Gastric development of pancreatic acinar cell metaplasia after Vonoprazan therapy in rats

BACKGROUND

Vonoprazan is a new acid-suppressing drug that received FDA approval in 2022. It reversibly inhibits gastric acid secretion by competing with the potassium ions on the luminal surface of the parietal cells (potassium-competitive acid blockers or P-CABs). Vonoprazan has been on the market for a short time and there are many clinical trials to support its clinical application. However, medical experience and comprehensive clinical data is still limited, especially on how and if, gastric histology is altered due to therapy.

METHODS

A 12-week experiment trial with 30 Wistar rats was to assess the presence of gastrointestinal morphologic abnormalities upon administration of omeprazole and vonoprazan. At six weeks of age, rats were randomly assigned to one of 5 groups: (1) saline as negative control group, (2) oral omeprazole (40 mg/kg), as positive control group, (3) oral omeprazole (40 mg/kg) for 4 weeks, proceeded by 8 weeks off omeprazole, (4) oral vonoprazan (4 mg/kg), as positive control group, and (5) oral vonoprazan (4 mg/kg) for 4 weeks, proceeded by 8 weeks off vonoprazan.

RESULTS

We identified non-inflammatory alterations characterized by parietal (oxyntic) cell loss and chief (zymogen) cell hyperplasia and replacement by pancreatic acinar cell metaplasia (PACM). No significant abnormalities were identified in any other tissues in the hepatobiliary and gastrointestinal tracts.

CONCLUSION

PACM has been reported in gastric mucosa, at the esophagogastric junction, at the distal esophagus, and in Barrett esophagus. However, the pathogenesis of this entity is still unclear. Whereas some authors have suggested that PACM is an acquired process others have raised the possibility of PACM being congenital in nature. Our results suggest that the duration of vonoprazan administration at a dose of 4 mg/kg plays an important role in the development of PACM.

Neutrophil Infiltration and Acinar-ductal Metaplasia Are the Main Pathological Findings in Pembrolizumab-induced Pancreatitis

The histopathological findings of immune checkpoint inhibitor (ICI)-induced pancreatitis have rarely been reported. A 56-year-old man with squamous cell carcinoma of the lung with bone metastasis was being treated with pembrolizumab, an anti-programmed cell death protein-1 antibody. After 13 doses, he was referred to our department due to pancreatitis. Despite characteristic symptoms of acute pancreatitis, imaging findings were similar to those of autoimmune pancreatitis. However, a histological examination showed neutrophil-based inflammatory cell infiltration and acinar-ductal metaplasia. Immunostaining showed CD8-positive T lymphocyte infiltration. This case revealed the characteristic histopathology of pembrolizumab-induced pancreatitis, which was previously poorly understood.

Prostatic metaplasia of the vagina in transmasculine individuals

PURPOSE

To determine the prevalence of prostatic metaplasia in an expanded cohort of transmasculine individuals undergoing gender-affirming resection of vaginal tissue.

METHODS

Institutional Review Board approval was obtained. Clinical records were reviewed for all transmasculine individuals undergoing vaginal tissue resection at our institution between January 2018 and July 2021. Corresponding pathology specimens were examined grossly and microscopically, including immunohistochemical stains for NKX3.1, prostate-specific antigen (PSA), and androgen receptor (AR). Vaginal specimens from three patients without androgen supplementation were used as controls.

RESULTS

Twenty-one patients met inclusion criteria. The median age at surgery was 26.4 years (range 20.6-34.5 years). All patients had been assigned female gender at birth and lacked endocrine or genetic abnormalities. All were on testosterone therapy; median duration of therapy at surgery was 4.4 years (range 1.4-12.1 years). In the transmasculine group, no gross lesions were identified. Microscopically, all specimens demonstrated patchy intraepithelial glandular proliferation along the basement membrane and/or nodular proliferation of prostate-type tissue within the subepithelial stroma. On immunohistochemical staining, performed for a subset of cases, the glandular proliferation was positive for NKX3.1 (16/16 cases; 100%), PSA (12/14 cases; 85.7%), and AR (8/8 cases; 100%). Controls showed no evidence of prostatic metaplasia.

CONCLUSION

One hundred percent of vaginal specimens obtained from transmasculine individuals on testosterone therapy (21/21 cases) demonstrated prostatic metaplasia. Further investigation is warranted to characterize the natural history and clinical significance of these changes. Patients seeking hormone therapy and/or gender-affirming surgery should be counseled on the findings and their yet-undetermined significance.

Dose-dependent association of proton pump inhibitors use with gastric intestinal metaplasia among Helicobacter pylori-positive patients

BACKGROUND

Gastric intestinal metaplasia is a pre-cancerous condition associated with multiple factors.

OBJECTIVE

We evaluated whether cumulative proton pump inhibitor dose is associated with the diagnosis of gastric intestinal metaplasia while controlling for multiple variables.

METHODS

We retrospectively identified patients who underwent upper endoscopy with gastric biopsy between 2005 and 2014. Covariate data retrieved included age, sex, ethnicity, smoking status, Helicobacter pylori status (based on clarithromycin-amoxicillin-proton pump inhibitor issued), cumulative proton pump inhibitor issued within 10 years (quartiles [PPI-Q1-4 ] of daily drug dose), anti-parietal cell antibodies, body mass index and comorbidity index.

RESULTS

Of the 14,147 included patients (median age 63.4 years; women 54.4%; Helicobacter pylori-positive 29.0%), 1244 (8.8%) had gastric intestinal metaplasia. Increasing age, Helicobacter pylori infection, smoking, anti-parietal cell antibodies and proton pump inhibitor use were all associated with the diagnosis of gastric intestinal metaplasia. Upper quartiles of cumulative proton pump inhibitor doses (PPI-Q4 and PPI-Q3 vs. PPI-Q1 ) were associated with the diagnosis of gastric intestinal metaplasia: adjusted odds ratios 1.32 (95% confidence interval [CI] 1.111.57) and 1.27 (95% CI 1.07-1.52), respectively, for the whole cohort (Ptotal 0.007, Ptrend 0.013), 1.69 (95% CI 1.23-2.33) and 1.40 (95% CI 1.04-1.89), respectively, for Helicobacter pylori-positive patients (Ptotal 0.004, Ptrend 0.005) and 1.21 (95% CI 0.98-1.49) and 1.20 (95% CI 0.96-1.49), respectively, for Helicobacter pylori-negative patients (Ptotal 0.288, Ptrend 0.018). Upper quartiles of proton pump inhibitor dose were associated with a 5-10-fold increased risk of low-grade dysplasia.

CONCLUSIONS

Among Helicobacter pylori-positive patients, proton pump inhibitor use appears to be associated with a dose-dependent increased likelihood of gastric intestinal metaplasia.

Group 2 Innate Lymphoid Cells Coordinate Damage Response in the Stomach

BACKGROUND & AIMS

Severe injury to the lining of the stomach leads to changes in the epithelium (reprogramming) that protect and promote repair of the tissue, including development of spasmolytic polypeptide-expressing metaplasia (SPEM) and tuft and foveolar cell hyperplasia. Acute gastric damage elicits a type-2 inflammatory response that includes production of type-2 cytokines and infiltration by eosinophils and alternatively activated macrophages. Stomachs of mice that lack interleukin 33 (IL33) or interleukin 13 (IL13) did not undergo epithelial reprogramming after drug-induced injury. We investigated the role of group 2 innate lymphoid cells (ILC2s) in gastric epithelial repair.

METHODS

Acute gastric injury was induced in C57BL/6J mice (wild-type and RAG1 knockout) by administration of L635. We isolated ILC2s by flow cytometry from stomachs of mice that were and were not given L635 and performed single-cell RNA sequencing. ILC2s were depleted from wild-type and RAG1-knockout mice by administration of anti-CD90.2. We assessed gastric cell lineages, markers of metaplasia, inflammation, and proliferation. Gastric tissue microarrays from patients with gastric adenocarcinoma were analyzed by immunostaining.

RESULTS

There was a significant increase in the number of GATA3-positive ILC2s in stomach tissues from wild-type mice after L635-induced damage, but not in stomach tissues from IL33-knockout mice. We characterized a marker signature of gastric mucosal ILC2s and identified a transcription profile of metaplasia-associated ILC2s, which included changes in expression of Il5, Il13, Csf2, Pd1, and Ramp3; these changes were validated by quantitative polymerase chain reaction and immunocytochemistry. Depletion of ILC2s from mice blocked development of metaplasia after L635-induced injury in wild-type and RAG1-knockout mice and prevented foveolar and tuft cell hyperplasia and infiltration or activation of macrophages after injury. Numbers of ILC2s were increased in stomach tissues from patients with SPEM compared with patients with normal corpus mucosa.

CONCLUSIONS

In analyses of stomach tissues from mice with gastric tissue damage and patients with SPEM, we found evidence of type 2 inflammation and increased numbers of ILC2s. Our results suggest that ILC2s coordinate the metaplastic response to severe gastric injury.

Decrease in MiR-148a Expression During Initiation of Chief Cell Transdifferentiation

Gastric chief cells differentiate from mucous neck cells and develop their mature state at the base of oxyntic glands with expression of secretory zymogen granules. After parietal cell loss, chief cells transdifferentiate into mucous cell metaplasia, designated spasmolytic polypeptide-expressing metaplasia (SPEM), which is considered a candidate precursor of gastric cancer. We examined the range of microRNA (miRNA) expression in chief cells and identified miRNAs involved in chief cell transdifferentiation into SPEM. Among them, miR-148a was strongly and specifically expressed in chief cells and significantly decreased during the process of chief cell transdifferentiation. Interestingly, suppression of miR-148a in a conditionally immortalized chief cell line induced up-regulation of CD44 variant 9 (CD44v9), one of the transcripts expressed at an early stage of SPEM development, and DNA methyltransferase 1 (Dnmt1), an established target of miR-148a. Immunostaining analyses showed that Dnmt1 was up-regulated in SPEM cells as well as in chief cells before the emergence of SPEM in mouse models of acute oxyntic atrophy using either DMP-777 or L635. In the cascade of events that leads to transdifferentiation, miR-148a was down-regulated after acute oxyntic atrophy either in xCT knockout mice or after sulfasalazine inhibition of xCT. These findings suggest that the alteration of miR-148a expression is an early event in the process of chief cell transdifferentiation into SPEM.

Eccrine squamous syringometaplasia in an allogenic stem cell transplant patient undergoing chemotherapy

Eccrine squamous syringometaplasia (ESS) is a rare finding defined as metaplastic change of the cuboidal epithelial cells of eccrine glands into two or more layers of squamous epithelial cells. We present a patient who developed ESS after induction of CLAG chemotherapy [2-Chlorodeoxyadenosine (2-CdA) with cytarabine (Ara-C) and (granulocyte-colony stimulating factor) G-CSF] for management of the blast crisis of his chronic myelogenous leukemia (CML). Our patient's ESS eruption presented with a variety of morphologies, thus multiple skin biopsies were taken to determine the possible diagnosis(es). All skin biopsies showed ESS and the eruption resolved with topical corticosteroids after CLAG therapy was finished.

Metaplastic phenotype in human primary bronchiolar epithelial cells after repeated exposure to native mainstream smoke at the air-liquid interface

3D constructs composed of primary normal differentiated human bronchiolar epithelial (NHBE) cells as mono- or co-culture in combination with normal human lung fibroblasts were exposed repeatedly at the air-liquid interface with non-lethal concentrations of mainstream cigarette smoke (4 cigarettes a day, 5days/week, 13 times repetition in total) to build up a permanent burden on the cells. Samples were taken after 4, 8 and 13 times of repeated smoke exposure and the cultures were analyzed by histopathological methods In comparison with the clean air exposure (process control) and incubator control cells the cigarette smoke exposed cultures showed a reduction of cilia bearing as well as mucus producing cells. In both mono- as well as co-cultures, hyperplasia was induced showing different histological cell types (undifferentiated secretory and squamous cell types). At the end of the exposure phase, we observed the development of non-hyperplastic areas strongly positive to CK13 antibody, commonly seen in squamous cells as a marker for non-cornified squamous epithelium, thus suggesting a transition of the normal bronchial epithelial cells towards metaplastic cells. The control cultures (clean air exposed and incubator cells) showed no comparable phenotypic changes. In conclusion, our in vitro model presents a valuable tool to study the induction of metaplastic alterations after exposure to airborne material.

Characterization of Bronchiolar Metaplasia of the Alveolar Epithelium in Female Sprague—Dawley Rats Exposed to 3,3',4,4',5-Pentachlorobiphenyl (PCB126)

To test the dioxin toxic equivalency factor methodology, the National Toxicology Program conducted a series of 2-year rat bioassays of dioxin-like compounds. Following gavage exposure of female Harlan Sprague—Dawley rats to 2,3',4,4',5-pentachlorobiphenyl (PCB126), pulmonary alveolar epithelium at the junction of terminal bronchioles and along alveolar ducts was replaced by cuboidal to columnar ciliated cells. Scattered among these were cells exhibiting characteristics consistent with those of Clara cells; they lacked cilia and had a smooth apical surface that protruded into the alveolar space. This lesion was not typical of alveolar epithelial hyperplasia seen in rodent lungs; therefore, studies were done to characterize the lesion. Results of periodic acid-Schiff (PAS) staining, alcian blue (AB) staining, and GSTPi immunohistochemical staining of the lesions seen in treated rats were more similar to normal bronchiolar epithelium than normal alveolar epithelium or alveolar epithelial hyperplasia. These findings, along with the morphology of the cells, provide evidence that this lesion is closer in character to bronchiolar epithelium than alveolar type I or alveolar type II epithelium, and as a result, was called bronchiolar metaplasia.

Effect of Saraca asoca (Asoka) on estradiol-induced keratinizing metaplasia in rat uterus

BACKGROUND

Estrogen-mediated uterus endometrium instability is considered as one of the etiological factors in dysfunctional uterine bleeding (DUB) and uterine cancer. Saraca asoca (Family: Fabaceae) and its fermented preparation, Asokarishta, are extensively used as uterine tonic to treat gynecological disorders in Ayurveda. The present study evaluated the effect of S. asoca (Asoka) on estrogen-induced endometrial thickening of rat uterus.

METHODS

Endometrial thickening was induced by intraperitoneal injection of estradiol (20 μg/kg b.wt) to 8-day-old immature rats for alternate 5 days. Methanolic extract (200 mg/kg b. wt) from S. asoca bark was given orally along with estradiol. Uterus endometrial thickening was analyzed histopathologically and serum estrogen level by radioimmunoassay (RIA). Cyclooxygenase (COX-2) expression in rat uterus was also estimated by Western blot. Anti-inflammatory activity of the extract was analyzed by formalin- and carrageenan-elicited paw edema models in mouse.

RESULTS

Uterus endometrium proliferation and keratinized metaplasia with seven to eight stratified epithelial layers on day 16 was observed in rats administered with estradiol. Treatment with S. asoca reduced the thickening to two to four layers and the serum estrogen level diminished significantly to 82.9±12.87 pg/mL compared to rats administered with estrogen alone (111.2±10.68 pg/mL). A reduction of formalin- and carrageenan-induced paw edema in mouse by S. asoca extract was observed. Lower level of lipopolysaccharides (LPS)-induced COX-2 enzyme in rat uterus by the extract further confirms its anti-inflammatory activity.

CONCLUSIONS

Present study reveals the antiproliferative and antikeratinizing effects of S. asoca in uterus endometrium possibly through its anti-estrogenic and anti-inflammatory properties.

Long-term proton pump inhibitor (PPI) use and the development of gastric pre-malignant lesions

BACKGROUND

Proton pump inhibitors (PPIs) are the most effective drugs to reduce gastric acid secretion. PPIs are one of the most commonly prescribed classes of medications worldwide. Apart from short-term application, maintenance therapy with PPIs is recommended and increasingly used in certain diseases, such as Zollinger-Ellison syndrome and gastro-oesophageal reflux disease, especially for people with erosive oesophagitis or Barrett's oesophagus. Although PPIs are generally safe, their efficacy and safety of long-term use remains unclear. The question of whether the long-term use of PPIs could promote the development of gastric pre-malignant lesions has been widely investigated, but results are inconsistent. Limited insight on this problem leads to a dilemma in decision making for long-term PPI prescription.

OBJECTIVES

To compare the development or progression of gastric pre-malignant lesions, such as atrophic gastritis, intestinal metaplasia, enterochromaffin-like (ECL) cell hyperplasia, and dysplasia, in people taking long-term (six months or greater) PPI maintenance therapy.

SEARCH METHODS

We searched the following databases (from inception to 6 August 2013): the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and CINAHL. In addition, we searched the reference lists of included trials and contacted experts in the field.

SELECTION CRITERIA

We searched for randomised controlled trials (RCTs) in adults (aged 18 years or greater) concerning the effects of long-term (six months or greater) PPI use on gastric mucosa changes, confirmed by endoscopy or biopsy sampling (or both).

DATA COLLECTION AND ANALYSIS

Two review authors independently performed selection of eligible trials, assessment of trial quality, and data extraction. We calculated odds ratios (OR) for analysis of dichotomous data and mean differences for continuous data, with 95% confidence intervals (CI).

MAIN RESULTS

We included seven trials (1789 participants). Four studies had high risk of bias and the risk of bias in the other three trials was unclear. In addition, it was difficult to assess possible reporting bias. We pooled 1070 participants from four RCTs to evaluate corporal atrophy development revealing an insignificantly increased OR of 1.50 (95% CI 0.59 to 3.80; P value = 0.39; low-quality evidence) for long-term PPI users relative to non-PPI users. In five eligible trials, corporal intestinal metaplasia was assessed among 1408 participants, also with uncertain results (OR 1.46; 95% CI 0.43 to 5.03; P value = 0.55; low-quality evidence). However, by pooling data of 1705 participants from six RCTs, our meta-analysis showed that participants with PPI maintenance treatment were more likely to experience either diffuse (simple) (OR 5.01; 95% CI 1.54 to 16.26; P value = 0.007; very-low-quality evidence) or linear/micronodular (focal) ECL hyperplasia (OR 3.98; 95% CI 1.31 to 12.16; P value = 0.02; low-quality evidence) than controls. No participant showed any dysplastic or neoplastic change in any included studies.

AUTHORS' CONCLUSIONS

There is presently no clear evidence that the long-term use of PPIs can cause or accelerate the progression of corpus gastric atrophy or intestinal metaplasia, although results were imprecise. People with PPI maintenance treatment may have a higher possibility of experiencing either diffuse (simple) or linear/micronodular (focal) ECL cell hyperplasia. However, the clinical importance of this outcome is currently uncertain.

A Case of Bleomycin-Induced Acral Erythema (AE) with Eccrine Squamous Syringometaplasia (ESS) and Summary of Reports of AE with ESS in the Literature

Chemotherapy-induced acral erythema (AE) is primarily induced by hydroxyurea, methotrexate, and cytarabine, although there are rare reports of AE induced by combination chemotherapy containing bleomycin. It is thought that the accumulation of chemotherapeutic drugs in eccrine glands may cause eccrine squamous syringometaplasia (ESS), which is characterized by metaplasia and focal necrosis of the epithelium of the eccrine duct. ESS is occasionally detected in conjunction with AE, but such occurrences are relatively uncommon. This is the first report of AE with ESS induced by the administration of bleomycin alone. We also provide a summary of past cases of AE with ESS in the literature.

[Influence of cancer chemotherapy on conjunctival epithelium and goblet cells]

PURPOSE

Evaluation of different types of chemotherapy schemes administered in lung, breast and bowel cancer on conjunctival epithelium and goblet cells morphology.

MATERIAL AND METHODS

36 patients (72 eyes) were enrolled to the study. Patients were divided into three groups depending on type of cancer and chemotherapy: group I - patients diagnosed with non- small cells lung cancer treated with PE schema (cisplatin, etoposide), group II - with breast cancer treated with FAC schema (fluorouracil, doxorubicin, cyclophosphamide), group Ill - bowel cancer treated with FU/LV schema (fluorouracil, leucovorin). Examinations were performed before chemotherapy and after Il'th, IV'th, VI'th chemotherapy cycle. Conjuntival specimen were obtained with exfoliative cytology, stained with PAS and hematoxyline.

RESULTS

Statistically significant deterioration of conjunctival epithelium and goblet cells in all the groups in each time of examination (p<0.001) was observed. Alterations were aggravated with duration of chemotherapy. Before chemotherapy all the patients had normal epithelium and goblet cells (grade 0 or 1 according to the Nelson's scale). Conjunctival cells status gradually deteriorated and altered from the normal glandular epithelium to the squamous cells epithelium through the process of squamous metaplasia. In further chemotherapy cycles each patient (1,0 fraction) had abnormal morphology of epithelium and goblet cells (grade 2 or 3 of Nelson's scale).

CONCLUSIONS

Chemotherapy induces squamous metaplasia of epithelium and the reduction of number of conjunctival goblet cells. This abnormalities were time dependent and increased with duration of chemotherapy and were not depended on type of chemotherapy scheme.

Protein kinase C iota regulates pancreatic acinar-to-ductal metaplasia

Pancreatic acinar-to-ductal metaplasia (ADM) is associated with an increased risk of pancreatic cancer and is considered a precursor of pancreatic ductal adenocarcinoma. Transgenic expression of transforming growth factor alpha (TGF-α) or K-ras^G12D in mouse pancreatic epithelium induces ADM in vivo. Protein kinase C iota (PKCι) is highly expressed in human pancreatic cancer and is required for the transformed growth and tumorigenesis of pancreatic cancer cells. In this study, PKCι expression was assessed in a mouse model of K-ras^G12D-induced pancreatic ADM and pancreatic cancer. The ability of K-ras^G12D to induce pancreatic ADM in explant culture, and the requirement for PKCι, was investigated. PKCι is elevated in human and mouse pancreatic ADM and intraepithelial neoplastic lesions in vivo. We demonstrate that K-ras^G12D is sufficient to induce pancreatic ADM in explant culture, exhibiting many of the same morphologic and biochemical alterations observed in TGF-α-induced ADM, including a dependence on Notch activation. PKCι is highly expressed in both TGF-α- and K-ras^G12D-induced pancreatic ADM and inhibition of PKCι significantly reduces TGF-α- and K-ras^G12D-mediated ADM. Inhibition of PKCι suppresses K-ras^G12D–induced MMP-7 expression and Notch activation, and exogenous MMP-7 restores K-ras^G12D–mediated ADM in PKCι-depleted cells, implicating a K-ras^G12D-PKCι-MMP-7 signaling axis that likely induces ADM through Notch activation. Our results indicate that PKCι is an early marker of pancreatic neoplasia and suggest that PKCι is a potential downstream target of K-ras^G12D in pancreatic ductal metaplasia in vivo.

Long-term administration of the fungus toxin, sterigmatocystin, induces intestinal metaplasia and increases the proliferative activity of PCNA, p53, and MDM2 in the gastric mucosa of aged Mongolian gerbils

OBJECTIVE

The causal agents of gastric cancer could include fungus toxins. Sterigmatocystin (ST), a fungus toxin, is a risk factor of gastric cancer. We investigated the effects of ST on the stomach tissues of Mongolian gerbils.

METHODS

Seventy-five-week-old male Mongolian gerbils received ST ad libitum at a concentration of 0 ppb (non-treated, n = 11), 100 ppb (n = 7), or 1000 ppb (n = 13) dissolved in drinking water for a period of 24 weeks. After administration, we tested the histopathological changes and immunostaining for proliferating cell nuclear antigen (PCNA), p53, and MDM2 expression.

RESULTS

We investigated the histopathological changes and determined the incidence of histopathological changes in animals with various gastric diseases after ST administration at a dose of 0 ppb (non-treated control), 100, or 1,000 ppb as follows: firstly, indices for gastritis were 18.2, 100, and 100%, those for erosion events were 9.1, 100, and 92.3%, and those for polyps were 0, 71.4, and 61.5%, respectively. These incidences in the ST-administered groups (100 or 1000 ppb) showed significant increases compared with those in the non-treated control group. And, lastly, indices for intestinal metaplasia were 0, 100, and 15.4%, respectively. Furthermore, immunostaining for PCNA, p53, and MDM2 expression showed significantly greater rates in the ST-administered groups (100 or 1000 ppb) than in the non-treated control group.

CONCLUSION

The histopathological and immunohistopathological findings of this study indicate that ST exerts a marked influence on gastric mucus and gland cells, showing dominant gastritis, erosion events, polyps, and intestinal metaplasia in these animals.

Gastric atrophy and intestinal metaplasia in a patient on long-term proton pump inhibitor therapy

We report the case of a patient with gastroesophageal reflux disease who developed gastric atrophy and intestinal metaplasia (IM) while on 20-year treatment with proton pump inhibitors. This is perhaps the first report in human beings. A 74-year-old man, who presented with heartburn, showed abnormally high gastric pH (average 6.57) on 24-hour dual channel pH-metry even after discontinuing acid suppressive drugs for one month. No significant esophageal acid exposure was noted, which may be related to an impairment of the acid secreting capacity of the stomach (percentage time esophageal pH<4 during 24-h period 0.3%). Upper gastrointestinal endoscopy was normal except for the prominent submucosal vessels in the body and fundus suggesting gastric atrophy. Histopathological examination of multiple biopsies from the body and antrum of stomach showed signs of gastric atrophy and IM. Rapid urease test and histopathology of gastric biopsies were negative for Helicobacter pylori. Anti-H.pylori IgG ELISA however, was positive. Patient was asked to stop all anti-secretory drugs and only prokinetics were prescribed following which his symptoms markedly improved. On follow-up, in April 2007, he developed symptoms of peripheral neuropathy; serum vitamin 812 level was low. He responded to parenteral vitamin 812 therapy. 24-h dual channel pH-metry repeated after one and a half years showed persistently high gastric pH (average pH 6.76). The patient remained well after discontinuing proton pump inhibitors and continuing prokinetics and vitamin B12 injections.

IL-9 and IL-13 induce mucous cell metaplasia that is reduced by IFN-gamma in a Bax-mediated pathway

One of the major aspects of airway remodeling in asthma is the development of mucous cell metaplasia (MCM). The role of cytokines in the generation and resolution of MCM has been studied in mice and in isolated airway epithelial cells in culture. However, studies using organ cultures that keep the tubular structure of the airways intact and allow studies in the absence of inflammatory cells have not been reported. We established an organ culture system that replicates the allergen-induced MCM in mice and analyzed the role of Bax in the IFN-gamma-induced resolution of MCM. IL-9 or IL-13 induced MCM independently, but a combined IL-9/IL-13 treatment enhanced MCM synergistically. Addition of IFN-gamma at 0.1 ng/ml concentration further increased MCM to levels observed in allergen-exposed mice in vivo. However, MCM was reduced when explants were treated with 50 ng/ml IFN-gamma after MCM was established. While IL-9/IL-13 induced MCM in bronchioles microdissected from bax(+/+) and bax(-/-) mice to a similar extent, IFN-gamma treatment reduced MCM only in bronchioles from bax(+/+) but not in bax(-/-) bronchioles. Restoration of Bax expression in bax(-/-) bronchioles using an adenoviral expression system reduced IL-9/IL-13-induced MCM while MCM was similar in noninfected or adenoviral green fluorescent protein-infected bax(-/-) bronchioles. Furthermore, expressing Bax using an adenoviral expression system reduced allergen-induced MCM in mice. These studies show that allergen-induced MCM is a response to a combination of various cytokines at defined concentrations and that IFN-gamma requires Bax for the resolution of MCM.

Toxicologic significance of histologic change in the larynx of the rat following inhalation exposure: a critical review

The larynx is a site in the respiratory tract of animals that often shows a response to inhaled substances. In many cases, the most sensitive endpoint in repeated dose inhalation studies is squamous metaplasia (often of minimal severity) of the larynx. The U.S. Environmental Protection Agency has speculated that squamous metaplasia in the rodent larynx might be a pre-neoplastic lesion or a precursor to other serious effects and has proposed to use the effect of squamous metaplasia occurring in subchronic inhalation toxicology studies as a toxicologic endpoint for use in quantitative risk assessment [U.S. Environmental Protection Agency, 2006a. Reregistration Eligibility Decision for MGK-264, U.S. Environmental Protection Agency, 2006b, Reregistration Eligibility Decision for Piperonyl Butoxide, U.S. Environmental Protection Agency, 2006c. Reregistration Eligibility Decision for Pyrethrins]. To reach a conclusion as to its significance, we sought to establish the nature of this effect in the relevant context of rodent inhalation studies. A comprehensive review of the literature shows that laryngeal metaplasia can be produced by a wide range of chemically dissimilar substances, and even by "non-chemical" means such as irritation by aerosols and particles, and dehydration by alcohols or low humidity air. There is no published evidence that this effect is pre-neoplastic and it is clearly and repeatedly characterized as an adaptive response. Moreover, the well-differentiated character of laryngeal squamous metaplasia, the reversibility of incidence and severity of it during recovery periods, combined with no significant clinical observations and the lack of progression over time indicates that this response is adaptive and should not be considered to be indicative of significant human risk. We therefore conclude that squamous metaplasia of the rodent larynx is not a relevant toxicologic endpoint.

An overview on the toxic morphological changes in the retinal pigment epithelium after systemic compound administration

Many medications that are administered systemically for nonocular conditions may evoke ocular toxicological complications. Therefore, the eye is routinely investigated histopathologically in preclinical in vivo toxicity studies. The retinal pigment epithelium is a likely target for systemically administered compounds, since the underlying choroid is highly vascularized. The specialized pigment epithelium has numerous functions that all maintain the integrity and function of photoreceptors. Consequently, toxic effects on the pigment epithelium will eventually affect the neural retina. The potential of pigment epithelial cells to respond to toxic injury is limited, but a standardized terminology to describe its morphological changes does not exist in the scientific literature. Detailed morphologic analysis, however, might allow early detection of retinotoxicity and may provide evidence on the underlying pathomechanism. We here review toxic effects on the pigment epithelium focusing in particular on the morphology of toxic cell injury. Morphological changes comprise hypertrophy, intracytoplasmic accumulation of cellular components, loss of cell polarity, degeneration, metaplasia, and formation of subretinal membranes. Some of these changes are reversible whereas others are permanent, leading to impaired function of the pigment epithelium and eventually to photoreceptor loss and retinal atrophy.

Potentiation of oxyntic atrophy-induced gastric metaplasia in amphiregulin-deficient mice

BACKGROUND & AIMS

The loss of parietal cells from the gastric mucosa (oxyntic atrophy) is a critical step in the pathogenesis of chronic gastritis and gastric adenocarcinoma. Parietal cells are known to secrete epidermal growth factor receptor (EGFR) ligands, which are critical regulators of differentiation in the gastric mucosa. Although all of the actions of EGFR ligands are mediated through a common EGFR protein, individual ligands may produce different physiologic responses. Previous investigations have suggested that a deficit in EGFR signaling in waved-2 mice accelerates the emergence of metaplasia after induction of acute oxyntic atrophy. We sought to determine whether specific EGFR ligands regulate the metaplastic response to oxyntic atrophy.

METHODS

To induce spasmolytic polypeptide-expressing metaplasia (SPEM), amphiregulin (AR) and transforming growth factor-alpha-deficient mice and their wild-type littermates were treated with DMP-777 for 0-14 days and for 14 days followed by 14 days of recovery off drug. We evaluated the gastric mucosal response to oxyntic atrophy using cell lineage-specific markers.

RESULTS

Although loss of transforming growth factor-alpha did not influence the induction of SPEM, loss of AR caused an acceleration and amplification in the induction of SPEM after acute oxyntic atrophy. Trefoil factor family 2/spasmolytic polypeptide and intrinsic factor dual-immunostaining cells significantly increased in the SPEM of AR-deficient mice. At the bases of glands, intrinsic factor immunoreactive cells also were costained for 5-bromo-2'-deoxyuridine, suggesting their re-entry into the cell cycle.

CONCLUSIONS

The absence of AR promoted the rapid emergence of SPEM in response to oxyntic atrophy.

Effects of simultaneous treatment with estrogen and testosterone on the uterus of female adult rats

BACKGROUND

Testosterone (T) associated with estrogen (E) has been used in hormonal replacement therapy in postmenopause women and the effects of this hormonal association on the uterus are not known.

OBJECTIVE

To study the effect of long-term simultaneous exposure to testosterone and estrogen on the uterus of non-castrated adult female rats.

METHODS

Groups of ten adult noncastrated female Wistar rats were treated with non-esterified testosterone and beta estradiol (subcutaneous implants with 50 mg of each hormone) or with testosterone cipionate and estradiol valerate (weekly intramuscularly or by subcutaneous injection of respectively, 2.85 mg/kg and 0.166 mg/kg). Control groups received no treatment (10 rats) or injections of diluents (6 rats). All animals were killed six months after hormonal exposure.

RESULTS

All rats treated with T+E developed hyperplasia and hyperkeratosis of the vaginal and cervical epithelium and focal metaplasia with keratinization of the endocervical and endometrial epithelium. Ascending pelvic inflammatory disease with pyometra and tuboovarian abscesses were frequent (25% mortality until the end of the experiment).

CONCLUSIONS

Testosterone associated with estrogen induced metaplasia of the genital epithelium but did not induce neoplastic lesions. The metaplasic lesions reduced the mucosal defense mechanisms enhancing ascending genital inflammatory disease. Although metaplasia of the cervical and endometrial epithelium has been observed after estrogen exposure in rats, testosterone does not appear to inhibit these estrogen effects.

Essential role of nitric oxide in VEGF-induced, asthma-like angiogenic, inflammatory, mucus, and physiologic responses in the lung

VEGF, nitric oxide (NO), inflammation, and vascular- and extravascular remodeling coexist in asthma and other disorders. In these responses, VEGF regulates angiogenesis. VEGF also induces inflammation and remodeling. The mechanisms of the latter responses have not been defined, however. We hypothesized that VEGF-induces extravascular tissue responses via NO-dependent mechanisms. To evaluate this hypothesis, we compared the effects of transgenic VEGF165 in lungs from normal mice, mice treated with pan-NO synthase (NOS) or endothelial NOS (eNOS) inhibitors, and mice with null mutations of inducible NOS (iNOS) or eNOS. These studies demonstrate that VEGF selectively stimulates eNOS and iNOS. They also demonstrate that VEGF induces pulmonary alterations via NO-dependent and -independent mechanisms with angiogenesis, edema, mucus metaplasia, airway hyperresponsiveness, lymphocyte accumulation, dendritic cell hyperplasia and S-nitrosoglutathione reductase stimulation being NO-dependent and dendritic cell activation being NO-independent. Furthermore, they demonstrate that eNOS and iNOS both contribute to these responses. NO/NOS-based interventions may be therapeutic in VEGF-driven inflammation and remodeling.

Role of glycogen synthase kinase 3 in squamous differentiation induced by cigarette smoke in porcine tracheobronchial epithelial cells

Epidemiological evidence suggests that cigarette smoke induces squamous metaplasia in human tracheobronchial epithelium that can progress to lung squamous carcinoma. But it is not well understood how tracheobronchial epithelial cells transduce the signals that mediate cigarette smoke-induced squamous differentiation or squamous metaplasia. In the present study, we found that in vitro cigarette smoke components notably inhibited glycogen synthase kinase 3 (GSK3) and induced the expression of involucrin, a marker of squamous differentiation. The inactivation of GSK3 by two highly selective inhibitors, lithium and SB216763, also significantly enhanced involucrin expression in cultured porcine tracheobronchial epithelial cells (PTBECs). Moreover, we demonstrated that cigarette smoke components significantly promoted activator protein-1 (AP-1) binding activities to the upstream regulatory region of involucrin gene, and similar results were observed by further studies through using GSK3 inhibitors to imitate the effects of cigarette smoke components. Taken together, we conclude that GSK3 is involved in involucrin expression induced by cigarette smoke in PTBEC probably via negatively regulating AP-1 activity, implying a possible mechanism responsible for squamous differentiation induced by cigarette smoke.

[Eccrine squamous syringometaplasia from chemotherapy extravasation]

Eccrine squamous syringometaplasia is a rare entity that occurs in patients who have received chemotherapy treatment. It also occurs in association with chronic ulcers, skin tumors, and after the ingestion of drugs, exposure to toxic agents and inflammatory processes. We present the case of a 47-year-old male diagnosed with microcytic lung carcinoma and superior vena cava syndrome. After receiving the third cycle of chemotherapy, and after accidental extravasation, he presented with an erythematous plaque. The histopathological study revealed eccrine squamous syringometaplasia together with interphase dermatitis and epidermal changes that may be responsible for the epidermal necrosis.

Epithelial and inflammatory responses in the airways of laboratory rats coexposed to ozone and biogenic substances: enhancement of toxicant-induced airway injury

People are often concurrently exposed to more than one air pollutant whether they are in outdoor or indoor environments. Therefore, inhalation studies that are designed to examine the toxicity of coexposures to two or more airborne toxicants may be more relevant for assessing human health risks than those studies that investigate the toxic effects of only one airborne toxicant at a time. Furthermore, airborne biogenic substances such as pollens, bacteria, fungi, and microbial toxins often coexist with common air pollutants in the ambient air, and when inhaled may also cause specific adverse effects on the respiratory tract. One such biogenic substance, bacterial endotoxin, is a potent stimulus of airway inflammation and is commonly found in domestic, agricultural, and industrial settings. Little is known about the interaction of exposures to biogenic substances and common air pollutants, such as ozone or airborne particulate matter. In the last few years, we have performed a series of in vivo studies using laboratory rodents that examined how airway surface epithelial cells are altered by coexposure to ozone and a biogenic substance, either bacterial endotoxin or a commonly used experimental aeroallergen (ovalbumin). Results from these studies indicate that the ozone-induced epithelial and inflammatory responses in laboratory rodents may be markedly enhanced by coexposure to an inhaled biogenic substance. Conversely, the adverse airway alterations caused by exposure to biogenic substances may be enhanced by coexposure to ozone. The results from these initial studies have also suggested some of the cellular and molecular mechanisms underlying the phenotypic epithelial alterations induced by these coexposures. Many more studies are needed to fully elucidate the potential risk to human health from coexposure to air pollutants and airborne biogenic substances.

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

The National Toxicology Program recently completed a series of studies to evaluate the relative potency for toxicity and carcinogenicity of several polyhalogenated aromatic hydrocarbons including dioxin-like compounds (DLCs) and polychlorinated biphenyls. Female Sprague-Dawley rats were administered by gavage 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); 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153); a tertiary mixture of TCDD, PCB126, and PeCDF; a binary mixture of PCB126 and 153; or a binary mixture of PCB126 and 2,3',4,4',5-pentachlorobiphenyl (PCB118); control animals received corn oil-acetone vehicle (99:1) alone. Nasal epithelial changes were observed only in animals exposed for 2 years to the higher doses of the binary mixtures of PCB126 + PCB153 (1000 ng/kg and 1000 microg/kg) and PCB126 + PCB118 (216 and 360 ng TCDD equivalents/kg). In both studies, the changes were of the same nonneoplastic nature, localized to nasal sections II and III located, respectively, at the level of the incisive papilla anterior to the first palatial ridge (section II) and through the middle of the second molar teeth (section III). The changes consisted of hyperplasia of the respiratory epithelium (level II) and metaplasia of olfactory epithelium to respiratory epithelium with further hyperplasia of the metaplastic respiratory epithelium (levels II and III). Variable amounts of acute inflammatory exudate appeared within the lumen of the nasal cavity, overlying the affected epithelium. Occasionally, the inflammation eroded through the skull and into the adjacent olfactory bulbs.

2,6-dichlorophenyl methylsulphone induced behavioural impairments in rats and mice in relation to olfactory mucosal metaplasia

2,6-Dichlorophenyl methylsulphone (2,6-diClPh-MeSO2) induces persistent olfactory mucosal metaplasia and a strong glial fibrillary acidic protein increase in the olfactory bulb of mice. Furthermore, 2,6-diClPh-MeSO2 gives rise to a long-lasting hyperactivity along with an impaired radial arm maze performance. To study cause-effect relationships, olfactory mucosal histopathology, glial fibrillary acidic protein induction and neurobehavioural deficits were re-examined in mice and rats of both sexes given a single intraperitoneal dose of 2,6-diClPh-MeSO2 (16 and 65 mg/kg). There was a clear difference in the character of the olfactory mucosal lesions in the two species. In mice, an extensive metaplasia characterised by severe fibrosis, cartilage and bone formation accompanied with large polyps filling the nasal lumen was confirmed. In rats, a dose-dependent weak metaplasia with patchy loss of olfactory epithelium was observed three weeks after dosing, preferentially at the dorsal meatus, nasal septum, and the tips of the middle ethmoturbinates. Large areas of intact olfactory epithelium remained in all animals, particularly in the low dose rats. In both species, 2,6-diClPh-MeSO2 gave rise to significantly increased motor-activities, impaired performance in the radial arm maze, and glial fibrillary acidic protein-induction. Only rats showed hyperactivity at the low dose. Performance in the Morris water maze was unaffected in rats of both sexes indicating that a general impairment in spatial learning could not be supported. We propose that the observed hyperactivity and radial arm maze acquisition deficits originated from a direct effect of 2,6-diClPh-MeSO2 in the brain rather than being a consequence of the olfactory mucosal lesion.

Genotoxic differences by sex in nasal epithelium and blood leukocytes in subjects residing in a highly polluted area

We describe differences by sex in genotoxic damage found in a population of medical students exposed to a highly oxidative atmosphere, compared with a control group, measured by the single-cell gel electrophoresis assay and histological changes in nasal epithelium smears. Cells were obtained from the nasal epithelium and blood leukocytes. Higher DNA damage in nasal cells and leukocytes was found in males compared to females and control subjects. The percentage of squamous metaplastic changes in the nasal epithelium was also higher in males compared with females and controls. The co-mutation of normal nasal epithelium by squamous cells might modify its protective function in the nose, increasing the risk of damage to the lower respiratory tract. Although, as medical students, males and females were exposed to the same environment and activity patterns, male genotoxicity damage was higher in control and exposed subjects. More research should be done in order to identify direct or indirect sexual hormone intervention.

Ozone exposure enhances endotoxin-induced mucous cell metaplasia in rat pulmonary airways

Coexposure to different airborne pollutants can be more toxic to airway epithelium than an inhalation exposure to a single pollutant. We have previously reported that coexposure to ozone, the primary oxidant gas in photochemical smog, and unique inflammatory biogenic substances such as allergens or bacterial endotoxin, results in augmented epithelial and inflammatory responses in rat nasal airways (M. V. Fanucchi et al., 1998, Toxicol. Appl. Pharmacol. 152, 1-9; J. G. Wagner et al., 2002a, Toxicol. Sci.67, 284-294). In the present study, we investigated the toxic interaction of ozone and endotoxin on the respiratory epithelium in the pulmonary airways of laboratory rodents. F344 rats were intranasally instilled with 0, 2, or 20 microg endotoxin dissolved in sterile saline (150 microl/nasal passage). Six h after instillation rats were exposed to air or 1 ppm ozone for 8 h. One day later, endotoxin and ozone exposures were repeated. Three days after the last exposure, rats were sacrificed, the lungs were lavaged with saline, and the collected bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cells and secreted mucosubstances (mucin 5AC). Lung tissues were processed for light microscopic examination and morphometric analysis of numeric density of epithelial cell populations and volume densities of intraepithelial mucosubstances (IM). Conducting airways were microdissected and analyzed by quantitative RT-PCR to determine steady-state mucin gene (rMuc5AC) mRNA levels in respiratory epithelium. Endotoxin instillation caused a dose-dependent increase in BALF neutrophils that was further increased twofold in ozone-exposed rats given 20 microg endotoxin. Mucin glycoprotein 5AC was elevated in BALF from rats exposed to 20 microg, but not 2 microg endotoxin. Exposure to ozone alone did not cause mucus hypersecretion, but ozone potentiated mucus secretion in rats given 2 or 20 microg endotoxin. Airways of rats exposed to air or ozone alone had scant amounts of IM. Endotoxin instillation induced a dose-dependent increase in IM in airway epithelium that was significantly increased (twofold) in rats that were also exposed to ozone. Expression of rMuc5AC was induced in axial pulmonary airways by 2 and 20 microg endotoxin, and was increased further by ozone-exposure in rats instilled with 20 microg endotoxin. These data demonstrate that ozone exposure potentiates neutrophilic inflammation and mucus production and secretion elicited by a biogenic substance in rat pulmonary airways.

Interleukin-9 induces mucous cell metaplasia independent of inflammation

Interleukin-9 (IL-9) has been strongly implicated in the pathogenesis of asthma, including the overproduction of mucus, in humans and in animal models. We evaluated the inflammatory changes associated with the upregulation of mucus production by examining the time course of inflammation after daily intratracheal IL-9 administration to naive C57Bl6 mice for 9 d. IL-9 induced an asthmatic phenotype, which in general took several days to develop, as assessed by the measurement of airway hyperresponsiveness, pulmonary inflammation, and serum immunoglobulin E. However, within 24 h of a single dose of IL-9, muc5ac mRNA upregulation occurred, and increased numbers of periodic acid Schiff/Alcian blue-positive mucous cells appeared. This response occurred before the development of an inflammatory cell influx and was the result of epithelial metaplasia. It seemed that IL-9 evoked mucous cell metaplasia independent of IL-13 because mRNA tissue evaluation indicated that muc5ac upregulation preceded any increase in IL-13 mRNA expression or detectable levels of IL-13 in the brochoalveolar lavage fluid. Therefore, the upregulation of IL-13 by IL-9 may be responsible for the amplification of mucus production but is not required for its initiation. IL-9 seems to directly stimulate mucous cell metaplasia without the requirement of inflammatory cell influx.

Globose basal cells are required for reconstitution of olfactory epithelium after methyl bromide lesion

Despite a remarkable regenerative capacity, recovery of the mammalian olfactory epithelium can fail in severely injured areas, which subsequently reconstitute as aneuronal respiratory epithelium (metaplasia). We contrasted the cellular response of areas of the rat epithelium that recover as olfactory after methyl bromide lesion with those undergoing respiratory metaplasia in order to identify stem cells that restore lesioned epithelium as olfactory. Ventral olfactory epithelium is at particular risk for metaplasia after lesion and patches of it are rendered acellular by methyl bromide exposure. In contrast, globose basal cells (GBCs, marked by staining with GBC-2) are preserved in surrounding ventral areas and uniformly throughout dorsal epithelium, which consistently and completely recovers as olfactory after lesion. Over the next few days, neurons reappear, but only in those areas in which GBCs are preserved and multiply. In contrast, parts of the epithelium in which GBCs are destroyed are repopulated in part by Bowman's gland cells, which pile up above the basal lamina. Electron microscopy confirms the reciprocity between gland cells and globose basal cells. By 14 days after lesion, the areas that are undergoing metaplasia are repopulated by typical respiratory epithelial cells. As horizontal basal cells are eliminated from all parts of the ventral epithelium, the data suggest that GBC-2(+) cells are ultimately responsible for regenerating olfactory neuroepithelium. In contrast, GLA-13(+) cells may give rise to respiratory metaplastic epithelium where GBCs are eliminated. Thus, we support the idea that a subpopulation of GBCs is the neural stem cell of the olfactory epithelium.

Long-term treatment with sterigmatocystin, a fungus toxin, enhances the development of intestinal metaplasia of gastric mucosa in Helicobacter pylori-infected Mongolian gerbils

BACKGROUND

Helicobacter pylori is a human gastric carcinogen. Sterigmatocystin (ST), a fungus toxin, is a risk factor of gastric cancer. Cytotoxin-vacuolation toxin A (VacA) present in supernatants of H. pylori suspensions can cause gastritis and ulcer. The aim of this study was to examine the effects of H. pylori, ST and VacA in Mongolian gerbils.

METHODS

Male Mongolian gerbils (n = 196) were treated with H. pylori supernatants (10 ml/1000 mg) mixed with diet or inoculated intragastrically with H. pylori alone or with ST (100 or 1000 ppb), and then killed 27 months later. Gastric tissue sections were stained with haematoxylin and eosin (H&E), periodic acid-Schiff (PAS), Alcian blue (AB, pH 2.5) and with immunostaining for PCNA and p53 expression.

RESULTS

In H. pylori-infected gerbils, the normal mucosa was replaced by hyperplastic epithelium. Severe gastritis, cystic dilatation of gastric glands, hyperplastic polyps and intestinal metaplasia were observed. In H. pylori + ST (1000 ppb) gerbils, intestinal metaplasia was significantly more frequent than in H. pylori alone animals. No pathological changes were observed in the H. pylori supernatant group. Osseous metaplasia was observed in the H. pylori + ST (100 ppb) group. Serum gastrin levels of the H. pylori + ST (1000 ppb) group were significantly higher than those of the other groups. PCNA labelling index and p53 index of infected gerbils were significantly higher than those of uninfected groups.

CONCLUSION

H. pylori causes gastritis, ulcer and intestinal metaplasia. ST enhances the development of intestinal metaplasia and increases gastrin levels in H. pylori-infected Mongolian gerbils.

Effects of topical chlorhexidine applied to the rabbit nasal mucosa

OBJECTIVE

To search the effects of administration of various concentrations of a wide-spectrum antimicrobial agent, chlorhexidine, to the nasal mucosa.

MATERIAL AND METHODS

About 0.20, 0.12, 0.06 and 0.03% concentrations of chlorhexidine gluconate were applied to the rabbit nasal mucosa as one puff twice a day throughout 5 days. Another group, treated with serum saline to the nose, behaved as the control group. On the fifth day following drug administration, specimens were taken from nasal mucosa of the rabbits and examined under light microscope.

RESULTS

As a result of comparison between drug treated group and control group, with increasing drug concentrations progressively increased neutrophil infiltration in mucosa, ciliary loss in cells, and occasional metaplasia were observed.

CONCLUSION

There is a linear, positive and strong association between concentrations of chlorhexidine and its irritative effects on rabbit nasal mucosa. While 0.20 and 0.12% concentrations of chlorhexidine cause excess irritation on the nasal cavity, 0.06 and 0.03% concentrations of chlorhexidine gluconate causes lower irritation and effects on the animals which have experimentally induced rhinosinusitis must be evaluated.

Responses in the respiratory tract of rats following exposure to sulphuric acid aerosols for 5 or 28 days

Sulphuric acid mists have been classified by the International Agency for Research on Cancer as being carcinogenic to humans based on epidemiological findings of respiratory tract tumours. To determine if early changes in the respiratory tract following exposure to sulphuric acid (H(2)SO(4)) aerosols are consistent with the possible development of tumours after extended periods of exposure, groups of female rats were exposed to respirable aerosols of H(2)SO(4) at target concentrations of 0, 0.2, 1.0 or 5.0 mg m(-3) for 6 h per day for either 5 days or for 5 days a week over a 28-day period. Additional groups exposed to 0 or 5.0 mg m(-3) over the 28-day period were retained after exposure for 4 or 8 weeks to assess recovery. Histopathological examinations and quantitative cell proliferation measurements were conducted on the nasal passages, larynx and lung. Achieved concentrations were 0.3, 1.38 and 5.52 mg m(-3) H(2)SO(4). Histological and cell proliferative changes were confined to the larynx and no effects were seen in the nasal passages or lungs. At the two highest concentrations, squamous metaplasia accompanied by significant cell proliferation was apparent after 5 and 28 days of exposure and there was a reduction in the severity of the pathological changes following the recovery periods. No effects were seen at 0.3 mg m(-3) after 5 days of exposure and only minimal metaplastic change was seen after 28 days in a few animals and was not accompanied by cell proliferation. The toxicological relevance of these findings is discussed.

Smoking cessation decreases the number of metaplastic secretory cells in the small airways of the Guinea pig

To ascertain whether cessation of smoke exposure would decrease small-airway secretory-cell metaplasia, guinea pigs were exposed to daily cigarette smoke using a nose-only exposure system for 4 and 8 mo; an additional group was exposed to smoke for 4 mo and then air recovery for 4 mo ("ex-smokers"). Numbers of secretory cells per millimeter of basement membrane were calculated for each bronchiole from measurements of histologic sections stained with Alcian blue/periodic acid Schiff, and cumulative histograms were constructed. Smoke exposure was associated with a significant increase in numbers of secretory cells at 4 mo and 8 mo, although there was no increase in numbers beyond the 4-mo exposure period. In the ex-smoking group, secretory cells were reduced compared to the 4- or 8-mo smoking group, but continued to be greater than controls. We conclude that, in a guinea pig model, smoking produces secretory-cell metaplasia in the airways and that smoking cessation allows partial recovery of normal structure.

The effect of benzalkonium chloride on rabbit nasal mucosa in vivo: an electron microscopy study

In this study we investigated the histopathological changes of nasal mucosa after the use of topical benzalkonium-chloride solution. In the study, 28 male New Zealand white rabbits were used. The animals were divided into two groups. In the first group, 50 micro l of 0.001% benzalkonium-chloride solution was sprayed into the right nostril and 50 micro l of 0.9% saline into the left twice daily for 14 days. In the second group, the same solutions were applied twice daily for 28 days. All of the biopsies from each nasal cavity were processed for electron microscopy. In the nostrils treated with 0.001% benzalkonium chloride, there were areas with obvious squamous cell metaplasia. Some cells showed broken cristae of the mitochondria. Degenerative changes in the supportive and olfactory cells, deformation of nuclei and the increase of heterochromatin were observed. The present investigation has shown that the application of topical benzalkonium chloride does induce degenerative morphologic changes in the nasal mucosa in rabbits in vivo.

Effects of nonylphenol, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), and pentachlorophenol on the adult female guinea pig reproductive tract

The guinea pig exhibits cyclic and luteal similarities to the human, a feature not present in other small experimental animals such as rats, mice, or rabbits. Studies were undertaken to investigate the in vivo effects of three persistent environmental xenobiotics (nonylphenol, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene [p,p'-DDE], and pentachlorophenol) on the microanatomy of the adult female guinea pig reproductive system. The effects brought about by these compounds (40 mg/kg/day) were compared to those caused by the synthetic estrogen diethylstilbestrol (DES; 50 microg/kg/day). Adult female guinea pigs, intact and castrated, were treated with 14 daily subcutaneous (s.c.) doses of one of these agents. The 50% decline in the weight of the tract that occurred following castration, was prevented by administration of nonylphenol, p,p'-DDE, and DES, but not of pentachlorophenol. Nonylphenol produced weak estrogenic stimulation of the tract of intact animals and maintained a relatively normal histologic appearance in castrated animals. Focal mucinous metaplasia of the endometrium, however, was observed in both groups. Treatment of intact and castrated animals with p,p'-DDE resulted in cystic hyperplasia and mucinous metaplasia of the endometrium, hyperplasia of the cervical epithelium, estrogenic stimulation of the vagina, and dilation of the rete ovarii. Treatment of intact or castrated animals with DES resulted in effects that were qualitatively similar to those caused by p,p'-DDE. The appearance of the vaginal epithelium, however, was abnormal and the rete ovarii were less dilated. Pentachlorophenol had minimal effect on the histology of the tract of castrated or intact animals. These data support our hypothesis that some environmental toxicants can substitute for estradiol in regulating the microanatomy of the female reproductive tract. They indicate the potential of these compounds to act as endocrine disrupting agents.

Effects of ozone and endotoxin coexposure on rat airway epithelium: potentiation of toxicant-induced alterations

Tropospheric ozone is the major oxidizing component in photochemical smog and is one of the most pervasive problems to human health of the criteria air pollutants for which the National Ambient Air Quality Standards have been designated by the Clean Air Act. Although many adverse health effects of ozone exposure have been documented in both humans and laboratory animals, controversy surrounds the establishment and implementation of ozone standards set forth by the U.S. Environmental Protection Agency. Because people are commonly exposed to more than one air pollutant at a time, studies that examine coexposures to airborne materials may be more relevant for assessing their risks to human health. Airborne biogenic substances such as pollens, spores, and bacterial products are ubiquitous in the environment, and when inhaled can cause adverse respiratory symptoms. One such biogenic agent, bacterial endotoxin, is a potent stimulus of airway inflammation and is a ubiquitous airborne contaminant commonly found in domestic, agricultural, and industrial settings. Little is known about the interaction of exposures to biogenic substances and criteria air pollutants such as ozone. In the last few years we have performed a series of studies in rodents that examined the biologic responses of the respiratory epithelium after airway exposures to both endotoxin and ozone. When exposed to ozone (0.5 ppm 8 hr/day for 3 days), Fischer rats develop lesions in the nasal transitional epithelium, whereas intranasal instillation of endotoxin (20 microg) elicits epithelial lesions in the respiratory epithelium of the nose and conducting airways. Our studies were designed to examine how exposure to one toxicant may affect the airway epithelial lesions induced by the other toxicant. We investigated the potential role of acute inflammation in the enhancement of airway epithelial lesions after exposure of these two toxicants in neutrophil-sufficient and neutrophil-deficient rodents. A summary of these results indicates that epithelial and inflammatory responses to coexposure of these two pollutants are greater than those elicited by either agent alone. Interestingly, each toxicant enhances the epithelial alterations induced by the other. Furthermore, the synergistic effects elicited by coexposure to ozone and endotoxin are mediated partly by neutrophils. These studies provided some new insights into how inhaled co-pollutants interact to initiate and promote alterations of airway epithelium. Further studies with these and other air pollutants will help define their true risk to human health.

Exposure to the dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces squamous metaplasia in the endocervix of cynomolgus macaques

Female cynomolgus macaques (n = 11) were treated orally with graded doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Cervical tissue was recovered at necropsy 1.2-2.7 years later and examined using routine histopathology. Results were compared histologically with cervical tissue from untreated, age- and parity-matched controls. Significant squamous epithelial metaplasia was observed in the endocervix of 9 of 11 TCDD-treated animals, and the degree of severity was dose dependent. In contrast, minimal or no pathological changes were observed in eight of nine control animals and one animal had only mild squamous metaplasia. These results suggest that TCDD exposure induces epithelial transdifferentiation in the primate cervix. Consequently, the TCDD-treated macaque may serve as a predictable animal model for the study of cervical epithelial transdifferentiation and for examining the relationship between squamous metaplasia and cervical oncogenesis both at the cellular and at the molecular level.

Cutaneous Reactions to Chemotherapeutic Agents

The task of evaluating a cutaneous eruption in the patient receiving chemotherapy can be quite formidable. Most of the time, these patients are receiving a multitude of agents and have profound immunosuppression. These factors may alter the more common manifestations of cutaneous eruptions. This article presents some of the more common cutaneous eruptions that may occur in an oncology patient receiving chemotherapy. It is hoped we may recognize clinical patterns seen with chemotherapeutic agents in the immunosuppressed population and, by recognizing these cutaneous eruptions, we may avoid the pitfalls of discontinuing medicines that may certainly be needed or altering the treatment course in a patient.

Quantitative analysis of disturbed cell maturation in dysplastic lesions of the respiratory tract epithelium

Autoradiographic patterns of [3H]thymidine incorporation, nuclear/cytoplasmic ratios (N/C), and the percentage of dark epithelial cells were analyzed in a group of epithelial lesions induced by 7,12-dimethylbenz[a]anthracene (DMBA) in rat tracheal transplants. It was found that similar lesions of different age exhibit the same labeling indices (LIs), therefore the lesions of different age were subsequently pooled in the following groups and studied by high resolution light microscopic autoradiography: squamous metaplasia without or with only mild atypia, squamous metaplasia with moderate atypia, squamous metaplasia with severe atypia, carcinoma in situ, and microinvasive carcinoma. Normal tracheal and esophageal epithelia were also analyzed. Whereas the normal tracheal basal layer exhibited an LI smaller than 1%, a clear difference between the carcinomas (in situ and invasive) on one hand (LI approximately 32%) and all the remaining epithelia on the other hand (LI approximately 18%) was detected. The LIs of the suprabasal cells exhibited a statistically significant difference between the squamous epithelia without atypia (LI approximately 2%) and the group comprising all the atypical lesions (LI approximately 9%). Gradients of increasing N/C (nucleus-cytoplasm ratios) values could be observed as the lesions increased in severity, especially in the middle and surface layers (e.g., in the surface layer regular metaplasia N/C = 0.08, squamous metaplasia with moderate atypia N/C = 0.26, and carcinoma in situ N/C = 0.50). Dark cells were absent in the normal esophageal epithelium, were present in moderate numbers in the basal layer of regular squamous metaplasia (18%), and increased markedly in the atypical epithelial lesions (approximately 50% in the atypical squamous metaplasias and 70% in carcinoma in situ). In the suprabasal layer dark cells increased from 3% in squamous metaplasia with moderate atypia to 28% in metaplasia with severe atypia and 56% in carcinoma in situ. The results confirm in a quantitative fashion that disturbances of cell maturation and cell proliferation are key features of dysplastic lesions induced by chemical carcinogens, and suggest the use of objective parameters for evaluation and classification of preneoplastic alterations.

Endotoxin enhancement of ozone-induced mucous cell metaplasia is neutrophil-dependent in rat nasal epithelium

Ozone, the primary oxidant gas in photochemical smog, causes neutrophilic inflammation and mucous cell metaplasia (MCM) in the nasal transitional epithelium (NTE) of rats and monkeys. Bacterial endotoxin is another common airborne agent that induces acute neutrophilic inflammation, but not MCM, in NTE. It does, however, enhance ozone-induced MCM in rat nasal airways (Fanucchi et al., 1998, Toxicol. Appl. Pharmacol. 152, 1-9). In the present study, F344 rats exposed to filtered air or 0.5 ppm ozone (8 h/day for 3 days) were intranasally instilled with sterile saline or 100 microg endotoxin 24 h and 48 h after the third ozone exposure. To determine the role of neutrophilic inflammation in endotoxin-induced potentiation of the MCM caused by ozone, half of the rats were depleted of circulating neutrophils prior to saline or endotoxin instillations. Rats were killed 6 h or 3 days after the last intranasal instillation, and nasal tissues were processed for (1) light microscopy and morphometric analysis to determine the number of infiltrating neutrophils and the volume amount (density) of stored mucosubstances in the NTE, and (2) quantitative RT-PCR analysis of steady-state mucin gene (rMuc-5AC) mRNA levels in the NTE. Endotoxin induced a transient influx of neutrophils in both air- and ozone-exposed rats that was completely blocked by neutrophil depletion. Endotoxin increased rMuc-5AC mRNA levels in the NTE of ozone-exposed rats. Neutrophil depletion, however, had no effect on endotoxin-induced upregulation of mucin gene mRNA levels. Endotoxin enhanced the ozone-induced increase in stored mucosubstances (4-fold increase), but only in neutrophil-sufficient rats. These data indicate that endotoxin enhancement of ozone-induced upregulation of rMuc-5AC mRNA levels is neutrophil-independent, while its effects on intraepithelial production and storage of mucus glycoproteins is dependent on the presence of neutrophils.

Ozone-induced mucous cell metaplasia

The article highlighted in this issue is "Endotoxin enhancement of ozone-induced mucous cell metaplasia is neutrophil-dependent in rat nasal epithelium," by James G. Wagner, Steven J. Van Dyken, Jon A. Hotchkiss, and Jack R. Harkema (pp. 338-347).

Methyl methacrylate toxicity in rat nasal epithelium: investigation of the time course of lesion development and recovery from short term vapour inhalation

An investigation of the time course of development and recovery of the nasal lesion induced in rats by inhalation of methyl methacrylate (MMA) was conducted. Groups of 45 female F344 rats (five animals per time point) were exposed whole body for 6 hours per day to 0 (control), 110 or 400 ppm MMA for 1, 2, 5, 10 or 28 consecutive days. Additional animals were retained for a period of 4, 13, 24 or 36 weeks following exposure to assess reversibility of any nasal tissue effects. After inhalation of MMA there was damage to the olfactory epithelium at 110 and 400 ppm. This was apparent following the first day of exposure, but recovery/regeneration was evident during the subsequent days of the exposure phase of the study. The most severely affected section of the nasal passages was that which included the ethmoturbinates. Focal adhesions between the septum and turbinates and between the turbinates themselves were seen in some animals exposed to 400 ppm MMA at time points after 5 days of exposure. There were no lesions in the squamous, transitional or respiratory epithelia and none in control rats. Lesions that developed in rats exposed to 110 ppm MMA subsequently repaired during the exposure period. At 400 ppm, the majority of the olfactory epithelium had returned to normal within 13 weeks of the end of the exposure phase, but minimal respiratory metaplasia remained evident and there were some focal adhesions between the septum and turbinates and between the turbinates themselves.