Lipid peroxidation (LPO) is a vital link in metabolic metabolism. Its main function is to renew the lipids of cell membranes.
In a he althy person, lipid peroxidation processes are controlled by the so-called antioxidant system, which regulates the rate and activity of phosphorylation by binding provoking factors or neutralizing enough peroxides to prevent an excess of end products of metabolism. Strengthening the oxidation process can be the starting point in the pathophysiological processes of a significant number of diseases. This process includes the steps of enzymatic and non-enzymatic autoxidation.
Views
To modify the phospholipid bilayer of cell membranes, enzymatic oxidation takes place. In addition, it is involved in the formation of biologically active substances, detoxification of the body, and metabolic reactions. Non-enzymatic oxidation, on the other hand, manifests itself as a destructive factor in the life of the cell. Due to educationa large number of free radicals and the accumulation of peroxides, the activity of the antioxidant system decreases and, as a result, the death of body cells is observed.
Sex cycle
To start lipid peroxidation, the presence of free oxygen radicals, which have one unpaired electron at the extreme energy level, is necessary. After the reduction of the molecule, oxygen superoxide is formed, which reacts with hydrogen atoms, turning into hydrogen peroxide. To regulate the amount of superoxides inside the cell, there is superoxide dismutase, which forms hydrogen peroxide, and catalase, peroxidase neutralize it to water. If a living organism has been exposed to ionizing radiation, the amount of free hydroxyl radicals will increase dramatically. In addition to oxygen hydroxide, its other active forms can act as initiators of lipid peroxidation.
Products of lipid peroxidation are either utilized by the body or used for the synthesis of prostaglandins (substances involved in inflammation reactions), thromboxanes (included in the cascade of thrombogenic reactions), adrenal hormones.
Control system
Depending on the basic structure of the cell membrane, the rate, activity and amount of the resulting oxidation products may vary. So, for example, the activity of lipid peroxidation is higher where unsaturated fatty acids predominate in the cell wall, and slower if cholesterol is the basis of CS. ExceptIn addition, metabolic enzymes are a factor regulating the amount and rate of formation of free oxygen radicals, as well as the utilization of peroxides. Substances that affect the lipid composition of the cell membrane and its arbitrary change in accordance with the needs of the body also take part in the lipid peroxidation reaction. These include vitamin E and K, thyroxine (thyroid hormone), hydrocortisone, cortisone, and aldosterone (feedback). Metal ions, vitamins C and D destabilize the cell wall.
Breach of process
Metabolic products of lipid peroxidation can accumulate in tissues and body fluids if the antioxidant system does not have time to utilize them at the required rate. As a result, the transport of ions across the cell membrane is disrupted, which can indirectly affect the ionic composition of the liquid part of the blood, the rate of polarization and depolarization of muscle cell membranes (impair the conduction of nerve impulses, their contractility, increase the refractory period), promote the release of fluid into the extracellular space (edema, blood clotting, electrolyte imbalance). In addition, the main products of lipid peroxidation, after a series of biochemical reactions, are converted into aldehydes, ketone bodies, acids, etc. These substances have a toxic effect on the body, manifested in a decrease in the rate of DNA synthesis, an increase in capillary permeability, an increase in oncotic pressure and, as consequence, sludge syndrome.
Clinical manifestations
Since an increase in the amount of oxygen free radicals has a damaging effect on the cell wall, and metabolic products disrupt the process of metabolism and synthesis of nucleic acids, and also poison the body, they are a pathophysiological factor in the development of a number of clinical conditions. The role of lipid peroxidation is important in diseases of the liver, joints, parasitic infectious diseases, hemodynamic disorders, cancer, injuries and burns. LPO is one of the factors in the development of atherosclerosis. Free radicals, oxidizing cholesterol and its low molecular weight fractions, form products that damage the vascular wall. This triggers a cascade of typical pathological reactions aimed at eliminating the damage. This provokes thrombosis, the accumulation of blood clots in the lumen of small vessels or attachment to their walls. As a result, the movement of blood in this area slows down, since the lumen of the vessel has become narrower. This contributes to the further accumulation of blood clots. The most susceptible to such changes are the coronary arteries, the aorta, which manifest themselves in the clinic as symptoms of coronary heart disease.
Preventive measures
Practitioners need to be aware that diagnostic and therapeutic procedures can activate the lipid peroxidation mechanism. The patient should be warned about this. Provoking factors include radiation therapy (for oncology), ultravioletirradiation (for rickets, inflammatory diseases of the sinuses, antibacterial treatment of premises), magnetic fields (MRI, CT, physiotherapy), sessions in a pressure chamber (for poliomyelitis, mountain sickness).
Prevention and therapy
Personnel working in x-ray rooms, nurses, physiotherapists, climbers, overweight people need to eat foods containing natural antioxidants: fish, sunflower or olive oil, herbs, eggs, green tea.
In addition to changing the diet, you can use drugs that bind certain groups of free radicals or combine with metals of variable valence. Thus, they replace free molecules of active oxygen, preventing them from binding to LPO enhancers.
Diagnosis
At the current stage of development of laboratory research, we have the opportunity to detect peroxides in the composition of biological fluids of the human body. This requires fluorescence microscopy. Simply put, identify lipid peroxidation. The significance of this diagnostic test needs no explanation. After all, the basis of a significant number of diseases is the excessive activity of lipid peroxidation. Identification of this condition determines the tactics of treatment.
From the point of view of normal physiology, lipid peroxidation is necessaryfor the formation of steroid hormones, inflammatory mediators, cytokines and thromboxanes. But when the amount of products of the exchange of these chemical reactions exceeds the permissible value and peroxides damage cell organelles, disrupt the synthesis of DNA and proteins, the antioxidant system comes into action, reducing the amount of free oxygen radicals, metal ions with variable valence. In addition, it increases the synthesis of catalase and peroxidase in order to utilize excess peroxides and products of their further metabolism.
