Reduced eosinophil apoptosis in induced sputum correlates with asthma severity

Abstract

This study was carried out to investigate the relationship between induced sputum eosinophil apoptosis and clinical severity score, airway obstruction and symptom scores in patients with chronic stable asthma.Altogether, 41 chronic stable asthmatic subjects of varying severity defined by Aas score and 17 control subjects underwent spirometry, symptom questionnaire and successful sputum induction. Sputum was processed and cytospins prepared for light microscopy to determine normal and apoptotic eosinophils.Mild asthmatic subjects had a significantly lower percentage sputum eosinophils and a significantly higher eosinophil apoptotic ratio (AR) than moderate or chronic severe asthmatics. Severe asthmatic subjects had a significantly greater age, duration of asthma and sputum eosinophil count?mL -1 than mild asthmatic subjects. Asthmatic subjects9 symptom scores, severity scores and age inversely correlated with AR and the percentage of sputum eosinophils. Baseline forced expiratory volume in one second inversely correlated with percentage sputum eosinophils and positively correlated with AR.The study demonstrates a relationship between reduced sputum eosinophil apoptosis and increased clinical severity of chronic stable asthma, providing additional evidence that eosinophil apoptosis may be important in the resolution of eosinophilic airway inflammation in asthma. Eur Respir J 2003; 22: 484-490.

Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse eosinophils

“…Apoptosis is an important mechanism to clear accumulated eosinophils and resolve airway eosinophilic inflammation, and correlates with the clinical severity of asthma. 38 In vitro antibody cross-linking of Siglec-8 on isolated human eosinophils is known to cause apoptosis, 12 and we also observed enhanced apoptosis of mouse eosinophils by antibody cross-linking of Siglec-F in vitro. By extending our observations, we propose that extensive cross-linking of Siglec-F by its ligands induces apoptosis of eosinophils under inflammatory conditions.…”

Airway neutrophilia in COPD is not associated with increased neutrophil survival

“…Studies in asthma have shown that sputum contains fewer apoptotic eosinophils, the numbers of which correlate negatively with disease severity [20]. Further studies using the sputum fluid phase and either guinea pig [21] or human [22] eosinophils have attributed this effect to the cytokines GM-CSF and IL-5 [21] and prostaglandin E 2 [22].…”

The CDK inhibitor, R‐roscovitine, promotes eosinophil apoptosis by down‐regulation of Mcl‐1

“…Eosinophils and their products have been demonstrated within airways, in lung parenchyma, at the site of eczematous skin lesions and in nasal mucosa. Evidence of their armamentarium has also been detected at sites of allergic inflammation and it has been shown that they contribute to airway epithelial damage and remodelling in asthma [1,[4][5][6][7]. Therapeutic strategies that decrease eosinophil recruitment and activation or enhance resolution of inflammation by driving eosinophil apoptosis and clearance should ameliorate allergic inflammatory disease [1,3,8].…”