Tetramethylpyrazine inhibited hypoxia-induced expression of calcium-sensing receptors in pulmonary artery smooth muscle cells in chickens

Tetramethylpyrazine (TMP) is a biologically active ingredient, which is isolated from a popularChinese medicinal plant. It has been used effectively to treat ischemic heart problems, cerebrovascular and thrombotic vascular diseases. This study was designed to evaluate the effect of TMP on calciumsensing receptors in pulmonary artery smooth muscle in chickens. For this purpose forty day-old chicks were distributed into five groups: the control group, the hypoxia group (kept under low Oxygen treatment), and TMP groups (kept under low Oxygen treatment along with treatment of different concentrations of TMP). The pulmonary artery smooth muscle cells were also cultured on 6-well plates in high glucose culture medium and divided into the same five groups. We used in vivo and in vitro study models by applying immunohistochemistry, RT-qPCR assay and Western blotting analysis. Our results showed that pre-incubation with hypoxia markedly stimulated the activation of calcium-sensing receptor (CaSR) in pulmonary artery smooth muscle cells (PASMCs). The TMP decreased the mRNA and protein levels of CaSR. Treatment with TMP clearly inhibited the activation of all CaSR in a dose-dependent manner. Our data demonstrated that TMP can down-regulate the expression of CaSR. Therefore, these findings provide a new target to treat pulmonary arterial hypertension (PAH) under hypoxic conditions.