Stress protein expression in primary and immortalized cultures of human thyroid cells: a model system for the study of stress proteins in the pathogenesis of autoimmune thyroid disease.

Stress has, for many years, been linked to the onset of autoimmune disease and, in particular, autoimmune thyroid disease (AITD). Whilst the exact mechanism of this association is unknown, it is clear that episodes of stress can induce profound changes in the immune system. More specifically, recent studies from several laboratories have shown an association between the expression of stress proteins and, particularly, the Hsp70 family with AITD. Our own studies describe a thyroid-specific Hsp70 which shares antigenicity with the key thyroid autoantigen, thyroid peroxidase. Further studies on the molecular basis for this observation are, however, hampered by the lack of a suitably validated thyroid cell model. In this paper we compare the response of primary cultures of human thyrocytes to hyperthermia with the response seen in the immortalized human thyroid cell line HTori3. Both cell types responded in a broadly similar manner, synthesizing proteins from two of the major stress protein families, Hsp70 and Hsp90. In the primary human thyrocyte cultures the 70 kDa proteins showed a 7.5-fold increase and the 90 kDa proteins a 2.7-fold increase with hyperthermia whilst in the HTori3 cells the increases in response to hyperthermia were 10- and 6.5-fold, respectively. We also show a dose-dependent stress response in HTori3 cells cultured in the presence of arsenite ions. We conclude that the response of this highly differentiated and stable thyroid cell line to stress is similar to that seen in primary cultures of human thyroid cells and that these immortalized cells will afford a convenient and effective model for the further study of the role of stress in the pathology of AITD.