Adiponectin induces the production of granulocyte colony-stimulating factor in macrophage

Objectives: Recent studies have reported that periodontal disease is exacerbated by some conditions associated with obesity, such as the metabolic syndrome. Adiponectin, an adipocyte-derived hormone, is abundantly present in the plasma of healthy humans (8.9 ± 5.4 µg/ml), whereas paradoxically, obese individuals exhibit comparatively decreased adiponectin levels. We investigated whether globular adiponectin (gAd) would affect the expression of inflammatory-related genes in mouse macrophages. Methods: Murine macrophage cell lines, RAW264 cells, were treated with various concentration of gAd for 0.5-24 h. Total RNA was extracted from cells. To investigate gAd-inducible genes, DNA microarray was performed by Affymetrix GeneChip Mouse Genome 430 2.0, and these data were analyzed by MAS 5.0 software. The mRNA levels of the granulocyte colony-stimulating factor (G-CSF) induced by gAd were determined with real-time PCR. G-CSF in the supernatants of RAW264 cells culture was determined by ELISA. Various inhibitors were used to determine signaling cascade for G-CSF transduction. To evaluate downstream signaling events phosphorylated proteins were detected by Western blot analysis. Results: Using DNA microarray analysis, expression of the G-CSF gene showed the most prominent change after treatment with 20 µg/ml gAd for 60 min: 104.0 times. gAd induced increased the secretion of G-CSF protein in a time- and dose-dependent manner. The gAd-induced G-CSF mRNA expression and protein secretion were significantly inhibited by U0126 (MEK1/2 inhibitor), PD98059 (MEK1 inhibitor), and BAY11-7082 (NF-kB inhibitor). Western blot analysis revealed that MEK1/2, ERK1/2, and IkB were strongly phosphorylated in gAd-stimulated RAW264 cells. Conclusion: We provided the first evidence that gAd induced the increased secretion of G-CSF in RAW264 cells. In addition, we demonstrated that intracellular signal transduction through the activation of MEK1/2-ERK1/2-NF-kB was involved in adiponectin-induced G-CSF secretion.