ABSTRACT
Chronic low-grade inflammation of adipose tissue plays a crucial role in the pathophysiology of obesity. Immunohistological microscopic analysis in obese fat tissue has demonstrated the infiltration of several immune cells such as macrophages, but dynamics of immune cells have not been fully elucidated and clarified. Here, by using intravital multiphoton imaging technique, to our knowledge for the first time, we analyzed and visualized the inflammatory processes in adipose tissue under high-fat and high-sucrose (HF/HS) diet with lysozyme M-EGFP transgenic (LysM(EGFP)) mice whose EGFP was specifically expressed in the myelomonocytic lineage. Mobility of LysM(EGFP)-positive macrophages was shown to be activated just 5 d after HF/HS diet, when the distinct hypertrophy of adipocytes and the accumulation of macrophages still have not become prominent. Significant increase of S100A8 was detected in mature adipocyte fraction just 5 d after HF/HS diet. Recombinant S100A8 protein stimulated chemotactic migration in vitro and in vivo, as well as induced proinflammatory molecules, both macrophages and adipocytes, such as TNF-α and chemokine (C-C motif) ligand 2. Finally, an antibody against S100A8 efficiently suppressed the HF/HS diet-induced initial inflammatory change, i.e., increased mobilization of adipose LysM(EGFP)-positive macrophages, and ameliorated HF/HS diet-induced insulin resistance. In conclusion, time-lapse intravital multiphoton imaging of adipose tissues identified the very early event exhibiting increased mobility of macrophages, which may be triggered by increased expression of adipose S100A8 and results in progression of chronic inflammation in situ.
Subject(s)
Adiposity , Calgranulin A/metabolism , Macrophages/pathology , Obesity/metabolism , Obesity/pathology , 3T3-L1 Cells , Adipocytes/drug effects , Adipocytes/metabolism , Adipocytes/pathology , Adiposity/drug effects , Animals , Antibodies/pharmacology , Calgranulin A/genetics , Chemotaxis/drug effects , Diet, High-Fat , Epididymis/drug effects , Epididymis/pathology , Green Fluorescent Proteins/metabolism , Inflammation/pathology , Insulin/pharmacology , Lipopolysaccharides/pharmacology , Macrophages/drug effects , Macrophages/metabolism , Male , Mice , Microscopy, Fluorescence, Multiphoton , Muramidase/metabolism , Obesity/blood , RNA, Messenger/genetics , RNA, Messenger/metabolism , Up-Regulation/drug effectsABSTRACT
Recent studies have shown that certain types of transformed cells are extruded from an epithelial monolayer. However, it is not known whether and how neighbouring normal cells play an active role in this process. In this study, we demonstrate that filamin A and vimentin accumulate in normal cells specifically at the interface with Src- or RasV12-transformed cells. Knockdown of filamin A or vimentin in normal cells profoundly suppresses apical extrusion of the neighbouring transformed cells. In addition, we show in zebrafish embryos that filamin plays a positive role in the elimination of the transformed cells. Furthermore, the Rho/Rho kinase pathway regulates filamin accumulation and filamin acts upstream of vimentin in the apical extrusion. This is the first report demonstrating that normal epithelial cells recognize and actively eliminate neighbouring transformed cells and that filamin is a key mediator in the interaction between normal and transformed epithelial cells.