Rehearsal For Thesis Presentation

Neuroinflammation is an immune and inflammatory response in the central nervous system (CNS) induced by infection, injury, toxic stimulation, or abnormal protein aggregation. Persistent neuroinflammation is associated with oxidative stress, immune imbalance, neuronal damage, and neurodegeneration. Recent studies have suggested that the microbiota–gut–brain axis bidirectionally regulates gut and brain functions through metabolites, immune signaling, and neurotransmission pathways. Dysbiosis of gut microbiota may promote the entry of lipopolysaccharide (LPS) in circulation systems through leaky intestinal epithelial barrier, which activates Toll-like receptors (TLRs) on microglia and triggers NF-κB and MAPK signaling pathways, thereby enhancing neuroinflammatory responses. Therefore, regulation of microglial activation has been considered a potential strategy for alleviating neuroinflammation. Liquorilactobacillus nagelii K38 was previously isolated from traditional fermented milk kefir, and showed anti-oxidative ability and regulation of dopamine in neuron cell lines, as well as showed improvement of learning ability and amelioration of neuron cell loss in ADHD (attention deficit/hyperactivity disorder) rat model. In this study, L. nagelii K38 and its cell-free fermentation supernatant (CFS) was collected to further investigate its anti-neuroinflammatory effects, and invrstigate its in vitro probiotic characterization for evaluating its commercial applications. Growth curve, acid tolerance, and bile salt tolerance assays demonstrated that K38 possessed good probiotic characteristics and gastrointestinal tolerance. An in vitro neuroinflammation model was established using LPS-stimulated BV-2 microglial cells to evaluate the effects of K38 CFS. The results showed that LPS significantly increased nitric oxide (NO) production without affecting BV-2 cell viability. In contrast, K38 CFS exhibited no cytotoxicity and significantly suppressed LPS-induced NO production. Further analysis revealed that K38 CFS reduced the secretion of pro-inflammatory cytokines TNF-α and IL-6, modulated IL-10 expression, and inhibited matrix metalloproteinase-9 (MMP-9) expression. In addition, K38 CFS suppressed NF-κB signaling by decreasing p-NF-κB p65 expression and restoring IκBα expression. In conclusion, L. nagelii K38 CFS exhibited the potential to regulate microglial inflammatory responses and alleviate neuroinflammation, suggesting its possible application as a microbiota-based therapeutic strategy for neuroinflammation-related diseases.
 
Keywords: Neuroinflammation、gut–brain axis、Cell-free supernatant、Probiotics、Kefir

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