In vivo effects of endotoxin on DNA synthesis in rat nasal epithelium

Lifetime occupational exposure to dusts, gases and fumes is associated with bronchitis symptoms and higher diffusion capacity in COPD patients

BACKGROUND

Occupational exposure to dusts, gases and fumes has been associated with reduced FEV1 and sputum production in COPD patients. The effect of occupational exposure on other characteristics of COPD, especially those reflecting emphysema, has not been studied in these patients.

METHODS

We studied 338 patients hospitalized for a first exacerbation of COPD in 9 Spanish hospitals, obtaining full occupational history in a face-to-face interview; job codes were linked to a job exposure matrix for semi-quantitative estimation of exposure to mineral/biological dust, and gases/fumes for each job held. Patients underwent spirometry, diffusing capacity testing and analysis of gases in stable conditions. Quality of life, dyspnea and chronic bronchitis symptoms were determined with a questionnaire interview. A high- resolution CT scan was available in 133 patients.

RESULTS

94% of the patients included were men, with a mean age of 68(8.5) years and a mean FEV1% predicted 52 (16). High exposure to gases or fumes was associated with chronic bronchitis, and exposure to mineral dust and gases/fumes was associated with higher scores for symptom perception in the St. George's questionnaire. No occupational agent was associated with a lower FEV1. High exposure to all occupational agents was associated with better lung diffusion capacity, in long-term quitters. In the subgroup with CT data, patients with emphysema had 18% lower DLCO compared to those without emphysema.

CONCLUSIONS

In our cohort of COPD patients, high exposure to gases or fumes was associated with chronic bronchitis, and high exposure to all occupational agents was consistently associated with better diffusion capacity in long-term quitters.

DNA synthesis and Bcl-2 expression during development of mucous cell metaplasia in airway epithelium of rats exposed to LPS

Exposure of pulmonary airways to environmental toxins and allergens may cause proliferation of airway epithelial cells and mucous cell metaplasia (MCM); however, it is unclear to what extent proliferating cells differentiate into mucus-storing cells and contribute to MCM. Our previous studies demonstrated that Bcl-2, an inhibitor of apoptosis with cell cycle regulatory functions, is expressed in metaplastic mucous cells. The purpose of the present study was to investigate the number of metaplastic mucous cells that are derived from proliferating epithelial cells and whether Bcl-2 has a role in cell cycle entry in these cells. Rats were intratracheally instilled with 100 microg of LPS from Pseudomonas aeruginosa in 500 microl of saline, and proliferating airway cells were labeled with bromodeoxyuridine (BrdU) by implanting a subcutaneous osmotic pump 24 h before instillation. The volume of stored mucosubstance and the number of mucous cells were increased 10- and 3-fold, respectively, from 24-48 h after instillation. The number of total epithelial cells per millimeter of basal lamina increased, and the number of serous cells per millimeter of basal lamina decreased during this time. Approximately 50% of Alcian blue-periodic acid Schiff-stained mucous cells were labeled with BrdU at 48 h after instillation, suggesting that one-half of the secretory cells were derived from proliferating cells. Furthermore, 50% of the Bcl-2-positive mucous cells were BrdU negative and therefore derived from nonproliferating, preexisting cells. Our findings demonstrate that preexisting and proliferating cells differentiate into mucous cells and compose LPS-induced metaplasia and that Bcl-2 does not have cell cycle regulatory function in these cells.

LPS-induced neutrophilic inflammation and Bcl-2 expression in metaplastic mucous cells

Our previous studies show that Bcl-2, a regulator of apoptosis, may be involved in the reduction of mucous cell metaplasia (MCM) during recovery from inflammatory responses. The present study was to determine whether neutrophilic inflammation mediates Bcl-2 expression in mucous cells. Rats were intratracheally instilled with 50-1000 microg of LPS. The number of neutrophils recovered by bronchoalveolar lavage (BAL) increased with the dose of LPS, and the percentage of Bcl-2-expressing cells increased with the numbers of neutrophils in the BAL. Depletion of neutrophils did not reduce MCM, but the percentage of Bcl-2-positive cells increased 1.8-fold in neutrophil-depleted compared with controls. Injection of rats with bezafibrate, an inducer of cytochrome P-450, doubled the number of neutrophils in the BAL, decreased MCM twofold compared with vehicle-injected controls, and reduced Bcl-2 expression. Bcl-2 mRNA levels decreased in a tracheal epithelial cell line treated with bezafibrate. These data demonstrate that Bcl-2 expression is independent of the number of neutrophils in the BAL and that bezafibrate may directly reduce Bcl-2 expression in epithelial cells.

Seroprevalence of antibodies specific for gram-negative core antigens in chickens on the basis of an Escherichia coli J5 enzyme-linked immunosorbent assay

Antibodies directed toward gram-negative core antigens (GNCAs) have been demonstrated in many mammalian species but to date are unexamined in any avian species. An enzyme-linked immunosorbent assay with phenol-killed whole cell Escherichia coli J5 was used to assess the presence of serum antibodies directed toward GNCAs in chickens. The first experiment consisted of collecting blood samples from randomly selected hens at egg laying ranches in northern California. The ages ranged from several days of age to 77 wk of age. Birds were classified into age groups (hatchling [1 day-4 wk], pullet [4-18 wk], pullet cycle [18-60 wk], and postmolt [>60 wk]) and husbandry style for titer comparison. The geometric mean titer (GMT) for all adult hens regardless of age was 2147. The geometric mean titers were 220, 5691, 2304, and 1776 for hatchlings, pullets, pullet cycle hens, and postmolt hens, respectively. The age group titer trends were similar to those of humans rather than those of farm animals in that the highest titers occurred during "adolescence" (pullets) and titers decreased slightly with maturity. The GMTs were 2870 for hens housed intensively and 1872 for those housed extensively. The second experiment looked at the progression of GNCA titers within individual birds over a 1-yr period. Individual titers increased slightly throughout the study time of the second experiment.

Bcl-2 in LPS- and allergen-induced hyperplastic mucous cells in airway epithelia of Brown Norway rats

Environmental toxins, infection, and allergens lead to a transient mucous cell hyperplasia (MCH) in airway epithelia; however, the mechanisms for reducing mucous cell numbers during recovery are largely unknown. This study investigated Bcl-2 expression in mucous cells induced by a neutrophilic or eosinophilic inflammatory response. Brown Norway rats intratracheally instilled with lipopolysaccharide (LPS) showed an inflammatory response characterized primarily by neutrophils. Secreted mucin was increased fourfold at 1 day, and the number of mucous cells was increased fivefold 2, 3, and 4 days post-LPS instillation compared with those in noninstilled rats. None of the mucous cells in non- or saline-instilled control animals expressed Bcl-2, whereas 20-30% of mucous cells were Bcl-2 positive 1 and 2 days post-LPS instillation. Brown Norway rats immunized and challenged with ovalbumin (OVA) for 2, 4, and 6 days showed an inflammatory response characterized primarily by eosinophils. Secreted mucin increased fivefold, and mucous cell number increased fivefold after 4 and 6 days of OVA exposure compared with water-immunized control rats challenged with OVA aerosols. Approximately 10-25% of mucous cells were Bcl-2 positive in OVA-immunized and -challenged rats. These data demonstrate Bcl-2 expression in hyperplastic mucous cells of Brown Norway rats regardless of the type of inflammatory response and indicate that apoptotic mechanisms may be involved in the resolution of MCHs.

Effects of pre-existing rhinitis on ozone-induced mucous cell metaplasia in rat nasal epithelium

Ozone causes rhinitis and nasal epithelial alterations. The toxicity of ozone on nasal airways with pre-existing rhinitis has not been investigated. The present study was designed to determine the effect of endotoxin-induced rhinitis on ozone-induced epithelial alterations, especially mucous cell metaplasia (MCM), in the nasal transitional epithelium (NTE) of rats. Six h prior to daily inhalation exposure, male F344/N rats were intranasally instilled with saline or endotoxin (100 microgram/day). Rats were killed 2 h or 4 days after 3-day (8 h/day) exposure to ozone (0.5 ppm) or filtered air (0 ppm). The maxilloturbinate from one nasal passage was processed for morphometric analyses of the numbers of neutrophils and epithelial cells and the amount of intraepithelial mucosubstances (IM) in the NTE. The maxilloturbinate from the other nasal passage was processed for a mucin-specific (rMuc-5AC) mRNA analysis. At 2 h postexposure, endotoxin/ozone-exposed rats had 48 and 3 times more neutrophils in the NTE than did saline/air- and saline/ozone-exposed rats, respectively. Ozone-exposed rats had 35% more NTE cells and 2-fold more mucin mRNA than did saline/air-exposed rats, independent of endotoxin exposure. At 4 days postexposure, endotoxin/ozone-exposed rats had 5 and 2 times more IM and mucous cells, respectively, than did saline/air- and saline/ozone-exposed rats. Though endotoxin/air-exposed rats killed at 2 h postexposure had more neutrophils (40-fold), epithelial cells (27%) and mucin mRNA (2-fold) in the NTE than did saline/air-exposed rats, no MCM was present in those rats killed at 4 days postexposure. The results of the present study indicated that pre-existing rhinitis augments ozone-induced MCM.

In vitro culture of microdissected rat nasal airway tissues

The surface epithelium lining the nasal airways is a potential target for inhaled contaminants such as ozone, endotoxin, formaldehyde, tobacco smoke, and organic dusts. The epithelial response to injury may depend on the toxicant, the type of epithelium, the severity of the injury, and the presence of inflammatory cells and their secreted products. To study mechanisms of toxicant-induced epithelial injury and repair, in the absence of cellular inflammation or other systemic effects, we have developed a culture system to maintain morphologically distinct nasal airway epithelium in vitro. Microdissected maxilloturbinates and proximal nasal septa of male F344/N rats were cultured at an air-liquid interface for up to 14 d in supplemented serum-free medium. Maxilloturbinates are lined by nonciliated cuboidal nasal transitional epithelium (NTE) with few or no mucous cells. The proximal nasal septum is lined by a mucociliary respiratory epithelium (RE) that normally contains numerous mucous cells. Preservation of the normal RE and NTE phenotype in culture was assessed by light and electron microscopy, and analysis of an airway mucin gene (rMuc-5AC) messenger RNA (mRNA). Both RE and NTE retained normal cell morphology for 14 d in culture (DIC). After 14 DIC there were 20% fewer RE cells in the septa (equal loss of ciliated and mucous cells) and 25% more NTE cells in the maxilloturbinates (increased number of basal cells). Compared with the RE, the NTE expressed consistently low levels of rMuc-5AC mRNA and had little to no histochemically detectable intraepithelial mucosubstances (IM) after 0, 3, 7, or 14 DIC. The amount of stored IM and the steady-state levels of rMuc-5AC mRNA in the RE decreased with time in culture. In summary, this culture system can maintain fully differentiated secretory and nonsecretory rat airway epithelia in vitro for up to 14 d. This study was an essential first step in developing a system to study the pathogenesis of toxicant-induced airway epithelial injury and mechanisms of cellular repair and adaptation in the absence of cellular inflammation and other systemic influences.

Clarithromycin suppresses proliferation of rat nasal epithelium exposed to endotoxin

A study was performed to elucidate the action of long-term macrolide therapy in chronic sinusitis. Clarithromycin (CAM) was administered orally once daily for 14 days. On the last 3 days, an endotoxin, lipopolysaccharide (LPS) was instilled intranasally. The extent of DNA synthesis acceleration was studied in both controls and pretreated animals by counting the number of 5-bromo-2'-deoxyuridine (BrdU)-labeled cells in the nasal transitional epithelium. Six hours after the final intranasal instillation of LPS, the number of BrdU-positive cells was significantly higher than control. Pretreatment with CAM for 2 weeks significantly inhibited this increase. Because similar results were obtained in neutrophil-depleted rats, LPS apparently promotes proliferation of the nasal epithelium in the absence of neutrophils: CAM-suppressed epithelial proliferation independently of the neutrophil count. Our results suggest that CAM inhibits LPS-induced increased rates of DNA synthesis by directly affecting the nasal epithelium. The mechanism by which macrolide therapy alleviates the signs and symptoms of chronic sinusitis might therefore involve suppression of inflammatory processes in the nasal and paranasal sinus epithelium.

Hypoxia-induced exocytosis of endothelial cell Weibel-Palade bodies. A mechanism for rapid neutrophil recruitment after cardiac preservation

The period of hypoxia is an important priming event for the vascular dysfunction that accompanies reperfusion, with endothelial cells (ECs) and neutrophils (PMNs) playing a central role. We hypothesized that EC Weibel-Palade (WP) body exocytosis during the hypoxic/ischemic period during organ preservation permits brisk PMN recruitment into postischemic tissue, a process further amplified in an oxidant-rich milieu. Exposure of human umbilical vein ECs to a hypoxic environment (pO2 approximately 20 torr) stimulated release of von Willebrand factor (vWF), stored in EC WP bodies, as well as increased expression of the WP body-derived PMN adhesion molecule P-selectin at the EC surface. Increased binding of 111In-labeled PMNs to hypoxic EC monolayers (compared with normoxic controls) was blocked with a blocking antibody to P-selectin, but was not affected by a nonblocking control antibody. Although increased P-selectin expression and vWF release were also noted during reoxygenation, hypoxia alone (even in the presence of antioxidants) was sufficient to increase WP body exocytosis. To determine the relevance of these observations to hypothermic cardiac preservation, during which the pO2 within the cardiac vasculature declines to similarly low levels, experiments were performed in a rodent (rat and mouse) cardiac preservation/transplantation model. Immunodepletion of recipient PMNs or administration of a blocking anti-P-selectin antibody before transplantation resulted in reduced graft neutrophil infiltration and improved graft survival, compared with identically preserved hearts transplanted into control recipients. To establish the important role of endothelial P-selectin expression on the donor vasculature, murine cardiac transplants were performed using homozygous P-selectin deficient and wild-type control donor hearts flushed free of blood/platelets before preservation/transplantation. P-selectin-null hearts transplanted into wild-type recipients demonstrated a marked (13-fold) reduction in graft neutrophil infiltration and increased graft survival compared with wild-type hearts transplanted into wild-type recipients. To determine whether coronary endothelial WP exocytosis may occur during cardiac preservation in humans, the release of vWF into the coronary sinus (CS) was measured in 32 patients during open heart surgery. CS samples obtained at the start and conclusion of the ischemic period demonstrated an increase in CS vWF antigen (by ELISA) consisting of predominantly high molecular weight multimers (by immunoelectrophoresis). These data suggest that EC WP exocytosis occurs during hypothermic cardiac preservation, priming the vasculature to recruit PMNs rapidly during reperfusion.