Identification and its functional analysis of ion channels involving in pathophysiologic remodeling of vascular smooth muscle

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Voltage-gated Na^+ channel currents (I(Na)) are expressed in several types of smooth muscle cells. We evaluated the expression of I(Na), its functional role, pathophysiology in cultured human (hASMCs) and rabbit aortic smooth muscle cells (rASMCs), and its association with vascular intimal hyperplasia. In whole cell voltage clamp, I(Na) was observed at potential positive to -40 mV, was blocked by tetrodotoxin (TTX), and replacing extracellular Na+ with N-methyl-d-glucamine in cultured hASMCs. In contrast to native aorta, cultured hASMCs strongly expressed SCN9A encoding Na(V)1.7, as determined by quantitative RT-PCR. I(Na) was abolished by the treatment with SCN9A small-interfering (si)RNA (P<0.01). TTX and SCN9A siRNA significantly inhibited cell migration (P<0.01, respectively) and horseradish peroxidase uptake (P<0.01, respectively). TTX also significantly reduced the secretion of matrix metalloproteinase-2 6 and 12 h after the treatment (P<0.01 and P<0.05, respectively). However, n … More either TTX nor siRNA had any effect on cell proliferation. L-type Ca^<2+> channel current was recorded, and I(Na) was not observed in freshly isolated rASMCs, whereas TTX-sensitive I(Na) was recorded in cultured rASMCs. Quantitative RT-PCR and immunostaining for Na(V)1.7 revealed the prominent expression of SCN9A in cultured rASMCs and aorta 48 h after balloon injury but not in native aorta. These studies showed that I(Na) is expressed in cultured and diseased conditions but not in normal aorta. The Na(V)1.7 plays an important role in cell migration, endocytosis, and secretion. Na(V)1.7 is also expressed in aorta after balloon injury, suggesting a potential role for Na(V)1.7 in the progression of intimal hyperplasia. In addition, serum amyloid A (SAA), an acute-phase protein, and lysophosphatidylcholine (LPC), an oxidized LDL component, contribute to physiological processes of atherosclerosis and cardiovascular disease. However, the effects of SAA/LPC on human coronary artery smooth muscle cells (hCASMCs) have not been fully investigated. Therefore, I examined the effects of SAA/LPC on Ca^<2+>/Mg^<2+> mobilization and its underlying mechanisms in hCASMCs. We showed that SAA/LPC activate Ca^<2+> influx in hCASMCs; SAA activates it via PTX-sensitive G-protein, PLC and TRPC pathways, where TRPC4 may be involved. On the other hand, LPC may activate it via TRPM7 independently of these pathways. Thus, TRP protein appears to be a target molecule of Ca^<2+> signaling in hCASMCs elicited by SAA/LPC, which may play roles in coronary muscle dysfunction under the pathophysiological and inflammatory conditions such as atherosclerosis. These results provide a possibility of ion channel blockers as a therapy for atherosclerotic diseases such as coronary artery diseases. Less