The possible role of maternal bonding style and CHRNB2 gene polymorphisms in nicotine dependence and related depressive phenotype

Abstract

Objectives: Neuronal nicotinic acetylcholinergic receptors (nAChR) and especially α4β2 nAChRs are the major targets for cessation medications and also for some promising antidepressant agents. Furthermore, depressive symptoms pose multifacet difficulties during cessation therapy. However, gene encoding for the β2 subunit of nAChRs has been poorly investigated in association with depression. Since both nicotine dependence (ND) and depressive phenotype are complex disorders, we investigated the effects of a significant early life experience, maternal bonding style (MB) and CHRNB2 gene SNPs on smoking-related depression.

Methods: We recruited two hundred and thirty-two treatment-seeking smokers in our study. Phenotypic variants were evaluated using the Fagerstrom Test for Nicotine Dependence (FTND), the Zung Self-Rating Depression Scale (ZSDS) and the Parental Bonding Instrument (PBI). Besides the total score (TS) of ZSDS, impulsivity (ZSDS-I) and suicidal ideation (ZSDS-S) were distinguished as phenotypic variable. DNAs were extracted from buccal mucosa samples and one SNP in promoter and two SNPs in 3' UTR of CHRNB2 gene were genotyped. GLM and ANOVA tests were performed for genotype associations and interaction analyses.

Results: Maternal bonding had a significant impact on depressive phenotypes. Low care, high protection and affectionless control (ALC) were associated with ZSDS-TS and all subphenotypes of ZSDS. One SNP, the rs2072660 in 3' UTR, had a significant effect on the FTND score (p=0.010). Direct association of CHRNB2 variants and depressive phenotypes were not significant. However, in interaction with ALC, rs2072660 was significantly associated with ZSDS-S (p=0.005). MB had no significant effect on smoking-related phenotype.

Conclusions: Our results highlight the important role of 3' UTR in the CHRNB2 gene in the shared molecular background of ND and depressive phenotype. Parental bonding style can be suggested as a significant environmental factor in further GxE studies of depression. The presented significant GxE interaction on smoking-related suicidal subphenotype may help establish further investigations on development of more effective and safer smoking cessation and antidepressant agents.

Keywords: Gene–environment interaction; Nicotine dependence; Parental bonding style; Suicidal ideation; α4β2 nAChRs.