ABSTRACT
Anxiety manifestations and cognitive dysfunction are common sequelae in patients with sepsis-associated encephalopathy (SAE). Microglia-mediated inflammatory signaling is involved in anxiety, depression, and cognitive dysfunction during acute infection with bacterial lipopolysaccharide (LPS). However, the molecular mechanisms underlying microglia activation and behavioral and cognitive deficits in sepsis have not been in fully elucidated. Based on previous research, we speculated that the CD137 receptor/ligand system modulates microglia function during sepsis to mediate classical neurological SAE symptoms. A murine model of SAE was established by injecting male C57BL/6 mice with LPS, and cultured mouse BV2 microglia were used for in vitro assays. RT-qPCR, immunofluorescence staining, flow cytometry, and ELISA were used to assess microglial activation and the expression of CD137L and inflammation-related cytokines in the mouse hippocampus and in cultured BV2 cells. In addition, behavioral tests were conducted in assess cognitive performance and behavioral distress. Immunofluorescence and RT-qPCR analyses showed that hippocampal expression of CD137L was upregulated in activated microglia following LPS treatment. Pre-treatment with the CD137L neutralizing antibody TKS-1 significantly reduced CD137L levels, attenuated the expression of M1 polarization markers in microglia, and inhibited the production of TNF-α, IL-1ß, and IL-6 in both LPS-treated mice and BV2 cells. Conversely, stimulation of CD137L signaling by recombinant CD137-Fc fusion protein activated the synthesis and release of pro-inflammatory cytokines in cultures BV2 microglia. Importantly, open field, elevated plus maze, and Y-maze spontaneous alternation test results indicated that TKS-1 administration alleviated anxiety-like behavior and spatial memory decline in mice with LPS-induced SAE. These findings suggest that CD137L upregulation in activated microglia critically contributes to neuroinflammation, anxiety-like behavior, and cognitive dysfunction in the mouse model of LPS-induced sepsis. Therefore, therapeutic modulation of the CD137L/CD137 signaling pathway may represent an effective way to minimize brain damage and prevent cognitive and emotional deficits associated with SAE.
Subject(s)
4-1BB Ligand , Sepsis-Associated Encephalopathy , Sepsis , Animals , Humans , Male , Mice , Cytokines/metabolism , Disease Models, Animal , Hippocampus , Lipopolysaccharides/toxicity , Mice, Inbred C57BL , Microglia , Neuroinflammatory Diseases , Sepsis/complications , Sepsis/drug therapy , Sepsis/metabolism , Sepsis-Associated Encephalopathy/drug therapy , Sepsis-Associated Encephalopathy/metabolism , 4-1BB Ligand/drug effects , 4-1BB Ligand/metabolism , Antibodies, Monoclonal/pharmacology , Antibodies, Monoclonal/therapeutic useABSTRACT
Human adipose tissues are an ideal source of stem cells. It is important to find inducers that can safely and effectively differentiate stem cells into functional neurons for clinical use. In this study, we investigate the use of Radix Angelicae Sinensis as an inducer of neuronal differentiation. Primary human adipose-derived stem cells were obtained from adult subcutaneous fatty tissue, then pre-induced with 10% Radix Angelicae Sinensis injection for 24 hours, and incubated in serum-free Dulbecco's modified Eagle's medium/Nutrient Mixture F-12 containing 40% Radix Angelicae Sinensis to induce its differentiation into neuron-like cells. Butylated hydroxyanisole, a common inducer for neuronal differentiation, was used as the control. After human adipose-derived stem cells differentiated into neuron-like cells under the induction of Radix Angelicae Sinensis for 24 hours, the positive expression of neuron-specific enolase was lower than that of the butylated hydroxyanisole-induced group, and the expression of glial fibrillary acidic protein was negative. After they were induced for 48 hours, the positive expression of neuron specific enolase in human adipose-derived stem cells was significantly higher than that of the butylated hydroxyanisole-induced group. Our experimental findings indicate that Radix Angelicae Sinensis can induce human adipose-derived stem cell differentiation into neuron-like cells and produce less cytotoxicity.
