氨基糖苷类抗生素耳毒性研究

由于抗菌谱广和价格便宜等原因，氨基糖苷类抗生素被广泛应用于临床。然而氨基糖苷类抗生素的耳毒性和肾毒性却使其在临床应用中受到一定限制。氨基糖苷类抗生素在耳蜗毛细胞中的主要积聚部位是线粒体和溶酶体。氨基糖苷类抗生素引起的细胞内氧自由基活动增强是毛细胞损害的重要因素之一，因此局部或者全身应用氧自由基清除剂可以保护耳蜗免受氨基糖苷类抗生素的损害。钙激活的蛋白酶在氨基糖苷类抗生素引起的毛细胞破坏过程中同样扮演了重要的角色，因此抑制钙激活蛋白酶的活性也能有效保护耳蜗毛细胞。急性氨基糖苷类抗生素耳中毒引起的毛细胞破坏大都死于细胞凋亡．其凋亡原因主要是因为线粒体被药物特异性结合并破坏后．其内部的细胞色素C被释放到细胞质中，因而刺激了Caspase-9并激发其下游的Caspase-3，从而导致毛细胞的程序化死亡。与此不同的是，慢性氨基糖苷类抗生素耳中毒引起的毛细胞破坏不仅包括细胞凋亡而且涉及细胞坏死。在氨基糖苷类抗生素引起的毛细胞坏死过程中．溶酶体的超载破裂最终造成毛细胞自溶性坏死是其典型特征。氨基糖苷类抗生素对螺旋神经节没有直接的毒性作用，但是在耳蜗毛细胞被破坏之后，螺旋神经节往往由于缺乏神经营养因子而发生延迟性神经元死亡，应用转基因技术将神经营养因子基因片段转染到耳蜗支持细胞使之产生分泌神经营养因子的功能，可以有效减轻延迟性神经元死亡的发生率。     

氨基糖苷类抗生素的耳毒性机制

由于具有高效性和低廉的价格优势,氨基糖苷类抗生素目前仍是临床最常用的抗生素之一,但其引起的急慢性耳中毒事件也频繁发生。近年对氦基糖苷类抗生素耳毒性机制方面的研究取得了一定的进展,本文就过氧化损伤、兴奋毒及遗传易感性等方面对氨基糖苷类抗生素的耳毒性机制做一综述。     

氨基糖苷类抗生素耳毒性的保护和修饰

目的氨基糖苷类抗生素的分离和鉴定距今已70多年,对治疗严重革兰阴性菌感染,如肠球菌和结核杆菌感染有着强大的功效。然而,随着氨基糖苷类抗生素用药疗程的延长或(和)剂量的增加往往导致肾毒性和耳毒性,阻碍了其在临床上的广泛应用。由于非耳毒性抗生素也具有较广的抗菌谱,用于许多系统感染性疾病的治疗,使得曾经作为优先选择使用的氨基糖苷类抗生素逐渐被取代。然而现在,氨基糖苷类抗生素处于一个潜伏的复兴时期,正逐渐用于治疗对大多数一线抗生素耐受生物所引起的严重性感染,如多重耐药结核、复杂性院内获得性急性尿路感染等。氨基糖苷类抗生素使用的增加,再次向科学家和医生提出了挑战,即肾毒性和耳毒性的问题,尤其该类抗生素导致的耳聋对于具有遗传易感性的患者往往是极重度且不可逆转的。基于这个原因,在过去二十年里,科学家提出了很多种分子治疗策略与氨基糖苷类抗生素导致的耳毒性副作用相抗衡。本文主要概述了:①氨基糖苷类药物杀菌的分子机制,②氨基糖苷类抗生素如何导致具有遗传易感倾向的患者发生耳毒性,③到目前为止,在临床实验和/或临床上已被证明的能阻止和调节氨基糖苷类耳毒性的药物和化合物,④减少氨基糖苷类抗生素剂量来减少耳毒性的发生率。     

氨基糖苷类抗生素耳毒性的机理及防治措施

氨基糖苷类抗生素（aminoglycoside antibiotics,AmAn）应用于临床已有半个多世纪,具有性质稳定、抗菌谱广、杀菌力强、使用简便及价格便宜等优点.但该类药物具有个体差异大、剂量依赖性毒性反应等缺点,应用不当,可引起肾毒性、耳毒性、神经肌肉阻滞作用和变应原性作用等不良反应.本从自由基细胞毒性、线粒体功能失常、细胞凋亡信号传导通路活化等方面就氨基糖苷类抗生素耳毒性的可能机理及临床应用进展作一介绍.     

氨基糖苷类药物耳毒性机制及耳保护策略研究进展

氨基糖苷类药物被认为是损伤内耳、导致听力损失的最常见药物之一,其导致的耳聋对于具有遗传易感性的患者往往是极重度且不可逆的.近些年,科学家对耳毒性过程以及如何在细胞水平上进行防护的研究进一步深入,并提出了一些耳保护策略与氨基糖苷类药物导致的耳毒性副作用相抗衡.本文对氨基糖苷类药物耳毒性的作用机制、影响因素以及当前的耳保护...     

氨基糖苷类抗生素的临床应用及耳毒性预防

虽具有耳毒性,氨基糖苷类抗生素在临床上仍然无法替代,在囊性纤维化伴肺部感染、严重尿路感染、巴尔通体菌血症、布鲁里溃疡病、肺结核等疾病的治疗中仍然发挥着重要作用。局部给药和药物植入物的使用可减少全身使用的副作用。曲美他嗪、雷沙吉兰、咖啡苯乙酯、特异性蛋白抑制剂等为临床预防耳毒性提供更多选择。本文对其在临床应用及耳毒性预防方面的进展进行综述。     

线粒体DNA缺失突变在氨基糖苷类抗生素耳毒易感？…

目的 建立大鼠线粒体ＤＮＡ（ｍｉｔｏｃｈｏｎｄｒｉａｌ ＤｎＡ,ｍｔＤＮＡ）缺失突变模型,探讨ｍｔＤＮＡ缺失突变在氨基糖苷类抗生素（ａｍｉｎｏｇｌｙｃｏｓｉｄｅ ａｎｔｉｂｉｏｔｉｃｓ,ＡｍＡｎ）耳毒易感性中的作用。方法 取Ｗｉｓｔａｒ大鼠随机分为Ａ、Ｂ两组,每组１５只,其中Ａ组大鼠以皮下注射阿毒素（ｄｏｘｏｒｕｂｉｃｉｎ,ＤＯＸ）２ｍｇ／ｋｇ体重,每周２次３个月,Ｂ组则以生理盐水取代ＤＯＸ,然后     

耳蜗传出神经系统和氨基糖苷类抗生素耳中毒

耳蜗传出神经系统在正常听觉和氨基糖苷类抗生素耳中毒中发挥着重要的作用,本文复习近年来相关文献,对耳蜗传出神经系统的形态、生理、耳蜗机械特性和听觉反应的调控机制的研究近况以及氨基糖苷类抗生素对耳蜗传出神经系统的影响进行综述.     

氨基糖苷类抗生素对耳蜗螺旋神经节的损害作用

氨基糖苷类药物(Am An)是一类经典的治疗革兰阴性菌感染的抗生素,但具有耳毒性和肾毒性。以往的研究认为Am An的耳毒性仅仅针对内耳毛细胞并可引起继发的延迟性螺旋神经节细胞(SGNs)死亡。但是随着关于Am An耳毒性和对耳蜗其他细胞的研究进展,人们逐渐意识到耳蜗内支持细胞的损害也是引起SGNs延迟死亡的重要原因之一。我们发现,不同的Am An对内耳的损害方式不同,以硫酸链霉素为代表的少数Am An可以不受血-迷路屏障阻碍直接进入内耳并首先损害内耳的周边神经元;而以往认为只能间接损害SGNs的其他那些难以跨越血-迷路屏障的Am An,比如卡那霉素,对出生后三天大鼠处于发育阶段的SGNs也具有直接的损害作用。因此我们提出一个根据不同内耳损害方式来区分Am An的分类建议,并希望本文介绍的新内容能够为更深入理解不同种类Am An的不同耳毒性机制以及听觉系统各个重要组织成分之间的相互作用关系提供新的参考信息。     

氨基糖甙类抗生素致聋的家族性与交叉易感性

对3个家族中氨基糖甙类抗生素中毒性耳聋患者的家族进行调查及分析，发现几种氨基糖甙类药物之间存在家族性和交叉易感性，即在有家族性耳毒性药物致聋的家族成员中，应用任何一种氨基糖甙类抗生素，都比一般人容易发生耳中毒；即使用量不大，也易引起严重后果，特别是年幼者。此种家族性与交叉易感性属常染色体显性遗传。提示临床医生用药前应仔细询问病史，特别是有母系家族耳聋史者应禁用氨基糖甙类全部抗生素，以预防子代耳聋的发生。     

Histological evaluation of ototoxic reaction due to some aminoglycoside antibiotics

Summary Twenty-one days s.c. treatment with netilmicin, gentamicin, sisomicin, and kanamicin at different doses were performed in albino guinea pigs of both sexes. Block surface preparation of Corti's organ was carried out and missing OHC_s and IHC_s counted in selected areas of each turn. The animals treated with gentamicin and sisomicin showed a dose-depending missing of hair cells, preferably relative to the outer ones and quantitatively the same for both the antibiotics. Furthermore, a characteristic distribution of the damage progressively increasing from the apex to the basal turn of the cochlea was detected. Kanamicin at 267 and 400 mg/kg gave the complete destruction of OHC_s and IHC_s along the whole cochlea while at 178 mg/kg did not show any significant damage in comparison to the control group. Finally, netilmicin neither damaged Corti's organ nor statistically determined missing OHC_s and IHC_s at all the doses used. These histological results and the previous electrophysiological and reflexological observations obtained in the guinea pig show a higher safety of netilmicin in comparison to the other aminoglycosides used for the problem relative to ototoxicity.     

Isolation of overexpressed yeast genes which prevent aminoglycoside toxicity

Aminoglycoside antibiotics at non-toxic levels can cause sensorineural hearing loss in genetically predisposed individuals. The major aminoglycoside hypersensitivity mutation that has been described in humans is at position 1555 in the mitochondrial 12S ribosomal RNA gene. In order to identify additional candidate genes for genetic susceptibility mutations in humans and possibly develop therapeutic interventions, we are using yeast as a model organism to identify genes whose products interact with aminoglycosides or bypass the effects of aminoglycoside poisoning. We have selected yeast genomic DNAs that, when cloned into a high copy number plasmid, confer neomycin resistance. We have previously described the first gene identified through this approach [Prezant, Chaltraw and Fischel-Ghodsian, Microbiology 142 (1996) 3407–3414] and have now completed this search by the exhaustive screening of 35 yeast genome equivalents. This has resulted in the identification of seven additional chromosomal regions. All seven chromosomal regions have been characterized and the most likely gene responsible for aminoglycoside resistance has been identified for each of them. While the mechanism of aminoglycoside resistance can be inferred for some of the gene products, it remains to be determined for others.     

In vitro prediction of aminoglycoside ototoxicity

Summary The first step by which a basic aminoglycoside (AG) causes ototoxicity is thought to be electron binding to such acidic substances as phosphatidylinositol diphosphate and acidic glycosaminoglycans (AGAGs). We studied the competitive binding ability of AGs and basic dyes to AGAG in order to determine if this meachanism was indeed responsible for ototoxicity. The negative charge of heparin was the strongest among the AGAGs examined when the molar ratio of AG to AGAG was small. Toluidine blue was a better basic dye than acridine orange, methylene blue, alcian blue, or neutral red. After we mixed toluidine blue, heparin and an AG, the absorbance of free toluidine blue was measured at 625 nm. The difference in the free dye released by the well-established AG showed a fairly good correlation with the ototoxic activity found in vivo. However, the predicted ototoxicities of newly prepared AGs were greater than estimated when testing their effects on experimental animals. The basicity of AGs will determine their binding affinities to cochlear hair cell membranes and is an important factor in predicting ototoxicity.     

Auditory function in guinea pigs treated with netilmicin and other aminoglycoside antibiotics

Summary The following aminoglycoside antibiotics netilmicin, sisomicin, gentamicin, and kanamycin were submitted to a comparative study of their ototoxicity using both reflexological (Preyer's pinnareflex) and electrophysiological (near and far field) methods. The daily s.c. administration of sisomicin, gentamicin, and kanamycin for 21 days provoked a dose-related impairment of the cochlear function, detected with all the employed techniques. On the other hand, a very low ototoxic effect of netilmicin was demonstrated with electrophysiological but not with the reflexological evaluation.The reliability of the methods used in these experiments is also compared.     

Introduction to the round table on application of psychoacoustical techniques to clinical audialogy

Paracetamol (acetaminophen) is currently one of the most widely used drugs. In large doses, paracetamol is both nephrotoxic and hepatotoxic, and this toxicity may arise through the production of free radicals. Recently, there has been a revival of interest in the hypothesis that aminoglycoside antibiotics are ototoxic because they facilitate free-radical production. Aminoglycosides interact strongly with loop diuretics, producing enhanced ototoxicity. The object of the present study was to determine whether paracetamol would also interact with a loop diuretic. Pigmented guinea pigs received a dose of 500 or 1 000 mg/kg paracetamol via an intragastric cannula. Compound action potentials (CAP) were recorded every 10 min for 2 h. Paracetamol alone had no effect on CAP thresholds, but significantly enhanced the CAP decrement induced by frusemide given intraperitoneally 1 h after paracetamol. This enhancement was larger in animals receiving 1 000 mg/kg paracetamol. Repetition of these drug doses in recovery experiments indicated that all threshold shifts recovered within 7 days.

Effets du paracétamol sur la cytotoxicité du furosémide

Le paracétamol (Acetaminophen) est un médicament couramment utilisé en clinique humaine. Employé à forte dose, il est à la fois néphrotoxique et hépatotoxique; la production de radicaux libres pourrait ětre la cause de cette toxicité. ‘hypothèse selon laquelle les antibiotiques aminoglycosides ont un effet ototoxique en facilitant la production de radicaux libres a bénéficié récemment’ un regain ‘intérět. Les aminoglycosides interagissent fortement avec les produits diurétiques et il en résulte une aggravation de’ effet ototoxique. Notre étude avait pour objet de rechercher ‘existence ’ une interaction entre le paracétamol et un diurétique (furosémide). Une dose de 500 ou 1 000 mg/kg de paracétamol a été injectée à des cobayes colorés par ‘intermédiaire’ une sonde gastrique. Le potentiel ‘action cochléaire (PAC) a été enregistré toutes les 10 min, durant les 2 h qui ont suivi’ injection. Le paracétamol ‘avait pas’ effet sur les seuils auditifs. Dans un second groupe animaux, une injection de furosémide a été pratiquée 1 h après celle du paracétamol: une élévation significative des seuils auditifs était observée dans ce cas et elle était plus importante chez les animaux ayant reçu 1 000 mg/kg paracétamol. Des enregistrements effectués 7 jours après les injections ont montré que les seuils auditifs étaient normaux.     

Specific glutathione-SH inhibition of toxic effects of metabolized gentamicin on isolated guinea pig hair cells

The present investigation has shown that only metabolized gentamicin (mG) but not native gentamicin (G) is cytotoxic for isolated guinea pig outer hair cells (OHC). Using FURA-2 fluorescence, both G and mG were found to reduce intracellular free Ca²⁺ concentrations in unstimulated OHC and inhibit increases in intracellular Ca²⁺ concentrations during K⁺-induced depolarization. Glutathione-SH (GSH), a detoxificating agent, did not interfere with G and mG effects on intracellular Ca²⁺ concentration. In non-stimulated OHC, mG but not G induced pathological OHC depolarization, indicating the opening of transduction channels to allow influx of K⁺ ions. GSH completely inhibited the lytic effect of mG. Electrophysiological investigations also revealed that GSH probably inhibits mG-induced pathological opening of transduction channels. These results suggest that GSH selectively inhibits mG-specific toxic effects on the guinea pig OHC, possibly by enzymatic detoxification.     

氨基甙类抗生素中毒性耳聋患者头发和 血液的基因突变位点检测

目的证实氨基甙类抗生素中毒性耳聋家系成员的头发与血细胞同样存在基因突变。方法采用聚合酶链式反应和单链构象多态性分析(PCR-SSCP)及限制性内切酶ALw26Ⅰ酶切技术,对此聋3个家系8例成员的血细胞和(或)头发毛囊细胞线粒体DNA进行检测。结果8例中7例此聋患者血细胞和(或)头发毛囊细胞线粒体DNA12SrRNA基因第1555位点均发生突变,而1例听力正常的父亲未发现此种突变。结论提示用头发代替血液检测,可对因氨基甙类抗生素致聋的家系成员进行基因诊断和筛选,以防此聋的发生。