Curcumin induces apoptosis in thyroid cells in rats: possible role of caspase 3

Background: Antioxidants could have a direct positive effect on the thyroid gland. Aim of the work: This study investigated the possible protective effect of curcumin, an antioxidant polyphenolic compound, against sodium chlorate (NaClO3) - induced hypothyroidism in rats and the possible role of caspase 3 in its mechanism of action. Materials and Methods: Rats were divided into three groups: group I: control; group II: NaClO3 exposed rats (2g/l in drinking water for three weeks); group III: NaClO3 exposed rats plus curcumin admixed with the diet (0.5% w/w) for one week before NaClO3 exposure and continued for three weeks after exposure. Triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH) and superoxide anion (as an index of oxidative stress) levels were determined in plasma. Thyroid sections were subjected to H&E staining, and immunohistochemical staining of caspase 3 as an index of apoptosis. Results: Curcumin pretreatment in NaClO3 exposed rats produced significant increase in plasma levels of T3 and T4 and decreased significantly TSH and superoxide anion levels in plasma as compared to NaClO3 non-treated rats. Histologically, curcumin pretreated rats showed neither follicular cellular hypertrophy nor hyperplasia as compared to non–treated NaClO3 exposed rats. Moreover, curcumin in NaClO3 pretreated rats significantly increased the mean area percent of caspase 3 in thyroid gland as compared to NaClO3 non-treated rats. Conclusion: These findings showed an improved effect of curcumin against NaClO3-induced hypothyroidism in rats possibly by its antioxidant property and its apoptotic effect which may be mediated by caspase 3.