Mitochondrial glutathione transporter SLC25A40 regulates macrophage cytokine production

Mitochondrial glutathione (mtGSH) supports iron-sulfur cluster (ISC) stability in the electron transport chain (ETC). Here we have investigated the role of the mtGSH transporter SLC25A40 in macrophage activation. SLC25A40 is present in both murine and human macrophages and its expression was increased by LPS treatment. Reducing SLC25A40 expression using siRNA destabilized ISC-rich ETC proteins and elevated mitochondrial and cellular reactive oxygen species (ROS). It also induced expression of the genes Gclc and Gclm, which are involved in GSH biosynthesis. SLC25A40 deficiency also diminished IL-1β and IL-10 production at the transcriptional level in response to LPS. As a result, the production of mature IL-1β was decreased following activation of NLRP3 by nigericin or ATP, with no effect on pyroptosis. Depleting mtGSH with mitochondrially-targeted CDNB phenocopied these defects, whereas supplementation with a cell-permeable GSH ester partially restored pro-IL-1β production. Together, these data identify SLC25A40 as a key regulator that sustains ETC integrity to promote cytokine production, revealing a previously unrecognized role for the SLC25A40-mtGSH axis in coupling mitochondrial redox control to macrophage activation.