pro-oxidant

Transition metals can serve as pro-oxidants. For example, chronic manganism is a classic "pro-oxidant" disease.{{cite journal |vauthors=Han SG, Kim Y, Kashon ML, Pack DL, Castranova V, Vallyathan V |title=Correlates of oxidative stress and free-radical activity in serum from asymptomatic shipyard welders |journal=Am. J. Respir. Crit. Care Med. |volume=172 |issue=12 |pages=1541–8 |date=December 2005 |pmid=16166614 |doi=10.1164/rccm.200409-1222OC |url=http://ajrccm.atsjournals.org/cgi/content/full/172/12/1541}} Another disease associated with the chronic presence of a pro-oxidant transition-series metal is hemochromatosis, associated with elevated iron levels. Similarly, Wilson's disease is associated with elevated tissue levels of copper. Such syndromes tend to be associated with common symptomology. Thus, all are occasional symptoms of (e.g) hemochromatosis, another name for which is "bronze diabetes". The pro-oxidant herbicide paraquat, Wilson's disease, and striatal iron have similarly been linked to human Parkinsonism. Paraquat also produces Parkinsonian-like symptoms in rodents.{{Cn|date=January 2021}}

Fibrosis or scar formation is another pro-oxidant-related symptom. E.g., interocular copper or vitreous chalicosis is associated with severe vitreous fibrosis, as is interocular iron. Liver cirrhosis is also a major symptom of Wilson's disease. The pulmonary fibrosis produced by paraquat and the antitumor agent bleomycin is also thought to be induced by the pro-oxidant properties of these agents. It may be that oxidative stress produced by such agents mimics a normal physiological signal for fibroblast conversion to myofibroblasts.{{Cn|date=January 2021}}

Vitamins that are reducing agents can be pro-oxidants. Vitamin C has antioxidant activity when it reduces oxidizing substances such as hydrogen peroxide,{{cite journal |vauthors=Duarte TL, Lunec J |title=Review: When is an antioxidant not an antioxidant? A review of novel actions and reactions of vitamin C |journal=Free Radic. Res. |volume=39 |issue=7 |pages=671–86 |year=2005 |pmid=16036346 |doi=10.1080/10715760500104025|s2cid=39962659 }} however, it can also reduce metal ions which leads to the generation of free radicals through the Fenton reaction.{{cite journal |vauthors=Carr A, Frei B |title=Does vitamin C act as a pro-oxidant under physiological conditions? |journal=FASEB J. |volume=13 |issue=9 |pages=1007–24 |date=1 June 1999|pmid=10336883 |doi=10.1096/fasebj.13.9.1007|doi-access=free |s2cid=15426564 }}{{cite journal |vauthors=Stohs SJ, Bagchi D |title=Oxidative mechanisms in the toxicity of metal ions |journal=Free Radic. Biol. Med. |volume=18 |issue=2 |pages=321–36 |year=1995 |pmid=7744317 |doi=10.1016/0891-5849(94)00159-H}}

::2 Fe²⁺ + 2 H₂O₂ → 2 Fe³⁺ + 2 OH· + 2 OH⁻

:2 Fe³⁺ + Ascorbate → 2 Fe²⁺ + Dehydroascorbate

The metal ion in this reaction can be reduced, oxidized, and then re-reduced, in a process called redox cycling that can generate reactive oxygen species.{{Cn|date=January 2021}}

The relative importance of the antioxidant and pro-oxidant activities of antioxidant vitamins is an area of current research, but vitamin C, for example, appears to have a mostly antioxidant action in the body.{{cite journal |vauthors=Valko M, Morris H, Cronin MT |title=Metals, toxicity and oxidative stress |journal=Curr. Med. Chem. |volume=12 |issue=10 |pages=1161–208 |year=2005 |pmid=15892631 |doi=10.2174/0929867053764635}} However, less data is available for other dietary antioxidants, such as polyphenol antioxidants,{{cite journal |author=Halliwell B |title=Dietary polyphenols: good, bad, or indifferent for your health? |journal=Cardiovasc. Res. |volume=73 |issue=2 |pages=341–7 |year=2007 |pmid=17141749 |doi=10.1016/j.cardiores.2006.10.004|doi-access=free }} zinc,{{cite journal |vauthors=Hao Q, Maret W |title=Imbalance between pro-oxidant and pro-antioxidant functions of zinc in disease |journal=J. Alzheimers Dis. |volume=8 |issue=2 |pages=161–70; discussion 209–15 |year=2005 |pmid=16308485|doi=10.3233/jad-2005-8209 }} and vitamin E.{{cite journal |author=Schneider C |title=Chemistry and biology of vitamin E |journal=Mol Nutr Food Res |volume=49 |issue=1 |pages=7–30 |year=2005 |pmid=15580660 |doi=10.1002/mnfr.200400049}}

Several important anticancer agents both bind to DNA and generate reactive oxygen species. These include adriamycin and other anthracyclines, bleomycin, and cisplatin. These agents may show specific toxicity towards cancer cells because of the low level of antioxidant defenses found in tumors. Recent research demonstrates that redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by pro-oxidant non-genotoxic redox chemotherapeutics.{{cite journal |author=Wondrak GT |title=Redox-directed cancer therapeutics: molecular mechanisms and opportunities |journal=Antioxid. Redox Signal. |volume=11 |issue=12 |pages=3013–69 |date=December 2009 |pmid=19496700 |pmc=2824519 |doi=10.1089/ARS.2009.2541 }}

Photodynamic therapy is used to treat some cancers as well as other conditions. It involves the administration of a photosensitizer followed by exposing the target to appropriate wavelengths of light. The light excites the photosensitizer, causing it to generate reactive oxygen species, which can damage or destroy diseased or unwanted tissue.{{Cn|date=January 2021}}

• Antioxidant
• Oxidizing agent
• Reducing agent
• Methylene blue
• DCPIP

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Category:Antioxidants

Category:Cell biology

Category:Chemical pathology

Category:Physiology

Category:Redox