Direct co-culture with human neural stem cells suppresses hemolysate-induced inflammation in RAW 264.7 macrophages through the extracellular signal-regulated kinase pathway

Background: Inflammation following stroke is associated with poor outcomes, and the anti-inflammatory effects of neural stem cells (NSCs) have been reported. However, the direct immunomodulatory effects of NSCs in hemorrhagic stroke remain unclear. In the present study, we investigated the anti-inflammatory mechanism of direct co-culture with NSCs on RAW 264.7 cells stimulated by hemolysate.Methods: RAW 264.7 cells were stimulated with the hemolysate for 4 hours to induce hemorrhagic inflammation in vitro. Regarding direct co-culture, RAW 264.7 cells were cultured with HB1.F3 cells for 24 hours in normal medium and stimulated with hemolysate for 4 hours. Inflammatory cell signaling molecules, including cycloxygenase-2 (COX-2), interleukin-1β (IL-1β), and extracellular signal-regulated kinase (ERK), as well as tumor necrosis factor-α (TNF-α), were evaluated.Results: After stimulation with the hemolysate, levels of the inflammatory markers COX-2, IL-1β, and TNF-α were increased in RAW264.7 cells. Inflammatory marker production was reduced in the group subjected to direct co-culture with HB1.F3 in comparison to that in the RAW264.7 group stimulated by the hemolysate. In addition, direct co-culture with HB1.F3 significantly suppressed the phosphorylation of ERK 1/2 in hemolysate-stimulated RAW 264.7 cells. Moreover, treatment of the ERK inhibitor (U0126) suppressed the expression levels of inflammatory markers in hemolysate-stimulated RAW246.7 cells.Conclusion: These results demonstrate that direct co-culture with HB1.F3 suppresses inflammation by attenuating the ERK pathway. These findings suggest that direct NSC treatment modulates the inflammatory response in hemorrhagic stroke.