Influences of Heat Stress on Glutamate Transmission-Dependent Expression Levels of IL-1β and IL-18 in BV-2 Microglial Cells

Abstract

ABSTRACT Objective This study aimed to explore the impact of heat stress (HS) on glutamate transmission-dependent expression levels of interleukin-1β (IL-1β) and IL-18 in BV-2 microglial cells. Methods BV-2 microglial cells were cultured in vitro, with cells maintained at 37 °C serving as the control. The HS group experienced incubation at 40 °C for 1 h, followed by further culturing at 37 °C for 6 or 12 h. The experimental group was pre-incubated with glutamate, the glutamate antagonist riluzole, or the mGluR5 agonist, 2-Chloro-5-hydroxyphenylglycine (CHPG), before HS. Glutamate content in BV-2 culture supernatant was assessed using colorimetric assay. Moreover, mRNA expression levels of EAAT3 and/or mGluR5 in BV-2 cells were determined via quantitative polymerase chain reaction. Interleukins (IL-1β and IL-18) in cell culture supernatant were measured using enzyme-linked immunosorbent assay. Western blot analysis was employed to assess protein levels of IL-1β and IL-18 in BV-2 cells. Results HS induced a significant release of glutamate and increased the expression levels of mGluR5 and EAAT3 in BV-2 cells. It also triggered the expression levels and release of pro-inflammatory factors, such as IL-1β and IL-18, synergizing with the effects of glutamate treatment. Preincubation with both riluzole and CHPG significantly reduced HS-induced glutamate release and mitigated the increased expression levels and release of IL-1β and IL-18 induced by HS. Conclusion The findings confirmed that microglia could be involved in HS primarily through glutamate metabolisms, influencing the expression levels and release of IL-1β and IL-18.