Mitochondria complex III-generated superoxide is essential for IL-10 secretion in macrophages

Mitochondrial electron transport chain (ETC) function modulates macrophage biology, however, mechanisms underlying mitochondrial ETC control of macrophage immune responses are not fully understood. Here we report that mutant mice with mitochondrial ETC complex III (CIII)-deficient macrophages exhibit increased susceptibility to influenza A virus and LPS-induced endotoxic shock. Cultured bone marrow-derived macrophages (BMDMs) isolated from these mitochondrial CIII-deficient mice released less IL-10 than controls following TLR3 or TLR4 stimulation. Surprisingly, restoring mitochondrial respiration without generating superoxide using alternative oxidase (AOX) was not sufficient to reverse LPS-induced endotoxic shock susceptibility or restore IL-10 release. However, activation of protein kinase A (PKA) rescued IL-10 release in mitochondrial CIII-deficient BMDMs following LPS stimulation. Additionally, mitochondrial CIII deficiency did not affect BMDM responses to interleukin-4 (IL-4) stimulation. Thus, our results highlight the essential role of mitochondrial CIII generated superoxide in the release of anti-inflammatory IL-10 in response to TLR stimulation Bone-marrow derived macrophages from mice with either intact QPC expression or QPC KO were treated with either LPS, IL-4, or vehicle. BMDMs were stimulated with 0.1µg/mL ultrapure O5:B55 LPS (Invivogen tlrl-pb5lps) or IL-4 10ng/mL for 18h prior to collection.