Effects of Aloe vera on the Regulation of Thyroxine Release in FRTL-5 Thyroid Cells

Abstract

To determine whether Aloe vera (AV), a traditional herbal medicine, could maintain homeostasis, we investigated its ability to regulate the production of hormones, particularly thyroid hormones. T4 ELISA assay with (6H media) and without thyrotropin (TSH) (5H media) showed that AV functions to maintain endocrine homeostasis. To understand the mechanisms by which AV regulates thyroxine release, we confirmed the protein expression of key upstream factors of thyroid hormone synthesis, such as phosphorylated extracellular signal-regulated kinase (ERK), phosphorylated cAMP response element binding protein (CREB), and phosphorylated protein kinase B (p-Akt). Although the protein expression of phosphorylated ERK and CREB were decreased in 6H media, they were increased and unchanged, respectively, in 5H media. However, protein expression of phosphorylated Akt was not changed by AV in both 6H and 5H media. Furthermore, inhibition of protein kinase A (PKA) by H89 eliminated AV-induced phosphorylation of ERK in 5H media. However, the inhibition of protein kinase C (PKC) by GF 109203X did not eliminate AV-induced ERK phosphorylation in 5H media. These results suggested that AV has TSH-like activity and could regulate thyroxine release through the TPO and PKA pathways. AV may regulate thyroid function to maintain a constant level of thyroid hormones in the body, and could be a candidate for thyroid disease therapies.