Background The interplay between microglia and neurons orchestrates neurorestorative processes after spinal cord injury. Interleukin-33 (IL-33), a member of the IL-1 superfamily, serves as a key mediator in fine-tuning microglia-neuron crosstalk during the pathogenesis of spinal cord injury. Here, we sought to elucidate how activated BV2 microglial cells regulate the proliferation and viability of PC12 cells.

Objective To investigate the regulatory effect of activated BV2 cells on the growth of PC12 cells.

Methods Cell viability and the number of activated BV2 microglial cells following treatment with varying concentrations of lipopolysaccharide (LPS) were quantified using the Cell Counting Kit-8 (CCK-8) assay to determine the optimal concentration for inducing activation. Morphological alterations, specifically process length and branching complexity, were evaluated via immunofluorescence staining. BV2 cells cultured in standard medium (control) or LPS-supplemented medium (LPS group) were subsequently co-cultured with PC12 cells, and neurite length and branching of PC12 cells were analyzed using immunofluorescence. Relative mRNA expression levels of the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), alongside the anti-inflammatory cytokines interleukin-4 (IL-4) and interleukin-10 (IL-10), were measured by real-time quantitative PCR (RT-qPCR). To assess the modulatory effect of IL-33, activated BV2 cells were treated with 10 ng/mL IL-33 prior to co-culture with PC12 cells, followed by immunofluorescence analysis to evaluate changes in PC12 neurite length and branching complexity.

Results CCK-8 assay results demonstrated that treatment with LPS at concentrations below 1 μg/mL induced minimal morphological activation, whereas concentrations above 1 μg/mL significantly reduced cell viability; thus, 1 μg/mL was identified as the optimal concentration for activating BV2 cells. Light microscopy and immunofluorescence analyses revealed that, compared with resting microglia, activated BV2 cells exhibited shortened processes, increased proximal branching, and an amoeboid morphology. RT-qPCR analysis showed that the mRNA expression levels of the pro-inflammatory cytokines IL-6 and TNF-α were significantly upregulated (P < 0.01), while the changes in the anti-inflammatory cytokines IL-4 and IL-10 were not statistically significant (P > 0.05). Furthermore, co-culture with activated BV2 cells resulted in markedly shortened neurites and reduced branching in PC12 cells, an effect that was notably attenuated by IL-33 intervention.

Conclusion IL-33 can regulate activated BV2 cells and reduce their inhibitory effect on PC12 cell growth.