Apoptosis Of Pulmonary Artery Smooth Muscle Cells Research Articles

Serotonin inhibits apoptosis of pulmonary artery smooth muscle cells through 5-HT2A receptors involved in the pulmonary artery remodeling of pulmonary artery hypertension

ABSTRACTDecreased pulmonary artery smooth muscle cell (PASMC) apoptosis play a key role in pulmonary artery remodeling during pulmonary artery hypertension (PAH), but the mechanisms involved are unclear. Serotonin (5-HT) inhibits apoptosis in many pathologic processes by activating the 5-HT2A receptor. Therefore, we hypothesized that 5-HT may be the promoter of decreased apoptosis in PAH through the 5-HT2A receptor. We found that inhibition of the 5-HT2A receptor prevented the increase in pulmonary artery pressure and pulmonary artery remodeling in rats stimulated by monocrotaline. This effect was accompanied by increased apoptosis in the pulmonary artery. Cultured PASMCs stimulated with 5-HT showed a decrease in apoptosis with increased phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2), pyruvate dehydrogenase kinase (PDK), and mitochondrial transmembrane potential. These effects were markedly prevented by a 5-HT2A receptor inhibitor, an ERK1/2 activation inhibitor peptide I, or a PDK inhibitor. In conclusion, 5-HT inhibited PASMC apoptosis by activating the 5-HT2A receptor through the pERK1/2 and PDK pathways.5-HT decreasing apoptosis through 5-HT2A receptor is involved, at least in part, in pulmonary artery remolding.

New hope for a microRNA therapy for pulmonary arterial hypertension

New hope for a microRNA therapy for pulmonary arterial hypertension

Mir-206 Regulates Pulmonary Artery Smooth Muscle Cell Proliferation and Differentiation

Pulmonary Arterial Hypertension (PAH) is a progressive devastating disease characterized by excessive proliferation of the Pulmonary Arterial Smooth Muscle Cells (PASMCs). Studies suggest that PAH and cancers share an apoptosis-resistant state featuring excessive cell proliferation. MicroRNA-206 (miR-206) is known to regulate proliferation and is implicated in various types of cancers. However, the role of miR-206 in PAH has not been studied. In this study, it is hypothesized that miR-206 could play a role in the proliferation of PASMCs. In the present study, the expression patterns of miR-206 were investigated in normal and hypertensive mouse PASMCs. The effects of miR-206 in modulating cell proliferation, apoptosis and smooth muscle cell markers in human pulmonary artery smooth muscle cells (hPASMCs) were investigated in vitro. miR-206 expression in mouse PASMCs was correlated with an increase in right ventricular systolic pressure. Reduction of miR-206 levels in hPASMCs causes increased proliferation and reduced apoptosis and these effects were reversed by the overexpression of miR-206. miR-206 over expression also increased the levels of smooth muscle cell differentiation markers α-smooth muscle actin and calponin implicating its importance in the differentiation of SMCs. miR-206 overexpression down regulated Notch-3 expression, which is key a factor in PAH development. These results suggest that miR-206 is a potential regulator of proliferation, apoptosis and differentiation of PASMCs, and that it could be used as a novel treatment strategy in PAH.

Effects of Trimethoxystilbene on Proliferation and Apoptosis of Pulmonary Artery Smooth Muscle Cells

Proliferation of pulmonary artery smooth muscle cells (PASMC) is an important contributor to the progress of pulmonary arterial hypertension (PAH). Anti-inflammatory therapies may have therapeutic applicability for PAH. Resveratrol (RES) has prominent anti-inflammatory effects in vitro, but in vivo its beneficial effects are limited by short systemic half life and poor lipotrophy. A derivative of RES, trimethoxystilbene (TMS), has higher lipotropy and extended half life compared with RES, and can potentially overcome the limitations of RES. In the present study, we studied the effects of TMS and RES on proliferation and apoptosis of PASMC stimulated with Tumor Necrosis Factor-α. The effects on PASMC proliferation were quantified by MTT, while apoptosis was assessed by flow cytometry (Annexin V/propidium iodide assay). We observed strong inhibitory effects of TMS on the growth of PASMC, and these effects were 20 times more potent than those of RES. We further documented induction of apoptosis in PASMC treated with TMS, again, to a higher degree than with RES. In conclusion, TMS is more potent than RES in the inhibition of proliferation and induction of apoptosis of PASMC, demonstrating its potentially beneficial role for treating PAH.

Response to Promotion of Apoptosis Does Not Necessarily Mean Inhibition of Remodeling

We thank Shi et al1 for their interest in our study. It is well known that vascular remodeling is characterized by changes in pulmonary vascular structure associated with medial hypertrophy because of an imbalance between proliferation and apoptosis of pulmonary artery smooth muscle cells (PASMCs).2–5 Exactly how apoptosis contributes to remodeling still remains unclear, but we disagree with the opinion expressed by Shi et al1 that increased PASMC apoptosis translates to inhibition of remodeling. On the contrary, increased PASMC proliferation and decreased PASMC apoptosis …

Enhancer of Zeste Homolog 2 Induces Pulmonary Artery Smooth Muscle Cell Proliferation

IntroductionPulmonary Arterial Hypertension (PAH) is a progressively devastating disease characterized by excessive proliferation of the Pulmonary Arterial Smooth Muscle Cells (PASMCs). Studies suggest that PAH and cancers share an apoptosis-resistant state featuring excessive cell proliferation. The proliferation of cancer cells is mediated by increased expression of Enhancer of Zeste Homolog 2 (EZH2), a mammalian histone methyltransferase that contributes to the epigenetic silencing of target genes. However, the role of EZH2 in PAH has not been studied. In this study, it is hypothesized that EZH2 could play a role in the proliferation of PASMCs.MethodsIn the present study, the expression patterns of EZH2 were investigated in normal and hypertensive mouse PASMCs. The effects of EZH2 overexpression on the proliferation of human PASMCs were tested. PASMCs were transfected with EZH2 or GFP using nucleofector system. After transfection, the cells were incubated for 48 hours at 37°C. Proliferation and cell cycle analysis were performed using flow cytometry. Apoptosis of PASMCs was determined using annexin V staining and cell migration was tested by wound healing assay.ResultsEZH2 protein expression in mouse PASMCs were correlated with an increase in right ventricular systolic pressure and Right Ventricular Hypertrophy (RVH). The overexpression of EZH2 in human PASMCs enhances proliferation, migration, and decrease in the rate of apoptosis when compared to GFP-transfected cells. In the G2/M phase of the EZH2 transfected cells, there was a 3.5 fold increase in proliferation, while there was a significant decrease in the rate of apoptosis of PASMCs, when compared to control.ConclusionThese findings suggest that EZH2 plays a role in the migration and proliferation of PASMCs, which is a major hallmark in PAH. It also suggests that EZH2 could play a role in the development of PAH and can serve as a potential target for new therapies for PAH.

BMP-2 Up-Regulates PTEN Expression and Induces Apoptosis of Pulmonary Artery Smooth Muscle Cells under Hypoxia

AimTo investigate the role of bone morphogenetic protein 2 (BMP-2) in regulation of phosphatase and tensin homologue deleted on chromosome ten (PTEN) and apoptosis of pulmonary artery smooth muscle cells (PASMCs) under hypoxia.MethodsNormal human PASMCs were cultured in growth medium (GM) and treated with BMP-2 from 5–80 ng/ml under hypoxia (5% CO2+94% N2+1% O2) for 72 hours. Gene expression of PTEN, AKT-1 and AKT-2 were determined by quantitative RT-PCR (QRT-PCR). Protein expression levels of PTEN, AKT and phosph-AKT (pAKT) were determined. Apoptosis of PASMCs were determined by measuring activities of caspases-3, -8 and -9. siRNA-smad-4, bpV(HOpic) (PTEN inhibitor) and GW9662 (PPARγ antagonist) were used to determine the signalling pathways.ResultsProliferation of PASMCs showed dose dependence of BMP-2, the lowest proliferation rate was achieved at 60 ng/ml concentration under hypoxia (82.2±2.8%). BMP-2 increased PTEN gene expression level, while AKT-1 and AKT-2 did not change. Consistently, the PTEN protein expression also showed dose dependence of BMP-2. AKT activity significantly reduced in BMP-2 treated PASMCs. Increased activities of caspase-3, -8 and -9 of PASMCs were found after cultured with BMP-2. PTEN expression remained unchanged when Smad-4 expression was inhibited by siRNA-Smad-4. bpV(HOpic) and GW9662 (PPARγ inhibitor) inhibited PTEN protein expression and recovered PASMCs proliferation rate.ConclusionBMP-2 increased PTEN expression under hypoxia in a dose dependent pattern. BMP-2 reduced AKT activity and increased caspase activity of PASMCs under hypoxia. The increased PTEN expression may be mediated through PPARγ signalling pathway, instead of BMP/Smad signalling pathway.

Trimethoxystilbene and its effects on the proliferation and apoptosis of PASMCs

To synthesize 3, 5, 4' -trimethoxystilbene (TMS) by methylation of resveratrol (Res), a natural compound extracted from polygonum cuspidatum, to identify the chemical structure of TMS, to test its pharmacokinetics, and to determine the effects of TMS on the growth inhibition and apoptosis in pulmonary artery smooth muscle cells (PASMCs). The chemical structure of TMS was analyzed by UV- and IR- absorption spectrometry, (1)H-NMR and (13)C-NMR spectroscopy and mass spectrometry. We measured the bioavailability, the characteristics of intestinal absorption, and the distribution of TMS in body and excretions of SD rats after oral administration of TMS. The acute toxicity of TMS in mice was tested. PASMCs were prepared from pulmonary artery of SD rats. The PASMCs were divided into 8 groups. Group of A (control) was cultured without TNF-α, TMS, or Res. Group of B (TNF-α) was cultured with 100 pg/mL TNF-α. Groups of C-E (low-high concentrations of TMS) were cultured with 100 pg/mL TNF-α and 5, 10, 20 μmol/L TMS, respectively. Groups of F-H (low-high concentrations of Res) were cultured with 100 pg/mL TNF-α and 50, 100, 200 μmol/L Res, respectively. The proliferation of PASMCs after treatment was determined by MTT assay. The apoptosis of PASMCs after treatment was determined by flow cytometry. The UV absorption map of TMS showed λmax(MeOH) at 318, 306.2, and 217.8 nm. Analysis of infrared spectrum of TMS showed IRvKBr max /cm at 2999, 2935, 2836, 1591, 1511 and 1456/cm. The (1)H-NMR map showed that the synthetic product contained three hydroxy groups, while (13)C-NMR map showed 17 carbon signals and some symmetrical structural fragments. Electospray ionization mass spectrometry of the productshowed m/z peaks corresponded to 271[M+H](+), 256[M+H-CH(3)](+) and 241[256-CH(3)](+); the implied relative molecular weight is 270 and the implied molecular formula is C17H18O3. These data confirm the product is 3,5,4' - trimethoxystilbene. The absolute bioavailability of TMS was 45.4%. TMS was well absorped in the upper small intestine; it was excreted in stool and bile and distributed into several tissues. The maximal tolerance dose (MTD) of TMS was 5.85 g/kg. MTT assay showed TMS inhibited the proliferation of PASMCs in a dose-dependent manner. The extent of growth inhibition in A-H groups were (4.07±2.12)%, (6.54±4.78)%, (9.35±4.26)%, (16.75±5.34)%, (23.74±7.07)%, (6.78±5.58) %, (8.81±5.16) %, and (17.81±6.03) %, respectively. Flow cytometry showed the extent of apoptosis in PASMCs (after being treated with TMS for 24 h) was significantly higher than that in PASMCs treated only with TNF-α. The apoptosis rates of A-H groups were (2.63±0.74)%, (3.54±0.81)%, (5.77±4.62)%, (11.68±5.35)%, (18.79±4.15)%, (4.11±3.59)%, (6.33±4.8) %, and (12.47±5.06)%, respectively. We have confirmed our synthetic product as 3,5,4'-trimethoxystilbene (TMS), with the molecular formula of C17H18O3 and appropriate molecular weight and absorbption and NMR spectra. The bioavailability of TMS was to 45%. It strongly inhibits the proliferation of PASMCs in a dose-dependent manner and induces apoptosis of PASMCs.

Puerarin Induces Mitochondria-Dependent Apoptosis in Hypoxic Human Pulmonary Arterial Smooth Muscle Cells

BackgroundPulmonary vascular medial hypertrophy in hypoxic pulmonary arterial hypertension (PAH) is caused in part by decreased apoptosis in pulmonary artery smooth muscle cells (PASMCs). Puerarin, an isoflavone purified from the Chinese medicinal herb kudzu, ameliorates chronic hypoxic PAH in animal models. Here we investigated the effects of puerarin on apoptosis of hypoxic human PASMCs (HPASMCs), and to determine the possible underlying mechanisms.Methodology/Principal FindingsHPASMCs were cultured for 24 h in normoxia or hypoxia (5% O2) conditions with and without puerarin. Cell number and viability were determined with a hemacytometer or a cell counting kit. Apoptosis was detected with a TUNEL test, rhodamine-123 (R-123) fluorescence, a colorimetric assay, western blots, immunohistochemical staining and RT-PCR. Hypoxia inhibited mitochondria-dependent apoptosis and promoted HPASMC growth. In contrast, after puerarin (50 µM or more) intervention, cell growth was inhibited and apoptosis was observed. Puerarin-induced apoptosis in hypoxic HPASMCs was accompanied by reduced mitochondrial membrane potential, cytochrome c release from the mitochondria, caspase-9 activation, and Bcl-2 down-regulation with concurrent Bax up-regulation.Conclusions/SignificancePuerarin promoted apoptosis in hypoxic HPASMCs by acting on the mitochondria-dependent pathway. These results suggest a new mechanism of puerarin relevant to the management of clinical hypoxic pulmonary hypertension.

Abstract P063: BMP-2 Upregulates PTEN Expression and Induces Apoptosis of Pulmonary Artery Smooth Muscle Cells Under Hypoxia

Background: Primary pulmonary hypertension is mainly caused by increased proliferation and decreased apoptosis in pulmonary artery smooth muscle cells (PASMCs). Aim: To investigate the role of BMP-2 in regulation of PTEN and apoptosis of PASMCs under hypoxia. Methods: Normal human PASMCs were cultured in basal medium (BM) or growth medium (GM) and treated with BMP-2 from 5–80 ng/ml under hypoxia (5% CO 2 + 94% N 2 +1% O 2 ) for 72 hours. Gene expression of PTEN, caspase−3, −8, and −9, AKT-1 and -2 were determined by quantitative RT-PCR (QRT-PCR). Protein expression levels of PTEN, AKT and phosph-AKT (pAKT) were determined. Apoptosis of PASMCs were determined by measuring activities of caspases-3, -8 and -9. siRNA-smad-4 was used to determine whether Smad signaling pathway was involved in the regulation of PTEN expression by BMP-2. bpV(HOpic) (PTEN inhibitor) and GW9662 (PPAR-r antagonist) were also used. Results: Proliferation of PASMCs showed dose dependence of BMP-2, the lowest proliferative rate was achieved at 40–60ng/ml under hypoxia (BM=77.2±4%, GM=80±2.8%). Increased gene expression levels of PTEN, caspases−3, −8 and −9 were found, while AKT-1, and -2 did not change. Consistently, the PTEN protein expression also showed dose dependence of BMP-2. Though AKT was unchanged in all treated samples, reduced pAKT was found in BMP-2 treated PASMCs. Increased activities of caspase-3, -8 and -9 of PASMCs were found after cultured with BMP-2 in both mediums. PTEN expression was unchanged when Smad-4 expression was inhibited. However pre-treat PASMCs with bpV(HOpic) and GW9662 (PPAR-r inhibitor) inhibited PTEN protein expression and recovered PASMCs proliferation rate. Conclusion: BMP-2 can increase PTEN expression under hypoxia in a dose dependent pattern. BMP-2 can increase apoptosis of PASMCs under hypoxia. The increased PTEN expression may be mediated through PPAR-r signalling pathway, instead of BMP/Smad signalling pathway.

15-Hydroxyeicosatetraenoic acid (15-HETE) protects pulmonary artery smooth muscle cells from apoptosis via inducible nitric oxide synthase (iNOS) pathway

15-Hydroxyeicosatetraenoic acid (15-HETE), one of many important metabolic products of arachidonic acid (AA) catalyzed by 15-lipoxygenase, plays an important role in pulmonary vascular smooth muscle remodeling. We have previously shown its unsubstituted effects on the apoptotic responses of pulmonary artery smooth muscle cells (PASMCs), but the underlying mechanisms are still poorly manifested. Previous studies have shown that inducible nitric oxide synthase (iNOS) plays an important protective role against sepsis-induced pulmonary apoptosis. Therefore, the purpose of this study is to determine whether 15-HETE anti-apoptotic process is mediated through the iNOS pathway in rat PASMCs. To test this hypothesis, we studied the contribution of iNOS to the 15-HETE induced anti-apoptotic responses using cell viability measurement, Western blot, mitochondrial potential analysis, nuclear morphology determination and TUNEL assay. Our results showed that both exogenous and endogenous 15-HETE up-regulated iNOS protein and mRNA expression and 15-HETE enhanced the cell survival, attenuated mitochondrial depolarization, up-regulated the expression of Bcl-2 and procaspase-3 in PASMCs under serum-deprived condition. These effects were reversed by iNOS inhibitor SMT or l-canavanine. Taken together, our data indicates that iNOS is a novel signaling transduction pathway, which is necessary for the effects of 15-HETE in protection PASMCs from apoptosis and may be an important mechanism underlying the treatment of pulmonary artery hypertension and also provides a novel therapeutic insight in future.

Puerarin induced apoptosis of pulmonary artery smooth muscle cell by mitochondrial pathway

To investigate the contribution of mitochondrial pathway in the apoptosis induced by puerarin (PUE) in pulmonary artery smooth muscle cells. Cultured rat pulmonary artery smooth muscle cells (PASMC) were intervened by high, middle and low dose of puerarin (1.5 x 10(-3), 1.5 x 10(-4), 1.5 x 10(-5) mol x L(-1)). The change of mitochondrial membrane potential was observed. Western blot detected the expression of apoptosis-related gene Caspase-9, Bax and Bcl-2 protein. Compared with the control group, mitochondrial membrane potential significantly decreased in puerarin groups. Puerarin can enhance the expression of Caspase-9 and Bax protein, decrease the expression of Bcl-2 protein. Puerarin also has a concentration-dependent on the induction of PASMC. Puerarin can induce PASMC apoptosis through mitochondrial pathway.

Pro-apoptotic effects of imatinib on PDGF-stimulated pulmonary artery smooth muscle cells from patients with idiopathic pulmonary arterial hypertension

BackgroundRemodeling of the pulmonary artery by an inappropriate increase of pulmonary artery smooth muscle cells (PASMCs) is problematic in the treatment of idiopathic pulmonary arterial hypertension (IPAH). Effective treatment that achieves reverse remodeling is required. The aim of this study was to assess the pro-apoptotic effects of imatinib, a platelet-derived growth factor (PDGF)-receptor tyrosine kinase inhibitor, on PASMCs obtained from patients with IPAH. MethodsPASMCs were obtained from 8 patients with IPAH undergoing lung transplantation. Cellular proliferation was assessed by 3H-thymidine incorporation. Pro-apoptotic effects of imatinib were examined using TUNEL and caspase-3,7 assays and using transmission electron microscopy. ResultsTreatment with imatinib (0.1 to 10μg/mL) significantly inhibited PDGF-BB (10ng/mL)-induced proliferation of PASMCs from IPAH patients. Imatinib (1μg/mL) did not induce apoptosis in quiescent IPAH-PASMCs, but it had a pro-apoptotic effect on IPAH-PASMCs stimulated with PDGF-BB. Imatinib did not induce apoptosis in normal control PASMCs with or without PDGF-BB stimulation. PDGF-BB induced phosphorylation of Akt at 15min, and Akt phosphorylation was inhibited by imatinib in IPAH-PASMCs. Akt-I-1/2 (1μmol/L), an Akt inhibitor, in the presence of PDGF-BB significantly increased apoptotic cells compared with the control condition. Thus, Akt-I-1/2 could mimic the effects of imatinib on PASMCs. ConclusionImatinib has anti-proliferative and pro-apoptotic effects on IPAH-PASMCs stimulated with PDGF. The inhibitory effect of imatinib on Akt phosphorylation induced by PDGF plays an important role in the pro-apoptotic effect.

Effect of TXA2 inhibitor on the proliferation and apoptosis of hypoxic pulmonary artery smooth muscle cells of porcines

To study the effect of Thromboxane A2 (TXA2) inhibitor on the proliferation of hypoxic pulmonary artery smooth muscle cells (PASMC) of porcines. The methods of 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), immunohistochemistry of Ki67 and TdT-mediated dUTP nick end labeling (TUNEL) were employed to measure the proliferation, inhibition rate and apoptosis of PASMC. U46619, a thromboxane A2 agonist, could promote the proliferation and expression of Ki67 in PASMC under hypoxic and normal conditions. It could also inhibit the apoptosis of PASMC. Ozagrel, a thromboxane A2 inhibitor, inhibited the proliferation and the expression of Ki67 in PASMC under hypoxia. The inhibition rate was 71.4%, but it had no effect on the proliferation and expression of Ki67 in PASMC under normal conditions. It promoted the apoptosis of PASMC. Ozagrel could inhibit the action of U46619 in promoting the proliferation and expression of Ki67 in PASMC and inhibit the apoptosis of PASMC. Ozagrel may be used in treating the pulmonary hypertension by inhibiting the proliferation of PASMC, pulmonary vascular remodeling, and promote the apoptosis of PASMC.

Dichloroacetate Inhibits Vascular Remodeling and Increases Voltage-gate K+ Expression in a High-altitude-induced Pulmonary Artery Hypertension Rat Model

To investigate the effect of dichloroacetate (DCA) on the mean pulmonary artery pressure (mPAP), pulmonary artery (PA) remodeling and voltage-gate K+ (Kv) channel expression in pulmonary arterial smooth muscle cells (PASMCs) in high altitude-induced pulmonary artery hypertension (HA-PAH) rats. Sprague-Dawley rats were randomly assigned to normal control (N), high altitude (HA), and HA+DCA (70 mg/kg DCA administration daily) groups (n=8 each). Rats were housed in a hypobaric, hypoxic chamber to mimic an altitude of 5000m for 21 days; then the mPAP and the wall thickness (WT) of the PA smooth muscle were measured. PASMCs apoptosis was examined using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) stain. Real-time PCR, immunohistochemistry and western blot analyses were carried out to detect Kv1.5 and Kv2.1 expression in PASMCs. The expression of Kv1.5 and Kv2.1 was decreased in HA rats. With DCA treatment, the expression of Kv1.5 and Kv2.1 was restored, and the established HA-PAH was ameliorated. Compared with the HA-PAH rats, the DCA-treated rats displayed a decreased mPAP, WT of the PAs, right ventricular hypertrophy and ([Ca2+]i), and more PASMCs were apoptotic. DCA partially reversed the downregulation of Kv1.5 and Kv2.1 in the PASMCs of HA-PAH rats. DCA can reverse the remodeling of the PA and upregulate Kv1.5 and Kv2.1 expression in the PASMCs of HA-PAH rats. This result suggests that DCA may be an effective drug for treating HA-PAH and that restoring Kv1.5 and Kv2.1 can partially decrease mPAP.

Involvement of Gax Gene in Hypoxia-Induced Pulmonary Hypertension, Proliferation, and Apoptosis of Arterial Smooth Muscle Cells

Hypoxia down-regulates the expression of the growth arrest-specific homeobox (Gax) in pulmonary arterial smooth muscle cells (PASMCs), resulting in increased cell proliferation and decreased apoptosis, but the mechanism for this response remains unclear. The present study investigated the role of Gax in the development of hypoxia-induced pulmonary hypertension (PH). We found that hypoxia suppressed the expression of endogenous Gax in rats, but not in those pretreated intratracheally with a Gax construct (Ad-Gax). Hypoxic rats pretreated with Ad-Gax were resistant to hypoxia-induced PH, right ventricular hypertrophy, increased wall thickness, and the muscularization of pulmonary arterioles. Hypoxia-induced PASMC proliferation and suppression of Gax expression were blocked by the Mitogen-activated protein kinase (MEK) inhibitor U0126. The PASMCs with Ad-Gax transfection exhibited hyperexpression of the Bcl-2-associated X protein (Bax) and hypoexpression of B-cell lymphoma 2 (Bcl-2), leading to cell apoptosis. Thus, our data indicate that the enhanced expression of Gax inhibits hypoxia-induced PASMC proliferation, probably via the extracellular-signal-regulated kinase (ERK) 1/2 pathway, and induces the apoptosis of hypoxic PASMCs via the Bcl-2/Bax pathway. Gax may be a potential new therapeutic target for pulmonary hypertension.

15-HETE protects rat pulmonary arterial smooth muscle cells from apoptosis via the PI3K/Akt pathway

15-Hydroxyeicosatetraenoic acid (15-HETE), a metabolic product of arachidonic acid (AA), plays an important role in pulmonary vascular smooth muscle remodeling. Although its effects on the apoptotic responses are known, the underlying mechanisms are still poorly understood. Since Akt is a critical regulator of cell survival and vascular remodeling, there may be a crosstalk between 15-HETE anti-apoptotic process and PI3K/Akt survival effect in rat pulmonary arterial smooth muscle cells (PASMCs). To test this hypothesis, we studied the effect of 15-HETE on cell survival and apoptosis using Western blot, cell viability measurement, nuclear morphology determination, TUNEL assay and mitochondrial potential analysis. We found that activation of the PI3K/Akt signaling system was necessary for the 15-HETE to suppress PASMC apoptosis and improve cell survival. Our results indicated that 15-HETE inhibited the apoptotic responses of PASMCs, including morphological alterations, mitochondrial depolarization and the expression apoptosis-specific proteins. These effects were likely to be mediated through the activation of PI3K/Akt. Two downstream signal molecules of PI3K/Akt were identified. Both FasL and Bad were down-regulated by 15-HETE and 15-HETE phosphorylated Bad. These changes depended on the PI3K/Akt signaling pathway in PASMCs. Thus a signal transduction pathway was demonstrated which is necessary for the effects of 15-HETE in protection PASMCs from apoptosis.

Abstract 5663: Imatinib Inhibits Proliferation and Migration and Induces Apoptosis in Pulmonary Artery Smooth Muscle Cells From Patients With Idiopathic Pulmonary Arterial Hypertension

Background : Idiopathic pulmonary arterial hypertension (IPAH) is characterized by inappropriate increase of pulmonary artery smooth muscle cells (PASMCs). We assessed the inhibitory effects of imatinib, a platelet-derived growth factor (PDGF)-receptor tyrosine kinase inhibitor, on PDGF-induced proliferation and migration of PASMCs obtained from patients with IPAH, and investigated whether imatinib induces apoptosis of PASMCs. Methods and Results : PASMCs were obtained from 7 patients with IPAH undergoing lung transplantation. PDGF (10 ng/mL) stimulation caused a higher growth rate of PASMCs from patients with IPAH than that of normal control PASMCs (n=6) as assessed by 3 H-thymidine incorporation (normal: 179±45 vs. IPAH: 310±31 % of counts before PDGF, P <0.05). After treatment with imatinib (0.1 and 1 μ g/mL), PDGF-induced cell proliferation of PASMCs from IPAH patients decreased by 51% and 90 % respectively (PDGF vs PDGF+imatinib (0.1 and 1 μ g/mL): P <0.001). Western blot analysis revealed that imatinib (1 μ g/mL) increased the expression of cyclin-dependent kinase inhibitor p27 in IPAH-PASMCs compared with treatment with PDGF (53%; PDGF vs. PDGF+imatinib, P <0.005). A time-lapse system revealed that PDGF increased the migration distance of IPAH-PASMCs compared to that of normal PASMCs ( P <0.0001), and imatinib (1 μ g/mL) inhibited PDGF-induced migration ( P <0.0001). TUNEL assay revealed that imatinib (1 μ g/mL) alone did not induce apoptosis in IPAH-PASMCs, but combination of imatinib and PDGF increased apoptotic cells (Figure ). Conclusions: Inhibition of PDGF signaling by imatinib may become a useful molecular-targeted therapy for IPAH. Figure. Effect of imatinib on apoptosis of PASMICs in Tunnel assay.

ROCK pathway participates in the processes that 15‐hydroxyeicosatetraenoic acid (15‐HETE) mediated the pulmonary vascular remodeling induced by hypoxia in rat

15-Hydroxyeicosatetraenoic acid (15-HETE), a product of arachidonic acid (AA) catalyzed by 15-lipoxygenase (15-LO), plays an essential role in hypoxic pulmonary arterial hypertension. We have previously shown that 15-HETE inhibits apoptosis in pulmonary artery smooth muscle cells (PASMCs). To test the hypothesis that such an effect is attributable to the hypoxia-induced pulmonary vascular remodeling (PVR), we performed these studies. We found subtle thickening of proximal media/adventitia of the pulmonary arteries (PA) in rats that had been exposed to hypoxia. This was associated with an up-regulation of the anti-apoptotic Bcl-2 expression and down-regulation of pro-apoptotic caspase-3 and Bax expression in PA homogenates. Nordihydroguaiaretic acid (NDGA), which inhibits the generation of endogenous 15-HETE, reversed all the alterations following hypoxia. In situ hybridization histochemistry and immunocytochemistry showed that the 15-LO-1 mRNA and protein were localized in pulmonary artery endothelial cells (PAECs), while the 15-LO-2 mRNA and protein were localized in both PAECs and PASMCs. Furthermore, the Rho-kinase (ROCK) pathway was activated by both endogenous and exogenous 15-HETE, alleviating the serum deprivation (SD)-induced PASMC apoptosis. Thus, these findings indicate that 15-HETE protects PASMC from apoptosis, contributing to pulmonary vascular medial thickening, and the effect is, at least in part, mediated via the ROCK pathway.

FLUOXETINE PROTECTS AGAINST MONOCROTALINE‐INDUCED PULMONARY ARTERIAL HYPERTENSION: POTENTIAL ROLES OF INDUCTION OF APOPTOSIS AND UPREGULATION OF Kv1.5 CHANNELS IN RATS

1. Suppressing apoptosis and downregulating K(+) channels in pulmonary artery smooth muscle cells (PASMC) have been implicated in the development of pulmonary vascular medial hypertrophy and pulmonary arterial hypertension (PAH). Previous studies have shown that selective serotonin re-uptake inhibitors (SSRIs) protected against PAH. The aim of the present study was to investigate the involvement of Kv1.5 channels and apoptosis in the protective effect of the SSRI fluoxetine against PAH. 2. Monocrotaline (MCT) was used to establish PAH in Wistar rats. Fluoxetine (2 and 10 mg/kg per day) was administered by gavage once a day for 3 weeks. Three weeks after the induction of PAH by MCT, pulmonary haemodynamic measurements and pulmonary artery morphological assessments were undertaken, along with detection of apoptosis and Kv1.5. 3. Fluoxetine (2 and 10 mg/kg per day) decreased pulmonary artery pressure, reduced the right ventricular index and inhibited the increase in medial wall thickness of pulmonary arteries in established PAH. Fluoxetine (10 mg/kg per day) reduced the expression of Bcl-2 and Bcl-xL protein, increased the expression of cleaved caspase 3 protein and enhanced the expression of Kv1.5 protein and mRNA in pulmonary arteries. Furthermore, fluoxetine (10 mg/kg per day) significantly suppressed proliferation and enhanced apoptosis of PASMC in MCT-induced PAH. 4. In conclusion, fluoxetine protects against MCT-induced PAH by suppressing PASMC proliferation, inducing PASMC apoptosis and upregulating Kv1.5 channels.