Cooperation of immune regulators Tollip and surfactant protein A inhibits influenza A virus infection in mice.

BACKGROUND: Influenza A virus (IAV) infection is a significant risk factor for respiratory diseases, but the host defense mechanisms against IAV remain to be defined. Immune regulators such as surfactant protein A (SP-A) and Toll-interacting protein (Tollip) have been shown to be involved in IAV infection, but whether SP-A and Tollip cooperate in more effective host defense against IAV infection has not been investigated. METHODS: Wild-type (WT), Tollip knockout (KO), SP-A KO, and Tollip/SP-A double KO (dKO) mice were infected with IAV for four days. Lung macrophages were isolated for bulk RNA sequencing. Precision-cut lung slices (PCLS) from WT and dKO mice were pre-treated with SP-A and then infected with IAV for 48 h. RESULTS: Viral load was significantly increased in bronchoalveolar lavage (BAL) fluid of dKO mice compared to all other strains of mice. dKO mice had significantly less recruitment of neutrophils into the lung compared to Tollip KO mice. SP-A treatment of PCLS enhanced expression of TNF and reduced viral load in dKO mouse lung tissue. Pathway analysis of bulk RNA sequencing data suggests that macrophages from IAV-infected dKO mice reduced expression of genes involved in neutrophil recruitment, IL-17 signaling, and Toll-like receptor signaling. CONCLUSIONS: Our data suggests that both Tollip and SP-A are essential for the lung to exert more effective innate defense against IAV infection.

Mitochondrial Dysfunction and Metabolic Reprogramming in Obesity and Asthma.

Mitochondrial dysfunction and metabolic reprogramming have been extensively studied in many disorders ranging from cardiovascular to neurodegenerative disease. Obesity has previously been associated with mitochondrial fragmentation, dysregulated glycolysis, and oxidative phosphorylation, as well as increased reactive oxygen species production. Current treatments focus on reducing cellular stress to restore homeostasis through the use of antioxidants or alterations of mitochondrial dynamics. This review focuses on the role of mitochondrial dysfunction in obesity particularly for those suffering from asthma and examines mitochondrial transfer from mesenchymal stem cells to restore function as a potential therapy. Mitochondrial targeted therapy to restore healthy metabolism may provide a unique approach to alleviate dysregulation in individuals with this unique endotype.

Role of Myeloid Cell-Specific TLR9 in Mitochondrial DNA-Induced Lung Inflammation in Mice.

Mitochondrial dysfunction is common in various pathological conditions including obesity. Release of mitochondrial DNA (mtDNA) during mitochondrial dysfunction has been shown to play a role in driving the pro-inflammatory response in leukocytes including macrophages. However, the mechanisms by which mtDNA induces leukocyte inflammatory responses in vivo are still unclear. Moreover, how mtDNA is released in an obese setting has not been well understood. By using a mouse model of TLR9 deficiency in myeloid cells (e.g., macrophages), we found that TLR9 signaling in myeloid cells was critical to mtDNA-mediated pro-inflammatory responses such as neutrophil influx and chemokine production. mtDNA release by lung macrophages was enhanced by exposure to palmitic acid (PA), a major saturated fatty acid related to obesity. Moreover, TLR9 contributed to PA-mediated mtDNA release and inflammatory responses. Pathway analysis of RNA-sequencing data in TLR9-sufficient lung macrophages revealed the up-regulation of axon guidance molecule genes and down-regulation of metabolic pathway genes by PA. However, in TLR9-deficient lung macrophages, PA down-regulated axon guidance molecule genes, but up-regulated metabolic pathway genes. Our results suggest that mtDNA utilizes TLR9 signaling in leukocytes to promote lung inflammatory responses in hosts with increased PA. Moreover, TLR9 signaling is involved in the regulation of axon guidance and metabolic pathways in lung macrophages exposed to PA.

Electronic Cigarette Exposure Increases the Severity of Influenza a Virus Infection via TRAIL Dysregulation in Human Precision-Cut Lung Slices.

The use of electronic nicotine dispensing systems (ENDS), also known as electronic cigarettes (ECs), is common among adolescents and young adults with limited knowledge about the detrimental effects on lung health such as respiratory viral infections and underlying mechanisms. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a protein of the TNF family involved in cell apoptosis, is upregulated in COPD patients and during influenza A virus (IAV) infections, but its role in viral infection during EC exposures remains unclear. This study was aimed to investigate the effect of ECs on viral infection and TRAIL release in a human lung precision-cut lung slices (PCLS) model, and the role of TRAIL in regulating IAV infection. PCLS prepared from lungs of nonsmoker healthy human donors were exposed to EC juice (E-juice) and IAV for up to 3 days during which viral load, TRAIL, lactate dehydrogenase (LDH), and TNF-α in the tissue and supernatants were determined. TRAIL neutralizing antibody and recombinant TRAIL were utilized to determine the contribution of TRAIL to viral infection during EC exposures. E-juice increased viral load, TRAIL, TNF-α release and cytotoxicity in IAV-infected PCLS. TRAIL neutralizing antibody increased tissue viral load but reduced viral release into supernatants. Conversely, recombinant TRAIL decreased tissue viral load but increased viral release into supernatants. Further, recombinant TRAIL enhanced the expression of interferon-ß and interferon-λ induced by E-juice exposure in IAV-infected PCLS. Our results suggest that EC exposure in human distal lungs amplifies viral infection and TRAIL release, and that TRAIL may serve as a mechanism to regulate viral infection. Appropriate levels of TRAIL may be important to control IAV infection in EC users.

Integrated genomics approaches identify transcriptional mediators and epigenetic responses to Afghan desert particulate matter in small airway epithelial cells.

Military Deployment to Southwest Asia and Afghanistan and exposure to toxic airborne particulates have been associated with an increased risk of developing respiratory disease, collectively termed deployment-related respiratory diseases (DRRDs). Our knowledge about how particulates mediate respiratory disease is limited, precluding the appropriate recognition or management. Central to this limitation is the lack of understanding of how exposures translate into dysregulated cell identity with dysregulated transcriptional programs. The small airway epithelium is involved in both the pathobiology of DRRD and fine particulate matter deposition. To characterize small airway epithelial cell epigenetic and transcriptional responses to Afghan desert particulate matter (APM) and investigate the functional interactions of transcription factors that mediate these responses, we applied two genomics assays, the assay for transposase accessible chromatin with sequencing (ATAC-seq) and Precision Run-on sequencing (PRO-seq). We identified activity changes in a series of transcriptional pathways as candidate regulators of susceptibility to subsequent insults, including signal-dependent pathways, such as loss of cytochrome P450 or P53/P63, and lineage-determining transcription factors, such as GRHL2 loss or TEAD3 activation. We further demonstrated that TEAD3 activation was unique to APM exposure despite similar inflammatory responses when compared with wood smoke particle exposure and that P53/P63 program loss was uniquely positioned at the intersection of signal-dependent and lineage-determining transcriptional programs. Our results establish the utility of an integrated genomics approach in characterizing responses to exposures and identifying genomic targets for the advanced investigation of the pathogenesis of DRRD.

Tollip interaction with STAT3: a novel mechanism to regulate human airway epithelial responses to type 2 cytokines.

BACKGROUND: Toll-interacting protein (Tollip) is one of the key negative regulators in host innate immunity. Genetic variation of Tollip has been associated with less Tollip expression and poor lung function in asthmatic patients, but little is known about the role of Tollip in human airway type 2 inflammatory response, a prominent feature in allergic asthma. OBJECTIVE: Our goal was to determine the role and underlying mechanisms of Tollip in human airway epithelial responses such as eotaxin to type 2 cytokine IL-13. METHODS: Tollip deficient primary human airway epithelial cells from 4 healthy donors were generated by the gene knockdown approach and stimulated with IL-13 to measure activation of transcription factor STAT3, and eotaxin-3, an eosinophilic chemokine. RESULTS: Following IL-13 treatment, Tollip deficient cells had significantly higher levels of STAT3 activation and eotaxin-3 than the scrambled control counterpart, which was reduced by a STAT3 inhibitor. Interaction between Tollip and STAT3 proteins was identified by co-immunoprecipitation. CONCLUSION: Our results, for the first time, suggest that Tollip inhibits excessive eotaxin-3 induction by IL-13, in part through the interaction and inhibition of STAT3. These findings lend evidence to the potential of a STAT3 inhibitor as a therapeutic target, especially for type 2 inflammation-high asthmatics with Tollip deficiency.

Electronic cigarette vapor exposure exaggerates the pro-inflammatory response during influenza A viral infection in human distal airway epithelium.

Electronic cigarettes or vaping products have been marketed as a safer alternative to smoking, but very little is known about the health effects in the human lung, particularly in the distal airways, a key site of airway obstruction and destruction in chronic obstructive pulmonary disease that is often exacerbated by viral infections. The aim of this study was to investigate the effects of electronic cigarette vapor (e-vapor) on human distal airway epithelial responses to influenza A virus (IAV) infection. We isolated primary small airway epithelial cells (SAECs) from donor lungs free of lung disease, and cultured them at air-liquid interface (ALI). To measure markers of epithelial injury such as integrity of epithelial barrier structure and function, we selected a regimen of non-toxic, barrier preserving e-vapor exposure of cultured cells to 15 puffs of e-vapor from a commercially available e-cigarette once per day for 3 days, prior to IAV infection. After 72 h of infection, media and cell lysates were collected to measure cytokines involved in inflammatory and antiviral responses. Pre-exposure to e-vapor with IAV infection, compared to IAV infection alone, significantly increased inflammatory and antiviral mediators including IL-8, CXCL10, IFN-beta, and MX1. Our results suggest that e-vapor exposure amplifies human distal airway pro-inflammatory response to IAV infection, independently of the severity of cell injury during viral infection.

Pulmonary surfactant lipids inhibit infections with the pandemic H1N1 influenza virus in several animal models.

The influenza A (H1N1)pdm09 outbreak in 2009 exemplified the problems accompanying the emergence of novel influenza A virus (IAV) strains and their unanticipated virulence in populations with no pre-existing immunity. Neuraminidase inhibitors (NAIs) are currently the drugs of choice for intervention against IAV outbreaks, but there are concerns that NAI-resistant viruses can transmit to high-risk populations. These issues highlight the need for new approaches that address the annual influenza burden. In this study, we examined whether palmitoyl-oleoyl-phosphatidylglycerol (POPG) and phosphatidylinositol (PI) effectively antagonize (H1N1)pdm09 infection. POPG and PI markedly suppressed cytopathic effects and attenuated viral gene expression in (H1N1)pdm09-infected Madin-Darby canine kidney cells. POPG and PI bound to (H1N1)pdm09 with high affinity and disrupted viral spread from infected to noninfected cells in tissue culture and also reduced (H1N1)pdm09 propagation by a factor of 102 after viral infection was established in vitro In a mouse infection model of (H1N1)pdm09, POPG and PI significantly reduced lung inflammation and viral burden. Of note, when mice were challenged with a typically lethal dose of 1000 plaque-forming units of (H1N1)pdm09, survival after 10 days was 100% (14 of 14 mice) with the POPG treatment compared with 0% (0 of 14 mice) without this treatment. POPG also significantly reduced inflammatory infiltrates and the viral burden induced by (H1N1)pdm09 infection in a ferret model. These findings indicate that anionic phospholipids potently and efficiently disrupt influenza infections in animal models.

Influenza virus infection increases ACE2 expression and shedding in human small airway epithelial cells.

BACKGROUND: Patients with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) demonstrate high rates of co-infection with respiratory viruses, including influenza A (IAV), suggesting pathogenic interactions. METHODS: We investigated how IAV may increase the risk of COVID-19 lung disease, focusing on the receptor angiotensin-converting enzyme (ACE)2 and the protease TMPRSS2, which cooperate in the intracellular uptake of SARS-CoV-2. RESULTS: We found, using single-cell RNA sequencing of distal human nondiseased lung homogenates, that at baseline, ACE2 is minimally expressed in basal, goblet, ciliated and secretory epithelial cells populating small airways. We focused on human small airway epithelial cells (SAECs), central to the pathogenesis of lung injury following viral infections. Primary SAECs from nondiseased donor lungs apically infected (at the air-liquid interface) with IAV (up to 3×105 pfu; ∼1 multiplicity of infection) markedly (eight-fold) boosted the expression of ACE2, paralleling that of STAT1, a transcription factor activated by viruses. IAV increased the apparent electrophoretic mobility of intracellular ACE2 and generated an ACE2 fragment (90 kDa) in apical secretions, suggesting cleavage of this receptor. In addition, IAV increased the expression of two proteases known to cleave ACE2, sheddase ADAM17 (TACE) and TMPRSS2 and increased the TMPRSS2 zymogen and its mature fragments, implicating proteolytic autoactivation. CONCLUSION: These results indicate that IAV amplifies the expression of molecules necessary for SARS-CoV-2 infection of the distal lung. Furthermore, post-translational changes in ACE2 by IAV may increase vulnerability to lung injury such as acute respiratory distress syndrome during viral co-infections. These findings support efforts in the prevention and treatment of influenza infections during the COVID-19 pandemic.

Role of Particulate Matter from Afghanistan and Iraq in Deployment-Related Lung Disease.

Approximately 3 million United States military personnel and contractors were deployed to Southwest Asia and Afghanistan over the past two decades. After returning to the United States, many developed persistent respiratory symptoms, including those due to asthma, rhinosinusitis, bronchiolitis, and others, which we collectively refer to as deployment-related lung diseases (DRLD). The mechanisms of different DRLD have not been well defined. Limited studies from us and others suggest that multiple factors and biological signaling pathways contribute to the onset of DRLD. These include, but are not limited to, exposures to high levels of particulate matter (PM) from sandstorms, burn pit combustion products, improvised explosive devices, and diesel exhaust particles. Once inhaled, these hazardous substances can activate lung immune and structural cells to initiate numerous cell-signaling pathways such as oxidative stress, Toll-like receptors, and cytokine-driven cell injury (e.g., interleukin-33). These biological events may lead to a pro-inflammatory response and airway hyperresponsiveness. Additionally, exposures to PM and other environmental hazards may predispose military personnel and contractors to more severe disease due to the interactions of those hazardous materials with subsequent exposures to allergens and cigarette smoke. Understanding how airborne exposures during deployment contribute to DRLD may identify effective targets to alleviate respiratory diseases and improve quality of life in veterans and active duty military personnel.

Resident mesenchymal vascular progenitors modulate adaptive angiogenesis and pulmonary remodeling via regulation of canonical Wnt signaling.

Adaptive angiogenesis is necessary for tissue repair, however, it may also be associated with the exacerbation of injury and development of chronic disease. In these studies, we demonstrate that lung mesenchymal vascular progenitor cells (MVPC) modulate adaptive angiogenesis via lineage trace, depletion of MVPC, and modulation of ß-catenin expression. Single cell sequencing confirmed MVPC as multipotential vascular progenitors, thus, genetic depletion resulted in alveolar simplification with reduced adaptive angiogenesis. Following vascular endothelial injury, Wnt activation in MVPC was sufficient to elicit an emphysema-like phenotype characterized by increased MLI, fibrosis, and MVPC driven adaptive angiogenesis. Lastly, activation of Wnt/ß-catenin signaling skewed the profile of human and murine MVPC toward an adaptive phenotype. These data suggest that lung MVPC drive angiogenesis in response to injury and regulate the microvascular niche as well as subsequent distal lung tissue architecture via Wnt signaling.

Neutrophils Deficient in Innate Suppressor IRAK-M Enhances Anti-tumor Immune Responses.

Tumor-associated immune-suppressive neutrophils are prevalent in various cancers, including colorectal cancer. However, mechanisms of immune-suppressive neutrophils are not well understood. We report that a key innate suppressor, IRAK-M (interleukin-1 receptor-associated kinase M), is critically involved in the establishment of immune-suppressive neutrophils. In contrast to the wild-type (WT) neutrophils exhibiting immune-suppressive signatures of CD11bhighPD-L1highCD80low, IRAK-M-deficient neutrophils are rewired with reduced levels of inhibitory molecules PD-L1 and CD11b, as well as enhanced expression of stimulatory molecules CD80 and CD40. The reprogramming of IRAK-M-deficient neutrophils is mediated by reduced activation of STAT1/3 and enhanced activation of STAT5. As a consequence, IRAK-M-deficient neutrophils demonstrate enhanced capability to promote, instead of suppress, the proliferation and activation of effector T cells both in vitro and in vivo. Functionally, we observed that the transfusion of IRAK-M-/- neutrophils can potently render an enhanced anti-tumor immune response in the murine inflammation-induced colorectal cancer model. Collectively, our study defines IRAK-M as an innate suppressor for neutrophil function and reveals IRAK-M as a promising target for rewiring neutrophils in anti-cancer immunotherapy.

A 20-Mer Peptide Derived from the Lectin Domain of SP-A2 Decreases Tumor Necrosis Factor Alpha Production during Mycoplasma pneumoniae Infection.

Human surfactant protein-A2 (hSP-A2) is a component of pulmonary surfactant that plays an important role in the lung's immune system by interacting with viruses, bacteria, and fungi to facilitate pathogen clearance and by downregulating inflammatory responses after an allergic challenge. Genetic variation in SP-A2 at position Gln223Lys is present in up to ∼30% of the population and has been associated with several lung diseases, such as asthma, pulmonary fibrosis, and lung cancer (M. M. Pettigrew, J. F. Gent, Y. Zhu, E. W. Triche, et al., BMC Med Genet 8:15, 2007, https://bmcmedgenet.biomedcentral.com/articles/10.1186/1471-2350-8-15; Y. Wang, P. J. Kuan, C. Zing, J. T. Cronkhite, et al., Am J Hum Genet 84:52-59, 2009, https://www.cell.com/ajhg/fulltext/S0002-9297(08)00595-8). Previous work performed by our group showed differences in levels of SP-A binding to non-live mycoplasma membrane fractions that were dependent on the presence of a lysine (K) or a glutamine (Q) at amino acid position 223 in the carbohydrate region of SP-A2. On the basis of these differences, we have derived 20-amino-acid peptides flanking this region of interest in order to test the ability of each to regulate various immune responses to live Mycoplasma pneumoniae in SP-A knockout mice and RAW 264.7 cells. In both models, the 20-mer containing 223Q significantly decreased both tumor necrosis factor alpha (TNF-α) mRNA levels and protein levels in comparison to the 20-mer containing 223K during M. pneumoniae infection. While neither of the 20-mer peptides (223Q and 223K) had an effect on p38 phosphorylation during M. pneumoniae infection, the 223Q-20mer peptide significantly reduced NF-κB p65 phosphorylation in both models. Taken together, our data suggest that small peptides derived from the lectin domain of SP-A2 that contain the major allelic variant (223Q) maintain activity in reducing TNF-α induction during M. pneumoniae infection.

Parkin, an E3 ubiquitin ligase, enhances airway mitochondrial DNA release and inflammation.

INTRODUCTION: Parkin (Park2), an E3 ubiquitin ligase, is critical to maintain mitochondrial function by regulating mitochondrial biogenesis and degradation (mitophagy), but recent evidence suggests the involvement of Parkin in promoting inflammation. In the present study, we determined if Parkin regulates airway mitochondrial DNA (mtDNA) release and inflammatory responses to type 2 cytokine interleukin (IL)-13 and allergens. METHODS: We measured Parkin mRNA expression in brushed bronchial epithelial cells and mtDNA release in the paired bronchoalveolar lavage fluid (BALF) from normal subjects and asthmatics. Parkin-deficient primary human tracheobronchial epithelial (HTBE) cells generated using the CRISPR-Cas9 system were stimulated with IL-13. To determine the in vivo function of Parkin, Parkin knockout (PKO) and wild-type (WT) mice were treated with IL-13 or allergen (house dust mite, HDM) in the presence or absence of mtDNA isolated from normal mouse lungs. RESULTS: Parkin mRNA expression in asthmatic airway epithelium was upregulated, which positively correlated with the levels of released mtDNA in BALF. IL-13-stimulated HTBE cells increased Parkin expression. Moreover, IL-13 induced mtDNA release in Parkin-sufficient, but not in Parkin-deficient HTBE cells. PKO (vs WT) mice attenuated airway mtDNA release and inflammation following IL-13 or HDM treatments. mtDNA amplified airway inflammation in mice treated with IL-13 or HDM. Notably, Parkin also mediated mtDNA-induced exacerbation of airway inflammation. CONCLUSION: Our research findings suggest that Parkin promotes mtDNA release and inflammation in airways, thus improving our understanding of the complex role of Parkin and mitochondrial dysfunction in asthma pathogenesis.

Possible two-photon absorption in the near-infrared region observed by cavity ring-down spectroscopy.

Two-photon absorption spectra are difficult to observe using direct absorption spectroscopy especially in the near-infrared region. Cavity ring-down spectroscopy is a promising absorption spectroscopy technique which has been widely applied to linear and saturated single-photon absorption spectra. In the present study, we report the observation of a possible two-photon absorption in the near-infrared using cavity ring-down spectroscopy, namely a two-photon resonance of methane. Using an optical frequency comb, the single-photon wavenumber of the double-quantum transition has been determined to be 182 207 682.645 MHz with a standard deviation of 75 kHz.

IL-33/ST2 signaling modulates Afghanistan particulate matter induced airway hyperresponsiveness in mice.

Increased symptoms of asthma-like respiratory illnesses have been reported in soldiers returning from tours of duty in Afghanistan. Inhalation of desert particulate matter (PM) may contribute to this deployment-related lung disease (DRLD), but little is known about disease mechanisms. The IL-33 signaling pathway, including its receptor ST2, has been implicated in the pathogenesis of lung diseases including asthma, but its role in PM-mediated airway dysfunction has not been studied. The goal of this study was to investigate whether IL-33/ST2 signaling contributes to airway dysfunction in preclinical models of lung exposure to Afghanistan PM (APM). Wild-type (WT) and ST2 knockout (KO) mice on the BALB/C background were oropharyngeally instilled with a single dose of saline or 50 µg of APM in saline. Airway hyperresponsiveness (AHR) and inflammation were assessed after 24 h. In WT mice, a single APM exposure induced AHR and neutrophilic inflammation. Unlike the WT mice, ST2 KO mice that lack the receptor for IL-33 did not demonstrate AHR although airway neutrophilic inflammation was comparable to the WT mice. Oropharyngeal delivery of a soluble ST2 decoy receptor in APM-exposed WT mice significantly blocked AHR. Additional data in mouse tracheal epithelial cell and lung macrophage cultures demonstrated a role of APM-induced IL-33/ST2 signaling in suppression of regulator of G protein signaling 2 (RGS2), a gene known to protect against bronchoconstriction. We present for the first time that APM may increase AHR, one of the features of asthma, in part through the IL-33/ST2/RGS2 pathway.

Interleukin 1 Receptor-Like 1 (IL1RL1) Promotes Airway Bacterial and Viral Infection and Inflammation.

Interleukin 1 receptor-like 1 (IL1RL1), also known as suppression of tumorigenicity 2 (ST2), is the receptor for interleukin 33 (IL-33) and has been increasingly studied in type 2 inflammation. An increase in airway IL-33/ST2 signaling in asthma has been associated with eosinophilic inflammation, but little is known about the role of ST2 in neutrophilic inflammation. Airway Mycoplasma pneumoniae and human rhinovirus (HRV) infections are linked to neutrophilic inflammation during acute exacerbations of asthma. However, whether ST2 contributes to M. pneumoniae- and HRV-mediated airway inflammation is poorly understood. The current study sought to determine the functions of ST2 during airway M. pneumoniae or HRV infection. In cultured normal human primary airway epithelial cells, ST2 overexpression (OE) increased the production of neutrophilic chemoattractant IL-8 in the absence or presence of M. pneumoniae or HRV1B infection. ST2 OE also enhanced HRV1B-induced IP-10, a chemokine involved in asthma exacerbations. In the M. pneumoniae-infected mouse model, ST2 deficiency, in contrast to sufficiency, significantly reduced the levels of neutrophils following acute (≤24 h) infection, while in the HRV1B-infected mouse model, ST2 deficiency significantly reduced the levels of proinflammatory cytokines KC, IP-10, and IL-33 in bronchoalveolar lavage (BAL) fluid. Overall, ST2 overexpression in human epithelial cells and ST2 sufficiency in mice increased the M. pneumoniae and HRV loads in cell supernatants and BAL fluid. After pathogen infection, ST2-deficient mice showed a higher level of the host defense protein lactotransferrin in BAL fluid. Our data suggest that ST2 promotes proinflammatory responses (e.g., neutrophils) to airway bacterial and viral infection and that blocking ST2 signaling may broadly attenuate airway infection and inflammation.

Red Blood Cell Lifespan Shortening in Patients with Early-Stage Chronic Kidney Disease.

BACKGROUND: Although reduced red blood cell (RBC) lifespan has been reported to be a contributory factor to anemia in patients with end-stage chronic kidney disease (CKD), there are limited data regarding RBC lifespan in early-stage CKD. Serum erythropoietin (EPO) is considered a primary causative factor of renal anemia. The aims of this study were to compare the RBC lifespan, serum EPO levels, and other renal anemia indicators across CKD-stage groups of patients and to analyze the impacts of etiological factors on renal anemia. METHODS: A cohort of 74 non-smoking patients with CKD were enrolled, including 15 in stage 1, 18 in stage 2, 15 in stage 3, 15 in stage 4, and 11 in stage 5. RBC lifespan was determined by CO breath tests. Potential correlations of hemoglobin (Hb) concentration with RBC lifespan, reticulocyte count (Ret), and levels of EPO, ferritin, folic acid, and vitamin B12 were analyzed. RESULTS: CKD progression was associated with decreases in (Hb) and RBC lifespan. RBC lifespan durations in CKD stages 1-5 were 122 ± 50, 112 ± 26, 90 ± 32, 88 ± 28, and 60 ± 24 days, respectively. RBC lifespan means for the stage 3, 4 and 5 groups were significantly shorter than those for the stage 1 and 2 groups. Serum EPO did not differ significantly between the CKD stage groups. (Hb) correlated directly with RBC lifespan (r = 0.372, p = 0.002) and Ret (r = 0.308, p = 0.011), but did not correlate with serum EPO, ferritin, folic acid, or vitamin B12 levels. CONCLUSIONS: Reduced RBC lifespan in early-stage CKD, demonstrated in this study, suggests that increased RBC destruction may play a more important etiological role in renal anemia than other indicators in patients with CKD.

Overproduction of growth differentiation factor 15 promotes human rhinovirus infection and virus-induced inflammation in the lung.

Human rhinovirus (HRV) is the most common virus contributing to acute exacerbations of chronic obstructive pulmonary disease (COPD) nearly year round, but the mechanisms have not been well elucidated. Recent clinical studies suggest that high levels of growth differentiation factor 15 (GDF15) protein in the blood are associated with an increased yearly rate of all-cause COPD exacerbations. Therefore, in the current study, we investigated whether GDF15 promotes HRV infection and virus-induced lung inflammation. We first examined the role of GDF15 in regulating host defense and HRV-induced inflammation using human GDF15 transgenic mice and cultured human GDF15 transgenic mouse tracheal epithelial cells. Next, we determined the effect of GDF15 on viral replication, antiviral responses, and inflammation in human airway epithelial cells with GDF15 knockdown and HRV infection. Finally, we explored the signaling pathways involved in airway epithelial responses to HRV infection in the context of GDF15. Human GDF15 protein overexpression in mice led to exaggerated inflammatory responses to HRV, increased infectious particle release, and decreased IFN-λ2/3 (IL-28A/B) mRNA expression in the lung. Moreover, GDF15 facilitated HRV replication and inflammation via inhibiting IFN-λ1/IL-29 protein production in human airway epithelial cells. Lastly, Smad1 cooperated with interferon regulatory factor 7 (IRF7) to regulate airway epithelial responses to HRV infection partly via GDF15 signaling. Our results reveal a novel function of GDF15 in promoting lung HRV infection and virus-induced inflammation, which may be a new mechanism for the increased susceptibility and severity of respiratory viral (i.e., HRV) infection in cigarette smoke-exposed airways with GDF15 overproduction.

Comparison of pro- and anti-inflammatory responses in paired human primary airway epithelial cells and alveolar macrophages.

BACKGROUND: Airway epithelial cells and alveolar macrophages (AMs) are the first line of defense in the lung during infection. Toll-like receptor (TLR) agonists have been extensively used to define the regulation of inflammation in these cells. However, previous studies were performed in non-paired airway epithelial cells and AMs. The major goal of our study was to compare the pro- and anti-inflammatory responses of paired human primary airway epithelial cells and AMs to TLR3 and TLR4 agonists. METHODS: Tracheobronchial epithelial cells (TBEC) and AMs from four smokers and four non-smokers without lung disease were cultured with or without Poly(I:C) (PIC) (a TLR3 agonist) or LPS (a TLR4 agonist) for 4, 24 and 48 h. The immune responses of paired cells were compared. RESULTS: TBEC and AMs showed stronger pro-inflammatory cytokine (e.g., IL-8) responses to PIC and LPS, respectively. TLR3 and TLR4 mRNA levels were similar in non-stimulated TBEC and AMs. However, PIC stimulation in AMs led to sustained up-regulation of the immune negative regulators Tollip and A20, which may render AMs less sensitive to PIC stimulation than TBEC. Unlike AMs, TBEC did not increase NF-κB activation after LPS stimulation. Interestingly, smoking status was correlated with less TLR3 and IRAK-M expression in non-stimulated TBEC, but not in AMs. PIC-stimulated TBEC and LPS-stimulated AMs from smokers vs. non-smokers produced more IL-8. Finally, we show that expression of A20 and IRAK-M is strongly correlated in the two paired cell types. CONCLUSIONS: By using paired airway epithelial cells and AMs, this study reveals how these two critical types of lung cells respond to viral and bacterial pathogen associated molecular patterns, and provides rationale for modulating immune negative regulators to prevent excessive lung inflammation during respiratory infection.