Avaliação dos efeitos de calcogenonucleosídeos derivados da zidovudina usando células sanguíneas como alvo toxicológico

Abstract

Zidovudine (AZT), a thymidine derivative, is widely used in antiretroviral regimens and more recently it has been indicated, in combination with other chemotherapeutics, for the treatment of some types of cancer. Patients under therapy with zidovudine (AZT) have experienced several side effects, highlighting the hematopoietic abnormalities. Consequently, the synthesis of new molecules modified from the structure of AZT that may present high therapeutic efficacy and low toxicity has attracted the interest of the scientific community in recent years. Taking into consideration these perspectives, we performed a screening to evaluate and compare the toxicity of three new compounds derived from the AZT molecule containing portions of selenium, the chalcogenonucleosides 5 '-(4-Chlorophenylselene)zidovudine (SZ1), 5'- (Phenylselene)zidovudine (SZ2) and 5 '-(4-Methylphenylselene)zidovudine (SZ3) in resting and stimulated mononuclear cells and erythrocytes isolated from human blood. PBMCs were exposed to AZT and derivatives at concentrations of 10 to 200μM for 24 and 72h. For erythrocytes and isolated membranes (Ghosts), the exposure occurred for 3 and 12h at concentrations ranging from 10 to 500μM. Cell viability, cell death, oxidative stress and inflammatory parameters were evaluated after the respective treatments. In order to analyze the toxicity of the compounds in vivo, adult mice received a single dose of AZT and derivatives (100μmol/kg, s.c.) and 72h after the administration, liver and renal biomarkers were analyzed. Exposure to SZ1 caused loss of viability, increased production of reactive species, delayed cell cycle, apoptosis and increased expression and production of proinflammatory cytokines in quiescent PBMCs. Most of these effects were also induced by SZ2. AZT and SZ3 did not cause significant toxicity in quiescent PBMCs. Similar results were found in PBMCs stimulated with phytohemagglutinin. In erythrocytes, SZ1 induced hemolysis and increased membrane fragility. Reactive species generation and lipid peroxidation in erythrocytes ghosts were also significantly increased in cells after exposure to the highest concentrations of SZ1. The activity of δ-ALA-D and Na+/ K+-ATPase enzymes was inhibited by SZ1 and SZ2. In addition, both derivatives caused eriptosis, cell death characterized by the translocation of phosphatidylserine to the membrane surface. AZT and SZ3 did not induce significant toxic effects on erythrocytes. In vivo, exposure to AZT and derivatives did not alter the body weight of mice and serum biochemical markers indicative of renal and hepatic function. However, the relative weights of liver, kidney and spleen were modified in animals treated with AZT, SZ1 and SZ2. These results show that derivatives SZ1 and SZ2, containing portions of chlorophenylselene and phenylselene, respectively, were toxic to PBMCs in different stages of division, as well as to erythrocytes, provoking cellular responses associated with redox imbalance, apoptosis and inflammation. On the other hand, SZ3 derivative exhibited AZT-like properties, emerging as a promising candidate to be tested in studies focusing on viral infections and/or cancer, where AZT is considered the therapeutic model.