Archives: Projekti

IMI projekti

Reproductive Health Effects of Metals in Men

MINISTRY OF SCIENCE, EDUCATION AND SPORTS OF THE REPUBLIC OF CROATIA (2007-2014)

Principal Investigator: Spomenka Telišman (until 31 December 2007), Alica Pizent (since 1 January 2008)

SUMMARY
Recent evidence has indicated a deterioration in the reproductive health of men in many countries over the past few decades, particularly a decrease in semen quality and an increase in prevalence of prostate cancer, but also great differences between and within some countries. The cause of these phenomena is unknown, although a complex role of environmental and lifestyle factors has been implicated. Lead (Pb) and cadmium (Cd) are toxic metals, pervasive in the human environment and accumulate in the human body over a lifetime. In addition to direct toxicity, they can interfere with the metabolism of several essential metals by reducing their bioavailability in the body, can contribute to oxidative stress (implicated in the pathogenesis of male infertility), and can inhibit DNA repair. Copper (Cu), zinc (Zn) and selenium (Se) are essential elements required for optimum activity of many enzymes, including the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) that are protective against oxidative stress. Particularly Zn and Se are important for male reproductive function and can reduce the toxicity of Pb and Cd. Varicocele belongs to the most important causes of male infertility, although the mechanism behind its adverse action is poorly known. Recent data indicate the association of varicocele with an increase in Cd and a decrease in Zn, and with altered activity of antioxidant enzymes in men. Prostate cancer is the 4th most common cancer in men worldwide, and the most common cancer in men in the USA as well as in Croatia. Recent data show a protective role of relatively high serum Se levels against the risk of prostate cancer in men, whereas chronic exposure to Pb and Cd has been shown to decrease Zn and Se, and cause impaired secretory function or damage of the prostate. The objective of this study is to determine the inter-relationship of the blood levels of Pb and Cd, serum levels of Cu, Zn and Se, activities of SOD and GPx in blood, and age, smoking, and alcohol consumption with respect to clinically defined presence and intensity of varicocele, and of prostate damage, in men with no occupational exposure to metals. The purpose is to provide relevant data concerning the etiology, possible substitutional therapy, and prevention of a further deterioration in the reproductive health in men, as well as to evaluate the contribution of each specific environmental and lifestyle factors. The study is important in view of a considerably lower serum Se level, and somewhat higher blood Pb and Cd levels, in the general population of Croatia than in many other countries.

The Exposure of Humans and Animals to Mycotoxins

Principal Investigator: Maja Peraica

SUMMARY
Mycotoxins are the metabolites of moulds with toxic, carcinogenic, genotoxic, mutagenic, and teratogenic properties. In our earlier studies, we found low concentrations of fumonisin B1 (FB1), fumonisin B2, ochratoxin A (OTA), and zearalenon in food samples collected in various regions of Croatia. OTA is considered to be involved in the development of endemic nephropathy (EN). This kidney disease of unknown etiology and high frequency of tumors of the upper urothelial tract appears in the western part of Brodska Posavina. It is speculated that, in addition to OTA, another nephrotoxic mycotoxin such as FB1 should be involved in the development of EN.
The mechanism of the toxicity of OTA and FB1 is not fully understood. It was proved on cultured cells that OTA and FB1 cause oxidative damage of lipids and DNA. However, it is not know whether low concentrations of these mycotoxins usually found in food can also cause oxidative damage of lipids, proteins and DNA in experimental animals. OTA and FB1 are frequently found together in cereals, and therefore it would be important to see whether their effect is synergistic or not. OTA is an organic anion that accumulates in the kidney cells and partially excretes in urine. OTA is partially reabsorbed due to organic anion transporters (OAT) on the epithelial cells along the nephron, which may contribute to its toxicity in specific parts of the kidney. Recent investigations have shown that the localization of specific OATs in rats is sex-related. Toxic effects of OTA are more severe in male rats, which could be due to the higher expression of OAT in males.
The proposed project will use recently developed methods, some of which will be used for the first time in the research of the mechanisms of action of mycotoxins.
The aim of this project is to clarify the role of oxidative stress caused by mycotoxins in damage of macromolecules (DNA, lipids, and proteins), as well as to improve the understanding of the mechanism of toxicity of OTA by investigating the changes in kidney OAT system. The other aim is to find out whether exposure to OTA and FB1 is involved in the development of EN.
We expect that our results will: a) show whether oxidative stress is involved in the mechanism of OTA and FB1 toxicity, and whether this effect is synergistic, b) show whether OTA affects the expression of OATs in the rat kidney and whether this effect is sex-related, and c) improve the knowledge about the mechanism of EN development.

022-0222148-2822 Transition Metal Complexes with Bioligands: Modelling and Interaction

MINISTRY OF SCIENCE, EDUCATION AND SPORTS OF THE REPUBLIC OF CROATIA (2007-2014)

Principal Investigator: Jasmina Sabolović

SUMMARY
Low-molecular-weight transition metal complexes with amino acids, peptides and proteins are supposed to be a part of exchangeable physiological pool for the storage and transport of essential metals for most tissues in living organisms. The binding affinity between a metal and a ligand affects the biological, chemical and toxicological properties of the metal. Redox potential, the metal-ligand bonding reversibility, ionic species distribution and stability constants in solutions can be measured by voltammetry, whereas the structural properties can be predicted and reproduced with theoretical molecular modelling methods. The Cu(II) complexes with Gly, Ala, Val, Leu, Ile show two-electron and quasi-reversible redox electrochemical behaviour in aqueous solution under physiological conditions. The changes between the vacuum geometries (calculated using quantum chemical methods) and experimental X-ray crystalline geometries of 7 Cu(II) amino acid complexes were revealed and attributed to the ligand-based strain and crystal lattice effects. These geometry changes can be simulated with our original molecular mechanics (MM) model and force field (named FFW) developed to reliably reproduce the experimental crystal and ab initio vacuum structures by geometry optimisation of a molecule in simulated crystalline surroundings and as an isolated system, respectively. By now FFW has been parametrised for bis-Cu(II) complexes with Gly, Ala, Val, Leu, Ile and their alkyl derivatives. The project goals are to gain new experimental and theoretical evidence of the physico-chemical properties of essential Cu and Zn and toxic Pb and Cd metal complexes with bioligands (amino acids, peptides) using theoretical methods (MM, molecular dynamics, quantum chemistry) and experimental methods (voltammetry, X-ray diffraction), and to predict and simulate the complexes’ properties in crystal, vacuum, and solution. Method development and the interplay of the experimental and theoretical results will contribute to the understanding of the metal-bioligand interactions and properties in different physico-chemical conditions. We expect that FFW enlarged with new empirical parameters for the Cu(II) and Zn(II) amino acidates will reliably predict the complexes” properties in a solution. The force field efficacy will be validated by the ability to reproduce experimental results. The proposed studies may lead to get new drugs for prevention of disturbed transition-metal metabolism effects in vivo.