The genotoxic effect of potassium metabisulfite using chromosome aberration, sister chromatid exchange, micronucleus tests in human lymphocytes and chromosome aberration test in bone marrow cells of rats

Sulfites

The Expert Panel for Cosmetic Ingredient Safety reviewed newly available studies since their original assessment in 1998, along with updated information regarding product types and concentrations of use, and confirmed that Sodium Sulfite, Potassium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite are safe as cosmetic ingredients in the practices of use and concentration as described in this report.

Methodology of Genotoxic and Teratogenic Studies in Rats

The genotoxicity methods applied to rats are tests that can detect any damage, including changes in the number of chromosomes or in the structure of chromosomes, and nucleotide changes with structural abnormality in the DNA of animal cells. However, the method of teratogenicity is used to detect the effects of chemicals which cause congenital defects in living organisms. This study contains information about the effectiveness, reliability, ways of application, and methodology of genotoxic and teratogenic methods applied in vivo in rats.

Genotoxic and mutagenic studies of teratogens in developing rat and mouse

In this review, genotoxic and mutagenic effects of teratogenic chemical agents in both rat and mouse have been reviewed. Of these chemicals, 97 are drugs and 33 are pesticides or belong to other groups. Large literature searches were conducted to determine the effects of chemicals on chromosome abnormalities, sister chromatid exchanges, and micronucleus formation in experimental animals such as rats and mice. In addition, studies that include unscheduled DNA synthesis, DNA adduct formations, and gene mutations, which help to determine the genotoxicity or mutagenicity of chemicals, have been reviewed. It has been estimated that 46.87% of teratogenic drugs and 48.48% of teratogenic pesticides are positive in all tests. So, all of the teratogens involved in this group have genotoxic and mutagenic effects. On the other hand, 36.45% of the drugs and 21.21% of the pesticides have been found to give negative results in at least one test, with the majority of the tests giving positive results. However, only 4.16% of the drugs and 18.18% of the pesticides were determined to give negative results in the majority of the tests. Among tests with major negative results, 12.50% of the teratogenic drugs and 12.12% of the teratogenic pesticides were negative in all conducted tests.

In vitro cytogenetic evaluation of the particular combination of flurbiprofen and roxithromycin

Flurbiprofen (FLB) (anti-inflammatory and analgesic drug) and roxithromycin (RXM) (antibiotic) were widely used in world wide. This study deals with investigation of genotoxicity, cytotoxicity, and oxidative stress effects of a particular combination of these drugs in human cultured lymphocytes. Also, DNA damaging-protective effects of combination of these drugs were analyzed on plasmid DNA. Human lymphocytes were treated with different concentrations (FLB + RXM; 10 μg/mL + 25 μg/mL, 15 μg/mL + 50 μg/mL, and 20 μg/mL + 100 μg/mL) of the drugs following by study of their genotoxic and cytotoxic effects by analysis of cytokinesis-block micronucleus test and nuclear division index, respectively. The effect of the combination in aspect of anti-oxidative and DNA damaging activity was evaluated on Pet-22b plasmid. According to our results, the combination of FLB and RXM did not show a notable genotoxic effect on cells. Although each of the substances had been shown as a cytotoxic agent by previous researchers, in this research, the combination of these drugs did not exhibit any adverse effect on cell division. FLB had DNA protection effect against H₂O₂ while in combination with RXM had not the same effect on the plasmid.

Micronucleus frequency among Iraqi thyroid disorder patients

Micronucleus (MN) assay has been extensively used in detection of DNA damage, instability in cancer, and genetic disorders. In the current study, MN, binucleated cells, and nuclear division index (NDI) were investigated in Iraqi patients with thyroid disorders. The results indicated significantly (p < 0.05) increased binucleated cells with micronucleus (BNMN) frequencies in thyroid cancer group (37.58 ± 3.07) versus other thyroid disorder groups (6.60 ± 1.29, 14.90 ± 1.69, 15.56 ± 1.76). On the other hand, the frequency of micronucleus per 1,000 and the NDI were significantly (p < 0.05) decreased in hypothyroidism (MN 1.55 ± 0.36) (NDI 0.009 ± 0.001) versus other thyroid disorder groups (MN: 6.05 ± 0.97, 6.09 ± 0.53, 5.34 ± 0.56) (NDI: 0.049 ± 0.003, 0.032 ± 0.002, 0.025 ± 0.002), with no difference versus healthy group (0.0 ± 0.0). The number of BNMN and MN are parallel to the severity of thyroid disorders which were 6.60 ± 1.29, 14.90 ± 1.69, 15.56 ± 1.76, and 37.58 ± 3.07 for hypothyroidism, thyroid toxic goiter, thyroid nontoxic goiter, and thyroid cancer, respectively. The number of BNMN and MN are parallel to the severity of thyroid disorders which were 6.60 ± 1.29, 14.90 ± 1.69, 15.56 ± 1.76, and 37.58 ± 3.07 for hypothyroidism, thyroid toxic goiter, thyroid nontoxic goiter, and thyroid cancer, respectively. The results also indicate that there were no significant differences among age and sex groups as related with BNMN formation within each thyroid disorder groups and healthy control group.

Base damage within single-strand DNA underlies in vivo hypermutability induced by a ubiquitous environmental agent

Chromosomal DNA must be in single-strand form for important transactions such as replication, transcription, and recombination to occur. The single-strand DNA (ssDNA) is more prone to damage than double-strand DNA (dsDNA), due to greater exposure of chemically reactive moieties in the nitrogenous bases. Thus, there can be agents that damage regions of ssDNA in vivo while being inert toward dsDNA. To assess the potential hazard posed by such agents, we devised an ssDNA-specific mutagenesis reporter system in budding yeast. The reporter strains bear the cdc13-1 temperature-sensitive mutation, such that shifting to 37°C results in telomere uncapping and ensuing 5' to 3' enzymatic resection. This exposes the reporter region, containing three closely-spaced reporter genes, as a long 3' ssDNA overhang. We validated the ability of the system to detect mutagenic damage within ssDNA by expressing a modified human single-strand specific cytosine deaminase, APOBEC3G. APOBEC3G induced a high density of substitutions at cytosines in the ssDNA overhang strand, resulting in frequent, simultaneous inactivation of two reporter genes. We then examined the mutagenicity of sulfites, a class of reactive sulfur oxides to which humans are exposed frequently via respiration and food intake. Sulfites, at a concentration similar to that found in some foods, induced a high density of mutations, almost always as substitutions at cytosines in the ssDNA overhang strand, resulting in simultaneous inactivation of at least two reporter genes. Furthermore, sulfites formed a long-lived adducted 2'-deoxyuracil intermediate in DNA that was resistant to excision by uracil-DNA N-glycosylase. This intermediate was bypassed by error-prone translesion DNA synthesis, frequently involving Pol ζ, during repair synthesis. Our results suggest that sulfite-induced lesions in DNA can be particularly deleterious, since cells might not possess the means to repair or bypass such lesions accurately.

Chondrotoxicity of low pH, epinephrine, and preservatives found in local anesthetics containing epinephrine

BACKGROUND

Recent clinical and basic science investigations have revealed the chondrotoxicity of local anesthetics, especially those containing epinephrine, administered via an intra-articular pain pump. However, the exact mechanism of toxicity is unknown. This study evaluates the chondrotoxicity of low pH, epinephrine, and preservatives found in commonly used local anesthetics.

HYPOTHESIS

The chondrotoxicity of local anesthetics containing epinephrine is due to low pH, epinephrine, or the preservative sodium metabisulfite.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human chondrocytes were harvested and cultured in a custom bioreactor designed to simulate metabolism of medication. Pain pumps were used to infuse one of the following medications into the culture system: control media; media titrated to pH 4.5, 5.0, 5.5, 6.0, 6.5; media with 1:100000 or 1:200000 epinephrine only; media with 0.5 mg/mL of sodium metabisulfite preservative; media with 0.5 mg/mL of methylparaben preservative, 0.25% bupivacaine, 0.25% bupivacaine with epinephrine, 1% lidocaine, and 1% lidocaine with epinephrine. Cultures were perfused for 24 hours and then were stained with live/dead cell viability assay. The chondrocytes were then examined by fluorescence microscopy and counted, and the percentage of cell death was calculated.

RESULTS

Cultures containing media titrated to pH 4.5 and 5.0 and local anesthetics containing epinephrine (pH 4.0-5.5) had high cell death rates compared with controls at all time points (P < .001), while cultures containing 1:100000 and 1:200000 epinephrine alone had no increased death rate. Also, 0.5 mg/mL sodium metabisulfite preservative had a significant effect on cell death (P < .034); however, the preservative methylparaben had no effect (P > .05). The percentage of cell death was not significant for 1% lidocaine (12.5%; P > .943) and 0.25% bupivacaine (16.5%; P > .609).

CONCLUSION

The marked chondrotoxicity of local anesthetics containing epinephrine appears to be a combined effect of low pH, as these medications are titrated to pH 4.0 to 5.5 for product stability, and the preservative sodium metabisulfite. Extreme caution should be exercised when using intra-articular pain pumps with local anesthetics containing epinephrine.

CLINICAL RELEVANCE

Understanding the causes of chondrotoxicity using local anesthetics containing epinephrine is critical to decrease complications associated with this class of medications.

Assessment of the genotoxicity of atenolol in human peripheral blood lymphocytes: correlation between chromosomal fragility and content of micronuclei

The antihypertensive drug atenolol was found to induce chromosome loss, detected as micronuclei in the peripheral lymphocytes of treated patients. The fundamental question which chromosomes the micronuclei were derived from remains to be answered. Analysis of structural chromosomal aberrations (CAs) and expression of fragile sites (FS) were pursued in this study. They revealed a significantly higher incidence of chromosomal aberrations (chromatid and chromosome breaks) in patients compared with controls, where 10 FS emerged as specific. Also, the band 17q12-21, where known fragile sites have not been reported, was only expressed in atenolol-treated patients. Fluorescence in situ hybridization using chromosome-specific probes revealed the preferential involvement of chromosomes 7, 11, 17 and X in the micronuclei (MN) of patients. The results also suggest a correlation between chromosomal fragility and content of MN, and support the findings for a linkage between hypertension and a locus on chromosome 17.