Low Folate Status Enhanced Benzene-Induced Cytogenetic Damage in Bone Marrow of Mice: A Relationship Between Dietary Intake and Tissue Levels of Folate

Abstract

We examined the protective effect of dietary folate on benzene-induced chromosomal damage in bone marrow of mice regarding folate levels in diet and tissue. Male mice were fed either a deficient, basal, or high folate diet (0, 2, or 8 mg/kg diet, respectively) for 4 wk followed by a single dose of benzene. Plasma folate levels corresponded to those of dietary intake. Meanwhile, bone marrow, erythrocyte, and liver folate were decreased to 40% in the deficient group and almost saturated in the high group. Plasma homocysteine levels negatively correlated to levels of tissue folate. Chromosomal damage, evaluated by micronucleus assay, was not affected by folate status alone but was markedly enhanced by benzene, particularly in the deficient group (P < 0.05 vs. the basal and high groups). The activities of hepatic drug-metabolizing enzymes did not enhance benzene metabolism in the deficient groups, indicating that enhanced chromosomal damage was solely due to the low folate status. These results suggest that a low folate status can increase the risk of benzene-induced chromosomal damage in bone marrow, but excess folate intake does not enhance protection, as it is saturated in tissue.

Acknowledgments and Notes

This study was financially supported in part by a research grant from the Ministry of Health, Labour, and Welfare in Japan.

Notes

a: Male ICR mice (4 wk old) were fed either a folate deficient diet (0 mg/kg), basal diet (2 mg/kg), or high folic acid diet (8 mg/kg) for 4 wk and then given benzene (1,600 mg/kg, per os, single dose) and sacrificed on Day 2 post administration. Values are the means ± SD, n = 6. Abbreviation is as follows: NS, nonsignificant.

b: Significant dietary effect (vs. basal folic acid diet group with same benzene dose; P < 0.05).

c: Significant benzene effect (vs. control group with the same diet treatment; P < 0.05).

a: Significant dietary effect (vs. basal folic acid diet group with same benzene dose; P < 0.05).

b: Significant benzene effect (vs. control group with the same diet treatment; P < 0.05).

a: Significant benzene effect (vs. control group with the same diet treatment; P < 0.05).

a: Refer to Table 1 legend for details. Abbreviation is as follows: CYP, cytochrome P450. The examined subtypes of CYP enzymes were ethoxyresorufin O-deethylase, CYP1A1; methoxyresorufin O-demethylase, CYP1A2; pentoxyresorufin O-dealkylase, CYP2B; (S)-warfarin 7-hydroxylase, CYP2C9; p-nitrophenol hydroxylase, CYP2E1; and testosterone 6-hydroxylase, CYP3A.

b: Significant benzene effect (vs. control group with the same diet treatment; P < 0.05).

c: Significant dietary effect (vs. basal folic acid diet group with same benzene dose; P < 0.05).