Chromosomal aberrations and micronuclei in lymphocytes of patients before and after exposure to anti-tuberculosis drugs

The first-line antituberculosis drugs, and their fixed-dose combination induced abnormal sperm morphology and histological lesions in the testicular cells of male mice

Rifampicin (RIF), Isoniazid (INH), Ethambutol (EMB), Pyrazinamide (PZA), and/or their fixed-dose combination (FDC) are extensively prescribed in the cure of Tuberculosis (TB) globally. In spite of the beneficial effect, these drugs are capable of inducing cellular toxicity. Existing information on the genotoxic effects of the first-line anti-TB drugs is limited and contentious. Herein, we evaluated the reproductive genotoxicity of RIF, INH, EMB, PZA, and their FDC utilizing the mouse sperm morphology assay. Histological examination of the testes of exposed mice was also performed. Male Swiss albino mice (11-13 weeks old) were intraperitoneally exposed for 5 consecutive days to each of the anti-TB drugs at four different doses of 6.25, 12.5, 25, and 50 mg/kg bw of PZA; 2.5, 5.0, 10, and 20 mg/kg bw of RIF; 1.25, 2.5, 5.0 and 10 mg/kg bw of INH; 3.75, 7.5, 15 and 30 mg/kg bw of EMB; and 7, 14, 28 and 56 mg/kg bw of FDC corresponding respectively to ×0.25, ×0.5, ×1 and ×2.0 of the standard daily dose. In comparison with the negative control (normal saline), there was no significant difference in the testicular weight and organo-somatic index of exposed mice. There was an increase (p > 0.05) in the frequency of abnormal spermatozoa at most of the tested doses of each drug and a dose-dependent decrease with the FDC. Each of the anti-TB drugs except the FDC induced pathological lesions in the testes. These findings suggest that the individual first-line anti-TB drug unlike the FDC has the potential to provoke testicular anomalies in male mice.

Recommendations and quality criteria for micronucleus studies with humans

Micronucleus (MN) analyses in peripheral blood lymphocytes and exfoliated cells from different organs (mouth, nose, bladder and cervix) are at present the most widely used approaches to detect damage of genetic material in humans. MN are extranuclear DNA-containing bodies, which can be identified microscopically. They reflect structural and numerical chromosomal aberrations and are formed as a consequence of exposure to occupational, environmental and lifestyle genotoxins. They are also induced as a consequence of inadequate intake of certain trace elements and vitamins. High MN rates are associated with increased risk of cancer and a range of non-cancer diseases in humans. Furthermore, evidence is accumulating that measurements of MN could be a useful tool for the diagnosis and prognosis of different forms of cancer and other diseases (inflammation, infections, metabolic disorders) and for the assessment of the therapeutic success of medical treatments. Recent reviews of the current state of knowledge suggest that many clinical studies have methodological shortcomings. This could lead to controversial findings and limits their usefulness in defining the impact of exposure concentrations of hazardous chemicals, for the judgment of remediation strategies, for the diagnosis of diseases and for the identification of protective or harmful dietary constituents. This article describes important quality criteria for human MN studies and contains recommendations for acceptable study designs. Important parameters that need more attention include sufficiently large group sizes, adequate duration of intervention studies, the exclusion of confounding factors which may affect the results (sex, age, body mass index, nutrition, etc.), the evaluation of appropriate cell numbers per sample according to established scoring criteria as well as the use of proper stains and adequate statistical analyses.

Nonclinical evaluation of IQG-607, an anti-tuberculosis candidate with potential use in combination drug therapy

New effective compounds to treat tuberculosis are urgently needed. IQG-607 is an orally active anti-tuberculosis drug candidate, with promising preliminary safety profile and anti-mycobacterial activity in both in vitro and in vivo models of tuberculosis infection. Here, we evaluated the mutagenic and genotoxic effects of IQG-607, and its interactions with CYP450 isoforms. Moreover, we describe for the first time a combination study of IQG-607 in Mycobacterium tuberculosis-infected mice. Importantly, IQG-607 had additive effects when combined with the first-line anti-tuberculosis drugs rifampin and pyrazinamide in mice. IQG-607 presented weak to moderate inhibitory potential against CYP450 isoforms 3A4, 1A2, 2C9, 2C19, 2D6, and 2E1. The Salmonella mutagenicity test revealed that IQG-607 induced base pair substitution mutations in the strains TA100 and TA1535. However, in the presence of human metabolic S9 fraction, no mutagenic effect was detected in any strain. Additionally, IQG-607 did not increase micronucleus frequencies in mice, at any dose tested, 25, 100, or 250 mg/kg. The favorable activity in combination with first-line drugs and mild to moderate toxic events described in this study suggest that IQG-607 represents a candidate for clinical development.

Mycobacterium tuberculosis promotes genomic instability in macrophages

BACKGROUND

Mycobacterium tuberculosis is an intracellular pathogen, which may either block cellular defensive mechanisms and survive inside the host cell or induce cell death. Several studies are still exploring the mechanisms involved in these processes.

OBJECTIVES

To evaluate the genomic instability of M. tuberculosis-infected macrophages and compare it with that of uninfected macrophages.

METHODS

We analysed the possible variations in the genomic instability of Mycobacterium-infected macrophages using the DNA breakage detection fluorescence in situ hybridisation (DBD-FISH) technique with a whole human genome DNA probe.

FINDINGS

Quantitative image analyses showed a significant increase in DNA damage in infected macrophages as compared with uninfected cells. DNA breaks were localised in nuclear membrane blebs, as confirmed with DNA fragmentation assay. Furthermore, a significant increase in micronuclei and nuclear abnormalities were observed in infected macrophages versus uninfected cells.

MAIN CONCLUSIONS

Genomic instability occurs during mycobacterial infection and these data may be seminal for future research on host cell DNA damage in M. tuberculosis infection.

DNA damage and cellular abnormalities in tuberculosis, lung cancer and chronic obstructive pulmonary disease

BACKGROUND

Tuberculosis (TB), Lung Cancer (LC) and Chronic Obstructive Pulmonary Diseases (COPD) affect millions of individuals worldwide. Monitoring of DNA damage in pathological situations has been investigated because it can add a new dimension to clinical expression and may represent a potential target for therapeutic intervention. The aim of this study was to evaluate DNA damage and the frequency of cellular abnormalities in TB, LC and COPD patients by comparing them to healthy subjects.

METHODS

The detection of DNA damage by a buccal micronucleus cytome assay was investigated in patients with COPD (n = 28), LC (n = 18) and TB (n = 22) and compared to control individuals (n = 17).

RESULTS

The COPD group had a higher frequency of apoptotic cells compared to TB and LC group. The TB group showed a higher frequency of DNA damage, defect in cytokinesis, apoptotic and necrotic cells. Patients with LC had low frequency of chromosomal aberrations than TB and COPD patients.

CONCLUSION

COPD patients showed cellular abnormalities that corresponded to cell death by apoptosis and necrosis, while patients with TB presented defects in cytokinesis and dysfunctions in DNA repair that resulted in the formation of micronucleus (MN) besides apoptotic and necrotic cells. Patients with COPD, TB and LC had a low frequency of permanent DNA damage.

A Rejection Principle for Sequential Tests of Multiple Hypotheses Controlling Familywise Error Rates

We present a unifying approach to multiple testing procedures for sequential (or streaming) data by giving sufficient conditions for a sequential multiple testing procedure to control the familywise error rate (FWER). Together we call these conditions a "rejection principle for sequential tests," which we then apply to some existing sequential multiple testing procedures to give simplified understanding of their FWER control. Next the principle is applied to derive two new sequential multiple testing procedures with provable FWER control, one for testing hypotheses in order and another for closed testing. Examples of these new procedures are given by applying them to a chromosome aberration data set and to finding the maximum safe dose of a treatment.

Cyto-genotoxicity Assessment of Potential Anti-tubercular Drug Candidate Molecule-trans-cyclohexane-1, 4-diamine Derivative-9u in Human Lung Epithelial Cells A549

Increasing incidences of multiple drug-resistance (MDR) in Mycobacterium tuberculosis are emerging as one among the serious public health threats and socio-economic burden to the third world countries including India. Last couples of decades are witnesses of the dedicated and sustained efforts made toward the development of target specific and cost-effective antimicrobial agents against MDR-M. tuberculosis. However, the drugs in use are still incapable of controlling the upsurge of MDR. Thus, in order to address the issue, we synthesized a library of symmetrical trans-cyclohexane-1, 4-diamine derivatives and evaluated their anti-mycobacterium activity in H₃₇RV strain of M. tuberculosis. A range of efficacy has been recorded in different derivatives of synthesized compounds and compound “9u” having i-propyl group substitution at p-position, was found to have more significant detrimental effects against the tested strain of M. tuberculosis. The present investigations were aimed to study whether the effective anti-mycobacterium concentrations of “9u” are biologically safe to human cells or not? The human lung epithelial cell line-A549 were exposed to a range of concentrations, i.e., at and above the anti-mycobacterium effective dose of “9u” for a period of 0-96 h. The standard endpoints of cytotoxicity viz., tetrazolium bromide salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide), neutral red uptake, lactate dehydrogenase release, trypan blue dye exclusion assays; and genotoxicity viz., micronucleus and chromosomal aberrations assays were used to evaluate the bio-safety of test compound. The compound “9u” shows no significant cytotoxicity and genotoxicity in A549 cells exposed to 10^-5 M for 72 h, a concentration substantially higher than the concentration kill the H₃₇Rv strain of M. tuberculosis. The compound 9u was found to be safe up to 10^-4 M if given for 24 h. The data reveal the therapeutic potential of compound 9u against M. tuberculosis without any having any cytotoxicity and genotoxicity responses.

In vitro toxic action potential of anti tuberculosis drugs and their combinations

Tuberculosis (TB) is one of the leading infectious causes of death due to single infectious agent after HIV/AIDS. Rifampicin (RIF), Isoniazid (INH), Ethambutol (EMB), Pyrazinamide (PZA) and/or their combinations are extensively prescribed to treat TB. Despite several therapeutic implications, these drugs also produce several toxic effects at cellular level. MTT assay and Ames test were adopted in this study for the determination of cytotoxic and mutagenic potential of these anti-TB drugs. Among all tested drugs, cytotoxic potential of RIF was strongest with highly significant decline (p<0.001) in cell numbers at the concentration of 250μg/ml with LC50 at 325μg/ml, while significant decline (p<0.01) in cell count was observed in INH treated group at the concentration 500μg/ml with LC50 at 1000μg/ml. Moreover, combination RIPE demonstrated significant reduction (p<0.01) in cell number at the concentration of 25-500-500-500μg/ml with LC50 at 60-1200-1200-1200μg/ml. It is apparent from the data that almost all drugs represented identical mutagenic pattern i.e., more significant results were achieved in TA100 with metabolic activation (+S9). RIF proved to be highly mutagenic of all tested drugs with significant mutagenicity (p<0.01) at 0.0525μg/plate against TA98 strain with S9. The combination RIPE exhibited highly significant mutagenic activity (p<0.01) at concentration 0.125-3-3-3μg/plate without S9, while addition of S9 resulted in similar activity at lower doses, i.e., 0.0525-1-1-1μg/plate. It was concluded from the data that all anti-TB drugs possess significant cytotoxic and mutagenic potential, especially in combination, making TB patient more vulnerable to cytotoxic and mutagenic effects of anti-TB drugs, which could produce further health complications in TB patients.

Antineoplastic Drugs as a Potential Risk Factor in Occupational Settings: Mechanisms of Action at the Cell Level, Genotoxic Effects, and Their Detection Using Different Biomarkers

U članku je prikazana osnovna podjela antineoplastičnih lijekova prema mehanizmima djelovanja na razini stanice. Objašnjeni su mehanizmi genotoksičnosti najvažnijih vrsta lijekova koji se primjenjuju u okviru uobičajenih protokola za liječenje zloćudnih novotvorina. Navedena je važeća klasifikacija antineoplastika prema kancerogenom potencijalu, podaci o mutagenom potencijalu te je prikazana njihova podjela u skladu s anatomsko-terapijsko-kemijskim sustavom klasifikacije. Sustavno su prikazani najvažniji rezultati svjetskih i hrvatskih istraživanja na populacijama radnika izloženih antineoplasticima, provedenih u razdoblju 1980.-2009. s pomoću četiri najčešće primjenjivane metode: analize izmjena sestrinskih kromatida, analize kromosomskih aberacija, mikronukleus-testa i komet-testa. Objašnjena su osnovna načela navedenih metoda te raspravljene njihove prednosti i nedostaci. Biološki pokazatelji daju važne podatke o individualnoj osjetljivosti profesionalno izloženih ispitanika koji mogu poslužiti unaprjeđenju postojećih uvjeta rada i upravljanju rizicima pri izloženosti genotoksičnim agensima. Na osnovi prednosti i nedostataka citogenetičkih metoda zaključeno je da je mikronukleus-test, koji podjednako uspješno dokazuje klastogene i aneugene učinke, jedna od najboljih metoda dostupnih za otkrivanje štetnih djelovanja antineoplastičnih lijekova koji su u aktivnoj primjeni.

Effects of low dose radiation and vitamin C treatment on chloroquine-induced genotoxicity in mice

Chloroquine (CHQ) is a commonly used antimalarial agent. We evaluated the genotoxic potential of CHQ using chromosome aberration (CA), micronucleus (MN), and sperm head abnormality (SA) assays in vivo in Swiss albino mice. The interaction between a low dose of radiation and CHQ, as well as the effect of vitamin C on CHQ-induced genotoxicity, was also evaluated. It was observed that CHQ induced CA, as well as MN, in the bone marrow cells under certain treatment conditions. Further, CHQ induced significant increase in the frequency of SA both at 24 hr and 21 days of the treatment. In the present study vitamin C pretreatment apparently reduced the frequency of CA, MN, and SA induced by CHQ. In the combination studies with radiation and CHQ, we found that exposure to low doses of radiation (0.5 Gy) either prior to or following CHQ treatment, in the dose ranges tested, has little or no synergistic effect in the mutagenic evaluations in somatic cells. However, radiation exposure along with CHQ treatment resulted in significant increase in the frequency of SA as compared to the groups receiving CHQ alone at 21 days of the treatment. In summary, CHQ has the potential to induce genotoxicity in mammalian cells. Further, germ cells may be relatively more sensitive as compared to the somatic cells.