Thyroid hormone attenuates vascular calcification induced by vitamin D3 plus nicotine in rats.

Thyroid hormones (THs) including thyroxine (T4) and triiodothyronine (T3) play critical roles in bone remodeling. However, the role and mechanism of THs in vascular calcification (VC) have been unclear. To explore the pathophysiological roles of T3 on VC, we investigated the changes in plasma and aortas of THs concentrations and the effect of T3 on rat VC induced by vitamin D3 plus nicotine (VDN). VDN-treated rat showed decreased plasma T3 content, increased vascular calcium deposition, and alkaline phosphatase (ALP) activity. Administration of T3 (0.2 mg/kg body weight IP) for 10 days greatly reduced vascular calcium deposition and ALP activity in calcified rat aortas when compared with controls. Concurrently, the loss of smooth muscle lineage markers α-actin and SM22a was restored, and the increased bone-associated molecules, such as runt-related transcription factor2 (Runx2), Osterix, and osteopontin (OPN) levels in calcified aorta, were reduced by administration of T3. The suppression of klotho in calcified rat aorta was restored by T3. Methimazole (400 mg/L) blocked the beneficial effect of T3 on VC. These results suggested that T3 can inhibit VC development.