ABCB1 gene polymorphisms are associated with suicide in forensic autopsies

The Future of Analytical and Interpretative Toxicology: Where are We Going and How Do We Get There?

(Forensic) toxicology has faced many challenges, both analytically and interpretatively, especially in relation to an increase in potential drugs of interest. Analytical toxicology and its application to medicine and forensic science have progressed rapidly within the past centuries. Technological innovations have enabled detection of more substances with increasing sensitivity in a variety of matrices. Our understanding of the effects (both intended and unintended) have also increased along with determination and degree of toxicity. However, it is clear there is even more to understand and consider. The analytical focus has been on typical matrices such as blood and urine but other matrices could further increase our understanding, especially in postmortem (PM) situations. Within this context, the role of PM changes and potential redistribution of drugs requires further research and identification of markers of its occurrence and extent. Whilst instrumentation has improved, in the future, nanotechnology may play a role in selective and sensitive analysis as well as bioassays. Toxicologists often only have an advisory impact on pre-analytical and pre-interpretative considerations. The collection of appropriate samples at the right time in an appropriate way as well as obtaining sufficient circumstance background is paramount in ensuring an effective analytical strategy to provide useful results that can be interpreted within context. Nevertheless, key interpretative considerations such as pharmacogenomics and drug-drug interactions as well as determination of tolerance remain and in the future, analytical confirmation of an individual's metabolic profile may support a personalized medicine and judicial approach. This should be supported by the compilation and appropriate application of drug data pursuant to the situation. Specifically, in PM circumstances, data pertaining to where a drug was not/may have been/was contributory will be beneficial with associated pathological considerations. This article describes the challenges faced within toxicology and discusses progress to a future where they are being addressed.

Combined influence of ABCB1 genetic polymorphism and DNA methylation on aspirin resistance in Chinese ischemic stroke patients

Genetic variants of ABCB1 may affect intestinal absorption of aspirin (ASA). However, it is unclear whether ABCB1 polymorphisms and DNA methylation are associated with ASA efficacy for ischemic stroke. Our aims is to investigate the association between ABCB1 polymorphisms and methylation status on the antiplatelet effects of ASA in Chinese Han ischemic stroke patients. This is a prospective cohort analysis of eligible stroke patients who received ASA. Patients were divided into two groups according to the thrombelastogram and platelet aggregation test: aspirin resistance (AR) and aspirin-sensitive (AS) groups. The ABCB1 genetic polymorphism and the methylation status of promoter regions were analyzed using PCR-RFLP and the combined bisulfite restriction analysis (COBRA). The number of genotype CC + TT of C3435T in the AR group was greater than that of the AS group (p = 0.007). The DNA methylation levels of ABCB1 promoter in the AS group was higher than that of the AR group (p < 0.001), and the promoter methylation levels showed significant different among the CC, CT, and TT genotypes of C3435T individuals (p = 0.006), while there was no obvious difference between different genotypes of C1236T and G2677T/A polymorphisms (p > 0.05). We also found that the methylation status of the ABCB1 promoter correlated positively with arachidonic acid inhibition (AA%) (R = 0.781, p < 0.001).The ABCB1 polymorphism and methylation status was associated with the reduced efficacy of ASA treatment in ischemic stroke. Genetic polymorphism and DNA methylation of ABCB1 should be concerned when prescribing ASA.

Post-mortem analysis of suicide victims shows ABCB1 haplotype 1236T-2677T-3435T as a candidate predisposing factor behind adverse drug reactions in females

BACKGROUND

Genetic variation in efflux transporter, permeability glycoprotein (P-gp), has recently been associated with completed violent suicides and also violent suicide attempts. As depression is known to be a risk factor for suicide and many antidepressants are P-gp substrates, it has been speculated that inadequate antidepressant treatment response or adverse side effects could be involved.

OBJECTIVES

The aim of this study was to investigate whether there is an association between the P-gp coding ABCB1 gene and completed suicides in citalopram users. Also, the effect of sex and suicide method used (violent vs. non-violent) was evaluated.

MATERIALS AND METHODS

All cases included in the study population, 349 completed suicide victims and 284 controls, were shown to be positive for antidepressant citalopram in a post-mortem toxicological drug screen. ABCB1 1236C>T, 2677G>T/A and 3435C>T polymorphisms were determined by TaqMan genotyping assays. Haplotypes were constructed from genotype data using the PHASE software. The association between the manner of death and the ABCB1 haplotype was tested with logistic regression analysis.

RESULTS

No statistically significant differences were observed in the ABCB1 allele or genotype frequencies between the suicide and control groups. However, the ABCB1 1236T-2677T-3435T haplotype was associated with completed suicides of female citalopram users (odds ratio: 2.23; 95% confidence interval: 1.22-4.07; P=0.009). After stratification by the method used for suicide, the association emerged in fatal intoxications (odds ratio: 2.51; 95% confidence interval: 1.29-4.87; P=0.007). In other groups, no statistically significant associations were observed.

CONCLUSION

Our results suggest that female citalopram users with ABCB1 1236T-2677T-3435T are more vulnerable to adverse effects of the drugs as this haplotype was enriched in non-violent suicides of female citalopram users. Even though the biological mechanism behind this observation is unknown, the results provide another example of the importance of sex-based segregation in pharmacogenetics studies.

The concept of violent suicide, its underlying trait and neurobiology: A critical perspective

Suicide is one of the leading causes of death and represents a significant public health problem world-wide. Individuals who attempt or die by suicide represent a highly heterogeneous population. Recently, efforts have been made to identify sub-populations and variables to categorize them. A popular dichotomy in suicide research of the past years is violent versus non-violent suicide - based on the method. This dichotomy is important given that there is an association between method of attempted suicide and risk of subsequent death by suicide. The differentiation concerning suicide methods is also critical regarding preventive efforts. In this review, we have tried to approach the concept of violent suicide from different perspectives, including a discussion about its definition and overlapping categories. In addition, we have critically discussed aggression as underlying trait, the question of intent to die, and sociodemographic, environmental, neuropsychological, and neurobiological factors potentially associated with violent suicide.

ABCB1 and CYP2D6 polymorphisms and treatment response of psychotic patients in a naturalistic setting

OBJECTIVES

The aim of our study was to examine the association between ABCB1 polymorphisms G2677T/A (rs2032582) and C3435T (rs1045642) and common CYP2D6 variants, with the response to antipsychotic treatment of psychotic patients, in a naturalistic setting, in Greece.

METHODS

One hundred patients suffering from schizophrenia and other psychotic disorders were included in the study. Dosages were normalized to chlorpromazine equivalents. Response following 1 month of treatment was assessed as either a continuous variable, using the distribution of the corrected Positive and Negative Syndrome Scale percent change, or as a dichotomous variable defined as the number of patients scoring ≥30% from the corrected baseline Positive and Negative Syndrome Scale score. Genotyping was achieved with established polymerase chain reaction-restriction fragment length polymorphism methods.

RESULTS

With response treated as a continuous variable, the homozygous recessive rs2032582 genotypes (TT) who were simultaneously carriers of a loss-of-function CYP2D6 allele (*4 or *5) responded significantly worse than the rest of the patients. Comparison of genotype frequencies revealed a statistically significant association of the above combination. No significant association between chlorpromazine equivalents and the tested genotypes was detected.

CONCLUSION

We have detected a possible interaction between ABCB1 and CYP2D6 in affecting response of psychotic patients to drug treatment, in a naturalistic setting.

Combined Influence of Genetic Polymorphism and DNA Methylation on ABCB1 Expression and Function in Healthy Chinese Males

BACKGROUND AND OBJECTIVES

It is well known that the expression and function of ATP-binding cassette transporter B1 (ABCB1) show high interindividual variability, but the reasons have not yet been fully elucidated. In this study, combined influence of genetic polymorphism and DNA methylation on ABCB1 mRNA expression and digoxin pharmacokinetics in healthy Chinese males was analyzed.

METHODS

A total of 93 subjects who were homozygous for the ABCB1 1236-2677-3435 TTT or CGC haplotype were enrolled in this study. DNA methylation status of the ABCB1 promoter and ABCB1 mRNA expression level in exfoliated intestinal epithelial cells were analyzed using bisulfite sequencing PCR and real-time PCR. The pharmacokinetics of digoxin in subjects were investigated after administration of a single oral dose of digoxin 0.5 mg.

RESULTS

The DNA methylation levels of ABCB1 promoter showed no significant difference between TTT/TTT and CGC/CGC carriers (P = 0.54). Subjects with TTT/TTT haplotype pair and high methylation status (TTT/TTT-HM) showed a significantly lower ABCB1 mRNA level compared to other subjects. Compared with TTT/TTT-HM subgroup, the area under the plasma concentration-time curve from time zero to 72 h (AUC_0-72) of digoxin was decreased by 26.9 %, the maximum plasma concentration (C _max) was decreased by 25 % and the apparent oral clearance (CL/F) was increased by 21.2 % in CGC/CGC-LM subgroup. The values of time to maximum concentration (t _max) and terminal elimination half-life (t _1/2) showed no significant difference.

CONCLUSIONS

Both genetic polymorphism and DNA methylation variation should be taken into consideration to explain the interindividual variability in ABCB1 expression and function more clearly.

An overview of the neurobiology of suicidal behaviors as one meta-system

Suicidal behaviors (SB) may be regarded as the outmost consequence of mental illnesses, or as a distinct entity per se. Regardless, the consequences of SB are very large to both society and affected individuals. The path leading to SB is clearly a complex one involving interactions between the subject's biology and environmental influences throughout life. With the aim to generate a representative and diversified overview of the different neurobiological components hypothesized or shown implicated across the entire SB field up to date by any approach, we selected and compiled a list of 212 gene symbols from the literature. An increasing number of novel gene (products) have been introduced as candidates, with half being implicated in SB in only the last 4 years. These candidates represent different neuro systems and functions and might therefore be regarded as competing or redundant explanations. We then adopted a unifying approach by treating them all as parts of the same meta-system, using bioinformatic tools. We present a network of all components connected by physical protein-protein interactions (the SB interactome). We proceeded by exploring the differences between the highly connected core (~30% of the candidate genes) and its peripheral parts, observing more functional homogeneity at the core, with multiple signal transduction pathways and actin-interacting proteins connecting a subset of receptors in nerve cell compartments as well as development/morphology phenotypes and the stress-sensitive synaptic plasticity processes of long term potentiation/depression. We suggest that SB neurobiology might also be viewed as one meta-system and perhaps be explained as intrinsic unbalances acting within the core or as imbalances arising between core and specific peripheral components.

ABCB1 gene polymorphisms and violent suicide attempt among survivors

INTRODUCTION

Those suicide attempters that choose violent methods dramatically diminish the possibility of survival. Completed suicide using violent means, which is common among first-time suicide attempters, was recently found to be more likely among T allele carriers in the three most common ABCB1 SNPs, encoding for P-gp. Thus, this study examined, for the first time, whether these ABCB1 SNPs were associated with the use of violent means among survivors of a suicide attempt.

MATERIAL AND METHODS

Suicide attempters (n = 578, 87.4% women; of whom 16.6% committed a violent intent) were genotyped for exonic SNPs in the ABCB1 (C1236T, G2677T/A, C3435T). The relations of the three genotypes and of the TTT haplotype with the use of a violent suicide method were evaluated separately. The impact of confounds on these variables was controlled.

RESULTS

A higher frequency (p = 0.02) of suicide attempters using violent methods was found among those carrying the ABCB1 haplotype (1236TT-2677TT-3435TT). Since gender and number of previous suicide attempts were identified as confounds, the relation was tested in the subset of women who were first-time attempters or second- and more-time attempters. The ABCB1 haplotype increased the risk more than three times in those women attempting a violent suicide for the first time (OR = 3.6; CI95%: 1.08-12.09; p = 0.04).

DISCUSSION

The ABCB1 haplotype (1236TT-2677TT-3435TT) was related to the use of a violent suicide attempt method. Genotyping for these three ABCB1 SNPs may be helpful to detect people at risk of first suicide intents using violent methods.