Mechanism of clastogenic and co-clastogenic activity of cremophore with benzene hi mice

Abstract

Cremophore E1 (CR), a frequently used solubilizer and emulsifier in the pharmaceutical, cosmetic and animal-raising industries, is made up of ethylene oxide and castor oil. Since ethylene oxide has been shown to be a potent genotoxic agent, we have studied the clastogenic activity of CR and its co-clastogenic activity with benzene (BZ) in mice. Male CD1 mice were divided into untreated, vehicle control and experimental groups. Mice in the experimental groups were treated orally with 0.03, 0.3 or 3% CR in water, 440 mg/kg BZ in olive oil, BZ plus the three different doses of CR (1 h apart) or BZ plus 3% CR separated by 1, 3 and 5 h intervals. Mice were killed at 30 h after the treatment for the single-treatment groups and after the first treatment for the combined treatment groups. Bone marrow cells were harvested for determination of micronuclei (MN) frequencies in polychromatic erythrocytes (PCE). The presence of known genotoxic metabolites of benzene (phenol and trans,trans muconic acid) was quantitated in collected urine. The effect on hepatic cytochrome P450 isoenzyme expression in livers of treated mice were also analyzed. We found that CR did not induce any significant or dose-dependent increase in MN. However, CR enhanced the clastogenic activity of BZ in a dose-dependent manner (from 41.6 to 47.3, 60.5 and 67.1 MN/1000 PCE respectively; P less than 0.05). The combined treatment showed an inverse time-dependent change in MN frequencies when CR was administered at 1, 3 and 5 h after BZ (41.6 to 67.1, 43.4 and 42.0 MN/1000 PCE respectively). The enhancement effect of CR is apparently due to its ability to induce significantly the cytochrome P450I family when CR was administered 1 h after treatment with BZ. However, no positive synergistic effect was observed when the combined treatment intervals were extended to 3 and 5 h. Enhanced induction of these isoenzymes is correlated with increased metabolic activation of BZ to excrete increased amounts of trans,trans muconic acid, the putative active metabolite of BZ, in urine. Our integrated study demonstrates that an apparently innocuous agent that is consumed by the general population can enhance the genotoxic activity of a ubiquitous environmental carcinogen. The potential existence of this type of interaction in our daily lives is frequently overlooked and should be investigated.