Summary Interleukin (IL)‐17 is a pro‐inflammatory cytokine produced by recently described T helper type 17 (Th17) cells, which have critical role in immunity to extracellular bacteria and the pathogenesis of several autoimmune disorders. IL‐6 and transforming growth factor (TGF)‐β are crucial for the generation of Th17 cells in mice, while the production of IL‐17 is supported by various cytokines, including IL‐23, IL‐1β, IL‐21, IL‐15 and tumour necrosis factor (TNF)‐α. In this study, the influence of a multifunctional cytokine, macrophage migration inhibitory factor (MIF), on IL‐17 production in mice was investigated. Treatment of lymph node cells (LNCs) with recombinant MIF up‐regulated mitogen‐stimulated IL‐17 expression and secretion. Additionally, LNCs from MIF knockout mice (mif−/−) had severely impaired production of IL‐17, as well as of IL‐1β, IL‐6, IL‐23 and TGF‐β. When stimulated with recombinant IL‐1β, IL‐23 or TNF‐α, mitogen‐triggered mif−/− LNCs were fully able to achieve the IL‐17 production seen in wild‐type (WT) LNCs, while the addition of IL‐6 and TGF‐β had no effect. Finally, after injection of mice with complete Freund’s adjuvant, secretion of IL‐17 as well as the number of IL‐17‐positive cells was significantly lower in the draining lymph nodes of mif−/− mice in comparison with WT mice. The effect of MIF on IL‐17 production was dependent on p38, extracellular signal‐regulated kinase (ERK), Jun N‐terminal kinase (JNK) and Janus kinase 2/signal transducer and activator of transcription 3 (Jak2/STAT3), and not on nuclear factor (NF)‐κB and nuclear factor of activated T cells (NFAT) signalling. Bearing in mind the contribution of MIF and IL‐17 to the pathology of inflammatory and autoimmune disorders, from the results presented here it seems plausible that targeting MIF biological activity could be a valid therapeutic approach for the treatment of such diseases.
Background: Diabetes is characterized by progressive failure of insulin producing beta cells. It is well known that both saturated fatty acids and various products of immune cells can contribute to the reduction of beta cell viability and functionality during diabetes pathogenesis. However, their joint action on beta cells has not been investigated, so far. Therefore, we explored the possibility that leukocytes and saturated fatty acids cooperate in beta cell destruction.
The health-promoting effects of various constituents of the olive tree (Olea europaea) are mainly associated with hypoglycaemic and insulinsensitising activities and have been widely demonstrated in the metabolic syndrome and type 2 diabetes. However, their biological activity in autoimmune type 1 diabetes (T1D) is poorly characterised. Therefore, the influence of O. europaea-derived components present in dry olive leaf extract (DOLE) was examined in two established preclinical models of human T1D, which differ in some aspects of diabetogenesis: multiple low-dose streptozotocin-induced diabetes in susceptible C57BL/6 and CBA/H mouse strains; cyclophosphamide-accelerated diabetes in non-obese diabetic mice. In both T1D models, in vivo administration of DOLE significantly reduced clinical signs of diabetes (hyperglycaemia and body weight loss) and led to complete suppression of histopathological changes in pancreatic islets. In line with these, insulin expression and release were restored in DOLE-treated mice. Interestingly, inducible NO synthase expression and NO production were significantly elevated in peripheral tissues but were down-regulated within the local environment of the endocrine pancreas. This interference was reflected in NO-mediated suppression of T lymphocyte proliferation and lower production of the proinflammatory cytokines interferon-g, IL-17 and TNF-a in the spleen, with subsequent blockade of b-cell destruction. The results suggest that DOLE interferes with development of autoimmune diabetes by downregulating production of proinflammatory and cytotoxic mediators. Therefore, the potential use of a DOLE-enriched diet for prophylaxis/treatment of human T1D, and possibly other autoimmune diseases, is worthy of further investigation. Type 1 diabetes: Olea europaea leaves: Cytokines: Nitric oxideThe term diabetes mellitus is used to describe a variety of chronic metabolic disorders characterised by elevated blood glucose levels now afflicting 3 % of the world population (1,2) . Diabetes mellitus can broadly be classified into two main types based on individual aetiologies. Type 1 diabetes (T1D) that accounts for approximately 5-10 % of all cases of diabetes, is an inflammatory autoimmune disease in which pancreatic insulin-producing b-cells are selectively destroyed by cells of the immune system (3) culminating in a state of hypoinsulinaemia and hyperglycaemia (4) . Type 2 diabetes (T2D) that is estimated to represent 90 -95 % of all cases is due to b-cell failure or various degrees of insulin resistance (5) . The only possible cure for T1D is control of the T cell autoimmunity against b-cells together with recovery and/or replacement of the destroyed b-cell mass. Over many years, various immunomodulatory regimens were tested with the aim of blocking autoimmunity against b-cell mass and promoting b-cell preservation. Despite considerable progress in the management of T1D with conventional drugs, a single effective immune-based therapeutic approach has not been identified so far (2,6 -9) . This pro...
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