Maleylated-BSA suppresses lipopolysaccharide-induced IL-6 production by activating the ERK-signaling pathway in murine RAW264.7 cells

• Maleylated-BSA suppresses LPS-induced IL-6 production in murine macrophages.
• Maleylated-BSA induces ERK phosphorylation.
• Inhibitory effect of maleylated-BSA is mediated by the activation of ERK.

Macrophages are well known for their ability to induce diverse beneficial immune responses, especially in the defense against pathogens. However, an excessive activation of macrophages may cause harmful inflammation. In this context, the suppression of excessive macrophage activation would be a promising therapeutic strategy for treating inflammatory diseases. We have previously found that maleylated-bovine serum albumin (maleylated-BSA) suppresses the production of inflammatory mediators in murine macrophages. However, the immunosuppressive effects and underlying mechanism(s) of maleylated-BSA remain unclear. Here, we report that pretreatment with maleylated-BSA strongly inhibited the production of interleukin 6 (IL-6) induced by bacterial lipopolysaccharide (LPS) in murine RAW264.7 cells. This inhibitory effect of maleylated-BSA on LPS-induced IL-6 production was eliminated by treatment with an extracellular signal-regulated kinase (ERK) inhibitor, U0126, indicating the involvement of ERK pathways. Taken together, we have shown that maleylated-BSA suppresses LPS-induced production of IL-6 via the activation of an ERK signaling pathway in murine macrophages. The findings of this study imply the possibility of a novel therapeutic strategy for inflammatory diseases.