title: Effects of hyperbaric oxygen and dexamethasone on proinflammatory cytokines of rat cochlea in noise-induced hearing loss.
abstract: OBJECTIVE
  To investigate effects of dexamethasone and hyperbaric oxygen therapy (HBOT) on proinflammatory cytokines and hearing levels in the noise-exposed cochlea of rats.
  
  
  BACKGROUND
  There is an arising concern about negative effects of early initiation of HBOT on hearing in noise-induced hearing loss. Furthermore, effects of HBOT and dexamethasone on cochlear cytokines are not fully elucidated.
  
  
  METHODS
  Twenty-six rats were divided into 3 groups: control, noise, and treatment groups. Five rats served as control group. White noise at 115 dB sound pressure level was applied to the noise group of 4 rats for 10 days. This group was assigned to a positive control group as it was equivalent to treatment groups. The treatment group of 17 rats underwent the same noise exposure, and then, they were divided into 3 groups based on treatment protocol: 5 and 6 rats received HBOT at the third hour and 24th hour after the noise, respectively, and 6 rats received dexamethasone. Auditory brain stem response threshold was measured in all groups before being assigned to the groups, after the noise exposure and right before being killed. Cytokine levels at the cochlear soft tissues were measured using enzyme-linked immunoassay.
  
  
  RESULTS
  Final thresholds (10 dB and 5 dB nHL-normal hearing level) of HBOT-24th hour and dexamethasone groups were significantly better than that of untreated noise group (22.5 dB nHL) (p < 0.05). There was no significant difference between HBOT-24th hour group (10 dB nHL) and dexamethasone group (5 dB nHL) (p > 0.05). IL-6 and IL-1β of HBOT-third hour group (2.30 ng/mg and 185.43 pg/mg) were significantly higher than those of the noise group (0.91 ng/mg and 131.40 pg/mg), dexamethasone group (1.19 ng/mg and 112.29 pg/mg) and HBOT-24th hour group (1.34 ng/mg and 106.69 pg/mg) (p < 0.05). There was no significant difference in IL-6 and IL-1β of HBOT-24th hour group, dexamethasone group, noise group, and control group (p > 0.05). There was no significant difference in TNF-α of the 3 treatment groups, noise group, and control group (p > 0.05).
  
  
  CONCLUSIONS
  The results showed that the most effective method in the treatment of noise-induced hearing loss was early initiation of dexamethasone therapy. There could be negative effects of HBOT on hearing if it is commenced early after the noise (first 3 h). HBOT treatment, which was started at the 24th hour, was found to be an effective method.
authors.affiliation: Department of Otorhinolaryngology and Head Neck Surgery, Gulhane Military Medical Academy, Ankara, Turkey.
authors.forename: Hasan Hüseyin
authors.initials: HH
authors.lastname: Arslan
authors.forename: Bulent
authors.initials: B
authors.lastname: Satar
authors.forename: Muhittin A
authors.initials: MA
authors.lastname: Serdar
authors.forename: Mehmet
authors.initials: M
authors.lastname: Ozler
authors.forename: Emine
authors.initials: E
authors.lastname: Yilmaz
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001309:Auditory Threshold; D003051:Cochlea / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism*; D006931:Hyperbaric Oxygenation; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008297:Male; D009622:Noise / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D000893:Anti-Inflammatory Agents; D016207:Cytokines; D053583:Interleukin-1beta; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone