Polychlorinated biphenyls modulate protooncogene expression in Chang liver cells

Effects of acute postnatal exposure to 3,3',4,4'-tetrachlorobiphenyl on sperm function and hormone levels in adult rats

Polychlorinated biphenyls (PCBs) are considered potential endocrine disruptors due to their ability to act as estrogens, antiestrogens and goitrogens. The aim of this study is to ascertain whether acute postnatal treatment with 3,3',4,4'-tetrachlorobiphenyl (CB 77) affects sperm function and hormone levels in adult rats. Male Sprague-Dawley rats received CB 77 by ip injection of 2 or 20 mg/kg at day 21 and sacrificed at day 112. At day 112, right and left testis weights were significantly increased, whereas sperm count, motility, total motile sperm count, curvilinear velocity, average path velocity, straight-line velocity, and beat-cross frequency for motile sperm were significantly decreased in rats treated with 20 mg/kg CB 77. Sperm-oocyte penetration rate was significantly reduced in rats treated with either 2 or 20 mg/kg CB 77. There was high sperm acrosome reaction rate (ARR) in the 20 mg/kg CB 77-treated rats. There was a significant increase in thyroid-stimulating hormone level in the 20 mg/kg CB 77 group. However, no changes were seen in serum testosterone, thyroid hormones, or prolactin concentrations at day 112. In summary, this study showed that postnatal exposure to CB 77 might affect spermatogenesis, motility, ARR, and ability of fertilizing oocytes in mature rats. These results suggest that the sperm functions may be more susceptible or adapt less readily than the thyroid functions to endocrine disruption caused by dioxin-like PCB congeners.

Exploring environmental causes of altered ras effects: fragmentation plus integration?

Mutations in ras genes are the most common abnormality of oncogenes in human cancer and a major example of activation by point mutation. Experimental and epidemiological studies support the notion that Ki-ras activation and expression may be chemically related. We discuss the potential role of several environmental compounds in the induction or promotion of ras mutations in humans, with a focus on exocrine pancreatic cancer, the human tumor with the highest prevalence at diagnosis of Ki-ras mutations. Organochlorine compounds, organic solvents, and coffee compounds may play an indirect role in causing Ki-ras mutations, rather than as direct inducers of the mutations. Although for some organochlorine compounds the induction of point mutations in ras oncogenes cannot be excluded, it seems more likely that the effects of these compounds are mediated through nongenomic or indirectly genotoxic mechanisms of action. Organic solvents also may act via enzymatic induction of ras mutagens or by providing a proliferation advantage to ras-mutated cell clones. In exocrine pancreatic cancer, caffeine, other coffee compounds, or other factors with which coffee drinking is associated could modulate Ki-ras activation by interfering with DNA repair, cell-cycle checkpoints, and apoptosis. Asbestos, cigarette smoking, and some dietary factors also may be involved in the initiation or the promotion of Ki-ras mutations in lung and colon cancers. Further development of the mechanistic scenarios proposed here could contribute to a meaningful integration of biological, clinical, and environmental knowledge on the causes of altered ras effects.

[Concentrations of persistent toxic compounds in the Spanish population: a puzzle without pieces and the protection of public health]

The contamination by persistent toxic compounds (PTCs) of the general population is a fact of relevance from a public health perspective. It is also relevant to health care professionals, as well as for environmental, food, industrial and economic policies. Though in Spain information on food contamination by PTCs shows large time and geographic gaps, the scarcity of data is even more severe on the concentrations that PTCs have in people: a representative study of a general healthy population living in a wide geographic area has never been conducted in the country. However, the available studies indicate that around 80-100% of the population has detectable concentrations of DDE, PCBs, hexachlorbenzene or lindane. Studies on the effects that PTCs have upon humans are extremely infrequent in Spain. Yet, the international literature suggests that some PTCs may induce significant biological and clinical effects at doses below those traditionally deemed "safe". The mechanism of action of PTCs are not restricted to endocrine disruption. Assessing the clinical and social relevance of the more subtle and long-term effects of PTCs presents interesting challenges and opportunities. Spain and other European countries lack population indicators on the impact that environmental processes have on human health. Several government levels have a role to fulfill in the monitoring of biological levels of PTCs among persons in order to assess the risks of adverse health effects. Along with over a hundred other countries. Spain will soon try to implement the Stockholm treaty on persistent organic pollutants (POPs). This constitutes a new opportunity to develop more efficient policies to control PTC residues in food, humans and the environment. As part of the treaty implementation it is necessary to launch a Report on factors that influence body concentrations of PTCs in the Spain general population.

Apoptosis-mediated immunotoxicity of polychlorinated biphenyls (PCBs) in murine splenocytes

Polychlorinated biphenyls (PCBs) exhibited immunotoxicity on antibody forming response to T-dependent antigen of sheep red blood cells, primary activation of T cells by mixed lymphocyte response, and lymphocyte proliferation induced by various mitogens. These immunosuppressions were related with the loss of lymphocyte viability which was determined by the propidium iodide method, and this death was proven to be linked with apoptosis which showed DNA fragmentation detected by the diphenylamine method and agarose gel electrophoresis. The degree of DNA fragmentation was increased in a dose- and time-dependent manner in PCB-treated splenocytes. In conclusion, it was assumed that apoptosis was attributable to the immunotoxicity of PCBs in murine splenocytes.

Embryotoxicity of polychlorinated biphenyls (PCBS) for preimplantation embryos

In a previous study oral administration of a commercial PCB mixture (Aroclor 1,260) to female rabbits (4 mg/kg b.wt. for 14 weeks) resulted in a significant accumulation of PCBs in 6-d-old blastocysts and increased preimplantation embryo mortality (1). In the present study, the direct toxicity of PCBs on preimplantation rabbit embryos was investigated during in vitro culture. One-day-old cleavage stages and 3-d-old rabbit morulae were cultured in BSM II medium supplemented with 1.5% BSA in a reduced oxygen concentration of 5% O2. They were exposed to 50, 5, or 0.5 microgram Aroclor 1,260/mL culture medium for 24 h. PCB (50 micrograms) led to a complete degeneration of the exposed embryos. Following exposure to 5 micrograms only 16% of the morulae developed into blastocysts. The others were either arrested in the morulae stage or were degenerated. Cell proliferation of the nondegenerated embryos was approximately 20% of that of corresponding control embryos. Compared with nonexposed controls, addition of 0.5 microgram PCB/mL showed either no or only a slight impairment of development. Preliminary embryo transfer experiments showed that morulae exposed to 5 micrograms PCB with clear signs of degeneration after 24 h in vitro culture were able to implant. Aroclor 1,260 is embryotoxic in a dose-dependent manner in cultured rabbit preimplantation embryos.