A morphological analysis of the short-term effects of benzene on the development of the hematological cells in the bone marrow of mice and the effects of interleukin-1 alpha on the process.

Chronic exposure of humans to benzene (BZ), a widely used industrial chemical and a ubiquitous environmental pollutant, causes aplastic anemia and acute myeloid leukemia. The purpose of the studies reported here was to determine whether the observed depression of bone marrow (BM) cellularity in mice administered benzene was reflected in a suppression of development of all of the hematopoietic lineages and to confirm the ability of interleukin-1 alpha (IL-1 alpha) to prevent BZ-induced BM cell depression. We report that BZ, administered twice per day for 2 days to C57B1/6J mice at a dose of 600 mg/kg body weight, caused a significant depression of the total number of nucleated BM cells per femur when measured on day 3. The observed depression reflects a complex situation that represents the net effect of a decrease in the total number of cells of the lymphocytic and erythroid lineages, along with an increase in the number of intermediate and terminally differentiated cells of the granulocytic lineage. An experiment to monitor the effects of BZ over a 7-day period showed a progressive depressive effect on the lymphocytes and an initial depression of the erythroid cells at day 3 that remained constant until day 7. Conversely, the numbers of intermediate and terminally differentiated granulocytes progressively increased over the 7 days. The BM appeared to recover from the depressive effects of BZ immediately upon cessation of exposure, as the number of nucleated BM cells began to rise by day 5 and was equal to that of the control group by day 7. The results expand our earlier finding (Renz and Kalf 1991) that the overall depression of BM cellularity occurs because of an inability of the stromal fibroblast to produce colony-stimulating factors essential for stem and progenitor cell survival. This results from inhibition by the BZ metabolite, hydroquinone (HQ), of the processing of pre-IL-1 alpha to the mature cytokine.(ABSTRACT TRUNCATED AT 250 WORDS)