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 mitochondria ETC control of macrophage immune responses are not fully understood. Here, we report that mutant mice with mitochondria ETC complex III (CIII)–deficient macrophages exhibit increased susceptibility to influenza A virus (IAV) and LPS-induced endotoxic shock. Cultured bone marrow–derived macrophages (BMDMs) isolated from these mitochondria CIII–deficient mice released less IL-10 than controls following TLR3 or TLR4 stimulation. Unexpectedly, 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 mitochondria CIII-deficient BMDMs following LPS stimulation. In addition, mitochondria CIII deficiency did not affect BMDM responses to interleukin-4 (IL-4) stimulation. Thus, our results highlight the essential role of mitochondria CIII–generated superoxide in the release of anti-inflammatory IL-10 in response to TLR stimulation.