Transcriptional Down-Regulation of Thromboxane A(2) Receptor Expression via Activation of MAPK ERK1/2, p38/NF-kappa B Pathways

Background: We have developed an in vitro model by organ culture of rat mesenteric arteries to imitate vascular smooth muscle cell (VSMC) receptor changes in cardiovascular disease. By using this model, alteration of VSMC thromboxane A(2) (TP) receptors was studied. Methods and Results: After organ culture of the arteries, VSMC TP receptors were studied by using myography, real-time PCR and immunohistochemistry. We observed that organ culture for 24 and 48 h resulted in depressed TP receptor-mediated contraction in the VSMC, in parallel with decreased TP receptor mRNA and protein expressions. Phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), p38 and nuclear factor-kappa B (NF-kappa B) was seen by Western blot within 1-3 h after organ culture. Inhibition of ERK1/2, p38 or NF-kappa B reversed depressed contraction as well as decreased receptor mRNA expression. Actinomycin D abolished decreased TP receptor-mediated contraction, while inhibition of translation, cyclooxygenase or nitric oxide synthase had no effect. TP receptor mRNA stability was unchanged during organ culture. Conclusions: The present study has demonstrated for the first time that organ culture of rat mesenteric arteries down-regulates VSMC TP receptor expression through activation of ERK1/2 and p38/NF-kappa B signal pathways. Copyright (C) 2008 S. Karger AG, Basel