SEMIQUANTITATIVE ANALYSIS OF INTERLEUKIN-1-ALPHA, INTERLEUKIN-6 AND INTERLEUKIN-8 MESSENGER-RNA EXPRESSION BY HUMAN THYROCYTES

It has been suggested that the thyroid itself may contribute to the inflammatory process observed in autoimmune thyroiditis by releasing the cytokines interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6) and interleukin-8 (IL-8), but studies of cytokine gene expression in thyrocytes have been limited and conflicting. A semi-quantitative reverse transcription-PCR technique has been used to investigate the expression of IL-1 alpha, IL-6 and IL-8 mRNA in the human thyroid cell line HTori3 and in cultures of primary human thyroid follicular cells (TFCs). Cytokine mRNA levels were examined over a 24-h period, and the modulatory effects of exogenous IL-1 alpha, interferon-gamma (IFN-gamma) and TSH investigated. Basal expression of IL-1 alpha, IL-6 and IL-8 mRNA was detected in HTori3 and primary TFC cultures. Stimulation with IL-1 (10 U/ml) for 12 h produced an increase in the level of IL-1 alpha mRNA in both primary TFC and HTori3 cultures. IL-6 and IL-8 mRNA levels were increased by the addition of IL-1 in both cell types, and this effect was detected throughout the 24-h time-course. IFN-gamma (100 U/ml) had no significant effect on cytokine gene expression. A higher concentration of IFN-gamma (500 U/ml) had no significant effect on the expression of IL-1 alpha or IL-8 but produced an increase in the level of IL-6 mRNA in primary cultures and in HTori3 cells. Addition of TSH (1 mU/ml) produced an increase in the level of IL-1 alpha mRNA in primary TFC and HTori3 cells, at 12 and 24 h. TSH had no significant effect on the expression of IL-6 or IL-8 mRNA. These results demonstrate that human TFCs constitutively express IL-1 alpha, IL-6 and IL-8 mRNA and that this expression can be modulated by IL-1, IFN-gamma and TSH.