Alcohol and nicotine interactions: pre-clinical models of dependence

Beer taxes associate with lower alcohol and cigarette use; cigarette taxes associate with lower cigarette but higher alcohol use

Background: There is a yet unmet opportunity to utilize data on taxes and individual behaviors to yield insight for analyzing studies involving alcohol and cigarette use.Objectives: To inform the direction and strength of their mutual associations by leveraging the fact that taxation can affect individual consumption, but individual consumption cannot affect taxation.Methods: We linked state-level data on cigarette and beer taxes in 2009-2020 with individual-level data on self-reported current cigarette and alcohol use from the Behavioral Risk Factor Surveillance System, a telephone survey by the Centers for Disease Control and Prevention that is representative of the population of each state in the United States. We constructed linear and logistic models to examine associations between a $1 increase in cigarette taxes per pack and a $1 increase in beer taxes per gallon and self-reported cigarette use and alcohol consumption (assessed as any current intake, average drinks/day, heavy drinking, and binge drinking), adjusting for survey year and individual characteristics.Results: Among 2,968,839,352 respondents (49% male), a $1 increase in beer taxes was associated with .003 (95% confidence interval [CI] -.013, .008) fewer drinks/day and lower odds of any drinking (odds ratio [OR] = .81 95%CI .80, .83), heavy drinking (OR = .96 95%CI .93, .99), binge drinking (OR = .82 95%CI .80, .83), and smoking (OR = .98 95%CI .96, 1.00). In contrast, a $1 increase in cigarette taxes was associated with lower odds of smoking (OR = .94 95%CI .94, .95) but .007 (95%CI .005, .010) more drinks/day, and higher odds of any drinking (OR = 1.10 95%CI 1.10, 1.11), heavy drinking (OR = 1.02 95%CI 1.01, 1.02), and binge drinking (OR = .82 95%CI .80, .83).Conclusion: Higher beer taxes were associated with lower odds of drinking and smoking, but higher cigarette taxes were associated with lower odds of smoking and higher alcohol consumption. These results suggest that alcohol intake may be a determinant of cigarette use rather than cigarette use as a determinant of alcohol intake.

Alcohol self-administration and nicotine withdrawal alter biomarkers of stress and inflammation and prefrontal cortex changes in Gβ subunits

Background: Although alcohol and nicotine are often used together, the biological consequences of these substances are not well understood. Identifying shared targets will inform cessation pharmacotherapies and provide a deeper understanding of how co-use of alcohol and nicotine impacts health, including biomarkers of stress and inflammation.Objective: We examined the effects of nicotine exposure and withdrawal on alcohol self-administration (SA), stress and inflammatory biomarkers, and a G-protein coupled receptor subunit (Gβ) in brain areas associated with drug use.Methods: Male rats were trained to SA alcohol and then received a nicotine pump (n = 7-8 per group). We assessed alcohol intake for 12 days during nicotine exposure and then following pump removal to elicit withdrawal. After the behavioral studies, we assessed plasma leptin, corticosterone, and interleukin-1β (IL-1β), and Gβ protein expression in the amygdala, nucleus accumbens (NAc), and prefrontal cortex (PFC).Results: Nicotine exposure or withdrawal did not alter alcohol intake (p > .05). Alcohol and nicotine withdrawal elevated corticosterone levels (p = .015) and decreased Gβ levels in the PFC (p = .004). In the absence of nicotine, alcohol SA suppressed IL-1β levels (p = .039). Chronic exposure to nicotine or withdrawal during alcohol SA did not alter leptin levels or Gβ expression in the amygdala or NAc (p's > .05).Conclusions: The combination of alcohol SA and nicotine withdrawal produced a persistent increase in stress biomarkers and a suppression in Gβ expression in the PFC, providing an important first step toward understanding the common biological mechanisms of alcohol/nicotine misuse.

Influence of catechol-O-methyltransferase enzyme gene polymorphism on alcohol and tobacco consumption in North Indian treatment seeking population

BACKGROUND

The co-occurrence of alcohol and tobacco dependence is frequently witnessed in treatment settings. It is a challenge for clinicians to treat such patients due to their powerful biological association.

AIM

The study is aimed to assess the relationship of Catechol-O-methyltransferase (COMT) Val158Met polymorphism with substance intake among individuals who are dependent on both alcohol and tobacco.

MATERIALS AND METHODS

A cross-sectional study involving patients coming to the outpatient department was planned. Brief information on their sociodemographic and substance use profile was recorded. Genotyping of COMT Val158Met was carried out using established polymerase chain reaction-restriction fragment length polymorphism method. The COMT genotyping was classified based on the presence or absence of Met allele using the dominant model. Descriptive statistics, Chi-square test, Mann-Whitney test, and Binary logistic regression analysis were performed to analyze the data.

RESULTS

The study included 104 alcohol and nicotine co-dependent subjects. More than eighty percent of the participants were educated above secondary level, married, and employed. The allele frequencies of met and Val were found to be 0.23 and 0.77, respectively. Forty percent of the participants reported tobacco-related health problems. The odds of consuming alcohol and nicotine were four times high among Met allele carriers. While the Fagerström test for nicotine dependence and heaviness of smoking index scores were up to four and eight times higher among met allele (odds ratio 4.3 and 8.9, respectively).

CONCLUSION

Patients carrying Met allele are reported to consume higher amounts of alcohol and tobacco and were likely to score high among measures of nicotine dependence. Thus met allele carriers needs additional attention for a successful treatment outcome.

'Time to first tobacco cigarette soon after waking' occurs more often among underage newly incident smokers in the United States, 2004-2017

AIMS

Time to first cigarette (TTFC) after waking is a highly regarded and readily measured manifestation of a tobacco dependence process. We aim to estimate short TTFC as it occurs very soon after the onset of cigarette smoking (CS) in a community sample of newly incident smokers, all 12-21 years of age, and to study risk variation with the age of CS onset.

METHODS

United States National Surveys on Drug Use and Health, 2004-2017, drew large nationally representative samples of 12-to-21-year-old community residents, and used computerized self-interviews to measure tobacco cigarette smoking, the Fagerstrom TTFC construct, and related variables. A 'short' TTFC was defined as smoking the first cigarette after waking up within 30 min vs. 'long' TTFC or smoking more than 30 min. We studied 8188 newly incident smokers, all assessed within six months after the first puff. Estimated age-specific cumulative incidence proportions (CIP) and odds ratios (OR) are estimated and compared, with due attention to complex survey design and weights.

RESULTS

Among underage newly incident smokers (12-17 years old), an estimated 5.2% experienced short TTFC within 6 months after CS onset (95% CI = 4.4%, 6.2%), versus 3.7% for older new smokers (18-21 years; 95% CI = 2.8%, 4.6%). Underage smokers are 1.5 times more likely to develop short TTFC compared to older initiates (95% CI = 1.1, 2.1). No male-female variations are seen, but exploratory analysis disclosed findings that involve Census-defined race-ethnicity subgroups. Non-Hispanic African-American initiates are twice as likely to develop short TTFC, and Hispanic initiates are less likely to develop short TTFC, as compared with non-Hispanic White smokers.

CONCLUSIONS

Based on US community samples our study offers new evidence about TTFC formation observed within six months after the first puff when cigarette smoking starts before age 18 years.

Increased alcohol preference and intake in nicotine-preferring rats

BACKGROUND

Alcohol and tobacco are among the leading substances that are misused together and shared genetic vulnerability is likely. Increased susceptibility to nicotine self-administration has been shown in alcohol-preferring rat-lines. However, a nicotine-preferring (nP) rat-line has not been studied for alcohol preference.

OBJECTIVES

To evaluate alcohol preference and intake in male and female nP rats. We hypothesized that nP rats and females would drink more ethanol than control rats and males, respectively.

METHODS

nP rats are being selectively outbred for high oral nicotine intake at Ege University. Seventeen nP (18^th generation) and 20 naïve female and male SD rats, not previously exposed to alcohol or nicotine, were used. Twelve-week-old rats were given intermittent access to 20% ethanol in a 2-bottle-choice-procedure for six weeks. After one week withdrawal, six weeks of oral nicotine self-administration was applied.

RESULTS

nP rats drank significantly more ethanol than controls and their preference for ethanol over water was higher. Female rats' ethanol intake was higher than males'. The nP rats' nicotine preference and intake were higher than controls, and they gained less weight.

CONCLUSION

We have shown for the first time that nP rats also have high alcohol intake. Our results support the hypothesis that shared genetic factors may underlie concurrent addiction to nicotine and alcohol and have translational value in understanding their misuse. Considering the increased vulnerability for alcohol use disorder in smokers and sex differences observed, early preventive measures in families with a history of tobacco addiction, specifically targeting female members, could have public health benefits.

Unequal interactions between alcohol and nicotine co-consumption: suppression and enhancement of concurrent drug intake

RATIONALE

Alcohol and nicotine addiction are prevalent conditions that co-occur. Despite the prevalence of co-use, factors that influence the suppression and enhancement of concurrent alcohol and nicotine intake are largely unknown.

OBJECTIVES

Our goals were to assess how nicotine abstinence and availability influenced concurrent alcohol consumption and to determine the impact of quinine adulteration of alcohol on aversion-resistant alcohol consumption and concurrent nicotine consumption.

METHODS

Male and female C57BL/6J mice voluntarily consumed unsweetened alcohol, nicotine, and water in a chronic 3-bottle choice procedure. In experiment 1, nicotine access was removed for 1 week and re-introduced the following week, while the alcohol and water bottles remained available at all times. In experiment 2, quinine (100-1000 μM) was added to the 20% alcohol bottle, while the nicotine and water bottles remained unaltered.

RESULTS

In experiment 1, we found that alcohol consumption and preference were unaffected by the presence or absence of nicotine access in both male and female mice. In experiment 2a, we found that quinine temporarily suppressed alcohol intake and enhanced concurrent nicotine, but not water, preference in both male and female mice. In experiment 2b, chronic quinine suppression of alcohol intake increased nicotine consumption and preference in female mice without affecting water preference, whereas it increased water and nicotine preference in male mice.

CONCLUSIONS

Quinine suppression of alcohol consumption enhanced the preference for concurrent nicotine preference in male and female mice, suggesting that mice compensate for the quinine adulteration of alcohol by increasing their nicotine preference.

Pharmacotherapeutic management of co-morbid alcohol and opioid use

Opioid use disorder (OUD) and alcohol use disorder (AUD) are two highly prevalent substance-related disorders worldwide. Co-use of the substances is also quite prevalent, yet there are no pharmacological treatment approaches specifically designed to treat co-morbid OUD and AUD. Here, the authors critically summarize OUD, AUD and opioid/alcohol co-use and their current pharmacotherapies for treatment. They also review the mechanisms of action of opioids and alcohol within the brain reward circuitry and discuss potential combined mechanisms of action and resulting neuroadaptations. Pharmacotherapies that aim to treat AUD or OUD that may be beneficial in the treatment of co-use are also highlighted. Preclinical models assessing alcohol and opioid co-use remain sparse. Lasting neuroadaptations in brain reward circuits caused by co-use of alcohol and opioids remains largely understudied. In order to fully understand the neurobiological underpinnings of alcohol and opioid co-use and develop efficacious pharmacotherapies, the preclinical field must expand its current experimental paradigms of 'single drug' use to encompass polysubstance use. Such studies will provide insights on the neural alterations induced by opioid and alcohol co-use, and may help develop novel pharmacotherapies for individuals with co-occurring alcohol and opioid use disorders.

Development of a novel alcohol and nicotine concurrent access (ANCA) self-administration procedure in baboons

BACKGROUND

Self-administration of either alcohol or nicotine under single-access conditions has been studied extensively in laboratory animals. Relatively few studies have examined the co-use of these substances, even though alcohol and nicotine use and abuse commonly co-occur in humans. The objectives of this study were to develop a baboon model of concurrent alcohol and nicotine self-administration, and examine effects of varenicline on alcohol and nicotine co-use.

METHODS

In Experiment 1, five male baboons were trained to self-administer drinks of alcohol (4% w/v) and injections of nicotine (0.032-0.1 mg/kg) under single-access and then concurrent-access conditions, and intake of alcohol (g/kg) and nicotine (mg/kg) was compared under single- and concurrent-access conditions. In Experiment 2, three male baboons self-administered drinks of alcohol (4% w/v) and injections of nicotine (0.056 mg/kg) under concurrent-access conditions. Pretreatment with varenicline (0.32-1.0 mg/kg, s.c.) or an equal volume of its vehicle before concurrent-access sessions was repeated for 5 consecutive days.

RESULTS

Self-administration of nicotine and alcohol was successfully established under both single- and concurrent-access conditions that produced reliable levels of voluntary alcohol and nicotine intake. Co-self-administration of both drugs produced levels of intake similar to that produced by each drug alone. Varenicline significantly reduced intake of both alcohol and nicotine when compared to the vehicle condition.

CONCLUSIONS

This baboon model provides a valuable tool for further investigation of the behavioral and pharmacological mechanisms involved in co-use of nicotine and alcohol. A single pharmacotherapeutic agent (e.g., varenicline) may be useful in treating nicotine and alcohol co-use.

E-cigarettes: Impact of E-Liquid Components and Device Characteristics on Nicotine Exposure

BACKGROUND

Electronic cigarette (e-cigarette) use has increased substantially in recent years. While e-cigarettes have been proposed as a potentially effective smoking cessation tool, dualuse in smokers is common and e-cigarettes are widely used by non-smokers, including youth and young-adult non-smokers. Nicotine, the primary addictive component in cigarettes, is present at varying levels in many e-liquids. E-cigarettes may lead to initiation of nicotine use in adult and youth non-smokers, re-initiation of nicotine dependence in ex-smokers or increased severity of nicotine dependence in dual-users of cigarettes and e-cigarettes. As such, there are important clinical and policy implications to understanding factors impacting nicotine exposure from e-cigarettes. However, the broad and rapidly changing range of e-liquid constituents and e-cigarette hardware which could impact nicotine exposure presents a challenge. Recent changes in regulatory oversight of e-cigarettes underscore the importance of synthesizing current knowledge on common factors which may impact nicotine exposure.

METHODS

This review focuses on factors which may impact nicotine exposure by changing e-cigarette use behavior, puff topography, altering the nicotine yield (amount of nicotine exiting the e-cigarette mouth piece including nicotine exhaled as vapor) or more directly by altering nicotine absorption and bioavailability.

RESULTS

Topics reviewed include e-liquid components or characteristics including flavor additives (e.g., menthol), base e-liquid ingredients (propylene glycol, vegetable glycerin), components commonly used to dissolve flavorants (e.g., ethanol), and resulting properties of the e-liquid (e.g., pH), e-cigarette device characteristics (e.g., wattage, temperature, model) and user behavior (e.g., puff topography) which may impact nicotine exposure.

CONCLUSION

E-liquid characteristics and components, e-cigarette hardware and settings, and user behavior can all contribute substantially to nicotine exposure from e-cigarettes.

Effects of Nicotine on Alcohol Drinking in Female Mice Selectively Bred for High or Low Alcohol Preference

BACKGROUND

Studies show that repeated nicotine use associates with high alcohol consumption in humans and that nicotine exposure sometimes increases alcohol consumption in animal models. However, the relative roles of genetic predisposition to high alcohol consumption, the alcohol drinking patterns, and the timing of nicotine exposure both with respect to alcohol drinking and developmental stage remain unclear. The studies here manipulated all these variables, using mice selectively bred for differences in free-choice (FC) alcohol consumption to elucidate the role of genetics and nicotine exposure in alcohol consumption behaviors.

METHODS

In Experiments 1 and 2, we assessed the effects of repeated nicotine (0, 0.5, or 1.5 mg/kg) injections immediately before binge-like (drinking-in-the-dark; Experiment 1) or during FC alcohol access (Experiment 2) on these alcohol drinking behaviors (immediately after injections and during re-exposure to alcohol access 14 days later) in adult high- (HAP2) and low-alcohol-preferring (LAP2) female mice (co-exposure model). In Experiments 3 and 4, we assessed the effects of repeated nicotine (0, 0.5, or 1.5 mg/kg) injections 14 days prior to binge-like and FC alcohol access on these alcohol drinking behaviors in adolescent HAP2 and LAP2 female mice (Experiment 3) or adult HAP2 female mice (Experiment 4).

RESULTS

In Experiment 1, we found that repeated nicotine (0.5 and 1.5 mg/kg) and alcohol co-exposure significantly increased binge-like drinking behavior in HAP2 but not LAP2 mice during the re-exposure phase after a 14-day abstinence period. In Experiment 2, 1.5 mg/kg nicotine injections significantly reduced FC alcohol intake and preference in the third hour postinjection in HAP2 but not LAP2 mice. No significant effects of nicotine treatment on binge-like or FC alcohol drinking were observed in Experiments 3 and 4.

CONCLUSIONS

These results show that the temporal parameters of nicotine and alcohol exposure, pattern of alcohol access, and genetic predisposition for alcohol preference influence nicotine's effects on alcohol consumption. These findings in selectively bred mice suggest that humans with a genetic history of alcohol use disorders may be more vulnerable to develop nicotine and alcohol co-use disorders.

Acute Ethanol Administration Upregulates Synaptic α4-Subunit of Neuronal Nicotinic Acetylcholine Receptors within the Nucleus Accumbens and Amygdala

Alcohol and nicotine are two of the most frequently abused drugs, with their comorbidity well described. Previous data show that chronic exposure to nicotine upregulates high-affinity nicotinic acetylcholine receptors (nAChRs) in several brain areas. Effects of ethanol on specific brain nAChR subtypes within the mesolimbic dopaminergic (DA) pathway may be a key element in the comorbidity of ethanol and nicotine. However, it is unknown how alcohol affects the abundance of these receptor proteins. In the present study, we measured the effect of acute binge ethanol on nAChR α4 subunit levels in the prefrontal cortex (PFC), nucleus accumbens (NAc), ventral tegmental area (VTA), and amygdala (Amg) by western blot analysis using a knock-in mouse line, generated with a normally functioning α4 nAChR subunit tagged with yellow fluorescent protein (YFP). We observed a robust increase in α4-YFP subunit levels in the NAc and the Amg following acute ethanol, with no changes in the PFC and VTA. To further investigate whether this upregulation was mediated by increased local mRNA transcription, we quantified mRNA levels of the Chrna4 gene using qRT-PCR. We found no effect of ethanol on α4 mRNA expression, suggesting that the upregulation of α4 protein rather occurs post-translationally. The quantitative counting of YFP immunoreactive puncta further revealed that α4-YFP protein is upregulated in presynaptic boutons of the dopaminergic axons projecting to the shell and the core regions of the NAc as well as to the basolateral amygdala (BLA), but not to the central or lateral Amg. Together, our results demonstrate that a single exposure to binge ethanol upregulates level of synaptic α4^∗ nAChRs in dopaminergic inputs to the NAc and BLA. This upregulation could be linked to the functional dysregulation of dopaminergic signalling observed during the development of alcohol dependence.