[Show abstract][Hide abstract] ABSTRACT: The pulmonary artery endothelial cells dysfunction and injury play a critical role in chronic hypoxia-induced hypertensive process. The influence of hypoxia on the endothelial cells proliferation remains to be explored in detail.
In the present study, we performed immunohistochemistry and western blot analysis and observed that hypoxia increased the expression of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in pulmonary vessels which was majorly localized in the vascular intima. Since 15-PGDH is responsible for catalyzing the 15(S)-hydroxyl group of 15-hydroxyeicosatetraenoic acid to 15-keto-6Z, 8Z, 11Z, 13E-eicosatetraenoic acid (15-KETE), the role of 15-PGDH/15-KETE pathway in the processes of hypoxia-induced endothelium proliferation and migration were detected by bromodeoxyuridine incorporation, cell cycle analysis, scratch-wound and tube formation assay.
We found that 15-KETE increased cells DNA sythesis and enhanced the cell-cycle transition from the G0 /G1 phase to the S phase in hypoxia. 15-PGDH inhibitor and 15-PGDH RNA interference reversed all the alterations. Meanwhile, our results indicated that ERK1/2 signaling system was activated by 15-KETE. Additionally, 15-KETE-induced cell migration and tube formation could be reversed after blocking ERK1/2 but not p38 MAPK pathway.
These observations suggest that 15-PGDH/15-KETE mediates hypoxia-induced endothelium proliferation and migration via the ERK1/2 signaling, an important underlying mechanism contributing to hypoxic pulmonary vascular remodeling.
Full-text · Article · Jan 2014 · British Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Pulmonary hypertension (PH) is characterized with pulmonary vasoconstriction and vascular remodeling mediated by 15-lipoxygenase (15-LO)/15-hydroxyeicosatetraenoic acid (15-HETE) according to our previous studies. Meanwhile, telomerase reverse transcriptase (TERT) activity is highly correlated with vascular injury and remodeling, suggesting that TERT may be an essential determinant in the development of PH. The aim of this study was to determine the contribution and molecular mechanisms of TERT in the pathogenesis of PH.
We measured the right ventricular systolic pressure (RVSP) and ventricular weight, analyzed morphometric change of the pulmonary vessels in the hypoxia or monocrotaline treated rats. Bromodeoxyuridine incorporation, transwell assay and flow cytometry in pulmonary smooth muscle cells were performed to investigate the roles and relationship of TERT and 15-LO/15-HETE in PH. We revealed that the expression of TERT was increased in pulmonary vasculature of patients with PH and in the monocrotaline or hypoxia rat model of PH. The up-regulation of TERT was associated with experimental elevated RVSP and pulmonary vascular remodeling. Coimmunoprecipitation experiments identified TERT as a novel interacting partner of 15-LO-2. TERT and 15-LO-2 augmented protein expression of each other. In addition, the proliferation, migration and cell-cycle transition from G0/G1 phase to S phase induced by hypoxia were inhibited by TERT knockdown, which were rescued by 15-HETE addition.
These results demonstrate that TERT regulates pulmonary vascular remodeling. TERT and 15-LO-2 form a positive feedback loop and together promote proliferation and migration of pulmonary artery smooth muscle cells, creating a self-amplifying circuit which propels pulmonary hypertension.
[Show abstract][Hide abstract] ABSTRACT: Our previous studies have proved that hypoxia enhances the 15-lipoxygenase (15-LO) expression and increases endogenous 15-hydroxyeicosatetraenoic acid (15-HETE) production to promote pulmonary vascular remodeling and angiogenesis, while the mechanisms of how hypoxia regulates 15-LO expression in endothelium is still unknown. As placenta growth factor (PlGF) promotes pathological angiogenesis by acting on the growth, migration and survival of endothelial cells, there may be some connections between PlGF and 15-LO in hypoxia induced endothelial cells proliferation. In this study, we performed immunohistochemistry, pulmonary artery endothelial cells migration and bromodeoxyuridine incorporation to determine the role of PlGF in pulmonary remodeling induced by hypoxia. Our results showed that hypoxia up-regulated PlGF expression, which was mediated by 15-LO/15-HETE pathway. Furthermore, we found that PlGF had a positive feedback regulation with 15-LO expression and 15-HETE generation. The interaction in hypoxia between 15-HETE and PlGF created a PlGF-15-LO-15-HETE loop, leading to endothelial dysfunction. Thus, these findings suggest a new therapeutic agent in combination with the blockade of PlGF as well as 15-LO in hypoxic pulmonary hypertension.
No preview · Article · Aug 2013 · Prostaglandins Leukotrienes and Essential Fatty Acids
[Show abstract][Hide abstract] ABSTRACT: Inhibition of pulmonary arterial smooth muscle cell (PASMC) apoptosis induced by hypoxia plays an important role in pulmonary arterial remodeling leading to aggravate hypoxic pulmonary arterial hypertension. However, the mechanisms of hypoxia acting on PASMC apoptosis remain exclusive. Biliverdin reductase (BVR) has many essential biologic roles in physiological and pathological processes. Nevertheless, it is unclear whether the hypoxia-induced inhibition on PASMC apoptosis is mediated by BVR. In the present work, we found BVR majorly localized in PASMCs and was up-regulated in levels of protein and mRNA by hypoxia. Then we studied the contribution of BVR to anti-apoptotic response of hypoxia in PASMCs. Our results showed that siBVR, blocking generation of bilirubin, reversed the effect of hypoxia on enhancing cell survival and apoptotic protein (Bcl-2, procasepase-9, procasepase-3) expression, preventing nuclear shrinkage, DNA fragmentation and mitochondrial depolarization in starved PASMCs, which were recovered by exogenous bilirubin. Moreover, the inhibitory effect of bilirubin on PASMC apoptosis under hypoxic condition was blocked by the inhibitor of ERK1/2 pathway. Taken together, our data indicate that BVR contributes to the inhibitory process of hypoxia on PASMC apoptosis, which is mediated by bilirubin through ERK1/2 pathway.
No preview · Article · May 2013 · Experimental Cell Research
[Show abstract][Hide abstract] ABSTRACT: Hepatocellular carcinoma is a typical hypervascular tumor resulted from excessive growth of tumor cells. Previous studies have demonstrated that the lipoxygenase is considered as a potential therapeutic target and have important influence on human cancers. However, whether the 15-lipoxygenase-1 (15-LO-1)/15-hydroxyeicosatetraenoic acid (15-HETE) pathway participates in the development and progression of hepatocellular carcinoma has not been reported until now. To test the hypothesis that the 15-LO-1/15-HETE signaling regulates hepatocellular carcinoma cells growth and metastasis via the phosphoinositide-3 kinase (PI3K)/protein kinase B (Akt)/heat shock protein 90 pathway, we performed these studies. Our results showed that hepatocellular carcinoma cell lines (HepG2 and SMMC7721) apoptosis and growth arrest occurred following blockade of the 15-LO pathway with a 15-LO-1 inhibitor or siRNA, and all the effects were reversed by exogenous 15-HETE. Meanwhile, 15-HETE strengthened the expression of phosphor-Akt and heat shock protein 90, and inhibited apoptosis induced by serum deprivation via promoting the interaction of Akt with heat shock protein 90. In addition, the invasion and migration of HepG2 enhanced by 15-HETE were both attenuated by the inhibitor of Akt or heat shock protein 90. These results indicate that the 15-LO-1/15-HETE pathway prevents hepatocellular carcinoma cells from apoptosis and promotes hepatocellular carcinoma progression via a specific intracellular signaling pathway centered by the interaction of Akt with heat shock protein 90, and suggest a new therapeutic target for hepatocellular carcinoma.
No preview · Article · Mar 2013 · The international journal of biochemistry & cell biology
[Show abstract][Hide abstract] ABSTRACT: We previously reported that 15-lipoxygenase (15-LO) induced by hypoxia catalyzed the conversion of arachidonic acid (AA) into 15-hydroxyeicosatetraenoic acid (15-HETE), which plays an essential role in the development of hypoxic pulmonary arterial hypertension (HPH). However, the mechanisms by which hypoxia up-regulated 15-LO are still unclear. Heme Oxygenase-1 (HO-1), an oxygen-dependent enzyme regulating vascular tone and cell proliferation, was implicated in HPH and was promoted by hypoxia. Therefore, the present study was carried out to determine whether hypoxia induced the expression of 15-LO via the HO-1 pathway. To test this hypothesis, we studied the role of HO-1 in HPH and 15-LO/15-HETE expression We found increased right ventricular systolic pressure and pulmonary arteries (PAs) reactivity to vasoconstrictors as well as intima-to-media ratio of PAs in HO-1 overexpressing transgenic mice. Moreover, HO-1 up-regulated 15-LO transcription and translation as well as 15-HETE in both transgenic mice and cultured pulmonary arterial smooth muscle cells (PASMCs). Results from immunoprecipitation and immunocytochemistry showed the interaction and colocalization of HO-1 and 15-LO. Together, these data suggest that HO-1 is an important upstream mediator in the hypoxia-induced 15-LO up-regulation during HPH. Unveiling the relevance of HO-1 signaling in PHP provides attractive treatment targets for HPH.
No preview · Article · Feb 2013 · The international journal of biochemistry & cell biology
[Show abstract][Hide abstract] ABSTRACT: 15-lipoxygenase (15-LO) is known to play an important role in chronic pulmonary hypertension. Accumulating evidence for its down-stream participants in the vasoconstriction and remodeling processes of pulmonary arteries, while how hypoxia regulates 15-LO/15-hydroxyeicosatetraenoic acid (15-HETE) to mediate hypoxic pulmonary hypertension is still unknown. Platelet-derived growth factor (PDGF) is an important vascular regulator whose concentration increases under hypoxic condition in the lungs of both humans and mice with pulmonary hypertension. The present study was carried out to determine whether hypoxia advances the pulmonary vascular remodeling through the PDGF/15-LO/15-HETE pathway. We found that pulmonary arterial medial thickening caused by hypoxia was alleviated after a treatment of the hypoxic rats with imatinib, which was associated with down-regulations of 15-LO-2 expression and 15-HETE production. Moreover, the increases in cell proliferation and endogenous 15-HETE content by hypoxia were attenuated by the inhibitors of PDGF-β receptor in pulmonary artery smooth muscle cells (PASMCs). The effects of PDGF-BB on cell proliferation and survival were weakened after the administration of 15-LO inhibitors or 15-LO RNA interference. These results suggest that hypoxia promotes PASMCs proliferation and survival, contributing to pulmonary vascular medial hypertrophy, which is likely to be mediated via the PDGF-BB/15-LO-2/15-HETE pathway.
No preview · Article · Jun 2012 · Cellular Signalling
[Show abstract][Hide abstract] ABSTRACT: Our laboratory has proved that 15-hydroxyeicosatetraenoic acid, a product of arachidonic acid catalyzed by 15-lipoxygenase (15-LO), plays a pivotal role in hypoxic pulmonary arterial hypertension. However, the mechanisms of how hypoxia regulates 15-LO expression are still unclear. As the formation of endogenous transforming growth factor-beta1 (TGF-β1), implicated in pulmonary arterial hypertension pathogenesis, was promoted by hypoxia, we suspect whether hypoxia-induced the expression of 15-LO is via the TGF-β1 pathway. We found that treatment of pulmonary artery smooth muscle cells with TGF-β1 significantly increased the expression of 15-LO and levels of 15-hydroxyeicosatetraenoic acid, product of 15-LO, which were inhibited by transforming growth factor-beta receptor I (TGFβRI) inhibitor, SD-208 and siRNA targeted to knockdown rat TGFβRI. Moreover, our results showed that TGF-β1 regulated the cell cycle progression and made more cells from the G(0)/G(1) phase to the G(2)/M+S phase and enhanced the microtubule formation in cell nucleus. Additionally, we found that the 15-LO pathway was involved in TGFβ-1-mediated cell viability, DNA synthesis and the cell cycle progression. Our data provide novel evidence that hypoxia induced 15-LO expression is through TGF-β1, and 15-LO pathway plays a critical role in TGFβRI mediated the proliferation of pulmonary artery smooth muscle cells induced by hypoxia. Thus, new strategies aimed at combined blockade of TGFβRI as well as 15-LO may yield optimal therapeutic benefits.
No preview · Article · Apr 2012 · The international journal of biochemistry & cell biology
[Show abstract][Hide abstract] ABSTRACT: Pulmonary artery endothelial plexiform lesion is responsible for pulmonary vascular remodeling (PVR), a basic pathological change of pulmonary arterial hypertension (PAH). Recent evidence suggests that epoxyeicosatrienoic acid (EET), which is derived from arachidonic acid by cytochrome p450 (CYP) epoxygenase, has an essential role in PAH. However, until now, most research has focused on pulmonary vasoconstriction; it is unclear whether EET produces mitogenic and angiogenic effects in pulmonary artery endothelial cells (PAEC). Here we found that 500 nM/l 8,9-EET, 11,12-EET, and 14,15-EET markedly augmented JNK and c-Jun activation in PAECs and that the activation of c-Jun was mediated by JNK, but not the ERK or p38 MPAK pathway. Moreover, treatment with 8,9-EET, 11,12-EET, and 14,15-EET promoted cell proliferation and cell-cycle transition from the G0/G1 phase to S phase and stimulated tube formation in vitro. All these effects were reversed after blocking JNK with Sp600125 (a JNK inhibitor) or JNK1/2 siRNA. In addition, the apoptotic process was alleviated by three EET region isomers through the JNK/c-Jun pathway. These observations suggest that 8,9-EET, 11,12-EET, and 14,15-EET stimulate PAEC proliferation and angiogenesis, as well as protect the cells from apoptosis, via the JNK/c-Jun pathway, an important underlying mechanism that may promote PAEC growth and angiogenesis during PAH.
No preview · Article · Apr 2012 · The Journal of Lipid Research
[Show abstract][Hide abstract] ABSTRACT: We have found that 15-hydroxyeicosatetraenoic acid (15-HETE) induced by hypoxia was an important mediator in the regulation of hypoxic pulmonary hypertension, including the pulmonary vasoconstriction and remodeling. However, the underlying mechanisms of the remodeling induced by 15-HETE are poorly understood. In this study, we performed immunohistochemistry, pulmonary artery endothelial cells migration and tube formation, pulmonary artery smooth muscle cells bromodeoxyuridine incorporation, and cell cycle analysis to determine the role of 15-HETE in hypoxia-induced pulmonary vascular remodeling. We found that hypoxia induced pulmonary vascular medial hypertrophy and intimal endothelial cells migration and angiogenesis, which were mediated by 15-HETE. Moreover, 15-HETE regulated the cell cycle progression and made more smooth muscle cells from the G(0)/G(1) phase to the G(2)/M+S phase and enhanced the microtubule formation in cell nucleus. In addition, we found that the Rho-kinase pathway was involved in 15-HETE-induced endothelial cells tube formation and migration and smooth muscle cell proliferation. Together, these results show that 15-HETE mediates hypoxia-induced pulmonary vascular remodeling and stimulates angiogenesis via the Rho-kinase pathway.
[Show abstract][Hide abstract] ABSTRACT: 15-Hydroxyeicosatetrenoic acid (15-HETE) is an important product of arachidonic acid catalyzed by 15-lipoxygenase (15-LO) in the wall of pulmonary vessels, which plays a key role in pulmonary arterial hypertension. The previous studies showed that 15-HETE inhibits apoptosis. It is still unknown, however, whether 15-HETE acts on the apoptotic responses through the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway. The aim of the study is to test the hypothesis that ERK1/2 pathway participates in the protective effects of 15-HETE on the cell survival. This hypothesis was validated by cell viability measurement, nuclear morphology determination, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay, mitochondrial potentials assay and Western blot. We found that 15-HETE enhanced cell survival, suppressed the expression of phosphatase and tensin homologue deleted on chromosome ten, upregulated X-linked inhibitor of apoptosis protein and Bcl-2 and attenuated mitochondrial depolarization in pulmonary artery muscle smooth cells (PASMCs) under serum-deprived conditions. These effects were reversed by ERK1/2 inhibitor PD98059. Taken together, our data indicated that the ERK1/2 kinase is a regulator of PASMC apoptosis, and potential therapeutical strategy for pulmonary hypertension may be developed by targeting at intracellular signaling systems centered by the kinase.
No preview · Article · Feb 2011 · Journal of Receptor and Signal Transduction Research
[Show abstract][Hide abstract] ABSTRACT: Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid (AA) catalyzed by cytochrome P450 (CYP), have many essential biologic roles in the cardiovascular system including inhibition of apoptosis in cardiomyocytes. In the present study, we tested the potential of 8,9-EET and derivatives to protect pulmonary artery smooth muscle cells (PASMCs) from starvation induced apoptosis. We found 8,9-epoxy-eicos-11(Z)-enoic acid (8,9-EET analog (214)), but not 8,9-EET, increased cell viability, decreased activation of caspase-3 and caspase-9, and decreased TUNEL-positive cells or nuclear condensation induced by serum deprivation (SD) in PASMCs. These effects were reversed after blocking the Rho-kinase (ROCK) pathway with Y-27632 or HA-1077. Therefore, 8,9-EET analog (214) protects PASMC from serum deprivation-induced apoptosis, mediated at least in part via the ROCK pathway. Serum deprivation of PASMCs resulted in mitochondrial membrane depolarization, decreased expression of Bcl-2 and enhanced expression of Bax, all effects were reversed by 8,9-EET analog (214) in a ROCK dependent manner. Because 8,9-EET and not the 8,9-EET analog (214) protects pulmonary artery endothelial cells (PAECs), these observations suggest the potential to differentially promote apoptosis or survival with 8,9-EET or analogs in pulmonary arteries.
Full-text · Article · Aug 2010 · Experimental Cell Research
[Show abstract][Hide abstract] ABSTRACT: 15-Hydroxyeicosatetraenoic acid (15-HETE), generated by hypoxia, is a product of arachidonic acid and mainly catalyzed by 15-lipoxygenase (15-LO) in pulmonary artery. As HSP90 is known to be involved in apoptosis in other tissues and cells, we aim to test whether anti-apoptotic effect of 15-HETE is regulated by the molecular chaperone in pulmonary artery smooth muscle cells.
To test this hypothesis, we performed cell viability analysis, mitochondrial potential assay, caspase-3 activity measurement, Western blot, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling with and without HSP90 inhibitor.
Our results showed that both exogenous and endogenous 15-HETE up-regulated HSP90 expression and prevented PASMC from serum deprivation-induced apoptosis. Serum deprivation lead to mitochondrial membrane depolarization, decreased expression of Bcl-2 and enhanced expression of Bax, and activation of caspase-3 and caspase-9 in PASMCs. 15-HETE reversed all these effects in a HSP90-dependent manner.
This study establishes the factor involved in 15-HETE-protecting PASMC from apoptosis and the regulation of HSP90 by 15-HETE may be an important mechanism underlying the treatment of pulmonary artery hypertension and provide a novel therapeutic target in future.
[Show abstract][Hide abstract] ABSTRACT: 15-Hydroxyeicosatetraenoic acid (15-HETE), a product of arachidonic acid (AA) catalyzed by 15-lipoxygenase (15-LO), plays an essential role in hypoxic pulmonary arterial hypertension. We have previously shown that 15-HETE inhibits apoptosis in pulmonary artery smooth muscle cells (PASMCs). To test the hypothesis that such an effect is attributable to the hypoxia-induced pulmonary vascular remodeling (PVR), we performed these studies. We found subtle thickening of proximal media/adventitia of the pulmonary arteries (PA) in rats that had been exposed to hypoxia. This was associated with an up-regulation of the anti-apoptotic Bcl-2 expression and down-regulation of pro-apoptotic caspase-3 and Bax expression in PA homogenates. Nordihydroguaiaretic acid (NDGA), which inhibits the generation of endogenous 15-HETE, reversed all the alterations following hypoxia. In situ hybridization histochemistry and immunocytochemistry showed that the 15-LO-1 mRNA and protein were localized in pulmonary artery endothelial cells (PAECs), while the 15-LO-2 mRNA and protein were localized in both PAECs and PASMCs. Furthermore, the Rho-kinase (ROCK) pathway was activated by both endogenous and exogenous 15-HETE, alleviating the serum deprivation (SD)-induced PASMC apoptosis. Thus, these findings indicate that 15-HETE protects PASMC from apoptosis, contributing to pulmonary vascular medial thickening, and the effect is, at least in part, mediated via the ROCK pathway.
No preview · Article · Jan 2010 · Journal of Cellular Physiology