Considerable efforts have been invested to understand the mechanisms by which

Considerable efforts have been invested to understand the mechanisms by which pro-inflammatory cytokines mediate the demise of -cells in type 1 diabetes but much less attention has been paid to the role of anti-inflammatory cytokines as potential cytoprotective agents in these cells. death might ensue. However, an increased generation of pro-inflammatory cytokines may not be the sole factor that drives -cell demise since a concomitant loss of anti-inflammatory cytokine signaling could also contribute. Anti-inflammatory cytokines are broadly antagonistic to their pro-inflammatory counterparts and are able to diminish inflammatory responses and to protect cells from otherwise cytotoxic insults. The importance of anti-inflammatory cytokines in protecting -cells is still open to debate although there is evidence that the production of these molecules may be reduced in type 1 diabetes.12-15 If this is also the case within the islet milieu, then this would tend to exacerbate any detrimental effects of pro-inflammatory cytokines. In the present review, we assess the current understanding of the effects of anti-inflammatory cytokines on the pancreatic -cell, specifically focusing on 3 key molecules (IL-4, IL-13 and IL-10) which have been implicated in the control of -cell viability. We note that other immune factors with anti-inflammatory properties may also be important in control of -cell function (e.g., TGF-, sIL-1ra, IL-11 and IL-35) and that the actions of some of these molecules have been reviewed elsewhere.16,17 Anti-inflammatory Cytokines and Type 1 Diabetes Anti-inflammatory cytokines are secreted by a number of immune cell subtypes including CD4+ Th2 cells, regulatory T cells, M2 macrophages, mast cells and regulatory B-cells. Many of these have been implicated as mediators of beneficial buy 867160-71-2 responses in the context of type 1 diabetes although most emphasis has been placed on the influence of T-helper and T-regulatory cells. For example, it is suggested that during the pathogenesis of human type 1 diabetes, a polarization of CD4+ T-helper cells occurs, leading to a predominance of the Th1 phenotype with a concomitant down-regulation of the Th2 response.18,19 Under such conditions, PBMCs isolated from the blood of T1D patients (or their first degree relatives) exhibit a Rabbit polyclonal to AKAP7 reduction in anti-inflammatory cytokine secretion when compared to healthy controls.12-15 The significance of this switch has been emphasized by the demonstration that administration of a cocktail of cytokines secreted from Th2 cells (including IL-4, IL-10 and IL-13) was protective against diabetes progression in rodents. Hence, numerous studies have revealed that treatment of NOD mice (a rodent model of type 1 diabetes) with IL-4, IL-13 or IL-10 delays the onset of spontaneous diabetes and also reduces its incidence.20-24 Furthermore, T-cells isolated from the blood of such mice exhibit a more Th2-like phenotype, releasing higher levels of anti-inflammatory cytokines than those of control NOD mice.22,25 The incidence of diabetes can also be delayed in the NOD mouse by generating animals that specifically express IL-4 in -cells26 or by the injection of dendritic cells which constitutively express this cytokine27 However, other studies have found that overexpression of IL-10 in islet endocrine cells may have little effect on diabetes progression, 28 and in some cases it can accelerate the disease process.29 This paradoxical effect may be explained by differences in factors such as the local concentration and localization of buy 867160-71-2 IL-10 between the study designs,30 and highlights the complexity in the function of these cytokines in diabetes. Given the body of evidence above, it buy 867160-71-2 may be significant for disease pathogenesis, that RT-PCR analysis has revealed that anti-inflammatory cytokines are expressed at only low levels in the immune cell infiltrates of 4 rodent models (NOD mouse, BB rat, buy 867160-71-2 Komeda rat, LEW.1AR1-iddm rat) and in human patients with type 1 diabetes.31 While many of their beneficial effects undoubtedly stem from the anti-inflammatory impact.