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Potentiation of hydrogen peroxide toxicity: From catalase inhibition to stable DNA-iron complexes. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2016; 773:274-281. [PMID: 28927535 DOI: 10.1016/j.mrrev.2016.08.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 08/29/2016] [Indexed: 12/15/2022]
Abstract
Hydrogen peroxide (H2O2) is unique among general toxins, because it is stable in abiotic environments at ambient temperature and neutral pH, yet rapidly kills any type of cells by producing highly-reactive hydroxyl radicals. This life-specific reactivity follows the distribution of soluble iron, Fe(II) (which combines with H2O2 to form the famous Fenton's reagent),Fe(II) is concentrated inside cells, but is virtually absent outside them. Because of the immediate danger of H2O2, all cells have powerful H2O2 scavengers, the equally famous catalases, which enable cells to survive thousand-fold higher concentrations of H2O2 and, in combination with adequate movement of H2O2 across membranes, make the killing H2O2 concentrations virtually impractical to generate in vivo. And yet, low concentrations of H2O2 are somehow used as an efficient biological weapon. Here we review several examples of how cells potentiate H2O2 toxicity with other chemicals. At first, these potentiators were thought to simply inhibit catalases, but recent findings with cyanide suggest that potentiators mostly promote the other side of Fenton's reaction, recruiting iron from cell depots into stable DNA-iron complexes that, in the presence of elevated H2O2, efficiently break duplex DNA, pulverizing the chromosome. This multifaceted potentiation of H2O2 toxicity results in robust and efficient killing.
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Wang F, Liu HM, Irwin MG, Xia ZY, Huang Z, Ouyang J, Xia Z. Role of protein kinase C β2 activation in TNF-α-induced human vascular endothelial cell apoptosis. Can J Physiol Pharmacol 2009; 87:221-9. [PMID: 19295663 DOI: 10.1139/y09-004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The circulatory inflammatory cytokine tumor necrosis factor alpha (TNF-α) is increased in pathologic conditions that initiate or exacerbate vascular endothelial injury, such as diabetes. Protein kinase C (PKC) has been shown to play a critical role in TNF-α-induced human endothelial cell apoptosis. However, the relative roles played by specific isoforms of PKC in TNF-α-induced human endothelial cell apoptosis have not been addressed. We investigated the effects of a selective PKCβ2 inhibitor (CGP53353) on TNF-α-induced apoptosis in human vascular endothelial cells (cell line ECV304) and on the production of reactive oxygen species and nitric oxide, and compared its effects with rottlerin, a reagent that has been shown to reduce PKCδ protein levels. Cultured human vascular endothelial cells (ECV304) were treated for 24 h with one of 4 regimes: 40 ng/mL TNF-α alone (TNF-α), TNF-α with 10 µmol/L rottlerin (T+rottlerin), TNF-α with 1 µmol/L CGP53353 (T+CGP), or untreated (control). Cell viability was measured by MTT assay, and cell apoptosis was assessed by flow cytometry. TNF-α-induced endothelial cell apoptosis was associated with dramatic increases in production of intracellular hydrogen peroxide (approximately 20 times greater than control) and superoxide (approximately 16 times greater than control), as measured by dichlorofluorescein and dihydroethidium fluorescent staining, respectively. This increase was accompanied by reduced activity of superoxide dismutase and glutathione peroxidase and, subsequently, an increase in the lipid peroxidation product malondialdehyde. CGP53353, but not rottlerin, abolished or attenuated all these changes. We conclude that PKCβ2 plays a major role in TNF-α-induced human vascular endothelial cell apoptosis.
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Affiliation(s)
- Fang Wang
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
| | - Hui-min Liu
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
| | - Michael G. Irwin
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
| | - Zhong-yuan Xia
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
| | - Zhiyong Huang
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
| | - Jingping Ouyang
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
| | - Zhengyuan Xia
- Anesthesiology Research Laboratory, Renmin Hospital, Wuhan University, Wuhan, Hubei, China
- Department of Anesthesiology, University of Hong Kong, Pokfulam Road, Hong Kong, China
- Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan, China
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