Deinoxanthin-Enriched Extracellular Vesicles from Deinococcus radiodurans Drive IL-10-Dependent Tolerogenic...

Extracellular vesicles (EVs) derived from bacteria are emerging as potent bioactive carriers that affect host immunity. Deinococcus radiodurans, an extremophilic bacterium with strong antioxidant capacity, produces EVs enriched in deinoxanthin (DX), a carotenoid with a reactive oxygen species-scavenging activity. Here, we assessed the antioxidant activity of D. radiodurans-derived EVs (R1-EVs) in biochemical assays and their immunomodulatory effects on dendritic cells (DCs). R1-EVs exhibited significantly higher antioxidant activity than EVs from a DX-deficient mutant strain (ΔcrtI-EVs), consistent with DX enrichment. Bone marrow-derived DCs treated with R1-EVs in the presence of lipopolysaccharide displayed reduced expression of surface maturation markers and pro-inflammatory cytokines, while interleukin-10 (IL-10) production and antigen uptake were preserved, indicating a tolerogenic phenotype. This tolerogenic program led to decreased proliferation and cytokine production in allogeneic CD4⁺ and CD8⁺ T cells. Mechanistically, R1-EVs inhibited mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling pathways, key regulators of the DC activation. Importantly, IL-10 neutralization reversed these effects, restoring DC and T cell activation. Notably, ΔcrtI-EVs showed weaker antioxidant and immunoregulatory activities. Together, our findings identify R1-EVs as dual-functions, DX- and IL-10-dependent nanoplatform that integrates antioxidant and tolerogenic properties, with potential applications in inflammatory and autoimmune disease control.