Effect of LPS treatment on tyrosine hydroxylase expression and Parkinson-like behaviors

The enduring effects of antimicrobials and lipopolysaccharide on the cellular mechanisms and behaviours associated with neurodegeneration in pubertal male and female CD1 mice

Puberty is a sensitive developmental period during which stressors can cause lasting brain and behavioural deficits. While the acute effects of pubertal lipopolysaccharide (LPS) and antimicrobial (AMNS) treatments are known, their enduring impacts on neurodegeneration-related mechanisms and behaviours remain unclear. This study examined these effects in male and female mice. At five weeks old, mice received 200ul of either broad-spectrum antimicrobials or water through oral gavage twice daily for seven days. At six weeks of age, they received an intraperitoneal injection of either saline or LPS. Four weeks later, adult mice underwent neurodegeneration-related behavioural tests, including the rotarod, forepaw stride length, reversed grid hang, open field, and buried pellet tests. Two days after the final test, brain and ileal samples were collected. Results showed that female mice treated with both AMNS and LPS exhibited deficits in neuromuscular strength, while males treated with LPS alone showed increased anxiety-like behaviours. Males treated with AMNS alone had decreased sigma-1 receptor (S1R) expression in the cornu ammonis 1 (CA1) and dentate gyrus (DG), while females treated with both AMNS and LPS had decreased S1R expression. Additionally, males treated with either LPS or AMNS had lower glial-derived neurotrophic factor receptor alpha-1 (GFRA1) expression in the primary motor cortex (M1) than females. Mice treated with LPS alone had decreased GFRA1 expression in the DG and decreased S1R expression in the secondary motor cortex (M2). These findings suggest that pubertal AMNS and LPS treatments may lead to enduring changes in biomarkers and behaviours related to neurodegeneration.

Sex-dependent effects of antimicrobials and lipopolysaccharide on blood-brain-barrier permeability in pubertal male and female CD1 mice

Exposure to stressors during puberty can disrupt normal development and possibly increase susceptibility to neurodegenerative disorders later in life. However, the mechanisms underlying the relationship between pubertal stress exposure and neurodegeneration remain unclear. As such, the current study was designed to examine the effects of pubertal antimicrobial (AMNS) and lipopolysaccharide (LPS) treatments on intestinal and blood-brain-barrier (BBB) permeability in male and female mice. Moreover, we also examined the sex-specific effects of pubertal AMNS and LPS treatments on gross motor activity, heart rate, and core body temperature. At four weeks of age, male and female CD1 mice were implanted with the G2 HR E-Mitter telemetry system. At five weeks of age, mice received 200 μL of broad-spectrum antimicrobial or water, through oral gavage, twice daily for seven days. Mice received an intraperitoneal injection of either saline or LPS at six weeks of age. BBB and intestinal permeability were examined 24 h, 72 h, and one week post-LPS/saline treatment. Telemetric data was collected for 48 h post-LPS/saline treatment. The results showed that pubertal AMNS and LPS treatments increased sickness behaviours and decreased body temperature and heart rate, in a sex-dependent manner. Furthermore, pubertal AMNS and LPS treatments resulted in sex-dependent regional increases in BBB permeability 24 h and 72 h post-LPS/saline treatment, while global increases in BBB permeability were only observed one week post-LPS/saline treatment. These results further our understanding of the combined effects of AMNS and LPS treatments on physiology and on the enduring negative changes observed following pubertal exposure to stressors.

The sex-dependent and enduring impact of pubertal stress on health and disease

Illness is often predicated long before the manifestation of its symptoms. Exposure to stressful experiences particularly during critical periods of development, such as puberty and adolescence, can induce various physical and mental illnesses. Puberty is a critical period of maturation for neuroendocrine systems, such as the hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-adrenal (HPA) axes. Exposure to adverse experiences during puberty can impede normal brain reorganizing and remodelling and result in enduring consequences on brain functioning and behaviour. Stress responsivity differs between the sexes during the pubertal period. This sex difference is partly due to differences in circulating sex hormones between males and females, impacting stress and immune responses differently. The effects of stress during puberty on physical and mental health remains under-examined. The purpose of this review is to summarize the most recent findings pertaining to age and sex differences in HPA axis, HPG axis, and immune system development, and describe how disruption in the functioning of these systems can propagate disease. Lastly, we delve into the notable neuroimmune contributions, sex differences, and the mediating role of the gut microbiome on stress and health outcomes. Understanding the enduring consequences of adverse experiences during puberty on physical and mental health will allow a greater proficiency in treating and preventing stress-related diseases early in development.

Pubertal consumption of R. badensis subspecies acadiensis modulates LPS-induced immune responses and gut microbiome dysbiosis in a sex-specific manner

Puberty is a critical period of development characterized by significant brain remodeling and increased vulnerability to immune challenges. Exposure to an immune challenge such as LPS during puberty can result in inflammation and gut dysbiosis which may lead to altered brain functioning and psychiatric illnesses later in life. However, treatment with probiotics during puberty has been found to mitigate LPS-induced peripheral and central inflammation, prevent LPS-induced changes to the gut microbiota and protect against enduring behavioural disorders in a sex-specific manner. Recent findings from our laboratory revealed that pubertal R. badensis subspecies acadiensis (R. badensis subsp. acadiensis) treatment prevents LPS-induced depression-like behavior and alterations in 5HT1A receptor expression in a sex-specific manner. However, the underlying mechanism remains unclear. Thus, the aim of this study was to gain mechanistic insights and to investigate the ability of R. badensis subsp. acadiensis consumption during puberty to mitigate the effects of LPS treatment on the immune system and the gut microbiome. Our results revealed that pubertal treatment with R. badensis subsp. acadiensis reduced sickness behaviors in females more than males in a time-specific manner. It also mitigated LPS-induced increases in pro-inflammatory cytokines in the blood and in TNFα mRNA expression in the prefrontal cortex and the hippocampus of female mice. There were sex-dependent differences in microbiome composition that persisted after LPS injection or R. badensis subsp. acadiensis consumption. R. badensis subsp. acadiensis had greater impact on the microbiota of male mice but female microbiota's were more responsive to LPS treatment. This suggested that female mice microbiota's may be more prone to modulation by this probiotic. These findings emphasize the sex-specific effects of probiotic use during puberty on the structure of the gut microbiome and the immune system and highlight the critical role of gut colonization with probiotics during adolescence on immunomodulation and prevention of the enduring effects of infections.

The acute effects of antimicrobials and lipopolysaccharide on the cellular mechanisms associated with neurodegeneration in pubertal male and female CD1 mice

Exposure to stressors during puberty can cause enduring effects on brain functioning and behaviours related to neurodegeneration. However, the mechanisms underlying these effects remain unclear. The gut microbiome is a complex and dynamic system that could serve as a possible mechanism through which early life stress may increase the predisposition to neurodegeneration. Therefore, the current study was designed to examine the acute effects of pubertal antimicrobial and lipopolysaccharide (LPS) treatments on the cellular mechanisms associated with neurodegenerative disorders in male and female mice. At five weeks of age, male and female CD-1 mice received 200 μL of broad-spectrum antimicrobials or water, through oral gavage, twice daily for seven days. Mice received an intraperitoneal (i.p.) injection of either saline or LPS at 6 weeks of age (i.e., pubertal period). Sickness behaviours were recorded and mice were euthanized 8 h post-injection. Following euthanasia, brains and blood samples were collected. The results indicated that puberal antimicrobial and LPS treatment induced sex-dependent changes in biomarkers related to sickness behaviour, peripheral inflammation, intestinal permeability, and neurodegeneration. The findings suggest that pubertal LPS and antimicrobial treatment may increase susceptibility to neurodegenerative diseases later in life, particularly in males.

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Pubertal antimicrobial and LPS treatment increase cytokine concentrations.

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Antimicrobial and LPS treatment have sex-specific effects on intestinal permeability.

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They also induce sex-specific changes in neurodegenerative markers.

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Antimicrobial treatment did not potentiate LPS-induced sickness behaviours.

Immune signaling as a node of interaction between systems that sex-specifically develop during puberty and adolescence

Adolescence is pivotal for neural and behavioral development across species. During this period, maturation occurs in several biological systems, the most well-recognized being activation of the hypothalamic-pituitary-gonadal axis marking pubertal onset. Increasing comparative studies of sex differences have enriched our understanding of systems integration during neurodevelopment. In recent years, immune signaling has emerged as a key node of interaction between a variety of biological signaling processes. Herein, we review the age- and sex-specific changes that occur in neural, hypothalamic-pituitary, and microbiome systems during adolescence. We then describe how immune signaling interacts with these systems, and review recent preclinical evidence indicating that immune signaling may play a central role in integrating changes in their typical and atypical development during adolescence. Finally, we discuss the translational relevance of these preclinical studies to human health and wellness.

The Role of MicroRNA and Microbiota in Depression and Anxiety

Depression and anxiety are devastating disorders. Understanding the mechanisms that underlie the development of depression and anxiety can provide new hints on novel treatments and preventive strategies. Here, we summarize the latest findings reporting the novel roles of gut microbiota and microRNAs (miRNAs) in the pathophysiology of depression and anxiety. The crosstalk between gut microbiota and the brain has been reported to contribute to these pathologies. It is currently known that some miRNAs can regulate bacterial growth and gene transcription while also modulate the gut microbiota composition, suggesting the importance of miRNAs in gut and brain health. Treatment and prevention strategies for neuropsychiatric diseases, such as physical exercise, diet, and probiotics, can modulate the gut microbiota composition and miRNAs expressions. Nonetheless, there are critical questions to be addressed to understand further the mechanisms involved in the interaction between the gut microbiota and miRNAs in the brain. This review summarizes the recent findings of the potential roles of microbiota and miRNA on the neuropathology of depression and anxiety, and its potential as treatment strategies.

Intrinsic cardiac adrenergic cells contribute to LPS-induced myocardial dysfunction

Intrinsic cardiac adrenergic (ICA) cells regulate both developing and adult cardiac physiological and pathological processes. However, the role of ICA cells in septic cardiomyopathy is unknown. Here we show that norepinephrine (NE) secretion from ICA cells is increased through activation of Toll-like receptor 4 (TLR4) to aggravate myocardial TNF-α production and dysfunction by lipopolysaccharide (LPS). In ICA cells, LPS activated TLR4-MyD88/TRIF-AP-1 signaling that promoted NE biosynthesis through expression of tyrosine hydroxylase, but did not trigger TNF-α production due to impairment of p65 translocation. In a co-culture consisting of LPS-treated ICA cells and cardiomyocytes, the upregulation and secretion of NE from ICA cells activated cardiomyocyte β₁-adrenergic receptor driving Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) to crosstalk with NF-κB and mitogen-activated protein kinase pathways. Importantly, blockade of ICA cell-derived NE prevented LPS-induced myocardial dysfunction. Our findings suggest that ICA cells may be a potential therapeutic target for septic cardiomyopathy.

Sex-specific responses of the pubertal neuroimmune axis in CD-1 mice

The mechanistic relationship between the sexually dimorphic neuroimmune system and the sex-specific outcomes of a pubertal immune challenge is unclear. Therefore, we examined sex differences in the progression of cytotoxic microglial responses and blood-brain barrier (BBB) disruption to a peripubertal lipopolysaccharide (LPS) treatment in brain regions relevant to stress responses and cognitive function. Six-week-old (i.e., stress-sensitive pubertal period) male and female CD-1 mice were treated with LPS (1.5 ​mg/kg body weight, ip) or 0.9% saline (LPS-matched volume, ip). Sex and treatment differences in microglial (Iba1⁺) and apoptotic neuronal (caspase-3⁺/NeuN⁺) and non-neuronal (caspase-3⁺/NeuN⁻) expression were examined in the hippocampus, medial prefrontal cortex (mPFC), and paraventricular nucleus 24 ​h (sickness), one week (symptomatic recovery) and four weeks (early adulthood) post-treatment (n ​= ​8/group). Microglial morphology was quantified with fractal analyses. Group differences in BBB permeability to ¹⁴C-sucrose were examined 24 ​h (whole-brain, hippocampus, prefrontal cortex, hypothalamus, and cerebellum) and one week (whole-brain) post-treatment. The acute effects of pubertal LPS were specific to females (i.e., global BBB disruption, altered microglial expression and morphology in the mPFC and hippocampus, increased hippocampal apoptosis). The residual effects of pubertal LPS-induced sickness observed in microglia persisted into adulthood in a sex- and region-specific manner. In addition to highlighting these sex-specific responses of the pubertal neuroimmune system, we report baseline region-specific sex differences in microglia spanning puberty through adulthood. We propose that these sex differences in neuroimmune-neurovascular interactions during the stress-sensitive pubertal period create sex biases in stress-related disorders of brain and behaviour.

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Pubertal LPS alters baseline sex differences in microglial numbers and morphology.

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Pubertal CD-1 mice mount sexually dimorphic neuroimmune responses to systemic LPS.

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Treatment effects on microglial expression and morphology differ by sex and region.

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The acute LPS-induced effects were specific to females.

Adolescent use of potential novel probiotic Rouxiella badensis subsp. acadiensis (Canan SV-53) mitigates pubertal LPS-Induced behavioral changes in adulthood in a sex-specific manner by modulating 5HT1A receptors expression in specific brain areas

Adolescence is a critical period of development during which the brain undergoes significant remodeling that impacts behavior later in life. Exposure to stress, and especially immune challenge, during this period triggers changes in brain function resulting in the development of mental disorders in adulthood, such as depression and anxiety. Previous studies from our laboratory have shown that a single exposure to LPS (lipopolysaccharide) during puberty causes enduring depression-like behaviour in females and anxiety-like behaviours in males. However, administration of probiotics during puberty blocked the enduring effects of LPS on depression-like and anxiety-like behaviors in female and male mice, respectively. These results suggest that the gut microbiome is a mediator of the effects of stress on mental health. The objective of the current study is to examine the effectiveness of a novel probiotic Rouxiella badensis subsp. acadiensis (Canan SV-53) in blocking LPS-induced anxiety-like and depression-like behaviors in adult male and female mice. Our results showed that Rouxiella badensis subsp. acadiensis (Canan SV-53) blocked LPS-induced depression-like behavior in female mice. We also found that pubertal treatment with Rouxiella badensis subsp. acadiensis (Canan SV-53) mitigated the LPS-induced decrease in 5HT1A expression in CA1 as well as the LPS-induced increase in 5HT1A expression in the raphe-nuclei in female mice. Contrary to our predictions, pubertal LPS treatment at 6 weeks of age did not induce enduring anxiety-like behavior in males. There was also no difference in anxiety-like behavior between the LPS-sucrose and LPS-probiotic male groups. However, pubertal LPS treatment increased the expression of 5HT1A receptors in the DRN in males, while probiotic exposure mitigated this increase. Our study highlights the consequences of stress exposure (immune challenge) on mental health in adulthood taking into consideration 5HT1A receptors expression at different regions of the brain. It also emphasizes on the importance of considering adolescence as window of opportunities during which probiotic use can alleviate the long-term neural and behavioral alterations induced by stress.

Pubertal LPS treatment selectively alters PSD-95 expression in male CD-1 mice

Puberty includes a highly stress-sensitive period with significant sex differences in the neurophysiological and behavioural outcomes of a peripheral immune challenge. Sex differences in the pubertal neuroimmune network's responses to systemic LPS may explain some of these enduring sex-specific outcomes of a pubertal immune challenge. However, the functional implications of these sex-specific neuroimmune responses on the local microenvironment are unclear. Western blots were used to examine treatment- and sex-related changes in expression of regulatory proteins in inflammation (NFκB), cell death (AIF), oxidative stress (SOD-1), and synaptic plasticity (PSD-95) following symptomatic recovery (i.e., one week post-treatment) from pubertal immune challenge. Across the four examined brain regions (i.e., hippocampus, PFC, hypothalamus, and cerebellum), only PSD-95 levels were altered one week post-treatment by the pubertal LPS treatment. Unlike their female counterparts, seven-week-old males showed increased PSD-95 expression in the hippocampus (p < .05). AIF, SOD-1, and NFκB levels in both sexes were unaffected by treatment (all p > .05), which suggests appropriate resolution of NFκB-mediated immune responses to pubertal LPS without stimulating AIF-mediated apoptosis and oxidative stress. We also report a significant male-biased sex difference in PSD-95 levels in the PFC and in cerebellar expression of SOD-1 during puberty (all p < .05). These findings highlight the sex-specific vulnerability of the pubertal hippocampus to systemic LPS and suggest that a pubertal immune challenge may expedite neurodevelopment in the hippocampus in a sex-specific manner.

Soluble Epoxide Hydrolase Inhibition to Face Neuroinflammation in Parkinson's Disease: A New Therapeutic Strategy

Neuroinflammation is a crucial process associated with the pathogenesis of neurodegenerative diseases, including Parkinson's disease (PD). Several pieces of evidence suggest an active role of lipid mediators, especially epoxy-fatty acids (EpFAs), in the genesis and control of neuroinflammation; 14,15-epoxyeicosatrienoic acid (14,15-EET) is one of the most commonly studied EpFAs, with anti-inflammatory properties. Soluble epoxide hydrolase (sEH) is implicated in the hydrolysis of 14,15-EET to its corresponding diol, which lacks anti-inflammatory properties. Preventing EET degradation thus increases its concentration in the brain through sEH inhibition, which represents a novel pharmacological approach to foster the reduction of neuroinflammation and by end neurodegeneration. Recently, it has been shown that sEH levels increase in brains of PD patients. Moreover, the pharmacological inhibition of the hydrolase domain of the enzyme or the use of sEH knockout mice reduced the deleterious effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. This paper overviews the knowledge of sEH and EETs in PD and the importance of blocking its hydrolytic activity, degrading EETs in PD physiopathology. We focus on imperative neuroinflammation participation in the neurodegenerative process in PD and the putative therapeutic role for sEH inhibitors. In this review, we also describe highlights in the general knowledge of the role of sEH in the central nervous system (CNS) and its participation in neurodegeneration. We conclude that sEH is one of the most promising therapeutic strategies for PD and other neurodegenerative diseases with chronic inflammation process, providing new insights into the crucial role of sEH in PD pathophysiology as well as a singular opportunity for drug development.

Pubertal probiotic blocks LPS-induced anxiety and the associated neurochemical and microbial outcomes, in a sex dependent manner

Puberty is a critical period of neural development, and exposure to stress and inflammation during this period is thought to increase vulnerability to mental illness. The gut microbiome influences brain functioning and behavior and impacts mental health. Yet, the role of the gut microbiome during puberty, a period during which mental health conditions tend to onset, remains largely uninvestigated. We first examined age and sex differences in gut microbial changes among CD-1 mice exposed to an immune challenge (lipopolysaccharide; LPS) at 6 weeks of age (during the pubertal stress-sensitive period) or at 10 weeks of age (in adulthood) (Experiment 1). Compared to their adult counterparts, pubertal males and females showed more significant changes in gut microbial composition following LPS treatment, including the depletion of numerous bacterial genera such as Lactobacillus. Given the beneficial effects of Lactobacillus strains on stress and behaviour, we next investigated whether replenishment of the gut with the probiotic Lactobacillus reuteri (L. reuteri) throughout pubertal development would modulate LPS-induced sickness and enduring effects on memory dysfunction, anxiety-like behaviour and stress reactivity in adulthood (Experiment 2). LPS treatment at 6 weeks of age created enduring changes in anxiety-like behaviors among males only. Similarly, only males showed the protective effects of L. reuteri supplementation during puberty in preventing longstanding LPS-induced changes in anxiety-like behavior and stress-induced brain activation. These findings demonstrate that colonizing the gut with L. reuteri during puberty modulates sickness responses and enduring behavioural and neurochemical outcomes in a sex-specific manner. Therefore, colonizing the gut with beneficial microbes may protect against the development of mental illnesses in adulthood.

Role of c-Myc/chloride intracellular channel 4 pathway in lipopolysaccharide-induced neurodegenerative diseases

LPS-induced neuronal apoptosis leads to neurodegenerative diseases (NDs). However, the mechanisms underlying NDs pathogenesis remains unclear. The apoptotic response to activation of the c-Myc/chloride intracellular channel (CLIC4) pathway is directed through a mitochondrial pathway. In this study, we aimed to explore the c-Myc/CLIC4 pathway in the progression of NDs induced by lipopolysaccharide (LPS). In an in vivo experiment, the results of HE staining, transmission electron microscopic, immunofluorescence microscopy of cleaved caspase-3 and Bax and the increasing expression of apoptotic pathway related proteins in mitochondria showed that LPS (10 mg/kg) administration damaged mitochondrial and induced hippocampal neuron apoptosis. The Western blot and RT-PCR indicated that LPS induced the activation of c-Myc/CLIC4 pathway. Furthermore, in an in vitro experiment, PC12 cells were exposed to LPS to induce cell injuries to mimic the model of NDs. To further confirm the role of the c-Myc/CLIC4 pathway in LPS-induced neuronal apoptosis, the gene knockout of c-Myc and CLIC4 were performed by CRISPR/Cas9. The results of the flow cytometry assay and Annexin V-FITC/PI showed that knocking out c-Myc and CLIC4 significantly reduced cell apoptosis. The results of Western blot and dual immunofluorescence with Cyt c and TOM20 showed that knocking out c-Myc and CLIC4 significantly reduced the expression of mitochondrial apoptosis-related proteins. Our data confirmed that LPS-induced apoptosis is regulated by the activation of c-Myc/CLIC4 pathway. These results support further research mechanisms underlying neurodegenerative diseases and can provide effective pharmacodynamic targets for the clinical development of therapeutic drugs for neurodegenerative diseases.

Probiotic consumption during puberty mitigates LPS-induced immune responses and protects against stress-induced depression- and anxiety-like behaviors in adulthood in a sex-specific manner

Puberty/adolescence is a significant period of development and a time with a high emergence of psychiatric disorders. During this period, there is increased neuroplasticity and heightened vulnerability to stress and inflammation. The gut microbiome regulates stress and inflammatory responses and can alter brain chemistry and behaviour. However, the role of the gut microbiota during pubertal development remains largely uninvestigated. The current study examined gut manipulation with probiotics during puberty in CD1 mice on lipopolysaccharide (LPS)-induced immune responses and enduring effects on anxiety- and depression-like behaviours and stress-reactivity in adulthood. Probiotics reduced LPS-induced sickness behaviour at 12 h in females and at 48 h following LPS treatment in males. Probiotics also reduced LPS-induced changes in body weight at 48 h post-treatment in females. Probiotic treatment also prevented LPS-induced increases in pro- and anti-inflammatory peripheral cytokines at 8 h following LPS treatment, reduced central cytokine mRNA expression in the hypothalamus, hippocampus and PFC, and prevented LPS-induced changes to in the gut microbiota. A single exposure to LPS during puberty resulted in enduring depression-like behaviour in female mice, and anxiety-like behaviour in male mice in adulthood. However, pubertal exposure to probiotics prevented enduring LPS-induced depression-like behaviour in females and anxiety-like behaviors in males. Moreover, probiotics altered toll-like receptor-4 activity in the paraventricular nucleus of the hypothalamus (PVN) in males in response to a novel stressor in adulthood. Our results suggest that the gut microbiome plays an important role in pubertal neurodevelopment. These findings indicate that exposure to probiotics during puberty mitigates inflammation and decreases stress-induced vulnerabilities to emotional behaviours later in life, in a sex-specific manner.

Effect of Photobiomodulation in Rescuing Lipopolysaccharide-Induced Dopaminergic Cell Loss in the Male Sprague-Dawley Rat

Photobiomodulation (PBM) provides neuroprotection against dopaminergic cell death and associated motor deficits in rodent and primate models of Parkinson’s disease (PD). However, it has not yet been tested in the lipopolysaccharide (LPS) model of PD, which leads to dopaminergic cell death through microglia-evoked neuroinflammation. We investigated whether transcranial PBM could protect against dopaminergic cell death within the substantia nigra in male Sprague–Dawley rats following supranigral LPS injection. PBM fully protected rats from 10 µg LPS which would have otherwise caused 15% cell loss, but there was no significant neuroprotection at a 20 µg dose that led to a 50% lesion. Cell loss at this dose varied according to the precise site of injection and correlated with increased local numbers of highly inflammatory amoeboid microglia. Twenty microgram LPS caused motor deficits in the cylinder, adjusted stepping and rotarod tests that correlated with dopaminergic cell loss. While PBM caused no significant improvement at the group level, motor performance on all three tests no longer correlated with the lesion size caused by 20 µg LPS in PBM-treated rats, suggesting extranigral motor improvements in some animals. These results provide support for PBM as a successful neuroprotective therapy against the inflammatory component of early PD, provided inflammation has not reached a devastating level, as well as potential benefits in other motor circuitries.

Pubertal immune stress transiently alters spatial memory processes in adulthood

Pubertal immune challenge can permanently alter hippocampus-dependent memory processes in a sex-specific manner. Although gonadal hormones can influence various cognitive processes, their role in regulating the cognitive sequelae to pubertal immune challenge has not been thoroughly assessed. We examined whether a pubertal immune challenge could affect hippocampus-dependent memory functions in adulthood and whether these effects are regulated by gonadal steroid hormones. We hypothesized that exposure to an immune challenge during puberty would induce sex-specific deficits in the behavioral and cellular correlates of hippocampus-dependent memory during adulthood. At six weeks of age, during the stress-vulnerable pubertal period, male and female CD-1 mice were injected with either saline or the bacterial endotoxin lipopolysaccharide (LPS). Three weeks later, mice underwent either gonadectomy or sham-surgery. At ten weeks of age (i.e., in adulthood), mice began behavioral testing in an open field, Barnes maze, and Morris water maze. Brain tissue was collected at 17 weeks of age and stained for doublecortin and Ki67 to examine migrating neuronal progenitor cells and cellular proliferation in the neurogenic subgranular zone (SGZ) and the cornus ammonis (CA)1 and CA3 regions of the hippocampus. Pubertal LPS treatment impaired learning during adulthood in both sexes and increased cellular proliferation in the CA1 region in castrated males only. Although adult sex hormones did not reliably modulate these changes, gonadectomy impaired learning during the Morris water maze in both sexes. Learning deficits were more prominent during the Barnes maze, which suggests a stress-dependent expression of LPS-induced cognitive deficits. Neurogenesis in the SGZ and cellular proliferation in the CA3 were not affected by pubertal LPS treatment or gonadectomy. These novel findings emphasize the sensitivity of developing cognitive processes during puberty to immune challenges and suggest a possible mechanism for learning-based difficulties in adulthood.

The adaptive immune and stress responses of adult female CD1 mice following exposure to a viral mimetic

Exposure to a bacterial endotoxin during puberty induces long-term changes to reproductive and non-reproductive behaviours. While the underlying mechanisms remain unknown, we have recently shown that there are age and sex differences in acute immune and stress responses following immune challenge. Given that it is unclear whether viral infections result in similar age and sex differences, the objective of this study was to examine the acute immune and stress responses following exposure to polyinosinic:polycytidylic acid (poly(I:C)), a viral mimetic, in CD1 mice and to investigate the role of gonadal hormones in these responses. CD1 male and female mice underwent sham-surgery or gonadectomy at 5 or 9 weeks of age. Following one week of recovery, at 6 (pubertal group) or 10 (adult group) weeks of age, mice were treated with either saline or poly(I:C). Poly(I:C) treatment induced greater sickness behaviour in males compared to females and increased peripheral corticosterone in adult mice relative to their pubertal counterparts. Changes in body temperature and central c-Fos expression were more prominent in adult females. Gonadectomy worsened poly(I:C)-induced sickness behaviour and altered body temperature in both sexes. The results demonstrate that adult females display the most pronounced acute changes in body temperature, corticosterone release, and c-Fos expression but show the fastest recovery in sickness behavior, indicating that, compared to males, females display an adaptive physiological response following immune stress due to higher circulating estradiol and progesterone.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.