Impact of maternal immune activation and sex on placental and fetal brain cytokine and gene expression profiles in a preclinical model of neurodevelopmental disorders.

Maternal inflammation during gestation is associated with a later diagnosis of neurodevelopmental disorders including autism spectrum disorder (ASD). However, the specific impact of maternal immune activation (MIA) on placental and fetal brain development remains insufficiently understood. This study aimed to investigate the effects of MIA by analyzing placental and brain tissues obtained from the offspring of pregnant C57BL/6 dams exposed to polyinosinic: polycytidylic acid (poly I: C) on embryonic day 12.5. Cytokine and mRNA content in the placenta and brain tissues were assessed using multiplex cytokine assays and bulk-RNA sequencing on embryonic day 17.5. In the placenta, male MIA offspring exhibited higher levels of GM-CSF, IL-6, TNFα, and LT-α, but there were no differences in female MIA offspring. Furthermore, differentially expressed genes (DEG) in the placental tissues of MIA offspring were found to be enriched in processes related to synaptic vesicles and neuronal development. Placental mRNA from male and female MIA offspring were both enriched in synaptic and neuronal development terms, whereas females were also enriched for terms related to excitatory and inhibitory signaling. In the fetal brain of MIA offspring, increased levels of IL-28B and IL-25 were observed with male MIA offspring and increased levels of LT-α were observed in the female offspring. Notably, we identified few stable MIA fetal brain DEG, with no male specific difference whereas females had DEG related to immune cytokine signaling. Overall, these findings support the hypothesis that MIA contributes to the sex- specific abnormalities observed in ASD, possibly through altered neuron developed from exposure to inflammatory cytokines. Future research should aim to investigate how interactions between the placenta and fetal brain contribute to altered neuronal development in the context of MIA.

Detection of abnormal behaviors in prenatal Poly(I:C) exposed mice in a group-rearing environment.

During pregnancy, the maternal environment is critical for normal ontogeny and central nervous system development. Occasionally, prenatal exposure to environmental factors affects tissue architecture and functional development of the brain, which causes developmental disorders, including disorders of the autism spectrum. One of these environmental factors is the exposure to infectious diseases during pregnancy. In this study, we generated mice with infectious disease-induced inflammation by prenatal exposure to 200 µg/kg polyinosinic-polycytidylic acid sodium salt [Poly(I:C)] at embryonic day 12.5 and analyzed their phenotypes on 30-weeks-old. We attempted to detect abnormalities in spontaneous activity and social interaction, which may be indicators of developmental disorder-like behavioral abnormalities, in free-ranging behaviors in multiple rearing environments using multiple animal positioning systems and UMATracker in mice with fetal inflammation. Increased spontaneous activity and abnormal social interactions were observed in mice in the Poly(I:C)-treated group compared with those in the control group. Prenatal exposure to Poly(I:C) increased motor activity and decreased social interaction, and social behavior in prenatally treated mice in a multiple-individual rearing environment. Poly(I:C) exposure during the fetal period resulted in developmental disorder-like behavioral abnormalities, such as increased activity and abnormal social interactions, even after maturation in a multiple-individual rearing environment. This experimental method may provide a new way to analyze the behavior of mouse models of developmental disorders in a multiple-individual rearing environment, in which free-ranging behavior is possible.

Maternal Immune Activation Induces Cortical Catecholaminergic Hypofunction and Cognitive Impairments in Offspring.

BACKGROUND: Impairment of specific cognitive domains in schizophrenia has been associated with prefrontal cortex (PFC) catecholaminergic deficits. Among other factors, prenatal exposure to infections represents an environmental risk factor for schizophrenia development in adulthood. However, it remains largely unknown whether the prenatal infection-induced changes in the brain may be associated with concrete switches in a particular neurochemical circuit, and therefore, if they could alter behavioral functions. METHODS: In vitro and in vivo neurochemical evaluation of the PFC catecholaminergic systems was performed in offspring from mice undergoing maternal immune activation (MIA). The cognitive status was also evaluated. Prenatal viral infection was mimicked by polyriboinosinic-polyribocytidylic acid (poly(I:C)) administration to pregnant dams (7.5 mg/kg i.p., gestational day 9.5) and consequences were evaluated in adult offspring. RESULTS: MIA-treated offspring showed disrupted recognition memory in the novel object recognition task (t = 2.30, p = 0.031). This poly(I:C)-based group displayed decreased extracellular dopamine (DA) concentrations compared to controls (t = 3.17, p = 0.0068). Potassium-evoked release of DA and noradrenaline (NA) were impaired in the poly(I:C) group (DA: Ft[10,90] = 43.33, p < 0.0001; Ftr[1,90] = 1.224, p = 0.2972; Fi[10,90] = 5.916, p < 0.0001; n = 11); (NA: Ft[10,90] = 36.27, p < 0.0001; Ftr[1,90] = 1.841, p = 0.208; Fi[10,90] = 8.686, p < 0.0001; n = 11). In the same way, amphetamine-evoked release of DA and NA were also impaired in the poly(I:C) group (DA: Ft[8,328] = 22.01, p < 0.0001; Ftr[1,328] = 4.507, p = 0.040; Fi[8,328] = 2.319, p = 0.020; n = 43); (NA: Ft[8,328] = 52.07; p < 0.0001; Ftr[1,328] = 4.322; p = 0.044; Fi[8,398] = 5.727; p < 0.0001; n = 43). This catecholamine imbalance was accompanied by increased dopamine D1 and D2 receptor expression (t = 2.64, p = 0.011 and t = 3.55, p = 0.0009; respectively), whereas tyrosine hydroxylase, DA and NA tissue content, DA and NA transporter (DAT/NET) expression and function were unaltered. CONCLUSIONS: MIA induces in offspring a presynaptic catecholaminergic hypofunction in PFC with cognitive impairment. This poly(I:C)-based model reproduces catecholamine phenotypes reported in schizophrenia and represents an opportunity for the study of cognitive impairment associated to this disorder.

Investigating the "two-hit hypothesis": Effects of prenatal maternal immune activation and adolescent cannabis use on neurodevelopment in mice.

Prenatal exposure to maternal immune activation (MIA) and chronic adolescent cannabis use are both risk factors for neuropsychiatric disorders. However, exposure to a single risk factor may not result in major mental illness, indicating that multiple exposures may be required for illness onset. Here, we examine whether combined exposure to prenatal MIA and adolescent delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, lead to enduring neuroanatomical and behavioural changes in adulthood. Mice were prenatally exposed to viral mimetic, poly I:C (5 mg/kg), or vehicle at gestational day (GD) 9, and postnatally exposed to chronic THC (5 mg/kg, intraperitoneal) or vehicle during adolescence (postnatal day [PND]28-45). Longitudinal magnetic resonance imaging (MRI) was performed pre-treatment, PND 25, post-treatment, PND 50, and in adulthood, PND85, followed by behavioural tests for anxiety-like, social, and sensorimotor gating. Post-mortem assessment of cannabinoid (CB)1 and 2 receptor expressing cells was performed in altered regions identified by MRI (anterior cingulate and somatosensory cortices, striatum, and hippocampus). Subtle deviations in neurodevelopmental trajectory and subthreshold anxiety-like behaviours were observed in mice exposed to both risk factors. Sex-dependent effects were observed in patterns of shared brain-behaviour covariation, indicative of potential sex differences in response to MIA and THC. Density of CB1 and CB2 receptor positive cells was significantly decreased in all mice exposed to MIA, THC, or both. These findings suggest that there may be a cumulative effect of risk factor exposure on gross neuroanatomical development, and that the endocannabinoid system may be sensitive to both prenatal MIA, adolescent THC, or the combination.

Transcriptional analyses provide novel insights into the transgenerational effects of Poly (I:C) on chickens.

Pathogenic microorganisms that are ubiquitous in the environment threaten human health and food safety. Polyinosinic:polycytidylic acid (Poly (I:C)) is a macromolecule with a double-stranded RNA structure, which is often used to simulate viruses. Our previous study found that Poly (I:C) maternal stimulation could affect the reproduction of laying hens and their offspring, but the underlying mechanism needed to be explored. In the present study, splenic transcriptomes were sequenced and analyzed from two groups (Poly (I:C) treatment as the challenged group and saline treatment as the control) and in three generations (maternal stimulated F0 hens, unchallenged F1 and F2 generations). The results showed that Poly (I:C) maternal stimulation affected gene expression patterns in laying hens and their offspring. A total of 27 differentially expressed genes (DEGs) with the same regulating trend were discovered in the F0 and F1 generations, indicating an influence of the intergenerational transmission effect. Functional enrichment analysis of Gene Ontology (GO) showed that lymphocyte differentiation, positive regulation of leukocyte differentiation, positive regulation of MAPK cascade, and T cell differentiation were the common biological processes between F0 and F1 generations, revealing Poly (I:C) could affect the immunity of the treated F0 hens and the unchallenged subsequent generations. Further study showed that pathways associated with growth, development, biosynthesis, and metabolism of F2 chicks were also affected by Poly (I:C) maternal stimulation. Correlation analysis between DEGs and reproductive traits revealed that PHLDA2 (pleckstrin homology-like domain family A member 2) and PODN (podocan) with inheritable effect were highly correlated with egg-laying rate and egg weight in F1 hens, suggesting their potential long-term role in regulating reproductive traits. ARHGAP40, FGB, HRH4, PHLDA2, PODN, NTSR1, and NMU were supposed to play important roles in regulating chickens' immunity and reproductive traits. This study reveals the far-reaching effect on transcriptome induced by Poly (I:C), reflecting the influence of the mother's living environment on the offspring. It is an important reference for future research into the multi-generational transmission of maternal stimulation and harmful environmental factors.

Maternal immune activation with high molecular weight poly(I:C) in Wistar rats leads to elevated immune cell chemoattractants.

Maternal immune activation (MIA) with poly(I:C) is a preclinical paradigm for schizophrenia and autism research. Methodological variations, including poly(I:C) molecular weight, contribute to inconsistencies in behavioural and molecular outcomes. We established in Wistar rats that 4 mg/kg high molecular weight (HMW)-poly(I:C) on GD19 induces maternal sickness, smaller litters and maternal elevations of serum cytokines, including increases in monocyte chemoattractants. In adult offspring, we found that males have higher serum cytokines than females, and MIA did not alter peripheral cytokines in either sex. Our study will contribute to the effective use of the MIA model to elucidate the neurobiology of neurodevelopmental disorders.

LPS versus Poly I:C model: comparison of long-term effects of bacterial and viral maternal immune activation on the offspring.

A prominent health issue nowadays is the COVID-19 pandemic, which poses acute risks to human health. However, the long-term health consequences are largely unknown and cannot be neglected. An especially vulnerable period for infection is pregnancy, when infections could have long-term health effect on the child. Evidence suggests that maternal immune activation (MIA) induced by either bacteria or viruses presents various effects on the offspring, leading to adverse phenotypes in many organ systems. This review compares the mechanisms of bacterial and viral MIA and the possible long-term outcomes for the offspring by summarizing the outcome in animal LPS and Poly I:C models. Both models are activated immune responses mediated by Toll-like receptors. The outcomes for MIA offspring include neurodevelopment, immune response, circulation, metabolism, and reproduction. Some of these changes continue to exist until later life. Besides different doses and batches of LPS and Poly I:C, the injection day, administration route, and also different animal species influence the outcomes. Here, we specifically aim to support colleagues when choosing their animal models for future studies.

Responses of increasingly complex intestinal epithelium in vitro models to bacterial toll-like receptor agonists.

The intestine fulfills roles in the uptake of nutrients and water regulation and acts as a gatekeeper for the intestinal microbiome. For the latter, the intestinal gut barrier system is able to respond to a broad range of bacterial antigens, generally through Toll-like receptor (TLR) signaling pathways. To test the capacity of various in vitro intestinal models, we studied IL-8 secretion, as a marker of pro-inflammatory response through the TLR pathway, in a Caco-2 monoculture, Caco-2/HT29-MTX di-culture, Caco-2/HT29-MTX/HMVEC-d tri-culture and in a HT29-p monoculture in response to exposure to various TLR agonists. Twenty-one-day-old differentiated cells in Transwells were exposed to Pam3CSK4 (TLR1/2), lipopolysaccharide (TLR4), single-stranded RNA (TLR7/8), Poly(i:C) (TLR3) and flagellin (TLR5) for 24 h. In all systems IL-8 secretion was increased in response to flagellin exposure, with HT29-p cells also responding to Poly(I:C) exposure. All other agonists did not induce an IL-8 response in the tested in vitro models, indicating that the specific TLRs are either not present or not functional in these models. This highlights the need for careful selection of in vitro models when studying intestinal immune responses and the need for improved in vitro models that better recapitulate intestinal immune responses.

Early life exposure to poly I:C impairs striatal DA-D2 receptor binding, myelination and associated behavioural abilities in rats.

Early-life viral infections critically influence the brain development and have been variously reported to cause neuropsychiatric diseases such as Schizophrenia, Parkinson's diseases, demyelinating diseases, etc. To investigate the alterations in the dopaminergic system, myelination and associated behavioral impairments following neonatal viral infection, the viral immune activation model was created by an intraperitoneal injection of Poly I:C (5 mg/kg bw/ip) to neonatal rat pups on PND-7. The DA-D2 receptor binding was assessed in corpus striatum by using 3H-Spiperone at 3, 6 and 12 weeks of age. MOG immunolabelling was performed to check myelination stature and myelin integrity, while corpus callosum calibre was assessed by Luxol fast blue staining. Relative behavioral tasks i.e., motor activity, motor coordination and neuromuscular strength were assessed by open field, rotarod and grip strength meter respectively at 3, 6 and 12 weeks of age. Following Poly I:C exposure, a significant decrease in DA-D2 receptor binding, reduction in corpus callosum calibre and MOG immunolabelling indicating demyelination and a significant decrease in locomotor activity, neuromuscular strength and motor coordination signify motor deficits and hypokinetic influence of early life viral infection. Thus, the findings suggest that early life poly I:C exposure may cause demyelination and motor deficits by decreasing DA-D2 receptor binding affinity.

Maternal Immune Activation during Pregnancy Alters Postnatal Brain Growth and Cognitive Development in Nonhuman Primate Offspring.

Human epidemiological studies implicate exposure to infection during gestation in the etiology of neurodevelopmental disorders. Animal models of maternal immune activation (MIA) have identified the maternal immune response as the critical link between maternal infection and aberrant offspring brain and behavior development. Here we evaluate neurodevelopment of male rhesus monkeys (Macaca mulatta) born to MIA-treated dams (n = 14) injected with a modified form of the viral mimic polyinosinic:polycytidylic acid at the end of the first trimester. Control dams received saline injections at the same gestational time points (n = 10) or were untreated (n = 4). MIA-treated dams exhibited a strong immune response as indexed by transient increases in sickness behavior, temperature, and inflammatory cytokines. Although offspring born to control or MIA-treated dams did not differ on measures of physical growth and early developmental milestones, the MIA-treated animals exhibited subtle changes in cognitive development and deviated from species-typical brain growth trajectories. Longitudinal MRI revealed significant gray matter volume reductions in the prefrontal and frontal cortices of MIA-treated offspring at 6 months that persisted through the final time point at 45 months along with smaller frontal white matter volumes in MIA-treated animals at 36 and 45 months. These findings provide the first evidence of early postnatal changes in brain development in MIA-exposed nonhuman primates and establish a translationally relevant model system to explore the neurodevelopmental trajectory of risk associated with prenatal immune challenge from birth through late adolescence.SIGNIFICANCE STATEMENT Women exposed to infection during pregnancy have an increased risk of giving birth to a child who will later be diagnosed with a neurodevelopmental disorder. Preclinical maternal immune activation (MIA) models have demonstrated that the effects of maternal infection on fetal brain development are mediated by maternal immune response. Since the majority of MIA models are conducted in rodents, the nonhuman primate provides a unique system to evaluate the MIA hypothesis in a species closely related to humans. Here we report the first longitudinal study conducted in a nonhuman primate MIA model. MIA-exposed offspring demonstrate subtle changes in cognitive development paired with marked reductions in frontal gray and white matter, further supporting the association between prenatal immune challenge and alterations in offspring neurodevelopment.

Hippocampal Sequencing Mechanisms Are Disrupted in a Maternal Immune Activation Model of Schizophrenia Risk.

Episodic memory requires information to be stored and recalled in sequential order, and these processes are disrupted in schizophrenia. Hippocampal phase precession and theta sequences are thought to provide a biological mechanism for sequential ordering of experience at timescales suitable for plasticity. These phenomena have not previously been examined in any models of schizophrenia risk. Here, we examine these phenomena in a maternal immune activation (MIA) rodent model. We show that while individual pyramidal cells in the CA1 region continue to precess normally in MIA animals, the starting phase of precession as an animal enters a new place field is considerably more variable in MIA animals than in controls. A critical consequence of this change is a disorganization of the ordered representation of experience via theta sequences. These results provide the first evidence of a biological-level mechanism that, if it occurs in schizophrenia, may explain aspects of disorganized sequential processing that contribute to the cognitive symptoms of the disorder.SIGNIFICANCE STATEMENT Hippocampal phase precession and theta sequences have been proposed as biophysical mechanisms by which the sequential structure of cognition might be ordered. Disturbances of sequential processing have frequently been observed in schizophrenia. Here, we show for the first time that phase precession and theta sequences are disrupted in a maternal immune activation (MIA) model of schizophrenia risk. This is a result of greater variability in the starting phase of precession, indicating that the mechanisms that coordinate precession at the assembly level are disrupted. We propose that this disturbance in phase precession underlies some of the disorganized cognitive symptoms that occur in schizophrenia. These findings could have important preclinical significance for the identification and treatment of schizophrenia risk factors.

N-acylethanolamine regulation of TLR3-induced hyperthermia and neuroinflammatory gene expression: A role for PPARα.

Increasing evidence suggests that SARS-CoV-2, the virus responsible for the COVID-19 pandemic, is associated with increased risk of developing neurological or psychiatric conditions such as depression, anxiety or dementia. While the precise mechanism underlying this association is unknown, aberrant activation of toll-like receptor (TLR)3, a viral recognizing pattern recognition receptor, may play a key role. Synthetic cannabinoids and enhancing cannabinoid tone via inhibition of fatty acid amide hydrolase (FAAH) has been demonstrated to modulate TLR3-induced neuroimmune responses and associated sickness behaviour. However, the role of individual FAAH substrates, and the receptor mechanisms mediating these effects, are unknown. The present study examined the effects of intracerebral or systemic administration of the FAAH substrates N-oleoylethanolamide (OEA), N-palmitoylethanolamide (PEA) or the anandamide (AEA) analogue meth-AEA on hyperthermia and hypothalamic inflammatory gene expression following administration of the TLR3 agonist, and viral mimetic, poly I:C. The data demonstrate that meth-AEA does not alter TLR3-induced hyperthermia or hypothalamic inflammatory gene expression. In comparison, OEA and PEA attenuated the TLR3-induced hyperthermia, although only OEA attenuated the expression of hyperthermia-related genes (IL-1ß, iNOS, COX2 and m-PGES) in the hypothalamus. OEA, but not PEA, attenuated TLR3-induced increases in the expression of all IRF- and NFκB-related genes examined in the hypothalamus, but not in the spleen. Antagonism of PPARα prevented the OEA-induced attenuation of IRF- and NFκB-related genes in the hypothalamus following TLR3 activation but did not significantly alter temperature. PPARα agonism did not alter TLR3-induced hyperthermia or hypothalamic inflammatory gene expression. These data indicate that OEA may be the primary FAAH substrate that modulates TLR3-induced neuroinflammation and hyperthermia, effects partially mediated by PPARα.

Clonazepam attenuates neurobehavioral abnormalities in offspring exposed to maternal immune activation by enhancing GABAergic neurotransmission.

Ample evidence indicates that maternal immune activation (MIA) during gestation is linked to an increased risk for neurodevelopmental and psychiatric disorders, such as autism spectrum disorder (ASD), anxiety and depression, in offspring. However, the underlying mechanism for such a link remains largely elusive. Here, we performed RNA sequencing (RNA-seq) to examine the transcriptional profiles changes in mice in response to MIA and identified that the expression of Scn1a gene, encoding the pore-forming α-subunit of the brain voltage-gated sodium channel type-1 (NaV1.1) primarily in fast-spiking inhibitory interneurons, was significantly decreased in the medial prefrontal cortex (mPFC) of juvenile offspring after MIA. Moreover, diminished excitatory drive onto interneurons causes reduction of spontaneous gamma-aminobutyric acid (GABA)ergic neurotransmission in the mPFC of MIA offspring, leading to hyperactivity in this brain region. Remarkably, treatment with low-dose benzodiazepines clonazepam, an agonist of GABAA receptors, completely prevented the behavioral abnormalities, including stereotypies, social deficits, anxiety- and depression-like behavior, via increasing inhibitory neurotransmission as well as decreasing neural activity in the mPFC of MIA offspring. Our results demonstrate that decreased expression of NaV1.1 in the mPFC leads to abnormalities in maternal inflammation-related behaviors and provides a potential therapeutic strategy for the abnormal behavioral phenotypes observed in the offspring exposed to MIA.

Inter-breeder differences in prepulse inhibition deficits of C57BL/6J mice in a maternal immune activation model.

Genetic and environmental factors interact with each other to influence the risk of various psychiatric diseases; however, the intensity and nature of their interactions remain to be elucidated. We established a maternal infection model using polyinosinic-polycytidylic acid (Poly(I:C)) to determine the relationship between the maternal breeding environment and behavioral changes in the offspring. We purchased pregnant C57BL/6J mice from three breeders and administered Poly(I:C) (2 mg/kg) intravenously in their tail vein on gestation day 15. The offspring were raised to 8-12 weeks old and subjected to the acoustic startle tests to compare their startle response intensity, prepulse inhibition levels, and degree of the adaptation of the startle response. No statistical interaction between Poly(I:C) administration and sex was observed for prepulse inhibition; thus, male and female mice were analyzed together. There was a statistical interaction between the breeder origin of offspring and prepulse inhibition; the Poly(I:C) challenge significantly decreased prepulse inhibition levels of the offspring born to the pregnant dams from Breeder A but not those from the other breeders. However, we failed to detect significant inter-breeder differences in Poly(I:C) effects on startle response and on startle adaptation with the given number of mice examined. The rearing environment of mouse dams has a prominent effect on the Poly(I:C)-induced prepulse inhibition deficits in this maternal immune activation model.

Impact of Poly I:C induced maternal immune activation on offspring's gut microbiome diversity - Implications for schizophrenia.

Background Immunopathological concepts have been intensively discussed for schizophrenia. The polyriboinosinic-polyribocytidylic (PolyI:C) mouse model has been well validated to invasively study this disease. The intestinal microbiome exhibits broad immunological and neuronal activities. The relevance of microbiome alterations in the PolyI:C model to human schizophrenia should be explored. Methods Feces of offspring from mice mothers, who were administered to PolyI:C or NaCl (controls) at ED 9, were collected at PND 30 and 180 (PolyI:C and control mice (N = 32 each; half males and females). This was analyzed for bacterial 16S ribosomal DNA (rDNA) using a gut microbiome polymerase chain reaction (PCR) microarray tool. Results Differences were found in species richness of microbiome between animals of different ages (PND 30 and 180), but also between offspring from PolyI:C vs. NaCl treated mothers. In female mice at PND 30, the abundance of Prevotellaceae and Porphyromonadaceae was lower and that of Lactobacillales was higher, whereas in male mice at the same time point the abundance of four families of the Firmicutes phylum (Clostridia vadinBB60 group, Clostridiales Family XIII, Ruminococcaceae and Erysipelotrichaceae) was increased relative to the control group. Limitations No further analyses of cell types or cytokines involved in autoimmune gut and brain processes. Conclusions These finding seem to be similar to microbiome disturbances in patients with schizophrenia. The differential bacterial findings at day 30 (i.e., similar to the prodromal phase in patients with schizophrenia) correspond to the tremendous activation of the immune system with a strong increase in microglial cells which might be responsible for neuroplasticity reduction in cortical areas in patients with schizophrenia.

Differences in fatigue-like behavior in the lipopolysaccharide and poly I:C inflammatory animal models.

Central fatigue is a condition associated with impairment of the central nervous system often leading to the manifestation of a range of debilitating symptoms. Fatigue can be a consequence of systemic inflammation following an infection. Administration of lipopolysaccharide (LPS) and polyriboinosinic:polyribocytidlic (poly I:C) to animals can induce systemic inflammation by mimicking a bacterial or viral infection respectively and therefore have been used as models of fatigue. We evaluated a range of phenotypic behaviors exhibited in the LPS and poly I:C animal models to assess whether they adequately replicate fatigue symptomology in humans. In addition to standard observation- and intervention-based behavioral assessments, we used powerful in-cage monitoring technology to quantify rodent behavior without external interference. LPS and poly I:C treated Sprague Dawley rats displayed 'sickness behaviors' of elevated temperature, weight loss and reduced activity in the open field test and with in-cage monitoring within 24 h post-treatment, but only LPS-treated rats displayed these behaviors beyond these acute timepoints. Once sickness behavior diminished, LPS-treated rats exhibited an increase in reward-seeking and motivation behaviors. Overall, these results suggest that the LPS animal model produces an extensive and sustained fatigue-like phenotype, whereas the poly I:C model only produced acute effects. Our results suggest that the LPS animal model is a more suitable candidate for further studies on central fatigue-like behavior.

Interaction of maternal immune activation and genetic interneuronal inhibition.

Genes and environment interact during intrauterine life, and potentially alter the developmental trajectory of the brain. This can result in life-long consequences on brain function. We have previously developed two transgenic mouse lines that suppress Gad1 expression in parvalbumin (PVALB) and neuropeptide Y (NPY) expressing interneuron populations using a bacterial artificial chromosome (BAC)-driven miRNA-based silencing technology. We were interested to assess if maternal immune activation (MIA), genetic interneuronal inhibition, and the combination of these two factors disrupt and result in long-term changes in neuroinflammatory gene expression, sterol biosynthesis, and acylcarnitine levels in the brain of maternally exposed offspring. Pregnant female WT mice were given a single intraperitoneal injection of saline or polyinosinic-polycytidilic acid [poly(I:C)] at E12.5. Brains of offspring were analyzed at postnatal day 90. We identified complex and persistent neuroinflammatory gene expression changes in the hippocampi of MIA-exposed offspring, as well in the hippocampi of Npy/Gad1 and Pvalb/Gad1 mice. In addition, both MIA and genetic inhibition altered the post-lanosterol sterol biosynthesis in the neocortex and disrupted the typical acylcarnitine profile. In conclusion, our findings suggest that both MIA and inhibition of interneuronal function have long-term consequences on critical homeostatic mechanisms of the brain, including immune function, sterol levels, and energy metabolism.

Statins attenuate antiviral IFN-ß and ISG expression via inhibition of IRF3 and JAK/STAT signaling in poly(I:C)-treated hyperlipidemic mice and macrophages.

Viral infection is a significant burden to health care worldwide. Statins, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors, are widely used as cholesterol-lowering drugs. Recently, long-term statin therapy was shown to reduce the antiviral immune response; however, the underlying molecular mechanisms are unclear. Here, we found that simvastatin decreased polyinosinic-polycytidylic acid [poly(I:C)]-induced expression of antiviral interferon (IFN)-ß and IFN-stimulated genes (ISGs) in the bronchoalveolar lavage fluid (BALF) and lungs of mice with high-fat diet-induced hyperlipidemia. Macrophages were the dominant cell type in the BALF of poly(I:C)-treated mice. We examined the effects of simvastatin in primary lung macrophages and found that simvastatin suppressed poly(I:C)-induced expression of IFN-ß and ISGs. We examined the molecular mechanisms of statin-mediated inhibition of antiviral gene expression using murine macrophage-like cell line, J774.1/JA-4. Simvastatin and pitavastatin decreased poly(I:C)-induced expression of IFN-ß and ISGs. Moreover, they repressed poly(I:C)-induced phosphorylation of IFN regulatory factor (IRF) 3 and signal transducers and activators of transcription (STAT) 1, which is involved in Janus kinase (JAK)/STAT signaling. Mevalonate and geranylgeranyl pyrophosphate (GGPP), but not cholesterol, counteracted the negative effect of statins on IFN-ß and ISG expression and phosphorylation of IRF3 and STAT1. The geranylgeranyltransferase inhibitor suppressed poly(I:C)-induced expression of IFN-ß and ISGs and phosphorylation of IRF3 and STAT1. These results suggest that statins suppressed the expression of IFN-ß and ISGs in poly(I:C)-treated hyperlipidemic mice and murine macrophages and that these effects occurred through the inhibition of IRF3 and JAK/STAT signaling in macrophages. Furthermore, GGPP recovered the statin-suppressed IRF3 and JAK/STAT signaling in poly(I:C)-treated macrophages.

Effect of lipopolysaccharide and polyinosinic:polycytidylic acid in a murine model of nasal polyp.

Several factors, including bacterial and viral infections, have been associated with rhinosinusitis and nasal tissue remodelling that may result in nasal polyp formation. However, the potential role of bacterial or viral stimuli triggering polyp development is unclear. Here, we used lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid [poly(I:C)] in a murine model of allergic rhinosinusitis to compare different effects of bacterial- and virus-derived stimuli in the pathogenesis of nasal polyp formation. Briefly, BALB/c mice were sensitised and challenged with ovalbumin and staphylococcal enterotoxin, with or without LPS or poly(I:C), and the consequent histopathological profiles, cytokines, and systemic humoral responses were studied. While no significant differences in polyp formations and epithelial disruptions were observed among the experimental groups, the local cell recruitment patterns slightly differed in animals that received either LPS or poly(I:C). Additionally, the local immune environments generated by LPS or poly(I:C) stimulation varied. LPS stimulation induced a marked Th1/Th17 response and predominantly neutrophilic nasal polyp formations, whereas poly(I:C) induced a Th2-skewed environment in neutrophilic nasal polyp development. Overall, our findings show that both cell recruitment patterns and local immune environments induced by these two stimuli differ, which may have implications in the physiopathology of rhinosinusitis with nasal polyp.

Interleukin-38 ameliorates poly(I:C) induced lung inflammation: therapeutic implications in respiratory viral infections.

Interleukin-38 has recently been shown to have anti-inflammatory properties in lung inflammatory diseases. However, the effects of IL-38 in viral pneumonia remains unknown. In the present study, we demonstrate that circulating IL-38 concentrations together with IL-36α increased significantly in influenza and COVID-19 patients, and the level of IL-38 and IL-36α correlated negatively and positively with disease severity and inflammation, respectively. In the co-cultured human respiratory epithelial cells with macrophages to mimic lung microenvironment in vitro, IL-38 was able to alleviate inflammatory responses by inhibiting poly(I:C)-induced overproduction of pro-inflammatory cytokines and chemokines through intracellular STAT1, STAT3, p38 MAPK, ERK1/2, MEK, and NF-κB signaling pathways. Intriguingly, transcriptomic profiling revealed that IL-38 targeted genes were associated with the host innate immune response to virus. We also found that IL-38 counteracts the biological processes induced by IL-36α in the co-culture. Furthermore, the administration of recombinant IL-38 could mitigate poly I:C-induced lung injury, with reduced early accumulation of neutrophils and macrophages in bronchoalveolar lavage fluid, activation of lymphocytes, production of pro-inflammatory cytokines and chemokines and permeability of the alveolar-epithelial barrier. Taken together, our study indicates that IL-38 plays a crucial role in protection from exaggerated pulmonary inflammation during poly(I:C)-induced pneumonia, thereby providing the basis of a novel therapeutic target for respiratory viral infections.