CKΒ8/CCL23 induces cell migration via the G_i/G_o protein/PLC/PKCδ/NF-κB and is involved in inflammatory responses

Aims: CKΒ8/CCL23 is a CC chemokine and alternative splicing of the CKΒ8 gene produces two mRNAs that encode CKΒ8 and its isoform CKΒ8-1. Although it has been reported that CKΒ8 and CKΒ8-1 are implicated in leukocyte trafficking and development of inflammation, the exact roles of these two chemokines in immune responses and the associated chemotaxis signaling are still obscure. Main methods: To understand the mechanism of CKΒ8- and CKΒ8-1-induced chemotaxis signaling, we examined the chemotactic activities of osteogenic sarcoma cells expressing CC chemokine receptor 1 in response to CKΒ8 and CKΒ8-1. We also examined involvement of CKΒ8 and CKΒ8-1 in inflammatory responses by determining the mRNA expression of pro-inflammatory molecules induced by two chemokines and expressions of these chemokines in foam cells. Key findings: Results from a chemotaxis assay using various inhibitors for signaling molecules showed that the chemotaxis signal pathway induced by both CKΒ8 and CKΒ8-1 was mediated via the G_i/G_o protein, phospholipase C (PLC) and protein kinase Cδ (PKCδ). Treatment with a nuclear factor κB (NF-κB) inhibitor reduced the chemotactic activities of CKΒ8 and CKΒ8-1, and NF-κB was activated in response to CKΒ8 and CKΒ8-1. In addition, CKΒ8 and CKΒ8-1 increased mRNA expression of pro-inflammatory cytokines and adhesion molecules. The mRNA levels of CKΒ8 and CKΒ8-1 were increased in foam cells. Significance: These results indicate that both CKΒ8 and CKΒ8-1 transduce the chemotaxis signal through the G_i/G_o protein, PLC, PKCδ, and NF-κB, and that CKΒ8 and CKΒ8-1 probably play important roles in inflammatory diseases such as atherosclerosis.