Abstract 152: Upregulation of the Cysteinyl Leukotriene Receptor-1 in Human Coronary Artery Smooth Muscle Cells Transduces Nuclear Calcium Signaling and Alterations of Gene Expression
Aim: Leukotrienes are pro-inflammatory mediators that are locally produced in coronary atherosclerotic plaques. This study aimed to elucidate cysteinyl leukotriene (CysLT) signaling in vascular smooth muscle cells (SMCs), and the effects of inflammation on this process.
Hypothesis: We tested the hypotheses that a) the CysLT1 receptor is upregulated in vascular SMCs in the context of atherosclerosis, and that b) CysLT1 receptor activation is coupled to nuclear calcium signaling, which c) leads to alterations in gene expression.
Methods & Results: Immunohistochemical analyses revealed that CysLT1 receptor expression co-localized with α-smooth muscle actin in human carotid endarterectomy samples, and that the CysLT1 receptor exhibited a perinuclear expression in human coronary artery SMCs. Real time quantitative PCR demonstrated that lipopolysaccharide (LPS) significantly upregulated CysLT1 receptor mRNA levels in a time-dependent fashion. Fluorescent calcium-signaling experiments showed that LPS significantly enhanced the changes in intracellular calcium induced by leukotriene C4 (LTC4) in these cells. LTC4 stimulation predominantly enhanced nuclear calcium increase, and this response was inhibited by the CysLT1 receptor-antagonist MK-571. Microarray analysis revealed that after 24h stimulation of human coronary artery SMCs with LTC4, there was a 5-fold increase mRNA levels for Plasminogen Activator Inhibitor (PAI)-2, among a number of significantly upregulated genes. The LTC4-induced increase in PAI-2 expression was confirmed by real time quantitative PCR and ELISA, and was inhibited both by MK-571 and by calcium chelators.
Conclusions: Pro-inflammatory stimulation of vascular SMCs upregulated CysLT1 receptor expression with perinuclear localization. CysLT1 receptor expression was coupled to nuclear calcium signaling and changes in gene expression, such as upregulation of PAI-2. Together, these findings suggest a role of nuclear CysLT1 receptor signaling in vascular SMCs including gene expression patterns associated with atherosclerosis.
- © 2012 by American Heart Association, Inc.