Mechanisms of H2O2-induced oxidative stress in endothelial cells

Coyle, Christian H.; Martínez, Luis Javier; Coleman, Mitchell C.; Spitz, Douglas R.; Weintraub, Neal L.; Kader, Khalid N.

doi:10.1016/j.freeradbiomed.2006.02.017

Cited by 125 publications

(79 citation statements)

References 250 publications

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“…24 In the present study we observed that apocynin is able to suppress the activation of the mitogen-activated protein kinases extracellular signalregulated kinase 1/2 and p38, as well as Akt, in response to H 2 O 2 . Although H 2 O 2 has been suggested to activate the NADPH oxidase in vascular cells, 25 this effect appears to be unrelated to oxidase activation, because a similar observation was made with menadione, an intracellular generator of ROS and redox cycler, and in cells treated with the highly effective unselective NADPH oxidase inhibitor DPI. These data establish that, at least in cultured cells, the predominant action of apocynin is the scavenging of ROS and not NADPH oxidase inhibition.…”

Section: Discussionmentioning

confidence: 81%

Apocynin Is Not an Inhibitor of Vascular NADPH Oxidases but an Antioxidant

et al. 2008

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Abstract-A large body of literature suggest that vascular reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases are important sources of reactive oxygen species. Many studies, however, relied on data obtained with the inhibitor apocynin (4Ј-hydroxy-3Јmethoxyacetophenone). Because the mode of action of apocynin, however, is elusive, we determined its mechanism of inhibition on vascular NADPH oxidases. In HEK293 cells overexpressing NADPH oxidase isoforms (Nox1, Nox2, or Nox4), apocynin failed to inhibit superoxide anion generation detected by lucigenin chemiluminescence. In contrast, apocynin interfered with the detection of reactive oxygen species in assay systems selective for hydrogen peroxide or hydroxyl radicals. Importantly, apocynin interfered directly with the detection of peroxides but not superoxide, if generated by xanthine/xanthine oxidase or nonenzymatic systems. In leukocytes, apocynin is a prodrug that is activated by myeloperoxidase, a process that results in the formation of apocynin dimers. Endothelial cells and smooth muscle cells failed to form these dimers and, therefore, are not able to activate apocynin. Dimer formation was, however, observed in Nox-overexpressing HEK293 cells when myeloperoxidase was supplemented. As a consequence, apocynin should only inhibit NADPH oxidase in leukocytes, whereas in vascular cells, the compound could act as an antioxidant. Indeed, in vascular smooth muscle cells, the activation of the redox-sensitive kinases p38-mitogen-activate protein kinase, Akt, and extracellular signal-regulated kinase 1/2 by hydrogen peroxide and by the intracellular radical generator menadione was prevented in the presence of apocynin. These observations indicate that apocynin predominantly acts as an antioxidant in endothelial cells and vascular smooth muscle cells and should not be used as an NADPH oxidase inhibitor in vascular systems. Key Words: apocynin Ⅲ NADPH oxidase Ⅲ Nox1 Ⅲ Nox4 Ⅲ leukocytes Ⅲ reactive oxygen species R eactive oxygen species (ROS) have a strong impact on vascular homeostasis. 1 ROS originate from several sources, including xanthine oxidase, cytochrome P450 monooxygenases, mitochondria, and uncoupled NO synthase, as well as from the proteins of the Nox family, the NADPH oxidases. The identification of the individual contribution of these generator systems to oxidative burden has been a focus of an impressive amount of publications. The motivation of these studies is that a site-directed ROS lowering therapy to inhibit individual generator systems should be superior to the presently unsuccessful approaches with antioxidants in preventing ROS-dependent cardiovascular diseases. 2 Although it is generally appreciated that molecular techniques involving antisense oligonucleotides, small-interfering RNA, or transgenic animals are to be preferred to pharmacological inhibitors to characterize the contribution of individual ROS generator systems, the latter studies still represent the majority of scientific contributions in the field.Different from N...

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Section: Discussionmentioning

confidence: 81%

Apocynin Is Not an Inhibitor of Vascular NADPH Oxidases but an Antioxidant

et al. 2008

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“…6), suggesting EGCG (as well as PP-60 and ECG) suppresses ONOO − formation and/or modulates nitrite levels. Previous studies have documented the oxidative effects of H 2 O 2 in vascular cells, demonstrating its use as a short-term stimulus for oxidative stress (Coyle et al, 2006;Li et al, 2001). In a study by Coyle et al (2006), H 2 O 2 was found to stimulate increased formation of O 2 −· in endothelial cells but not in bladder cells, suggesting a potential for differential ROS signaling between endothelial and urothelial cells.…”

Section: Discussionmentioning

confidence: 94%

“…H 2 O 2 is an oxidative agent, which has been shown to induce ROS formation in multiple cell types (Coyle et al, 2006;Li et al, 2001 (Fig. 3B), in comparison to control cells (p < 0.01, n=12-16).…”

Section: Pp-60 Ecg and Egcg Catechins Protect Human Bladder Cells Frmentioning

confidence: 93%

Antioxidant effects of green tea and its polyphenols on bladder cells

et al. 2008

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Genitourinary tract inflammation/ailments affect the quality of life and health of a large segment of society. In recent years, studies have demonstrated strong anti-oxidant effects of green tea and its associated polyphenols in inflammatory states. This in vitro study examined the antioxidant capabilities (and putative mechanisms of action) of green tea extract (GTE), polyphenon-60 (PP-60, 60 % pure polyphenols), (−)-epicatechin-3-gallate (ECG) and (−)-epigallocatechin-3-gallate (EGCG) in normal/malignant human bladder cells following catechin treatment ± 1 mM H 2 O 2 (oxidative agent). Cell viability, apoptosis and reactive oxygen species (ROS) formation were evaluated. Our results showed that H 2 O 2 exposure significantly reduced normal (UROtsa) and highgrade (TCCSUP, T24) bladder cancer (BlCa) cell viability compared with control-treated cells (p < 0.001). No affect on low-grade RT4 and SW780 BlCa cell viability was observed with exposure to H 2 O 2 . Compared to H 2 O 2 -treated UROtsa, treatment with PP-60, ECG and EGCG in the presence of H 2 O 2 significantly improved UROtsa viability (p < 0.01), with strongest effects evoked by ECG. Additionally, though not as effective as in UROtsa cells, viability of both high-grade TCCSUP and T24 BlCa cells, in comparison to H 2 O 2 -treated cells, were significantly improved (p < 0.01) by treatment with PP-60, ECG, and EGCG in the presence of H 2 O 2 . Overall, our findings demonstrate that urothelium cell death via H 2 O 2 -induced oxidative stress is mediated, in part, through superoxide (O 2 −· ), and potentially, direct H 2 O 2 mechanisms, suggesting that green tea polyphenols can protect against oxidative stress/damage and bladder cell death.

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“…Previous studies have implicated various individual components of this pathway in endothelial cell oxidant stress and/or monocyte adhesive interactions with endothelium induced by pharmacologic agents (e.g., LPS, PAF, and H 2 O 2 ) (33,46,(57)(58)(59). The significance of our findings is 1) the use of an in vitro construct of the pulmonary vascular-interstitial interface using cells relevant to sepsis-induced ALI/ARDS (e.g., AM), and 2) the sequential positioning of these components into a pathway responsible for endothelial-dependent PMN migration.…”

Section: Discussionmentioning

confidence: 99%

Alveolar Macrophages from Septic Mice Promote Polymorphonuclear Leukocyte Transendothelial Migration via an Endothelial Cell Src Kinase/NADPH Oxidase Pathway

Wang

Tao

Yang

et al. 2008

The Journal of Immunology

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Alveolar macrophages (AMφ) have been implicated in the polymorphonuclear leukocyte (PMN) recruitment to the lungs during sepsis. Using an in vivo murine model of sepsis (feces in the peritoneum), we show that peritonitis leads to increased activation of AMφ and PMN migration into pulmonary alveoli. To assess cellular mechanisms, an in vitro construct of the pulmonary vascular-interstitial interface (murine AMφ, pulmonary endothelial cells, and PMN) and a chimera approach were used. Using immunologic (Abs) and genetic blockade (CXCR2-deficient AMφ), we show that CXC chemokines in septic plasma are responsible for the activation of AMφ. The activated AMφ can promote PMN transendothelial migration, even against a concentration gradient of septic plasma, by generating platelet-activating factor and H2O2. Platelet-activating factor/H2O2 induce an oxidant stress in the adjacent endothelial cells, an event that appears to be a prerequisite for PMN transendothelial migration, since PMN migration is abrogated across Cu/Zn-superoxide dismutase overexpressing endothelial cells. Using gp91-deficient endothelial cells, we show that NADPH oxidase plays an important role in the AMφ-induced PMN transendothelial migration. Pharmacologic/small interfering RNA blockade of Src kinase inhibits AMφ-induced endothelial NADPH oxidase activation and PMN migration. Collectively, our findings indicate that the PMN transendothelial migration induced by septic AMφ is dependent on the generation of superoxide in endothelial cells via the Src kinase/NADPH oxidase signaling pathway.

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Mechanisms of H2O2-induced oxidative stress in endothelial cells

Cited by 125 publications

References 250 publications

Apocynin Is Not an Inhibitor of Vascular NADPH Oxidases but an Antioxidant

Apocynin Is Not an Inhibitor of Vascular NADPH Oxidases but an Antioxidant

Antioxidant effects of green tea and its polyphenols on bladder cells

Alveolar Macrophages from Septic Mice Promote Polymorphonuclear Leukocyte Transendothelial Migration via an Endothelial Cell Src Kinase/NADPH Oxidase Pathway

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