Figure 1.

Peroxisomal metabolites and immunity. The metabolites influenced by peroxisomal function (in bold) with downstream processes or derived metabolites (listed in grey boxes) with examples of their roles in the immune system activation and regulation are depicted. Peroxisomal β-oxidation is both involved in the degradation and synthesis of polyunsaturated fatty acids (PUFAs). Moreover, peroxisomes are needed for the production of plasmalogens (ether lipids), which in turn are a source for PUFAs. Arachidonic acid is used for the production of eicosanoids with proinflammatory (prostaglandins, leukotrienes, thromboxanes) or anti-inflammatory functions (lipoxins). Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) serve as precursors for resolvins, protectins, and maresins, which are important for the resolution of inflammation. Furthermore, peroxisomes are needed for the regulation of overall fatty acid composition by degrading very long-chain fatty acids (VLCFAs) and regulating the catabolism of LCFAs/MCFAs. Additionally, peroxisomes are involved in cholesterol homeostasis, intracellular trafficking of cholesterol, and the balance of free and esterified cholesterol. Oxysterols, formed through enzymatic or non-enzymatic cholesterol oxidation, are impacted by the redox balance in the cell, which depends on peroxisomal function. Peroxisomes are involved in the degradation and production of polyamines and might play a role in the degradation and production of other yet unknown modulators of the immune system.