Genotoxicity and cell death induced by tinidazole (TNZ).

Tinidazole (TNZ), a second-generation 5-nitroimidazole compound chemically related to metronidazole (MTZ), has been widely used throughout Europe and developing countries for the treatment of amoebic and parasitic infections. Despite TNZ's increasing use in therapeutics, scarce experimental reports are available in literature on its potential genotoxicity in human cells. Therefore, the aim of the present study was to achieve a precise characterization of the cytotoxic and genotoxic activities of this nitroimidazole in cultured human lymphocytes at therapeutic concentrations (0.1, 1, 10 and 50 microg/ml of culture) and evaluate the possible cell death mechanism associated with it. The endpoints analyzed included: mitotic index (MI), replication index (RI), sister chromatid exchange (SCE) and chromosomal aberrations (CA). A significant decrease (p<0.0001) in MI as well as an increase in SCE (p<0.0001) and CA (p<0.0001) frequencies were observed. No modifications in RI were found. The results suggest a genotoxic and cytotoxic effect of TNZ related with cell death process. Therefore, we evaluated this mechanism by DNA fragmentation (laddering), fluorescence microscopy using acridine orange/ethidium bromide (AO/EB) staining and flow cytometry propidium iodide (PI). DNA extracts of TNZ-treated cells resulted in nucleosomal DNA ladder pattern after 48 h of cell treatment; meanwhile no differences were detected in untreated cells. This pattern correlated with the observed decrease in cellular viability (p<0.05), morphological evidence of apoptosis and increase in the percentage of nuclei with hypodiploid DNA content of TNZ exposed cultures compared with control (p<0.05). We concluded that TNZ is genotoxic, cytotoxic and is able to modulate cell death through apoptotic mechanisms in the experimental design employed.

Teratogenic evaluation of metronidazole and ornidazole using Drosophila melanogaster as an experimental model.

BACKGROUND: Drosophila and vertebrates show similarities that suggest that the mechanisms involved in the induction of developmental defects may be similar in both. Therefore, Drosophila has been proposed as a useful, rapid, and economical model in the preliminary screening for teratology studies. The objective of the present study was to investigate the effect of metronidazole (MTZ) and ornidazole (ONZ) on the developmental stages of Drosophila melanogaster. METHODS: Samarkand wild-type females were allowed to lay eggs for 24 hr in media containing MTZ or ONZ at concentrations of 0, 500, 1000, and 2000 microg/ml. When larvae completed their development, the emerging flies were counted and examined for morphological abnormalities. RESULTS: After the analysis of 400-1000 flies for each concentration, ONZ-treated flies did not show an incidence of malformations above control values, although a significant high number of individuals with reduced body size was observed (p < 0.005, chi2 test). On the other hand, the 1000- and 2000-microg/ml MTZ-treated series presented higher frequencies of total abnormalities than did concurrent and historic controls (p < 0.05, chi2 test), indicating an MTZ effect during developmental morphogenesis. CONCLUSIONS: These findings contribute to the characterization of both nitroimidazoles, which are widely used, especially in underdeveloped countries. At the same time, this Drosophila bioassay is sensitive enough to detect differential effects of MTZ and ONZ (abnormalities vs. growth effects), showing specificity and selectivity.

Cytogenetic evaluation of two nitroimidazole derivatives.

5-Nitroimidazoles are a well-established group of antiprotozoal and antibacterial agents. Thanks to their antimicrobial activity these chemotherapeutic agents inhibit the growth of both anaerobic bacteria and certain anaerobic protozoa such as Trichomonas vaginalis, Entamoeba histolytica and Giardia lamblia. The aim of the present study is to achieve a precise characterization of the genotoxic activity of these compounds and to establish the value of cytogenetic assays in order to determine the effect of these drugs, at therapeutic doses, to settle an improved risk assessment. Two nitroimidazole were studied, metronidazole and ornidazole, at four different concentrations (0.1, 1, 10 and 50 microg/ml of peripheral blood lymphocyte culture). Endpoints analyzed included: mitotic index (MI), replication index (RI), sister chromatid exchange (SCE) and chromosomal aberrations (CA). An analysis of variance test (ANOVA) was performed to evaluate the results. A significant decrease (P<0.0001) in MI as well as an increase in SCE (P<0.0001) and CA (0.0001) frequencies for both drugs was observed. No modifications in RI were found. The results suggest a genotoxic and cytotoxic effect of MTZ and ONZ in human peripheral blood cultures in vitro.

Evaluation of genetic damage induced by a nitroimidazole derivative in human lymphocytes: Tinidazole (TNZ).

One of the useful drugs in the treatment against infestations caused by Trichomonas vaginalis, Entamoeba histolytica and Giardia lamblia is Tinidazole (TNZ) 1-[2-(ethylsulfonyl) ethyl]-2-methyl-5-nitroimidazole) (Gilman R.H., Marquis G.S., Miranda E., Vestegui M., Martinez H., 1988. Rapid reinfection by Giardia lamblia after treatment in a hyperendemic third world community. Lancet i, 343-345). We decided to evaluate the potential genetic damage induced by TNZ using different biological biomarkers such as the mitotic index (MI), sister chromatid exchange (SCE) and cell proliferation kinetics (CPK). We observed a significant decrease (P<0.0005) in the MI as well as an increase (P<0.0005) in SCE frequency and no modifications in the replication index (RI). The results obtained suggest a potential genotoxic and cytotoxic effect of TNZ in human peripheral blood cultures in vitro.