Rat Pulmonary Artery Smooth Muscle Cells Research Articles

Qibai Pingfei capsule medicated serum inhibits the proliferation of hypoxia-induced pulmonary arterial smooth muscle cells via the Ca2+/calcineurin/nuclear factor of activated T-cells 3 pathway

ObjectiveTo observe the effect of Qibai Pingfei capsule (QBPF) medicated serum on the proliferation of rat pulmonary arterial smooth muscle cells (PASMCs) under hypoxia conditions and to investigate its key molecular effects on the Ca2+/calcineurin/nuclear factor of activated T-cells 3 (NFATc3) signaling pathway. MethodsQBPF was provided to rats via continuous gavage for 10 days. Primary rat PASMCs were cultured using the direct adherent culture method. Methyl thiazolyl tetrazolium assay was used to evaluate the effect of QBPF on PASMCs proliferation under hypoxia conditions. Laser scanning confocal microscopy was used to detect changes in intracellular free calcium ([Ca2+]i) in PASMC-loaded Fluo-3-AM. Real-time quantitative polymerase chain reaction and western blot were used to detect the transcription and protein expression levels of calcineurin and NFATc3 genes in PASMCs. ResultsCompared with normoxia conditions, PASMCs proliferated at 12, 24, 48, and 72 h under hypoxia conditions. QBPF at concentrations of 5%, 10%, and 20% could inhibit hypoxia-induced PASMC proliferation to different degrees. The inhibitory effect was most significant in the 20% QBPF group under 24 h hypoxia conditions. The concentration of [Ca2+]i in PASMCs under hypoxia was increased and [Ca2+]i was significantly decreased when co-incubated with QBPF at 5%, 10%, and 20%. Compared with normoxia conditions, the mRNA and protein expression levels of calcineurin and NFATc3 in PASMCs induced by hypoxia were up-regulated. QBPF application significantly down-regulated mRNA and protein expression levels of calcineurin and NFATc3 in PASMCs. ConclusionQBPF can effectively inhibit hypoxia-induced proliferation of PASMCs through down-regulation of key molecular expression via the Ca2+/calcineurin/NFATc3 pathway.

Involvement of Ca2+-activated K+ channel 3.1 in hypoxia-induced pulmonary arterial hypertension and therapeutic effects of TRAM-34 in rats.

Pulmonary artery hypertension (PAH) is an incurable disease associated with the proliferation of pulmonary artery smooth muscle cells (PASMCs) and vascular remodeling. The present study examined whether TRAM-34, a highly selective blocker of calcium-activated potassium channel 3.1 (Kca3.1), can help prevent such hypertension by reducing proliferation in PASMCs. Rats were exposed to hypoxia (10% O2) for 3 weeks and treated daily with TRAM-34 intraperitoneally from the first day of hypoxia. Animals were killed and examined for vascular hypertrophy, Kca3.1 expression, and downstream signaling pathways. In addition, primary cultures of rat PASMCs were exposed to hypoxia (3% O2) or normoxia (21% O2) for 24 h in the presence of TRAM-34 or siRNA against Kca3.1. Activation of cell signaling pathways was examined using Western blot analysis. In animal experiments, hypoxia triggered significant medial hypertrophy of pulmonary arterioles and right ventricular hypertrophy, and it significantly increased pulmonary artery pressure, Kca3.1 mRNA levels and ERK/p38 MAP kinase signaling. These effects were attenuated in the presence of TRAM-34. In cell culture experiments, blocking Kca3.1 using TRAM-34 or siRNA inhibited hypoxia-induced ERK/p38 signaling. Kca3.1 may play a role in the development of PAH by activating ERK/p38 MAP kinase signaling, which may then contribute to hypoxia-induced pulmonary vascular remodeling. TRAM-34 may protect against hypoxia-induced PAH.

Inhibition of phosphodiesterase-5 suppresses calcineurin/NFAT- mediated TRPC6 expression in pulmonary artery smooth muscle cells

The up-regulation of transient receptor potential channel 6 (TRPC6) has been found to contribute to the proliferation of pulmonary artery smooth muscle cells (PASMCs), and inhibition of phosphodiesterase-5 (PDE5) has been shown to suppress TRPC6 expression in PASMCs. However, the molecular mechanisms underlying the up-regulation of TRPC6 expression and PDE5 modulation of TRPC6 expression in PASMCs remain largely unclear. The aim of this study is to address these issues. Endothelin-1 (ET-1) dose and time-dependently up-regulated TRPC6 expression in primary cultured rat PASMCs, and this was accompanied with the activation of calcineurin and subsequent translocation of NFATc4 to the nucleus. Further study indicated that inhibition of calcineurin by cyclosporine A or knockdown of NFATc4 using small interfering RNA suppressed ET-1-induced TRPC6 up-regulation. In addition, luciferase reporter assay showed that NFATc4 directly regulated the expression of TRPC6 in PASMCs. Inhibition of PDE5 by sildenafil suppressed ET-1-induced activation of calcineurin/NFATc4 signaling pathway and consequent TRPC6 up-regulation in PASMCs, while these inhibitory effects of sildenafil were abolished by PKG inhibitor Rp-8Br-cGMPs. Taken together, our study indicates that ET-1 stimulates TRPC6 expression by activation of calcineurin/NFATc4 signaling pathway, and inhibition of PDE5 suppresses calcineurin/NFATc4- mediated TRPC6 expression in PASMCs in a cGMP-PKG-dependent manner.

MicroRNA-27a/b mediates endothelin-1-induced PPARγ reduction and proliferation of pulmonary artery smooth muscle cells.

The down-regulation of peroxisome proliferator-activated receptor γ (PPARγ) expression has been found to correlate with the proliferation of pulmonary artery smooth muscle cells (PASMC), pulmonary vascular remodeling and pulmonary hypertension, while the molecular mechanisms underlying PPARγ reduction in PASMC remain largely unclear. The aim of the current study is to address this issue. Endothelin-1 (ET-1) dose- and time-dependently resulted in PPARγ reduction and proliferation of primary cultured rat PASMC, which was accompanied by the activation of nuclear factor-kappaB (NF-κB) and subsequent induction of microRNA-27a/b (miR-27a/b) expression. Chromatin immunoprecipitation assay revealed that NF-κB directly bound to the promoter regions of miR-27a/b. Luciferase reporter assay identified that miR-27a/b directly regulates the expression of PPARγ in PASMC. Further study indicated that the presence of either NF-κB inhibitor pyrrolidinedithiocarbamate or prior silencing miR-27a/b with anti-miRNA oligonucleotides suppressed ET-1-induced PPARγ reduction and proliferation of PASMC, while overexpression of miR-27a/b reduced PPARγ expression and enhanced PASMC proliferation. Taken together, our study demonstrates that ET-1 stimulates miR-27a/b expression by activation of the NF-κB pathway, which in turn results in PPARγ reduction and contributes to ET-1-induced PASMC proliferation.

Effects of endogenous sulfur dioxide on the oxidative stress induced by cobalt chloride in the rat pulmonary artery smooth muscle cells

Objective To investigate the effects of endogenous sulfur dioxide (SO2) on the oxidative stress induced by cobalt chloride (CoCl2) in the rat pulmonary artery smooth muscle cells (PASMCs). Methods Rat PASMCs were treated with 200 μmol/L CoCl2 to mimic the hypoxia insult.Endogenous SO2 generating enzyme aspartate aminotransferase 1(AAT1) expression was upregulated or downregulated (AAT1sh) by transfection with lentivirus.Rat PASMCs were randomly divided into 8 groups: vehicle group, vehicle + CoCl2 group, AAT1 group, AAT1 + CoCl2 group, scramble group, scramble + SO2 group, AAT1sh group and AAT1sh + SO2 group.SO2 donor Na2SO3/NaHSO3 at concentration of 100 μmol/L were added in scramble + SO2 group and AAT1sh + SO2 group.The expressions of AAT1, superoxide dismutase 1(SOD1) and SOD2 in PASMCs were detected by Western blot method.In situ SO2 content in PASMCs was detected by fluorescent probe.The superoxide anions in PASMCs were labeled by dihydroethidium (DHE) probe under fluorescent microscope. Results Compared with the vehicle group, the levels of SO2 and the expressions of AAT1(0.221±0.002 vs.0.446±0.004), SOD1(0.076±0.028 vs.0.171±0.019)and SOD2(0.080±0.031 vs.0.196±0.018) significantly decreased (all P< 0.01), and superoxide anion increased in rat PASMCs of vehicle + CoCl2 group.Meanwhile, compared with vehicle + CoCl2 group, the levels of SO2 and the expressions of AAT1(0.839±0.056 vs.0.221±0.002), SOD1(0.177±0.020 vs.0.076±0.028)and SOD2(0.195±0.018 vs.0.080±0.031)markedly increased (all P< 0.01), and superoxide anion decreased in rat PASMCs of AAT1 + CoCl2 group.On the contrary, compared with the scramble group, the levels of SO2 and the expressions of AAT1(0.062±0.017 vs.0.354±0.034), SOD1(0.054±0.029 vs.0.157±0.023) and SOD2(0.180±0.100 vs.0.586±0.176)significantly decreased (all P<0.01), and superoxide anion increased in rat PASMCs of AAT1sh group.Furthermore, compared with the AAT1sh group, the levels of SO2 and the expressions of SOD1(0.155±0.022 vs.0.054±0.029) and SOD2(0.578±0.200 vs.0.180±0.100) significantly increased (all P< 0.01), and superoxide anion decreased in rats PASMCs of AAT1sh + SO2 group. Conclusion Endogenous SO2/AAT1 inhibits CoCl2-induced oxidative stress in rat PASMCs. Key words: Sulfur dioxide; Aspartate aminotransferase 1; Endogenous; Pulmonary artery smooth muscle cells; Oxidative stress

Protein kinase Cα stimulates hypoxia‑induced pulmonary artery smooth muscle cell proliferation in rats through activating the extracellular signal‑regulated kinase 1/2 pathway.

Hypoxic pulmonary hypertension (HPH) may contribute to vascular remodeling, and pulmonary artery smooth muscle cell (PASMC) proliferation has an important role in this process. However, no relevant information concerning the role and mechanism of protein kinase C (PKC)α in hypoxia-induced rat PASMC proliferation has been elucidated. The present study aimed to further investigate this by comparison of rat PASMC proliferation among normoxia for 72 h (21% O2), hypoxia for 72 h (3% O2), hypoxia + promoter 12-myristate 13-acetate control, hypoxia + safingol control, hypoxia + PD98059 control and hypoxia + U0126 control groups. The present study demonstrated that protein expression levels of PKCα in rat PASMCs were elevated. In conclusion, through activating the extracellular signal-regulated 1/2 signaling pathway, PKCα is involved in and initiates PASMC proliferation, thus bringing about pulmonary artery hypertension. These results add to the understanding of the mechanism PKCα in PH formation and lays a theoretical basis for prevention as well as treatment of HPH.

Roles of the ERK1/2 and PI3K/PKB signaling pathways in regulating the expression of extracellular matrix genes in rat pulmonary artery smooth muscle cells.

To investigate the mechanisms by which PD98059 and LY294002 interfere with the abnormal deposition of extracellular matrix regulated by connective tissue growth factor (CTGF) of rat pulmonary artery smooth muscle cells (PASMCs). Rat PASMCs were cultured and separated into a control group. Real-time fluorescence quantitative PCR was performed to detect the expression of collagen III and fibronectin mRNA. Immunohistochemistry and western blot analyses were performed to detect the expression of collagen III protein. The expression of collagen III and fibronectin mRNA was greater in PASMCs stimulated with CTGF for 48 h, than in the control group. After 72h of stimulation, the expression of collagen III protein in the PASMCs was greater than in the control. The equivalent gene and protein expression of the CPL group were much more significant. CTGF can stimulate the gene expression of collagen III and fibronectin in PASMCs, which may be one of the factors that promote pulmonary vascular remodeling (PVR) under the conditions of pulmonary arterial hypertension (PAH). PD98059 and LY294002 can inhibit the ERK1/2 and PI3K/PKB signaling pathways, respectively, thus interfering with the biological effects of CTGF. This may be a new way to reduce PAH-PVR.

Hypoxia‐induced proliferation and migration in pulmonary arterial smooth muscle cells requires β‐catenin.

Exposure to hypoxia causes proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) in the distal vasculature, leading to structural remodeling of these arteries and contributing to the pathogenesis of pulmonary hypertension. In past studies, we showed that expression of the water channel, aquaporin 1 (AQP1), was upregulated by both in vivo and in vitro exposure to hypoxia, and that this channel mediated PASMC proliferation and migration. The effects of AQP1 were independent of channel water transport, but were associated with increased expression of β‐catenin, a dual function protein that is involved in the Wnt signaling pathway. β‐catenin activates transcription of genes involved in cell growth and survival and regulates the coordination of cell‐cell adhesion. Thus, we explored whether β‐catenin was required for hypoxia‐induced PASMC migration and proliferation. Primary cultures of rat PASMCs were harvested from distal pulmonary arteries and exposed to in vitro hypoxia (4% O2 ‐ 5% CO2) or control conditions. Proliferation and migration were measured using BrdU incorporation and transwell filters, respectively. Exposure to hypoxia for 24–72 h increased PASMC migration and proliferation and β‐catenin protein, but not mRNA, levels. Silencing β‐catenin in PASMCs had no significant effect on cell function under control conditions, but prevented hypoxia‐induced proliferation and migration. Based on our findings, we conclude that increases in β‐catenin protein stability/synthesis, perhaps mediated by AQP1, are crucial for hypoxia‐induced PASMC proliferation and migration.Support or Funding InformationThis work was funded by HL‐07963 and AHA0755479.

The regulation of MAPK signaling pathway on cell proliferation and apoptosis in hypoxic PASMCs of rats

To explore the relationship between hypoxic pulmonary arterial smooth muscle cells(PASMCs)proliferation, apop-tosis and mitogen-activated protein kinases(MAPK) signal pathway in rats. PASMCs were obtained from male SD rats by the enzyme digestion method and primarily cultured; PASMCs were identified through two methods:immunofluorescence staining and light microscopy; the 4~6th generation PASMCs of logarithmic growth state of good growth period were selected, and randomly divided into 7 groups:normoxic con-trol group (N), hypoxia group (H), DMSO group (D), extracellular signal-regulated kinase1/2(ERK1/2) inhibitor-U0126 group (U) and p38MAPK inhibitor-SB203580 group (S), the p38MAPK activator-Anisomycin group (A), the ERK1/2 activator-Staurosporine Aglycone group (SA). When all the models were completed, the all groups joined the CCK-8 to measure cell proliferation; cell apoptosis of each group was detected by TUNEL kit after the modeling. Compared with N group, the expression of OD value in H group was up-regulated (0.990 ±0.041 vs 1.143 ±0.033,P < 0.01). There was no statistical significance on PASMCs apoptosis index(AI) in H group (4.913 ±0.451 vs 5.452 ±0.557, P > 0.05); Compared With H group, there were no statistical significance on the expression of PASMCs OD value and apoptosis index(AI)in D group (1.143 ±0.033 vs 1.142 ±0.049,5.452 ±0.557 vs 5.402 ±0.651,P > 0.05); the expression of OD value in U group was down-regulated, and the expression of AI was up-regulated (1.143 ±0.033 vs 0.985 ±0.078, 5.452 ±0.557 vs 10.145 ±2.545, P < 0.01); the expression of OD value in S group was up-regulated, and the expression of AI was down-regulated (1.143 ±0.033 vs 1.295 ±0.039, 5.452 ±0.557 vs 3.093 ±0.409, P < 0.01); the expression of OD value in A group was down-regulated, and the expres-sion of AI was up-regulated (1.143 ±0.033 vs 0.347 ±0.067, 5.452 ±0.557 vs 25.753 ±1.262, P < 0.01); the expression of OD value in SA group was up-regulated, and the expression of AI was down-regulated (1.143 ±0.033 vs 1.685 ±0.100, 5.452 ±0.557 vs 1.700 ±0.095, P < 0.01). The regulation of PASMCs' proliferation and apoptosis under hypoxia condition have a relationship with the participation of MAPK signal pathway.

LPS enhances TLR4 expression and IFN‑γ production via the TLR4/IRAK/NF‑κB signaling pathway in rat pulmonary arterial smooth muscle cells.

The aim of the present study was to investigate the role of the Toll-like receptor (TLR)4 signaling pathway in cellular response to lipopolysaccharide (LPS) in rat pulmonary artery smooth muscle cells (PASMCs). Chronic obstructive pulmonary disease (COPD) rats were established with passive inhaling cigarette smoke plus injection of LPS. The TLR4 protein in lung tissues was determined with immunohistochemical staining and protein levels of the components of the TLR4 pathway in PASMCs were analyzed with western blotting. The production of interferon (IFN)-γ upon LPS stimulation in PASMCs was measured with ELISA. TLR4 expression in lung tissue from COPD rats was increased obviously compared with that in normal group. LPS enhances TLR4 expression in rat PASMCs and induced production of IFN-γ dramatically. LPS treatment resulted in increased phosphor-interleukin-1 receptor-associated kinase (IRAK), IκB and IκB kinase, as well as the total protein of nuclear factor (NF)-κB p65. TLR4 inhibitor TAK-242, IRAK1/4 inhibitor and NF-κB inhibitor Bay 117082 were capable of suppressing the effects of LPS. TLR4 signaling pathway is functional in PASMCs, and may be involved in the inflammatory response during the pathogenesis of COPD.

Bortezomib inhibits hypoxia-induced increase of Orai-1 expression in pulmonary arterial smooth muscle cell

Objective: In this study, a primary culture system for the rat distal pulmonary arterial smooth muscle cell (PASMC) was established to observe the effect of Bortezomib a treatment on the basal intracellular calcium concentration ([Ca(2+) ](i)), store operated calcium entry (SOCE) and Orai-1 expression in rat PASMC. Methods: We employed the primary culture method for the rat distal PASMC including the enzymatically dissociation of PASMC from the freshly isolated distal pulmonary artery and the culture of PASMC. The In Cyte system was used to measure the basal [Ca(2+) ](i) and SOCE after substantial treatment.Orai-1 protein expression in rat pulmonary artery smooth muscle was detected by Western blot. Results: Compared with Hypoxia group, the basal [Ca(2+) ](i) were significantly reduced in Hypoxia+ BTZ group(P<0.01). The basal [Ca(2+) ](i) A340/A380 ratio of Normoxia group was(1.07±0.02). The basal [Ca(2+) ](i) of Hypoxia group was(1.49±0.03); The Hypoxia+ BTZ group was(1.17±0.03). Compared with Hypoxia group, the store operated calcium entry were significantly reduced in Hypoxia+ BTZ group(P<0.01). The SOCE A340/A380 ratio of Normoxia group was(0.56±0.02). The SOCE of Hypoxia group was(0.84±0.02); The Hypoxia+ BTZ group was(0.66±0.02). The level of Orail-1 protein in pulmonary artery smooth muscle of Hypoxia group was (181.5±12.7)% higher than control group which was(100±0)%, (P<0.05). In the Hypoxia+ BTZ group Orai-1 protein expression was recovered(146.7±15.1)%, (P<0.05). Conclusion: Bortezomib inhibit chronically hypoxic enhancement of Orail-1 protein expression, basal [Ca(2+) ](i) and SOCE in rat distal pulmonary arterial smooth muscle cells.

The effects of ERK1/2 pathway on the expression of calcium activated chloride channel in hypoxia in PASMCs rat model

To investigate the expression of mRNA and protein of Calcium activated chloride channel (CLCA2) in hypoxic pulmonary artery smooth muscle cell (PASMCs) of rat and it's relationship with ERK1/2 signal pathway. PASMCs were randomly divided into 5 groups including normal group(N group), hypoxia group(H group), DMSO group(D group), U0126 group (U group) and Staurosporine aglycone group(SA group). The protein expression of CLCA2 in PASMCs was detected by Western blot.The mRNA expression of CLCA2 was detected by half quantitative reverse transcription polymerase chain reaction (RT-PCR). The mRNA and protein expressions of CLCA2 in H group were significantly higher than N group (P<0.01). Comparing with D group,the mRNA and protein expressions of CLCA2 were significantly increased in U group (P<0.01),the mRNA expression of CLCA2 in SA group was obviously decreased (P<0.01) with slightly decreasing of its protein expression. Hypoxia promotes the expressions of mRNA and protein of CLCA2 in rat PASMCs. The ERK1/2 pathway activator Staurosporine aglycone reduces the mRNA and protein expression of CLCA2 in rats PASMCs and the ERK1/2 pathway inhibitor U0126 induces the upregulation of the mRNA and protein expressiosn of CLCA2 in rats PASMCs.

Calcium signalling induced by in vitro exposure to silicium dioxide nanoparticles in rat pulmonary artery smooth muscle cells.

The development and use of nanomaterials, especially engineered nanoparticles (NP), is expected to provide many benefits. But at the same time the development of such materials is also feared because of their potential human health risks. Indeed, NP display some characteristics similar to ultrafine environmental particles which are known to exert deleterious cardiovascular effects including pro-hypertensive ones. In this context, the effect of NP on calcium signalling, whose deregulation is often involved in hypertensive diseases, remain poorly described. We thus assessed the effect of SiO2 NP on calcium signalling by fluorescence imaging and on the proliferation response in rat pulmonary artery smooth muscle cells (PASMC). In PASMC, acute exposure to SiO2 NP, from 1 to 500μg/mL, produced an increase of the [Ca2+]i. In addition, when PASMC were exposed to NP at 200μg/mL, a proliferative response was observed. This calcium increase was even greater in PASMC isolated from rats suffering from pulmonary hypertension. The absence of extracellular calcium, addition of diltiazem or nicardipine (L-type voltage-operated calcium channel inhibitors both used at 10μM), and addition of capsazepine or HC067047 (TRPV1 and TRPV4 inhibitors used at 10μM and 5μM, respectively) significantly reduced this response. Moreover, this response was also inhibited by thapsigargin (SERCA inhibitor, 1μM), ryanodine (100μM) and dantrolene (ryanodine receptor antagonists, 10μM) but not by xestospongin C (IP3 receptor antagonist, 10μM). Thus, NP induce an intracellular calcium rise in rat PASMC originating from both extracellular and intracellular calcium sources. This study also provides evidence for the implication of TRPV channels in NP induced calcium rise that may highlight the role of these channels in the deleterious cardiovascular effects of NP.

BK channels in rat and human pulmonary smooth muscle cells are BKα-β1 functional complexes lacking the oxygen-sensitive stress axis regulated exon insert.

A loss of K+ efflux in pulmonary arterial smooth muscle cells (PASMCs) contributes to abnormal vasoconstriction and PASMC proliferation during pulmonary hypertension (PH). Activation of high-conductance Ca2+-activated (BK) channels represents a therapeutic strategy to restore K+ efflux to the affected PASMCs. However, the properties of BK channels in PASMCs-including sensitivity to BK channel openers (BKCOs)-are poorly defined. The goal of this study was to compare the properties of BK channels between PASMCs of normoxic (N) and chronic hypoxic (CH) rats and then explore key findings in human PASMCs. Polymerase chain reaction results revealed that 94.3% of transcripts encoding BKα pore proteins in PASMCs from N rats represent splice variants lacking the stress axis regulated exon insert, which confers oxygen sensitivity. Subsequent patch-clamp recordings from inside-out (I-O) patches confirmed a dense population of BK channels insensitive to hypoxia. The BK channels were highly activated by intracellular Ca2+ and the BKCO lithocholate; these responses require BKα-β1 subunit coupling. PASMCs of CH rats with established PH exhibited a profound overabundance of the dominant oxygen-insensitive BKα variant. Importantly, human BK (hBK) channels in PASMCs from human donor lungs also represented the oxygen-insensitive BKα variant activated by BKCOs. The hBK channels showed significantly enhanced Ca2+ sensitivity compared with rat BK channels. We conclude that rat BK and hBK channels in PASMCs are oxygen-insensitive BKα-β1 complexes highly sensitive to Ca2+ and the BKCO lithocholate. BK channels are overexpressed in PASMCs of a rat model of PH and may provide an abundant target for BKCOs designed to restore K+ efflux.

Iptakalim induces mitochondria-dependent apoptosis in hypoxic rat pulmonary arterial smooth muscle cells.

Pulmonary vascular medial hypertrophy in hypoxic pulmonary arterial hypertension (HPH) is caused in part by decreased apoptosis in pulmonary artery smooth muscle cells (PASMCs). Iptakalim (Ipt), an ATP sensitive potassium channel opener, ameliorates HPH in animal models. Here we investigated the effects of Ipt on proliferation and apoptosis of hypoxic rat PASMCs, and to determine the possible underlying mechanisms. Primary rat PASMCs were isolated and cultured. PASMCs were cultured for 24h in normoxia or hypoxia (5% O2) conditions with and without Ipt. Cell proliferation and cycle were determined by MTT assay and flow cytometry, respectively. Mitochondrial membrane potential (Δym) was detected by fluorescence microscope Western blot assays were used to examine the expression of cyclin D, CDK4, endothelin-1 (ET-1), hypoxia-inducible factor-1 (HIF-1), platelet-derived growth factor-BB (PDGF-BB), Bax, Bcl-2, cytochrome c (Cyt c), caspase-9, and caspase-3 in PASMCs. We found that hypoxia significantly stimulated proliferation and rendered resistance to apoptosis in PASMCs. Ipt suppressed proliferation and induced cell cycle arrest in hypoxia PASMCs. Ipt decreased the expression of cyclin D, CDK4, HIF-1, ET-1, and PDGF-BB in hypoxia PASMCs. It reversed the depolarization of Δψm in hypoxia PASMCs too. Ipt significantly upregulated Bax expression and downregulated Bcl-2 expression, and promoted the release of Cyt c from mitochondria to cytoplasm in hypoxia PASMCs. Furthermore, Ipt significantly activated the caspase cascades evidenced by increased expression of caspase-9 and caspase-3 in hypoxia PASMCs. Ipt could inhibit cell proliferation and induce apoptosis associated with cell cycle arrest, decreased ET-1, HIF-1, cyclin D, CDK4, PDGF-BB and Δψm, increased Bax/Bcl-2 ratio, enhanced Cyt c release, and activation of caspases in PASMCs under hypoxia status. Our data indicated that Ipt could be a therapeutic candidate for treatment of HPH.

Chronic hypoxia increases intracellular Ca(2+) concentration and augments proliferation by enhancing store-operated Ca(2+) entry in pulmonary arterial smooth muscle cells

To determine whether store-operated Ca(2+) entry (SOCE) is involved in chronic hypoxia-induced alteration of intracellular Ca(2+) concentration ([Ca(2+) ]i) and proliferation in pulmonary arterial smooth muscle cells (PASMC). Rat PASMCs were cultured and treated in normoxia (21%O2) or hypoxia (4%O2) condition. The proliferation of PASMC was detected by cell counting kit-8 (CCK-8) assay. [Ca(2+) ]i, SOCE and the effects of store-operated Ca(2+) channel (SOCC) inhibitors, SKF96365 and NiCl2, on SOCE in hypoxic PASMCs were tested by InCyte [Ca(2+) ]i measurement system. Hypoxia for 24-60 h augmented PASMC proliferation (1.12±0.09 vs 0.71±0.05, P<0.05) and [Ca(2+) ]i [(214.8 ± 20.4) nmol/L vs (115.2±13.2) nmol/L, P<0.05] in a time-dependent manner with the maximum effect at 60 h. Perfusion of Ca(2+) -free Krebs solution containing nifedipine (5 μmol/L), cyclopiazonic acid (CPA, 10 μmol/L) in PASMCs caused a small transient increase of [Ca(2+) ]i with peak [Ca(2+) ]i (113.3±49.3) nmol/L.Chronic hypoxia (4% O2, 60 h) enhanced [Ca(2+) ]i level with peak value of (193.2±22.7) nmol/L (P<0.05) in PASMC.After restoration of extracellular Ca(2+) , CPA caused marked increase of [Ca(2+) ]i with peak value of (328.0 ±56.7) nmol/L.Chronic hypoxia strengthened CPA-induced increase of [Ca(2+) ]i with peak value of (526.0±33.7) nmol/L (P<0.05) in PASMCs.Either SKF96365 50 μmol/L or NiCl2 500 μmol/L distinctly attenuated CPA-induced enhancement of [Ca(2+) ]i, the peak value of which dropped from (526.0±33.7) nmol/L to (170.4±26.4) nmol/L (P<0.05) or (177.4±45.9) nmol/L (P<0.05) respectively. Chronic hypoxia boosts the release of Ca(2+) from sarcoplasmic reticulum and promotes the activity of SOCC and SOCE, leading to [Ca(2+) ]i elevation and proliferation of rat PASMCs.

Notch activation of Ca2+-sensing receptor mediates hypoxia-induced pulmonary hypertension.

A recent study from our group demonstrated that the Ca2+-sensing receptor (CaSR) was upregulated and that the extracellular Ca2+-induced increase in the cytosolic Ca2+ concentration [Ca2+]cyt was enhanced in pulmonary arterial smooth muscle cells (PASMCs) from patients with idiopathic pulmonary arterial hypertension. Here, we examined whether hypoxia-induced activation of Notch signaling leads to the activation and upregulation of CaSR in hypoxia-induced pulmonary hypertension (HPH). The activation of Notch signaling with Jag-1, a Notch ligand, can activate the function and increase the expression of CaSR in acute and chronic hypoxic PASMCs. Downregulation of Notch3 with a siRNA attenuates the extracellular Ca2+-induced increase in [Ca2+]cyt and the increase in hypoxia-induced PASMC proliferation in acute hypoxic rat PASMCs. Furthermore, we tested the prevention and rescue effects of a γ-secretase inhibitor (DAPT) in HPH rats. For the Jag-1-treated group, right ventricular systolic pressure (RVSP), right heart hypertrophy (RV/LV+S ratio), and the level of right ventricular myocardial fibrosis were higher than the hypoxia alone group. Meanwhile, DAPT treatment prevented and rescued pulmonary hypertension in HPH rats. The Notch activation of CaSR mediates hypoxia-induced pulmonary hypertension. Understanding the new molecular mechanisms that regulate [Ca2+]cyt and PASMC proliferation is critical to elucidating the pathogenesis of HPH and the development of novel therapies for pulmonary hypertension.

Bortezomib alleviates experimental pulmonary hypertension by regulating intracellular calcium homeostasis in PASMCs.

The ubiquitin-proteasome system is considered to be the key regulator of protein degradation. Bortezomib (BTZ) is the first proteasome inhibitor approved by the US Food and Drug Administration for treatment of relapsed multiple myeloma and mantle cell lymphoma. Recently, BTZ treatment was reported to inhibit right ventricular hypertrophy and vascular remodeling in hypoxia-exposed and monocrotaline-injected rats. However, the underlying mechanisms remain poorly understood. We previously confirmed that hypoxia-elevated basal intracellular Ca(2+) concentration ([Ca(2+)]i) and store-operated Ca(2+) entry (SOCE) in pulmonary artery smooth muscle cells (PASMCs) are involved in pulmonary vascular remodeling. In this study we aim to determine whether BTZ attenuates the hypoxia-induced elevation of [Ca(2+)] in PASMCs and the signaling pathway involved in this mechanism. Our results showed that 1) in hypoxia- and monocrotaline-induced rat pulmonary hypertension (PH) models, BTZ markedly attenuated the development and progression of PH, 2) BTZ inhibited the hypoxia-induced increase in cell proliferation, basal [Ca(2+)]i, and SOCE in PASMCs, and 3) BTZ significantly normalized the hypoxia-upregulated expression of hypoxia-inducible factor-1α, bone morphogenetic protein 4, canonical transient receptor potential isoforms 1 and 6, and the hypoxia-downregulated expression of peroxisome proliferator-activated receptor-γ in rat distal pulmonary arteries and PASMCs. These results indicate that BTZ exerts its protective role in the development of PH potentially by inhibiting the canonical transient receptor potential-SOCE-[Ca(2+)]i signaling axis in PASMCs.

Inhibitory effect of Bailing capsule on hypoxia-induced proliferation of rat pulmonary arterial smooth muscle cells.

Objectives:To investigated the effects of Bailing capsule on hypoxia-induced proliferation of pulmonary arterial smooth muscle cells (PASMCs).Methods:This prospective study was performed at the Central Laboratory, Chengdu Medical College, Chengdu, China between April 2012 and November 2014. Ten healthy adult male Wistar rats were administrated with gastric perfusion of Bailing capsule to obtain serum containing the tested drugs. Proliferation of pulmonary arterial smooth muscle cells proliferation was measured using cell counting kit-8 assay. Production of reactive oxygen species (ROS) in rat PASMCs was determined through a fluorometric assay, whereas production of endothelin-1 (ET-1) was detected by ELISA and quantitative real-time PCR (qRT-PCR). Expression of proliferating cell nuclear antigen (PCNA), c-fos, and c-jun in PASMCs was also determined using immunohistochemistry staining and qRT-PCR.Results:We observed that the medicated serum obviously inhibited hypoxia-induced cell proliferation in a concentration-dependent manner. Moreover, the medicated serum significantly reduced hypoxia-induced production of ROS and ET-1, as well as expression of PCNA, c-fos, and c-jun, in PASMCs.Conclusion:Results demonstrated that Bailing capsule can inhibit hypoxia-induced PASMC proliferation possibly by suppressing ET-1 and ROS production and by inhibiting expression of PCNA, c-fos, and c-jun. These results suggest that Bailing possess antiproliferative property, which is probably one of the underlying mechanisms of Bailing capsule for the clinical treatment of chronic obstructive pulmonary disease.

A method of primary cell culture of rat pulmonary artery smooth muscle cells and effects of platelet-derived growth factor induced proliferation and migration

To establish an easy, not depending on advanced laboratory apparatus method to isolate and culture rat pulmonary artery smooth muscle cells (PASMCs), and to explore the effects of platelet-derived growth factor (PDGF) on cell proliferation and migration. The right ventricle was perfused with the mixture of iron, agarose, and the PASMCs and iron could adhere to agarose. The iron-con-taining tissue would move to side of the tube next to the magnet and could be digested by collagenase I. By the method, vessel-containing tissue could be attained. With 3-4 weeks' purification, the PASMCs could be obtained. The PASMCs morphology was observed by an inverted micro-scope, and identified by immunocytochemistry and immunofluorescence. The effects of PDGF on cell proliferation and migration was detected by MTT assay and scratch wound assay. 14 days、21 days and primary culture after isolation, the PASMCs was identified, and the re-sult showed that isolation and primary culture of the cells were PASMCs. Compared with the cells with no stimulation, the proliferation of PASMCs exposed to PDGF was increased significantly(P<0.05), and scratch wound assay demonstrated that PDGF induced the significant increase of migration of PASMCs. This method to isolate and culture rat PASMCs is simple, not depending on advanced laborato-ry. PDGF can promote the proliferation and migration of PASMCs.