5, 10?6 M of oestradiol inhibited apoptosis of Fas-expressing cells to a similar extent to 10 g/ml of anti-FasL monoclonal antibody (mAb) treatment. expression of Fas ligand (FasL) in activated SLE T cells at the both protein and mRNA levels. In contrast, testosterone increased FasL expression dose-dependently in SLE T cells stimulated with PMA plus ionomycin. The inhibitory effect of oestradiol on FasL expression was mediated through binding to its receptor, as co-treatment of tamoxifen, an oestrogen receptor inhibitor, completely nullified the oestradiol-induced Senegenin decrease in FasL mRNA expression. Moreover, pre-treatment of FasL-transfected L5178Y cells with either oestradiol or anti-FasL antibody inhibited significantly the apoptosis of Fas-sensitive Hela cells when two types of cells were co-cultured. These data suggest that oestrogen inhibits activation-induced apoptosis of SLE T cells by down-regulating the expression of FasL. Oestrogen inhibition of T cell apoptosis may allow for the persistence of autoreactive T cells, thereby exhibiting the detrimental action of oestrogen on SLE activity. Keywords: apoptosis, estrogen, lupus, T cells, testosterone Introduction Defective control of T cell apoptosis is considered to be one of the pathogenetic mechanisms in systemic lupus erythematosus (SLE). A number of genetic and environmental factors contribute to the T cell defect in SLE; however, the greatest risk factor for developing SLE is usually female gender. In Rabbit Polyclonal to KCY addition, SLE activity flares up Senegenin after administration of female sex hormones, such as oestrogen [1]. Conversely, anti-oestrogenic brokers, including danazole and prolactin, are effective in the amelioration of SLE symptoms [2,3]. Several studies have implicated oestrogen as one of the important factors responsible for the development and exacerbation of SLE [1,4C6], as it stimulates interferon (IFN)-, interleukin (IL)-1, IL-5, IL-6 and IL-10 secretion, supports B cell survival and enhances antibody production [1]. Oestrogen has also been shown to accelerate immune complex glomerulonephritis in autoimmune Murphy Roths Large lymphoproliferation (MRL lpr/lpr) mice [4]. Further, it up-regulates Bcl-2 expression, blocks tolerance induction of naive B cells [5] and enhances the production of anti-double-stranded Senegenin DNA (dsDNA) antibody and immunoglobulin G in peripheral blood mononuclear cells of SLE patients [6]. Despite these reports, the exact role of oestrogen in SLE T cell apoptosis Senegenin has yet to be documented. The Fas/Apo-1 molecule is usually a cell surface receptor belonging to the tumour necrosis factor (TNF) receptor superfamily and is expressed constitutively in various tissues [7,8]. The triggering of Fas by its ligand results in quick induction of apoptosis in susceptible cells [7,8]. On the other hand, the Fas ligand (FasL), which is usually expressed in activated T cells, dendritic cells and natural killer (NK) cells [8], is usually a 40-kDa type II integral membrane protein and a member of the TNF superfamily [8,9]. It has been reported that mice transporting the lpr and generalized lymphoproliferative disease (gld) mutations have defects in the Fas and FasL gene, respectively, developed lymphadenopathy and suffered from a SLE-like Senegenin autoimmune diseases [9,10]. Therefore, dysfunction in the Fas/FasL system could represent one of the crucial factors responsible for the apoptotic defect of SLE T cells. Activation-induced cell death (AICD) is a process of apoptosis induced by repeated activation of T cells by their cognate antigen [11]. In T cells, the principal mechanism of AICD is the co-expression of Fas and FasL, followed by engagement of Fas, and a subsequent delivery of a death-inducing transmission [8C10]. T cells of SLE patients can be activated by self-antigens such as dsDNA and nucleosomes [12], and in mice, nucleosomes were reported to act as effective initiators of autoreactive T cell development [13]. Moreover, T cell responses to nucleosomes were increased in SLE patents [14]. If Fas-mediated apoptosis of T cells is usually defective, activated T cells reactive to self-antigens may escape apoptosis and proliferate abnormally, resulting in the destruction of target tissues. Given that oestrogen triggers SLE activity, which correlates with an apoptotic defect of T cells [15], it can be postulated that oestrogen may impact the survival of activated T cells and their associated molecules, even though direct effects of oestrogen on SLE T cells have not yet been tested. The aim of this study was to determine whether oestrogen functions as a regulator of AICD and FasL expression in SLE T cells. Materials and methods Isolation and culture of T cells This work was approved by the institutional review committees of the Catholic Medical Center (Seoul, Republic of Korea). Heparinized peripheral blood (100 ml) was collected aseptically from SLE patients. Informed consent for usage of cells was obtained from all the SLE patients included in this study. Peripheral blood mononuclear cells were isolated by density gradient centrifugation on a Ficoll-Hypaque. Sorting of CD3+, CD4+ and CD8+ T cells (1 105 cells) was performed using anti-CD3, anti-CD4.