SLC25A33-mediated mitochondrial DNA synthesis plays a critical role in the inflammatory response of M1 macrophages by contributing to mitochondrial ROS and VDAC oligomerization

M1 macrophage polarization is modulated by the release of mitochondrial DNA (mtDNA) and subsequent its inflammatory response is augmented by production of mitochondrial reactive oxygen species (mtROS). The pyrimidine-transporting carrier SLC25A33 is located in the mitochondrial inner membrane and has been linked to mtDNA synthesis, but the role of SLC25A33 in inflammatory response of M1 macrophage remains unclear. Here, we elucidate the regulatory mechanisms responsible for up-regulation of SLC25A33 during M1 macrophage polarization and SLC25A33-mediated mtROS production and inflammatory response. Our findings reveal that expression of SLC25A33 was significantly elevated in CD14+ monocytes derived from a patient with sepsis and LPS/IFN-γ-stimulated PMs. We demonstrate that SLC25A33 is upregulated by ATF4 through the MyD88-PI3K-mTORC1 pathway in LPS/IFN-γ-stimulated PMs. Furthermore, SLC25A33 enhanced mtDNA synthesis and its release into the cytosol, facilitated by mtROS-mediated VDAC oligomer formation, thereby contributing to activation of the cGAS-STING inflammatory pathway. Conversely, SLC25A33 knockdown and pyridoxal 5'-phosphate treatment mitigate mtDNA release and reduce M1 polarization and associated inflammatory responses. These findings were consistent across in vitro and in vivo sepsis models, as well as in septic patients with liver abscess. Our findings underscore the significant role of SLC25A33 in inflammation, suggesting that targeting of SLC25A33 could represent a promising therapeutic strategy for managing M1 macrophage-mediated inflammatory diseases, including sepsis.