Novel Mode of Interference with Nuclear Factor of Activated T-cells Regulation in T-cells by the Bacterial Metaboliten-Butyrate

Abstract

The transcription factor nuclear factor of activated T-cells (NF-AT) plays an essential role in the activation of many early immune response genes. A dynamic equilibrium between calcineurin and cellular kinases controls its phosphorylation and thus regulates its activity by determining its subcellular localization. Here, we demonstrate that T-cell activation in the presence of the bacterial metabolite n-butyrate, which leads to inhibition of interleukin-2 transcription, is characterized by the maintenance of the activity of counter-regulatory kinases glycogen synthase kinase 3 and protein kinase A as well as persistence of intracellular cAMP levels, whereas calcium response and mitogen-activated protein kinase activation were indistinguishable from cells stimulated in the absence of n-butyrate. Nuclear binding of NF-AT was decreased but other transcription factors implicated in interleukin-2 expression such as AP1 and nuclear factor B were unaffected. The effect on NF-AT binding appeared to be the result of increased nuclear export because the export inhibitor leptomycin B completely restored nuclear binding of NF-AT. We, therefore, provide first evidence for interference with NF-AT regulation alternative to the currently understood inhibition of nuclear import. This mechanism might represent a bacterial strategy to subvert host defense, which could be of particular clinical importance in the gastrointestinal tract where high amounts of nbutyrate are physiologically present.

Butyrate in vitro immune-modulatory effects might be mediated through a proliferation-related induction of apoptosis

“…We examined the effect of butyrate on ERK, JNK and p38 and also on the NF-kB signalling pathways activated by LPS and Con A, since they have been described to be directly involved in the control of the expression of IL-8 in epithelial cells (Böcker et al, 2000), several cytokines in T-lymphocytes (Feske et al, 2001;Ortega-Pé rez et al, 2005;Paccani et al, 2002) and most of the inflammatory markers expressed in macrophages (Comalada et al, 2003a(Comalada et al, , 2003bXaus et al, 2000bXaus et al, , 2001. NFAT signalling pathway clearly participates in IL-2 production in lymphocytes, and it has been even described to be affected by butyrate in some studies (Diakos et al, 2002); however, we decided not to check this signalling pathway since its role in macrophages or epithelial cells, if any, is negligible (Comalada et al, 2006). Unfortunately, no modification on any of the tested signalling pathways was observed after butyrate treatment in macrophages and T-cells.…”

Inhibition of Histone Deacetylase Suppresses Osteoclastogenesis and Bone Destruction by Inducing IFN-β Production

“…Translocation of NFATc1 to nuclei is regulated by Ca 2ϩ /calcineurindependent phosphatase pathway (47). Recently, it is shown that HDI NaB inhibited IL-2 transcription by affecting cellular localization of NFATc1 protein (48). Interestingly, it is reported that in addition to calcium-mediated signals, the TRAF6 and c-fos pathways were required in RANKL-induced NFATc1 expression (6).…”

Anti-cancer effects of butyrate: use of micro-array technology to investigate mechanisms

“…Faust et al (2001) have argued that the anti-inflammatory actions of butyrate in the intestinal mucosa are unlikely to occur by direct regulation of cytokine-induced anti-inflammatory protein expression. Recent data from Diakos et al (2002) indicate that at relatively low concentrations (1 mM) butyrate inhibits production of the growth factor IL-2 (which is required for expansion of antigen-specific T cells) by decreasing nuclear binding of the transcription factor nuclear factor of activated T cells in both Jurkat cells and in primary T cells.…”