This study shows that aspartame, at dietary-relevant doses, induces cytotoxicity, cellular distress associated with endoplasmic reticulum stress, oxidative stress, DNA replication and repair mechanism disturbance culminating in epithelial barrier damage. Aspartame triggers NF-κB activation via induction of oxidative stress, leading to proinflammatory cytokine and chemokine release. Aspartame metabolites synergistically contribute to cytotoxicity, oxidative stress and epithelial barrier disruption.

Spatial transcriptomics demonstrated that AD lesions showed reduced expression of key barrier genes, including CLDN1, FLG, and FLG2. IL-4, IL-13, and IL-22 disrupted the skin barrier in the ex vivo human skin. Combining type-2 cytokines and IL-22 alone downregulated genes critical for barrier function and keratinization. In addition, IL-4 and IL-13 downregulated antimicrobial peptides, while IL-22 upregulated them. Interestingly, IL-4 and IL-13 reduced IL-22Rα1, and IL-22 upregulated IL-4Rα, suggesting immune cross-regulation. Proteomic analysis confirmed that all three cytokines (IL-4, IL-13, and IL-22) reduced the expression of key skin barrier proteins, particularly filaggrin and claudin-1. Dupilumab treatment of AD patients for 3 months restored IL-4/IL-13-dysregulated genes, whereas it had limited effect on IL22-associated pathways.