Lactic acid bacteria reduced pro-inflammatory cytokines expression and oxidative stress on BV-2 microglia cells stimulated with amyloid beta oligomer

Abstract

Neuroinflammation and oxidative stress have been implicated as a common hallmark in some neurodegenerative diseases,including Alzheimer?s disease (AD). Activation of microglia has been proposed to be one of the first steps in the onset of AD,generating neurotoxic compounds and pro-inflammatory cytokines. Lactic acid bacteria (LAB) are well knownmicroorganisms and are widely studied for their various benefits to human health. Currently, there is an increasing interest inusing these microorganisms as alternative therapies because of the role that gut microbiota seems to play in the pathogenesisof AD. In the present study, we examined the effects of three LAB strains on oxidative stress and inflammation-related geneexpression on BV-2 microglial cells stimulated with β-amyloid oligomers (oAβ1-42). BV-2 cells were treated with 5 µM oAβand the effect of LAB was evaluated under three different conditions: using living bacteria, heat-inactivated bacteria, andbacterial conditioned media (BCM). After 8 hours of treatment, BV2 cells and supernatants were harvested separately. TotalRNA was extracted from BV2 cells and the expression of TNF-α, IL-1β, IL-6, iNOS and SOD was examined by RT-qPCR.oAβ1-42 resulted in an increased expression of pro-inflammatory cytokines and oxidative stress in BV2 cells. Living and deadbacteria did not induced any significant changes in mRNA expression of the evaluated genes with respect to control groups.However, BCM from Enterococcus mundtii CRL 35, Lactobacillus delbrueckii subsp. lactis CRL 581 and Levilactobacillusbrevis CRL 2013 significantly reduced IL-1β and IL-6 expression. Additionally, TNF-α expression was down-regulated onBV-2 cells treated with BCM from CRL 35. No significant differences were found in iNOS and SOD expression. Finally, totalantioxidant activity of all the supernatant from BV-2 cells treated with BCM was measured using both the ABTS decolorizationand the CUPRAC assays. We found that all the supernatants from microglia cells treated with BCM were capable of reducingABTS+cations and only treatment with BCM from CRL 35 reduced cupric ions, indicating a significant antioxidant activity.Our results show that conditioned media from E. mundtii CRL 35, L. delbrueckii subsp. lactis CRL 581 and L. brevis CRL2013 have the ability to reduced inflammatory and oxidative stress markers produced by beta-amyloid oligomers in vitro. Weare currently examining the mechanisms and LAB metabolites implicated in these effects.