Thymoquinone exposure on BV2 microglial cell line: an in vitro study on cell viability, lactate dehydrogenase activity, microglial morphological changes, and TNF-α protein expression

Objective Thymoquinone (TQ), isolated from the black seeds of Nigella sativa , has been known to possess various pharmacologic properties. It has been proven to exhibit remarkable anti-inflammatory and neuroprotective properties in neuronal disease models. Although there is unclear evidence on its mechanism to protect the neurons, TQ is hypothesized to play an important role in modulating the activation of microglia cells in the brain. Considering the potential of TQ, this study aims to examine the effects of TQ on BV2 microglia cells by evaluating the morphological changes, cell viability, lactate dehydrogenase (LDH) activity, and tumour necrosis factor-alpha (TNF-α). Methods Cell viability was assessed using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The morphology of the cells was observed under an inverted microscope. Meanwhile, LDH activity and TNF-α protein expression were quantified using ELISA kits. Results This study found that the IC 50 of TQ after 24 h of incubation was 17 µM. Exposure of BV2 microglia cells to TQ at 2-µM concentration for 1 h and 24 h did not cause significant morphological changes, but 8 µM and 12 µM of TQ resulted in obvious changes in the cells’ morphology compared to the untreated group. All doses of TQ showed no significant increase in LDH activity compared to the untreated group. However, TNF-α protein expression was significantly reduced in 8 µM and 12 µM of TQ-treated groups compared to the untreated group ( P ≤ 0.05). Conclusion Overall, this study suggested that at higher doses, TQ could change the morphology of BV2 microglia cells from a resting state to an activated state without a significant effect on LDH activity. These interesting findings supported the evidence for TQ as a therapy for neurological-related diseases. The next level of study should be done on the quantification of pro-inflammatory and anti-inflammatory cytokines following TQ exposure in microglia cells to further support its therapeutic potential.