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

Abstract 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.