Impact of Succinate Dehydrogenase Inhibitors on THP-1 Derived Human Macrophages Viability, Mitochondrial Bioenergetics, and Immune Profile

Abstract

Background: Succinate dehydrogenase inhibitors (SDHIs) are active compounds in a group of fungicides used extensively worldwide particularly to limit the proliferation of molds on plants and plants products. SDHIs mediate their effect through the inhibition of the universally preserved mitochondrial succinate dehydrogenase (SDH), which controls cellular bioenergetics and metabolism, both meticulously regulated for an adapted inflammatory response. We therefore set out to provide a highly integrated picture depicting the impact of SDHIs on the inflammatory process. Aim: In a set of preliminary studies, we assessed in THP-1 (monocytic leukemia cells) derived human macrophages (TDM) the cytotoxicity of SDHIs namely, bixafen, fluopyram, boscalid, and cyflumetofen, as well as their specificity towards SDH. Moreover, we aimed at determining the impact of SDHIs on the pro-inflammatory cytokines expression profile. Methods: THP-1 cells will be differentiated into TDM by incubation for 72 hours in the presence of PMA (Phorbol-12-mysristate13-acetate). Subsequently, cells will be treated with different concentrations of SDHIs in presence or absence of glucose for 24, 48, 72 hours and their viability will be assessed using Neutral Red assay. The specificity of SDHIs will be determined by kinetic studies of several mitochondrial enzymes (Complexes I, II, and the glycerol-3-phosphate dehydrogenase) in the presence of various SDHIs using THP-1 macrophage homogenates. Finally, the expression level of chosen pro-inflammatory cytokines/chemokines will be determined using quantitative polymerase chain reaction (RT-PCR). All over, this study will allow us to determine the intricate role of the mitochondrial SDH using SDHI inhibitors on the inflammatory process that is mediated by macrophages.