Neonatal immune challenge influences the microbiota and behaviour in a sexually dimorphic manner

Age and sex-dependent gut alterations in mice induced by neonatal immune activation with lipopolysaccharide

Neonatal immune activation (NIA) through exposure to lipopolysaccharide (LPS) induces adult behavioral changes in rodents that resemble symptoms of developmental disorders, such as autism spectrum disorder. The neonatal timing of LPS exposure appears to play a crucial role in determining the nature and extent of long-term changes. This study aims to explore whether a 3-day LPS-NIA triggers sex- and age-related changes in gut function, potentially linking LPS-NIA to gastrointestinal dysfunction. Male and female Swiss mice received intraperitoneal injections of LPS or saline on postnatal days (PN) 3, 5, and 7. At PN35 (juvenile) and PN70 (adult), gut inflammation and oxidative stress were evaluated in addition to assessments of working memory, depressive-like symptoms, sociability, and repetitive behavior. Gut examination showed elevated C-X-C motif chemokine receptor 3 (CXCR3) in LPS-NIA mice, while MyD88 and Zonulin expressions were significantly higher only in adult LPS-NIA females. Interleukin (IL)-23 expression increased in juvenile and adult male and juvenile female LPS-NIA mice. Oxidative changes included decreased duodenal reduced glutathione (GSH) in juvenile females and ileal GSH in adult females exposed to LPS-NIA. Regarding behavioral alterations, adult LPS-NIA females exhibited depressive-like behavior. Working memory deficits were observed across all LPS-NIA groups. Only juvenile LPS-NIA females increased grooming, while rearing was higher in adult LPS-NIA mice of both sexes. The findings imply that LPS-NIA impacts intestinal barrier function and causes gut inflammatory alterations that are sex- and age-specific. These findings pave the way for exploring potential mechanisms that could contribute to LPS-induced gastrointestinal disturbances among individuals with ASD.

Effects of different types of induced neonatal inflammation on development and behavior of C57BL/6 and BTBR mice

Neuroinflammation in the early postnatal period can disturb trajectories of the completion of normal brain development and can lead to mental illnesses, such as depression, anxiety disorders, and personality disorders later in life. In our study, we focused on evaluating short- and long-term effects of neonatal inflammation induced by lipopolysaccharide, poly(I:C), or their combination in female and male C57BL/6 and BTBR mice. We chose the BTBR strain as potentially more susceptible to neonatal inflammation because these mice have behavioral, neuroanatomical, and physiological features of autism spectrum disorders, an abnormal immune response, and several structural aberrations in the brain. Our results indicated that BTBR mice are more sensitive to the influence of the neonatal immune activation (NIA) on the formation of neonatal reflexes than C57BL/6 mice are. In these experiments, the injection of lipopolysaccharide had an effect on the formation of the cliff aversion reflex in female BTBR mice. Nonetheless, NIA had no delayed effects on either social behavior or anxiety-like behavior in juvenile and adolescent BTBR and C57BL/6 mice. Altogether, our data show that NIA has mimetic-, age-, and strain-dependent effects on the development of neonatal reflexes and on exploratory activity in BTBR and C57BL/6 mice.

The medulla oblongata shows a sex-specific inflammatory response to systemic neonatal lipopolysaccharide

Early life inflammation has been linked to long-term modulation of behavioural outcomes due to the central nervous system, but it is now becoming apparent it is also linked to dysfunction of visceral physiology. The medulla oblongata contains a number of nuclei critical for homeostasis, therefore we utilised the well-established model of neonatal lipopolysaccharide (LPS) exposure to examine the immediate and long-term impacts of systemic inflammation on the medulla oblongata. Wistar rats were injected with LPS or saline on postnatal days 3 and 5, with tissues collected on postnatal days 7 or 90 in order to assess expression of inflammatory mediators and microglial morphology in autonomic regions of the medulla oblongata. We observed a distinct sex-specific response of all measured inflammatory mediators at both ages, as well as significant neonatal sex differences in inflammatory mediators within saline groups. At both ages, microglial morphology had significant changes in branch length and soma size in a sex-specific manner in response to LPS exposure. This data not only highlights the strong sex-specific response of neonates to LPS administration, but also the significant life-long impact on the medulla oblongata and the potential altered control of visceral organs.

The influence of long-term housing in enriched environment on behavior of normal rats and subjected to neonatal pro-inflammatory challenge

It is well known that neonatal pro-inflammatory challenge (NPC) acquire a predisposition to the development of a number of neuropsychiatric diseases: depression, anxiety disorders, autism, attention deficit hyperactivity disorder. Symptoms of these diseases can manifest themselves in adulthood and adolescent after repeated exposure to negative influences. Preventing the development of the negative consequences of NPC is one of the main tasks for researchers. The exposure to an enriched environment (EE) was shown to have anxiolytic, anti-depressive, and pro-cognitive effects. The present work was aimed to investigate the effects of the long-term EE on anxious-depressive and conditioned fear behavior in normal male and female rats and subjected to NPC. The NPC was induced by subcutaneous administration of lipopolysaccharide (LPS, 50 μg/kg) on 3d and 5th PNDs. The control animals received saline (SAL). The rats were placed in the EE from 25 to 120 PND. Animals housed in the standard conditions (STAND) served as controls. In adult female and male rats of the STAND groups, LPS did not affect the anxiety, depressive-like behavior and conditioned fear. The EE increased motor and search activity in males and females. In the open field, the EE reduced anxiety in males of the SAL and LPS groups and in females of SAL groups compared to the STAND housed animals. In the elevated plus maze, the EE decreased anxiety only in males of the SAL group. In the sucrose preference test, the EE did not change sucrose consumption in males and females of SAL and LPS groups, while, in the forced swimming test, the EE reduced depressive-like behavior in females of both SAL and LPS groups. The enrichment decreased the contextual conditioned fear in male and female of SAL groups, but not of the LPS group, and did not affect the cue conditioned fear. The corticosterone reactivity to the forced swimming stress increased in males of the EE groups. The basal level of IL-1beta in blood serum decreased in males of the SAL-EE group. Thus, the EE reduced anxiety in males, depressive-like behavior in females, and contextual conditioned fear in males and females compared to the STAND housed animals. Although the NPC did not affect these behaviors in the STAND groups, LPS prevented the beneficial EE effects on anxiety and conditioned fear. The opposing effects of LPS were dependent on sex and type of testing.

The influence of antibiotic treatment on the behavior and gut microbiome of adult rats neonatally insulted with lipopolysaccharide

The present study investigated whether neonatal exposure to the proinflammatory endotoxin lipopolysaccharide (LPS) followed by an antibiotic (ATB)-induced dysbiosis in early adulthood could induce neurodevelopmental disorders-like behavioral changes in adult male rats. Combining these two stressors resulted in decreased weight gain, but no significant behavioral abnormalities were observed. LPS treatment resulted in adult rats' hypoactivity and induced anxiety-like behavior in the social recognition paradigm, but these behavioral changes were not exacerbated by ATB-induced gut dysbiosis. ATB treatment seriously disrupted the gut bacterial community, but dysbiosis did not affect locomotor activity, social recognition, and acoustic reactivity in adult rats. Fecal bacterial community analyses showed no differences between the LPS challenge exposed/unexposed rats, while the effect of ATB administration was decisive regardless of prior LPS exposure. ATB treatment resulted in significantly decreased bacterial diversity, suppression of Clostridiales and Bacteroidales, and increases in Lactobacillales, Enterobacteriales, and Burkholderiales. The persistent effect of LPS on some aspects of behavior suggests a long-term effect of early toxin exposure that was not observed in ATB-treated animals. However, an anti-inflammatory protective effect of ATB cannot be assumed because of the increased abundance of pro-inflammatory, potentially pathogenic bacteria (Proteus, Suttrella) and the elimination of the bacterial families Ruminococcaceae and Lachnospiraceae, which are generally considered beneficial for gut health.

Crosstalk between Gut Microbiota and Host Immunity: Impact on Inflammation and Immunotherapy

Gut microbes and their metabolites are actively involved in the development and regulation of host immunity, which can influence disease susceptibility. Herein, we review the most recent research advancements in the gut microbiota-immune axis. We discuss in detail how the gut microbiota is a tipping point for neonatal immune development as indicated by newly uncovered phenomenon, such as maternal imprinting, in utero intestinal metabolome, and weaning reaction. We describe how the gut microbiota shapes both innate and adaptive immunity with emphasis on the metabolites short-chain fatty acids and secondary bile acids. We also comprehensively delineate how disruption in the microbiota-immune axis results in immune-mediated diseases, such as gastrointestinal infections, inflammatory bowel diseases, cardiometabolic disorders (e.g., cardiovascular diseases, diabetes, and hypertension), autoimmunity (e.g., rheumatoid arthritis), hypersensitivity (e.g., asthma and allergies), psychological disorders (e.g., anxiety), and cancer (e.g., colorectal and hepatic). We further encompass the role of fecal microbiota transplantation, probiotics, prebiotics, and dietary polyphenols in reshaping the gut microbiota and their therapeutic potential. Continuing, we examine how the gut microbiota modulates immune therapies, including immune checkpoint inhibitors, JAK inhibitors, and anti-TNF therapies. We lastly mention the current challenges in metagenomics, germ-free models, and microbiota recapitulation to a achieve fundamental understanding for how gut microbiota regulates immunity. Altogether, this review proposes improving immunotherapy efficacy from the perspective of microbiome-targeted interventions.