, energy metabolism, myocyte survival or death, vascular resistance. The effects of the opioid system in the regulation of systemic circulation at both the central and peripheral level are presented. The pathways are discussed under physiological (i.e., aging) and pathological conditions (atherosclerosis, heart failure, essential hypertension, ischemic stress). Stimulation of OPRs not only inhibits cardiac excitation-contraction coupling, but also protects the heart against hypoxic and ischemic injury. An enhanced sensitivity to opioids of endocrine organs and neuronal systems is operative in hypertensive patients. The opioid system can be pharmacologically engaged to selectively mimic these responses via cardiac and nervous signaling. The clinical opportunities for the use of cardioprotective effects of opioids require future investigations to provide more specific details of the impact on cardiac performance and electrophysiological properties.

Opioids in Cardiovascular Disease: Therapeutic Options

The World Health Organization suggests that the cardiovascular diseases (CVDs) are the major cause of mortality and account for two-thirds of the deaths all over the world. These diseases kill about 17 million people every year and 3 in every 10 deaths are due to these diseases. The past decade has seen considerable improvements in diagnosis as well as treatment of various heart diseases. Various new therapeutic targets are being identified through in-depth knowledge of the disease mechanisms which has favored the testing of new strategies leading to newer treatment options. Opioid peptides and G-protein-coupled opioid receptors (ORs) have been previously studied widely in terms of central nervous system actions in mitigating the pain and drug abuse. The OR agonism or antagonism induces cytoprotective states in the myocardium, rendering these receptors as an attractive target for protection of heart from the fatal heart diseases. The opioids can provide an extended window of protection of the heart from various diseases. Although the mechanisms may not be fully understood, they seem to play a crucial role in various CVDs such as hypertension, hyperlipidemia, ischemic heart disease myocardial ischemia, and congestive heart failure. Since these compounds are already being used in acute and chronic pain, soon these compounds might be approved for use as cardioprotective agents. The following review focuses on the new information acquired on the role of the ORs in various CVDs.

Endothelin-1 and psychosocial risk factors for cardiovascular disease: a systematic review

OBJECTIVES

Psychosocial factors (i.e., social environment and emotional factors) contribute to an increased risk of cardiovascular disease (CVD). Perturbation in a potent vasoconstrictive peptide endothelin (ET)-1 could be one of the mechanisms linking psychosocial factors to CVD. Our aim was to evaluate the literature on the relationship between plasma ET-1 and psychosocial risk factors for CVD.

METHODS

MEDLINE and PsycINFO databases were searched for articles on human studies published in peer-reviewed English-language journals through September 2012.

RESULTS

Of the 20 studies that met the inclusion criteria, 14 were experimental studies of acute psychological/mental challenges and 6 were observational studies of psychological and social factors. The inferences drawn from this review were as follows: a) laboratory-induced acute psychological/mental stress may result in exaggerated plasma ET-1 release in those with CVD and those at risk for CVD (positive studies: 5/10); b) chronic/episodic psychosocial factors may have a positive relationship to plasma ET-1 (positive studies: 3/5); and c) race (African American), sex (male), and individual differences in autonomic and hemodynamic responses to stress (parasympathetic withdrawal and elevated blood pressure responsiveness) may moderate the relationship between psychosocial factors and plasma ET-1.

CONCLUSIONS

This review indicates that psychosocial risk factors for CVD are associated with elevated plasma ET-1; however, the relatively small number of studies, methodological differences, and variable assessment tools preclude definitive conclusions about the strength of the association. Specific suggestions regarding the selection of psychosocial factors, optimization of acute challenge protocols, and standardization of methods and timing of the ET-1 measures are provided.

Effects of beta-endorphin on endothelial/monocytic endothelin-1 and nitric oxide release mediated by mu1-opioid receptors: a potential link between stress and endothelial dysfunction?

Observations have been made linking the presence of psychosocial factors associated with elevated beta-endorphin concentrations with atherosclerosis. In this study, the authors assume an important role of the stress hormone beta-endorphin in several mechanisms that contribute to a dysbalance of human endothelial and monocytic endothelin (ET)-1 and nitric oxide (NO) release, mediated by mu1-opioid receptors. ET-1 and NO release were quantified via enzyme-linked immunosorbent assay (ELISA) or fluorometrically. mu1-Opioid receptors were identified by polymerase chain reaction (PCR) after stimulation with beta-endorphin. beta-Endorphin significantly increased endothelial and monocytic ET-1 release. The effect was mediated by mu1-opioid receptors and abolished by naloxonazine, a selective mu1-opioid receptor antagonist. In contrast, NO release was decreased under the influence of beta-endorphin. mu1-Opioid receptors on human monocytes and endothelial cells mediated a beta-endorphin-induced stimulation of ET-1 release, whereas NO release was decreased. Thus, the authors hypothesize a role of beta-Endorphin in the pathogenesis of stress-induced endothelial dysfunction through peripherally circulating beta-endorphin, which may offset the balance of vasoactive mediators, leading to an unopposed vasoconstriction. The data may also provide a new concept of mu1-opioid receptor antagonists, preventing beta-endorphin-induced disorders of vascular biology.

Mental stress hemodynamic responses and myocardial ischemia: does left ventricular dysfunction alter these relationships?

OBJECTIVE

To assess if mental stress hemodynamic responses are impaired and related to mental stress (MS) ischemia in patients with left ventricular (LV) dysfunction.

BACKGROUND

Impaired LV function is an important coronary artery disease (CAD) risk factor and hemodynamic characteristics play an important role in clinical outcomes. Patients with severe LV dysfunction (SLVD) are frequently excluded from prior studies and the effects of LV dysfunction on MS hemodynamic responses are not known.

METHODS

Fifty-eight patients with CAD, consisting of 22 patients with normal LV function (ejection fraction (EF) > or =50%), 16 patients with mild-to-moderate LV dysfunction (30% < EF < 50%), and 20 patients with severe LV dysfunction (EF < or =30) underwent bicycle exercise (EX) and MS testing with 12-lead electrocardiogram and monitoring of vital signs on consecutive days in random order. Blood pressure and heart rate (HR) measurements were obtained. Ischemia was measured using single photon emission computed tomography.

RESULTS

Both MS and EX produced significant increases in all hemodynamic measurements. HR levels were higher both at rest and during MS in SLVD patients. LV groups increased similarly from rest to stress (both MS and EX) for all measurements except HR during MS, which increased more in patients with SLVD than patients with normal LV function. Hemodynamic responses to MS were not related to myocardial ischemia or heart failure symptoms.

CONCLUSIONS

HR response during MS is increased in patients with SLVD, whereas blood pressure responses are similar to those in patients with preserved LV function. Hemodynamic reactivity is unrelated to MS-induced ischemia.

Effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides from 1994 through 1998

Effects of peptides on the central nervous system are presented in two ways so as to provide a cross-listing. In the first table, the peptides are listed alphabetically. In the second table, the central nervous system effects are arranged alphabetically. No longer can there be any doubt that peptides affect the central nervous system, sometimes in several ways.