The role of nicotinic receptor genes (CHRN) in the pathways of prenatal tobacco exposure on smoking behavior among young adult light smokers

Candidate gene-environment interactions in substance abuse: A systematic review

BACKGROUND

The abuse of psychogenic drugs can lead to multiple health-related problems. Genetic and environmental vulnerabilities are factors in the emergence of substance use disorders. Empirical evidence regarding the gene-environment interaction in substance use is mixed. Summaries of the latest findings from a candidate gene approach will be useful for revealing the significance of particular gene contributions. Thus, we aim to identify different gene-environment interactions in patterns of substance use and investigate whether any effects trend notably across different genders and races.

METHODS

We reviewed published studies, until March 1, 2022, on substance use for candidate gene-environment interaction. Basic demographics of the included studies, target genes, environmental factors, main findings, patterns of gene-environment interaction, and other relevant information were collected and summarized.

RESULTS

Among a total of 44 studies, 38 demonstrated at least one significant interaction effect. About 61.5% of studies on the 5-HTTLPR gene, 100% on the MAOA gene, 42.9% on the DRD2 gene, 50% on the DRD4 gene, 50% on the DAT gene, 80% on the CRHR1 gene, 100% on the OPRM1 gene, 100% on the GABRA1 gene, and 50% on the CHRNA gene had a significant gene-environment interaction effect. The diathesis-stress model represents a dominant interaction pattern (89.5%) in the studies with a significant interaction effect; the remaining significant effect on substance use is found in the differential susceptibility model. The social push and swing model were not reported in the included studies.

CONCLUSION

The gene-environment interaction research on substance use behavior is methodologically multidimensional, which causes difficulty in conducting pooled analysis, or stated differently-making it hard to identify single sources of significant influence over maladaptive patterns of drug taking. In decreasing the heterogeneity and facilitating future pooled analysis, researchers must (1) replicate the existing studies with consistent study designs and measures, (2) conduct power calculations to report gene-environment correlations, (3) control for covariates, and (4) generate theory-based hypotheses with factorial based experiments when designing future studies.

Sex- and Genotype-Dependent Nicotine-Induced Behaviors in Adolescent Rats with a Human Polymorphism (rs2304297) in the 3'-UTR of the CHRNA6 Gene

In human adolescents, a single nucleotide polymorphism (SNP), rs2304297, in the 3′-UTR of the nicotinic receptor subunit gene, CHRNA6, has been associated with increased smoking. To study the effects of the human CHRNA6 3′-UTR SNP, our lab generated knock-in rodent lines with either C or G SNP alleles. The objective of this study was to determine if the CHRNA6 3′-UTR SNP is functional in the knock-in rat lines. We hypothesized that the human CHRNA6 3′-UTR SNP knock-in does not impact baseline but enhances nicotine-induced behaviors. For baseline behaviors, rats underwent food self-administration at escalating schedules of reinforcement followed by a locomotor assay and a series of anxiety tests (postnatal day (PN) 25-39). In separate cohorts, adolescent rats underwent 1- or 4-day nicotine pretreatment (2×, 30 μg/kg/0.1 mL, i.v.). After the last nicotine injection (PN 31), animals were assessed behaviorally in an open-field chamber, and brain tissue was collected. We show the human CHRNA6 3′-UTR SNP knock-in does not affect food reinforcement, locomotor activity, or anxiety. Further, 4-day, but not 1-day, nicotine exposure enhances locomotion and anxiolytic behavior in a genotype- and sex-specific manner. These findings demonstrate that the human CHRNA6 3′-UTR SNP is functional in our in vivo model.

Estimating causal and time-varying effects of maternal smoking on youth smoking

INTRODUCTION

Maternal smoking is a well-known risk factor for youth smoking, yet whether this relationship is causal remains unresolved. This study utilizes propensity score methods for causal inference to robustly account for shared risk factors between maternal and offspring smoking.

METHODS

An 8-year longitudinal cohort of 900 adolescents in the Chicago area were followed starting from approximately age 15.6. The effects of maternal lifetime smoking (MLS) and prenatal tobacco exposure (PTE) (among participants reporting MLS) on offspring's past 30-day smoking, daily smoking status and smoking frequency were examined using logistic regression and Poisson regression after nearest-neighbor propensity matching. Age dependency of this relationship was then examined across the age range of 15-25 using time-varying effect modeling.

RESULTS

Propensity matching yielded 438 and 132 pairs for MLS and PTE study samples, respectively. MLS demonstrated significant associations with past 30-day smoking (RR 1.09; 95% CI 1.04-1.14), daily smoking (RR 1.08; 95% CI 1.05-1.12), and smoking frequency of offspring (RR 1.32; 95% CI 1.15-1.52), with stable effects across age. Among participants reporting MLS, having PTE showed significant additional effects on daily smoking (RR 1.09; 95% CI 1.02-1.17) and age-dependency that showed significance during young adulthood but not adolescence.

CONCLUSION

The relationship between maternal and offspring smoking was not fully accounted for by shared risk factors, suggesting possible causation with PTE having a delayed effect across age. Targeted prevention efforts should be made on maternal smoking-exposed adolescents to mitigate their risks of developing heavy smoking habits in adulthood.

Cholinergic receptor nicotinic beta 3 subunit polymorphisms and smoking in male Chinese patients with schizophrenia

OBJECTIVE

The aim of this study was to examine if cholinergic receptor nicotinic beta 3 subunit (CHRNB3) was a common genetic basis for both nicotine dependence and schizophrenia.

METHODS

Two CHRNB3 promoter single nucleotide polymorphisms (SNPs) were genotyped in 773 patients with schizophrenia and 302 healthy volunteers. Associations between smoking, schizophrenia, smoking+schizophrenia and CHRNB3 were analyzed. The mRNA expression of CHRNB3 in human brains was examined, and the expression correlations between CHRNB3 and dopaminergic and GABAergic receptor genes were evaluated.

RESULTS

The association between CHRNB3 and smoking was significant in the total sample, less significant in the smoking with schizophrenia, and suggestive in the smoking without schizophrenia. CHRNB3 had significant mRNA expression that was correlated with dopaminergic or GABAergic receptor expression in human brains. The two CHRNB3 SNPs had significant cis-acting regulatory effects on CHRNB3 mRNA expression.

CONCLUSIONS

Risk for smoking behavior was associated with CHRNB3. CHRNB3 mRNA is abundant in human brain and could play important role in the pathogenesis of smoking behavior.

The effect of maternal smoking on offspring smoking is unrelated to heritable personality traits or initial subjective experiences

INTRODUCTION

Maternal smoking is a risk factor for offspring smoking. Lifetime maternal smoking vs. prenatal tobacco exposure (PTE) appear to act through different mechanisms. This study tested the hypothesis that maternal smoking measures' effects on offspring smoking could be attributable to hereditary mechanisms: personality traits (novelty-seeking, impulsivity, neuroticism, self-esteem) and initial subjective smoking experiences (pleasurable, unpleasurable, dizziness).

METHODS

Data were drawn from the Social and Emotional Contexts of Adolescent Smoking Patterns (SECASP) study, an 8-year longitudinal study of 9 th or 10 th graders at baseline (≈age 15) who experiment with smoking (<100 lifetime cigarettes; N=594) at baseline. Young adult smoking frequency at the 8-year follow-up (≈age 23) was examined as a function of baseline characteristics (heritable trait, maternal smoking, PTE, sex) and baseline smoking frequency and nicotine dependence. Structural equation models determined whether inclusion of each heritable trait among offspring confounded the effects of maternal smoking (PTE or maternal smoking) on offspring smoking and nicotine dependence.

RESULTS

Impulsiveness was associated with intermediate adolescent smoking frequency (B=0.135, SD=0.043 p=0.002) and nicotine dependence (B=0.012, SD=0.003, p<0.001). Unpleasurable first experience (B=0.886, SD=0.374, p=0.018) and dizziness (B=0.629, SD=0.293, p=0.032) showed a trend with intermediate smoking frequency that was non-significant after correcting for multiple comparisons. These traits did not confound maternal smoking's effects.

CONCLUSIONS

None of the heritable traits examined in this model explained the effect of maternal smoking measures on adolescence or young adulthood offspring smoking. Further research is needed to elucidate the mechanism by which PTE and maternal smoking are linked to offspring smoking.