Chronic Naltrexone Therapy Is Associated with Improved Cardiac Function in Volume Overloaded Rats

The activated caveolin-3/μ-opioid receptor complex drives morphine-induced rescue therapy in failing hearts

BACKGROUND AND PURPOSE

Opioid analgesics can alleviate ischaemia/reperfusion (I/R) injury in chronic heart failure. However, the underlying mechanisms and targets remain unknown. Here, we investigate if caveolin-3 (Cav3) interacts with μ opioid receptors and if Cav3-μ receptor interactions play a role in morphine-induced cardioprotection in failing hearts.

EXPERIMENTAL APPROACH

Cav3 and μ receptor proteins in human and rat heart tissue were determined by western blot, immunofluorescence and co-immunoprecipitation. Methyl-β-cyclodextrin (MβCD), a destroyer of caveolae, and AAV-Cav3 shRNA were used to reduce Cav3 expression in failing rat hearts. CTOP, a specific μ antagonist, was administrated before morphine preconditioning in perfused failing heart models of myocardial I/R injury.

KEY RESULTS

Levels of Cav3 and μ receptor proteins were significantly higher in human and rat myocardial tissues with heart failure than in control tissues. Cav3 and μ receptor expression levels were positively correlated with disease severity. The signal of the cardiac Cav3 protein was colocalized with μ receptor in both the human and rat heart sections. Disruption of caveolae in the failing heart by either MβCD or AAV-Cav3 shRNA significantly inhibits morphine-induced phosphorylation of ERK1/2 and cardioprotection. Administration of CTOP substantially reduced Cav3 expression and morphine-induced cardioprotective effect in heart failure.

CONCLUSION AND IMPLICATIONS

Our data suggest that up-regulation of the Cav3/μ receptor complex is critical for morphine protection of the failing heart against I/R injury by regulating the ERK1/2 pathway. The activated Cav3/μ receptor complex is an understudied therapeutic target for opioid treatment of heart failure and ischaemic insult.

Blood pressure response to extended-release naltrexone in heroin and prescription opioid users and its implications for cardiovascular morbidity

BACKGROUND

Consuming opioid agonists is a risk factor for cardiovascular disease particularly in intravenous heroin users. The monthly injectable extended-release opioid antagonist, naltrexone (XR-NTX) is an effective treatment for opioid use disorder. The impact of opioid receptor blockade through XR-NTX on blood pressure, a critical risk factor for cardiovascular morbidity, has not yet been characterized.

METHODS

The study evaluated the change in blood pressure during XR-NTX treatment among 14 patients who predominately used intravenous heroin and 24 patients who used prescription oral opioids, all with opioid use disorder. Blood pressure was measured in each patient immediately before the first XR-NTX injection and ∼two weeks after the first injection. The change in diastolic and systolic pressure was compared between the heroin users and the prescription opioids users using analysis of variance.

RESULTS

XR-NTX treatment was associated with significant decreases in diastolic blood pressure in the heroin group, but not in the prescription opioids group. Systolic blood pressure values in the heroin users showed a decline at trend level only.

CONCLUSIONS

Further research is warranted to replicate our findings and to determine whether XR-NTX effect is relatively specific to blood pressure or generalizes to other components of metabolic syndrome. Distinguishing between heroin and prescription opioid users could shed light on the unique clinical and pharmacological profiles of opioid drugs, particularly regarding their cardiovascular safety. This information can be useful in developing personalized therapeutic strategies based on the route of opioid administration.

Influence of a chronic beta-blocker therapy on perioperative opioid consumption - a post hoc secondary analysis

BACKGROUND

Beta-blocker (BB) therapy plays a central role in the treatment of cardiovascular diseases. An increasing number of patients with cardiovascular diseases undergoe noncardiac surgery, where opioids are an integral part of the anesthesiological management. There is evidence to suggest that short-term intravenous BB therapy may influence perioperative opioid requirements due to an assumed cross-talk between G-protein coupled beta-adrenergic and opioid receptors. Whether chronic BB therapy could also have an influence on perioperative opioid requirements is unclear.

METHODS

A post hoc analysis of prospectively collected data from a multicenter observational (BioCog) study was performed. Inclusion criteria consisted of elderly patients (≥ 65 years) undergoing elective noncardiac surgery as well as total intravenous general anesthesia without the use of regional anesthesia and duration of anesthesia ≥ 60 min. Two groups were defined: patients with and without BB in their regular preopreative medication. The administered opioids were converted to their respective morphine equivalent doses. Multiple regression analysis was performed using the morphine-index to identify independent predictors.

RESULTS

A total of 747 patients were included in the BioCog study in the study center Berlin. 106 patients fulfilled the inclusion criteria. Of these, 37 were on chronic BB. The latter were preoperatively significantly more likely to have arterial hypertension (94.6%), chronic renal failure (27%) and hyperlipoproteinemia (51.4%) compared to patients without BB. Both groups did not differ in terms of cumulative perioperative morphine equivalent dose (230.9 (BB group) vs. 214.8 mg (Non-BB group)). Predictive factors for increased morphine-index were older age, male sex, longer duration of anesthesia and surgery of the trunk. In a model with logarithmised morphine index, only gender (female) and duration of anesthesia remained predictive factors.

CONCLUSIONS

Chronic BB therapy was not associated with a reduced perioperative opioid consumption.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov ( NCT02265263 ) on the 15.10.2014 with the principal investigator being Univ.-Prof. Dr. med. Claudia Spies.

Prenatal Morphine Exposure Increases Cardiovascular Disease Risk and Programs Neurogenic Hypertension in the Adult Offspring

BACKGROUND

The opioid overdose and opioid use disorder epidemics are concomitant with increased metabolic and CVD risk. Although opioid use disorder causes adverse pregnancy outcomes, the offspring's cardiovascular health is understudied. We hypothesized that offspring exposed to in utero morphine exposure (IUME) would show increased CVD risk factors and endogenous opioid system dysregulation.

METHODS

Sprague Dawley dams were treated with saline (vehicle, n=10) or escalating doses of morphine (5-20 mg/kg per day, SC, n=10) during gestation. Cardiovascular and metabolic parameters were assessed in adult offspring.

RESULTS

Litter size and pups' birth weight were not different in response to IUME. Female and male IUME offspring showed reduced body length at birth (P<0.05) and body weight from weeks 1 to 3 of life (P<0.05), followed by a catch-up growth effect. By week 16, female and male IUME rats showed reduced tibia length (P<0.05) and fat mass. IUME increases the mean arterial pressure and the depressor response to mecamylamine (5 mg/kg per day, IP) induced by IUME were abolished by a chronic treatment with an alpha-adrenergic receptor blocker (prazosin; 1 mg/kg per day, IP). Although circulating levels of angiotensin peptides were similar between groups, IUME exacerbated maximal ex vivo Ang (angiotensin) II-induced vasoconstriction (P<0.05) and induced endothelial dysfunction in a sex-specific manner (P<0.05). Proenkephalin, an endogenous opioid peptide that lowers blood pressure and sympathetic-mediated vasoconstriction, showed reduced mRNA expression in the heart, aorta, and kidneys from morphine versus vehicle group (P<0.05).

CONCLUSIONS

Among the effects of IUME, neurogenic hypertension, vascular dysfunction, and metabolic dysfunction could be associated with the dysregulation of the endogenous opioid system.

Endogenous opiates and behavior: 2021

This paper is the forty-fourth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2021 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonizts and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Naltrexone-Induced Cardiac Function Improvement is Associated With an Attenuated Inflammatory Response and Lipid Perioxidation in Volume Overloaded Rats

In previous studies, upregulation of myocardial opioid receptors as well as the precursors of their endogenous ligands were detected in the failing heart due to chronic volume overload. Moreover, opioid receptor blockade by naltrexone improved left ventricular function. In parallel, inflammatory processes through cytokines have been confirmed to play an important role in the pathogenesis of different forms of heart failure. Thus, the present study examined the systemic and myocardial inflammatory response to chronic volume overload and its modulation by chronic naltrexone therapy. Chronic volume overload was induced in male Wistar rats by applying an infrarenal aortocaval fistula (ACF) for 28 days during which the selective opioid receptor antagonist naltrexone (n = 6) or vehicle (n = 6) were administered via a subcutaneously implanted Alzet minipump. The ultrastructural, morphometric and hemodynamic characterization of ACF animals were performed using an intraventricular conductance catheter in vivo and electron microscopy in vitro. Co-localization of mu-, delta- and kappa-opioid receptor subtypes (MOR, DOR, and KOR respectively) with the voltage gated L-type Ca2+ channel (Cav1.2), the ryanodine receptor (RyR), and mitochondria in cardiomyocytes as well as IL-6, IL-12, TNF-alpha, and Malondialdehyde (MDA) were determined using double immunofluorescence confocal microscopy, RT-PCR and ELISA, respectively. In rat left ventricular myocardium, three opioid receptor subtypes MOR, DOR, and KOR colocalized with Cav1.2, RyR and mitochondria suggesting a modulatory role of the excitation-contraction coupling. In rats with ACF-induced volume overload, signs of heart failure and myocardial ultrastructural damage, chronic naltrexone therapy improved cardiac function and reversed the systemic and myocardial inflammatory cytokine expression as well as lipid peroxidation. In conclusion, antagonism of the cardiodepressive effects of the myocardial opioid system does not only improve left ventricular function but also blunts the inflammatory response and lipid peroxidation.

Naltrexone alters cardiovascular function following acute forced swimming in mice

Purpose

Naltrexone (NTX) is an opioid antagonist that can reverse the physiological effects of opioid receptors when bound. Opioid receptors have been found to play a role in cardiovascular (CV) function, and thus, binding of NTX may alter CV activity at rest and in response to acute and chronic exercise (EX). We hypothesized that opioid receptor blockade will alter the typical CV responses following acute EX.

Methods

We assessed the effects of opioid receptor blockade on CV function via echocardiography in mice following an acute bout of forced swimming (FSw), a model of rodent EX. We administered opioid receptor antagonist, NTX, or saline in mice before FSw and in the absence of an FSw perturbation. Furthermore, we assessed how NTX can influence maximal EX capacity on a rodent treadmill.

Results

Our data shows that NTX administration does not decrease maximal EX capacity in mice (P > 0.05). However, NTX attenuated cardiac output following FSw (FSw = 52.5 ± 2.5 ml/min vs. FSw + NTX = 32.7 ± 5.2 ml/min; P < 0.05) when compared with saline control (33.5 ± 3.8 ml/min). Further, the administration of NTX in the non-EX condition significantly (P < 0.05) reduced ejection fraction.

Conclusion

These data suggest that normal opioid receptor activation is necessary for typical CV function following FSw.