Loss of PPAR? in endothelial cells leads to impaired angiogenesis.
Journal of cell science
2016; 129 (4): 693-705
Tie2 promoter-mediated loss of peroxisome proliferator-activated receptor gamma (PPARγ) in mice leads to osteopetrosis and pulmonary arterial hypertension. Vascular disease is associated with loss of PPARγ in pulmonary microvascular endothelial cells (PMVEC), we evaluated the role of PPARγ in PMVEC functions, such as angiogenesis and migration. The role of PPARγ in angiogenesis was evaluated in Tie2CrePPARγ(flox/flox) and wild type (WT) mice, and in mouse and human PMVECs. RNA-sequencing and bioinformatic approaches were utilized to reveal angiogenesis-associated targets for PPARγ. Tie2CrePPARγ(flox/flox) mice showed an impaired angiogenic capacity. Analysis of endothelial progenitor-like cells using bone marrow transplantation combined with evaluation of isolated PMVECs revealed that loss of PPARγ attenuates the migration and angiogenic capacity of mature PMVECs. PPARγ-deficient human PMVECs showed a similar migration defect in culture. Bioinformatic and experimental analyses revealed E2F1 as a novel target of PPARγ in the regulation of PMVEC migration. Disruption of the PPARγ-E2F1 axis was associated with a dysregulated Wnt pathway related to the GSK3β interaction protein. In conclusion, PPARγ plays an important role in sustaining angiogenic potential in mature PMVECs through E2F1-mediated gene regulation.
View details for DOI 10.1242/jcs.169011
View details for PubMedID 26743080
RNA Sequencing Analysis Detection of a Novel Pathway of Endothelial Dysfunction in Pulmonary Arterial Hypertension
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE
2015; 192 (3): 356-366
Pulmonary arterial hypertension is characterized by endothelial dysregulation, but global changes in gene expression have not been related to perturbations in function.RNA sequencing was utilized to discriminate changes in transcriptomes of endothelial cells cultured from lungs of patients with idiopathic pulmonary arterial hypertension vs. controls and to assess the functional significance of major differentially expressed transcripts.The endothelial transcriptomes from seven control and six idiopathic pulmonary arterial hypertension patients' lungs were analyzed. Differentially expressed genes were related to BMPR2 signaling. Those downregulated were assessed for function in cultured cells, and in a transgenic mouse.Fold-differences in ten genes were significant (p<0.05), four increased and six decreased in patients vs.No patient was mutant for BMPR2. However, knockdown of BMPR2 by siRNA in control pulmonary arterial endothelial cells recapitulated six/ten patient-related gene changes, including decreased collagen IV (COL4A1, COL4A2) and ephrinA1 (EFNA1). Reduction of BMPR2 regulated transcripts was related to decreased β-catenin. Reducing COL4A1, COL4A2 and EFNA1 by siRNA inhibited pulmonary endothelial adhesion, migration and tube formation. In mice null for the EFNA1 receptor, EphA2, vs. controls, VEGF receptor blockade and hypoxia caused more severe pulmonary hypertension, judged by elevated right ventricular systolic pressure, right ventricular hypertrophy and loss of small arteries.The novel relationship between BMPR2 dysfunction and reduced expression of endothelial COL4 and EFNA1 may underlie vulnerability to injury in pulmonary arterial hypertension.
View details for DOI 10.1164/rccm.201408-1528OC
View details for PubMedID 26030479
Elafin Reverses Pulmonary Hypertension via Caveolin-1-Dependent Bone Morphogenetic Protein Signaling
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE
2015; 191 (11): 1273-1286
Pulmonary arterial hypertension is characterized by endothelial cell dysfunction, impaired BMPR2 signaling, and increased elastase activity. Synthetic elastase inhibitors reverse experimental pulmonary hypertension but cause hepatotoxicity in clinical studies. The endogenous elastase inhibitor elafin attenuates the development of hypoxic pulmonary hypertension in mice, but its potential to improve endothelial cell function and BMPR2 signaling, and to reverse severe experimental pulmonary hypertension or vascular pathology in the human disease was unknown.To assess elafin-mediated regression of pulmonary vascular pathology in rats with pulmonary hypertension induced by VEGF receptor blockade and hypoxia (Sugen/Hypoxia), and in lung explants from pulmonary hypertension patients. To determine if elafin amplifies BMPR2 signaling in pulmonary artery endothelial cells from controls and patients, and to elucidate the underlying mechanism. Methods, Measurements and Main Results: In Sugen/Hypoxia rats, elafin reduced elastase activity and reversed pulmonary hypertension, judged by regression of right ventricular systolic pressure and hypertrophy and pulmonary artery occlusive changes. Elafin improved endothelial function by increasing apelin, a product of BMPR2 signaling. Elafin induced apoptosis in human pulmonary arterial smooth muscle cells and in lung organ culture elafin decreased neointimal lesions. In normal and patient pulmonary artery endothelial cells, elafin enhanced survival and promoted angiogenesis by increasing pSMAD dependent and independent BMPR2 signaling. This was linked mechanistically to augmented interaction of BMPR2 with caveolin-1 via elafin-mediated stabilization of caveolin-1 on endothelial surfaces.Elafin reverses obliterative changes in rat and human pulmonary arteries via elastase inhibition and caveolin-1 dependent amplification of BMPR2 signaling.
View details for DOI 10.1164/rccm.201412-2291OC
View details for Web of Science ID 000356105000014
View details for PubMedID 25853696
BMPR2 Preserves Mitochondrial Function and DNA during Reoxygenation to Promote Endothelial Cell Survival and Reverse Pulmonary Hypertension
2015; 21 (4): 596-608
Mitochondrial dysfunction, inflammation, and mutant bone morphogenetic protein receptor 2 (BMPR2) are associated with pulmonary arterial hypertension (PAH), an incurable disease characterized by pulmonary arterial (PA) endothelial cell (EC) apoptosis, decreased microvessels, and occlusive vascular remodeling. We hypothesized that reduced BMPR2 induces PAEC mitochondrial dysfunction, promoting a pro-inflammatory or pro-apoptotic state. Mice with EC deletion of BMPR2 develop hypoxia-induced pulmonary hypertension that, in contrast to non-transgenic littermates, does not reverse upon reoxygenation and is associated with reduced PA microvessels and lung EC p53, PGC1α and TFAM, regulators of mitochondrial biogenesis, and mitochondrial DNA. Decreasing PAEC BMPR2 by siRNA during reoxygenation represses p53, PGC1α, NRF2, TFAM, mitochondrial membrane potential, and ATP and induces mitochondrial DNA deletion and apoptosis. Reducing PAEC BMPR2 in normoxia increases p53, PGC1α, TFAM, mitochondrial membrane potential, ATP production, and glycolysis, and induces mitochondrial fission and a pro-inflammatory state. These features are recapitulated in PAECs from PAH patients with mutant BMPR2.
View details for DOI 10.1016/j.cmet.2015.03.010
View details for Web of Science ID 000352500800014
View details for PubMedID 25863249
Whole-Exome Sequencing Reveals TopBP1 as a Novel Gene in Idiopathic Pulmonary Arterial Hypertension
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE
2014; 189 (10): 1260-1272
Idiopathic pulmonary arterial hypertension (IPAH) is a life-threatening disorder characterized by progressive loss of pulmonary microvessels. Although mutations in the bone morphogenetic receptor 2 (BMPR2) are found in 80% of heritable and ∼15% of patients with IPAH, their low penetrance (∼20%) suggests that other unidentified genetic modifiers are required for manifestation of the disease phenotype. Use of whole-exome sequencing (WES) has recently led to the discovery of novel susceptibility genes in heritable PAH, but whether WES can also accelerate gene discovery in IPAH remains unknown.To determine whether WES can help identify novel gene modifiers in patients with IPAH.Exome capture and sequencing was performed on genomic DNA isolated from 12 unrelated patients with IPAH lacking BMPR2 mutations. Observed genetic variants were prioritized according to their pathogenic potential using ANNOVAR.A total of nine genes were identified as high-priority candidates. Our top hit was topoisomerase DNA binding II binding protein 1 (TopBP1), a gene involved in the response to DNA damage and replication stress. We found that TopBP1 expression was reduced in vascular lesions and pulmonary endothelial cells isolated from patients with IPAH. Although TopBP1 deficiency made endothelial cells susceptible to DNA damage and apoptosis in response to hydroxyurea, its restoration resulted in less DNA damage and improved cell survival.WES led to the discovery of TopBP1, a gene whose deficiency may increase susceptibility to small vessel loss in IPAH. We predict that use of WES will help identify gene modifiers that influence an individual's risk of developing IPAH.
View details for DOI 10.1164/rccm.201310-17490C
View details for Web of Science ID 000336017200018
View details for PubMedID 24702692
View details for PubMedCentralID PMC4225850
FK506 activates BMPR2, rescues endothelial dysfunction, and reverses pulmonary hypertension.
journal of clinical investigation
2013; 123 (8): 3600-3613
Dysfunctional bone morphogenetic protein receptor-2 (BMPR2) signaling is implicated in the pathogenesis of pulmonary arterial hypertension (PAH). We used a transcriptional high-throughput luciferase reporter assay to screen 3,756 FDA-approved drugs and bioactive compounds for induction of BMPR2 signaling. The best response was achieved with FK506 (tacrolimus), via a dual mechanism of action as a calcineurin inhibitor that also binds FK-binding protein-12 (FKBP12), a repressor of BMP signaling. FK506 released FKBP12 from type I receptors activin receptor-like kinase 1 (ALK1), ALK2, and ALK3 and activated downstream SMAD1/5 and MAPK signaling and ID1 gene regulation in a manner superior to the calcineurin inhibitor cyclosporine and the FKBP12 ligand rapamycin. In pulmonary artery endothelial cells (ECs) from patients with idiopathic PAH, low-dose FK506 reversed dysfunctional BMPR2 signaling. In mice with conditional Bmpr2 deletion in ECs, low-dose FK506 prevented exaggerated chronic hypoxic PAH associated with induction of EC targets of BMP signaling, such as apelin. Low-dose FK506 also reversed severe PAH in rats with medial hypertrophy following monocrotaline and in rats with neointima formation following VEGF receptor blockade and chronic hypoxia. Our studies indicate that low-dose FK506 could be useful in the treatment of PAH.
View details for DOI 10.1172/JCI65592
View details for PubMedID 23867624
Loss of adenomatous poliposis coli-a3 integrin interaction promotes endothelial apoptosis in mice and humans.
2012; 111 (12): 1551-1564
Pulmonary hypertension (PH) is characterized by progressive elevation in pulmonary pressure and loss of small pulmonary arteries. As bone morphogenetic proteins promote pulmonary angiogenesis by recruiting the Wnt/β-catenin pathway, we proposed that β-catenin activation could reduce loss and induce regeneration of small pulmonary arteries (PAs) and attenuate PH.This study aims to establish the role of β-catenin in protecting the pulmonary endothelium and stimulating compensatory angiogenesis after injury.To assess the impact of β-catenin activation on chronic hypoxia-induced PH, we used the adenomatous polyposis coli (Apc(Min/+)) mouse, where reduced APC causes constitutive β-catenin elevation. Surprisingly, hypoxic Apc(Min/+) mice displayed greater PH and small PA loss compared with control C57Bl6J littermates. PA endothelial cells isolated from Apc(Min/+) demonstrated reduced survival and angiogenic responses along with a profound reduction in adhesion to laminin. The mechanism involved failure of APC to interact with the cytoplasmic domain of the α3 integrin, to stabilize focal adhesions and activate integrin-linked kinase-1 and phospho Akt. We found that PA endothelial cells from lungs of patients with idiopathic PH have reduced APC expression, decreased adhesion to laminin, and impaired vascular tube formation. These defects were corrected in the cultured cells by transfection of APC.We show that APC is integral to PA endothelial cells adhesion and survival and is reduced in PA endothelial cells from PH patient lungs. The data suggest that decreased APC may be a cause of increased risk or severity of PH in genetically susceptible individuals.
View details for DOI 10.1161/CIRCRESAHA.112.267849
View details for PubMedID 23011394
PAX Genes in Cancer; Friends or Foes?
Frontiers in genetics
2012; 3: 6-?
PAX genes have been shown to be critically required for the development of specific tissues and organs during embryogenesis. In addition, PAX genes are expressed in a handful of adult tissues where they are thought to play important roles, usually different from those in embryogenesis. A common theme in adult tissues is a requirement for PAX gene expression in adult stem cell maintenance or tissue regeneration. The connections between adult stem cell PAX gene expression and cancer are intriguing, and the literature is replete with examples of PAX gene expression in either situation. Here we systematically review the literature and present an overview of postnatal PAX gene expression in normal and cancerous tissue. We discuss the potential link between PAX gene expression in adult tissue and cancer. In addition, we discuss whether persistent PAX gene expression in cancer is favorable or unfavorable.
View details for DOI 10.3389/fgene.2012.00006
View details for PubMedID 22303411
PAX8 promotes tumor cell growth by transcriptionally regulating E2F1 and stabilizing RB protein
2011; 30 (48): 4824-4834
The retinoblastoma protein (RB)-E2F1 pathway has a central role in regulating the cell cycle. Several PAX proteins (tissue-specific developmental regulators), including PAX8, interact with the RB protein, and thus regulate the cell cycle directly or indirectly. Here, we report that PAX8 expression is frequent in renal cell carcinoma, bladder, ovarian and thyroid cancer cell lines, and that silencing of PAX8 in cancer cell lines leads to a striking reduction in the expression of E2F1 and its target genes, as well as a proteasome-dependent destabilization of RB protein, with the RB1 mRNA level remaining unaffected. Cancer cells expressing PAX8 undergo a G(1)/S arrest and eventually senesce following PAX8 silencing. We demonstrate that PAX8 transcriptionally regulates the E2F1 promoter directly, and E2F1 transcription is enhanced after RB depletion. RB is recruited to the PAX8-binding site, and is involved in PAX8-mediated E2F1 transcription in cancer cells. Therefore, our results suggest that, in cancer, frequent and persistent expression of PAX8 is required for cell growth control through transcriptional activation of E2F1 expression and upregulation of the RB-E2F1 pathway.
View details for DOI 10.1038/onc.2011.190
View details for Web of Science ID 000298134700006
View details for PubMedID 21602887
PAX3 knockdown in metastatic melanoma cell lines does not reduce MITF expression.
PAX3 and MITF are important transcriptional activators in the melanocyte lineage and PAX3 is thought to control MITF expression during normal melanocyte differentiation. However, it is not clear whether this is still true in melanoma and whether the effects of knockdown of PAX3 on the inhibition of melanoma growth or survival are by its regulation of MITF. By western blot and quantitative real-time reverse transcription-PCR, we investigated the relationship between PAX3 and MITF expression in 27 metastatic melanoma and one immortalized melanocyte cell lines. All lines were found to express both PAX3 and MITF proteins but levels varied by 15 fold and more than 100 fold, respectively. The expression of PAX3 protein was correlated with that of MITF (r=0.75; P<0.001) but the expression of PAX3 protein and MITF mRNA was not. Immunofluorescence microscopy showed that individual cells expressed widely differing relative amounts of PAX3 and MITF protein. By MTT cell proliferation and flow cytometry assays, both MITF and PAX3 proteins seemed to be functional, as knockdown with siRNA led to reduced proliferation and induction of apoptosis. However, knockdown of PAX3 with small interfering RNA did not decrease MITF expression and vice versa. In one cell line (NZM15), silencing of PAX3 induced terminal differentiation whereas silencing of MITF induced expression of FOXD3, a repressor of melanogenesis. The results suggest that the melanoma lines used in this study show considerable phenotypic variation of expression of these two transcriptional activators and reflect a deregulation of the developmental process operating in the genesis of the melanocyte lineage, and that they probably function independently to enhance the survival of melanoma cells.
View details for DOI 10.1097/CMR.0b013e328341c7e0
View details for PubMedID 21164369