Résumé
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.
Résumé
Alzheimer's disease (AD) is the most common neurodegenerative disease in the aging population. Abnormal hyperphosphorylation of tau is the main cause of AD. Protein phosphatases 2A (PP2A) can increase the hyperphosphorylation of tau. Cornel iridoid glycoside (CIG) is one of the main components extracted from Cornus of ficinalis. The aim of the present study was to investigate the effects and the underlying mechanisms of CIG on enhancing PP2A activity. SK-N-SH cells were exposed to 20 nmol·L-1 okadaic acid (OA, an inhibitor of PP2A) for 6 h to induce the hyper-phosphorylation of tau, in order to define the effect of CIG on the activity of PP2A and posttranslational modification of PP2A catalytic subunit C (PP2Ac). We found that OA significantly decreased PP2A activity, increased the phosphorylation of PP2Ac, and enhanced tau hyper-phosphorylation. Pre-incubation of CIG significantly attenuated the OA-induced tau hyper-phosphorylation at Ser 199/202 and Ser 396, and recovered the activity of PP2A. CIG inhibited PP2Ac phosphorylation at Tyr 307 and increased Src phosphorylation. In conclusion, the mechanism of CIG inhibition of tau hyper-phosphorylation was activation of PP2A to reduce the level of p-Src for a reduction of PP2Ac phosphorylation at Tyr307.
Résumé
@#Objective To observe the effects of cornel iridoid glycoside (CIG) on nervous function and neuronal survival in focal cerebral ischemic rat model.MethodsThe animal model was induced by occlusion of middle cerebral artery with suture embolus. Nervous function defect and survival number of neuron were detected with nervous function score and Nissl's staining respectively.ResultsCompared with Sham operation group, nervous function score increased and nervous survival number decreased obviously in model rats. Compared with model group, CIG decreased nervous function score and increased survival neurons significantly. ConclusionCIG may have theraputic effect on cerebral infarct through improving nervous function and increasing survival neurons.