Hypoxia-induced Pulmonary Artery Smooth Muscle Cells Research Articles

GLI1-mediated pulmonary artery smooth muscle cell pyroptosis contributes to hypoxia-induced pulmonary hypertension.

Pulmonary hypertension (PH) is a clinically common malignant cardiovascular disease. Pyroptosis is a new form of inflammatory cell death that is involved in many disease processes. Glioma-associated oncogene family zinc finger 1 (GLI1) is a transcriptional activator that participates in many diseases, but its role has never been explored in inducing pyroptosis and the progress of PH. In this study, we used an animal model and cell molecular biology to determine the effect of GLI1 on chronic hypoxia-mediated PH progression and pulmonary artery smooth muscle cell (PASMC) pyroptosis. The major findings of the present study are as follows: Hypoxia induced aberrant expression of GLI1. The inhibition of GLI1 attenuated hypoxia-induced PH and PASMC pyroptosis. Meanwhile, GLI1 enhanced apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) expression by binding with its promoter. GLI1 may promote PASMC pyroptosis through ASC to affect the progression of PH. These findings may identify novel targets for molecular therapy of PH.

Long Noncoding RNA-Maternally Expressed Gene 3 Contributes to Hypoxic Pulmonary Hypertension.

The expression and function of long noncoding RNAs (lncRNAs) in the development of hypoxic pulmonary hypertension (HPH), especially in the proliferation of pulmonary artery smooth muscle cells (PASMCs), are largely unknown. Herein, we examined the expression and role of lncRNA-maternally expressed gene 3 (lncRNA-MEG3) in HPH. lncRNA-MEG3 was significantly increased and primarily localized in the cytoplasm of hypoxic PASMCs. lncRNA-MEG3 knockdown by lung-specific delivery of small interfering RNAs (siRNAs) significantly inhibited the development of HPH invivo. Silencing of lncRNA-MEG3 by siRNAs and gapmers attenuated proliferation and cell-cycle progression in both PASMCs from idiopathic pulmonary arterial hypertension (iPAH) patients (iPAH-PASMCs) and hypoxia-exposed PASMCs invitro. Mechanistically, we found that lncRNA-MEG3 interacts with and leads to the degradation of microRNA-328-3p (miR-328-3p), leading to upregulation of insulin-like growth factor 1 receptor (IGF1R). Additionally, higher expression of lncRNA-MEG3 and IGF1R and lower expression of miR-328-3p were observed in iPAH-PASMCs and relevant HPH models. These data provide insights into the contribution of lncRNA-MEG3 to HPH. Upregulation of lncRNA-MEG3 sequesters cytoplasmic miR-328-3p, eventually leading to expression of IGF1R, revealing a regulatory mechanism by lncRNAs in hypoxia-induced PASMC proliferation.

Inactivation of carboxyl terminus of Hsc70-interacting protein prevents hypoxia-induced pulmonary arterial smooth muscle cells proliferation by reducing intracellular Ca2+ concentration.

Carboxyl terminus of Hsc70-interacting protein (CHIP) is a 35-kDa cytoplasmic protein expressed in human striated muscle, brain, aortic smooth muscle, endothelial cells, and other tissues. Studies have confirmed that CHIP regulates cell growth, apoptosis, cell phenotype, metabolism, neurodegeneration, etc. However, whether CHIP is involved in pulmonary artery smooth muscle cell (PASMC) proliferation, a vital contributor to chronic hypoxia-induced pulmonary hypertension (CHPH), remains unknown. In this study, we first evaluated CHIP expression in the pulmonary arteries (PAs) of CHPH model rats. Subsequently, by silencing CHIP, we investigated the effect of CHIP on hypoxia-induced PASMC proliferation and the underlying mechanism. Our results showed that CHIP expression was upregulated in the PAs of CHPH model rats. Silencing CHIP significantly suppressed the hypoxia-triggered promotion of proliferation, [Ca2+]i, store-operated Ca2+ entry (SOCE), and some regulators of SOCE such as TRPC1 and TRPC6 in cultured PASMCs. These results indicate that CHIP likely contributes to hypoxia-induced PASMC proliferation by targeting the SOCE-[Ca2+]i pathway through the regulation of TRPC1 and TRPC6 in the PASMCs. In conclusion, the findings of the current study clarify the role of CHIP in hypoxia-induced PASMC proliferation.

Beraprost Upregulates KV Channel Expression and Function via EP4 Receptor in Pulmonary Artery Smooth Muscle Cells Obtained from Rats with Hypoxia-Induced Pulmonary Hypertension

The reduced expression and function of voltage-dependent potassium (K_V) channels have been involved in the pathogenesis of hypoxia-induced pulmonary hypertension (HPH), leading to pulmonary vasoconstriction and vascular remodeling, while the upregulation of K_V channels is of therapeutic significance for pulmonary hypertension. Beraprost sodium (BPS) has been shown to be effective in patients with pulmonary hypertension. However, the effect of BPS on O₂-sensitive K_V channels in pulmonary artery smooth muscle cells (PASMCs) remains unclear. In the present study, the effect of BPS on rats with HPH was observed, and the influence of BPS on the expression and function of O₂-sensitive K_V channels in PASMCs was investigated. The results revealed that BPS reduced mean pulmonary artery pressure, suppressed right ventricular hypertrophy, and attenuated the remodeling of pulmonary arteries in rats exposed to discontinuous hypoxia for 4 weeks (8 h/day). This was accompanied with the significantly upregulated expression of K_V channel α-subunits (K_V1.2, K_V1.5 and K_V2.1) and O₂-sensitive voltage-gated K⁺ (K_V) channel current (I_K(V)) in small pulmonary arteries in HPH model rats, as well as in hypoxia-induced PASMCs. Furthermore, in vitrostudies have revealed that the upregulation of BPS on O₂-sensitive K_V channels was significantly inhibited after treatment with prostaglandin E₂ receptor subtype EP₄ antagonist GW627368X. Taken together, these results suggest that BPS attenuates the development of HPH through the upregulation of O₂-sensitive K_V channels, which was probably via the EP₄ receptor-related pathway.

5-Aza-2′-deoxycytidine, a DNA methylation inhibitor, attenuates hypoxic pulmonary hypertension via demethylation of the PTEN promoter

Phosphatase and tensin homolog (PTEN) plays an important role in the pathogenesis of hypoxic pulmonary hypertension (HPH). A decrease in PTEN expression is associated with the hypermethylation of its promoter. However, whether the demethylation of the PTEN gene could attenuate HPH remains unknown. 5-Aza-2′-deoxycytidine (5-Aza-dC) is a DNA methyltransferase (DNMT) inhibitor. The present study was designed to investigate the effects and mechanisms of 5-Aza-dC on HPH. The proliferation, migration and apoptosis of rat pulmonary artery smooth muscle cells (PASMCs) induced by hypoxia and treated with 5-Aza-dC were detected. The expression of PTEN and DNMTs and the PTEN methylation status of PASMCs were detected. SD rats were randomly divided into normal group, hypoxia group and hypoxia + 5-Aza-dC group. The expression of PTEN was decreased, the expression of DNMTs was increased, and the methylation status of PTEN was increased in hypoxia-induced PASMCs. However, 5-Aza-dC can rescue the decreased PTEN, inhibit DNMT levels in a dose-dependent manner and suppress PTEN methylation. Furthermore, the demethylation of PTEN, which was induced by 5-Aza-dC, inhibited the proliferation, migration and promoted apoptosis in PASMCs. In vivo studies further demonstrated that the expression of PTEN, mean pulmonary artery pressure and right ventricular hypertrophy index in HPH rats was attenuated by 5-Aza-dC. 5-Aza-dC also suppressed the expression of DNMTs and PTEN methylation in the lungs of HPH rats. These results indicated that PTEN promoter methylation status is involved in HPH. 5-Aza-dC, as a DNMT inhibitor, has the potential to attenuate HPH via demethylation of the PTEN promoter.

Baicalin promotes apoptosis and inhibits proliferation and migration of hypoxia-induced pulmonary artery smooth muscle cells by up-regulating A2a receptor via the SDF-1/CXCR4 signaling pathway

BackgroundBaicalin is a flavonoid compound that exerts specific pharmacological effect in attenuating the proliferation, migration, and apoptotic resistance of hypoxia-induced pulmonary artery smooth muscle cells (PASMCs). However, the underlying mechanism has not been fully elucidated yet. Although our previous studies had indicated that activation of A2aR attenuates CXCR expression, little is known about the relationship between A2aR and SDF-1/CXCR4 axis in hypoxic PASMCs. In this study, we aimed to investigate the effect of A2aR on the SDF-1/CXCR4 axis in hypoxic PASMCs, the mechanism underlying this effect, and whether baicalin exerts its protective functions though A2aR.MethodsRat PASMCs were cultured under normoxia/hypoxia and divided into nine groups: normoxia, hypoxia, hypoxia + AMD3100 (a CXCR4 antagonist), hypoxia + baicalin, hypoxia + negative virus, normoxia + A2aR knockdown, hypoxia + A2aR knockdown, hypoxia + CGS21680 (an A2aR agonist), and hypoxia + A2aR knockdown + baicalin. Lentiviral transfection methods were used to establish the A2aR knockdown model in PASMCs. Cells were incubated under hypoxic conditions for 24 h. Expression levels of A2aR, SDF-1, and CXCR4 were detected using RT-qPCR and western blot. The proliferation and migration rate were observed via CCK-8 and Transwell methods. Cell cycle distribution and cell apoptosis were measured by flow cytometry (FCM) and the In-Situ Cell Death Detection kit (Fluorescein).ResultsUnder hypoxic conditions, levels of A2aR, SDF-1, and CXCR4 were significantly increased compared to those under normoxia. The trend of SDF-1 and CXCR4 being inhibited when A2aR is up-regulated was more obvious in the baicalin intervention group. Baicalin directly enhanced A2aR expression, and A2aR knockdown weakened the function of baicalin. SDF-1 and CXCR4 expression levels were increased in the hypoxia + A2aR knockdown group, as were the proliferation and migration rates of PASMCs, while the apoptotic rate was decreased. Baicalin and CGS21680 showed opposite effects.ConclusionsOur data indicate that baicalin efficiently attenuates hypoxia-induced PASMC proliferation, migration, and apoptotic resistance, as well as SDF-1 secretion, by up-regulating A2aR and down-regulating the SDF-1/CXCR4 axis.

MicroRNA-150 relieves vascular remodeling and fibrosis in hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is a dangerous disease, featured by pulmonary vascular remodeling. Excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) and pulmonary artery endothelial cells (PAECs) plays crucial roles in this process. MicroRNA-150 (miR-150) level has been found to be reduced in patients with PH, and correlated with the poor survival. This study aimed to investigate the beneficial effect of miR-150 on PH in hypoxia-induced rats, PASMCs and PAECs. The results showed that miR-150 level was reduced in the lung tissue and plasma of hypoxia-treated rats. Lentivirus-mediated overexpression of miR-150 restrained hypoxia-induced increase in right ventricular systolic pressure and decrease in cardiac output. Moreover, as assessed by HE staining, hypoxia-induced thickening of vessel wall was relieved by miR-150 up-regulation. Overexpression of miR-150 also suppressed hypoxia-induced formation of collagen fiber, expressions of α-SMA, TGF-β1, and collagen I in lung tissues and PASMCs. In addition, the excessive proliferation of PASMCs induced by hypoxia was repressed by miR-150 overexpression via AKT/mTOR signaling pathway. Increased NFATc3 expression in response to hypoxia was restrained by miR-150 overexpression in lung tissue and PAMSCs. Finally, miR-150 overexpression inhibited hypoxia-induced proliferation and apoptosis resistance in PAECs. In conclusion, these results indicate that miR-150 protects against hypoxia-induced pulmonary vascular remodeling, fibrosis, abnormal proliferation of PASMCs and PAECs, which suggests miR-150 as a promising therapeutic target for PH.

Smooth muscle cell-specific FoxM1 controls hypoxia-induced pulmonary hypertension

RationaleForkhead box M1 (FoxM1) is a transcription factor that promotes cell proliferation by regulating a broad spectrum of genes that participate in cell cycle regulation, such as Cyclin B, CDC25B, and Aurora B Kinase. We have shown that hypoxia, a well-known stimulus for pulmonary hypertension (PH), induces FoxM1 in pulmonary artery smooth muscle cells (PASMC) in a HIF-dependent pathway, resulting in PASMC proliferation, while the suppression of FoxM1 prevents hypoxia-induced PASMC proliferation. However, the implications of FoxM1 in the development of PH remain less known. MethodsWe determined FoxM1 levels in the lung samples of idiopathic PAH (pulmonary arterial hypertension) (IPAH) patients and hypoxia-induced PH mice. We generated constitutive and inducible smooth muscle cell (SMC)-specific FoxM1 knockdown or knockout mice as well as FoxM1 transgenic mice which overexpress FoxM1, and exposed them to hypoxia (10% O2, 90% N2) or normoxia (Room air, 21% oxygen) for four weeks, and measured PH indices. We also isolated mouse PASMC (mPASMC) and mouse embryonic fibroblasts (MEF) from these mice to examine the cell proliferation and expression levels of SMC contractile proteins. ResultsWe showed that in hypertensive human lungs or mouse lungs, FoxM1 levels were elevated. Constitutive knockout of FoxM1 in mouse SMC caused early lethality, whereas constitutive knockdown of FoxM1 in mouse SMC prevented hypoxia-induced PH and PASMC proliferation. Inducible knockout of FoxM1 in SMC reversed hypoxia-induced pulmonary artery wall remodeling in existing PH. Overexpression of FoxM1 enhanced hypoxia-induced pulmonary artery wall remodeling and right ventricular hypertrophy in mice. Alteration of FoxM1 status did not affect hypoxia-induced hypoxia-inducible factor (HIF) activity in mice. Knockout of FoxM1 decreased PASMC proliferation and induced expression of SMC contractile proteins and TGF-β/Smad3 signaling. ConclusionsOur studies provide clear evidence that altered FoxM1 expression in PASMC contributes to PH and uncover a correlation between Smad3-dependent signaling in FoxM1-mediated proliferation and de-differentiation of PASMC.

Paeonol regulates hypoxia-induced proliferation of pulmonary artery smooth muscle cells via EKR 1/2 signalling

Pulmonary hypertension (PH) is a disease with a developmental origin characterized by obstructive vascular remodelling that is partially due to excessive pulmonary arterial smooth muscle cells (PASMCs) proliferation. Paeonol has important effects on vascular cell proliferation, migration, and inflammation, but researchers have not determined whether paeonol participates in the development and progression of pulmonary vascular remodelling. We explored the remarkable anti-proliferative effects of paeonol on hypoxic PASMCs, which are postulated to be mediated by the extracellular signal-regulated kinase 1 and 2 (ERK1/2) signalling pathway. In this study, hypoxic rodent PH models, Western blotting, flow cytometry, immunochemistry, and morphometric analyses of the lung vasculature and right ventricle (RV) vessels were performed. Paeonol reversed hypoxia-induced increases in right ventricular function, right ventricular systolic pressure and thickening of medial walls. Meanwhile, paeonol ameliorated the hypoxia-induced PASMCs proliferation. Furthermore, paeonol modulated cell proliferation and cell cycle transitions from G0/G1 phase to S phase and G2/M phase in an ERK1/2-dependent manner. Our findings emphasize the central function of paeonol in regulating PASMCs proliferation in subjects with PH. Therefore, paeonol represents a potential novel therapeutic approach for the treatment of PH.

Inhibition of miR-361-5p suppressed pulmonary artery smooth muscle cell survival and migration by targeting ABCA1 and inhibiting the JAK2/STAT3 pathway

MicroRNAs play a crucial role in the progression of pulmonary arterial hypertension (PAH). The aim of this study was to investigate the effect of miR-361-5p on the proliferation, migration and apoptosis of pulmonary artery smooth muscle cells (PASMCs) that under the treatment of hypoxia and explore the underlying mechanisms. The results proved that hypoxia noticeably up-regulated the expression of miR-361-5p in PASMCs in comparison to the normoxia-treated cells, while TNF-α and IL-6 stimulation had no obvious effects on miR-361-5p level. Hypoxia induced miR-361-5p elevation in a HIF-1α-dependent manner. Inhibition of miR-361-5p dramatically inhibited hypoxia-induced cell proliferation and migration. miR-361-5p inhibition also rescued hypoxia exposure caused suppression of PASMCs apoptosis. In addition, the results showed that ABCA1 was a direct target of miR-361-5p and was down-regulated in hypoxia-induced PASMCs. Hypoxia and TNF-α or IL-6 stimulation significantly inhibited ABCA1 expression. In addition, overexpression of ABCA1 enhanced the effect of miR-361-5p on hPASMCs. Furthermore, the inhibition of miR-361-5p significantly down-regulated the expression level of p-JAK2 and p-STAT3. In conclusion, it may suggest that the suppression of miR-361-5p suppressed PASMC survival and migration by targeting ABCA1 and inhibiting the JAK2/STAT3 pathway.

NOD2 deficiency exacerbates hypoxia-induced pulmonary hypertension and enhances pulmonary vascular smooth muscle cell proliferation.

Expression of nucleotide-binding oligomerization domain protein 2 (NOD2) is upregulated in pulmonary artery smooth muscle cells (PASMCs) during hypoxia. To investigate the involvement of NOD2 in the pulmonary vascular response to hypoxia, we subjected wild-type and NOD2-deficient mice to chronic normobaric hypoxic conditions. Compared to wild-type mice, NOD2-deficient mice developed severe pulmonary hypertension with exaggerated elevation of right ventricular systolic pressure, profound right ventricular hypertrophy and striking vascular remodeling after exposure to hypoxia. Pulmonary vascular remodeling in NOD2-deficient mice was characterized by increased PASMC proliferation. Furthermore, hypoxia-inducible factor-1α expression and Akt phosphorylation were upregulated in PASMCs from NOD2-deficient mice exposed to hypoxia. Our findings revealed that the absence of NOD2 exacerbated hypoxia-induced PASMC proliferation, pulmonary hypertension and vascular remodeling, but had no effect on PASMC migration or contractility.

Up-regulation of caveolin-1 by DJ-1 attenuates rat pulmonary arterial hypertension by inhibiting TGFβ/Smad signaling pathway

Pulmonary arterial hypertension (PAH), characterized by excessive proliferation and apoptosis resistance of pulmonary artery smooth muscle cells (PASMCs), is closely associated with the imbalance in vasoactive mediators and massive remodeling of pulmonary vasculature. DJ-1/park7, a multifunctional protein, plays a critical defense role in several cytobiological activity, such as transcriptional regulation, anti-oxidative stress and tumor formation. In this study, we investigated the effects of DJ-1 on hypoxia-induced PAH model rats and PASMCs, as well as its possible molecular mechanism. First, the low expressions of DJ-1 and caveolin-1 (Cav-1) were synchronously detected in lung tissue of PAH model rats and hypoxia-induced PASMCs by Western blot. Then, the DJ-1 wild type (WT) or Knock out (KO) rats were exposed to chronic hypoxia to mimic a hypoxic PAH condition. The protein level of Cav-1 was markedly decreased in the tissue of DJ-1 KO rats, and additionally lower in tissue of the hypoxia group than that in the normoxia group for DJ-1 WT and KO rats. In vivo, hemodynamic data showed that the pulmonary arterial pressure (mPAP), right ventricle systolic pressure (RVSP) and pulmonary arterial systolic pressure (PASP), as well as the weight of the right ventricle/left ventricle plus septum (RV/LV+S) ratio of PAH model rats were higher in the DJ-1 KO group than those in the DJ-1 WT group. Moreover, knockout of DJ-1 also results in the phenotype switch from contractile to synthetic PASMC, which is reflected by reduced calponin and SM22α expressions. In vitro, DJ-1 overexpression reversed hypoxia-induced elevation of PASMC cell proliferation, migration and Ca2+ concentration, which were not obviously observed in Cav-1 shRNA (sh-Cav-1) and DJ-1 co-transfected cells. Then the increased levels of calponin and SM22α were detected in the DJ-1 group; similarly those levels were not changed in the DJ-1+sh-Cav-1 group. Finally, the expression of TGFβ1, p-Smad2 and p-Smad3 were obviously decreased in the ad-DJ-1 group, however those were all elevated in the DJ-1 and sh-Cav-1 co-transfected groups. In conclusion, these results indicate that DJ-1 may alleviate hypoxia-induced PASMCs injury by Cav-1 through inhibiting the TGFβ/Smad signaling pathway.

LOX-1 mediated phenotypic switching of pulmonary arterial smooth muscle cells contributes to hypoxic pulmonary hypertension

In pulmonary hypertension (PH), pulmonary arterial smooth muscle cells (PASMCs) are dedifferentiated, undergoing a contractile-to-synthetic phenotypic switching. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) plays diverse roles in the cardiovascular system, but its contribution to PH remains to be fully defined. The present study was undertaken to explore the role of LOX-1 in PASMCs dedifferentiation in hypoxia-induced pulmonary vascular remodeling and PH. In a rat model of hypoxic PH, pulmonary vascular remodeling was accompanied by increased expression of LOX-1 in pulmonary arteries. In primary rat PASMCs, hypoxia-induced PASMCs dedifferentiation occurred concomitantly with LOX-1 upregulation. Inhibition of LOX-1 by either siRNA knockdown or neutralizing antibody significantly ameliorated PASMCs dedifferentiation. Mechanistically, LOX-1 promotes PASMCs dedifferentiation under hypoxic conditions via ERK1/2-Elk-1/MRTF-A/SRF signaling pathway. In conclusion, our data uncovers an important role of LOX-1 in the maintenance of PASMCs phenotype. Therapeutic targeting of LOX-1/ERK1/2-Elk-1/MRTF-A/SRF signaling axis would be exploited to treat hypoxic PH.

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.

Inhibition of mitochondrial fission prevents hypoxia-induced metabolic shift and cellular proliferation of pulmonary arterial smooth muscle cells

Chronic hypoxia exacerbates proliferation of pulmonary arterial smooth muscle cells (PASMC), thereby reducing the lumen of pulmonary arteries. This leads to poor blood oxygenation and cardiac work overload, which are the basis of diseases such as pulmonary artery hypertension (PAH). Recent studies revealed an emerging role of mitochondria in PAH pathogenesis, as key regulators of cell survival and metabolism. In this work, we assessed whether hypoxia-induced mitochondrial fragmentation contributes to the alterations of both PASMC death and proliferation. In previous work in cardiac myocytes, we showed that trimetazidine (TMZ), a partial inhibitor of lipid oxidation, stimulates mitochondrial fusion and preserves mitochondrial function. Thus, here we evaluated whether TMZ-induced mitochondrial fusion can prevent human PASMC proliferation in an in vitro hypoxic model. Using confocal fluorescence microscopy, we showed that prolonged hypoxia (48h) induces mitochondrial fragmentation along with higher levels of the mitochondrial fission protein DRP1. Concomitantly, both mitochondrial potential and respiratory rates decreased, indicative of mitochondrial dysfunction. In accordance with a metabolic shift towards non-mitochondrial ATP generation, mRNA levels of glycolytic markers HK2, PFKFB2 and GLUT1 increased during hypoxia. Incubation of PASMC with TMZ, prior to hypoxia, prevented all these changes and precluded the increase in PASMC proliferation. These findings were also observed using Mdivi-1 (a pharmacological DRP1 inhibitor) or a dominant negative DRP1 K38A as pre-treatments. Altogether, our data indicate that TMZ exerts a protective role against hypoxia-induced PASMC proliferation, by preserving mitochondrial function, thus highlighting DRP1-dependent morphology as a novel therapeutic approach for diseases such as PAH.

Epigallocatechin-3-gallate ameliorates hypoxia-induced pulmonary vascular remodeling by promoting mitofusin-2-mediated mitochondrial fusion

Pulmonary hypertension (PH) mainly results from excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) and displays mitochondrial abnormalities such as mitochondrial fragmentation. Epigallocatechin-3-gallate (EGCG), an efficient antiproliferative compound in green tea, has recently been demonstrated to inhibit PASMCs proliferation. However, the pre-clinical issues as to whether EGCG attenuates PH and the underlying mechanisms have yet to be addressed. The present study was undertaken to investigate the therapeutic effects of EGCG on PH and its effects on mitochondrial fragmentation in PASMCs. Rats exposed to hypoxia (10% O2, 3 weeks) developed PH. EGCG (50, 100 or 200mg/kg/d, i.g.) dose-dependently attenuated right ventricular systolic pressure, pulmonary vascular remodeling and right ventricular hypertrophy, increased expression of mitochondrial fusion protein - mitofusin-2 (MFN-2), and promoted mitochondrial fusion as evidenced by decreased number and volume of mitochondria in PASMCs of pulmonary arteries. Notably, EGCG (50μM) downregulated hypoxia-induced (3% O2, 48h) PASMCs mitochondrial fragmentation and inhibited PASMCs proliferation via KLF-4/MFN-2/p-Erk signaling pathway. Collectively, our data demonstrated that EGCG exerts antiproliferative effects via regulating mitochondrial fragmentation of PASMCs and EGCG holds the promise as a drug against PH.

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.

Docosahexaenoic acid inhibits hypoxia-induced pulmonary arterial smooth muscle cells phenotype switching by inhibiting NFATc1 signaling

Objective: To explore the molecular mechanism of docosahexaenoic acid (DHA) on regulating the phenotype switching of hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs). Methods: The PASMCs were isolated from Sprague Dawley rats. PASMCs were divided into five groups: normal control group, hypoxia group (1%O(2, )94%N(2, )5% CO(2) stimulation for 12 hours), hypoxia+ DHA group (10 μmol/L DHA pretreatment followed by 12 hours hypoxia), hypoxia+ DHA+ NFATc1 overexpression group (transfection of the NFATc1 lentivirus for 24 hours, followed by hypoxia stimulation for 12 hours after 10 μmol/L DHA treatment), and hypoxia+ DHA+ siNFATc1 group (transfection the siNFATc1 for 24 hours, followed by hypoxia stimulation for 12 hours after 10 μmol/L DHA treatment). The hypoxia stimulation was achieved by use of a special hypoxia incubator (1%O(2, )94%N(2, )5%CO(2)). The expressions of NFATc1 of various groups were determined by qRT-PCR and Western blot. The expression of α-SMA was determined by immunofluorescence staining, qRT-PCR and Western blot. The expression of SM22 was determined by qRT-PCR. The proliferation of PASMC was determined by EDU staining. Results: The mRNA and protein expression levels of NFATc1 were significantly upregulated in hypoxia group compared with the normal control group (P<0.05), while hypoxia-induced upregulation of NFTAc1 could be significantly downregulated by DHA treatment (P<0.05). The α-SMA positive cell number, protein and mRNA levels of α-SMA and the mRNA level of SM22 were significantly lower in the hypoxia group than in normal control group, which could be significantly reversed by DHA, the protective effects could then be abolished by NFATc1 overexpression. Above indices were significantly lower in the hypoxia+ DHA+ siNFATc1 group than in hypoxia+ DHA+ NFATc1 overexpression group (P<0.05). The proliferation of PASMCs was significantly higher in the hypoxia group than in the control group (P<0.05), and which could be significantly reduced by DHA (P<0.05), and the protective effect of DHA could be significantly abolished by overexpression of NFATc1 (P<0.05). The proliferation of PASMCs was significantly lower in the hypoxia+ DHA+ siNFATc1 group than in the hypoxia+ DHA+ overexpression NFATc1 group (P<0.05). Conclusion: DHA could prevent hypoxia-induced PASMCs phenotype switching and proliferation by inhibiting NFATc1 signaling.

Negative feedback regulation between microRNA let-7g and LOX-1 mediated hypoxia-induced PASMCs proliferation

BackgroundPulmonary hypertension (PH) is a proliferative disorder associated with enhanced proliferation and suppressed apoptosis of pulmonary artery smooth muscle cells (PASMCs). Our lately study demonstrated that let-7g inhibited hypoxia-induced proliferation of PASMCs via repressing c-myc-Bmi-1-p16 signaling pathway. However, the upstream of let-7g has not yet been fully defined. Previous studies have shown that LOX-1, a target of let-7g, could also regulate the expression of let-7g in human aortic endothelial cells. In this present study, we aimed to investigate whether there is a negative feedback regulation between microRNA let-7g and LOX-1 in hypoxia-induced proliferation of PASMCs. MethodsSD Rats were exposed to hypoxia (10% O2, 3 weeks) to induce PH. HE staining was used to evaluate pulmonary artery remodeling. in situ hybridization and immunohistochemistry were performed to assess the expression and distribution of let-7g and LOX-1, respectively. MTS, EDU and flow cytometry were performed to evaluate PASMCs proliferation. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were conducted to assess the expression of let-7g, LOX-1, calpain-1,-2,-4, and OCT-1. ResultsThe expression of let-7g was significantly down-regulated in pulmonary arteries of hypoxia-induced PH rats accompanied by pulmonary vascular remodeling, whereas let-7g mimic inhibited hypoxia-induced proliferation of PASMCs and up-regulation of LOX-1 expression. LOX-1 blocking reversed hypoxia-induced down-regulation of let-7g expression. Calpains, protein kinase C and OCT-1 were involved in negative feedback regulation between let-7g and LOX-1. ConclusionNegative feedback regulation between let-7g and LOX-1 mediated hypoxia-induced proliferation of in PASMCs.

Schisandrin B displays a protective role against primary pulmonary hypertension by targeting transforming growth factor β1

Pulmonary arterial smooth muscle cells (PASMCs) in the medial layer of the vessel wall are involved in vessel homeostasis, but also for pathologic vascular remodeling in diverse diseases, such as pulmonary arterial hypertension (PAH). Pulmonary vascular remodeling in PAH results in vascular disorders, but its underlying molecular mechanisms are still not to be fully disclosed. In this study, we investigated the expression and function of the transforming growth factor (TGF)-β1 in human PASMC cultured under the condition of hypoxia and elucidated the effect of schisandra chinensis and its active ingredients on proliferation, migration, and apoptosis in human PASMCs. We demonstrated that schisandrin B (Sch.B) alleviated the severity of PAH in PASMCs cultured under the condition of hypoxia. Significant upregulation of TGF-β1 was observed in hypoxia-induced human PASMCs. Interestingly, administration of Sch.B substantially attenuated TGF-β1 level in these PASMCs. In order to elucidate Sch.B function, the hypoxia-induced human PASMC was stimulated with Sch.B or cotreatment with TGF-β1 in vitro. In agreement with its TGF-β1-reducing effect, Sch B relieved human PASMCs migration and promoted the apoptosis of human PASMCs, by activation of TGF-β1 downstream signal pathways in PASMCs. In contrast, co-treatment with TGF-β1 promoted human PASMC proliferation and migration and inhibited the apoptosis of human PASMC, which can attenuate the protective role of Sch.B in human PASMC. Taken collectively, these findings suggest that the vascular relaxation evoked by Sch.B was mediated by direct effect on vascular smooth muscle cell via TGF-β1 downstream signal pathways.