Methylmercury intoxication activates nitric oxide synthase in chick retinal cell culture

The visual system is a potential target for methylmercury (MeHg) intoxication. Nevertheless, there are few studies about the cellular mechanisms of toxicity induced by MeHg in retinal cells. Various reports have indicated a critical role for nitric oxide synthase (NOS) activation in modulating MeHg neurotoxicity in cerebellar and cortical regions. The aim of the present study is to describe the effects of MeHg on cell viability and NOS activation in chick retinal cell cultures. For this purpose, primary cultures were prepared from 7-day-old chick embryos: retinas were aseptically dissected and dissociated and cells were grown at 37ºC for 7-8 days. Cultures were exposed to MeHg (10 µM, 100 µM, and 1 mM) for 2, 4, and 6 h. Cell viability was measured by MTT method and NOS activity by monitoring the conversion of L-[H3]-arginine to L-[H3]-citrulline. The incubation of cultured retina cells with 10 and 100 µM MeHg promoted an increase of NOS activity compared to control (P < 0.05). Maximum values (P < 0.05) were reached after 4 h of MeHg incubation: increases of 81.6 ± 5.3 and 91.3 ± 3.7%, respectively (data are reported as mean ± SEM for 4 replicates). MeHg also promoted a concentration- and time-dependent decrease in cell viability, with the highest toxicity (a reduction of about 80% in cell viability) being observed at the concentration of 1 mM and after 4-6 h of incubation. The present study demonstrates for the first time the modulation of MeHg neurotoxicity in retinal cells by the nitrergic system

Mutagenicity of hydroxyurea in lymphocytes from patients with sickle cell disease

Hydroxyurea is commonly used in the treatment of myeloproliferative diseases and in patients with sickle cell disease (SCD). The use of this antineoplastic agent in patients with SCD is justified because of the drug's ability to increase fetal hemoglobin levels, thereby decreasing the severity of SCD. However, high doses or prolonged treatment with hydroxyurea can be cytotoxic or genotoxic for these patients, with an increased risk of developing acute leukemia. This danger can be avoided by monitoring the lymphocytes of patients treated with hydroxyurea. Cytogenetic tests are important endpoints for monitoring the physiological effects of physical and chemical agents, including drugs. In this work, we assessed the genotoxicity of hydroxyurea in short-term cultures of lymphocytes from SCD patients. Hydroxyurea was not cytotoxic or genotoxic at the concentrations tested in the G2 phase of the cell cycle. These results support the use of hydroxyurea in the treatment of SCD, although further work is necessary to understand the effects of this drug in vivo