Neutrophil influx and interleukin-8 release after segmental allergen or saline challenge in asthmatics

Selected hematological abnormalities and their associated factors among asthmatic patients in Northwest Ethiopia: a cross-sectional study

Background

Asthma is a chronic inflammatory disease that affects the lungs. Variation in whole blood cell lines is caused by the progression and severity of asthma. Common hematological abnormalities encountered during asthma include eosinophilia, neutrophilia, leukocytosis, and increased erythrocyte sedimentation rate. The main aim of this study was to assess the selected hematological abnormalities and their associated factors among asthmatic patients in Northwest Ethiopia from March to May 2021.

Methodology

A hospital-based cross-sectional study was conducted on a total of 320 asthmatic patients in Northwest Ethiopia. A simple random sampling technique was employed to select study participants. A pre-tested structured questionnaire and a checklist were used to collect data. Blood samples were collected from asthmatic patients for complete blood count and erythrocyte sedimentation rate determination. Hematological profiles were analyzed by Unicel DxH 800 (Beckman Coulter, Ireland). The erythrocyte sedimentation rate was determined by using the Westergren method. The data were entered into EpiData version 3.0.4 and analyzed with a statistical package for social science version 20 software. The bi-variable and multi-variable binary logistic regression models were used to assess the factors associated with hematological abnormalities. A p value of less than 0.05 in the multivariable logistic regression analysis was considered statistically significant.

Results

The overall prevalence of neutrophilia, eosinophilia, thrombocytopenia, leukocytosis, and basophilia was 35.3%, 20%, 11.9%, 10.3%, and 4.1%, respectively. Neutrophilia was associated with a lack of physical activity (AOR = 3.25; 95% CI 1.43–7.37) and a history of taking non-asthmatic drugs within the previous three months (AOR = 2.63; 95% CI 1.22–5.65). Being admitted to the emergency department (AOR = 0.27; 95% CI 0.11–5.67) was found to be associated with eosinophilia. In addition, being admitted to the emergency department (AOR = 5.44; 95%CI: 2.6–11.3) was associated with thrombocytopenia.

Conclusion

The current study demonstrated the predominant prevalence of neutrophilia, followed by eosinophilia, among asthma patients. Therefore, hematological abnormalities should be taken into account for proper monitoring and management of asthmatic patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02020-z.

Airway Exposure to 1,3-Beta-d-Glucan Induces Airway Hyperresponsiveness in Guinea Pigs

1,3-Beta-d-glucan (β-glucan) is a component of mold cell walls and is frequently found in fungi and house dust mites. The studies of β-glucan are inconsistent, although it has been implicated in airway adverse responses. This study was carried out to determine whether airway hyperresponsiveness was seen 24 h after airway exposure to β-glucan in guinea pigs. Two matching guinea pigs were exposed intratracheally to either β-glucan or its vehicle. Twenty-four hours after intratracheal instillation, there was no difference between these two groups in the baseline of the total pulmonary resistance (R _L), dynamic lung compliance (C _dyn), arterial blood pressure, and heart rate. In contrast, the responses of R _L to capsaicin injection were significantly increased in β-glucan animals; capsaicin at the same dose of 3.2 μg/kg increased R _L by 184% in vehicle animals and by 400% in β-glucan animals. The effective dose 200% to capsaicin injection was lower in the β-glucan animals. Furthermore, the increases in R _L were partially reduced after transient lung hyperinflation to recruit the occluding airways; however, the R _L induced by capsaicin injection after lung hyperinflation was significantly larger than the baseline in β-glucan animals; also, the lung wet-to-dry ratio in capsaicin-injected animals was augmented in the β-glucan group. Moreover, the airway hyperresponsiveness was accompanied by increases in neutrophils in the bronchoalveolar lavage fluid in the β-glucan animals. Furthermore, the levels of substance P and the calcitonin gene-related peptide in the bronchoalveolar lavage fluid collected after capsaicin injection were increased in β-glucan animals. We provide definitive evidence that β-glucan can induce airway hyperresponsiveness in guinea pigs, and the neuropeptide releases play an important role in this airway hyperresponsiveness.

γδ T Lymphocytes Coordinate Eosinophil Influx during Allergic Responses

Tissue eosinophil infiltration, which is a hallmark of allergic and helminthic diseases, is mainly coordinated by T lymphocytes, via the production of eosinophilotactic chemokines. Among T lymphocyte subsets, lymphocytes expressing γδ T cell receptor have been determined as a key factor for eosinophil accumulation via direct and indirect mechanisms. This knowledge is strongly supported by the fact that, in different experimental models of eosinophilic airway inflammation and helminth-induced Th2 lung inflammation, an evident tissue accumulation of γδ T lymphocytes is observed. In addition, the depletion of γδ T lymphocytes is correlated with the impairment of eosinophil accumulation in inflamed tissue. γδ T lymphocytes are non-conventional T lymphocytes, which comprise a minor T lymphocyte subset, mainly distributed in the tissue, and present crucial roles in innate and acquired immune responses. γδ T lymphocytes recognize several danger- and pathogen-associated molecular pattern molecules and stress antigens in a MHC-independent fashion and can provide rapid tissue-specific responses, via the production of a wide range of chemical mediators capable to modulate other cell populations. These mediators include chemoattractant cytokines and chemokines that attract eosinophils into the tissue by either direct recognition (such as IL-5, CCL11/eotaxin), or indirect mechanisms via the modulation of αβ T lymphocytes and macrophages (through the production of interferon-γ, IL-4, and CCL2/Monocyte chemoattractant protein-1, MCP-1, for example). The present review presents an overview of how γδ T lymphocytes coordinate eosinophil accumulation in allergy, by focusing on their role in airway inflammation and by discussing the involvement of cytokines and chemokines in this phenomenon.

Artificial airways for the study of respiratory disease

This review will focus on human cell-based experimental models to study respiratory diseases, in particular models of the large airways relevant to asthma and chronic obstructive pulmonary disease. Such models have the advantage of incorporating cells that can be derived from disease-relevant tissue and so have retained important genetic and epigenetic features that contribute to the human disease. These models can be used for mechanistic studies, target identification and validation and toxicological testing. While many models have been developed to varying degrees of sophistication, the challenge remains to develop an integrated system that recapitulates the complex cell-cell and cell-matrix interactions that occur in vivo and to provide these with a 'circulation' to study the dynamics of immune and inflammatory cell influx and efflux.

T(H)2 cytokines modulate the IL-9R expression on human neutrophils

Interleukin (IL)-9 is associated with key pathological features of asthma such as airway hyperresponsiveness, bronchoconstriction and mucus production. Inflammatory responses mediated by IL-9 rely on the expression of the IL-9R which has been reported on lung epithelial cells, T lymphocytes and recently on airway granulocyte infiltrates. In this study, we assessed the regulatory and constitutive cell surface expression of the IL-9Ralpha in unfractionated and purified human neutrophils from atopic asthmatics, atopic non-asthmatics and healthy normal controls. We demonstrate that T(H)2 cytokines (IL-4 or IL-13) and granulocyte macrophage-colony stimulating factor (GM-CSF) up-regulated mRNA and cell surface expression levels of the IL-9Ralpha in primary human and HL-60 differentiated neutrophils. Pharmacological inhibition of NF-kappaB did not affect T(H)2-mediated IL-9Ralpha expression in human neutrophils although IFN-gamma and IL-10 down-regulated IL-9Ralpha expression when co-incubated with IL-4, IL-13 or GM-CSF. Collectively, our results reveal a regulatory function for IFN-gamma and IL-10 on modulating the inducible IL-9Ralpha expression levels on peripheral blood neutrophils by T(H)2 cytokines.

Sensitizing effects of chronic exposure and acute inhalation of ovalbumin aerosol on pulmonary C fibers in rats

The effect of ovalbumin (Ova) sensitization on pulmonary C-fiber sensitivity was investigated. Brown-Norway rats were sensitized by intraperitoneal injection of Ova followed by aerosolized Ova three times per week for 3 wk. Control rats received the vehicle. At the end of the third week, single-unit fiber activities (FA) of pulmonary C fibers were recorded in anesthetized, artificially ventilated rats. Our results showed the following: 1) Ova sensitization induced airway inflammation (infiltration of eosinophils and neutrophils) and airway hyperresponsiveness in rats; 2) baseline FA in sensitized rats was significantly higher than that in control ones; 3) similarly, the pulmonary C-fiber response to right atrial injection of capsaicin was markedly higher in sensitized rats, which were significantly amplified after the acute Ova inhalation challenge; and 4) similar patterns, but smaller magnitudes of the differences in C-fiber responses to adenosine and lung inflation, were also found between sensitized and control rats. In conclusion, Ova sensitization elevated the baseline FA and excitability of pulmonary C fibers, and the hypersensitivity was further potentiated after the acute Ova inhalation challenge in sensitized rats. Chronic allergic inflammatory reactions in the airway probably contributed to the sensitizing effect on these lung afferents.

Neutrophils in asthma

Asthma is a complex disease with a significant inflammatory component. Multiple cell types are involved in its pathophysiology. The presence of eosinophils, the cell usually associated with allergic diseases, does not fully explain the inflammation found in asthma. Neutrophils are present in the airway of the patient with asthma in special circumstances and may represent different asthma phenotypes. Neutrophils are activated and are able to release mediators that promote and prolong asthma symptoms. Increasing evidence suggest that neutrophils may be central players with an important role in the pulmonary inflammatory process present in asthma.

Handle with care: targeting neutrophils in chronic obstructive pulmonary disease and severe asthma?

Neutrophils play an important role in the pathogenesis of airway inflammation in both chronic obstructive pulmonary disease (COPD) and severe asthma. Currently available drugs have only limited effects on neutrophilic airway inflammation, particularily in COPD. Therefore, great efforts are undertaken to address neutrophilic inflammation in chronic respiratory disorders, in particular COPD. This review summarizes the rationale for anti-neutrophilic treatment in COPD and asthma and gives a critical overview of current developments in drug therapy. Moreover, unanswered questions and limitations of clinical trial design and choice of outcome parameters for proof-of-concept studies with novel anti-neutrophilic drugs are discussed as well as potential safety issues.

Factors contributing to nasal allergic late phase eosinophilia

OBJECTIVE

This study focused on factors contributing to eosinophilia after intranasal allergen challenge.

METHODS

Nasal secretions of 13 allergic individuals were gained over a period of 8 hours after nasal allergen challenge. Early and late phase reactions were determined by acoustic rhinometry and changes of volume and total protein in nasal secretions. Eosinophilia was demonstrated by nasal eosinophilic cationic protein. Interleukin (IL)-5; the chemokines IL-8, monocyte chemotactic protein (MCP)-1 and MCP-3, and eotaxin; soluble vascular cell adhesion molecule 1 (sVCAM-1); and the leukotriene C4 (LTC4) were analyzed by enzyme-linked immunosorbent assay for their suggested impacts on tissue eosinophilia.

RESULTS

By means of rhinometry, we observed in 69% an alternating type of late phase response, followed by a bilateral (15%) or unilateral (8%) type. A biphasic kinetic could be demonstrated by changes in nasal volume and total protein of nasal secretions, reflecting the early and late phase responses. A typical late phase kinetic was observed for IL-5, MCP-1, eotaxin, sVCAM-1, and LTC4. Interleukin 8 was characteristic for early phase reaction but increased in late phase as well. We could not detect any MCP-3 in our samples.

CONCLUSIONS

Our data point to a relevant role of the T(H)2 cytokine IL-5; of the chemokines IL-8, MCP-1, and eotaxin; of the adhesion molecule sVCAM-1; and of the leukotriene LTC4 for the allergic late phase eosinophilia.

Cytokine expression in allergic inflammation: systematic review of in vivo challenge studies

BACKGROUND

Allergic inflammatory responses are driven by cells of the immune system that rely on cytokines to regulate the activity of other immune and structural cells.

OBJECTIVE

To review published studies to (1) identify cytokines consistently increased after allergen challenge in atopic patients and (2) investigate temporal variation in cytokine expression.

METHODS

A PUBMED systematic search was used to extract data from studies involving analysis of cytokine expression in fluids or biopsies following in vivo allergen challenge in atopic patients.

RESULTS

Data were extracted from 82 studies. There were no consistent reports of cytokine protein increase in fluids of patients at 0-1 h after challenge. At 4-12 h, the chemokines eotaxin, macrophage inflammatory protein-1alpha, RANTES (regulated on activation normal T cell expressed and secreted) and interleukin (IL)-8 have all been consistently reported to be up-regulated. At 18-24 h after challenge, the lymphokines IL-4, IL-5 and IL-13, as well as the pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor, tumour necrosis factor-alpha and IL-6 are consistently increased when compared with the respective control value. There were no reports of up-regulation in interferon-gamma protein and mRNA and in IL-2 mRNA.

CONCLUSION

The expression of granulocyte-macrophage colony-stimulating factor is consistently increased in tissues at 4-12 h after challenge. The influence of this cytokine on antigen capture and presentation by dendritic cells should be further investigated. Additionally, allergen challenge studies are needed that investigate the expression of macrophage-derived chemokine and thymus-regulated and activation-regulated chemokine in tissues of atopic patients. Blocking the effects of these lymphocyte-specific chemokines might provide new therapeutic approaches for the control of allergic inflammation.

Lipid mediators from pollen act as chemoattractants and activators of polymorphonuclear granulocytes

BACKGROUND

Under natural exposure conditions, pollen grains function as allergen carriers that release allergens from internal binding sites on contact with the aqueous phase of mucosa membranes. In addition, we recently demonstrated that pollen are a rich source of eicosanoid-like mediators, which are rapidly released on contact with the aqueous phase.

OBJECTIVE

The current study was designed to characterize the biochemical nature of pollen-derived lipid mediators in more detail and to delineate their biologic activity on polymorphonuclear granulocytes (PMNs).

METHODS

Aqueous and lipid extracts from Phleum pratense L and Betula alba L pollen were analyzed by means of HPLC. PMNs were exposed to aqueous extracts or lipid fractions from pollen or to HPLC-purified lipid mediators identified in pollen extracts. Effects on PMNs were tested with transwell migration, calcium mobilization, and surface expression of CD11b.

RESULTS

Aqueous pollen extracts (APEs) contained predominantly monohydroxylated products derived of linoleic acid and linolenic acid. In chemotaxis assays PMNs displayed significant migration to APEs. Lipid extracts from pollen and the HPLC fraction containing 13-hydroxy-octadecadienoic acid/hydroxy-linoleic acid and 13-hydroxy-octadecatrienoic acid/hydroxy-linolenic acid induced migratory responses, although to a lesser degree than the APEs. In addition, APE, as well as lipid, extracts induced PMN activation, as documented by means of calcium mobilization and upregulation of CD11b.

CONCLUSION

Pollen grains release mediators that recruit and activate PMNs in vitro. Similar mechanisms may be effective in vivo, suggesting that pollen-derived lipid mediators may act as adjuvants in the elicitation phase of allergic reactions.

The role of eosinophils and neutrophils in inflammation

The eosinophil is well recognized as a central effector cell in the inflamed asthmatic airway. Eosinophils release toxic basic proteins and lipid mediators such as cysteinyl-leukotrienes that cause bronchial epithelial damage and airflow obstruction. Eosinophil-selective cytokines and chemokines including interleukin (IL)-5, eotaxin and RANTES may represent targets for novel asthma therapies. In contrast, the role of the neutrophil in asthma remains relatively obscure. Recent evidence from the ENFUMOSA project and elsewhere suggests that neutrophils not only contribute to acute asthma exacerbations, but also are present in high numbers in the airways of patients with chronic severe asthma. Production by neutrophils of lipid mediators, reactive oxygen intermediates (ROI) and proteases such as elastase, may contribute to airflow obstruction, epithelial damage and remodelling. Leukotriene B4 and cytokines such as IL-8, granulocyte-macrophage colony stimulating factor (GM-CSF), and tumour necrosis factor (TNF)alpha chemoattract neutrophils and reduce neutrophil apoptosis, and selective agents directed against these may prevent neutrophil influx and accumulation. Airway neutrophilia remains apparent in severe asthma patients even after treatment with high doses of corticosteroids. In vitro, corticosteroids paradoxically enhance neutrophil survival by reducing apoptosis, so corticosteroid therapy may exacerbate neutrophil activity in vivo. Both corticosteroids and cytokines may suppress neutrophil apoptosis by upregulating endogenous synthesis of leukotriene (LT)B4. Specific blockade of LTB4 synthesis or LTB4 receptors may induce neutrophil apoptosis and combat the unwanted effects of high-dose steroids on neutrophil survival. Phagocytosis of apoptotic neutrophils stimulates important signals that down-regulate pro-inflammatory cytokine production by macrophages, allowing resolution and repair processes to prevail.

Segmental allergen challenge induces plasma protein leakage into the airways of asthmatic subjects at 4 hours but not at 5 minutes after challenge

We have investigated whether increased plasma protein leakage is present early after segmental allergen challenge in allergic asthma. Seven asthmatic subjects with mild allergy (AA group) and 5 non-asthmatic subjects with allergy (ANA group) were challenged with allergen doses based on similar early skin reactions; 5 healthy control subjects without allergy (C group) were challenged with the highest dose applied in the subjects with allergy. Bronchoalveolar lavage (BAL) fluid was obtained before, at 5 minutes after, and at 4 hours after challenge from different segments. Levels of albumin (Alb) and alpha2-macroglobulin (A2M) were measured in BAL fluid and serum. In addition, we calculated the relative coefficient of excretion as follows: RCE = ((A2M in BAL fluid)/(A2M in serum))/((Alb in BAL fluid)/(Alb in serum)). Also, levels of tryptase as a marker of mast cell activation and tumor necrosis factor-alpha (TNF-alpha), a possible inducer of plasma protein leakage, were determined. At 5 minutes after challenge, in none of the groups was a significant change found in the parameters for protein leakage. Levels of tryptase were increased in the subjects with allergy at 5 minutes after challenge only (P = .004). At 4 hours after challenge, levels of Alb (P = .03) and A2M (P = .04) and the RCE (P = .04) were increased in the AA group only. At 4 hours, levels of TNF-alpha were increased, with no significant differences among the three groups. In the asthmatic subjects with allergy, levels of TNF-alpha correlated with levels of Alb (r = 0.85, P = .02). In conclusion, at 4 hours after segmental allergen challenge, plasma protein leakage was increased in the asthmatic subjects only. The increase in levels of TNF-alpha in all groups indicates that the presence of TNF-alpha alone was not sufficient to cause plasma protein leakage within 4 hours after allergen challenge. Our results confirm the concept that plasma exudation after allergen exposure is a pathophysiologic event associated with asthma.

Role of bronchoscopy in asthma research

Over the past 15 years, much has been learned about the presence of airway inflammation in asthma through the use of investigative bronchoscopy. It has become quite clear that inflammation is present even in mild asthma. In addition to the eosinophils, T-lymphocytes and a variety of cytokines have been identified to play a prominent role in asthmatic inflammation. The concept of delayed asthmatic response after allergen exposure and its relationship to cellular inflammation and airway hyper-reactivity has become more clearly established. Our understanding of asthmatic airway inflammation, however, is incomplete. As interesting as the database has been so far, investigative FB has not defined a unique profile for patients with asthma. Specifically, lavage or endobronchial biopsy has not identified parameters that help in the diagnosis, assessment of disease severity, prognosis, or likelihood to respond to specific therapies. Also, the exact relationship between parameters in lavage compared with mucosal biopsy and how these are related to airway hyper-reactivity and the clinical syndrome of asthma remains poorly understood. In this regard, it must be confessed that currently FB with lavage and biopsy in asthmatics needs to be considered as a research tool for specimen retrieval to help characterize and express inflammation. Although these techniques have contributed immensely to our understanding of asthma pathogenesis, presently these techniques do not have any practical role or clinical usefulness.

Animal models of asthma: role of chemokines

In studies of disease processes, increasing knowledge leads to an increased awareness of the complexity of the underlying mechanisms. The intense research activity in the chemokine field has made this acutely manifest. Numerous chemokines have been discovered through the use of (1) bioassay of in vitro cell culture supernatants and in vivo exudates from animal models of inflammation and (2) molecular biology techniques. Any one chemokine can often be produced by a number of different cell types and exert its effects on different target cells. This has been interpreted by some as implying a high degree of redundancy. Although this is understandable, in disease processes parallel and sequential mechanisms are possible, and potentially important therapeutic targets have emerged. There is compelling evidence from animal and clinical studies that eosinophils are important effector cells in asthma, but this relationship is as yet unproven in the human disease. Two possible targets to prevent eosinophil recruitment to the lung are IL-5 and its receptor, which are important in several aspects of eosinophil biology, and eotaxin and its receptor, CCR3. The eotaxin receptor is particularly attractive as a target as it is expressed in high numbers on eosinophils, but not other leukocytes, and appears to be the major detector of the eosinophil for eotaxin and other chemokines such as MCP-4. Eotaxin and CCR3 knockout mice are being developed, and animal models will continue to be invaluable when antagonists are available. In the shape of receptor antagonists, the chemokine field may yet provide the final proof of concept for the long-established eosinophil theory of asthma in humans.