by Natalya KALETINA, Dr. Sc. (Biol.), Grigory KALETIN, Cand. Sc. (Med.), Center of Biotic Medicine (Moscow)
Iron and zinc, molybdenum and selenium, copper and cobalt - these and tens of other chemical elements are present in human body in minimum amounts-10-3 - 10-12 percent. However, their effect on metabolism and other processes are great. Their excess or deficiency in organs and tissues lead to diseases. What are the mechanisms of microelement action? Why even one and the same element, though in different doses and forms, can play both a creative and destructive role?
Articles in this rubric reflect the authors' opinion. - Ed.
According to Alexander Avtsyn (1908 - 1993), a well-known pathologist and physiologist, Member of the USSR Academy of Medical Sciences, trace elements are "most likely not stray ingredients of tissues and liquids of organisms, but are components of the naturally existing very ancient and intricate physiological system, involved in the regulation of vital functions at all stages of development". They are unevenly distributed in human organs and liquids. Vitally important, or essential elements, such as iron, iodine, zinc, cobalt, chromium, molybdenum, nickel, selenium, manganese, fluorine, silica, etc. are present in significantly higher (sometimes by orders of magnitude) concentrations than toxic elements (cadmium, arsenic, mercury, antimony, barium, boron, lead, etc.). Their effects depend not only on the quantitative factor, but also on the form of the element: coordination-bound or ionic.
Let us once more note, that cell life is determined by proteins, while the nucleic acids just present the plan of its activity. Protein molecule composition depends on many factors: oxygen supply, stress exposure, drugs, nutrition. The organism always reacts to environmental changes, trying to retain the physiological balance. By contrast, environmental conditions are aimed at violating this balance. The maintenance of homeostasis is associated with protein synthesis, transformation, and degradation, while metal ions determine the real possibility of these processes, their direction and velocity. The role of metal ions in cell growth, differentiation, reparation and regeneration, apoptosis, necrosis, survival, and in the pathogenesis of chronic inflammatory and degenerative diseases is proven.
Let us illustrate the variety of trace element forms in a live body by several examples. Hemoproteins (hemoglobin, myoglobin, cytochromes, and many others) are the most important iron-containing proteins. More than 200 enzymes contain zinc; it is present in the structure of thymulin (active hormone of the thymus) and participates in insulin "packing". Zinc is justly called the main inorganic hormone. Copper is a dopamine-beta-hydroxylase coenzyme*, essential for the synthesis of neuromediators. Cobalt is the key component of
* Coenzymes are non-protein compounds of some enzymes. - Ed.
vitamin B12 coenzyme. Nickel was detected in human hydrolytic enzymes and in the blood in complexes with histamine and albumins. The biological role of iodine, a component of many hormones, is well known.
Biomagnetism is a phenomenon characteristic of many live objects, from bacteria to humans. Magnetite (iron oxide) performs the function of their orientation in the magnetic field of the Earth and is located in special formations (magnetosomes), representing chains of 10 - 25 crystals (total length about 50 nm). Recently German scientists identified the part of DNA, carrying complete genetic information, essential for the formation of magnetosomal particles. This genome fragment contains at least 25 - 30 different magnetosomal genes, whose role was heretofore unknown in detail.
Each element has a specific range of safe exposure, thus ensuring the optimal tissue concentrations; on the other hand, each element has a toxic range as well. For example, many years ago felt for hats was treated with mercuric salts. The life of a hatter was therefore short and ended, as a rule, in mental disorders. The English even say "Mad as a hatter". But there is another saying: "A doctor who knows the curative effects of herbs and radices is a human being; a doctor who knows the force of a prayer is a prophet; a doctor who knows the force of mercury is God." Since the discovery of selenium (1817) till the middle of the 20th century this element was believed to be one of the most toxic elements of D. Mendeleev's Periodical System. The attitude to it was revised after natural amino acids selenocystein and selenome-thionin had been found in live organisms and plants. However, the assumption that "selenium is toxic" cannot be considered erroneous. It can be toxic and essential at the same time.
One of the modes of metal toxicity manifestation is competition and replacement of vitally important cations, when the "useful" is replaced by a "harmful" one. For example, lead can replace zinc in Zn-containing enzymes under certain conditions, thus inhibiting their function. But if we remember that zinc promotes immunogenesis, spermatogenesis, reproduction, wound healing, we shall see the hazards of environment pollution by lead, this "toxicant No. 1", particularly for children. Lead intoxication can result in serious problems in training, behavioral disorders (aggressiveness), hyperagitation or lethargy. By modulating the activities of certain enzymes involved in the genome biosynthesis, lead modulates the hemopoietic system. The result is decreased hemoglobin level and anemia.
Next. Hookah, pipe, cigarette smoke contains an appreciable amount of cadmium, a lung carcinogen. Irreversible neurological condition, close to Parkinson's disease, characterized by abnormal behavior and "masklike" look, result from chronic exposure to high levels of manganese and are often seen in narcomaniac adolescent users of ephedron derived at home.
Let us note that coordinated effects of several trace elements are observed in nature, when the effect of one is enhanced or suppressed in the presence of another. Pairs and triads of elements with synergic (coordinated) or antagonistic effects on various normal and pathological parameters are known, for example: iron-manganese, iron-zinc, zinc-copper, cadmium-copper, copper-molybdenum pairs, etc.; triads: iodine-calcium-phosphoric acid residue, molybdenum-copper-sulfuric acid residue. Copper and manganese, as molybdenum antagonists, promote the development of its pronounced deficiency, which is regarded as a factor of liability to oncological diseases. Low level of selenium in the blood serum indicates decreased antioxidant defense of the body. Antagonists of this metal are lead, mercury, cadmium, arsenic. The mechanism of toxic effects of these elements is known. However, their toxicity is mediated through decrease in selenium level. That is why low concentration of selenium in the blood serum and its
Each element is characterized by a specific toxic range.
Coordination effects of trace elements are prevalent in nature.
increase in the hair can serve as one of the tests for early diagnosis of toxic effects of selenium antagonists. However, only the sum of data (multi-element analysis of metals and measurements of clinically significant indicators of their imbalance) give a positive result. The information on the content of as many as possible elements in one sample simultaneously and in different biological objects (for example, in the blood and hair) is important.
Human body is a dynamic polyligand* and polymetallic system; the maintenance of homeostasis is essential for its functioning. Exchange, circulation, and deposition of metal ions are explained by their capacity to participate in the processes of complex formation with the natural endogenous (nucleic acids, carbohydrates, amino acids, peptides, proteins, vitamins, hormones) and exogenous ligands (drugs, foodstuffs, etc.). Disorders in homeostasis are caused by predominance or deficiency of metal ions (for example, modification ofthegeochemical habitat, disease), increase or decrease in the ligand concentration (long drug therapy, diet).
As the central atoms of complex compounds, the majority of trace elements form biocomplexes in vivo. Their stability plays the basic role in the intra- and extracellular changes, antagonism, synergism, and pharmacodynamic effects of metals. The greater part of them are present in the body in the form of chelates** of microelements with bioactive substances with a central atom located inside them.
Stable complexes are always present in the body and play a strictly determined functional role, for example, hemoglobin, vitamin B12, cytochromes (respiratory enzymes). Unstable complexes form only to perform certain functions and are destroyed after these functions are over. Metal ions in these cases serve as enzyme activators for the period of their catalytic effect. For example, manganese, cobalt, iron, nickel ions in metal-polynucleotide complexes stabilize the DNA double strand and can replace each other. The stability of biocomplexes is however determined by many factors, the most important of which are complementarity***, nature of trace elements and ligands, inter- and intramolecular interactions, kinetics of complex formation, etc. For example, copper (Cu2+), nickel (Ni2+), cobalt (Co2+), and zinc (Zn2+) ions effectively compete with protons for nitrogen atom in nitrogen-containing ligands. Steric (spatial) features of the resultant complexes promote an increase in their capacity to penetrate through cell membranes and modulate the availability for various cell receptors. Close kinetic parameters of these structures' formation are responsble for parallelism in the behavior of some metals (magnesium, manganese, cobalt, zinc, copper, mercury, lead, etc.).
Metal biocomplexes are a unique group of compounds involved in the maintenance of the cell integrity. "Union" of one and the same bioligand with different metal ions can be characterized by different biochemical properties. This explains the multiplicity of biological effects of these complexes. Different degree of these ions' affinity for this or that bioligand can cause their antagonism. Metallothionein protein contains 61 amino acid residues, binds 7 - 10 zinc, copper, cadmium, mercury, gold, and silver atoms, and thus prevents intoxication with their ions. Two antagonists (copper and zinc) are transported inside the cell within a complex with metallothionein; zinc is deposited (removed from the process for some time). Ions of these metals stimulate production of this protein, the activity of zinc being more pronounced, but the complex compounds with copper ions are more stable. Increase in the concentration of zinc ions causes the production of additional metallothionein, binding copper ions, thus
* Ligands: molecules or ions related to the central atom (complex former) in complex compounds. - Ed.
** Chelates are complex compounds of cyclic structure, in which the ligand is connected to the central metal atom by two or more bonds. - Ed.
*** Complementarity is mutual correspondence of two macromolecules, providing their interaction, in chemical structure. Complementary structures fit each other as the key fits the lock. - Ed.
Lead content in the hair of children living in Moscow (Professor Skalny's data).
decreasing their plasma concentration. Another example. Some substances present in foodstuffs can impede metal absorption. For example, iron ions form stable complexes with polyphenol compounds, and tea, coffee, soybean protein, containing these structures, significantly inhibit this process.
Cell-to-cell interactions in a multicellular organism are not only mechanical, but communicational as well. There is plenty of mechanisms for information exchange between the cells. The capacity to perceive external signals is determined by receptors, a special class of protein molecules. They have one or several centers for signal molecule binding and exhibit high affinity for their ligands. Forming a bond with a receptor, extracellular chemical mediators modulate the course of physiologically important processes in the target cell. Metal ions participate in these mechanisms to this or that measure. Investigations showed that calcium or zinc ions mediate numerous important cell reactions.
As we showed above, competition between metal ions is possible for many reasons. Violation of balance between intracellular trace elements in the body, for example, entry of ions from the environment (widely advertised biological additives, foodstuffs, water, air contaminated by metal ions, etc.) can have a serious impact on the work of the system mediating extracellular signals of different chemical nature.
APOPTOSIS: CAUSES OF FAILURE
Permanent number of cells in the body is maintained due to their multiplication and apoptosis (programmed death). Metals can disturb its regulation, thus increasing mutation and clonal growth. Trace elements are involved in autoassembly and synthesis of mitochondrial enzymes, and hence, in the respiratory chain complexes work. Lead, nickel, cadmium, mercury salts, some other ecopathogens with genotoxic effects and causing DNA defects can block these enzymes, which leads to mitochondrial insufficiency. This effect can be augmented by deficiency or excess or imbalance of some vitally important trace elements. Apoptosis inhibitors play an important role in gene regulation of apoptosis; these inhibitors are bcl-2 protein with antioxidant action, sort of a trap for free radicals, and p53 protein. Apoptosis induced by agents causing DNA ruptures (metals, radiation) depends on p53 transcription. Many metal ions, for example nickel (Ni2+), lead (Pb2+), cadmium (Cd2+), and others, can induce mutations or damage of Rb gene (tumor growth suppressor), which leads to mutant cell cloning. Chromium, lead, mercury, cadmium augment the genotoxic effects. Groups containing selenium, zinc, iron, and copper prevent the realization of gene-damaging effects. The maintenance of a stable level of intracellular trace elements is an
important homeostasis factor, as their imbalance indirectly triggers the mechanism of apoptosis disorder. Imbalance can be a result of improper nutrition, lack of socioeconomic well-being, very low or, vice versa, very high levels of some trace elements in soil and water, intoxication caused by xenobiotics (drugs, ethanol, or narcotics). It can also result from unreasonable medical preventive measures, such as overall iodine prophylaxis, anemia "control", use of multimineral mixtures with vitamins of different chemical groups in children's institutions.
Apoptosis dysregulation can lead to diseases: its hyperactivation, linked with the function of calcium (Ca2+) and magnesium (Mg2+) ions, is a component in the pathogenesis of AIDS, neurodegenerative and ischemic diseases; its inhibition caused by zinc ion (Zn2+) determines tumors of different nature, viral infections. Each carcinogenic metal seems to possess a unique mechanism of action and a specific route of entry. Cadmium and 6-valent chromium are carcinogenic only upon inhalation entry, while mercury and beryllium are hazardous upon inhalation, oral, and presumably, dermal penetration.
Our experiments with iron and cobalt complexes with derivatives of some drugs (ligands) showed a relationship between physiological effects of metals and their bio-complexes and the changes in the electron structure of the central atom. The effects of trace elements on the cell depend on the immediate ligand environment, pH medium values, oxidation degree, ionogenic or covalent form of the element presence in the sample; depending on these factors, they can act as apoptosis regulation inductors or inhibitors. Like iron ions (Fe2+), cobalt ions (Co2+) induce lipid peroxidation, suppress DNA repair, and together with nickel (Ni22+), lead (Pb2+), and cadmium (Cd2+) ions exhibit comutagenic (close and intensifying) effects and trigger the synthesis of antiinflammatory cytokine causing apoptosis and necrosis of target cells.
Today we can speak with certainty about facts of macro- and trace element participation in apoptosis processes. For example, various mitochondrial defects in patients with Wilson-Konovalov's disease (hereditary disease characterized by copper accumulation in the liver) suggest a relationship between copper metabolism level and stability of mitochondrial genome. Accumulation of toxicants (copper, mercury, lead), excessive release of vitally important bound trace elements (iron, cobalt, copper, selenium) provoke the generation of active oxygen forms, which leads to increase of the potential risk of tumor-associated protein gene damage. This is the cause of the mutant cell apoptosis inhibition and cancer development. Hemochromatosis* and Wilson-Konovalov's disease increase the risk of liver cancer because of accumulation of the mutant protein.
Increase in hemochromatosis incidence in Russia, observed during recent years, is due to use of narcotics, alcoholism, and overall consumption of bear in metal cans. Correlation between increased level of iron in the body and early development of atherosclerosis, coronary disease, and tumors was detected. On the one hand, iron is a vitally important element, on the other, its ions (Fe2+), as lipid peroxidation inductors, provoke DNA ruptures, are involved in mutagenesis and carcinogenesis. In vivo iron is present in complexes in transferrin*** and ferritin***, discontinuing the chain of subsequent reactions of genome damage. According to the published data and our findings, organic complexes of this metal stabilize the genome, but iron ions can cause DNA damage and provoke cell death.
An appreciable part of population of the Earth suffers from diseases associated with deficiency of vitally important trace elements. For example, up to 1 bin people suffer from iron and selenium deficiency, up to 3 bin people have chromium deficiency, 3.6 - 3.8 bin people suffer from copper and up to 4.5 bin people from zinc deficiency. Restoration of the balance may become "the little key which can open the large box" with recipes of new pharmacological methods for the treatment of various diseases, improvement of the quality of life, and prolongation of life with intact intellect.
NEW MEASUREMENT METHODS
In order to make well-based conclusions on the results of pathogenic effects of chemical ultramicropulses on human body they should be diagnosed throughout the life span of a generation. Reliable data of overall studies can be obtained at laboratories using sensitive methods for analysis, such as mass spectrometry with inductive bound plasma, gamma-resonance spectrometry, gas chromatography with mass spectrometry and some others. We suppose that gamma-resonance spectrometers can also become effective instruments for creation of a bank of reference samples to be used for identification and reflecting the levels of different forms of iron, cobalt, tin in the body in health and disease. Modern equipment allows to determine 60 and more macro-, trace, and ultratrace elements in one sample simultaneously, which is very important for evaluating interrelations and interactions of these elements in man. Unfortunately, high price of this equipment still impedes its introduction. Russian high-quality devices can be utilized for wide-scale use of new analytical methods, for example, devices designed at the RAS Institute of Analytical Instrument-Making (St. Petersburg).
* Hemochromatosis is a genetic disorder characterized by abnormally high iron turn-over in the enteric cells and its accumulation in tissues, such as liver, heart, and pancreas, leading to their damage. - Ed.
** Transferrin is a conjugate protein carrying trivalent iron in the body. Was detected in blood plasma, milk, egg white. Its deficit leads to metabolic disorders. - Ed.
*** Ferritin is an iron-containing protein of the liver, spleen, bone marrow, and other tissues. Stores iron in the body. - Ed.
There are still no clearly formulated indications for obligatory element analysis in medical diagnostic studies in the Russian Federation; however, this analysis can become an important instrument for search of rational treatment strategies to be used in chronic and tumorous diseases. Today the number of laboratories for multi-element analysis of biological substrates, certified in accordance with the international standards, is very insignificant (in Moscow the only laboratory with such status, available for patients, is the Center of Biotic Medicine, headed by Professor Anatoly Skalny).
It was found out that more than 80 percent medicinal preparations and foodstuffs can form complexes with metals in vivo, thus causing cellular trace element imbalance and diseases associated with it (microelementoses). What is the norm in biological samples? It is not necessarily the mean value, but something based mainly on the optimal function and excellent health. It is much more difficult and important to determine the normal value for a variable than to determine some mean index. For example, zinc concentration in the hair drops during the first three years of life in children, while concentrations of chromium and silica in some tissues decrease throughout the entire life span. It is known that the lungs, skin, nails, hair can be used as indicators of chronic exposure to trace elements. Available data indicate that their content in the hair reflects the respective body status in general. These tests provide an integral index of mineral metabolism.
Element analysis should become a component of the procedure of quality control of substances, plant raw material, and other means of medical use. For example, iron-containing preparations are widely used in medicine. Loss of activity and increase in the toxicity of these preparations during storage are characterized by increasing share of trivalent iron in comparison with bivalent. Gamma-resonance spectrometry detects various forms of iron and determines the degree of its oxidation in biological material. Complex preclinical evaluation of the safety of potential preparations detects the majority of toxic and unfavorable side effects. Despite the mediated character of the majority of biological processes, going on in the organism with the participation of metals, today it is really possible to evaluate the latter quantitatively.
Medicinal plants are most important objects of ecological monitoring. Trace elements capable of active complex formation can be present in this raw material in the form of compounds with carbohydrates, alkaloids, polyphenols, etc. We know some plants, mushrooms, and microorganisms, which due to metabolic processes extract toxic metals from the soil, this being fraught with the risk of their further transposition via the alimentary chain. Some mold species can be cultured under conditions when they reduce ionic to element mercury; and its vapor rapidly diffuses through cell membranes. "Inorganic" lead can similarly undergo biotransformation to tetraethyl lead in some bacteria; this organic substance is transported through biological membranes and is rather toxic.
Numerous studies showed that high level of man-made loading of the motherfetus system leads to trace element imbalance in the biological media of the fetoplacental complex (providing the development of the fetus). Analysis of metal content in the soil and drinking water in the territories of regions with different degree of pollution and measurements of trace element accumulation in the placenta and fetal blood showed priority ecotoxicants. Thus, the soil of the Yaroslavl, Ivanovo, and adjacent northern regions of Russia possess extremely low level of iron, while the Kursk and western part of the Moscow region are saturated with it. Future mothers, as before, are recommended herbal
The greater part of metals are present in the body as chelates (claw-shaped complexes) with bioactive substances.
preparations as the most safe drugs, but their complete element composition, in accordance with the norm-setting documents of the Russian Federation, is not controlled.
METAL AND LIGAND IMBALANCE
Oncological and neurodegenerative diseases, atherosclerosis, hypertension, and other "diseases of civilization" have common risk factors, from the molecular medicine viewpoint. The priority factor is oxidative stress with generation of highly active free radicals and nonradical particles with oxygen or nitrogen atom. The function of active oxygen forms (ROS) is dubious: positive (cell-to-cell signaling, phagocytosis, energy production, etc.), but, in case of hyperproduction, negative (impairment of cell membrane lipids, proteins, carbohydrates, nucleic acids).
Metal ions, for example, bivalent iron and univalent copper, can stimulate the production of ROS, such as highly aggressive OH hydroxyl radical. Binding of these ions into a complex appreciably reduces the velocity of free radical processes. Zinc, copper, cobalt, iron, nickel biocomplexes inhibit many other enzymes involved in the generation of ROS or active nitrogen forms.
Selenium, chromium, manganese, zinc, cobalt, copper, iron, etc. occupy the leading place among exo- and endoantioxidants, but on condition of their presence in the coordination-bound form. Trace element capacity to form intra- and intermolecular complexes with virtually all endogenous ligands becomes the key factor in evaluation of the activity of metal-containing medicinal preparations in order to prevent the manifestation of toxic effects by their components.
Recommendations on the use of nutritive metal-containing additives often imply: "The more, the better." This advice neglects the potential toxic effects of not merely excessive consumption of trace elements, but of their form (ionic or coordination-bound) in the recommended preparation. Meanwhile, the effects of their excess are also undesirable. In high doses they act as prooxidants generating free radicals or as inhibitors of the key enzymes involved in metabolism. For example, aluminum, copper, cadmium, lead ions play the etiological role in the development of such neurodegenerative diseases as Alzheimer's or Parkinson's diseases. The effect of pyroglutamyl aminopeptidase (enzyme involved in inactivation of neuromediator-gamma-aminobutyric acid) is suppressed by low concentrations of these metals; iron, nickel, copper ions selectively disturb the metabolic processes of another neuromediator, dopamine. "Aluminum" encephalopathy indirectly leads to significant oxidant stress in the neuron cytostructure. Recent studies showed that excessive aluminum is incorporated in transferrin and occupies the place of iron. In addition, it binds ferritin, thus impairing iron release, as a result of which oxidative damage to tissues increases. As imbalance between the pro- and antioxidant molecules in the body is the key factor in diseases of civilization, the use of metal-containing nutritive additives, special diets, "harmless" herbal preparations should be preceded by element diagnosis of the patient.
Our method for correction of trace element imbalance is based on an integral approach to information on the time course of their content in the body in certain diseases, on modification of the metal and ligand (preparation) properties during complex formation, on the principle of "recognition" of structures close to the natural biomolecules by cell membranes. We synthesized and patented in the Russian Federation more than 100 new substances made according to the principle of biocoordination and nitrogen-glycosylated zinc, cobalt, copper, nickel, iron, and manganese structures with medicinal preparations. Experiments confirmed the bactericidal and bacteriostatic, antioxidant, immuno-modulating, anti-inflammatory, wound healing, and radioprotective activities of these preparations. They restore the trace element imbalance and the metallig-and homeostasis.
The optimal variant of treatment can be selected on the base of individual elementogram of the patient, which suggests considering the trace element biocomplexes as a new generation of preparations. The data on changes in the element composition in disease are extremely important, but are unco-ordinated up to the present time and little available for medical practice in the Russian Federation. However, the realization of many tasks of personalized medicine, for example, the genetic passport of an individual, can become technologically possible in 2 - 3 years. It seems that measurements of concentrations of metals correlating with DNA genetic information will be practiced in Russia as well. Thus, the notions of trace element deficiency, excess, and imbalance will acquire a strictly analytical meaning.
Illustrations provided by the authors
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