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?

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.

Understanding the Connection between Gut Homeostasis and Psychological Stress

Long-term exposure to adverse life events that provoke acute or chronic psychological stress (hereinafter "stress") can negatively affect physical health and even increase susceptibility to psychological illnesses, such as anxiety and depression. As a part of the hypothalamic-pituitary-adrenal axis, corticotropin-releasing factor (CRF) released from the hypothalamus is primarily responsible for the stress response. Typically, CRF disrupts the gastrointestinal system and leads to gut microbiota dysbiosis, thereby increasing risk of functional gastrointestinal diseases, such as irritable bowel syndrome. Furthermore, CRF increases oxidative damage to the colon and triggers immune responses involving mast cells, neutrophils, and monocytes. CRF even affects the differentiation of intestinal stem cells (ISCs), causing enterochromaffin cells to secrete excessive amounts of 5-hydroxytryptamine (5-HT). Therefore, stress is often accompanied by damage to the intestinal epithelial barrier function, followed by increased intestinal permeability and bacterial translocation. There are multi-network interactions between the gut microbiota and stress, and gut microbiota may relieve the effects of stress on the body. Dietary intake of probiotics can provide energy for ISCs through glycolysis, thereby alleviating the disruption to homeostasis caused by stress, and it significantly bolsters the intestinal barrier, alleviates intestinal inflammation, and maintains endocrine homeostasis. Gut microbiota also directly affect the synthesis of hormones and neurotransmitters, such as CRF, 5-HT, dopamine, and norepinephrine. Moreover, the Mediterranean diet enhances the stress resistance to some extent by regulating the intestinal flora. This article reviews recent research on how stress damages the gut and microbiota, how the gut microbiota can improve gut health by modulating injury due to stress, and how the diet relieves stress injury by interfering with intestinal microflora. This review gives insight into the potential role of the gut and its microbiota in relieving the effects of stress via the gut-brain axis.

A pathway phenotype linking metabolic, immune, oxidative, and opioid pathways with comorbid depression, atherosclerosis, and unstable angina

BACKGROUND

There is strong comorbidity between atherosclerosis (ATS) and depression which is attributed to increased atherogenicity, insulin resistance (IR), and immune and oxidative stress.

AIM OF THE STUDY

To examine the role of the above pathways and mu-opioid receptor (MOR), β-endorphin levels, zinc, copper, vitamin D3, calcium, and magnesium in depression due to ATS/unstable angina (UA).

METHODS

Biomarkers were assayed in 58 controls and 120 ATS patients divided into those with moderate and severe depression according to the Beck Depression Inventory-II (BDI-II) scores >19 and >29, respectively.

RESULTS

Neural network and logistic regression models showed that severe depression due to ATS/UA was best predicted by interleukin-6 (IL-6), UA, MOR, zinc, β-endorphin, calcium and magnesium, and that moderate depression was associated with IL-6, zinc, MOR, β-endorphin, UA, atherogenicity, IR, and calcium. Neural networks yielded a significant discrimination of severe and moderate depression with an area under the receiver operating curves of 0.831 and 0.931, respectively. Using Partial Least Squares path analysis, we found that 66.2% of the variance in a latent vector extracted from ATS/UA clinical features, and the BDI-II scores, atherogenicity, and IR could be explained by the regression on IL-6, IL-10, zinc, copper, calcium, MOR, and age. The BDI-II scores increased from controls to ATS to UA class III to UA class IV.

CONCLUSIONS

Immune activation, the endogenous opioid system, antioxidants, trace elements, and macrominerals modulate a common core shared by increased depressive symptoms, ATS, UA, atherogenicity, and IR.

Trace element, immune and opioid biomarkers of unstable angina, increased atherogenicity and insulin resistance: Results of machine learning

BACKGROUND

Aberrations in endothelial cells, immune and oxidative pathways are associated with atherosclerosis (ATS) and unstable angina (UA). The role of trace elements, minerals, and the endogenous opioid system (EOS) in UA are less well established.

METHODS

We measured lipid, insulin resistance (IR), and immune, trace element (copper and zinc), mineral (magnesium, calcium), EOS (β-endorphin and mu-opioid receptor (MOR)) and antioxidant (vitamin D3) biomarkers in patients with ATS (n = 60) and UA (n = 60) and healthy controls (n = 58).

RESULTS

ATS patients showed increased atherogenic and IR indices, IL-6, IL-10, β-endorphin, copper and magnesium, and lower zinc than healthy controls. Logistic regression showed that UA was significantly discriminated from ATS without UA with an accuracy of 85.5 % using calcium, IL-10, β-endorphin, MOR, triglycerides, IR (all positively), and copper and vitamin D3 (inversely). Neural networks showed that UA was discriminated from ATS without UA with an area under the ROC curve of 0.942 using MOR, β-endorphin, calcium, insulin resistance, vitamin D3 and copper as input variables. We found that 50.0 % of the variance in IR was explained by the regression on copper, IL-10, IL-6 (all positively), and zinc (inversely), while 32.9 % of the variance in the atherogenic index of plasma was explained by copper, IL-10 (both positively), and magnesium (inversely).

CONCLUSION

UA is not only mediated by insulin resistance, atherogenicity, and immune disorders, but also by aberrations in the endogenous opioid system and trace elements as well as lowered antioxidant levels. Copper appears to play a key role in IR and atherogenicity.

β-Endorphin Mediates the Development and Instability of Atherosclerotic Plaques

β-Endorphin, an endogenous opioid peptide, and its μ-opioid receptor are expressed in brain, liver, and peripheral tissues. β-Endorphin induces endothelial dysfunction and is related to insulin resistance. We clarified the effects of β-endorphin on atherosclerosis. We assessed the effects of β-endorphin on the inflammatory response and monocyte adhesion in human umbilical vein endothelial cells (HUVECs), foam cell formation, and the inflammatory phenotype in THP-1 monocyte-derived macrophages, and migration and proliferation of human aortic smooth muscle cells (HASMCs) in vitro. We also assessed the effects of β-endorphin on aortic lesions in Apoe ^-/- mice in vivo. The μ-opioid receptor (OPRM1) was expressed in THP-1 monocytes, macrophages, HASMCs, HUVECs, and human aortic endothelial cells. β-Endorphin significantly increased THP-1 monocyte adhesion to HUVECs and induced upregulation of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin via nuclear factor-κB (NF-κB) and p38 phosphorylation in HUVECs. β-Endorphin significantly increased HUVEC proliferation and enhanced oxidized low-density lipoprotein-induced foam cell formation in macrophages. β-Endorphin also significantly shifted the macrophage phenotype to proinflammatory M1 rather than anti-inflammatory M2 via NF-κB phosphorylation during monocyte-macrophage differentiation and increased migration and apoptosis in association with c-jun-N-terminal kinase, p38, and NF-κB phosphorylation in HASMCs. Chronic β-endorphin infusion into Apoe ^-/- mice significantly aggravated the development of aortic atherosclerotic lesions, with an increase in vascular inflammation and the intraplaque macrophage/smooth muscle cell ratio, an index of plaque instability. Our study provides the first evidence that β-endorphin contributes to the acceleration of the progression and instability of atheromatous plaques. Thus, μ-opioid receptor antagonists may be useful for the prevention and treatment of atherosclerosis.

Out-of-Hospital Cardiac Arrests During the Japanese Professional Baseball Championship Series

Because the Japan Professional Baseball Championship Series (Japan Series) is a stressful sports event, it is possible that watching Japan Series matches may increase the risk of cardiovascular events. Therefore, we investigated the potential association between the Japan Series and the incidence of out-of-hospital cardiac arrest (OHCA) events. National registry data for all cases of OHCA between 2005 and 2014 from 47 prefectures of Japan were obtained. We used a time-stratified case-crossover design with a conditional Poisson regression model to compare OHCA events during the Japan Series with those events that occurred during the periods except for dates of the Japan Series. The estimated associations for each prefecture were pooled at the nationwide level using a random-effects meta-analysis. In total, 666,020 OHCAs of presumed cardiac origin were reported during the study period. On days of Japan Series matches, the pooled relative risk of OHCA was 1.033 (95% confidence interval 1.012 to 1.055; p = 0.002; I² = 3.5%, P for heterogeneity = 0.405). Stratified analyses by gender revealed that the substantial increase in OHCA during the events was observed for men, whereas we found no significant increase for women. We also found a considerable rise in OHCA among patients aged ≥65 years; however, there was no significant evidence of increased risk in those aged 18 to 64 years. In conclusion, stressful baseball match is associated with an increased risk of OHCA. Prevention measures for severe emotional stress-related OHCA should be implemented, particularly for elderly men.

Activation of adult rat CNS endothelial cells by opioid-induced toll-like receptor 4 (TLR4) signaling induces proinflammatory, biochemical, morphological, and behavioral sequelae

CNS immune signaling contributes to deleterious opioid effects including hyperalgesia, tolerance, reward, and dependence/withdrawal. Such effects are mediated by opioid signaling at toll-like receptor 4 (TLR4), presumptively of glial origin. Whether CNS endothelial cells express TLR4 is controversial. If so, they would be well positioned for activation by blood-borne opioids, contributing to opioid-induced pro-inflammatory responses. These studies examined adult primary rat CNS endothelial cell responses to (-)-morphine or its mu opioid receptor (MOR)-inactive metabolite morphine-3-glucuronide (M3G), both known TLR4 agonists. We demonstrate that adult rat CNS endothelial cells express functional TLR4. M3G activated nuclear factor kappaB (NF-κB), increased tumor necrosis factor-α (TNFα) and cyclooxygenase-2 (COX2) mRNAs, and released prostaglandin E2 (PGE2) from these cells. (-)-Morphine-induced upregulation of TNFα mRNA and PGE2 release were unmasked by pre-treatment with nalmefene, a MOR antagonist without TLR4 activity (unlike CTAP, shown to have both MOR- and TLR4-activity), suggestive of an interplay between MOR and TLR4 co-activation by (-)-morphine. In support, MOR-dependent Protein Kinase A (PKA) opposed TLR4 signaling, as PKA inhibition (H-89) also unmasked (-)-morphine-induced TNFα and COX2 mRNA upregulation. Intrathecal injection of CNS endothelial cells, stimulated in vitro with M3G, produced TLR4-dependent tactile allodynia. Further, cortical suffusion with M3G in vivo induced TLR4-dependent vasodilation. Finally, endothelial cell TLR4 activation by lipopolysaccharide and/or M3G was blocked by the glial inhibitors AV1013 and propentofylline, demonstrating endothelial cells as a new target of such drugs. These data indicate that (-)-morphine and M3G can activate CNS endothelial cells via TLR4, inducing proinflammatory, biochemical, morphological, and behavioral sequelae. CNS endothelial cells may have previously unanticipated roles in opioid-induced effects, in phenomena blocked by presumptive glial inhibitors, as well as TLR4-mediated phenomena more broadly.

Drug abuse and the neurovascular unit

Drug abuse continues to create a major international epidemic affecting society. A great majority of past drug abuse research has focused mostly on the mechanisms of addiction and the specific effects of substance use disorders on brain circuits and pathways that modulate reward, motivation, craving, and decision making. Few studies have focused on the neurobiology of acute and chronic substance abuse as it relates to the neurovascular unit (brain endothelial cell, neuron, astrocyte, microglia, and pericyte). Increasing research indicates that all cellular components of the neurovascular unit play a pivotal role in both the process of addiction and how drug abuse affects the brain response to diseases. This review will focus on the specific effects of opioids, amphetamines, alcohol, and nicotine on the neurovascular unit and its role in addiction and adaption to brain diseases. Elucidation of the role of the neurovascular unit on the neurobiology associated with drug addiction will help to facilitate the development of better therapeutic approaches for drug-dependent individuals.

Effects of serum lipid smoothness on the progression and vulnerability of atherosclerotic plaques in rabbits

Objective

We aimed to explore the effects of lipid smoothness on the progression and vulnerability of atherosclerotic plaques.

Approach

24 rabbits were divided into three groups randomly. Group 1 was given standard chow diet; group 2 was fed with cholesterol-rich diet; for group 3, subjects were planned to take cholesterol-rich diet at the first phase for 12 weeks and during the second phase, low-fat and cholesterol-rich diet was then applied alternately every three weeks till the end of the experiment. Lipid profiles, inflammatory factors, endothelium functions, pathological and histological changes were examined. Expressions of matrix metalloproteinase-9 and lectin-like oxidized LDL receptor-1 were measured by immunohistochemical staining.

Results

According to data collected during the whole experiment, lipid smoothness index of group 3 was the lowest. Compared with group 2, statistics of the group 3 indicated that: the development of plaques progressed faster; the plaque area and plaque thickness (53.53[22.6]% vs 33.90[24.91]% , 800.38[98.25]µm vs 675.00[109.67]µm) were higher while the fibrous cap thickness (103.50[45.66]µm vs 295.83[97.90]µm) was lower; hs-CRP (0.53[0.07]mg/dL vs 0.45[0.06]mg/dL), interleukin-18 (186.01[8.41]ng/L vs 158.08[2.37]ng/L), OX-LDL (177.15[5.93]µg/L vs 139.57[2.35] µg/L) and endothelin-1 (164.66[9.54]ng/L vs 131.52[4.39]ng/L) were higher while nitric-oxide (22.41[1.69]µmol/L vs 27.23[1.36]µmol/L) was lower; expressions of matrix metalloproteinase-9 (IOD: 37375.87[5634.52] vs 20956.57[4616.93]) and lectin-like oxidized LDL receptor-1 (IOD: 45213.04[16653.81] vs 21921.68[6142.32]) were higher.

Conclusions

Lipids fluctuation could accelerate the progression and vulnerability of atherosclerotic plaques through worsening arterial endothelium dysfunction and inflammatory reactions.

How mental stress affects endothelial function

Mental stress is an important factor contributing to recognized mechanisms underlying cardiovascular events. Among these, stress-related endothelial dysfunction is an early risk factor that predicts future development of severe cardiovascular disorders. Acute mental stress by a variety of tests impairs endothelial function in humans, although the opposite results have been reported by some investigators. Chronic stress always deteriorates endothelial function in humans and experimental animals. Stress hormones, such as glucocorticoids and pro-inflammatory cytokines, and endothelin-1 liberated in response to mental stress participate in endothelial dysfunction possibly via downregulation of endothelial nitric oxide synthase (eNOS) expression, eNOS inactivation, decreased nitric oxide (NO) actions, and increased NO degradation, together with vasoconstriction counteracting against NO-induced vasodilatation. Catecholamines do not directly affect endothelial function but impair its function when blood pressure elevation by the amines is sustained. Endogenous opioids favorably affect endothelial function, which counteract deteriorating effects of other stress hormones and mediators. Inhibition of cortisol and endothelin-1 production, prevention of pro-inflammatory mediator accumulation, hypnotics, mirthful laughter, humor orientation, and lifestyle modification would contribute to the prevention and treatment for stress-related endothelial dysfunction and future serious cardiovascular disease.

Modification of endothelial biology by acute and chronic stress hormones

OBJECTIVE

An increasing number of studies have examined the role of emotional stress and coronary heart disease; the underlying pathophysiology is still poorly understood. The present study was designed to evaluate the relationship between acute (epi- and norepinephrine) and chronic stress hormones (dexamethasone, beta-endorphin, corticotropin releasing hormone) and endothelial dysfunction.

METHODS

Human microvascular endothelial cells were incubated with stress hormones for 6 and 24 h. ET-1 release and ADMA were quantified via ELISA, NO release by using cell permeable 4.5-diaminofluorescein diacetate (DAF2-DA), oxidative stress fluometrically by the ROS-sensitive carboxy-H2-DCFDA method, mitochondrial metabolic activity by using the colorimetric assay WST-1, ET-1 receptor type A (ET(A)R) protein expression by Western blot, and cell proliferation activity was assessed by the colorimetric assay BrdU.

RESULTS

With respect to analysed acute and chronic stress hormones, ET-1 release was significantly increased. Likewise, protein expression was enhanced after long term incubation (24 h) with norepinephrine and dexamethasone. In contrast, endothelial NO-levels were only influenced by short term stimulation of dexamethasone (upregulation of NO release) and norepinephrine (downregulation of NO release), whereas modified NO concentration mimics altered mitochondrial metabolic activity. Unexpectedly, both oxidative stress and cell proliferation were not modified by stress hormones.

CONCLUSION

Results suggest that acute and chronic stress hormones induce a significant ET-1 release whereas NO release remained mainly unchanged. The imbalance of pro- and antiatherosclerotic factors may play a pivotal role in the initiation of stress-related endothelial dysfunction up to myocardial infarction.

Chronic discrimination predicts higher circulating levels of E-selectin in a national sample: the MIDUS study

Chronic discrimination in both minority and non-minority populations is linked to adverse health outcomes, including increased risk of cardiovascular disease and increased mortality, but the biological processes through which discrimination affects health are unclear. The current study tested the hypothesis that discrimination in a sample of Caucasians would predict elevated serum levels of E-selectin, an indication of endothelial dysfunction which itself is associated with atherosclerosis and cardiovascular disease risk. Participants (N=804) in the biomarker sample from the Survey of Midlife in the United States (MIDUS) provided information about experiences of both major and everyday discrimination at two times separated by a 9-10 year interval. The discrimination measures were designed to assess perceived unfair treatment (e.g. being fired unfairly) independently of the perceived reasons for the unfair treatment (e.g. race, gender). Serum E-selectin was measured at the second wave of data collection. Women reported significantly more instances of major (P<0.05) and everyday P<0.001) discrimination than men. Analyses of Covariance (ANCOVA) showed that both greater lifetime exposure to major discrimination (P<0.05) and chronic exposure to everyday discrimination (P<0.05) predicted higher circulating levels of E-selectin, but only in men. These associations remained statistically significant after adjustments for potential confounding variables, including age, race, socioeconomic status, health status, and health behavior. These results highlight a potential biological mechanism by which exposure to unfair treatment may be related to health, particularly cardiovascular function. Moreover, they add to a growing literature suggesting that unfair treatment in general may predict adverse health outcomes.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Cardiovascular events during World Cup soccer

BACKGROUND

The Fédération Internationale de Football Association (FIFA) World Cup, held in Germany from June 9 to July 9, 2006, provided an opportunity to examine the relation between emotional stress and the incidence of cardiovascular events.

METHODS

Cardiovascular events occurring in patients in the greater Munich area were prospectively assessed by emergency physicians during the World Cup. We compared those events with events that occurred during the control period: May 1 to June 8 and July 10 to July 31, 2006, and May 1 to July 31 in 2003 and 2005.

RESULTS

Acute cardiovascular events were assessed in 4279 patients. On days of matches involving the German team, the incidence of cardiac emergencies was 2.66 times that during the control period (95% confidence interval [CI], 2.33 to 3.04; P<0.001); for men, the incidence was 3.26 times that during the control period (95% CI, 2.78 to 3.84; P<0.001), and for women, it was 1.82 times that during the control period (95% CI, 1.44 to 2.31; P<0.001). Among patients with coronary events on days when the German team played, the proportion with known coronary heart disease was 47.0%, as compared with 29.1% of patients with events during the control period. On those days, the highest average incidence of events was observed during the first 2 hours after the beginning of each match. A subanalysis of serious events during that period, as compared with the control period, showed an increase in the incidence of myocardial infarction with ST-segment elevation by a factor of 2.49 (95% CI, 1.47 to 4.23), of myocardial infarction without ST-segment elevation or unstable angina by a factor of 2.61 (95% CI, 2.22 to 3.08), and of cardiac arrhythmia causing major symptoms by a factor of 3.07 (95% CI, 2.32 to 4.06) (P<0.001 for all comparisons).

CONCLUSIONS

Viewing a stressful soccer match more than doubles the risk of an acute cardiovascular event. In view of this excess risk, particularly in men with known coronary heart disease, preventive measures are urgently needed.