Impaired cellular immune response in rats exposed perinatally to Baltic Sea herring oil or 2,3,7,8-TCDD

Abstract

While the immunotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been well established, the eects of complex environmental mixtures of polyhalogenated aromatic hydrocarbons (PHAHs) are poorly understood. Many PHAHs, including the polychlorinated-biphenyls (PCBs), -dibenzofurans (PCDFs), and dibenzo-p-dioxins (PCDDs), possess`dioxin-like' activities, and accumulate in the aquatic food chain. Organisms occupying high trophic levels may therefore be exposed to concentrations which may present an immunotoxic risk. In this study, pregnant PVG rats were administered a daily oral dose of 1 ml of the following during pregnancy and lactation: (1) oil extracted from herring caught in the relatively uncontaminated Atlantic Ocean; (2) oil extracted from herring caught in the contaminated Baltic Sea; or (3) the Atlantic herring oil extract spiked with 2,3,7,8-TCDD. The daily intakes of aryl hydrocarbon (Ah)-receptor dependent toxic equivalents (TEQ) for mothers were 0.3 in the Atlantic group, 2.1 in the Baltic group, and 134 ng/kg body wt. in the 2,3,7,8-TCDD positive control group. Immune function and host resistance to rat cytomegalovirus (RCMV) were assessed in ospring aged 11, 25, 46 or 59 days. Rat pups in the positive control TCDD-spiked group exhibited immunosuppression characterized by reduced thymus weight and cellularity, reduced thymocyte and splenocyte proliferative responses to T-dependent mitogens in vitro, reduced virus-associated natural killer (NK) cell and speci®c antibody responses. While less pronounced, a similar pattern of eects was observed in the rat pups exposed only to the Baltic Sea herring oil. These immunotoxic eects were transient in both exposure groups, with a time-related recovery in immune function possibly due to the half-life of TCDD in rats and the waning exposure levels in the rapidly growing pups. We previously demonstrated that the same Baltic Sea herring led to impaired natural killer cell and Tlymphocyte function in harbour seals during the course of a long-term captive feeding study. The collective results of these studies in rats and seals indicate the immunotoxic potential of environmental mixtures at current levels in the aquatic environment, and suggest that the developing immune system of young mammals may be at particular risk.

Time-of-flight secondary ion mass spectrometry imaging demonstrates the specific localization of deca-bromo-diphenyl-ether residues in the ovaries and adrenal glands of exposed rats

“…Among others, it has been demonstrated that PCBs and some of their hydroxylated metabolites target the adrenal glands of marine mammals, inducing the hyperplasia of the cortical area [46]. The immunotoxicity of PCBs was demonstrated in another study with rats, which is consistent with the known deregulation of the immune system by corticosteroids [47]. In the case of PCBs, cortical hyperplasia of the adrenal glands is hypothesized to be correlated with an increased production of cortisol, which in turn triggers the down regulation of the immune system.…”

Impact of PCB on resistance to Flavobacterium psychrophilum after experimental infection of rainbow trout Oncorhynchus mykiss eggs by nanoinjection

“…It might be possible that exposure to contaminants before the immune system has developed, has caused as yet unknown effects. The developing immune system in mammals has been shown to be highly sensitive to environmental contaminants (Ross et al 1997) and the same could be expected in fish.…”

“…It might be possible that exposure to contaminants before the immune system has developed, has caused as yet unknown effects. The developing immune system in mammals has been shown to be highly sensitive to environmental contaminants (Ross et al 1997) and the same could be expected in fish.In an experimental infection with Flavobacterium psychrophilum using the nanoinjection method (Ekman et al 2003) the clinical signs of disease and pathological findings of dead and moribund fry are in accordance with those described in the present study. However, lesions on the yolk sac with vesicles, ulcerations and leakage of yolk were not noted in the previous study.…”

Risks and Management of Dioxins and Dioxin-like Compounds in Baltic Sea Fish: An Integrated Assessment

“…Effects assessment less susceptible to immune effects than harbour seals; most effects have been transient and weak (Ross et al 1997). Collectively, these findings indicate that immunosuppression has occurred in multiple marine mammal species as a result of consumption of a diet consisting predominantly of Baltic herring, and DLCs are strongly suspected although not proven to have caused this.…”

“…The observed seasonal changes in NK cell activity were also mentioned as a potentially relevant factor. Ross et al (1997) pointed out that young individuals may be at particular risk; their studies did not cover the perinatal period. Van Loveren et al (2000) added that long-lasting exposure occurs in the wild.…”