Manganese exposure augments misfolded alpha-synuclein-induced proinflammatory M1 microglial phenotype and inflammasome activated

Sustained microglial activation is a key player in the immunopathogenesis of several neurodegenerative disorders including Parkinson's disease (PD). Chronic exposure to the environmental toxicant manganese (Mn) has been implicated as a risk factor for PD. We have previously demonstrated that misfolded and aggregated human α‐synuclein (αSyn PFF ) induces microglial activation. Recently, we have shown that chronic Mn exposure induces neuroinflammation by impairing mitochondrial dynamics. In this study, we determined whether Mn exposure alters the specific RNA transcripts in response to the αSyn PFF proteostatic challenge. We systematically characterized the transcriptome of mouse microglia in response to Mn and/or αSyn PFF using RNA sequencing. Treating a mouse microglial cell model with αSyn PFF significantly induced both cytokine and interferon‐g signaling pathways. In contrast, Mn treatment caused distinct changes to pathways related to cellular senescence and apoptosis. Intriguingly, co‐treatment with Mn and αSyn PFF caused profound enrichment of transcripts, including IL‐6, IL‐12b, IFN‐β, IL‐1α, and IL‐1β CXCL2, CXCL3, CXCL10, CCL5‐R, and Nos2 , that signify the proinflammatory M1 microglial phenotype. These targets were further validated by real‐time qRT‐PCR, immunoblotting, and immunocytochemistry. As anticipated, cotreatment with Mn and αSyn PFF lead to significant upregulation of the mRNA expression of IL‐6, Nos2, IL‐1α, and IL‐1β in a synergistic manner when compared to either treatment alone. Additionally, Mn and αSyn PFF co‐treatment elicited NLRP3 inflammasome activation when compared to either treatment alone or untreated control cells. Taken together, these findings identify that environmental toxicants, such as Mn, perturb microglial homeostasis, thereby leading to transformation to a pro‐inflammatory M1 microglial phenotypic state. Importantly, our study suggests that the environmental toxicant Mn can augment αSyn PFF ‐induced neuroinflammatory processes in microglia to accelerate neurodegeneration. Support or Funding Information NIH grants ES026892, NS088206, and W. Eugene Linda Lloyd Endowed Chair This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .