Mixtures of recombinant growth factors inhibit the production of pro-inflammatory mediators and cytokines in LPS-stimulated RAW 264.7 cells by inactivating the ERK and NF-kappa B pathways

Abstract

Growth factors are important for regulating a variety of cellular processes and typically act as signaling Molecules between cells. In the present study, we examined the mechanisms underlying the inhibitory effects of mixtures of recombinant growth factors (MRGFs) on nitric oxide (NO) and pro-inflammatory cytokine production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. We also examined whether these effects are mediated through the mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-kappa B) signal transduction pathways. NO production was assessed by measuring nitrite acucmulation using the Greiss reaction. Cytokine concentrations were measured using respective ELISA kits for each cytokine. Our results revealed that the MRGFs significantly attenuated the LPS-induced production of pro-inflammatory cytokines and NO in a dose-dependent manner. To elucidate the mechanisms underlying the inhibitory effects of MRGFs, we examined the effects of the LPS-induced phosphorylation of MAPKs and the activation of the NF-kappa B ignaling pathway on the stabilization of NF-kappa B nuclear translocation and inhibitory factor-kappa B (I kappa B) degradation. Western blot analysis was performed to determine the total and phosphorylated levels of ERK, as well as the nuclear translocation of NF-kappa B, and I kappa B phosphorylation and degradation. Our results demonstrated that treatment with MRGFs resulted in a reduction in the phosphorylation of the ERK and NF-kappa B signaling pathways, whereas the phosphorylation of JNK and p38 was not affected. Taken together, our results suggest that MRGFs inhibit the production of pro-inflammatory cytokines and NO by downregulating inducible NO synthase gene expression and blocking the phosphorylation of the ERK and NF-kappa B signaling pathways. These findings may provide direct evidence of the potential application of MRGFs in the prevention and treatment of inflammatory diseases.