Introduction to sex differences in neurotoxic effects

Whole transcriptome analysis in offspring whose fathers were exposed to a developmental insult: a novel avian model

Although the effects of paternal exposure to insults on the offspring received limited attention in the past, it is currently gaining interest especially after understanding the mechanisms which may mediate such exposure effects. In the current study, the well-controlled avian model (Fayoumi) was utilized to investigate the effects of paternal exposure to the developmental insult, chlorpyrifos on the offspring's gene expression via mRNA and small RNA sequencing. Numerous mRNA gene expression changes were detected in the offspring after paternal exposure to the developmental insult, especially in genes related to neurogenesis, learning and memory. qPCR analysis of several genes, that were significantly changed in mRNA sequencing, confirmed the results obtained in mRNA sequencing. On the other hand, small RNA sequencing did not identify significant microRNA genes expression changes in the offspring after paternal exposure to the developmental insult. The effects of the paternal exposure were more pronounced in the female offspring compared to the male offspring. The results identified expression alterations in major genes (some of which were pertinent to the functional changes observed in other forms of early developmental exposure) after paternal insult exposure and provided a direction for future studies involving the most affected genes.

Scoping review on environmental enrichment: Are critical periods and sex differences adequately studied?

BACKGROUND

Decades of research have shown the robust behavioral, structural, and molecular effects of environmental enrichment (EE) which predominantly improves neuropathological conditions. However, systematic examination of age and sex influences in response to EE is limited.

OBJECTIVE

Examine the use of EE and evaluate where sex differences (or similarities) are described and whether critical developmental periods are addressed. A critical examination of review articles about EE will establish a framework for the context of the findings of EE-induced effects, improve the impact of future EE studies and improve translatability.

ELIGIBILITY CRITERIA

Narrative, systematic reviews (not original reports) and meta-analyses of any animal species published during 2011 to 2021. Clinical and farming studies were excluded.

SOURCES OF EVIDENCE

Indexed review articles in Pubmed and Psychinfo.

RESULTS

Most studies examine EE during adulthood such as following an injury or following repeated addictive drug exposure. However, in various genetic models of disease states, little attention is paid to effects of EE at different ages. Only some reviews acknowledge that sex differences exist even when the disease state under study is known to be sexually dimorphic. Identified issues include lack of systematic reporting; status of the "control group" (i.e., isolation or pair housing); the use and reporting of proper statistical analyses.

CONCLUSION

Reviews have concluded that EE is most effective when administered early in life but that EE during adulthood is certainly effective. Too few review studies have compared sexes for the effects of EE to make a statement about sex differences. Overall, articles reflect a lack of integration of information on age and sex differences in response to EE. Future studies of EE should examine both sexes and consider critical periods of the lifespan in the experimental models to facilitate the adequate translation of EE as a non-pharmaceutical intervention.

A Benchmark Dose Analysis for Maternal Pregnancy Urine-Fluoride and IQ in Children

As a guide to establishing a safe exposure level for fluoride exposure in pregnancy, we applied benchmark dose modeling to data from two prospective birth cohort studies. We included mother-child pairs from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort in Mexico and the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort in Canada. Maternal urinary fluoride concentrations (U-F, in mg/L, creatinine-adjusted) were measured in urine samples obtained during pregnancy. Children were assessed for intelligence quotient (IQ) at age 4 (n = 211) and between six and 12 years (n = 287) in the ELEMENT cohort, and three to four years (n = 407) in the MIREC cohort. We calculated covariate-adjusted regression coefficients and their standard errors to assess the association of maternal U-F concentrations with children's IQ measures. Assuming a benchmark response of 1 IQ point, we derived benchmark concentrations (BMCs) and benchmark concentration levels (BMCLs). No deviation from linearity was detected in the dose-response relationships, but boys showed lower BMC values than girls. Using a linear slope for the joint cohort data, the BMC for maternal U-F associated with a 1-point decrease in IQ scores was 0.31 mg/L (BMCL, 0.19 mg/L) for the youngest boys and girls in the two cohorts, and 0.33 mg/L (BMCL, 0.20 mg/L) for the MIREC cohort and the older ELEMENT children. Thus, the joint data show a BMCL in terms of the adjusted U-F concentrations in the pregnant women of approximately 0.2 mg/L. These results can be used to guide decisions on preventing excess fluoride exposure in pregnant women.

Reversal of prenatal heroin-induced alterations in hippocampal gene expression via transplantation of mesenchymal stem cells during adulthood

Neurobehavioral teratology is the study of typically subtle neurobehavioral birth defects. Our previously described mouse model demonstrated septohippocampal cholinergic innervation-related molecular and behavioral deficits after prenatal exposure to heroin. Since the alterations are below malformation level, they are likely to represent consequences of regulatory processes, feasibly gene expression. Consequently, in the present study pregnant mice were injected with heroin on gestation days 9-18 and were transplanted with mesenchymal stem cells (MSC) on postnatal day (PD) 105. The hippocampi of the offspring were analyzed on PD120 for the expression of the pertinent genes. Heroin induced global gender-dependent statistically significant changes in the expression of several genes. Significant Treatment X Sex interaction occurred in D1 and SOX2 genes (p < 0.01). Transplantation of MSC reversed the prenatal heroin-induced alterations in approximately 80% of the genes. The reversal index (RI), shifting the score of the heroin-exposed offspring by transplantation back toward the control level, was 0.61 ± 0.10 for the difference from RI = 0 (p < 0.001), confirming the validity of the effect of the neuroteratogens across variations among different genes. The present study suggests that neurobehavioral defects induced by prenatal heroin exposure are likely to be a consequence of regulatory changes. This study on prenatal exposure to insults with subsequent MSC therapy provides a model for elucidating the mechanisms of both the neuroteratogenicity and the therapy, steps that are critical for progress toward therapeutic applications.

Prenatal cocaine exposure, early cannabis use, and risky sexual behavior at age 25

BACKGROUND

Prior research on prenatal cocaine exposure (PCE) indicates that exposed children experience behavioral dysregulation resulting in risky adolescent behavior including earlier initiation of cannabis use and sexual intercourse. The goal of this study was to examine the long-term effects of PCE on adult sexual behavior.

METHODS

This is a prospective cohort study of the association between PCE and risky adult sexual behavior and sexually transmitted infections (STIs) in 202 young adults (mean age = 27, SD = 0.98 years). The sample was 55% female, 46% White, and 54% Black. Data from the prenatal, childhood, and adolescent phases of the study were used to delineate pathways from PCE to adult sexual behavior.

RESULTS

The most common risky sexual behavior was having sex while drunk or high (63%). One-third of the sample reported that they "almost always" had sex while drunk or high. We found evidence for an indirect pathway from PCE to adult sex while drunk or high via early cannabis initiation. There were no other effects of PCE on adult risky sexual behavior or on risk for STIs, after controlling for sex assigned at birth, race, age at sexual initiation, and family history of drug and alcohol problems.

CONCLUSIONS

Although PCE has been associated with earlier initiation of sex in prior studies, PCE was not directly associated with risky adult sex or history of STI. Exposed individuals were at greater risk of sex under the influence of alcohol or drugs via earlier initiation of cannabis use during adolescence.