Summary:
Impairment of thyroid function has been described in up to 50% of the patients after
external irradiation of the neck region as well as after mantle irradiation. In order
to assess radiation-induced alterations in cultured thyroid cells, the occurrence
of apoptosis and necrosis as well as the expression of thyroid peroxidase (TPO) and
of two members of the 70 kD heat shock family, HSP-73 and HSP-72, were analysed following
gamma irradiation. Human thyroid epithelial cells (TEC) were purified from surgical
tissue specimens, were cultured and irradiated with a single dose of 5 Gy or 50 Gy
using Co60 as radioactive source. Analysis was performed 1, 3 and 5 day(s) after irradiation.
Apoptosis and necrosis were assessed by DNA staining with propidium iodide and FACS
analysis, TPO and HSP expression by SDS-PAGE and Western blotting. The cell viability
of TEC was not affected by irradiation and there was no induction of HSP-72, a sensitive
indicator of acute cellular stress. Interestingly, the expression of TPO, a key enzyme
of thyroid hormone synthesis, decreased significantly in irradiated TEC, while HSP-73
expression remained unchanged. Decreased expression of TPO with a resulting suppression
of thyroid hormone synthesis could contribute to an early development of thyroid dysfunction
following irradiation. Thus, analysis of thyroid function, even early after external
radiation therapy of the neck or after total body irradiation, seems to be indicated.
Key words:
Thyroid peroxidase - thyroid cells - irradiation - apoptosis - heat shock protein
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Beatrix Grubeck-LoebensteinMD
Institute for Biomedical Aging Researchof the Austrian Academy of Sciences
Rennweg 10
A-6020 Innsbruck, Austria
Phone: +43 512 583919-14
Fax: +43 512 583919-8
Email: Beatrix.Grubeck@oeaw.ac.at