Pinja Ilmarinen

Eosinophil apoptosis as a therapeutic target in allergic asthma.

Asthma is a chronic inflammatory disease of the airways manifesting in many different phenotypes. Allergic asthma, comprising approximately half of patients with asthma, is characterized by the accumulation of eosinophils into the lungs. Eosinophils release factors that damage the surrounding cells and participate in the maintenance and exacerbation of inflammation. In the absence of any inflammatory survival-prolonging factors, eosinophils die by apoptosis in few days but in inflamed airways, eosinophil survival is thought to be prolonged due to the surrounding pro-inflammatory factors such as IL-5, IL-3 and GM-CSF. Resolution of eosinophilic inflammation is an important goal in the treatment of allergic asthma. Apoptosis is a physiological and non-inflammatory way to eliminate these harmful cells, and development of drugs targeting eosinophil apoptosis is one possible strategy for the therapy of allergic asthma. Importance of this strategy is supported by the fact that promotion of eosinophil apoptosis is a property of many anti-asthmatic agents such as glucocorticoids, the current main anti-inflammatory therapy of asthma, theophylline and leukotriene modifiers. β2 agonists have been shown to modulate eosinophil longevity by increasing survival. Also, anti-IL-5 antibody mesolizumab has shown efficacy in reducing asthma exacerbations in patients with severe eosinophilic asthma. Many potential future anti-asthmatic agents, such as Siglec-8 activating antibody and novel humanized anti-IL-5 antibody MEDI-563, have the property of inducing eosinophil apoptosis. This MiniReview aims to present eosinophil apoptosis as a therapeutic target in the treatment of allergic asthma. We summarize the effects and mechanisms of current and potential future anti-asthmatic drugs on eosinophil apoptosis and additionally, discuss the potential factors that promote eosinophil longevity in the lungs.

Phenotypes, Risk Factors, and Mechanisms of Adult-Onset Asthma

Asthma is a heterogeneous disease with many phenotypes, and age at disease onset is an important factor in separating the phenotypes. Genetic factors, atopy, and early respiratory tract infections are well-recognized factors predisposing to childhood-onset asthma. Adult-onset asthma is more often associated with obesity, smoking, depression, or other life-style or environmental factors, even though genetic factors and respiratory tract infections may also play a role in adult-onset disease. Adult-onset asthma is characterized by absence of atopy and is often severe requiring treatment with high dose of inhaled and/or oral steroids. Variety of risk factors and nonatopic nature of adult-onset disease suggest that variety of mechanisms is involved in the disease pathogenesis and that these mechanisms differ from the pathobiology of childhood-onset asthma with prevailing Th2 airway inflammation. Recognition of the mechanisms and mediators that drive the adult-onset disease helps to develop novel strategies for the treatment. The aim of this review was to summarize the current knowledge on the pathogenesis of adult-onset asthma and to concentrate on the mechanisms and mediators involved in establishing adult-onset asthma in response to specific risk factors. We also discuss the involvement of these mechanisms in the currently recognized phenotypes of adult-onset asthma.

Tumour Necrosis Factor-α Regulates Human Eosinophil Apoptosis via Ligation of TNF-Receptor 1 and Balance between NF-κB and AP-1

Eosinophils play a central role in asthma. The present study was performed to investigate the effect of tumour necrosis factor-α (TNF-α) on longevity of isolated human eosinophils. In contrast to Fas, TNF-α inhibited eosinophil apoptosis as evidenced by a combination of flow cytometry, DNA fragmentation assay and morphological analyses. The effect of TNF-α on eosinophil apoptosis was reversed by a TNF-α neutralising antibody. The anti-apoptotic effect of TNF-α was not due to autocrine release of known survival-prolonging cytokines interleukins 3 and 5 or granulocyte-macrophage-colony-stimulating factor as their neutralisation did not affect the effect of TNF-α. The anti-apoptotic signal was mediated mainly by the TNF-receptor 1. TNF-α induced phosphorylation and degradation of IκB and an increase in NF-κB DNA-binding activity. The survival-prolonging effect of TNF-α was reversed by inhibitors of NF-κB pyrrolidinedithiocarbamate and gliotoxin and by an inhibitor of IκB kinase, BMS-345541. TNF-α induced also an increase in AP-1 DNA-binding activity and the antiapoptotic effect of TNF-α was potentiated by inhibitors of AP-1, SR 11302 and tanshinone IIA and by an inhibitor of c-jun-N-terminal kinase, SP600125, which is an upstream kinase activating AP-1. Our results thus suggest that TNF-α delays human eosinophil apoptosis via TNF-receptor 1 and the resulting changes in longevity depend on yin-yang balance between activation of NF-κB and AP-1.

Antieosinophilic activity of orazipone.

Orazipone is a novel sulfhydryl-reactive compound that has been previously shown to reduce lung eosinophilia in guinea pigs and rats and to inhibit degranulation in mast cells and cytokine production in monocytes and T-cells. However, the effects of orazipone on granulocyte longevity are unknown. Orazipone and its derivative 3-(4-chloro-3-nitro-benzylidene)-pentane-2,4-dione (OR-2370) reversed interleukin-5-afforded survival of human eosinophils by inducing apoptosis. In contrast, orazipone did not affect granulocyte macrophage-colony-stimulating factor-induced survival of human neutrophils. The effect of orazipone on eosinophil apoptosis is different from that of glucocorticoids in that even high con-centrations of interleukin-5 were not able to overcome the effect of orazipone. Orazipone further enhanced spontaneous apoptosis as well as that induced by CD95 ligation without inducing primary necrosis. OR-2370-induced DNA fragmentation was shown to be dependent on caspases 3 and 6 and c-jun-N-terminal kinase, whereas extracellular regulated kinase, p38 mitogen-activated protein kinase, and phosphatidylinositol 3-kinase as well as caspases 4, 8, and 9 seem not to mediate its actions. Our results suggest that orazipone and its derivative OR-2370 possess strong antieosinophilic activity and thus may have anti-inflammatory efficacy in the treatment of asthma and/or allergic conditions.

Emerging Comorbidities in Adult Asthma: Risks, Clinical Associations, and Mechanisms

Asthma is a heterogeneous disease with many phenotypes, and age at disease onset is an important factor in separating the phenotypes. Most studies with asthma have been performed in patients being otherwise healthy. However, in real life, comorbid diseases are very common in adult patients. We review here the emerging comorbid conditions to asthma such as obesity, metabolic syndrome, diabetes mellitus type 2 (DM2), and cardiac and psychiatric diseases. Their role as risk factors for incident asthma and whether they affect clinical asthma are evaluated. Obesity, independently or as a part of metabolic syndrome, DM2, and depression are risk factors for incident asthma. In contrast, the effects of comorbidities on clinical asthma are less well-known and mostly studies are lacking. Cross-sectional studies in obese asthmatics suggest that they may have less well controlled asthma and worse lung function. However, no long-term clinical follow-up studies with these comorbidities and asthma were identified. These emerging comorbidities often occur in the same multimorbid adult patient and may have in common metabolic pathways and inflammatory or other alterations such as early life exposures, systemic inflammation, inflammasome, adipokines, hyperglycemia, hyperinsulinemia, lung mechanics, mitochondrial dysfunction, disturbed nitric oxide metabolism, and leukotrienes.

Bacterial DNA delays human eosinophil apoptosis

Oligodeoxynucleotide (ODN) sequences containing unmethylated cytidine phosphate guanosine (CpG) motifs prevalent in bacterial DNA attenuate allergic lung inflammation in experimental models of asthma but failed to inhibit eosinophilia and improve lung function in patients with asthma. Bacterial respiratory tract infections exacerbate asthma in humans. Increased eosinophil survival is a critical factor leading to persistent eosinophilic airway inflammation. Apoptosis is regarded as a key mechanism in the resolution of eosinophilic inflammation. The aim of this study was to investigate the effects of bacterial DNA and CpG ODNs on human eosinophil apoptosis in vitro and to elucidate the signalling pathway. Eosinophils were isolated from human peripheral blood by CD16- or CD16-, CD19- and CD304-negative selection. Apoptosis was determined by flow cytometric analysis of relative DNA content, Annexin-V staining and/or morphological analysis. Toll-like receptor 9 (TLR9) expression was studied by using western blotting and intracellular flow cytometry. Bacterial DNA and phosphorothioate-modified CpG ODNs, but not vertebrate DNA, were found to delay spontaneous eosinophil apoptosis. The effect of CpG ODNs was dependent on endosomal acidification and reversed by inhibitory ODN, which suggests involvement of TLR9 pathway. Furthermore, we demonstrated TLR9 expression in eosinophils derived from both atopic and healthy donors. Non-CpG ODNs had occasionally parallel but less profound effect on eosinophil apoptosis, which was not dependent on endosomal acidification. The anti-apoptotic effect of CpG ODNs was dependent on phosphatidylinositol 3-kinase (PI3K) and nuclear factor-kappaB (NF-kappaB) but not mitogen-activated protein kinases (MAPKs) as determined by inhibitor studies. Although our results suggest CpG-dependent involvement of TLR9 in the action of phosphorothioate-modified ODNs, we interestingly found that the anti-apoptotic action of native bacterial DNA in eosinophils is not dependent on unmethylated CpG motifs. This suggests that bacterial DNA contains a currently unknown recognition structure lacking from vertebrate DNA. Bacterial DNA-mediated suppression of eosinophil apoptosis is a novel mechanism for exacerbation of eosinophilic lung inflammation associated with bacterial respiratory tract infection.

The effect of smoking on lung function: a clinical study of adult-onset asthma.

The aim of this study was to evaluate the effect of smoking on lung function decline in adult-onset asthma in a clinical, 12-year follow-up study. In the Seinäjoki Adult Asthma Study, 203 patients were followed for 12 years (1999–2013) after diagnosis of new-onset adult asthma. Patients were divided into two groups based on smoking history: <10 or ≥10 pack-years. Spirometry evaluation points were: 1) baseline, 2) the maximum lung function during the first 2.5 years after diagnosis (Max0–2.5) and 3) after 12 years of follow-up. Between Max0–2.5 and follow-up, the median annual decline in absolute forced expiratory volume in 1 s (FEV1) was 36 mL in the group of patients with <10 pack-years of smoking and 54 mL in those with smoking history ≥10 pack-years (p=0.003). The annual declines in FEV1 % pred (p=0.006), forced vital capacity (FVC) (p=0.035) and FEV1/FVC (p=0.045) were also accelerated in the group of patients with ≥10 pack-years smoked. In multivariate regression analysis, smoking history ≥10 pack-years became a significant predictor of accelerated decline in FEV1. Among patients with clinically defined adult-onset asthma, smoking history ≥10 pack-years is associated with accelerated loss of lung function. In adult-onset asthma, smoking history ≥10 pack-years is associated with accelerated loss of lung function http://ow.ly/zZep302fJob

Mitochondria in the Center of Human Eosinophil Apoptosis and Survival

Eosinophils are abundantly present in most phenotypes of asthma and they contribute to the maintenance and exacerbations of the disease. Regulators of eosinophil longevity play critical roles in determining whether eosinophils accumulate into the airways of asthmatics. Several cytokines enhance eosinophil survival promoting eosinophilic airway inflammation while for example glucocorticoids, the most important anti-inflammatory drugs used to treat asthma, promote the intrinsic pathway of eosinophil apoptosis and by this mechanism contribute to the resolution of eosinophilic airway inflammation. Mitochondria seem to play central roles in both intrinsic mitochondrion-centered and extrinsic receptor-mediated pathways of apoptosis in eosinophils. Mitochondria may also be important for survival signalling. In addition to glucocorticoids, another important agent that regulates human eosinophil longevity via mitochondrial route is nitric oxide, which is present in increased amounts in the airways of asthmatics. Nitric oxide seems to be able to trigger both survival and apoptosis in eosinophils. This review discusses the current evidence of the mechanisms of induced eosinophil apoptosis and survival focusing on the role of mitochondria and clinically relevant stimulants, such as glucocorticoids and nitric oxide.

A 12-year prognosis of adult-onset asthma: Seinäjoki Adult Asthma Study

RATIONALE Long-term prognosis of adult-onset asthma is poorly known. OBJECTIVE To evaluate 12-year prognosis of adult-onset asthma and the factors associated with disease prognosis. METHODS Seinäjoki Adult-onset Asthma Study (SAAS) is a 12-year real-life single-center follow-up study of new-onset asthma diagnosed at adult age and treated in primary and specialized care. Remission was defined by no symptoms and no asthma medication use for 6 months. Asthma control was evaluated according to Global Initiative for Asthma 2010. Factors associated with current asthma control were analyzed by multinomial multivariate logistic regression. MAIN RESULTS A total of 203 patients (79% of the baseline population) were followed for 12 years. Remission occurred in 6 (3%) patients. In 34% asthma was controlled, in 36% it was partially controlled and in 30% uncontrolled. Uncontrolled asthma was predicted by elevated body-mass index at baseline, smoking (pack-years) and current allergic or persistent rhinitis. Elevated blood eosinophils and good lung function (FEV1) at baseline protected from uncontrolled asthma. In contrast, gender, age at the onset or baseline symptoms (Airways Questionnaire 20) were not significant predictors of uncontrolled disease. CONCLUSIONS During a 12-year follow-up, remission of adult-onset asthma was rare occurring in only 3% of patients. The majority of patients (66%) presented either with uncontrolled or partially controlled asthma. This study is registered at ClinicalTrials.gov with identifier number NCT02733016.

Comorbidities and elevated IL-6 associate with negative outcome in adult-onset asthma

The effect of systemic inflammation and comorbidities on treatment and outcome of adult-onset asthma remains unknown and is the objective of this study. As part of the Seinäjoki Adult Asthma Study (SAAS) with a 12-year follow-up, serum interleukin (IL)-6, high-sensitivity C-reactive protein (hsCRP) and lung function were measured and clinical information on comorbidities and medication collected from 170 patients with adult-onset asthma without chronic obstructive pulmonary disease. At follow-up visit, 54% of the patients had systemic inflammation as indicated by elevated IL-6 or hsCRP, 58% had at least one comorbidity and 30% at least two comorbidities (other than asthma related). Patients with systemic inflammation were treated with higher dose of inhaled corticosteroid (ICS) and they had lower lung function and higher blood neutrophils compared with patients without. Patients having ≥2 comorbidities had lower Asthma Control Test score and this association remained significant in adjusted analysis. Patients with both systemic inflammation and comorbidities showed poorest outcome of asthma. In multivariate regression analysis, high ICS dose was predicted by elevated IL-6, elevated blood neutrophils and eosinophils and poorer lung function at baseline and follow-up. Altogether, in patients with adult-onset asthma, elevated IL-6 was associated with use of high-dose ICS while multi-morbidity was linked to worse symptoms of asthma. In adult-onset asthma elevated IL-6 is linked to high ICS dose and multimorbidity to worse symptoms of asthma http://ow.ly/IUtG3010z3v