Effect of inhibitor of poly (ADP-ribose) polymerase in blood lymphocyte cultures of untreated leprosy patients.

Poly (ADP-ribose) polymerase is a cellular repair enzyme synthesised following damage to DNA. 3-Aminobenzamide (3-AB) is an inhibitor of this repair enzyme. To study repair efficiency in leprosy patients, who usually show a significantly higher frequency of spontaneous chromosome aberrations and sister-chromatid exchanges (SCEs), their blood lymphocyte cultures were treated with 3-AB. A marginal increase in the frequency of chromosome aberrations was observed following treatment with 3-AB in controls as well as in patient groups. There was also no significant difference in the frequency of SCEs in control cultures with or without 3-AB. A significant increase in the frequency of SCEs was observed in lymphocyte cultures of paucibacillary (PB) and multibacillary (MB) patients treated with 3-AB when compared with controls. Observation of a significant increase in the frequency of SCEs in 3-AB-treated cultures over the untreated value indicates that DNA damage caused in leprosy patients following mycobacterial infection is not repaired because of the presence of the inhibitor of repair enzyme.

Cytogenetic studies in leprosy patients before and after chemotherapy.

The frequencies of chromosome aberrations and sister chromatid exchanges (SCEs), cell proliferation kinetics and mitotic indices were studied in peripheral blood lymphocyte cultures of leprosy patients both before and after chemotherapy. The differences in the frequencies of chromosome aberrations and SCEs between controls, paucibacillary and multibacillary patients were found to be statistically highly significant (P less than 0.001). The extent of cytogenetic damage seemed to depend on the severity of the disease. Lymphocytes of untreated leprosy patients showed a low mitotic index and a slow rate of cell proliferation. Following combined treatment with dapsone and rifampicin there was an increase, but to a lesser degree (P less than 0.01), in the frequency of SCEs and chromosome aberrations while the drug combination of dapsone, rifampicin and clofazamine had a nonmutagenic effect on chromosomes of the patient. Furthermore, after drug treatment, the cell proliferation rate and mitotic indices in paucibacillary patients were comparable to that of controls. These results indicate the clastogenic potency of Mycobacterium leprae and the remedial effects that follow therapeutic drug treatment.

Evaluation of genotoxicity of clofazimine, an antileprosy drug, in mice in vivo. III. Sister chromatid exchange analysis in bone marrow cells.

The potential genotoxicity of an antileprosy drug, clofazimine, was evaluated in mice in an in vivo model by sister chromatid exchange (SCE) analysis. Three different dose levels (4, 20 and 40 mg/kg) were tested, and the animals were treated once daily for 15 days. Sister chromatid differential staining was done by BrdU-tablet implantation and FPG technique. All the doses tested here elevated the SCE frequencies significantly and the increases showed a significant positive correlation with the doses. The results confirm our earlier findings based on metaphase analysis and micronucleus test in the same species.

Effects of lepromatous leprosy (LL) serum factor(s) on normal blood lymphocytes.

To investigate the clastogenic activity of sera from leprosy patients, normal peripheral blood lymphocytes were cultured in both inactivated and noninactivated lepromatous leprosy (LL) sera. An increase in the frequency of chromosome aberrations was observed in normal lymphocyte cultures supplemented with both inactivated (5.2%) and noninactivated (5.0%) LL serum compared to that of cultures supplemented with normal human AB+ serum (2.4%). An enhanced frequency of sister chromatid exchanges (SCEs) was also observed in normal lymphocyte cultures supplemented with both inactivated (8.2 +/- 3.85) (mean +/- S.D.) and noninactivated (8.3 +/- 4.61) LL serum compared to that of controls (6.8 +/- 3.45). The normal blood lymphocyte cultures with LL serum have revealed a slow cell-cycle kinetics at a 48-hr incubation period, but a slightly faster proliferation rate was observed at 72 hr compared to cultures supplemented with normal human AB+ serum, indicating a depressive effect of LL serum on normal blood lymphocyte proliferation. The results obtained from the inactivated LL serum showed that the factor(s) which induce chromosomal damage, depress the mitotic index and the cell proliferation rate were not destroyed at 56 degrees C. These results are the first documentation of cytogenetic effects of LL sera on normal human peripheral blood lymphocytes.

Differential sensitivity of peripheral blood lymphocytes of untreated leprosy patients to mitomycin C.

The effects of a bifunctional alkylating agent mitomycin C (MMC), an effective inducer of chromosome aberrations and sister-chromatid exchanges (SCEs), have been studied in untreated leprosy patients. This was done to study the mutagen sensitivity of the leprosy patients. The frequency of chromosomal aberrations induced by MMC (conc. 0.01 microgram/ml) was 2.5% in controls, 3.6% in paucibacillary (PB), and 6.8% in multibacillary (MB) patients. The difference in the frequency of MMC-induced chromosome aberrations between the 3 groups studied was highly significant (p less than 0.01). Cultures grown with MMC showed the frequency of SCEs/cell to be 12.70 +/- 1.19 in controls, 19.97 +/- 3.51 in PB, and 29.66 +/- 5.92 in MB patients. The differences in the frequency of MMC-induced SCEs between the 3 groups were found to be highly significant (p less than 0.01). The enhanced frequencies of spontaneous and MMC-induced chromosome aberrations and SCEs observed in PB and MB patients indicate a clear differential mutagen sensitivity between PB and MB patients who are known to have different immunological status and thereby differ in the severity of the disease.