ATP-induced mitogenesis is mediated by cyclic AMP response element-binding protein-enhanced TRPC4 expression and activity in human pulmonary artery smooth muscle cells

Abstract

. ATP-induced mitogenesis is mediated by cyclic AMP response element-binding protein-enhanced TRPC4 expression and activity in human pulmonary artery smooth muscle cells. Am J Physiol Cell Physiol 287: C1192-C1201, 2004. First published June 30, 2004 doi:10.1152/ajpcell.00158.2004.-Extracellular ATP and intracellular cyclic AMP response element-binding protein (CREB, a transcription factor) promote cell proliferation in many cell types. The canonical transient receptor potential (TRPC) channels, which putatively participate in forming store-and receptor-operated Ca 2ϩ channels, have been implicated in the pulmonary vascular remodeling processes. A link between extracellular ATP, CREB activation, and TRPC4 channel expression and activity has not been shown in human pulmonary artery smooth muscle cells (PASMC). Long-term (24 -48 h) treatment of human PASMC with a low dose (100 M) of ATP, which did not trigger a transient rise in free cytosolic Ca 2ϩ concentration ([Ca 2ϩ ]i) when applied acutely to the cells, caused marked increases in CREB phosphorylation and TRPC4 protein expression. The time course indicated that the ATP-mediated CREB phosphorylation preceded TRPC4 upregulation, whereas transfection of a nonphosphorylatable CREB mutant abolished ATP-mediated TRPC4 expression. Furthermore, treatment of human PASMC with ATP also enhanced the amplitude of capacitative Ca 2ϩ entry (CCE) induced by passive store depletion, whereas the small interfering RNA specifically targeting TRPC4 attenuated ATP-mediated increases in TRPC4 expression and CCE amplitude and inhibited ATP-induced PASMC proliferation. These data suggest that low-dose ATP exerts part of its mitogenic effect in human PASMC via CREB-mediated upregulation of TRPC4 channel expression and activity and the subsequent increase in CCE and [Ca 2ϩ ]i.capacitative Ca 2ϩ entry; proliferation; vascular smooth muscle NUCLEOTIDES SUCH AS ATP, ADP, AND UTP act as extracellular messengers and play an important role in regulating vascular tone and cell proliferation and differentiation (12,18,25,41,56). Intracellular ATP is an essential molecular energy source, while extracellular ATP, which can be released from vascular endothelial cells (44, 71), damaged vessel walls (4), hypoxic myocardium (15), and aggregating platelets (29), serves as a potent vasoconstrictor (20, 24) and smooth muscle and endothelial cell mitogen (7,19). ATP also can be released from perivascular nerves as an excitatory neurotransmitter (6). The contractile and mitogenic effects of extracellular ATP on vascular smooth muscle cells (VSMC) are mediated by activation of a family of G protein-coupled receptors, P 2 purinoceptors (including at least 6 subtypes: P 2X , P 2Y , P 2T , P 2U , P 2Z , and P 2D ), which are linked to phospholipases and adenylate cyclase (7, 65). Activation of P 2 purinoceptors by ATP and UTP (24) in pulmonary artery smooth muscle cells (PASMC) causes pulmonary vasoconstriction and in fibroblasts promotes the progression of pulmonary vascular remodeling by stimulating f...

Pathophysiology and Therapeutic Potential of Purinergic Signaling

“…This is likely to result in the loss of local control of total pulmonary vascular resistance in the lung. Low-dose ATP exerts mitogenic actions on human pulmonary artery smooth muscle cells, which may be relevant to the pathophysiological basis of severe pulmonary hypertension (Zhang et al, 2004b). Pulmonary hypertension can be a problem in patients with chronic obstructive pulmonary disease, which also has other causes; it is a life-threatening condition, and intravenous ATP infusion produces a significant decrease in mean pulmonary arterial pressure and pulmonary vascular resistance without changing the mean systemic arterial pressure (Brook et al, 1994).…”

The non-excitable smooth muscle: Calcium signaling and phenotypic switching during vascular disease

“…ATP-induced mitogenesis in pulmonary artery SMC was shown to be mediated through CREB-induced TRPC4 gene transcription [162]. The in vivo relevance of TRPC isoform upregulation in human pulmonary artery SMC was observed in patients with idiopathic pulmonary arterial hypertension (IPAH), a disease characterized by excessive pulmonary artery SMC proliferation [43].…”

“…In recent years, increasing number of studies have focused on the ion channels and pumps acquired or lost during VSMC switch to the synthetic phenotype and their role in proliferation [14,32,74,82]. The transcription factors that control the gene regulation of these proteins are starting to emerge [32,75,149,150,160,162]. However, the pro-proliferative downstream signaling pathways that they regulate remain poorly understood.…”

“…The expression levels of TRPC channels appear to be under the control of growth factors. Indeed, studies from one laboratory showed that TRPC6 cation channel was upregulated through the c-Jun/STAT-3 pathway during PDGF-induced pulmonary VSMC proliferation [160], and that TRPC4 was upregulated in ATP-induced mitogenesis through cAMP response element-binding protein (CREB) activation in the same cells [162], providing a mechanism for upregulation of these channels during cell proliferation. Furthermore, SERCA2a expression (or loss thereof) in proliferative VSMC seems to depend on a proliferative signal because expression of SERCA2a can be regained when VSMC are growth arrested [82].…”

Signalling pathways involved in the contractile response to 5-HT in the human pulmonary artery

“…The SOCC has also been described in cultured human PASMCs and this conductance is insensitive to nifedipine, another dihydropyridine calcium channel antagonist, but fully inhibited by 0.5 mM Ni 2+ [30]. By means of siRNA or antisense oligonucleotides, the contribution of the canonical transient receptor potential (TRPC)1 and 4 proteins to endogenous SOCC was demonstrated in human cultured PASMCs [31,32]. Hence, in rat primary cultured PASMCs, we have previously shown that 5-HT activates a transient receptor potential vanilloid (TRPV)4-like calcium influx, potentially involved in PASMC proliferation [20].…”