Wong Helen, Hoeffer Charles
Institute for Behavioral Genetics, University of Colorado-Boulder, CO 80303, United States; Department of Integrative Physiology, University of Colorado-Boulder, Boulder, CO 80303, United States; Linda Crnic Institute, University of Colorado-Anschutz Medical Campus, Aurora, CO 80045, United States.
Institute for Behavioral Genetics, University of Colorado-Boulder, CO 80303, United States; Department of Integrative Physiology, University of Colorado-Boulder, Boulder, CO 80303, United States; Linda Crnic Institute, University of Colorado-Anschutz Medical Campus, Aurora, CO 80045, United States.
Exp Neurol. 2018 Jan;299(Pt A):228-240. doi: 10.1016/j.expneurol.2017.04.010. Epub 2017 Apr 25.
Although autism spectrum disorder (ASD) has a strong genetic basis, its etiology is complex, with several genetic factors likely to be involved as well as environmental factors. Immune dysregulation has gained significant attention as a causal mechanism in ASD pathogenesis. ASD has been associated with immune abnormalities in the brain and periphery, including inflammatory disorders and autoimmunity in not only the affected individuals but also their mothers. Prenatal exposure to maternal immune activation (MIA) has been implicated as an environmental risk factor for ASD. In support of this notion, animal models have shown that MIA results in offspring with behavioral, neurological, and immunological abnormalities similar to those observed in ASD. This raises the question of how MIA exposure can lead to ASD in susceptible individuals. Recent evidence points to a potential inflammation pathway linking MIA-associated ASD with the activity of T helper 17 (Th17) lymphocytes and their effector cytokine interleukin-17A (IL-17A). IL-17A has been implicated from human studies and elevated IL-17A levels in the blood have been found to correlate with phenotypic severity in a subset of ASD individuals. In MIA model mice, elevated IL-17A levels also have been observed. Additionally, antibody blockade to inhibit IL-17A signaling was found to prevent ASD-like behaviors in offspring exposed to MIA. Therefore, IL-17A dysregulation may play a causal role in the development of ASD. The source of increased IL-17A in the MIA mouse model was attributed to maternal Th17 cells because genetic removal of the transcription factor RORγt to selectively inhibit Th17 differentiation in pregnant mice was able to prevent ASD-like behaviors in the offspring. Similar to ASD individuals, the MIA-exposed offspring also displayed cortical dysplasia which could be prevented by inhibition of IL-17A signaling in pregnant mice. This finding reveals one possible cellular mechanism through which ASD-related cognitive and behavioral deficits may emerge following maternal inflammation. IL-17A can exert strong effects on cell survival and differentiation and the activity of signal transduction cascades, which can have important consequences during cortical development on neural function. This review examines IL-17A signaling pathways in the context of both immunity and neural function that may contribute to the development of ASD associated with MIA.
尽管自闭症谱系障碍（ASD）有很强的遗传基础，但其病因复杂，可能涉及多个遗传因素以及环境因素。免疫失调作为ASD发病机制中的一种因果机制已受到广泛关注。ASD与大脑和外周的免疫异常有关，包括不仅在受影响个体中，而且在其母亲中出现的炎症性疾病和自身免疫。产前暴露于母体免疫激活（MIA）已被认为是ASD的一种环境风险因素。支持这一观点的是，动物模型表明，MIA会导致后代出现与ASD中观察到的类似的行为、神经和免疫异常。这就提出了一个问题，即MIA暴露如何导致易感个体患ASD。最近的证据指向一条潜在的炎症途径，将与MIA相关的ASD与辅助性T细胞17（Th17）淋巴细胞及其效应细胞因子白细胞介素-17A（IL-17A）的活性联系起来。人类研究表明IL-17A与ASD有关，并且在一部分ASD个体中发现血液中IL-17A水平升高与表型严重程度相关。在MIA模型小鼠中也观察到IL-17A水平升高。此外，发现抑制IL-17A信号的抗体阻断可预防暴露于MIA的后代出现ASD样行为。因此，IL-17A失调可能在ASD的发展中起因果作用。MIA小鼠模型中IL-17A增加的来源归因于母体Th17细胞，因为在怀孕小鼠中通过基因去除转录因子RORγt以选择性抑制Th17分化能够预防后代出现ASD样行为。与ASD个体类似，暴露于MIA的后代也表现出皮质发育异常，而这可以通过抑制怀孕小鼠中的IL-17A信号来预防。这一发现揭示了母体炎症后可能出现ASD相关认知和行为缺陷的一种可能的细胞机制。IL-17A可对细胞存活、分化以及信号转导级联反应的活性产生强大影响，这在皮质发育过程中对神经功能可能产生重要影响。本综述探讨了在免疫和神经功能背景下可能导致与MIA相关的ASD发展的IL-17A信号通路。
