Multiple pathogens, such as bacteria, fungi, and viruses, have been frequently found in asthmatic airways and are associated with the pathogenesis and exacerbation of asthma. Among these pathogens, Alternaria alternata (Alt), a universally present fungus, and human rhinovirus have been extensively studied. However, their interactions have not been investigated. In the present study, we tested the effect of Alt exposure on virus-induced airway epithelial immunity using live virus and a synthetic viral mimicker, double-stranded RNA (dsRNA). Alt treatment was found to significantly enhance the production of proinflammatory cytokines (e.g., IL-6 and IL-8) induced by virus infection or dsRNA treatment. In contrast to this synergistic effect, Alt significantly repressed type I and type III IFN production, and this impairment led to elevated viral replication. Mechanistic studies suggested the positive role of NF-κB and mitogen-activated protein kinase pathways in the synergism and the attenuation of the TBK1-IRF3 pathway in the inhibition of IFN production. These opposite effects are caused by separate fungal components. Protease-dependent and -independent mechanisms appear to be involved. Thus, Alt exposure alters the airway epithelial immunity to viral infection by shifting toward more inflammatory but less antiviral responses.
Toll-like receptor 3; antiviral; epithelium; Alternaria; rhinovirus
Bacterial strains resistant to various antibiotic drugs are frequently encountered in clinical infections, and the rapid identification of drug-resistant strains is highly essential for clinical treatment. We developed a locked nucleic acid (LNA)-based quantitative real-time PCR (LNA-qPCR) method for the rapid detection of 13 antibiotic resistance genes and successfully used it to distinguish drug-resistant bacterial strains from positive blood culture samples. A sequence-specific primer-probe set was designed, and the specificity of the assays was assessed using 27 ATCC bacterial strains and 77 negative blood culture samples. No cross-reaction was identified among bacterial strains and in negative samples, indicating 100% specificity. The sensitivity of the assays was determined by spiking each bacterial strain into negative blood samples, and the detection limit was 1–10 colony forming units (CFU) per reaction. The LNA-qPCR assays were first applied to 72 clinical bacterial isolates for the identification of known drug resistance genes, and the results were verified by the direct sequencing of PCR products. Finally, the LNA-qPCR assays were used for the detection in 47 positive blood culture samples, 19 of which (40.4%) were positive for antibiotic resistance genes, showing 91.5% consistency with phenotypic susceptibility results. In conclusion, LNA-qPCR is a reliable method for the rapid detection of bacterial antibiotic resistance genes and can be used as a supplement to phenotypic susceptibility testing for the early detection of antimicrobial resistance to allow the selection of appropriate antimicrobial treatment and to prevent the spread of resistant isolates.
Club (Clara) Cell Secretory Protein (CCSP, or CC16) is produced mainly by non-ciliated airway epithelial cells including bronchiolar club cells and the change of its expression has been shown to associate with the progress and severity of Chronic Obstructive Pulmonary Disease (COPD). In an animal model, the lack of CC16 renders the animal susceptible to the tumorigenic effect of a major CS carcinogen. A recent population-based Tucson Epidemiological Study of Airway Obstructive Diseases (TESAOD) has indicated that the low serum CC16 concentration is closely linked with the smoke-related mortality, particularly that driven by the lung cancer. However, the study of CC16 expression in well-defined smoke exposure models has been lacking, and there is no experimental support for the potential causal link between CC16 and CS-induced pathophysiological changes in the lung. In the present study, we have found that airway CC16 expression was significantly repressed in COPD patients, in monkey CS exposure model, and in CS-induced mouse model of COPD. Additionally, the lack of CC16 exacerbated airway inflammation and alveolar loss in the mouse model. Therefore, CC16 may play an important protective role in CS-related diseases.
Airway epithelial cells are the first line of defense against viral infections and are instrumental in coordinating the inflammatory response. In this study, we demonstrate the synergistic stimulation of CXCL10 mRNA and protein, a key chemokine responsible for the early immune response to viral infection, following treatment of airway epithelial cells with IFN γ and influenza virus. The synergism also occurred when the cells were treated with IFN γ and a viral replication mimicker (dsRNA) both in vitro and in vivo. Despite the requirement of type I interferon (IFNAR) signaling in dsRNA-induced CXCL10, the synergism was independent of the IFNAR pathway since it wasn’t affected by the addition of a neutralizing IFNAR antibody or the complete lack of IFNAR expression. Furthermore, the same synergistic effect was also observed when a CXCL10 promoter reporter was examined. Although the responsive promoter region contains both ISRE and NFκB sites, western blot analysis indicated that the combined treatment of IFN γ and dsRNA significantly augmented NFκB but not STAT1 activation as compared to the single treatment. Therefore, we conclude that IFN γ and dsRNA act in concert to potentiate CXCL10 expression in airway epithelial cells via an NFκB-dependent but IFNAR-STAT independent pathway and it is at least partly regulated at the transcriptional level.
The emergence and rapid spreading of multidrug-resistant Acinetobacter baumannii strains has become a major health threat worldwide. To better understand the genetic recombination related with the acquisition of drug-resistant elements during bacterial infection, we performed complete genome analysis on three newly isolated multidrug-resistant A. baumannii strains from Beijing using next-generation sequencing technology.
Whole genome comparison revealed that all 3 strains share some common drug resistant elements including carbapenem-resistant blaOXA-23 and tetracycline (tet) resistance islands, but the genome structures are diversified among strains. Various genomic islands intersperse on the genome with transposons and insertions, reflecting the recombination flexibility during the acquisition of the resistant elements. The blood-isolated BJAB07104 and ascites-isolated BJAB0868 exhibit high similarity on their genome structure with most of the global clone II strains, suggesting these two strains belong to the dominant outbreak strains prevalent worldwide. A large resistance island (RI) of about 121-kb, carrying a cluster of resistance-related genes, was inserted into the ATPase gene on BJAB07104 and BJAB0868 genomes. A 78-kb insertion element carrying tra-locus and blaOXA-23 island, can be either inserted into one of the tniB gene in the 121-kb RI on the chromosome, or transformed to conjugative plasmid in the two BJAB strains. The third strains of this study, BJAB0715, which was isolated from spinal fluid, exhibit much more divergence compared with above two strains. It harbors multiple drug-resistance elements including a truncated AbaR-22-like RI on its genome. One of the unique features of this strain is that it carries both blaOXA-23 and blaOXA-58 genes on its genome. Besides, an Acinetobacter lwoffii adeABC efflux element was found inserted into the ATPase position in BJAB0715.
Our comparative analysis on currently completed Acinetobacter baumannii genomes revealed extensive and dynamic genome organizations, which may facilitate the bacteria to acquire drug-resistance elements into their genomes.
Toll–IL-1 receptor (TIR) domain-containing adaptor molecule-1 (TICAM1, also called TRIF) is an important adaptor protein in TLR3 and TLR4 signaling pathways that mediate proinflammatory cytokine and IFN responses. Negative regulation of TICAM1 by exogenous viral protease or by endogenous caspase and proteasome have been reported to shut down TICAM1-mediated signaling. In this study, we discovered that down-regulation of TICAM1, but not other components in this signaling pathway, occurred in a natural process of TLR3 activation induced by double-stranded RNA or human rhinovirus (RV) infection in airway epithelial cells and various other cell types. TICAM1 was essential for IFN expression, and the loss of TICAM1 significantly elevated RV production. The low level of TICAM1 protein expression, caused by the prior double-stranded RNA treatment, led to a lack of IFN production upon additional treatment, suggesting receptor desensitization. In follow-up studies, TICAM1 down-regulation was found to be dependent on TLR3 but not RIG1, MDA5, or PKR and appeared to be regulated post-translationally. Neither proteasome nor caspase inhibitors could prevent TICAM1 down-regulation. Instead, a lysosome-mediated process appeared to be involved, suggesting a novel mechanism that is different from previous reports. In conclusion, TICAM1 down-regulation is an essential step in TLR3 activation, and its function is to stop TLR3-mediated IFN production.
TLR3; airway; desensitization; TICAM1; virus
Cigarette smoke (CS) has been reported to induce autophagy in airway epithelial cells. The subsequent autophagic cell death has been proposed to play an important pathogenic role in chronic obstructive pulmonary disease (COPD); however, the underlying molecular mechanism is not entirely clear. Using CS extract (CSE) as a surrogate for CS, we found that it markedly increased the expressions of both LC3B-I and LC3B-II as well as autophagosomes in airway epithelial cells. This is in contrast to the common autophagy inducer (i.e., starvation) that increases LC3B-II but reduces LC3B-I. Further studies indicate that CSE regulated LC3B at transcriptional and post-translational levels. In addition, CSE, but not starvation, activated Nrf2-mediated adaptive response. Increase of cellular Nrf2 by either Nrf2 overexpression or the knockdown of Keap1 (an Nrf2 inhibitor) significantly repressed CSE-induced LC3B-I and II as well as autophagosomes. Supplement of NAC (a GSH precursor) or GSH recapitulated the effect of Nrf2, suggesting the increase of cellular GSH level is responsible for Nrf2 effect on LC3B and autophagosome. Interestingly, neither Nrf2 activation nor GSH supplement could restore the repressed activities of mTOR or its downstream effctor-S6K. Thus, the Nrf2-dependent autophagy-suppression was not due to the re-activation of mTOR-the master repressor of autophagy. To search for the downstream effector of Nrf2 on LC3B and autophagosome, we tested Nrf2-dependent genes (i.e., NQO1 and P62) that are also increased by CSE treatment. We found that P62, but not NQO1, could mimic the effect of Nrf2 activation by repressing LC3B expression. Thus, Nrf2->P62 appears to play an important role in the regulation of CSE-induced LC3B and autophagosome.
DNA sequencing using reversible terminators, as one sequencing by synthesis strategy, has garnered a great deal of interest due to its popular application in the second-generation high-throughput DNA sequencing technology. In this review, we provided its history of development, classification, and working mechanism of this technology. We also outlined the screening strategies for DNA polymerases to accommodate the reversible terminators as substrates during polymerization; particularly, we introduced the “REAP” method developed by us. At the end of this review, we discussed current limitations of this approach and provided potential solutions to extend its application.
DNA polymerases; Sequencing technology; Modified nucleotide; Primer extension; Reversible terminator; Sequencing by synthesis
MUC5AC is the most abundant gel-forming mucin in the ocular system. However, the specific function is unknown. In the present study, a Muc5ac knockout (KO) mouse model was subject to various physiological measurements as compared to its wide-type (WT) control. Interestingly, when KO mice were compared to WT mice, the mean tear break up time (TBUT) values were significantly lower and corneal fluorescein staining scores were significantly higher. But the tear volume was not changed. Despite the lack of Muc5ac expression in the conjunctiva of KO mice, Muc5b expression was significantly increased in these mice. Corneal opacification, varying in location and severity, was found in a few KO mice but not in WT mice. The present results suggest a significant difference in the quality, but not the quantity, of tear fluid in the KO mice compared to WT mice. Dry eye disease is multifactorial and therefore further evaluation of the varying components of the tear film, lacrimal unit and corneal structure of these KO mice may help elucidate the role of mucins in dry eye disease. Because Muc5ac knockout mice have clinical features of dry eye, this mouse model will be extremely useful for further studies regarding the pathophysiology of the ocular surface in dry eye in humans.
The most recently discovered gel-forming mucin, MUC19, is expressed in both salivary glands and tracheal submucosal glands. We previously cloned the 3′−end partial sequence (AY236870), and here report the complete sequencing of the entire MUC19 cDNA. One highly variable region (HVR) was discovered in the 5′ end of MUC19. A total of 20 different splicing variants were detected in HVR, and 18 variants are able to translate into proteins along with the rest of the MUC19 sequence. The longest variant of MUC19 consists of 182 exons, with a transcript of approximately 25 kb. A central exon of approximately 12 kb contains highly repetitive sequences and has no intron interruption. The deduced MUC19 protein has the bona fide gel-forming mucin structure, VWD-VWD-VWD-“threonine/serine-rich repeats”-VWC-CT. An unusual structural feature of MUC19, which is lacking in other gel-forming mucins, is its long amino terminus upstream of the first VWD domain. The long amino terminus is mostly translated from the sequences in HVR, and contains serine-rich repetitive sequences. To validate the integrity of the MUC19 sequence, primers from both the 3′ and 5′ end were used to demonstrate a similar tissue expression pattern of MUC19 in trachea and salivary glands. In addition, antibodies were developed against either the amino (N) or carboxy (C) terminus of MUC19, and similar antibody staining patterns were observed in both salivary and tracheal submucosal glands. In conclusion, we have cloned and elucidated the entire MUC19 gene, which will facilitate understanding of the function and regulation of this important, yet understudied, mucin gene in airway diseases.
mucin; MUC19; airway; epithelium; gland
The accurate detection of mycobacterial species from isolates and clinical samples is important for pathogenic diagnosis and treatment and for disease control. There is an urgent need for the development of a rapid, simple, and accurate detection method. We established a biochip assay system, including a biochip, sample preparation apparatus, hybridization instrument, chip washing machine, and laser confocal scanner equipped with interpretation software for automatic diagnosis. The biochip simultaneously identified 17 common mycobacterial species by targeting the differences in the 16S rRNA. The system was assessed with 64 reference strains and 296 Mycobacterium tuberculosis and 243 nontuberculous mycobacterial isolates, as well as 138 other bacteria and 195 sputum samples, and then compared to DNA sequencing. The entire biochip assay took 6 h. The concordance rate between the biochip assay and the DNA sequencing results was 100%. In conclusion, the biochip system provides a simple, rapid, reliable, and highly accurate clinical assay for determination of mycobacterial species in a 6-h procedure, from either culture isolates or sputum samples, allowing earlier pathogen-adapted antimicrobial therapy in patients.
Mucociliary clearance is a critical innate defense system responsible for clearing up invading pathogens including bacteria and virus. Although the right amount of mucus is good, excessive mucus causes airway obstruction and tends to precipitate disease symptoms. Rhinovirus (RV) is a common cold virus that causes asthma and chronic obstructive pulmonary disease exacerbation. Mucus overproduction has been linked to the pathogenesis of RV-induced diseases and disease exacerbations. However, the molecular mechanism is not clear. In this study, using one of the major airway mucin-MUC5AC as marker, we found that both major and minor groups of RV induced mucin production in primary human epithelial cells and cell line. RV1A (a minor group of RV) could induce mucous cell metaplasia in vivo. Viral replication was needed for RV-induced mucin expression, and this induction was also dependent on TLR3, suggesting the involvement of double-stranded (ds) RNA signaling. Indeed, dsRNA alone could also induce mucin expression. TLR3-mediated mucin induction was negatively regulated by MyD88, and only partially dependent on TRIF, which suggests a departure from well-documented TLR3 signaling paradigm that mediates inflammatory and other innate defense gene inductions. In addition, TLR3 signaling activated epidermal growth factor receptor (EGFR) through inductions of the expression of EGFR ligands (transforming growth factor-α and amphiregulin), which in turn activated EGFR-ERK signaling and mucin expression through an autocrine/paracrine loop. This novel coupling of antiviral defense machinery (i.e., TLR3) and major epithelial proliferation/repair pathway (i.e., EGFR) might play an important role in viral-induced airway remodeling and airway disease exacerbation.
mucin; airway epithelium; TLR3; rhinovirus