Arachidonic acid metabolites in experimental otitis media and effects of anti-inflammatory drugs

Leukotriene B4 Is a Major Determinant of Leukocyte Recruitment During Otitis Media

Background

Pathogens of otitis media (OM) induce inflammatory responses in the middle ear (ME), characterized by mucosal hyperplasia, leukocyte infiltration, and inflammatory mediators, including arachidonic acid metabolites. We studied the role of the eicosanoid leukotriene B4 (LTB4) in OM.

Methods

Expression of LTB4-related genes was evaluated by gene array and single-cell RNA-Seq in MEs infected with nontypeable Haemophilus influenzae (NTHi). An inhibitor of LTB4 receptor 1 (i.e. U75302) was also used to block LTB4 responses.

Results

ME expression of LTB4-related genes was observed by gene arrays and scRNA-Seq. However, not all genes involved in LTB4 generation occurred in any one specific cell type. Moreover, LTB4 receptor inhibition significantly reduced mucosal hyperplasia and virtually eliminated leukocyte infiltration.

Conclusions

ME expression of LTB4-related genes suggest a functional role in OM disease. The fact that LTB4-generation is spread across different cell types is consistent with a transcellular pathway of eicosanoid biosynthesis involving cell-to-cell signaling as well as transfer of biosynthetic intermediates between cells. The dramatic reduction in ME leukocyte infiltration caused by U75302 indicates that LTB4 plays a major role in ME inflammatory cell recruitment, acting via the LTB4R1 receptor. Given that there are many other chemotactic factors that occur in the ME during OM, the ability of LTB4 to activate leukocytes and stimulate their extravasation may explain the effects of inhibition. Reduction in mucosal hyperplasia due to U75302 administration may be secondary to the reduction in leukocytes since LTB4R1 is not expressed by mucosal epithelial or stromal cells. The results suggest that LTB4 receptor antagonists could be useful in treating OM.

The effects of methylprednisolone, montelukast and indomethacine in experimental otitis media with effusion

OBJECTIVES

The present study aimed to investigate the effects of indomethacine, montelukast and methylprednisolone in management of experimental otitis media with effusion.

METHODS

Forty Wistar albino rats of which the weights ranged between 310 and 370 g were included in this study. Middle ear effusion was created by transtympanic histamine injection. The presence of effusion was confirmed by otomicroscopic examination. Thirty-seven rats with effusion were divided into 4 groups (methylprednisolone, montelukast, indomethacine and saline-control groups). All agents were administered for a period of consecutive 10 days. At the 11th days of administration, the recovery of effusion was confirmed by otomicroscopic examination. Tympanic bullae of the rats were removed and histopathological examinations were carried out. In the histopathological examination, the neutrophil leukocytes accumulated in the middle ear submucosa were counted.

RESULTS

The mean numbers of submucosal neutrophils in the methylprednisolone, montelukast, indomethacine, and saline groups were 24.6±8.1, 54.1±6.2, 52.3±7.3, 55.7±8.3, respectively. The otomicroscopic recovery rates of effusion in the methylprednisolone, montelukast, indomethacine, and saline groups were 18/18 (100%), 8/18 (44%), 2/14 (14%), 2/18 (11%) respectively.

CONCLUSIONS

Methylprednisolone and montelukast ameliorate the middle ear effusion. However, only methylprednisolone reduces the submucosal infiltration of the neutrophil leukocytes which are the most evident cell of inflammatory process. Montelukast is effective in the resolution of experimental otitis media with effusion.

The role of inflammatory mediators in the pathogenesis of otitis media and sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K⁺ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

Cyclooxygenase 2 expression in otitis media with effusion

OBJECTIVES

To study whether cyclooxygenase 2 (COX-2) plays a role in the development of otitis media with effusion (OME).

STUDY DESIGN/METHODS

An experimental model of endotoxin-induced OME was used in healthy BALB/c mice. Solutions of Salmonella typhimurium endotoxin were injected into the middle ears of the mice, and COX-2 expression in the middle ears was studied using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization (ISH).

RESULTS

Analysis by RT-PCR showed that COX-2 expression in the middle ear increased in a dose-dependent fashion after injection of endotoxin. ISH demonstrated that COX-2 had distinct expression patterns in the epithelium of middle ears with endotoxin-induced OME. COX-2 expression, however, was not detected in normal middle ears.

CONCLUSIONS

COX-2 expression may be one factor contributing to the development of OME.

Nutritional Supplements and Upper Respiratory Tract Illnesses in Young Children in the United States

Key Points

In the United States, children have lower blood levels than adults of eicosapentaenoic acid (EPA), an important ω-3 fatty acid that helps decrease inflammation; vitamin A, the “anti-infective” vitamin; and selenium (Se), a trace metal that is an intrinsic part of glutathione peroxidase, an important free-radical scavenging enzyme.

EPA, vitamin A, and Se are important in controlling inflammation and can be supplied by oral nutritional supplements.

Cod liver oil contains EPA (and other important ω-3 fatty acids), and vitamin A as well as vitamin D.

Fish oil contains ω-3 fatty acids (including EPA) but no vitamins.

Our clinical research demonstrates that daily supplementation with a flavored cod liver oil (which meets European purity standards) and a children’s multivitamin-mineral with trace metals, including Se, can decrease morbidity from upper respiratory tract illnesses, otitis media, and sinusitis in young children living in the United States.

These supplements can be used by practitioners on an individual basis, when clinically indicated; the supplements can be purchased in the United States without a prescription.

Socioeconomically disadvantaged children are at risk for micronutrient deficiencies. However, their families may not be able to afford to purchase these supplements, which are not available through Medicaid, The Special Supplemental Nutrition Program for Women, Infants and Children, or the Food Stamp Program.

If our results are confirmed in larger studies, a system change will be needed to provide these supplements to nutritionally vulnerable, socioeconomically disadvantaged children living in the United States.

Lemon-flavored cod liver oil and a multivitamin-mineral supplement for the secondary prevention of otitis media in young children: pilot research

We measured blood levels of fatty acids, vitamin A, and trace metals in children undergoing ambulatory surgery for placement of tympanostomy tubes and a comparison group having other ambulatory surgical procedures. We then performed a small, outpatient, secondary prevention study using nutritional supplements chosen on the basis of those blood levels. The study subjects had lower levels of red blood cell eicosapentaenoic acid (EPA) than did adult controls. Consistent with previous reports, the levels of vitamin A were < or = 40 microg/dL for 69% of our subjects, and the plasma selenium levels for children were lower than published values for adults. We then studied one otitis media (OM) season; 8 children (0.8 to 4.4 years of age) received 1 teaspoon of lemon-flavored cod liver oil (containing both EPA and vitamin A) and 1 half-tablet of a selenium-containing children's chewable multivitamin-mineral tablet per day. During this OM season, study subjects received antibiotics for OM for 12.3% +/- 13.4% (SD; p < .05) fewer days during supplementation than before supplementation. Larger, controlled trials are warranted to assess the utility of cod liver oil (of acceptable purity and taste) and a children's multivitamin-mineral preparation containing selenium, both for the prevention of OM and for the acceptance of delayed prescription of antibiotics for this disorder.

Efficacy of bactericidal/permeability-increasing protein in experimental otitis media with effusion in rats: a new therapy for mucosal infections

Otitis media with effusion (OME) is characterized by the presence of fluid in the middle ear without signs or symptoms of acute infection and by persistent changes in the middle ear mucosa. These are mainly induced by gram-negative bacterial infection and dysfunction of the eustachian tube (ET). Gram-negative bacteria (GNB) contain lipopolysaccharide (LPS) in their outer membrane that is responsible for inflammatory reactions in the middle ear. In this study we investigated the therapeutic effect of a recombinant LPS-binding protein, bactericidal/permeability-increasing protein (rBPI21), on the repair of mucosal damage in rats with experimentally induced OME. OME was induced by obstruction of the eustachian tube in combination with LPS injection. Twelve weeks after OME induction, secretory cells in the tympanic orifice of the middle ear were increased from an average of 14 +/- 2 to 31 +/- 5, ciliated cells were decreased from 24 +/- 4 to 6 +/- 4, and the number of macrophages in the subepithelial layer increased from 13 +/- 4 to 27 +/- 3. A single dose of rBPI21 was administered directly into the middle ear cavity 2 weeks after the induction of OME. Histologic examination of the middle ear mucosa at 4 and 12 weeks after OME induction showed that mucosal changes were restored by rBPI21 treatment. These results demonstrate that the middle ear mucosa recovers from inflammatory changes associated with OME after treatment with rBPI21. This suggests that rBPI21 may be useful in the treatment of OME and of mucosal infections of the respiratory tract.

The role of inflammatory mediators and anti-inflammatory drugs in otitis media

Despite multiple studies, the role of anti-inflammatory drugs in the treatment of AOM and OME is unclear. Although the AHCPR was against the use of steroids in OME, other studies suggest a possible role with potential cost savings and a decrease in the need for surgery in some patients. But the risk-benefit ratio of steroid treatment is unclear. There is some evidence that NSAIDs may decrease otalgia associated with AOM, but no proof that NSAIDs reduce or prevent inflammatory changes in the middle ear associated with AOM and OME.

Eicosanoid synthesis and inactivation in healthy and infected chinchilla middle ears

Otitis media (OM) is an inflammatory reaction of the middle ear (ME) elicited by a variety of stimuli including tubal obstruction, allergy and bacterial infection. The leukotrienes and prostaglandins are among the earliest mediators produced in response to these insults. Their measured levels in human and animal models span a broad range of concentrations. However, their baseline levels and metabolic fates are unknown for the ME. Their dynamics in the ME were examined using the chinchilla animal model, tritiated eicosanoids and a lavage procedure. Prostaglandin levels in the normal ME were 10 times higher than the 34 pg/ear observed for the leukotrienes and thromboxane B2. These levels were significantly increased by the calcium ionophore A23187 and bacterial infection. Leukotrience C4 was the most and prostaglandin E2 the least persistent eicosanoid in the ME. Their residence time in the ME was increased by infection. The rank order of eicosanoid concentrations among comparable studies was surprisingly constant, with prostaglandin E2 the most abundant and the leukotrienes the least. Comparisons of eicosanoid levels from A23187 stimulation and the infectious models sampled at 3 days suggest that the higher levels observed in the infectious models may represent basal eicosanoid production for hyperplastic ME mucosa.