Mitochondrial respiratory complex III sustains IL-10 production in activated macrophages and promotes tumor-mediated immune evasion.

The cytokine interleukin-10 (IL-10) limits the immune response and promotes resolution of acute inflammation. Because of its immunosuppressive effects, IL-10 up-regulation is a common feature of tumor progression and metastasis. Recently, IL-10 regulation has been shown to depend on mitochondria and redox-sensitive signals.

Itaconate drives mtRNA-mediated type I interferon production through inhibition of succinate dehydrogenase.

Itaconate is one of the most highly upregulated metabolites in inflammatory macrophages and has been shown to have immunomodulatory properties. Here, we show that itaconate promotes type I interferon production through inhibition of succinate dehydrogenase (SDH). Using pharmacological and genetic approaches, we show that SDH inhibition by endogenous or exogenous itaconate leads to double-stranded mitochondrial RNA (mtRNA) release, which is dependent on the mitochondrial pore formed by VDAC1.

Endogenously produced itaconate negatively regulates innate-driven cytokine production and drives global ubiquitination in human macrophages.

A wide variety of electrophilic derivatives of itaconate, the Kreb's cycle-derived metabolite, are immunomodulatory, yet these derivatives have overlapping and sometimes contradictory activities. Therefore, we generated a genetic system to interrogate the immunomodulatory functions of endogenously produced itaconate in human macrophages. Endogenous itaconate is driven by multiple innate signals restraining inflammatory cytokine production.

Metabolic Messengers: itaconate.

The metabolite itaconate has emerged as an important immunoregulator with roles in antibacterial defence, inhibition of inflammation and, more recently, as an inhibitory factor in obesity. Itaconate is one of the most upregulated metabolites in inflammatory macrophages. It is produced owing to the disturbance of the tricarboxylic acid cycle and the diversion of aconitate to itaconate via the enzyme aconitate decarboxylase 1.