Superantigen-induced corticosteroid resistance of human T cells occurs through activation of the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK-ERK) pathway

Abstract

Background Microbial superantigens induce human T-cell resistance to corticosteroids. Objective Understanding the molecular pathways resulting in corticosteroid-resistant T cells is important because this condition can complicate the treatment of inflammation. Methods The response of human PBMCs to steroids was assessed by using proliferation assays after stimulation with superantigens or anti-CD3 in the presence of various kinase inhibitors. Glucocorticoid receptor alpha (GCRalpha) localization was defined on the basis of intracellular staining. Protein phosphorylation was measured by means of Western blotting. Results In the current study we found that PBMCs stimulated with superantigen, but not anti-CD3, induced corticosteroid-resistant T cells. However, the purified T cells stimulated either with staphylococcal enterotoxin B (SEB) or anti-CD3 are susceptible to corticosteroid inhibition. These results imply that signals on antigen-presenting cells might act in concert with the T-cell receptor to cause steroid resistance. Blockade of CD40-CD40 ligand interaction had no effect on superantigen-induced corticosteroid resistance. However, CD28 costimulation with T-cell receptor activation induced corticosteroid resistance of human T cells in a dose-dependent manner. Superantigen stimulation, compared with anti-CD3 stimulation, was found to induce a more rapid and sustained phosphorylation of mitogen-activated extracellular signal-regulated kinase (ERK). Treatment with PD98059…