Skin Protection Effects of Lactobacillus paragasseri HN910 Lysate and the Role of Alanine

Skin aging is influenced by structural alterations, oxidative stress, inflammation, and microbiome changes, and a comprehensive approach to addressing these factors may be effective for mitigating skin aging. This study evaluates the multifaceted anti-aging effects of heat-killed (HK-HN910) and lysed (LS-HN910) forms of Lactobacillus paragasseri HN910. Protective effects on cell viability, cell permeability, nitric oxide (NO) production, and skin anti-aging gene expression for both HK-HN910 and LS-HN910 were observed. Both forms significantly enhanced tight junction (TJ) protein zonula occludens- 1 (ZO- 1) and antioxidant enzyme glutathione peroxidase (GPx) gene expression, while significantly downregulating that of senescence-associated secretory phenotype pro-inflammatory cytokines interleukin (IL)- 1α, IL- 1β, IL- 6, IL- 8, and tumor necrosis factor-alpha (TNFα). LS-HN910 showed significantly greater upregulation of ZO- 1 and GPx and greater downregulation of IL- 1β and TNFα expression compared to HK-HN910. Cell wall component D-alanine (D-Ala) was released in higher amounts in LS-HN910 than in HK-HN910 and demonstrated anti-aging effects. D-Ala upregulated gene expression of skin barrier ZO- 1, claudin- 1 (Cla- 1), occludin (OCC), filaggrin (FLG), and sphingomyelin phosphodiesterase 2 (SMPD2) and antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and GPx, while downregulating IL- 1α, IL- 1β, IL- 6, IL- 8, and TNFα. LS-HN910 treatment clinically revealed improvements in anti-aging parameters, including transepidermal water loss, skin water contents, sebum levels, dermal density, eye wrinkle index, skin pH, brightness, and microbiota composition, with a significant increase in Rhodococcus abundance. These findings indicate that LS-HN910, containing released D-Ala, is a promising cosmeceutical for preventing skin aging by enhancing the skin barrier, promoting oxidative defense, modulating inflammatory responses, and influencing skin microbiota.