鳥塚 通弘

AIM: Given that alterations in oxytocinergic and immune systems have been implicated in the social and emotional difficulties of autism spectrum disorder (ASD), yet the associations between these biological factors and internal psychological constructs remain unclear, we examined the relationship between salivary oxytocin (OT) levels, inflammatory markers (interleukin-1β [IL-1β], IL-6, IL-8), self-esteem, and perceived social support in children and adolescents with and without ASD. METHODS: 26 children and adolescents with ASD and 23 typically developing (TD) controls were included. Salivary OT and inflammatory cytokine levels were measured using enzyme-linked immunosorbent and multiplex immunoassays. RESULTS: Salivary oxytocin levels were significantly lower in the ASD group than in the TD group after adjusting for age. In contrast, no significant group differences were observed in inflammatory markers (IL-1β, IL-6, or IL-8). However, across participants, including those with ASD, higher OT levels were associated with greater self-esteem and perceived social support. These findings suggest that oxytocin-related socio-emotional processes may be associated with socio-emotional functioning across children and adolescents, including those with ASD. Participants with higher OT levels were associated with greater self-esteem and perceived social support. Among the inflammatory markers, none of the cytokines (IL-1β, IL-6, or IL-8) showed significant associations with the psychological measures, including AQ-J total scores. CONCLUSION: OT levels may be associated with socio-emotional functioning and psychological well-being across children and adolescents with and without ASD, regardless of diagnostic status. In contrast, no significant associations were observed between inflammatory markers and psychological measures in the present sample.

Sex differences in autism spectrum disorder (ASD) are increasingly recognized, not only in symptom presentation but also in underlying neurobiology and response to environmental factors. However, current diagnostic practices and animal models are male-centric, overlooking female-specific phenotypes and mechanisms. We conducted a multimodal, cross-species study to assess sex-dependent ASD phenotypes. In high-functioning adults with ASD and typically developing (TD) controls, we evaluated self-reported autistic traits, self-reported sensory sensitivity, and clinician-observed behaviors using standardized tools: Autism-Spectrum Quotient, Adolescent/Adult Sensory Profile, and Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). In parallel, we assessed behavioral phenotypes in a paternal 15q11-q13 duplication mouse model (15q dup/+) using open-field, light-dark transition, and augmented reality-based behavioral assays. Among humans, individuals with ASD showed greater self-reported sensory sensitivity and autistic traits than TD individuals. Within the ASD group, female participants reported greater self-reported sensory sensitivity and exhibited lower clinician-rated impairments (ADOS-2) than male participants, despite comparable self-reported autistic traits. No sex differences were found among TD individuals. In contrast, female 15q dup/+ mice exhibited heightened light-related sensory reactivity and reduced exploratory behavior under bright light. These findings suggest that sex differences in light-related sensory reactivity may be more readily detected through behavioral measures in animal models. Our findings underscore the importance of considering sex as a biological and behavioral variable in ASD research. Cross-species, phenotype-oriented approaches that integrate human and animal data may uncover subtle phenotypic variations and enhance sex-informed diagnostics and interventions.

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by impaired social communication and restricted repetitive behaviors, yet the contribution of trace elements remains poorly defined. We profiled 21 trace elements in individuals with ASD and identified significantly reduced copper levels, which negatively correlated with social symptom severity. Magnetic resonance imaging revealed decreased white matter volume in ASD, which also correlated with social impairment. To explore the mechanisms, we generated a copper-deficient mouse model that displayed ASD-like behaviors and impaired oligodendrocyte (OL) development. Copper deficiency disrupted hypoxia-inducible factor 1α (HIF1α)–dependent angiogenesis and metabolic regulation in the embryonic brain, leading to oxidative stress, mitochondrial dysfunction, and BCL2 interacting protein 3 (BNIP3)-mediated mitophagy in oligodendrocyte progenitor cells. These processes suppressed mechanistic target of rapamycin kinase (mTOR) signaling, reduced OL-lineage cells, and caused hypomyelination. Restoring mTOR activity rescued OL maturation and improved social behavior in copper-deficient mice. These findings identify a copper-HIF1α-BNIP3-mTOR signaling axis that links trace element imbalance to glial dysfunction and ASD-relevant behavioral phenotypes, providing mechanistic insight into neurodevelopment.

Neuropsychiatric disorders pose profound challenges to both research and treatment, largely due to their clinical heterogeneity and the limited understanding of their underlying biological mechanisms. While bulk RNA sequencing (bulk RNA-seq) has been widely used to study gene expression, it cannot resolve cell-type-specific signals or detect rare cellular subpopulations. In contrast, single-cell RNA sequencing (scRNA-seq) and single-nucleus RNA sequencing (snRNA-seq) have emerged as transformative technologies, enabling transcriptomic profiling at single-cell resolution. These approaches have revealed immunological alterations across a wide range of disorders. This review introduces recent findings from sc/snRNA-seq studies of immune-related mechanisms in psychiatric disorders-including schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorder, and attention-deficit/hyperactivity disorder-as well as in neurological conditions such as Alzheimer's disease, Parkinson's disease, dementia with Lewy bodies, multiple sclerosis, and anti-NMDA receptor encephalitis. While sc/snRNA-seq overcome averaging effects of bulk RNA-seq by resolving cell types, these methods still face challenges. We outline a roadmap that integrates bulk RNA-seq and sc/snRNA-seq to mitigate the remaining gaps.

Oxytocin has been implicated in regulating social behaviour and emotional responses; however, the underlying neural circuits remain incompletely understood. Neurons expressing oxytocin receptors (OTRs) in the paraventricular thalamus (PVT) are emerging as a potential modulator of these processes. In this study, we investigated the specific role of OTR-expressing PVT neurons in sociability and fear-related behaviours. Using chemogenetic approaches, we found that bidirectional manipulation of these neurons significantly modulated social behaviour and fear extinction in mice. Inhibition of OTR-expressing PVT neurons impaired sociability and fear extinction, whereas activation selectively enhanced early extinction learning without affecting sociability. Electrophysiological analyses revealed that oxytocin increases tonic firing in PVT neurons, suggesting a mechanism for heightened excitability. In contrast, manipulation of OTR-expressing neurons in the medial prefrontal cortex had no effect on sociability. In a complementary human dataset, salivary oxytocin levels were modestly associated with thalamic microstructure and autism spectrum disorder trait severity. Although the experimental paradigms differed across species, these findings collectively suggest that OTR-expressing PVT neurons may contribute to social and emotional behaviours through circuit-specific mechanisms. These findings may have implications for psychiatric conditions such as autism spectrum disorder and anxiety. Future translational studies should explore the therapeutic potential of targeting oxytocin-related PVT function to treat social and fear-related deficits. Overall, these findings advance our understanding of the role of oxytocin in brain function and its relevance to mental health.