Influence of inhaled cadmium on the immune response to influenza virus

Proinflammatory effects of environmental cadmium boost resistance to opportunistic pathogen Aspergillus fumigatus: Implications for sustained low-level pulmonary inflammation?

Cadmium (Cd) is one of the most toxic environmental heavy metals to which the general population is exposed mainly via the oral route. Owing to its immunomodulatory potential, orally acquired Cd affects antimicrobial immune defense in several organs, including the lungs. While there are data concerning Cd and viral and bacterial pulmonary infections, effects on fungal infections are not studied yet. In the present study, the effect of the Cd (5 mg/L for 30 days, in drinking water, the average daily Cd intake 0.641 ± 0.089 mg/kg) on the immune response of rats to pulmonary A. fumigatus infection was examined. Data obtained showed that orally acquired cadmium does not affect the elimination of the fungus in immunocompetent rats owing to the preservation of some aspects of innate immune responses (lung leukocyte infiltration and NBT reduction) and an increase in other (increased numbers of mucus-producing goblet cells, MPO release). Cd does not affect an IFN-γ response in lung leukocytes during the infection (despite suppression of cytokine production in cells of lung-draining lymph nodes), while it stimulates IL-17 and suppresses IL-10 response to the fungus. As a result, the elimination of the fungus occurs in a milieu with the prevailing proinflammatory response in Cd-exposed animals that preserved fungal elimination from the lungs, though with more intense injury to the lung tissue. Therefore, the proinflammatory microenvironment in the lungs created by Cd that sustains inflammatory/immune response to the fungus to which humans are exposed for a lifetime, raises a concern of orally acquired Cd as a risk factor for the development of chronic low-grade pulmonary inflammation.

Interactions among infections, nutrients and xenobiotics

During recent years there have been several incidents in which symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Furthermore, outbreaks of infections in food-producing animals have attracted major attention regarding the safety of consumers, e.g., Bovine Spongiform Encephalitis (BSE) and influenza in chicken. As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and associated complications. Moreover, during ongoing infection, xenobiotic uptake and distribution are often changed resulting in increased toxic insult to the host. The interactions among infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology as well as in food-borne diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects among microorganisms, nutrients, and xenobiotics will have to be considered. Otherwise, such effects may gradually change the disease panorama in society.

Immune responses and resistance to viral-induced myocarditis in mice exposed to cadmium

The effects of 10 weeks of treatment with cadmium (Cd) on the immune function and resistance to coxsackievirus B3 (CB3)-induced myocarditis in female Balb/c mice were investigated. A 2mM dose of Cd in the drinking water did not influence mortality due to the CB3 infection. The inflammatory and necrotic lesions in the ventricular myocardium seven days after inoculation (2.94% of tissue section area) were not increased by Cd (2.82% of tissue section area). The response pattern of lymphocyte subsets in situ in myocardial inflammatory lesions was elucidated by an immune histochemical staining technique. With Cd treatment the number of cytotoxic T cells and B cells in these lesions decreased by 22% (n.s.) and 21% (p < 0.05), respectively. Spleen weight and the lymphoproliferative response to the B-lymphocyte mitogen increased by 19% (p < 0.05) and 23% (n.s.), respectively. The titers of neutralizing antibodies increased by 22% (n.s.) with Cd treatment. However, the activity of spleen T lymphocytes and spontaneous cell-mediated cytotoxicity (NK-cell) was unchanged. Thymus weight and WBC count in peripheral blood tended to decrease. Thus, Cd exposure seems to result in a decreased maturation and mobilization of T and B lymphocytes, but increased humoral immune host responses.

Altered distribution of 109cadmium in mice during viral infection

The distribution of the toxic heavy metal cadmium (Cd) was studied in Coxsackie virus B3 (CB3)-infected Balb/c mice by whole-body autoradiography and gamma-counting. The distribution of 109Cd was studied 4 days post CB3-inoculation and 10 min after intravenous injection of 0.21 microgram of Cd/kg body weight. Whole-body autoradiography results showed that the distribution of 109Cd is greatly changed during this viral infection. This newly discovered distribution was mainly visible as a greatly increased accumulation in the renal and adrenal cortices. After impulse counting of selected organs it was found that the normal accumulation of 109Cd in the kidneys (184,354 +/- 30,961 c.p.m.) was increased by 47% (P less than 0.05) during CB3 infection (270,503 +/- 54,780 c.p.m.). In contrast to healthy animals, some infected mice showed accumulation of 109Cd in the spleen. These results show for the first time that an invading micro-organism can change the distribution of an environmental pollutant.