Clinical pharmacology of beta-endorphin in depression and schizophrenia

Biomarkers in the cerebrospinal fluid of patients with psychotic disorders compared to healthy controls: a systematic review and meta-analysis

Psychotic disorders are severe mental disorders with poorly understood etiology. Biomarkers in the cerebrospinal fluid (CSF) could provide etiological clues and diagnostic tools for psychosis; however, an unbiased overview of CSF alterations in individuals with psychotic disorders is lacking. The objective of this study was to summarize all quantifiable findings in CSF from individuals with psychotic disorders compared to healthy controls (HC). Studies published before January 25th, 2023 were identified searching PubMed, EMBASE, Cochrane Library, Web of Science, ClinicalTrials.gov, and PsycINFO. Screening, full-text review, data extraction, and risk of bias assessments were performed by two independent reviewers following PRISMA guidelines. Findings in patients and healthy controls were compared and summarized using random-effects analyses and assessment of publication bias, subgroup and sensitivity analyses were performed. 145 studies, covering 197 biomarkers, were included, of which 163 biomarkers have not previously been investigated in meta-analyses. All studies showed some degree of bias. 55 biomarkers measured in CSF were associated with psychosis and of these were 15 biomarkers measured in ≥2 studies. Patients showed increased levels of noradrenaline (standardized mean difference/SMD, 0.53; 95% confidence interval/CI, 0.16 to 0.90) and its metabolite 3-methoxy-4-hydroxyphenylglycol (SMD, 0.30; 95% CI: 0.05 to 0.55), the serotonin metabolite 5-hydroxyindoleacetic acid (SMD, 0.11; 95% CI: 0.01 to 0.21), the pro-inflammatory neurotransmitter kynurenic acid (SMD, 1.58; 95% CI: 0.34 to 2.81), its precursor kynurenine (SMD,0.99; 95% CI: 0.60 to 1.38), the cytokines interleukin-6 (SMD, 0.58; 95% CI: 0.39 to 0.77) and interleukin-8 (SMD, 0.43; 95% CI: 0.24 to 0.62), the endocannabinoid anandamide (SMD, 0.78; 95% CI: 0.53 to 1.02), albumin ratio (SMD, 0.40; 95% CI: 0.08 to 0.72), total protein (SMD, 0.29; 95% CI: 0.16 to 0.43), immunoglobulin ratio (SMD, 0.45; 95% CI: 0.06 to 0.85) and glucose (SMD, 0.48; 95% CI: 0.01 to 0.94). Neurotensin (SMD, -0.67; 95% CI: -0.89 to -0.46) and γ-aminobutyric acid (SMD, -0.29; 95% CI: -0.50 to -0.09) were decreased. Most biomarkers showed no significant differences, including the dopamine metabolites homovanillic acid and 3,4-dihydroxyphenylacetic acid. These findings suggest that dysregulation of the immune and adrenergic system as well as blood-brain barrier dysfunction are implicated in the pathophysiology of psychotic disorders.

Melatonin and morphine: potential beneficial effects of co-use

Morphine is a potent analgesic agent used to control acute or chronic pain. Chronic administration of morphine results in analgesic tolerance, hyperalgesia, and other side effects including dependence, addiction, respiratory depression, and constipation, which limit its clinical usage. Therefore, identifying the new analgesics with fewer side effects which could increase the effect of morphine and reduce its side effects is crucial. Melatonin, a multifunctional molecule produced in the body, is known to play an important role in pain regulation. The strong anti-inflammatory effect of melatonin is suggested to be involved in the attenuation of the pain associated with inflammation. Melatonin also increases the anti-nociceptive actions of opioids, such as morphine, and reverses their tolerance through regulating several cellular signaling pathways. In this review, published articles evaluating the effect of the co-consumption of melatonin and morphine in different conditions were investigated. Our results show that melatonin has pain-killing properties when administered alone or in combination with other anti-nociceptive drugs. Melatonin decreases morphine consumption in different pathologies. Furthermore, attenuation of morphine intake can be accompanied by reduction of morphine-associated side-effects, including physical dependence, morphine tolerance, and morphine-related hyperalgesia. Therefore, it is reasonable to believe that the combination of melatonin with morphine could reduce morphine-induced tolerance and hyperalgesia, which may result from anti-inflammatory and antioxidant properties of melatonin. Overall, we underscore that, to further ameliorate patients' life quality and control their pain in various pathological conditions, melatonin deserves to be used with morphine by anesthesiologists in clinical practice.

A Novel Paradigm for Sacubitril/Valsartan: Beta-Endorphin Elevation as a Contributor to Exercise Tolerance Improvement in Rats With Preexisting Heart Failure Induced by Pressure Overload

BACKGROUND

Simultaneous angiotensin receptor (AT1) blockade and neprilysin inhibition with the use of sacubitril/valsartan has been recently approved to treat patients with heart failure (HF). Therapeutic benefits of this therapy have been attributed to natriuretic peptide elevation and AT1 receptor blockade. However, that pharmacologic picture may not be complete. The aims of this study were to investigate the pharmacology of sacubitril/valsartan compared with sacubitril and valsartan alone and to examine their impact on peptides up-regulated by neprilysin inhibition, such as beta-endorphin.

METHODS AND RESULTS

An HF model was induced by pressure overload via constriction of the suprarenal abdominal aorta in rats. Sacubitril/valsartan (68 mg/kg), valsartan (31 mg/kg), sacubitril (31 mg/kg), or placebo was administered by daily oral gavage (starting 4 weeks after pressure overload onset and continued for 4 additional weeks; n = 8 in each group). Exercise tolerance testing was conducted using a rodent treadmill and hemodynamic assessments were conducted under anesthesia with the use of Millar left ventricular (LV) conductance technology. Pressure overload led to exercise intolerance by 4 weeks and to hypertension and LV dysfunction and remodeling by 8 weeks. Both sacubitril/valsartan and sacubitril elevated beta-endorphin levels, by 40% and 54%, respectively, and improved exercise tolerance, by 93% and 112%, whereas valsartan did not. Indices of LV dysfunction persisted with the use of sacubitril/valsartan and valsartan therapies and even deteriorated in sacubitril group.

CONCLUSIONS

When added to valsartan, sacubitril increases beta-endorphin concentrations and improves exercise tolerance. These data suggest beta-endorphin elevation as a potential mechanism of action leading to improvement in exercise tolerance that is seen with sacubitril/valsartan. This therapeutic benefit is potentially independent from LV function.

Reconsidering anhedonia in depression: lessons from translational neuroscience

Anhedonia is a core symptom of major depressive disorder (MDD), the neurobiological mechanisms of which remain poorly understood. Despite decades of speculation regarding the role of dopamine (DA) in anhedonic symptoms, empirical evidence has remained elusive, with frequent reports of contradictory findings. In the present review, we argue that this has resulted from an underspecified definition of anhedonia, which has failed to dissociate between consummatory and motivational aspects of reward behavior. Given substantial preclinical evidence that DA is involved primarily in motivational aspects of reward, we suggest that a refined definition of anhedonia that distinguishes between deficits in pleasure and motivation is essential for the purposes of identifying its neurobiological substrates. Moreover, bridging the gap between preclinical and clinical models of anhedonia may require moving away from the conceptualization of anhedonia as a steady-state, mood-like phenomena. Consequently, we introduce the term "decisional anhedonia" to address the influence of anhedonia on reward decision-making. These proposed modifications to the theoretical definition of anhedonia have implications for research, assessment and treatment of MDD.

The role of beta-endorphin in the pathophysiology of major depression

A role for beta-endorphin (beta-END) in the pathophysiology of major depressive disorder (MDD) is suggested by both animal research and studies examining clinical populations. The major etiological theories of depression include brain regions and neural systems that interact with opioid systems and beta-END. Recent preclinical data have demonstrated multiple roles for beta-END in the regulation of complex homeostatic and behavioural processes that are affected during a depressive episode. Additionally, beta-END inputs to regulatory pathways involving feeding behaviours, motivation, and specific types of motor activity have important implications in defining the biological foundations for specific depressive symptoms. Early research linking beta-END to MDD did so in the context of the hypothalamic-pituitary-adrenal (HPA) axis activity, where it was suggested that HPA axis dysregulation may account for depressive symptoms in some individuals. The primary aims of this paper are to use both preclinical and clinical research (a) to critically review data that explores potential roles for beta-END in the pathophysiology of MDD and (b) to highlight gaps in the literature that limit further development of etiological theories of depression and testable hypotheses. In addition to examining methodological and theoretical challenges of past clinical studies, we summarize studies that have investigated basal beta-END levels in MDD and that have used challenge tests to examine beta-END responses to a variety of experimental paradigms. A brief description of the synthesis, location in the CNS and behavioural pharmacology of this neuropeptide is also provided to frame this discussion. Given the lack of clinical improvement observed with currently available antidepressants in a significant proportion of depressed individuals, it is imperative that novel mechanisms be investigated for antidepressant potential. We conclude that the renewed interest in elucidating the role of beta-END in the pathophysiology of MDD must be paralleled by consensus building within the research community around the heterogeneity inherent in mood disorders, standardization of experimental protocols, improved discrimination of POMC products in analytical techniques and consistent attention paid to important confounds like age and gender.

Opioid peptide response to spinal cord stimulation in chronic critical limb ischemia

Twelve patients with chronic critical limb ischemia in whom a spinal cord stimulation (SCS) system had been implanted for at least one year had increased microvascular flow and achieved healing of trophic acral lesions. After switching off the system, the clinical improvement persisted for 10 days and the neurohormonal pattern showed high plasma values of beta-endorphin and Met-enkephalin, normal dynorphin B, endothelin-1 and catecholamines, and low nitric oxide. Met-enkephalin levels were further increased (P < 0.01) immediately after switching on the electrical stimulation again. The persistence of high plasma opioid levels after switching off the spinal cord stimulation explains the absence of subjective complaints and suggests an involvement of opioids in the regulation and improvement of the microcirculation.

beta-Endorphin modulation of pressor response to hyperventilation in hypertensive patients

After hyperventilation, systolic and diastolic blood pressure (BP) significantly decreased in 14 hypertensive patients (group 1), did not change in 9 (group 2) and increased in 8 (group 3). Basal BP, norepinephrine and dynorphin B levels were higher in group 1 than in groups 2 and 3. The decrease in BP after hyperventilation was associated with a decrease in plasma norepinephrine, Met-enkephalin and dynorphin B and an increase in beta-endorphin. Naloxone abolished the hyperventilation-induced BP and norepinephrine decreases. Our findings indicate that hyperventilation may select hypertensive patients with different sympatho-adrenergic activity and that the increase in beta-endorphin reduces BP response to hyperventilation in patients with high sympatho-adrenergic tone.

Pressor effects of endogenous opioid system during acute episodes of blood pressure increases in hypertensive patients

To investigate the involvement of endogenous opioids in acute increases in blood pressure and their functional relationship with atrial natriuretic factor and endothelin-1, we assessed plasma levels of beta-endorphin, met-enkephalin, dynorphin B, catecholamines, atrial natriuretic factor, and endothelin-1 before and after administration of the opioid antagonist naloxone hydrochloride (8 mg i.v.) in 28 hypertensive patients with a stress-induced acute increase in blood pressure. Ten patients with established mild or moderate essential hypertension and 10 normotensive subjects served as control groups. Opioids, atrial natriuretic factor, and endothelin-I were radioimmunoassayed after chromatographic preextraction; catecholamines were determined by high-performance liquid chromatography with electrochemical detection. Patients with an acute increase in blood pressure (systolic, 203.2 +/- 2.2 mm Hg; diastolic, 108.4 +/- 1.3) had plasma opioid, catecholamine, and atrial natriuretic factor levels significantly (P < .01) higher than hypertensive control patients (systolic pressure, 176.4 +/- 1.0 mm Hg; diastolic, 100.0 +/- 1.4), who had a hormonal pattern similar to that of normotensive subjects (systolic pressure, 123.2 +/- 1.5 mm Hg; diastolic, 75.0 +/- 2.0). Endothelin-1 did not differ in any group. In patients with an acute increase in blood pressure, naloxone significantly (P < .01) reduced blood pressure, heart rate, opioids, catecholamines, and atrial natriuretic factor 10 minutes after administration. Naloxone effects on blood pressure, heart rate, opioids, and catecholamines wore off within 20 minutes. In control groups, naloxone failed to modify any of the considered parameters. Our findings suggest that pressor effects of opioid peptides mediated by the autonomic nervous system during stress-induced acute episodes of blood pressure increase in hypertensive patients.

Relapse to opiate use provokes biphasic changes of blood pressure in heroin-withdrawn addicts treated with clonidine

The effect of relapse to opiate use on blood pressure and heart rate has been studied in heroin-withdrawn addicts treated with clonidine in an outpatient detoxification procedure. The daily dose of clonidine was established according to body weight and amount of heroin usually consumed at the onset of treatment. Patients who returned to heroin use were detected by increased urinary levels of opiates. Clonidine elicited significant reductions of blood pressure and heart rate reaching a plateau in the second day of treatment. Heroin consumption was found to provoke a further decrease of both systolic and diastolic pressure when the time interval between the relapse and the cardiovascular determinations was about 3 h as estimated by the patients. At longer intervals (16 h) this effect was reversed and both the hypotensive and the bradycardiac actions of clonidine seemed to be impaired. The possible impact of endogenous opioids and alpha-2 receptor sensitivity on these biphasic alterations is discussed.

Acupuncture relief of chronic pain syndrome correlates with increased plasma met-enkephalin concentrations

In twenty patients with chronic pain syndrome, acupuncture treatment resulted in significant improvement of both pain and psychiatric symptoms and higher plasma concentrations of metenkephalin. Plasma beta-endorphin concentrations were unchanged. The degree of symptom relief was correlated with the increase in plasma met-enkephalin.