The nitroxide TEMPO is an efficient scavenger of protein radicals: cellular and kinetic studies

TY - JOUR

T1 - The nitroxide TEMPO is an efficient scavenger of protein radicals

T2 - cellular and kinetic studies

AU - Pattison, David I

AU - Lam, Magdalena

AU - Shinde, Sujata S

AU - Anderson, Robert F

AU - Davies, Michael Jonathan

N1 - Copyright © 2012 Elsevier Inc. All rights reserved.

PY - 2012/10/1

Y1 - 2012/10/1

N2 - Protein oxidation occurs during multiple human pathologies, and protein radicals are known to induce damage to other cell components. Such damage may be modulated by agents that scavenge protein radicals. In this study, the potential protective reactions of the nitroxide TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl radical) against Tyr- and Trp-derived radicals (TyrO./TrpN.) have been investigated. Pretreatment of macrophage cells with TEMPO provided protection against photo-oxidation-induced loss of cell viability and Tyr oxidation, with the nitroxide more effective than the hydroxylamine or parent amine. Pulse radiolysis was employed to determine rate constants, k, for the reaction of TEMPO with TyrO. and TrpN. generated on N-Ac-Tyr-amide and N-Ac-Trp-amide, with values of k~10(8) and 7×10(6)M(-1)s(-1), respectively, determined. Analogous studies with lysozyme, chymotrypsin, and pepsin yielded k for TEMPO reacting with TrpN. ranging from 1.5×10(7) (lysozyme) to 1.1×10(8) (pepsin)M(-1)s(-1). Pepsin-derived TyrO. reacted with TEMPO with k~4×10(7)M(-1)s(-1); analogous reactions for lysozyme and chymotrypsin TyrO. were much slower. These data indicate that TEMPO can inhibit secondary reactions of both TyrO. and TrpN., though this is protein dependent. Such protein radical scavenging may contribute to the positive biological effects of nitroxides.

AB - Protein oxidation occurs during multiple human pathologies, and protein radicals are known to induce damage to other cell components. Such damage may be modulated by agents that scavenge protein radicals. In this study, the potential protective reactions of the nitroxide TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl radical) against Tyr- and Trp-derived radicals (TyrO./TrpN.) have been investigated. Pretreatment of macrophage cells with TEMPO provided protection against photo-oxidation-induced loss of cell viability and Tyr oxidation, with the nitroxide more effective than the hydroxylamine or parent amine. Pulse radiolysis was employed to determine rate constants, k, for the reaction of TEMPO with TyrO. and TrpN. generated on N-Ac-Tyr-amide and N-Ac-Trp-amide, with values of k~10(8) and 7×10(6)M(-1)s(-1), respectively, determined. Analogous studies with lysozyme, chymotrypsin, and pepsin yielded k for TEMPO reacting with TrpN. ranging from 1.5×10(7) (lysozyme) to 1.1×10(8) (pepsin)M(-1)s(-1). Pepsin-derived TyrO. reacted with TEMPO with k~4×10(7)M(-1)s(-1); analogous reactions for lysozyme and chymotrypsin TyrO. were much slower. These data indicate that TEMPO can inhibit secondary reactions of both TyrO. and TrpN., though this is protein dependent. Such protein radical scavenging may contribute to the positive biological effects of nitroxides.

KW - Animals

KW - Azides

KW - Cell Line

KW - Cell Survival

KW - Chymotrypsin

KW - Cyclic N-Oxides

KW - Electron Spin Resonance Spectroscopy

KW - Free Radical Scavengers

KW - Free Radicals

KW - Hydroxylamine

KW - Kinetics

KW - Macrophages

KW - Mice

KW - Muramidase

KW - Nitrogen Oxides

KW - Oxidants, Photochemical

KW - Oxidation-Reduction

KW - Pepsin A

KW - Pulse Radiolysis

KW - Tryptophan

KW - Tyrosine

U2 - 10.1016/j.freeradbiomed.2012.08.578

DO - 10.1016/j.freeradbiomed.2012.08.578

M3 - Journal article

C2 - 22974763

SN - 0891-5849

VL - 53

SP - 1664

EP - 1674

JO - Free Radical Biology & Medicine

JF - Free Radical Biology & Medicine

IS - 9

ER -