The Study Of Eicosapentaenoic Acid Attenuates Imbalance In Microglia Activation And Improves Alzheimer’s Disease

Background:Alzheimer’s disease（AD）is a chronic neurodegenerative disease with a high incidence in the elderly or pre-elderly population.Although the accurate pathogenesis of AD is still being explored so far,more and more research data show that:the central nervous system Inflammation plays an important role in the process of pathological injury of AD neurons.Microglial cells are the main immune cells of the central nervous system（CNS）.Under physiological conditions,microglial cells are in a resting state.When they are activated by external and external signals,they exhibit a"Classically-activated（M1）"that induces damage and neuroprotective"alternatively-activated（M2）".Our research has observed that with the development of AD disease,the activation state of microglia M1 increases and the activation state of M2 decreases,that is,the inflammation-related microglia M1-M2 activation imbalance exists in the brain of AD animals.Obviously,improving the imbalance of microglial activation will help weaken the central inflammatory effect and improve AD.Eicosapentaenoic acid（EPA）is a polyunsaturated fatty acid essential for the body but unable to self-synthesize.It affects the stability of cell membranes and participates in the regulation of various cell functions.The research team reported that EPA can improve the loss of inflammation-related neuron damage,showing a potential improvement in neuro-inflammatory-related anti-AD effects.At the same time,the research team also reported that with the inflammatory effects of the central nervous system,the endoplasmic reticulum stress continued to increase,and the endoplasmic reticulum stress apoptotic signal was activated to induce neuronal apoptosis.But:1)Does EPA have a clear anti-AD effect?2)Is there any involvement of EPA in improving inflammation and anti-AD-like effects in regulating the imbalance of microglial activation?3)Does EPA improve inflammation and play a cytoprotective role related to relieving endoplasmic reticulum stress?The current research is not clear.Therefore,based on the experimental reports of EPA participation in cell function regulation and the previous research work of the research group,this study speculates that:EPA may improve the imbalance of central microglial activation by intervening microglial activation,and then limit central inflammation and endoplasmic reticulum stress,thereby achieving a neuroprotective effect,and finally exhibiting an anti-AD effect.In order to verify the above hypothesis,this study used the amyloidβ-protein 1-42(Aβ_1-42)intracerebral injection to induce AD model in animals,and implemented EPA intervention to detect animal cognition under different experimental conditions.Function,microglial activation status,central inflammatory effects,endoplasmic reticulum stress and neuronal damage,etc.To analyze the anti-AD effect of EPA and its relationship with microglial activation-neuritism-endoplasmic reticulum association,explore the possible mechanism of EPA to improve AD,and provide a theoretical basis for the application of EPA in the prevention and treatment of AD.Method:C57BL/6 mice were injected with Aβ_1-42 toxic fragment（2μg/head）in the brain to induce AD model,12 animals/group.Experimental setting:normal control group:fed with 0.8%palm oil feed+intracerebral injection of PBS;EPA control group:fed with 0.8%EPA feed+brain injected PBS;AD model group:fed with 0.8%palm oil feed+Aβinjection in brain;EPA experimental group:fed with 0.8%EPA feed+Aβinjection in brain.After 28 days of EPA feeding,the animals of the AD model group and the EPA experimental group were injected with Aβin the brain once,and the animals of the other groups were injected with the same volume of PBS,and then the EPA was fed for 14 days,that is,the total length of EPA feeding was 42 days.After feeding,Morris water maze test was used to detect the spatial learning and memory ability of animals,and real-time PCR was used to detect interleukin-1 beta（IL-1β）,tumor necrosis factor alpha（TNF-α）,brain-derived neurotrophic factor（BDNF）,nerve growth factor（NGF）expression in hippocampus.Western Blot method to detect hippocampal tissue CCL2,Ym1,Calpain-2,glucose regulated protein78（GRP78）,C/EBP-homologous protein（CHOP）protein expression,TUNEL method to detect apoptosis in hippocampal tissue cells.Results:1.Morris water maze behavioral test results show that Aβinjection significantly impairs the spatial learning and memory abilities of animals,and EPA intervention significantly combats Aβ-induced learning and memory impairment,suggesting that EPA has the effect of improving AD-related cognitive impairment;2.Western Blot results showed that the expression of M1-type microglial marker CCL2 was up-regulated under the action of Aβ,while the expression of Ml-type microglial marker Ym1 was down-regulated,and EPA feeding significantly inhibited Aβ-induced CCL2 expression up-regulation,no significant effect on Ym1 expression,suggesting that EPA may restrict M1 microglia over-activation;3.Real-time PCR results showed that the expression of inflammatory factors IL-1βand TNF-αincreased and the expression of neuroprotective factors BDNF and NGF weakened under the action of Aβ;while EPA feeding reduced the expression of neurotrophic factors and the expression of inflammatory factors both can be effectively improved,suggesting that EPA may limit central inflammatory effects and enhance neurotrophic effects and exert anti-AD effects;Western Blot and TUNEL results showed that Calpain-2,GRP78,and CHOP protein expression increased and the number of TUNEL-positive cells increased significantly under the effect of Aβ;EPA feeding could effectively alleviate the above-mentioned changes induced by Aβ,suggesting that EPA may improve the continuous endoplasmic reticulum stress reduces apoptosis associated with endoplasmic reticulum stress signals activated by inflammatory effects.Conclusions:1.EPA improves AD-like cognitive impairment and has definite anti-AD effect;2.EPA fights AD-related M1 microglia over-activation and clearly improves central microglia activation imbalance effect;3.EPA down-regulates the expression of inflammatory factors such as IL-1β,and maintains the expression of neurotrophic factors such as BDNF,showing a significant anti-inflammatory effect;4.EPA plays an anti-AD neuron damage loss role by improving inflammation-related endoplasmic reticulum stress.