Screening for Lactic Acid Bacterial Strains as Probiotics Exhibiting Anti-inflammatory and Antioxidative Characteristic Via Immune Modulation in HaCaT Cell

In this study, the basic probiotic characteristics and functional properties of lactic acid bacteria (LAB) were investigated using two in vitro models of inflammation induced by lipopolysaccharide (LPS) and H2O2. Fifteen strains were prescreened out of 60 LAB candidates based on their radical scavenging activity to determine the antioxidant capacity of the strains. The top 15 candidates were further investigated to evaluate their survival rate under low pH and bile salt conditions that mimic the intestinal environment. Three strains, Levilactobacillus brevis D70 (Levilact), Lactiplantibacillus pentosus S16 (Lactipla), and Limosilactobacillus fermentum MF10 (Limosilact), were capable of scavenging free radicals and survived under artificial intestinal conditions. Therefore, Levilact. brevis D70, Lactipla. pentosus S16, and Limosilact. fermentum MF10 were selected for further antioxidant, anti-inflammation, and mitochondrial activity examinations via cell models of inflammation and oxidative stress. Among the three strains, Limosilact. fermentum MF10 showed the highest anti-inflammatory activities by significantly downregulating the relative mRNA expression levels of inflammatory biomarkers such as interleukin 8 (IL-8) and interferon-gamma (IFN-γ) induced by LPS (P < 0.05). Moreover, Limosilact. fermentum MF10 was also capable of upregulating the gene expression levels of antioxidative mediator glutathione peroxidase 4 (GPX4) induced by reactive oxygen species (ROS) in both human HT-29 epithelial cells and human HaCaT keratinocytes. Limosilact. fermentum MF10 was also capable of regulating mitochondrial membrane potential (MMP), which plays a key role in the mitochondrial activity of HaCaT cells. As a result, Limosilact. fermentum MF10 showed the highest potential for probiotic properties and impacts the immune-related gut-skin axis by altering proinflammatory cytokines, antioxidative biomarkers, and MMP.