Gene expression differences in infected and noninfected middle ear complementary DNA libraries

Expression of calcium-binding proteins S100A8, S100A9 and S100A12 in otitis media

OBJECTIVES

Calgranulins (calcium-binding proteins S100A8, S100A9 and S100A12) are predominant cytoplasmic proteins of neutrophils and produced by various cells, playing multiple functions in innate immunity and the inflammatory process. Although up-regulated expression of S100A8 and S100A9 genes were observed in an animal model of otitis media (OM), their expressions have not been studied in human middle ear epithelial cells in response to the OM pathogen or in patients with recurrent or chronic OM (recurrent OM/RecOM or chronic OM with effusion/COME).

STUDY DESIGN

Gene expressions were compared between Streptococcus pneumoniae (SP)-infected and non-infected human middle ear epithelial cells (HMEECs) as well as between chronic OM patients and control patients (CI).

METHODS

Gene expressions were profiled by quantitative real time PCR (qPCR). S100 proteins in OM patient and CI middle ear biopsies were detected by immunostaining.

RESULTS

S100A8, S100A9 and S100A12 gene expressions were elevated in SP-infected HMEECs in time-dependent manner. S100A8 and S100A9 but not S100A12 gene expression was significantly elevated in the middle ear mucosa of OM patients. S100A8 and S100A9 protein were observed in middle ear mucosa of OM, but not CI patients. Minimal co-localization was observed between S100A8 and S100A9 with neutrophil elastase and cytokeratin in ME sections of OM patients.

CONCLUSION

Elevated S100A8 and S100A9 gene expression in SP-infected HMEECs and in the middle ear mucosa of OM, minor co-localized with neutrophil markers suggests that middle ear epithelial cell secretion of S100A8 and S100A9 may play a role in the pathogenesis of recurrent and chronic OM.

Differences in innate immune response gene regulation in the middle ear of children who are otitis prone and in those not otitis prone

OBJECTIVE

Acute otitis media (AOM) causes an inflammatory response in the middle ear. We assessed differences in innate immune responses involved in bacterial defense at onset of AOM in children who were stringently defined as otitis prone (sOP) and children not otitis prone (NOP).

STUDY DESIGN

Innate immune genes analysis from middle ear fluid (MEF) samples of children.

METHODS

Genes of toll-like receptors (TLR), nod-like and retinoic acid-inducible gene-I-like receptors, downstream effectors important for inflammation and apoptosis, including cytokines and chemokines, were studied from MEF samples by using a real-time polymerase chain reaction array. Protein levels of differentially regulated genes were measured by Luminex.

RESULTS

Gene expression in MEF among children who were sOP was significantly different in upregulation of interleukin 8, secretory leukocyte peptidase inhibitor, and chemokine (C-C motif) ligand 3, and in downregulation of interferon regulatory factor 7 and its related signaling molecules interferon alpha, Toll-like receptor adaptor molecule 2, chemokine (C-C motif) ligand 5, and mitogen-activated protein kinase 8 compared with children who were NOP. Differences in innate gene regulation were similar when AOM was caused by Streptococcus pneumoniae or nontypeable Haemophilus influenzae.

CONCLUSION

Innate-immune response genes are differentially regulated in children who were sOP compared with children with NOP.

Comprehensive Proteomic and Metabolomic Signatures of Nontypeable Haemophilus influenzae-Induced Acute Otitis Media Reveal Bacterial Aerobic Respiration in an Immunosuppressed Environment

A thorough understanding of the molecular details of the interactions between bacteria and host are critical to ultimately prevent disease. Recent technological advances allow simultaneous analysis of host and bacterial protein and metabolic profiles from a single small tissue sample to provide insight into pathogenesis. We used the chinchilla model of human otitis media to determine, for the first time, the most expansive delineation of global changes in protein and metabolite profiles during an experimentally induced disease. After 48 h of infection with nontypeable Haemophilus influenzae, middle ear tissue lysates were analyzed by high-resolution quantitative two-dimensional liquid chromatography-tandem mass spectrometry. Dynamic changes in 105 chinchilla proteins and 66 metabolites define the early proteomic and metabolomic signature of otitis media. Our studies indicate that establishment of disease coincides with actin morphogenesis, suppression of inflammatory mediators, and bacterial aerobic respiration. We validated the observed increase in the actin-remodeling complex, Arp2/3, and experimentally showed a role for Arp2/3 in nontypeable Haemophilus influenzae invasion. Direct inhibition of actin branch morphology altered bacterial invasion into host epithelial cells, and is supportive of our efforts to use the information gathered to modify outcomes of disease. The twenty-eight nontypeable Haemophilus influenzae proteins identified participate in carbohydrate and amino acid metabolism, redox homeostasis, and include cell wall-associated metabolic proteins. Quantitative characterization of the molecular signatures of infection will redefine our understanding of host response driven developmental changes during pathogenesis. These data represent the first comprehensive study of host protein and metabolite profiles in vivo in response to infection and show the feasibility of extensive characterization of host protein profiles during disease. Identification of novel protein targets and metabolic biomarkers will advance development of therapeutic and diagnostic options for treatment of disease.

The inflammasome adaptor ASC contributes to multiple innate immune processes in the resolution of otitis media

This study was designed to understand the contribution of the inflammasome and IL-1β activation in otitis media (OM). We examined the middle ear (ME) response to non-typeable Haemophilus influenzae (NTHi) in wild type (WT) mice using gene microarrays and a murine model of acute OM. Expression of members of the NOD domain-like receptor family of inflammasome genes was significantly up-regulated early in NTHi infection of the ME, potentially activating specific downstream regulatory cascades that contribute to the proliferative inflammatory response observed during OM. Expression of the pro-forms of the inflammasome targets IL-1β and IL-18 were also up-regulated. To evaluate the role of inflammasome-mediated cytokine maturation, NTHi-induced OM was examined in Asc(-/-)-deficient mice and compared with that seen in WT mice. Mice lacking the Asc gene showed near absence of IL-1β maturation in the ME and a reduction in leukocyte recruitment and infiltration to the cavity, and their macrophages exhibited reduced phagocytosis of NTHi. These inflammatory defects were linked to an increase in the degree and duration of mucosal epithelial hyperplasia in the ME of Asc(-/-) mice, as well as a delay in bacterial clearance from their MEs. These data demonstrate an important role for the inflammasome and cytokine processing in the course and resolution of OM.

Use of the Chinchilla model to evaluate the vaccinogenic potential of the Moraxella catarrhalis filamentous hemagglutinin-like proteins MhaB1 and MhaB2

Moraxella catarrhalis causes significant health problems, including 15–20% of otitis media cases in children and ∼10% of respiratory infections in adults with chronic obstructive pulmonary disease. The lack of an efficacious vaccine, the rapid emergence of antibiotic resistance in clinical isolates, and high carriage rates reported in children are cause for concern. In addition, the effectiveness of conjugate vaccines at reducing the incidence of otitis media caused by Streptococcus pneumoniae and nontypeable Haemophilus influenzae suggest that M. catarrhalis infections may become even more prevalent. Hence, M. catarrhalis is an important and emerging cause of infectious disease for which the development of a vaccine is highly desirable. Studying the pathogenesis of M. catarrhalis and the testing of vaccine candidates have both been hindered by the lack of an animal model that mimics human colonization and infection. To address this, we intranasally infected chinchilla with M. catarrhalis to investigate colonization and examine the efficacy of a protein-based vaccine. The data reveal that infected chinchillas produce antibodies against antigens known to be major targets of the immune response in humans, thus establishing immune parallels between chinchillas and humans during M. catarrhalis infection. Our data also demonstrate that a mutant lacking expression of the adherence proteins MhaB1 and MhaB2 is impaired in its ability to colonize the chinchilla nasopharynx, and that immunization with a polypeptide shared by MhaB1 and MhaB2 elicits antibodies interfering with colonization. These findings underscore the importance of adherence proteins in colonization and emphasize the relevance of the chinchilla model to study M. catarrhalis–host interactions.

Panel 3: Recent advances in anatomy, pathology, and cell biology in relation to otitis media pathogenesis

BACKGROUND AND OBJECTIVES

The pathogenesis of otitis media (OM) involves a number of factors related to the anatomy, pathology, and cell biology of the middle ear, the mastoid, the Eustachian tube, and the nasopharynx. Although some issues of pathogenesis are fairly well established, others are only marginally indicated by current knowledge, and yet others remain undisclosed. The objective of this article is to provide a state-of-the-art review on recent scientific achievements in the pathogenesis of OM, as related to anatomy, pathology, and cell biology.

DATA SOURCES

PubMed, Ovid Medline, and Cochrane Library.

REVIEW METHODS

Articles published on the pathogenesis of OM and the anatomy, pathology, and cell biology of the middle ear, the mastoid, the Eustachian tube, and the nasopharynx between January 2007 and June 2011 were identified. Among almost 1900 abstracts, the authors selected 130 articles for full article review and inclusion in this report.

RESULTS

New knowledge on a number of issues emerged, including cell-specific expression and function of fluid transportation and innate immune system molecules, mucous cell metaplasia, mucin expression, bacterial adherence, and epithelial internalization, as well as the occurrence, composition, dynamics, and potential role of bacterial biofilm. In addition, the potential role of gastroesophageal reflux disease and cigarette smoke exposure has been explored further.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Over the past 4 years, considerable scientific progress has been made on the pathogenesis of OM, as related to issues of anatomy, pathology, and cell biology. Based on these new achievements and a sustained lack of essential knowledge, suggestions for future research are outlined.

A novel model of spontaneous otitis media with effusion (OME) in the Oxgr1 knock-out mouse

OBJECTIVE

A novel mouse model with a specific genetic mutation in a G protein coupled receptor (GPCR) encoded by the Oxgr1 gene results in a predisposition to spontaneous otitis media with effusion. As a primary component of interest in OME, mucin expression was examined in this model to assess expression as compared to wild type animals and suitability as a murine model of OME.

METHOD

Mutant (Oxgr1(-/-)) and wild-type (Oxgr1(+/+)) mice between ages of 2 and 5 months were examined by otoscopy and auditory brainstem response (ABR). Histology changes in the middle ear were evaluated. Expression of mucin genes in the middle ear epithelium was determined using RT-PCR and quantitative PCR.

RESULT

Otoscopic exam showed signs of inflammation in 82% of mutant mice. Significant elevated ABR thresholds were detected in mutant mice indicating hearing loss. Histology analysis of the middle ears demonstrated the presence of inflammatory cells, changes in the mucosal epithelium, and middle ear fluid. RT PCR using universal primers for bacterial 18s rRNA suggested the absence of bacteria in the middle ear. The knockout mice demonstrated expression of Muc1, Muc2, Muc3, Muc4, Muc5AC, Muc5B, Muc9, Muc10, Muc13, Muc15, Muc16, Muc18, Muc19 and Muc20. There was a trend of increase in Muc5B and Muc19 expression in the middle ear of the knockout mice compared to that of wild-type. There was no significant change in the level of Muc2, and Muc5AC was expressed at a level below the detection limit of quantification.

CONCLUSION

Development of a murine model with genetic defect has several attractive features. The rate of OME in these animals is high at 82%. It is clear that this OME is related to histopathologic changes in the middle ear epithelium of these knock-out mice. Induction of mucus effusion is evident though the viation in dysregulation of GFM does exist in this non-challenge study condition. The underlying cause of these differences between individual animal requires further investigation. Given this, the Oxgr1(-/-) model is likely to be an ideal model to examine mucin regulation in MEE and potentially develop novel GPCR-specific targeted interventions to regulate these processes.

Replication of respiratory syncytial virus is inhibited by the host defense molecule viperin

Respiratory syncytial virus (RSV) is an important viral pathogen of otitis media, bronchiolitis, and pneumonia. As infection of the upper airways is a precondition for the development of these diseases, understanding RSV pathogenesis and the host response induced by RSV in this niche may enable the development of novel therapeutic strategies against this virus. We have used a microarray approach and showed that expression of the gene that encodes the antiviral protein viperin was significantly upregulated in the chinchilla nasopharynx up to 1 week after RSV challenge. Overexpression of human viperin in vitro diminished the ability of RSV to infect HeLa or A549 cells. Furthermore, transduction of the chinchilla airways with a recombinant adeno-associated virus vector that encodes viperin resulted in reduced titers of RSV in the nasopharyngeal lavage fluid. Collectively, these data indicated that viperin plays a significant role in the innate immune defense against RSV.

Phosphodiesterase 4B mediates extracellular signal-regulated kinase-dependent up-regulation of mucin MUC5AC protein by Streptococcus pneumoniae by inhibiting cAMP-protein kinase A-dependent MKP-1 phosphatase pathway

Otitis media (OM) is the most common childhood bacterial infection and the major cause of conductive hearing loss in children. Mucus overproduction is a hallmark of OM. Streptococcus pneumoniae is the most common gram-positive bacterial pathogen causing OM. Among many mucin genes, MUC5AC has been found to be greatly up-regulated in the middle ear mucosa of human patients with OM. We previously reported that S. pneumoniae up-regulates MUC5AC expression in a MAPK ERK-dependent manner. We also found that MAPK phosphatase-1 (MKP-1) negatively regulates S. pneumoniae-induced ERK-dependent MUC5AC up-regulation. Therapeutic strategies for up-regulating the expression of negative regulators such as MKP-1 may have significant therapeutic potential for treating mucus overproduction in OM. However, the underlying molecular mechanism by which MKP-1 expression is negatively regulated during S. pneumoniae infection is unknown. In this study we show that phosphodiesterase 4B (PDE4B) mediates S. pneumoniae-induced MUC5AC up-regulation by inhibiting the expression of a negative regulator MKP-1, which in turn leads to enhanced MAPK ERK activation and subsequent up-regulation of MUC5AC. PDE4B inhibits MKP-1 expression in a cAMP-PKA-dependent manner. PDE4-specific inhibitor rolipram inhibits S. pneumoniae-induced MUC5AC up-regulation both in vitro and in vivo. Moreover, we show that PDE4B plays a critical role in MUC5AC induction. Finally, topical and post-infection administration of rolipram into the middle ear potently inhibited S. pneumoniae-induced MUC5AC up-regulation. Collectively, these data demonstrate that PDE4B mediates ERK-dependent up-regulation of mucin MUC5AC by S. pneumoniae by inhibiting cAMP-PKA-dependent MKP-1 pathway. This study may lead to novel therapeutic strategy for inhibiting mucus overproduction.

Porcine S100A8 and S100A9: molecular characterizations and crucial functions in response to Haemophilus parasuis infection

S100 calcium-binding protein A8 (S100A8) and S100 calcium-binding protein A9 (S100A9) are pivotal mediators of inflammatory and protective anti-infection responses for the mammalian host. In this study, we present the molecular cloning of porcine S100A8 (pS100A8) and porcine S100A9 (pS100A9). Both genes comprise 3 exons and 2 introns and are located on pig chromosome 4q21-q23 (closely linked to SW512). Homology comparison to other mammalian species affirmed that critical functional amino acids for post-transcriptional modification, inflammatory regulation, and formation of heterodimeric complexes exist in pS100A8 and pS100A9. Under normal conditions, both genes are preferentially expressed in porcine immune or immune-related organs, e.g., bone marrow, spleen, lymph nodes, and lung. Upon stimulation in porcine whole blood cultures with LPS or Poly(I:C), they are dramatically induced. Interestingly, the maximum increase of mRNA levels in blood cultures of Meishan pigs is significantly greater than that in Duroc pigs. We previously showed that pS100A8 and pS100A9 mRNA were up-regulated following Haemophilus parasuis (HPS) infection. We herein further confirm their up-regulation at the protein level in multiple HPS infected tissues (spleen, lung and liver). Functional cluster and network analysis based on our previous microarray data discovered that CEBPB may be one of the key transcription factors. A pS100A8/pS100A9-CASP3-SLC1A2 pathway regulating lipid metabolism was found. Both of their pro- and anti-inflammatory functions in response to HPS infection are highlighted.

The toll-Like receptor adaptor TRIF contributes to otitis media pathogenesis and recovery

Background

Toll-like receptor (TLR) signalling is crucial for innate immune responses to infection. The involvement of TLRs in otitis media (OM), the most prevalent childhood disease in developed countries, has been implicated by studies in middle ear cell lines, by association studies of TLR-related gene polymorphisms, and by altered OM in mice bearing mutations in TLR genes. Activated TLRs signal via two alternative intracellular signaling molecules with differing effects; MyD88 (Myeloid differentiation primary response gene 88) inducing primarily interleukin expression and TRIF (Tir-domain-containing adaptor inducing interferon β) mediating type I interferon (IFN) expression. We tested the hypothesis that TRIF and type I IFN signaling play a role in OM, using a murine model of OM induced by non-typeable Haemophilus influenzae (NTHi). The ME inflammatory response to NTHi was examined in wild-type (WT) and TRIF-/- mice by qPCR, gene microarray, histopathology and bacterial culture.

Results

Expression of TRIF mRNA was only modesty enhanced during OM, but both type I IFN signalling genes and type I IFN-inducible genes were significantly up-regulated in WT mice. TRIF-deficient mice showed reduced but more persistent mucosal hyperplasia and less leukocyte infiltration into the ME in response to NTHi infection than did WT animals. Viable bacteria could be cultured from MEs of TRIF-/- mice for much longer in the course of disease than was the case for middle ears of WT mice.

Conclusion

Our results demonstrate that activation of TRIF/type I IFN responses is important in both the pathogenesis and resolution of NTHi-induced OM.