TGFβ Decreases Soluble Guanylate Cyclase subunit mRNA Expression in Pulmonary Artery Smooth Muscle Cells via MEK/ERK Signaling

Exposure of rat pulmonary artery smooth muscle cells (rPASMC) to cytokines leads to nitric oxide (NO) production by NO synthase 2 (NOS2). NO stimulates cGMP synthesis by soluble guanylate cyclase (sGC), a heterodimer composed of α1- and β1-subunits. Prolonged exposure of rPASMC to NO decreases sGC subunit mRNA and protein levels. The objective of this study was to determine whether levels of NO produced endogenously by NOS2 are sufficient to decrease sGC expression in rPASMC. Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) increased NOS2 mRNA levels and decreased sGC subunit mRNA levels. Exposure of rPASMC to IL-1β and TNF-α for 24 h decreased sGC subunit protein levels and NO-stimulated sGC enzyme activity.l- N 6-(1-iminoethyl)lysine (NOS2 inhibitor) or 1 H-[1,2,4]oxadiazolo-[4,3- a]quinoxalin-1-one (sGC inhibitor) partially prevented the cytokine-mediated decrease in sGC subunit mRNA levels. However, cytokines also decreased sGC subunit mRNA levels in PASMC derived from NOS2-deficient mice. These results demonstrate that levels of NO and cGMP produced in cytokine-exposed PASMC are sufficient to decrease sGC subunit mRNA levels. In addition, cytokines can decrease sGC subunit mRNA levels via NO-independent mechanisms.

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Bone morphogenetic protein-2 upregulates expression and function of voltage-gated K+ channels in human pulmonary artery smooth muscle cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00191.2005 ◽

2006 ◽

Vol 291 (5) ◽

pp. L993-L1004 ◽

Cited By ~ 32

Author(s):

Ivana Fantozzi ◽

Oleksandr Platoshyn ◽

Ada H. Wong ◽

Shen Zhang ◽

Carmelle V. Remillard ◽

...

Keyword(s):

Smooth Muscle ◽

Pulmonary Artery ◽

Smooth Muscle Cells ◽

Mrna Expression ◽

Muscle Cells ◽

Channel Activity ◽

Whole Cell ◽

Voltage Gated ◽

Normal Human ◽

Pulmonary Artery Smooth Muscle

Activity of voltage-gated K+ (KV) channels in pulmonary artery smooth muscle cells (PASMC) plays an important role in control of apoptosis and proliferation in addition to regulating membrane potential and pulmonary vascular tone. Bone morphogenetic proteins (BMPs) inhibit proliferation and induce apoptosis in normal human PASMC, whereas dysfunctional BMP signaling and downregulated KV channels are involved in pulmonary vascular medial hypertrophy associated with pulmonary hypertension. This study evaluated the effect of BMP-2 on KV channel function and expression in normal human PASMC. BMP-2 (100 nM for 18–24 h) significantly (>2-fold) upregulated mRNA expression of KCNA5, KCNA7, KCNA10, KCNC3, KCNC4, KCNF1, KCNG3, KCNS1, and KCNS3 but downregulated (at least 2-fold) KCNAB1, KCNA2, KCNG2, and KCNV2. The most dramatic change was the >10-fold downregulation of KCNG2 and KCNV2, two electrically silent γ-subunits that form heterotetramers with functional KV channel α-subunits (e.g., KCNB1–2). Furthermore, the amplitude and current density of whole cell KV currents were significantly increased in PASMC treated with BMP-2. It has been demonstrated that K+ currents generated by KCNB1 and KCNG1 (or KCNG2) or KCNB1 and KCNV2 heterotetramers are smaller than those generated by KCNB1 homotetramers, indicating that KCNG2 and KCNV2 (2 subunits that were markedly downregulated by BMP-2) are inhibitors of functional KV channels. These results suggest that BMP-2 divergently regulates mRNA expression of various KV channel α-, β-, and γ-subunits and significantly increases whole cell KV currents in human PASMC. Finally, we present evidence that attenuation of c-Myc expression by BMP-2 may be involved in BMP-2-mediated increase in KV channel activity and regulation of KV channel expression. The increased KV channel activity may be involved in the proapoptotic and/or antiproliferative effects of BMP-2 on PASMC.

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