ABSTRACT
Multiple sclerosis(MS)is a systemic inflammatory illness of the central nervous system that involves demyelinating lesions in the myelin-rich white matter and pathology in the grey matter.Despite signifi-cant advancements in drug research for MS,the dis-ease's complex pathophysiology makes it difficult to treat the progressive forms of the disease.In this study,we identified a natural flavonoid compound icariin(ICA)as a potent effective agent for MS in ameliorating the deterioration of symptoms including the neurological defi-cit score and the body weight in a murine experimental autoimmune encephalomyelitis(EAE)model.These improvements were associated with decreased demyelin-ation in the corpus callosum and neuron loss in the hippo-campus and cortex confirmed by immunohistochemistry analysis.Meanwhile,it was observed that the activation of microglia in cerebral cortex and hippocampus were inhibited followed by the neuroinflammatory cytokines downregulation such as IL-1β,IL-6 and TNF-α after ICA treatment,which was probably attributable to the sup-pression of microglial NLRP3 inflammasome activation.Additionally,molecular docking also revealed the binding force of ICA to NLRP3 inflammasome protein complexes in vitro.Taken together,our findings have demonstrated that ICA,as pleiotropic agent,prevents EAE-induced MS by improving demyelination and neuron loss,which inter-feres with the neuroinflammation via microglial NLRP3 inflammasome activation.
ABSTRACT
OBJECTIVE Alzheimer's disease(AD)is the most common neurodegenerative disease worldwide.Neuroinflammation is a potential target for the patients with AD.It is attributed to activated microglia and the release of various inflammatory mediators from infec-tion,ischemia and toxin accumulation.Accumulating evi-dence has indicated that the cGAS-STING pathway driven neuroinflammation in neurological disease.TSG is a main natural active ingredient that derived from polyg-onum multiflorum.Previous research from our group found that TSG has beneficial effects of anti-aging,anti-inflammatory action and improving memory function in APP/PS1 transgenic AD mice.Here,we investigated the effects of TSG on cognitive impairment and neuroinflam-mation in APP/PS1-AD mice and explore the underly-ing mechanism by which TSG ameliorates memory func-tion in the cGAS-STING-mediated inflammatory response.METHODS The Morris water mace test and the novel object recognition test were performed to test the effects of TSG on spatial learning and cognitive and memory abil-ity in APP/PS1 double transgenic AD mice model.In addi-tion,real-time quantitative PCR,Western blotting,ELISA analysis,and flow cytometry to examine gene and pro-tein expression of cGAS-STING related pro-inflammatory cytokines and chemokines.Statistical analyses were ana-lyzed using the SPSS 25.0 package by analysis of vari-ance(ANOVA).Neuman-Keuls or Tukey's multiple-com-parisons test were conducted as ANOVA justified post hoc comparisons between group means.RESULTS We demonstrated that AD transgenic mice exhibited cognitive deficits accompanied by the elevated serum and brain inflammation.The expressions of serum inflammatory cytokines and the activation of microglia in cerebral cor-tex and hippocampus were suppressed after TSG treat-ment,which was probably attributable to the decrease of cyclic GMP-AMP synthase(cGAS)and stimulator of interferon genes(STING)triggered immune response.Additionally,the data showed that TSG treatment reduced the expression level of inflammatory cytokines(IL-1β,TNF-α,IFN-β,IFN-α)in microglial cells BV2 primed with LPS and IFN-γ.CONCLUSION TSG implicated the health benefits in preventing cognitive disorders by inhib-iting neuroinflammation via cGAS-STING signalling path-way in AD.
ABSTRACT
OBJECTIVE Vascular dementia(VaD)is associated with cerebral hypoperfusion,which results in long-term cognitive impairment and memory loss.Neuroin-flammation is an important mechanism of vascular demen-tia.Cornel iridoid glycoside(CIG)is the major active con-stituent isolated from the ripe fruit of Cornus officinalis.Previous studies have shown that CIG enhances neuro-logical function in VaD rats.In the present research,we attempted to clarify the molecular processes underlying the role of CIG on neuroinflammation in VaD.METHODS In vivo,we created a chronic cerebral ischemia rat model by ligation of the bilateral common carotid arteries(2VO).The rats were divided into sham operation,2VO,2VO + CIG(60 and120 mg·kg-1·d-1),and 2VO+ butylphthalide(100 mg·kg-1·d-1)groups and then treated rats with differ-ent concentrations of CIG.In vitro,BV2 microglia cells were induced with bacterial lipopolysaccharide(LPS)and interferon-γ(IFN-γ)to construct the model of microglias with analog neuroinflammation.Histopathology and biel-schowsky silver staining were used to detect myelin integrity and neuronal loss.Immunofluorescence was used to observe changes in microglia.Magnetic Luminex Assay was used to detect changes in inflammatory fac-tors.Western blotting,ELISA or calpain activity assay was used to measure the expression and activity of cal-pain,as well as the expression of NLRP3 inflammasome protein.Furthermore,NLRP3 overexpressing cells were used to further elucidate the potential anti-inflammatory molecular mechanism of CIG.RESULTS ① CIG improved neuronal impairment in the brain of 2VO rats.②CIG increased white matter(WM)integrity in 2VO rats.③ CIG reduced microglia inflammatory response in the cortex and hippocampus of 2VO rats.④ CIG inhibited calpain activity in the cortex and hippocampus of 2VO rats.⑤ CIG exerted anti-inflammatory effects on BV2 cells stimulated by LPS and IFN-γ.⑥ CIG Inhibited the expression and activity of calpain in LPS/IFN-γ-activated BV2 cells.⑦ The main component of CIG had a weak binding force to calpain1.⑧ CIG inhibited the activation of the NLRP3 inflammasome.⑨CIG reduced the activity of calpain induced by NLRP3 overexpression.CONCLU-SION CIG inhibits microglial polarization into a proinflam-matory state by attenuating the assembly of the NLRP3 inflammasome and calpain activation,thus reducing brain inflammation,WM injury,and the loss of neurons.To sum up,the present study suggests that CIG inhibits neuroinflammation.The NLRP3/calpain pathway may be the main pathway by which CIG protects against neuroin-flammation.