Effect of Prenatal Glucocorticoid Exposure on Circadian Rhythm Gene Expression in the Brains of Adult Rat Offspring

Hippocampus under Pressure: Molecular Mechanisms of Development of Cognitive Impairments in SHR Rats

Data from clinical trials and animal experiments demonstrate relationship between chronic hypertension and development of cognitive impairments. Here, we review structural and biochemical alterations in the hippocampus of SHR rats with genetic hypertension, which are used as a model of essential hypertension and vascular dementia. In addition to hypertension, dysfunction of the hypothalamic-pituitary-adrenal system observed in SHR rats already at an early age may be a key factor of changes in the hippocampus at the structural and molecular levels. Global changes at the body level, such as hypertension and neurohumoral dysfunction, are associated with the development of vascular pathology and impairment of the blood-brain barrier. Changes in multiple biochemical glucocorticoid-dependent processes in the hippocampus, including dysfunction of steroid hormones receptors, impairments of neurotransmitter systems, BDNF deficiency, oxidative stress, and neuroinflammation are accompanied by the structural alterations, such as cellular signs of neuroinflammation micro- and astrogliosis, impairments of neurogenesis in the subgranular neurogenic zone, and neurodegenerative processes at the level of synapses, axons, and dendrites up to the death of neurons. The consequence of this is dysfunction of hippocampus, a key structure of the limbic system necessary for cognitive functions. Taking into account the available results at various levels starting from the body and brain structure (hippocampus) levels to molecular one, we can confirm translational validity of SHR rats for modeling mechanisms of vascular dementia.

Sex-dependent circadian alterations of both central and peripheral clock genes expression and gut-microbiota composition during activity-based anorexia in mice

RATIONALE

Patients with anorexia nervosa (AN) often present sleep disorders and circadian hormonal dysregulation. The role of the microbiota-gut-brain axis in the regulation of feeding behavior has emerged during the last decades but its relationships with the circadian rhythm remains poorly documented. Thus, we aimed to characterize the circadian clock genes expression in peripheral and central tissues in the activity-based anorexia mouse model (ABA), as well as the dynamics of the gut-microbiota composition.

METHODS

From day 1 to day 17, male and female C57Bl/6 mice were submitted or not to the ABA protocol (ABA and control (CT) groups), which combines a progressive limited access to food and a free access to a running wheel. At day 17, fasted CT and ABA mice were euthanized after either resting (EoR) or activity (EoA) phase (n = 10-12 per group). Circadian clock genes expression was assessed by RT-qPCR on peripheral (liver, colon and ileum) and central (hypothalamic suprachiasmatic nucleus or SCN) tissues. Cecal bacterial taxa abundances were evaluated by qPCR. Data were compared by two-way ANOVA followed by post-tests.

RESULTS

ABA mice exhibited a lower food intake, a body weight loss and an increase of diurnal physical activity that differ according with the sex. Interestingly, in the SCN, only ABA female mice exhibited altered circadian clock genes expression (Bmal1, Per1, Per2, Cry1, Cry2). In the intestinal tract, modification of clock genes expression was also more marked in females compared to males. For instance, in the ileum, female mice showed alteration of Bmal1, Clock, Per1, Per2, Cry1, Cry2 and Rev-erbα mRNA levels, while only Per2 and Cry1 mRNAs were affected by ABA model in males. By contrast, in the liver, clock genes expression was more markedly affected in males compared to females in response to ABA. Finally, circadian variations of gut-bacteria abundances were observed in both male and female mice and sex-dependent alteration were observed in response to the ABA model.

CONCLUSIONS

This study shows that alteration of circadian clock genes expression at both peripheral and central levels occurs in response to the ABA model. In addition, our data underline that circadian variations of the gut-microbiota composition are sex-dependent.

Overexpression of FRA1 (FOSL1) Leads to Global Transcriptional Perturbations, Reduced Cellular Adhesion and Altered Cell Cycle Progression

FRA1 (FOSL1) is a transcription factor and a member of the activator protein-1 superfamily. FRA1 is expressed in most tissues at low levels, and its expression is robustly induced in response to extracellular signals, leading to downstream cellular processes. However, abnormal FRA1 overexpression has been reported in various pathological states, including tumor progression and inflammation. To date, the molecular effects of FRA1 overexpression are still not understood. Therefore, the aim of this study was to investigate the transcriptional and functional effects of FRA1 overexpression using the CGL1 human hybrid cell line. FRA1-overexpressing CGL1 cells were generated using stably integrated CRISPR-mediated transcriptional activation, resulting in a 2-3 fold increase in FRA1 mRNA and protein levels. RNA-sequencing identified 298 differentially expressed genes with FRA1 overexpression. Gene ontology analysis showed numerous molecular networks enriched with FRA1 overexpression, including transcription-factor binding, regulation of the extracellular matrix and adhesion, and a variety of signaling processes, including protein kinase activity and chemokine signaling. In addition, cell functional assays demonstrated reduced cell adherence to fibronectin and collagen with FRA1 overexpression and altered cell cycle progression. Taken together, this study unravels the transcriptional response mediated by FRA1 overexpression and establishes the role of FRA1 in adhesion and cell cycle progression.

The molecular mechanisms in prenatal drug exposure-induced fetal programmed adult cardiovascular disease

The "developmental origins of health and disease" (DOHaD) hypothesis posits that early-life environmental exposures have a lasting impact on individual's health and permanently shape growth, structure, and metabolism. This reprogramming, which results from fetal stress, is believed to contribute to the development of adulthood cardiovascular diseases such as hypertension, coronary artery disease, heart failure, and increased susceptibility to ischemic injuries. Recent studies have shown that prenatal exposure to drugs, such as glucocorticoids, antibiotics, antidepressants, antiepileptics, and other toxins, increases the risk of adult-onset cardiovascular diseases. In addition, observational and animal experimental studies have demonstrated the association between prenatal drug exposure and the programming of cardiovascular disease in the offspring. The molecular mechanisms underlying these effects are still being explored but are thought to involve metabolism dysregulation. This review summarizes the current evidence on the relationship between prenatal drug exposure and the risk of adult cardiovascular disorders. Additionally, we present the latest insights into the molecular mechanisms that lead to programmed cardiovascular phenotypes after prenatal drug exposure.

Case Report: A novel KNCH2 variant-induced fetal heart block and the advantages of fetal genomic sequencing in prenatal long-term dexamethasone exposure

Background: Fetal bradycardia is a common but severe condition. In addition to autoimmune-mediated fetal heart block, several types of channelopathies induce high-degree atrioventricular block (AVB). Long QT syndrome (LQTS) is a major cause of non-autoimmune-mediated fetal heart block. Due to the limitations of prenatal diagnostic technologies, LQTS is seldom identified unless fetal genetic screening is performed. Thus, long-term prenatal dexamethasone (DEX) exposure can become a challenge for these patients. We report on a rare case of a novel KCNH2 variant related to LQTS and associated with high-degree fetal AVB with long-term DEX exposure. This case led us to review our prenatal administration strategy for such patients.

Case Presentation: A fetus was identified with high-degree AVB (2:1 transduction at 28 + 2 gestational weeks). Typical tests of immune function in the pregnant woman were conducted including tests for thyroid function, rheumatic screening, autoimmune antibodies (such as anti-Ro/SSA and anti-La/SSB), and anti-nuclear antibodies (anti-ANA). Following the recommended protocol, the pregnant patient received DEX (0.75 mg/day) during pregnancy. Subsequently, the fetal AVB changed from 2:1 to prolonged AV intervals with ventricular tachycardia, which suggested a therapeutic benefit of DEX in some respects. However, a high-degree AVB with a significantly prolonged QTc interval was identified in the neonate following birth. Genetic testing revealed that a KCNH2 c.1868C>A variant induced LQTS. The body length remained approximately -3.2 SD from the reference value after prenatal long-term DEX exposure, which indicated a developmental restriction. Additionally, the functional validation experiments were performed to demonstrate the prolonged duration of calcium transit both in depolarization and repolarization with the KCNH2 c.1868C>A variant.

Conclusion: Genetic screening should be recommended in fetuses with autoimmune antibody negative high-degree AVB, especially for 2:1 transduction AVB and in fetuses with changes in fetal heart rhythm following initial DEX treatment. Genetic screening may help identify genetic variant–related channelopathies and avoid unexpected prenatal exposure of DEX and its possible long-term adverse postnatal complications.