Oral Administration of Alpha Linoleic Acid Rescues Aß-Induced Glia-Mediated Neuroinflammation and Cognitive Dysfunction in C57BL/6N Mice.

ABSTRACT

In this work, we evaluated the effects of alpha linoleic acid (ALA), an omega-3 polyunsaturated fatty acid, on amyloid-beta-induced glial-cell-mediated neuroinflammation, amyloidogenesis, and cognitive dysfunction in mice. After an infusion of Aß1-42 (Aß1-42, 5 µL/5 min/mouse, intracerebroventricular injection (i.c.v), and respective treatments of ALA (60 mg/kg per oral for six weeks), neuroinflammation, apoptotic markers, and synaptic markers were evaluated by Western blot and immunofluorescence analyses. According to our findings, the infusion of Aß1-42 activated Toll-like receptor 4 (TLR4), glial fibrillary acidic protein (GFAP), and ionized calcium adaptor molecule 1 (Iba-1) in the frontal cortices and hippocampi of the Aß1-42-injected mice to a greater extent than the Aß1-42 + ALA-cotreated mice. Similarly, there was an elevated expression of phospho-c-Jun-N-terminal kinase (p-JNK), phospho-nuclear factor-kB p65 (p-NF-kB p65 (Ser536)), and tissue necrosis factor (TNF) in the Aß1-42 infused mouse brains; interestingly, these markers were significantly reduced in the Aß + ALA-cotreated group. The elevated expression of pro-apoptotic markers was observed during apoptotic cell death in the Aß1-42-treated mouse brains, whereas these markers were markedly reduced in the Aß + ALA-cotreated group. Moreover, Aß1-42 infusion significantly increased amyloidogenesis, as assessed by the enhanced expression of the amyloid precursor proteins (APP) beta-amyloid cleaving enzyme-1 (BACE-1) and amyloid-beta (Aß1-42) in the mouse brains, whereas these proteins were markedly reduced in the Aß + ALA-cotreated group. We also checked the effects of ALA against Aß-triggered synaptic dysfunction and memory dysfunction, showing that ALA significantly improved memory and synaptic functions in Aß-treated mouse brains. These results indicated that ALA could be an applicable intervention in neuroinflammation, apoptotic cell loss, amyloidogenesis, and memory dysfunction via the inhibition of TLR4 and its downstream targets in Aß + ALA-cotreated mouse brains.