Investigation of the Relationship Between Lipid Peroxidation and Changes in the Mitochondrial Genome of Animals of Different Ages

The investigation is devoted to the study of the relationship between lipid peroxidation and mitochondrial genome damage in animals of different ages. The role of oxidative stress caused by the production of reactive oxygen species predominantly in the mitochondria in the mechanisms of age-related changes is examined. Special attention is given to the dynamics of mitochondrial DNA fragmentation under the influence of extreme factors such as immobilization stress, as well as the possibilities of its protection using antioxidant preparations, including phytoadaptogens. The investigation is conducted on laboratory animals (rats) during ontogeny and is aimed at identifying age-related patterns in the state of the free radical oxidation system and antioxidant defense, as well as at evaluating the prospects for the application of geroprotectors to preserve the genetic stability of mitochondria.

Relevance of the Problem. Statistical data indicate a progressive decline in average life expectancy in recent decades in Russia and the Ural region in particular. At the same time, medical literature practically lacks protocols for disease therapy depending on belonging to a particular age group, as well as geroprophylactic measures. This is especially relevant for individuals with polyorganic pathology caused by the action of extreme factors, including the numerous group of combat participants. The situation is complicated by the discrepancy in most cases between the calendar age of a rapidly aging patient and his true biological age [119, 145, 161].

In gerontology, a large body of information has accumulated on where and how various structurally-functional damages occur and accumulate with age. However, to date, there is no answer to the question about the mechanism of these damages. The free radical theory proposed by D. Harman, which has undergone a number of modifications as a result of domestic and foreign research [158, 206, 213], claims the role of a universal hypothesis of aging. In recent decades, data have accumulated indicating that organism aging is associated with genetic instability, and long-lived species are endowed with a more stable system for protecting the genetic apparatus from the action of free radicals (FR) [184, 206].

The main tenet of the modern version of the free radical theory of aging is that during normal metabolism, oxygen free radicals are produced, the primary source of which in eukaryotic cells are the mitochondria. Oxidative phosphorylation (OP) reactions are controlled by enzyme complexes localized in the inner mitochondrial membrane and are accompanied by the consumption of 90–95% of the oxygen entering the cells, up to 4% of which is converted into free radicals [281]. Mitochondrial (mt)DNA has a high mutagenesis constant and a low level of repair mechanisms compared to nuclear (n)DNA [174, 192]. The accumulation of damaged mtDNA molecules leads to disruption of OP, a decrease in ATP production, and impaired biogenesis of both mitochondria and the nuclear genome. At the same time, the level of free radical production and the accumulation of structures damaged by them, which increase the mutagenesis process, rises [105, 142, 266]. The process becomes self-accelerating: the level of energy production decreases and does not meet the tissue energy demand. As a result, age-related degenerative diseases arise, the development of which may be exacerbated by the action of unfavorable internal and external factors: stresses, ionizing radiation, improper nutrition, intoxications [105, 213].

Thus, the normal functioning of mitochondria, necessary for maintaining the energy supply of the organism, determines the process of its aging [169, 170]. According to estimates by some researchers, the damaging effect of free radicals can be reduced by antioxidant drugs, which can be used in geriatric practice [85, 99, 190, 227, 247, 254].

In this work, an attempt is made to examine the relationship between free radical oxidation (FRO) and mitochondrial genome damage.

The aim of the work: to investigate the state of the mitochondrial genome of animals during ontogeny under the influence of extreme factors and geroprophylactic agents that realize their effect through an impact on free radical oxidation in the organism.

Research objectives:

1. To assess the state of the FRO/AS system in animals of different age groups.

2. To investigate age-related changes in mtDNA in experimental animals.

3. To determine the change in the state of the mitochondrial genome in animals of different ages under conditions of immobilization stress.

4. To establish changes in the FRO/AS system after the administration of antioxidant drugs in animals of different ages under conditions of immobilization stress.

5. To determine the change in the state of mtDNA under the influence of antioxidant drugs in animals of different ages under extreme conditions.

6. To draw a conclusion about the relationship between free radical oxidation processes and changes in the mitochondrial genome in animals during ontogeny, under conditions of immobilization, and after the administration of antioxidants.

Scientific novelty.

A connection between mitochondrial genome changes and the processes of organism aging has been established. The role of FRO as a mediator influencing the genome under conditions of extreme factor exposure has been determined, and a search for factors allowing the impact on organism aging processes under these conditions has been conducted. New data on the role of the state of the mitochondrial genome in the processes of organism aging under the influence of factors inducing FRO have been obtained.

Age-related features of the influence of FRO and the antioxidant system (AS) on the degree of mitochondrial genome damage have been investigated. It has been shown that the level of mtDNA fragmentation is directly dependent on the activity of FRO and AS processes. A pattern of mutual increase in FRO activity and mtDNA fragmentation under extreme conditions has been revealed. It has been established that the prooxidant effect of stress influence can be reduced by using phytoantioxidant preparations. The maximum geroprophylactic effect was observed when using preparations of pink rhodiola and vitamin E. It has been established that the best geroprophylactic effect was observed in old animals.

Practical significance and pathways of implementation.

The results of the work provide grounds for the development of geroprotectors capable of protecting the genome of cells from the damaging action of FRO and influencing the processes of organism aging. It has been established that certain phytoadaptogens capable of inhibiting FRO processes in the organism can be used for this purpose. In this case, the positive effect of their use can be realized in a certain age period. Determination of the state of the mitochondrial genome can be used in the comprehensive assessment of bioage in geriatric practice.

Implementation of the research results.

The research results are used in the educational process at the departments of pathological physiology, biochemistry, and pharmacology of the Ural State Medical Academy: 1) in the sections: pathophysiology of aging, free radical lipid peroxidation and antioxidant protection, stress and adaptation, hypoxia; 2) in practical sessions; 3) in the preparation of term papers; 4) included in the lecture course. Recommendations for the use of a phytocomplex in states of immunodeficiency have been developed.

The results of the work will help in the search for geroprotectors capable of protecting the genome from the damaging action of FRO and inhibiting the aging process of the organism; they have been used in the development of schemes for correcting metabolic disorders in patients consulted at the Laboratory of Pathophysiology of Aging of the Sverdlovsk Regional Clinical Psychoneurological Hospital for Veterans (Yekaterinburg).

The obtained data were used in the preparation of a patent on the use of phytopreparations for increasing the resistance of the organism under the action of a damaging factor: 'Antitumor Phytocomplex and Method of Its Use in Oncology', patent application dated February 3, 2005. A priority certificate No. 2005102688 (003570) has been obtained.

Validation of the work. The dissertation materials were presented at:

1. The 56th Student and Young Scientists Conference 'Actual Issues of Modern Medical Science and Healthcare', Yekaterinburg, 2001.

2. The Interregional Scientific and Practical Conference 'Gerontology and Geriatrics', Yekaterinburg, 2002.

3. The Ural Regional Scientific Conference: 'Actual Problems of Morphogenesis and Regeneration of Thoracic and Abdominal Organs', Yekaterinburg, 2003.

4. The 59th Student and Young Scientists Conference 'Actual Issues of Modern Medical Science and Healthcare', Yekaterinburg, 2004.

5. The XIX Congress of the I.P. Pavlovian Physiological Society, Yekaterinburg, 2004.

6. The III Russian Congress on Pathophysiology with International Participation, Moscow, 2004.

7. The 60th Student and Young Scientists Conference 'Actual Issues of Modern Medical Science and Healthcare', Yekaterinburg, 2005.

8. The All-Russian Congress of Physiologists, Sochi, 2005.

Publications. 10 works have been published on the topic of the dissertation.

The following statements are presented for defense:

1. The aging process in experimental animals is accompanied by an increase in the activity of FRO processes.

2. The level of mtDNA fragmentation in old animals substantially exceeds this indicator in young and mature animals.

3. The action of an extreme factor that increases FRO activity is accompanied by an intensification of mitochondrial genome damage.

4. The administration of preparations with antioxidant activity reduces mitochondrial genome damage.

5. A direct correlation has been established in experimental animals between FRO activity and the state of the mitochondrial genome.

Volume and Structure of the Dissertation.

The dissertation is presented on 153 pages of text, typed on a computer in the Microsoft Word text editor, and contains 29 tables and 12 figures. The dissertation consists of an introduction, a literature review, two chapters of original research, a general conclusion, conclusions, and a list of references comprising 159 works in Russian and 129 works in foreign languages, and 3 references to electronic resources.