Hypoxic regulation of endothelial glyceraldehyde-3-phosphate dehydrogenase

Selection and stability validation of reference gene candidates for transcriptional analysis in Rousettus aegyptiacus

Bats are the only mammals capable of powered flight and their body temperature can reach up to 42 °C during flight. Additionally, bats display robust type I IFN interferon (IFN-I) responses and some species constitutively express IFN-α. Reference genes with stable expression under temperature oscillations and IFN-I release are therefore critical for normalization of quantitative reverse-transcription polymerase chain reaction (qRT-PCR) data in bats. The expression stability of reference genes in Rousettus aegyptiacus remains elusive, although this species is frequently used in the infection research. We selected ACTB, EEF1A1, GAPDH and PGK1 as candidate reference genes and evaluated their expression stability in various tissues and cells from this model bat species upon IFN-I treatment at 35 °C, 37 °C and 40 °C by qRT-PCR. We employed two statistical algorithms, BestKeeper and NormFinder, and found that EEF1A1 exhibited the highest expression stability under all tested conditions. ACTB and GAPDH displayed unstable expression upon temperature change and IFN-I treatment, respectively. By normalizing to EEF1A1, we uncovered that GAPDH expression was significantly induced by IFN-I in R. aegyptiacus. Our study identifies EEF1A1 as the most suitable reference gene for qRT-PCR studies upon temperature changes and IFN-I treatment and unveils the induction of GAPDH expression by IFN-I in R. aegyptiacus. These findings are pertinent to other bat species and may be relevant for non-volant mammals that show physiological fluctuations of core body temperature.

Regulation of glyceraldehyde-3-phosphate dehydrogenase by hypoxia inducible factor 1 in the white shrimp Litopenaeus vannamei during hypoxia and reoxygenation

Hypoxia is a frequent source of stress in the estuarine habitat of the white shrimp Litopenaeus vannamei. During hypoxia, L. vannamei gill cells rely more heavily on anaerobic glycolysis to obtain ATP. This is mediated by transcriptional up-regulation of glycolytic enzymes including glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The hypoxia inducible factor 1 (HIF-1) is an important transcriptional activator of several glycolytic enzymes during hypoxia in diverse animals, including crustaceans. In this work, we cloned and sequenced a fragment corresponding to the 5' flank of the GAPDH gene and identified a putative HIF-1 binding site, as well as sites for other transcription factors involved in the hypoxia signaling pathway. To investigate the role of HIF-1 in GAPDH regulation, we simultaneously injected double-stranded RNA (dsRNA) into shrimp to silence HIF-1α and HIF-1β under normoxia, hypoxia, and hypoxia followed by reoxygenation, and then measured gill HIF-1α, HIF-1β expression, GAPDH expression and activity, and glucose and lactate concentrations at 0, 3, 24 and 48 h. During normoxia, HIF-1 silencing induced up-regulation of GAPDH transcripts and activity, suggesting that expression is down-regulated via HIF-1 under these conditions. In contrast, HIF-1 silencing during hypoxia abolished the increases in GAPDH expression and activity, glucose and lactate concentrations. Finally, HIF-1 silencing during hypoxia-reoxygenation prevented the increase in GAPDH expression, however, those changes were not reflected in GAPDH activity and lactate accumulation. Altogether, these results indicate that GAPDH and glycolysis are transcriptionally regulated by HIF-1 in gills of white shrimp.

Up-regulation of Key Glycolysis Proteins in Cancer Development

In rapid proliferating cancer cells, there is a need for fast ATP and lactate production, therefore cancer cells turn off oxidative phosphorylation and turn on the so called "Warburg effect". This regulating the expression of genes involved in glycolysis. According to many studies, glucose transporter 1, which supplies glucose to the cell, is the most abundantly expressed transporter in cancer cells. Hexokinase 2, is one of four hexokinase isoenzymes, is also another highly expressed enzyme in cancer cells and it functions to enhance the glycolytic rate. The up-regulation of these two proteins has been established as an important factor in promoting development and metastasis in many types of cancer. Furthermore, other enzymes involved in glycolysis pathway such as phosphoglucose isomerase and glyceraldehyde 3-phosphate dehydrogenase, exhibit additional functions in promoting tumor growth in a non-glycolytic way. This review demonstrates the pivotal role of GLUT1, HK2, PGI and GAPDH in cancer development. In particular, we look at how the multifunctional proteins, PGI and GAPDH, affect cancer cell survival. We also present various clinical cancer cases in terms of the overexpression of selected proteins, which may be considered as a therapeutic target.

Glyceraldehyde-3-phosphate dehydrogenase is an inappropriate housekeeping gene for normalising gene expression in sepsis

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has long been used as a default reference gene in quantitative mRNA profiling experiments. However, its expression reportedly varies in response to a range of pathophysiological variables (inflammation, oxidative stress, hyperinsulinaemia, hypoxia) which feature prominently in sepsis. We therefore assessed the applicability of using GAPDH as a reference gene for expression studies in sepsis compared to other housekeeping genes (succinate dehydrogenase complex subunit A (SDHA), hypoxanthine phosphoribosyltransferase (HPRT)-1). Severe sepsis resulted in a 42.4-fold increase in median GAPDH expression (P<0.001), whereas median HPRT expression was raised more modestly (2.9-fold; P<0.001), and there was no significant difference in SDHA expression between sepsis and control patients. HPRT was identified by NormFinder to be the most stably expressed single gene. In order to assess the impact of this variability on data interpretation, interleukin (IL)-10 expression was normalised separately to GAPDH and to the geometric mean of HPRT and SDHA. In the former case, there was no significant difference in IL-10 expression between controls and septic patients, whilst in the latter, a significant 8.5-fold increase in median IL-10 expression was noted (P<0.001). GAPDH is thus an unreliable housekeeping gene for normalising gene expression in sepsis which should be replaced by alternative, validated reference genes.

Identification of hypoxia-regulated proteins using MALDI-mass spectrometry imaging combined with quantitative proteomics

Hypoxia is present in most solid tumors and is clinically correlated with increased metastasis and poor patient survival. While studies have demonstrated the role of hypoxia and hypoxia-regulated proteins in cancer progression, no attempts have been made to identify hypoxia-regulated proteins using quantitative proteomics combined with MALDI-mass spectrometry imaging (MALDI-MSI). Here we present a comprehensive hypoxic proteome study and are the first to investigate changes in situ using tumor samples. In vitro quantitative mass spectrometry analysis of the hypoxic proteome was performed on breast cancer cells using stable isotope labeling with amino acids in cell culture (SILAC). MS analyses were performed on laser-capture microdissected samples isolated from normoxic and hypoxic regions from tumors derived from the same cells used in vitro. MALDI-MSI was used in combination to investigate hypoxia-regulated protein localization within tumor sections. Here we identified more than 100 proteins, both novel and previously reported, that were associated with hypoxia. Several proteins were localized in hypoxic regions, as identified by MALDI-MSI. Visualization and data extrapolation methods for the in vitro SILAC data were also developed, and computational mapping of MALDI-MSI data to IHC results was applied for data validation. The results and limitations of the methodologies described are discussed.

Nickel alloys in the oral environment

The use of nickel casting alloys for long-term restorations in dentistry has long been controversial. A 'tug-of-war' between economic, engineering and biological considerations is central to this controversy; nickel-casting alloys have low costs and favorable physical properties, but are corrosion-prone in the oral environment. Clinicians and researchers have questioned the safety of nickel-containing dental alloys because several nickel compounds are known to cause adverse biological effects in vivo and in vitro in contexts outside of dentistry. The debate revolves around the extent to which corrosion products from oral restorations cause intraoral or systemic biological problems. Current evidence suggests that nickel alloys may be used successfully and safely in dentistry if clinical risks are taken into account. However, these alloys may cause significant clinical problems, primarily allergenic and inflammatory, if the risks are ignored.

Hypoxia Induces Mesenchymal Gene Expression in Renal Tubular Epithelial Cells: An in vitro Model of Kidney Transplant Fibrosis

BACKGROUND

The development of interstitial fibrosis and tubular atrophy is a common complication after kidney transplantation and is associated with reduced long-term outcome. The hallmark of tubulointerstitial fibrosis is an increase in extracellular matrix resulting from exaggerated activation of fibroblasts/myofibroblasts, and tubular atrophy is characterized by a decrease in tubular diameter and loss of function. Atrophic epithelial cells may undergo epithelial-to-mesenchymal transition (EMT) with potential differentiation into interstitial fibroblasts. One potential driver of EMT in developing interstitial fibrosis and tubular atrophy is chronic hypoxia.

METHODS

The expression of 46 EMT-related genes was analyzed in an in vitro hypoxia model in renal proximal tubular epithelial cells (RPTEC). Furthermore, the expression of 342 microRNAs (miR) was evaluated in hypoxic culture conditions.

RESULTS

Hypoxic RPTEC expressed markers of a more mesenchymal phenotype and showed an increased expression of matrix metalloproteinase-2 (MMP2). MMP2 expression in RPTEC correlated inversely with a decreased expression of miR-124, which was found to have a putative binding site for the MMP2 transcript. Overexpression of miR-124 inhibited MMP2 protein translation. Hypoxia was associated with increased migration/proliferation of RPTEC which was reversed by miR-124.

CONCLUSIONS

These results indicate that hypoxia promotes a mesenchymal and migratory phenotype in renal epithelial cells, which is associated with increased MMP2 expression. Hypoxia-dependent MMP2 expression is regulated via a reduced transcription of miR-124. Overexpression of miR-124 antagonizes hypoxia-induced cell migration. Further research is needed to elucidate the functional role of miR-124 and MMP2 in the development of fibrosis in renal transplant degeneration.

Vascular cell-adhesion molecule-1 plays a central role in the proangiogenic effects of oxidative stress

Oxidative stress exacerbates neovascularization (NV) in many disease processes. In this study we investigated the mechanism of that effect. Mice deficient in superoxide dismutase 1 (Sod1(-/-) mice) have increased oxidative stress and show severe ocular NV that is reduced to baseline by antioxidants. Compared with wild-type mice with ischemic retinopathy, Sod1(-/-) mice with ischemic retinopathy had increased expression of several NF-κB-responsive genes, but expression of vascular cell-adhesion molecule-1 (Vcam1) was particularly high. Intraocular injection of anti-VCAM-1 antibody eliminated the excessive ischemia-induced retinal NV. Elements that contributed to oxidative stress-induced worsening of retinal NV that were abrogated by blockade of VCAM-1 included increases in leukostasis, influx of bone marrow-derived cells, and capillary closure. Compared with ischemia alone, ischemia plus oxidative stress resulted in increased expression of several HIF-1-responsive genes caused in part by VCAM-1-induced worsening of nonperfusion and, hence, ischemia, because anti-VCAM-1 significantly reduced the increased expression of all but one of the genes. These data explain why oxidative stress worsens ischemia-induced retinal NV and may be relevant to other neovascular diseases in which oxidative stress has been implicated. The data also suggest that antagonism of VCAM-1 provides a potential therapy to combat worsening of neovascular diseases by oxidative stress.

Proteomics in aquatic amphipods: can it be used to determine mechanisms of toxicity and interspecies responses after exposure to atrazine?

Proteomics has gained popularity in the field of ecotoxicology as a holistic tool for unraveling novel mechanisms of toxicity and elucidating subtle effects of contaminant exposure. The holoarctic amphipod Diporeia spp. is declining at precipitous rates in the Great Lakes, and we are evaluating the use of the well-studied amphipod model Hyalella azteca as a surrogate for Diporeia spp. This article presents proteomics data from both amphipod species exposed to atrazine (ATZ) and one of its metabolites, desethylatrazine (DEA; 3 and 30 µg/L for 21 and 42 d). We used a proteomics approach to determine whether these two species of amphipods responded similarly to the same chemicals and to understand better the mechanisms of toxicity of ATZ and DEA in aquatic invertebrates. We observed disruption in energy production and mitochondrial function as well as hormesis in exposed organisms. In addition, we identified a two proteins (GAPDH and HSP 90 kDa) that have been linked to hormonal disruptions, suggesting potential endocrine disruption. Finally, we found that H. azteca and Diporeia spp. responded with similar proteomic profiles after ATZ and DEA exposure, suggesting that H. azteca may be used as a surrogate model organism for Diporeia spp.

Regulation of pregnancy-associated plasma protein A2 (PAPPA2) in a human placental trophoblast cell line (BeWo)

BACKGROUND

Pregnancy-associated plasma protein A2 (PAPPA2) is an insulin-like growth factor-binding protein (IGFBP) protease expressed at high levels in the placenta and upregulated in pregnancies complicated by preeclampsia and HELLP (Hemolytic anemia, Elevated Liver enzymes, and Low Platelet count) syndrome. However, it is unclear whether elevated PAPPA2 expression causes abnormal placental development, or whether upregulation compensates for placental pathology. In the present study, we investigate whether PAPPA2 expression is affected by hypoxia, oxidative stress, syncytialization factors or substances known to affect the expression of PAPPA2's paralogue, PAPPA.

METHODS

BeWo cells, a model of placental trophoblasts, were treated with one of the following: hypoxia (2% O2), oxidative stress (20 microM hydrogen peroxide), forskolin (10 microM and 100 microM), TGF-beta (10 and 50 ng/mL), TNF-alpha (100 ng/mL), IL-1beta (100 ng/mL) or PGE2 (1 microM). We used quantitative RT-PCR (qRT-PCR) to quantify the mRNA levels of PAPPA2, as well as those of PAPPA and ADAM12 since these proteases have similar substrates and are also highly expressed in the placenta. Where we observed significant effects on PAPPA2 mRNA levels, we tested for effects at the protein level using an in-cell Western assay.

RESULTS

Hypoxia, but not oxidative stress, caused a 47-fold increase in PAPPA2 mRNA expression, while TNF-alpha resulted in a 6-fold increase, and both of these effects were confirmed at the protein level. PGE2 resulted in a 14-fold upregulation of PAPPA2 mRNA but this was not reflected at the protein level. Forskolin, TGF-beta and IL-1beta had no significant effect on PAPPA2 mRNA expression. We observed no effects of any treatment on PAPPA or ADAM12 expression.

CONCLUSION

Our study demonstrates that factors previously known to be highly expressed in preeclamptic placentae (PGE2 and TNF-alpha), contribute to the upregulation of PAPPA2. Hypoxia, known to occur in preeclamptic placentae, also increased PAPPA2 expression. These results are consistent with the hypothesis that PAPPA2 is upregulated as a consequence of placental pathology, rather than elevated PAPPA2 levels being a cause of preeclampsia.

Altered transcriptional activity of gene encoding GAPDH in peripheral blood mononuclear cells from patients with cardiac syndrome X - an important part in pathology of microvascular angina?

INTRODUCTION

Cardiac syndrome X (CSX) is characterized by anginal pain with ECG suggestive of ischaemia and normal coronary arteries at angiography. Pathology of CSX involves microvascular dysfunction and is possibly linked with metabolic syndrome. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an enzyme involved in glycolysis. The GAPDH gene is a "housekeeping" gene and is used for normalization in quantitative gene expression assays. The aim of the study was to evaluate GAPDH gene expression in CSX.

MATERIAL AND METHODS

The study was performed in 35 CSX patients and 10 control subjects. mRNA was extracted from peripheral blood mononuclears and the mRNA was assessed by QRT-PCR.

RESULTS

GAPDH gene expression was enhanced in CSX patients vs. controls (93022 ±23837 copies/μg vs. 1067 ±240 copies/μg respectively; p < 0.001). Moreover, transcriptional activity of the GAPDH gene was heterogeneous within the CSX group.

CONCLUSIONS

GAPDH gene expression is markedly enhanced in CSX, which reflects carbohydrate metabolism disturbances and makes the GAPDH gene unsuitable as an endogenous control in patients with CSX.

Genome-wide gene expression analysis of chemoresistant pulmonary carcinoid cells

PURPOSE

Carcinoids are highly chemoresistant tumors associated with a dismal prognosis. This study involved a comparison of the genome-wide gene expression pattern of a chemoresistant and a chemosensitive pulmonary carcinoid cell line to reveal factors that contribute to the resistant phenotype.

MATERIALS AND METHODS

Gene expression of UMC-11 chemoresistant carcinoid cells as assessed by 32 K microarray was compared with H835 chemosensitive carcinoid cells, and the genes that were differentially expressed and expected to be related to chemoresistance were selected.

RESULTS

Drug-resistant UMC-11 cells exhibited increased expression of transcripts known to confer resistance to different cytostatics such as P-glycoprotein, multidrug resistance-associated proteins 2 and 3, effectors of the glutathione detoxification and xenobiotics degradation pathways, and ion transporters including Na⁺/K⁺-adenosine triphosphatase. In addition, enhanced transcription of several S100 proteins, capable of suppressing apoptosis, regulation of topoisomerase I (topo I) expression by antisense transcripts from TOPO1 pseudogenes, and alterations of the cytoskeleton seem to contribute to the multidrug-resistant phenotype. A multitude of epidermal growth factor (EGF)-related and neuropeptide growth factors, overexpression of proteases, and appearance of aerobic glycolytic metabolism complement the malignant phenotype of the UMC-11 cells.

CONCLUSION

The multidrug-resistant phenotype of the UMC-11 pulmonary carcinoid cell line seems to be mediated by classical efflux pumps, drug metabolization or conjugation systems, and, possibly, modulation of apoptotic cell death by S100 proteins and topo I expression by pseudogene transcripts. Autocrine or paracrine stimulation by a host of EGF-related and neuropeptide growth factors, as well as high metastatic potency indicated by increased expression of components of aerobic glycolysis and proteolytic enzymes, may furthermore account for the failure of therapeutic interventions.

Selection of reference genes for real-time quantitative reverse transcription-polymerase chain reaction in hippocampal structure in a murine model of temporal lobe epilepsy with focal seizures

Reference genes are often used to normalize expression of data from real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR), and only a validation of their stability during a given experimental paradigm leads to reliable interpretations. The present study was thus designed to validate potential reference genes in a mouse model of mesiotemporal lobe epilepsy (MTLE) with focal seizures after unilateral intrahippocampal injection of kainate (KA). Ipsilateral and contralateral hippocampi were removed during nonconvulsive status epilepticus (5 hr), epileptogenesis (7 days), and the chronic period of recurrent focal seizures (21 days). Naive animals were equally studied. The stability of eight potential reference genes (hypoxanthine phosphoribosyltransferase, Hprt1; peptidylprolyl isomerase A, Ppia; TATA box binding protein, Tbp; beta-actin, Actb; acidic ribosomal phosphoprotein P0, Arbp; glyceraldehyde-3-phosphate dehydrogenase, Gapdh; ribosomal RNA 18S, 18S rRNA; and glucuronidase beta, Gusb) were determined using geNorm and NormFinder software. The first five (Hprt1, Ppia, Tbp, Actb, and Arbp) were found to be stable across the different phases of the disease and appeared adequate for normalizing RT-qPCR data in this model. This was in contrast to the other three (18S rRNA, Gapdh, and Gusb), which showed unstable expressions and should be avoided. The analysis of KA-induced changes in the expression of glial fibrillary acidic protein (Gfap) gene resulted in various relative expressions or even a completely different pattern when unstable reference genes were used. These results highlight the absolute need to validate the reference genes for a correct interpretation of mRNA quantification.

Absence of GAPDH regulation in tumor-cells of different origin under hypoxic conditions in - vitro

Background

Gene expression studies related to cancer diagnosis and treatment are important. In order to conduct such experiment accurately, absolutely reliable housekeeping genes are essential to normalize cancer related gene expression. The most important characteristics of such genes are their presence in all cells and their expression levels remain relatively constant under different experimental conditions. However, no single gene of this group of genes manifests always stable expression levels under all experimental conditions. Incorrect choice of housekeeping genes leads to interpretation errors of experimental results including evaluation and quantification of pathological gene expression. Here, we examined (a) the degree of GAPDH expression regulation in Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines as well as in human lung adenocarcinoma epithelial cell line (A-549) in addition to both HT-29, and HCT-116 colon cancer cell lines, under hypoxic conditions in vitro in comparison to other housekeeping genes like β-actin, serving as experimental loading controls, (b) the potential use of GAPDH as a target for tumor therapeutic approaches was comparatively examined in vitro on both protein and mRNA level, by western blot and semi quantitative RT-PCR, respectively.

Findings

No hypoxia-induced regulatory effect on GAPDH expression was observed in the cell lines studied in vitro that were; Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines, Human lung adenocarcinoma epithelial cell line (A-549), both colon cancer cell lines HT-29, and HCT-116.

Conclusion

As it is the case for human hepatocellular carcinoma, mouse hepatoma, human colon cancer, and human lung adenocarcinoma, GAPDH represents an optimal choice of a housekeeping gene and/(or) loading control to determine the expression of hypoxia induced genes in tumors of different origin. The results confirm our previous findings in human glioblastoma that this gene is not an attractive target for tumor therapeutic approaches because of the lack of GAPDH regulation under hypoxia.

Instability of standard PCR reference genes in adipose-derived stem cells during propagation, differentiation and hypoxic exposure

Background

For the accurate determination of gene expression changes during growth and differentiation studies on adipose-derived stem cells (ASCs), quantitative real-time RT-PCR has become a method of choice. The technology is very sensitive, however, without a proper selection of reference genes, to which the genes of interest are normalized, erroneous results may be obtained.

Results

In this study, we have compared the gene expression levels of a panel of twelve widely used reference genes during hypoxic culture, osteogenic and chondrogenic differentiation, and passaging of primary human ASCs. We found that several of the commonly used reference genes including 18S rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and beta-actin were unsuitable for normalization in the conditions we tested, whereas tyrosine 3/tryptophan 5-monooxygenase activation protein (YMHAZ), TATAA-box binding protein (TBP), beta-glucuronidase (GUSB) were the most stable across all conditions.

Conclusion

When determining gene expression levels in adipose-derived stem cells, we recommend normalizing transcription levels to the geometric mean of YMHAZ, TBP and GUSB.

Identification of early markers for symptomatic vasospasm in human cerebral microdialysate after subarachnoid hemorrhage: preliminary results of a proteome-wide screening

A major complication of aneurysmal subarachnoid hemorrhage (SAH) is symptomatic vasospasm, a complex syndrome consisting of neurological deterioration and exclusion of other sources of ischemia. Approximately 30% of SAH patients are affected. Although symptomatic vasospasm is associated with high mortality and poor clinical outcome, it is not possible to identify the individual risk on a molecular level for patients before symptoms have developed. In this study, we hypothesize that protein changes occur in the cerebral microdialysate of patients who later develop symptomatic vasospasm which are not found in matched-pairs control subjects. We searched for changes in protein concentrations in microdialysate sampled from the fronto-temporal brain tissue of five vasospastic and five nonvasospastic SAH patients using proteomics technology based on two-dimensional gel electrophoresis and mass spectrometry. Microdialysate samples were taken at least 1.5 days before the onset of symptomatic vasospasm. Comparing protein expression profiles, we found that the protein concentrations of several isoforms of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were 1.79-fold+/-1.29 (N=5, P<0.05) higher in the group which later developed symptomatic vasospasm, whereas heat-shock cognate 71 kDa protein (HSP7C) isoforms were decreased to 0.50-fold+/-0.19 (N=5, P<0.05; all expression data means+/-s.d.). The changes in protein concentrations were detected 3.8+/-1.7 days (N=5, P<0.05) before symptomatic vasospasm developed. We conclude that GAPDH and HSP7C may be used as early markers indicating the later development of symptomatic vasospasm after SAH, enabling selective early therapeutic intervention in this high-risk group of patients.

GAPDH is not regulated in human glioblastoma under hypoxic conditions

Background

Gene expression studies related to cancer diagnosis and treatment are becoming more important. Housekeeping genes that are absolutely reliable are essential for these studies to normalize gene expression. An incorrect choice of housekeeping genes leads to interpretation errors of experimental results including evaluation and quantification of pathological gene expression. Here, we examined (a) the degree of regulation of GAPDH expression in human glioblastoma cells under hypoxic conditions in vitro in comparison to other housekeeping genes like β-actin, serving as experimental loading controls, (b) the potential use of GAPDH as a target for tumor therapeutic approaches and (c) differences in GAPDH expression between low-grade astrocytomas and glioblastomas, for which modest and severe hypoxia, respectively, have been previously demonstrated. GAPDH and β-actin expression was comparatively examined in vivo in human low-grade astrocytoma and glioblastoma on both protein and mRNA level, by Western blot and semiquantitative RT-PCR, respectively. Furthermore, the same proteins were determined in vitro in U373, U251 and GaMG human glioblastoma cells using the same methods. HIF-1α protein regulation under hypoxia was also determined on mRNA level in vitro in GaMG and on protein level in U251, U373 and GaMG cells.

Results

We observed no hypoxia-induced regulatory effect on GAPDH expression in the three glioblastoma cell lines studied in vitro. In addition, GAPDH expression was similar in patient tumor samples of low-grade astrocytoma and glioblastoma, suggesting a lack of hypoxic regulation in vivo.

Conclusion

GAPDH represents an optimal choice of a housekeeping gene and/or loading control to determine the expression of hypoxia induced genes at least in glioblastoma. Because of the lack of GAPDH regulation under hypoxia, this gene is not an attractive target for tumor therapeutic approaches in human glioblastoma.

Characterization of CoCl2-induced reactive oxygen species (ROS): Inductions of neurite outgrowth and endothelin-2/vasoactive intestinal contractor in PC12 cells by CoCl2 are ROS dependent, but those by MnCl2 are not

CoCl(2) and MnCl(2) are hypoxic mimetic agents. We previously found that expression of ET-2/VIC, one of hypoxia-related factors, and the induction of neurite outgrowth in PC12 cells through ROS induced by CoCl(2). MnCl(2) also are known to induce neurite outgrowth in PC12 cells. However, it is unclear whether the mechanism of the effect induced by these metals is same. In the present study, we evaluated biological effects induced by MnCl(2) and compared with those induced by CoCl(2). Furthermore, we analyzed sources of CoCl(2)-induced ROS generation. MnCl(2) up-regulated ET-2/VIC gene expression and ET-2/VIC peptide production as CoCl(2) did, but not affect ET-1 gene expression, in the neurite outgrowth of PC12 cells. NAC did not at all inhibit the effects induced by MnCl(2). Furthermore, addition of MnCl(2) to the culture medium did not generate ROS as CoCl(2) did. These results indicate that ET-2/VIC expression is a common pathway in neurite outgrowth induced by CoCl(2) and MnCl(2), but the effects induced by CoCl(2) are ROS dependent, whereas the effects induced by MnCl(2) are ROS independent. Taken together, the mechanism for the effects by CoCl(2) was different from that by MnCl(2). The ROS, were not decomposed by catalase or SOD, were rapidly generated by reaction of CoCl(2) mainly with components of HS rather than with FBS or DMEM. Some ROS generated by reaction of CoCl(2) with components of HS may participate in the observed neurite outgrowth of PC12 cells.

Comparative SAGE analysis of the response to hypoxia in human pulmonary and aortic endothelial cells

We utilized serial analysis of gene expression (SAGE) to analyze the temporal response of human pulmonary artery endothelial cells (HPAECs) to short-term chronic hypoxia at the level of transcription. Primary cultures of HPAECs were exposed to 1% O2hypoxia for 8 and 24 h and compared with identical same-passage cells cultured under standard (5% CO2-95% air) conditions. Hierarchical clustering of significant hypoxia-responsive genes identified temporal changes in the expressions of a number of well-described gene families including those encoding proteins involved in thrombosis, stress response, apoptosis, angiogenesis, and cell proliferation. These experiments build on previously published data describing the transcriptomic response of human aortic endothelial cells (HAECs) obtained from the same donor and cultured under identical conditions, and we have thus taken advantage of the immortality of SAGE data to make direct comparisons between these two data sets. This approach revealed comprehensive information relating to the similarities and differences at the level of mRNA expression between HAECs and HPAECs. For example, we found differences in the cell type-specific response to hypoxia among genes encoding cytoskeletal factors, including paxillin, and proteins involved in metabolic energy production, the response to oxidative stress, and vasoreactivity (e.g., endothelin-1). These efforts contribute to the expanding collection of publicly available SAGE data and provide a foundation on which to base further efforts to understand the characteristics of the vascular response to hypoxia in the pulmonary circulation relative to systemic vasculature.

Hypoxia regulation of expression and angiogenic effects of vasoactive intestinal peptide (VIP) and VIP receptors in LNCaP prostate cancer cells

Vascular endothelial growth factor (VEGF) is a main factor promoting neovascularization (angiogenesis) of solid tumours as prostate carcinoma. Hypoxia stimulates VEGF gene expression by activating the hypoxia-inducible factor-1 (HIF-1alpha). In the present study, the hypoxia-mimicking agent Ni(2+) induced vasoactive intestinal peptide (VIP) expression at both mRNA and peptide levels but it did not modify the expression of VIP receptors (VPAC(1), VPAC(2) and PAC(1) receptors) in androgen-dependent human LNCaP prostate cancer cells. VIP increased the mRNA levels of VPAC(1) and PAC(1) receptors whereas it decreased VPAC(2) receptor mRNA level. These features support that hypoxia up-regulation of VIP gene expression in prostatic carcinoma may lead to VIP regulation of the expression of its receptors by means of autocrine/paracrine mechanisms. Either VIP or hypoxia mimetics with Ni(2+) increased VEGF expression whereas both conditions together resulted in an additive response. It suggests two independent mechanisms for the observed pro-angiogenic activities of VIP and hypoxia. VIP did not stimulate HIF-1alpha mRNA expression but increased the translocation of HIF-1alpha from the cytosolic compartment to the cell nucleus. Moreover, VIP was unable to modify the expression of the HIF-1alpha inhibitor FIH-1 discarding the possibility of an indirect effect of VIP on HIF-1 transactivation.

Increased gene expression of collagen Types I and III is inhibited by beta-receptor blockade in patients with dilated cardiomyopathy

AIMS

To elucidate the cellular mechanisms of cardioprotection of beta-blockers in patients with heart failure, we investigated the effects of beta-blockers on collagen synthesis in patients with dilated cardiomyopathy (DCM).

METHODS AND RESULTS

We examined the gene expression before and 4 months after the administration of a beta-blocker in 17 DCM patients. The messenger ribonucleic acid expression of collagen Types I and III (Col I and III) and transforming growth factor-beta(1) (TGF-beta(1)) of right ventricular tissues obtained by the endomyocardial biopsy were assessed by quantitative reverse transcriptase-polymerase chain reaction. Cardiac sympathetic nerve activity was assessed by the washout rate (WR) of (123)I-metaiodobenzylguanidine from the heart. Left ventricular ejection fraction (21 +/- 7 vs. 35 +/- 9%) and WR (53+/-14 vs. 42 +/- 13%) improved significantly. Before the beta-blocker treatment, the expressions of both Col I (r = 0.560, P = 0.041) and Col III (r = 0.630, P = 0.008) genes were correlated with WR. The expression levels of both Col I (1.08 +/- 0.72 vs. 0.65 +/- 0.26, P = 0.024) and Col III (2.06 +/- 1.81 vs. 1.05 +/- 0.74, P = 0.018) were reduced by a beta-blocker. Changes in TGF-beta(1) correlated with those in WR (r = 0.606, P = 0.002).

CONCLUSION

beta-Blockers are considered to inhibit the expression of collagen-related genes in DCM, which seems to be mediated by TGF-beta(1).

Stress induced in heart and other tissues by rat dermal exposure to JP-8 fuel

Limited information is available regarding the development of systemic organ stress by dermal exposure to JP-8 fuel. In this study, the systemic stress potential of this fuel is evaluated in a rat model subjected to dermal applications of JP-8 for 7 days at 300 microl per day. Tissue histology indicated that JP-8 induces morphological alterations that suggest that tissue stress in the heart is more substantial than stress in the kidney and liver. Immunoblot analysis of tissues revealed increased levels of the inducible heat shock protein 70 (HSP70) in the heart, kidney, and liver after this dermal JP-8 exposure. This exposure also leads to increased levels of heme oxygenase-1 (HO-1/HSP3) in the liver. Additionally during this exposure, a negative regulator of inflammation, IkappaBalpha (inhibitor of NF-kappaB), was increased in the liver, slightly increased in the kidney, and not increased in the heart. Two regions of the rat brain were also examined and HSP70 and IkappaBalpha were increased in the cerebellum but not significantly increased in the cortex. This study indicates dermal JP-8 exposure causes systemic alterations that are associated with cytoprotective activities (e.g., in the liver) as well as potentially toxic mechanisms (heart and kidney).

Effect of hypoxia and reoxygenation on gene expression and response to interleukin-1 in cultured articular chondrocytes

OBJECTIVE

To determine the effects of hypoxia and reoxygenation on the metabolism of chondrocytes and their response to interleukin-1beta (IL-1beta). The study included activation of hypoxia-inducible factor 1 (HIF-1), NF-kappaB, and activator protein 1 (AP-1) transcription factors, expression of matrix components and metalloproteases and transforming growth factor beta (TGFbeta) and TGFbeta receptors, and production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)).

METHODS

Bovine articular chondrocytes (BACs) were cultured to confluency in either 5% O(2) (hypoxia) or 21% O(2) (normoxia) in media supplemented with 10% fetal calf serum (FCS). BACs were preincubated for 18 hours in media with 1% FCS only and then incubated for 24 hours in the presence of IL-1beta. For reoxygenation experiments, cells were treated in the same way in 5% O(2), except that cultures were transferred to normal atmospheric conditions and used after 4 hours for RNA extraction or after 30 minutes for cytoplasmic or nuclear protein extraction.

RESULTS

In hypoxic and reoxygenated chondrocytes, we observed strong DNA binding of HIF-1. IL-1beta-induced DNA binding of NF-kappaB and AP-1 was significantly higher in hypoxic and reoxygenated cultures than in normoxia. Greater activation of the MAPKs was also observed with IL-1beta treatment in hypoxia compared with normoxia. Steady-state levels of type II collagen and aggrecan core protein messenger RNA (mRNA) were decreased by IL-1beta in all instances. Matrix metalloprotease 1 (MMP-1) and MMP-3 mRNA were increased by IL-1beta in normoxia and hypoxia, whereas only MMP-3 mRNA was enhanced in reoxygenated cultures. The MMP-2 mRNA level was not significantly affected by IL-1beta in normoxia or hypoxia, whereas it was enhanced in reoxygenated cultures. MMP-9 mRNA was dramatically decreased by IL-1beta only in low oxygen tension. Tissue inhibitor of metalloproteinases 1 (TIMP-1) message was significantly enhanced by the cytokine in most instances, whereas TIMP-2 message was markedly decreased by IL-1beta in reoxygenated cultures. Stimulation of TGFbeta1 expression by IL-1beta was observed only in normal atmospheric conditions. One of the more striking findings of the study was the greater stimulating effect of IL-1beta on NO production observed in hypoxia, which was much higher than in normoxia, whereas the reverse was observed for IL-1beta-induced PGE(2) production.

CONCLUSION

Oxygen level and reoxygenation stress significantly modulate gene expression and the response of articular chondrocytes to cytokines such as IL-1beta. In hypoxic conditions, which mimic the in vivo condition of cartilage, the effects of IL-1beta on both synthesis and degradative processes are significantly different from those in normoxia, conditions that are unlikely encountered by chondrocytes in a normal state. In low oxygen tension, high IL-1beta-induced NO production is associated with a significant decrease in PGE(2) synthesis. These data should influence our concept of the role of oxygen in the pathophysiology of joint disease and may help define the best conditions in which to develop bioartificial cartilage.

Hypoxia upregulates the expression of the NDRG1 gene leading to its overexpression in various human cancers

Background

The expression of NDRG1 gene is induced by nickel, a transition metal sharing similar physical properties to cobalt. Nickel may create hypoxia-like conditions in cells and induce hypoxia-responsive genes, as does cobalt. Therefore NDRG1 is likely to be another gene induced by hypoxia. HIF-1 is a transcription factor which has a major role in the regulation of hypoxia-responsive genes, and thus it could be involved in the transcriptional regulation of NDRG1 gene. Hypoxia is such a common feature of solid tumours that it is of interest to investigate the expression of Ndrg1 protein in human cancers.

Results

Hypoxia and its mimetics induce in vitro expression of NDRG1 gene and cause the accumulation of Ndrg1 protein. Protein levels remain high even after cells revert to normoxia. Although HIF-1 is involved in the regulation of NDRG1, long term hypoxia induces the gene to some extent in HIF-1 knock-out cells. In the majority of human tissues studied, Ndrg1 protein is overexpressed in cancers compared to normal tissues and also reflects tumour hypoxia better than HIF-1 protein.

Conclusions

Hypoxia is an inducer of the NDRG1 gene, and nickel probably causes the induction of the gene by interacting with the oxygen sensory pathway. Hypoxic induction of NDRG1 is mostly dependent on the HIF-1 transcription factor, but HIF-1 independent pathways are also involved in the regulation of the gene during chronic hypoxia. The determination of Ndrg1 protein levels in cancers may aid the diagnosis of the disease.

Genome-wide analysis of the endothelial transcriptome under short-term chronic hypoxia

We have utilized serial analysis of gene expression (SAGE) to analyze the temporal response of human aortic endothelial cells (HAECs) to short-term chronic hypoxia at the level of transcription. Primary cultures of HAECs were exposed to 1% O2hypoxia for 8 and 24 h and compared with identical same passage cells cultured under standard (5% CO2-95% air) conditions. A total of 121,446 tags representing 37,096 unique tags were sequenced and genes whose expression levels were modulated by hypoxia identified by novel statistical analyses. Hierarchical clustering of genes displaying statistically significant hypoxia-responsive alterations in expression revealed temporal modulation of a number of major functional gene families including those encoding heat shock factors, glycolytic enzymes, extracellular matrix factors, cytoskeletal factors, apoptotic factors, cell cycle regulators and angiogenic factors. Within these families we documented the coordinated modulation of both previously known hypoxia-responsive genes, numerous genes whose expressions have not been previously shown to be altered by hypoxia, tags matching uncharacterized UniGene entries and entirely novel tags with no UniGene match. These preliminary data, which indicate a reduction in cell cycle progression, elevated metabolic stress and increased cytoskeletal remodeling under acute hypoxic stress, provide a foundation for further analyses of the molecular mechanisms underlying the endothelial response to short-term chronic hypoxia.

Changes in myocardial gene expression associated with beta-blocker therapy in patients with chronic heart failure

BACKGROUND

The left ventricular functional recovery by beta-blocker therapy is now attributed to time-dependent biologic effects on cardiomyocytes.

METHODS AND RESULTS

To elucidate the cellular mechanism of these biologic effects, we treated 9 patients with dilated cardiomyopathy for 4 months with beta-blockers and examined the gene expressions linked to an improvement of left ventricular ejection fraction (EF). Gene expressions of the biopsied right ventricular endomyocardium were assessed by real-time reverse transcription-polymerase chain reaction. A decrease in beta-myosin heavy chain (1.23+/-0.49 versus 0.86+/-0.45, P<.05) was observed 4 months after the administration of beta-blockers. The expression levels of both sarcoplasmic reticulum Ca(2+) ATPase (SERCA) (0.80+/-0.28 versus 1.39+/-0.44, P<.01) and phospholamban (PLB) (0.49+/-0.08 versus 0.88+/-0.34, P<.05) increased, whereas the expression levels of Na(+)-Ca(2+) exchanger (NCX), beta-adrenoreceptor kinase 1, and ryanodine receptor 2 were unchanged. The SERCA/NCX ratio (0.68+/-0.14 versus 0.96+/-0.33, P<.05) also increased. The increase in SERCA mRNA expression correlated with the degree of changes in EF (%deltaEF) (r=0.679, P<.05), and none of changes in these genes expression correlated with changes in the plasma brain natriuretic peptide concentration.

CONCLUSIONS

The functional recovery resulting from beta-blockers may be associated with the restoration of the unfavorable gene expression that controls Ca(2+) handlings in the failing heart.

Hypoxic up-regulation of triosephosphate isomerase expression in mouse brain capillary endothelial cells

A protein with a molecular mass of 27kDa was induced by hypoxia in a mouse brain capillary endothelial cell line and identified as triosephosphate isomerase (TPI) by amino-terminal sequencing. Hypoxia caused an elevation of the TPI protein level, concomitant with an increase of the TPI mRNA level. However, hypoxia resulted in an insufficient elevation of TPI activity level, compared to an increase of TPI protein level. When cells expressing the recombinant TPI protein with histidine tag were exposed to hypoxia and the TPI protein was affinity-purified, the catalytic activity (specific activity) of the TPI protein purified from hypoxic cells was substantially lower than that obtained from normoxic cells. In addition, three TPI isoforms with an electrophoretic multiplicity were found; two of the three isoforms were substantially increased in response to the hypoxia, but the level of the most acidic isoform was barely changed. The induction of TPI gene expression by hypoxia was suppressed by (1) a chelator of intracellular Ca(2+), (2) a blocker of non-selective cation channels, (3) a blocker of Na(+)/Ca(2+) exchangers, (4) an inhibitor of Ca(2+)/calmodulin-dependent protein kinases, and (5) an inhibitor of c-jun/AP-1 activation.

Transcriptional effects of hypoxia on fusiogenic syncytin and its receptor ASCT2 in human cytotrophoblast BeWo cells and in ex vivo perfused placental cotyledons

OBJECTIVE

The purpose of this study was to test the hypothesis that hypoxia down-regulates placental syncytin, which could play a role in altered placentogenesis; we investigated the influence of hypoxia on syncytin and its receptor ASCT2 gene expression in BeWo cells and in ex vivo perfused human cotyledons.

STUDY DESIGN

BeWo cells were incubated with deferoxamine or cobalt chloride under normoxia and hypoxia. Additionally, a model of dually ex vivo perfused cotyledons was applied. Under hypoxic and cobalt chloride stimuli syncytin, ASCT2, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta-actin, and beta(2)-microglobulin (beta(2)-MG) messenger RNAs were analyzed with the use of real-time polymerase chain reaction.

RESULTS

Hypoxia, deferoxamine, and cobalt chloride markedly decreased syncytin messenger RNA in BeWo cells, whereas ASCT2 messenger RNA was not altered significantly. In isolated perfused cotyledons, hypoxia also reduced syncytin (P<.05) but not ASCT2 messenger RNA.

CONCLUSION

Our data provide first evidence that syncytin gene expression is down-regulated by hypoxia, which strengthens the hypothesis that syncytin is reduced in disturbed pregnancies in the course of placental hypoxia.

Inhalant nitrite exposure alters mouse hepatic angiogenic gene expression

Inhalant nitrites are drugs of abuse that have been shown to enhance tumor growth rate in mice and are epidemiologically linked to an increased risk of Kaposi's sarcoma. Because nitrites produce nitric oxide, we hypothesized that their toxicological effects might be partly mediated via regulation of angiogenic factors such as vascular endothelial growth factor (VEGF). Preliminary studies showed that isobutyl nitrite (ISBN) incubation stimulated VEGF protein expression in J774 macrophage cells. C57BL/6 mice exposed to ISBN in air exhibited significant up-regulation of VEGF protein and mRNA in the liver, but not in the lung. Liver mRNA expression of VEGF receptor 2 (VEGFR-2), VEGFR-3, Smad5, and Smad7 was also significantly altered. These results demonstrate that in vivo exposure to an inhalant nitrite results in altered tissue expression of VEGF and its receptors, suggesting that some of its toxicological effects may be mediated partly through a mechanism involving angiogenesis.

Fibroblast growth factor mediates hypoxia-induced endothelin-- a receptor expression in lung artery smooth muscle cells

We have previously demonstrated that endothelin (ET)-1 and its subtype A receptor (ET-AR) expression are increased in lung under hypoxic conditions and that activation of ET-AR by ET-1 is a major mediator of hypoxia-induced pulmonary hypertension in the rat. The present study tested the hypothesis that the hypoxia-responsive tyrosine kinase receptor-activating growth factors fibroblast growth factor (FGF)-1, FGF-2, and platelet-derived growth factor (PDGF)-BB stimulate expression of the ET-AR in pulmonary arterial smooth muscle cells (PASMCs). Quiescent rat PASMCs were incubated under hypoxia (1% O2), or with FGF-1, FGF-2, PDGF-BB, vascular endothelial growth factor, ET-1, angiotensin II, or atrial natriuretic peptide under normoxic conditions for 24 h. FGF-1 and -2 and PDGF-BB, but not hypoxia, vascular endothelial growth factor, ET-1, angiotensin II, or atrial natriuretic peptide, significantly increased ET-AR mRNA levels. FGF-1-induced ET-AR expression was inhibited by FGF-receptor inhibitor PD-166866, MEK inhibitor U-0126, transcription inhibitor actinomycin D, and translation inhibitor cycloheximide. In contrast, the stimulatory effect of FGF-1 on ET-AR mRNA expression was not altered by PI3 kinase, PKA, PKC, or adenylate cyclase inhibitors. PASMC ET-AR gene transcription, assessed by nuclear-runoff analysis, was increased by FGF-1. These results provide novel finding that ET-AR in PASMCs in vitro is unresponsive to hypoxia per se but is robustly simulated by tyrosine kinase receptor-associated growth factors (FGF-1, FGF-2, PDGF-BB) that themselves are stimulated by hypoxia in lung. This observation suggests a novel signaling mechanism that may be responsible for overexpression of ET-AR in lung, and may contribute to the hypoxia-induced pulmonary vasoconstriction, hypertension, and vascular remodeling in hypoxia-adapted animal.

In vitro effect of metal ions on the activity of two amphibian glyceraldehyde-3-phosphate dehydrogenases: potential metal binding sites

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) was purified from two amphibian species, Xenopus laevis and Pleurodeles waltl. Comparative studies revealed that the two proteins differ by their subunit molecular masses, pI values and V8 digested peptide maps. The effect of zinc, cadmium and copper ions on GAPDH enzymatic activity has been examined in vitro. A time, metal concentration and metal type dependent inhibition was observed for both enzymes. X. laevis and P. waltl GAPDHs exhibit a much greater sensitivity to copper than to cadmium or zinc ions. Different half-lives and differential sensitivity to various metals was observed between the two enzymes with P. waltl GAPDH being remarkably tolerant to cadmium ions compared to the X. laevis enzyme. In order to understand the differential sensitivity of the two enzymes to metals, we produced 3D models of both X. laevis and P. waltl GAPDH structures based upon known 3D structures of GAPDHs from other species. This necessitated, in a first step, to clone a 900 bp cDNA fragment encoding the nearly full-length P. waltl GAPDH. Spatial motif searches on the homology models indicated potential metal binding sites involving cysteine and histidine residues outside the catalytic sites, existing only in either the X. laevis or the P. waltl GAPDH sequences.

Hypoxia enhances Ecto-5'-Nucleotidase activity and cell surface expression in endothelial cells: role of membrane lipids

Extracellular adenosine production by the glycosyl-phosphatidyl-inositol-anchored Ecto-5'-Nucleotidase plays an important role in the defense against hypoxia, particularly in the intravascular space. The present study was designed in order to elucidate the mechanisms underlying hypoxia-induced stimulation of Ecto-5'-Nucleotidase in endothelial cells. For this purpose, aortic endothelial cells (SVARECs) were submitted to hypoxic gas mixture. Hypoxia (0% O2 for 18 hours) induced a 2-fold increase of Ecto-5'-Nucleotidase activity (Vmax 19.78+/-0.53 versus 8.82+/-1.12 nmol/mg protein per min), whereas mRNA abundance and total amount of the protein were unmodified. By contrast, hypoxia enhanced cell surface expression of Ecto-5'-Nucleotidase, as evidenced both by biotinylation and immunostaining. This effect was accompanied by a decrease of Ecto-5'-Nucleotidase endocytosis, without modification of Ecto-5'-Nucleotidase association with detergent-resistant membranes. Finally, whereas cholesterol content was unmodified, hypoxia induced a time-dependent increase of saturated fatty acids in SVARECs, which was reversed by reoxygenation, in parallel to Ecto-5'-Nucleotidase stimulation. Incubation of normoxic cells with palmitic acid enhanced Ecto-5'-Nucleotidase activity and cell surface expression. In conclusion, hypoxia enhances cell surface expression of Ecto-5'-Nucleotidase in endothelial cells. This effect could be supported by a decrease of Ecto-5'-Nucleotidase endocytosis through modification of plasma membrane fatty acid composition.

HIF-2alpha regulates glyceraldehyde-3-phosphate dehydrogenase expression in endothelial cells

Endothelial cells (EC) express both hypoxia inducible factor-1alpha (HIF-1alpha) and -2alpha (HIF-2alpha), yet their roles in the EC hypoxic response are unclear. Hypoxia upregulates the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in EC through a 5' hypoxic regulatory element (HRE). We compared the upregulation of GAPDH in human lung microvascular EC to that in hep3B cells, another cell type known to express both HIF-1alpha and HIF-2alpha. GAPDH mRNA increased to a lesser extent in hypoxic hep3B cells than in EC, yet upregulation occurred through the same HRE that was active in EC. HIF-1alpha protein induction in response to hypoxia was similar in both cell types. In contrast, HIF-2alpha protein levels were upregulated to a greater extent and for a longer period of time by hypoxia in EC than in hep3B cells. Correspondingly, electrophoretic mobility supershift assays showed that, in EC, there was preferential binding of HIF-2alpha to the GAPDH HRE while, in hep3B cells, there was binding of both HIF-1alpha and HIF-2alpha. The preferential binding of HIF-2alpha to the GAPDH HRE in EC may account for their higher level of induction of GAPDH. These findings suggest that cell-specific patterns of HIF-1alpha and HIF-2alpha expression lead to cell-specific gene upregulation during hypoxia.

Mechanisms of endothelial survival under shear stress

Endothelial cells (ECs) are exposed to cytotoxic reactive oxygen species and oxidation products of NO, yet they are characterized by low apoptotic rates and have an average life span of many years. EC exposure to flow has been shown to downregulate cell cycle-related genes and cause cytoskeletal rearrangement. We hypothesized that exposure to flow also causes molecular and physiological changes that induce antioxidant properties in ECs. We used cDNA array expression profiling and protein analysis to study the responses of human ECs exposed to flow in a hollow fiber apparatus or the same ECs grown under static conditions. Our results show that shear-induced synchronized expression of processes control oxidant production; these changes included upregulation of NADH-producing enzymes (Krebs cycle dehydrogenases and glyceraldehyde-3-phosphate dehydrogenase [GAPDH]) accompanied by simultaneous decrease in NADH-depleting pathways (e.g., lactate dehydrogenase [LDH]) and diminished production of lactate. Exposure to flow upregulated cytoskeletal genes. Our results suggest that, in addition to inhibition of cell cycle, exposure to flow influences ECs by controlling expression of enzymes involved in the generation of antioxidant intermediates and in adaptive control of cell shape. These changes may explain longevity and antioxidant efficiency of ECs and may provide insight in mechanisms leading to pathological conditions such as arteriosclerosis.

Hypoxia up-regulates glyceraldehyde-3-phosphate dehydrogenase in mouse brain capillary endothelial cells: involvement of Na+/Ca2+ exchanger

The molecular regulatory mechanisms and the characterization of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in hypoxia were studied in a mouse brain capillary endothelial cell line, MBEC4. Activation of GAPDH gene expression by hypoxia was suppressed by an intracellular Ca(2+) chelator and inhibited by a non-selective cation channel blocker or a Na(+)/Ca(2+) exchanger (NCX) blocker. Sequencing of reverse transcription-PCR products demonstrated that MBEC4 expressed an mRNA encoding NCX3, which functions even under cellular ATP-depleted conditions, in addition to mRNAs encoding NCX1 and NCX2. The inhibition of Ca(2+)/calmodulin-dependent protein kinases or c-Jun/AP-1 activation caused a significant decrease in the activation of GAPDH mRNA by hypoxia. These results suggest that hypoxia stimulates Ca(2+) influx through non-selective cation channels and causes the reverse operation of the three NCX isoforms, and consequently, increased intracellular Ca(2+) up-regulates GAPDH gene expression through an AP-1-dependent pathway. Furthermore, subcellular fractionation experiments showed that hypoxia increased GAPDH proteins not only in the cytosolic fraction, but also in the nuclear and particulate fractions, in which GAPDH should play no roles in glycolysis. However, the GAPDH activity did not rise in proportion to the increase of GAPDH protein by hypoxia even in the cytosolic fraction. These results suggest that not all hypoxia-induced GAPDH molecules contribute to glycolysis.

Altered protein profile and possible hypoxia in the placenta of 2,3,7,8-tetrachlorodibenzo-p-dioxin-exposed rats

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during pregnancy causes fetal death in many animal species. In an earlier study we observed alteration of placental glucose kinetics at the same TCDD exposure level that resulted in fetal death (Ishimura et al., Toxicol. Appl. Pharmacol. 178, 161-171, 2002). In the present study, in order to identify the molecules that might explain the alterations of placental function and the mechanism of fetal death, we used two-dimensional gel electrophoresis (2D/E) to detect and identify placental proteins whose amounts changed after exposure to TCDD and we examined the expression properties of these proteins in the placenta during hypoxia by using the uterine artery ligation model. Pregnant Holtzman rats were given a single oral dose of 1600 ng TCDD/kg body wt or an equivalent volume of vehicle (control) on gestational day (GD) 15 and placental tissue was collected on GD16 and GD20. The 15,000 g supernatant fractions of placental homogenates from the control group and TCDD-exposed group were subjected to the 2D/E analysis, and the protein spots whose amounts had changed after exposure to TCDD were characterized by amino acid sequence analysis. The amounts of heat shock protein 27 (Hsp27) and beta-tropomyosin (beta-TM) in TCDD-exposed placentas tended to have increased on GD16 and had increased significantly on GD20, and these changes were followed by an approximately twofold increase in glyceraldehyde 3-phosphate dehydrogenase (GAPDH) on GD20. Next, the uterine-artery ligation model was prepared on GD15, and the hypoxic placentas were collected on GD20. Two-D/E analysis of the 15,000 g supernatant proteins of the placentas revealed an increased level of GAPDH but not of other proteins, including Hsp27 and beta-TM. The results of this study showed that the increase in GAPDH level during hypoxia previously observed in endothelial cells occurs in the placenta and indicated that the TCDD-exposed placentas were in a hypoxic state at the end of pregnancy. Finally, the results of this study suggested the possibility that the increased incidence of fetal death after exposure to TCDD was due to the placental hypoxia.

Increasing plasmalogen levels protects human endothelial cells during hypoxia

Supplementation of cultured human pulmonary arterial endothelial cells (PAEC) with sn-1-O-hexadecylglycerol (HG) resulted in an approximately twofold increase in cellular levels of plasmalogens, a subclass of phospholipids known to have antioxidant properties; this was due, primarily, to a fourfold increase in the choline plasmalogens. Exposure of unsupplemented human PAEC to hypoxia (PO(2) = 20-25 mmHg) caused an increase in cellular reactive oxygen species (ROS) over a period of 5 days with a coincident decrease in viability. In contrast, HG-supplemented cells survived for at least 2 wk under these conditions with no evidence of increased ROS. Hypoxia resulted in a selective increase in the turnover of the plasmalogen plasmenylethanolamine. Human PAEC with elevated plasmalogen levels were also more resistant to H(2)O(2), hyperoxia, and the superoxide generator plumbagin. This protection was seemingly specific to cellular stresses in which significant ROS were generated because the sensitivity to lethal heat shock or glucose deprivation was not altered in HG-treated human PAEC. HG, by itself, was not sufficient for protection; HG supplementation of bovine PAEC had no effect upon plasmalogen levels and did not rescue these cells from the cytotoxic effects of hypoxia. This is the initial demonstration that plasmalogen content can be substantially enhanced in a normal cell. These data also demonstrate that HG can protect cells during hypoxia and other ROS-mediated stress, likely due to the resulting increase in these antioxidant phospholipids.

Nickel essentiality, toxicity, and carcinogenicity

The increasing utilization of heavy metals in modern industries leads to an increase in the environmental burden. Nickel represents a good example of a metal whose use is widening in modern technologies. As the result of accelerated consumption of nickel-containing products nickel compounds are released to the environment at all stages of production and utilization. Their accumulation in the environment may represent a serious hazard to human health. Among the known health related effects of nickel are skin allergies, lung fibrosis, variable degrees of kidney and cardiovascular system poisoning and stimulation of neoplastic transformation. The mechanism of the latter effect is not known and is the subject of detailed investigation. This review provides an analysis of the current state in the field.

Real-time RT-PCR for the detection of beta-adrenoceptor messenger RNAs in small human endomyocardial biopsies

Quantification of mRNAs from extremely small human samples remains a challenge. Requiring minimal amounts of tissue and no post-reaction manipulation, real-time reverse transcriptase-polymerase chain reaction (RT-PCR) is an attractive method to quantitatively assess the expression of rare mRNAs. We evaluated the applicability of the technique on RNA extracted from human endomyocardial biopsies and isolated cardiomyocytes, and compared the technique to the RT-competitive PCR approach. Primers and probes were designed to amplify the three subtypes of human beta -adrenoceptors (beta1-, beta2- and beta3 AR), as well as reference genes such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Hypoxanthine-guanine phosphoribosyltransferase (HPRT), and the oncogene ABL by real-time RT-PCR. Specific primers and a deleted competitor were synthetized to compare the quantitation of the beta 3 AR mRNA expression by RT-competitive PCR. We validated the technique on human cardiomyocytes either freshly isolated or selectively excised from fixed sections of human myocardium by Laser Capture Microdissection. The standard curves obtained for the cDNA's analysed showed mean slopes comprised between -3.3 and -3.7. Inter- and intra-assay variability of gene quantitation was reflected by mean values of the variance coefficients of Ct of 4.84+/-1.13% and 2.73+/-0.39% or 3.32+/-1.03% and 2.21+/-0.24% (corresponding to percent variances of copy numbers of 83.07+/-12.72% and 34.45+/-9.03% or 47.40+/-8.59% and 23.83+/-3.16%) for human beta3 AR and GAPDH genes, respectively. The expression of GAPDH, HPRT and ABL mRNA was characterized by a very low dispersion of individual values across cardiac pathologies, suggesting that these genes may be used as reference genes in quantitative PCR studies. Finally, we applied the technique to detect rare mRNAs, such as beta -AR mRNAs, from small human endomyocardial biopsies and even isolated cardiomyocytes. Real-time RT-PCR is appropriate to quantitate rare messenger RNAs, including in extremely small human tissue samples. This method appears very promising for futures studies of gene expression in several pathophysiological conditions, including heart failure.

Tyrosine kinase receptor activation inhibits NPR-C in lung arterial smooth muscle cells

We have previously demonstrated that expression of the atrial natriuretic peptide (ANP) clearance receptor (NPR-C) is reduced selectively in the lung of rats and mice exposed to hypoxia but not in pulmonary arterial smooth muscle cells (PASMCs) cultured under hypoxic conditions. The current study tested the hypothesis that hypoxia-responsive growth factors, fibroblast growth factors (FGF-1 and FGF-2) and platelet-derived growth factor-BB (PDGF-BB), that activate tyrosine kinase receptors can reduce expression of NPR-C in PASMCs independent of environmental oxygen tension. Growth-arrested rat PASMCs were incubated under hypoxic conditions (1% O2) for 24 h; with FGF-1, FGF-2, or PDGF-BB (0.1-20 ng/ml for 1-24 h); or with ANG II (1-100 nM), endothelin-1 (ET-1, 0.1 microM), ANP (0.1 microM), sodium nitroprusside (SNP, 0.1 microM), or 8-bromo-cGMP (0.1 mM) for 24 h under normoxic conditions. Steady-state NPR-C mRNA levels were assessed by Northern blot analysis. FGF-1, FGF-2, and PDGF-BB induced dose- and time-dependent reduction of NPR-C mRNA expression within 1 h at a threshold concentration of 1 ng/ml; hypoxia, ANG II, ET-1, ANP, SNP, or cGMP did not decrease NPR-C mRNA levels in PASMCs under the above conditions. Downregulation of NPR-C expression by FGF-1, FGF-2, and PDGF-BB was inhibited by the selective FGF-1 receptor tyrosine kinase inhibitor PD-166866 and mitogen-activated protein/extracellular signal-regulated kinase inhibitors U-0126 and PD-98059. These results indicate that activation of tyrosine kinase receptors by hypoxia-responsive growth factors, but neither hypoxia per se nor activation of G protein-coupled receptors, inhibits NPR-C gene expression in PASMCs. These results suggest that FGF-1, FGF-2, and PDGF-BB play a role in the signal transduction pathway linking hypoxia to altered NPR-C expression in lung.

Modulation of bovine articular chondrocyte gene expression in vitro by oxygen tension

OBJECTIVE

Adult articular cartilage is a physiologically hypoxic tissue with a proposed gradient of oxygen tension ranging from <10% oxygen at the cartilage surface to <1% in the deepest layers. This gradient may be disturbed during diseases of the joint, for example in rheumatoid arthritis when synovial fluid pO(2)falls. We investigated whether changes in oxygen tension modulate gene expression in articular chondrocytes.

DESIGN

Bovine articular chondrocytes were cultured in alginate beads in medium maintained at <0.1, 5, 10 or 20% oxygen. A modified RNA arbitrarily primed polymerase chain reaction (RAP-PCR) technique was used to identify several genes whose mRNA abundance in articular chondrocytes was dependent upon oxygen tension. Northern hybridization slot blots were used to quantify changes in mRNA level relative to a housekeeping gene, beta-actin.

RESULTS

Genes found by RAP-PCR to undergo up-regulation in hypoxia included TIMP-1 and integrin-linked kinase. Collagen V mRNA levels were down-regulated in hypoxic chondrocytes. This led us to examine mRNA levels for various cytokines, matrix structural molecules and beta1 integrin. Interleukin 1beta, transforming growth factor beta and connective tissue growth factor were all up-regulated by low oxygen tensions, as was beta1 integrin. Collagen II (COL2A1) was down-regulated by hypoxia but aggrecan mRNA levels remained unchanged. The mRNA levels for GAPDH, the archetypal hypoxia responsive gene, were not modulated in articular chondrocytes by changes in oxygen tension.

CONCLUSIONS

Oxygen tension modulates the abundance of mRNAs encoding structural molecules, several cytokines, beta1 integrin and integrin-linked kinase in articular chondrocytes. This may be important during disease progression. Chondrocytes are unusual in their response to hypoxia, presumably because they exist physiologically in a low oxygen environment.

Quantitative mRNA expression analysis from formalin-fixed, paraffin-embedded tissues using 5' nuclease quantitative reverse transcription-polymerase chain reaction

Analysis of gene expression and correlation with clinical parameters has the potential to become an important factor in therapeutic decision making. The ability to analyze gene expression in archived tissues, for which clinical followup is already available, will greatly facilitate research in this area. A major obstacle to this approach, however, has been the uncertainty about whether gene expression analyses from routinely archived tissues accurately reflect expression before fixation. In the present study we have optimized the RNA isolation and reverse transcription steps for quantitative reverse transcription-polymerase chain reaction (RT-PCR) on archival material. Using tissue taken directly from the operating room, mRNAs with half-lives from 10 minutes to >8 hours were isolated and reverse transcribed. Subsequent real-time quantitative PCR methodology (TaqMan) on these cDNAs gives a measurement of gene expression in the fixed tissues comparable to that in the fresh tissue. In addition, we simulated routine pathology handling and demonstrate that this method of mRNA quantitation is insensitive to pre-fixation times (time from excision to fixation) of up to 12 hours. Therefore, it should be feasible to analyze gene expression in archived tissues where tissue collection procedures are largely unknown.