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Immunotoxic Effects of Sodium Tungstate Dihydrate on Female B6C3F1/N Mice When Administered in Drinking Water

Frawley RP, Smith MJ, White KL Jr, Elmore SA, Herbert R, Moore R, Staska LM, Behl M, Hooth MJ, Kissling GE, Germolec DR.
J Immunotoxicol. (2016). DOI: https://doi.org/10.3109/1547691X.2016.1154118 PMID: 27223060

Publication

Abstract

Tungsten is a naturally occurring, high-tensile strength element that has been used in a number of consumer products. Tungsten has been detected in soil, waterways, groundwater, and human tissue and body fluids. Elevated levels of tungsten in urine were reported for populations exposed to tungstate in drinking water in areas where natural tungsten formations were prevalent. Published reports indicated that sodium tungstate may modulate hematopoiesis, immune cell populations, and immune responses in rodent models. The objective of this study was to assess potential immunotoxicity of sodium tungstate dihydrate (STD), a drinking water contaminant. Female B6C3F1/N mice received 0-2000 mg STD/L in their drinking water for 28 d, and were evaluated for effects on immune cell populations in spleen and bone marrow, and humoral-mediated, cell-mediated, and innate immunity. Three different parameters of cell-mediated immunity were similarly affected at 1000 mg STD/L. T-cell proliferative responses against allogeneic leukocytes and anti-CD3 were decreased 32%, and 21%, respectively. Cytotoxic T-lymphocyte activity was decreased at all effector:target cell ratios examined. At 2000 mg STD/L, the absolute numbers of CD3(+) T-cell progenitor cells in bone marrow were increased 86%, but the alterations in B-lymphocyte and other progenitor cells were not significant. There were no effects on bone marrow DNA synthesis or colony forming capabilities. STD-induced effects on humoral-mediated immunity, innate immunity, and splenocyte sub-populations were limited. Enhanced histopathology did not detect treatment-related lesions in any of the immune tissues. These data suggest exposure to STD in drinking water may adversely affect cell-mediated immunity.

Figures

Figure 1. Cytotoxic T-lymphocyte and mixed-leukocyte responses in female B6C3F1/N mice.

Cytotoxic T-lymphocyte and mixed-leukocyte responses in female B6C3F1/N mice exposed to STD in drinking water for 28 d.
Panel A: cytotoxic T-lymphocyte (CTL) response. Splenocytes were cultured for 5 d with P815 mastocytoma cells (induction phase), harvested, and incubated in the presence of [51Cr]-labeled P815 cells for 4 h (effector phase). Release of [51Cr] into the supernatant was used as the endpoint of the assay. Spontaneous release over the 4-h incubation period was 11.1% of maximum release.
Panel B: mixed-leukocyte response. Splenocytes were cultured for 5 d in the presence of mitomycin C-treated DBA/2 allogenic stimulator cells. R = responder (B6C3F1/N) cells only, R + S = responder and stimulator (DBA/2) cells. All MLR cultures were labeled with [3H]-thymidine 18–24 h prior to harvest. [3H]-thymidine incorporation into proliferating cells was used as the endpoint of the assay.
Results are expressed as percent cytotoxicity for the CTL, CPM/105 splenocytes for the MLR. Asterisks indicate statistically significant differences from VH control; *p ≤ 0.05; N = 7–8 mice/group for VH, STD and CPS (MLR only); N = 4 for the CPS (CTL) group. Due to the reduction in spleen weight and cell number, it was necessary to pool splenocytes from two positive control CPS-treated animals to achieve the necessary cell concentrations for the CTL assay.

Figure 2. Anti-CD3-mediated splenic T-cell proliferation and delayed-type hypersensitivity responses.

Anti-CD3-mediated splenic T-cell proliferation and delayed-type hypersensitivity responses in female B6C3F1/N mice exposed to STD in drinking water for 28 d. Panel A: anti-CD3 mediated proliferation. Splenocytes were cultured in the presence (stimulated) or absence (unstimulated) of anti-CD3 antibody in 96-well plates for 3 d. All anti-CD3 cultures were labeled with [3H]-thymidine 18–24 h prior to harvest. Incorporation of [3H]-thymidine into proliferating cells was used as the endpoint of the assay. Panel B: delayed-type hypersensitivity response. Mice were sensitized on Day 21 with formalin-fixed C. albicans, and challenged in the right footpad on Day 29 with the C. albicans antigen, chitosan. Footpad swelling was determined 24 h post-challenge. Results are expressed as CPM/2 × 105 splenocytes for the anti-CD3 assay, and as mm × 100 for the DTH assay. N = 8 mice/group. Asterisks indicate statistically significant differences from VH control; *p ≤ 0.05

Tables

Table 1. Hematology and blood leukocyte differentials in female B6C3F1/N mice.

Hematology and blood leukocyte differentials in female B6C3F1/N mice exposed to STD in the drinking water for 28 d.

Table 2. Functional activity of the mononuclear phagocytic system.

Functional activity of the mononuclear phagocytic system in mice exposed to STD in the drinking water for 28 d.

Table 3. Bone marrow cell immunophenotyping.

Bone marrow cell immunophenotyping in female B6C3F1/N mice exposed to STD in the drinking water for 28 d.