Glucose modulates handling of apoptotic cells by mesangial cells: involvement of TGF-beta1.
Glucose stimulates proapoptotic signalling pathways in mesangial cells. Studies focused on inflammatory glomerular injury have demonstrated that removal of apoptotic mesangial cells occurs by neighbouring non-apoptotic mesangial cells. The aim of this study was to define the effect of ambient glucose concentration on mesangial handling of apoptotic cells, and in addition to examine the response made by the mesangial cell. We used a co-culture model in which neutrophils aged overnight to induce apoptosis, or apoptotic mesangial cells, labelled with a fluorescent dye, were added to mesangial cells to study phagocytosis. Exposure of mesangial cells to an ambient glucose concentration of 25 mM D-glucose before addition of apoptotic cells led in an increase in mesangial cell phagocytosis. Ingestion of apoptotic cells was inhibited by blocking alpha v beta 3 integrin-vitronectin receptor or thrombospondin-1. Furthermore, glucose-dependent stimulation of phagocytosis was inhibited by a blocking antibody to TGF-beta1. Co-culture of apoptotic cells with mesangial cells stimulated synthesis of TGF-beta1 as compared to freshly isolated neutrophils. Increased TGF-beta1 synthesis was dependent on direct contact between the two cell types but was not dependent on phagocytosis of apoptotic cells, as TGF-beta1 generation was not affected by inhibition of the thrombospondin-1 pathway. We propose a model in which apoptotic cell binding but not phagocytosis stimulates enhanced mesangial cell TGF-beta1 synthesis. Furthermore phagocytosis, which involves the thrombospondin-1 pathway, is uncoupled from binding of apoptotic cells, which stimulated TGF-beta1 synthesis.
Khera
Tarnjit K
TK
Institute of Nephrology, School of Medicine, Cardiff University, Wales, UK.
Martin
John
J
Riley
Stephen G
SG
Steadman
Robert
R
Phillips
Aled O
AO
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D005947:Glucose / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D050527:Mesangial Cells / Q000166:cytology / Q000378:metabolism*; D008954:Models, Biological; D009504:Neutrophils / Q000502:physiology; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology; D051381:Rats; D015398:Signal Transduction; D019700:Thrombospondin 1 / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis* / Q000187:drug effects / Q000378:metabolism
D005456:Fluorescent Dyes; D039302:Integrin alphaVbeta3; D009842:Oligopeptides; D019700:Thrombospondin 1; D053773:Transforming Growth Factor beta1; C046617:arginyl-glycyl-aspartyl-serine; D005947:Glucose