Ozone-induced airway epithelial cell death, the neurokinin-1 receptor pathway, and the postnatal developing lung.

Children are uniquely susceptible to ozone because airway and lung growth continue for an extensive period after birth. Early-life exposure of the rhesus monkey to repeated ozone cycles results in region-specific disrupted airway/lung growth, but the mediators and mechanisms are poorly understood. Substance P (SP), neurokinin-1 receptor (NK-1R); and nuclear receptor Nur77 (NR4A1) are signaling pathway components involved in ozone-induced cell death. We hypothesize that acute ozone (AO) exposure during postnatal airway development disrupts SP/NK-1R/Nur77 pathway expression and that these changes correlate with increased ozone-induced cell death. Our objectives were to 1) spatially define the normal development of the SP/NK-1R/Nur77 pathway in conducting airways; 2) compare how postnatal age modulates responses to AO exposure; and 3) determine how concomitant, episodic ozone exposure modifies age-specific acute responses. Male infant rhesus monkeys were assigned at age 1 mo to two age groups, 2 or 6 mo, and then to one of three exposure subgroups: filtered air (FA), FA+AO (AO: 8 h/day × 2 days), or episodic biweekly ozone exposure cycles (EAO: 8 h/day × 5 days/14-day cycle+AO). O3 = 0.5 ppm. We found that 1) ozone increases SP/NK-1R/Nur77 pathway expression in conducting airways, 2) an ozone exposure cycle (5 days/cycle) delivered early at age 2 mo resulted in an airway that was hypersensitive to AO exposure at the end of 2 mo, and 3) continued episodic exposure (11 cycles) resulted in an airway that was hyposensitive to AO exposure at 6 mo. These observations collectively associate with greater overall inflammation and epithelial cell death, particularly in early postnatal (2 mo), distal airways.

Inflammatory dilated cardiomyopathy in Abcg5-deficient mice.

Dilated cardiomyopathy (DCM) in A/J mice homozygous for the spontaneous thrombocytopenia and cardiomyopathy (trac) mutation results from a single base pair change in the Abcg5 gene. A similar mutation in humans causes sitosterolemia with high plant sterol levels, hypercholesterolemia, and early onset atherosclerosis. Analyses of CD3+ and Mac-3+ cells and stainable collagen in hearts showed inflammation and myocyte degeneration in A/J-trac/trac mice beginning postweaning and progressed to marked dilative and fibrosing cardiomyopathy by 140 days. Transmission electron microscopy (TEM) demonstrated myocyte vacuoles consistent with swollen endoplasmic reticulum (ER). Myocytes with cytoplasmic glycogen and irregular actinomyosin filament bundles formed mature intercalated disks with normal myocytes suggesting myocyte repair. A/J-trac/trac mice fed lifelong phytosterol-free diets did not develop cardiomyopathy. BALB/cByJ-trac/trac mice had lesser inflammatory infiltrates and later onset DCM. BALB/cByJ-trac/trac mice changed from normal to phytosterol-free diets had lesser T cell infiltrates but persistent monocyte infiltrates and equivalent fibrosis to mice on normal diets. B- and T-cell-deficient BALB/cBy-Rag1(null) trac/trac mice fed normal diets did not develop inflammatory infiltrates or DCM. We conclude that the trac/trac mouse has many features of inflammatory DCM and that the reversibility of myocardial T cell infiltration provides a novel model for investigating the progression of myocardial fibrosis.

2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced MUC5AC expression: aryl hydrocarbon receptor-independent/EGFR/ERK/p38-dependent SP1-based transcription.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental toxicant. Epidemiological studies have associated TCDD exposure with the development of chronic obstructive pulmonary disease, which is manifested by mucous/goblet cell hyperplasia. The purpose of this research was to elucidate the pathway/mechanisms that lead to TCDD-induced gene expression in both primary normal human bronchial epithelial cells and an immortalized cell line, HBE1, under air-liquid interface conditions. TCDD exposure induced a time-dependent elevation of MUC5AC mRNA and protein synthesis, and cytochrome p450 1A1 (CYP1A1) expression in these cells. Treatment with an aryl hydrocarbon receptor antagonist had no effect on TCDD-induced MUC5AC expression, but significantly suppressed CYP1A1 induction. However, treatments with inhibitors of signaling pathways and the expression of dominant negative mutants of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and p38, but not the inhibition of c-Jun N-terminal kinase pathway, abrogated MUC5AC induction, but not that of CYP1A1. These effects also occurred at the MUC5AC promoter-reporter level using the chimeric construct for a transient transfection study. Western blot analysis confirmed the phosphorylation of activated EGFR, ERK, and p38 signaling molecules, but not the c-Jun N-terminal kinase, in cells after TCDD exposure. Specificity protein 1 (Sp1) phosphorylation also occurred in cells after TCDD exposure. Both MUC5AC expression and the promoter activity were inhibited by mithramycin A, an inhibitor specific to Sp1-based transcription. These results lead to the conclusion that TCDD induced MUC5AC expression through a noncanonical aryl hydrocarbon receptor-independent, EGFR/ERK/p38-mediated signaling pathway-mediated/Sp1-based transcriptional mechanism.

Stereological analysis of bacterial load and lung lesions in nonhuman primates (rhesus macaques) experimentally infected with Mycobacterium tuberculosis.

Infection with Mycobacterium tuberculosis primarily produces a multifocal distribution of pulmonary granulomas in which the pathogen resides. Accordingly, quantitative assessment of the bacterial load and pathology is a substantial challenge in tuberculosis. Such assessments are critical for studies of the pathogenesis and for the development of vaccines and drugs in animal models of experimental M. tuberculosis infection. Stereology enables unbiased quantitation of three-dimensional objects from two-dimensional sections and thus is suited to quantify histological lesions. We have developed a protocol for stereological analysis of the lung in rhesus macaques inoculated with a pathogenic clinical strain of M. tuberculosis (Erdman strain). These animals exhibit a pattern of infection and tuberculosis similar to that of naturally infected humans. Conditions were optimized for collecting lung samples in a nonbiased, random manner. Bacterial load in these samples was assessed by a standard plating assay, and granulomas were graded and enumerated microscopically. Stereological analysis provided quantitative data that supported a significant correlation between bacterial load and lung granulomas. Thus this stereological approach enables a quantitative, statistically valid analysis of the impact of M. tuberculosis infection in the lung and will serve as an essential tool for objectively comparing the efficacy of drugs and vaccines.

Evaluation of MUC5AC expression and upregulation in airway epithelial cells of horses.

OBJECTIVE: To isolate and culture primary equine airway epithelial cells in vitro and elucidate the major cytokines involved in expression of the gel-forming mucin gene MUC5AC in horses. SAMPLE POPULATION: 12 tracheas obtained within 5 hours after euthanasia from horses free from respiratory tract disease. PROCEDURES: Tracheal rings were digested overnight in 0.2% protease, and dissociated airway epithelial cells were grown in a serum-free defined medium at an air-liquid interface until confluence was achieved. Differentiated airway epithelial cells were treated with a panel of recombinant equine cytokines followed by quantitative reverse transcriptase PCR assay for mRNA of equine MUC5AC and the control gene glyceraldehyde 3-phosphate dehydrogenase. Cultures were incubated in the presence of isohelenin, a nuclear factor kappaB-DNA-binding inhibitor, to investigate transcriptional regulation of MUC5AC. RESULTS: Light and electron microscopy revealed a differentiated epithelium with ciliated cells, nonciliated mucous cells, and basal-like cells. Recombinant equine tumor necrosis factor-alpha was the major mediator in the cytokine panel that significantly increased MUC5AC mRNA by a factor of 5 in a dose- and time-dependent manner. This enhancement was attenuated by isohelenin. CONCLUSIONS AND CLINICAL RELEVANCE: Data suggested that a nuclear factor KB-based transcriptional mechanism is involved in induction of MUC5AC expression by tumor necrosis factor-A. Understanding the molecular mechanism of cytokine-enhanced MUC5AC expression in horses may lead to better treatment options and understanding of the pathogenesis of equine pulmonary diseases.

Activation of calcitonin gene-related peptide receptor during ozone inhalation contributes to airway epithelial injury and repair.

The authors investigated the importance of the neuropeptide, calcitonin gene-related peptide (CGRP), in epithelial injury, repair, and neutrophil emigration after ozone exposure. Wistar rats were administered either a CGRP-receptor antagonist (CGRP(8-37)) or saline and exposed to 8 hours of 1-ppm ozone or filtered air with an 8-hour postexposure period. Immediately after exposure, ethidium homodimer was instilled into lungs as a marker of necrotic airway epithelial cells. After fixation, airway dissected lung lobes were stained for 5'-bromo-2'-deoxyuridine, a marker of epithelial proliferation. Positive epithelial cells were quantified in specific airway generations. Rats treated with CGRP(8-37) had significantly reduced epithelial injury in terminal bronchioles and reduced epithelial proliferation in proximal airways and terminal bronchioles. Bronchoalveolar lavage and sections of terminal bronchioles showed no significant difference in the number of neutrophils emigrating into airways in CGRP(8-37)-treated rats. The airway epithelial cell line, HBE-1, showed no difference in the number of oxidant stress positive cells during exposure to hydrogen peroxide and a range of CGRP(8-37) doses, demonstrating no antioxidant effect of CGRP(8-37). We conclude that activation of CGRP receptors during ozone inhalation contributes to airway epithelial injury and subsequent epithelial proliferation, a critical component of repair, but does not influence neutrophil emigration into airways.

Extraintestinal pathogenic Escherichia coli-induced pneumonia in three kittens and fecal prevalence in a clinically healthy cohort population.

Three kittens, ages 5, 9, and 17 weeks, were found dead by separate caregivers and were submitted for necropsy. At gross necropsy, each kitten had hemorrhagic or bloody fibrinoserous thoracic fluid and differing distributions of pulmonary consolidation. On histologic examination, the pulmonary lesion in each kitten was similar and was characterized by acute necrotizing and hemorrhagic pneumonia and pleuritis, with numerous intralesional small Gram-negative rods. A pure culture of a distinct serotype of Escherichia coli was identified in lung tissue from each kitten (O4H5, O6H7, O6H5). Lung isolates, genotyped by polymerase chain reaction, carried genes that are characteristic of extraintestinal pathogenic E. coli (ExPEC), including cnf-1, papG allele I, papA, papC, sfa, fim, hlyD, malX, iroN, fyuA, kpsMII, and ompT. Escherichia coli isolates from the intestines of 2 of the kittens were 100% related to the respective lung isolate, as determined by pulsed-field gel electrophoresis. Cultures of fecal samples collected from a clinically healthy cohort population of kittens revealed 16 of 19 tested kittens (84%) to be shedding hemolytic E. coli. Ten different serotypes were identified from 43 hemolytic E. coli fecal isolates from the cohort population, each of which had a genetic profile consistent with that typical of ExPEC. To the authors' knowledge, this is the first report to describe a cluster of isolated cases of pneumonia in kittens caused by distinct serotypes of ExPEC and to evaluate the prevalence of hemolytic E. coli carrying ExPEC-associated genes in the feces of a cohort population of kittens.

Activation of neurokinin-1 receptors during ozone inhalation contributes to epithelial injury and repair.

We investigated the importance of neurokinin (NK)-1 receptors in epithelial injury and repair and neutrophil function. Conscious Wistar rats were exposed to 1 ppm ozone or filtered air for 8 hours, followed by an 8-hour postexposure period. Before exposure, we administered either the NK-1 receptor antagonist, SR140333, or saline as a control. Ethidium homodimer was instilled into lungs as a marker of necrotic airway epithelial cells. After fixation, whole mounts of airway dissected lung lobes were immunostained for 5-bromo-2'-deoxyuridine, a marker of epithelial proliferation. Both ethidium homodimer and 5-bromo-2'-deoxyuridine-positive epithelial cells were quantified in specific airway generations. Rats treated with the NK-1 receptor antagonist had significantly reduced epithelial injury and epithelial proliferation compared with control rats. Sections of terminal bronchioles showed no significant difference in the number of neutrophils in airways between groups. In addition, staining ozone-exposed lung sections for active caspase 3 showed no apoptotic cells, but ethidium-positive cells colocalized with the orphan nuclear receptor, Nur77, a marker of nonapoptotic, programmed cell death mediated by the NK-1 receptor. An immortalized human airway epithelial cell line, human bronchial epithelial-1, showed no significant difference in the number of oxidant stress-positive cells during exposure to hydrogen peroxide and a range of SR140333 doses, demonstrating no antioxidant effect of the receptor antagonist. We conclude that activation of the NK-1 receptor during acute ozone inhalation contributes to epithelial injury and subsequent epithelial proliferation, a critical component of repair, but does not influence neutrophil emigration into airways.

Synergistic up-regulation of CXCL10 by virus and IFN γ in human airway epithelial cells.

Airway epithelial cells are the first line of defense against viral infections and are instrumental in coordinating the inflammatory response. In this study, we demonstrate the synergistic stimulation of CXCL10 mRNA and protein, a key chemokine responsible for the early immune response to viral infection, following treatment of airway epithelial cells with IFN γ and influenza virus. The synergism also occurred when the cells were treated with IFN γ and a viral replication mimicker (dsRNA) both in vitro and in vivo. Despite the requirement of type I interferon (IFNAR) signaling in dsRNA-induced CXCL10, the synergism was independent of the IFNAR pathway since it wasn't affected by the addition of a neutralizing IFNAR antibody or the complete lack of IFNAR expression. Furthermore, the same synergistic effect was also observed when a CXCL10 promoter reporter was examined. Although the responsive promoter region contains both ISRE and NFκB sites, western blot analysis indicated that the combined treatment of IFN γ and dsRNA significantly augmented NFκB but not STAT1 activation as compared to the single treatment. Therefore, we conclude that IFN γ and dsRNA act in concert to potentiate CXCL10 expression in airway epithelial cells via an NFκB-dependent but IFNAR-STAT independent pathway and it is at least partly regulated at the transcriptional level.

Idiopathic microscopic colitis of rhesus macaques: quantitative assessment of colonic mucosa.

Idiopathic chronic diarrhea (ICD) is a common cause of morbidity and mortality among juvenile rhesus macaques. While lesions may be absent at colonoscopy, the histopathologic evaluation of the biopsy specimens is consistent with human macroscopic colitis (MC). In this study, we developed an isotropic uniform random sampling method to evaluate macroscopic and microscopic changes and applied it on proximal ascending colon in monkeys. Colonic tissue and peripheral blood specimens were collected from six MC and six control juvenile macaques at necropsy. Uniform random samples were collected from the colon using punch biopsy tools. The volume of epithelium and lamina propria were estimated in thick (25 µm) sections using point probes and normalized to the area of muscularis mucosae. Our data suggests a significant increase of the Vs of the lamina propria (1.9-fold, P = 0.02) and epithelium (1.4-fold, P = 0.05) in subjects with MC. The average colonic surface mucosa area in the MC monkeys increased 1.4-fold over the controls (P = 0.02). The volume of the proximal colon in animals with MC showed a 2.4-fold increase over the non-diarrhea control monkeys (P = 0.0001). Cytokine, chemokine, and growth factor levels in peripheral blood were found to be correlated with the volume estimate of the lamina propria and epithelium. We found that ICD in macaques has features which simulates human MC and can be used as a spontaneous animal model for human MC. Furthermore, this developed sampling method can be used for unbiased preclinical evaluation of therapeutics in this animal model.

Influenza-induced innate immunity: regulators of viral replication, respiratory tract pathology & adaptive immunity.

Influenza virus infections usually cause mild to moderately severe respiratory disease, however some infections, like those involving the avian H5N1 virus, can cause massive viral pneumonia, systemic disease and death. The innate immune response of respiratory tract resident cells is the first line of defense and limits virus replication. Enhanced cytokine and chemokine production following infection, however, appears to underlie much of the pathology that develops after infection with highly pathogenic strains. A so-called `cytokine storm' can damage the lung tissue and cause systemic disease, despite the control of viral replication. By summarizing current knowledge of the innate responses mounted to influenza infection, this review highlights the importance of the respiratory tract epithelial cells as regulators of innate and adaptive immunity to influenza virus.

Oxidant-injured airway epithelial cells upregulate thioredoxin but do not produce interleukin-8.

We tested the hypothesis that oxidant-injured cells upregulate thioredoxin, whereas oxidant-stressed, but not injured, cells upregulate interleukin (IL)-8 after injury. We exposed primary human tracheobronchial epithelial cells and transformed human bronchial epithelial cells (BEAS-2B S.6) to 0, 200, 400, or 600 microM H(2)O(2) for 1 h followed by an additional 7 h of incubation. Subsequently, the cells were double-labeled with markers of injury (either Ethidium Homodimer-1 for cellular injury or MitoTracker dye for functional mitochondria) or oxidant stress (5-[and 6]-chloromethyl-2',7'-dicholorodihydrofluorescein diacetate) and antibodies specific for the chemoattractants IL-8 or thioredoxin. We found significant inverse relationships between numbers and stained chemoattractant volumes of IL-8 and thioredoxin-positive cells with increasing H(2)O(2) dose. Cells with mitochondrial injury produced thioredoxin but not IL-8, and oxidant-stressed cells were more likely to produce thioredoxin than IL-8. Isolated human neutrophils were more likely to colocalize with thioredoxin-positive BEAS-2B S.6 cells than thioredoxin-negative cells. The H(2)O(2) injury did not induce significant apoptosis in the BEAS-2B S.6 cells as measured by caspase 3 activation. We conclude that oxidant-injured and stressed airway epithelial cells upregulate thioredoxin, but produce little IL-8, which may be important in airway epithelial cell-mediated multistep navigation of neutrophils to sites of oxidant injury.