Time-window analysis of lipopolysaccharide-induced activation and M1 polarization in BV2 microglial cells

Objective: This study aimed to systematically investigate lipopolysaccharide (LPS)-induced activation of BV2 microglial cells and to evaluate the effects of different exposure durations on cellular activation, cytokine release, and polarization status, thereby clarifying the role of LPS in microglial activation and defining an optimal stimulation window for model establishment.
Methods: BV2 microglial cells treated with LPS for different time intervals were analyzed using ELISA kits, quantitative PCR (qPCR), and Western blotting. Specifically, morphological changes were documented by inverted microscopy by recording cell size, the number of processes, and cytoplasmic granularity; the expression levels of pro-inflammatory cytokines (IL-6, IL-1β) and anti-inflammatory cytokines (IL-10) were measured; and the mRNA and protein expression of the polarization-related marker cyclooxygenase-2 (COX-2) were determined.
Results: LPS induced time-dependent microglial activation with coordinated shifts in polarization markers and cytokine profiles. After 6 h, the anti-inflammatory marker CD206 was significantly downregulated (P < 0.05), whereas the M1-associated marker COX-2 was markedly upregulated (P < 0.01), accompanied by increased pro-inflammatory cytokines including IL-6 and IL-1β (P < 0.01) and a reduction in IL-10. These changes became more pronounced at 12 and 24 h, with further elevations of pro-inflammatory indices and continued decreases of anti-inflammatory indicators, consistent with a progressive shift toward an M1-like phenotype under sustained stimulation.
Conclusion: LPS effectively induces inflammatory activation of BV2 microglia and drives a shift toward an M1-like pro-inflammatory phenotype. Integrating morphological changes, cytokine profiles, and polarization marker expression, 12 h appears to represent a robust and relatively stable time window for model establishment.