[HTML][HTML] Interaction of Apoptotic Cells with Macrophages Upregulates COX-2/PGE2 and HGF Expression via a Positive Feedback Loop

JY Byun, YS Youn, YJ Lee, YH Choi, SY Woo… - Mediators of …, 2014 - hindawi.com
JY Byun, YS Youn, YJ Lee, YH Choi, SY Woo, JL Kang
Mediators of inflammation, 2014hindawi.com
Recognition of apoptotic cells by macrophages is crucial for resolution of inflammation,
immune tolerance, and tissue repair. Cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE 2)
and hepatocyte growth factor (HGF) play important roles in the tissue repair process. We
investigated the characteristics of macrophage COX-2 and PGE 2 expression mediated by
apoptotic cells and then determined how macrophages exposed to apoptotic cells in vitro
and in vivo orchestrate the interaction between COX-2/PGE 2 and HGF signaling pathways …
Recognition of apoptotic cells by macrophages is crucial for resolution of inflammation, immune tolerance, and tissue repair. Cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) and hepatocyte growth factor (HGF) play important roles in the tissue repair process. We investigated the characteristics of macrophage COX-2 and PGE2 expression mediated by apoptotic cells and then determined how macrophages exposed to apoptotic cells in vitro and in vivo orchestrate the interaction between COX-2/PGE2 and HGF signaling pathways. Exposure of RAW 264.7 cells and primary peritoneal macrophages to apoptotic cells resulted in induction of COX-2 and PGE2. The COX-2 inhibitor NS-398 suppressed apoptotic cell-induced PGE2 production. Both NS-398 and COX-2-siRNA, as well as the PGE2 receptor EP2 antagonist, blocked HGF expression in response to apoptotic cells. In addition, the HGF receptor antagonist suppressed increases in COX-2 and PGE2 induction. The in vivo relevance of the interaction between the COX-2/PGE2 and HGF pathways through a positive feedback loop was shown in cultured alveolar macrophages following in vivo exposure of bleomycin-stimulated lungs to apoptotic cells. Our results demonstrate that upregulation of the COX-2/PGE2 and HGF in macrophages following exposure to apoptotic cells represents a mechanism for mediating the anti-inflammatory and antifibrotic consequences of apoptotic cell recognition.
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