Olfactory epithelial metaplasia and hyperplasia in female Harlan Sprague-Dawley rats following chronic treatment with polychlorinated biphenyls

Increased risk of head and neck cancer in Agent Orange exposed Vietnam Era veterans

IMPORTANCE

United States military personnel during the Vietnam Era were potentially exposed to Agent Orange, a known carcinogen. The link between Agent Orange and head and neck cancers is largely unknown; laryngeal cancer is currently the only subsite with sufficient evidence of an Agent Orange association.

OBJECTIVE

We aim to determine the relationship between Agent Orange exposure and the incidence of head and neck cancers in Vietnam Era veterans as well as any relationship with head and neck cancer survival.

MATERIALS AND METHODS

The present study utilizes the Veterans Affairs Corporate Data Warehouse (VA CDW) to identify Vietnam Era veterans, their Agent Orange exposure status, limited demographic data, presence of head and neck cancer, and survival data.

RESULTS

Of 8,877,971 Vietnam Era veterans, 22% self-reported exposure to Agent Orange, and 54,717 had a diagnosis of head and neck cancer. Agent Orange exposure significantly predicted upper aerodigestive tract carcinoma, with a relative risk (RR) of 1.10. On subsite analysis, Agent Orange exposure (as well as race, gender, and substance use) was significantly associated with oropharyngeal (RR 1.16), nasopharyngeal (RR 1.22), laryngeal (1.11), and thyroid (1.24) cancers. Agent Orange exposure was associated with improved 10-year overall survival in upper aerodigestive tract cancer patients.

CONCLUSIONS AND RELEVANCE

Self-reported Agent Orange exposure correlated with increased risks of oropharyngeal, nasopharyngeal, laryngeal, and thyroid cancers, and predicted improved survival in upper aerodigestive tract cancer patients. These findings broaden our understanding of the risks of Agent Orange exposure.

EUCOLEUS BOEHMI INFECTION IN THE NASAL CONCHAE AND PARANASAL SINUSES OF RED FOX (VULPES VULPES) ON PRINCE EDWARD ISLAND, CANADA

Eucoleus boehmi (Nematoda: Capillariidae) occurs in the nasal conchae and paranasal sinuses of wild and domestic canids. We surveyed the red fox ( Vulpes vulpes ) on Prince Edward Island, Canada, for E. boehmi infection and characterized the associated histopathology. Nasal capillarid infections were detected based on histologic examination of three coronal sections of the nasal cavity and by centrifugal flotation examination (CFE) of rectal feces. Capillarids were detected in histologic sections in 28 of 36 (78%) foxes; detection occurred most frequently in the caudal section (28 foxes) and least in the rostral section (10 foxes). Adult worm morphology was typical for capillarids (stichosome esophagus, bacillary bands, bipolar plugged eggs); E. boehmi eggs were specifically identified based on the characteristic pitted shell wall surface. Adult worms were detected in histologic sections in all 28 and E. boehmi eggs in 21 of the positive foxes. No eggs of Eucoleus aerophilus were observed in any of the sections. Affected foxes had an eosinophilic and lymphoplasmacytic rhinitis with goblet cell hyperplasia. Eggs of E. aerophilus were detected on CFE in 20 of 36 (56%) foxes; 19 of the histologically positive foxes were coinfected with E. aerophilus. Eggs of E. boehmi were detected on CFE in 26 of 36 (72%) foxes and were consistent in size and morphology with those described from wild canids, but they differed from those reported from cases of infection in dogs. Prevalence based on identification of eggs on histologic section or CFE indicated 27 of 36 (75%) red foxes examined were infected with E. boehmi.

Histopathologic alterations associated with global gene expression due to chronic dietary TCDD exposure in juvenile zebrafish

The goal of this project was to investigate the effects and possible developmental disease implication of chronic dietary TCDD exposure on global gene expression anchored to histopathologic analysis in juvenile zebrafish by functional genomic, histopathologic and analytic chemistry methods. Specifically, juvenile zebrafish were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100 ppb, and fish were sampled following 0, 7, 14, 28 and 42 d after initiation of the exposure. TCDD accumulated in a dose- and time-dependent manner and 100 ppb TCDD caused TCDD accumulation in female (15.49 ppb) and male (18.04 ppb) fish at 28 d post exposure. Dietary TCDD caused multiple lesions in liver, kidney, intestine and ovary of zebrafish and functional dysregulation such as depletion of glycogen in liver, retrobulbar edema, degeneration of nasal neurosensory epithelium, underdevelopment of intestine, and diminution in the fraction of ovarian follicles containing vitellogenic oocytes. Importantly, lesions in nasal epithelium and evidence of endocrine disruption based on alternatively spliced vasa transcripts are two novel and significant results of this study. Microarray gene expression analysis comparing vehicle control to dietary TCDD revealed dysregulated genes involved in pathways associated with cardiac necrosis/cell death, cardiac fibrosis, renal necrosis/cell death and liver necrosis/cell death. These baseline toxicological effects provide evidence for the potential mechanisms of developmental dysfunctions induced by TCDD and vasa as a biomarker for ovarian developmental disruption.

Gene expression and pathologic alterations in juvenile rainbow trout due to chronic dietary TCDD exposure

The goal of this project was to use functional genomic methods to identify molecular biomarkers as indicators of the impact of TCDD exposure in rainbow trout. Specifically, we investigated the effects of chronic dietary TCDD exposure on whole juvenile rainbow trout global gene expression associated with histopathological analysis. Juvenile rainbow trout were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100 ppb (ngTCDD/g food), and fish were sampled from each group at 7, 14, 28 and 42 days after initiation of feeding. 100 ppb TCDD caused 100% mortality at 39 days. Fish fed with 100 ppb TCDD food had TCDD accumulation of 47.37 ppb (ngTCDD/g fish) in whole fish at 28 days. Histological analysis from TCDD-treated trout sampled from 28 and 42 days revealed that obvious lesions were found in skin, oropharynx, liver, gas bladder, intestine, pancreas, nose and kidney. In addition, TCDD caused anemia in peripheral blood, decreases in abdominal fat, increases of remodeling of fin rays, edema in pericardium and retrobulbar hemorrhage in the 100 ppb TCDD-treated rainbow trout compared to the control group at 28 days. Dose- and time-dependent global gene expression analyses were performed using the cGRASP 16,000 (16K) cDNA microarray. TCDD-responsive whole body transcripts identified in the microarray experiments have putative functions involved in various biological processes including growth, cell proliferation, metabolic process, and immune system processes. Nine microarray-identified genes were selected for QPCR validation. CYP1A3 and CYP1A1 were common up-regulated genes and HBB1 was a common down-regulated gene among each group based on microarray data, and their QPCR validations are consistent with microarray data for the 10 and 100 ppb TCDD treatment groups after 28 days exposure (p<0.05). In addition, in the 100 ppb group at 28 days, expression of complement component C3-1 and trypsin-1 precursor have a more than 10-fold induction from the microarray experiments, and their QPCR validations are consistent and showed significant induction in the 100 ppb group at 28 days (p<0.05). Overall, lesion in nasal epithelium is a novel and significant result in this study, and TCDD-responsive rainbow trout transcripts identified in the present study may lead to the development of new molecular biomarkers for assessing the potential impacts of environmental TCDD on rainbow trout populations.

Reproductive Lesions in Female Harlan Sprague-Dawley Rats Following Two-Year Oral Treatment with Dioxin and Dioxin-like Compounds

Results from previously published animal studies suggest that prenatal and postnatal exposure to dioxin and dioxin-like compounds (DLCs) may profoundly affect the reproductive system of both sexes via endocrine disruption. In the present work, we evaluate the toxicity and carcinogenicity of various DLCs, with an emphasis on their effect on the reproductive organs, induced by chronic exposure of female adult Harlan Sprague-Dawley rats. This investigation represents part of an initiative of the National Toxicology Program to determine the relative potency of chronic toxicity and carcinogenicity of polychlorinated dioxins, furans, and biphenyls. For fourteen, thirty-one, or fifty-three weeks or for two years, animals were administered by gavage 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD); 3,3′,4,4′,5-pentachlorobiphenyl (PCB126); 2,3,4,7,8-pentachlorodibenzofuran (PeCDF); 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB153); 2,3′,4,4′,5-pentachlorobiphenyl (PCB118); a tertiary mixture of TCDD, PCB126, and PeCDF; a binary mixture of PCB126 and 153; or a binary mixture of PCB126 and PCB118.

The ranges of treatment-related changes in the reproductive system included chronic active inflammation in the ovary that occurred in the 1,000 and 3,000 μg/kg core groups (two-year exposure) of PCB153 and in the 300 ng/3,000 μg/kg core group of binary mixture of PCB126 and PCB153. Increases in the incidence of acute and/or chronic active inflammation of the uterus were observed in all dosed groups, including the stop-exposure group (withdrawal after thirty-week exposure) of PeCDF and the 1,000 μg/kg and/or higher group dosed with PCB153. The incidence of cystic endometrial hyperplasia was marginally increased in the 92 PeCDF ng/kg group at two years. The incidence of squamous metaplasia was significantly increased in the 44 ng/kg and higher dose group, including the stop-exposure group. The incidence of uterine squamous cell carcinoma was significantly or marginally increased in the 6 ng/kg core and 100 ng/kg stop-exposure groups of TCDD and in the 300 ng/300 μg/kg core group that received the binary mixture of PCB126 and 153. The incidence of uterine carcinoma was marginally increased in the 92 ng/kg PeCDF group at two years and clearly increased in the 1,000 and 4,600 μg/kg PCB118 core group and the 4,600 μg/kg stop group. In the studies of PCB 126, the tertiary mixture, and the binary mixture of PCB126 and PCB118, no increased incidence of any change occurred in the reproductive systems. The range of changes seen with the different compounds suggests that more than one mechanism may have been involved in promoting the female reproductive pathology.

Inflammatory and chloracne-like skin lesions in B6C3F1 mice exposed to 3,3',4,4'-tetrachloroazobenzene for 2 years

Exposure to dioxin and dioxin-like compounds (DLCs) has been connected to the induction of chloracne in humans and animals. 3,3',4,4'-Tetrachloroazobenzene (TCAB) is an environmental contaminant that induces chloracne in humans. TCAB has been studied only to a limited extent in laboratory animals. While performing a 2-year gavage study in B6C3F1 mice to evaluate the toxic and carcinogenic effects of TCAB, we also explored potential chloracnegenic properties. Groups of 50 male and 50 female B6C3F1 mice were exposed by gavage to TCAB at dose levels of 0, 3, 10 and 30 mg/kg for 5 days a week for 2 years. The animals developed treatment-related gross inflammatory skin lesions, which were characterized histologically by inflammation, fibrosis, hyperplasia, and ulcers. Additionally, many of the animals developed follicular dilatation and sebaceous gland atrophy, consistent with chloracne-like lesions. This current 2-year study supports recently published papers showing susceptibility to chloracne in mouse strains other than hairless mice. The chloracne-like lesions were not clinically evident; therefore, our study highlights the need for careful examination of the skin in order to identify subtle lesions consistent with chloracne-like changes in rodents exposed to dioxin and DLCs. Since previous short-term studies did not demonstrate any skin lesions, we suggest that reliable assessment of all safety issues involving dioxin and DLCs requires evaluation following chronic exposure. Such studies in animal models will help to elucidate the mechanisms of dioxin-related health hazards.

Intranasal immunization with Naegleria fowleri lysates and Cry1Ac induces metaplasia in the olfactory epithelium and increases IgA secretion

According to previous reports, intranasal administration of the Cry1Ac protein alone or with amoebic lysates increases protection against Naegleria fowleri meningoencephalitis in mice, apparently by eliciting IgA responses in the nasal mucosa. In the current study, we performed an immunohistochemical analysis of IgA in the nasal mucosa of mice immunized intranasally with Cry1Ac, and amoebic lysates or a combination of both. The animals were sacrificed 24 h after the last immunization or after an intranasal lethal challenge with N. fowleri. Our results indicate that all of the intranasal immunizations provoked an increase in areas with metaplasia in the olfactory epithelium, allowing for secretion of IgA. As a result, IgA antibodies were found interacting with trophozoites in the nasal lumen, and there was a marked increase of IgA in the metaplasic epithelium. On the other hand in nonimmunized mice trophozoites were observed invading the nasal mucosa, which was not the case for immunized mice. Our results suggest that intranasal immunization provokes cellular changes in the olfactory epithelium, leading to greater protection against N. fowleri that is probably caused by an increased secretion of IgA. The increased IgA response induced in the nasal mucosa by immunization probably impedes both amoebic adhesion and subsequent invasion of the parasite to the nasal epithelium.

A critical comparison of murine pathology and epidemiological data of TCDD, PCB126, and PeCDF

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, or dioxin) and dioxin-like compounds (DLCs) induce numerous toxicities, including developmental, endocrine, immunological, and multi-organ carcinogenic, in animals and/or humans. Multiple studies completed by the National Toxicology Program (NTP) focused on the effects caused in Harlan Sprague-Dawley rats by specific DLCs, among them the prototypical dioxin, TCDD. Because humans are exposed daily to a combination of DLCs, primarily via ingestion of food, the Toxic Equivalency Factor (TEF) was developed in order to evaluate health hazards caused by these mixtures. Herein we review the pathological effects reported in humans exposed to TCDD; 3,3',4,4',5-pentachlorobiphenyl (PCB 126); and 2,3,4,7,8,-pentachlorodibenzofuran (PeCDF) and compare them to similar changes seen in NTP murine studies performed with the same compounds. While there were differences in specific pathologies observed, clear consistency in the target organs affected (liver, oral cavity, cardiovascular system, immune system, thyroid, pancreas, and lung) could be seen in both human studies and rodent toxicity and carcinogenicity investigations.

Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds

Dioxin and dioxin-related compounds have been associated with high incidences of pulmonary dysfunctions and/or cancers in humans. To evaluate the relative potencies of effects of these compounds, the National Toxicology Program completed a series of two-year bioassays which were conducted using female Harlan Sprague-Dawley rats. The rats were treated orally for up to 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3,3',4,4',5-pentachlorobiphenyl (PCB126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and a ternary mixture of TCDD, PCB126 and PeCDF. In addition to treatment-related effects reported in other organs, a variety of pulmonary lesions were observed that were related to exposure. Pulmonary CYP1A1-associated 7-ethoxyresorufin-O-deethylase (EROD) activity was increased in all dosed groups. The most common non-neoplastic lesions, which occurred in all studies, were bronchiolar metaplasia and squamous metaplasia of the alveolar epithelium. Cystic keratinizing epithelioma was the most commonly observed neoplasm which occurred in all studies. A low incidence of squamous cell carcinoma was associated only with PCB126 treatment. Potential mechanisms leading to altered differentiation and/or proliferation of bronchiolar and alveolar epithelia may be through CYP1A1 induction or disruption of retinoid metabolism.

Respiratory tract lesions in noninhalation studies

This paper reviews respiratory tract lesions observed in rodents administered various chemicals by noninhalation routes. Chemicals administered by inhalation caused lesions in the respiratory tract and were well described; however, when chemicals were administered by noninhalation routes the effort to evaluate tissues for lesions may have been less or not considered, especially in the upper respiratory tract, and some lesions may have gone undetected. Lesions described in this review mostly occurred in rodent chronic noninhalation studies conducted by the National Toxicology Program; however, some were noted in studies of shorter duration. The nasal cavity was vulnerable to damage when chemicals were administered by noninhalation routes. Changes included respiratory epithelial hyperplasia, degeneration and necrosis of olfactory epithelium, olfactory epithelial metaplasia, adenoma, adenocarcinoma, squamous cell carcinoma, and neuroblastoma. In the lung, compound-related lesions included alveolar histiocytosis, alveolar epithelial hyperplasia, bronchiolar metaplasia of the alveolar epithelium, squamous metaplasia, alveolar/bronchial adenoma and carcinoma, and squamous tumors. Pathogenesis of these lesions included regurgitation of volatiles, metabolites arriving from the blood stream, and additional metabolism by olfactory epithelium or Clara cells. The presence of respiratory tract lesions in noninhalation studies emphasizes the need for a thorough examination of the respiratory tract including nasal passages, regardless of the route of administration.

Nasal cytotoxic and carcinogenic activities of systemically distributed organic chemicals

Toxicity and carcinogenicity in the mucosa of the nasal passages in rodents has been produced by a variety of organic chemicals which are systemically distributed. In this review, 14 such chemicals or classes were identified that produced rodent nasal cytotoxicity, but not carcinogenicity, and 11 were identified that produced nasal carcinogenicity. Most chemicals that affect the nasal mucosa were either concentrated in that tissue or readily activated there, or both. All chemicals with effects in the nasal mucosa that were DNA-reactive, were also carcinogenic, if adequately tested. None of the rodent nasal cytotoxins has been identified as a human systemic nasal toxin. This may reflect the lesser biotransformation activity of human nasal mucosa compared to rodent and the much lower levels of human exposures. None of the rodent carcinogens lacking DNA reactivity has been identified as a nasal carcinogen or other cancer hazard to humans. Some DNA-reactive rodent carcinogens that affect the nasal mucosa, as well as other tissues, have been associated with cancer at various sites in humans, but not the nasal cavity. Thus, findings in only the rodent nasal mucosa do not necessarily predict either a toxic or carcinogenic hazard to that tissue in humans.

Histological changes in rat nasal epithelia after unilateral neonatal naris occlusion

The authors studied the extent of the different epithelia lining the nasal fossae of the albino rat after neonatal closure of one naris. Newborn pups were anesthetized by hypothermia and the external opening of their right naris cauterized, while littermates served as controls. Animals were sacrificed at 3 months, and the occluded (OCF) and nonoccluded (NOF) fossae of experimental animals as well as both fossae of control animals (CTF) were histologically studied. In both control and experimental animals, nasal fossae were lined by five different types of epithelia: squamous stratified, transitional, metaplastic, respiratory, and olfactory epithelia. It was found that closure of one naris provokes reorganization of the epithelial lining in both the occluded and nonoccluded side. In CTF airflow, physical conditions as well as pollutants and biological agents irritate the epithelial lining, causing squamous metaplasia as well as metaplastic epithelium showing inflammation in rostral levels. In CTF caudal levels, the metaplastic epithelium appears to a lesser degree and the respiratory epithelium prevails, except for the most caudal level where the olfactory epithelium is prevalent. In OCF, the protected environment created prevents the occurrence of metaplastic epithelium, the transitional, respiratory, and olfactory epithelia developing in the corresponding area instead. In NOF, where the airflow is double, the same pattern occurs as in CTF, although metaplastic epithelium values are approximately double, suggesting a clear linear effect. An outstanding feature observed was the increased extent of the olfactory epithelium in OCF regarding NOF, although changes in its morphological structure were not found. Airflow properties, including pressure, coldness, velocity, and turbulence, as well as biological and chemical hazards present in inflow, cause histological reorganization of the nasal epithelium lining during postnatal development. Results prove the need to consider airflow changes in nasal fossae surgery and point to the protective value of naris closure in ENT clinics, supporting it as a treatment of atrophic rhinitis.