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A review of the evidence supporting melatonin's role as an antioxidant.
J Pineal Res. 1995 Jan; 18(1):1-11.JP

Abstract

This survey summarizes the findings, accumulated within the last 2 years, concerning melatonin's role in defending against toxic free radicals. Free radicals are chemical constituents that have an unpaired electron in their outer orbital and, because of this feature, are highly reactive. Inspired oxygen, which sustains life, also is harmful because up to 5% of the oxygen (O2) taken in is converted to oxygen-free radicals. The addition of a single electron to O2 produces the superoxide anion radical (O2-.); O2-. is catalytic-reduced by superoxide dismutase, to hydrogen peroxide (H2O2). Although H2O2 is not itself a free radical, it can be toxic at high concentrations and, more importantly, it can be reduced to the hydroxyl radical (.OH). The .OH is the most toxic of the oxygen-based radicals and it wreaks havoc within cells, particularly with macromolecules. In recent in vitro studies, melatonin was shown to be a very efficient neutralizer of the .OH; indeed, in the system used to test its free radical scavenging ability it was found to be significantly more effective than the well known antioxidant, glutathione (GSH), in doing so. Likewise, melatonin has been shown to stimulate glutathione peroxidase (GSH-Px) activity in neural tissue; GSH-PX metabolizes reduced glutathione to its oxidized form and in doing so it converts H2O2 to H2O, thereby reducing generation of the .OH by eliminating its precursor. More recent studies have shown that melatonin is also a more efficient scavenger of the peroxyl radical than is vitamin E. The peroxyl radical is generated during lipid peroxidation and propagates the chain reaction that leads to massive lipid destruction in cell membranes. In vivo studies have demonstrated that melatonin is remarkably potent in protecting against free radical damage induced by a variety of means. Thus, DNA damage resulting from either the exposure of animals to the chemical carcinogen safrole or to ionizing radiation is markedly reduced when melatonin is co-administered. Likewise, the induction of cataracts, generally accepted as being a consequence of free radical attack on lenticular macromolecules, in newborn rats injected with a GSH-depleting drug are prevented when the animals are given daily melatonin injections. Also, paraquat-induced lipid peroxidation in the lungs of rats is overcome when they also receive melatonin during the exposure period. Paraquat is a highly toxic herbicide that inflicts at least part of its damage by generating free radicals.(

ABSTRACT

TRUNCATED AT 400 WORDS)

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Authors+Show Affiliations

Reiter RJ
Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio 78284-7762, USA.
Melchiorri D
No affiliation info available
Sewerynek E
No affiliation info available
Poeggeler B
No affiliation info available
Barlow-Walden L
No affiliation info available
Chuang J
No affiliation info available
Ortiz GG
No affiliation info available
Acuña-Castroviejo D
No affiliation info available

MeSH

AnimalsAntioxidantsFree Radical ScavengersFree RadicalsHumansLipid PeroxidationMelatoninOxidative Stress

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.
Review

Language

eng

PubMed ID

7776173

Citation

Reiter, R J., et al. "A Review of the Evidence Supporting Melatonin's Role as an Antioxidant." Journal of Pineal Research, vol. 18, no. 1, 1995, pp. 1-11.
Reiter RJ, Melchiorri D, Sewerynek E, et al. A review of the evidence supporting melatonin's role as an antioxidant. J Pineal Res. 1995;18(1):1-11.
Reiter, R. J., Melchiorri, D., Sewerynek, E., Poeggeler, B., Barlow-Walden, L., Chuang, J., Ortiz, G. G., & Acuña-Castroviejo, D. (1995). A review of the evidence supporting melatonin's role as an antioxidant. Journal of Pineal Research, 18(1), 1-11.
Reiter RJ, et al. A Review of the Evidence Supporting Melatonin's Role as an Antioxidant. J Pineal Res. 1995;18(1):1-11. PubMed PMID: 7776173.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - A review of the evidence supporting melatonin's role as an antioxidant. AU - Reiter,R J, AU - Melchiorri,D, AU - Sewerynek,E, AU - Poeggeler,B, AU - Barlow-Walden,L, AU - Chuang,J, AU - Ortiz,G G, AU - Acuña-Castroviejo,D, PY - 1995/1/1/pubmed PY - 1995/1/1/medline PY - 1995/1/1/entrez SP - 1 EP - 11 JF - Journal of pineal research JO - J Pineal Res VL - 18 IS - 1 N2 - This survey summarizes the findings, accumulated within the last 2 years, concerning melatonin's role in defending against toxic free radicals. Free radicals are chemical constituents that have an unpaired electron in their outer orbital and, because of this feature, are highly reactive. Inspired oxygen, which sustains life, also is harmful because up to 5% of the oxygen (O2) taken in is converted to oxygen-free radicals. The addition of a single electron to O2 produces the superoxide anion radical (O2-.); O2-. is catalytic-reduced by superoxide dismutase, to hydrogen peroxide (H2O2). Although H2O2 is not itself a free radical, it can be toxic at high concentrations and, more importantly, it can be reduced to the hydroxyl radical (.OH). The .OH is the most toxic of the oxygen-based radicals and it wreaks havoc within cells, particularly with macromolecules. In recent in vitro studies, melatonin was shown to be a very efficient neutralizer of the .OH; indeed, in the system used to test its free radical scavenging ability it was found to be significantly more effective than the well known antioxidant, glutathione (GSH), in doing so. Likewise, melatonin has been shown to stimulate glutathione peroxidase (GSH-Px) activity in neural tissue; GSH-PX metabolizes reduced glutathione to its oxidized form and in doing so it converts H2O2 to H2O, thereby reducing generation of the .OH by eliminating its precursor. More recent studies have shown that melatonin is also a more efficient scavenger of the peroxyl radical than is vitamin E. The peroxyl radical is generated during lipid peroxidation and propagates the chain reaction that leads to massive lipid destruction in cell membranes. In vivo studies have demonstrated that melatonin is remarkably potent in protecting against free radical damage induced by a variety of means. Thus, DNA damage resulting from either the exposure of animals to the chemical carcinogen safrole or to ionizing radiation is markedly reduced when melatonin is co-administered. Likewise, the induction of cataracts, generally accepted as being a consequence of free radical attack on lenticular macromolecules, in newborn rats injected with a GSH-depleting drug are prevented when the animals are given daily melatonin injections. Also, paraquat-induced lipid peroxidation in the lungs of rats is overcome when they also receive melatonin during the exposure period. Paraquat is a highly toxic herbicide that inflicts at least part of its damage by generating free radicals.(ABSTRACT TRUNCATED AT 400 WORDS) SN - 0742-3098 UR - https://www.unboundmedicine.com/medline/citation/7776173/A_review_of_the_evidence_supporting_melatonin's_role_as_an_antioxidant_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0742-3098&date=1995&volume=18&issue=1&spage=1 DB - PRIME DP - Unbound Medicine ER -