Allosteric inhibition of CXCR1 and CXCR2 abrogates Th2/Th17-associated Allergic Lung Inflammation in Mice.

Background: IL4, IL5, IL13, and IL17-producing CD4 T helper 2 (Th2)-cells and IL17-producing CD4 T helper 17 (Th17)-cells contribute to chronic eosinophilic and neutrophilic airway inflammation in asthma and allergic airway inflammation. Chemokines and their receptors are upregulated in Th2/Th17-mediated inflammation. However, the ability of CXCR1 and CXCR2 modulate Th2 and Th17-cell-mediated allergic lung inflammation has not been reported. Methods: Mice sensitized and challenged with cat dander extract (CDE) mount a vigorous Th2-Th17-mediated allergic lung inflammation. Allosteric inhibitor of CXCR1 and CXCR2, ladarixin was orally administered in this model. The ability of ladarixin to modulate allergen-challenge induced recruitment of CXCR1 and CXCR2-expressing Th2 and Th17-cells and allergic lung inflammation were examined. Results: Allergen challenge in sensitized mice increased mRNA expression levels of Il4, Il5, Il13, Il6, Il1ß, Tgfß1, Il17, Il23, Gata3, and Rorc , and induced allergic lung inflammation characterized by recruitment of CXCR1- and CXCR2-expressing Th2-cells, Th17-cells, neutrophils, and eosinophils. Allosteric inhibition of CXCR1 and CXCR2 vigorously blocked each of these pro-inflammatory effects of allergen challenge. CXCL chemokines induced a CXCR1 and CXCR2-dependent proliferation of IL4, IL5, IL13, and IL17 expressing T-cells. Conclusion: Allosteric inhibition of CXCR1 and CXCR2 abrogates blocks recruitment of CXCR1- and CXCR2-expressing Th2-cells, Th17-cells, neutrophils, and eosinophils in this mouse model of allergic lung inflammation. We suggest that the ability of allosteric inhibition of CXCR1 and CXCR2 to abrogate Th2 and Th17-mediated allergic inflammation should be investigated in humans.

The DNA glycosylase NEIL2 is protective during SARS-CoV-2 infection.

SARS-CoV-2 infection-induced aggravation of host innate immune response not only causes tissue damage and multiorgan failure in COVID-19 patients but also induces host genome damage and activates DNA damage response pathways. To test whether the compromised DNA repair capacity of individuals modulates the severity of COVID-19 infection, we analyze DNA repair gene expression in publicly available patient datasets and observe a lower level of the DNA glycosylase NEIL2 in the lungs of severely infected COVID-19 patients. This observation of lower NEIL2 levels is further validated in infected patients, hamsters and ACE2 receptor-expressing human A549 (A549-ACE2) cells. Furthermore, delivery of recombinant NEIL2 in A549-ACE2 cells shows decreased expression of proinflammatory genes and viral E-gene, as well as lowers the yield of viral progeny compared to mock-treated cells. Mechanistically, NEIL2 cooperatively binds to the 5'-UTR of SARS-CoV-2 genomic RNA to block viral protein synthesis. Collectively, these data strongly suggest that the maintenance of basal NEIL2 levels is critical for the protective response of hosts to viral infection and disease.

The DNA glycosylase NEIL2 plays a vital role in combating SARS-CoV-2 infection.

Compromised DNA repair capacity of individuals could play a critical role in the severity of SARS-CoV-2 infection-induced COVID-19. We therefore analyzed the expression of DNA repair genes in publicly available transcriptomic datasets of COVID-19 patients and found that the level of NEIL2, an oxidized base specific mammalian DNA glycosylase, is particularly low in the lungs of COVID-19 patients displaying severe symptoms. Downregulation of pulmonary NEIL2 in CoV-2-permissive animals and postmortem COVID-19 patients validated these results. To investigate the potential roles of NEIL2 in CoV-2 pathogenesis, we infected Neil2-null (Neil2-/-) mice with a mouse-adapted CoV-2 strain and found that Neil2-/- mice suffered more severe viral infection concomitant with increased expression of proinflammatory genes, which resulted in an enhanced mortality rate of 80%, up from 20% for the age matched Neil2+/+ cohorts. We also found that infected animals accumulated a significant amount of damage in their lung DNA. Surprisingly, recombinant NEIL2 delivered into permissive A549-ACE2 cells significantly decreased viral replication. Toward better understanding the mechanistic basis of how NEIL2 plays such a protective role against CoV-2 infection, we determined that NEIL2 specifically binds to the 5'-UTR of SARS-CoV-2 genomic RNA and blocks protein synthesis. Together, our data suggest that NEIL2 plays a previously unidentified role in regulating CoV-2-induced pathogenesis, via inhibiting viral replication and preventing exacerbated proinflammatory responses, and also via its well-established role of repairing host genome damage.

Protocols to Measure Oxidative Stress and DNA Damage in Asthma.

Asthma is associated with oxidative stress and oxidative damage of biomolecules, including DNA. Here, we describe the protocols to quantify reactive oxygen species (ROS) and oxidative stress markers in a mouse model of allergic airway inflammation. We also provide detailed methods to measure DNA damage by long-run real-time PCR for DNA-damage quantification (LORD-Q) assay and gene-specific DNA damage analyses by long amplicon (LA)-qPCR. Additionally, we describe methods to quantify oxidized DNA base lesions in lung genomic DNA by mass spectrometry, and to measure enzymatic activity of 8-oxoguanine DNA glycosylase (OGG1). Using these methods, the levels of oxidative stress and DNA damage in allergic inflammation and asthma can be elucidated.

Intrapulmonary administration of purified NEIL2 abrogates NF-κB-mediated inflammation.

Aberrant or constitutive activation of nuclear factor kappa B (NF-κB) contributes to various human inflammatory diseases and malignancies via the upregulation of genes involved in cell proliferation, survival, angiogenesis, inflammation, and metastasis. Thus, inhibition of NF-κB signaling has potential for therapeutic applications in cancer and inflammatory diseases. We reported previously that Nei-like DNA glycosylase 2 (NEIL2), a mammalian DNA glycosylase, is involved in the preferential repair of oxidized DNA bases from the transcriptionally active sequences via the transcription-coupled base excision repair pathway. We have further shown that Neil2-null mice are highly sensitive to tumor necrosis factor α (TNFα)- and lipopolysaccharide-induced inflammation. Both TNFα and lipopolysaccharide are potent activators of NF-κB. However, the underlying mechanism of NEIL2's role in the NF-κB-mediated inflammation remains elusive. Here, we have documented a noncanonical function of NEIL2 and demonstrated that the expression of genes, such as Cxcl1, Cxcl2, Cxcl10, Il6, and Tnfα, involved in inflammation and immune cell migration was significantly higher in both mock- and TNFα-treated Neil2-null mice compared with that in the WT mice. NEIL2 blocks NF-κB's binding to target gene promoters by directly interacting with the Rel homology region of RelA and represses proinflammatory gene expression as determined by co-immunoprecipitation, chromatin immunoprecipitation, and electrophoretic mobility-shift assays. Remarkably, intrapulmonary administration of purified NEIL2 via a noninvasive nasal route significantly abrogated binding of NF-κB to cognate DNA, leading to decreased expression of proinflammatory genes and neutrophil recruitment in Neil2-null as well as WT mouse lungs. Our findings thus highlight the potential of NEIL2 as a biologic for inflammation-associated human diseases.

Molecular mechanisms and epidemiology of COVID-19 from an allergist's perspective.

The global pandemic caused by the newly described severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused worldwide suffering and death of unimaginable magnitude from coronavirus disease 2019 (COVID-19). The virus is transmitted through aerosol droplets, and causes severe acute respiratory syndrome. SARS-CoV-2 uses the receptor-binding domain of its spike protein S1 to attach to the host angiotensin-converting enzyme 2 receptor in lung and airway cells. Binding requires the help of another host protein, transmembrane protease serine S1 member 2. Several factors likely contribute to the efficient transmission of SARS-CoV-2. The receptor-binding domain of SARS-CoV-2 has a 10- to 20-fold higher receptor-binding capacity compared with previous pandemic coronaviruses. In addition, because asymptomatic persons infected with SARS-CoV-2 have high viral loads in their nasal secretions, they can silently and efficiently spread the disease. PCR-based tests have emerged as the criterion standard for the diagnosis of infection. Caution must be exercised in interpreting antibody-based tests because they have not yet been validated, and may give a false sense of security of being "immune" to SARS-CoV-2. We discuss how the development of some symptoms in allergic rhinitis can serve as clues for new-onset COVID-19. There are mixed reports that asthma is a risk factor for severe COVID-19, possibly due to differences in asthma endotypes. The rapid spread of COVID-19 has focused the efforts of scientists on repurposing existing Food and Drug Administration-approved drugs that inhibit viral entry, endocytosis, genome assembly, translation, and replication. Numerous clinical trials have been launched to identify effective treatments for COVID-19. Initial data from a placebo-controlled study suggest faster time to recovery in patients on remdesivir; it is now being evaluated in additional controlled studies. As discussed in this review, till effective vaccines and treatments emerge, it is important to understand the scientific rationale of pandemic-mitigation strategies such as wearing facemasks and social distancing, and implement them.

Mucosal bromodomain-containing protein 4 mediates aeroallergen-induced inflammation and remodeling.

BACKGROUND: Frequent exacerbations of allergic asthma lead to airway remodeling and a decrease in pulmonary function, producing morbidity. Cat dander is an aeroallergen associated with asthma risk. OBJECTIVE: We sought to elucidate the mechanism of cat dander-induced inflammation-remodeling. METHODS: We identified remodeling in mucosal samples from allergic asthma by using quantitative RT-PCR. We developed a model of aeroallergen-induced experimental asthma using repetitive cat dander extract exposure. We measured airway inflammation using immunofluorescence, leukocyte recruitment, and quantitative RT-PCR. Airway remodeling was measured by using histology, collagen content, myofibroblast numbers, and selected reaction monitoring. Inducible nuclear factor κB (NF-κB)-BRD4 interaction was measured by using a proximity ligation assay in situ. RESULTS: Enhanced mesenchymal signatures are observed in bronchial biopsy specimens from patients with allergic asthma. Cat dander induces innate inflammation through NF-κB signaling, followed by production of a profibrogenic mesenchymal transition in primary human small airway epithelial cells. The IκB kinase-NF-κB signaling pathway is required for mucosal inflammation-coupled airway remodeling and myofibroblast expansion in the mouse model of aeroallergen exposure. Cat dander induces NF-κB/RelA to complex with and activate BRD4, resulting in modifying the chromatin environment of inflammatory and fibrogenic genes through its atypical histone acetyltransferase activity. A novel small-molecule BRD4 inhibitor (ZL0454) disrupts BRD4 binding to the NF-κB-RNA polymerase II complex and inhibits its histone acetyltransferase activity. ZL0454 prevents epithelial mesenchymal transition, myofibroblast expansion, IgE sensitization, and fibrosis in airways of naive mice exposed to cat dander. CONCLUSIONS: NF-κB-inducible BRD4 activity mediates cat dander-induced inflammation and remodeling. Therapeutic modulation of the NF-κB-BRD4 pathway affects allergen-induced inflammation, epithelial cell-state changes, extracellular matrix production, and expansion of the subepithelial myofibroblast population.

Interleukin-4/interleukin-13 versus interleukin-5: a comparison of molecular targets in biologic therapy for the treatment of severe asthma.

PURPOSE OF REVIEW: Asthma is a chronic, inflammatory disorder of the airways caused by a complex interplay of various biologic mechanisms. Several monoclonal antibody therapies targeting interleukin (IL)-4/IL-13 and IL-5 cytokine pathways have been developed for the treatment of severe eosinophilic asthma. As individuals can display biomarkers and clinical features characteristic of several asthma phenotypes, selection of anoptimal biologic can be difficult. RECENT FINDINGS: Dupilumab, a monoclonal antibody that binds to the α subunit of the IL-4 receptor (IL-4Rα) and has been approved for the treatment of adults with severe atopic dermatitis, has been shown in recent phase 3 trials to also have significant clinical benefits in the asthmatic population irrespective of baseline eosinophil counts. SUMMARY: As monoclonal antibodies targeting either IL-4 or IL-13 cytokines individually have failed to demonstrate significant clinical benefits, biologics that target cytokine receptors may be more efficacious compared to those that target cytokines. Furthermore, inhibition of the IL-4/IL-13 signaling cascades may disrupt a broader Th2 inflammatory response compared to a more selective impairment of eosinophil proliferation and activity via blockage of the IL-5 pathway. Future research with independently funded, head-to-head trials of approved biologics is needed to elucidate a favorable therapeutic option.

Excision release of 5?hydroxycytosine oxidatively induced DNA base lesions from the lung genome by cat dander extract challenge stimulates allergic airway inflammation.

BACKGROUND: Ragweed pollen extract (RWPE) induces TLR4-NFκB-CXCL-dependent recruitment of ROS-generating neutrophils to the airway and OGG1 DNA glycosylase-dependent excision of oxidatively induced 8-OH-Gua DNA base lesions from the airway epithelial cell genome. Administration of free 8-OH-Gua base stimulates RWPE-induced allergic lung inflammation. These studies suggest that stimulation of innate receptors and their adaptor by allergenic extracts initiates excision of a set of DNA base lesions that facilitate innate/allergic lung inflammation. OBJECTIVE: To test the hypothesis that stimulation of a conserved innate receptor/adaptor pathway by allergenic extracts induces excision of a set of pro-inflammatory oxidatively induced DNA base lesions from the lung genome that stimulate allergic airway inflammation. METHODS: Wild-type (WT), Tlr4KO, Tlr2KO, Myd88KO, and TrifKO mice were intranasally challenged once or repeatedly with cat dander extract (CDE), and innate or allergic inflammation and gene expression were quantified. We utilized GC-MS/MS to quantify a set of oxidatively induced DNA base lesions after challenge of naïve mice with CDE. RESULTS: A single CDE challenge stimulated innate neutrophil recruitment that was partially dependent on TLR4 and TLR2, and completely on Myd88, but not TRIF. A single CDE challenge stimulated MyD88-dependent excision of DNA base lesions 5-OH-Cyt, FapyAde, and FapyGua from the lung genome. A single challenge of naïve WT mice with 5-OH-Cyt stimulated neutrophilic lung inflammation. Multiple CDE instillations stimulated MyD88-dependent allergic airway inflammation. Multiple administrations of 5-OH-Cyt with CDE stimulated allergic sensitization and allergic airway inflammation. CONCLUSIONS AND CLINICAL RELEVANCE: We show for the first time that CDE challenge stimulates MyD88-dependent excision of DNA base lesions. Our data suggest that the resultant-free base(s) contribute to CDE-induced innate/allergic lung inflammation. We suggest that blocking the MyD88 pathway in the airways with specific inhibitors may be a novel targeted strategy of inhibiting amplification of innate and adaptive immune inflammation in allergic diseases by oxidatively induced DNA base lesions.

Asthma versus chronic obstructive pulmonary disease, the Dutch versus British hypothesis, and role of interleukin-5.

PURPOSE OF REVIEW: Asthma and COPD represent heterogeneous disorders with broad ranging impact on patients and health systems. This review focuses on evidence for early attempts at understanding their pathogenesis by the British and Dutch hypotheses. It also addresses the role of eosinophils, IL-5, and biologics targeting these pathways in asthma and COPD. RECENT FINDINGS: Among asthma and COPD patients, clusters exist based on phenotypic and biologic markers allowing for further understanding of endotypes. Recent studies suggest the role of eosinophils and optimal therapies for each condition may be different. SUMMARY: Although patients with ACOS or overlap symptoms may be an exception, overall there appears to be more evidence supporting that asthma and COPD are distinct processes. Targeting eosinophils with anti-IL-5 therapy appears to be an exciting pathway in the properly selected patient with asthma and recent data also supports its use in COPD.

Role of epigenetics and DNA-damage in asthma.

PURPOSE OF REVIEW: Although asthma is a common disease worldwide, its pathogenesis remains to be fully elucidated. There is increasing evidence of the interaction between epigenetics, DNA-damage, and environmental allergens in the development of asthma. In this review, we will focus on the role of epigenetics and DNA-damage in asthma. RECENT FINDINGS: There is growing evidence of environmental allergens, particularly house dust mite, stimulating oxidative DNA damage in airway epithelial cells. The repair of this DNA damage has been implicated in the secretion of Th2 cytokines and the induction of allergic inflammation. SUMMARY: Studies of the role of epigenetics, DNA-damage, and environmental allergens have begun to reveal the their complex interactions and their roles in the development of asthma. Further study in these areas may lead to novel prevention and treatment approaches.

Pollen-induced oxidative DNA damage response regulates miRNAs controlling allergic inflammation.

A mucosal oxidative burst is a hallmark response to pollen exposure that promotes allergic inflammatory responses. Reactive species constituents of oxidative stress signal via the modification of cellular molecules including nucleic acids. One of the most abundant forms of oxidative genomic base damage is 8-oxo-7,8-dihydroguanine (8-oxoG), which is removed from DNA by 8-oxoguanine DNA glycosylase 1 (OGG1). OGG1 in complex with 8-oxoG acts as a GDP-GTP exchange factor and induces acute inflammation; however, the mechanism(s) by which OGG1 signaling regulates allergic airway inflammation is not known. Here, we postulate that the OGG1 signaling pathway differentially altered the levels of small regulatory RNAs and increased the expression of T helper 2 (Th2) cytokines in ragweed pollen extract (RWPE)-challenged lungs. To determine this, the lungs of sensitized mice expressing or lacking OGG1 were challenged with RWPE and/or with OGG1's excision product 8-oxoG. The responses in lungs were assessed by next-generation sequencing, as well as various molecular and histological approaches. The results showed that RWPE challenge induced oxidative burst and damage to DNA and activated OGG1 signaling, resulting in the differential expression of 84 micro-RNAs (miRNAs), which then exacerbated antigen-driven allergic inflammation and histological changes in the lungs. The exogenous administration of the downregulated let-7b-p3 mimetic or inhibitors of upregulated miR-23a or miR-27a decreased eosinophil recruitment and mucus and collagen production via controlling the expression of IL-4, IL-5, and IL-13. Together, these data demonstrate the roles of OGG1 signaling in the regulation of antigen-driven allergic immune responses via differential expression of miRNAs upstream of Th2 cytokines and eosinophils.

IgE and eosinophils as therapeutic targets in asthma.

PURPOSE OF REVIEW: Asthma is a chronic inflammatory disorder characterized by reversible airflow obstruction, which is being more widely recognized as a broad-spectrum disease that encompasses multiple patient characteristics and pathophysiologic mechanisms. Suboptimal asthma control leads to increasing burden of healthcare costs and loss of productivity to society. Biologic therapies targeted at IgE and eosinophils can be used in poorly controlled allergic and eosinophilic asthma, respectively. The purpose of this review is to analyze the advancements in currently available biologic therapies targeted at IgE and eosinophils in asthma and to identify how these therapies may impact overall healthcare costs. RECENT FINDINGS: Omalizumab is an anti-IgE antibody that is approved for use of poorly controlled moderate-to-severe asthma. Many studies have confirmed that omalizumab not only improves quality of life and symptom scores, but also decreases urgent care and emergency department visits and hospitalizations. Dupilumab is a biologic agent targeted at TH2 cytokines, but indirectly impacts IgE and is an important biologic agent for atopic disease. Mepolizumab, reslizumab, and benralizumab target IL-5, a key cytokine for eosinophils. For patients with poorly controlled eosinophilic asthma, these biologic agents improve asthma symptoms, reduce exacerbations, and reduce emergency visits and hospitalizations. SUMMARY: Poorly controlled severe asthma affects a small portion of patients with asthma in the United States and yet it accounts for large portion of healthcare utilization. Biological therapies in poorly controlled severe persistent asthma have been identified to reduce healthcare utilization, including emergency visits and hospitalizations. Biologic agents have a clear beneficial role in the management of severe asthma, and further evaluations should be continued in identifying optimal patient characteristics for the various agents and overall benefit toward healthcare utilization and cost.

Myeloid differentiation protein 2 facilitates pollen- and cat dander-induced innate and allergic airway inflammation.

BACKGROUND: The National Health and Nutrition Examination Survey identified several pollens and cat dander as among the most common allergens that induce allergic sensitization and allergic diseases. We recently reported that ragweed pollen extract (RWPE) requires Toll-like receptor 4 (TLR4) to stimulate CXCL-mediated innate neutrophilic inflammation, which in turn facilitates allergic sensitization and airway inflammation. Myeloid differentiation protein 2 (MD2) is a TLR4 coreceptor, but its role in pollen- and cat dander-induced innate and allergic inflammation has not been critically evaluated. OBJECTIVE: We sought to elucidate the role of MD2 in inducing pollen- and cat dander-induced innate and allergic airway inflammation. METHODS: TCM(Null) (TLR4(Null), CD14(Null), MD2(Null)), TLR4(Hi), and TCM(Hi) cells and human bronchial epithelial cells with small interfering RNA-induced downregulation of MD2 were stimulated with RWPE, other pollen allergic extracts, or cat dander extract (CDE), and activation of nuclear factor κB (NF-κB), secretion of the NF-κB-dependent CXCL8, or both were quantified. Wild-type mice or mice with small interfering RNA knockdown of lung MD2 were challenged intranasally with RWPE or CDE, and innate and allergic inflammation was quantified. RESULTS: RWPE stimulated MD2-dependent NF-κB activation and CXCL secretion. Likewise, Bermuda, rye, timothy, pigweed, Russian thistle, cottonwood, walnut, and CDE stimulated MD2-dependent CXCL secretion. RWPE and CDE challenge induced MD2-dependent and CD14-independent innate neutrophil recruitment. RWPE induced MD2-dependent allergic sensitization and airway inflammation. CONCLUSIONS: MD2 plays an important role in induction of allergic sensitization to cat dander and common pollens relevant to human allergic diseases.

Neutrophil recruitment by allergens contribute to allergic sensitization and allergic inflammation.

PURPOSE OF REVIEW: To discuss the presence and role of neutrophils in asthma and allergic diseases, and outline the importance of pollen and cat dander-induced innate neutrophil recruitment in induction of allergic sensitization and allergic inflammation. RECENT FINDINGS: Uncontrolled asthma is associated with elevated numbers of neutrophils, and levels of neutrophil-attracting chemokine IL-8 and IL-17 in bronchoalveolar lavage fluids. These parameters negatively correlate with lung function. Pollen allergens and cat dander recruit neutrophils to the airways in a toll-like receptor 4, myeloid differentiation protein-2, and chemokine (C-X-C motif) receptor (CXCR) 2-dependent manner. Repeated recruitment of activated neutrophils by these allergens facilitates allergic sensitization and airway inflammation. Inhibition of neutrophil recruitment with CXCR2 inhibitor, disruption of toll-like receptor 4, or small interfering RNA against myeloid differentiation protein-2 also inhibits allergic inflammation. The molecular mechanisms by which innately recruited neutrophils contribute to shifting the airway inflammatory response induced by allergens from neutrophilic to an eosinophilic-allergic is an area of active research. SUMMARY: Recent studies have revealed that neutrophil recruitment is important in the development of allergic sensitization and inflammation. Inhibition of neutrophils recruitment may be a strategy to control allergic inflammation.