Mechanisms and Clinical Features of Co-occurring Opioid and Nicotine Use

Competitive Antagonism of Xylazine on α7 Nicotinic Acetylcholine Receptors and Reversal by Curcuminoids

Co-use of xylazine with opioids is a major health threat in the United States. However, a critical knowledge gap exists in the understanding of xylazine-induced pharmacological and pathological impact. Xylazine is mostly known as an agonist of α2-adrenergic receptors (α2-ARs), but its deleterious effects on humans cannot be fully reversed by the α2-AR antagonists, suggesting the possibility that xylazine targets receptors other than α2-ARs. Here, we report the discovery of α7 nicotinic acetylcholine receptors (α7 nAChRs) as targets of xylazine. In Xenopus oocytes expressing α7 nAChRs, xylazine competitively antagonizes channel currents elicited by the agonist acetylcholine. In PC12 cells, xylazine suppresses choline-stimulated intracellular calcium ([Ca2+]in) transients that are mediated by endogenously expressed α7 nAChRs. Furthermore, we find that curcuminoids, ivermectin, and the α7-specific positive allosteric modulator PNU120596 can effectively offset the xylazine inhibition of α7 nAChRs. Considering the prominent role of α7 nAChRs in the cholinergic anti-inflammatory pathway and wide expression in the human body, our findings present a potential new strategy to reverse xylazine-caused damage using curcuminoids or repurposing ivermectin. This α7 nAChR-focused strategy may offer an immediate deployment that is likely effective in improving xylazine-related treatment outcomes.

Lifestyle factors and long-term survival in patients with chronic non-cancer pain: a nationwide cohort study in South Korea

PURPOSE

This study aimed to investigate the association of modifiable lifestyle factors with long-term survival outcomes in patients with chronic non-cancer pain (CNCP) in South Korea.

METHODS

This population-based cohort study used data from the National Health Insurance Service database in South Korea. We considered three lifestyle factors from the standard health examination (smoking status, alcohol consumption, and physical activity).

RESULTS

A total of 1,298,314 patients with CNCP were analyzed; moreover, the 5-year all-cause mortality rate was 3.3% (42,875 patients). In the multivariable Cox regression model, in the previous-smoker and current-smoker groups, it was 5% (hazard ratio [HR]:1.05, 95% confidence interval [CI]:1.02-1.08; P = 0.003) and 65% (HR: 1.65, 95% CI: 1.60-1.69; P < 0.001) higher, respectively, than that in the never-smoker group. The 5-year all-cause mortality was 19% (HR: 1.19, 95% CI: 1.14-1.24; P < 0.001) higher in the heavy-alcohol-consumption group than in the non-alcohol-consumption group. Compared with those without mild physical activity, patients who engaged in mild physical activity for 1-3 (HR: 0.89, 95% CI: 0.87-0.92; P < 0.001), 4-5 (HR: 0.88, 95% CI: 0.86-0.91; P < 0.001), and 6-7 (HR: 0.90, 95% CI: 0.88-0.93; P < 0.001) days per week exhibited a significantly decreased 5-year all-cause mortality. The association between moderate/intensive physical activity and 5-year all-cause mortality yielded similar results.

CONCLUSION

Lifestyle factors, including previous/current smoking, heavy alcohol consumption, and physical activity, were associated with a higher 5-year all-cause mortality risk among patients with CNCP in South Korea.

CpH methylome analysis in human cortical neurons identifies novel gene pathways and drug targets for opioid use disorder

Introduction

DNA methylation (DNAm), an epigenetic mechanism, has been associated with opioid use disorder (OUD) in preclinical and human studies. However, most of the studies have focused on DNAm at CpG sites. DNAm at non-CpG sites (mCpHs, where H indicates A, T, or C) has been recently shown to have a role in gene regulation and to be highly abundant in neurons. However, its role in OUD is unknown. This work aims to evaluate mCpHs in the human postmortem orbital frontal cortex (OFC) in the context of OUD.

Methods

A total of 38 Postmortem OFC samples were obtained from the VA Brain Bank (OUD = 12; Control = 26). mCpHs were assessed using reduced representation oxidative bisulfite sequencing in neuronal nuclei. Differential analysis was performed using the "methylkit" R package. Age, ancestry, postmortem interval, PTSD, and smoking status were included as covariates. Significant mCpHs were set at q-value < 0.05. Gene Ontology (GO) and KEGG enrichment analyses were performed for the annotated genes of all differential mCpH loci using String, ShinyGO, and amiGO software. Further, all annotated genes were analyzed using the Drug gene interaction database (DGIdb).

Results

A total of 2,352 differentially methylated genome-wide significant mCpHs were identified in OUD, mapping to 2,081 genes. GO analysis of genes with differential mCpH loci showed enrichment for nervous system development (p-value = 2.32E-19). KEGG enrichment analysis identified axon guidance and glutamatergic synapse (FDR 9E-4-2.1E-2). Drug interaction analysis found 3,420 interactions between the annotated genes and drugs, identifying interactions with 15 opioid-related drugs, including lofexidine and tizanidine, both previously used for the treatment of OUD-related symptoms.

Conclusion

Our findings suggest a role of mCpHs for OUD in cortical neurons and reveal important biological pathways and drug targets associated with the disorder.

Effect of brief nicotine corrective messaging on nicotine beliefs in persons who use opioids

This pilot study tested the effect of a brief nicotine education messaging exposure on beliefs about nicotine, nicotine-replacement therapy (NRT), and e-cigarettes. Participants ages 18 and older were recruited via Amazon Mechanical Turk to complete a 20-min online survey in April/May 2020 to assess relationships between opioid use, smoking, and other behaviors. Participants with past-month extra-medical opioid use completed questions on background characteristics and literacy and then were randomized in a 2:1 ratio of two conditions: nicotine education (n = 362) or no message control (n = 181). Beliefs about nicotine, NRT, and e-cigarettes were asked of all participants; this occurred after message exposure for the nicotine education condition. Bivariate and multivariable analyses examined differences in beliefs by study condition. Brief nicotine messaging increased the probability of a correct response to "Nicotine is a cause of cancer" (false, 63% vs. 36%) and reduced the probability of a don't know response (9% vs. 17%) compared to the no message control condition. Nicotine education also reduced false beliefs about harms of long-term NRT use compared to cigarettes (p < .05). In adjusted models, participants in the nicotine education group had lower mean false beliefs about nicotine (p < .001) and to a lesser extent NRT (p = .053) compared with the control group; there was no difference in mean false beliefs about e-cigarettes (p = .547) between groups. A brief education intervention produced similar changes in nicotine beliefs in adults with past-month extra-medical opioid use as in a general adult sample. Findings support the potential for impact of nicotine public education messaging in vulnerable populations. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

High smoking and low cessation rates among patients in treatment for opioid and other substance use disorders

BACKGROUND

Smoking is a well-documented cause of health problems among individuals with substance use disorders. For patients in opioid maintenance treatment (OMT), the risk for somatic health problems, including preventable diseases associated with tobacco smoking, increases with age. Our aim was to describe smoking among patients entering substance use disorder (SUD) treatment, investigate changes in smoking from the start of treatment to 1-year follow-up, and explore factors related to smoking cessation.

METHODS

We employed data from the Norwegian Cohort of Patient in Opioid Maintenance Treatment and Other Drug Treatment Study (NorComt). Participants were 335 patients entering SUD treatment at 21 participating facilities across Norway. They were interviewed at the start of treatment and at 1-year follow-up. The main outcomes were smoking and smoking cessation by treatment modality. A logistic regression identified factors associated with smoking cessation.

RESULTS

High levels of smoking were reported at the start of treatment in both OMT (94%) and other SUD inpatient treatment patients (93%). At 1-year follow-up most patients in OMT were still smoking (87%), and the majority of the inpatients were still smoking (69%). Treatment as an inpatient was positively associated and higher age was negatively associated with smoking cessation. Most patients who quit smoking transitioned to smokeless tobacco or kept their existing smokeless habit.

CONCLUSION

As illustrated by the high smoking prevalence and relatively low cessation levels in our sample, an increased focus on smoking cessation for patients currently in OMT and other SUD treatment is warranted. Harm-reduction oriented smoking interventions may be relevant.

Smoking cessation after cancer diagnosis reduces the risk of severe cancer pain: A longitudinal cohort study

Background

Whether abstinence from smoking among cancer patients reduces cancer pain is still unclear. Opioids can act as a surrogate index for evaluating the incidence of severe cancer pain in countries where opioid abuse is infrequent. This study aimed to investigate whether changed smoking behavior after cancer diagnosis influences the incidence of severe cancer pain as determined by strong opioid use.

Methods

Using a large Japanese insurance claims database (n = 4,797,329), we selected 794,702 insured employees whose annual health checkup data could be confirmed ≥6 times between January 2009 and December 2018. We selected 591 study subjects from 3,256 employees who were diagnosed with cancer pain and had health checkup data at the year of cancer pain diagnosis.

Results

A significantly greater proportion of patients who continued smoking after cancer diagnosis (“current smoker”, n = 133) received strong opioids (36.8%) compared with patients who had never smoked or had stopped before cancer diagnosis (“non-smoker”, n = 383, 20.6%; p<0.05) but also compared with patients who had quit smoking after cancer diagnosis (“abstainer:”, n = 75, 24.0%; p<0.05). In multivariable Cox proportional hazards regression analysis, abstainers had a significantly lower risk of receiving strong opioids than current smokers (hazard ratio: 0.57, 95% CI: 0.328 to 0.997). These findings were consistent across multiple sensitivity analyses.

Conclusion

Our study demonstrated that patients who quit smoking after cancer diagnosis have a lower risk of severe cancer pain. This information adds clinical incentives for improving quality of life among those who smoked at the time of cancer diagnosis.

Morphine Exposure Reduces Nicotine-Induced Upregulation of Nicotinic Receptors and Decreases Volitional Nicotine Intake in a Mouse Model

INTRODUCTION

Nicotine addiction remains a primary health concern as tobacco smoking remains the number one cause of preventable death in America. At the same time, America is still facing the threat of the opioid epidemic. While the prevalence of smoking combustible cigarettes or electronic nicotine delivery systems in the United States varies between 12% and 35%, the smoking rates among the opioid use dependent (OUD) population is 74%-97%. We examined changes in brain reward mechanisms in which co-use of nicotine and opioids may result in enhanced reward and reinforcement.

AIMS AND METHODS

Adult male and female α4-mCherryα6-GFP mice (C57BL/6J) were used in conditioned place preference (CPP) and microscopy assays to examine reward-related behavior and nicotinic acetylcholine receptor (nAChR) upregulation following treatments with saline, nicotine, morphine, or nicotine plus morphine. Following this, separate mice were trained in e-Vape self-administration assays to examine morphine's impact on nicotine reinforcement.

RESULTS

We observed that nicotine and morphine coexposure in a CPP assay did not produce enhanced reward-related behavior when compared with nicotine or morphine alone. In parallel we observed coexposure reduced nicotine-induced upregulation of nAChRs on ventral tegmental area dopamine and GABA neurons. Additionally, we observed that concurrent morphine exposure reduced nicotine (plus menthol) vapor self-administration in male and female mice.

CONCLUSIONS

While nicotine use is high among OUD individuals, our CPP assays suggest coexposure not only fails to enhance reward-related behavior but also reduces nicotine-induced changes in ventral tegmental area neurobiology. Our self-administration assays suggest that morphine exposure during nicotine acquisition reduces nicotine reinforcement-related behavior.

IMPLICATIONS

While some may postulate that the co-use of opioids and nicotine may be driven by reward-related mechanisms, our data indicate that opioid exposure may hinder nicotine intake due to reduced upregulation of nAChRs critical for nicotine reward and reinforcement. Thus, the high co-use in OUD individuals may be a result of other mechanisms and this warrants further investigations into nicotine and opioid co-use.