Mohammadkhani Ghassem, Pourbakht Akram, Khanavi Mahnaz, Faghihzadeh Soghrat
Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, IR Iran.
Department of Audiology, Rehabilitation Research Center, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, IR Iran.
Iran Red Crescent Med J. 2013 Nov;15(11):e8890. doi: 10.5812/ircmj.8890. Epub 2013 Nov 5.
Hearing capability plays a principal role on human's communication. Noise-induced hearing loss (NIHL) caused by exposure to high noise levels is a serious socio-economic problem in modern societies. NIHL can either be reversible, resulting in a temporary threshold shifts (TTS) or irreversible, resulting in a permanent threshold shifts (PTS). PTS is often confirmed in the time span of between 2 - 6 weeks. NIHL may be prevented by avoidance of excessive amounts of noise or reducing the sound energy entering the inner ear using hearing protective devices. However, there are some conditions that such prevention is not possible such as noise exceeding the protective capabilities of the hearing protection device, working in military or the person does not tolerate the protection device. Thus the protective agent for preventing NIHL would be useful.
Free radical molecules and consequence oxidative stress have been shown to play a significant role in noise-induced hearing loss. Silymarin is an antioxidant flavonoid complex derived from the herb milk thistle has ability to mitigating the oxidative stress, scavenge free radicals. In the current study, we aimed to evaluate the protective effect of silymarin on noise induced hearing loss in guinea pig by auditory brain stem response.
Twenty guinea pigs randomly divided into 2 groups. The animals in the experimental group were intraperitoneally injected with 100 mg/kg/day silymarin dissolved in propylene glycol for 6 consecutive days. The control subjects were intraperitoneally injected with propylene glycol for 6 consecutive days. All animals were exposed to 4 kHz octave band noise at 120 dB SPL for 6 hours. Auditory brainstem responses (ABRs) at frequencies of 2, 4, 6, 8, 12, 16 and 20 kHz were precisely recorded before intervention and then on intervals of 0, 3, 10 and 15 days after noise exposure. Data were analyzed using repeated measures ANOVA.
Threshold shifts for the experimental group at all frequencies immediately, 3, 10 and 15 days after noise exposure were significantly reduced compared to the control group (P < 0.01).
The findings indicate a protective effect of silymarin on temporary and permanent noise-induced hearing loss.
听力在人类交流中起着主要作用。暴露于高强度噪声导致的噪声性听力损失（NIHL）是现代社会中一个严重的社会经济问题。NIHL 既可能是可逆的，导致暂时性阈移（TTS），也可能是不可逆的，导致永久性阈移（PTS）。PTS 通常在 2 - 6 周的时间跨度内得到确认。避免过量噪声或使用听力保护装置减少进入内耳的声能可预防 NIHL。然而，在某些情况下，如噪声超过听力保护装置的防护能力、在军事环境中工作或个人不耐受保护装置时，这种预防是不可能的。因此，预防 NIHL 的保护剂将是有用的。
自由基分子及随之产生的氧化应激已被证明在噪声性听力损失中起重要作用。水飞蓟素是一种从水飞蓟草本植物中提取的抗氧化类黄酮复合物，具有减轻氧化应激、清除自由基的能力。在本研究中，我们旨在通过听性脑干反应评估水飞蓟素对豚鼠噪声性听力损失的保护作用。
将 20 只豚鼠随机分为 2 组。实验组动物连续 6 天腹腔注射溶于丙二醇的 100 mg/kg/天的水飞蓟素。对照组动物连续 6 天腹腔注射丙二醇。所有动物均暴露于 120 dB SPL 的 4 kHz 倍频程带噪声中 6 小时。在干预前以及噪声暴露后 0、3、10 和 15 天精确记录 2、4、6、8、12、16 和 20 kHz 频率的听性脑干反应（ABR）。数据采用重复测量方差分析进行分析。
与对照组相比，实验组在噪声暴露后即刻、3、10 和 15 天所有频率的阈移均显著降低（P < 0.01）。
研究结果表明水飞蓟素对暂时性和永久性噪声性听力损失具有保护作用。
