Moonlighting glyceraldehyde-3-phosphate dehydrogenase of Lactobacillus gasseri inhibits keratinocyte apoptosis and skin inflammation in experimental atopic dermatitis

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disorder affecting up to 20% of children in developed countries. Although probiotics have shown promise as adjuvant treatments for AD, their mechanisms are not well understood. Objective: Building upon our previous studies, we investigated whether Lactobacillus gasseri and its moonlighting glyceraldehyde 3-phosphate dehydrogenase (GAPDH), namely LGp40, could be beneficial in AD management. Methods: In AD mouse models (SKH and C57BL/6J mice) with ovalbumin (OVA) and Dermatophagoides pteronyssinus (Der p) allergens, aligning with the “outside-in” and “inside-out” hypotheses, we administered L. gasseri orally and LGp40 intraperitoneally to investigate their protective effects. The evaluation involved measuring physiological, pathological, and immune function parameters. To delve deeper into the detailed mechanism of LGp40 protection in AD, additional assays were conducted using human skin keratinocytes (HaCaT) and monocytes (THP1) cell lines. Results: L. gasseri and LGp40 enhanced skin barrier function and increased skin moisture retention. They also led to reduced infiltration of Langerhans cells in the dermis and mitigated skewed Th2 and Th17 immune responses. Moreover, LGp40 inhibited allergen-induced keratinocyte apoptosis through the blockade of the caspase-3 cascade and reduced the NLR family pyrin domain containing 3 (NLRP3) inflammasome in macrophages. These inhibitions were achieved through the activation of the peroxisome proliferator-activated receptor gamma (PPARγ) pathway. Conclusion: The results of this study provide a novel insight into the mechanism of action of probiotics in the prevention and treatment for allergic disorders through the moonlighting GAPDH protein.