A549 cells can express interleukin-16 and stimulate eosinophil chemotaxis

SARS-CoV-2 nucleocapsid protein, rather than spike protein, triggers a cytokine storm originating from lung epithelial cells in patients with COVID-19

PURPOSE

The aim of this study was to elucidate the factors associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that may initiate cytokine cascades and correlate the clinical characteristics of patients with coronavirus disease 2019 (COVID-19) with their serum cytokine profiles.

METHODS

Recombinant baculoviruses displaying SARS-CoV-2 spike or nucleocapsid protein were constructed and transfected into A549 cells and THP-1-derived macrophages, to determine which protein initiate cytokine release. SARS-CoV-2-specific antibody titers and cytokine profiles of patients with COVID-19 were determined, and the results were associated with their clinical characteristics, such as development of pneumonia or length of hospital stay.

RESULTS

The SARS-CoV-2 nucleocapsid protein, rather than the spike protein, triggers lung epithelial A549 cells to express IP-10, RANTES, IL-16, MIP-1α, basic FGF, eotaxin, IL-15, PDGF-BB, TRAIL, VEGF-A, and IL-5. Additionally, serum CTACK, basic FGF, GRO-α, IL-1α, IL-1RA, IL-2Rα, IL-9, IL-15, IL-16, IL-18, IP-10, M-CSF, MIF, MIG, RANTES, SCGF-β, SDF-1α, TNF-α, TNF-β, VEGF, PDGF-BB, TRAIL, β-NGF, eotaxin, GM-CSF, IFN-α2, INF-γ, and MCP-1 levels were considerably increased in patients with COVID-19. Among them, patients with pneumonia had higher serum IP-10 and M-CSF levels than patients without. Patients requiring less than 3 weeks to show negative COVID-19 tests after contracting COVID-19 had higher serum IP-10 levels than the remaining patients.

CONCLUSION

Our study revealed that nucleocapsid protein, lung epithelial cells, and IP-10 may be potential targets for the development of new strategies to prevent, or control, severe COVID-19.

Evaluation of 6-PPD quinone toxicity on lung of male BALB/c mice by quantitative proteomics

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ), a transformation product of tyre-derived 6-PPD, has been frequently detected in different environments. After 6-PPDQ exposure, we here aimed to examine dynamic lung bioaccumulation, lung injury, and the underlying molecular basis in male BALB/c mice. After single injection at concentration of 4 mg/kg, 6-PPDQ remained in lung up to day 28, and higher level of 6-PPDQ bioaccumulation in lung was observed after repeated injection. Severe inflammation was observed in lung after both single and repeated 6-PPDQ injection as indicated by changes of inflammatory cytokines (TNF-α, IL-6 and IL-10). Sirius red staining and hydroxyproline content analysis indicated that repeated rather than single 6-PPDQ injection induced fibrosis in lung. Repeated 6-PPDQ injection also severely impaired lung function in mice by influencing chord compliance (Cchord) and enhanced pause (Penh). Proteomes analysis was further carried out to identify molecular targets of 6-PPDQ after repeated injection, which was confirmed by transcriptional expression analysis and immunohistochemistry staining. Alterations in Ripk1, Fadd, Il-6st, and Il-16 expressions were identified to be associated with inflammation induction of lung after repeated 6-PPDQ injection. Alteration in Smad2 expression was identified to be associated with fibrosis formation in lung of 6-PPDQ exposed mice. Therefore, long-term and repeated 6-PPDQ exposure potentially resulted in inflammation and fibrosis in lung by affecting certain molecular signals in mammals. Our results suggested several aspects of lung injury caused by 6-PPDQ and provide the underlying molecular basis. These observations implied the possible risks of long-term 6-PPDQ exposure to human health.

4-Octyl Itaconate Alleviates Airway Eosinophilic Inflammation by Suppressing Chemokines and Eosinophil Development

4-Octyl itaconate (4-OI) is a derivative of the Krebs cycle-derived metabolite itaconate and displays an array of antimicrobial and anti-inflammatory properties through modifying cysteine residues within protein targets. We have found that 4-OI significantly reduces the production of eosinophil-targeted chemokines in a variety of cell types, including M1 and M2 macrophages, Th2 cells, and A549 respiratory epithelial cells. Notably, the suppression of these chemokines in M1 macrophages was found to be NRF2-dependent. In addition, 4-OI can interfere with IL-5 signaling and directly affect eosinophil differentiation. In a model of eosinophilic airway inflammation in BALB/c mice, 4-OI alleviated airway resistance and reduced eosinophil recruitment to the lungs. Our findings suggest that itaconate derivatives could be promising therapeutic agents for the treatment of eosinophilic asthma.

Therapeutic Potential of Chungsangboha-tang for the Treatment of Asthma: A Review of Preclinical and Clinical Studies

In traditional Korean medicine, Chungsangboha-tang (CSBHT) and its modified forms are used to treat various respiratory disorders, including asthma. This study aimed to identify research trends, clarify the effectiveness of CSBHT and related prescriptions, and lay a foundation for future research. We conducted a literature review using PubMed, Embase, Google Scholar, Oriental Medicine Advanced Searching Integrated System, National Digital Science Links, Korean Medical Database, Wanfang Data, and Chinese National Knowledge Infrastructure databases. We analyzed 25 studies, including 5 in vitro studies, 6 animal studies, and 14 human studies. Many studies evaluated the efficacy of CSBHT and its related prescriptions, including experimental studies on its effectiveness in asthma. The main mechanism of action involves the anti-inflammatory effect caused by the regulation of various immune cells, cytokines, and chemokines. In addition, clinical trials on asthma reported the benefits of CSBHT and its related prescriptions. However, there has been no randomized controlled study of clinical trials on the clinical effectiveness of CSBHT in asthma. Therefore, large-scale randomized controlled studies should be conducted in the future.

Interleukin 16 Enhances the Host Susceptibility to Influenza A Virus Infection

Influenza A virus (IAV) is a major respiratory pathogen that causes seasonal and pandemic flu, being a threat to global health. Various viral and cellular factors have been characterized to support or limit IAV infection. Interleukin 16 (IL16) has been known as one of the blood signature biomarkers discriminating systemic inflammation due to viral infection vs. other etiologies. Here, we report that the level of IL16 was elevated in the serum samples, lung homogenates, and bronchoalveolar lavage fluid of IAV-infected mice. IL16 overexpression facilitated IAV replication. Conversely, loss of IL16 reduced the host susceptibility to IAV infection in vitro and in vivo. Furthermore, IL16 deficiency blocked IAV-induced body weight loss and attenuated lung injury in the infected mice. Molecular mechanism analyses further revealed that IL16 could directly inhibit IFN-β transcription and suppress the expression of IFN-β and IFN-stimulated gene. In conclusion, these findings demonstrate that IL16 is a supporting factor for IAV infection.

IL-16 effects on A549 lung epithelial cells: dependence on CD9 as an IL-16 receptor?

Interleukin-16 (IL-16) is a pro-inflammatory cytokine released by many types of cells found in the lungs, including normal airway and alveolar epithelial cells. Though a chemotactin for CD4(+) cells and eosinophils, IL-16 also modulates their production of factors that influence inflammatory lung diseases, e.g., asthma and allergic rhinitis. To date, little is known about any potential autocrine-like regulatory effects of IL-16. Using a model human alveolar basal epithelial A549 cell line, the present study sought to assess lung epithelial cell responses to IL-16. Potential induced effects on cell growth/function were assessed using MTT reduction, lactate dehydrogenase release, and 5-bromo-2-deoxyuridine incorporation assays. As IL-16 (at locally high levels) can induce CD4(+) cell death via apoptosis, this potential outcome among the A549 cells was also evaluated using TUNEL and changes in expression of caspase-3 and the pro-apoptotic and anti-apoptotic proteins of Bcl-2 family. The data here indicated that IL-16 inhibited A549 cell growth/function and this was associated with a marked increase in apoptosis characterized by DNA fragmentation, activation of caspase-3, and altered pro-apoptotic protein expression. Since lung epithelial cells lack the CD4 that may bind IL-16, it has been suggested that CD9 may act as an alternate receptor for this cytokine (i.e., an IL-16R). Thus, these studies also sought to determine the extent of CD9 expression on A549 cells and if any/all observed IL-16-induced changes were mediated by CD9. Flow cytometric analyses revealed the cells to be CD9(+)CD4(-). However, neutralization of the purported IL-16R with anti-CD9 antibody could not block the cytotoxic/growth inhibiting effects of IL-16. The only exception appeared to be a mitigation of a chemotactic effect of IL-16; however, studies with an equal amount of non-specific antibody (of same isotype as the anti-CD9) revealed this effect to be artefactual. The neutralization study results thus suggest to us that as-yet undefined pathway(s) exist through which IL-16 may act to exert growth inhibiting/apoptosis-inducing effects on A549 cells, a cell line routinely used as a model for lung epithelial cells.

A new compound, 1H,8H-pyrano[3,4-c]pyran-1,8-dione, suppresses airway epithelial cell inflammatory responses in a murine model of asthma

Clinical and experimental studies have established eosinophilia as a sign of allergic disorders. Activation of eosinophils in the airways is believed to cause epithelial tissue injury, contraction of airway smooth muscle and increased bronchial responsiveness. As part of the search for new antiasthmatic agents produced by medicinal plants, the effects of 270 standardized medicinal plant extracts on cytokine-activated A549 human lung epithelial cells were evaluated. After several rounds of activity-guided screening, the new natural compound, 1H,8H-Pyrano[3,4-c]pyran-1,8-dione (PPY), was isolated from Vitex rotundifolia L. To elucidate the mechanism by which the anti-asthmatic responses of PPY occurred in vitro, lung epithelial cells (A549 cell) were stimulated with TNF-alpha, IL-4 and IL-1beta to induce the expression of chemokines and adhesion molecules involved in eosinophil chemotaxis. PPY treatments reduced the expression of eotaxin, IL-8, IL-16 and VCAM-1 mRNA significantly. Additionally, PPY reduced eotaxin secretion in a dose-dependent manner and significantly inhibited eosinophil migration toward A549 medium. In addition, PPY treatment suppressed the phosphorylation of p65 and ERK1/2, suggesting that it can inhibit the MAPK/NF-KB pathway. To clarify the anti-inflammatory and antiasthmatic effects of PPY in vivo, we examined the influence of PPY on the development of pulmonary eosinophilic inflammation in a murine model of asthma. To accomplish this, mice were sensitized and challenged with ovalbumin (OVA) and then examined for the following typical asthmatic reactions: an increase in the number of eosinophils in BALF; the presence of Th2 cytokines such as IL-4 and IL-5 in the BALF; the presence of allergen-specific IgE in the serum; and a marked influx of inflammatory cells into the lung. Taken together, our results revealed that PPY exerts profound inhibitory effects on the accumulation of eosinophils into the airways while reducing the levels of IL-4, IL-5, and IL-13 in the BALF. Therefore, these results suggest that PPY may be useful as a new therapeutic drug for the treatment of allergic asthma.

Inhibition effects of Vitex rotundifolia on inflammatory gene expression in A549 human epithelial cells

BACKGROUND

Vitex rotundifolia has long been used in traditional medicine to treat asthma and other allergic diseases.

OBJECTIVE

To evaluate the anti-inflammatory mechanisms of V rotundifolia in cultured A549 human alveolar epithelial cells.

METHODS

In the present study, A549 cells were stimulated with tumor necrosis factor alpha, interleukin 4, and interleukin 1beta to induce expression of chemokines and adhesion molecules involved in eosinophil chemotaxis. The anti-inflammatory effects of V rotundifolia on stimulated A549 cells were then evaluated by analyzing eotaxin secretion and eosinophil migration. In addition, the effects of V rotundifolia on gene expression profiles in stimulated A549 cells were evaluated by oligonucleotide microarray and real-time reverse transcription-polymerase chain reaction (RTRP).

RESULTS

The V rotundifolia-treated A549 cells had significantly suppressed eotaxin secretion and eosinophil migration in a dose-dependent manner. In addition, the results of the microarray analysis and RTRP revealed that inflammation-related genes and cell adhesion-related genes were down-regulated in V rotundifolia-treated A549 cells. Furthermore, several genes related to the mitogen-activated protein kinase pathway were down-regulated in V rotundifolia-treated A549 cells.

CONCLUSIONS

The mechanism responsible for the effects of V rotundifolia on A549 cells is closely associated with regulation of the mitogen-activated protein kinase pathway. Thus, V rotundifolia may be useful in the treatment of asthma and other allergic diseases.

The role of interleukin-16 in eosinophilic chronic rhinosinusitis

Eosinophilic granulocytes (Eos) are found in great numbers both in the tissue and in the mucus of patients suffering from chronic rhinosinusitis with polyposis (ECRS). Interleukin-16 (IL-16) is known as a highly potent chemotactic and chemoattractant molecule (ED 10-11) for Eos. In an open, explorative, controlled study we examined the presence of IL-16 in mucosa tissue, mucus and serum in patients suffering from ECRS and its association to Eos activation. Tissue and nasal mucus specimen from 10 previously untreated, non allergic ECRS-patients undergoing paranasal sinus surgery and from 10 healthy non sinusitis subjects, undergoing nasal surgery because of anatomic nasal obstruction were investigated by real-time (RT-) PCR targeting human IL-16 mRNA. Haematoxylin-eosin (HE) staining and immunohistochemistry of formalin embedded tissue and mucus were applied for detection and determination of the proportion of activated Eos (aEos) and IL-16. Serum IL-16 was analyzed by enzyme-linked-immunosorbent assay (ELISA). IL-16 mRNA and IL-16 protein levels were elevated in nasal mucus, polyp tissue and in the serum of ECRS patients compared to healthy controls. There was a high proportion of aEos in ECRS patients compared to healthy subjects. Serum IL-16, IL-16 mRNA expression and IL-16 protein in mucus and tissue specimens were significantly associated with the presence of aEos in polyps of ECRS patients. Immunohistochemically IL-16 protein was mainly expressed in aEos, mast cells, lymphocytes and epithelial cells. In conclusion our data indicate that IL-16 may stimulate the migration and persistence of activated Eos in ECRS. IL-16 production in ECRS patients is not mediated by Immunglobuline-E (IgE).

Respiratory immunotoxicity: An in vitro assessment

As yet, in vitro assessment of the immunotoxic potency of respiratory agents is not possible. The complexity of the endpoint and the respiratory tract, and the limited availability of well-documented respiratory agents are the main reasons. The evidence that epithelial cells (ECs) are triggered by compounds to express in vitro surface proteins and soluble mediators, has stimulated their use for developing tests for respiratory immunotoxicity. A variety of airway ECs and EC-lines have been assessed, but the available information seems to point at human alveolar cells (e.g., A549) as the most convenient cell type. EC-based test formats with various degrees of complexity have been assessed. Sofar, promising results were obtained using a 3D model using the human A549 lung cell line. Dendritic cells (DCs) have been subjected to intensive research. However, currently available tests are not well suited to discern among the potency of sensitizers. Potential explanations include the lack of standardised protocols for the generation of DCs, no good standards for estimating the quality of in vitro derived DC-cultures, and limited dynamics of the currently used end-points. Alveolar macrophages (AMs) have so far received less attention. This may proof unjustified as macrophages may link innate responses to adaptive immunity. The observation that ECs, DCs and AMs affect each other, suggests that test formats are required combining at least two of these cell types if ranking of compounds according to their sensitising potency is the aim. In addition, the capacity of compounds to cross a cellular membrane is an important property of an immunotoxic compound, which can be assessed only in 3D reconstituted human tissue models. While promising data have been reported for the skin, immunocompetent 3D reconstituted human lung remains to be evaluated for respiratory immunotoxicity. Obviously, the success of any of these simplified test (as compared to the complexity of the immune response) is highly dependent on the availability of early stage biomarkers (expressed at mucosal barrier level) that are predictive for relevant immunotoxicity mechanisms occurring down-stream of the immune response. As yet, such biomarkers are not yet available.

The therapeutic potential in targeting CCR5 and CXCR4 receptors in infectious and allergic pulmonary disease

Targeting chemokines and chemokine receptors in various acute and chronic pulmonary diseases remains a vibrant area of basic and clinical research despite major hurdles including cross-species barriers, toxicity, and redundancy. In this review, we draw upon our basic research with a murine model in which innate and acquired immunity are linked in the development and maintenance of chronic asthma due to Aspergillus fumigatus. Using intact and genetically altered mice, studies have also been undertaken to elucidate safe and effective therapeutic strategies that interrupt the initiation and amplification of inflammatory and immune events that follow the intrapulmonary introduction of Aspergillus into A. fumigatus-sensitized mice. These events include resident immune cell activation, immune and inflammatory cell recruitment to the airways, changes in lung physiology, and profound changes in the architecture of the airway due to the activation of lung resident cells. The expression of 2 major chemokine receptors, namely, CC chemokine receptor (CCR) 5 and CXC chemokine receptor (CXCR) 4, has been identified and their roles in innate and acquired immune events during fungal asthma have been explored. CCR5 and CXCR4 are best known for their roles in human immunodeficiency virus-1 (HIV-1) infection, but both are attractive targets in the context of overt inflammatory and remodeling responses in the lung. This avenue of research is markedly enhanced by the existence of numerous small molecule antagonists that are available to selectively target these receptors.

Melatonin promoted chemotaxins expression in lung epithelial cell stimulated with TNF-alpha

BACKGROUND

Patients with asthma demonstrate circadian variations in the airway inflammation and lung function. Pinealectomy reduces the total inflammatory cell number in the asthmatic rat lung. We hypothesize that melatonin, a circadian rhythm regulator, may modulate the circadian inflammatory variations in asthma by stimulating the chemotaxins expression in the lung epithelial cell.

METHODS

Lung epithelial cells (A549) were stimulated with melatonin in the presence or absence of TNF-alpha(100 ng/ml). RANTES (Regulated on Activation Normal T-cells Expressed and Secreted) and eotaxin expression were measured using ELISA and real-time RT-PCR, eosinophil chemotactic activity (ECA) released by A549 was measured by eosinophil chemotaxis assay.

RESULTS

TNF-alpha increased the expression of RANTES (307.84 +/- 33.56 versus 207.64 +/- 31.27 pg/ml of control, p = 0.025) and eotaxin (108.97 +/- 10.87 versus 54.00 +/- 5.29 pg/ml of control, p = 0.041). Melatonin(10(-10) to 10(-6)M) alone didn't change the expression of RNATES (204.97 +/- 32.56 pg/ml) and eotaxin (55.28 +/- 6.71 pg/ml). However, In the presence of TNF-alpha (100 ng/ml), melatonin promoted RANTES (410.88 +/- 52.03, 483.60 +/- 55.37, 559.92 +/- 75.70, 688.42 +/- 95.32, 766.39 +/- 101.53 pg/ml, treated with 10(-10), 10(-9), 10(-8), 10(-7),10(-6)M melatonin, respectively) and eotaxin (151.95 +/- 13.88, 238.79 +/- 16.81, 361.62 +/- 36.91, 393.66 +/- 44.89, 494.34 +/- 100.95 pg/ml, treated with 10(-10), 10(-9), 10(-8), 10(-7), 10(-6)M melatonin, respectively) expression in a dose dependent manner in A549 cells (compared with TNF-alpha alone, P < 0.05). The increased release of RANTES and eotaxin in A549 cells by above treatment were further confirmed by both real-time RT-PCR and the ECA assay.

CONCLUSION

Taken together, our results suggested that melatonin might synergize with pro-inflammatory cytokines to modulate the asthma airway inflammation through promoting the expression of chemotaxins in lung epithelial cell.

CD40 on adult human airway epithelial cells: expression and proinflammatory effects

CD40/CD40 ligand interaction is an important pathway for B and T cell cooperation and function; functional CD40 molecules have recently been found on nonhematopoietic cells. We detected CD40 in vivo on normal human respiratory epithelial cells and showed that its expression is increased on inflamed airway epithelium. Subsequently, we analyzed its expression and function on primary cultures of human airway epithelial cells. Our data show that CD40 is up-regulated by IFN-beta and IFN-gamma, its ligation increases the surface expression of CD54 and CD106 and it may stimulate the release of IL-6 and IL-8. The use of Janus kinase 3 (JAK3) and NF-kappaB inhibitors suggests that both basal and CD40-induced release of the two cytokines is JAK3-dependent. Using colocalization techniques, we revealed the existence of CD40/JAK3 and CD40/TNFR-associated factor 2 interplay. The extent of these interactions may be partial (2-40% of the cells) or massive (80-90% of the cells) in cultured cells. Stimulation via CD40 causes a significant increase in the number of cells expressing colocalization only in the cultures displaying low frequency of initial colocalization. Thus, airway epithelial cells, activated by CD40, may behave as effector cells of the inflammation process and should be considered priority targets for anti-inflammatory therapy. This work identifies CD40 and the correlated JAK3 signaling molecule as potential molecular targets to block the inflammatory functions of epithelial cells.

Role of monocytes and eosinophils in human respiratory syncytial virus infection in vitro

RSV infection in airway epithelial cells (EC) results in production of the chemokines RANTES and MIP1alpha and the leukocyte differentiation factor GM-CSF. The chemokines attract monocytes and eosinophils to the site of infection, where GM-CSF may influence their function and differentiation. In turn, these inflammatory cells may limit the progression of RSV infection, as well as initiate immune responses. In the present study, the effect of monocytes and eosinophils on viral replication and infection-dependent release of EC-derived cytokines was investigated. The modulation of immune cell costimulatory molecules, CD80, CD86, CD40, and HLA-DR, and the release of the CD4(+) T cell chemoattractant IL-16 were also investigated. Employing immunofluorescence techniques, monocytes and eosinophils in cocultures with infected EC were found to inhibit the spread of RSV to uninfected cells. Monocytes also had a significant effect on replication of RSV. Monocytes phagocytized the virus, while eosinophils inhibited reinfection mainly by extracellular means. The release of G-CSF and GM-CSF in the infected cultures was not significantly affected by either monocytes or eosinophils, while RANTES release was significantly decreased. The expression of CD40, CD80, CD86, and HLA-DR on monocytes, but not on eosinophils, increased in an RSV-dose-dependent manner. IL-16 release was not induced in RSV-infected EC, but was significantly increased in coculture with monocytes. These results suggest that both monocytes and eosinophils attracted to the site of RSV infection play an important role in confining infection, while RSV-exposed monocytes may be involved in promoting/polarizing immune responses to RSV.