Converging Effects of Three Different Endocrine Disrupters on Sox and Pou Gene Expression in Developing Rat Hippocampus: Possible Role of microRNA in Sex Differences

High throughput LC-MS/MS method for steroid hormone analysis in rat liver and plasma - unraveling methodological challenges

Comprehensive reference data for steroid hormones are lacking in rat models, particularly for early developmental stages and unconventional matrices as the liver. Therefore, we developed and validated an enzymatic, solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify a panel of 23 steroid hormones in liver and plasma from adult and neonatal rats. Our approach tackles methodological challenges, focusing on undesired byproducts associated with specific enzymatic treatment, and enables a thorough assessment of potential interferences in complex matrices by utilizing unstripped plasma and liver. We propose an optimized enzymatic hydrolysis protocol using a recombinant β-glucuronidase/sulfatase mix (BGS mix) to efficiently deconjugate steroid phase II conjugates. The streamlined sample preparation and high-throughput solid phase extraction in a 96-well plate significantly accelerate sample processing for complex matrices and alarge number of samples. We were able to achieve the necessary sensitivity for accurately measuring the target analytes, particularly estrogens, in small sample sizes of 5-20 mg of liver tissue and 100 μL of plasma. Through the analysis of liver and plasma samples from adult and neonatal rats, including both sexes, our study showed a novel set of steroid hormone reference intervals. This study provides a reliable diagnostic tool for the quantification of steroids in rat models and gives insight in liver and plasma-related steroid hormone dynamics at early developmental stages. In addition, the method covers several pathway intermediates and extend the list of steroid hormones to be investigated.

Activation of NLRP3 Inflammasome in Liver of Long Evans Lactating Rats and Its Perinatal Effects in the Offspring after Bisphenol F Exposure

The liver is the organ responsible for the metabolism and detoxification of BPF, the BPA analogue that is replacing it in plastic-based products. It is not known whether BPF can trigger inflammatory responses via the NLRP3 inflammasome, which plays a major role in the development of liver disease. The aim of this study was to evaluate nitrosative stress species (RNS) and NLRP3 inflammasome activation in the liver of lactating dams after BPF exposure. Moreover, it was studied whether this effect could also be observed in the liver of female and male offspring at postnatal day 6 (PND6). 36 Long Evans rats were randomly distributed according to oral treatment into three groups: Control, BPF-low dose (LBPF; 0.0365 mg/kg b.w./day) group and BPF-high dose (HBPF; 3.65 mg/kg b.w./day) group. The levels of nitrosative stress-inducing proteins (eNOS, iNOS, HO-1d), NLRP3 inflammasome components (NLRP3, PyCARD, CASP1) and proinflammatory cytokines (IL-1β, IL-18, IFN-γ and TNF-α) were measured by gene and protein expression in the liver of lactating dams and in female and male PND6 offspring. Lactating dams treated with LBPF showed a significant increase in iNOS and HO-1d, activation of NLRP3 components (NLRP3, PyCARD, CASP1) and promoted the release of proinflammatory cytokines such as IL-1β, IL-18, IFN-γ and TNF-α. Similar effects were found in female and male PND6 offspring after perinatal exposure. LBPF oral administration and perinatal exposure caused an increase of nitrosative stress markers and proinflammatory cytokines. Also, NLRP3 inflammasome activation was significantly increased in in the liver of lactating dams and PND6 offspring.

Oxidative stress increases in liver of lactating rats after BPF-low-dose exposure: perinatal effects in the offspring

Bisphenol F (BPF) is replacing Bisphenol A (BPA) in the manufacture of products due to endocrine-disrupting effects. BPF monomers can also be released into the environment and enter the food chain, resulting in human exposure to low doses. Since bisphenols are primarily metabolized by the liver, this organ is more vulnerable to lower doses of bisphenols than others. Exposure during prenatal development may increase the risk of diseases in adulthood. The aim was to evaluate whether BPF administration could generate oxidative stress in liver of lactating rats, and whether these effects may be also observed in female and male postnatal day 6 (PND6) offspring. Long Evans rats received oral treatment: Control, BPF-low-dose (LBPF) 0.0365 mg/kg b.w./day, and BPF-high-dose (HBPF) 3.65 mg/kg b.w./day. The levels of antioxidant enzymes (CAT, SOD, GR, GPx and GST), glutathione system (GSH, GSSG) and lipid damage markers (MDA, LPO) were measured using colorimetric methods in liver of both lactating dams and in PND6 offspring. Mean values were analyzed using Prism-7. LBPF affected liver defense mechanisms (antioxidant enzymes and glutathione system), increasing ROS levels and producing lipid peroxidation in lactating dams. Similar effects were found in female and male PND6 offspring as a consequence of perinatal exposure.

Endocrine-Disrupting Chemicals and Hippocampal Development: The Role of Estrogen and Androgen Signaling

Hormones are important regulators of key processes during fetal brain development. Thus, the developing brain is vulnerable to the action of chemicals that can interfere with endocrine signals. Epidemiological studies have pointed toward sexually dimorphic associations between neurodevelopmental outcomes, such as cognitive abilities, in children and prenatal exposure to endocrine-disrupting chemicals (EDCs). This points toward disruption of sex steroid signaling in the development of neural structures underlying cognitive functions, such as the hippocampus, an essential mediator of learning and memory processes. Indeed, during development, the hippocampus is subjected to the organizational effects of estrogens and androgens, which influence hippocampal cell proliferation, differentiation, dendritic growth, and synaptogenesis in the hippocampal fields of Cornu Ammonis and the dentate gyrus. These early organizational effects correlate with a sexual dimorphism in spatial cognition and are subject to exogenous chemical perturbations. This review summarizes the current knowledge about the organizational effects of estrogens and androgens on the developing hippocampus and the evidence for hippocampal-dependent learning and memory perturbations induced by developmental exposure to EDCs. We conclude that, while it is clear that sex hormone signaling plays a significant role during hippocampal development, a complete picture at the molecular and cellular levels would be needed to establish causative links between the endocrine modes of action exerted by EDCs and the adverse outcomes these chemicals can induce at the organism level.

microRNA-dependent regulation of gene expression in GABAergic interneurons

Information processing within neuronal circuits relies on their proper development and a balanced interplay between principal and local inhibitory interneurons within those circuits. Gamma-aminobutyric acid (GABA)ergic inhibitory interneurons are a remarkably heterogeneous population, comprising subclasses based on their morphological, electrophysiological, and molecular features, with differential connectivity and activity patterns. microRNA (miRNA)-dependent post-transcriptional control of gene expression represents an important regulatory mechanism for neuronal development and plasticity. miRNAs are a large group of small non-coding RNAs (21-24 nucleotides) acting as negative regulators of mRNA translation and stability. However, while miRNA-dependent gene regulation in principal neurons has been described heretofore in several studies, an understanding of the role of miRNAs in inhibitory interneurons is only beginning to emerge. Recent research demonstrated that miRNAs are differentially expressed in interneuron subclasses, are vitally important for migration, maturation, and survival of interneurons during embryonic development and are crucial for cognitive function and memory formation. In this review, we discuss recent progress in understanding miRNA-dependent regulation of gene expression in interneuron development and function. We aim to shed light onto mechanisms by which miRNAs in GABAergic interneurons contribute to sculpting neuronal circuits, and how their dysregulation may underlie the emergence of numerous neurodevelopmental and neuropsychiatric disorders.