The Involvement Of TLR4 In Lithium Regulated LPS-induced Astrocytes Activation

Background:Neuroinflammation plays a key role in the occurrence and development of chronic neurodegenerative diseases.Conventional wisdom suggest that the advanced activity,such as cognitive and memory,is accomplished by the neuros,in the hippocampus and cortex.As the largest nunber of glia cells in the central nervous system,astrocytes not only provide energy and metabolic support for neurons,but also play an important role in formation and maintenance of the blood-brain barrier,neurotransmission and regulation of synaptic plasticity.Astrocytes can detect and integrate signals of neuronal damage and inflammation to regulate the neuroidflammatory response.Therefore,inhibiting inflammatory cytokines production induced by activated astrocytes may be beneficial for prevention of degenerative diseases of the nervous system.TLR4,a pattern-recognition receptor that recognizes distinct pathogen-associated molecular patterns(PAMPs),can recruit signaling adaptors such as lipopolysaccharide(LPS),and cytokines,resulting in the activation of NF-?B and the release of inflammatory cytokines.More and more studies have revealed the dominant role of TLR4 in the activation of astrocytes and the following inflarmatory response.Lithium,an effective mood stabilizer for the treatment of bipolar disorder,is a neuroprotective and neurotrophic agent efficacious in the treatlent of several neurodegenerative conditions.Our preliminary study found that lithium can ameliorate neuroflanrmation by TLR4.However,it is unknown whether lithium has anti-inflammatory effects on astrocytes and the nature of its relationship with TLR4.In the present study,we investigated the effects of lithium on LPS-induced astrocytes activation in vitro and explored the possible mechanisms of its neuroprotective properties.Objective:The experimental is scheduled to study the influence of lithium chloride on the LPS-induced inflammation response of astrocytes in vitro,and the involvment of TLR4,so to deeply explore its mechanism.Methods:Astrocytes were culture in vitro with LPS to simulating inflammatory environment and observing the influence of lithium chloride on inflammation.The expression level of inflammatory cytokines IL-6 and TNF-? was detected by ELISA,The levels of GFAP mRNA expression were analyzed by quantitative RT-PCR and WB.To futher investigate whether TLR4 is required for LPS-induced inflammation cytokines,TLR4 small interfering RNA-mediated gene silencing(siRNA)was applied to astrocytes to knock-down the translation and suppress TLR4 activity.GFAP-immunopositive expression(green)and TLR4-immunopositive expression(red)on activated astrocytes were observed using confocal.Results:Compared with the control group,lithium significantly inhibited the LPS-mediated up-regulated mRNA expression levels of GFAP,and subsequently downregulates the production of IL-6 and TNF-?.The LPS-induced inflammatory response was significantly reduced after application of TLR4 siRNA.Lithium significantly inhibited the TLR4 expression induced by LPS.Consistent with the above phenomenon,the level of GFAP was markedly decreased by lithium.Conclusion:Lithium can inhibit LPS-induced TLR4 expression and astrocytes activation.These results indicate that lithium plays an important role in astrocytes activation and neuroinflammation-related diseases.