P-371 Rhythmicity in Hypertensive Arterial Smooth Muscle is Linked to Transient Receptor Potential Canonical Channels

In pulmonary arterial smooth muscle cells (PASMCs), Ca2+ influx through store-operated Ca2+ channels thought to be composed of canonical transient receptor potential (TRPC) proteins is an important determinant of intracellular free calcium concentration ([Ca2+]i) and pulmonary vascular tone. Sildenafil, a type V phosphodiesterase inhibitor that increases cellular cGMP, is recently identified as a promising agent for treatment of pulmonary hypertension. We previously demonstrated that chronic hypoxia elevated basal [Ca2+]i in PASMCs due in large part to enhanced store-operated Ca2+ entry (SOCE); moreover, ex vivo exposure to prolonged hypoxia (4% O2 for 60 h) upregulated TRPC1 and TRPC6 expression in PASMCs. We examined the effect of sildenafil on basal [Ca2+]i, SOCE, and the expression of TRPC in PASMCs under prolonged hypoxia exposure. We also examined the effect of sildenafil on TRPC1 and TRPC6 expression in pulmonary arterial smooth muscle (PA) from rats that developed chronically hypoxic pulmonary hypertension (CHPH). Compared with vehicle control, treatment with sildenafil (300 nM) inhibited prolonged hypoxia induced increases of 1) basal [Ca2+]i, 2) SOCE, and 3) mRNA and protein expression of TRPC in PASMCs. Moreover, sildenafil (50 mg · kg−1 · day−1) inhibited mRNA and protein expression of TRPC1 and TRPC6 in PA from chronically hypoxic (10% O2 for 21 days) rats, which was associated with decreased right ventricular pressure and right ventricular hypertrophy. Furthermore, we found, in PASMCs exposed to prolonged hypoxia, that knockdown of TRPC1 or TRPC6 by their specific small interference RNA attenuated the hypoxic increases of SOCE and basal [Ca2+]i, suggesting a cause and effect link between increases of TRPC1 and TRPC6 expression and the hypoxic increases of SOCE and basal [Ca2+]i. These results suggest that sildenafil may alter basal [Ca2+]i in PASMCs by decreasing SOCE through downregulation of TRPC1 and TRPC6 expression, thereby contributing to decreased vascular tone of pulmonary arteries during the development of CHPH.

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Increased arterial smooth muscle Ca2+ signaling, vasoconstriction, and myogenic reactivity in Milan hypertensive rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00950.2011 ◽

2012 ◽

Vol 302 (3) ◽

pp. H611-H620 ◽

Cited By ~ 27

Author(s):

Cristina I. Linde ◽

Eiji Karashima ◽

Hema Raina ◽

Alessandra Zulian ◽

Withrow G. Wier ◽

...

Keyword(s):

Smooth Muscle ◽

Transient Receptor Potential ◽

Genetic Model ◽

Receptor Potential ◽

Whole Body ◽

Resistance Arteries ◽

Arterial Smooth Muscle ◽

Functional Changes ◽

Arterial Constriction ◽

Transient Receptor

The Milan hypertensive strain (MHS) rats are a genetic model of hypertension with adducin gene polymorphisms linked to enhanced renal tubular Na+ reabsorption. Recently we demonstrated that Ca2+ signaling is augmented in freshly isolated mesenteric artery myocytes from MHS rats. This is associated with greatly enhanced expression of Na+/Ca2+ exchanger-1 (NCX1), C-type transient receptor potential (TRPC6) protein, and sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2) compared with arteries from Milan normotensive strain (MNS) rats. Here, we test the hypothesis that the enhanced Ca2+ signaling in MHS arterial smooth muscle is directly reflected in augmented vasoconstriction [myogenic and phenylephrine (PE)-evoked responses] in isolated mesenteric small arteries. Systolic blood pressure was higher in MHS (145 ± 1 mmHg) than in MNS (112 ± 1 mmHg; P < 0.001; n = 16 each) rats. Pressurized mesenteric resistance arteries from MHS rats had significantly augmented myogenic tone and reactivity and enhanced constriction to low-dose (1–100 nM) PE. Isolated MHS arterial myocytes exhibited approximately twofold increased peak Ca2+ signals in response to 5 μM PE or ATP in the absence and presence of extracellular Ca2+. These augmented responses are consistent with increased vasoconstrictor-evoked sarcoplasmic reticulum (SR) Ca2+ release and increased Ca2+ entry, respectively. The increased SR Ca2+ release correlates with a doubling of inositol 1,4,5-trisphosphate receptor type 1 and tripling of SERCA2 expression. Pressurized MHS arteries also exhibited a ∼70% increase in 100 nM ouabain-induced vasoconstriction compared with MNS arteries. These functional alterations reveal that, in a genetic model of hypertension linked to renal dysfunction, multiple mechanisms within the arterial myocytes contribute to enhanced Ca2+ signaling and myogenic and vasoconstrictor-induced arterial constriction. MHS rats have elevated plasma levels of endogenous ouabain, which may initiate the protein upregulation and enhanced Ca2+ signaling. These molecular and functional changes provide a mechanism for the increased peripheral vascular resistance (whole body autoregulation) that underlies the sustained hypertension.

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Involvement of transient receptor potential canonical 1 (TRPC1) in angiotensin II-induced vascular smooth muscle cell hypertrophy

Atherosclerosis ◽

10.1016/j.atherosclerosis.2006.12.033 ◽

2007 ◽

Vol 195 (2) ◽

pp. 287-296 ◽

Cited By ~ 64

Author(s):

Yoichiro Takahashi ◽

Hiroyuki Watanabe ◽

Manabu Murakami ◽

Takayoshi Ohba ◽

Milena Radovanovic ◽

...

Keyword(s):

Smooth Muscle ◽

Angiotensin Ii ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cell ◽

Muscle Cell ◽

Vascular Smooth Muscle Cell ◽

Transient Receptor Potential ◽

Receptor Potential ◽

Transient Receptor Potential Canonical ◽

Transient Receptor

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Effects of chronic exposure to cigarette smoke on canonical transient receptor potential expression in rat pulmonary arterial smooth muscle

AJP Cell Physiology ◽

10.1152/ajpcell.00048.2013 ◽

2014 ◽

Vol 306 (4) ◽

pp. C364-C373 ◽

Cited By ~ 23

Author(s):

Jian Wang ◽

Yuqin Chen ◽

Chunyi Lin ◽

Jing Jia ◽

Lichun Tian ◽

...

Keyword(s):

Smooth Muscle ◽

Transient Receptor Potential ◽

Receptor Potential ◽

Arterial Smooth Muscle ◽

Nicotine Treatment ◽

Canonical Transient Receptor Potential ◽

Pulmonary Arterial ◽

Pulmonary Arterial Smooth Muscle ◽

Transient Receptor

To clarify the possible mechanism of cigarette smoke (CS)-induced pulmonary hypertension and furthermore provide effective targets for prevention and treatment, the effects of chronic CS on rat pulmonary arterial smooth muscle in vivo and nicotine treatment on rat pulmonary arterial smooth muscle cells (PASMCs) in vitro were investigated. In this study, we demonstrated that chronic CS exposure led to rat weight loss, right ventricular hypertrophy, and pulmonary arterial remodeling. A fluorescence microscope was used to measure intracellular calcium concentration ([Ca2+]i) in rat distal PASMCs. Results showed that basal [Ca2+]i and store-operated calcium entry (SOCE) levels in PASMCs from 3- and 6-mo CS-exposed rats were markedly higher than those in cells from the unexposed control animals (the increases in 6-mo CS group were more significant than that in 3-mo group), accompanied with increased canonical transient receptor potential 1 (TRPC1) and TRPC6 expression at both mRNA and protein levels in isolated distal PA. Simultaneously, in vitro study showed that nicotine treatment (10 nM) significantly increased basal [Ca2+]i and SOCE and upregulated TRPC1 and TRPC6 expression in cultured rat distal PASMCs. TRPC siRNA knockdown strategies revealed that the elevations of basal [Ca2+]i and SOCE induced by nicotine in PASMCs were TRPC1 and TRPC6 dependent. These results suggested that chronic CS-induced changes in vascular tone and structure in PA and the development of pulmonary hypertension might be largely due to upregulation of TRPC1 and TRPC6 expression in PASMCs, in which nicotine played an important role.

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