Original Contribution PREVENTION OF FLIGHT ACTIVITY PROLONGS THE LIFE SPAN OF THE HOUSEFLY, MUSCA DOMESTICA, AND ATTENUATES THE AGE-ASSOCIATED OXIDATIVE DAMAGE TO SPECIFIC MITOCHONDRIAL PROTEINS LIANG-JUN YAN 1 and RAJINDAR S. SOHAL Department of Biological Sciences, Southern Methodist University, Dallas, TX, USA (Received 26 June 2000; Revised 8 August 2000; Accepted 24 August 2000) Abstract—The purpose of this study was to explore the mechanisms by which oxidative stress affects the aging process. The hypothesis that the rate of accumulation of oxidative damage to specific mitochondrial proteins is linked to the life expectancy of animals was tested in the housefly. The rate of oxygen consumption and life expectancy of the flies were experimentally altered by confining the flies in small jars, where they were unable to fly. Prevention of flight activity decreased the rate of oxygen utilization of flies and almost tripled their life span as compared to those permitted to fly. Rate of mitochondrial H 2 O 2 generation at various ages was lower in the low activity flies than in the high activity flies. Oxidative damage to mitochondrial proteins, adenine nucelotide translocase, and aconitase, detected as carbonyl modifications, was attenuated; and the loss in their functional activity occurring with age was retarded in the long-lived low activity flies as compared to the short-lived high activity flies. The two proteins were previously identified to be the only mitochondrial proteins exhibiting age-related increases in carbonylation. Results support the hypothesis that accrual of oxidative damage to specific protein targets and the consequent loss of their function may constitute a mechanism by which oxidative stress controls the aging process. © 2000 Elsevier Science Inc. Keywords—Aging, Aconitase, Protein carbonyls, Adenine nucleotide translocase (ANT), Mitochondria, Metabolic rate, Oxidative damage, Free radicals INTRODUCTION The aging process, or senescence, is characterized by a progressive decline in the functional capacity of a variety of physiological systems, ultimately ending in the death of the organism. The nature of the mechanisms causing the age-related deleterious alterations is presently not well understood, but remains under intense investigation. One hypothesis postulates that accrual of molecular ox- idative damage, inflicted by reactive oxygen species (ROS), is a fundamental causal factor in the functional losses occurring during the aging process [1]. This hy- pothesis is supported by several lines of evidence, in- cluding the demonstration that the rate of mitochondrial O 2 -• /H 2 O 2 generation and the steady-state amounts of oxidative damage to macromolecules such as proteins, DNA, and lipids increase with age in the tissues of a variety of phylogenetically diverse species [2– 4]. Oxidative damage to proteins is hypothesized to play a key role in the aging process because oxidatively modified proteins are generally dysfunctional, lose cata- lytic and structural integrity, and undergo preferential degradation [5–12]. Proteins exhibit a variety of oxida- tive alterations, including the loss of sulfhydryl groups and the conversion of tyrosine residues to dityrosine, among others [13]. The most frequently encountered modification, however, is the addition of carbonyl groups to certain amino acid residues [13,14]. Indeed, an in- crease in the amount of protein carbonyls in tissue ho- mogenates is one of the most ubiquitous biochemical alterations occurring during aging [2,3]. It is widely thought that oxidative damage to proteins is inflicted 1 Present address: Department of Internal medicine, Division of Car- diology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-8573, USA. Address correspondence to: Rajindar S. Sohal, Department of Mo- lecular Pharmacology and Toxicology, University of Southern Califor- nia, 1985 Zonal Avenue, Los Angeles, CA 90089, USA; Tel: (323) 442-1860; Fax: (323) 224-7473; E-Mail: sohal@usc.edu. Free Radical Biology & Medicine, Vol. 29, No. 11, pp. 1143–1150, 2000 Copyright © 2000 Elsevier Science Inc. Printed in the USA. All rights reserved 0891-5849/00/$–see front matter PII S0891-5849(00)00423-8 1143