Vatiquinone inhibits neuroinflammation in lipopolysaccharide-activated BV2 microglia

Introduction

Vatiquinone (alpha-tocotrienol quinone) is a para-benzoquinone analogue, which inhibits the 15-lipoxygenase (15-LO) enzyme and targets inflammation and oxidative stress in mitochondrial diseases [1–3]. In this study, we aimed to determine whether the compound could be repurposed to inhibit neuroinflammation. We therefore investigated effects of vatiquinone on the release of proinflammatory mediators in lipopolysaccharide (LPS)-activated BV2 microglia.

Method

Cultured BV2 microglial cells were treated with vatiquinone at concentrations of 5, 10 and 20 μM for 1 h. Thereafter, cells were stimulated with lipopolysaccharide (100 ng/ml) for 24 h. Effects of treatment and stimulation on microglial cell viability were determined using the CellTiter 96® AQueous One Solution cell proliferation assay (Promega, UK). Effects of vatiquinone (5, 10 and 20 μM) on the production of proinflammatory cytokines tumour necrosis factor alpha (TNFα) and interleukin-6 (IL-6) in LPS-stimulated microglia were determined in cell culture supernatants using ELISA (Biolegend, UK). Cell lysates were also analysed for levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) using mouse ELISA kits (Abcam, UK). Statistical significance of data was determined using one-way ANOVA and Dunnett's multiple comparison tests.

Results

Results of MTS experiments revealed that treatment of LPS-stimulated BV2 microglia with 5-, 10- and 20-μM vatiquinone did not result in significant reduction in cell viability. Analyses of cell supernatants showed that LPS stimulation of BV2 cells caused significant (P < 0.05) increase in the secretion of TNFα and IL-6. However, pretreating the cells with vatiquinone (5–10 μM) resulted in significant (P < 0.05) and concentration-dependent reduction in the levels of both proinflammatory cytokines. Similarly, elevated protein levels of both iNOS and COX-2 following LPS stimulation were significantly reduced (P < 0.05) in the presence of 5, 10 and 20 μM of vatiquinone.

Conclusions

These results show that vatiquinone produces anti-inflammatory activity in LPS-activated BV2 microglia and suggest that the compound could be repurposed to target neuroinflammation in some neurodegenerative and neurological conditions.