289 Braz J Med Biol Res 35(3) 2002 Iodide, Fas, Fas-L and Bcl-w mRNA expression in thyroid Brazilian Journal of Medical and Biological Research (2002) 35: 289-295 ISSN 0100-879X Effect of iodide on Fas, Fas-ligand and Bcl-w mRNA expression in thyroid of NOD mice pretreated with methimazole Disciplina e Laboratório de Imunologia, Departamento de Clínica Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brasil L.H.B. Boechat, C.A. Vilella and R.L. Zollner Abstract Nonobese diabetic (NOD) mice and a derived strain, NOD.H.2h4, have been used as a model for experimental spontaneous thyroiditis and thyroiditis induced by iodide excess after a goiter-inducing pe- riod. Some authors have proposed that iodide, given after methima- zole or propylthiouracil, is capable of inducing apoptosis in thyroid cells and that anti-thyroid drugs can modulate the expression of apoptosis components such as Fas and its ligand (Fas-L). Here we evaluated the effect of potassium iodide (20 µg/animal for 4 days, ip) given to NOD mice at the 10th week of life after exposure to methima- zole (1 mg/ml) in drinking water from the 4th to the 10th week of life. Fas, Fas-L and Bcl-w expression were analyzed semiquantitatively by RT-PCR immediately after potassium iodide administration (group MI44D) or at week 32 (MI32S). Control groups were added at 10 (C10) and 32 weeks (C32), as well as a group that received only methimazole (CM10). An increase in the expression of Fas-L and Bcl- w (P<0.01, ANOVA) was observed in animals of group MI44D, while Fas was expressed at higher levels (P = 0.02) in group C32 (72.89 ± 47.09 arbitrary units) when compared to group C10 (10.8 ± 8.55 arbitrary units). Thus, the analysis of Fas-L and Bcl-w expression in the MI44D group and Fas in group C32 allowed us to detect two different patterns of expression of these apoptosis components in thyroid tissue of NOD mice. Correspondence R.L. Zollner Disciplina e Laboratório de Imunologia Departamento de Clínica Médica FCM, UNICAMP Caixa Postal 6111 13081-970 Campinas, SP Brasil Fax: + 55-19-3289-3709 E-mail: zollner@unicamp.br Research supported by CNPq (No. 141759/95-0). L.H.B. Boechat was the recipient of a CNPq fellowship. Publication supported by FAPESP. Received June 8, 2001 Accepted January 29, 2002 Key words · Thyroiditis · Nonobese diabetic mice · Apoptosis · Methimazole · Iodide · Fas mRNA · Fas-L mRNA · Bcl-w mRNA Introduction Over the last decade, apoptosis has be- come one of the main topics of interest in the biological sciences. This phenomenon is criti- cal to life and disease processes, playing a key role in regulatory activities, including immunology and immunopathology (1). Fas (CD95) and its natural ligand (Fas-L) are transmembrane proteins belonging to the fam- ily of tumor necrosis factor and ligands. The association of Fas-L with cells expressing Fas leads to apoptosis through the activation of a complex intracellular signaling path- way, resulting in cell death (2). Bcl-w is one of the members of the Bcl-2 family recently described as one of the anti-apopto- tic proteins constitutively expressed in many