Increased TLR7 expression in the adenoids among children with otitis media with effusion

Toll-Like Receptors: Expression and Roles in Otitis Media

Otitis media is mainly caused by upper respiratory tract infection and eustachian tube dysfunction. If external upper respiratory tract infection is not detected early in the middle ear, or an appropriate immune response does not occur, otitis media can become a chronic state or complications may occur. Therefore, given the important role of Toll-like receptors (TLRs) in the early response to external antigens, we surveyed the role of TLRs in otitis media. To summarize the role of TLR in otitis media, we reviewed articles on the expression of TLRs in acute otitis media (AOM), otitis media with effusion (OME), chronic otitis media (COM) with cholesteatoma, and COM without cholesteatoma. Many studies showed that TLRs 1–10 are expressed in AOM, OME, COM with cholesteatoma, and COM without cholesteatoma. TLR expression in the normal middle ear mucosa is absent or weak, but is increased in inflammatory fluid of AOM, effusion of OME, and granulation tissue and cholesteatoma of COM. In addition, TLRs show increased or decreased expression depending on the presence or absence of bacteria, recurrence of disease, tissue type, and repeated surgery. In conclusion, expression of TLRs is associated with otitis media. Inappropriate TLR expression, or delayed or absent induction, are associated with the occurrence, recurrence, chronicization, and complications of otitis media. Therefore, TLRs are very important in otitis media and closely related to its etiology.

Impact of Plant Extracts and Antibiotics on Biofilm Formation of Clinical Isolates From Otitis Media

Background:

Otitis media can lead to severe health consequences, and is the most common reason for antibiotic prescriptions and biofilm-mediated infections. However, the increased pattern of drug resistance in biofilm forming bacteria complicates the treatment of such infections.

Objectives:

This study was aimed to estimate the biofilm formation potential of the clinical isolates of otitis media, and to evaluate the efficacy of antibiotics and plant extracts as alternative therapeutic agents in biofilm eradication.

Materials and Methods:

The ear swab samples collected from the otitis media patients visiting the Mayo Hospital in Lahore were processed to isolate the bacteria, which were characterized using morphological, biochemical, and molecular (16S rRNA ribotyping) techniques. Then, the minimum inhibitory concentrations (MICs) of the antibiotics and crude plant extracts were measured against the isolates. The cell surface hydrophobicity and biofilm formation potential were determined, both qualitatively and quantitatively, with and without antibiotics. Finally, the molecular characterization of the biofilm forming proteins was done by amplifying the ica operon.

Results:

Pseudomonas aeruginosa (KC417303-05), Staphylococcus hemolyticus (KC417306), and Staphylococcus hominis (KC417307) were isolated from the otitis media specimens. Among the crude plant extracts, Acacia arabica showed significant antibacterial characteristics (MIC up to 13 mg/ml), while these isolates exhibited sensitivity towards ciprofloxacin (MIC 0.2 µg/mL). All of the bacterial strains had hydrophobic cellular surfaces that helped in their adherence to abiotic surfaces, leading to strong biofilm formation potential (up to 7 days). Furthermore, the icaC gene encoding polysaccharide intercellular adhesion protein was amplified from S. hemolyticus.

Conclusions:

The bacterial isolates exhibited strong biofilm formation potential, while the extracts of Acacia arabica significantly inhibited biofilm formation among the isolates and, therefore, could be executed in the development of cost-effective biofilm inhibitor medicines.

Adenoids in children: Advances in immunology, diagnosis, and surgery

Adenoids are strategically located for mediating local and regional immune functions as they are exposed to antigens from both the outside air and the alimentary tract. Recurrent or chronic respiratory infections can induce histomorphological and functional changes in the adenoidal immunological barrier, sometimes making surgical treatment necessary. Our aim in this review is to summarize the crucial points about not only the immunological histopathology of adenoidal tissue, especially in patients with adenoid hypertrophy, but also the most common and useful diagnostic techniques and surgical options.

Molecular mechanisms of moraxella catarrhalis-induced otitis media

Moraxella catarrhalis is a Gram-negative bacterium, exclusively present in humans and a leading causative agent of otitis media (OM) in children. Most children (80 %) experience at least one episode of OM by their third birthday and half suffer multiple episodes of infection. Over the last 10 years, increased evidence suggests that M. cat possesses multiple virulence factors which can be carried through biologically active outer membrane vesicles (OMVs) that are themselves able to activate host-immune responses. It has also been noted that multiple toll-like receptors are responsible for M. cat recognition. This review is intended to summarize the key findings and progress in recent years of the molecular mechanisms of M. cat-induced otitis media with particular emphasis on adhesion, invasion, and activation of the host immune system, biofilm formation, and vaccine development.

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.

Moraxella catarrhalis activates murine macrophages through multiple toll like receptors and has reduced clearance in lungs from TLR4 mutant mice

Moraxella catarrhalis is a Gram negative bacterium and a leading causative agent of otitis media (OM) in children. Several recent reports have provided strong evidence for an association between toll like receptors and OM. It has been found that both Streptococcus pneumoniae and nontypeable Haemophilus influenzae activate host protective immune responses through toll like receptors (TLRs), however, the precise mechanism by which Moraxella catarrhalis initiates the host immune response is currently unknown. In this report, using murine macrophages generated from a series of knock-out mice, we have demonstrated that M. catarrhalis lipooligosaccharide (LOS) and either heat killed or live bacteria are recognized by one or more TLRs. LOS activates the host immune response through a membrane bound CD14-TLR4 complex, while both heat killed and live M.cat require recognition by multiple toll like receptors such as TLR2, TLR4 and TLR9 without the requirement of CD14. We have also shown that M.cat stimuli are capable of triggering the host innate immune response by both MyD88- and TRIF- dependent signaling pathways. We further showed that M.cat induced activation of mitogen activated protein kinase (MAPK) is essential in order to achieve optimal secretion of pro-inflammatory cytokine TNF-α. We finally showed that TLR4 mutant C3H/HeJ mice produce significantly lower levels of pro-inflammatory cytokines TNF-α and IL-6 in vivo, An increased bacterial loads at 12 and 24 hours (P<0.001) in their lungs upon challenge with live M.cat in an aerosol chamber compared to wild-type (WT) control mice. These data suggest that TLRs are crucial for an effective innate immune response induced by M.cat. The results of these studies contribute to an increased understanding of molecular mechanism and possible novel treatment strategies for diseases caused by M.cat by specifically targeting TLRs and their signaling pathways.

HIF-VEGF pathways are critical for chronic otitis media in Junbo and Jeff mouse mutants

Otitis media with effusion (OME) is the commonest cause of hearing loss in children, yet the underlying genetic pathways and mechanisms involved are incompletely understood. Ventilation of the middle ear with tympanostomy tubes is the commonest surgical procedure in children and the best treatment for chronic OME, but the mechanism by which they work remains uncertain. As hypoxia is a common feature of inflamed microenvironments, moderation of hypoxia may be a significant contributory mechanism. We have investigated the occurrence of hypoxia and hypoxia-inducible factor (HIF) mediated responses in Junbo and Jeff mouse mutant models, which develop spontaneous chronic otitis media. We found that Jeff and Junbo mice labeled in vivo with pimonidazole showed cellular hypoxia in inflammatory cells in the bulla lumen, and in Junbo the middle ear mucosa was also hypoxic. The bulla fluid inflammatory cell numbers were greater and the upregulation of inflammatory gene networks were more pronounced in Junbo than Jeff. Hif-1α gene expression was elevated in bulla fluid inflammatory cells, and there was upregulation of its target genes including Vegfa in Junbo and Jeff. We therefore investigated the effects in Junbo of small-molecule inhibitors of VEGFR signaling (PTK787, SU-11248, and BAY 43-9006) and destabilizing HIF by inhibiting its chaperone HSP90 with 17-DMAG. We found that both classes of inhibitor significantly reduced hearing loss and the occurrence of bulla fluid and that VEGFR inhibitors moderated angiogenesis and lymphangiogenesis in the inflamed middle ear mucosa. The effectiveness of HSP90 and VEGFR signaling inhibitors in suppressing OM in the Junbo model implicates HIF–mediated VEGF as playing a pivotal role in OM pathogenesis. Our analysis of the Junbo and Jeff mutants highlights the role of hypoxia and HIF–mediated pathways, and we conclude that targeting molecules in HIF–VEGF signaling pathways has therapeutic potential in the treatment of chronic OM.

Otitis media with effusion (OME) is the commonest cause of hearing loss in children, and treatment using grommets remains the commonest surgical procedure in children. Chronic forms of OM are known from human population studies to have a significant genetic component, but little is known of the underlying genes or pathways involved. We have analyzed two chronic OM mouse models, the Junbo and Jeff mutants, and have found that both demonstrate hypoxia and hypoxia-inducible factor (HIF) mediated responses. There is upregulation of inflammatory pathways in the mutant middle ears and in Junbo elevation of cytokines that modulate Hif-1α. Hif-1α levels are raised in the middle ear as well as downstream targets of HIF such as Vegfa. We explored the effects of small-molecule inhibitors of HSP90 and VEGF receptor signaling in the Junbo mutant and found significant reductions in hearing loss, the occurrence of bulla fluid, and moderation of vascular changes in the inflamed middle ear mucosa with the VEGF receptor inhibitors. The study of the Junbo and Jeff mutants demonstrates the role of hypoxia and HIF mediated pathways in OM pathogenesis, and it indicates that targeting the HIF–VEGF pathway may represent a novel approach to therapeutic intervention in chronic OM.

TLR-9, NOD-1, NOD-2, RIG-I and immunoglobulins in recurrent otitis media with effusion

OBJECTIVES

Pattern recognition receptors (PRRs) induce appropriate immune responses after recognizing certain molecular characteristics of pathogens. It is not known, however, whether PRRs are expressed in middle ear infections and whether the expression of PRRs and immunoglobulins is correlated in recurrent otitis media with effusion (OME). We therefore investigated the expression of PRRs and immunoglobulins in children with OME.

MATERIALS AND METHODS

The study population consisted of 66 children with OME, of whom 27 had more than 4 episodes in 12 months or more than 3 episodes in 6 months (otitis-prone group), and 39 had fewer than 4 episodes in 12 months or 3 episodes in 6 months (non-otitis-prone group). The expression in middle ear effusion of Toll-like receptor (TLR)-9, nucleotide-binding oligomerization domain (NOD)-1, NOD-2, and retinoic acid-inducible gene (RIG)-I mRNA, as determined by real-time PCR, and the concentrations of IgG, IgA, and IgM, as determined by ELISA, were compared between the two groups.

RESULTS

The levels of TLR-9, NOD-1 and RIG I mRNAs were significantly lower in the otitis-prone than in the non-otitis-prone group (p<0.05 each). The concentrations of IgG, IgA and IgM in effusion fluid did not differ significantly between the two groups (p>0.05), and there were no correlations between immunoglobulin concentration and the expression of PRPs (p>0.05).

CONCLUSIONS

Decreased expression of PRRs may be associated with increased susceptibility to OME.