Micronucleus evaluation in mitogen-stimulated lymphocytes of PUVA treated patients

Cytotoxic and genotoxic effects of acitretin, alone or in combination with psoralen-ultraviolet A or narrow-band ultraviolet B-therapy in psoriatic patients

Acitretin is currently used alone or combined with PUVA (psoralen + UVA) or with narrow-band ultraviolet B (NBUVB), to treat moderate and severe psoriasis. However, little is known about the potential genotoxic/carcinogenic risk and the cytostatic/cytotoxic effects of these treatments. Our aim was to study the cytotoxic and genotoxic effects of acitretin - alone or in combination with PUVA or NBUVB - by performing studies with blood from patients with psoriasis vulgaris who were treated with acitretin, acitretin+PUVA or acitretin+NBUVB for 12 weeks, and in vitro studies with blood from healthy volunteers, which was incubated with acitretin at different concentrations. The cytotoxic and genotoxic effects were evaluated by the cytokinesis-blocked micronucleus test and the comet assay. Our results show that psoriatic patients treated with acitretin alone or with acitretin+NBUVB, did not show genotoxic effects. In addition, these therapies reduced the rate of proliferation and induced apoptosis and necrosis of lymphocytes; the same occurred with lymphocyte cultures incubated with acitretin (1.2-20μM). The acitretin+PUVA reduced also the proliferation rate, and increased the necrotic lymphocytes. Our studies suggest that therapy with acitretin alone or combined with NBUVB, as used in psoriatic patients, does not show genotoxic effects, reduces the rate of proliferation and induces apoptosis and necrosis of lymphocytes. The combination of acitretin with PUVA also reduces the proliferation rate and increases the number of necrotic lymphocytes. However, as it induced slight genotoxic effects, further studies are needed to clarify its genotoxic potential.

Increased micronucleus frequency in phytohaemagglutinin-stimulated blood cells of patients with vitiligo

BACKGROUND

Vitiligo is a relatively common, acquired pigmentary disorder characterized by areas of depigmented skin resulting from loss of melanocytes in the epidermis. Although several hypotheses have been proposed for the aetiology and pathogenesis of vitiligo, the cause of vitiligo remains unclear.

OBJECTIVE

To evaluate spontaneous micronucleus (MN) frequency using the cytokinesis block MN assay to determine damages at the DNA or chromosome level in phytohaemagglutinin (PHA)-stimulated blood cells of patients with vitiligo and healthy control subjects.

METHODS

Peripheral blood samples were obtained and cultured from 21 patients with vitiligo (mean age: 21.48 +/- 9.78 years) and 21 age- and sex-matched healthy control subjects (mean age: 21.52 +/- 9.80 years). MN values were scored in binucleated cells obtained from whole-blood cultures of patients and control subjects.

RESULTS

MN frequencies (mean +/- SD) in PHA-stimulated blood cells of patients with vitiligo and control subjects were 0.94 +/- 0.58 and 0.58 +/- 0.32, respectively. Compared with control subjects, MN frequencies of patients with vitiligo were found significantly higher than those of the control subjects (P = 0.012).

CONCLUSION

Our results indicate unexpectedly some chromosomal/DNA damage in whole-blood cultures of patients with vitiligo. We do not know, however, if these chromosome/DNA instabilities observed in the cells of vitiligo patients resulted from the cause or from the consequences of the disorder.

Vitamin B12 reduces ribavirin-induced genotoxicity in phytohemaglutinin-stimulated human lymphocytes

Ribavirin, an N-glycosyl nucleoside (1-beta-D-ribofuranosyl-1, 2, 4-triazole-3 carboxamide), is a synthetic purine nucleoside analogue with a broad spectrum of antiviral activity, however, its high toxicity poses a major disadvantage of its use as a therapeutic. Various studies have shown that vitamin B12 plays a significant role in maintaining the stability of the human genome. We therefore investigated the potential beneficial effect of vitamin B12 in reducing ribavirin-induced genotoxicity. To test this, we used the cytokinesis-block micronucleus (CBMN) assay. Human blood cells were treated in vitro with increasing doses of ribavirin (0.05, 0.17, 0.32, 0.47 and 0.65 micromol/ml) for three different periods of time (2, 4 and 17 hrs). Duplicate cultures were supplemented with 50 mul of vitamin B12 during the drug treatment (final concentration of 13.5 microg/ml). Micronuclei formation and cell proliferation potential were then scored in both sets of samples and the corresponding controls. The results showed that supplementation with vitamin B12 lowered the frequency of micronuclei (Z = 2.02, p < 0.04) and recovered the proliferation potential of the treated cells for each treatment period, except for the conditions with the highest concentration of ribavirin and the shortest time. These observations underscore the unique beneficial effects of vitamin B12 in reducing genotoxicity, particularly by recovering the proliferation potential of treated cells, as demonstrated by the decrease in mononucleated cells and enhancement of binucleated and polynucleated cells. The mechanism by which vitamin B12 reduces ribavirin-induced genotoxicity is related to de novo synthesis of nucleotides, and is worthy of further investigation.

Genotoxicity of thallium-201 in patients with angina pectoris undergoing myocardial perfusion study

Thallium-201 (201Tl) has been widely used as a nuclear reagent for myocardial blood flow imaging. The purpose of this study was to investigate genotoxic effects of 201Tl in patients with angina pectoris (n = 21), who had undergone myocardial perfusion imaging. Lymphocytes were isolated from each patient before, and 3, 30 and 90 days after 201Tl administration (111 MBq, 3 mCi) and were analyzed for chromosomal aberrations, sister chromatid exchanges, mitotic index and replicative index. There were significant increases in chromosomal aberrations and sister chromatid exchanges 3 days after 201Tl administration (p < 0.001), although no difference was noted in these values after 30 and 90 days (p > 0.05). Moreover, decreased mitotic index and replicative index were noted after 3 days of 201Tl administration (p < 0.001). These results suggest that the administration of 201Tl for myocardial blood flow imaging may induce genetic damage.

Micronucleus evaluation in mitogen-stimulated lymphocytes of narrow-band (311 nm TL01) UVB-treated patients

BACKGROUND

Narrow-band UVB (311 nm) lamps (TL01) are being increasingly used for phototherapy of psoriasis and other dermatoses, for their excellent effect compared with broad-band UVB sources and photochemotherapy. It is acknowledged that the TL01 lamp is probably two to three times more carcinogenic per minimum erythema dose than broad-band UVB, but the cumulative dose is considerably less than broadband UVB sources. Micronucleus (MN) test is used to detect both clastogenic (breaking) and aneugenic (abnormal segregation) effect of physical/chemical agents on chromosomes. The aim of this study is to evaluate MN frequencies in mitogen-stimulated lymphocytes of narrow-band UVB-treated patients.

METHODS

Frequency of micronuclei in 72 h cultivated/mitogen-stimulated lymphocytes of 36 patients (age 7-73 years, mean+/-SD: 25.33+/-18.54) have been evaluated at pretreatment and after 20, 40, 60 sessions of narrowband UVB treatment.

RESULTS

While the beginning MN frequency +/-SD (%) was 1.07+/-0.63, it increased to 1.47+/-0.92, 1.47+/- 0.77, 1.41+/-0.31 corresponding, respectively, to 20, 40, 60 sessions. These sessions reciprocally correspond to 0.85+/-0.23, 2.97+/-0.72, 5.68+/-1.46 J/cm(2) doses of narrow-band UVB. Difference of MN frequency was statistically significant (P=0.002). Significant differences have been observed between the initial MN frequency and after that of 20, 40, 60 sessions (P=0.001, 0.004, 0.002, respectively).

CONCLUSIONS

The results of this study show that narrow-band UVB treatment causes a detectable chromosome damaging effect.