Abstract Introduction Immunometabolism is an emerging field. We and others have shown that activation of macrophages leads to metabolic changes including increased succinate levels. As an immunometabolite succinate has been reported to drive lipopolysaccharide (LPS)-induced Interleukin-1 beta (IL-1β) production through activation of hypoxia inducible factor 1 subunit alpha (HIF-1α) in macrophages. However, the mechanisms by which succinate exerts its effects on HIF-1α stabilization and IL-1β are not understood. We hypothesized that succinate dehydrogenase (SDH), which is the enzyme that metabolizes succinate, is required for LPS-induced HIF-1α stabilization and IL-1β release. Methods We generated bone marrow-derived macrophages (BMDMs) from control and Sdhbfl/fl:LysM-CreERT2+/− (Sdhb-/-) mice. Cells were then treated with LPS (20ng/ml) for 4 hours in the presence and absence of exogenous succinate and their inflammatory phenotype was assessed via western blot, qPCR, and standard ELISA. We also assessed HIF-1α protein stabilization by Western blot. Cellular succinate and other metabolites levels were measured by GC-MS. Results Compared to control BMDMs, Sdhb-/- BMDMs had significantly higher levels of succinate. LPS treatment led to an increase in intracellular succinate levels in control BMDMs; however, the increase was significantly lower than the levels observed in Sdhb-/- BMDMs. Treatment of control BMDMs with exogenous succinate increased intracellular levels of succinate but there was no change in LPS-induced HIF-1α activation or IL-1β production. Despite having significantly high levels of succinate, Sdhb-/- BMDMs had lower HIF-1α protein expression and IL-1β production in response to LPS. Conclusions While LPS increases succinate levels in macrophages, it is not the elevated succinate levels but succinate dehydrogenase reaction itself that determines HIF-1α stabilization and IL-1β production. Targeting succinate dehydrogenase may potentially be used to attenuate inflammatory response. This abstract is funded by: NIH and DoD
Woods et al. (Fri,) studied this question.