Effects Of Teasaponin On Expression Of Complement Component 3 In Mice Brain Induced By Chronic Systemic Inflammation

Objective:Neurodegenerative diseases are a class of progressive neurological diseases characterized by progressive loss of neuronal structure and function to death.At present,there is no cure for neurodegenerative diseases,and clinical treatment drugs and methods can only alleviate symptoms and delay disease progression.Studies have found that chronic low-grade systemic inflammation can induce neuroinflammation and is associated with the progression of neurodegenerative diseases.Overactivation of the complement system in the central nervous system and increased C3 protein levels can lead to the occurrence of neuroinflammatory responses and neuronal damage.In this study,low-dose LPS was used to induce chronic systemic inflammation,and tea saponin was used to intervene prophylactically to observe the changes of microglia activation,complement C3 protein level and mRNA expression in the brain of mice,and the effects of tea saponin on the above changes,so as to provide a basis for further elucidating the role of complement C3 in neurodegenerative diseases and the preventive and therapeutic mechanism of tea saponin.Methods: Chronic systemic inflammation was induced by continuous intraperitoneal injection of low-dose LPS(250 mg/kg/d)for 4 days,and tea saponin(2.5 mg/kg/d)was gavaged from 7 days before LPS intraperitoneal injection until mice execution.Mice were sampled 1 or 14 days after LPS injection was stopped.Immunofluorescence staining was used to observe the changes of microglia activation in the brain of mice.Fluorescence quantitative PCR and ELISA were used to detect the changes of complement C3 mRNA expression and protein levels in different regions of the peripheral and brain,respectively.Evans blue(EB)was used to observe the integrity of the blood-brain barrier.Results: 1.Immunofluorescence staining showed that microglia in the frontal cortex of mice showed obvious activation 14 days after LPS injection was stopped,and the occurrence time was delayed compared with peripheral endotoxemia,while chronic treatment with tea saponin could inhibit LPS-induced microglia activation.2.The results of EB assay showed that low-dose LPS and tea saponin did not cause changes in blood-brain barrier permeability.3.The results of ELISA showed that peripheral LPS could induce the elevation of C3 levels in serum and liver tissues,which was consistent with the time of endotoxemia,while the elevation of C3 levels in different regions of brain induced by LPS was delayed compared with the change of peripheral C3.Tea saponin can inhibit the increase of C3 level in peripheral and brain caused by LPS.4.The results of fluorescence quantitative PCR showed that LPS could induce the upregulation of hepatic C3 mRNA expression,which coincided with the time of endotoxemia,while the upregulation of hepatic C3 mRNA induced by LPS was delayed compared with the changes of peripheral C3 in different regions of the brain.Tea saponin can inhibit the upregulation of C3 mRNA expression in peripheral and brain caused by LPS.Conclusion: LPS-induced chronic systemic inflammation can lead to the occurrence of neuroinflammation,while tea saponin can inhibit LPS-induced microglial activation and up-regulation of complement C3 mRNA expression in the brain,which may be one of the molecular mechanisms of its inhibition of neuroinflammation.