Corticotropin-Releasing Hormone Suppresses Synapse Formation in the Hippocampus of Male Rats via Inhibition of CXCL5 Secretion by Glia

Sex-specificities in offspring neurodevelopment and behaviour upon maternal glycation: Putative underlying neurometabolic and synaptic changes

AIM

Lactation is an important programming window for metabolic disease and neuronal alterations later in life. We aimed to study the effect of maternal glycation during lactation on offspring neurodevelopment and behaviour, assessing possible sex differences and underpinning molecular players.

METHODS

Female Wistar rats were treated with the Glyoxalase-1 inhibitor S-p-Bromobenzylguthione cyclopentyl diester (BBGC 5 mg/kg). A control and vehicle group treated with dimethyl sulfoxide were considered. Male and female offspring were tested at infancy for neurodevelopment hallmarks. After weaning, triglycerides and total antioxidant capacity were measured in breast milk. At adolescence, offspring were tested for locomotor ability, anxious-like behaviour, and recognition memory. Metabolic parameters were assessed, and the hippocampus and prefrontal cortex were collected for molecular analysis.

KEY FINDINGS

Maternal glycation reduced triglycerides and total antioxidant capacity levels in breast milk. At infancy, both male and female offspring presented an anticipation on the achievement of neurodevelopmental milestones. At adolescence, male offspring exposed to maternal glycation presented hyperlocomotion, whereas offspring of both sexes presented a risk-taking phenotype, accompanied by GABA_A receptor upregulation in the hippocampus. Females also demonstrated GABA_A and PSD-95 changes in prefrontal cortex. Furthermore, lower levels of GLO1 and consequently higher accumulation of AGES were also observed in both male and female offspring hippocampus.

SIGNIFICANCE

Early exposure to maternal glycation induces changes in milk composition leading to neurodevelopment changes at infancy, and sex-specific behavioural and neurometabolic changes at adolescence, further evidencing that lactation period is a critical metabolic programming window and in sculpting behaviour.

Local CRF and oxytocin receptors correlate with female experience-driven avoidance change and hippocampal neuronal plasticity

Understanding how experiences affect females' behaviors and neuronal plasticity is essential for uncovering the mechanism of neurodevelopmental disorders. The study explored how neonatal maternal deprivation (MD) and post-weaning environmental enrichment (EE) impacted the CA1 and DG's neuronal plasticity in the dorsal hippocampus, and its relationships with passive avoidance, local corticotrophin-releasing factor (CRF) levels, and oxytocin receptor (OTR) levels in female BALB/c mice. The results showed that MD damaged passive avoidance induced by foot shock and hotness, and EE restored it partially. In the CA1, MD raised CRF levels and OTR levels. Parallelly, MD increased synaptic connection levels but reduced the branches' numbers of pyramidal neurons. Meanwhile, in the DG, MD increased OTR levels but lowered CRF levels, DNA levels, and spine densities. EE did not change the CA1 and DG's CRF and OTR levels. However, EE added DG's dendrites of granular cells. The additive of MD and EE raised CA1's synaptophysin and DG's postsynaptic density protein-95 and OTR levels, and meanwhile, shaped avoidance behaviors primarily similar to the control. The results suggest that experience-driven avoidance change and hippocampal neuronal plasticity are associated with local CRF and OTR levels in female mice.

Effects of maternal deprivation and environmental enrichment on anxiety-like and depression-like behaviors correlate with oxytocin system and CRH level in the medial-lateral habenula

The medial-lateral habenula (LHbM)'s role in anxiety and depression behaviors in female mice remains unclear. Here, we used neonatal maternal deprivation (MD) and post-weaning environmental enrichment (EE) to treat female BALB/c offspring and checked anxiety-like and depression-like behaviors as well as the corticotropin-releasing hormone (CRH), oxytocin receptor (OTR), estrogen receptor-beta (ERβ) levels in their LHbM at adulthood. We found that MD enhanced state anxiety-like behaviors in the elevated plus-maze test, and EE caused trait anxiety-like behaviors in the open field test and depression-like behaviors in the tail suspension test. The immunochemistry showed that MD reduced OT immunoreactive neuron numbers in the hypothalamic paraventricular nucleus but increased OTR levels in the LHbM; EE increased CRH levels in the LHbM but decreased OTR levels in the LHbM. The additive effects of EE and MD maintained the behavioral parameters, OT-ir neuronal numbers, CRH levels, and OTR levels similar to the additive of non-MD and non-EE. The correlation analysis showed that CRH levels correlated with synaptic connection levels, OTR levels correlated with nucleus densities, and ERβ levels correlated with Nissl body levels and body weights in female mice. Neither MD nor EE affected ERβ levels in the LHbM. Together, the study revealed the relationships between behaviors and neuroendocrine and neuronal alterations in female LHbM and the effects of experiences including MD and EE on them.

Spatial learning and memory deficits induced by prenatal glucocorticoid exposure depend on hippocampal CRHR1 and CXCL5 signaling in rats

Background

Prenatal synthetic glucocorticoid (sGC) exposure increases the susceptibility to cognitive and affective disorders in postnatal life. We previously demonstrated that prenatal sGC exposure results in an increase in corticotropin-releasing hormone (CRH) receptor type 1 (CRHR1) expression in the hippocampus of rats, and CRHR1 is involved in synapse formation via regulation of C-X-C chemokine ligand 5 (CXCL5) in hippocampus. We sought to investigate that the roles of CRHR1 and CXCL5 in learning and memory impairment caused by prenatal sGC exposure.

Methods

Pregnant rats were administered with saline or dexamethasone (DEX) from gestational day (GD) 14 to GD21. DEX offspring at 2-day old were treated with saline and CRHR1 antagonists (antalarmin and CP154526) for 7 days. Some DEX offspring received intra-hippocampal injection of AAV9 carrying CXCL5 gene. Spatial learning and memory was assessed by Morris water maze test. Immunofluorescence analysis was applied to show synapsin I and PSD95 signals in hippocampus. Synapsin I and PSD95 protein level and CXCL5 concentration were determined by western blotting and ELISA, respectively. Organotypic hippocampal slice cultures were used to investigate the effect of DEX on CXCL5 production in vitro.

Results

Both male and female DEX offspring displayed impairment of spatial learning and memory in adulthood. Synapsin I and PSD95 signals and CXCL5 levels were decreased in DEX offspring. DEX offspring with antalarmin and CP154526 treatment showed improved spatial learning and memory. Antalarmin and CP154526 treatment increased synapsin I and PSD95 signals and CXCL5 concentration in hippocampus. Bilaterally hippocampal injection of AAV9 carrying CXCL5 gene improved the spatial learning and memory and increased CXCL5 concentration and synapsin I and PSD95 levels in hippocampus. DEX dose-dependently suppressed CXCL5 production in cultured hippocammpal slices, which was prevented by antalarmin treatment.

Conclusion

CRHR1 and CXCL5 signaling in the hippocampus are involved in spatial learning and memory deficits caused by prenatal DEX exposure. CRHR1 activation contributes to decreased CXCL5 production in hippocampus induced by prenatal DEX treatment. Our study provides a molecular basis of prenatal GC exposure programming spatial learning and memory.

Mast Cells in Stress, Pain, Blood-Brain Barrier, Neuroinflammation and Alzheimer's Disease

Mast cell activation plays an important role in stress-mediated disease pathogenesis. Chronic stress cause or exacerbate aging and age-dependent neurodegenerative diseases. The severity of inflammatory diseases is worsened by the stress. Mast cell activation-dependent inflammatory mediators augment stress associated pain and neuroinflammation. Stress is the second most common trigger of headache due to mast cell activation. Alzheimer's disease (AD) is a progressive irreversible neurodegenerative disease that affects more women than men and woman's increased susceptibility to chronic stress could increase the risk for AD. Modern life-related stress, social stress, isolation stress, restraint stress, early life stress are associated with an increased level of neurotoxic beta amyloid (Aβ) peptide. Stress increases cognitive dysfunction, generates amyloid precursor protein (APP), hyperphosphorylated tau, neurofibrillary tangles (NFTs), and amyloid plaques (APs) in the brain. Stress-induced Aβ persists for years and generates APs even several years after the stress exposure. Stress activates hypothalamic-pituitary adrenal (HPA) axis and releases corticotropin-releasing hormone (CRH) from hypothalamus and in peripheral system, which increases the formation of Aβ, tau hyperphosphorylation, and blood-brain barrier (BBB) disruption in the brain. Mast cells are implicated in nociception and pain. Mast cells are the source and target of CRH and other neuropeptides that mediate neuroinflammation. Microglia express receptor for CRH that mediate neurodegeneration in AD. However, the exact mechanisms of how stress-mediated mast cell activation contribute to the pathogenesis of AD remains elusive. This mini-review highlights the possible role of stress and mast cell activation in neuroinflammation, BBB, and tight junction disruption and AD pathogenesis.

Recent advances in the neurobiology of posttraumatic stress disorder: A review of possible mechanisms underlying an effective pharmacotherapy

Recent progress in the field of neurobiology supported by clinical evidence gradually reveals the mystery of human brain functioning. So far, many psychiatric disorders have been described in great detail, although there are still plenty of cases that are misunderstood. These include posttraumatic stress disorder (PTSD), which is a unique disease that combines a wide range of neurobiological changes, which involve disturbances of the hypothalamic-pituitary-adrenal gland axis, hyperactivation of the amygdala complex, and attenuation of some hippocampal and cortical functions. Such multiplicity results in differential symptomatology, including elevated anxiety, nightmares, fear retrieval episodes that may trigger delusions and hallucinations, sleep disturbances, and many others that strongly interfere with the quality of the patient's life. Because of widespread neurological changes and the disease manifestation, the pharmacotherapy of PTSD remains unclear and requires a multidimensional approach and involvement of polypharmacotherapy. Hopefully, more and more neuroscientists and clinicians will study PTSD, which will provide us with new information that would possibly accelerate establishment of well-tolerated and effective pharmacotherapy. In this review, we have focused on neurobiological changes regarding PTSD, addressing the most disturbed brain structures and neurotransmissions, as well as discussing in detail the recently taken and novel therapeutic paths.