Anti-photoaging and anti-melanogenesis effects of heat-inactivated Lactobacillus plantarum ATCC 8014 on UVB-exposed skin cells

Abstract:

[Objective] Ultraviolet B (UVB) irradiation is one of the main environmental causes of skin photoaging and hyperpigmentation. Lactobacillus plantarum is a well-studied species of probiotics that can benefit human health. The present study investigated the anti-photoaging and anti-melanogenesis effects of heat-inactivated L. plantarum (LP) ATCC 8014 on the skin cells (normal human dermal fibroblast (NHDF) cells and B16F10 murine melanoma cells) exposed to UVB irradiation. [Methods] The viability, DNA damage, and reactive oxygen species (ROS) levels of NHDF and B16F10 cells were determined by methyl thiazolyl tetrazolium (MTT) assay, terminal-deoxynucleoitidyl transferase dUTP nick end labeling (TUNEL) assay, and 2′,7′-dichlorofluorescin diacetate (DCFH-DA), respectively. The level of collagen I in NHDF cells was determined by enzyme-linked immunosorbent assay (ELISA). The melanin production and tyrosinase activity in B16F10 cells were measured by NaOH lysis method and L-DOPA oxidation method, respectively. qRT-PCR and Western blotting were employed to measure the expression levels of genes and proteins associated with photoaging and melanin production. [Results] (1) LP inhibited UVB-induced cytotoxicity by reducing the ROS-mediated DNA damage in NHDF and B16F10 cells; (2) LP down-regulated the mRNA levels of matrix metalloproteinase (MMP)-1, MMP-3, and MMP-9 (rather than MMP-2), relating to inhibit the extracellular signal-regulated kinase (ERK), p38 (rather than JNK)/c-Fos (rather than c-Jun) signaling pathway. It up-regulated the protein level of procollagen type-1 alpha 1 (COL1A1), thereby increasing the content of type I collagen; (3) LP as an autophagy inducer (up-regulating the protein levels of LC3-II and Beclin 1 and increasing the LC3-II/LC3-I ratio) inhibited the activities and/or expression of tyrosinase, tyrosinase-related protein (TYRP)-1, and TYRP-2 by inhibiting the PKA/CREB/MITF signaling pathway, thereby decreasing the melanin content. [Conclusion] LP has potential anti-photoaging and anti-melanogenesis effects on the skin cells exposed to UVB.