Induction of Chemokines through LTB4 Receptors, BLT1 and BLT2, in Primary Human Monocytes (B47)

• DOI: 10.4049/jimmunol.178.supp.b47
• Publication Date: 2023-01-02T07:15:22Z
• Authors: Binggang Sun; Jing-Feng Huang; Heng Dai; Karlsson Lars; Anne Fourie
• Keywords: 0303 health sciences; 03 medical and health sciences

Abstract Leukotriene B4 (LTB4) is a potent lipid mediator of inflammation. The biological functions of LTB4 are mediated through two homologous receptors with high and low affinities, namely, BLT1 and BLT2. Using human primary monocytes, we are trying to understand the functions of LTB4 in atherosclerosis from a transcriptional activation perspective. We have also examined the contributions from each receptor. Primary human monocytes were treated with LTB4 and total RNA prepared and analyzed by microarray. Of particular interest, among genes upregulated were 4 chemokines including CCL2/MCP-1, CCL7/MCP-3, CXCL2/Groβ and CXCL3/Groγ. Follow up analysis with real-time PCR and ELISA showed time- and dose-dependent induction of these chemokines. The induction of MCP-1 is Gi-coupled since PTX effectively blocked the induction. BLT2 antagonist LY255283 dose-dependently inhibited the induction of MCP-1 gene expression, while BLT1 agonist, U75302 did the opposite. Selective inhibitors of Ca2+ signaling, PI3K, tyrosine kinase and ERK1/2, but not JNK, effectively blocked the LTB4-induced MCP-1 production. To understand the relative contributions of each receptor, we used receptor specific agonist U75302 for BLT1 and 12(S)-HETE for BLT2. We showed that both agonists induced the expression of all four genes, suggesting overlapping roles of the two receptors in induction of gene expression of these chemokines. More interestingly, 12(S)-HETE greatly increased the induction of MCP-1, MCP-3 and CXCL2 by U75302, suggesting synergistic effect between the two receptors.