Heptachlor epoxide in marine mammals

Effect of the chlorinated hydrocarbons heptachlor, chlordane, and toxaphene on retinoblastoma tumor suppressor in human lymphocytes

Organochlorine use over the past 50 years has resulted in the contamination of soil, water, plant and animal species. This contamination has created a long-lasting environmental problem, as the members of the organochlorine class of pesticides are resistant to degradation and have been labeled as persistent bioaccumulators. Studies have shown certain organochlorines to be tumor promoters, liver toxicants and to induce immune cell dysfunction in rats and mice. Our laboratory has shown that the organochlorines heptachlor and chlordane affect leukocytic gene expression and differentiation. In this study, experiments with CEM x 174 cells, a hybrid of human T and B cells, were performed to investigate the effects of the tumor promoter heptachlor and its congeners chlordane and toxaphene on retinoblastoma (Rb) gene expression. The results indicated that heptachlor, chlordane or toxaphene, in the range of 10-50 microM, were able to reduce Rb protein levels in a concentration-dependent manner. In the case of heptachlor, the reduction could be seen as early as 12 h and was time-dependent. Analysis of Rb mRNA levels revealed no detectable difference over the same concentration range. These results suggest that members of the organochlorine class are able to downregulate Rb expression at the post-transcriptional level, an effect similar to that on p53 tumor suppressor previously reported by our laboratory.

Induction of differentiation in human myeloblastic leukemia ML-1 cells by heptachlor, a chlorinated hydrocarbon insecticide

Effects of heptachlor, an organochlorine pesticide, on human myeloblastic leukemia ML-1 cells were determined. Similar to 12-O-tetradecanoylphorbol-13-acetate (TPA), a known tumor promoter, heptachlor induced cell adherence and formation of extended cytoplasmic pseudopodia in ML-1 cells. The growth of ML-1 was slightly stimulated by low concentrations (less than 30 nM) of heptachlor. A dose-responsive cell death was also observed when ML-1 cells were treated with heptachlor at concentrations greater than 80 microM. Examination by light microscopy of the cells treated with 80 microM heptachlor revealed a gradual appearance of differentiation characteristics in the culture. On Day 3 of the treatment, 41% of the cells remained unchanged as ML-1, 39% of the cells showed changes and apparent cell differentiation, and 20% of the cells were induced to differentiate to monocyte- or macrophage-like cell type. Electron microscopy also revealed cellular differentiation and the presence of monocyte- and macrophage-like cell types (22%) was confirmed by positive esterase staining.