Eotaxin expression in Sephadex-induced lung injury in rats

Two-start design within a Sephadex inflammatory model--a means to generate reliable ED50 data whilst significantly reducing the number of animals used

Pulmonary inflammation disorders represent a major healthcare burden, and novel anti-inflammatory agents are critically needed for the treatment of patients unresponsive to current therapies. In vivo animal models play a key role in the preclinical assessment of novel anti-inflammatory compounds. The implementation of streamlined in vivo experimental designs that are time-and cost-efficient, while keeping animal usage low, is a key consideration for drug optimization programs. The Sephadex rat model of pulmonary inflammation captures many pathophysiologic characteristics of clinical asthma and allergy, such as eosinophilic infiltration andinterstitial edema. Using the in vivo Sephadex model, we compared two different study designs that were implemented to screen and select two novel candidate drugs for a drug discovery project. The traditional one-start design, which utilizes few dose-testing groups with many animals per group, was used to select the first candidate drug. Due to tight timelines, the selection process for the second candidate drug had to be optimized, leading to the development of the novel two-start design, an approach whereby dose ranges are optimized in two experimental phases. Here we show that both study designs were comparable in their generation of robust median effective dose values for selected candidate drugs, as represented by similar confidence interval ratios. However, implementation of the two-start design resulted in approximately 50% fewer animals and 50% less time taken to assess the efficacy of an equal number of compounds compared with the one-start design. These results demonstrate that the two-start design is a more efficient experimental approach, and its widespread implementation in drug optimization programs will impact upon the selection process for candidate drugs with regards to time, cost, and animal usage.

Effects of uridine, isomatitol and 4-thiouridine on in vitro cell adhesion and in vivo effects of 4-thiouridine in a lung inflammation model

Since leukocyte adhesion to endothelial cells is crucial for extravasation of leukocytes to sites of inflammation, inhibition of cell-cell adhesion has been suggested as a means to achieve selective modulation of the immune system. We have, using a static in vitro adhesion assay involving adhesion of granulocytes to tumor necrosis factor alpha (TNFalpha)-stimulated human umbilical vein endothelial cells (HUVEC), found three substances--uridine, isomaltitol and 4-thiouridine-that, independently and significantly, reduced leukocyte adhesion by approximately 30-65%. 4-Thiouridine was also tested in an in vivo model of Sephadex (SDX)-induced lung inflammation with Sprague-Dawley rats. Intratracheal instillation of Sephadex (5 mg/kg) alone resulted in a dramatic increase in lung edema and total leukocyte count after 24 h. A differential count of bronchoalveolar lavage (BAL) cells indicated an increased influx of macrophages, eosinophils and neutrophils. Co-administration of 4-thiouridine significantly reduced lung edema by 38%. There was also a significant reduction of the total leukocyte count by 58%. The differential leukocyte count indicated that eosinophil influx alone was reduced by 70%. After Sephadex challenge, we found elevated levels of TNFalpha--an important inflammatory mediator--in the bronchoalveolar lavage fluid (BALF). TNFalpha levels were significantly reduced by more than 80% by co-administration of 4-thoiuridine. These results suggest that uridine, isomaltitol and, especially, 4-thiouridine affect adhesion between leukocytes and activated endothelium, and warrant further in vitro and in vivo studies.

Production of granulomatous inflammation in lungs of rat pups and adults by Sephadex beads

Granulomatous inflammation is a process that involves mononuclear leukocytes as well as other inflammatory cells. The heterogeneity of its appearance may be due to the variety of cytokines and chemokines that are involved. In this study, we compared granuloma formation and bronchoalveolar leukocyte differential in the lungs of rats (2- and 8-wk-old) that were treated intravenously with Sephadex beads. In addition, the kinetics of cytokine and chemokine production was determined in these groups. In adults, the beads caused lung granulomas associated with infiltration of eosinophils and neutrophils and increased eosinophil and neutrophil counts in the bronchoalveolar lavage fluid within 16 h. In pups, the granulomas were formed slowly and did not reach the size achieved in adults. Eosinophils and neutrophils were sparsely found in the periphery of the granulomas, even at 32 h. Pups were also unable to respond rapidly to Sephadex bead treatment with eosinophil and neutrophil infiltration in the bronchoalveolar lavage fluid. Tumor necrosis factor-alpha was significantly increased in both groups, but the cytokine was lower in pups than in adults. Interferon-gamma and eotaxin were increased only in adults, and IL-4 and regulated on activation, normal T cell expressed, and secreted was increased only in pups. In conclusion, the i.v. administration of Sephadex beads produced granulomatous inflammation in the lungs of adult rats, but pups were unable to respond as rapidly to the treatment. In addition, the difference in response between the two age groups was associated with the kinetics of cytokine and chemokine production.

Vitamin A reduces lung granulomatous inflammation with eosinophilic and neutrophilic infiltration in Sephadex-treated rats

Vitamin A is known to suppress the activity of the transcription factors, nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), as do glucocorticoids. The possibility that vitamin A exerts various anti-inflammatory effects therefore seems likely. Sephadex beads were administered intravenously to anesthesized rats pretreated with a subcutaneous injection of vitamin A (3000, 10,000, or 30,000 IU/kg) or vehicle once daily for 3 days. After 16 h, the leukocyte differential, tumor necrosis factor (TNF)-alpha and eotaxin, and the DNA-binding activity of NF-kappaB were measured in bronchoalveolar lavage fluid (BALF). Additionally, lung histology was assessed using preparations stained with May-Giemsa stain. Sephadex beads caused histological granulomatous changes and eosinophilic and neutrophilic infiltration into the lung, and markedly increased cell counts of eosinophils and neutrophils, concentrations of TNF-alpha and eotaxin, and NF-kappaB binding to DNA in BALF. Vitamin A significantly inhibited all responses. Vitamin A may inhibit Sephadex-induced lung granulomatous formation, and eosinophilic and neutrophilic infiltration due to its suppression of TNF-alpha and eotaxin production, and NF-kappaB activation.

Dexamethasone reduces lung eosinophilia, and VCAM-1 and ICAM-1 expression induced by Sephadex beads in rats

Airway eosinophilia is one of the key pathophysiologic features in asthma. The endothelial adhesion molecules, vascular cell adhesion molecule (VCAM-1) and intercellular adhesion molecule (ICAM-1), have previously been shown to play a crucial role in eosinophil recruitment into the inflamed airway. We have investigated the effects of dexamethasone on eosinophilia into the bronchoalveolar lavage fluid, and the upregulation of VCAM-1 and ICAM-1 expression, measured by immunoblotting, induced by i.v. injection of Sephadex beads into rats. The beads significantly increased the lung eosinophilia, and expression of VCAM-1 and ICAM-1 in the lung. Pretreatment with dexamethasone (0.1 to 2 mg/kg i.p.) strongly inhibited all the airway inflammatory events in a dose-dependent manner. In conclusion, glucocorticoids may be potent inhibitors of lung eosinophilia, at least in part, due to the prevention of the upregulation of VCAM-1 and ICAM-1 expression.

Increased surfactant protein D in rat airway goblet and Clara cells during ovalbumin-induced allergic airway inflammation

BACKGROUND

Structural remodelling of airways in asthma that follows inflammation may be affected by surfactant protein D (SP-D)-mediated effects on the immune response.

OBJECTIVE

To determine potential sites of SP-D interaction with the pulmonary immune response, we examined the distribution of immunoreactive SP-D in an experimental model of allergen-induced airway inflammation using immunohistochemistry, biochemical methods and in situ hybridization.

METHODS

The experimental model used subcutaneous injection of ovalbumin in adult rats, which induced an airway response to inhaled nebulized ovalbumin. Three groups of rats (ovalbumin, ovalbumin + dexamethasone and saline) were challenged thrice weekly for 3 weeks. A fourth group of seven rats (naive) were taken from the same delivery of rats as the other groups. Lungs were then lavaged to determine total cell count, eosinophil count, ovalbumin-specific IgE by enzyme-linked immunosorbent assay and SP-D by immunoblot. Tissue samples were fixed and embedded, and sections were studied for the infiltration of eosinophils and for expression of SP-D protein by histochemistry and mRNA by in situ hybridization.

RESULTS

Ovalbumin induced perivascular and peribronchiolar eosinophilia which could be prevented by dexamethasone treatment. In addition, the ovalbumin-specific IgE levels in serum and bronchoalveolar lavage fluid of ovalbumin-challenged animals were enhanced. Increased amount of SP-D in lavage and tissue, particularly in type II pneumocytes, in Clara cells and, surprisingly, in hyperplastic goblet cells of inflamed lungs was found. SP-D mRNA was detected in goblet cells as well as in type II pneumocytes and Clara cells. Dexamethasone treatment did not affect level of SP-D immunoreactivity.

CONCLUSION

SP-D accumulation is increased in this model of allergen-induced eosinophilia, both in upper and lower airways. The increase is unaffected by dexamethasone.

Activated eosinophils in upper gastrointestinal tract of patients with graft-versus-host disease

Digestive tract damage during graft-versus-host reaction (GVHR) causes high morbidity and mortality. Diagnosis is often late because biopsies are performed when clinical signs are severe and pathologic markers of early inflammatory lesions are lacking. Eosinophils are inflammatory cells, cytotoxic in vitro to digestive epithelium; they are found in biopsy specimens taken during acute flare-ups of inflammatory bowel disease. We performed systematic duodenal biopsies immediately after digestive symptoms occurred and found a digestive GVHR incidence of 73.1% (n = 93), higher than that found when digestive biopsies were performed immediately after severe clinical signs. Eosinophils were only present when there were histologic signs of GVHR; eosinophil presence correlated with GVHR severity. Electron microscopy with immunogold staining showed pathologic signs of in situ eosinophil activation, such as cytoplasmic granule alterations, and eosinophil peroxidase release in all patients. Interleukin-5 presence in activated eosinophils suggests eosinophil recruitment in digestive GVHR is an autocrine mechanism. Eosinophil density also correlated with GVHR severity, whether in acute or chronic clinical phases. Tissue eosinophils could thus be a marker of acute inflammatory flare-ups in GVHR. Systematic duodenal biopsy performed at the onset of digestive symptoms should allow early GVHR detection, and pathologic signs of GVHR, together with eosinophil density, might help modulate immunosuppressive therapy.

Critical role for T cells in Sephadex-induced airway inflammation: pharmacological and immunological characterization and molecular biomarker identification

Intratracheal instillation of Sephadex particles is a convenient model for assessing the impact of potential anti-inflammatory compounds on lung eosinophilia thought to be a key feature in asthma pathophysiology. However, the underlying cellular and molecular mechanisms involved are poorly understood. We have studied the time course of Sephadex-induced lung eosinophilia, changes in pulmonary T cell numbers, and gene and protein expression as well as the immunological and pharmacological modulation of these inflammatory indices in the Sprague Dawley rat. Sephadex increased T cell numbers (including CD4(+) T cells) and evoked a pulmonary eosinophilia that was associated with an increase in gene/protein expression of the Th2-type cytokines IL-4, IL-5, and IL-13 and eotaxin in lung tissue. Sephadex instillation also induced airway hyperreactivity to acetylcholine and bradykinin. A neutralizing Ab (R73) against the alphabeta-TCR caused 54% depletion of total (CD2(+)) pulmonary T cells accompanied by a significant inhibition of IL-4, IL-13 and eotaxin gene expression together with suppression (65% inhibition) of eosinophils in lung tissue 24 h after Sephadex treatment. Sephadex-induced eosinophilia and Th2 cytokine gene and/or protein expression were sensitive to cyclosporin A and budesonide, compounds that inhibit T cell function, suggesting a pivotal role for T cells in orchestrating Sephadex-induced inflammation in this model.

Lung tissue eosinophils may be cleared through luminal entry rather than apoptosis: effects of steroid treatment

Spontaneous or steroid-induced eosinophil apoptosis occurring in vitro has not been demonstrated in lung tissues in vivo. This study examines cell apoptosis in rat lungs using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) technique and transmission electron microscopy (TEM). After establishing sustained lung edema and eosinophilia by challenge with Sephadex beads intratracheally, budesonide treatment was started intratracheally. Sephadex alone increased the total number of apoptotic cells, which were not efficiently engulfed by macrophages or other cells, in vivo. Yet apoptotic tissue eosinophils were exceedingly rare (1 of 360 TEM-analyzed eosinophils). By contrast, approximately 20% of eosinophils in the airway lumen were apoptotic, and unengulfed. Budesonide promptly inhibited edema but 3 d of steroid treatment were required to reduce the established tissue eosinophilia. Not at any time point did budesonide induce eosinophil apoptosis (0 of 318 TEM-analyzed tissue eosinophils). We conclude that (1) eosinophil apoptosis can occur but is a rare event in vivo in respiratory tract tissues; (2) airway tissue eosinophils, rather than undergoing apoptosis, are eliminated by migration into airway lumen followed by apoptosis and mucociliary clearance; (3) anti-inflammatory steroid treatment may not increase eosinophil apoptosis in vivo nor may it affect the luminal entry of eosinophils; (4) steroids permit elimination of eosinophils into airway lumen and slowly resolve established lung eosinophilia.

Regulatory effects of eotaxin on acute lung inflammatory injury

Eotaxin, which is a major mediator for eosinophil recruitment into lung, has regulatory effects on neutrophil-dependent acute inflammatory injury triggered by intrapulmonary deposition of IgG immune complexes in rats. In this model, eotaxin mRNA and protein were up-regulated during the inflammatory response, resulting in eotaxin protein expression in alveolar macrophages and in alveolar epithelial cells. Ab-induced blockade of eotaxin in vivo caused enhanced NF-kappaB activation in lung, substantial increases in bronchoalveolar lavage levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant (CINC), and increased MIP-2 and CINC mRNA expression in alveolar macrophages. In contrast, TNF-alpha levels were unaffected, and IL-10 levels fell. Under these experimental conditions, lung neutrophil accumulation was significantly increased, and vascular injury, as reflected by extravascular leak of (125)I-albumin, was enhanced. Conversely, when recombinant eotaxin was administered in the same inflammatory model of lung injury, bronchoalveolar lavage levels of MIP-2 were reduced, as was neutrophil accumulation and the intensity of lung injury. In vitro stimulation of rat alveolar macrophages with IgG immune complexes greatly increased expression of mRNA and protein for MIP-2, CINC, MIP-1alpha, MIP-1beta, TNF-alpha, and IL-1beta. In the copresence of eotaxin, the increased levels of MIP-2 and CINC mRNAs were markedly diminished, whereas MIP-1alpha, MIP-1beta, TNF-alpha, and IL-1beta expression of mRNA and protein was not affected. These data suggest that endogenous eotaxin, which is expressed during the acute lung inflammatory response, plays a regulatory role in neutrophil recruitment into lung and the ensuing inflammatory damage.