DNA breakage due to metronidazole treatment

Metronidazole promotes oxidative stress and DNA fragmentation-mediated myocardial injury in albino mice

The purpose of the present study was to investigate the cardiotoxic effects of Metronidazole (Mtz) in albino mice. The mice were divided into four experimental groups: Gp.I (control group): saline, Gp.II:125 mg/kg b.w Mtz, Gp.III:250 mg/kg b.w, Gp.IV:500 mg/kg b.w Mtz. Heart weight ratio, markers of cardiac injury, markers of oxidative stress, histopathological examinations, DNA fragmentation and spectral analysis were used to determine cardiotoxicity. Administration of 125-500 mg/kg Mtz caused an increase in heart weight and a decrease in body weight. Administration of 500 mg/kg Mtz increased heart weight by 35.5% and decreased body weight by 21.9% compared with control. Mtz-treated mice showed a significant increase in cardiac injury biomarkers and serious alterations in cardiac oxidative stress markers. Histopathological changes of cardiac tissues observed in mice treated with Mtz include myocardial hypertrophy, fibrosis, myocarditis, separation of the muscle fibers, congestion-narrowing in vessels, necrosis, myocardium-vacuolation, myocytolysis, myocyte degeneration, nuclear aggregation, cytoplasmic fragmentation and prevalent nuclei. Mtz treatment already resulted in a significant decrease in the percentage of head DNA and an increase in the percentage of tail DNA. The most striking tail formation among the Mtz-treated groups was observed in the group receiving 500 mg/kg Mtz. In the presence of Mtz, there was a hypochromic shift in the absorption spectrum of DNA, and the potential DNA-Mtz interaction was found to occur in the intercalation mode. These results show that Mtz used against anaerobic bacteria and protozoa in gastrointestinal infections can cause severe cardiotoxic findings in albino mice and cause fragmentation in DNA.

The use of metronidazole in acute diarrhea in dogs: a narrative review

Acute diarrhea is a common reason for non-wellness veterinary visits in dogs. Treatment for acute diarrhea usually consists of supportive care with nutritional intervention, fluid therapy, anthelmintics, and often an antibiotic - commonly metronidazole in North America. The empirical use of metronidazole for acute diarrhea in dogs has been a common practice in veterinary medicine for many decades; however, recent studies evaluating its use suggest it may be inappropriately utilized in many cases. Herein, we review the evidence evaluating the use of metronidazole and other antibiotics in acute diarrhea in the human and veterinary literature. Recommendations on the use of metronidazole and other antibiotics as well as other therapeutic considerations in the treatment of acute diarrhea are also provided.

The Hitchhiker's Guide to Deep Learning Driven Generative Chemistry

This microperspective covers the most recent research outcomes of artificial intelligence (AI) generated molecular structures from the point of view of the medicinal chemist. The main focus is on studies that include synthesis and experimental in vitro validation in biochemical assays of the generated molecular structures, where we analyze the reported structures' relevance in modern medicinal chemistry and their novelty. The authors believe that this review would be appreciated by medicinal chemistry and AI-driven drug design (AIDD) communities and can be adopted as a comprehensive approach for qualifying different research outcomes in AIDD.

Genotoxicity from metronidazole detected in vitro, but not in vivo, in healthy dogs in a randomized clinical trial

OBJECTIVE

To determine whether metronidazole (MTZ), at recommended therapeutic dosages in dogs, induces peripheral blood cell (PMBC) genotoxicity, using the γ-H2AX assay as a sensitive measure of DNA breaks. The secondary aim was to assess dose-dependent genotoxicity in vitro in dog and cat PBMCs exposed to increasing MTZ concentrations.

ANIMALS

12 healthy employee- and student-owned dogs and blood samples from 2 other healthy untreated dogs and 2 healthy untreated cats.

PROCEDURES

Screened dogs were randomized to receive lower-dose MTZ (7.5 mg/kg, PO, q 12 h) or higher-dose MTZ (20 mg/kg, PO, q 12 h) for 7 days. Blood was drawn at baseline, after the 1 week of treatment, and after a 1-week washout, for DNA damage assessment and serum MTZ concentration measurements. For in vitro studies, PBMCs from untreated healthy dogs and cats were exposed to 0 to 500 μg/mL MTZ.

RESULTS

No dogs showed a significant increase in DNA damage at these MTZ dosages for 1 week. The highest serum MTZ concentration observed 1 hour after dosing was 36 μg/mL. In vitro, MTZ led to a significant increase in DNA damage at 100 μg/mL in both canine and feline PBMCs.

CLINICAL RELEVANCE

Although MTZ was not significantly genotoxic in vivo in the healthy dogs in this study, MTZ was significantly genotoxic to canine PBMCs in vitro at 3-fold higher concentrations than those documented in vivo. The safety of MTZ in clinically ill dogs, which may have impaired MTZ clearance or DNA repair, should be assessed next.

Integrated Genotoxicity Testing of three anti-infective drugs using the TGx-DDI transcriptomic biomarker and high-throughput CometChip® assay in TK6 cells

Genotoxicity testing relies on the detection of gene mutations and chromosome damage and has been used in the genetic safety assessment of drugs and chemicals for decades. However, the results of standard genotoxicity tests are often difficult to interpret due to lack of mode of action information. The TGx-DDI transcriptomic biomarker provides mechanistic information on the DNA damage-inducing (DDI) capability of chemicals to aid in the interpretation of positive in vitro genotoxicity data. The CometChip^® assay was developed to assess DNA strand breaks in a higher-throughput format. We paired the TGx-DDI biomarker with the CometChip^® assay in TK6 cells to evaluate three model agents: nitrofurantoin (NIT), metronidazole (MTZ), and novobiocin (NOV). TGx-DDI was analyzed by two independent labs and technologies (nCounter^® and TempO-Seq^®). Although these anti-infective drugs are, or have been, used in human and/or veterinary medicine, the standard genotoxicity testing battery showed significant genetic safety findings. Specifically, NIT is a mutagen and causes chromosome damage, and MTZ and NOV cause chromosome damage in conventional in vitro tests. Herein, the TGx-DDI biomarker classified NIT and MTZ as non-DDI at all concentrations tested, suggesting that NIT’s mutagenic activity is bacterial specific and that the observed chromosome damage by MTZ might be a consequence of in vitro test conditions. In contrast, NOV was classified as DDI at the second highest concentration tested, which is in line with the fact that NOV is a bacterial DNA-gyrase inhibitor that also affects topoisomerase II at high concentrations. The lack of DNA damage for NIT and MTZ was confirmed by the CometChip^® results, which were negative for all three drugs except at overtly cytotoxic concentrations. This case study demonstrates the utility of combining the TGx-DDI biomarker and CometChip^® to resolve conflicting genotoxicity data and provides further validation to support the reproducibility of the biomarker.

Metronidazole enhances steatosis-related early-stage hepatocarcinogenesis in high fat diet-fed rats through DNA double-strand breaks and modulation of autophagy

Nonalcoholic fatty liver disease is a hepatic disorder with deposition of fat droplets and has a high risk of progression to steatosis-related hepatitis and irreversible hepatic cancer. Metronidazole (MNZ) is an antiprotozoal and antimicrobial agent widely used to treat patients infected with anaerobic bacteria and intestinal parasites; however, MNZ has also been shown to induce liver tumors in rodents. To investigate the effects of MNZ on steatosis-related early-stage hepatocarcinogenesis, male rats treated with N-nitrosodiethylamine following 2/3 hepatectomy at week 3 were received a control basal diet, high fat diet (HFD), or HFD containing 0.5% MNZ. The HFD induced obesity and steatosis in the liver, accompanied by altered expression of Pparg and Fasn, genes related to lipid metabolism. MNZ increased nuclear translocation of lipid metabolism-related transcription factor peroxisome proliferator-activated receptor gamma in hepatocytes, together with altered liver expression of lipid metabolism genes (Srebf1, Srebf2, Pnpla2). Furthermore, MNZ significantly increased the number of preneoplastic liver foci, accompanied by DNA double-strand breaks and late-stage autophagy inhibition, as reflected by increased levels of γ-H2AX, LC3, and p62. Therefore, MNZ could induce steatosis-related hepatocarcinogenesis by inducing DNA double-strand breaks and modulating autophagy in HFD-fed rats.

Design and Synthesis of IMR-23, an Oxime Derived from Nitroimidazole as an Immunomodulatory Molecule

BACKGROUND

Adjuvants have been obtained empirically by trial and error experiments and today, there is a tendency to the rational design of adjuvants candidates, which will increasingly achieve effective and safe products. The aim of this work was to design and evaluate the compound IMR-23 derived from nitroimidazole as an immunomodulatory molecule.

MATERIALS AND METHODS

The IMR-23 molecule was obtained by a condensation reaction, cytotoxicity was tested by the sulforhodamine B assay. Adjuvanticity was evaluated in vivo and in vitro in J774A.1 cells and in the mouse model, respectively.

RESULTS

IMR-23 that did not show cytotoxicity on HeLa, Vero cells and macrophages J774A.1, was able to induce the production of molecules involved in the inflammatory process, such as cytokines and chemokines determined by ELISA, to induce the production of antibodies and to generate antigenspecific cells to ovalbumin and against the antigen GST-L1b.

CONCLUSION

These results open the possibility of further studies to obtain a proper balance of immunogenicity- toxicity in the use of IMR-23 as an adjuvant molecule.

Nanomolar photodynamic activity of porphyrins bearing 1,4,7-trioxanonyl and 2-methyl-5-nitroimidazole moieties against cancer cells

Despite the continuous development of medicine, there is still a lack of effective and fully safe protocols for the treatment of neoplastic diseases. The drug-drug conjugates approach seems to give a chance to obtain more efficient molecules. New alkoxy and metronidazole substituted porphyrins were synthesized. Novel porphyrins were purified by flash column chromatography and characterized using NMR, MS, UV-Vis and HPLC. The Nuclear Magnetic Resonance study was performed to annotate experimentally observed ¹H NMR and ¹³C NMR signals of new compounds. The 2D NMR techniques such as ¹H-¹H COSY (Correlation Spectroscopy), ¹H-¹³C HSQC (Heteronuclear Single Quantum Correlation) and 1H-13C HMBC (Heteronuclear Multiple Bond Correlation) were used for the structure elucidation of the new compounds. In the range of 250-450 nm of the absorption spectra, the Soret band was observed, whereas the Q band was noted in the range of 500-650 nm. Compounds revealed a fluorescence quantum yield in the range 0.03-0.12. Singlet oxygen generation quantum yields up to 0.54 were determined. Electrochemical properties has also been studied. It has been noticed electropolymerization of compound bearing 5-nitroimidazole substituents. The photodynamic activity of the studied porphyrins against A549 and HEK001/HPV16 cancer cells were examined. The most active against A549 and HEK 001/HPV16 was light-excited trioxanonylporphyrin with the values of IC₅₀ equal to 0.49 μM and 50 nM respectively.

A Case of Aplastic Anemia Associated With Long-Term Metronidazole Use

Metronidazole is a nitroimidazole antibacterial agent that is highly effective for the treatment of protozoal and anaerobic infections. Metronidazole is known to cause hematologic adverse effects, including a reversible mild neutropenia; in rare circumstances, thrombocytopenia has been associated with metronidazole treatment. We present a case of aplastic anemia related to the extended use of metronidazole.

Two DNA binding modes of a zinc-metronidazole and biological evaluation as a potent anti-cancer agent

A complex of metronidazole (MTZ) with zinc ion was synthesized and characterized by UV-Vis, Fourier transform infrared (FT-IR), ¹H-NMR, X-ray crystallography and thermal gravimetric-differential thermal analysis (TG-DTA). The cytotoxicity effect of the synthesized complex investigated over SKNMC, A549, MCF-7, and MCDK cell lines and the results have shown that it has high cytotoxic potential over cancer cell lines. In order to clarify the mechanism of cell cytotoxicity, the oxidative stress and binding of the complex to the calf thymus-DNA studied by evaluating the intrinsic binding constant and defining thermodynamic parameters of complex over the DNA accompanying with in silico molecular modeling method. For this purpose, the complex optimized at the B3LYP/LANL2DZ level and docked over the DNA structure. The results revealed that the metronidazole-zinc complex interacted with DNA via hydrogen binding and electrostatic interaction to the minor groove region and phosphate backbone of DNA, respectively.

The Occurrence of Metronidazole-Induced Encephalopathy in Cancer Patients: A Hospital-Based Retrospective Study

Background:

Metronidazole-induced encephalopathy (MIE) is a rare but serious complication caused by metronidazole, a widely used antianaerobic drug. Previous studies prescribed MIE including dysarthria, cerebellar ataxia, and confusion after long-term use of metronidazole. Malignancy has been proposed one of the predisposing conditions for MIE. However, the occurrence of MIE in cancer patients remains unknown.

Methodology:

We investigated the occurrence of MIE and analyzed retrospectively by hospital-based data of 4160 cancer patients from January 2014 to December 2016.

Results:

Findings in 793 cancer patients who underwent metronidazole therapy for anaerobic infection revealed two cases of MIE. One had renal cell carcinoma and the other had bladder urothelial carcinoma. Both of their initial presentation were cerebellar dysfunction. The occurrence of MIE was 8.6% for cases who received >30 g of cumulative dose. Hypertension was the most common comorbidity, followed by chronic renal disease and diabetes mellitus.

Conclusion:

In cancer patients, MIE should be monitored in those with genitourinary cancer, especially with renal dysfunction. Longer duration with more cumulative dose also has a greater risk of MIE. Early consideration of MIE with prompt cessation of metronidazole may result in better outcome.

Effect of Metronidazole on the Oxidoreductive Processes in the Submandibular and Parotid Glands in Experimental Research

Oxidative stress takes part in the pathomechanisms of many diseases, including oral disorders. The imbalance between oxidative and antioxidative processes may lead to periodontitis, osteitis, or oral cancers. Furthermore, many chemotherapeutics, e.g., metronidazole (MTZ), may also cause toxic reactions and affect oxidative reactions. The research focused on MTZ influence on oxidative destruction in the parotid and submandibular gland tissue in animal experimental model. Therefore, the concentrations of enzymatic and nonenzymatic markers of oxidative stress were measured in these two rat glands in the control and experimental MTZ-treated groups. The material for analysis included parotid and submandibular glands of male Wistar rats, which were treated with metronidazole for 7 days by gastric tube in a dose of 100 mg/kg b.w. On day 8, the material was obtained and frozen in temp. -80°C. Then, the following seven enzymatic and nonenzymatic parameters were measured: GPx, TOS, TAS, SOD, LPO, CAT, and GSH. The data were analysed using Statistica 10.0. Metronidazole treatment in the experimental model showed an increase in LPO, TOS, and TOS/TAS and a decrease in CAT, SOD, GPx, and TAS. The conclusions of this research were made. Metronidazole treatment in a dose of 100 mg/kg b.w. caused imbalance between oxidative and antioxidative reactions in the rat parotid and submandibular glands. An increase was observed in LPO, TOS, and TOS/TAS in both glands exposed to metronidazole. Decreased activity of CAT, SOD, GPx, and TAS was noted, which indicates attenuation of the gland antioxidative protective barrier.

Click Chemistry-Facilitated Structural Diversification of Nitrothiazoles, Nitrofurans, and Nitropyrroles Enhances Antimicrobial Activity against Giardia lamblia

Giardia lamblia is an important and ubiquitous cause of diarrheal disease. The primary agents in the treatment of giardiasis are nitroheterocyclic drugs, particularly the imidazoles metronidazole and tinidazole and the thiazole nitazoxanide. Although these drugs are generally effective, treatment failures occur in up to 20% of cases, and resistance has been demonstrated in vivo and in vitro Prior work had suggested that side chain modifications of the imidazole core can lead to new effective 5-nitroimidazole drugs that can combat nitro drug resistance, but the full potential of nitroheterocycles other than imidazole to yield effective new antigiardial agents has not been explored. Here, we generated derivatives of two clinically utilized nitroheterocycles, nitrothiazole and nitrofuran, as well as a third heterocycle, nitropyrrole, which is related to nitroimidazole but has not been systematically investigated as an antimicrobial drug scaffold. Click chemistry was employed to synthesize 442 novel nitroheterocyclic compounds with extensive side chain modifications. Screening of this library against representative G. lamblia strains showed a wide spectrum of in vitro activities, with many of the compounds exhibiting superior activity relative to reference drugs and several showing >100-fold increase in potency and the ability to overcome existing forms of metronidazole resistance. The majority of new compounds displayed no cytotoxicity against human cells, and several compounds were orally active against murine giardiasis in vivo These findings provide additional impetus for the systematic development of nitroheterocyclic compounds with nonimidazole cores as alternative and improved agents for the treatment of giardiasis and potentially other infectious agents.

Bioassay-guided fractionation of extracts from Codiaeum variegatum against Entamoeba histolytica discovers compounds that modify expression of ceramide biosynthesis related genes

Leaves of Codiaeum variegatum ("garden croton") are used against bloody diarrhoea by local populations in Cameroon. This study aims to search for the active components from C. variegatum against Entamoeba histolytica, and thereby initiate the study of their mechanism of action. A bioassay-guided screening of the aqueous extracts from C. variegatum leaves and various fractions was carried out against trophozoites of E. histolytica axenic culture. We found that the anti-amoebic activity of extracts changed with respect to the collection criteria of leaves. Thereby, optimal conditions were defined for leaves' collection to maximise the anti-amoebic activity of the extracts. A fractionation process was performed, and we identified several sub-fractions (or isolated compounds) with significantly higher anti-amoebic activity compared to the unfractionated aqueous extract. Anti-amoebic activity of the most potent fraction was confirmed with the morphological characteristics of induced death in trophozoites, including cell rounding and lysis. Differential gene expression analysis using high-throughput RNA sequencing implies the potential mechanism of its anti-amoebic activity by targeting ceramide, a bioactive lipid involved in disturbance of biochemical processes within the cell membrane including differentiation, proliferation, cell growth arrest and apoptosis. Regulation of ceramide biosynthesis pathway as a target for anti-amoebic compounds is a novel finding which could be an alternative for drug development against E. histolytica.

Metronidazole affects breast cancer cell lines

PURPOSE

The aim of our study was to evaluate the impact of metronidazole (MTZ) on cytotoxicity and DNA synthesis in MCF-7 (estrogen receptor positive) and MDA-MB-231 (estrogen receptor negative) breast cancer cell lines.

MATERIAL/METHODS

Toxicity of MTZ was determined by MTT test. MCF-7 and MDA-MB-231 cells were incubated with metronidazole used in different concentrations for 24, 48 and 72 hours. The effect of MTZ on DNA synthesis was measured as [3H]-thymidine incorporation.

RESULTS

We showed that MTZ in concentration 250 μg/ml significantly increases the growth of MCF-7 cell lines after 24 hours of incubation, but it reduces cell viability in concentrations 1 and 10 μg/ml 72 hours after the drug application. Significant increase of MDA-MB-231 cell viability was obtained in MTZ concentration of 250 μg/ml after 24 and 72 hours. The increase of [3H]-thymidine incorporation in MCF-7 cell line treated with MTZ in concentration 250 μg/ml was statistically significant after 24 hours. Great suppression of cell proliferation was obtained in MDA-MB-231 breast cell line after application of the following concentrations of MTZ: 0.1 μg/ml (after 24 hours) and 0.1, 10, 50, 250 μg/ml (after 72h).

CONCLUSIONS

We found that metronidazole exerts different dose- and time- dependent effects on human breast cancer cell lines characterized by presence or absence of estrogen receptors. We suggest that these discrepancies may be influenced by the estrogen signaling.

Evidence for induction of integron-based antibiotic resistance by the SOS response in a clinical setting

Bacterial resistance to β-lactams may rely on acquired β-lactamases encoded by class 1 integron-borne genes. Rearrangement of integron cassette arrays is mediated by the integrase IntI1. It has been previously established that integrase expression can be activated by the SOS response in vitro, leading to speculation that this is an important clinical mechanism of acquiring resistance. Here we report the first in vivo evidence of the impact of SOS response activated by the antibiotic treatment given to a patient and its output in terms of resistance development. We identified a new mechanism of modulation of antibiotic resistance in integrons, based on the insertion of a genetic element, the gcuF1 cassette, upstream of the integron-borne cassette bla_OXA-28 encoding an extended spectrum β-lactamase. This insertion creates the fused protein GCUF1-OXA-28 and modulates the transcription, the translation, and the secretion of the β-lactamase in a Pseudomonas aeruginosa isolate (S-Pae) susceptible to the third generation cephalosporin ceftazidime. We found that the metronidazole, not an anti-pseudomonal antibiotic given to the first patient infected with S-Pae, triggered the SOS response that subsequently activated the integrase IntI1 expression. This resulted in the rearrangement of the integron gene cassette array, through excision of the gcuF1 cassette, and the full expression the β-lactamase in an isolate (R-Pae) highly resistant to ceftazidime, which further spread to other patients within our hospital. Our results demonstrate that in human hosts, the antibiotic-induced SOS response in pathogens could play a pivotal role in adaptation process of the bacteria.

The bacterial SOS response is a conserved regulatory network that is induced in response to DNA damage. Its activation in vitro leads to the emergence of resistance to antibiotics, leading to speculation that this is an important clinical mechanism of acquiring resistance. We found evidence here that antibiotic-induced SOS response plays a role in bacterial genome rearrangement in vivo within humans. The major classes of antibiotics can trigger the bacterial SOS response and our data raise questions about their wide use and their subsequent effect on the bacterial genetic adaptability. This suggests that emergence of antibiotic resistance during therapy could be reduced by inhibiting the bacterial SOS response. We showed that acquired resistance genes could spread latently in susceptible bacterial strains until needed. These findings could impact current policies for control of antibiotic resistance, which rely on the detection of resistant bacteria and on the assumption that resistance mechanisms have a functional cost to the bacteria. More generally, SOS response may spur changes in the behavior of bacteria and their faster adaptation to hostile environments, including humans.

The evaluation of genotoxic potential of ornidazole, nitroimidazole, in lymphocyte culture of patients with amebiasis

The genotoxicity study of ornidazole (ONZ) was carried out on human lymphocyte chromosomes, using sister chromatid exchange (SCE) and micronucleus (MN). Thirty-two patients with Entemoeba histolitica infection who received 1000 mg/day for 10 days were included in this study. SCE and MN were measured before and after therapy. A statistically significant increase was observed in the SCE (P < 0.001) and MN frequencies (P < 0.001) after ornidazole therapy. It was concluded that ONZ has a potential geno- and cytotoxic effect in human peripheral lymphocyte cultures. For this reason, further, detailed studies are needed to elucidate the ONZ mechanism of genotoxicity and its carcinogenic potential.

The role of paraoxonase polymorphisms in the induction of micronucleus in paraoxon-treated human lymphocytes

Human paraoxonase-1 (PON1) is a high-density lipoprotein-associated enzyme that has a role in the detoxification of organophosphorus compounds by hydrolyzing the bioactive oxons. PON1 polymorphims are responsible, at least in part, for the variation in the catalytic activity and expression of the enzyme and have been associated with susceptibility to organophosphorus pesticide toxicity, mainly neurotoxicity. The aim of this study was to determine whether paraoxon induced micronuclei and to examine the role of PON1 polymorphism in paraoxon's genotoxic potential. First, dose finding cytogenetic experiments were performed on lymphocyte cultures from three donors and a range of paraoxon concentration (1-25 microM) were tested. In a second set of experiments, 5 microM paraoxon was added to blood cultures of 11 donors with two different PON1 haplotypes (PON T(-108)M(55)Q(192) with low activity and haplotype PON C(-108)L(55) R(192) with high activity, referred to as PON1QQ and as PON1 RR, respectively). Because PON1 is present in blood, the effect of adding 5 microM paraoxon and 70 microl of autologous plasma to lymphocyte cultures also was examined. Paraoxon had no effect on cell viability, but caused a significant dose-dependent increase in MN frequency. The basal MN frequencies were similar on QQ and RR genotypes. A significant difference was observed in the MN frequency only in lymphocytes from individuals with the QQ genotype treated with 5 microM paraoxon and the autologous plasma did not modify these effects. The results obtained in this study suggest that PON1 genotype might have an important role in the identification of individuals at risk for cancer development due to occupational exposure to pesticides.

Genotoxicity revaluation of three commercial nitroheterocyclic drugs: nifurtimox, benznidazole, and metronidazole

Nitroheterocyclic compounds are widely used as therapeutic agents against a variety of protozoan and bacterial infections. However, the literature on these compounds, suspected of being carcinogens, is widely controversial. In this study, cytotoxic and genotoxic potential of three drugs, Nifurtimox (NFX), Benznidazole (BNZ), and Metronidazole (MTZ) was re-evaluated by different assays. Only NFX reduces survival rate in actively proliferating cells. The compounds are more active for base-pair substitution than frameshift induction in Salmonella; NFX and BNZ are more mutagenic than MTZ; they are widely dependent from nitroreduction whereas microsomal fraction S9 weakly affects the mutagenic potential. Comet assay detects BNZ- and NFX-induced DNA damage at doses in the range of therapeutically treated patient plasma concentration; BNZ seems to mainly act through ROS generation whereas a dose-dependent mechanism of DNA damaging is suggested for NFX. The lack of effects on mammalian cells for MTZ is confirmed also in MN assay whereas MN induction is observed for NFX and BNZ. The effects of MTZ, that shows comparatively low reduction potential, seem to be strictly dependent on anaerobic/hypoxic conditions. Both NFX and BNZ may not only lead to cellular damage of the infective agent but also interact with the DNA of mammalian cells.

Single-dose pharmacokinetics and genotoxicity of metronidazole in cats

Single-dose pharmacokinetics and genotoxicity of metronidazole in cats were evaluated. Cats received either 5 mg/kg metronidazole intravenously, or 20 mg/kg metronidazole benzoate (12.4 mg/kg metronidazole base) orally in a single dose. Serial plasma samples were collected and assayed for metronidazole using high pressure liquid chromatography (HPLC). Genotoxicity was assessed in vitro in feline peripheral blood mononuclear cells (PBMC) and a feline T-cell lymphoma line incubated with metronidazole, and in vivo in PBMC collected before, during and 7 days after oral metronidazole, by use of the COMET assay. Systemic absorption of metronidazole was variable (mean=65±28%) with a peak of 8.84±5.4 μg/ml at 3.6±2.9 h. The terminal half-life was 5.34 h from the intravenous dose and 5.16 h from the oral dose. Systemic clearance was low (mean=91.57 ml/h/kg [1.53 ml/kg/min]), and the apparent volume of distribution (steady state) was 0.650±0.254 l/kg. Genotoxicity was detected at all concentrations of metronidazole in feline PBMC and the T-cell lymphoma line in vitro. Genotoxicity was also observed in PBMC collected from cats after 7 days of oral metronidazole but resolved within 6 days of discontinuing metronidazole.

In vitro effect of garlic extract and metronidazole against Neoparamoeba pemaquidensis, page 1987 and isolated amoebae from Atlantic salmon

Neoparamoeba pemaquidensis believed to be the most prevalent parasite of Atlantic salmon industry in Australia. In the present study, the in vitro effects of crude extract of garlic and metronidazole were investigated using a primary culture toxicity assay. Garlic extract appeared to be completely effective at killing a cultured strain (NP251002) of Neoparamoeba pemaquidensis in vitro at a dilution of 1:100 with in 24 h. The number of viable Amoebae after using garlic extract in lower dilutions (1:200, 1:400, 1:800, 1:1000) for 24 h, also were significantly lower than in the control group. Garlic extract was also efficacious at killing wild type Amoebae that isolated from the diseased fish showing clinical signs of AGD. Metronidazole had no clear effect against Neoparamoeba pemaquidensis (NP251002) even in a concentration of 50 mg L(-1) for 24 h. However some morphological changes have occurred in metronidazole-treated Amoebae after 5 days of exposure.

Solid phase synthesis of a metronidazole oligonucleotide conjugate

Direct, solid phase synthesis of an oligonucleotide conjugate of the antibiotic drug metronidazole was accomplished by the phosphoramidite method. Removal of protecting groups and cleavage from the controlled pore glass (CPG) solid support was successful using mild conditions (20% Et(3)N in pyridine, then conc. NH(3) (aq) at rt for 30 min) whereas standard conditions (conc. NH(3) (aq) at 55 degrees C for 16 h) cleaved the drug.

Voltammetry of the interaction of metronidazole with DNA and its analytical applications

Voltammetric methods were used to probe the interaction of antimicrobial drug metronidazole (MTZ) with calf thymus DNA. Binding constants (K) and binding site sizes (s) were determined from the voltammetric data, i.e., shifts in potential and changes in limiting current with the addition of DNA. MTZ showed appreciable electrostatic binding to DNA in solution with K=2.2(+/- 1.3) x 10(4) M(-1) and s=0.34 bp. One reduction peak of MTZ at the bare glassy carbon electrode (GCE) split into two peaks at the DNA modified GCE (DNA/GCE). These changes in the cyclic voltammogram can only be due to the interaction of MTZ with the surface-confined DNA. In addition, the peak current of MTZ at the DNA/GCE was nearly 8-fold of the response at the bare GCE. The low detection limit of 2.0 x 10(-8) M made the DNA/GCE a promising biosensor for MTZ determination. And this method was successfully applied with high precision and accuracy compared with spectroscopic methods (relative error < 6%) for estimation of the total MTZ drug content in pharmaceutical dosage forms.

Implication of nitro group reduction in the mutagenic and chromosome damaging activities of 22 new 5-nitroisoquinolines by the Salmonella mutagenicity test and the cytokinesis-blocked micronucleus assay

The mutagenic (MUT) and chromosome-damaging (CHR) activities of 22 potential antimalarial drugs (5-nitroisoquinoline derivatives) were evaluated by the Salmonella test and the cytokinesis-blocked micronucleus assay (CBMN). The Salmonella mutagenicity test was performed with and without metabolic activation (S9 mix) in S. typhimurium strains TA100 and YG1042 (an overproducing nitroreductase and O-acetyltransferase TA100 strain). The CBMN was carried out on human lymphocytes without metabolic activation. Four concentrations were tested: 1, 10, 100 and 1000 ng/ml. MUT was expressed as minimal mutagenic concentrations (MMC, microM) and CHR was expressed as minimal chromosome-damaging concentrations (MCDC, nM) to compare both activities. All the 5-nitroisoquinoline compounds were mutagenic in TA100. MMC ranged from 0.1 to 52.9 microM in TA100. A statistically significant decrease in MMC was observed in YG1042 (8 x 10(-3) to 3.5 microM), implicating reduction of the nitro group. Modulation of MUT by S9 mix was not significant in TA100 and YG1042. CHR was detected in 13 products for at least one concentration. Among the chromosome-damaging compounds, the MCDC ranged from 2.9 x 10(-3) to 3.6 nM. No relationship was found between MUT and CHR, suggesting two distinct pathways of DNA damage.

Supramolecular structures of metronidazole and its copper(II), cobalt(II) and zinc(II) coordination compounds

In this work we present the synthesis and structural and spectroscopic characterization of Cu(II), Co(II) and Zn(II) coordination compounds with the antibiotic metronidazole ([double bond]emni). Coordination to metal ions is through its imidazolic nitrogen, while the hydroxyethyl and nitro groups act as supramolecular synthons. [Co(emni)(2)Br(2)], and [Zn(emni)(2)X(2)] (X(-)=Cl, Br) stabilize zig-zag chains, and a 2D supramolecular structure is formed by inter-chain contacts through inter-molecular hydrogen-bonding. Pleated sheet or layers are formed by [Co(emni)(2)Cl(2)] and [Cu(emni)(2)Cl(H(2)O)](2)Cl(2), respectively. The dinuclear Cu(II) compound [Cu(emni)mu(O(2)CMe)(2)](2) gives a one-dimensional zig-zag arrangement. The contribution of metal ions in metronidazole coordination compounds is shown in the stabilization of the different aggregate structures.

Genotoxicity assessment of the antiepileptic drug AMP397, an Ames-positive aromatic nitro compound

AMP397 is a novel antiepileptic agent and the first competitive AMPA antagonist with high receptor affinity, good in vivo potency, and oral activity. AMP397 has a structural alert (aromatic nitro group) and was mutagenic in Salmonella typhimurium strains TA97a, TA98 and TA100 without S9, but negative in the nitroreductase-deficient strains TA98NR and TA100NR. The amino derivative of AMP397 was negative in wild-type strains TA98 and TA100. AMP397 was negative in a mouse lymphoma tk assay, which included a 24h treatment without S9. A weak micronucleus induction in vitro was found at the highest concentrations tested in V79 cells with S9. AMP397 was negative in the following in vivo studies, which included the maximum tolerated doses of 320mg/kg in mice and 2000mg/kg in rats: MutaMouse assay in colon and liver (5x320mg/kg) at three sampling times (3, 7 and 31 days after the last administration); DNA binding study in the liver of mice and rats after a single treatment with [14C]-AMP397; comet assay (1x2000mg/kg) in jejunum and liver of rats, sampling times 3 and 24h after administration; micronucleus test (2x320mg/kg) in the bone marrow of mice, sampling 24h after the second administration. Based on these results, it was concluded that AMP397 has no genotoxic potential in vivo. In particular, no genotoxic metabolite is formed in mammalian cells, and, if formed by intestinal bacteria, is unable to exert any genotoxic activity in the adjacent intestinal tissue. These data were considered to provide sufficient safety to initiate clinical development of the compound.

Role of P53 functionality in the genotoxicity of metronidazole and its hydroxy metabolite

P53 mediates several biological processes for preservation of genetic stability such as the induction of cell cycle arrest, DNA repair or apoptosis in response to DNA damage. The antiparasitic drug, 1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole (metronidazole, MTZ) is able to increase lymphocyte proliferation inducing at the same time chromosomal aberrations. Trying to understand this unexpected event we used cell lines with different P53 functionality, determining the proliferation capacity and the induction of micronuclei (MN) after the treatment with MTZ or its hydroxy metabolite. Our results show that MTZ increased proliferation in a dose response manner in all P53 functional cell lines without inducing changes on the levels of P53 nor MN. However, MTZ hydroxy metabolite induced a dose response increase of P53 and MN, while cell proliferation was not increased. Several studies have shown that the hydroxy metabolite is more potent than MTZ itself. Only in cell lines that do not have a functional P53, MTZ and its metabolite increased both cell proliferation and MN. MTZ use is increasing and its carcinogenicity has not been discarded. Our data indicate that MTZ hydroxy metabolite is potentially a carcinogen and needs to be further studied.