Screening for Inhibitors of Microglia to Reduce Neuroinflammation

BACKGROUND: Despite the significant role microglia play in the pathology of multiple sclerosis (MS), medications that act within the central nervous system (CNS) to inhibit microglia have not yet been identified as treatment options. OBJECTIVE: We screened 1040 compounds with the aim of identifying inhibitors of microglia to reduce neuroinflammation. METHODS: The NINDs collection of 1040 compounds, where most are therapeutic medications, was tested at 10 µM final concentration on lipopolysaccharide (LPS)-activated human microglia. An ELISA was run on the media to measure the level of TNF-α as an indicator of microglia activity. For compounds that reduce LPS-activated TNF-α levels by over 50%, considered as a potential inhibitor of interest, toxicity tests were conducted to exclude non-specific cytotoxicity. Promising compounds were subjected to further analyses, including toxicity to other CNS cell types, and multiplex assays. RESULTS: Of 1040 compounds tested, 123 reduced TNF-α levels of LPS-activated microglia by over 50%. However, most of these were cytotoxic to microglia at the concentration tested while 54 were assessed to be non-toxic. Of the latter, spironolactone was selected for further analyses. Spironolactone reduced TNF-α levels of activated microglia by 50-60% at 10 µM, and this concentration did not kill microglia, neurons or astrocytes. In multiplex assays, spironolactone reduced several molecules in activated microglia. Finally, during the screening, we identified 9 compounds that elevated further the TNF-α levels in LPS-activated microglia. CONCLUSION: Many of the non-toxic compounds identified in this screen as inhibitors of microglia, including spironolactone, may be explored as viable therapeutic options in MS.