INVESTIGATING THE EFFECTS OF ARSENIC EXPOSURE ON DENDRITIC CELL GENE EXPRESSION, ACTIVATION, AND MIGRATION
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Arsenic is a naturally occurring chemical element in the Earth’s crust and one of the most prevalent contaminants in drinking water across the globe. Although a provisional limit of 10 g/L (ppb) has been established by the World Health Organization (WHO), at least 140 million people consume drinking water contaminated with arsenic at concentrations above this limit. Previous experiments in our lab have shown reduced homing dendritic cell migration to the lymph nodes and increased morbidity and mortality in arsenic-exposed mice following infection with influenza A virus (IAV), but the implicated pathways and the effect of arsenic on dendritic cell activation has yet to be explored. To test the hypothesis that inorganic arsenic (iAs) exposure dampens the immune response by targeting dendritic cell activation and migration in response to IAV infection, in vitro and ex vivo experiments were conducted. GM-CSF+IL-4 differentiated bone marrow-derived dendritic cells (GM-CSF-BMDCs) exposed to 0 or 0.1 M iAs in vivo were analyzed using Gene Set Enrichment Analysis (GSEA) of RNA sequencing (RNA-seq) data. A transwell migration assay was optimized to assess the migratory capacity of FLT3L and GM-CSF differentiated BMDCs (CD103+ BMDCs) exposed to 0 or 0.1 M iAs in vitro. Flow cytometric analyses were used to identify the effect of arsenic on CD103+ BMDCs. GM-CSF-BMDCs exposed to arsenic in vivo exhibit positive enrichment in the expression of several genes relevant to DCs. Although preliminary data on CD103+ BMDCs did not exhibit any significant changes in activation markers following exposure to 0.1 M iAs arsenic, there was an increase in the CD103+ BMDC population frequency following exposure to R848, a TLR7/8 agonist that mimics immune activation to viral RNA. This thesis supports the immunomodulatory effects of low-dose arsenic exposure in drinking water, particularly for females, but these results remain to be validated. Furthermore, it contributes mechanistic evidence and provides potential gene targets to consider during IAV infection in populations exposed to arsenic. While the effects of arsenic on BMDCs in this thesis were analyzed in the context of influenza, these findings may be applicable to other respiratory diseases that continue to burden global healthcare systems.