Reduced monoamine oxidase A activity in pregnant smokers and in their newborns

Genetic and early environmental influences on the serotonin system: consequences for brain development and risk for psychopathology

BACKGROUND

Despite more than 60 years of research in the role of serotonin (5-HT) in psychopathology, many questions still remain. From a developmental perspective, studies have provided more insight into how 5-HT dysfunctions acquired in utero or early in life may modulate brain development. This paper discusses the relevance of the developmental role of 5-HT for the understanding of psychopathology. We review developmental milestones of the 5-HT system, how genetic and environmental 5-HT disturbances could affect brain development and the potential role of DNA methylation in 5-HT genes for brain development.

METHODS

Studies were identified using common databases (e.g., PubMed, Google Scholar) and reference lists.

RESULTS

Despite the widely supported view that the 5-HT system matures in early life, different 5-HT receptors, proteins and enzymes have different developmental patterns, and development is brain region-specific. A disruption in 5-HT homeostasis during development may lead to structural and functional changes in brain circuits that modulate emotional stress responses, including subcortical limbic and (pre)frontal areas. This may result in a predisposition to psychopathology. DNA methylation might be one of the underlying physiologic mechanisms.

LIMITATIONS

There is a need for prospective studies. The impact of stressors during adolescence on the 5-HT system is understudied. Questions regarding efficacy of drugs acting on 5-HT still remain.

CONCLUSION

A multidisciplinary and longitudinal approach in designing studies on the role of 5-HT in psychopathology might help to bring us closer to the understanding of the role of 5-HT in psychopathology.

Maternal smoking cessation and reduced academic and behavioral problems in offspring

BACKGROUND

There is some debate whether smoking during pregnancy causes or is only a risk factor for negative academic outcomes and increased risk of psychopathology in offspring. This study evaluated whether maternal smoking cessation would reduce the risk of adverse outcomes in school-aged children.

METHODS

Women completed an online survey that included items about child scholastic performance and the Child Behavior Checklist (CBCL). Mothers were divided based on pre-pregnancy and pregnancy smoking status into: (1) Nonsmokers (N=320); (2) Women that smoked in the 3 months preceding and throughout pregnancy (Smokers, N=83); and (3) Smoking before, but not during pregnancy (Quitters, N=72).

RESULTS

The Smokers and Quitters groups each had lower education and incomes compared to Nonsmokers but were indistinguishable from each other on these measures. The offspring of Smokers were more likely (p<.05) to be behind their peers on standardized tests in math (27.8%) relative to both Nonsmokers (17.4%) and Quitters (13.0%) with similar findings for reading. Smokers reported more behavioral problems by their children in several areas including Hyperactivity and Impulsivity, Social problems, and Externalizing problems including Aggression and Rule-Breaking. Further, the children of Quitters had significantly fewer Attention and Externalizing problems than Smokers. These outcomes were observed even after accounting for the variance attributable to maternal education and several other potential confounds.

CONCLUSIONS

Together, these findings indicate that smoking cessation is associated with reduced risk of having children with academic and neuropsychological difficulties. These outcomes are discussed within the framework that nicotine may be a neurobehavioral teratogen.

Executive function profile in the offspring of women that smoked during pregnancy

INTRODUCTION

Smoking tobacco during pregnancy results in exposure to the fetal neuroteratogen nicotine. The current study evaluated if the offspring of smokers show abnormalities in maternal ratings of executive function, prevalence of Attention Deficit Hyperactivity Disorder (ADHD), and academic performance. A secondary objective was to determine the utility of online data collection.

METHODS

Mothers (N = 357) completed the parent form of the Behavioral Rating Inventory of Executive Function (BRIEF) and provided information about smoking during pregnancy.

RESULTS

The internal consistency of the BRIEF when administered electronically was quite satisfactory (Cronbach's α = .98). As anticipated, ADHD was more frequently diagnosed in the offspring of women that smoked at least 10 cigarettes/day (odds ratio [OR] = 2.64, 95% CI = 1.22-5.71). Higher (i.e., more problematic) ratings relative to unexposed children (p < .01) were only identified on the total BRIEF score, the Metacognition Index, and on the Initiate, Plan/Organize, and Monitor scales among children exposed to ≥10 cigarettes/day. Nicotine-exposed children were also more likely to perform less well than their classmates in math (OR = 2.78, 95% CI = 1.59-4.87) and reading (OR = 2.00, 95% CI = 1.10-3.63), and these academic effects were independent of maternal education levels.

CONCLUSIONS

This report provides preliminary evidence that the BRIEF has adequate psychometric properties when administered electronically and that mothers who smoke have offspring with lower executive function proficiency. These findings contribute to a larger literature that indicates that smoking during pregnancy results in adverse reproductive outcomes and, possibly, subtle but enduring deficits in prefrontal function.

Smoking related diseases: the central role of monoamine oxidase

Smoking is a major risk factor of morbidity and mortality. It is well established that monoamine oxidase (MAO) activity is decreased in smokers. Serotonin (5-HT), a major substrate for MAO that circulates as a reserve pool stored in platelets, is a marker of platelet activation. We recently reported that smoking durably modifies the platelet 5-HT/MAO system by inducing a demethylation of the MAO gene promoter resulting in high MAO protein concentration persisting more than ten years after quitting smoking. The present data enlarges the results to another MAO substrate, norepinephrine (NE), further confirming the central role of MAO in tobacco use-induced diseases. Thus, MAO could be a readily accessible and helpful marker in the risk evaluation of smoking-related diseases, from cardiovascular and pulmonary diseases to depression, anxiety and cancer. The present review implements the new finding of epigenetic regulation of MAO and suggests that smoking-induced MAO demethylation can be considered as a hallmark of smoking-related cancers similarly to other aberrant DNA methylations.