42-day repeated oral 6PPD-quinone exposure is associated with splenic injury, reduced mtDNA abundance, and cGAS-STING-related signaling in mice.

6PPD-quinone (6PPD-Q), a tire rubber-derived contaminant, has raised concern because of its widespread occurrence and potential systemic toxicity. Here, we examined splenic injury and associated innate immune signaling changes after repeated oral 6PPD-Q exposure. Male C57BL/6 mice received 60 μg/kg/day 6PPD-Q by oral gavage for 42 days. Exposure was associated with a reduced spleen index and histopathological disruption, together with increased MDA and 8-OHdG and altered antioxidant indices. qPCR targeting D-loop, CYTB, ND1, and ND4 showed reduced relative mtDNA abundance; these measurements do not directly establish structural mtDNA damage or cytosolic mtDNA release. Concurrently, cGAS-STING-related protein changes and increased phosphorylation ratios of STING, TBK1, and IRF3 were observed, accompanied by NF-κB-related signaling changes. NLRP3-, ASC-, GSDMD-, and inflammatory cytokine-related markers also changed, consistent with altered NLRP3- and pyroptosis-associated signaling. Because cytosolic mtDNA, pathway-specific intervention, and direct pyroptotic cell-death endpoints were not assessed, the observed molecular changes are interpreted as associations rather than evidence of a causal mtDNA-cGAS-STING-pyroptosis axis. These findings identify the spleen as a potential target of repeated 6PPD-Q exposure and provide evidence of splenic injury associated with altered redox status, reduced mtDNA abundance, and innate immune signaling changes.