Eosinophilia in Pulmonary Disorders

Eosinophilic Airway Diseases: From Pathophysiological Mechanisms to Clinical Practice

Eosinophils play a key role in airway inflammation in many diseases, such as allergic and non-allergic asthma, chronic rhinosinusitis with nasal polyps, and chronic obstructive pulmonary disease. In these chronic disabling conditions, eosinophils contribute to tissue damage, repair, remodeling, and disease persistence through the production a variety of mediators. With the introduction of biological drugs for the treatment of these respiratory diseases, the classification of patients based on clinical characteristics (phenotype) and pathobiological mechanisms (endotype) has become mandatory. This need is particularly evident in severe asthma, where, despite the great scientific efforts to understand the immunological pathways underlying clinical phenotypes, the identification of specific biomarkers defining endotypes or predicting pharmacological response remains unsatisfied. In addition, a significant heterogeneity also exists among patients with other airway diseases. In this review, we describe some of the immunological differences in eosinophilic airway inflammation associated with severe asthma and other airway diseases and how these factors might influence the clinical presentation, with the aim of clarifying when eosinophils play a key pathogenic role and, therefore, represent the preferred therapeutic target.

Clinical analysis of hypereosinophilic syndrome first presenting with asthma-like symptoms

INTRODUCTION

Clinical manifestations of hypereosinophilic syndrome (HES) are diverse. This study aimed to summarise these clinical characteristics with asthma-like onset as the first symptom, and compare these characteristics and treatment strategies between idiopathic and parasitic HES.

MATERIALS AND METHODS

We retrospectively analysed 36 HES patients with asthma-like symptoms as the first episode, between January 2013 and October 2019. Data of patients with HES of an unknown cause (idiopathic HES) and parasitic infection (parasite HES) were analysed.

RESULTS

The idiopathic and parasite HES groups included 16 and 20 patients, respectively, with more males in the parasite HES group (p < .05). Wheezing and dry rales was the most common symptom and signs, with no significant differences in symptoms and signs between the groups. The most often misdiagnosed disease was bronchial asthma. The peripheral blood eosinophil count was significantly increased compared with normal counts in both groups (p > .05). Abnormal pulmonary function is mainly manifested as obstructive ventilatory disorder and mixed ventilatory disorder. Chest computed tomography showed extensive ground-glass exudation, patches, consolidation, nodules, and pleural effusion. Histopathological examination showed eosinophilic infiltration without vasculitis or granuloma. Glucocorticoids had a significant therapeutic effect, and the parasite HES group required combined deworming drugs. The duration of corticosteroids therapy in the idiopathic HES group was significantly longer than that in the parasite HES group (p < .05). The overall prognosis was good, and 81.25% of the patients were clinically cured in the parasite HES group; however, relapse occurred easily in the idiopathic HES group.

CONCLUSIONS

Asthma-like symptoms, obstructive ventilatory disorder or positive bronchial dilation test, and poor response to inhaled corticosteroids are not necessarily indicative of refractory asthma; HES should be considered. The clinical characteristics of HES of different aetiologies are similar. Systemic corticosteroid therapy is preferred for idiopathic and parasitic infections. Idiopathic HES is treated with prolonged corticosteroids and relapses easily.Key MessagesAsthma-like symptoms, obstructive ventilatory disorder or positive bronchial dilation tests, and poor responses to inhaled corticosteroids are not necessarily indicative of refractory asthma, and hypereosinophilic syndrome should be considered.The clinical characteristics of hypereosinophilic syndrome of different aetiologies are similar, and systemic glucocorticoid therapy is preferred for both idiopathic and parasitic infections.Idiopathic hypereosinophilic syndrome is treated with prolonged corticosteroids and relapses easily.

Image challenge: Beware of diagnostic anchoring - An offshore vessel welding inspector with eosinophilia and a cough productive of 'worms'

A 38-year old male was referred from an Acute Medical Unit to a regional Tropical Infectious Disease Unit with a seven-week history of dyspnoea, wheeze and cough reportedly productive of worms. The patient had taken photographs of the expectorated substance which allowed macroscopic examination by a consultant in infectious diseases. Fresh samples were also sent for histological examination. Initial investigations showed a prominent eosinophilia of 2.5 × 10⁹/ml (0.0-0.4 × 10⁹/ml).

Chronic eosinophilic pneumonia: clinical perspectives

Chronic eosinophilic pneumonia (CEP) is an eosinophilic lung disease that is typically diagnosed by a triad of clinical symptoms including pulmonary symptoms, eosinophilia and characteristic radiographic abnormalities. It requires a high index of suspicion given its overlap with other eosinophilic conditions and lack of a specific diagnostic test. The diagnosis is made after careful consideration of other secondary causes of eosinophilia, such as infectious, drugs, or toxic etiologies. CEP generally responds rapidly to treatment, which primarily consists of corticosteroid therapy, but relapses are common. Novel therapies are being explored as more information is being discovered about the pathophysiology of eosinophilic disease processes. Close follow-up is important given the difficulty in weaning patients from glucocorticoids with many patients developing sequelae of chronic glucocorticoid therapy. Therefore, exploring alternative treatments is of upmost importance.

Aqueous extracts from Uncaria tomentosa (Willd. ex Schult.) DC. reduce bronchial hyperresponsiveness and inflammation in a murine model of asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Uncaria tomentosa (Willd. Ex Schult) DC is used by indigenous tribes in the Amazonian region of Central and South America to treat inflammation, allergies and asthma. The therapeutic properties of U. tomentosa have been attributed to the presence of tetracyclic and pentacyclic oxindole alkaloids and to phenolic acids.

AIMS OF THE STUDY

To characterize aqueous bark extracts (ABE) and aqueous leaf extracts (ALE) of U. tomentosa and to compare their anti-inflammatory effects.

MATERIALS AND METHODS

Constituents of the extracts were identified by ultra performance liquid chromatography-mass spectrometry. Anti-inflammatory activities were assessed in vitro by exposing lipopolysaccharide-stimulated macrophage cells (RAW264.7-Luc) to ABE, ALE and standard mitraphylline. In vivo assays were performed using a murine model of ovalbumin (OVA)-induced asthma. OVA-sensitized animals were treated with ABE or ALE while controls received dexamethasone or saline solution. Bronchial hyperresponsiveness, production of Th1 and Th2 cytokines, total and differential counts of inflammatory cells in the bronchoalveolar lavage (BAL) and lung tissue were determined.

RESULTS

Mitraphylline, isomitraphylline, chlorogenic acid and quinic acid were detected in both extracts, while isorhyncophylline and rutin were detected only in ALE. ABE, ALE and mitraphylline inhibited the transcription of nuclear factor kappa-B in cell cultures, ALE and mitraphylline reduced the production of interleukin (IL)-6, and mitraphylline reduced production of tumor necrosis factor-alpha. Treatment with ABE and ALE at 50 and 200 mg kg^-1, respectively, reduced respiratory elastance and tissue damping and elastance. ABE and ALE reduced the number of eosinophils in BAL, while ALE at 200 mg kg^-1 reduced the levels of IL-4 and IL-5 in the lung homogenate. Peribronchial inflammation was significantly reduced by treatment with ABE and ALE at 50 and 100 mg kg^-1 respectively.

CONCLUSION

The results clarify for the first time the anti-inflammatory activity of U. tomentosa in a murine model of asthma. Although ABE and ALE exhibited distinct chemical compositions, both extracts inhibited the production of pro-inflammatory cytokines in vitro. In vivo assays revealed that ABE was more effective in treating asthmatic inflammation while ALE was more successful in controlling respiratory mechanics. Both extracts may have promising applications in the phytotherapy of allergic asthma.

Eosinophil Development, Disease Involvement, and Therapeutic Suppression

Human eosinophils have characteristic morphologic features, including a bilobed nucleus and cytoplasmic granules filled with cytotoxic and immunoregulatory proteins that are packaged in a specific manner. Eosinophil production in the bone marrow is exquisitely regulated by timely expression of a repertoire of transcription factors that work together via collaborative and hierarchical interactions to direct eosinophil development. In addition, proper granule formation, which occurs in a spatially organized manner, is an intrinsic checkpoint that must be passed for proper eosinophil production to occur. In eosinophil-associated disorders, eosinophils and their progenitors can be recruited in large numbers into tissues where they can induce proinflammatory organ damage in response to local signals. Eosinophils are terminally differentiated and do not proliferate once they leave the bone marrow. The cytokine IL-5 specifically enhances eosinophil production and, along with other mediators, promotes eosinophil activation. Indeed, eosinophil depletion with anti-IL-5 or anti-IL-5Rα is now proven to be clinically beneficial for several eosinophilic disorders, most notably severe asthma, and several therapeutics targeting eosinophil viability and production are now in development. Significant progress has been made in our understanding of eosinophil development and the consequences of tissue eosinophilia. Future research efforts focused on basic eosinophil immunobiology and translational efforts to assist in the diagnosis, treatment selection, and resolution of eosinophil-associated disorders will likely be informative and clinically helpful.

Eosinophilic Lung Disease

Eosinophils are involved in the pathogenesis of a number of lung diseases. Recent advances in eosinophil biology have now produced clinically applicable therapies that seek to counter eosinophilia in blood and lungs. This article reviews the basic biology of eosinophils and their role in mediating T-helper 2 cell responses. The current status of anticytokine therapy for eosinophilic lung disease is discussed. A clinical approach to eosinophilic lung disease based on symptoms and radiography is generated. The clinical significance of persistent eosinophilia in lung transplant patients and patients with asthma will receive special emphasis.

Eosinophilic granulomatosis with polyangiitis (formerly known as Churg-Strauss syndrome) as a differential diagnosis of hypereosinophilic syndromes

Eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as Churg-Strauss syndrome, is a rare systemic disease situated between primary small vessel vasculitides associated with antineutrophil cytoplasmic antibodies (ANCAs) and hypereosinophilic syndromes (HES). Here, we present a case of EGPA in a 38-year-old male, with a previous diagnosis of asthma, who presented with fever, migratory lung infiltrates and systemic eosinophilia that was refractory to previous courses of antibiotics. This case highlights the importance of the primary care physician understanding the differential diagnosis of pulmonary eosinophilic syndromes.

Blood and Bone Marrow Evaluation for Eosinophilia

Evaluation of peripheral blood and bone marrow for an indication of persistent eosinophilia can be a challenging task because there are many causes of eosinophilia and the morphologic differences between reactive and neoplastic causes are often subtle or lack specificity. The purpose of this review is to provide an overview of the differential diagnosis for eosinophilia, to recommend specific steps for the pathologist evaluating blood and bone marrow, and to emphasize 2 important causes of eosinophilia that require specific ancillary tests for diagnosis: myeloproliferative neoplasm with PDGFRA rearrangement and lymphocyte-variant hypereosinophilic syndrome.

A standardized methanol extract of Eclipta prostrata (L.) L. (Asteraceae) reduces bronchial hyperresponsiveness and production of Th2 cytokines in a murine model of asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Eclipta prostrata (L.) L. (Asteraceae) has been used in Brazilian traditional medicine to treat asthma and other respiratory illnesses.

AIMS OF THE STUDY

To investigate the effects of different doses of a standardized extract of E. prostrata using a murine model of allergen induced asthma.

MATERIALS AND METHODS

Balb/c mice were sensitized twice with ovalbumin (OVA) administered intraperitoneally and challenged over four alternate days with nasal instillations of OVA solution. The standardized methanol extract of E. prostrata was administered in doses of 100, 250 and 500mgkg^-1 concomitantly with nasal instillation over seven consecutive days. Control animals were treated with dexamethasone or saline solution. Bronchial hyperresponsiveness, production of Th1 and Th2 cytokines, allergen sensitization, airway and lung inflammation, mucous secretion and airway remodeling were assessed.

RESULTS

The concentrations of chemical markers in the standardized methanol extract were 0.02% oroboside, 1.69% demethylwedelolactone and 1.71% wedelolactone. Treatment with 250mgkg^-1 of extract, which provided 0.745, 4.22 and 4.30mgkg^-1day^-1 of oroboside, demethylwedelolactone and wedelolactone, respectively, significantly reduced (P<0.05) respiratory resistance and elastance. Such effects were comparable with those produced by dexamethasone. The total number of inflammatory cells and eosinophils in the bronchoalveolar lavage and the concentrations of interleukin (IL)-4, IL-5 and IL-13 in lung homogenate were significantly reduced (P<0.05) by the methanol extract of E. prostrata.

CONCLUSION

The results presented herein demonstrate for the first time the anti-inflammatory activity of E. prostrata in a murine model of asthma, thereby supporting the ethnopharmacological uses of the plant.