Different anti-apoptotic effects of normal and asthmatic serum on normal eosinophil apoptosis depending on house dust mite-specific IgE

Eosinophil-targeted treatment strategies for long-term outcomes in severe eosinophilic asthma

BACKGROUND

Airway eosinophilic inflammation is a key pathobiologic trait of severe asthma, a complex chronic disease which affects about 5-10% of asthmatic patients worldwide. Therefore, an in-depth knowledge of the immunopathologic mechanisms underlying severe eosinophilic asthma (SEA) is essential to understand the beneficial effects of currently available, eosinophil-targeted anti-asthma treatments, as well as to develop new therapeutic strategies.

AREAS COVERED

This narrative review article aims to provide a concise coverage of the pathophysiology of severe eosinophilic asthma, followed by an updated overview of current and newly emerging therapeutic approaches capable of counteracting airway eosinophilic inflammation. All information reported comes from an extensive literature search conducted on PubMed.

EXPERT OPINION

The recent advances regarding our understanding of the proinflammatory pathways characterizing the various SEA endotypes are allowing to shape effective therapeutic options, driven by the accurate selection of relevant molecular targets. Such successful developments are at the basis of the sustained clinical remission of eosinophilic asthma, which today represents a realistic goal for many severe asthmatic patients.

Type 2 severe asthma: pathophysiology and treatment with biologics

INTRODUCTION

The hallmark of most patients with severe asthma is type 2 inflammation, driven by innate and adaptive immune responses leading to either allergic or non-allergic eosinophilic infiltration of airways. The cellular and molecular pathways underlying severe type 2 asthma can be successfully targeted by specific monoclonal antibodies.

AREAS COVERED

This review article provides a concise overview of the pathophysiology of type 2 asthma, followed by an updated appraisal of the mechanisms of action and therapeutic efficacy of currently available biologic treatments used for management of severe type 2 asthma. Therefore, all reported information arises from a wide literature search performed on PubMed.

EXPERT OPINION

The main result of the recent advances in the field of anti-asthma biologic therapies is the implementation of a personalized medicine approach, aimed to achieve clinical remission of severe asthma. Today this accomplishment is made possible by the right choice of the most beneficial biologic drug for the pathologic traits characterizing each patient, including type 2 severe asthma and its comorbidities.

Der f 38 Is a Novel TLR4-Binding Allergen Related to Allergy Pathogenesis from Dermatophagoides farinae

It is difficult to treat allergic diseases including asthma completely because its pathogenesis remains unclear. House dust mite (HDM) is a critical allergen and Toll-like receptor (TLR) 4 is a member of the toll-like receptor family, which plays an important role in allergic diseases. The purpose of this study was to characterize a novel allergen, Der f 38 binding to TLR4, and unveil its role as an inducer of allergy. Der f 38 expression was detected in the body and feces of Dermatophagoides farinae (DF). Electron microscopy revealed that it was located in the granule layer, the epithelium layer, and microvilli of the posterior midgut. The skin prick test showed that 60% of allergic subjects were Der f 38-positive. Der f 38 enhanced surface 203c expression in basophils of Der f 38-positive allergic subjects. By analysis of the model structure of Der p 38, the expected epitope sites are exposed on the exterior side. In animal experiments, Der f 38 triggered an infiltration of inflammatory cells. Intranasal (IN) administration of Der f 38 increased neutrophils in the lung. Intraperitoneal (IP) and IN injections of Der f 38 induced both eosinophils and neutrophils. Increased total IgE level and histopathological features were found in BALB/c mice treated with Der f 38 by IP and IN injections. TLR4 knockout (KO) BALB/c mice exhibited less inflammation and IgE level in the sera compared to wild type (WT) mice. Der f 38 directly binds to TLR4 using biolayer interferometry. Der f 38 suppressed the apoptosis of neutrophils and eosinophils by downregulating proteins in the proapoptotic pathway including caspase 9, caspase 3, and BAX and upregulating proteins in the anti-apoptotic pathway including BCL-2 and MCL-1. These findings might shed light on the pathogenic mechanisms of allergy to HDM.

Evolution of our view on the IgE molecule role in bronchial asthma and the clinical effect of its modulation by omalizumab: Where do we stand today?

Bronchial asthma is a heterogeneous disease whose definition and treatment are based on evidence of variable airway obstruction and airway inflammation. Despite the enormous increase in the amount of information on the pathogenesis of this disease, diagnosis is still an unresolved problem, as we still lack sensitive and specific biomarkers. On the other hand, at the turn of the 20th and 21st century, there was a rapid development of therapeutic modalities based on the principle of biological therapy. The first authorized drug matching these characteristics was omalizumab – a monoclonal antibody directed against immunoglobulin E (IgE). It has been used for the treatment of severe forms of bronchial asthma for more than 15 years, which is a sufficient time to acquire ways of its effective use and to assess whether the treatment with omalizumab has met our expectations. However, we continue to discover new and surprising facts about the effects of omalizumab treatment which leads to widening of therapeutic indications. In this work, a basic overview of the very complex role of the IgE molecule in the organism (with a special emphasis on allergic asthma) is discussed, and the most important practical and clinical consequences resulting from its modulation by targeted therapy with omalizumab are summarized.

Real-life effects of benralizumab on allergic chronic rhinosinusitis and nasal polyposis associated with severe asthma

The aim of this study has been to evaluate the efficacy of the IL-5 receptor blocker benralizumab on chronic rhinosinusitis with nasal polyposis (CRSwNP), associated with severe eosinophilic allergic asthma. Ten patients with severe eosinophilic allergic asthma and CRSwNP were enrolled. Sino-nasal outcome test (SNOT-22), numerical rating scale (NRS), endoscopic nasal polyp score, Lund Mackey CT (computed tomography) score, and blood eosinophil count were measured at baseline and after 24 weeks of treatment with benralizumab. All the above clinical, endoscopic, imaging, and hematological parameters significantly improved after 24 weeks of treatment with benralizumab. In particular, SNOT-22 decreased from 61.10 ± 17.20 to 26.30 ± 19.74 (P < 0.001), NRS decreased from 7.20 ± 1.55 to 3.40 ± 2.22 (P < 0.001), the endoscopic polyp nasal score decreased from 4.20 ± 1.32 to 2.50 ± 1.78 (P < 0.001), the Lund-Mackay CT score decreased from 16.60 ± 5.50 to 6.90 ± 5.99 (P < 0.001), and blood eosinophil count decreased from 807.3 ± 271.1 cells/μL to 0 cells/μL (P < 0.0001). These results strongly suggest that benralizumab exerted a very effective therapeutic action on CRSwNP associated with severe asthma, thus improving nasal symptoms and decreasing polyp size.

Omalizumab lowers asthma exacerbations, oral corticosteroid intake and blood eosinophils: Results of a 5-YEAR single-centre observational study

Omalizumab is a humanized monoclonal antibody which binds to human immunoglobulins E (IgE), thus preventing their interactions with both high affinity and low affinity IgE receptors. Therefore, omalizumab is currently recommended for add-on biological therapy of uncontrolled allergic asthma, mainly characterized by type 2 airway eosinophilic inflammation. Because omalizumab has been the first, and for a long time the only available monoclonal antibody for add-on treatment of type 2 asthma, some long-term studies have been published which provide a clear evidence of the therapeutic effectiveness of the anti-IgE pharmacological strategy. Within this context, the present single-centre observational study refers to 15 patients with severe allergic asthma, treated with omalizumab for at least 5 years at the Respiratory Unit of "Magna Græcia" University Hospital located in Catanzaro, Italy. In these asthmatic subjects we observed significant increases in asthma control test (ACT) score, with respect to baseline (14.60 ± 2.97), after 1 year (19.20 ± 2.98; p < 0.0001) and 5 years (21.67 ± 2.38; p < 0.0001) of add-on treatment with omalizumab. More importantly, omalizumab significantly lowered the number of annual asthma exacerbations (baseline: 3.66 ± 2.01) after 1 year (0.83 ± 1.14; p < 0.0001) and 5 years (0.63 ± 0.99; p < 0.0001), respectively. This excellent therapeutic outcome made it possible to drastically decrease the daily oral intake of prednisone (baseline: 22.50 ± 5.17 mg) after 1 year (1.83 ± 4.06 mg; p < 0.0001), as well as after 5 years (1.66 ± 3.61 mg; p < 0.0001). With regard to lung function, omalizumab significantly and persistently enhanced FEV₁ (baseline: 1636 ± 628.4 mL) after 1 year (2000 ± 679.7 mL; p < 0.05) and 5 years (1929 ± 564.8 mL; p < 0.05), respectively. Such relevant clinical and functional improvements were associated with reductions of blood eosinophil counts (baseline: 646.0 ± 458.9 cells/μl), already detectable after 1 year (512.7 ± 327.8 cells/μl; not significant), which reached the threshold of statistical significance after 5 years (326.0 ± 171.8 cells/μl; p < 0.05). Therefore, these real-life data referring to our single-centre observational investigation further corroborate the long-term therapeutic ability of omalizumab to improve several clinical, functional and haematological signatures of severe type 2 asthma.

Omalizumab, the first available antibody for biological treatment of severe asthma: more than a decade of real-life effectiveness

Omalizumab was the first, and for a long time the only available monoclonal antibody for the add-on treatment of severe allergic asthma. In particular, omalizumab selectively targets human immunoglobulin (Ig)E, forming small-size immune complexes that inhibit IgE binding to its high- and low-affinity receptors. Therefore, omalizumab effectively blunts the immune response in atopic asthmatic patients, thus significantly improving the control of asthma symptoms and successfully preventing disease exacerbations. These very positive effects of omalizumab make it possible to drastically decrease both referrals to the emergency room and hospitalizations for asthma exacerbations. Such important therapeutic actions of omalizumab have been documented by several randomized clinical trials, and especially by more than 10 years of real-life experience in daily clinical practice. Omalizumab can also interfere with airway remodelling by inhibiting the activation of IgE receptors located on structural cells such as bronchial epithelial cells and airway smooth muscle cells. Moreover, omalizumab is characterized by a very good safety and tolerability profile. Hence, omalizumab represents a valuable therapeutic option for the add-on biological treatment of severe allergic asthma.

Cytokine secreted by S100A9 via TLR4 in monocytes delays neutrophil apoptosis by inhibition of caspase 9/3 pathway

Dysregulation of neutrophil apoptosis causes pathogenesis and aggravation of allergy. S100A9 exists as one of the proteins in the neutrophils, triggering inflammatory responses by activating the immune cells. In this study, we investigated whether S100A9 affects constitutive neutrophil apoptosis by activating the monocytes in normal and allergic subjects. Supernatant from human monocytic THP-1 cells after treatment with S100A9 suppressed normal neutrophil apoptosis by inhibiting the activations of caspase 9 and caspase 3. S100A9 upregulated the release of MCP-1, IL-6, and IL-8 in THP-1 cells. An increase in cytokine was suppressed by CLI-095, a Toll-like receptor (TLR) 4 inhibitor, PP2, a Src inhibitor, rottlerin, a PKCδ inhibitor, MAP kinase inhibitors, including PD98059, SB202190, and SP600125, and BAY-11-7085, an NF-κB inhibitor. Src, PKCδ, ERK1/2, p38 MAPK, and JNK were phosphorylated by S100A9. The phosphorylation of Src and PKCδ was suppressed by CLI-095, and the activation of ERK1/2, p38 MAPK, and JNK was inhibited by CLI-095, PP2, and rottlerin. S100A9 induced NF-κB activity, and the activation was suppressed by CLI-095, PP2, rottlerin, and MAPK kinase inhibitors. In normal and allergic subjects, supernatant from normal and allergic monocytes after stimulation with S100A9 suppressed normal and allergic neutrophil apoptosis, respectively; MCP-1, IL-6, and IL-8 in the supernatant was increased by S100A9. The cytokine secretion induced by S100A9 is related to TLR4, Src, PKCδ, ERK1/2, p38 MAPK, JNK, and NF-κB. Taken together, S100A9 induces anti-apoptotic effect on normal and allergic neutrophils by increasing cytokine secretion of monocytes. These findings may help us to better understand neutrophil apoptosis regulated by S100A9 and pathogenesis of allergic diseases.

Regulation of constitutive neutrophil apoptosis due to house dust mite allergen in normal and allergic rhinitis subjects

House dust mite (HDM) is a primary allergen in allergic rhinitis (AR) and asthma. Neutrophil apoptosis is associated with allergic diseases and innate immunity to infection. The present study examined how HDM affects constitutive neutrophil apoptosis in normal and AR subjects. Total IgE increased in AR subjects when compared to normal subjects, and patients with AR were HDM-specific IgE positive (+), which is specific IgE to Dermatophagoides pteronissinus and Dermatophagoides farinae. In normal and AR subjects, neutrophil apoptosis was inhibited by extract of Dermatophagoides pteronissinus (DP), but not by extract of Dermatophagoides farina (DF). Aprotinin (serine protease inhibitor) and E64 (cysteine protease inhibitor) have no effect on neutrophil apoptosis due to DP. The anti-apoptotic effect of DP was blocked by TLR4i, an inhibitor of TLR4, rottlerin, an inhibitor of PKCδ, PD98059, an inhibitor of ERK, and BAY-11-7085, an inhibitor of NF-κB. DP induced PKCδ, ERK, and NF-κB activation in a time-dependent manner. DP inhibited the cleavage of procaspase 3 and procaspase 9. The expression of IL-6, IL-8, TNF-α, G-CSF, GM-CSF, and CCL2 increased in the supernatant collected from the normal and AR neutrophils after DP treatment and the supernatant inhibited the apoptosis of normal and AR neutrophils. In summary, DP has anti-apoptotic effects on neutrophils of normal and AR subjects through the TLR4/PKCδ/ERK/NF-κB pathway, and this finding may contribute to solution of the pathogenic mechanism of allergic diseases triggered by DP.