Hydrogen peroxide induces mRNA for tumour necrosis factor alpha in human endothelial cells

Automated detection of apoptotic versus nonapoptotic cell death using label-free computational microscopy

Identification of cell death mechanisms, particularly distinguishing between apoptotic versus nonapoptotic pathways, is of paramount importance for a wide range of applications related to cell signaling, interaction with pathogens, therapeutic processes, drug discovery, drug resistance, and even pathogenesis of diseases like cancers and neurogenerative disease among others. Here, we present a novel high-throughput method of identifying apoptotic versus necrotic versus other nonapoptotic cell death processes, based on lensless digital holography. This method relies on identification of the temporal changes in the morphological features of mammalian cells, which are unique to each cell death processes. Different cell death processes were induced by known cytotoxic agents. A deep learning-based approach was used to automatically classify the cell death mechanism (apoptotic vs necrotic vs nonapoptotic) with more than 93% accuracy. This label free approach can provide a low cost (<$250) alternative to some of the currently available high content imaging-based screening tools.

Central role of the p53 pathway in the noncoding-RNA response to oxidative stress

Oxidative stress plays a fundamental role in many conditions. Specifically, redox imbalance inhibits endothelial cell (EC) growth, inducing cell death and senescence. We used global transcriptome profiling to investigate the involvement of noncoding-RNAs in these phenotypes. By RNA-sequencing, transcriptome changes were analyzed in human ECs exposed to H₂O₂, highlighting a pivotal role of p53-signaling. Bioinformatic analysis and validation in p53-silenced ECs, identified several p53-targets among both mRNAs and long noncoding-RNAs (lncRNAs), including MALAT1 and NEAT1. Among microRNAs (miRNAs), miR-192-5p was the most induced by H₂O₂ treatment, in a p53-dependent manner. Down-modulated mRNA-targets of miR-192-5p were involved in cell cycle, DNA repair and stress response. Accordingly, miR-192-5p overexpression significantly decreased EC proliferation, inducing cell death. A central role of the p53-pathway was also confirmed by the analysis of differential exon usage: Upon H₂O₂ treatment, the expression of p53-dependent 5'-isoforms of MDM2 and PVT1 increased selectively. The transcriptomic alterations identified in H₂O₂-treated ECs were also observed in other physiological and pathological conditions where redox control plays a fundamental role, such as ECs undergoing replicative senescence, skeletal muscles of critical limb-ischemia patients and the peripheral-blood mononuclear cells of long-living individuals. Collectively, these findings indicate a prominent role of noncoding-RNAs in oxidative stress response.

Human decidua basalis mesenchymal stem/stromal cells protect endothelial cell functions from oxidative stress induced by hydrogen peroxide and monocytes

Background

Human decidua basalis mesenchymal stem/multipotent stromal cells (DBMSCs) inhibit endothelial cell activation by inflammation induced by monocytes. This property makes them a promising candidate for cell-based therapy to treat inflammatory diseases, such as atherosclerosis. This study was performed to examine the ability of DBMSCs to protect endothelial cell functions from the damaging effects resulting from exposure to oxidatively stress environment induced by H₂O₂ and monocytes.

Methods

DBMSCs were co-cultured with endothelial cells isolated from human umbilical cord veins in the presence of H₂O₂ and monocytes, and various functions of endothelial cell were then determined. The effect of DBMSCs on monocyte adhesion to endothelial cells in the presence of H₂O₂ was also examined. In addition, the effect of DBMSCs on HUVEC gene expression under the influence of H₂O₂ was also determined.

Results

DBMSCs reversed the effect of H₂O₂ on endothelial cell functions. In addition, DBMSCs reduced monocyte adhesion to endothelial cells and also reduced the stimulatory effect of monocytes on endothelial cell proliferation in the presence of H₂O₂. Moreover, DBMSCs modified the expression of many genes mediating important endothelial cell functions. Finally, DBMSCs increased the activities of glutathione and thioredoxin reductases in H₂O₂-treated endothelial cells.

Conclusions

We conclude that DBMSCs have potential for therapeutic application in inflammatory diseases, such as atherosclerosis by protecting endothelial cells from oxidative stress damage. However, more studies are needed to elucidate this further.

Tumor necrosis factor-alpha upregulated PHLPP1 through activating nuclear factor-kappa B during myocardial ischemia/reperfusion

AIMS

The pleckstrin homology domain leucine-rich repeat protein phosphatase 1 (PHLPP1) specifically regulates phospho-Ser473 of protein kinase B (PKB, Akt) opposing cell survival during myocardial ischemia/reperfusion (I/R). Previous studies demonstrated PHLPP1 expression level was controlled by several mechanisms. However, the regulation mechanism of cardiac PHLPP1 expression following myocardial I/R remains unknown.

MAIN METHODS

The current study utilized the mouse model of myocardial I/R injury in vivo and the neonatal rat ventricular myocytes (NRVMs) of hypoxia/reoxygenation (H/R) injury in vitro. Expression of PHLPP1, nuclear factor-kappa B (NF-κB) and pNF-κB were determined by western blot. The expression of PHLPP1 and translocation of NF-κB was assessed by immunofluorescence. Chromatin immunoprecipitation (ChIP) assay was used to detect the binding of NF-κB to the promoter region of phlpp1 gene.

KEY FINDINGS

Myocardial I/R had no effect on cardiac PHLPP1 expression following I/R (30 min/2 h) but decreased after 4 h reperfusion. In vitro, H/R (4 h/1 h) and tumor necrosis factor-alpha (TNF-α)-stimulation resulted in upregulation of PHLPP1 in NRVMs, which was blocked with etanercept. Yet, H₂O₂-induced oxidative stress had no obvious effect on PHLPP1 expression of NRVMs at early stage but N-acetylcysteine (NAC) pretreatment increased PHLPP1 levels after 4 h H₂O₂ stimulation. TNF-α and H/R led to both expression and transcriptional activity of NF-κB, accompany with higher expression of PHLPP1. Pyrrolidine dithiocarbamate (PDTC), a NF-κB inhibitor, prevented the response not only in TNF-α-treated cardiomyocytes but also in H/R-treated group.

SIGNIFICANCE

These results implicated that TNF-α involved in cardiac PHLPP1 upregulation during reoxygenation, which was mediated by NF-κB transcriptional activity.

Protective mechanisms of melatonin against hydrogen-peroxide-induced toxicity in human bone-marrow-derived mesenchymal stem cells

Many obstacles compromise the efficacy of bone marrow mesenchymal stem cells (BM-MSCs) by inducing apoptosis in the grafted BM-MSCs. The current study investigates the effect of melatonin on important mediators involved in survival of BM-MSCs in hydrogen peroxide (H₂O₂) apoptosis model. In brief, BM-MSCs were isolated, treated with melatonin, and then exposed to H₂O₂. Their viability was assessed by MTT assay and apoptotic fractions were evaluated through Annexin V, Hoechst staining, and ADP/ATP ratio. Oxidative stress biomarkers including ROS, total antioxidant power (TAP), superoxide dismutase (SOD) and catalase (CAT) activity, glutathione (GSH), thiol molecules, and lipid peroxidation (LPO) levels were determined. Secretion of inflammatory cytokines (TNF-α and IL-6) were measured by ELISA assay. The protein expression of caspase-3, Bax, and Bcl-2, was also evaluated by Western blotting. Melatonin pretreatment significantly increased viability and decreased apoptotic fraction of H₂O₂-exposed BM-MSCs. Melatonin also decreased ROS generation, as well as increasing the activity of SOD and CAT enzymes and GSH content. Secretion of inflammatory cytokines in H₂O₂-exposed cells was also reduced by melatonin. Expression of caspase-3 and Bax proteins in H₂O₂-exposed cells was diminished by melatonin pretreatment. The findings suggest that melatonin may be an effective protective agent against H₂O₂-induced oxidative stress and apoptosis in MSC.

Hydrogen peroxide induces overexpression of angiotensin-converting enzyme in human umbilical vein endothelial cells

Oxidative stress has been linked to endothelial dysfunction in atherosclerosis and hypertension. The present study was designed to investigate the effect of hydrogen peroxide (H2O2) on angiotensin-converting enzyme (ACE), a key regulator of the renin-angiotensin system, and the mechanisms underlying ACE regulation in human umbilical vein endothelial cells (HUVECs). We used Tetrazolium bromide (MTT) assay for cell viability, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay for cell apoptosis, enzyme-linked immunosorbent assay (ELISA) for cAMP measurement, real-time PCR for mRNA detection, and Western blot for protein analysis in the study. Our results demonstrated that H2O2 (50-1000 μM) decreased HUVECs viability by inducing apoptosis. Notably, H2O2 upregulated ACE expression in a concentration-dependent manner. H2O2 100 μM significantly enhanced cyclic adenosine monophosphate (cAMP) expression by 1.48-fold (P<0.05). Additionally, forskolin 10 μM, a cAMP agonist, was also found to enhance ACE expression by 1.78-fold (P<0.05); in contrast, H-89 10 μM, a protein kinase A (PKA) inhibitor, abolished H2O2-induced ACE expression and prevented the enhancing effect of forskolin-induced ACE expression. Similar effects on ACE mRNA were also observed. cAMP-response element-specific decoy oligodeoxynucleotides (CRE-dODN) containing binding sites for cAMP-response element-binding protein (CREB) inhibited ACE expression at both the mRNA and protein levels. Negative control CRE-dODN had no effect on ACE expression. We conclude that H2O2 upregulates the expression of ACE through the activation of cAMP/PKA/CREB signal pathway in HUVECs, indicating a role of oxidative stress in the pathophysiology of hypertension.

miR-200c is upregulated by oxidative stress and induces endothelial cell apoptosis and senescence via ZEB1 inhibition

We examined the effect of reactive oxygen species (ROS) on MicroRNAs (miRNAs) expression in endothelial cells in vitro, and in mouse skeletal muscle following acute hindlimb ischemia. Human umbilical vein endothelial cells (HUVEC) were exposed to 200 μM hydrogen peroxide (H(2)O(2)) for 8 to 24 h; miRNAs profiling showed that miR-200c and the co-transcribed miR-141 increased more than eightfold. The other miR-200 gene family members were also induced, albeit to a lower level. Furthermore, miR-200c upregulation was not endothelium restricted, and occurred also on exposure to an oxidative stress-inducing drug: 1,3-bis(2 chloroethyl)-1nitrosourea (BCNU). miR-200c overexpression induced HUVEC growth arrest, apoptosis and senescence; these phenomena were also induced by H(2)O(2) and were partially rescued by miR-200c inhibition. Moreover, miR-200c target ZEB1 messenger RNA and protein were downmodulated by H(2)O(2) and by miR-200c overexpression. ZEB1 knockdown recapitulated miR-200c-induced responses, and expression of a ZEB1 allele non-targeted by miR-200c, prevented miR-200c phenotype. The mechanism of H(2)O(2)-mediated miR-200c upregulation involves p53 and retinoblastoma proteins. Acute hindlimb ischemia enhanced miR-200c in wild-type mice skeletal muscle, whereas in p66(ShcA -/-) mice, which display lower levels of oxidative stress after ischemia, upregulation of miR-200c was markedly inhibited. In conclusion, ROS induce miR-200c and other miR-200 family members; the ensuing downmodulation of ZEB1 has a key role in ROS-induced apoptosis and senescence.

Ophiopogonin D prevents H2O2-induced injury in primary human umbilical vein endothelial cells

AIM OF THE STUDY

Vessel endothelium injury caused by reactive oxygen species (ROS) including H(2)O(2) plays a critical role in the pathogenesis of cardiovascular disorders. Therefore, drug targeting ROS elimination has highly clinical values in cardiovascular therapy. The plant of Radix Ophiopogon japonicus is a traditional Chinese herbal medicine that has been commonly used for prevention and treatment of cardiovascular diseases for a long history. However, the effective component mediating its beneficial effects remains unknown. In the present study, we investigated the action of Ophiopogonin D (OP-D), one of the most bioactive components of Radix Ophiopogon japonicus, in an endothelial injury model induced by H(2)O(2).

MATERIALS AND METHODS

Primarily cultured human umbilical vein endothelial cells (HUVECs) were pretreated with increased doses of OP-D overnight and then challenged with H(2)O(2). The protective effects of OP-D against H(2)O(2) were evaluated.

RESULTS

We found that OP-D inhibited mRNA levels of antioxidant, inflammatory and apoptotic genes in a dose-dependent manner in HUVECs. H(2)O(2)-induced lipid peroxidation and protein carbonylation were reduced by OP-D pretreatment. Mitochondrial ROS generation and cell apoptosis were also attenuated in OP-D pretreated cells. In addition, OP-D restored cellular total antioxidative capacity and inhibited the release of inflammatory cytokines. Furthermore, OP-D suppressed the enzymatic activity of catalase, HO-1, and caspases. Finally, OP-D blocked activation of NF-kappaB and ERK signaling cascades.

CONCLUSION

Our findings provide the first evidence that OP-D plays a protective role as an effective antioxidant in H(2)O(2)-induced endothelial injury. Ophiopogonin D can be therefore developed as a novel drug for the therapy of cardiovascular disorders.

Divergent and convergent effects on gene expression and function in acute versus chronic endothelial activation

Activation of the vascular endothelium with cytokines such as TNF is widely used to study the role of the vasculature in proinflammatory disease. To gain insight into mechanisms of prolonged vascular endothelial activation we compared changes in gene expression induced by continuous activation in stable tmTNF-expressing cells with changes due to acute TNF challenge in vitro. Affymetrix Genechip analysis was performed on RNA from control, acute and continuous TNF-activated endothelial cells. Only 36% of the significant changes in gene expression were convergent between the acute and continuously activated endothelial cells compared with the control. From the divergently regulated genes, for example the cytokine ENA-78 was specifically induced in chronically activated cells, while E-selectin, a cell adhesion molecule, was upregulated only in acutely activated endothelial cells. Antioxidant SOD gene induction was noted in acute activation, while a regulatory NADPH oxidase subunit was selectively upregulated in continuously activated endothelium in accordance with significant reactive oxygen species induction occurred only in these cells. Accordingly, p38 and ERK1/2, two MAP kinases downstream of reactive oxygen species, were activated in stable transmembrane-spanning precursor (tm) TNF-expressing cells and were refractory to activation with soluble TNF or VEGF. In consequence, the increased p38 MAP kinase activity contributed to increased endothelial cell migration in tmTNF-expressing cells. These data suggest that continuous activation of endothelial cells leads to specific expression and functional changes, consistent with alterations observed in dysfunctional endothelium exposed to or involved in chronic inflammation.

Continuous Endothelial Cell Activation Increases Angiogenesis: Evidence for the Direct Role of Endothelium Linking Angiogenesis and Inflammation

There is increasing evidence that chronic inflammation is tightly linked to diseases associated with endothelial dysfunction, including the induction of aberrant angiogenesis. While leukocytes have been described as mediators of inflammation-associated angiogenesis, the effects of direct chronic endothelial activation have not been addressed in this context. Using an uncleavable mutant of the transmembrane form of tumor necrosis factor-alpha (TNF-alpha), we have established models of stable TNF-alpha expression in endothelial cells in vitro and in transgenic mice in vivo. In the in vitro model, continuous endothelial activation leads to increased leukocyte cellular adhesion molecule expression and intracellular reactive oxygen species, hallmarks of a proinflammatory and dysfunctional endothelium. In addition, stable expression of TNF-alpha in endothelial cells increased angiogenic sprout formation in the presence but also in the absence of angiogenic growth factors. The partial neutralization of this effect by TNF-alpha antibodies and the inability of conditioned media from stable TNF-alpha-expressing endothelial cells to induce angiogenic activities in control endothelial cells suggest that this effect does not require expression of additional autocrine factors, but is an autonomous effect of the transmembrane TNF on the endothelial cells. Furthermore, using the Matrigel plug assay in vivo, increased angiogenesis was observed in endothelial TNF-alpha-expressing transgenic versus control mice. In conclusion, chronic inflammatory changes mediated by TNF-alpha can induce angiogenesis in vitro and in vivo, suggesting endothelial cell activation as a direct link between inflammation and angiogenesis.

Differential role of hydrogen peroxide and staurosporine in induction of cell death in glioblastoma cells lacking DNA-dependent protein kinase

Various DNA double-strand break repair mechanisms, in which DNA-dependent protein kinase (DNA-PK) has a major role, are involved both in the development and treatment of glioblastoma. The aim of the present study was to investigate how glioblastoma cells responded to hydrogen peroxide and staurosporine (STS) and how such a response is related to DNA-PK. Two human glioblastoma cell lines, M059J cells that lack DNA-PK activity, and M059K cells that express a normal level of DNA-PK, were exposed to hydrogen peroxide or STS. The response of the cells to hydrogen peroxide or STS was recorded by measuring cell death, which was detected by three different methods-MTT, annexin-V and propidium iodide staining, and JC-1 mitochondrial probe. The result showed that both hydrogen peroxide and STS were able to induce cell death of the glioblastoma cells and that the former was mainly associated with necrosis and the latter with apoptosis. Glioblastoma cells lacking DNA-PK were less sensitive to STS treatment than those containing DNA-PK. However, DNA-PK had no significant influence on hydrogen peroxide treatment. We further found that catalase, an antioxidant enzyme, could prevent cell death induced by hydrogen peroxide but not by STS, suggesting that the pathways leading to cell death by hydrogen peroxide and STS are different. We conclude that hydrogen peroxide and STS have differential effects on cell death of glioblastoma cells lacking DNA-dependent protein kinase. Such differential roles in the induction of glioblastoma cell death can be of significant value in selecting and/or optimizing the treatment for this malignant brain tumor.

Glucose enhances endothelial LOX-1 expression: role for LOX-1 in glucose-induced human monocyte adhesion to endothelium

Endothelial dysfunction is an early and key determinant of diabetic vascular complications that is elicited at least in part by oxidized LDL (oxLDL). The recent observation that lectin-like oxLDL receptor-1 (LOX-1) expression is increased in the vascular endothelium of diabetic rats suggests a role for LOX-1 in the pathogenesis of diabetic vascular dysfunction. Because postprandial plasma glucose has been recently proposed as an independent risk factor for cardiovascular diseases in patients with diabetes, we evaluated, in the current study, the in vitro effect of high glucose on LOX-1 expression by human aortic endothelial cells (HAECs) and the role of this receptor in glucose-induced human monocyte adhesion to endothelium. Exposure of HAECs to high D-glucose concentrations (5.6-30 mmol/l) enhanced, in a dose- and time-dependent manner, LOX-1 expression, both at the gene and protein levels. The stimulatory effect of glucose on LOX-1 gene expression in HAECs was abolished by antioxidants and inhibitors of nuclear factor (NF)-kappaB, protein kinase C (PKC), and mitogen-activated protein kinases (MAPKs). Electrophoretic mobility shift assay data demonstrated that high glucose enhanced, in HAECs, the nuclear protein binding to the NF-kappaB regulatory element of the LOX-1 gene. Finally, our results showed that incubation of HAECs with high glucose increased human monocyte adhesion to endothelium through a LOX-1-dependent signaling mechanism. Overall, these results demonstrate that high glucose induces endothelial LOX-1 expression. This effect appears to be exerted at the transcriptional level through increased oxidant stress and NF-kappaB, PKC, and MAPK activation. The study also suggests a role for LOX-1 as mediator of the stimulatory effect of high glucose on monocyte adhesion.

Toll-like receptor 2 participates in mediation of immune response in experimental pneumococcal meningitis

Heterologous expression of Toll-like receptor (TLR)2 and CD14 in Chinese hamster ovary fibroblasts was reported to confer responsiveness to pneumococcal peptidoglycan. The present study characterized the role of TLR2 in the host immune response and clinical course of pneumococcal meningitis. Pneumococcal infection of mice caused a significant increase in brain TLR2 mRNA expression at both 4 and 24 h postchallenge. Mice with a targeted disruption of the TLR2 gene (TLR2-/-) showed a moderate increase in disease severity, as evidenced by an aggravation of meningitis-induced intracranial complications, a more pronounced reduction in body weight and temperature, and a deterioration of motor impairment. These symptoms were associated with significantly higher cerebellar and blood bacterial titers. Brain expression of the complement inhibitor complement receptor-related protein y was significantly higher in infected TLR2-/- than in wild-type mice, while the expression of the meningitis-relevant inflammatory mediators IL-1beta, TNF-alpha, IL-6, macrophage-inflammatory protein (MIP)-2, inducible NO synthase, and C3 was similar in both genotypes. We first ectopically expressed single candidate receptors in HEK293 cells and then applied peritoneal macrophages from mice lacking TLR2 and/or functional TLR4 for further analysis. Overexpression of TLR2 and TLR4/MD-2 conferred activation of NF-kappaB in response to pneumococcal exposure. However, pneumococci-induced TNF-alpha release from peritoneal macrophages of wild-type and TLR2/functional TLR4/double-deficient mice did not differ. Thus, while TLR2 plays a significant role in vivo, yet undefined pattern recognition receptors contribute to the recognition of and initiation of the host immune defense toward Streptococcus pneumoniae infection.

Participation of the calcium/calmodulin-dependent kinases in hydrogen peroxide-induced Ikappa B phosphorylation in human T lymphocytes

NF-kappaB is an important transcription factor that has a role in a variety of responses such as inflammation, oncogenesis, apoptosis, and viral replication. Oxidative stress is well known to induce the activation of NF-kappaB. Cells can be exposed to either endogenously produced oxidants or oxidants produced by surrounding cells. In addition, ischemia reperfusion and certain cancer therapies such as chemotherapy and photodynamic therapy are thought to result in oxygen radical production. Because of the important role that NF-kappaB has in multiple responses, it is critical to determine the mechanisms by which oxidative stress induces NF-kappaB activity. We report that the calmodulin antagonist W-7 and the calcium/calmodulin-dependent (CaM) kinase inhibitors KN-93 and K252a, can block oxidative stress-induced IkappaB phosphorylation in Jurkat T lymphocytes. Furthermore, KN-93 but not KN-92 can block hydrogen peroxide-induced Akt and IKK phosphorylation. In addition, we found that expression of a kinase-dead CaM-KIV construct in two cell lines inhibits IkappaB phosphorylation or degradation and that expression of CaM-KIV augments hydrogen peroxide-induced IkappaB phosphorylation and degradation. Although the CaM kinases appear to be required for this response, increases in intracellular calcium do not appear to be required. These results identify the CaM kinases as potential targets that can be used to minimize NF-kappaB activation in response to oxidative stress.

Chronic inflammation and protection from acute hepatitis in transgenic mice expressing TNF in endothelial cells

Endothelial activation is an important feature of many inflammatory diseases and has been implicated as the cause of vascular complications in disorders such as diabetes, atherosclerosis, and transplant rejection. One of the most potent activators of the endothelium is TNF, which can also be expressed by endothelial cells, causing a permanent, autocrine stimulatory signal. To establish a model of continuous endothelial activation and to elucidate the role of endothelial derived TNF in vivo, we generated transgenic mice expressing a noncleavable transmembrane form of TNF under the control of the endothelial-specific tie2 promoter. Adult tie2-transmembrane TNF-transgenic mice developed chronic inflammatory pathology in kidney and liver, characterized by perivascular infiltration of mononuclear cells into these organs. Along with the infiltrate, an up-regulation of the adhesion molecules ICAM-1 and VCAM-1, but not E-selectin, in the endothelium was observed. Despite predisposition to chronic inflammation these mice were protected from immune-mediated liver injury in a model of Con A-induced acute hepatitis. Although the blood levels of soluble TNF and IFN-gamma were increased in transgenic animals after challenge with Con A, no damage of hepatocytes could be detected, as assessed by the lack of increase in plasma transaminase activities and the absence of TUNEL staining in the liver. We conclude that expression of transmembrane TNF in the endothelium causes continuous endothelial activation, leading to both proinflammatory and protective events.