Tumor necrosis factor-α expression aberration of M1/M2 macrophages in adult high-functioning autism spectrum disorder

Innate Immune Dysfunction and Neuroinflammation in Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder characterized by communication and social behavior deficits. The presence of restricted and repetitive behaviors often accompanies these deficits, and these characteristics can range from mild to severe. The past several decades have seen a significant rise in the prevalence of ASD. The etiology of ASD remains unknown; however, genetic and environmental risk factors play a role. Multiple hypotheses converge to suggest that neuroinflammation, or at least the interaction between immune and neural systems, may be involved in the etiology of some ASD cases or groups. Repeated evidence of innate immune dysfunction has been seen in ASD, often associated with worsening behaviors. This evidence includes data from circulating myeloid cells and brain resident macrophages/microglia in both human and animal models. This comprehensive review presents recent findings of innate immune dysfunction in ASD, including aberrant innate cellular function, evidence of neuroinflammation, and microglia activation. Appeared originally in Brain Behav Immun 2023; 108:245-254.

Granulocyte macrophage colony-stimulating factor-induced macrophages of individuals with autism spectrum disorder adversely affect neuronal dendrites through the secretion of pro-inflammatory cytokines

BACKGROUND

A growing body of evidence suggests that immune dysfunction and inflammation in the peripheral tissues as well as the central nervous system are associated with the neurodevelopmental deficits observed in autism spectrum disorder (ASD). Elevated expression of pro-inflammatory cytokines in the plasma, serum, and peripheral blood mononuclear cells of ASD has been reported. These cytokine expression levels are associated with the severity of behavioral impairments and symptoms in ASD. In a prior study, our group reported that tumor necrosis factor-α (TNF-α) expression in granulocyte-macrophage colony-stimulating factor-induced macrophages (GM-CSF MΦ) and the TNF-α expression ratio in GM-CSF MΦ/M-CSF MΦ (macrophage colony-stimulating factor-induced macrophages) was markedly higher in individuals with ASD than in typically developed (TD) individuals. However, the mechanisms of how the macrophages and the highly expressed cytokines affect neurons remain to be addressed.

METHODS

To elucidate the effect of macrophages on human neurons, we used a co-culture system of control human-induced pluripotent stem cell-derived neurons and differentiated macrophages obtained from the peripheral blood mononuclear cells of five TD individuals and five individuals with ASD. All participants were male and ethnically Japanese.

RESULTS

Our results of co-culture experiments showed that GM-CSF MΦ affect the dendritic outgrowth of neurons through the secretion of pro-inflammatory cytokines, interleukin-1α and TNF-α. Macrophages derived from individuals with ASD exerted more severe effects than those derived from TD individuals.

LIMITATIONS

The main limitations of our study were the small sample size with a gender bias toward males, the use of artificially polarized macrophages, and the inability to directly observe the interaction between neurons and macrophages from the same individuals.

CONCLUSIONS

Our co-culture system revealed the non-cell autonomous adverse effects of GM-CSF MΦ in individuals with ASD on neurons, mediated by interleukin-1α and TNF-α. These results may support the immune dysfunction hypothesis of ASD, providing new insights into its pathology.

Alterations in Plasma Cytokine Levels in Korean Children with Autism Spectrum Disorder

PURPOSE

Numerous studies have supported the role of the immune dysfunction in the pathogenesis of autism spectrum disorder (ASD); however, to our knowledge, no study has been conducted on plasma cytokine levels in children with ASD in South Korea. In this study, we aimed to analyze the immunological characteristics of Korean children with ASD through plasma cytokine analysis.

MATERIALS AND METHODS

Blood samples were collected from 94 ASD children (mean age 7.1; 81 males and 13 females) and 48 typically developing children (TDC) (mean age 7.3; 30 males and 18 females). Plasma was isolated from 1 mL of blood by clarifying with centrifugation at 8000 rpm at 4℃ for 10 min. Cytokines in plasma were measured with LEGENDplex HU Th cytokine panel (BioLegend, 741028) and LEGENDplex HU cytokine panel 2 (BioLegend, 740102).

RESULTS

Among 25 cytokines, innate immune cytokine [interleukin (IL)-33] was significantly decreased in ASD children compared with TDC. In acute phase proteins, tumor necrosis factor α (TNF-α) was significantly increased, while IL-6, another inflammation marker, was decreased in ASD children compared with TDC. The cytokines from T cell subsets, including interferon (IFN)-γ, IL-5, IL-13, and IL-17f, were significantly decreased in ASD children compared to TDC. IL-10, a major anti-inflammatory cytokine, and IL-9, which modulates immune cell growth and proliferation, were also significantly decreased in ASD children compared to TDC.

CONCLUSION

We confirmed that Korean children with ASD showed altered immune function and unique cytokine expression patterns distinct from TDC.

Mini review of molecules involved in altered postnatal neurogenesis in autism

The neurobiology of autism is complex, but emerging research points to potential abnormalities and alterations in neurogenesis. The aim of the present review is to describe the advances in the understanding of the role of selected neurotrophins, neuropeptides, and other compounds secreted by neuronal cells in the processes of postnatal neurogenesis in conjunction with autism. We characterize the fundamental mechanisms of neuronal cell proliferation, generation of major neuronal cell types with special emphasis on neurogenic niches - the subventricular zone and hippocampal areas. We also discuss changes in intracellular calcium levels and calcium-dependent transcription factors in the context of the regulation of neurogenesis and cell fate determination. To sum up, this review provides specific insight into the known association between alterations in the function of the entire spectrum of molecules involved in neurogenesis and the etiology of autism pathogenesis.

Sensor Array-Enabled Identification of Drugs for Repolarization of Macrophages to Anti-Inflammatory Phenotypes

Macrophages are key components of the innate immune system that have essential functions in physiological processes and diseases. The phenotypic plasticity of macrophages allows cells to be polarized into a multidimensional spectrum of phenotypes, broadly classed as pro-inflammatory (M1) and anti-inflammatory (M2) states. Repolarization of M1 to M2 phenotypes alters the immune response to ameliorate autoimmune and inflammation-associated diseases. Detection of this repolarization, however, is challenging to execute in high-throughput applications. In this work, we demonstrate the ability of a single polymer fabricated to provide a six-channel sensor array that can determine macrophage polarization phenotypes. This sensing platform provides a sensitive and high-throughput tool for detecting drug-induced M1-to-M2 repolarization, allowing the identification of new therapeutic leads for inflammatory diseases. The ability of this sensor array to discriminate different M2 subtypes induced by drugs can also improve the efficacy evaluation of anti-inflammatory drugs and avoid adverse effects.

Maternal Chronic Ultrasound Stress Provokes Immune Activation and Behavioral Deficits in the Offspring: A Mouse Model of Neurodevelopmental Pathology

Neurodevelopmental disorders stemming from maternal immune activation can significantly affect a child's life. A major limitation in pre-clinical studies is the scarcity of valid animal models that accurately mimic these challenges. Among the available models, administration of lipopolysaccharide (LPS) to pregnant females is a widely used paradigm. Previous studies have reported that a model of 'emotional stress', involving chronic exposure of rodents to ultrasonic frequencies, induces neuroinflammation, aberrant neuroplasticity, and behavioral deficits. In this study, we explored whether this model is a suitable paradigm for maternal stress and promotes neurodevelopmental abnormalities in the offspring of stressed females. Pregnant dams were exposed to ultrasound stress for 21 days. A separate group was injected with LPS on embryonic days E11.5 and E12.5 to mimic prenatal infection. The behavior of the dams and their female offspring was assessed using the sucrose test, open field test, and elevated plus maze. Additionally, the three-chamber sociability test and Barnes maze were used in the offspring groups. ELISA and qPCR were used to examine pro-inflammatory changes in the blood and hippocampus of adult females. Ultrasound-exposed adult females developed a depressive-like syndrome, hippocampal overexpression of GSK-3β, IL-1β, and IL-6 and increased serum concentrations of IL-1β, IL-6, IL-17, RANTES, and TNFα. The female offspring also displayed depressive-like behavior, as well as cognitive deficits. These abnormalities were comparable to the behavioral changes induced by LPS. The ultrasound stress model can be a promising animal paradigm of neurodevelopmental pathology associated with prenatal 'emotional stress'.

Cadmium Exposure Is Associated with Behavioral Deficits and Neuroimmune Dysfunction in BTBR T+ Itpr3tf/J Mice

Autism spectrum disorders (ASD) are neurobehavioral disabilities characterized by impaired social interactions, poor communication skills, and restrictive/repetitive behaviors. Cadmium is a common heavy metal implicated in ASD. In this study, we investigated the effects of Cd exposure on BTBR T+ Itpr3tf/J (BTBR) mice, an ASD model. We looked for changes in repetitive behaviors and sociability through experiments. We also explored the molecular mechanisms underlying the effects of Cd exposure, focusing on proinflammatory cytokines and pathways. Flow cytometry measured IL-17A-, IL-17F-, IL-21-, TNF-α-, STAT3-, and RORγt-expressing CD4+ T cells from the spleens of experimental mice. We then used RT-PCR to analyze IL-17A, IL-17F, IL-21, TNF-α, STAT3, and RORγ mRNA expression in the brain. The results of behavioral experiments showed that Cd exposure significantly increased self-grooming and marble-burying in BTBR mice while decreasing social interactions. Cd exposure also significantly increased the number of CD4+IL-17A+, CD4+IL-17F+, CD4+IL-21+, CD4+TNF-α+, CD4+STAT3+, and CD4+RORγt+ cells, while upregulating the mRNA expression of the six molecules in the brain. Overall, our results suggest that oral exposure to Cd aggravates behavioral and immune abnormalities in an ASD animal model. These findings have important implications for ASD etiology and provide further evidence of heavy metals contributing to neurodevelopmental disorders through proinflammatory effects.

Innate immune dysfunction and neuroinflammation in autism spectrum disorder (ASD)

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder characterized by communication and social behavior deficits. The presence of restricted and repetitive behaviors often accompanies these deficits, and these characteristics can range from mild to severe. The past several decades have seen a significant rise in the prevalence of ASD. The etiology of ASD remains unknown; however, genetic and environmental risk factors play a role. Multiple hypotheses converge to suggest that neuroinflammation, or at least the interaction between immune and neural systems, may be involved in the etiology of some ASD cases or groups. Repeated evidence of innate immune dysfunction has been seen in ASD, often associated with worsening behaviors. This evidence includes data from circulating myeloid cells and brain resident macrophages/microglia in both human and animal models. This comprehensive review presents recent findings of innate immune dysfunction in ASD, including aberrant innate cellular function, evidence of neuroinflammation, and microglia activation.

Inflammation and the Potential Implication of Macrophage-Microglia Polarization in Human ASD: An Overview

Autism spectrum disorder (ASD) is a heterogeneous collection of neurodevelopmental disorders, difficult to diagnose and currently lacking treatment options. The possibility of finding reliable biomarkers useful for early identification would offer the opportunity to intervene with treatment strategies to improve the life quality of ASD patients. To date, there are many recognized risk factors for the development of ASD, both genetic and non-genetic. Although genetic and epigenetic factors may play a critical role, the extent of their contribution to ASD risk is still under study. On the other hand, non-genetic risk factors include pollution, nutrition, infection, psychological states, and lifestyle, all together known as the exposome, which impacts the mother's and fetus's life, especially during pregnancy. Pathogenic and non-pathogenic maternal immune activation (MIA) and autoimmune diseases can cause various alterations in the fetal environment, also contributing to the etiology of ASD in offspring. Activation of monocytes, macrophages, mast cells and microglia and high production of pro-inflammatory cytokines are indeed the cause of neuroinflammation, and the latter is involved in ASD's onset and development. In this review, we focused on non-genetic risk factors, especially on the connection between inflammation, macrophage polarization and ASD syndrome, MIA, and the involvement of microglia.

Mechanism of protection from insulin resistance by toll-like receptor 2 deficiency in high-fat diet fed mice: involvement in macrophage polarization

BACKGROUND

Toll-like receptor 2 (TLR2) deficiency can increase insulin sensitivity and improves glucose tolerance. However, it is not yet fully understood about its underlying mechanism. The regulation of M1/M2 macrophage polarization has been verified to involve in insulin resistance. Here, we evaluated whether the beneficial effect of TLR2 deficiency is mediated by TLR2-associated macrophage polarization in mice fed with high-fat diet (HFD).

METHODS AND RESULTS

Wild-type and TLR2 knockout (TLR2^-/-) mice received HFD for two months. Following intraperitoneal glucose tolerance and insulin resistance tests, peripheral monocytes were isolated, and in vitro induced for differentiation into M1 and M2 macrophages, respectively. Macrophages polarization was evaluated using flow cytometry. The expression of macrophage polarization marker genes and cytokine production in visceral adipose tissue were measured by qRT-PCR and ELISA. Compared to wild-type mice, TLR2^-/- mice showed higher glucose tolerance and insulin sensitivity, along with significantly reduced the population of M1 and increased M2 count in vitro. Additionally, TLR2^-/- mice demonstrated higher expression of M2 marker iNOS mRNA and interleukin-10 level in adipose tissues.

CONCLUSIONS

Our results reveal that TLR2 knockout-mediated macrophages M2 polarization is a crucial factor for preventing against diet-induced insulin resistance in mice. These findings deepen our knowledge about the mechanism underlying HFD-induced insulin resistance.