Search PubMed⌕ Search

Biomedical subjects

L Uller

Publications and source records attributed to L Uller.

7 recordsLinked to original sources
PubMed2006

Direct evidence of secondary necrosis of neutrophils during intense lung inflammation.

Several pulmonary inflammatory conditions are characterised by infiltration of neutrophils. Normally, neutrophils are silently removed by apoptosis, followed by phagocytosis. However, if phagocytosis fails, apoptotic cells undergo secondary necrosis. Recent findings of increased levels of the pan-necrosis marker lactate dehydrogenase in bronchoalveolar lavage from lipopolysaccharide-exposed mice implies potential involvement of secondary necrosis. Using a similar model, this study aimed to identify the source of lactate dehydrogenase and to search for direct histological evidence of secondary necrosis. Lipopolysaccharide (LPS) was administered to the lungs of BALB/c mice, and bronchoalveolar lavage and tissue samples were collected 4, 12, 24, 36, 48, 60 and 72 h after administration. LPS induced a patchy neutrophil-rich lung inflammation, where the numbers of terminal deoxynucleotide transferase-mediated dUTP nick-end labelling-positive neutrophils were increased at 12 h and onwards. Lavage levels of neutrophils and lactate dehydrogenase increased significantly at 4 and 24 h, respectively. Detailed electron microscopic assessment of neutrophil activation and death modes revealed that up to 14% of the neutrophils were undergoing secondary necrosis, whereas apoptotic or primary necrotic structural cells were rarely found. In summary, this study provides direct evidence that secondary necrosis of neutrophils is a common process during intense lung inflammation. This implies that neutrophil apoptosis may cause rather than resolve airway inflammation.

Animals↗
PubMed2006

Effects of steroid treatment on lung CC chemokines, apoptosis and transepithelial cell clearance during development and resolution of allergic airway inflammation.

BACKGROUND: Steroid treatment of allergic eosinophilic airway diseases is considered to attenuate cell recruitment by inhibiting several chemokines and to cause eosinophil clearance through inducement of apoptosis of these cells. However, roles of these mechanisms in the actions of steroids in vivo have not been fully established. Also, as regards clearance of tissue eosinophils other mechanisms than apoptosis may operate in vivo. OBJECTIVE: This study explores anti-inflammatory effects of steroids instituted during either development or resolution of airway allergic inflammation. METHODS: Immunized mice were subjected to week-long daily allergen challenges (ovalbumin). Steroid treatment was instituted either amidst the challenges or exclusively post-allergen challenge. CC chemokines, goblet cell hyperplasia, occurrence of eosinophil apoptosis, and airway tissue as well as lumen eosinophilia were examined at different time-points. RESULTS: Daily steroids instituted amid the allergen challenges non-selectively attenuated a range of chemokines, permitted egression of tissue eosinophils into airway lumen to increase, and reduced development of lung tissue eosinophilia. Steroid treatment instituted post-challenge selectively inhibited the CC-chemokine regulation upon activation, normal T cell expressed and secrted (RANTES), permitted continued egression of eosinophils into airway lumen, and resolved the tissue eosinophilia. Eosinophil apoptosis rarely occurred at development and resolution of the allergic eosinophilic inflammation whether the animals were steroid treated or not. However, anti-Fas monoclonal antibodies given to mice with established eosinophilia post-challenge produced apoptosis of the tissue eosinophils indicating that apoptotic eosinophils, if they occur, are well detectible in vivo. CONCLUSION: Airway tissue eosinophils are likely eliminated through egression into airway lumen with little involvement of apoptosis and phagocytosis. Our data further suggest that therapeutic steroids may resolve airway inflammation by permitting clearance of tissue eosinophils through egression and inhibiting RANTES-dependent cell recruitment to lung tissues.

Allergens↗
PubMed2005

Blockade of CTLA-4 promotes airway inflammation in naive mice exposed to aerosolized allergen but fails to prevent inhalation tolerance.

In subjects not developing allergy, inhalation of nonpathogenic protein antigens causes no harm and is associated with tolerance induction. Repeated exposure to aerosolized ovalbumin (OVA) likewise does not evoke airway inflammation and induces inhalation tolerance in experimental animals. The present study explored the role of the inhibitory T-cell receptor CTLA-4, in preventing inflammation and in establishing inhalation tolerance in response to a protein antigen. Naive BALB/c mice were injected intraperitoneally with anti-CTLA-4 monoclonal antibody or control immunoglobulin G (IgG) and exposed daily to aerosolized saline or OVA over 10 or 20 consecutive days. OVA-specific IgE levels and the inflammatory response in airway tissues were assessed 2 days after last exposure. The OVA-specific IgE response was also evaluated in mice subjected to a subsequent immunogenic OVA challenge 18 days after last aerosol exposure. Additional mice were made tolerant by 10 days of OVA aerosol exposure and were then subjected to an immunogenic OVA challenge combined with CTLA-4 blockade or control IgG treatment. Repeated inhalation of aerosolized OVA alone did not cause a pulmonary inflammatory response. In contrast, 10 days of OVA exposure combined with blockade of CTLA-4 led to development of eosinophilic lung infiltrates, BAL fluid eosinophilia, goblet cell hyperplasia and increased OVA-specific IgE. By 20 days of OVA exposure and blockade of CTLA-4, the inflammatory response remained. Mice exposed to aerosolized OVA for 10 days exhibited greatly reduced OVA-specific IgE responses to subsequent immunogenic OVA challenge. Blockade of CTLA-4 during the period of OVA aerosol exposure did not prevent this suppression of the OVA-specific IgE response. Neither did blockade of CTLA-4 during immunogenic OVA challenge alter the allergen-specific IgE response. Our results indicate that in vivo blockade of CTLA-4 modulates the initial immune response to a protein antigen allowing the development of allergen-induced airway inflammation in naive mice. However, this initial exaggerated immune response is followed by the induction of inhalation tolerance, demonstrating that CTLA-4 signalling is not decisive in this process. Our findings also show that once inhalation tolerance is established it may not be disrupted by blockade of CTLA-4.

Aerosols↗
PubMed2004

Rapid and efficient clearance of airway tissue granulocytes through transepithelial migration.

BACKGROUND: Clearance of tissue granulocytes is central to the resolution of airway inflammation. To date the focus has been on apoptotic mechanisms of cell removal and little attention has been given to alternative processes. The present study explores transepithelial migration as a mechanism of cell clearance. METHOD: Guinea pig tracheobronchial airways where eosinophils are constitutively present in the mucosal tissue were studied. A complex topical stimulus (allergen challenge) was applied and the fate of the eosinophils was determined by selective tracheobronchial lavage and histological examination of the tissue. RESULTS: Within 10 minutes of the allergen challenge, massive migration of eosinophils into the airway lumen occurred together with a reduction in tissue eosinophil numbers. Cell clearance into the lumen continued at high speed and by 30 and 60 minutes the tissue eosinophilia had been reduced by 63% and 73%, respectively. The marked transepithelial migration (estimated maximal speed 35,000 cells/min x cm2 mucosal surface) took place ubiquitously between epithelial cells without affecting epithelial integrity as assessed by transmission and scanning electron microscopy. Eosinophil apoptosis was not detected but occasional cytolytic eosinophils occurred. CONCLUSION: This study shows that luminal entry has a remarkably high capacity as a granulocyte elimination process. The data also suggest that an appropriate stimulus of transepithelial migration may be used therapeutically to increase the resolution of inflammatory conditions of airway tissues.

Allergens↗
PubMed2001

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.

Animals↗
PubMed2000

Role of macrophage migration inhibitory factor (MIF) in allergic and endotoxin-induced airway inflammation in mice.

Macrophage migration inhibitory factor (MIF) has recently been forwarded as a critical regulator of inflammatory conditions, and it has been hypothesized that MIF may have a role in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). Hence, we examined effects of MIF immunoneutralization on the development of allergen-induced eosinophilic inflammation as well as on lipopolysaccharide (LPS)-induced neutrophilic inflammation in lungs of mice. Anti-MIF serum validated with respect to MIF neutralizing capacity or normal rabbit serum (NRS) was administered i.p. repeatedly during allergen aerosol exposure of ovalbumin (OVA)-immunized mice in an established model of allergic asthma, or once before instillation of a minimal dose of LPS into the airways of mice, a tentative model of COPD. Anti-MIF treatment did not affect the induced lung tissue eosinophilia or the cellular composition of bronchoalveolar lavage fluid (BALF) in the asthma model. Likewise, anti-MIF treatment did not affect the LPS-induced neutrophilia in lung tissue, BALF, or blood, nor did it reduce BALF levels of tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-1alpha (MIP-1alpha). The present data suggest that MIF is not critically important for allergen-induced eosinophilic, and LPS-induced neutrophilic responses in lungs of mice. These findings do not support a role of MIF inhibition in the treatment of inflammatory respiratory diseases.

Animals↗