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Critical Care and Emergency Medicine - Immunology - Molecular Biology


Pre-Treatment of Recombinant Mouse MFG-E8 Downregulates LPS-Induced TNF-a Production in Macrophages via STAT3-Mediated SOCS3 Activation
Published: Tuesday, November 15, 2011
Author: Monowar Aziz et al.

by Monowar Aziz, Asha Jacob, Akihisa Matsuda, Rongqian Wu, Mian Zhou, Weifeng Dong, Weng-Lang Yang, Ping Wang

Milk fat globule-epidermal growth factor factor 8 (MFG-E8) regulates innate immune function by modulating cellular signaling, which is less understood. Herein, we aimed to investigate the direct anti-inflammatory role of MFG-E8 in macrophages by pre-treatment with recombinant murine MFG-E8 (rmMFG-E8) followed by stimulation with LPS in RAW264.7 cells and in peritoneal macrophages, isolated from wild-type (WT) or MFG-E8-/- mice. RAW264.7 cells and mouse peritoneal macrophages treated with rmMFG-E8 significantly downregulated LPS-induced TNF-a mRNA by 25% and 24%, and protein levels by 29% and 23%, respectively (P<0.05). Conversely, peritoneal macrophages isolated from MFG-E8-/- mice produced 28% higher levels of TNF-a, as compared to WT mice when treated with LPS. In in vivo, endotoxemia induced by intraperitoneal injection of LPS (5 mg/kg BW), at 4 h after induction, serum level of TNF-a was significantly higher in MFG-E8-/- mice (837 pg/mL) than that of WT (570 pg/mL, P<0.05). To elucidate the direct anti-inflammatory effect of MFG-E8, we examined STAT3 and its target gene, SOCS3. Treatment with rmMGF-E8 significantly induced pSTAT3 and SOCS3 in macrophages. Similar results were observed in in vivo treatment of rmMFG-E8 in peritoneal cells and splenic tissues. Pre-treatment with rmMFG-E8 significantly reduced LPS-induced NF-?B p65 contents. These data clearly indicated that rmMFG-E8 upregulated SOCS3 which in turn interacted with NF-?B p65, facilitating negative regulation of TLR4 signaling for LPS-induced TNF-a production. Our findings strongly suggest that MFG-E8 is a direct anti-inflammatory molecule, and that it could be developed as a therapy in attenuating inflammation and tissue injury.
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