Cytotoxicity and DNA damaging potency of chloramphenicol and six metabolites: a new evaluation in human lymphocytes and Raji cells

Metabolomic Profile of Primary Turkey and Rat Hepatocytes and Two Cell Lines after Chloramphenicol Exposure

The purpose of this study was to assess the formation of chloramphenicol metabolites in primary turkey and rat hepatocyte cultures and human hepatoma (HepG2) cells and nonhepatic, Balb/c 3T3 fibroblasts. Additionally, the cytotoxicity of the drug was assessed through three biochemical endpoints: mitochondrial and lysosomal activity and cellular membrane integrity after 24 and 48 h exposure. The two metabolites of the drug, chloramphenicol glucuronide and nitroso-chloramphenicol, were detected to the greatest extent in both primary hepatocyte cultures by liquid chromatography-tandem mass spectrometry. Toxic nitroso-chloramphenicol was the main metabolite in the primary turkey hepatocyte cultures, but it was not in the primary rat hepatocyte cultures. The most affected endpoint in turkey and rat hepatocyte cultures was the disintegration of the cellular membrane, but in the cell lines, mitochondrial and lysosomal activities underwent the greatest change. The primary hepatocyte cultures represent valuable tools with which to study the species differences in the biotransformation and toxicity of drugs. To the best of our knowledge, this is the first report of differences in chloramphenicol metabolism in primary turkey and rat hepatocyte cultures.

The photocatalytic degradation of chloramphenicol with electrospun Bi2O2CO3-poly(ethylene oxide) nanofibers: the synthesis of crosslinked polymer, degradation kinetics, mechanism and cytotoxicity

Insoluble poly(ethylene oxide) (PEO) nanofibers were synthesized by adding pentaerythrotol triacrylate (PETA) into precursor solutions prior to electrospinning, and then the obtained fibers were exposed to an electron beam (EB) irradiation. Bi₂O₂CO₃ was incorporated into these fibers to extend their photocatalytic properties. Studies confirmed that EB irradiation induced characteristic changes in PEO and led to the formation of a crosslinked structure, from which we optimized the irradiation dose of fibers as 210 kGy. The optimum PEO/Bi₂O₂CO₃ membranes achieved 99.5% CPL degradation within 60 min, and we also proposed the possible degradation pathways of CPL in this study. Besides, all the water samples and extracts of nanomaterials showed no cytotoxicity on L-929 cells. The subtle variations in the cell viability of treated and untreated water samples could be due to the toxic intermediates arising from the photocatalytic process. Therefore, this photocatalyst-polymer membrane can be considered as a biocompatible composite system that can change the solubility of a polymer and also act as a highly efficient photocatalyst for organic wastewater treatments.

Insoluble poly(ethylene oxide) (PEO) nanofibers were synthesized by adding pentaerythrotol triacrylate (PETA) into precursor solutions prior to electrospinning, and then the obtained fibers were exposed to an electron beam (EB) irradiation.

Brain-derived neurotrophic factor as an indicator of chemical neurotoxicity: an animal-free CNS cell culture model

Recent changes to the legislation on chemicals and cosmetics testing call for a change in the paradigm regarding the current 'whole animal' approach for identifying chemical hazards, including the assessment of potential neurotoxins. Accordingly, since 2004, we have worked on the development of the integrated co-culture of post-mitotic, human-derived neurons and astrocytes (NT2.N/A), for use as an in vitro functional central nervous system (CNS) model. We have used it successfully to investigate indicators of neurotoxicity. For this purpose, we used NT2.N/A cells to examine the effects of acute exposure to a range of test chemicals on the cellular release of brain-derived neurotrophic factor (BDNF). It was demonstrated that the release of this protective neurotrophin into the culture medium (above that of control levels) occurred consistently in response to sub-cytotoxic levels of known neurotoxic, but not non-neurotoxic, chemicals. These increases in BDNF release were quantifiable, statistically significant, and occurred at concentrations below those at which cell death was measureable, which potentially indicates specific neurotoxicity, as opposed to general cytotoxicity. The fact that the BDNF immunoassay is non-invasive, and that NT2.N/A cells retain their functionality for a period of months, may make this system useful for repeated-dose toxicity testing, which is of particular relevance to cosmetics testing without the use of laboratory animals. In addition, the production of NT2.N/A cells without the use of animal products, such as fetal bovine serum, is being explored, to produce a fully-humanised cellular model.

Determination of chloramphenicol in shrimp by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS)

A liquid chromatographic method with electrospray ionization tandem mass spectrometric (LC-ESI-MS-MS) detection and identification is described for the determination of chloramphenicol (CAP) in shrimp tissue. Homogenized shrimp samples were extracted by liquid-liquid extraction using ethyl acetate. d5-Chloramphenicol (5D-CAP) was used as the internal standard. Data acquisition was in negative-ion multiple reaction monitoring (NMRM) mode using three transition reactions for CAP (m/z 321 --> 152, m/z 321 --> 257 and m/z 321 --> 194) and two for d5-chloramphenicol (m/z 326 --> 262 and m/z 326 --> 157). Method validation was carried out according to European Commission decision 2002/657/EC. The calibration curve was linear in the range 0.10-2.00 microg l(-1), with typical r2 > 0.99. The decision limit (CC alpha) and detection capability (CC beta) were 0.06 and 0.10 microg kg(-1), respectively. There was no influence of the matrix on the determination of chloramphenicol.

Chloramphenicol-induced mitochondrial stress increases p21 expression and prevents cell apoptosis through a p21-dependent pathway

Pretreatment of HepG2 and H1299 cells with chloramphenicol rendered the cells resistant to mitomycin-induced apoptosis. Both mitomycin-induced caspase 3 activity and PARP activation were also inhibited. The mitochondrial DNA-encoded Cox I protein, but not nuclear-encoded proteins, was down-regulated in chloramphenicol-treated cells. Cellular levels of the p21(waf1/cip1) protein and p21(waf1/cip1) mRNA were increased through a p53-independent pathway, possibly because of the stabilization of p21(waf1/cip1) mRNA in chloramphenicol-treated cells. The p21(waf1/cip1) was redistributed from the perinuclear region to the cytoplasm and co-localized with mitochondrial marker protein. Several morphological changes and activation of the senescence-associated biomarker, SA beta-galactosidase, were observed in these cells. Both p21(waf1/cip1) antisense and small interfering RNA could restore apoptotic-associated caspase 3 activity, PARP activation, and sensitivity to mitomycin-induced apoptosis. Similar effects were seen with other antibiotics that inhibit mitochondrial translation, including minocycline, doxycycline, and clindamycin. These findings suggested that mitochondrial stress causes resistance to apoptosis through a p21-dependent pathway.

History of antibiotic use and risk of non-Hodgkin's lymphoma (NHL)

A population-based, incidence case-control study was conducted among women in upstate New York to determine whether histories of certain infections and antibiotic use are associated with risk of non-Hodgkin's lymphoma (NHL). Our study involved 376 cases of NHL identified through the New York State Cancer Registry and 463 controls selected from the Medicare beneficiary files and state driver's license records. Information about use of common medications including antibiotics, history of selected infectious diseases and potential confounding variables was obtained by telephone interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using an unconditional logistic regression model. There was a progressive increase in risk of NHL with increasing frequency and duration of systemic antibiotic use, as assessed over the period of 2-20 years before the interview. The ORs for the highest exposure categories, >/=36 episodes and >/=366 days of use, were 2.56 (95% CI 1.33-4.94) and 2.66 (95% CI 1.35-5.27), respectively. These associations were primarily due to antibiotic use against respiratory infections and dental conditions. Moreover, the association with frequency of antibiotic use for respiratory infections was pronounced for marginal zone B-cell lymphoma and for respiratory tract lymphoma. Analyses by class of antibiotics did not suggest that a general cytotoxic effect of antibiotics was responsible for these increased risks. Although recall bias and selection bias remain potential concerns in our study, the results are generally consistent with the hypothesis that persistent infection/inflammation predisposes individuals to the development of NHL. However, a direct role of antibiotics in NHL induction has not been ruled out.

Molecular features determining lymphocyte reactivity in allergic contact dermatitis to chloramphenicol and azidamphenicol

BACKGROUND

We report on two cases of allergic contact dermatitis to chloramphenicol and azidamphenicol respectively, with in vivo and in vitro lymphocyte reactivity to both compounds. The molecular features determining lymphocyte reactivity were explored because chloramphenicol, azidamphenicol, and thiamphenicol exhibit almost identical chemical structures.

METHODS

With chloramphenicol, azidamphenicol, and the chemically related thiamphenicol, we performed patch tests and lymphocyte transformation tests with both patients. Furthermore, the interleukin-5 and interferon-gamma concentrations in the cultures of peripheral blood mononuclear cells of one patient were determined.

RESULTS

Patch tests showed delayed hypersensitivity reactions to chloramphenicol and azidamphenicol, but not to thiamphenicol. These results were confirmed by lymphocyte transformation tests with peripheral blood mononuclear cells of the patients, showing a proliferative T-cell response to azidamphenicol and chloramphenicol. Moreover, lymphocytes from one patient secreted large amounts of interleukin-5, but not of interferon-gamma upon coculture with azidamphenicol.

CONCLUSIONS

Since lymphocyte reactivity was observed to chloramphenicol and azidamphenicol, but not to thiamphenicol, the epitope(s) recognized by the allergen-reactive T cells may be formed by the nitro-group of the benzene ring shared by chloramphenicol and azidamphenicol.

Cycloheximide and 4-OH-TEMPO suppress chloramphenicol-induced apoptosis in RL-34 cells via the suppression of the formation of megamitochondria

Toxic effects of chloramphenicol, an antibiotic inhibitor of mitochondrial protein synthesis, on rat liver derived RL-34 cell line were completely blocked by a combined treatment with substances endowed with direct or indirect antioxidant properties. A stable, nitroxide free radical scavenger, 4-hydroxy-2,2,6, 6-tetramethylpiperidine-1-oxyl, and a protein synthesis inhibitor, cycloheximide, suppressed in a similar manner the following manifestations of the chloramphenicol cytotoxicity: (1) Oxidative stress state as evidenced by FACS analysis of cells loaded with carboxy-dichlorodihydrofluorescein diacetate and Mito Tracker CMTH2MRos; (2) megamitochondria formation detected by staining of mitochondria with MitoTracker CMXRos under a laser confocal microscopy and electron microscopy; (3) apoptotic changes of the cell detected by the phase contrast microscopy, DNA laddering analysis and cell cycle analysis. Since increases of ROS generation in chloramphenicol-treated cells were the first sign of the chloramphenicol toxicity, we assume that oxidative stress state is a mediator of above described alternations of RL-34 cells including MG formation. Pretreatment of cells with cycloheximide or 4-hydroxy-2,2, 6,6-tetramethylpiperidine-1-oxyl, which is known to be localized into mitochondria, inhibited the megamitochondria formation and succeeding apoptotic changes of the cell. Protective effects of cycloheximide, which enhances the expression of Bcl-2 protein, may further confirm our hypothesis that the megamitochondria formation is a cellular response to an increased ROS generation and raise a possibility that antiapoptotic action of the drug is exerted via the protection of the mitochondria functions.

Use of human lymphoblastoid cells to detect the toxic effect of chloramphenicol and metabolites possibly involved in aplastic anemia in man

Some Chloramphenicol (CAP) metabolites are suspected to be involved in the etiology of bone marrow aplasia in man. The objective of the present study was to investigate the cytotoxicity as well as the genotoxicity of CAP and six of its metabolites on human bone marrow cells (RiBM cells) and to compare these results with those obtained on human peripheral blood lymphocytes in order to estimate the relative sensitivity of the two types of cells. Three CAP metabolites NO-CAP, DH-CAP and NPAP inhibited 3H thymidine incorporation in RiBM cells at concentrations ranging from 2.10(-5) M to 2.10(-4) M. NO-CAP appeared as the most potent cytotoxic compound. CAP itself and NAPD presented some toxic effect at high concentration (1-2.10(-3) M). CAPG and HAP did not present any cytotoxic effect. By comparison, the response of human lymphocytes to CAP and its metabolites showed a similar pattern but DH-CAP was the most inhibitory compound. Concerning the genotoxic potential, NO-CAP and DH-CAP induced DNA single strand breaks in RiBM cells at concentrations of 1 and 2.10(-4) M with a dose response relationship. CAP and other metabolites were completely devoid of genotoxicity up to 4.10(-3) M. The results clearly showed that RiBM cells were much less susceptible to the genotoxic effect of CAP metabolites than human lymphocytes.

Widespread ocular use of topical chloramphenicol: is there justifiable concern regarding idiosyncratic aplastic anaemia?

A theoretical but as yet not conclusively proved risk of chloramphenicol induced idiosyncratic aplastic anaemia exists with topical ophthalmic therapy, with the absolute, but highly improbable, maximum risk of death (equalling that of systemic therapy) being 1 in 50,000 to 90,000. To put this in realistic perspective, one must note that the comparable risk of fatal anaphylaxis resulting from penicillin therapy, from any route, is similar at 1 in 100,000. Indeed, it has been noted recently that with more than 200 million ocular chloramphenicol products dispensed in the UK in the past 10 years, only 11 reports (all non-fatal) of suspected topical chloramphenicol induced blood dyscrasia have been reported to the Committee on the Safety of Medicines since 1966. One also has to consider that inadvertent exposure to minute quantities of chloramphenicol (ng/ml) may occur through consumption of livestock that have been treated with chloramphenicol. Broad statements condemning topical chloramphenicol need to be tempered with its proved safety, tolerance, cost, and efficacy while acknowledging an extremely remote risk of the very serious adverse effect of drug induced aplastic anaemia. Risk-benefit assessment is the duty of all prescribing physicians and a decision to prescribe or not prescribe must be made on the basis of personal judgment and an awareness of the statistics in perspective. The only known factor to be associated with vulnerability in the case of topical chloramphenicol is family history. There is no evidence to date that suggests children are any more susceptible than adults.

Assessment of DNA damage in leukocytes from infected and malnourished children by single cell gel electrophoresis/comet assay

The alkaline single cell gel (SCG) assay is a sensitive electrophoretic technique for detecting the presence of DNA single strand breaks and alkali-labile damage in individual cells. This technique was used to assess and compare the level of DNA damage in peripheral blood leukocytes/lymphocytes from well-nourished children with infection, well-nourished children with infection and under drug treatment, and from malnourished infected children with and without previous drug treatment. The present study shows that severe infection is associated with a significant increase in DNA damage. The average migration length was five times greater in severely infected well-nourished children compared to that found in healthy, well-nourished children. The results obtained in this study indicate that malnutrition is another factor associated with an increase in DNA migration. The average tail length for malnourished, severely infected children was twice as great as that obtained for cells from well-nourished, severely infected children. We also detected a variable increase in DNA migration associated with treatment for severe infection. Nevertheless, the excessive heterogeneity, the concurrent number of drugs used and the limited size of the treated population precludes an accurate assessment of which drugs were involved in the increase in DNA damage. Further studies will be necessary involving a large number of patients to address the relation between levels of DNA damage and specific kinds of infection, various drug treatments, and the type and severity of malnutrition. The increased level of DNA damage in severely infected and malnourished children could be related to negative effects such as a deficient immune response resulting in an increased susceptibility to malignant transformation.