Inflammatory cytokines stimulate the chemokines CCL2/MCP-1 and CCL7/MCP-3 through NFkB and MAPK dependent pathways in rat astrocytes [corrected].

The chemokines CCL2 and CCL7 are upregulated in the brain during several neurodegenerative and acute diseases associated with infiltration of peripheral leukocytes. Astrocytes can respond to inflammatory cytokines like IL-1beta and TNF-alpha by producing chemokines. This study aims to test the ability of IL-1beta and TNF-alpha to stimulate CCL2 and CCL7 protein production in rat astrocyte cultures, and to elucidate signaling pathways involved in the cytokine-stimulated chemokine upregulation. Astrocytes were stimulated with IL-1beta or TNF-alpha, and CCL2 and CCL7 levels determined by ELISA. Our results show that IL-1beta and TNF-alpha each stimulate production of the chemokines CCL2 and CCL7 in astrocytes in a concentration- and time-dependent manner, with CCL2 showing a more rapid and robust response to the cytokine treatment than CCL7. As a first step to determine the signaling pathways involved in CCL2 and CCL7 upregulation, we stimulated astrocytes with IL-1beta or TNF-alpha in the presence of selective inhibitors of MAPK pathways (SB203580 and SB202190 for p38, SP600125 for JNK, and U0126 for ERK) or NFkappaB pathways (MG-132 and SC-514). We found that NFkappaB pathways are important for the cytokine-stimulated CCL2 and CCL7 production, whereas MAPK pathways involving p38 and JNK, but not ERK, may also contribute but to a lesser extent. These data document for the first time that CCL7 protein production can be stimulated in astrocytes by cytokines, and that the upregulation may involve NFkappaB- and p38/JNK-regulated pathways. In addition, our results suggest that CCL2 and CCL7 share similarities in the signaling pathways necessary for their upregulation.