Milk fat globule-epidermal growth factor-factor 8 attenuates neutrophil infiltration in acute lung injury via modulation of CXCR2.
Excessive neutrophil infiltration to the lungs is a hallmark of acute lung injury (ALI). Milk fat globule epidermal growth factor-factor 8 (MFG-E8) was originally identified for phagocytosis of apoptotic cells. Subsequent studies revealed its diverse cellular functions. However, whether MFG-E8 can regulate neutrophil function to alleviate inflammation is unknown. We therefore aimed to reveal MFG-E8 roles in regulating lung neutrophil infiltration during ALI. To induce ALI, C57BL/6J wild-type (WT) and Mfge8(-/-) mice were intratracheally injected with LPS (5 mg/kg). Lung tissue damage was assessed by histology, and the neutrophils were counted by a hemacytometer. Apoptotic cells in lungs were determined by TUNEL, whereas caspase-3 and myeloperoxidase activities were assessed spectrophotometrically. CXCR2 and G protein-coupled receptor kinase 2 expressions in neutrophils were measured by flow cytometry. Following LPS challenge, Mfge8(-/-) mice exhibited extensive lung damage due to exaggerated infiltration of neutrophils and production of TNF-α, MIP-2, and myeloperoxidase. An increased number of apoptotic cells was trapped into the lungs of Mfge8(-/-) mice compared with WT mice, which may be due to insufficient phagocytosis of apoptotic cells or increased occurrence of apoptosis through the activation of caspase-3. In vitro studies using MIP-2-mediated chemotaxis revealed higher migration of neutrophils of Mfge8(-/-) mice than those of WT mice via increased surface exposures to CXCR2. Administration of recombinant murine MFG-E8 reduces neutrophil migration through upregulation of GRK2 and downregulation of surface CXCR2 expression. Conversely, these effects could be blocked by anti-α(v) integrin Abs. These studies clearly indicate the importance of MFG-E8 in ameliorating neutrophil infiltration and suggest MFG-E8 as a novel therapeutic potential for ALI.
Center for Immunology and Inflammation, Feinstein Institute for Medical Research, Manhasset, NY 11030, USA.
Monowar
M
Aziz
Akihisa
A
Matsuda
Weng-Lang
WL
Yang
Asha
A
Jacob
Ping
P
Wang
D055371:Acute Lung Injury / Q000276:immunology* / Q000473:pathology / Q000628:therapy*; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000276:immunology*; D006017:Glycolipids / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D006023:Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D018836:Inflammation Mediators / Q000502:physiology; D066292:Lipid Droplets; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008894:Milk Proteins / Q000235:genetics; D020556:Neutrophil Infiltration / Q000235:genetics / Q000276:immunology*; D023063:Receptors, Interleukin-8B / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000235:genetics / Q000627:therapeutic use
D000954:Antigens, Surface; D051017:Apoptosis Regulatory Proteins; D006017:Glycolipids; D006023:Glycoproteins; D018836:Inflammation Mediators; C490919:Mfge8 protein, mouse; D008894:Milk Proteins; D023063:Receptors, Interleukin-8B; D011994:Recombinant Proteins; C110367:milk fat globule