Attenuation of Immunogenicity in MOG-Induced Oligodendrocytes by the Probiotic Bacterium Lactococcus Sp. PO3

Background and Objectives: Milk is healthy and includes several vital nutrients and microbiomes. Probiotics in milk and their derivatives modulate the immune system, fight inflammation, and protect against numerous diseases. The present study aimed to isolate novel bacterial species with probiotic potential for neuroinflammation. Materials and Methods: Six milk samples were collected from lactating dairy cows. Bacterial isolates were obtained using standard methods and were evaluated based on probiotic characteristics such as the catalase test, hemolysis, acid/bile tolerance, cell adhesion, and hydrophobicity, as well as in vitro screening. Results: Nine morphologically diverse bacterial isolates were found in six different types of cow's milk. Among the isolates, PO3 displayed probiotic characteristics. PO3 was a Gram-positive rod cell that grew in an acidic (pH-2) salty medium containing bile salt and salinity (8% NaCl). PO3 also exhibited substantial hydrophobicity and cell adhesion. The sequencing comparison of the 16S rRNA genes revealed that PO3 was Lactococcus raffinolactis with a similarity score of 99.3%. Furthermore, PO3 was assessed for its neuroanti-inflammatory activity on human oligodendrocyte (HOG) cell lines using four different neuroimmune markers: signal transducer and activator of transcription (STAT-3), myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), and GLAC in HOG cell lines induced by MOG. Unlike the rest of the evaluated neuroimmune markers, STAT-3 levels were elevated in the MOG-treated HOG cell lines compared to the untreated ones. The expression level of STAT-3 was attenuated in both PO3-MOG-treated and only PO3-treated cell lines. On the contrary, in PO3-treated cell lines, MBP, GFAP, and GLAC were significantly expressed at higher levels when compared with the MOG-treated cell lines. Conclusions: The findings reported in this article are to be used as a foundation for further in vivo research in order to pave the way for the possible use of probiotics in the treatment of neuroinflammatory diseases, including multiple sclerosis.