Genomic and non-genomic effects of different glucocorticoids on mouse thymocyte apoptosis Stefano Bruscoli, Rosa Di Virgilio, Valerio Donato, Enrico Velardi, Monia Baldoni, Cristina Marchetti, Graziella Migliorati, Carlo Riccardi ⁎ Department of Clinical and Experimental Medicine, Section of Pharmacology, Perugia University Medical School, Via del Giochetto, 06122 Perugia, Italy Received 4 April 2005; received in revised form 25 October 2005; accepted 26 October 2005 Available online 1 December 2005 Abstract Glucocorticoids, widely used therapeutic agents for several pathologies, act upon diverse cells and tissues, including the lympho-haemopoietic system. Glucocorticoid-mediated apoptosis has been described as one of the mechanisms underlying their pharmacological and physiological effects. Glucocorticoids induce apoptosis in thymocytes through genomic and non-genomic signals. We tested thymocyte apoptosis rates as induced by a panel of glucocorticoids. Using four glucocorticoids that are widely adopted in clinical practice we compared their induction of thymocyte apoptosis and activation of non-genomic and genomic signals, including phosphatidylinositol–specific phospholipase C (PI–PLC), caspase-8, -9 and -3, and Glucocorticoid-Induced Leucine Zipper (GILZ). GILZ is a protein that is rapidly induced by glucocorticoids treatment and involved in apoptosis modulation. Results indicate different glucocorticoids have different apoptotic activity which is related to their ability to induce both genomic, evaluated as caspases activation and GILZ expression, and non-genomic effects, evaluated as PI–PLC phosphorylation. © 2005 Elsevier B.V. All rights reserved. Keywords: Glucocorticoid; Glucocorticoid-induced leucine zipper (GILZ); Apoptosis; Thymocyte; Genomic effect; Non-genomic effect 1. Introduction Although synthetic glucocorticoids are used as therapeutic agents in several acute and chronic inflammatory and autoimmune diseases, in organ transplantation and in the treatment of leukemia and lymphoma (Barnes and Adcock, 1993; Cupps and Fauci, 1982; Hoffman, 1993), systemic side effects, e.g. excessive immunosuppression and metabolic disturbances, limit their use as long-term therapy. The molecular mechanisms underlying many of the benefits and adverse side effects of glucocorticoids are still today unknown but always involve the glucocorticoid receptor, a transcription factor which, after activation by glucocorticoids, translocates into the nucleus and modifies gene expression by either transactivation or transrepression (Barnes and Adcock, 1993; Cupps and Fauci, 1982). The study of the effects of new synthetic glucocorticoids with different affinity for the glucocorticoid receptor is important, considering that glucocorticoid actions are mediated by interactions with its receptor. Glucocorticoids influence the growth and differentiation of haemopoietic cells including T lymphocytes and thymocytes through several mechanisms including apoptosis, which is triggered by genomic (transcription dependent) and non- genomic (non-transcription dependent) stimuli (Ashwell et al., 2000; Cifone et al., 1999; Wyllie, 1980). Among the genes regulated by glucocorticoids, GILZ (Glucocorticoid-Induced Leucine Zipper) is rapidly up-regulated mainly in lymphoid organs at mRNA and protein levels by dexamethasone (D'Adamio et al., 1997). GILZ provides a direct genomic mechanism through which glucocorticoids induce thymocyte apoptosis (Delfino et al., 2004). Thymocyte apoptosis depends upon activation of different caspase pathways, such as caspase-8/3, a membrane receptor- dependent (extrinsic pathway), and caspase-9/3, a stress signal- dependent (intrinsic pathway) (Alam et al., 1997; Budihardjo et European Journal of Pharmacology 529 (2006) 63 – 70 www.elsevier.com/locate/ejphar ⁎ Corresponding author. Department of Clinical and Experimental Medicine Section of Pharmacology, University of Perugia Via del Giochetto 06100 Perugia, Italy. Tel.: +39 075 5857467; fax: +39 075 5857405. E-mail address: riccardi@unipg.it (C. Riccardi). 0014-2999/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2005.10.053