Milk Fat Globule-Epidermal Growth Factor-Factor 8 Attenuates Neutrophil Infiltration in Acute Lung Injury via Modulation of CXCR2

Abstract

Excessive neutrophil infiltration to the lungs is a hallmark of acute lung injury (ALI). Milk fat globule-EGF 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 intra-tracheally 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, while caspase-3 and MPO activities were assessed spectrophotometrically. CXCR2 and GRK2 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 MPO. Increased number of apoptotic cells was trapped into the lungs ofMfge8−/− mice than 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 WT mice via increased surface exposures to CXCR2. Administration of recombinant mouse (rm)MFG-E8 reduces neutrophil migration through up-regulation of GRK2, and down-regulation of surface CXCR2 expression. Conversely, these effects could be blocked by anti-αv-integrin antibodies. These studies clearly indicate the importance of MFG-E8 in ameliorating neutrophil infiltration and suggest MFG-E8 as a novel therapeutic potential for ALI.

Mfge8 suppresses airway hyperresponsiveness in asthma by regulating smooth muscle contraction

“…We have previously found no differences in lung inflammation in bleomycin-treated Mfge8 −/− mice (29). Other studies have shown that Mfge8 −/− mice develop exaggerated lung inflammation after intratracheal LPS instillation or after reperfusion injury secondary to intestinal ischemia (42,43). Given the important role of the immune system in asthma, we were curious to determine whether there would be differences in airway inflammation in Ova-challenged Mfge8 −/− mice.…”

Efferocytosis and Lung Disease

“…50 In lipopolysaccharide-induced acute ALI, gene-targeted mice lacking MFG-E8 showed increased neutrophil infi ltration, increased infl ammatory cytokines, and decreased survival. 51 Resolvin E1 enhances apoptosis and uptake of human neutrophils induced by microbe ingestion and reduced lung infl ammation in three murine models. 52 Conversely, instillation of apoptotic cells into the lungs of mice following bleomycin lung injury reduced infl ammatory cytokine production and lung fi brosis via hepatocyte growth factor-dependent mechanisms, resulting in increased survival.…”

Розвиток Імунної Відповіді При Стафілококовій Пневмонії (Частина 5)

“…Также внутрибрюшинное введение мышам экзогенного опсонина -факто-ра 8 эпидермального фактора роста, ассоциирован-ного с глобулой молочного жира (milk fat globule-EGF factor 8 protein -MFG-E8), способствующего эффероцитозу, сопровождается снижением уров-ня продукции провоспалительных цитокинов в ткани легких, уменьшением объема поражения легких и уровня летальности экспериментальных мышей [19]. С другой стороны, при остром LPS-индуцированном поражении легких мышей с нока-утным геном Mfg-E8 наблюдаются высокая степень инфильтрации нейтрофилами очага поражения лег-ких, более высокий уровень провоспалительных ци-токинов и низкий уровень выживаемости экспери-ментальных животных [7]. Также введение TNF-α сопровождается подавлением активности клиренса апоптотических клеток из легких и, вероятно, ассо-циированным с данным феноменом увеличением уровня воспаления легких [12].…”