Dietary n-3 fatty acids increase spleen size and postendotoxin circulating TNF in mice; role of macrophages, macrophage precursors, and colony-stimulating factor-1.

W.L. Blok, M.F.T.R. de Bruijn, P.J.M. Leenen, W.M.C. Eling, N. van Rooijen, R. Stanley, W.A. Buurman, J.W.M. van der Meer

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Abstract

Dietary n-3 fatty acids increase spleen size and postendotoxin circulating TNF in mice; role of macrophages, macrophage precursors, and colony-stimulating factor-1.

Blok WL, de Bruijn MF, Leenen PJ, Eling WM, van Rooijen N, Stanley ER, Buurman WA, van der Meer JW.

Department of General Internal Medicine, University Hospital Nijmegen, The Netherlands.

In experimental studies in mice, dietary supplementation with n-3 fatty acids (FA) alleviates inflammation and increases resistance to infection. Nevertheless, TNF production capacity was found to be increased in n-3 FA-fed mice. We previously found increased relative spleen weights in n-3 FA-fed mice. In this study, the nature of this increased spleen size was further investigated. Spleen cellularity was increased significantly in mice fed n-3 FA (fish oil 15% w/w), compared with controls fed corn oil (15%) or normal lab chow (p < 0.05). Experiments with T cell-deficient nude mice and experiments using macrophage depletion through liposomal dichloromethylene-biphosphonate revealed that the increase in spleen cellularity is T cell independent and largely due to macrophage accumulation in the spleen. Accumulation of marginal zone and red pulp macrophages was histologically and immunohistochemically confirmed. n-3 FA induced peripheral blood monocytosis and an aspecific increase in bone marrow cellularity. Postendotoxin circulating TNF concentrations were increased significantly in n-3 FA-fed mice compared with controls. Splenectomy did not abolish this increase in circulating TNF. However, after macrophage depletion through liposomal dichloromethylene-biphosphonate, circulating TNF was not detectable after endotoxin challenge. Circulating concentrations of CSF-1 did not differ between the various experimental groups. It is suggested that the cellular changes observed relate to increased constitutive production of TNF.
Original languageEnglish
Pages (from-to)5569-5573
JournalJournal of Immunology
Volume157
Publication statusPublished - 1 Jan 1996

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