Anti-inflammatory effects of medications used for viral infection-induced respiratory diseases

Respiratory viruses like rhinovirus, influenza virus, respiratory syncytial virus, and coronavirus cause several respiratory diseases, such as bronchitis, pneumonia, pulmonary fibrosis, and coronavirus disease 2019, and exacerbate bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis, and diffuse panbronchiolitis. The production of inflammatory mediators and mucin and the accumulation of inflammatory cells have been reported in patients with viral infection-induced respiratory diseases. Interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α, granulocyte-macrophage colony-stimulating factor, and regulated on activation normal T-cell expressed and secreted are produced in the cells, including human airway and alveolar epithelial cells, partly through the activation of toll-like receptors, nuclear factor kappa B and p44/42 mitogen-activated protein kinase. These mediators are associated with the development of viral infection-induced respiratory diseases through the induction of inflammation and injury in the airway and lung, airway remodeling and hyperresponsiveness, and mucus secretion. Medications used to treat respiratory diseases, including corticosteroids, long-acting β₂-agonists, long-acting muscarinic antagonists, mucolytic agents, antiviral drugs for severe acute respiratory syndrome coronavirus 2 and influenza virus, macrolides, and Kampo medicines, reduce the production of viral infection-induced mediators, including cytokines and mucin, as determined in clinical, in vivo, or in vitro studies. These results suggest that the anti-inflammatory effects of these medications on viral infection-induced respiratory diseases may be associated with clinical benefits, such as improvements in symptoms, quality of life, and mortality rate, and can prevent hospitalization and the exacerbation of chronic obstructive pulmonary disease, bronchial asthma, bronchiectasis, and diffuse panbronchiolitis.     

The contribution of viral respiratory infections to the pathogenesis of airway hyperreactivity

From this review, it is apparent that the effects of respiratory viral infection on airway reactivity are multiple. Although virus-associated changes are many, we have at present no evidence to show that respiratory viruses cause intrinsic abnormalities in airway smooth muscle function. Rather, respiratory viruses influence bronchial smooth muscle function through a variety of other means: epithelial injury, PMN-dependent inflammation, and greater mediator release. These observations suggest that a common pathway to development of airway hyperreactivity during respiratory viral illnesses is to enhance those factors which participate in the inflammatory response. When the target of this enhanced inflammatory response becomes the airway, greater bronchial reactivity and obstruction result. Although many questions remain to be answered, we feel that future studies to evaluate the biology of respiratory virus effects on mechanisms of airway responsiveness will lead to a greater understanding of asthma pathogenesis.     

The role of respiratory viruses in acute and chronic asthma

Respiratory infections can have dual effects related to asthma. First, there is increasing evidence that severe infections with RSV and PIV in infancy can alter lung development and physiology to increase the risks of subsequent wheezing and asthma. Second, infections with common cold viruses and influenza commonly precipitate wheezing symptoms in children and adults who already have established asthma, and RV appears to be the most important virus in producing exacerbations of the disease. The principal mechanisms by which this occurs appears to be viral replication in epithelial cells, triggering a cascade of inflammation involving granulocytes, macrophages, T cells, and secreted cytokines and mediators. The inflammatory process, although essential to clear the infection, augments pre-existing airway inflammation in asthma, leading to increased airway obstruction and lower respiratory tract symptoms. Greater understanding of virus-induced changes in inflammation and corresponding changes in airway physiology may lead to new therapeutic approaches to the treatment and prevention of virus-induced airway dysfunction.     

The pathogenesis and therapy of virus infection-induced senile bronchial asthma

We investigated the pathogenesis and therapy of virus infection-induced senile bronchial asthma in vitro. To examine the effects of rhinovirus infection on the production of cytokines and intercellular adhesion molecule-1 (ICAM-1), human tracheal epithelial cells and submucosal gland cells were cultured, and infected with human rhinovirus. Rhinovirus upregulated the production of interleukin (IL)-1 beta, IL-6, IL-8, tumor necrosis factor (TNF)-alpha in supernatants of epithelial cells and submucosal-gland cells, and IL-1 alpha and granulocyte macrophage colony-stimulating factor (GM-CSF) in supernatants of submucosal gland cells. Rhinovirus upregulated the expression of ICAM-1 mRNA. Rhinovirus infection also increased epithelial permeability. These events may be important for the spread of airway inflammation after rhinovirus infection. Furthermore, we studied the effects of dexamethasone and erythromycin on the modulation of virus infection and induction of cytokines and ICAM-1 in tracheal epitherial cells. Both of them reduced viral titers of rhinovirus type 14, a major group rhinovirus, and cytokine production of supernatants, and ICAM-1 mRNA expression in the cells. Because it is known that acidic conditions by proton pumps are needed for rhinovirus entry into the cells, we studied the effects of H+ ATPase inhibitor bafilomycin A1. Bafilomycin A1 reduced the virus titers of both rhinovirus type 2 and 14 in supernatants. These findings in our in vitro study suggest that dexamethasone, erythromycin and bafilomycin A1 may inhibit rhinovirus infection and modulate airway inflammation induced by rhinovirus infection.     

Understanding asthma pathophysiology.

Asthma is best described as a chronic disease that involves inflammation of the pulmonary airways and bronchial hyperresponsiveness that results in the clinical expression of a lower airway obstruction that usually is reversible. Physiologically, bronchial hyperresponsiveness is documented by decreased bronchial airflow after bronchoprovocation with methacholine or histamine. Other triggers that provoke airway obstruction include cold air, exercise, viral upper respiratory infection, cigarette smoke, and respiratory allergens. Bronchial provocation with allergen induces a prompt early phase immunoglobulin E (IgE)-mediated decrease in bronchial airflow (forced expiratory volume in 1 second) followed in many patients by a late-phase IgE-mediated reaction with a decrease in bronchial airflow for 4-8 hours. The gross pathology of asthmatic airways displays lung hyperinflation, smooth muscle hypertrophy, lamina reticularis thickening, mucosal edema, epithelial cell sloughing, cilia cell disruption, and mucus gland hypersecretion. Microscopically, asthma is characterized by the presence of increased numbers of eosinophils, neutrophils, lymphocytes, and plasma cells in the bronchial tissues, bronchial secretions, and mucus. Initially, there is recruitment of leukocytes from the bloodstream to the airway by activated CD4 T-lymphocytes. The activated T-lymphocytes also direct the release of inflammatory mediators from eosinophils, mast cells, and lymphocytes. In addition, the subclass 2 helper T-lymphocytes subset of activated T-lymphocytes produces interleukin (IL)-4, IL-5, and IL-13. IL-4 in conjunction with IL-13 signals the switch from IgM to IgE antibodies. The cross-linkage of two IgE molecules by allergen causes mast cells to degranulate, releasing histamine, leukotrienes, and other mediators that perpetuate the airway inflammation. IL-5 activates the recruitment and activation of eosinophils. The activated mast cells and eosinophils also generate their cytokines that help to perpetuate the inflammation. Regardless of the triggers of asthma, the repeated cycles of inflammation in the lungs with injury to the pulmonary tissues followed by repair may produce long-term structural changes ("remodeling") of the airways. This review will discuss in greater detail the relationships of inflammation and airway hyperresponsiveness to the pathophysiology of asthma.     

The immunology of virus infection in asthma.

The respiratory tract is commonly infected by a range of viruses with overlapping pathologies. The majority of episodic exacerbations of asthma are associated with viral infection, in particular with rhinovirus infections. Experimental rhinovirus infection in human volunteers provides a useful model of natural virus-induced asthma. The asthmatic airway is characterized by an infiltrate of eosinophils and T-lymphocytes expressing the type 2 cytokines interleukin (IL)-4, IL-5 and IL-13. An effective antiviral immune response requires early viral clearance and appropriate termination of the immune response to minimize associated immunopathology and tissue damage. The antiviral immune response is made up of innate (nonspecific) and specific components, and requires the coordinated actions of many different cell types including neutrophils, macrophages, eosinophils, dendritic cells, epithelial cells, mast cells, natural killer cells and B- and T-lymphocytes. Coordination of this response involves numerous cytokines and chemokines. T-lymphocytes expressing type 1 cytokines including interferon-gamma play a key role. Pre-existing asthmatic inflammation in the lower airway may modify the immune response to viral infection by altering the balance of T-cell cytokine expression from type 1 towards a type 2 in what is always a mixed response. The consequence is delayed viral clearance, persistent virus-induced inflammation and amplification of the allergic inflammation.     

Regulation of Viral Infection-induced Airway Remodeling Cytokine Production by the TLR3-EGFR Signaling Pathway in Human Bronchial Epithelial Cells

Toll-like receptor 3 (TLR3) is involved in the virus-induced pulmonary inflammatory response, but its role in airway remodeling after viral infection is unclear. We explored the role of TLR3 in poly(I:C)-induced inflammatory cytokines and mucin 5AC (MUC5AC) production in human bronchial epithelial cells by Western blotting, RT-PCR and ELISA. The expression of TLR3, MUC5AC, Matrixmetalloproteinase (MMP9), Transforming growth factor (TGF-β1) and Vascular endothelial growth factor (VEGF) in human bronchial epithelial cells increased in a dose-dependent manner after exposure to poly(I:C), and this effect was inhibited by treatment with TLR3 siRNA. The phosphorylation of epithelial growth factor receptor (EGFR)/ERK/P38 Mitogen-activated protein kinases (MAPK) proteins increased after poly(I:C) treatment, and inhibition of this signaling pathway decreased TLR3 expression and MUC5AC and TGF-β1 production in human bronchial epithelial cells. The TLR3-EGFR signaling pathway is involved in the production of airway remodeling cytokines after virus infection. Inhibiting EGFR and its signaling pathway may be a therapeutic strategy for modifying airway remodeling.     

Airway epithelial cell release of cytokines: modulation by various therapeutic agents.

The airway epithelial cell plays a central role in asthma pathogenesis and potential remodeling in secreting numerous cytokines, growth factors, chemokines, and nitric oxide. The role of various therapeutic agents on in vivo and in vitro antigen, growth factor, and respiratory syncytial virus-stimulated human small airway bronchial and alveolar epithelial cells will be reviewed. The experimental studies presented here, which used human airway epithelial cell cultures, may identify new therapeutic options in preventing amplified airway inflammation and remodeling in a subset of asthmatic or bronchiolitis patients with an atopic pre-disposition.     

Viral "bronchitis" in childhood: relationship to asthma and obstructive lung disease

Lower respiratory tract infections in children, including group, bronchiolitis, and bronchitis are frequently associated with recurrent episodes of wheezing. Different respiratory viruses assume greater importance at different ages of children. Respiratory syncytial virus is the most prevalent viral respiratory infection in preschool children, while rhinovirus is of increasing importance in older children. Asymptomatic virus shedding and mild respiratory infections do not provoke asthma symptoms nor do bacteria, except in association with sinusitis. Furthermore, epidemiologic studies strongly suggest that viral lower respiratory tract illness in early childhood is associated with pulmonary abnormalities, including bronchial hyperreactivity and peripheral airway obstruction that may persist for many years, and is possibly a cause of chronic airway obstruction in adulthood. Several different mechanisms have been identified by which respiratory viruses provoke asthma. No one single mechanism, however, adequately explains virus-induced asthma. Nonetheless, a common thread to these various proposed mechanisms is the ability of respiratory viruses to cause airway inflammation, either directly, through cytopathic effects, or indirectly, by increasing the inflammatory processes of respiratory cells. The consequence of these effects causes increased airway responsiveness and asthma.     

Emerging mediators of airway smooth muscle dysfunction in asthma

Phenotypic changes in airway smooth muscle are integral to the pathophysiological changes that constitute asthma – namely inflammation, airway wall remodelling and bronchial hyperresponsiveness. In vitro and in vivo studies have shown that the proliferative, secretory and contractile functions of airway smooth muscle are dysfunctional in asthma. These functions can be modulated by various mediators whose levels are altered in asthma, derived from inflammatory cells or produced by airway smooth muscle itself. In this review, we describe the emerging roles of the CXC chemokines (GROs, IP-10), Th17-derived cytokines (IL-17, IL-22) and semaphorins, as well as the influence of viral infection on airway smooth muscle function, with a view to identifying new opportunities for therapeutic intervention in asthma.     

酪氨酸激酶信号级联与支气管哮喘发病的关系

支气管哮喘的发病机制涉及炎症细胞和气道结构细胞、细胞因子、趋化因子、生长因子和炎症介质的相互作用.酪氨酸激酶信号级联在变应性气道炎症中起重要作用,活化的酪氨酸激酶激活了多重下游信号转导途径如磷酯酰肌醇3激酶、丝裂原活化蛋白激酶和核因子κB,导致细胞的分化、存活、增殖、脱颗粒和趋化.     

Toll-like receptors in the respiratory system: Their roles in inflammation

Allergic airway inflammation develops in the context of innate immune cells that express Toll-like receptors (TLRs). TLRs recognize microbial components and evoke diverse responses in immune and other respiratory cells through distinct signaling pathways. Bacterial and viral infection in the airway modulates the extent of allergic inflammation. TLR stimulation controls T helper (Th) 1, Th2, and Th17 cell differentiation, cytokine production in mast cells, and activation of eosinophils via direct and indirect pathways. TLR signals in dendritic cells increase expression of major histocompatibility complex proteins and T-cell coreceptors, resulting in greater T-cell activation with Th1 bias. TLR signals in mast cells increase their release of IL-5, and TLR signals in airway epithelial cells enhance airway generation of proallergic cytokines. Although these responses play an important protective role in infection, they may exacerbate allergic inflammation. Under some conditions, TLR stimulation, especially via TLR9, reduces Th2-dependent allergic inflammation through induction of Th1 responses. Therefore, understanding the regulatory role of TLRs in the pathogenesis of allergic airway inflammation may shed light on improving inflammation control in asthmatic patients.     

Invariant natural killer T (iNKT) cells in asthma: a novel insight into the pathogenesis of asthma and the therapeutic implication of glycolipid ligands for allergic diseases.

Allergic bronchial asthma is a complex inflammatory diseases originated from dysregulated immune responses in the respiratory mucosa. The inflammatory state in asthmatic lung is characterized by massive infiltration with eosinophils, lymphocytes, and mast cells in the airway mucosa leading to airway hyperseisitivity, goblet cell hyperplasia and mucus overproduction. The inflammatory process is thought to be the result of intensive T helper (Th) 2-biased immune response. Over the past several years, there has been enormous progress in understanding the mechanisms for development of Th2-biased responses after inhaled exposure to allergens and the characteristics of CD4+ T cells prominently involved in this process. Recently, a new population of T cells, invariant natural killer T (iNKT) cells has been shown to play an important role in the pathogenesis of mouse model of allergic airway inflammation. iNKT cells are one of the most potent immune modulators through a massive production of a various cytokines including IL-4 and IFN-gamma upon activation, and are involved in a variety of immunoregulations including infection, autoimmunity, and tumor surveillance. The potent pathogenic role of iNKT cells in the development of bronchial asthma is due to their ability to produce predominant Th2 cytokines in a given condition. The involvement of iNKT cells in the pathogenesis of asthma might have been underestimated in the past studies demonstrating the involvement of CD4+ T cells in asthma because of the difficulty in the detection of iNKT cells. Meanwhile, growing evidences have demonstrated that iNKT cells could be a promising target for immune-based therapies for autoimmune diseases, tumor, and infection due to the invariance of their TCR usage, the restriction to the evolutionally-conserved non-polymorphic antigen-presenting molecule CD1d, and their outstanding ability to produce both Th1- and Th2-cytokines. In this review, we will overview current understanding of the pathophysiological roles of iNKT cells in asthma. We would also discuss on possible therapeutic approaches to bronchial asthma employing glycolipid ligands for iNKT cells.     

Asthma death, CD8+ T cells, and viruses

Despite advances in the understanding of the pathophysiology of asthma and the availability of effective treatment, the World Health Organization estimates that asthma accounts for 1 in every 250 deaths worldwide. Viruses are associated with half of all asthma exacerbations. The immune response to viral infection may enhance preexisting airway inflammation via the release of chemokines and cytokines and local recruitment of inflammatory cells. Murine models have provided evidence for a deleterious role for CD8+ T cells in the context of respiratory viral infection. Passive transfer of respiratory syncytial virus-specific cytotoxic T lymphocytes (CTLs) to infected mice results in virus clearance, which is associated with acute and sometimes fatal pulmonary disease. Compared with control subjects, CD8+ cells appear to be preferentially sequestered in the airways of individuals with asthma during acute exacerbations. In addition, an expanded CD8+ T cell population, dominated by activated cytotoxic CD8+ lymphocytes, has been documented in biopsies from patients dying as a result of acute asthma in association with a viral infection. Undoubtedly, CD8+ CTLs are a crucial in cell-mediated immunity in response to respiratory viruses. However, it would appear that an aberrant CD8+ T cell response in the context of a viral infection may place individuals with asthma at risk for fatal asthma.     

Synthetic Response of Stimulated Respiratory Epithelium: Modulation by Prednisolone and iKK2 Inhibition

BackgroundThe airway epithelium plays a central role in wound repair and host defense and is implicated in the immunopathogenesis of asthma. Whether there are intrinsic differences between the synthetic capacity of epithelial cells derived from subjects with asthma and healthy control subjects and how this mediator release is modulated by antiinflammatory therapy remains uncertain. We sought to examine the synthetic function of epithelial cells from different locations in the airway tree from subjects with and without asthma and to determine the effects of antiinflammatory therapies upon this synthetic capacity.MethodsPrimary epithelial cells were derived from 17 subjects with asthma and 16 control subjects. The release of 13 cytokines and chemokines from nasal, bronchial basal, and air-liquid interface differentiated epithelial cells before and after stimulation with IL-1β, IL-1β and interferon-γ, or Poly-IC (Toll-like receptor 3 agonist) was measured using MesoScale discovery or enzyme-linked immunosorbent assay, and the effects of prednisolone and an inhibitor of nuclear factor κ-B2 (IKK2i) were determined.ResultsThe pattern of release of cytokines and chemokines was significantly different between nasal, bronchial basal, and differentiated epithelial cells but not between health and disease. Stimulation of the epithelial cells caused marked upregulation of most mediators, which were broadly corticosteroid unresponsive but attenuated by IKK2i.ConclusionSynthetic capacity of primary airway epithelial cells varied between location and degree of differentiation but was not disease specific. Activation of epithelial cells by proinflammatory cytokines and toll-like receptor 3 agonism is attenuated by IKK2i, but not corticosteroids, suggesting that IKK2i may represent an important novel therapy for asthma.     

The interaction of neutrophils with respiratory epithelial cells in viral infection

Viral respiratory infection is very common. Respiratory syncytial virus (RSV) infects almost all children during the first 2 years of life. Respiratory syncytial virus is the most frequent cause of bronchiolitis, which is strongly linked with asthma. However, the pathophysiology of RSV bronchiolitis is unclear. Neutrophils are the predominant airway leucocytes in RSV bronchiolitis and other viral infections. Neutrophils and their products are likely to play an important role in viral infection. Current evidence indicates that: (i) viral infection of epithelial cells increases the production of neutrophil chemoattractants or chemokines, which induce neutrophil migration into the inflammatory sites; (ii) the expression of adhesion molecules on neutrophils and epithelial cells is up-regulated in viral infection, and neutrophil-epithelial adhesion is increased; (iii) neutrophils augment epithelial damage and detachment induced by viral infection and contribute to the pathophysiology of viral disease; (iv) neutrophil apoptosis is up-regulated in RSV infection, which may be an in vivo mechanism to limit neutrophil-induced epithelial damage; (v) inhibitors of chemokines, adhesion molecules or neutrophil proteases may be useful in prevention of neutrophil-induced epithelial damage. In conclusion, neutrophils play an important role in viral infection, and intervention to prevent neutrophil-induced epithelial damage may be a potential clinical therapy.     

Mechanisms of airway remodeling in asthma.

Asthma is a chronic inflammatory disease characterized by reversible airflow limitation and airway hyperresponsiveness. Persistent inflammation in airway tissues may lead to structural changes known as airway remodeling and consequently airway obstruction that is not fully reversible and progressive loss of lung function over time. It is generally accepted that airway remodeling is closely related to progression of airway hyperresponsiveness, and the severity of asthma. The structural changes observed in chronic persistent asthma, which includes airway smooth muscle hypertrophy and hyperplasia, collagen deposition to sub-epithelial basement membrane, hyperplasia of goblet cells, thickening of airway mucosa and an increase in vascularity, are derived from airway inflammation. For instance, the thickened airway mucosa might be produced by cytokines and growth factors released from inflammatory cells and airway epithelial cells, and associated with bronchial hyperreactivity and asthma severity. To date, many studies have identified candidate mechanisms and mediators for these observed structural changes, which are thus potential targets in the treatment of asthma. In this review, we describe the recent knowledge of the mechanisms and clinical implications of airway remodeling in asthma.     

Roles of IL-18 in basophils and mast cells.

Basophils and mast cells are effecter cells in allergen/IgE-mediated immune responses. They induce type 1 immediate immune response in airway or other organ, resulting in bronchial asthma and other allergic diseases. However, they also play a critical role in host defense against infection with helminthes. Upon linkage of FcepsilonRI with a complex of allergen and IgE, basophils and mast cells release a large amount of Th2 cytokines and chemical mediators. Therefore these responses are "acquired allergic responses" and induce allergic diseases, such as bronchial asthma. However, basophils and mast cells derived from cultured bone marrow cells with IL-3 for 10 days express IL-18Ralpha chain and produce Th2 cytokines in response to the stimulation with IL-3 and IL-18 without FcepsilonRI cross-linkage. Furthermore, they produce Th2 cytokines upon stimulation with several TLR ligands, such as LPS. This finding may suggest the presence of allergen/IgE-independent allergic responses, which we would like to designate as "innate allergic response". However, in vivo treatment with IL-18 and IL-2 protects against gastrointestinal nematode infection by activating intestinal mucosal mast cells in STAT6-independent manner, suggesting the importance of innate allergic response against helminth infection. Here we discuss the functional role of IL-18-induced "innate allergic response" in disease and host defense.     

Toll样受体与支气管哮喘气道重塑

气道重塑是除气道慢性炎症以外支气管哮喘的又一重要特征.近年来研究表明,Toll样受体可通过调节多种致气道重塑因子如生长因子、细胞因子、炎性介质、趋化因子等的生成和活化,最终导致气道重塑.