Alterations in immune function and CYP450 activity in adult male deer mice (Peromyscus maniculatus) following exposure to benzo[a]pyrene, pyrene, or chrysene.

Polycyclic aromatic hydrocarbons (PAHs) are among the most common classes of chemical contaminants found at hazardous waste sites. Deer mice (Peromyscus maniculatus) exhibit a wide geographic distribution throughout North America and have been suggested as a terrestrial biomonitoring species to facilitate comparisons between superfund sites. Chemicals tested were benzo[a]pyrene (BaP; CAS number 50-32-8), pyrene (Pyr; CAS number 129-00-0), and chrysene (Chr; CAS number 218-01-9). Adult male deer mice were exposed via intraperitoneal (i.p.) injection every other day for 11 d to the PAHs (0.3, 1, 3, 10, or 30 mg/kg) or a corn oil carrier control. Both BaP and Chr suppressed the plaque-forming cell (PFC) response at all treatment levels. Pyr exposure (1-30 mg/kg) also resulted in suppression of this response. Macrophage pinocytosis was suppressed only by Chr (3, 10, and 30 mg/kg). Concanavalin A-induced proliferation was stimulated by BaP at all dose levels, by Pyr at 1-30 mg/kg, and by Chr at 30 mg/kg. Chr did not affect pokeweed mitogen (PWM)-induced proliferation; however, BaP (1-30 mg/kg) and Pyr (0.3-30 mg/kg) produced stimulation of this response as compared to respective controls. BaP and Chr stimulated cytochrome P-450 1A1 (CYP1A1) activity (3, 10, or 30 mg/kg) as measured by ethoxyresorufin O-deethylase (EROD) activity, but Pyr did not. These results indicate that immune function endpoints appear to be more sensitive to these PAHs than measured hepatic CYP450 activity.

Immunological and hematological effects observed in B6C3F1 mice exposed to JP-8 jet fuel for 14 days.

JP-8 is the primary jet fuel used by the U.S. Air Force and NATO allies. Exposure is likely to be widespread and to include both military and aviation industry personnel as well as residents living near fuel contaminated sites. This study examines the effects of JP-8 on humoral and cell-mediated and hematological parameters. A suite of immunotoxicological endpoints was evaluated in adult female B6C3F1 mice gavaged with JP-8 (in an olive oil carrier) ranging from 250-2500 mg/kg/d for 14 d. One day following the last exposure, significant increases in liver mass were detected beginning at exposure levels of 1000 mg/kg/d, while thymic mass was decreased at exposure levels of 1500 mg/kg/d and above. Decreases in thymic cellularity, however, were only observed at exposure levels of 2000 mg/kg/d and above. Mean corpuscular volume was increased (1500-2500 mg/kg/d), while the hematocrit, hemoglobin concentration, and red blood cell count were decreased only at the 2500 mg/kg/d exposure level. Natural killer cell (NK) activity and T- and B-cell proliferation were not altered. Decreases in the plaque-forming cell (PFC) response were dose responsive at levels of 500 mg/kg/d and greater, while unexpectedly, serum levels of anti-SRBC immunoglobulin M (IgM) were not altered. Alterations were detected in thymic and splenic CD4/8 subpopulations, and proliferative responses of bone marrow progenitor cells were enhanced in mice exposed to 2000 mg/kg/d of JP-8. This study establishes that humoral immune function is impaired with lower exposure levels of JP-8 than are required to affect primary and secondary immune organ weights and cellularities, CD4/8 subpopulations, and hematological endpoints.

Pyridostigmine bromide (PYR) alters immune function in B6C3F1 mice.

Pyridostigmine bromide (PYR) is an anticholinesterase drug indicated for the treatment of myasthenia gravis and neuromuscular blockade reversal. It acts as a reversible cholinesterase inhibitor and was used as a pretreatment for soldiers during Operation Desert Storm to protect against possible nerve gas attacks. Since that time, PYR has been implicated as a possible causative agent contributing to Gulf War Illness. PYR's mechanism of action has been well-delineated with regards to its effects on the nervous system, yet little is known regarding potential effects on immunological function. To evaluate the effects of PYR on immunological function, adult female B6C3F1 mice were gavaged daily for 14 days with PYR (0, 1, 5, 10, or 20 mg/kg/day). Immune parameters assessed were lymphoproliferation, natural killer cell activity, the SRBC-specific antibody plaque-forming cell (PFC) response, thymus and spleen weight and cellularity, and thymic and splenic CD4/CD8 lymphocyte subpopulations. Exposure to PYR did not alter splenic and thymus weight or splenic cellularity. However, 20 mg PYR/kg/day decreased thymic cellularity with decreases in both CD4+/CD8+ (20 mg/kg/day) and CD4-/CD8- (10 and 20 mg/kg/day) cell types. Functional immune assays indicated that lymphocyte proliferative responses and natural killer cell activity were normal; whereas exposure to PYR significantly decreased primary IgM antibody responses to a T-cell dependent antigen at the 1, 5, 10 and 20 mg/kg treatment levels for 14 days. This is the first study to examine the immunotoxicological effects of PYR and demonstrate that this compound selectively suppresses humoral antibody responses.

Subchronic exposure to ellagic acid impairs cytotoxic T-cell function and suppresses humoral immunity in mice.

Ellagic acid (EA) is present in a variety of foods such as grapes, strawberries, raspberries, and nuts. It is a dietary plant phenol that has been shown to inhibit oxidative stress and chemical carcinogenesis. Although several studies have examined the protective mechanisms of dietary EA including the induction of detoxifying enzymes, regulation of cell cycle, chelation of nickel, and prevention of DNA methylation, none have addressed the role of EA in immunological surveillance. This study investigates the status of immune function in B6C3F1 mice exposed continuously to EA in drinking water at 0.5, 1.0, or 2.0 mg/kg/day for 28 days. Although this range of exposure is above the estimated human daily intake (approximately 940 microg/day for 70 kg person or 13.4 microg/kg/day), these levels would not be unreasonable if EA were used as a dietary supplement or as a chemotherapeutic agent. Previous reports have demonstrated the anticarcinogenic effects of EA at levels 10- to 250-fold greater than those applied in this study. Immunological parameters assessed included natural killer (NK) cell activity, cytotoxic T lymphocyte (CTL) activity, IgM antibody plaque forming cell (PFC) response, thymus, spleen, kidney, and liver mass, and total cellularity for the thymus and spleen. Subchronic exposure to EA for 28 days in drinking water caused significant suppression of specific IgM antibody responses in the 2.0 mg/kg EA treatment group and suppressed cytotoxic T-cell function in the 0.5 and 1.0 mg/kg EA treatment groups. All other immunological parameters were within normal ranges. Kidney and liver mass were not altered after treatment with EA. The results from this study indicate that EA suppressed both IgM antibody responses and CTLs. These observations suggest important implications on human health should EA be prescribed as a chemotherapeutic agent or a preventative dietary supplement for cancer.

An aryl hydrocarbon receptor independent mechanism of JP-8 jet fuel immunotoxicity in Ah-responsive and Ah-nonresponsive mice.

JP-8 jet fuel is handled extensively by personnel in the military and commercial airlines, despite the paucity of information regarding its potential human health effects. JP-8 is a complex mixture primarily consisting of kerosene plus aliphatic and aromatic hydrocarbons. Recent reports indicate that acute JP-8 exposure via inhalation or dermal routes can overtly and persistently impair immune function in mice. Data from preliminary studies in this laboratory assessing the immunotoxicity of JP-8 indicated that oral JP-8 exposure caused an increase in liver weight, a decrease in thymus weight, and a decrease in the PFC response. As these results were similar to classic effects elicited by TCDD, a strong AhR ligand, it was hypothesized that JP-8 may exert immunosuppression via a similar mechanism. To test this hypothesis, an Ah-responsive mouse strain (B6C3F1) and a classically non-responsive mouse strain (DBA/2) bearing a lower affinity AhR were gavaged with JP-8 for 7 days. The results suggest that both mouse strains were equally sensitive to JP-8's toxicity at several endpoints including thymus weight and cellularity, liver weight, and specific IgM antibody responses. Furthermore, JP-8 did not induce CYP1A1 or promote down regulation of the AhR when evaluated by Western blot in either B6C3F1 or DBA/2 mice. In vitro studies corroborated these findings as JP-8 did not induce CYP1A1, promote down regulation of the AhR, or activate an XRE-driven reporter gene in murine Hepa-1 cells. These results suggest that JP-8 may exert its toxicity via an AhR-independent mechanism.

Effects of in ovo exposure to 2,3,7,8-TCDD on F1 generation adult chickens (Gallus gallus).

White Leghorn chickens (Gallus gallus) were used as surrogate species for the resident wild turkeys found on the Times Beach, Missouri, Superfund site. Parental chickens were injected with concentrations of 2,3,7,8-TCDD which modeled soil concentrations before (200 ppb) and after remediation (1ppb)[1]. Offspring were followed through development to assess alterations in reproductive maturity through the use of a four-way breeding study. F1 adult females exposed to a maternal dose of 8.6 ng/day began egg production approximately two weeks later than did F1 control adult females. By week eight, however, egg production between groups was equivalent. No differences were observed in eggshell gland estrogen or progesterone receptor levels.

Effects of environmentally relevant concentrations of 2,3,7,8-TCDD on domestic chicken immune function and CYP450 activity: F1 generation and egg injection studies.

Domestic chickens (Gallus gallus) were used as a surrogate species for wild turkey to assess risk from environmental 2,3,7,8-TCDD exposure. Lymphocyte proliferation and CYP450 induction were assessed in adults exposed via i.m. injection, in F1 14-day old hatchlings, in F1 adults (30-weeks old), and in 14-day old hatchlings exposed via yolk sac injections. Hatchlings from injected eggs exhibited a dose-response in lymphocyte proliferation, IgM titers, EROD, and PROD endpoints. Exposed adults showed a significant dose-dependent increase in CYP450 induction. F1 14-day old chicks exhibited a significant dose-dependent suppression of B-cell proliferation and induction of CYP450 enzymes. F1 adult proliferative responses exhibited B-cell suppression, that was not statistically significant. Significant sex-dependent EROD and MROD induction was also observed in F1 adults, indicating mixed-function oxidase imprinting from maternal exposure.