Mitochondrial DNA-Activated cGAS-STING Signaling in Environmental Dry Eye.

Purpose: The cGAS-STING pathway has been shown to be an important mediator of inflammation. There is emerging evidence of the importance of this signaling cascade in a variety of inflammatory diseases settings. Here, we present evidence that the mitochondrial DNA (mtDNA) damage-mediated cGAS-STING pathway plays an important role in the induction of inflammation in environmental dry eye (DE). Methods: RT-qPCR and Western blot were used to assess the induction of the cGAS-STING pathway and inflammatory cytokines in environmental DE mouse model, primary human corneal epithelial cells (pHCECs), and patients with DE. RNA sequencing was used to determine mRNA expression patterns of high osmotic pressure (HOP)-stimulated pHCECs. mtDNA was detected with electron microscopy, flow cytometry, and immunofluorescent staining. mtDNA was isolated and transfected into pHCECs for evaluating the activation of the cGAS-STING pathway. Results: The expression levels of cGAS, STING, TBK1, IRF3, and IFNß were significantly increased in an environmental DE model and HOP-stimulated pHCECs. The STING inhibitor decreased the expression of inflammatory factors in DE. An upregulation of STING-mediated immune responses and IRF3 expression mediated by TBK1 were observed in the HOP group. HOP stimulation induced mitochondrial oxidative damage and the leakage of mtDNA into the cytoplasm. Then, mtDNA activated the cGAS-STING pathway and induced intracytoplasmic STING translocated to the Golgi apparatus. Finally, we also found activated cGAS-STING signaling in the human conjunctival blot cell of patients with DE. Conclusions: Our findings suggest that the cGAS-STING pathway is activated by recognizing cytoplasmic mtDNA leading to STING translocation, further exacerbating the development of inflammation in environmental DE.

Single-cell landscape reveals the epithelial cell-centric pro-inflammatory immune microenvironment in dry eye development.

Dry eye disease (DED) is a prevalent chronic eye disease characterized by an aberrant inflammatory response in ocular surface mucosa. The immunological alterations underlying DED remain largely unknown. In this study, we employed single-cell transcriptome sequencing of conjunctival tissue from environment-induced DED mice to investigate multicellular ecosystem and functional changes at different DED stages. Our results revealed an epithelial subtype with fibroblastic characteristics and pro-inflammatory effects emerging in the acute phase of DED. We also found that T helper (Th)1, Th17, and regulatory T cells (Treg) were the dominant clusters of differentiation (CD)4+ T-cell types involved in regulating immune responses and identified three distinct macrophage subtypes, with the CD72+CD11c+ subtype enhancing chronic inflammation. Furthermore, bulk transcriptome analysis of video display terminal-induced DED consistently suggested the presence of the pro-inflammatory epithelial subtype in human conjunctiva. Our findings have uncovered a DED-associated pro-inflammatory microenvironment in the conjunctiva, centered around epithelial cells, involving interactions with macrophages and CD4+ T cells, which deepens our understanding of ocular surface mucosal immune responses during DED progression.

Epigenetic Activation of Circadian Clock Genes Elicits Inflammation in Experimental Murine Dry Eye.

PURPOSE: To explore whether circadian clock genes contribute to elicit inflammation in experimental dry eye (EDE). METHODS: RNA sequencing analyzed mRNA expression patterns in EDE model. RT-qPCR and/or Western blot determined the expression of inflammatory factors and circadian genes during EDE. MethylTarget™ assays determined the promoter methylation levels of Per genes in vivo. Per2 or Per3 knockdown assessed their effects on inflammatory factors in vitro. RESULTS: We utilized an intelligently controlled environmental system (ICES) to establish a mouse EDE model. The significant upregulated genes were enriched for circadian rhythms. Therein lied oscillatory and time-dependent upregulation of PER2 and PER3, as well as their promoter hypomethylation during EDE. Silencing PER2 or PER3 significantly decreased inflammatory factor expression and also reversed such increased inflammatory response in azacitidine (AZA) treatment in vitro model. CONCLUSIONS: Our findings suggest that DNA methylation mediated the upregulation of PER2 and PER3, leading to inflammatory response in EDE.

Proteomic identification of sperm from mice exposed to sodium fluoride.

Fluoride is a widespread environmental pollutant which can induce low sperm quality and fertilizing ability. However, effect of fluoride on proteomic changes of sperm is unknown. In this study, two-dimensional electrophoresis (2DE) and mass spectrometry (MS) were used to investigate the differently expressed proteins of sperm from mice exposed to fluoride. 180 male mice were randomly divided into three groups, and were administrated with the distilled water containing 0, 25, and 100 mg L-1 NaF, respectively. After 45, 90 and 180 day's exposure, mice were sacrificed and sperm from the cauda epididymis and vas deferens were collected for 2DE. 16 differently expressed spots were picked up to identify using MS, 15 of which were successfully identified. Many of them are associated with the sperm function such as sperm motility, maturation, capacitation and acrosome reaction, lipid peroxidation, detoxification, inflammation, and stability of membrane structure. These results could contribute to the explanation and further research of mechanisms underlying sperm damage induced by fluoride.

Paternal bisphenol a diet changes prefrontal cortex proteome and provokes behavioral dysfunction in male offspring.

Relatively little attention has been given paternal effects on next generation. Given that Bisphenol A (BPA), a ubiquitous compound in maternal diet, may disrupt brain development and behavior, we hypothesized that paternal BPA diet (PBD) could affect offspring development. Prefrontal cortex (PFC), a vital brain region, is involved in emotion and social behavior. To test whether PBD could alter developing PFC, we carried out a proteomics approach for PFC in male juvenile offspring that responded to PBD (50 mg BPA/kg diet). We found that PBD altered the expressions of binding immunoglobulin protein (BIP), CCAAT/-enhancer-binding protein homologous protein (CHOP) and B-cell lymphoma-2 (BCL-2), which could reflect endoplasmic reticulum (ER) stress. In addition, downregulation of myelinogenesis genes and myelin basic protein (MBP) could provoke myelin deficiency. Furthermore, PBD significantly increased anxiety-like behavior and impaired social behavior in male offspring. Taken together, these results revealed the alterations of ER stress and myelin destruction related molecules induced by PBD might be a potential mechanism for the behavior deficits in their male offspring. These findings remind us of the importance of paternal effects in the further environmental exposure research.

Chronic fluoride exposure-induced testicular toxicity is associated with inflammatory response in mice.

Previous studies have indicated that fluoride (F) can affect testicular toxicity in humans and rodents. However, the mechanism underlying F-induced testicular toxicity is not well understood. This study was conducted to evaluate the sperm quality, testicular histomorphology and inflammatory response in mice followed F exposure. Healthy male mice were randomly divided into four groups with sodium fluoride (NaF) at 0, 25, 50, 100 mg/L in the drinking water for 180 days. At the end of the exposure, significantly increased percentage of spermatozoa abnormality was found in mice exposed to 50 and 100 mg/L NaF. Disorganized spermatogenic cells, vacuoles in seminiferous tubules and loss and shedding of sperm cells were also observed in the NaF treated group. In addition, chronic F exposure increased testicular interleukin-17(IL-17), interleukin-17 receptor C (IL-17RC), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in transcriptional levels, as well as IL-17 and TNF-α levels in translational levels. Interestingly, we observed that F treated group elevated testicular inducible nitric oxide synthase (iNOS) mRNA level and nitric oxide (NO) concentration. Taken together, these results indicated that testicular inflammatory response could contribute to chronic F exposure induced testicular toxicity in mice.

Fluoride exposure changed the structure and the expressions of reproductive related genes in the hypothalamus-pituitary-testicular axis of male mice.

Numerous studies have shown that fluoride exposure adversely affected the male reproductive function, while the molecular mechanism is not clear. The present study was to investigate the effects of fluoride exposure (60 days) on the expressions of reproductive related genes, serum sex hormone levels and structures of the hypothalamus-pituitary-testicular axis (HPTA), which plays a vital role in regulating the spermatogenesis in male mice. In this study, 48 male mice were administrated with 0, 25, 50, and 100 mg/L NaF through drinking water. Results showed that the malformation ratio of sperm was significantly increased (P<0.05). At transcriptional level, the expression levels of follicle-stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), inhibin alpha (INHα), inhibin beta-B (INHßB), and sex hormone binding globulin (SHBG) mRNA in testis were significantly decreased (P<0.05). Moreover, histological lesions in testis and ultrastructural alterations in hypothalamus, pituitary and testis were obvious. However, the same fluoride exposure did not lead to significant changes of related mRNA expressions in hypothalamus and pituitary (P>0.05). Also, there were no marked changes in serum hormones. Taken together, we conclude that the mechanism of HPTA dysfunction is mainly elucidated through affecting testes, and its effect on hypothalamus and pituitary was secondary at exposure for 60 days.

Maternal bisphenol a diet induces anxiety-like behavior in female juvenile with neuroimmune activation.

Maternal Bisphenol A (BPA) diet triggers anxiety in rodents, but the underlying mechanism is still unclear. Accumulating epidemiological and experimental data have demonstrated that the anxiety is associated with aberrant neuroimmune response. In this study, we found that maternal BPA diet (MBD) exacerbated anxiety-like behavior in female juvenile mice, and the molecular evidence further showed that this behavioral phenotype was connected to the neuroimmune activation, such as elevated tumor necrosis factor alpha (TNF-α) and interleukin (IL)-6 levels in prefrontal cortex (PFC) rather than in peripheral blood, which indicated that neuroimmune response might be ascribed to neuroglial activation because activated neuroglia cells could secrete proinflammatory cytokines. Subsequently, we found that ionized calcium-binding adapter molecule (Iba)-1 as a selective marker for microglia and glial fibrillary acidic protein as a specific marker for astrocyte were significantly increased at transcriptional and translational levels, which confirmed the neuroglial activation in this model. Therefore, we conclude that MBD induces excessive anxiety-like behavior in female juvenile with elevated TNF-α and IL-6 levels, as well as activated microglia and astrocyte in PFC. Herein caution must be taken to prevent potential risks from MBD becuase exacerbated anxiety-like behavior in female juvenile by MBD may be a critical contribution for subsequent growth or mental disorders.

Pubertal exposure to Bisphenol A increases anxiety-like behavior and decreases acetylcholinesterase activity of hippocampus in adult male mice.

The negative effects of Bisphenol A (BPA) on neurodevelopment and behaviors have been well established. Acetylcholinesterase (AChE) is a regulatory enzyme which is involved in anxiety-like behavior. This study investigated behavioral phenotypes and AChE activity in male mice following BPA exposure during puberty. On postnatal day (PND) 35, male mice were exposed to 50mg BPA/kg diet per day for a period of 35 days. On PND71, a behavioral assay was performed using the elevated plus maze (EPM) and the light/dark test. In addition, AChE activity was measured in the prefrontal cortex, hypothalamus, cerebellum and hippocampus. Results from our behavioral phenotyping indicated that anxiety-like behavior was increased in mice exposed to BPA. AChE activity was significantly decreased in the hippocampus of mice with BPA compared to control mice, whereas no difference was found in the prefrontal cortex, hypothalamus and cerebellum. Our findings showed that pubertal BPA exposure increased anxiety-like behavior, which may be associated with decreased AChE activity of the hippocampus in adult male mice. Further studies are necessary to investigate the cholinergic signaling of the hippocampus in PBE induced anxiety-like behaviors.