Behavior And Relevant Pathological Changes Of Depression Induced By LPS:Treatment Mechanism Of N-3 Unsaturated Fatty Acids

In the past two decades,many studies have provided strong evidence that inflammation significantly contribute to the etiology of depression and neurodegeneration.Peripheral inflammation,mental stress or brain injury stimulates the hypothalamic-pituitary-adrenal axis to secret glucocorticoids and activates glial cells to release proinflammatory mediators.Excessive production of these factors could induce the impairment of mood and cognitive behavior,dysfunction of neurotransmission and neuron death.Thus,studying and developing anti-inflammatory treatments without side effects became a hot research area.Studies from epidemiological investigations,clinical trials,and animal models support the therapeutic use of dietary omega(n)-3 polyunsaturated fatty acids(PUFA),particularly docosahexaenoic acid(DHA)and eicosapentaenoic acid(EPA)are beneficial in the treatment of depression and neurodegeneration.Furthermore,we have revealed that DHA and EPA may exert neuroprotective functions via anti-inflammation or neugenesis within the brain.However,most results in this field came from animals fed n-3 fatty acids.However,the experimental results of different diets,food impurities,flavors,calories and other components resulted in uncertainty.In this study,With wild type C57BL/6 mice and transgenic Fat-1 mice which brains can directly produce n-3 fatty acids as the research objects,after 24 h central administration of lipopolysaccharide(LPS)and saline,the behavior,neuroinflammation(glial functions and inflammatory signals)will be evaluated.The project will explain several epidemiological and clinical observations and lead to new strategies for the prevention or treatment of brain diseases;correct the concepts of current PUFAs products on the markets,and provide scientific evidence for developing of PUFA products.Method:(1)The male transgenic Fat-1 mice were crossed with female C57 BL / 6(wild type group,WT)mice,and the male mice were identified by PCR.The positive expression of Fat-1 gene is Fat-1 mice and negative expression of WT mice.Male mice identified as non-transgenic with the same nest were used as negative controls;(2)At 8 weeks,Fat-1 mice and wild-type littermates were treated with lateral ventricle surgery.After 2 weeks of operation,1 ?L(saline)or LPS(3 ?g / ?L)was injected to induce brain inflammation;(3)Sucrose preference,forced swimming,suspension test,open field maze and elevated plus maze are used to assay the feasibility of LPS model;(4)The cell viability were measured by neutral red method and MTT method.ELISA kits are used to detect hormone levels and inflammatory factors IL-1?;(5)The expression level and relative ratio of n-3 and n-6 PUFAs in the brain were measured by gas chromatography;(6)The expression of M1: IL-1?,TNF-?,IL-6,IL-17 and M2: IL-4,IL-10,TGF?1,IL-13 related neuroinflammatory factors and oxidative stress-related factors: iNOS,NO protein expression in hippocampus of mice was detected by ELISA kit;(7)The expression of microglia M1 phenotype:CD11b,CD68,and M2 phenotype: Arg-1and neurotrophic factor : Pro-BDNF,BDNF,NGF and its receptors: p75 and Trk B in hippocampal were analyzed by fluorescence quantitative PCR(qPCR)and Western blot.Result:(1)Intraventricular injection of LPS resulted in a significant reduction in sucrose preference in WT mice,a significant increase in immobility times in forced-swimming,a significant decrease in exploratory ability and activity in open field experiments,and a significant increase in anxiety in elevated-plus maze;however,Fat-1 mice have improved effect on their behavioral changes compared with WT mice;(2)Intraventricular injection of LPS activated peripheral macrophages,Fat-1 mice can reverse it;(4)The content of EPA,DHA and total n-3 unsaturated fat in Fat-1 mice were significantly higher than those in WT mice,n-3/n-6 PUFAs was significantly lower than that of WT mice;(5)IL-1?,TNF-?,IL-17 and IL-13 in the hippocampus of WT mice were significantly increased and TGF-?1 significantly decreased,while Fat-1 mice significantly reversed the expression of the above factors variety;(6)Quantitative PCR and Western Blot showed that intraventricular injection of LPS increased the expression of CD11 b in M1 phenotype of mouse hippocampal microglia,decreased the expression of Arg-1 in M2 phenotype,decreased the expression of BDNF and its receptor Increased Pro-BDNF,p75,GFAP expression;however,Fat-1 mice have some improvement effect.Conclusion:(1)Intraventricular LPS administration can induce mice depression-like behavior,increased the expression of M1 phenotype and reduce the expression of M2 phenotype of microglia,reduce the expression of neurotrophic factors and their receptors.(2)n-3 PUFAs can improve the symptoms of depression induced by LPS administration by anti-inflammatory and certain neuroprotective effects.