Journal of Gastroenterology and Hepatology (2001) 16, 438–444 liver disease. 9–12 Kupffer cells produce a large range of cytokines including tumor necrosis factor-a (TNF-a), transforming growth factor-b1 (TGF-b1), granulocyte macrophage colony stimulating factor (GMCSF) and various interleukins, such as interleukin-6 (IL-6) and interleukin-1a (IL-1a), which may contribute to hepatic injury, inflammation and fibrosis. 13–23 In chronic iron overload, liver injury and fibrosis occur in the absence of significant inflammation. Kupffer cells may contribute to iron-induced liver injury via the production of cytokines, 15,24–26 possibly as a result of phagocytosis of hepatocellular debris 18,27 or exposure to products of lipid peroxidation, which in turn may acti- vate hepatic stellate cells. 15,28,29 While cytokines are INTRODUCTION Kupffer cells are the resident macrophages of the sinu- soids in the liver and represent approximately 30% of the sinusoidal cells. 1 Kupffer cells are a heterogeneous population of cells in terms of size and function. Kupffer cells in zone 1 of the liver lobule are larger and exhibit positive staining with antibodies to the surface and cytoplasmic antigens ED1 and ED2 compared with smaller Kupffer cells located in zone 3, which are pre- dominantly ED2 negative. 2–8 Much evidence has accu- mulated in support of a role for Kupffer cells in liver injury and fibrosis. Kupffer cell proliferation and acti- vation has been observed early in various models of LIVER CIRRHOSIS: GASTROPATHY AND IRON OVERLOAD Iron overload impairs pro-inflammatory cytokine responses by Kupffer cells JOHN K OLYNYK* AND SHARON L CLARKE † *Department of Medicine,The University of Western Australia, Nedlands and † Department of Gastroenterology, Fremantle Hospital, Fremantle,Western Australia Abstract Aim: The aim of the present study was to determine the effect of chronic iron overload on Kupffer cell cytokine production. Methods: Kupffer cells were isolated from rats that were fed either a control or iron-supplemented diet for 12 months. Cytokine mRNA and protein levels were determined by using a ribonuclease protection assay and ELISA, respectively. Results: Baseline levels of tumor necrosis factor-a, transforming growth factor-b1, interleukin-6 and granulocyte macrophage colony stimulating factor were similar in iron-loaded and control Kupffer cells. Following the addition of lipopolysaccharide to control cells, tumor necrosis factor-alpha, interleukin- 1a and interleukin-6 mRNA levels increased. Tumor necrosis factor-alpha mRNA and protein levels were reduced by 40 and 60%, respectively, in iron-loaded cells compared with controls following the addition of lipopolysaccharide. Interleukin-6 mRNA levels in iron-loaded Kupffer cells were also reduced. Granulocyte macrophage colony stimulating factor mRNA levels remained unchanged in con- trols, but were significantly elevated in iron-loaded cells. Tumor growth factor-b1 mRNA and protein levels were similar in control and iron-loaded cells. Conclusion: Deposition of iron in Kupffer cells in chronic dietary iron overload results in an impaired pro-inflammatory cytokine response to lipopolysaccharide. Our observations may have relevance to the altered immune function observed in chronic iron-overload syndromes. © 2001 Blackwell Science Asia Pty Ltd Key words: cytokine, immunocytochemistry, interleukin-6, iron, Kupffer cell, lipopolysaccharide, tumor necrosis factor-a. Correspondence: Assoc. Prof. J Olynyk, University Department of Medicine, PO Box 480, Fremantle 6959, Western Australia, Australia. Email: jolynyk@cyllene.uwa.edu.au Accepted for publication 8 December 2000.