Oxidative stress-induced apoptosis of endothelial cells

Dengue Envelope Protein as a Cytotoxic Factor Inducing Hemorrhage and Endothelial Cell Death in Mice

Dengue virus (DENV) infection, prevalent in tropical and subtropical regions, can progress to dengue hemorrhagic fever (DHF), which increases mortality during secondary infections. DHF is characterized by endothelial damage and vascular leakage. Despite its severity, no specific antiviral treatments exist, and the viral factors responsible for endothelial damage remain unclear. This study examines the role of the DENV envelope protein domain III (EIII) in inducing endothelial apoptosis using a mouse model. Additionally, we aim to explore whether cell death-inducing pathways could serve as drug targets to ameliorate EIII-induced endothelial injury and hemorrhage. In vitro experiments using human endothelial HMEC-1 cells demonstrated that both recombinant EIII (rEIII) and DENV markedly induced caspase-3-mediated endothelial cell death, an effect that was attenuated by co-treatment with chondroitin sulfate B (CSB), N-acetyl cysteine (NAC), and the caspase-3 inhibitor z-DEVD-FMK. In vivo, sequential injections of rEIII and anti-platelet immunoglobulin in mice, designed to mimic the clinical phase of DHF with peak viremia followed by an increase in DENV-induced Ig, including autoantibodies, revealed that these dual treatments markedly triggered caspase-3-dependent apoptosis in vascular endothelial cells at hemorrhage sites. Treatments with z-DEVD-FMK effectively reduced DHF-like symptoms such as thrombocytopenia, hemorrhage, inflammation, hypercoagulation, and endothelial damage. Additionally, CSB and NAC alleviated hemorrhagic symptoms in the mice. These results suggest that targeting EIII, reactive oxygen species, and caspase-3-mediated apoptosis could offer potential therapeutic strategies for addressing EIII-induced hemorrhagic pathogenesis.

Oxidative Stress and Intracranial Hypertension after Aneurysmal Subarachnoid Hemorrhage

Intracranial hypertension is a common phenomenon in patients with aneurysmal subarachnoid hemorrhage (aSAH). Elevated intracranial pressure (ICP) plays an important role in early brain injuries and is associated with unfavorable outcomes. Despite advances in the management of aSAH, there is no consensus about the mechanisms involved in ICP increases after aSAH. Recently, a growing body of evidence suggests that oxidative stress (OS) may play a crucial role in physio-pathological changes following aSAH, which may also contribute to increased ICP. Herein, we discuss a potential relation between increased ICP and OS, and resultantly propose antioxidant mechanisms as a potential therapeutic strategy for the treatment of ICP elevation following aSAH.

Synthetic enamine naphthoquinone derived from lawsone as cytotoxic agents assessed by in vitro and in silico evaluations

We synthesized ten enamine naphthoquinones with yields ranging from 43 to 76%. These compounds were screened for their in vitro antiproliferative activities by MTT assay against four types of human cancer cell lines: HCT116, PC3, HL60 and SNB19. The naphthoquinones bearing the picolylamine (7) and quinoline (12) moieties were the most actives (IC₅₀ < 24 μM for all the cell lines), which were comparable or better to the values obtained for the control drugs. In silico evaluations allowed us to develop a qualitative Structure-Activity Relationship which suggest that electrostatic features, particularly the C₂-C₃ internuclear repulsion and the molecular dipole moment, relate to the biological response. Furthermore, Molecular Docking simulations indicate that the synthetic compounds have the potential to act as anticancer molecules by inhibiting topoisomerase-II and thymidylate synthase.

Menadione-induced endothelial inflammation detected by Raman spectroscopy

In this work, the effect of an early oxidative stress on human endothelial cells induced by menadione was studied using a combined methodology of label-free Raman imaging and fluorescence staining. Menadione-induced ROS-dependent endothelial inflammation in human aorta endothelial cells (HAEC) was studied with focus on changes in cytochrome, proteins, nucleic acids and lipids content and their distribution in cells. Fluorescence staining (ICAM-1, VCAM-1, vWF, LipidTox, MitoRos and DCF) was used to confirm endothelial inflammation and ROS generation. The results showed that short time, exposure to menadione did not cause their apoptosis or necrosis (Annexin V Apoptosis Detection Kit) within the 3 h timescale of measurement. On the other hand, 3 h of incubation, did result in endothelial inflammation (ICAM-1, VCAM-1, vWF) that was associated with an increased ROS formation (MitoRos and DCF) suggesting the oxidative stress-mediated inflammation. Chemometric analysis of spectral data enabled the determination of spectroscopic markers of menadione-induced oxidative stress-mediated endothelial inflammation including a decrease of the bands intensity of cytochrome (604, 750, 1128, 1315 and 1585 cm^-1), nucleic acids bands (785 cm^-1), proteins (1005 cm^-1) and increased intensity of lipid bands (722, 1085, 1265, 1303, 1445 and 1660 cm^-1), without changes in the spectroscopic signature of the cell nucleus. In conclusion, oxidative stress resulting in endothelial inflammation was featured by significant alterations in the number of biochemical changes in mitochondria and other cellular compartments detected by Raman spectroscopy. Most of these, coexisted with results from fluorescence imaging, and most importantly occurred earlier than the detection of increased ROS or markers of endothelial inflammation.

Alpha-lipoic acid ameliorates H2O2-induced human vein endothelial cells injury via suppression of inflammation and oxidative stress

The study was aimed to investigate the effect of alpha-lipoic acid (ALA) on human umbilical vein endothelial cells (HUVECs) injury induced by hydrogen peroxide (H₂O₂) and to explore its possible mechanisms. We established the H₂O₂-induced HUVECs injury model and the ALA treatment groups in which HUVECs were co-incubated with H₂O₂ (250 μmol/L) and different final concentrations of ALA (100,200,400 μmol/L) for 48 h. Cell survival rate assay and LDH activity assay were carried out. The levels of related proteins were performed by Western Blot. We observed that H₂O₂ administration resulted in an increase in the LDH activity and a decrease in cell survival rate. The expression levels of Nox4, Bax, NF-κB p65, Caspase-9, Caspase-3, iNOS, VCAM-1 and ICAM-1 were up-regulated, while the expression level of Bcl-2 was down-regulated. All these factors were significantly improved by ALA treatment. In brief, ALA treatment ameliorates H₂O₂-induced HUVECs damage by inhibiting inflammation and oxidative stress.

Theophylline exerts complex anti-ageing and anti-cytotoxicity effects in human skin ex vivo

OBJECTIVE

Theophylline is a phosphodiesterase inhibitor that is being used clinically for asthma therapy. In addition, it is recognized as a cosmetic agent with possible anti-ageing and anti-oxidative properties. Nevertheless, how it affects human skin is still poorly examined.

METHODS

Theophylline (10 or 100 µM) was administered to the culture medium of full-thickness human skin ex vivo for 24 or 72 h.

RESULTS

Theophylline stimulated protein expression of the anti-oxidant metallothionein-1 and mRNA levels of collagen I and III. Assessment of fibrillin-1 immunohistology revealed enhanced structural stability of dermal microfibrils. Theophylline also exerted extracellular matrix-protective effects by decreasing MMP-2 and MMP-9 mRNA levels, partially antagonizing the effects of menadione, the potent, toxic ROS donor. In addition, it decreased menadione-stimulated epidermal keratinocytes apoptosis. Interestingly, theophylline also increased the level of intracutaneously produced melatonin, that is the most potent ROS-protective and DNA damage repair neuromediator, and tendentially increased protein expression of MT1, the melatonin receptor. Theophylline also increased the expression of keratin 15, the stem cell marker, in the epidermal basal layer but did not change mitochondrial activity or epidermal pigmentation.

CONCLUSION

This ex vivo pilot study in human skin shows that theophylline possesses several interesting complex skin-protective properties. It encourages further examination of theophylline as a topical candidate for anti-ageing treatment.

Cysteine Glutathionylation Acts as a Redox Switch in Endothelial Cells

Oxidative post-translational modifications (oxPTM) of receptors, enzymes, ion channels and transcription factors play an important role in cell signaling. oxPTMs are a key way in which oxidative stress can influence cell behavior during diverse pathological settings such as cardiovascular diseases (CVD), cancer, neurodegeneration and inflammatory response. In addition, changes in oxPTM are likely to be ways in which low level reactive oxygen and nitrogen species (RONS) may contribute to redox signaling, exerting changes in physiological responses including angiogenesis, cardiac remodeling and embryogenesis. Among oxPTM, S-glutathionylation of reactive cysteines emerges as an important regulator of vascular homeostasis by modulating endothelial cell (EC) responses to their local redox environment. This review summarizes the latest findings of S-glutathionylated proteins in major EC pathways, and the functional consequences on vascular pathophysiology. This review highlights the diversity of molecules affected by S-glutathionylation, and the complex consequences on EC function, thereby demonstrating an intricate dual role of RONS-induced S-glutathionylation in maintaining vascular homeostasis and participating in various pathological processes.

Nicotine-Induced Oxidative Stress in Human Primary Endometrial Cells

Nicotine is a major component of tobacco plants and is responsible for the development of reproductive problems in smokers. Nicotine has been recognized to result in oxidative stress by inducing the generation of reactive oxygen species (ROS) in some parts of female reproductive system, but the effect of nicotine on endometrium that plays an important role in reproductive biology stays unexplored. The aim of this work was to clarify the direct effects of nicotine administration on the antioxidant defense system and lipid peroxidation in human endometrial cells. Human endometrial stromal primary cells were treated with nicotine (0, 10−11, 10−8, and 10−6 M) for 24 hours. On nicotine administration, the endometrial cells were associated with a decrease in antioxidant defense markers such as Glutathione (GSH) level, glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT) enzymes activity and higher levels of malondialdehyde (MDA) in a dose-dependent manner when compared to the control. We concluded that nicotine as a pro-oxidant affects the oxidative state of the endometrial cells.

Peptides from Cauliflower By-Products, Obtained by an Efficient, Ecosustainable, and Semi-Industrial Method, Exert Protective Effects on Endothelial Function

The large amount of cauliflower industry waste represents an unexplored source of bioactive compounds. In this work, peptide hydrolysates from cauliflower leaves were characterized by combined bioanalytical approaches. Twelve peptide fractions were studied to evaluate unexplored biological activities by effect-based cellular bioassays. A potent inhibition of intracellular xanthine oxidase activity was observed in human vascular endothelial cells treated with one fraction, with an IC50 = 8.3 ± 0.6 μg/ml. A different fraction significantly induced the antioxidant enzyme superoxide dismutase 1 and decreased the tumor necrosis factor α-induced VCAM-1 expression, thus leading to a significant improvement in the viability of human vascular endothelial cells. Shotgun peptidomics and bioinformatics were used to retrieve the most probable bioactive peptide sequences. Our study shows that peptides from cauliflower waste should be recycled for producing valuable products useful for the prevention of endothelial dysfunction linked to atherogenesis progression.

Initial Assessment of Variability of Responses to Toxicants in Donor-Specific Endothelial Colony Forming Cells

There is increased interest in using high throughput in vitro assays to characterize human population variability in response to toxicants and drugs. Utilizing primary human endothelial colony-forming cells (ECFCs) isolated from blood would be highly useful for this purpose because these cells are involved in neonatal and adult vasculogenesis. We characterized the cytotoxicity of four known toxic chemicals (NaAsO2, CdCl2, tributyltin [TBT], and menadione) and their four relatively nontoxic counterparts (Na2HAsO4, ZnCl2, SnCl2, and phytonadione, respectively) in eight ECFC clones representing four neonatal donors (2 male and 2 female donors, 2 clones per donor). ECFCs were exposed to 9 concentrations of each chemical in duplicate; cell viability was evaluated 48 h later using the fluorescent vital dye fluorescent dye 5-Carboxyfluorescein Diacetate (CFDA), yielding concentration-effect curves from each experiment. Technical (day-to-day) variability of the assay, assessed from three independent experiments, was low: p-values for the differences of results were 0.74 and 0.64 for the comparison of day 2 vs. day 1 and day 3 vs. day 1, respectively. The statistical analysis used to compare the entire concentration-effect curves has revealed significant differences in levels of cytotoxicity induced by the toxic and relatively nontoxic chemical counterparts, demonstrating that donor-specific ECFCs can clearly differentiate between these two groups of chemicals. Partitioning of the total variance in the nested design assessed the contributions of between-clone and between-donor variability for different levels of cytotoxicity. Individual ECFC clones demonstrated highly reproducible responses to the chemicals. The most toxic chemical was TBT, followed by NaAsO2, CdCl2, and Menadione. Nontoxic counterparts exhibited low cytotoxicity at the higher end of concentration ranges tested. Low variability was observed between ECFC clones obtained from the same donor or different donors for CdCl2, NaAsO2, and TBT, but for menadione, the between-donor variability was much greater than the between-clone variability. The low between-clone variability indicates that an ECFC clone may represent an individual donor in cell-based assays, although this finding must be confirmed using a larger number of donors. Such confirmation would demonstrate that an in vitro ECFC-based testing platform can be used to characterize the inter-individual variability of neonatal ECFCs exposed to drugs and/or environmental toxicants.

Acylated ghrelin protects aorta damage post-MI via activation of eNOS and inhibition of angiotensin-converting enzyme induced activation of NAD(P)H-dependent oxidase

NAD(P)H dependent oxidase derived-reactive oxygen species (ROS) due to activation of the renin-angiotensin-aldosterone system (RAAS) in blood vessels postmyocardial infarction MI or during the HF leads to endothelium dysfunction and enhanced apoptosis. Acylated ghrelin (AG) is a well-reported cardioprotective and antiapoptotic agent for the heart. AG receptors are widely distributed in most of blood vessels, suggesting a role in the regulation of endothelial function and survival. This study investigated if AG can protect aorta of rats' postmyocardial infarction (MI)-induced damage and endothelial dysfunction. Adult male rats were divided into four groups of (1) Sham, (2) Sham + AG, (3) MI, and (4) MI + AG. Vehicle (normal saline) or AG (100 µ/kg) was administered to rats for 21 consecutive days, after which, numerous biochemical markers were detected by blot. Both histological and electron microscope studies were carried on aortic samples from MI-induced rats. AG increased protein levels of both total and phosphorylated forms of endothelial nitric oxide synthase (eNOS and p-eNOS, respectively). Only in MI-treated rats, AG prevented the decreases in the levels of reduced glutathione (GSH) and superoxide dismutase (SOD) and lowered levels of malondialdehyde (MDA) and glutathione disulfide (GSSG). Concomitantly, it lowered the increased protein levels of angiotensin-converting enzyme (ACE), p22phox and cleaved caspase-3 and prevented the aorta histological and ultrustructural abnormalities induced by MI.

Tanshinone IIA Protects Endothelial Cells from H₂O₂-Induced Injuries via PXR Activation

Tanshinone IIA (Tan IIA) is a pharmacologically active substance extracted from the rhizome of Salvia miltiorrhiza Bunge (also known as the Chinese herb Danshen), and is widely used to treat atherosclerosis. The pregnane X receptor (PXR) is a nuclear receptor that is a key regulator of xenobiotic and endobiotic detoxification. Tan IIA is an efficacious PXR agonist that has a potential protective effect on endothelial injuries induced by xenobiotics and endobiotics via PXR activation. Previously numerous studies have demonstrated the possible effects of Tan IIA on human umbilical vein endothelial cells, but the further mechanism for its exerts the protective effect is not well established. To study the protective effects of Tan IIA against hydrogen peroxide (H₂O₂) in human umbilical vein endothelial cells (HUVECs), we pretreated cells with or without different concentrations of Tan IIA for 24 h, then exposed the cells to 400 μM H₂O₂ for another 3 h. Therefore, our data strongly suggests that Tan IIA may lead to increased regeneration of glutathione (GSH) from the glutathione disulfide (GSSG) produced during the GSH peroxidase-catalyzed decomposition of H₂O₂ in HUVECs, and the PXR plays a significant role in this process. Tan IIA may also exert protective effects against H₂O₂-induced apoptosis through the mitochondrial apoptosis pathway associated with the participation of PXR. Tan IIA protected HUVECs from inflammatory mediators triggered by H₂O₂ via PXR activation. In conclusion, Tan IIA protected HUVECs against H₂O₂-induced cell injury through PXR-dependent mechanisms.

Cytotoxic and apoptotic effects of menadione on rat hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common cancers, which may lead to death. Menadione shows cytotoxic activity thought affecting redox cycling in cancer cells. The aim of the present study was to investigate the effects of menadione on rat hepatocellular carcinoma (H4IIE) cell morphology, cytotoxicity, apoptosis and DNA damage or repair in vitro. Cell morphology evaluated by microscopy and cell viability was determined using the 3-[4,5-dimethylthiazol-2yl]-diphenyltetrazolium bromide test. Apoptotic cell death was assessed in H4IIE cells treated with menadione by 4',6-diamidino-2-phenylindole staining. Quantitative real time polymerase chain reaction used to determine the expression level of poly (ADP-ribose) polymerase 1 (PARP1) gene. According to the results of this study menadione has got a cytotoxic activity (IC50 25 µM) and change the cell fate in H4IIE cells. Menadione treatments lead to PARP1 activation in a dose dependent manner and induce DNA damage and apoptosis, and this may suggest its use as a therapeutic agent in HCC treatment.

Effect of nitric oxide on naphthoquinone toxicity in endothelial cells: role of bioenergetic dysfunction and poly (ADP-ribose) polymerase activation

When produced at physiological levels, reactive oxygen species (ROS) can act as signaling molecules to regulate normal vascular function. Produced under pathological conditions, ROS can contribute to the oxidative damage of cellular components (e.g., DNA and proteins) and trigger cell death. Moreover, the reaction of superoxide with nitric oxide (NO) produces the strong oxidant peroxynitrite and decreases NO bioavailability, both of which may contribute to activation of cell death pathways. The effects of ROS generated from the 1,4-naphthoquinones alone and in combination with NO on the activation status of poly(ADP-ribose) polymerase (PARP) and cell viability were examined. Treatment with redox cycling quinones activates PARP, and this stimulatory effect is attenuated in the presence of NO. Mitochondria play a central role in cell death signaling pathways and are a target of oxidants. We show that simultaneous exposure of endothelial cells to NO and ROS results in mitochondrial dysfunction, ATP and NAD(+) depletion, and cell death. Alone, NO and ROS have only minor effects on cellular bioenergetics. Further, PARP inhibition does not attenuate reduced cell viability or mitochondrial dysfunction. These results show that concomitant exposure to NO and ROS impairs energy metabolism and triggers PARP-independent cell death. While superoxide-mediated PARP activation is attenuated in the presence of NO, PARP inhibition does not modify the loss of mitochondrial function or adenine and pyridine nucleotide pools and subsequent bioenergetic dysfunction. These findings suggest that the mechanisms by which ROS and NO induce endothelial cell death are closely linked to the maintenance of mitochondrial function and not overactivation of PARP.

Age-related decrease in cerebrovascular-derived neuroprotective proteins: effect of acetaminophen

As the population ages, the need for effective methods to maintain brain function in older adults is increasingly pressing. Vascular disease and neurodegenerative disorders commonly co-occur in older persons. Cerebrovascular products contribute to the neuronal milieu and have important consequences for neuronal viability. In this regard vascular derived neuroprotective proteins, Such as vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), and pituitary adenylate cyclase activating peptide (PACAP) are important for maintaining neuronal viability, especially in the face of injury and disease. The objective of this study is to measure and compare levels of VEGF, PEDF and PACAP released from isolated brain microvessels of Fischer 344 rats at 6, 12, 18, and 24 months of age. Addition of acetaminophen to isolated brain microvessels is employed to determine whether this drug affects vascular expression of these neuroprotective proteins. Experiments on cultured brain endothelial cells are performed to explore the mechanisms/mediators that regulate the effect of acetaminophen on endothelial cells. The data indicate cerebrovascular expression of VEGF, PEDF and PACAP significantly decreases with age. The age-associated decrease in VEGF and PEDF is ameliorated by addition of acetaminophen to isolated brain microvessels. Also, release of VEGF, PEDF, and PACAP from cultured brain endothelial cells decreases with exposure to the oxidant stressor menadione. Acetaminophen treatment upregulates VEGF, PEDF and PACAP in brain endothelial cells exposed to oxidative stress. The effect of acetaminophen on cultured endothelial cells is in part inhibited by the selective thrombin inhibitor hirudin. The results of this study suggest that acetaminophen may be a useful agent for preserving cerebrovascular function. If a low dose of acetaminophen can counteract the decrease in vascular-derived neurotrophic factors evoked by age and oxidative stress, this drug might be useful for improving brain function in the elderly.

Volumetric interpretation of protein adsorption: interfacial packing of protein adsorbed to hydrophobic surfaces from surface-saturating solution concentrations

The maximum capacity of a hydrophobic adsorbent is interpreted in terms of square or hexagonal (cubic and face-centered-cubic, FCC) interfacial packing models of adsorbed blood proteins in a way that accommodates experimental measurements by the solution-depletion method and quartz-crystal-microbalance (QCM) for the human proteins serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa). A simple analysis shows that adsorbent capacity is capped by a fixed mass/volume (e.g. mg/mL) surface-region (interphase) concentration and not molar concentration. Nearly analytical agreement between the packing models and experiment suggests that, at surface saturation, above-mentioned proteins assemble within the interphase in a manner that approximates a well-ordered array. HSA saturates a hydrophobic adsorbent with the equivalent of a single square or hexagonally-packed layer of hydrated molecules whereas the larger proteins occupy two-or-more layers, depending on the specific protein under consideration and analytical method used to measure adsorbate mass (solution depletion or QCM). Square or hexagonal (cubic and FCC) packing models cannot be clearly distinguished by comparison to experimental data. QCM measurement of adsorbent capacity is shown to be significantly different than that measured by solution depletion for similar hydrophobic adsorbents. The underlying reason is traced to the fact that QCM measures contribution of both core protein, water of hydration, and interphase water whereas solution depletion measures only the contribution of core protein. It is further shown that thickness of the interphase directly measured by QCM systematically exceeds that inferred from solution-depletion measurements, presumably because the static model used to interpret solution depletion does not accurately capture the complexities of the viscoelastic interfacial environment probed by QCM.

Novel synthetic SOD/catalase mimetics can mitigate capillary endothelial cell apoptosis caused by ionizing radiation

Numerous in vitro and in vivo studies have shown that the endothelial cells of the microvasculature of the lung and kidney are damaged by exposure to ionizing radiation, and this sustained endothelial cell injury is involved in the early and late radiation effects observed in these tissues. It is well accepted that ionizing radiation causes the generation of reactive oxygen species during exposure that results in damage to DNA and cellular organelles. It is more controversial, however, whether additional biochemical events or long-lived radicals occur and persist postirradiation that amplify and initiate new forms of cellular damage. Two families of Eukarion (EUK) compounds have been synthesized that possess superoxide dismutase (SOD), catalase and peroxidase activities. The Mn porphyrins are available orally whereas the salen Mn complexes are administered by injection. In the present study we have examined the ability of these SOD/catalase mimetics to prevent apoptosis of endothelial cells when administered 1 h postirradiation (mitigation). A range of salen Mn complex (EUK-189 and EUK-207) and Mn porphyrins (EUK-418, -423, -425, -450, -451, -452, -453) were used to treat endothelial cells 1 h after the cells received 2-20 Gy ionizing radiation in vitro. Two lead compounds, EUK-207 at a dose of 30 microM and EUK-451 at a dose of 10 microM, exhibited low toxicity and mitigated radiation-induced apoptosis. Future animal studies will test whether these compounds protect when administered after radiation exposure as would be done after a radiological accident or a terrorism event.

An in vitro comparative study with furyl-1,4-quinones endowed with anticancer activities

We describe the biological activity of some furylbenzo- and naphthoquinones (furylquinones) on hepatocarcinoma cells and healthy rat liver slices. The effects of furylquinones on cancer cells (Transplantable Liver Tumor, TLT) were assessed by measuring cell death (membrane cell lysis); intracellular contents of ATP and GSH and the activity of caspase-3 were used to determine the type of cell death. Most of the furylquinones tested (at a concentration of 25 μg/ml) induced caspase-independent cell death but compound 4 had no cytotoxic effects. The levels of both ATP and GSH were severely affected by quinones 1, 2 and 5, while no effect was observed with compound 4. These cytotoxic properties of quinones are associated with physico-chemical properties as shown by the LUMO energies and lipophilicity. Interestingly, no cytotoxic effects of furylquinones were detected when the in vitro model of precision-cut liver slices (PCLS) was used. Indeed, although CYP2E1 activity was slightly affected, ATP and GSH levels as well as protein synthesis were not modified by furylquinones. Paracetamol, a well-known hepatotoxicant, reduced these parameters by more than 80% compared to control conditions. Taking into account the considerable incidence of adverse-effects induced by most current anticancer drugs, the selective cytotoxicity shown by compounds 1, 2 and 5, in particular that of 1, represents a safety factor that encourages the further development of these quinones as new drugs in cancer therapy.

Structure-activity relationships in the cytoprotective effect of caffeic acid phenethyl ester (CAPE) and fluorinated derivatives: effects on heme oxygenase-1 induction and antioxidant activities

To determine the relationship between catechol ring modifications and the activity of caffeic acid phenethyl ester (CAPE) as a cytoprotective agent, six catechol ring-fluorinated CAPE derivatives were evaluated for their cytoprotective abilities, as well as for their antioxidant and heme oxygenase-1 (HO-1) inducing capacity in a human umbilical vein endothelial cell (HUVEC) model of oxidant stress. To ascertain the involvement of HO-1 induction in the cytoprotective effects of CAPE analogues, their ability to induce HO-1 at 20microM was determined by reverse transcriptase polymerase chain reaction, western blotting and the use of HO-1 inhibitor tin protoporphyrin IX. There was significant induction of HO-1 by CAPE derivatives. Inhibition of HO-1 enzymatic activity resulted in reduced cytoprotection. Modification of the catechol ring of CAPE by introduction of fluorine at various positions resulted in dramatic changes in cytoprotective activity. The maintenance of at least one hydroxyl group on the CAPE catechol ring and the phenethyl ester portion was required for HO-1 induction. CAPE and its derivatives were screened for their ability to scavenge intracellular reactive oxygen species generated in HUVECs by measuring 5-(and-6)-chlormethyl-2', 7'-dichlorodihydrofluorescein diacetate oxidation. The maintenance of 3, 4-dihydroxyl groups on the catechol ring was required for antioxidant activity, but antioxidant activity did not guarantee cytoprotection. Methylation or replacement of one hydroxyl group on the catechol ring of CAPE, however, provided both pro-oxidant and cytoprotective activities. These results indicate that the induction of HO-1 plays a more important role in the cytoprotective activity of CAPE derivatives than their direct antioxidant activity.

Acetaminophen inhibits neuronal inflammation and protects neurons from oxidative stress

Background

Recent studies have demonstrated a link between the inflammatory response, increased cytokine formation, and neurodegeneration in the brain. The beneficial effects of anti-inflammatory drugs in neurodegenerative diseases, such as Alzheimer's disease (AD), have been documented. Increasing evidence suggests that acetaminophen has unappreciated anti-oxidant and anti-inflammatory properties. The objectives of this study are to determine the effects of acetaminophen on cultured brain neuronal survival and inflammatory factor expression when exposed to oxidative stress.

Methods

Cerebral cortical cultured neurons are pretreated with acetaminophen and then exposed to the superoxide-generating compound menadione (5 μM). Cell survival is assessed by MTT assay and inflammatory protein (tumor necrosis factor alpha, interleukin-1, macrophage inflammatory protein alpha, and RANTES) release quantitated by ELISA. Expression of pro- and anti-apoptotic proteins is assessed by western blots.

Results

Acetaminophen has pro-survival effects on neurons in culture. Menadione, a superoxide releasing oxidant stressor, causes a significant (p < 0.001) increase in neuronal cell death as well as in the release of tumor necrosis factor alpha, interleukin-1, macrophage inflammatory protein alpha, and RANTES from cultured neurons. Pretreatment of neuronal cultures with acetaminophen (50 μM) increases neuronal cell survival and inhibits the expression of these cytokines and chemokines. In addition, we document, for the first time, that acetaminophen increases expression of the anti-apoptotic protein Bcl2 in brain neurons and decreases the menadione-induced elevation of the proapoptotic protein, cleaved caspase 3. We show that blocking acetaminophen-induced expression of Bcl2 reduces the pro-survival effect of the drug.

Conclusion

These data show that acetaminophen has anti-oxidant and anti-inflammatory effects on neurons and suggest a heretofore unappreciated therapeutic potential for this drug in neurodegenerative diseases such as AD that are characterized by oxidant and inflammatory stress.

Nuclear localization of active matrix metalloproteinase-2 in cigarette smoke-exposed apoptotic endothelial cells

Cigarette smoke (CS)-induced activation of proteases such as matrix metalloproteinases (MMPs) contributes to lung alveolar destruction due to cell death. The aim of this study was to determine whether MMPs are produced in pulmonary artery endothelial cells (PAECs) and whether CS activation of MMPs is associated with apoptosis. Cultured PAECs were exposed to CS and subjected to assessments of apoptosis and MMPs. Western blotting and in situ zymography were performed to localize gelatinolytic activity and to identify enzymes. CS-induced apoptosis, i.e., enhanced annexin V binding and cleaved poly-ADP-ribose-polymerase (PARP), correlated with increased degradation of gelatin, a substrate of MMPs. The levels of pro-MMP-2 and active MMP-2 were increased in cytosolic and nuclear fractions isolated from CS-exposed cells. MMP-2 protein colocalized with gelatinolytic activity in the nucleus of CS-exposed cells undergoing apoptosis. These observations support the notion that MMP-2 contributes to CS-induced gelatinase activity, which localizes in the nuclear region primarily and correlates with annexin V binding and PARP cleavage. This suggests a novel function of MMP-2 in the degradation of the nuclear matrix in CS-induced endothelial apoptosis.

Attenuation of lipopolysaccharide-induced oxidative stress and apoptosis in fetal pulmonary artery endothelial cells by hypoxia

Pulmonary vascular endothelial injury resulting from lipopolysaccharide (LPS) and oxygen toxicity contributes to vascular simplification seen in the lungs of premature infants with bronchopulmonary dysplasia. Whether the severity of endotoxin-induced endothelial injury is modulated by ambient oxygen tension (hypoxic intrauterine environment vs. hyperoxic postnatal environment) remains unknown. We posited that ovine fetal pulmonary artery endothelial cells (FPAEC) will be more resistant to LPS toxicity under hypoxic conditions (20-25 Torr) mimicking the fetal milieu. LPS (10 microg/ml) inhibited FPAEC proliferation and induced apoptosis under normoxic conditions (21% O(2)) in vitro. LPS-induced FPAEC apoptosis was attenuated in hypoxia (5% O(2)) and exacerbated by hyperoxia (55% O(2)). LPS increased intracellular superoxide formation, as measured by 2-hydroxyethidium (2-HE) formation, in FPAEC in normoxia and hypoxia. 2-HE formation in LPS-treated FPAEC increased in parallel with the severity of LPS-induced apoptosis in FPAEC, increasing from hypoxia to normoxia to hyperoxia. Differences in LPS-induced apoptosis between hypoxia and normoxia were abolished when LPS-treated FPAEC incubated in hypoxia were pretreated with menadione to increase superoxide production. Apocynin decreased 2-HE formation, and attenuated LPS-induced FPAEC apoptosis under normoxic conditions. We conclude that ambient oxygen concentration modulates the severity of LPS-mediated injury in FPAEC by regulating superoxide levels produced in response to LPS.

Multidrug-resistance-associated protein plays a protective role in menadione-induced oxidative stress in endothelial cells

AIMS

Menadione, a redox-cycling quinone known to cause oxidative stress, binds to reduced glutathione (GSH) to form glutathione S-conjugate. Glutathione S-conjugates efflux is often mediated by multidrug-resistance-associated protein (MRP). We investigated the effect of a transporter inhibitor, MK571 (3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid), on menadione-induced oxidative stress in bovine aortic endothelial cells (BAECs).

MAIN METHODS

BAECs were treated with menadione and MK571, and cell viability was measured. Modulation of intracellular GSH levels was performed with buthionine sulfoximine and GSH ethyl ester treatments. Intracellular superoxide was estimated by dihydroethidium oxidation using fluorescence microscopy or flow cytometry. Expression of MRP was determined by flow cytometry using phycoerythrin-conjugated anti-MRP monoclonal antibody.

KEY FINDINGS

Intracellular GSH depletion by buthionine sulfoximine promoted the loss of viability of BAECs exposed to menadione. Exogenous GSH, which does not permeate the cell membrane, or GSH ethyl ester protected BAECs against the loss of viability induced by menadione. The results suggest that GSH binds to menadione outside the cells as well as inside. Pretreatment of BAECs with MK571 dramatically increased intracellular levels of superoxide generated from menadione, indicating that menadione may accumulate in the intracellular milieu. Finally, we found that MK571 aggravated menadione-induced toxicity in BAECs and that MRP levels were increased in menadione-treated cells.

SIGNIFICANCE

We conclude that MRP plays a vital role in protecting BAECs against menadione-induced oxidative stress, presumably due to its ability to transport glutathione S-conjugate.

Hydroxysafflor yellow A enhances survival of vascular endothelial cells under hypoxia via upregulation of the HIF-1 alpha-VEGF pathway and regulation of Bcl-2/Bax

Hydroxysafflor yellow A (HSYA) is a component of the flower Carthamus tinctorius L. The present investigation determines whether HSYA can modify the effects of hypoxia on vascular endothelial cells (EC) and its mechanisms. Human EC line (EAhy926) viability was determined using the MTT assay. EC cycle phase distribution was done with PI staining and flow cytometric analysis, and EC apoptosis was done by AnnexinV-FITC detection and the TUNEL assay. The protein levels of VEGF, Bcl-2, Bax, and HIF-1 alpha were determined by ELISA or Western blot analysis, and the mRNA expression of these genes by RT-PCR analysis. HIF-1 alpha transcriptional activity was measured using a reporter gene assay. HSYA improved cell viability under hypoxia in a concentration-dependent manner by attenuating its cycle arrest and inhibiting its apoptosis. HSYA upregulated the bcl-2/bax ratio, which is downregulated under hypoxia, increased VEGF protein concentration and VEGF mRNA expression and enhanced HIF-1 alpha protein accumulation and its transcriptional activity. In conclusion, HSAY could enhance the survival of ECs under hypoxia, which may be correlated with its effect of upregulating the bcl-2/bax ratio and promoting HIF-1 alpha protein accumulation, which increases VEGF. These findings provide evidence for the mechanisms by which HSYA maintains EC survival under hypoxia.

Involvement of Glycogen Synthase Kinase-3β in Palmitate-Induced Human Umbilical Vein Endothelial Cell Apoptosis

BACKGROUND/AIMS

The death of endothelial cells may play a critical role in the development of various vascular diseases, including atherosclerosis. While free fatty acids (FFAs) may stimulate endothelial apoptosis, the molecular and cellular mechanisms of this effect have not been studied intensively. To elucidate the mechanisms involved in FFA-induced endothelial cell apoptosis, we investigated the effect of different pharmacological inhibitors on palmitate-induced apoptosis in human umbilical vein endothelial cells (HUVECs). Interestingly, lithium, a glycogen synthase kinase-3 (GSK-3) inhibitor, showed a strong protective effect.

METHODS AND RESULTS

To examine the involvement of GSK-3beta in palmitate-induced HUVEC apoptosis, its dephosphorylation at Ser9 and enzymatic activation in response to palmitate treatment were monitored by immunoblotting and in vitro kinase assays, respectively. GSK-3beta was dephosphorylated and its enzymatic activity increased in palmitate-treated HUVECs. In addition, pretreatment with other GSK-3beta inhibitors, e.g. SB216763 or TDZD-8, as well as adenoviral transduction with a catalytically inactive GSK-3beta had significant protective effects against palmitate-induced HUVEC apoptosis.

CONCLUSION

These results demonstrate that the GSK-3beta signalling pathway is involved in palmitate-induced HUVEC apoptosis.

The magnitude and time-dependence of the apoptotic response of normal and malignant cells subjected to ionizing radiation versus hyperthermia

PURPOSE

The purpose of the study was to examine the optimal time of exposure and dose of heat and ionizing radiation that results in the killing of human cancer cells in vitro via apoptosis vs. necrosis.

MATERIALS AND METHODS

Human mammary carcinoma, colorectal carcinoma and normal bovine capillary endothelial (BCE) cell lines were subjected to 20 Gy ionizing radiation and 6, 12, 24, and 72 h later assessed for apoptosis using detection of apoptotic bodies and caspase assays. Necrosis was detected by loss of cells from the surface and lactate dehydrogenase (LDH) release. The colorectal carcinoma cells were subjected to hyperthermia using temperatures ranging from 39 - 44 degrees C for 5, 15 or 45 min. exposures and at varying times post-treatment, apoptosis and necrosis were measured.

RESULTS

In response to ionizing radiation, none of the cells underwent necrosis and some cell types apoptosed 24 and 72 h posttreatment. The colorectal cancer cells exhibited a steady increase of apoptosis at 6, 12, and 24 h. When these cells were exposed to 40 degrees C for 5 min, caspases increased within 6 h and a significant fraction (50%) of cells apoptosed. If the time of exposure to 40 degrees C was increased to 15 or 45 min, 80% and 100% of the dying cells apoptosed, respectively. A temperature of 39 degrees C did not cause cell death even after 45 min exposures. If heat was elevated to 42 or 44 degrees C, increased necrosis was observed with a corresponding decrease in apoptosis.

CONCLUSIONS

These studies reveal time and temperature dependent in vitro cell responses to ionizing radiation and water-bath hyperthermia.

Inhibition of apoptosis by menadione on exposure to UVA

Quinones are widely distributed in the environment, both as natural products and as pollutants. This paper reports that one of the simplest quinones, 2-methyl-1,4-naphthoquinone (menadione), effectively inhibited apoptosis in the presence of UVA. Menadione suppressed the apoptosis induced by serum depletion and cell detachment. This effect was significantly enhanced by UVA irradiation. An antioxidant, N-acetylcysteine, completely inhibited the antiapoptotic effects of both menadione itself and menadione plus UVA, and peroxidation of the cells after treatment was observed using a probe to detect the intracellular production of peroxides. By contrast, 2-hydroxy-1,4-naphtoquinone (lawsone) showed no antiapoptotic effect in the presence or absence of UVA. Lawsone is reported not to undergo the redox process that produces reactive oxygen species. These results indicated that intracellular peroxidation contributed to the antiapoptotic effects of both menadione itself and menadione plus UVA. Dysregulation of the apoptotic process is critical to carcinogenesis. The photosensitization of quinone compounds as it relates to the inhibition of apoptosis should be examined in the future.

Enhancement of quinone redox cycling by ascorbate induces a caspase-3 independent cell death in human leukaemia cells. An in vitro comparative study

Since the higher redox potential of quinone molecules has been correlated with enhanced cellular deleterious effects, we studied the ability of the association of ascorbate with several quinones derivatives (having different redox potentials) to cause cell death in K562 human leukaemia cell line. The rationale is that the reduction of quinone by ascorbate should be dependent of the quinone half-redox potential thus determining if reactive oxygen species (ROS) are formed or not, leading ultimately to cell death or cell survival. Among different ROS that may be formed during redox cycling between ascorbate and the quinone, the use of different antioxidant compounds (mannitol, desferal, N-acetylcysteine, catalase and superoxide dismutase) led to support H2O2 as the main oxidizing agent. We observed that standard redox potentials, oxygen uptake, free ascorbyl radical formation and cell survival were linked. The oxidative stress induced by the mixture of ascorbate and the different quinones decreases cellular contents of ATP and GSH while caspase-3-like activity remains unchanged. Again, we observed that quinones having higher values of half-redox potential provoke a severe depletion of ATP and GSH when they were associated with ascorbate. Such a drop in ATP content may explain the lack of activation of caspase-3. In conclusion, our results indicate that the cytotoxicity of the association quinone/ascorbate on K562 cancer cells may be predicted on the basis of half-redox potentials of quinones.

Autologous bone marrow cell transplantation improves left ventricular function in rabbit hearts with cardiomyopathy via myocardial regeneration-unrelated mechanisms

Recent studies suggest transplanted bone marrow cells (BMCs) can be used to reconstitute coronary vessels and myocardium following acute myocardial infarction, thereby improving cardiac function. We sought to investigate the therapeutic potential of BMC transplantation in the treatment of nonischemic cardiomyopathy. Experimental cardiomyopathy was produced by treating rabbits for 8 weeks with doxorubicin (2 mg/kg per week). Two weeks after the treatment was finished, freshly aspirated BMCs or an equivalent volume of phosphate-buffered saline was injected directly into the left ventricular free wall. Four weeks later, heart function was examined during perfusion on a Langendorff apparatus. Left ventricular developed pressure and +/-dp/dt were significantly better in the transplantation group, among which echocardiography also showed significantly better ejection fractions. In addition, left ventricular weights as a fraction of body weight and left ventricular wall thicknesses were both lower in rabbits transplanted with BMCs than in controls. Immunohistochemical analyses carried out 2 weeks after transplantation showed no new myocardium and a very small number of endothelial cells originating from BMCs. On the other hand, immunoblotting revealed upregulated expression of transforming growth factor-beta1 and downregulated expression of matrix metalloproteinase-1 and tumor necrosis factor-alpha following BMC transplantation. In conclusion, autologous BMC transplantation into cardiomyopathic rabbit hearts ameliorates the decline in ventricular function without regenerating cardiomyocytes, most likely by altering expression of various cytokines.

Hypoxia of endothelial cells leads to MMP-2-dependent survival and death

Exposure of endothelial cells (ECs) to hypoxia has separately been shown to induce their angiogenesis or death. Matrix metalloproteinase (MMP)-2 is associated with EC angiogenesis, although recent studies also implicate this molecule in EC death. We studied the effect of hypoxia in the absence or presence of TNF-alpha (characteristic of the inflammatory microenvironment accompanying hypoxia) on MMP-2 expression and its role in angiogenesis (proliferation, migration, and tube formation) and in the death of primary human umbilical vein endothelial cells (HUVECs). Hypoxia alone (24-48 h in 0.3% O(2) in the hypoxic chamber) and furthermore, when combined with TNF-alpha, significantly enhanced MMP-2 expression and activity. Hypoxia also led to a reduction in membrane type 1 MMP (MT1-MMP) and tissue inhibitor of metalloproteinase-2 mRNA and protein while enhancing the expression of alpha(v)beta(3) integrin and the cytoskeletal protein phosphopaxillin. Moreover, hypoxia led to colocalization of alpha(v)beta(3) and MMP-2, but not MT1-MMP, with phosphopaxillin in ECs. These results suggest MT1-MMP-independent activation of MMP-2 during hypoxia and support interactions between the ECM, integrins, and the cytoskeleton in hypoxia-induced MMP-2-related functions. Hypoxia enhanced EC migration in an MMP-2-dependent manner while leading to a reduction of cell number via their apoptosis, which was also dependent on MMP-2. In addition, hypoxia caused an aberrant tubelike formation on Matrigel that appeared to be unaffected by MMP-2. The hypoxia-induced, MMP-2-dependent migration of ECs is in accordance with the proangiogenic role ascribed to MMP-2, while the involvement of this protease in the hypoxia-related death of ECs supports an additional apoptotic role for this protease. Hence, in the hypoxic microenvironment, MMP-2 appears to have a dual autocrine role in determining the fate of ECs.

Reactive oxygen species and human inflammatory periodontal diseases

Reactive oxygen species (ROS) have emerged as important signaling molecules in the regulation of various cellular processes. They can be generated by the mitochondrial electron transport chain in mitochondria and activation of polymorphonuclear leukocytes (PMN) during inflammatory conditions. Excessive generation of ROS may result in attack of and damage to most intracellular and extracellular components in a living organism. Moreover, ROS can directly induce and/or regulate apoptotic and necrotic cell death. Periodontal pathologies are inflammatory and degenerative diseases. Several forms of periodontal diseases are associated with activated PMN. Damage of tissues in inflammatory periodontal pathologies can be mediated by ROS resulting from the physiological activity of PMN during the phagocytosis of periodontopathic bacteria.

Oxidative Stress Promotes Endothelial Cell Apoptosis and Loss of Microvessels in the Spontaneously Hypertensive Rats

OBJECTIVE

Endothelial cell apoptosis caused by oxidative stress may lead to the loss of microvessels (rarefaction) in hypertension. We examine here the effects of antioxidants on cell apoptosis and rarefaction.

METHODS AND RESULTS

The juvenile spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were treated with superoxide scavengers, Tempol or Tiron, during growth. After the treatment, oxidative stress status, endothelial cell apoptosis rate, and microvessel length density in skeletal muscle and mesentery were evaluated in comparison with age-matched controls. Untreated 16-week-old SHR had higher oxidative stress (P<0.01) and cell apoptosis rate (P<0.05) and lower microvessel length density (371+/-17 mm/mm3 [P<0.01]) compared with age-matched WKY rats (435+/-15 mm/mm3). In the SHR, but not in WKY rats, systemically applied antioxidants attenuated oxidative stress and cell apoptosis rate (P<0.05 versus untreated controls) and prevented the loss of microvessels (411+/-15 mm/mm3 for Tempol [P<0.01 versus untreated control] and 399+/-17 mm/mm3 for Tiron [P<0.05]).

CONCLUSIONS

Antioxidant treatment with cell-permeable superoxide scavengers inhibits endothelial cell apoptosis and prevents microvessel rarefaction in the SHR during growth.

Selective role for superoxide in InsP3 receptor-mediated mitochondrial dysfunction and endothelial apoptosis

Reactive oxygen species (ROS) play a divergent role in both cell survival and cell death during ischemia/reperfusion (I/R) injury and associated inflammation. In this study, ROS generation by activated macrophages evoked an intracellular Ca2+ ([Ca2+]i) transient in endothelial cells that was ablated by a combination of superoxide dismutase and an anion channel blocker. [Ca2+]i store depletion, but not extracellular Ca2+ chelation, prevented [Ca2+]i elevation in response to O2*- that was inositol 1,4,5-trisphosphate (InsP3) dependent, and cells lacking the three InsP3 receptor (InsP3R) isoforms failed to display the [Ca2+]i transient. Importantly, the O2*--triggered Ca2+ mobilization preceded a loss in mitochondrial membrane potential that was independent of other oxidants and mitochondrially derived ROS. Activation of apoptosis occurred selectively in response to O2*- and could be prevented by [Ca2+]i buffering. This study provides evidence that O2*- facilitates an InsP3R-linked apoptotic cascade and may serve a critical function in I/R injury and inflammation.

Expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in human preeclamptic placenta: possible implications in the process of trophoblast apoptosis

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was originally identified as a receptor for oxidatively modified low-density lipoprotein. It has been reported that oxidative stress and hyperlipidemia play important roles in the etiology of preeclampsia, and that placental oxidative stress may stimulate syncytiotrophoblast apoptosis in preeclampsia. In this study, we examined the expression of LOX-1 in the human placentas of normal pregnancies and in preeclampsia using immunohistochemistry and Western blot analysis, and proposed that LOX-1 has a role in trophoblast apoptosis. To analyze apoptotic activity, the expression of the specific caspase cleavage site within cytokeratin 18 was assessed immunohistochemically using the monoclonal antibody M30 CytoDeath. Both LOX-1 and M30 immunoreactivity occurred predominantly in syncytiotrophoblasts. A significantly higher number of LOX-1 and M30-positive cells were found in preeclamptic placentas than in normal placentas. The number of M30-positive cells correlated with the apoptotic index of trophoblasts determined by TdT-mediated dUTP nick-end labeling (TUNEL). Syncytiotrophoblasts showing apoptotic activity were immunopositive to LOX-1 by double immunohistochemical fluorescence. We suggest that the functional role of syncytiotrophoblasts in placental dysfunction results from the localization and upregulation of LOX-1 in the preeclamptic placenta, possible implications in upregulation of syncytiotrophoblast apoptotic activity in preeclampsia.

Inhibition by doxycycline of angiogenesis in the chicken chorioallantoic membrane (CAM)

Doxycycline, a tetracycline derivative, has many properties in addition to its antibiotic activity, including inhibition of matrix metalloproteinases (MMPs) and the ability to chelate divalent cations including Ca(2+). It has been shown to inhibit endothelial cell growth in vitro, and reduce the development of experimental tumours, especially bone metastasis in a model of breast cancer. We examined the effects of doxycycline on angiogenesis in the chicken chorioallantoic membrane (CAM) model, and showed that doxycycline will cause loss of the chorionic plexus in CAMs when applied at day 8 of incubation, and the duration of this inhibition was dose-dependent. Repeated doses prolonged the inhibition, but following removal of the doxycycline there was rapid recovery of the chorionic plexus. The effects of doxycycline are in part mimicked by the MMP inhibitor 1,10-phenanthroline, and more closely by the Ca(2+)-chelating agent EGTA. Doxycycline was equally effective in causing loss of the chorionic plexus by day 11 in CAMs, a time at which the blood vessels are established. Doxycycline has important potential as an antiangiogenic treatment. It is capable of inhibiting angiogenesis in an in vivo model, including the removal of comparatively mature endothelial cells. The response is sensitive to the dosing regimen and the effect is rapidly reversible.

Detection of Apoptosis and Drug Resistance of Human Breast Cancer Cells to Taxane Treatments Using Quartz Crystal Microbalance Biosensor Technology

Taxanes are used for the treatment of many human cancers, as first- and second-line chemotherapeutics. In the course of treatment many patients develop resistance or hypersensitivity to one form of taxane and require a different taxane to rescue the therapeutic benefit of the drug. There is currently no method to reliably predict tumor responses to taxanes prior to therapy or when resistance or hypersensitivity develops. We adapted the quartz crystal microbalance (QCM) biosensor technique to study responses of human mammary epithelial tumor cells to taxanes. Studies indicate that stable frequency and resistance levels are reached at 24 h. Cells in the QCM can then be treated with taxanes and responses monitored in real time via frequency and resistance changes reflecting alterations of cell mass distribution and viscoelastic properties. Distinct shifts in frequency and resistance accurately predicted apoptosis or resistance to treatment, as determined in parallel convention assays. QCM analysis accurately predicted docetaxel was more effective than paclitaxel and MCF-7 cells were more resistant to taxanes compared to MDA-MB-231 cells. These studies suggest "signature" patterns for taxane responsivity could be compared to those of patient biopsy samples to predict therapy outcome prior to treatment for initial therapy or to rescue therapy efficacy.

Histone hypoacetylation is involved in 1,10-phenanthroline?Cu2+-induced human hepatoma cell apoptosis

The 1,10-orthophenanthroline (OP)-Cu(2+) combination, one generally used reactive oxygen species (ROS) generation system, is known to induce cell apoptosis, but the mechanism of ROS generation in this process remains unclear. Here we found that in the presence of 5 microM Cu(2+), OP inhibited histone acetyltransferase (HAT) activity, resulting in decreased acetylation in both histone H3 and H4. This inhibition of histone acetylation and HAT activity was significantly attenuated by preventing or scavenging ROS generation with the Cu(2+) chelator of bathocuproine disulfonate, or the antioxidants of N-acetyl-cysteine and mannitol, respectively, indicating the involvement of ROS generation in OP-Cu(2+) -induced histone hypoacetylation. At the same time, this ROS generation is found to be involved in OP-Cu(2+) -induced apoptosis in human hepatoma Hep3B cells. The important role of histone hypoacetylation in the induction of apoptosis was also proven by the marked diminution of apoptosis by 100 nM trichostatin A, a specific inhibitor of histone deacetylase, or the overexpression of p300, an HAT protein. Collectively, these observations suggest that histone hypoacetylation represents one unrevealed mechanism involved in the in vivo function of OP-Cu(2+) -generated ROS, at least in their induction of cell apoptosis.

Retinoids and TIMP1 prevent radiation-induced apoptosis of capillary endothelial cells

Radiation-induced changes in capillaries constitute a basic injury in the pathogenesis of chronic radiation damage to the heart, lung, liver, kidney and brain. It is important to identify new radioprotectors for capillary endothelial cells for use during radiotherapy to minimize normal tissue damage and possibly to increase the deliverable dose. Previously we demonstrated that exposure to ionizing radiation (10 Gy) results in death of bovine adrenal capillary endothelial cells in confluent monolayers by apoptosis. We also showed that retinoids inhibit the growth of endothelial cells, induce their differentiation, down-regulate matrix metalloproteinase (MMP) production, and up-regulate tissue inhibitors of matrix metalloproteinases (TIMPs). In the present studies, we demonstrated that radiation (10 Gy) induced an immediate increase in the amounts and activation of MMP1 and MMP2 in the cell fraction and medium of bovine capillary endothelial cells followed by an incidence of apoptosis. We also obtained data indicating that radiation-induced apoptosis can be inhibited by exposing bovine capillary endothelial cells to all-trans-retinol or all-trans-retinoic acid for 6 days before irradiation, even when the vitamins were removed 24 h before irradiation. Finally, we determined that inhibition of MMPs by TIMP was sufficient to block radiation-induced apoptosis, suggesting that the mechanism of protection by retinoids is through the alteration of levels of MMPs and TIMPs produced by the cells.

Pesticide mixtures potentiate the toxicity in murine thymocytes

The immunotoxic risks of multiple pesticide exposure were evaluated. C57BL/6 mouse thymocytes were exposed to lindane, malathion, and permethrin, either separately or in mixtures of two pesticides, in vitro. These pesticide exposures caused both apoptotic and necrotic cell death in thymocytes as evaluated by flow cytometric analysis in combination with 7-aminoactinomycin-D (7-AAD), Annexin-V/propidium iodide (PI) staining assays and lactate dehydrogenase release assays. When cells exposed to mixtures of two pesticides, a significantly greater than additive interaction was observed in both apoptotic and necrotic populations of cells. The gel electrophoresis of DNA of cells showed DNA ladder formation with limited genomic DNA and increased laddering in mixture exposures. Based on these findings, it is suggested that these pesticides are potent immunotoxicants, in vitro, and that the mechanism of cytotoxicity observed upon exposure to these pesticides may, at least in part, be due to induction of apoptosis. We also provided evidence that induction of drug metabolizing mixed function oxidase system with lindane may, in part, be responsible for the potentiation of cytotoxicity in the combined exposures. As more information is obtained on the potential immunotoxic effects of pesticides, further insights will be gained for the risk assessment of these environmental pollutants.

Free fatty acids trigger apoptosis and inhibit cell cycle progression in human vascular endothelial cells

Plasma free fatty acid (FFA) concentrations are increased in states of insulin resistance and impair endothelial function. Because the underlying mechanisms are largely unknown, we examined selected, purified FFAs' (100-300 micromol/l, 24-48 h) action on apoptosis, cell cycle distribution, and associated gene/protein expression in human umbilical vein endothelial cells (HUVECs). Stearic acid, but not oleic acid, time and concentration dependently increased endothelial apoptosis by fivefold (n=6, P<0.01), whereas polyunsaturated FFAs (PUFAs; linoleic, gamma-linolenic, and arachidonic acid) exerted proapoptotic activity only at 300 micromol/l (P<0.05). Proapoptotic FFA action increased with FFAs' number of double bonds and with protein expression of the apoptosis promotor bak. The G0/G1 cell cycle arrest (n=6, P<0.05) induced by stearic acid (+14%) and PUFAs (+30%) is reflected by up-regulation of p21(WAF-1/Cip1). In addition, all FFAs concentration dependently reduced (P<0.05) gene/protein expression of clusterin (-54%), NF-kappaB's inhibitor, IkappaBalpha (-50%), endothelin-1 (-44%), and endothelial NO synthase (-44%). Plasma samples obtained from individuals with elevated plasma FFAs (372+/-22 micromol/l) increased endothelial apoptosis by 4.2-fold (P<0.001, n=10) compared with intra-individually matched low plasma FFA (56+/-21 micromol/l) conditions, underlining the results obtained by defined FFA stimulation. In conclusion, FFA structure differently affects endothelial cell proliferation and apoptosis, both representing key factors in the development of micro- and macrovascular dysfunction.

Oxidative stress and apoptosis interact and cause emphysema due to vascular endothelial growth factor receptor blockade

We have previously demonstrated that a failure of pulmonary endothelial cell survival induced by vascular endothelial growth factor (VEGF) receptor blockade results in lung alveolar septal cell apoptosis and emphysema. Because apoptosis and oxidative stress may be pathobiologically linked, we hypothesized that oxidative stress has a central role in alveolar septal cell apoptosis and emphysema induced by VEGF receptor blockade. When compared with control animals, rats treated with the VEGF receptor blocker SU5416 showed increased alveolar enlargement, alveolar septal cell apoptosis, and expression of markers of oxidative stress, all of which were prevented by the superoxide dismutase mimetic M40419. The preservation of lung structure in SU5416+M40419-treated lungs was associated with increased septal cell proliferation, and enhanced phosphorylation of the prosurvival and antiapoptotic Akt, when compared with SU5416-treated lungs. Consistent with a positive feedback interaction between oxidative stress and apoptosis, we found that apoptosis predominated in areas of oxidative stress, and that apoptosis blockade by a broad spectrum caspase inhibitor markedly reduced the expression of markers of oxidative stress induced by SU5416 treatment. Oxidative stress and apoptosis, which cause lung cellular destruction in emphysema induced by VEGF receptor blockade, may be important mediators common to human and experimental emphysema.

Menadione causes endothelial barrier failure by a direct effect on intracellular thiols, independent of reactive oxidant production

Menadione (MQ), a quinone used with cancer chemotherapeutic agents, causes cytotoxicity to endothelial cells (EC). Previous studies have suggested that MQ induces an oxidative stress and dysfunction in EC by either increasing hydrogen peroxide (H(2)O(2)) production or depleting intracellular glutathione (GSH), the main intracellular antioxidant. Since a primary function of EC is to form a barrier to fluid movement into tissues, protecting organs from edema formation and dysfunction, our aim was to see if MQ would cause a barrier dysfunction and to ascertain the mechanism. Using diffusional permeability to fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) as a measure of barrier function, we found that 15 micro M MQ incubated with a bovine pulmonary artery EC (BPAEC) monolayer for 4 h produced a profound barrier failure ( approximately 7-fold increase in permeability) with a parallel fall in glutathione, almost to depletion. These two events were highly correlated. Immunofluorescent imaging showed formation of paracellular holes consistent with a loss or rearrangement of cell-cell and cell-matrix adhesion molecules. H(2)O(2) (100 micro M), a concentration which gave about the same increase in permeability as MQ, only slightly decreased GSH concentration. Antioxidants, such as catalase (CAT) and dimethylthiourea (DMTU), which were able to block the H(2)O(2)-induced changes, had no effect on the MQ-induced permeability and GSH changes, suggesting that H(2)O(2) was not involved in MQ-induced effects. MQ caused a severe EC cytotoxicity as judged by lactate dehydrogenase (LDH) leakage from the EC, whereas H(2)O(2) caused only a minor increase. Also, MQ profoundly inhibited the activities of glucose-6-phosphate dehydrogenase (G6PDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), key thiol enzymes involved in glutathione and ATP metabolism, whereas H(2)O(2) produced only a slight decrease in these activities. We conclude that the cytotoxicity of MQ and resulting barrier dysfunction correlate with GSH depletion and inactivation of key metabolic enzymes, compromising antioxidant defenses, rather than being consistent with H(2)O(2)-mediated oxidative stress.

The association of vitamins C and K3 kills cancer cells mainly by autoschizis, a novel form of cell death. Basis for their potential use as coadjuvants in anticancer therapy

Deficiency of alkaline and acid DNase is a hallmark in all non-necrotic cancer cells in animals and humans. These enzymes are reactivated at early stages of cancer cell death by vitamin C (acid DNase) and vitamin K(3) (alkaline DNase). Moreover, the coadministration of these vitamins (in a ratio of 100:1, for C and K(3), respectively) produced selective cancer cell death. Detailed morphological studies indicated that cell death is produced mainly by autoschizis, a new type of cancer cell death. Several mechanisms are involved in such a cell death induced by CK(3), they included: formation of H(2)O(2) during vitamins redox cycling, oxidative stress, DNA fragmentation, no caspase-3 activation, and cell membrane injury with progressive loss of organelle-free cytoplasm. Changes in the phosphorylation level of some critical proteins leading to inactivation of NF-kappaB appear as main intracellular signal transduction pathways. The increase knowledge in the mechanisms underlying cancer cells death by CK(3) may ameliorate the techniques of their in vivo administration. The aim is to prepare the introduction of the association of vitamins C and K(3) into human clinics as a new, non-toxic adjuvant cancer therapy.

TGF-beta 1 attenuates myocardial ischemia-reperfusion injury via inhibition of upregulation of MMP-1

Ischemia-reperfusion (I/R) is thought to upregulate the expression and activity of matrix metalloproteinases (MMPs), which regulate myocardial and vascular remodeling. Previous studies have shown that transforming growth factor-beta(1) (TGF-beta(1)) can attenuate myocardial injury induced by I/R. TGF-beta(1) is also reported to suppress the release of MMPs. To study the modulation of MMP-1 by TGF-beta(1) in I/R myocardium, Sprague-Dawley rats were given saline and subjected to 1 h of myocardial ischemia [total left coronary artery (LCA) ligation] followed by 1 h of reperfusion (n = 9). Parallel groups of rats were pretreated with recombinant TGF-beta(1) (rTGF-beta(1), 1 mg/rat, n = 9) before reperfusion or exposure to sham I/R (control group). I/R caused myocardial necrosis and dysfunction, indicated by decreased first derivative of left ventricular pressure, mean arterial blood pressure, and heart rate (all P < 0.01 vs. sham-operated control group). Simultaneously, I/R upregulated MMP-1 (P < 0.01). Treatment of rats with rTGF-beta(1) reduced the extent of myocardial necrosis and dysfunction despite I/R (all P < 0.01). rTGF-beta(1) treatment also inhibited the upregulation of MMP-1 in the I/R myocardium (P < 0.05). To determine the direct effect of MMP-1 on the myocardium, isolated adult rat myocytes were treated with active MMP-1, which caused injury and death of cultured myocytes, measured as lactate dehydrogenase release and trypan blue staining, in a dose- and time-dependent manner (P < 0.05). Pretreatment with PD-166793, a specific MMP inhibitor, attenuated myocardial injury and death induced by active MMP-1. The present study for the first time shows that MMP-1 can directly cause myocyte injury or death and that attenuation of myocardial I/R injury by TGF-beta(1) may, at least partly, be mediated by the inhibition of upregulation of MMP-1.

Review article: oxidative stress as a pathogenic factor in inflammatory bowel disease--radicals or ridiculous?

Virtually all inflammatory mediators investigated to date seem to be dysregulated in the inflamed intestinal mucosa of patients with inflammatory bowel disease. However, which of these are actually involved in the initiation and perpetuation of intestinal tissue damage is still not fully understood. Amongst these mediators are the reactive oxygen metabolites, produced in large amounts by the massively infiltrating leucocytes. These reactive oxygen metabolites are believed to constitute a major tissue-destructive force and may contribute significantly to the pathogenesis of inflammatory bowel disease. This paper provides a concise overview of reactive oxygen metabolite biochemistry, the types of cell and tissue damage potentially inflicted by them, and the endogenous antioxidants which should prevent these harmful effects. An up-to-date summary of the available human experimental data suggests that reactive oxygen metabolite-mediated injury is important in both the primary and downstream secondary pathophysiological mechanisms underlying intestinal inflammation. Nonetheless, how the individual components of the mucosal antioxidant enzymatic cascade respond to inflammatory conditions is a neglected area of research. This particular aspect of intestinal mucosal oxidative stress therefore merits further study, in order to provide a sound, scientific basis for the design of antioxidant-directed treatment strategies for inflammatory bowel disease patients.