β-胡萝卜素对D-半乳糖致仔鼠耳毒性的保护作用

目的观察孕期和哺乳期β-胡萝卜素干预D-半乳糖致仔鼠听力损伤及耳蜗毛细胞凋亡的作用。方法将18只孕鼠随机分为3组(对照组、半乳糖组、半乳糖+β-胡萝卜素组),自妊娠6 d起,对照组喂饲普通饲料,半乳糖组喂饲混合饲料(30%D-半乳糖),半乳糖+β-胡萝卜素组喂饲混合饲料(30%D-半乳糖和1%β-胡萝卜素)。仔鼠出生后21 d,检测血清半乳糖、β-胡萝卜素,全血超氧化物歧化酶(SOD)、还原型谷胱甘肽(GSH)、谷胱甘肽过氧化物酶(GSH-Px)和血浆丙二醛(MDA),测畸变产物耳声发射(distortion product otoacousticemission,DPOAE),应用硝酸银染色全耳蜗铺片观察。应用原位末端转移酶标记技术(terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labelling,TUNEL)染色和免疫组化检测毛细胞凋亡情况。结果β-胡萝卜素可减弱孕期和哺乳期D-半乳糖暴露致仔鼠脂质过氧化,DPOAE降低和耳蜗毛细胞缺失,并延缓耳蜗细胞凋亡发生及Caspase-3免疫阳性表达。结论β-胡萝卜素对D-半乳糖致仔鼠耳毒性具有预防作用。     

Gentamicin vestibulotoxicity with modern systemic dosing regimens: a prospective study using video-oculography

Abstract

Objectives: To determine the incidence of gentamicin vestibulotoxicity with current dosing regimens, and to evaluate the feasibility of routine video-oculography on all patients given gentamicin.

Materials and methods: In this prospective incidence study serial horizontal vestibulo-ocular reflex (HVOR) gain measurements were recorded using video-oculography on adult inpatients receiving intravenous gentamicin. The primary outcome was the proportion of patients developing impairment of their HVOR gain.

Results: After exclusions, 42 patients were included in the analysis. Three patients (7.1%) developed asymptomatic vestibulotoxicity, exact 95% confidence interval 1.5–19.5%. In two of these patients the deficit resolved within several hours. No patients developed symptomatic vestibulotoxicity. There was no evidence for a generalised reduction in group HVOR gain with time. HVOR gain was not associated with total gentamicin dose, dynamic visual acuity or subjective imbalance.

Conclusions and significance: Gentamicin may cause reversible, asymptomatic vestibulotoxicity. Video-oculography may be useful to monitor for vestibulotoxicity in patients treated with gentamcin; however, testing all patients routinely may be challenging.     

Macrophage contribution to the response of the rat organ of Corti to amikacin

Transdifferentiation of nonsensory supporting cells into sensory hair cells occurs naturally in the damaged avian inner ear. Such transdifferentiation was achieved experimentally in the cochlea of deaf guinea pigs through Atoh 1 gene transfection. Supporting cells may therefore serve as targets for transdifferentiation therapy. Supporting cells rapidly degenerate after hair cell disappearance, however, limiting the therapeutic window for gene transfer. We studied the time course of ultrastructural and phenotypical changes occurring in Deiters cells (hair cell supporting cells) after ototoxic treatment in the rat. The presence of macrophages in the cochlea was also investigated, to study any deleterious effects they may have on pathologic tissues. One week after treatment most hair cells had disappeared. Deiters cells no longer expressed the glial marker vimentin but instead displayed typical hair cell markers, the calcium binding proteins calbindin and parvalbumin. This suggests that a process of transdifferentiation of Deiters cells into hair cells was activated. By 3 weeks post-treatment, however, the Deiters cells began to degenerate and by 10 weeks post-treatment the organ of Corti was degraded fully. Interestingly, a marked increase in macrophage density was seen after the end of amikacin treatment to 10 weeks post-treatment. This suggests chronic inflammation is involved in epithelium degeneration. Consequently, early treatments with anti-inflammatory factors might promote supporting cell survival, thus improving the efficacy of more specific strategies aimed to regenerate hair cells from nonsensory cells.     

阿米卡星在耐多药结核病治疗中引起耳毒性研究进展

阿米卡星（又称“丁胺卡那霉素”）对结核分枝杆菌及革兰阴性杆菌均有良好的抗菌活性。因疗效明确、价格低廉,其在耐多药结核病的治疗中占据重要地位,虽然2018年WHO耐药结核病治疗指南中将阿米卡星归入C组药物,但鉴于我国贝达喹啉、利奈唑胺获取困难及喹诺酮耐药率高,阿米卡星可能仍将是我国治疗耐多药结核病的重要药物。在耐多药结核病治疗中需使用至少6个月阿米卡星,长疗程使用阿米卡星引起的耳毒性发生率高,严重的耳鸣和听力减退不仅为患者带来了痛苦,而且还可能导致治疗的中断。本文通过总结近年来国内外对阿米卡星引起耳毒性的发生情况、机制、危险因素、预防的研究进展,为临床应对阿米卡星引起的耳毒性提供帮助。     

Assessment of Nutrient Supplement to Reduce Gentamicin-Induced Ototoxicity

Gentamicin is an aminoglycoside antibiotic used to treat gram-negative bacterial infections. Treatment with this antibiotic carries the potential for adverse side effects, including ototoxicity and nephrotoxicity. Ototoxic effects are at least in part a consequence of oxidative stress, and various antioxidants have been used to attenuate gentamicin-induced hair cell death and hearing loss. Here, a combination of nutrients previously shown to reduce oxidative stress in the hair cells and attenuate hearing loss after other insults was evaluated for potential protection against gentamicin-induced ototoxicity. Guinea pigs were maintained on a nutritionally complete standard laboratory animal diet or a diet supplemented with β-carotene, vitamins C and E, and magnesium. Three diets with iterative increases in nutrient levels were screened; the final diet selected for study use was one that produced statistically reliable increases in plasma levels of vitamins C and E and magnesium. In two separate studies, significant decreases in gentamicin-induced hearing loss at frequencies including 12 kHz and below were observed, with less benefit at the higher frequencies. Consistent with the functional protection, robust protection of both the inner and outer hair cell populations was observed, with protection largely in the upper half of the cochlea. Protection was independently assessed in two different laboratories, using two different strains of guinea pigs. Additional in vitro tests did not reveal any decrease in antimicrobial activity with nutrient additives. Currently, there are no FDA-approved treatments for the prevention of gentamicin-induced ototoxicity. The current data provide a rationale for continued investigations regarding translation to human patients.     

WR-2721 (Amifostine) Ameliorates Cisplatin-Induced Hearing Loss But Causes Neurotoxicity In Hamsters: Dose-Dependent Effects

Chemoprotective agents reduce the toxic side effects of chemotherapy agents such as cisplatin. The conventional belief is that the chemoprotective agent WR-2721 (Amifostine), while protecting against most cisplatin-induced side effects, does not protect against cisplatin-induced ototoxicity (i.e., hearing loss). There is no knowledge, however, about the efficacy of high doses of WR-2721 (WR) in possibly protecting against cisplatin-induced ototoxicity. Thus, the dose-dependent effects of WR in possibly ameliorating cisplatin-induced ototoxicity were investigated. Hamsters were given a series of 5 cisplatin injections (3 mg/kg/injection once every other day, i.p.) either alone or in combination with 18, 40, 80, or 400 mg/kg/injection of the rescue agent WR (n = 5 or 10/group). Other groups received either 80 mg/kg/injection WR alone (n = 5) or were untreated (n = 14). Ototoxicity was assessed by auditory brain stem responses (ABR). WR provided dose-dependent rescue from cisplatins ototoxicity with no protection at the low dose of 18 mg/kg, moderate protection at 40 mg/kg, and nearly complete protection at 80 and 400 mg/kg. However, WR doses of 40 mg/kg or higher caused neurotoxicity as evidenced by prolongations in the ABRs interpeak latencies. Thus, high doses of WR provided the beneficial effect of protecting against cisplatin-induced ototoxicity, but had the harmful side effect of neurotoxicity. Previous failures to find chemoprotection from cisplatin-induced ototoxicity were likely due to the use of WR doses that were too small. The clinical implications of the beneficial and harmful effects of high doses of WR are discussed.     

庆大霉素对豚鼠耳蜗琥珀酸脱氢酶的影响

目的观察庆大霉素（ＧＥ）对耳蜗毛细胞琥珀酸脱氢酶（ＳＤＨ）的影响。方法用组织化学染色方法,观察ＧＥ引起的豚鼠耳蜗毛细胞ＳＤＨ的变化。结果正常豚鼠耳蜗内毛细胞的ＳＤＨ呈深蓝色染色,显示毛细胞排列形式;ＧＥ耳中毒豚鼠耳蜗毛细胞内的ＳＤＨ显示变淡,甚至消失,毛细胞破坏显著。结论实验结果表明,ＧＥ引起的耳蜗毛细胞的损坏与线粒体呼吸酶活性变化有关,可能由于呼吸酶活性降低,导致细胞供能障碍,最终引起毛细胞的坏死     

抗癌药顺铂对小鼠的耳、肾和肝毒性及其机制的研究

目的　以小鼠为实验对象建立抗癌药顺铂毒性研究的实验动物模型 ,并探讨其毒性作用产生的可能机制 ,为进一步对顺铂毒性作用的防治研究提供科学参考资料。方法　选择♂昆明种小鼠 ,经腹腔连续注射顺铂 5d ,观察不同剂量顺铂对小鼠的听力、肾脏和肝脏的毒性作用及肝和肾组织抗氧化系统各指标的变化。结果　顺铂可引起小鼠体重明显下降、全频率的听力阈值升高 ,肝和肾的脏器系数、血清尿素氮 (BUN)含量和丙氨酸氨基转换酶 (ALT)活性等指标的异常 ,并呈剂量依赖关系。此外 ,顺铂还可引起肝和肾抗氧化及氧化损伤指标的异常。结论　 3 0～ 4 0mg·kg-1b w的顺铂可引起小鼠出现明显的听力、肾和肝组织的损伤。氧化损伤是抗癌药顺铂产生其毒性作用的可能机制之一 ,但对于不同的脏器和在不同的给药时期 ,其发挥的作用不同     

Gene expression in cisplatin ototoxicity and protection with p53 inhibitor

Cisplatin damages cochlear hair cells and spiral ganglion neurons through cell death signaling pathways that are not fully understood. We used focused apoptosis gene microarrays to study early changes in gene expres-sion in cochlear cultures from P3 neonatal rats treated with cisplatin (0.2 mM). After 12 hours of cisplatin treat-ment, more than 50% of the 96 genes on the array showed a significant decrease in expression, consistent with widespread cell death. However, after 3 hours of cisplatin treatment, 10 genes showed significant increase in ex-pression in total cochlear tissue. In experiments with subsets of cochlear tissues, at 3h, cisplatin induced increased expression of 12 genes in the cochlear sensory epithelium (basilar membrane) and 11 genes in the spiral ganglion (tissue of Rosenthal's canal, containing the spiral ganglion). These included pro- and anti-apoptotic genes in-volved in the p53 signaling pathway, TNF receptor family, NF-kappaB pathway, death domain family, death effec-tor domain family, Bcl-2 family, CARD. family, TRAF family, and GTP signal transduction. Although the changes in gene expression showed an overlap between basilar membrane and spiral ganglion, other changes, which may reflect the unique response of each tissue, were also observed. Pifithrin-ot blocked cisplatin-induced up-regulation of genes in the p53 signaling pathway when assayed by both superarray and real time PCR. The data add to our understanding of the involvement of p53 in cisplatin-induced ototoxicity and otoprotection, conferred by the p53 inhibitor Pifithrin-α.     

Using the Zebrafish Lateral Line to Screen for Ototoxicity

The zebrafish is a valuable model for studying hair cell development, structure, genetics, and behavior. Zebrafish and other aquatic vertebrates have hair cells on their body surface organized into a sensory system called the lateral line. These hair cells are highly accessible and easily visualized using fluorescent dyes. Morphological and functional similarities to mammalian hair cells of the inner ear make the zebrafish a powerful preparation for studying hair cell toxicity. The ototoxic potential of drugs has historically been uncovered by anecdotal reports that have led to more formal investigation. Currently, no standard screen for ototoxicity exists in drug development. Thus, for the vast majority of Food and Drug Association (FDA)-approved drugs, the ototoxic potential remains unknown. In this study, we used 5-day-old zebrafish larvae to screen a library of 1,040 FDA-approved drugs and bioactives (NINDS Custom Collection II) for ototoxic effects in hair cells of the lateral line. Hair cell nuclei were selectively labeled using a fluorescent vital dye. For the initial screen, fish were exposed to drugs from the library at a 100-muM concentration for 1 h in 96-well tissue culture plates. Hair cell viability was assessed in vivo using fluorescence microscopy. One thousand forty drugs were rapidly screened for ototoxic effects. Seven known ototoxic drugs included in the library, including neomycin and cisplatin, were positively identified using these methods, as proof of concept. Fourteen compounds without previously known ototoxicity were discovered to be selectively toxic to hair cells. Dose-response curves for all 21 ototoxic compounds were determined by quantifying hair cell survival as a function of drug concentration. Dose-response relationships in the mammalian inner ear for two of the compounds without known ototoxicity, pentamidine isethionate and propantheline bromide, were then examined using in vitro preparations of the adult mouse utricle. Significant dose-dependent hair cell loss in the mouse utricle was demonstrated for both compounds. This study represents an important step in validating the use of the zebrafish lateral line as a screening tool for the identification of potentially ototoxic drugs.