CHRNA5 variant predicts smoking cessation in patients with acute myocardial infarction

A novel smoking cessation behavior based on quit attempts may identify new genes associated with long-term abstinence

BACKGROUND

Smoking cessation at any age has been shown to improve quality of life, decrease illness, and reduce mortality. About half of smokers attempt to quit each year, but only ∼ 7 % maintain long-term abstinence unaided. Few genetic factors have been consistently associated with smoking cessation, possibly due to poor phenotype definition.

METHODS

We performed a genome-wide association study (GWAS) with an alternative phenotype based on the difficulty of quitting smoking (DQS) in the Cancer Prevention Study-3 cohort. Difficult quitters were defined as having made at least ten quit attempts, whether successful or not, and easy quitters as having quit after only one attempt. Only individuals of European ancestry were selected for the study. Among 10,004 smokers (5,071 difficult quitters, 4,933 easy quitters), we assessed the genetic heritability of DQS and evaluated associations between DQS and each genome-wide variant using logistic regression while adjusting for confounders, including smoking intensity (cigarettes per day).

RESULTS

The genetic heritability of the DQS phenotype was 13 %, comparable to, or higher than, the reported heritability of other smoking behaviors (e.g., smoking intensity, cessation). Although no variants were genome-wide significant, several genes were identified at a subthreshold level (p < 10-4). A variant in MEGF9 (rs149760032), a transmembrane protein largely expressed in the central nervous system, showed the strongest association with DQS (OR = 0.60, p = 1.3x10-7). Additional variants associated with DQS independently by smoking intensity were also detected in GLRA3 (rs73006492, OR = 0.77, p = 5.6x10-7) and FOCAD (rs112251973, OR = 1.96, p = 1.8x10-6) and are plausibly related to smoking cessation through pathways in the brain and respiratory system.

CONCLUSIONS

The use of an alternative cessation phenotype based on difficulty quitting smoking facilitated the identification of new pathways that could lead to unique smoking treatments.

The identification of key genes and pathways in polycystic ovary syndrome by bioinformatics analysis of next-generation sequencing data

Background

Polycystic ovary syndrome (PCOS) is a reproductive endocrine disorder. The specific molecular mechanism of PCOS remains unclear. The aim of this study was to apply a bioinformatics approach to reveal related pathways or genes involved in the development of PCOS.

Methods

The next-generation sequencing (NGS) dataset GSE199225 was downloaded from the gene expression omnibus (GEO) database and NGS dataset analyzed is obtained from in vitro culture of PCOS patients’ muscle cells and muscle cells of healthy lean control women. Differentially expressed gene (DEG) analysis was performed using DESeq2. The g:Profiler was utilized to analyze the gene ontology (GO) and REACTOME pathways of the differentially expressed genes. A protein–protein interaction (PPI) network was constructed and module analysis was performed using HiPPIE and cytoscape. The miRNA-hub gene regulatory network and TF-hub gene regulatory network were constructed. The hub genes were validated by using receiver operating characteristic (ROC) curve analysis.

Results

We have identified 957 DEG in total, including 478 upregulated genes and 479 downregulated gene. GO terms and REACTOME pathways illustrated that DEG were significantly enriched in regulation of molecular function, developmental process, interferon signaling and platelet activation, signaling, and aggregation. The top 5 upregulated hub genes including HSPA5, PLK1, RIN3, DBN1, and CCDC85B and top 5 downregulated hub genes including DISC1, AR, MTUS2, LYN, and TCF4 might be associated with PCOS. The hub gens of HSPA5 and KMT2A, together with corresponding predicted miRNAs (e.g., hsa-mir-34b-5p and hsa-mir-378a-5p), and HSPA5 and TCF4 together with corresponding predicted TF (e.g., RCOR3 and TEAD4) were found to be significantly correlated with PCOS.

Conclusions

These study uses of bioinformatics analysis of NGS data to obtain hub genes and key signaling pathways related to PCOS and its associated complications. Also provides novel ideas for finding biomarkers and treatment methods for PCOS and its associated complications.

A systematic review of genetic variation within nicotinic acetylcholine receptor genes and cigarette smoking cessation

BACKGROUND

Nicotine produces its effects by binding to nicotinic acetylcholine receptors (nAChRs). Variants of genes encoding properties of nAChRs are candidates for affecting likelihood of smoking cessation.

METHODS

A systematic review was conducted summarizing evidence of associations between single nucleotide polymorphisms (SNPs) of nAChR genes and smoking cessation. From 24 articles meeting inclusion criteria, summary odds ratios (ORs) for associations between nine SNPs and smoking cessation were calculated from 26 studies (N = 233-29,072) stratified by gene, ancestry, study design, and pharmacotherapy; SNPs in linkage disequilibrium were pooled. Results for a tenth SNP from two GWAS were summarized.

RESULTS

People of European ancestry with minor alleles of CHRNA5 rs16969968 and CHRNA3 rs1051730 had longer time to cessation [HR = 0.90, 95 % CI 0.88 - 0.92 (n = 2 studies)] and lower odds of cessation [OR = 0.88, 95 % CI 0.80 - 0.97 (n = 5 cohort studies), OR = 0.64, 95 % CI 0.45 - 0.90 (n = 4 placebo arms)]. Risk of persistent smoking associated with these alleles was attenuated in smokers receiving nicotine replacement therapy (NRT). Recipients of bupropion alone or with NRT with these alleles had higher, though not statistically significant, odds of cessation. Results for CHRNA5 rs588765 and rs680244 were similar to rs16969968/rs1051730 findings. Evidence was limited for other SNPs.

CONCLUSION

Evidence consistently indicates the minor alleles of four SNPs within CHRNA3 or CHRNA5 are risk alleles for cessation failure. Analysis by pharmacotherapy revealed bupropion may be the most efficacious intervention for people with these alleles.

Smoking cessation after acute coronary syndrome: A systematic review and meta-analysis

BACKGROUND

Smoking cessation is an effective secondary prevention measure after acute coronary syndrome (ACS). We conducted a systematic review with the aim to better understand which patients have a greater propensity to quit smoking and the risk factors for continued smoking after ACS.

METHODS

We searched MEDLINE and EMBASE for studies that evaluated smoking cessation after ACS. The pooled rate of smoking cessation across included studies was performed. Random effects meta-analysis for different variables and their association with smoking cessation was conducted.

RESULTS

A total of 39 studies with 11 228 patients were included in this review. The pooled rate of smoking cessation following ACS across 38 studies was 45.0%. Factors associated with greater likelihood of smoking cessation were attendance at cardiac rehabilitation (OR 1.90 95% CI 1.44-2.51), married/not alone (OR 1.68 95% CI 1.32-2.13), intention/attempt to quit smoking (OR 1.27 95% CI 1.11-1.46), diabetes mellitus (OR 1.24 95% CI 1.03-1.51) and hospitalised duration (OR 1.09 95% CI 1.02-1.15). Variables associated with a lower likelihood of smoking cessation were depression (OR 0.57 95% CI 0.43-0.75), chronic obstructive pulmonary disease/lung disease (OR 0.73 95% CI 0.57-0.93), previous admission with acute myocardial infarction/cardiac admission (OR 0.61 95% CI 0.47-0.80), cerebrovascular disease/transient ischaemic attack (OR 0.42 95% CI 0.30-0.58) and unemployment (OR 0.37 95% CI 0.17-0.80).

CONCLUSIONS

The majority of smokers with an ACS continue to smoke after admission. Patients attending cardiac rehabilitation show increased odds of quitting while people who are depressed and those with chronic lung disease were less likely to quit smoking and should be targeted for intensive smoking cessation interventions.

Tobacco Smoking: Risk to Develop Addiction, Chronic Obstructive Pulmonary Disease, and Lung Cancer

BACKGROUND

The morbidity and mortality associated with tobacco smoking is well established. Nicotine is the addictive component of tobacco. Nicotine, through the non-neuronal α7nicotinic receptor, induces cell proliferation, neo-angiogenesis, epithelial to mesenchymal transition, and inhibits drug-induced apoptosis.

OBJECTIVE

To understand the genetic, molecular and cellular biology of addiction, chronic obstructive pulmonary disease and lung cancer.

METHODS

The search for papers to be included in the review was performed during the months of July- September 2018 in the following databases: PubMed (http://www.ncbi.nlm.nih.gov), Scopus (http://www.scopus.com), EMBASE (http://www.elsevier.com/online-tools/embase), and ISI Web of Knowledge (http://apps.webofknowledge.com/). The following searching terms: "nicotine", "nicotinic receptor", and "addiction" or "COPD" or "lung cancer" were used. Patents were retrieved in clinicaltrials.gov (https://clinicaltrials.gov/). All papers written in English were evaluated. The reference list of retrieved articles was also reviewed to identify other eligible studies that were not indexed by the above-mentioned databases. New experimental data on the ability of nicotine to promote transformation of human bronchial epithelial cells, exposed for one hour to Benzo[a]pyrene-7,8-diol-9-10-epoxide, are reported.

RESULTS

Nicotinic receptors variants and nicotinic receptors upregulation are involved in addiction, chronic obstructive pulmonary disease and/or lung cancer. Nicotine through α7nicotinic receptor upregulation induces complete bronchial epithelial cells transformation.

CONCLUSION

Genetic studies highlight the involvement of nicotinic receptors variants in addiction, chronic obstructive pulmonary disease and/or lung cancer. A future important step will be to translate these genetic findings to clinical practice. Interventions able to help smoking cessation in nicotine dependence subjects, under patent, are reported.

Smoking cessation and risk of recurrent cardiovascular events and mortality after a first manifestation of arterial disease

AIMS

To quantify the relation between smoking cessation after a first cardiovascular (CV) event and risk of recurrent CV events and mortality.

METHODS

Data were available from 4,673 patients aged 61 ± 8.7 years, with a recent (≤1 year) first manifestation of arterial disease participating in the SMART-cohort. Cox models were used to quantify the relation between smoking status and risk of recurrent major atherosclerotic cardiovascular events (MACE including stroke, MI and vascular mortality) and mortality. In addition, survival according to smoking status was plotted, taking competing risk of non-vascular mortality into account.

RESULTS

A third of the smokers stopped after their first CV event. During a median of 7.4 (3.7-10.8) years of follow-up, 794 patients died and 692 MACE occurred. Compared to patients who continued to smoke, patients who quit had a lower risk of recurrent MACE (adjusted HR 0.66, 95% CI 0.49-0.88) and all-cause mortality (adjusted HR 0.63, 95% CI 0.48-0.82). Patients who reported smoking cessation on average lived 5 life years longer and recurrent MACE occurred 10 years later. In patients with a first CV event >70 years, cessation of smoking had improved survival which on average was comparable to former or never smokers.

CONCLUSIONS

Irrespective of age at first CV event, cessation of smoking after a first CV event is related to a substantial lower risk of recurrent vascular events and all-cause mortality. Since smoking cessation is more effective in reducing CV risk than any pharmaceutical treatment of major risk factors, it should be a key objective for patients with vascular disease.

A novel genetic marker of decreased inflammation and improved survival after acute myocardial infarction

The CHRNA5 gene encodes a neurotransmitter receptor subunit involved in multiple processes, including cholinergic autonomic nerve activity and inflammation. Common variants in CHRNA5 have been linked with atherosclerotic cardiovascular disease. Association of variation in CHRNA5 and specific haplotypes with cardiovascular outcomes has not been described. The aim of this study was to examine the association of CHRNA5 haplotypes with gene expression and mortality among patients with acute myocardial infarction (AMI) and explore potential mechanisms of this association. Patients (N = 2054) hospitalized with AMI were genotyped for two common variants in CHRNA5. Proportional hazard models were used to estimate independent association of CHRNA5 haplotype with 1-year mortality. Both individual variants were associated with mortality (p = 0.0096 and 0.0004, respectively) and were in tight LD (D' = 0.99). One haplotype, HAP3, was associated with decreased mortality one year after AMI (adjusted HR = 0.42, 95% CI 0.26, 0.68; p = 0.0004). This association was validated in an independent cohort (N = 637) of post-MI patients (adjusted HR = 0.23, 95% CI 0.07, 0.79; p = 0.019). Differences in CHRNA5 expression by haplotype were investigated in human heart samples (n = 28). Compared with non-carriers, HAP3 carriers had threefold lower cardiac CHRNA5 mRNA expression (p = 0.023). Circulating levels of the inflammatory marker hsCRP were significantly lower in HAP3 carriers versus non-carriers (3.43 ± 4.2 versus 3.91 ± 5.1; p = 0.0379). Activation of the inflammasome, an important inflammatory complex involved in cardiovascular disease that is necessary for release of the pro-inflammatory cytokine IL-1 β, was assessed in bone marrow-derived macrophages (BMDM) from CHRNA5 knockout mice and wild-type controls. In BMDM from CHRNA5 knockout mice, IL-1β secretion was reduced by 50% compared to wild-type controls (p = 0.004). Therefore, a common haplotype of CHRNA5 that results in reduced cardiac expression of CHRNA5 and attenuated macrophage inflammasome activation is associated with lower mortality after AMI. These results implicate CHRNA5 and the cholinergic anti-inflammatory pathway in survival following AMI.

Kynurenine 3-Monooxygenase Gene Associated With Nicotine Initiation and Addiction: Analysis of Novel Regulatory Features at 5' and 3'-Regions

Tobacco smoking is widespread behavior in Qatar and worldwide and is considered one of the major preventable causes of ill health and death. Nicotine is part of tobacco smoke that causes numerous health risks and is incredibly addictive; it binds to the α7 nicotinic acetylcholine receptor (α7nAChR) in the brain. Recent studies showed α7nAChR involvement in the initiation and addiction of smoking. Kynurenic acid (KA), a significant tryptophan metabolite, is an antagonist of α7nAChR. Inhibition of kynurenine 3-monooxygenase enzyme encoded by KMO enhances the KA levels. Modulating KMO gene expression could be a useful tactic for the treatment of tobacco initiation and dependence. Since KMO regulation is still poorly understood, we aimed to investigate the 5' and 3'-regulatory factors of KMO gene to advance our knowledge to modulate KMO gene expression. In this study, bioinformatics methods were used to identify the regulatory sequences associated with expression of KMO. The displayed differential expression of KMO mRNA in the same tissue and different tissues suggested the specific usage of the KMO multiple alternative promoters. Eleven KMO alternative promoters identified at 5'-regulatory region contain TATA-Box, lack CpG Island (CGI) and showed dinucleotide base-stacking energy values specific to transcription factor binding sites (TFBSs). The structural features of regulatory sequences can influence the transcription process and cell type-specific expression. The uncharacterized LOC105373233 locus coding for non-coding RNA (ncRNA) located on the reverse strand in a convergent manner at the 3'-side of KMO locus. The two genes likely expressed by a promoter that lacks TATA-Box harbor CGI and two TFBSs linked to the bidirectional transcription, the NRF1, and ZNF14 motifs. We identified two types of microRNA (miR) in the uncharacterized LOC105373233 ncRNA, which are like hsa-miR-5096 and hsa-miR-1285-3p and can target the miR recognition element (MRE) in the KMO mRNA. Pairwise sequence alignment identified 52 nucleotides sequence hosting MRE in the KMO 3' UTR untranslated region complementary to the ncRNA LOC105373233 sequence. We speculate that the identified miRs can modulate the KMO expression and together with alternative promoters at the 5'-regulatory region of KMO might contribute to the development of novel diagnostic and therapeutic algorithm for tobacco smoking.

Smoking Interacts With CHRNA5, a Nicotinic Acetylcholine Receptor Subunit Gene, to Influence the Risk of IBD-Related Surgery

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic luminal disease with genetic and environmental factors affecting phenotype. This study evaluated the relationship between CHRNA5, a nicotinic receptor subunit gene, and smoking in predicting IBD-related surgery as well as the relationship between CHRNA5 and nicotine dependence.

METHODS

Participants completed a smoking questionnaire and were genotyped for CHRNA5 rs16969968. Demographic and clinical data were obtained from medical records. Wilcoxon, ANOVA, Chi square, and Fisher's exact tests were used for comparisons. Logistic regression was used to evaluate the effect of clinical and genetic predictors on surgery, stratified by disease subtype given paradoxical effects of smoking. Kaplan-Meier curves were used to examine the effect of smoking and genotype on time to surgery. (Significance: P < 0.05 for main effects; P < 0.2 for interaction terms).

RESULTS

400 (65.8%) patients had Crohn's disease (CD) and 208 (34.2%) had ulcerative colitis (UC). 298 (49%) underwent an IBD-related surgery. There was a trend towards significance between rs16969968 and smoking behavior (smoking status [P = 0.05], nicotine dependence [AA > AG > GG; P = 0.08]). Smoking and genotype were not independently associated with surgery in UC or CD. However, interaction between rs16969968 and smoking in predicting surgery was observed for both UC (OR = 2.72; P = 0.05) and CD (OR = 2.88; P = 0.1). CHRNA5 genotype, but not smoking, predicted time to surgery in patients with UC (P = 0.007) but not in patients with CD. The interaction between smoking and genotype was not significantly associated with time to surgery in UC or CD.

CONCLUSIONS

The CHRNA5 rs16969968 A variant interacts with smoking to influence IBD-related surgery. 10.1093/ibd/izx094_video1izx094.video15775248538001.

Pathways to precision medicine in smoking cessation treatments

Cigarette smoking is highly addictive and modern genetic research has identified robust genetic influences on nicotine dependence. An important step in translating these genetic findings to clinical practice is identifying the genetic factors affecting smoking cessation in order to enhance current smoking cessation treatments. We reviewed the significant genetic variants that predict nicotine dependence, smoking cessation, and response to cessation pharmacotherapy. These data suggest that genetic risks can predict smoking cessation outcomes and moderate the effect of pharmacological treatments. Some pharmacogenetic findings have been replicated in meta-analyses or in multiple smoking cessation trials. The variation in efficacy between smokers with different genetic markers supports the notion that personalized smoking cessation intervention based upon genotype could maximize the efficiency of such treatment while minimizing side effects, thus influencing the number needed to treat (NNT) and the number needed to harm. In summary, as precision medicine is revolutionizing healthcare, smoking cessation may be one of the first areas where genetic variants may identify individuals at increased risk. Current evidence strongly suggests that genetic variants predict cessation failure and that cessation pharmacotherapy effectiveness is modulated by biomarkers such as nicotinic cholinergic receptor α5 subunit (CHRNA5) genotypes or nicotine metabolism ratio (NMR). These findings strengthen the case for the development and rigorous testing of treatments that target patients with different biological risk profiles.

Toward the implementation of genomic applications for smoking cessation and smoking-related diseases

The incorporation of genomic information into routine care settings is a burgeoning area for investigation in behavioral medicine. The past decade has witnessed rapid advancements in knowledge of genetic biomarkers associated with smoking behaviors and tobacco-related morbidity and mortality, providing the basis for promising genomic applications in clinical and community settings. We assessed the current state of readiness for implementing genomic applications involving variation in the α5 nicotinic cholinergic receptor subunit gene CHRNA5 and smoking outcomes (behaviors and related diseases) using a process that could be translatable to a wide range of genomic applications in behavioral medicine. We reviewed the scientific literature involving CHRNA5 genetic variation and smoking cessation, and then summarized and synthesized a chain of evidence according to analytic validity, clinical validity, clinical utility, and ethical, legal, and social implications (ACCE), a well-established set of criteria used to evaluate genomic applications. Our review identified at least three specific genomic applications for which implementation may be considered, including the use of CHRNA5 genetic test results for informing disease risk, optimizing smoking cessation treatment, and motivating smoking behavior change. For these genomic applications, we rated analytic validity as convincing, clinical validity as adequate, and clinical utility and ethical, legal, and social implications as inadequate. For clinical genomic applications involving CHRNA5 variation and smoking outcomes, research efforts now need to focus on establishing clinical utility. This approach is compatible with pre-implementation research, which is also needed to accelerate translation, improve innovation design, and understand and refine system processes involved in implementation. This study informs the readiness to incorporate smoking-related genomic applications in real-world settings and facilitates cross-disciplinary collaboration to accelerate the integration of evidence-based genomics in behavioral medicine.

The DRD2/ANKK1 Taq1A polymorphism is associated with smoking cessation failure in patients with coronary heart disease

AIM

We speculated whether DRD2 or CHRN subunit polymorphisms might be associated with the risk of smoking cessation failure in subjects after coronary heart disease (CHD) manifestation.

METHODS

A total of 964 patients with CHD, mean age 64.3 years (standard deviation [SD] 9.0), examined in the EUROASPIRE III and IV surveys were genotyped for rs1800497 (DRD2/ANKK1 Taq1A), rs578776 (CHRNA5-A3-B4), rs16969968 (CHRNA5) and rs1051730 (CHRNA3) SNPs.

RESULTS

The presence of DRD2/ANKK1 Taq1A minor T allele was independently associated with increased relative risk of smoking persistence (odds ratio: 1.79; 95% CI: 1.13-4.35). We observed no association between CHRN SNPs and smoking habit.

CONCLUSION

DRD2/ANKK1 Taq1A polymorphism is associated with a decreased likelihood of smoking cessation in patients after CHD manifestation.

Contribution of Variants in CHRNA5/A3/B4 Gene Cluster on Chromosome 15 to Tobacco Smoking: From Genetic Association to Mechanism

Cigarette smoking is the major cause of preventable death and morbidity throughout the world. Many compounds are present in tobacco, but nicotine is the primary addictive one. Nicotine exerts its physiological and pharmacological roles in the brain through neuronal nicotinic acetylcholine receptors (nAChRs), which are ligand-gated ion channels consisting of five membrane-spanning subunits that can modulate the release of neurotransmitters, such as dopamine, glutamate, and GABA and mediate fast signal transmission at synapses. Considering that there are 12 nAChR subunits, it is highly likely that subunits other than α4 and β2, which have been intensively investigated, also are involved in nicotine addiction. Consistent with this hypothesis, a number of genome-wide association studies (GWAS) and subsequent candidate gene-based associated studies investigating the genetic variants associated with nicotine dependence (ND) and smoking-related phenotypes have shed light on the CHRNA5/A3/B4 gene cluster on chromosome 15, which encodes the α5, α3, and β4 nAChR subunits, respectively. These studies demonstrate two groups of risk variants in this region. The first one is marked by single nucleotide polymorphism (SNP) rs16969968 in exon 5 of CHRNA5, which changes an aspartic acid residue into asparagine at position 398 (D398N) of the α5 subunit protein sequence, and it is tightly linked SNP rs1051730 in CHRNA3. The second one is SNP rs578776 in the 3'-untranslated region (UTR) of CHRNA3, which has a low correlation with rs16969968. Although the detailed molecular mechanisms underlying these associations remain to be further elucidated, recent findings have shown that α5* (where "*" indicates the presence of additional subunits) nAChRs located in the medial habenulo-interpeduncular nucleus (mHb-IPN) are involved in the control of nicotine self-administration in rodents. Disruption of α5* nAChR signaling diminishes the aversive effects of nicotine on the mHb-IPN pathway and thereby permits more nicotine consumption. To gain a better understanding of the function of the highly significant genetic variants identified in this region in controlling smoking-related behaviors, in this communication, we provide an up-to-date review of the progress of studies focusing on the CHRNA5/A3/B4 gene cluster and its role in ND.