Earnest O. John

Protective Effect of Corticosteroid against the Cytotoxicity of Aminoglycoside Otic Drops on Isolated Cochlear Outer Hair Cells

Objectives Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanic membrane perforation or tympanostomy tube. Many studies demonstrated the ototoxicity of aminoglycoside. In our previous study, we observed that gentamicin (GM), when activated with liver extract, demonstrated significant cytotoxicity. The purpose of this study was to assess the protective effect of corticosteroid against the cytotoxicity of GM and tobramycin drops using isolated cochlear outer hair cells (OHCs) in vitro with liver extract.

Determination of Ototoxicity of Common Otic Drops Using Isolated Cochlear Outer Hair Cells

Objectives Otic drops are commonly used not only for otitis externa, but also for otorrhea in the presence of tympanostomy tubes or tympanic membrane perforations. Many studies have demonstrated the ototoxicity of common otic preparations such as Cortisporin® otic drops (Monarch Pharmaceuticals, Bristol, TN). The purpose of this study was to assess the relative ototoxicity of common otic preparations by direct exposure to isolated cochlear outer hair cells (OHCs).

Effects of Common Topical Otic Preparations on the Morphology of Isolated Cochlear Outer Hair Cells

Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanostomy tube or tympanic membrane perforation. Many studies have demonstrated the ototoxicity of common otic preparations such as Cortisporin otic drops. Recent studies have suggested the use of fluoroquinolone antibiotic drops as an alternative owing to their excellent antimicrobial coverage and no ototoxic effect. The purpose of this study was to assess the relative ototoxicity of four common otic preparations by direct exposure to isolated cochlear outer hair cells (OHCs). OHCs from adult chinchilla cochlea were exposed to standard bathing solution (control), Cortisporin, Cipro HC, Ciloxan, and Floxin. The cells were observed using an inverted microscope, and the images recorded in digital still-frame and video, and analyzed on the Image Pro-Plus 3.0 program. As measured by time to cell death and change in morphology of OHCs, Cortisporin was most toxic to OHCs. Among the fluoroquinolone drops, Floxin was more toxic than Ciloxan or Cipro HC.Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanostomy tube or tympanic membrane perforation. Many studies have demonstrated the ototoxicity of common otic preparations such as Cortisporin® otic drops. Recent studies have suggested the use of fluoroquinolone antibiotic drops as an alternative owing to their excellent antimicrobial coverage and no ototoxic effect. The purpose of this study was to assess the relative ototoxicity of four common otic preparations by direct exposure to isolated cochlear outer hair cells (OHCs). OHCs from adult chinchilla cochlea were exposed to standard bathing solution (control), Cortisporin, Cipro HC®, Ciloxan®, and Floxin®. The cells were observed using an inverted microscope, and the images recorded in digital still-frame and video, and analyzed on the Image Pro-Plus® 3.0 program. As measured by time to cell death and change in morphology of OHCs, Cortisporin was most toxic to OHCs. Among the fluoroquinolone drops, Floxin was more toxic than Ciloxan or Cipro HC.

Concentration of nitric oxide metabolites in middle ear effusion

Free radicals such as nitric oxide (NO) seem to be important in the pathogenesis of otitis media with effusion (OME). NO can be quantitated by measuring its metabolites, nitrate (NO(3)(-)) and nitrite (NO(2)(-)). The purpose of this study is to determine the concentrations of NO in human middle ear effusion (MEE). Samples of human MEE were collected at the time of myringotomy and tympanostomy tube insertions. The type of MEE was classified as serous (SOM), mucoid (MOM) or purulent (POM) at the time of surgery. Samples of MEE were assayed for NO metabolites (nitrate and nitrite) with colorimetric assay (Griess method). Concentrations of NO metabolites were highest in MOM followed by SOM and POM. This study suggests that NO is present in human MEE and may play an important role in the pathogenesis of OME.

Effects of nitric oxide on morphology of isolated cochlear outer hair cells: Possible involvement in sensorineural hearing loss

Hypothesis One of the inflammatory mediators of otitis media, nitric oxide, can damage cochlear outer hair cells. Background Free radicals, including nitric oxide, have been detected in middle ear effusion. Increasing evidence implicates free radicals in the pathogenesis of otitis media and possibly in the development of sensorineural hearing loss. Methods Isolated outer hair cells from adult chinchilla cochlea were exposed to standard bathing solution (Control Group 1) or the nitric oxide-producing compounds, S-nitroso-N-acetyl, l-penicillamine (1–1.5 mg/ml, Experimental Group 1) or 3-morpholinosynonimine (1–1.5 mg/ml, Experimental Group 2). Since nitric oxide is readily converted to nitrite and nitrate in vivo, a second control group using sodium nitrite was used to separate potential effects of nitric oxide from nitrite (Control Group 2). All experiments were performed at an osmolality of 305 ± 5 mOsm at room temperature, and with exposure time up to 90 minutes. The cells were observed using an inverted microscope, and the images were recorded and analyzed on the IMAGE Pro-Plus program. Results Outer hair cells exposed to either standard bathing solution or sodium nitrite (Control Groups 1 and 2) showed no significant change in cell shape or length. Cells exposed to S-nitroso-N-acetyl and l-penicillamine or 3-morpholinosynonimine exhibited ballooning and significant shortening in mean cell length (p < 0.01). Conclusion This study demonstrates that exposure to nitric oxide causes irreversible morphologic changes in isolated outer hair cells, suggesting possible involvement of nitric oxide radical in the development of sensorineural hearing loss as a sequela of chronic otitis media.

Effect of round window membrane application of nitric oxide on hearing and nitric oxide concentration in perilymph.

Nitric oxide (NO), a free radical, has been found to be important in the development of middle ear effusions. However, the effect of NO in the middle ear effusion on cochlear function and on perilymph concentrations of NO has not been reported. We placed S-nitroso-N-acetylpenicillamine (SNAP), a NO donor compound, on the round window membrane (RWM) of adult chinchillas. Auditory brainstem response (ABR) thresholds were measured before and after the placement of SNAP on the RWM and hourly for 8 h after SNAP placement. Samples of perilymph were collected 2 h after application of SNAP and were assayed for total nitrate and nitrite, the end products of NO. Experimental ears demonstrated significant ABR threshold elevations after 5 h and elevated nitrate/nitrite in the perilymph. These findings suggest that NO present in the middle ear passes through the RWM into the inner ear and can cause significant hearing loss.

Effect of topical dexamethasone versus rimexolone on middle ear inflammation in experimental otitis media with effusion

Conclusion. The lipopolysaccharide (LPS)-induced chinchilla otitis media (OM) model was proven useful in screening anti-inflammatory agents for topical use. Both 1% rimexolone and 1% dexamethasone are effective in reducing the volume of middle ear effusion and mucosal thickness compared with control groups. Topical corticosteroid therapy was efficacious in reducing middle ear mucosal inflammation. Objective. OM is one of the most common diseases in the pediatric population. Our previous studies have shown that treatment with systemic antibiotics and corticosteroids was more efficacious than antibiotics alone. The purpose of this study was to determine the effectiveness of topically applied corticosteroids on the outcome of OM. The long-term goal of this study was to develop a better method of OM treatment by demonstrating effectiveness of topically applied anti-inflammatory agents, such as corticosteroids, avoiding systemic side effects. Materials and methods. Three experimental groups were studied in chinchillas. OM with effusion was induced in all groups by injecting LPS. Group 1 consisted of controls in three subgroups as follows. Control-LPS alone, vehicle of dexamethasone (control-dexa), vehicle of rimexolone (control-rimex). Group 2 was treated with dexamethasone and included subgroups of separate concentrations of dexamethasone: 0.1% and 1% suspensions. Group 3 was treated with rimexolone and included subgroups of separate concentrations of rimexolone: 0.1% and 1% suspensions. A total of 58 animals were used: 18 for controls and 40 for experimental groups. All test substances (saline, control-dexa, control-rimex, dexamethasone and rimexolone, 200 µl) were injected at −2, 48 and 60 h; LPS was injected at 0 h. Animals were monitored by daily otomicroscopy. After 4 days, samples of middle ear effusion (MEE) were collected for analysis and temporal bones were harvested for histopathological studies. Results. At the end of 4 days, only in five ears (3/20 with 1% dexamethasone, 1/20 with 1% rimexolone, and 1/20 with 0.1% rimexolone) had the fluid diminished to the point of being unobservable. The volume of MEE, thickness of mucoperiosteum, and the degree of inflammation of middle ear mucosa with 1% dexamethasone and 1% rimexolone was significantly less compared with other groups.

Effect of Corticosteroid on Salicylate-Induced Morphological Changes of Isolated Cochlear Outer Hair Cells

Our previous studies showed that pretreatment with corticosteroids, which inhibits release of arachidonic acid (precursor of prostaglandins and leukotrienes), partially prevented salicylate-induced hearing loss in vivo. The purpose of this study was to determine the effect of pretreatment with corticosteroid (dexamethasone sodium phosphate) on isolated cochlear outer hair cells (OHCs) exposed to salicylate in vitro. Isolated OHCs from the chinchilla cochlea were exposed to salicylate with or without pretreatment with dexamethasone. Images were stored and analyzed on the Image program. The OHCs exposed to salicylate demonstrated a significant shortening in cell length. The OHCs exposed to salicylate after pretreatment with dexamethasone exhibited no significant change in cell length. We conclude that corticosteroid treatment of isolated OHCs is effective in blocking the morphological changes induced by salicylate. This study gives additional evidence that salicylate ototoxicity is mediated by alteration in the levels of arachidonic acid metabolites.

Effect of Nitric Oxide on Mucin Production in Experimental Otitis Media

OBJECTIVE: The purpose of this study was to determine the role of nitric oxide (NO) in the pathogenesis of mucold otitis media (OM) in lipopolysaccha-ride (LPS)-induced OM. METHODS: OM was induced in chinchillas by injecting S-nitroso-N-acetylpenicillamine (SNAP), LPS, and LPS + SNAP into the superior bullae. Auditory brainstem response thresholds were measured every 24 hours. Samples of middle ear fluid were collected and analyzed for mucin by the periodic acid-Schiff method. At the end of each experiment, temporal bones were harvested for histopathologic study. RESULTS: Mucin concentration was greatest in the LPS + the SNAP group and least in the SNAP-alone group. Auditory brainstem response threshold was highest in the LPS group and lowest in the SNAP group, although not significantly. Histopathology showed the greatest mucosal thickening and inflammation in the LPS + SNAP group. CONCLUSION: The addition of NO in LPS-induced OM increased the mucin concentration in middle ear fluid and increased mucosal thickness and inflammation in middle ear mucosa. SIGNIFICANCE: In the OM disease process, NO may contribute to the pathogenesis of mucold OM.

Effect of inflammatory mediators of otitis media and otic drops on morphology of isolated cochlear outer hair cells: review and update

Biochemical or chemical substances in the middle ear cavity can affect inner ear function. Among them, inflammatory mediators (IMs) in the middle ear effusion may induce sensorineural hearing loss (SNHL). Otic drops used for otorrhea in the presence of tympanostomy tubes or tympanic membrane perforation may also cause SNHL. The purpose of this study was to determine ototoxicity of IMs of otitis media and common otic drops using isolated cochlear outer hair cells (OHCs) in vitro. OHCs from cochleae of adult chinchilla were isolated and exposed to standard bathing solution (SBS) (control group), albumin‐phosphate buffer saline solution (albumin control), various IMs, and otic drops. All experiments were performed at an osmolality of 305 ± 5 mOsm, room temperature, and for 60 minutes. The cells were observed with inverted microscope; images were stored and analyzed on the IMAGE PRO‐plus program. The change in cell length of OHCs exposed to cyclooxygenase metabolites and the albumin control were not significantly different from the SBS control group (p > 0.05). The OHCs in the lipoxygenase metabolites, platelet activating factor, tumor necrosis factor‐α, histamine, nitric oxide donor compound, 3‐morpholinosynonimine (SIN‐1) and S‐nitroso‐N‐acetyl‐L‐penicillamine (SNAP) groups demonstrated significant shortening (p < 0.05). Among the otic drops, Vosol was the most toxic and CiproHC was the least toxic to OHCs. The GM with liver extract group was significantly more cytotoxic than the GM alone group. This study demonstrated that IMs of otitis media and otic drops can change the morphology of OHCs in vitro and suggests the involvement of these IMs and otic drops in the pathogenesis of SNHL observed in patients with chronic otitis media.