Recent research on the etiology of autism spectrum disorder (ASD) has shifted in part from a singular focus on genetic causes to the involvement of environmental factors and their gene interactions. This shift in focus is a result of the rapidly increasing prevalence of ASD coupled with the incomplete penetrance of this disorder in monozygotic twins. One such area of environmentally focused research is the association of exposures to endocrine disrupting compounds (EDCs) with elevated risk for ASD. EDCs are exogenous chemicals that can alter endogenous hormone activity and homeostasis, thus potentially disrupting the action of sex and other natural hormones at all stages of human development. Inasmuch as sex hormones play a fundamental role in brain development and sexual differentiation, exposure to EDCs in utero during critical stages of development can have lasting neurological and other physiological influences on the developing fetus and, ultimately, the child as well as adult. This review will focus on the possible contributions of EDCs to autism risk and pathogenesis by first discussing the influence of endogenous sex hormones on the autistic phenotype, followed by a review of documented human exposures to EDCs and associations with behaviors relevant to ASD. Mechanistic links between EDC exposures and aberrant neurodevelopment and behaviors are then considered, with emphasis on EDC-induced transcriptional profiles derived from animal and cellular studies. Finally, this review will discuss possible mechanisms through which EDC exposure can lead to persistent changes in gene expression and phenotype, which may in turn contribute to transgenerational inheritance of ASD.

Neutrophils sense and migrate through an enormous range of chemoattractant gradients through adaptation. Here, we reveal that in human neutrophils, calcium-promoted Ras inactivator (CAPRI) locally controls the GPCR-stimulated Ras adaptation. Human neutrophils lacking CAPRI (caprikd) exhibit chemoattractant-induced, nonadaptive Ras activation; significantly increased phosphorylation of AKT, GSK-3α/3β, and cofilin; and excessive actin polymerization. caprikd cells display defective chemotaxis in response to high-concentration gradients but exhibit improved chemotaxis in low- or subsensitive-concentration gradients of various chemoattractants, as a result of their enhanced sensitivity. Taken together, our data reveal that CAPRI controls GPCR activation-mediated Ras adaptation and lowers the sensitivity of human neutrophils so that they are able to chemotax through a higher-concentration range of chemoattractant gradients.

Neutrophils sense and migrate through an enormous range of chemoattractant gradients through adaptation. Here, we reveal that, in human neutrophils, Calcium-promoted Ras inactivator (CAPRI) locally controls the GPCR-stimulated Ras adaptation. Human neutrophils lacking CAPRI (caprikd) exhibit chemoattractant-induced non-adaptive Ras activation; significantly increased phosphorylation of AKT, GSK3α/3β, and cofilin; and excessive actin polymerization. caprikd cells display defective chemotaxis in response to high-concentration gradients but exhibit improved chemotaxis in low- or subsensitive-concentration gradients of various chemoattractants as a result of their enhanced sensitivity. Taken together, our data reveal that CAPRI controls GPCR activation-mediated Ras adaptation and lowers the sensitivity of human neutrophils so that they are able to chemotax through a higher concentration range of chemoattractant gradients.Significance StatementNeutrophils provide first-line host defense by migrating through chemoattractant gradients to the sites of inflammation. Inappropriate recruitment and mis-regulated activation of neutrophils contribute to tissue damage and cause autoimmune and inflammatory disease. One fascinating feature of chemotactic neutrophils is their ability to migrate through an enormous concentration range of chemoattractant gradients (10−9 ∼ 10−5 M) through “adaptation,” in which cells no longer respond to the present stimuli, but remain sensitive to stronger stimuli. The inhibitory mechanism largely remains elusive, although many molecules of the excitatory signaling pathway have been identified. Our study reveals, for the first time, that the inhibitory component, CAPRI, is essential for both the sensitivity and the GPCR-mediated adaptation of human neutrophils.

The current dogma is that chemoattractants G protein-coupled receptors (GPCRs) activate β phospholipase C (PLCβ) while receptor tyrosine kinases (RTKs) activate γ phospholipase C (PLCγ). Here, we show that chemoattractant/GPCR-mediated membrane recruitment of PLCγ2 constitutes GPCR-mediated phospholipase C (PLC) signaling and is essential for neutrophil polarization and migration during chemotaxis. In response to a chemoattractant stimulation, cells lacking PLCγ2 (plcg2kd) displayed altered dynamics of diacylglycerol (DAG) production and calcium response; increased Ras/PI3K/Akt activation; elevated GSK3 phosphorylation and cofilin activation; impaired dynamics of actin polymerization; and consequently, defects in cell polarization and migration during chemotaxis. The study reveals a molecular mechanism of membrane targeting of PLCγ2 and the signaling pathways by which PLCγ2 plays an essential role in neutrophil chemotaxis.