Aflatoxin B1-induced micronuclei and cell cycle alterations in lung and bone marrow cells and their modulation by...

Aflatoxin B, (AFB1) is a clastogen that causes cellular damage by covalent modification of nucleic acids. In this investigation, male rats were injected i.p. with AFB1 (8 mg/kg b.w.) in DMSO and the same dose of AFB1 was also administered intratracheally (i.t.) to the animals separately. The animals were killed after 26 h of the carcinogen treatment, femur bone was removed, and bone marrow cells were isolated and stained with Mayer's hematoxylin and eosin. Micronuclei (Mn) were scored by using light microscopy. Bronchoalveolar lavage (BAL) was prepared from rats administered AFB1 i.t. A part of BAL was fixed with 70% ethanol, stained with the fluorochrome DAPI, and analysed for cell cycle variations; the other part of the lavage was used for making slides to record Mn with a fluorescent microscope. A significantly greater proportion of lung cells were found to enter cell cycle with extended S-phase due to AFB1 treatment. Mn were induced in polychromatic erythrocytes (PCE) as compared to normochromatic erythrocytes (NCE) in the bone marrow of AFB1-treated rats, where there was nearly a three-fold increase in the number of Mn of bone marrow cells. The administration of AFB1 resulted in a two-fold rise in the Mn in the lung cells. The effect of BSO, DEM, and PB, the modulators of AFB1 metabolism, was studied on AFB1-induced Mn formation. A significant increase in the Mn score in PCEs of BSO- and DEM-treated rats was noted, while a slight reduction in the Mn score was noted in the case of PB-treated rats. The administration of the methanol extract of the leaves of Piper argyrophyllum (taken up in DMSO) to rats for a week exhibited normalising effect on AFB1-induced Mn in bone marrow cells. These observations record the induction of Mn in lung cells due to AFB1 for the first time. We propose the utility of AFB1-induced Mn as a model for screening plant extracts as inhibitors of genotoxicity. Prevention of genotoxic changes described above by phytochemicals is being pursued in our Laboratories.