Bi-phasic regulation of miR-17~92 transcription during hypoxia: Roles of HIF1 and p53 hyperphosphorylation at ser15.

We have reported previously that during hypoxia exposure, the expression of mature miR-17~92 was first upregulated and then downregulated in pulmonary artery smooth muscle cells (PASMC) and in mouse lungs in vitro and in vivo. Here we investigated the mechanisms regulating this bi-phasic expression of miR-17~92 in PASMC in hypoxia. We measured the level of primary miR-17~92 in PASMC during hypoxia exposure and found that short-term hypoxia exposure (3%O2, 6 hours) induced the level of primary miR-17~92, while long-term hypoxia exposure (3%O2, 24 hours) decreased its level, suggesting a bi-phasic regulation of miR-17~92 expression at the transcriptional level. We found that short-term hypoxia-induced upregulation of miR-17~92 was HIF1α and E2F1 dependent. Two HIF1α binding sites on miR-17~92 promoter were identified. We also found that long-term hypoxia-induced suppression of miR-17~92 expression could be restored by silencing of p53. Mutation of the p53-binding sites in the miR-17~92 promoter increased miR-17~92 promoter activity in both normoxia and hypoxia. Our findings suggest that the bi-phasic transcriptional regulation of miR-17~92 during hypoxia is controlled by HIF1/E2F1 and p53 in PASMC: during short-term hypoxia exposure, stabilization of HIF1 and induction of E2F1 induces the transcription of miR-17~92; while during long-term hypoxia exposure, hyperphosphorylation of p53 suppresses the expression of miR-17~92.

PAI-1 is a novel component of the miR-17~92 signaling that regulates pulmonary artery smooth muscle cell phenotypes.

We have previously reported that miR-17~92 is critically involved in the pathogenesis of pulmonary hypertension (PH). We also identified two novel mR-17/20a direct targets, PDZ and LIM domain protein 5 (PDLIM5) and prolyl hydroxylase 2 (PHD2), and elucidated the signaling pathways by which PDLIM5 and PHD2 regulate functions of pulmonary artery smooth muscle cells (PASMCs). In addition, we have shown that plasminogen activator inhibitor-1 (PAI-1) is also downregulated in PASMCs that overexpress miR-17~92. However, it is unclear whether PAI-1 is a direct target of miR-17~92 and whether it plays a role in regulating the PASMC phenotype. In this study, we have identified PAI-1 as a novel target of miR-19a/b, two members of the miR-17~92 cluster. We found that the 3'-untranslated region (UTR) of PAI-1 contains a miR-19a/b binding site and that miR-19a/b can target this site to suppress PAI-1 protein expression. MiR-17/20a, two other members of miR-17~92, may also indirectly suppress PAI-1 expression through PDLIM5. PAI-1 is a negative regulator of miR-17~92-mediated PASMC proliferation. Silencing of PAI-1 induces Smad2/calponin signaling in PASMCs, suggesting that PAI-1 is a negative regulator of the PASMC contractile phenotype. We also found that PAI-1 is essential for the metabolic gene expression in PASMCs. Furthermore, although there is no significant change in PAI-1 levels in PASMCs isolated from idiopathic pulmonary arterial hypertension and associated pulmonary arterial hypertension patients, PAI-1 is downregulated in hypoxia/Sugen-induced hypertensive rat lungs. These results suggest that miR-17~92 regulates the PASMC contractile phenotype and proliferation coordinately and synergistically by direct and indirect targeting of PAI-1.

Endothelial and Smooth Muscle Cell Interactions in the Pathobiology of Pulmonary Hypertension.

In the pulmonary vasculature, the endothelial and smooth muscle cells are two key cell types that play a major role in the pathobiology of pulmonary vascular disease and pulmonary hypertension. The normal interactions between these two cell types are important for the homeostasis of the pulmonary circulation, and any aberrant interaction between them may lead to various disease states including pulmonary vascular remodeling and pulmonary hypertension. It is well recognized that the endothelial cell can regulate the function of the underlying smooth muscle cell by releasing various bioactive agents such as nitric oxide and endothelin-1. In addition to such paracrine regulation, other mechanisms exist by which there is cross-talk between these two cell types, including communication via the myoendothelial injunctions and information transfer via extracellular vesicles. Emerging evidence suggests that these nonparacrine mechanisms play an important role in the regulation of pulmonary vascular tone and the determination of cell phenotype and that they are critically involved in the pathobiology of pulmonary hypertension.

Suppression of von Hippel-Lindau Protein in Fibroblasts Protects against Bleomycin-Induced Pulmonary Fibrosis.

We have reported that von Hippel-Lindau protein (pVHL) expression is elevated in human and mouse fibrotic lungs and that overexpression of pVHL stimulates fibroblast proliferation. We sought to determine whether loss of pVHL in fibroblasts prevents injury and fibrosis in mice that are treated with bleomycin. We generated heterozygous fibroblast-specific pVHL (Fsp-VHL) knockdown mice (Fsp-VHL(+/-)) and homozygous Fsp-VHL knockout mice (Fsp-VHL(-/-)) by crossbreeding vhlh 2-lox mice (VHL(fl/fl)) with Fsp-Cre recombinase mice. Our data show that Fsp-VHL(-/-) mice, but not Fsp-VHL(+/-) mice, have elevated red blood cell counts, hematocrit, hemoglobin content, and expression of hypoxia-inducible factor (HIF) targets, indicating HIF activation. To examine the role of pVHL in bleomycin-induced lung injury and fibrosis in vivo, we administered PBS or bleomycin to age-, sex-, and strain-matched 8-week-old VHL(fl/fl), Fsp-VHL(+/-), and Fsp-VHL(-/-) mice. In Fsp-VHL(+/-) and Fsp-VHL(-/-) mice, bleomycin-induced collagen accumulation, fibroblast proliferation, differentiation, and matrix protein dysregulation were markedly attenuated. Suppression of pVHL also decreased bleomycin-induced Wnt signaling and prostaglandin E2 signaling but did not affect bleomycin-induced initial acute lung injury and lung inflammation. These results indicate that pVHL has a pivotal role in bleomycin-induced pulmonary fibrosis, possibly via an HIF-independent pathway. Paradoxically, pVHL does not affect bleomycin-induced lung injury and inflammation, indicating a separation of the mechanisms involved in injury/inflammation from those involved in pulmonary fibrosis.

Loss of microRNA-17∼92 in smooth muscle cells attenuates experimental pulmonary hypertension via induction of PDZ and LIM domain 5.

RATIONALE: Recent studies suggest that microRNAs (miRNAs) play important roles in regulation of pulmonary artery smooth muscle cell (PASMC) phenotype and are implicated in pulmonary arterial hypertension (PAH). However, the underlying molecular mechanisms remain elusive. OBJECTIVES: This study aims to understand the mechanisms regulating PASMC proliferation and differentiation by microRNA-17∼92 (miR-17∼92) and to elucidate its implication in PAH. METHODS: We generated smooth muscle cell (SMC)-specific miR-17∼92 and PDZ and LIM domain 5 (PDLIM5) knockout mice and overexpressed miR-17∼92 and PDLIM5 by injection of miR-17∼92 mimics or PDLIM5-V5-His plasmids and measured their responses to hypoxia. We used miR-17∼92 mimics, inhibitors, overexpression vectors, small interfering RNAs against PDLIM5, Smad, and transforming growth factor (TGF)-ß to determine the role of miR-17∼92 and its downstream targets in PASMC proliferation and differentiation. MEASUREMENTS AND MAIN RESULTS: We found that human PASMC (HPASMC) from patients with PAH expressed decreased levels of the miR-17∼92 cluster, TGF-ß, and SMC markers. Overexpression of miR-17∼92 increased and restored the expression of TGF-ß3, Smad3, and SMC markers in HPASMC of normal subjects and patients with idiopathic PAH, respectively. Knockdown of Smad3 but not Smad2 prevented miR-17∼92-induced expression of SMC markers. SMC-specific knockout of miR-17∼92 attenuated hypoxia-induced pulmonary hypertension (PH) in mice, whereas reconstitution of miR-17∼92 restored hypoxia-induced PH in these mice. We also found that PDLIM5 is a direct target of miR-17/20a, and hypertensive HPASMC and mouse PASMC expressed elevated PDLIM5 levels. Suppression of PDLIM5 increased expression of SMC markers and enhanced TGF-ß/Smad2/3 activity in vitro and enhanced hypoxia-induced PH in vivo, whereas overexpression of PDLIM5 attenuated hypoxia-induced PH. CONCLUSIONS: We provided the first evidence that miR-17∼92 inhibits PDLIM5 to induce the TGF-ß3/SMAD3 pathway, contributing to the pathogenesis of PAH.

MicroRNAs in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a devastating disease without effective treatment. Despite decades of research and the development of novel treatments, PAH remains a fatal disease, suggesting an urgent need for better understanding of the pathogenesis of PAH. Recent studies suggest that microRNAs (miRNAs) are dysregulated in patients with PAH and in experimental pulmonary hypertension. Furthermore, normalization of a few miRNAs is reported to inhibit experimental pulmonary hypertension. We have reviewed the current knowledge about miRNA biogenesis, miRNA expression pattern, and their roles in regulation of pulmonary artery smooth muscle cells, endothelial cells, and fibroblasts. We have also identified emerging trends in our understanding of the role of miRNAs in the pathogenesis of PAH and propose future studies that might lead to novel therapeutic strategies for the treatment of PAH.

The sphingosine kinase 1/sphingosine-1-phosphate pathway in pulmonary arterial hypertension.

RATIONALE: Sphingosine kinases (SphKs) 1 and 2 regulate the synthesis of the bioactive sphingolipid sphingosine-1-phosphate (S1P), an important lipid mediator that promotes cell proliferation, migration, and angiogenesis. OBJECTIVES: We aimed to examine whether SphKs and their product, S1P, play a role in the development of pulmonary arterial hypertension (PAH). METHODS: SphK1(-/-), SphK2(-/-), and S1P lyase heterozygous (Sgpl1(+/-)) mice, a pharmacologic SphK inhibitor (SKI2), and a S1P receptor 2 (S1PR2) antagonist (JTE013) were used in rodent models of hypoxia-mediated pulmonary hypertension (HPH). S1P levels in lung tissues from patients with PAH and pulmonary arteries (PAs) from rodent models of HPH were measured. MEASUREMENTS AND MAIN RESULTS: mRNA and protein levels of SphK1, but not SphK2, were significantly increased in the lungs and isolated PA smooth muscle cells (PASMCs) from patients with PAH, and in lungs of experimental rodent models of HPH. S1P levels were increased in lungs of patients with PAH and PAs from rodent models of HPH. Unlike SphK2(-/-) mice, SphK1(-/-) mice were protected against HPH, whereas Sgpl1(+/-) mice were more susceptible to HPH. Pharmacologic SphK1 and S1PR2 inhibition prevented the development of HPH in rodent models of HPH. Overexpression of SphK1 and stimulation with S1P potentially via ligation of S1PR2 promoted PASMC proliferation in vitro, whereas SphK1 deficiency inhibited PASMC proliferation. CONCLUSIONS: The SphK1/S1P axis is a novel pathway in PAH that promotes PASMC proliferation, a major contributor to pulmonary vascular remodeling. Our results suggest that this pathway is a potential therapeutic target in PAH.

Conjugated polymer-based broadband terahertz wave modulator.

An optical broadband terahertz (THz) wave modulator, based on a polymer-inorganic interface, is investigated. The THz pulse transmission was efficiently modulated by an external continuous wave (CW) laser. The effects on the poly[2-methoxy-5-(2'-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV)/silicon interface were measured by THz time-domain spectroscopy. The modulation factor reached 99.6%, at an external laser beam intensity of 6.3 W/cm2. In the proposed THz-CW system, a significant fall (in both THz transmission and reflection) was also observed at the MEH-PPV/Si interface. This reduction in THz transmission and reflection has been induced by absorption at the MEH-PPV/Si interface. The results show that an optically controlled polymer/inorganic broadband THz modulator can be realized.

Effects of cold acclimation and storage temperature on crucian carp (Carassius auratus gibelio) in a waterless preservation.

The research aims to explore the impact of cold acclimation and storage temperature on crucian carp in a waterless preservation. It is conducted by studying the influence of cold acclimation on crucian carp in temperatures of 5 and 1 °C h(-1), followed by having them preserved under waterless conditions at 4 and 0 °C for 24 h to analyze their aerobic and anaerobic capacities. The research findings revealed that the temperature drop at 1 °C h(-1) is conducive to preserving the activity of lactate dehydrogenase. The activity of isocitrate dehydrogenase was maintained, and the brain succinate dehydrogenase remained unchanged. With regards to alanine transaminase, its activity, being sensitive to the changes of storage temperatures, was maintained when the temperature was decreased to 0 °C and malondialdehyde was accumulated at the same temperature. Stored in cold environment, blood catalase was accumulated; however, obvious changes were not found in the liver. It is likely that cold acclimation contributes to retaining aerobic and anaerobic metabolism under waterless preservation as well as decreasing the damage of blood oxidation.

Adenosine monophosphate-activated protein kinase is required for pulmonary artery smooth muscle cell survival and the development of hypoxic pulmonary hypertension.

Human pulmonary artery smooth muscle cells (HPASMCs) express both adenosine monophosphate-activated protein kinase (AMPK) α1 and α2. We investigated the distinct roles of AMPK α1 and α2 in the survival of HPASMCs during hypoxia and hypoxia-induced pulmonary hypertension (PH). The exposure of HPASMCs to hypoxia (3% O2) increased AMPK activation and phosphorylation, and the inhibition of AMPK with Compound C during hypoxia decreased their viability and increased lactate dehydrogenase activity and apoptosis. Although the suppression of either AMPK α1 or α2 expression led to increased cell death, the suppression of AMPK α2 alone increased caspase-3 activity and apoptosis in HPASMCs exposed to hypoxia. It also resulted in the decreased expression of myeloid cell leukemia sequence 1 (MCL-1). The knockdown of MCL-1 or MCL-1 inhibitors increased caspase-3 activity and apoptosis in HPASMCs exposed to hypoxia. On the other hand, the suppression of AMPK α1 expression alone prevented hypoxia-mediated autophagy. The inhibition of autophagy induced cell death in HPASMCs. Our results suggest that AMPK α1 and AMPK α2 play differential roles in the survival of HPASMCs during hypoxia. The activation of AMPK α2 maintains the expression of MCL-1 and prevents apoptosis, whereas the activation of AMPK α1 stimulates autophagy, promoting HPASMC survival. Moreover, treatment with Compound C, which inhibits both isoforms of AMPK, prevented and partly reversed hypoxia-induced PH in mice. Taking these results together, our study suggests that AMPK plays a key role in the pathogenesis of pulmonary arterial hypertension, and AMPK may represent a novel therapeutic target for the treatment of pulmonary arterial hypertension.

Current challenges and future directions for engineering extracellular vesicles for heart, lung, blood and sleep diseases.

Extracellular vesicles (EVs) carry diverse bioactive components including nucleic acids, proteins, lipids and metabolites that play versatile roles in intercellular and interorgan communication. The capability to modulate their stability, tissue-specific targeting and cargo render EVs as promising nanotherapeutics for treating heart, lung, blood and sleep (HLBS) diseases. However, current limitations in large-scale manufacturing of therapeutic-grade EVs, and knowledge gaps in EV biogenesis and heterogeneity pose significant challenges in their clinical application as diagnostics or therapeutics for HLBS diseases. To address these challenges, a strategic workshop with multidisciplinary experts in EV biology and U.S. Food and Drug Administration (USFDA) officials was convened by the National Heart, Lung and Blood Institute. The presentations and discussions were focused on summarizing the current state of science and technology for engineering therapeutic EVs for HLBS diseases, identifying critical knowledge gaps and regulatory challenges and suggesting potential solutions to promulgate translation of therapeutic EVs to the clinic. Benchmarks to meet the critical quality attributes set by the USFDA for other cell-based therapeutics were discussed. Development of novel strategies and approaches for scaling-up EV production and the quality control/quality analysis (QC/QA) of EV-based therapeutics were recognized as the necessary milestones for future investigations.

Cell growth arrest and apoptosis induced by Oct4 or Nanog knockdown in mouse embryonic stem cells: a possible role of Trp53.

It has been clear that both Oct4 and Nanog play essential roles in maintaining embryonic stem cells (ESCs) undifferentiation. However, the roles of Oct4 and Nanog in ESCs growth and apoptosis have been much less explored. In this study, we systematically examined the effects of Oct4 or Nanog knockdown on mouse ESCs (mESCs) growth and apoptosis as well as potential mechanisms. Our results show that Oct4 or Nanog knockdown induces growth arrest and apoptosis in mESCs, indicating that the two genes also play important roles in mESCs survival and growth. Moreover, upregulation in Trp53 and its downstream genes expression was detected in Oct4 or Nanog knockdown mESCs, suggesting a possible role of Trp53 in Oct4 or Nanog knockdown induced mESCs growth arrest and apoptosis.

Extracellular vesicles derived from endothelial cells in hypoxia contribute to pulmonary artery smooth muscle cell proliferation in-vitro and pulmonary hypertension in mice.

In the lung, communication between pulmonary vascular endothelial cells (PVEC) and pulmonary artery smooth muscle cells (PASMC) is essential for the maintenance of vascular homeostasis. In pulmonary hypertension (PH), the derangement in their cell-cell communication plays a major role in the pathogenesis of pulmonary vascular remodeling. In this study, we focused on the role of PVEC-derived extracellular vesicles (EV), specifically their microRNA (miRNA, miR-) cargo, in the regulation of PASMC proliferation and vascular remodeling in PH. We found that the amount of pro-proliferative miR-210-3p was increased in PVEC-derived EV in hypoxia (H-EV), which contributes to the H-EV-induced proliferation of PASMC and the development of PH.

MicroRNA-212-5p, an anti-proliferative miRNA, attenuates hypoxia and sugen/hypoxia-induced pulmonary hypertension in rodents.

MicroRNAs (miRNA, miR-) play important roles in disease development. In this study, we identified an anti-proliferative miRNA, miR-212-5p, that is induced in pulmonary artery smooth muscle cells (PASMCs) and lungs of pulmonary hypertension (PH) patients and rodents with experimental PH. We found that smooth muscle cell (SMC)-specific knockout of miR-212-5p exacerbated hypoxia-induced pulmonary vascular remodeling and PH in mice, suggesting that miR-212-5p may be upregulated in PASMCs to act as an endogenous inhibitor of PH, possibly by suppressing PASMC proliferation. Extracellular vesicles (EVs) have been shown recently to be promising drug delivery tools for disease treatment. We generated endothelium-derived EVs with an enriched miR-212-5p load, 212-eEVs, and found that they significantly attenuated hypoxia-induced PH in mice and Sugen/hypoxia-induced severe PH in rats, providing proof of concept that engineered endothelium-derived EVs can be used to deliver miRNA into lungs for treatment of severe PH.

Tumor progression of culture-adapted human embryonic stem cells during long-term culture.

Human embryonic stem cells (hESCs) during long-term culture acquire chromosomal changes similar to those occurring in tumorigenesis. This was raised concerns about the progression from hESCs to malignant cells. This study aimed to investigate the changes in chromosomes, cell phenotype, and genes in culture-adapted hESCs to ascertain whether tumorigenic transformation occurred. By cytogenetic analysis we found progressive karyotypic changes from simple to complex in chHES-3, one of the hESC lines established in our laboratory, during a long-term suboptimal culture. We further compared chHES-3 cells at different karyotypic stages in cell surface markers, in vivo differentiation, cell cycle, apoptosis, and gene expression profiles. We found that the karyotypically aberrant chHES-3 had higher S-phase fraction in cell cycle distributions and antiapoptosis ability. In vivo differentiation of karyotypically normal chHES-3 resulted in relatively mature teratoma, whereas karyotypically aberrant chHES-3 formed immature teratoma (grade III), in which more primary neural epithelium was revealed by pathological analysis. The microarray analysis and real-time PCR results showed that some oncogenes were upregulated in karyotypically aberrant chHES-3 cells, whereas the genes related to differentiation were downregulated, and that Wnt signal pathway was activated. In conclusion, chHES-3 cells underwent deregulation of self-renewal and dysfunction of related genes in long-term culture adaptation, leading to malignant transformation.

MicroRNA410 Inhibits Pulmonary Vascular Remodeling via Regulation of Nicotinamide Phosphoribosyltransferase.

Nicotinamide phosphoribosyltransferase (NAMPT) upregulation in human pulmonary artery endothelial cells (hPAECs) is associated with pulmonary arterial hypertension (PAH) progression and pulmonary vascular remodeling. The underlying mechanisms regulating NAMPT expression are still not clear. In this study, we aimed to study the regulation of NAMPT expression by microRNA410 (miR410) in hPAECs and explore the role of miR410 in the pathogenesis of experimental pulmonary hypertension. We show that miR410 targets the 3' UTR of NAMPT and that, concomitant with NAMPT upregulation, miR410 is downregulated in lungs of mice exposed to hypoxia-induced pulmonary hypertension (HPH). Our results also demonstrate that miR410 directly inhibits NAMPT expression. Overexpression of miR410 in hPAECs inhibits basal and VEGF-induced proliferation, migration and promotes apoptosis of hPAECs, while miR410 inhibition via antagomirs has the opposite effect. Finally, administration of miR410 mimics in vivo attenuated induction of NAMPT in PAECs and prevented the development of HPH in mice. Our results highlight the role of miR410 in the regulation of NAMPT expression in hPAECs and show that miR410 plays a potential role in PAH pathobiology by targeting a modulator of pulmonary vascular remodeling.

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

RATIONALE: Forkhead 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. METHODS: We 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. RESULTS: We 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-ß/Smad3 signaling. CONCLUSIONS: Our 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.

Downregulation of PKCζ/Pard3/Pard6b is responsible for lung adenocarcinoma cell EMT and invasion.

Atypical protein kinase C ζ (PKCζ) forms an apico-basal polarity complex with Partitioning Defective (Pard) 3 and Pard6 to regulate normal epithelial cell apico-basolateral polarization. The dissociation of the PKCζ/Pard3/Pard6 complex is essential for the disassembly of the tight/adherens junction and epithelial-mesenchymal transition (EMT) that is critical for tumor spreading. Loss of cell polarity and epithelial organization is strongly correlated with malignancy and tumor progression in some other cancer types. However, it is unclear whether the PKCζ/Pard3/Pard6 complex plays a role in the progression of non-small-cell lung cancer (NSCLC). We found that hypoxia downregulated the PKCζ/Pard3/Pard6 complex, correlating with induction of lung cancer cell migration and invasion. Silencing of the PKCζ/Pard3/Pard6 polarity complex components induced lung cancer cell EMT, invasion, and colonization in vivo. Suppression of Pard3 was associated with altered expression of genes regulating wound healing, cell apoptosis/death and cell motility, and particularly upregulation of MAP3K1 and fibronectin which are known to contribute to lung cancer progression. Human lung adenocarcinoma tissues expressed less Pard6b and PKCζ than the adjacent normal tissues and in experimental mouse lung adenocarcinoma, the levels of Pard3 and PKCζ were also decreased. In addition, we showed that a methylation locus in the gene body of Pard3 is positively associated with the expression of Pard3 and that methylation of the Pard3 gene increased cellular sensitivity to carboplatin, a common chemotherapy drug. Suppression of Pard3 increased chemoresistance in lung cancer cells. Together, these results suggest that reduced expression of PKCζ/Pard3/Pard6 contributes to NSCLC EMT, invasion, and chemoresistance.

miR-17/20 Controls Prolyl Hydroxylase 2 (PHD2)/Hypoxia-Inducible Factor 1 (HIF1) to Regulate Pulmonary Artery Smooth Muscle Cell Proliferation.

BACKGROUND: Previously we found that smooth muscle cell (SMC)-specific knockout of miR-17~92 attenuates hypoxia-induced pulmonary hypertension. However, the mechanism underlying miR-17~92-mediated pulmonary artery SMC (PASMC) proliferation remains unclear. We sought to investigate whether miR-17~92 regulates hypoxia-inducible factor (HIF) activity and PASMC proliferation via prolyl hydroxylases (PHDs). METHODS AND RESULTS: We show that hypoxic sm-17~92-/- mice have decreased hematocrit, red blood cell counts, and hemoglobin contents. The sm-17~92-/- mouse lungs express decreased mRNA levels of HIF targets and increased levels of PHD2. miR-17~92 inhibitors suppress hypoxia-induced levels of HIF1α, VEGF, Glut1, HK2, and PDK1 but not HIF2α in vitro in PASMC. Overexpression of miR-17 in PASMC represses PHD2 expression, whereas miR-17/20a inhibitors induce PHD2 expression. The 3'-UTR of PHD2 contains a functional miR-17/20a seed sequence. Silencing of PHD2 induces HIF1α and PCNA protein levels, whereas overexpression of PHD2 decreases HIF1α and cell proliferation. SMC-specific knockout of PHD2 enhances hypoxia-induced vascular remodeling and exacerbates established pulmonary hypertension in mice. PHD2 activator R59949 reverses vessel remodeling in existing hypertensive mice. PHDs are dysregulated in PASMC isolated from pulmonary arterial hypertension patients. CONCLUSIONS: Our results suggest that PHD2 is a direct target of miR-17/20a and that miR-17~92 contributes to PASMC proliferation and polycythemia by suppression of PHD2 and induction of HIF1α.

A High-Throughput Screening Platform Targeting PDLIM5 for Pulmonary Hypertension.

Pulmonary arterial hypertension is a complex disease with multiple etiologic factors. PDLIM5, a member of the Enigma subfamily of PDZ and LIM domain protein family, contains an N-terminal PDZ domain and three LIM domains at its C-terminus. We have previously shown that overexpression of PDLIM5 prevents hypoxia-induced pulmonary hypertension (PH), and deletion of PDLIM5 in smooth muscle cells enhances hypoxia-induced PH in vivo. These results suggest that PDLIM5 may be a novel therapeutic target of PH. In this study, we aim to establish a high-throughput screening platform for PDLIM5-targeted drug discovery. We generated a stable mink lung epithelial cell line (MLEC) containing a transforming growth factor-ß/Smad luciferase reporter with lentivirus-mediated suppression of PDLIM5 (MLEC-shPDLIM5) and measured levels of Smad2/3 and pSmad2/3. We found that in MLEC, suppression of PDLIM5 decreased Smad-dependent luciferase activity, Smad3, and pSmad3. We used MLEC-shPDLIM5 and a control cell line (MLEC-shCTL) to screen the Prestwick library (1200 compounds) and identified and validated paclitaxel as a PDLIM5 inhibitor in MLEC. Furthermore, we showed that paclitaxel inhibited Smad2 expression and Smad3 phosphorylation in A549 cells. Our study suggests that this system is robust and suitable for PDLIM5-targeted drug discovery.