Estradiol-17beta stimulates specific receptor and endogenous nitric oxide-dependent dynamic endothelial protein S-nitrosylation: analysis of endothelial nitrosyl-proteome

Roles of Protein S-Nitrosylation in Endothelial Homeostasis and Dysfunction

Significance: Nitric oxide (NO) plays several distinct roles in endothelial homeostasis. Except for activating the guanylyl cyclase enzyme-dependent cyclic guanosine monophosphate signaling pathway, NO can bind reactive cysteine residues in target proteins, a process known as S-nitrosylation (SNO). SNO is proposed to explain the multiple biological functions of NO in the endothelium. Investigating the targets and mechanism of protein SNO in endothelial cells (ECs) can provide new strategies for treating endothelial dysfunction-related diseases. Recent Advances: In response to different environments, proteomics has identified multiple SNO targets in ECs. Functional studies confirm that SNO regulates NO bioavailability, inflammation, permeability, oxidative stress, mitochondrial function, and insulin sensitivity in ECs. It also influences EC proliferation, migration, apoptosis, and transdifferentiation. Critical Issues: Single-cell transcriptomic analysis of ECs isolated from different mouse tissues showed heterogeneous gene signatures. However, litter research focuses on the heterogeneous properties of SNO proteins in ECs derived from different tissues. Although metabolism reprogramming plays a vital role in endothelial functions, little is known about how protein SNO regulates metabolism reprogramming in ECs. Future Directions: Precisely deciphering the effects of protein SNO in ECs isolated from different tissues under different conditions is necessary to further characterize the relationship between protein SNO and endothelial dysfunction-related diseases. In addition, identifying SNO targets that can influence endothelial metabolic reprogramming and the underlying mechanism can offer new views on the crosstalk between metabolism and post-translational protein modification. Antioxid. Redox Signal. 40, 186-205.

Global, regional, and national incidence, mortality, and disability-adjusted life years of non-rheumatic valvular heart disease and trend analysis from 1990 to 2019: Results from the Global Burden of Disease study 2019

BACKGROUND

In the context of the population growing and aging worldwide, the incidence of non-rheumatic valvular heart disease increased rapidly. This study aimed to describe the burden of non-rheumatic valvular heart disease, providing an up-to-date and comprehensive analysis on the global and regional levels and time trends from 1900 to 2019.

METHODS

The Global Burden of Disease 2019 was used to obtain data for this analysis. Non-rheumatic valvular heart disease in the Global Burden of Disease study includes both non-rheumatic calcific aortic valve disease and non-rheumatic degenerative mitral valve disease. The incidence, mortality, and disability-adjusted life year in 204 countries from 1990 to 2019 were analyzed by location, year, sex, age, and socio-demographic index. Estimated annual percentage change was calculated to represent the temporal trends from 1990 to 2019. Spearman's rank order correlation was used to determine the correlation between socio-demographic index and the incidence and burden of non-rheumatic valvular heart disease.

RESULTS

Globally, there were 1.65 million (95% uncertainty interval, 1.56-1.76 million) incident cases, 0.16 million (95% uncertainty interval, 0.14-0.18 million) death cases, and 2.79 million (95% uncertainty interval, 2.52-3.31 million) disability-adjusted life years of non-rheumatic valvular heart disease. Compared with 1990, the number of incident cases, death cases, and disability-adjusted life years in 2019 increased by 104.58%, 210.60%, and 167.62%, respectively, the age-standardized incidence rate (estimated annual percentage change, 0.39; 95% confidence interval, 0.29 to 0.49) increased due to population growth, and the age-standardized death rates (estimated annual percentage change, -0.32; 95% confidence interval, -0.39 to -0.25) and age-standardized disability-adjusted life year rate (estimated annual percentage change, -0.81; 95% confidence interval, -0.87 to -0.74) decreased during this period. Regarding the socio-demographic index, the highest age-standardized incidence, death, and disability-adjusted life year rates of non-rheumatic valvular heart disease were found in high-socio-demographic index countries in 2019. Meantime, the age-standardized incidence rate remained increased from 1990 to 2019, while significant decreases were found in the age-standardized death rate and age-standardized disability-adjusted life year rate. Females have higher age-standardized incidence rate, while higher age-standardized death rate and age-standardized disability-adjusted life year rate belong to males globally during the period of 1990-2019. Increasing trends were observed for both incidence, death, and disability-adjusted life year rates with age. High systolic blood pressure was the leading cause for non-rheumatic valvular heart disease across all ages.

CONCLUSIONS

From 1990 to 2019, the age-standardized incidence rate of non-rheumatic valvular heart disease remained increased, while age-standardized death rate and age-standardized disability-adjusted life year rate decreased, resulting from the growing population worldwide and improving medical resources. The aged, who has high systolic blood pressure and diet high in sodium, should pay more attention to, especially in high-socio-demographic index regions. With the population aging, the number of patients who require heart valve replacement is estimated to increase significantly in the future. Effective measures are warranted to control and treat the incidence and burden of non-rheumatic valvular heart disease.

Estrogen Receptors and Estrogen-Induced Uterine Vasodilation in Pregnancy

Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal–fetal exchanges of respiratory gases and to provide sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remain incompletely understood, but this is associated with elevated estrogens, which stimulate specific estrogen receptor (ER)-dependent vasodilator production in the uterine artery (UA). The classical ERs (ERα and ERβ) and the plasma-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. The activation of these three ERs by estrogens enhances the endothelial production of nitric oxide (NO), which has been shown to play a key role in uterine vasodilation during pregnancy. However, the local blockade of NO biosynthesis only partially attenuates estrogen-induced and pregnancy-associated uterine vasodilation, suggesting that mechanisms other than NO exist to mediate uterine vasodilation. In this review, we summarize the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a “new” UA vasodilator hydrogen sulfide (H₂S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.

Structural analysis of estrogen receptors: interaction between estrogen receptors and cav-1 within the caveolae†

Pregnancy is a physiologic state of substantially elevated estrogen biosynthesis that maintains vasodilator production by uterine artery endothelial cells (P-UAECs) and thus uterine perfusion. Estrogen receptors (ER-α and ER-β; ESR1 and ESR2) stimulate nongenomic rapid vasodilatory responses partly through activation of endothelial nitric oxide synthase (eNOS). Rapid estrogenic responses are initiated by the ∼4% ESRs localized to the plasmalemma of endothelial cells. Caveolin-1 (Cav-1) interactions within the caveolae are theorized to influence estrogenic effects mediated by both ESRs. Hypothesis: Both ESR1 and ESR2 display similar spatial partitioning between the plasmalemma and nucleus of UAECs and have similar interactions with Cav-1 at the plasmalemma. Using transmission electron microscopy, we observed numerous caveolae structures in UAECs, while immunogold labeling and subcellular fractionations identified ESR1 and ESR2 in three subcellular locations: membrane, cytosol, and nucleus. Bioinformatics approaches to analyze ESR1 and ESR2 transmembrane domains identified no regions that facilitate ESR interaction with plasmalemma. However, sucrose density centrifugation and Cav-1 immunoisolation columns uniquely demonstrated very high protein-protein association only between ESR1, but not ESR2, with Cav-1. These data demonstrate (1) both ESRs localize to the plasmalemma, cytosol and nucleus; (2) neither ESR1 nor ESR2 contain a classic region that crosses the plasmalemma to facilitate attachment; and (3) ESR1, but not ESR2, can be detected in the caveolar subcellular domain demonstrating ESR1 is the only ESR bound in close proximity to Cav-1 and eNOS within this microdomain. Lack of protein-protein interaction between Cav-1 and ESR2 demonstrates a novel independent association of these proteins at the plasmalemma.

S-nitrosylation and its role in breast cancer angiogenesis and metastasis

S-nitrosylation, the modification by nitric oxide of free sulfhydryl groups in cysteines, has become an important regulatory mechanism in carcinogenesis and metastasis. S-nitrosylation of targets in tumor cells contributes to metastasis regulating epithelial to mesenchymal transition, migration and invasion. In the tumor environment, the role of S-nitrosylation in endothelium has not been addressed; however, the evidence points out that S-nitrosylation of endothelial proteins may regulate angiogenesis, adhesion of tumor cells to the endothelium, intra and extravasation of tumor cells and contribute to metastasis.

Human trophoblast-derived hydrogen sulfide stimulates placental artery endothelial cell angiogenesis

Endogenous hydrogen sulfide (H2S), mainly synthesized by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH), has been implicated in regulating placental angiogenesis; however, the underlying mechanisms are unknown. This study was to test a hypothesis that trophoblasts synthesize H2S to promote placental angiogenesis. Human choriocarcinoma-derived BeWo cells expressed both CBS and CTH proteins, while the first trimester villous trophoblast-originated HTR-8/SVneo cells expressed CTH protein only. The H2S producing ability of BeWo cells was significantly inhibited by either inhibitors of CBS (carboxymethyl hydroxylamine hemihydrochloride, CHH) or CTH (β-cyano-L-alanine, BCA) and that in HTR-8/SVneo cells was inhibited by CHH only. H2S donors stimulated cell proliferation, migration, and tube formation in ovine placental artery endothelial cells (oFPAECs) as effectively as vascular endothelial growth factor. Co-culture with BeWo and HTR-8/SVneo cells stimulated oFPAEC migration, which was inhibited by CHH or BCA in BeWo but CHH only in HTR-8/SVneo cells. Primary human villous trophoblasts (HVT) were more potent than trophoblast cell lines in stimulating oFPAEC migration that was inhibited by CHH and CHH/BCA combination in accordance with its H2S synthesizing activity linked to CBS and CTH expression patterns. H2S donors activated endothelial nitric oxide synthase (NOS3), v-AKT murine thymoma viral oncogene homolog 1 (AKT1), and extracellular signal-activated kinase 1/2 (mitogen-activated protein kinase 3/1, MAPK3/1) in oFPAECs. H2S donor-induced NOS3 activation was blocked by AKT1 but not MAPK3/1 inhibition. In keeping with our previous studies showing a crucial role of AKT1, MAPK3/1, and NOS3/NO in placental angiogenesis, these data show that trophoblast-derived endogenous H2S stimulates placental angiogenesis, involving activation of AKT1, NOS3/NO, and MAPK3/1.

Quantitative Proteomics Analysis of VEGF-Responsive Endothelial Protein S-Nitrosylation Using Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC) and LC-MS/MS

Adduction of a nitric oxide moiety (NO•) to cysteine(s), termed S-nitrosylation (SNO), is a novel mechanism for NO to regulate protein function directly. However, the endothelial SNO-protein network that is affected by endogenous and exogenous NO is obscure. This study was designed to develop a quantitative proteomics approach using stable isotope labeling by amino acids in cell culture for comparing vascular endothelial growth factor (VEGFA)- and NO donor-responsive endothelial nitroso-proteomes. Primary placental endothelial cells were labeled with "light" (L-(12)C6 (14)N4-Arg and L-(12)C6 (14)N2-Lys) or "heavy" (L-(13)C6 (15)N4-Arg and L-(13)C6 (15)N2-Lys) amino acids. The light cells were treated with an NO donor nitrosoglutathione (GSNO, 1 mM) or VEGFA (10 ng/ml) for 30 min, while the heavy cells received vehicle as control. Equal amounts of cellular proteins from the light (GSNO or VEGFA treated) and heavy cells were mixed for labeling SNO-proteins by the biotin switch technique and then trypsin digested. Biotinylated SNO-peptides were purified for identifying SNO-proteins by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Ratios of light to heavy SNO-peptides were calculated for determining the changes of the VEGFA- and GSNO-responsive endothelial nitroso-proteomes. A total of 387 light/heavy pairs of SNO-peptides were identified, corresponding to 213 SNO-proteins that include 125 common and 27 VEGFA- and 61 GSNO-responsive SNO-proteins. The specific SNO-cysteine(s) in each SNO-protein were simultaneously identified. Pathway analysis revealed that SNO-proteins are involved in various endothelial functions, including proliferation, motility, metabolism, and protein synthesis. We collectively conclude that endogenous NO on VEGFA stimulation and exogenous NO from GSNO affect common and different SNO-protein networks, implicating SNO as a critical mechanism for VEGFA stimulation of angiogenesis.

S-Nitrosylation of NF-κB p65 Inhibits TSH-Induced Na(+)/I(-) Symporter Expression

Nitric oxide (NO) is a ubiquitous signaling molecule involved in a wide variety of cellular physiological processes. In thyroid cells, NO-synthase III-endogenously produced NO reduces TSH-stimulated thyroid-specific gene expression, suggesting a potential autocrine role of NO in modulating thyroid function. Further studies indicate that NO induces thyroid dedifferentiation, because NO donors repress TSH-stimulated iodide (I(-)) uptake. Here, we investigated the molecular mechanism underlying the NO-inhibited Na(+)/I(-) symporter (NIS)-mediated I(-) uptake in thyroid cells. We showed that NO donors reduce I(-) uptake in a concentration-dependent manner, which correlates with decreased NIS protein expression. NO-reduced I(-) uptake results from transcriptional repression of NIS gene rather than posttranslational modifications reducing functional NIS expression at the plasma membrane. We observed that NO donors repress TSH-induced NIS gene expression by reducing the transcriptional activity of the nuclear factor-κB subunit p65. NO-promoted p65 S-nitrosylation reduces p65-mediated transactivation of the NIS promoter in response to TSH stimulation. Overall, our data are consistent with the notion that NO plays a role as an inhibitory signal to counterbalance TSH-stimulated nuclear factor-κB activation, thus modulating thyroid hormone biosynthesis.

The S-nitrosylation status of PCNA localized in cytosol impacts the apoptotic pathway in a Parkinson's disease paradigm

It is generally accepted that nitric oxide (NO) or its derivatives, reactive nitrogen species (RNS), are involved in the development of Parkinson's disease (PD). Recently, emerging evidence in the study of PD has indicated that protein S-nitrosylation triggers the signaling changes in neurons. In this study, SH-SY5Y cells treated with rotenone were used as a model of neuronal death in PD. The treated cells underwent significant apoptosis, which was accompanied by an increase in intracellular NO in a rotenone dose-dependent manner. The CyDye switch approach was employed to screen for changes in S-nitrosylated (SNO) proteins in response to the rotenone treatment. Seven proteins with increased S-nitrosylation were identified in the treated SH-SY5Y cells, which included proliferating cell nuclear antigen (PCNA). Although PCNA is generally located in the nucleus and participates in DNA replication and repair, significant PCNA was identified in the SH-SY5Y cytosol. Using immunoprecipitation and pull-down approaches, PCNA was found to interact with caspase-9; using mass spectrometry, the two cysteine residues PCNA-Cys81 and -Cys162 were identified as candidate S-nitrosylated residues. In addition, the evidence obtained from in vitro and the cell model studies indicated that the S-nitrosylation of PCNA-Cys81 affected the interaction between PCNA and caspase-9. Furthermore, the interaction of PCNA and caspase-9 partially blocked caspase-9 activation, indicating that the S-nitrosylation of cytosolic PCNA may be a mediator of the apoptotic pathway.

S-nitrosylation of cofilin-1 mediates estradiol-17β-stimulated endothelial cytoskeleton remodeling

Rapid nitric oxide (NO) production via endothelial NO synthase (eNOS) activation represents a major signaling pathway for the cardiovascular protective effects of estrogens; however, the pathways after NO biosynthesis that estrogens use to function remain largely unknown. Covalent adduction of a NO moiety to cysteines, termed S-nitrosylation (SNO), has emerged as a key route for NO to directly regulate protein function. Cofilin-1 (CFL1) is a small actin-binding protein essential for actin dynamics and cytoskeleton remodeling. Despite being identified as a major SNO protein in endothelial cells, whether SNO regulates CFL-1 function is unknown. We hypothesized that estradiol-17β (E2β) stimulates SNO of CFL1 via eNOS-derived NO and that E2β-induced SNO-CFL1 mediates cytoskeleton remodeling in endothelial cells. Point mutation studies determined Cys80 as the primary SNO site among the 4 cysteines (Cys39/80/139/147) in CFL1. Substitutions of Cys80 with Ala or Ser were used to prepare the SNO-mimetic/deficient (C80A/S) CFL1 mutants. Recombinant wild-type (wt) and mutant CFL1 proteins were prepared; their actin-severing activity was determined by real-time fluorescence imaging analysis. The activity of C80A CFL1 was enhanced to that of the constitutively active S3/A CFL1, whereas the other mutants had no effects. C80A/S mutations lowered Ser3 phosphorylation. Treatment with E2β increased filamentous (F)-actin and filopodium formation in endothelial cells, which were significantly reduced in cells overexpressing wt-CFL. Overexpression of C80A, but not C80S, CFL1 decreased basal F-actin and further suppressed E2β-induced F-actin and filopodium formation compared with wt-CFL1 overexpression. Thus, SNO(Cys80) of cofilin-1 via eNOS-derived NO provides a novel pathway for mediating estrogen-induced endothelial cell cytoskeleton remodeling.

Endogenous NO upon estradiol-17β stimulation and NO donor differentially regulate mitochondrial S-nitrosylation in endothelial cells

Adduction of a nitric oxide (NO) moiety (NO(•)) to cysteines termed as S-nitrosylation (SNO) has emerged as a crucial mechanism for NO signaling crucial for mediating the vascular effects of estrogens. Mitochondrion is a known vascular risk factor; however, the effects of estrogens on mitochondrial SNO are incompletely understood. In this study we determined the effects of estradiol-17β (E2β) on mitochondrial protein SNO in primary human umbilical vein endothelial cells and compared the mitochondrial nitroso-proteomes in E2β- and a NO donor S-nitrosoglutathione (GSNO)-treated cells using a proteomics approach. Treatment with 10 nM E2β and 1 mM GSNO for 30 minutes significantly increased the levels of mitochondrial SNO-proteins. Subcellular localization of SNO-proteins showed mitochondria as the major cellular organelle for protein SNO in response to E2β and GSNO. E2β stimulated mitochondrial endothelial nitric oxide synthase (eNOS) phosphorylation and mitochondrial protein SNO that was enhanced by overexpression of mitochondrion or Golgi, but not membrane targeting eNOS constructs. We identified 11, 32, and 54 SNO-proteins in the mitochondria from the untreated, E2β-, and GSNO-treated human umbilical vein endothelial cells, respectively. Comparisons of the nitroso-proteomes revealed that common and different mitochondrial SNO-proteins were affected by endogenous NO on E2β stimulation and exogenous NO from donor. These SNO-proteins were associated with various mitochondrial functions, including energy and redox regulation, transport, iron homeostasis, translation, mitochondrial morphology, and apoptosis, etc. Collectively, we conclude that estrogens rapidly stimulate protein SNO in endothelial mitochondria via mitochondrial eNOS, providing a mechanism for mediating the vascular effects of estrogens.

Mechanisms of estrogen effects on the endothelium: an overview

In this review, we aim to provide an overview of the recent advances in understanding estrogen effects on the vascular endothelium. Epidemiological studies suggest the female sex hormone estrogen mediates the relative protection of premenopausal women against cardiovascular disease, compared with age-matched men. However, results from clinical trials of exogenous estrogen supplementation in postmenopausal women have been disappointing, generating much controversy about the role of estrogen and demonstrating the need for further research in this field. Here we have discussed the roles of different estrogen receptors (ERs) such as ERα, ERβ, and G-protein coupled receptor 30; the complex genomic and nongenomic signalling pathways downstream to ER activation and the factors such as age, menopause, pregnancy, and diabetes that might alter estrogen responses. The common themes of this discussion are the complexity and diversity of endothelial estrogen responses and their modulation by 1 or more coexisting factors. Finally, we summarize the emerging therapeutic options including improved targeting of individual ERs and signalling pathways that might maximize the therapeutic potential of estrogenic compounds while minimizing their harmful side effects.

Evidence for gating roles of protein kinase A and protein kinase C in estradiol-induced luteinizing hormone receptor (lhcgr) expression in zebrafish ovarian follicle cells

Estradiol (E2) stimulates luteinizing hormone receptor (lhcgr) expression in zebrafish follicle cells via nuclear estrogen receptors (nERs) that are likely expressed on the membrane, and lhcgr responds to E2 in a biphasic manner during 24-h treatment. These observations raise an interesting question on the signaling mechanism underlying E2 regulation, in particular the biphasic response of lhcgr expression. In the present study, we demonstrated that E2 regulation of lhcgr was significantly influenced by the activity of cAMP-PKA pathway. Activation of cAMP-PKA pathway by forskolin or db-cAMP suppressed E2-stimulated lhcgr expression in short-term (3 h) but enhanced its effect in long-term (24 h), suggesting differential roles of PKA at these two phases of lhcgr response. PKA inhibitor H89 showed reversed effects. In contrast, PKC pathway had consistent permissive effect on E2-induced lhcgr expression as evidenced by strong inhibition of E2 effect by PKC inhibitors GF109203X and Ro-31-8220 at both 3 and 24 h. One of the mechanisms by which PKA and PKC gated E2 effect might be through regulating nERs, particularly esr2a. Despite the strong influence of PKA and PKC, our data did not suggest direct mediating roles for these two pathways in E2 stimulation of lhcgr expression; yet they likely play critical gating roles in E2 signal transduction. As a follow-up study to our previous report on E2 regulation of gonadotropin receptors in the zebrafish ovary, the present study provides further evidence for the involvement of classical intracellular signal transduction pathways in E2 stimulation of lhcgr expression in the follicle cells.

Testosterone and β-oestradiol prevent inward remodelling of rat small mesenteric arteries: role of NO and transglutaminase

Increasing evidence shows that sex hormones exert a protective effect on the vasculature, especially in the regulation of the active vasomotor responses. However, whether sex hormones affect vascular remodelling is currently unclear. In the present study, we tested the hypothesis that testosterone in males and β-oestradiol in females prevent inward remodelling, possibly through inhibition of cross-linking activity induced by enzymes of the TG (transglutaminase) family. Small mesenteric arteries were isolated from male and female Wistar rats. Dose-dependent relaxation to testosterone and β-oestradiol was inhibited by the NO synthase inhibitor L-NAME (NG-nitro-L-arginine methyl ester), confirming that these hormones induce NO release. When arteries were cannulated, pressurized and kept in organ culture with ET-1 (endothelin-1) for 3 days we observed strong vasoconstriction and inward remodelling. Remodelling was significantly inhibited by testosterone in males, and by β-oestradiol in females. This preventive effect of sex hormones was not observed in the presence of L-NAME. Inward remodelling was also reduced by the inhibitor of TG L682.777, both in males and females. In arteries from female rats, ET-1 increased TG activity, and this effect was prevented by β-oestradiol. L-NAME induced a significant increase in TG activity in the presence of sex hormones in arteries from both genders. We conclude that testosterone and β-oestradiol prevent constriction-induced inward remodelling. Inward remodelling, both in males and females, depends on NO and TG activity. In females, inhibition of inward remodelling could be mediated by NO-mediated inhibition of TG activity.

Identification of the Transmembrane Glucose Regulated Protein 78 as a Biomarker for the Brain Cancer Glioblastoma Multiforme by Gene Expression and Proteomic Studies

The prognosis of patients with Glioblastoma Multiforme (GBM), the most malignant adult glial brain tumor, remains poor in spite of advances in treatment procedures, including surgical resection, irradiation and chemotherapy. Genetic heterogeneity of GBM warrants extensive studies to gain a thorough understanding of the biology of this tumor. While there have been several studies of global transcript profiling of glioma with the identification of gene signatures for diagnosis and disease management, translation into clinics is yet to happen. In the present study, we report a novel proteomic approach by using two-dimensional difference gel electrophoresis (2D-DIGE) followed by spot picking and analysis of proteins/peptides by Mass Spectrometry. We report Glucose Regulated Protein 78 (GRP78) as a differentially expressed protein in the GBM cell line compared to human normal Astrocyte cells.

In addition to proteomic studies, we performed microarray analysis which further confirmed up regulation of GRP78 in GBM cells compared to human normal Astrocyte cells.

GRP78 has long been recognized as a molecular chaperone in the endoplasmic reticulum (ER) and can be induced by the ER stress response. Besides its location in the ER, GRP78 has been found in cell plasma membrane, cytoplasm, mitochondria, nucleus and other cellular secretions. GRP78 is implicated in tumor cell proliferation, apoptosis resistance, immune escape, metastasis and angiogenesis, and its elevated expression usually correlates with a variety of tumor micro environmental stresses, including hypoxia, glucose deprivation, lactic acidosis and inflammatory response. GRP78 protein acts as a centrally located sensor of stress, which senses and facilitates the adaptation to the tumor microenvironment.

Our findings showed differential expression of this gene in brain cancer GBM and thus confirm similarities in findings in existing transcriptional and translational studies. Thus, these findings could be of further importance for diagnostic, therapeutic and prognostic approaches for dealing with this highly malignant cancer.

iNOS-selective inhibitors for cancer prevention: promise and progress

Nitric oxide (NO) is involved in various physiological functions and its role in tumorigenesis has been well studied. A large majority of human and experimental tumors appear to progress owing to NO resulting from iNOS, further stimulated by proinflammatory cytokines. Conversely, in some cases, NO is associated with induction of apoptosis and tumor regression. This dichotomy of NO is largely explained by the complexity of signaling pathways in tumor cells, which respond to NO very differently depending on its concentration. In addition, NO alters many signaling pathways through chemical modifications, such as the addition of S-nitrosothiols and nitrosotyrosine to target proteins altering various biological pathways. Hence, iNOS inhibitors are designed and developed to inhibit various organ site cancers including the colon. Here, we review iNOS expression, generation of NO, involvement of NO in altering signaling pathways, and iNOS select inhibitors and their possible use for the prevention and treatment of various cancers.

Preeclampsia up-regulates angiogenesis-associated microRNA (i.e., miR-17, -20a, and -20b) that target ephrin-B2 and EPHB4 in human placenta

CONTEXT

Placental angiogenesis contributes to the pathogenesis of preeclampsia (PE) that affects 5-8% of all human pregnancies. MicroRNA (miRNA) are a class of noncoding 21- to 25-nucleotide RNA that negatively regulate gene expression posttranscriptionly.

OBJECTIVE

The aim of this study was to test the hypothesis that miRNA are differentially expressed in healthy term and PE placentas and a subclass of angiogenesis-associated miRNA are increased by PE.

DESIGN

Total miRNA were extracted from villous placental tissues from healthy term and severe preeclamptic pregnancies. Differential miRNA expression was analyzed by microarray and real-time quantitative PCR. Angiogenesis-associated miRNA were analyzed by target prediction databases. In situ hybridization was used to localize miRNA. Target verification was performed by transfection of miRNA precursors or antagomirs into endothelial and BeWo cells and luciferase reporter assays.

RESULTS

Three highly expressed miRNA (miR-17, -20a, and -20b) were found significantly increased in PE compared with healthy term placentas (n = 10 per group). They target on the same group of genes important for angiogenesis. miR-20b was expressed primarily in villous syncytiotrophoblasts in term placenta. Overexpression or inhibition of miR-20b differentially regulated mRNA expression of those genes in endothelial vs. trophoblast cells. Luciferase reporter assay showed that miR-20b targets EPHB4 and ephrin-B2 that have been shown to be critical for early human placental development. Placental ephrin-B2 mRNA was significantly down-regulated in PE compared with normotensive pregnancies.

CONCLUSION

miR-17, miR-20a, and miR-20b are differentially regulated in human placentas by PE. They regulate EPHB4 and ephrin-B2 expression in trophoblast and endothelial cells via the same "seed" sequence, suggesting their roles in early placental development.

Search for a diagnostic/prognostic biomarker for the brain cancer glioblastoma multiforme by 2D-DIGE-MS technique

The prognosis of patients with glioblastoma multiforme, the most malignant adult glial brain tumor, remains poor in spite of advances in treatment procedures, including surgical resection, irradiation, and chemotherapy. Genetic heterogeneity of glioblastoma warrants extensive studies to gain a thorough understanding of the biology of this tumor. While there have been several studies of global transcript profiling of glioma with the identification of gene signatures for diagnosis and disease management, translation into clinics is yet to happen. In the present study, we report a novel proteomic approach by using two-dimensional difference gel electrophoresis followed by spot picking and analysis of proteins/peptides by Mass spectrometry. We report at least ten different novel proteins/peptides as identified by this technique which are differentially expressed in this cancer and could be of further importance for diagnostic, therapeutic, and prognostic approaches.

Estrogens and atherosclerosis: insights from animal models and cell systems

Estrogens not only play a pivotal role in sexual development but are also involved in several physiological processes in various tissues including vasculature. While several epidemiological studies documented an inverse relationship between plasma estrogen levels and the incidence of cardiovascular disease and related it to the inhibition of atherosclerosis, an interventional trial showed an increase in cardiovascular events among postmenopausal women on estrogen treatment. The development of atherosclerotic lesions involves complex interplay between various pro- or anti-atherogenic processes that can be effectively studied only in vivo in appropriate animal models. With the advent of genetic engineering, transgenic mouse models of atherosclerosis have supplemented classical dietary cholesterol-induced disease models such as the cholesterol-fed rabbit. In the last two decades, these models were widely applied along with in vitro cell systems to specifically investigate the influence of estrogens on the development of early and advanced atherosclerotic lesions. The present review summarizes the results of these studies and assesses their contribution toward better understanding of molecular mechanisms underlying anti- and/or pro-atherogenic effects of estrogens in humans.

Estrogen receptor-α and estrogen receptor-β in the uterine vascular endothelium during pregnancy: functional implications for regulating uterine blood flow

The steroid hormone estrogen and its classical estrogen receptors (ERs), ER-α and ER-β, have been shown to be partly responsible for the short- and long-term uterine endothelial adaptations during pregnancy. The ER-subtype molecular and structural differences coupled with the differential effects of estrogen in target cells and tissues suggest a substantial functional heterogeneity of the ERs in estrogen signaling. In this review we discuss (1) the role of estrogen and ERs in cardiovascular adaptations during pregnancy, (2) in vivo and in vitro expression of ERs in uterine artery endothelium during the ovarian cycle and pregnancy, contrasting reproductive and nonreproductive arterial endothelia, (3) the structural basis for functional diversity of the ERs and estrogen subtype selectivity, (4) the role of estrogen and ERs on genomic responses of uterine artery endothelial cells, and (5) the role of estrogen and ERs on nongenomic responses in uterine artery endothelia. These topics integrate current knowledge of this very rapidly expanding scientific field with diverse interpretations and hypotheses regarding the estrogenic effects that are mediated by either or both ERs and their relationship with vasodilatory and angiogenic vascular adaptations required for modulating the dramatic physiological rises in uteroplacental perfusion observed during normal pregnancy.

Estrogen-responsive nitroso-proteome in uterine artery endothelial cells: role of endothelial nitric oxide synthase and estrogen receptor-β

Covalent adduction of a NO moiety to cysteines (S-nitrosylation or SNO) is a major route for NO to directly regulate protein functions. In uterine artery endothelial cells (UAEC), estradiol-17β (E2) rapidly stimulated protein SNO that maximized within 10-30 min post-E2 exposure. E2-bovine serum albumin stimulated protein SNO similarly. Stimulation of SNO by both was blocked by ICI 182, 780, implicating mechanisms linked to specific estrogen receptors (ERs) localized on the plasma membrane. E2-induced protein SNO was attenuated by selective ERβ, but not ERα, antagonists. A specific ERβ but not ERα agonist was able to induce protein SNO. Overexpression of ERβ, but not ERα, significantly enhanced E2-induced SNO. Overexpression of both ERs increased basal SNO, but did not further enhance E2-stimulated SNO. E2-induced SNO was inhibited by N-nitro-L-arginine-methylester and specific endothelial NO synthase (eNOS) siRNA. Thus, estrogen-induced SNO is mediated by endogenous NO via eNOS and mainly ERβ in UAEC. We further analyzed the nitroso-proteomes by CyDye switch technique combined with two-dimensional (2D) fluorescence difference gel electrophoresis. Numerous nitrosoprotein (spots) were visible on the 2D gel. Sixty spots were chosen and subjected to matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Among the 54 identified, nine were novel SNO-proteins, 32 were increased, eight were decreased, and the rest were unchanged by E2. Tandom MS identified Cys139 as a specific site for SNO in GAPDH. Pathway analysis of basal and estrogen-responsive nitroso-proteomes suggested that SNO regulates diverse protein functions, directly implicating SNO as a novel mechanism for estrogen to regulate uterine endothelial function and thus uterine vasodilatation.

Differential regulation of gonadotropin receptors (fshr and lhcgr) by estradiol in the zebrafish ovary involves nuclear estrogen receptors that are likely located on the plasma membrane

FSH and LH are gonadotropins (GTH) that control all major events of gonadal function. FSH and LH signal through their cognate receptors, FSH receptor and LH/choriogonadotropin receptor, respectively, across vertebrates. Compared with the information in mammals, very little is known about these receptors in fish, especially the regulation of their expression. In female zebrafish, fshr and lhcgr exhibit significant temporal difference in expression, with fshr increasing first when the follicles are activated to enter the vitellogenic growth phase and lhcgr lagging behind. This raises an interesting question on the differential regulation of these two GTH receptors (GTHR) during folliculogenesis. Using a primary follicle cell culture, the present study demonstrated that 17β-estradiol (E2), but not testosterone, was a potent endocrine hormone that differentially regulated the expression of fshr and lhcgr. Although E2 stimulated both receptors, its effect on the steady-state level of lhcgr mRNA was much higher (>8-fold up-regulation) than that of fshr (∼0.5-fold increase). E2 likely acted at the transcription level via its nuclear estrogen receptors (ERα and ERβ), because ICI 182,780 could abolish its effects. However, our evidence suggested that these receptors might be localized on the plasma membrane, because β-estradiol 6-(O-carboxy methyl)oxime:BSA could fully mimic the effects of E2. Demonstrating that E2 is likely one of the differentiating factors for the distinct expression of the two GTHR in the zebrafish ovary, this study sheds important light on the functions of the two GTH and their receptors in fish as well as the conservation and diverse aspects of GTHR regulation across vertebrates.

Spinal cord injury induced arrest in estrous cycle of rats is ameliorated by S-nitrosoglutathione: novel therapeutic agent to treat amenorrhea

INTRODUCTION

Amenorrhea following spinal cord injury (SCI) has been well documented. There has been little research on the underlying molecular mechanisms and therapeutics.

AIM

The purpose of the present study was to investigate the effect of GSNO in ameliorating SCI-induced amenorrhea through affecting the expression of CX43, NFkB, and ERβ protein.

METHODS

SCI was induced in female SD rats at the T9-T10 level. Estrous stage was determined by vaginal smear. GSNO (50 µg/kg body weight) was gavage fed daily. Animals were sacrificed on day 7 and 14 post SCI. Ovaries were fixed for histological and biochemical studies. Expression levels of ERβ, CX-43, and NFkB were analyzed by Western blot and immunofluorescence.

MAIN OUTCOME MEASURES

GSNO hastens resumption of the estrous cycle following SCI-induced transient arrest.

RESULTS

Resumption of estrous cycle was hastened by GSNO. Atretic and degenerating follicles seen in the ovary of SCI rats on day 14 post-SCI were decreased in GSNO treated animals. The increased CX43 expression observed with SCI ovary was decreased by GSNO. ERβ expression decreased significantly on day 7 and 14 post-SCI and was restored with GSNO treatment. Following SCI, NFkB expression was increased in the ovarian follicles and the expression was reduced with GSNO administration. The number of terminal deoxynucleotidyl transferase-mediated biotinylated uridine triphosphate (UTP) nick end labeling positive follicular and luteal cells was increased after SCI. GSNO-treated animals had significantly fewer apoptotic cells in the ovary.

CONCLUSION

SCI-induced amenorrhea is accompanied by an increase in CX43 expression and a decrease in ERβ expression. SCI animals treated with GSNO resumed the estrous cycle significantly earlier. These results indicate a potential therapeutic value for GSNO in treating amenorrhea among SCI patients.

S-nitrosylation in the regulation of gene transcription

BACKGROUND

Post-translational modification of proteins by S-nitrosylation serves as a major mode of signaling in mammalian cells and a growing body of evidence has shown that transcription factors and their activating pathways are primary targets. S-nitrosylation directly modifies a number of transcription factors, including NF-κB, HIF-1, and AP-1. In addition, S-nitrosylation can indirectly regulate gene transcription by modulating other cell signaling pathways, in particular JNK kinase and ras.

SCOPE OF REVIEW

The evolution of S-nitrosylation as a signaling mechanism in the regulation of gene transcription, physiological advantages of protein S-nitrosylation in the control of gene transcription, and discussion of the many transcriptional proteins modulated by S-nitrosylation is summarized.

MAJOR CONCLUSIONS

S-nitrosylation plays a crucial role in the control of mammalian gene transcription with numerous transcription factors regulated by this modification. Many of these proteins serve as immunomodulators, and inducible nitric oxide synthase (iNOS) is regarded as a principal mediatiator of NO-dependent S-nitrosylation. However, additional targets within the nucleus (e.g. histone deacetylases) and alternative mechanisms of S-nitrosylation (e.g. GAPDH-mediated trans-nitrosylation) are thought to play a role in NOS-dependent transcriptional regulation.

GENERAL SIGNIFICANCE

Derangement of SNO-regulated gene transcription is an important factor in a variety of pathological conditions including neoplasia and sepsis. A better understanding of protein S-nitrosylation as it relates to gene transcription and the physiological mechanisms behind this process is likely to lead to novel therapies for these disorders. This article is part of a Special Issue entitled Regulation of Cellular Processes by S-nitrosylation.

S-nitrosylation of proteins: a new insight into endothelial cell function regulated by eNOS-derived NO

Nitric oxide (NO) is a messenger molecule that is highly diffusible and short-lived. Despite these two characteristics, seemingly unsuitable for intracellular reactions, NO modulates a variety of cellular processes via the mechanism of S-nitrosylation. An important factor that determines the specificity of S-nitrosylation as a signaling mechanism is the compartmentalization of nitric oxide synthase (NOS) with its target proteins. Endothelial NOS (eNOS) is unique among the NOS family members by being localized mainly near specific intracellular membrane domains including the cytoplasmic face of the Golgi apparatus and plasma membrane caveolae. Nitric oxide produced by eNOS localized on the Golgi apparatus can react with thiol groups on nearby Golgi proteins via a redox mechanism resulting in S-nitrosylation of these proteins. This modification influences their function as regulators of cellular processes such as protein trafficking (e.g., exocytosis and endocytosis), redox state, and cell cycle. Thus, eNOS-derived NO regulates a wide range of endothelial cell functions, such as inflammation, apoptosis, permeability, migration, and cell growth.

Analysis of nitroso-proteomes in normotensive and severe preeclamptic human placentas

Nitric oxide (NO) plays a key role in placental biology, and placental dysfunction is the main pathogenesis pathway for preeclampsia, yet the direct placental targets of NO actions have not been determined. Covalent adduction of an NO moiety to cysteines, termed S-nitrosylation (SNO), is emerging as a key route by which NO can directly modulate protein functions. This study was conducted to analyze global S-nitroso (SNO)-proteins in human placentas and to determine if their levels differ in normotensive versus severe preeclamptic placentas. Although total nitrite/nitrate increased, total levels of SNO-proteins and nitrosylated forms of endothelial NO synthase and heat shock protein 90 were decreased by preeclampsia. We further compared normotensive and preeclamptic placental nitroso-proteomes (total SNO-protein profiles) by using a biotin and CyDye switch test combined with two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and identified SNO-proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Numerous SNO-proteins were displayed as spots on 2D-DIGE gels. One hundred spots of interest were excised; 46 spots were identified, of which 8 spots were novel SNO-proteins; levels of 15 spots were increased, and 6 spots were decreased, and the rest were unchanged by preeclampsia. Pathway analysis suggested that placental SNO-proteins are involved in regulating various cellular functions including protein synthesis, cell movement and metabolism, cell signaling, and other functions. These data therefore show for the first time that SNO is a crucial mechanism by which NO directly regulates placental proteins linked to various biological pathways. The significantly altered placental nitroso-proteome in preeclampsia suggests that SNO plays a role in the placental pathophysiology in preeclampsia.