Serum oxidative biomarkers associated with genital HPV infection and cervical lesions in women.

Human papillomavirus (HPV) infection is a major cause of cervical cancer. Studies showed HPV carcinogenesis may be induced by oxidative stress affecting the host immune system. The objective of this study is to evaluate levels of four circulating oxidative stress biomarkers associated with the HPV infection, persistence, and cervical lesion status in women. The three serum biomarkers measuring oxidative damage to biomolecules (8-oxodG, 8-oxo-7,8-dihydro-2'-deoxyguanosine [8-oxodG] for DNA, 4-hydroxy-2-nonenal [4-HNE] for lipid, and protein carbonyl [PC] for protein) and one antioxidant (glutathione, GSH) collected from 38 women were evaluated. The PC levels were significantly higher for women with oncogenic HPV infection (p = 0.047) and persistence (p = 0.053) based on the unadjusted linear model. In particular, women with ≥3 oncogenic HPV types had a higher PC level than those without HPV infection (p = 0.041). Women with low-grade squamous intraepithelial lesions showed an elevated PC (p = 0.058). These trends remained similar after adjusting for age. The GSH levels were lower for women infected with ≥3 oncogenic HPV types based on age-adjusted results (p = 0.061). This study supported that serum PC was associated with HPV infection, persistence, and cervical lesions, so it can potentially be used to monitor HPV carcinogenesis. Further large-scale studies will be needed to confirm these findings.

Forkhead Box Transcription Factors of the FOXA Class Are Required for Basal Transcription of Angiotensin-Converting Enzyme 2.

Angiotensin-converting enzyme 2 (ACE2) has protective effects on a wide range of morbidities associated with elevated angiotensin-II signaling. Most tissues, including pancreatic islets, express ACE2 mainly from the proximal promoter region. We previously found that hepatocyte nuclear factors 1α and 1ß stimulate ACE2 expression from three highly conserved hepatocyte nuclear factor 1 binding motifs in the proximal promoter region. We hypothesized that other highly conserved motifs would also affect ACE2 expression. By systematic mutation of conserved elements, we identified five regions affecting ACE2 expression, of which two regions bound transcriptional activators. One of these is a functional FOXA binding motif. We further identified the main protein binding the FOXA motif in 832/13 insulinoma cells as well as in mouse pancreatic islets as FOXA2.

Determining the Enzymatic Activity of Angiotensin-Converting Enzyme 2 (ACE2) in Brain Tissue and Cerebrospinal Fluid Using a Quenched Fluorescent Substrate.

Angiotensin-converting enzyme 2 (ACE2) is a component of the renin-angiotensin system (RAS) which plays an important role in the regulation of blood pressure and volume homeostasis. Accumulating evidence shows alterations in ACE2 expression and activity in several hypertensive animal models, as well as in patients with hypertension. In order to assess the role of brain ACE2 in hypertension, a specific ACE2 assay is required. Based on a quenched fluorescent substrate, we describe an easy-to-use method for determining ACE2 activity in brain tissue and cerebrospinal fluid. The method can further be adapted for other tissues, plasma, cell extracts, and cell culture supernatants.

Dynamics of ADAM17-Mediated Shedding of ACE2 Applied to Pancreatic Islets of Male db/db Mice.

Angiotensin-converting enzyme 2 (ACE2) gene therapy aimed at counteracting pancreatic ACE2 depletion improves glucose regulation in two diabetic mouse models: db/db mice and angiotensin II-infused mice. A disintegrin and metalloproteinase 17 (ADAM17) can cause shedding of ACE2 from the cell membrane. The aim of our studies was to determine whether ADAM17 depletes ACE2 levels in pancreatic islets and ß-cells. Dynamics of ADAM17-mediated ACE2 shedding were investigated in 832/13 insulinoma cells. Within a wide range of ACE2 expression levels, including the level observed in mouse pancreatic islets, overexpression of ADAM17 increases shed ACE2 and decreases cellular ACE2 levels. We provide a mathematical description of shed and cellular ACE2 activities as a function of the ADAM17 activity. The effect of ADAM17 on the cellular ACE2 content was relatively modest with an absolute control strength value less than 0.25 and approaching 0 at low ADAM17 activities. Although we found that ADAM17 and ACE2 are both expressed in pancreatic islets, the ß-cell is not the major cell type expressing ACE2 in islets. During diabetes progression in 8-, 12-, and 15-week-old db/db mice, ACE2 mRNA and ACE2 activity levels in pancreatic islets were not decreased over time nor significantly decreased compared with nondiabetic db/m mice. Levels of ADAM17 mRNA and ADAM17 activity were also not significantly changed. Inhibiting basal ADAM17 activity in mouse islets failed to affect ACE2 levels. We conclude that whereas ADAM17 has the ability to shed ACE2, ADAM17 does not deplete ACE2 from pancreatic islets in diabetic db/db mice.

The transcription factor HNF1α induces expression of angiotensin-converting enzyme 2 (ACE2) in pancreatic islets from evolutionarily conserved promoter motifs.

Pancreatic angiotensin-converting enzyme 2 (ACE2) has previously been shown to be critical for maintaining glycemia and ß-cell function. Efforts to maintain or increase ACE2 expression in pancreatic ß-cells might therefore have therapeutic potential for treating diabetes. In our study, we investigated the transcriptional role of hepatocyte nuclear factor 1α (HNF1α) and hepatocyte nuclear factor 1ß (HNF1ß) in induction of ACE2 expression in insulin-secreting cells. A deficient allele of HNF1α or HNF1ß causes maturity-onset diabetes of the young (MODY) types 3 and 5, respectively, in humans. We found that ACE2 is primarily transcribed from the proximal part of the ACE2 promoter in the pancreas. In the proximal part of the human ACE2 promoter, we further identified three functional HNF1 binding sites, as they have binding affinity for HNF1α and HNF1ß and are required for induction of promoter activity by HNF1ß in insulinoma cells. These three sites are well-conserved among mammalian species. Both HNF1α and HNF1ß induce expression of ACE2 mRNA and lead to elevated levels of ACE2 protein and ACE2 enzymatic activity in insulinoma cells. Furthermore, HNF1α dose-dependently increases ACE2 expression in primary pancreatic islet cells. We conclude that HNF1α can induce the expression of ACE2 in pancreatic islet cells via evolutionarily conserved HNF1 binding sites in the ACE2 promoter. Potential therapeutics aimed at counteracting functional HNF1α depletion in diabetes and MODY3 will thus have ACE2 induction in pancreatic islets as a likely beneficial effect.

Pancreatic angiotensin-converting enzyme 2 improves glycemia in angiotensin II-infused mice.

An overactive renin-angiotensin system (RAS) is known to contribute to type 2 diabetes mellitus (T2DM). Although ACE2 overexpression has been shown to be protective against the overactive RAS, a role for pancreatic ACE2, particularly in the islets of Langerhans, in regulating glycemia in response to elevated angiotensin II (Ang II) levels remains to be elucidated. This study examined the role of endogenous pancreatic ACE2 and the impact of elevated Ang II levels on the enzyme's ability to alleviate hyperglycemia in an Ang II infusion mouse model. Male C57bl/6J mice were infused with Ang II or saline for a period of 14 days. On the 7th day of infusion, either an adenovirus encoding human ACE2 (Ad-hACE2) or a control adenovirus (Ad-eGFP) was injected into the mouse pancreas. After an additional 7-8 days, glycemia and plasma insulin levels as well as RAS components expression and oxidative stress were assessed. Ang II-infused mice exhibited hyperglycemia, hyperinsulinemia, and impaired glucose-stimulated insulin secretion from pancreatic islets compared with control mice. This phenotype was associated with decreased ACE2 expression and activity, increased Ang II type 1 receptor (AT1R) expression, and increased oxidative stress in the mouse pancreas. Ad-hACE2 treatment restored pancreatic ACE2 expression and compensatory activity against Ang II-mediated impaired glycemia, thus improving ß-cell function. Our data suggest that decreased pancreatic ACE2 is a link between overactive RAS and impaired glycemia in T2DM. Moreover, maintenance of a normal endogenous ACE2 compensatory activity in the pancreas appears critical to avoid ß-cell dysfunction, supporting a therapeutic potential for ACE2 in controlling diabetes resulting from an overactive RAS.

Species-specific inhibitor sensitivity of angiotensin-converting enzyme 2 (ACE2) and its implication for ACE2 activity assays.

Angiotensin-converting enzyme 2 (ACE2) is a component of the renin-angiotensin system, and its expression and activity have been shown to be reduced in cardiovascular diseases. Enzymatic activity of ACE2 is commonly measured by hydrolysis of quenched fluorescent substrates in the absence or presence of an ACE2-specific inhibitor, such as the commercially available inhibitor DX600. Whereas recombinant human ACE2 is readily detected in mouse tissues using 1 µM DX600 at pH 7.5, the endogenous ACE2 activity in mouse tissues is barely detectable. We compared human, mouse, and rat ACE2 overexpressed in cell lines for their sensitivity to inhibition by DX600. ACE2 from all three species could be inhibited by DX600, but the half maximal inhibitory concentration (IC(50)) for human ACE2 was much lower (78-fold) than for rodent ACE2. Following optimization of pH, substrate concentration, and antagonist concentration, rat and mouse ACE2 expressed in a cell line could be accurately quantified with 10 µM DX600 (>95% inhibition) but not with 1 µM DX600 (<75% inhibition). Validation that the optimized method robustly quantifies ACE2 in mouse tissues (kidney, brain, heart, and plasma) was performed using wild-type and ACE2 knockout mice. This study provides a reliable method for measuring human, as well as endogenous ACE2 activity in rodents. Our data underscore the importance of validating the effect of DX600 on ACE2 from each particular species at the experimental conditions employed.

Human glucocorticoid receptor alpha transcript splice variants with exon 2 deletions: evidence for tissue- and cell type-specific functions.

Alternative splicing of exon 9 in human glucocorticoid receptor (hGR) transcripts yields two native hGR transcripts and proteins, hGRalpha and hGRbeta. We have now identified four novel hGRalpha transcripts that have various deletions of exon 2 sequences. Among these hGRalpha splice variants, three of them, 1A1/E2dist hGRalpha, 1A2/E2prox hGRalpha, and 1A3/E3 hGRalpha, arise from the hGR 1A promoter, while 1B/E3 hGRalpha comes from the hGR 1B promoter. When fused to Flag and enhanced green fluorescent protein (EGFP) tags at the carboxy terminus, all transcript variants can be correctly translated in vitro and in vivo. The Flag-tagged hGRalpha protein variants can functionally bind to a glucocorticoid response element (GRE) and can mediate hormonal stimulation of a pGRE-luciferase reporter gene. Compared to the "classical", native hGRalpha, these four variants exhibit a cell type-specific activation of a reporter gene, and this is influenced by the hGRalpha 3' untranslated region in the hGR transcript. When equal amounts of the cDNAs for these GRalpha variant proteins are transfected into cells, they can exhibit lower or higher transcriptional activation compared to the classical GR. Furthermore, the EGFP-tagged proteins are nuclear localized, even in the absence of hormone. Using quantitative reverse transcription PCR, we found that these transcripts exist at a low level in CEM-C7 cells and IM-9 cells, although the concentrations of the 1A3/E3 hGRalpha and 1B/E3 hGRalpha transcripts are higher than for hGRbeta transcripts, while 1A1/E2dist hGRalphaand 1A2/E2prox hGRalpha transcript levels are comparable to the 1A1 hGRalpha and 1A2 hGRalpha (without the exon 2 deletions) transcript levels, respectively. Because these novel hGR, N-terminal deleted, protein variants have altered biological activity, their expression could potentially affect the hormone sensitivity or resistance in leukemia and be useful in diagnosing hormone-sensitive or -resistant disease.

Interaction between the interferon signaling pathway and the human glucocorticoid receptor gene 1A promoter.

The newly described 1A promoter of the human glucocorticoid receptor (hGR) gene contains an interferon (IFN) regulatory factor element (IRF-E), a binding motif for the family of proteins termed IFN regulatory factors (IRFs) that are regulated by IFNs. To examine the in vivo role of IFNs in hGR gene regulation, human T cell lines (CEM-C7 and Jurkat) were treated with IFN gamma. IFN gamma rapidly induces the expression of IRF-1 proteins in a dose- and time-dependent manner. Luciferase expression is induced by IFN treatment in Jurkat cells transfected with an hGR 1A promoter IRF-E/luciferase reporter gene, but induction is lost with deletion of the IRF-E. Electrophoretic mobility shift and supershift analyses indicate an increase in the binding of IRF-1 to oligonucleotides containing the hGR 1A promoter IRF-E after IFN gamma treatment, whereas IRF-2 binding to this oligonucleotide is unchanged. Human IRF-1 and IRF-2 proteins expressed in Chinese hamster ovary cells bind to the hGR 1A promoter IRF-E; however, only IRF-1 activates transcription. Although IFNs clearly activate a transfected reporter gene containing the hGR 1A promoter in T cells, they do not alter the sensitivity of CEM-C7 cells to glucocorticoid-induced apoptosis. Additional studies revealed that the glucocorticoid steroid hormone, dexamethasone (DEX), completely blocks IFN induction of IRF-1 mRNA levels. This could explain the lack of any greater apoptotic response to a combination of DEX plus IFN compared with the response to DEX alone. In addition, treatment with IFN gamma alone does not alter endogenous GR mRNA levels (including exon 1A-containing transcripts derived from the hGR 1A promoter) in T lymphoblast cells, even though IRF-1 levels are induced. The difference in IRF-1-driven transcription between the hGR 1A reporter construct and the endogenous hGR 1A promoter could potentially be due to epigenetic effects, such as methylation.

Three mechanisms are involved in glucocorticoid receptor autoregulation in a human T-lymphoblast cell line.

Glucocorticoids up-regulate the glucocorticoid receptor (GR) in the human T-lymphoblast cell line CEM-C7. One mechanism for the up-regulation of the GR protein is the well-known up-regulation of GR transcripts. We have investigated the effect of other factors on the up-regulation. At least three promoters (1A, 1B, and 1C) exist, which give rise to GR transcripts with different exon 1 sequences. Transcripts with different exon 1 sequences have similar stabilities. Glucocorticoids have little, if any, effect on mRNA stability. In transfection experiments of the GR-deficient mouse fibroblast cell line E8.2, different exon 1 sequences furthermore caused no significant differences in the translational efficiencies of GR transcripts. However, the ratio between the concentrations of the glucocorticoid receptor B (GR-B) isoform and the glucocorticoid receptor A (GR-A) isoform was higher for transcripts containing the exon 1A3 sequence arising from promoter 1A than in transcripts containing exon 1 sequences from promoters 1B and 1C. Because the GR-B isoform is more active in transactivation then GR-A, this would tend to fine-tune glucocorticoid responsiveness of CEM-C7 cells, which express exon 1A3-containing transcripts. We also found that glucocorticoids do not decrease the stability of the GR protein in CEM-C7 cells. In contrast to other cell lines that downregulate GR expression in response to glucocorticoids, CEM-C7 lymphoblasts possess three mechanisms ensuring high glucocorticoid responsiveness: an up-regulation of GR mRNA by glucocorticoids, no destabilization of GR protein by glucocorticoids, and a high activity of promoter 1A with concomitant high expression of the GR-B isoform.

Quantification and glucocorticoid regulation of glucocorticoid receptor transcripts in two human leukemic cell lines.

We have quantified the basal and glucocorticoid-regulated levels of different transcripts from the human glucocorticoid receptor (GR) gene in the T-cell acute lymphoblastic leukemia cell line, CEM-C7, and in the B lymphoblastoid cell line, IM-9. Highly specific quantitative, reverse transcription-polymerase chain reaction assays measured total GR transcripts, transcripts encoding the isoforms glucocorticoid receptor alpha (GRalpha) and glucocorticoid receptor beta (GRbeta), and transcripts containing different forms of exon 1: 1A1, 1A2, 1A3, 1B, and 1C. GRalpha and GRbeta transcripts are coordinately upregulated in CEM-C7 cells and coordinately downregulated in IM-9 cells by dexamethasone. The concentration of GRalpha mRNA is more than a 1000-fold higher than that for GRbeta mRNA. Transcripts with different exon 1 forms are all upregulated in CEM-C7 cells and all downregulated in IM-9 cells by dexamethasone, but transcripts containing exons 1A1, 1A2, or 1A3 are regulated to a higher degree than transcripts containing exon 1B or exon 1C. However, exon 1B- and exon 1C-containing transcripts are substantially more abundant than exon 1A-containing transcripts, with exon 1A3-containing transcripts more abundant than exon 1A1- or exon 1A2-containing transcripts. Analysis using models for glucocorticoid receptor autoregulation kinetics suggests that the minor 1A3-containing transcript component could be important for GR protein upregulation, and hence apoptosis, in CEM-C7 cells. These studies suggest that GRalpha transcripts containing exons 1A3, 1B, and 1C contribute most to the intracellular level of GR mRNA and may be the most relevant for steroid-mediated apoptosis in T-lymphoblasts.