DHA Attenuates Aβ-induced Necroptosis Through The RIPK1/RIPK3 Signaling Pathway In THP-1 Monocytes

BackgroundThe neuropathological changes of Alzheimer disease(AD)consist of abundant amyloid plaques and neurofibrillary tangles,neuropil threads,and dystrophic neurites containing hyperphosphorylated tau.AD is likely caused at least in part by an imbalance between amyloid-β(Aβ)protein production and clearance,which leads to Aβ accumulation in the central nervous system(CNS).Docosahexaenoic acid(DHA)is an essential omega-3 polyunsaturated fatty acid(PUFA),Preclinical and clinical studies have demonstrated that DHA exerts a neuroprotective effect in the context of several neurodegenerative diseases,including AD.Compared to monocytes,microglia have a limited ability to degrade Aβ plaques,resulting from the low activity levels of several microglial lysosomal enzymes.The experiments in this current study were designed to further explore possible mechanisms of interaction between monocytes and Aβ.Necroptosis is a type of programmed cell death different from apoptosis and traditional necrosis,which involves several neurodegenerative diseases,including AD.NF-κB plays a key role in modulating immune and inflammatory responses,while mitogen-activated protein kinases(MAPKs)(P38,ERK1/2)are key regulators of a variety of cellular functions including cell survival,apoptosis and cellular responses to inflammation.Therefore,we further investigated a possible mechanism for Aβ-mediated regulation of necroptosis,MAPK and NF-kB signaling pathways in monocytes.ObjectiveThe experiments in this study were designed to further explore possible mechanisms by which monocytes and Aβ protein might interact.We also investigated the role of DHA in modulating Aβ-regulated signaling pathways and whether DHA indirectly suppressed THP-1 cell-mediated neuronal activation.Methods1.CCK8 viability assay detected THP 1 cells,SY5Y and primary neuron cell activity.2.LDH detected the cell toxicity of THP-1.3.Flow analysis detected differentiation and apoptosis(necrosis)of THP-1 cells.4.Transwell migration assays evaluated THP-1 cells’ migration.5.Western blot analysis detected the protein expression of THP-1 cells.Results1.CCK8 viability assay and LDH results showed Aβ25-3 5 has a "Hormesis"effect on THP-1 cells viability.2.Flow analysis results indicated Aβ25-35 has a "Hormesis" effect on THP-1 cells necroptosis,and Aβ25-35 treatment influences THP-1 cells differentiation3.CCK8 viability assay results showed DHA indirectly suppresses THP-1 cell-mediated neuronal activation.4.Transwell migration assays results indicated DHA restored the THP-1 migration treated with Aβ25-35.5.DHA treatment suppressed Aβ-induced protein expression of TNF-α,IL-1β,IL-6,RIPK1,RIPK3,MLKL and the phosphorylation levels of ERK1/2,but does not affect p38 or NF-κB/p65 signaling in THP-1 cells.6.DHA treatment suppressed Aβ-induced activation of the RIPK1/RIPK3 and reduce the phosphorylation status of ERK1/2 in THP-1 monocytesConclusions1.Aβ25-35 has a "Hormesis" effect on THP-1 cells viability.2.Aβ25-35 has a "Hormesis" effect on THP-1 cells necroptosis,and Aβ25-35 treatment influences THP-1 cells differentiation.3.DHA indirectly suppresses THP-1 cell-mediated neuronal activation.4.DHA restored the THP-1 migration treated with Aβ25-35.5.AP25-35 induction of necroptosis through activation of the RIPK1/RIPK3 and the phosphorylation status of ERK1/2 are attenuated with DHA treatment in THP-1 monocytes.