Zileuton, a 5-Lipoxygenase Inhibitor, Attenuates Haemolysate-Induced BV-2 Cell Activation by Suppressing the MyD88/NF-κB Pathway

M1 microglia induce neuroinflammation-related neuronal death in animal models of spontaneous subarachnoid haemorrhage. Zileuton is a 5-lipoxygenase inhibitor that reduces the levels of downstream pro-inflammatory cytokines. This study aimed to investigate whether zileuton inhibits microglial activation and describe its underlying mechanisms. BV-2 cells were exposed to 1 mg/mL haemolysate for 30 min, followed by treatment with different concentrations (5, 10, 15, or 20 μM) of zileuton for 24 h. The cells were then assessed for viability, polarisation, and protein expression levels. Haemolysate increases the viability of BV-2 cells and induces M1 polarisation. Subsequent exposure to high concentrations of zileuton decreased the viability of BV-2 cells, shifted the polarisation to the M2 phenotype, suppressed the expression of 5-lipoxygenase, decreased tumour necrosis factor α levels, and increased interleukin-10 levels. Furthermore, high concentrations of zileuton suppressed the expression of myeloid differentiation primary response protein 88 and reduced the phosphorylated-nuclear factor-kappa B (NF-kB)/NF-kB ratio. Therefore, phenotype reversal from M1 to M2 is a possible mechanism by which zileuton attenuates haemolysate-induced neuroinflammation after spontaneous subarachnoid haemorrhage.