Enkephalins and the Opioid System of the Heart

A common gene signature of the right ventricle in failing rat and human hearts

The molecular mechanisms of progressive right heart failure are incompletely understood. In this study, we systematically examined transcriptomic changes occurring over months in isolated cardiomyocytes or whole heart tissues from failing right and left ventricles in rat models of pulmonary artery banding (PAB) or aortic banding (AOB). Detailed bioinformatics analyses resulted in the identification of gene signature, protein and transcription factor networks specific to ventricles and compensated or decompensated disease states. Proteomic and RNA-FISH analyses confirmed PAB-mediated regulation of key genes and revealed spatially heterogeneous mRNA expression in the heart. Intersection of rat PAB-specific gene sets with transcriptome datasets from human patients with chronic thromboembolic pulmonary hypertension (CTEPH) led to the identification of more than 50 genes whose expression levels correlated with the severity of right heart disease, including multiple matrix-regulating and secreted factors. These data define a conserved, differentially regulated genetic network associated with right heart failure in rats and humans.

Opioids-Induced Long QT Syndrome: A Challenge to Cardiac Health

The challenge posed by opioid overdose has become a significant concern for health systems due to the complexities associated with drug prohibition, widespread clinical use, and potential abuse. In response, healthcare professionals have primarily concentrated on mitigating the hallucinogenic and respiratory depressant consequences of opioid overdose to minimize associated risks. However, it is crucial to acknowledge that most opioids possess the capacity to prolong the QT interval, particularly in cases of overdose, thereby potentially resulting in severe ventricular arrhythmias and even sudden death if timely intervention is not implemented. Consequently, alongside addressing the typical adverse effects of opioids, it is imperative to consider their cardiotoxicity. To enhance comprehension of the correlation between opioids and arrhythmias, identify potential targets for prompt intervention, and mitigate the hazards associated with clinical utilization, an exploration of the interaction between drugs and ion channels, as well as their underlying mechanisms, becomes indispensable. This review primarily concentrates on elucidating the impact of opioid drugs on diverse ion channels, investigating recent advancements in this domain, and attaining a deeper understanding of the mechanisms underlying the prolongation of the QT interval by opioid drugs, along with potential interventions.

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.

Neprilysin Inhibitors in Heart Failure: The Science, Mechanism of Action, Clinical Studies, and Unanswered Questions

This article provides a contemporary review and a new perspective on the role of neprilysin inhibition in heart failure (HF) in the context of recent clinical trials and addresses potential mechanisms and unanswered questions in certain HF patient populations. Neprilysin is an endopeptidase that cleaves a variety of peptides such as natriuretic peptides, bradykinin, adrenomedullin, substance P, angiotensin I and II, and endothelin. It has a broad role in cardiovascular, renal, pulmonary, gastrointestinal, endocrine, and neurologic functions. The combined angiotensin receptor and neprilysin inhibitor (ARNi) has been developed with an intent to increase vasodilatory natriuretic peptides and prevent counterregulatory activation of the angiotensin system. ARNi therapy is very effective in reducing the risks of death and hospitalization for HF in patients with HF and New York Heart Association functional class II to III symptoms, but studies failed to show any benefits with ARNi when compared with angiotensin-converting enzyme inhibitors or angiotensin receptor blocker in patients with advanced HF with reduced ejection fraction or in patients following myocardial infarction with left ventricular dysfunction but without HF. These raise the questions about whether the enzymatic breakdown of natriuretic peptides may not be a very effective solution in advanced HF patients when there is downstream blunting of the response to natriuretic peptides or among post-myocardial infarction patients in the absence of HF when there may not be a need for increased natriuretic peptide availability. Furthermore, there is a need for additional studies to determine the long-term effects of ARNi on albuminuria, obesity, glycemic control and lipid profile, blood pressure, and cognitive function in patients with HF.

Proenkephalin and the risk of new-onset heart failure: data from prevention of renal and vascular end-stage disease

Background

Enkephalins of the opioid system exert several cardiorenal effects. Proenkephalin (PENK), a stable surrogate, is associated with heart failure (HF) development after myocardial infarction and worse cardiorenal function and prognosis in patients with HF. The association between plasma PENK concentrations and new‐onset HF in the general population remains to be established.

Hypothesis

We hypothesized that plasma PENK concentrations are associated with new‐onset HF in the general population.

Methods

We included 6677 participants from the prevention of renal and vascular end‐stage disease study and investigated determinants of PENK concentrations and their association with new‐onset HF (both reduced [HFrEF] and preserved ejection fraction [HFpEF]).

Results

Median PENK concentrations were 52.7 (45.1–61.9) pmol/L. Higher PENK concentrations were associated with poorer renal function and higher NT‐proBNP concentrations. The main determinants of higher PENK concentrations were lower estimated glomerular filtration rate (eGFR), lower urinary creatinine excretion, and lower body mass index (all p < .001). After a median 8.3 (7.8–8.8) years follow‐up, 221 participants developed HF; 127 HFrEF and 94 HFpEF. PENK concentrations were higher in subjects who developed HF compared with those who did not, 56.2 (45.2–67.6) versus 52.7 (45.1–61.6) pmol/L, respectively (p = .003). In competing‐risk analyses, higher PENK concentrations were associated with higher risk of new‐onset HF (hazard ratio [HR] = 2.09[1.47–2.97], p < .001), including both HFrEF (HR = 2.31[1.48–3.61], p < .001) and HFpEF (HR = 1.74[1.02–2.96], p = .042). These associations were, however, lost after adjustment for eGFR.

Conclusions

In the general population, higher PENK concentrations were associated with lower eGFR and higher NT‐proBNP concentrations. Higher PENK concentrations were not independently associated with new‐onset HFrEF and HFpEF and mainly confounded by eGFR.