CXCL-mediated oxidative DNA damage promotes Th2 cytokine responses

Allergen challenge to the lung induces oxidative DNA base lesions, including 5-hydroxycytosine (5-OH-Cyt), as well as upregulation of CXC chemokine ligands (CXCLs), both of which have been implicated in allergic inflammation. The precise mechanisms by which specific DNA lesions modulate immune responses and exacerbate allergic lung inflammation remain unclear. This study aimed to investigate the role of 5-OH-Cyt in the CXCL-CXCR1/2-mediated response and its role in promoting Th2 immune responses.

Wild-type mice were sensitized with cat dander extract (CDE) and subsequently challenged with PBS or CDE. Lung DNA damage was evaluated by γH2AX immunostaining, pATM expression, and gene-specific long-amplicon qPCR. The role of CXCL-CXCR1/2 signaling was examined using the allosteric CXCR1/2 inhibitor ladarixin. In parallel, naïve CD4⁺ T cells were cultured under Th2-skewing conditions with oxidatively damaged DNA bases to assess their effects on Th2 cytokine production.

CDE challenge significantly increased γH2AX + neutrophils and pATM + eosinophils in the lungs, confirming allergen-induced DNA damage. Intranasal administration of 5-OH-Cyt to naïve mice upregulated lung Cxcl1 and Cxcl2 expression. Oral administration of ladarixin markedly reduced lung γH2AX expression and increased long-amplicon PCR amplification of pol β and β-globin, indicating partial restoration of genomic integrity. Administration of recombinant CXCLs also induced lung DNA damage, which was suppressed by ladarixin. Naïve CD4⁺ T cells were cultured under Th2-polarizing conditions with individual oxidatively damaged DNA bases. Exposure to 5-OH-Cyt, Fapy-Ade, 8-oxo-Gua, and 5-OH-Ura significantly increased IL-4, IL-5, and IL-13 secretion, while Fapy-Gua did not affect cytokine production.

These findings suggest that 5-OH-Cyt acts as a damage-associated molecular pattern that both drives Th2 immune responses and exacerbates lung DNA damage through a CXCL-mediated positive feedback loop, highlighting CXCR1/2 inhibition as a potential therapeutic strategy to mitigate double-strand DNA damage and allergic lung inflammation.