Exploration of the Anti-Photoaging Mechanisms of _Lactiplantiobacillus plantarum_ TWK10 in a UVB-Induced Mouse Model  
[PERSON]  
1 Department of Food Science, Fu Jen Catholic University, New Taipei City 242062, Taiwan; [EMAIL_ADDRESS] (T.-H.L. ); [EMAIL_ADDRESS] (W-J.L.) [PERSON]  
1 Department of Food Science, Nutrition, and Nitroaut  
of the dermis, leading to the degradation and loss of collagen as well as the abnormal accumulation of elastin fibers [2; 5; 6]. This ultimately increases epidermal thickness and decreases skin elasticity, leading to skin aging and damage [7]. Photoaging is characterized by deep wrinkle formation, loss of lightness and elasticity, uneven pigmentation, laxity, roughness, and capillary dilation [8; 9]. UV waves, which are electromagnetic waves with wavelengths of 10-400 nm, are classified based on wavelength into UVA (320-400 nm), UVB (280-320 nm), and UVC (100-280 nm) [10]. Of the UV radiation reaching the surface of the Earth, 5-10% is UVB, and 90-95% is UVA. However, UVB has higher energy levels than those of UVA and acts on the epidermis [11], making it more damaging to the skin than UVA and a major contributor to epidermal cell hypertrophy, keratosis, and dermatitis. Prolonged skin exposure to UVB promotes the production of large amounts of reactive oxygen species (ROS), resulting in imbalanced oxidative stress in the body, which directly damages cellular DNA and cell membrane lipids and proteins, increases prostaglandin E\({}_{2}\) levels and generates nitric oxide [12]. Furthermore, these effects result in inflammatory reactions such as erythema, sunburn, sensation of heat, and eventually skin cancer [13]. UV irradiation of the skin causes excessive production of ROS and pro-inflammatory hormones such as tumor necrosis factor-\(\alpha\) (TNF-\(\alpha\)), interleukin (IL)-6, and IL-1\(\beta\) and activates the mitogen-activated protein kinase (MAPK) signaling pathway, causing NF-\(\kappa\)B and activator protein-1 (AP-1) to enter the nucleus, thereby regulating downstream biological responses. This upregulates matrix metalloproteinase (MMP) expression in the skin, leading to collagen breakdown [14]. In particular, IL-1\(\alpha\), IL-1\(\beta\), and TNF-\(\alpha\) enhance IL-6 production and release in keratinocytes [15]; IL-6 can also induce MMPs through an autocrine mechanism [2]. In addition, UV modulates the transforming growth factor-\(\beta\) signaling pathway and inhibits collagen regeneration, leading to photoaging-related phenomena such as skin dryness and wrinkles [16]. Previous experimental results from our laboratory have demonstrated that the indigenous lactic acid bacterial strain _Lactiplantiobacillus plantarum_ TWK10 (LPTWK10), derived from Taiwanese pickles, not only has the capacity to modulate blood pressure in spontaneously hypertensive rats [17] but also alleviates cognitive impairments associated with hypertension-induced vascular dementia [18]. Continuous administration of TWK10-fermented soy milk to hypertensive rats with vascular dementia for 13 weeks led to significant reductions in escape latency times in the Morris water maze test, including in reference memory, probe trials, and working memory assessments [18]. Furthermore, both animal models and human studies have indicated that TWK10 supplementation significantly enhances muscle mass and improves exercise performance [19]. Additionally, [PERSON] et al. (2015) demonstrated that the ethanol extract of TWK10-fermented soy milk, when co-cultured with B16 melanoma cells, effectively inhibits melanin synthesis by modulating the expression of melanin biosynthesis-related proteins [20]. Further investigations by our team have explored the potential dermatological benefits of TWK10, revealing that the ethanol extract of TWK10-fermented soy milk not only attenuates the rate of blood glucose elevation in diabetic rats but also promotes wound healing [21].