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Immunotoxic and Hepatotoxic Effects of Perfluoro-n-decanoic Acid (PFDA) on Female Harlan Sprague–Dawley Rats and B6C3F1/N Mice when Administered by Oral Gavage for 28 Days

Rachel P. Frawley, Matthew Smith, Mark F. Cesta, Schantel Hayes-Bouknight, Chad Blystone, Grace E. Kissling, Shawn Harris & Dori Germolec.
Journal of Immunotoxicology (2018) DOI: https://doi.org/10.1080/1547691X.2018.1445145 PMID: 29514525

Publication

Abstract

Poly- and perfluoroalkyl substances (PFAS) are chemically and thermally stable, hydrophobic, lipophobic compounds used in stain repellants and water and oil surfactants, and associated with immunosuppression and peroxisome proliferator activity. Perfluoro-n-decanoic acid (PFDA, (CF3(CF2)8COOH), a fluorinated straight chain fatty acid compound, is reported to induce thymic atrophy and reversible bone marrow hypocellularity in rodent models. The objective of this study was to assess potential immunotoxicity of PFDA, due to its structural similarity to other immunosuppressive PFASs. Female Harlan Sprague-Dawley rats were exposed to 0-2.0 mg PFDA/kg by oral gavage daily for 28 d. Female B6C3F1/N mice were exposed once/week to 0-5.0 mg PFDA/kg by gavage for 4 weeks. Animals were evaluated for effects on immune cell populations in spleen and bone marrow, and innate, humoral-, and cell-mediated immunity. Mice were also evaluated for resistance to Influenza virus. Treatment-related hepatocyte necrosis and hepatomegaly were observed in rats treated with 0.5 mg PFDA/kg/d. In mice, hepatomegaly (26-89%) was observed following exposure to ≥0.625 mg PFDA/kg/week, while splenic atrophy (20%) was observed at 5.0 mg PFDA/kg/week. At 5.0 mg PFDA/kg/week, total spleen cells, and Ig + and NK + cells were decreased (17.6-27%). At ≥ 1.25 mg PFDA/kg/week the numbers of splenic CD3+, CD4+, CD8+, and Mac3+ cells were decreased (10.5-39%). No changes were observed in leukocyte subpopulations in PFDA-exposed rats. Phagocytosis by fixed-tissue macrophages was decreased in liver (specific activity, 24-39%) at ≥0.25 mg PFDA/kg/d in rats. PFDA-induced effects on humoral- and cell-mediated immunity, host resistance, and bone marrow progenitor cells were limited. These data suggest that exposure to PFDA may induce adverse effects in rat liver in a manner consistent with the PFAS class, and may also alter the balance of immune cell populations in lymphoid tissues in mice.

Figures

Figure 1. Hepatocyte necrosis in Harlan Sprague–Dawley rats exposed to PFDA for 28 d.

Liver tissue from PFDA-treated and control rats was fixed in 10% neutral buffered formalin and evaluated using enhanced histopathology guidelines (see Methods section). Liver of (A) control or (B) rat treated with 0.5 mg PFDA/kg/d. Centrilobular, single cell, hepatocyte necrosis (arrows) was present in 3/8 rats and of minimal severity (grade 1.0). Note randomly scattered shrunken hepatocytes containing hyper-eosinophilic cytoplasm with small-to-occasionally pyknotic nuclei.

Figure 2. Vascular half-life of [51Cr]-SRBC in rats exposed to PFDA for 28 d.

Rats were injected intravenously with [51Cr]-SRBC on Day 29 at an amount equal to 20% of their hematocrit. Blood samples were collected over a 30-min period, and counted in a γ-counter to determine clearance of [51Cr]-SRBC from the blood and the vascular half-life. N = 8 rats/group for VH control and PFDA treated groups, N = 7 for MVE treated group. *p ≤ 0.05, Trend p = 0.158. VH: vehicle control; MVE: maleic vinyl ether (positive control for assay).

Figure 3. Functional activity of the mononuclear phagocytic system in the liver and thymus.

Functional activity of the mononuclear phagocytic system in the liver and thymus of rats exposed to PFDA for 28 d. Rats were injected intravenously with [51Cr]-SRBC on Day 29 and the vascular half-life was determined. Sixty minutes after injection, tissues were excised and counted in a γ-counter to determine organ uptake of labeled SRBC. N = 8 rats/group for VH control and PFDA-treated groups, N = 7 for the MVE-treated group. *Value significantly different from VH control; *p ≤ 0.05. Specific activity = cpm 51Cr-SRBC/mg tissue. Specific activity trend: Liver p < 0.001. Total activity = total cpm 51Cr-SRBC measured in tissue. Total activity trend: Liver p = 0.051. % Uptake = % of total counts [51Cr]-SRBC injected into the animal. % Uptake trend: Liver p = 0.029. VH: vehicle control; MVE: maleic vinyl ether (positive control for assay).

Tables

Table 1. Body and organ weights in female Harlan Sprague–Dawley rats.

Body and organ weights in female Harlan Sprague–Dawley rats exposed to perfluoro-n-decanoic acid for 28 d.

Table 2. Body and organ weights in female B6C3F1/N mice.

Body and organ weights in female B6C3F1/N mice exposed to perfluoro-n-decanoic acid for 28 d.

Table 3. Spleen cell immunophenotyping in female Harlan Sprague–Dawley rats.

Spleen cell immunophenotyping in female Harlan Sprague–Dawley rats exposed to perfluoro-n-decanoic acid for 28 d.

Table 4. Spleen cell immunophenotyping in female B6C3F1/N mice.

Spleen cell immunophenotyping in female B6C3F1/N mice exposed to perfluoro-n-decanoic acid for 28 d.

Table 5. Functional activity of the mononuclear phagocytic system.

Functional activity of the mononuclear phagocytic system in female Harlan Sprague–Dawley rats exposed to perfluoro-n-decanoic acid for 28 d.

Supplemental Materials

Supplemental Material

Individual Animal Data

Individual Animal Data - Rats

Individual Animal Data - Mice

Statistical Analysis

Statistical Analysis