顺铂耳毒性的研究进展

顺铂被广泛用于治疗各种癌症,但具有一定的耳毒性作用。近年来的研究发现,顺铂可通过多种途径诱导听力减退,主要包括耳蜗组织损害、氧化应激损伤和细胞凋亡等。某些基因的突变或者缺失会加重或改善顺铂造成的耳毒性。另外,铁死亡也参与顺铂引起的耳毒性作用。对顺铂耳毒性相关机制的不断研究,将促进听力保护药物的研发及临床应用。     

顺铂耳毒性机制及抗氧化药物局部应用的预防作用

顺铂是临床普遍应用的广谱高效抗肿瘤药物,与多种抗肿瘤药有协同效应、无交叉耐药等特点,为当前联合化疗中最常用的药物之一。然而,顺铂的毒副作用严重困扰着癌症患者,其耳毒性尤为突出。顺铂耳毒性多为双侧、进展性、不可逆性、剂量依赖性听力损伤,往往导致成人、尤其是儿童患者出现语言交流障碍。大量研究证实,顺铂通过诱发活性氧(ROS)升高导致听觉毛细胞发生caspase-3激活的细胞凋亡。哺乳动物听觉毛细胞无自发再生能力,一旦损伤即为永久性。因此,顺铂耳毒性预防的药物研发或治疗策略开发至关重要。目前,越来越多的药物被证实在细胞和动物水平上具有顺铂耳毒性保护作用。然而,绝大部分药物经系统性用药后拮抗顺铂抗肿瘤疗效,无法实现临床上的有效应用。至今仍无有效顺铂耳毒性保护药物被批准上市。耳蜗局部鼓室内用药可部分缓解耳毒性保护候选药物对顺铂抗肿瘤疗效的干扰,但因顺铂需周期性用药,多次鼓室内给予耳毒性保护药物易引起局部创伤和感染。本文总结了具有代表性抗氧化药物预防顺铂耳毒性的基础和临床研究进展,为顺铂耳毒性新药研发提供理论依据。     

顺氯氨铂的耳毒性

由于抗癌药物顺铂的广泛应用,对其副作用,如耳毒性引起临床普遍关注。本文就顺铂耳毒性特点、中毒因素、病理改变、中毒机制及预防方法等方面作简要综述。认为严密观察、给予适当治疗,可望改善其耳毒性作用。     

顺铂耳毒性的研究

顺铂是临床上常用的抗癌药物之一，但有较强的肾毒性和耳毒性，其肾毒性可以通过水化疗法、利尿剂和肾保护剂的使用等方法得到明显缓解，其耳毒性除中断治疗外，尚无明确的防护措施，顺铂耳毒性的产生机制及防护方法就成为当前人们关注的热点。本文就顺铂对耳蜗形态学和功能的影响及其发生的可能机制和防治方法进行综述。     

黑素和抑制剂对顺铂耳毒性的影响

作回顾了顺铂药效学、耳毒性及黑素和一些抑制剂对其耳毒性的影响；并就黑素、磷霉素和自由基清除剂ＬＡＺＡＲＯＩＤＳ与顺铂耳毒性的相互关系进行了实验研究，认为黑素是影响顺铂耳中毒易感性的一个肯定因素，磷霉素和Ｕ７８５１７Ｆ有希望成为预防顺铂耳中毒的保护剂。     

磷霉素减轻顺铂耳毒性的实验研究

本文以听性脑干反应测听、扫描电镜为指标，观察磷霉素对顺铂耳毒性的拮抗作用．用药后顺铂组豚鼠4、8KHzABR阈均明显提高；顺铂 磷霉素组豚鼠仅8KHzABR阈提高。扫描电镜示顺铂组耳蜗第一、二国外毛细胞严重性嵌损；顺铂 磷霉素组耳蜗第一、二回病变轻微。结果表明磷霉素能有效地减轻顺铂引起的耳毒性。     

铜转运蛋白与顺铂耳毒性研究

顺铂是临床上常用的化疗药物,具有抗肿瘤谱广、临床效果显著、价格低廉等优点,然而其耳毒性一直是困扰临床工作者的难题。近年研究发现铜转运蛋白在顺铂进出细胞过程中发挥重要作用。本文就铜转运蛋白与顺铂耳毒性研究的国内外最新进展做一综述。     

应用畸变产物耳声发射和扩展高频测听对顺铂耳毒性的临床研究

目的：应用0．5—16kHz畸变产物耳声发射(distortion product otoacoustic emissions,DPOAE)和扩展高频测听对顺铂耳毒性进行临床研究。方法:对24例应用顺铂进行初次化疗的妇科肿瘤病人于化疗前后分别进行0．5—16kHz DPOAE、常频纯音测听及扩展高频测听检查，比较DPOAE和常频纯音测听、扩展高频测听的结果。结果：顺铂化疗后扩展高频区纯音听阈升高，DPOAE在3kHz、4kHz处及扩展高频区下降明显。结论：常频DPOAE较常频纯音测听更敏感，和扩展高频测听检查一样均可用于顺铂耳毒性的监测。扩展高频DPOAE可能比常频DPOAE更敏感。DPOAE与纯音听闻可能并非一一对应关系。病人对顺铂的易感性可能随着年龄的增加逐渐减低。     

顺铂及其耳毒性

顺铂是一种用于化疗的铂制剂，在临床上广泛应用于抗肿瘤治疗。然而由于顺铂所具有的肾毒性和耳毒性以及神经毒性等毒副作用，致使其临床应用受到一定的限制。顺铂损害耳蜗的三个主要靶目标分别是血管纹和毛细胞以及螺旋神经节，这三个靶目标在顺铂的作用下都以细胞凋亡的方式实现其程序化自我毁灭，因此顺铂耳中毒模型是一个典型的内耳细胞凋亡模型。顺铂造成的细胞内氧自由基活动增加和抗氧化酶类的活性丧失是产生细胞损害的重要因素之一，因而抗氧化治疗可有效降低顺铂对耳蜗中上述三个靶目标的破坏程度。顺铂在Caspase（半胱氨酸天冬氨酸蛋白酶）径路上激发的毛细胞凋亡是首先启动Caspase－8的活动，说明毛细胞膜表面的细胞死亡因子受体是顺铂诱导毛细胞凋亡的一根导火索；螺旋神经节细胞的凋亡却是被顺铂同时启动了Caspase－8和Caspase－9，因此螺旋神经节细胞的凋亡不但是因为细胞膜表面的死亡因子受体因受顺铂刺激而发出凋亡的信号，而且还会被从线粒体释放出的细胞色素C启动其凋亡自毁程序。肿瘤抑制基因p53是出现在顺铂耳中毒早期的一个促使细胞凋亡的重要“杀手”，应用Superarray技术发现顺铂激发的耳蜗毛细胞和螺旋神经节凋亡基因主要涉及p53，肿瘤坏死因子家族，Death domain family（死亡结构域家族），Bcl－2family，Card family（Caspase相关的招募域家族），和GTP signal transdution（三磷酸鸟苷信号转导）等多条凋亡通路，其中p53信号通路是顺铂诱导毛细胞和螺旋神经节凋亡的主线，因此应用p53抑制剂－Pifithrin仅可以通过有效阻止p53的活动而减轻顺铂诱导的毛细胞凋亡。分裂素激活的蛋白激酶在顺铂诱导的内耳细胞凋亡过程中也扮演了重要的角色．应用PD98059可以通过暂时抑制分裂素激活的蛋白激酶活性和p53磷酸化以及Caspase的活动延迟耳蜗毛细胞凋亡的起始阶段，但不能完全阻止病变的扩展，因而PD98059对顺铂引起的耳蜗毛细胞凋亡仅具有短期保护效应。     

葡萄糖酸锌对顺铂耳毒性保护作用的实验研究

本文用豚鼠做实验。用葡萄糖酸锌140mg／kg／日口服5天，然后同时用顺铂2mg／kg／口腹腔注射5天，与单纯顺铂腹腔注射组及生理盐水腹腔注射组对照，观察葡萄糖酸锌对顺铂的耳毒性有无保护作用。结果发现葡萄糖酸锌＋顺铂组豚鼠的耳廓反射的减退和耳蜗外毛细胞损害程度均较单用顺铂组轻，提示葡萄糖酸锌对顺铂的耳毒性有保护作用。     

The histone deacetylase inhibitor sodium butyrate protects against cisplatin-induced hearing loss in guinea pigs

OBJECTIVE: There is a need for otoprotective agents that can be administered systemically without compromising cancer treatment. Histone deacetylase inhibitors are anticancer agents that act by upregulating the expression of cell-cycle control genes. They are also neuroprotective, leading us to hypothesize that they might be otoprotective. The goal of this study was to determine if the antitumor agent sodium butyrate (a histone deacetylase inhibitor) protects against cisplatin ototoxicity when administered systemically. STUDY DESIGN: This was an animal study. METHODS:: Cisplatin was administered to guinea pigs who received either 12 days of sodium butyrate (7 d before and 5 d after cisplatin) or equivolume saline injections. Hearing was tested with distortion product otoacoustic emission (DPOAE) analysis before the start of the study and 2 weeks after cisplatin treatment. RESULTS: Guinea pigs given a single intraperitoneal injection of 14 mg/kg cisplatin experience a mean hearing loss of 8 dB across the frequencies of 3.5, 5, 7, 10, 14, and 20 kHz. Intraperitoneal injection of 1.2 mg/kg sodium butyrate per day for 7 days before and 5 days after cisplatin almost completely eliminates this threshold shift (P=.0011). CONCLUSIONS: The histone deacetylase inhibitor sodium butyrate gives almost complete protection in a single-dose model of cisplatin ototoxicity in guinea pigs. Because histone deacetylase inhibitors are anticancer agents with very few side effects, they may be candidates for clinical use during cisplatin chemotherapy.     

Acceleration of cisplatin ototoxicity by perilymphatic application of 4-methylthiobenzoic acid

The antitumor agent cisplatin has dose-limiting side effects such as ototoxicity. Systemical co-treatment with anti-oxidants like 4-methylthiobenzoic acid (MTBA) and sodium thiosulfate (STS) provides protection against cisplatin ototoxicity. However, systemically administered protective agents may reduce the chemotherapeutic effect of cisplatin. Local application of the protective agents could avoid this undesirable effect. In the present study, we aimed at suppressing cisplatin-induced ototoxicity in guinea pigs by administering MTBA or STS perilymphatically through cochlear perfusion. Guinea pig cochleas were perfused for 10 min with artificial perilymph (ArtP) containing cisplatin at 0.3 mg/ml, either alone, or in combination with MTBA (0.1 or 1.0 mg/ml) or STS (0.75 or 3.0 mg/ml). The compound action potential (CAP) and the summating potential (SP), evoked by 8 kHz tone bursts, and the endocochlear potential (EP; MTBA only) were measured just before and 1, 2, 3 and 4 h after perfusion. Cisplatin gradually reduced the CAP amplitude in time. Adding MTBA only accelerated this ototoxic effect. After cisplatin treatment a decline was found in the EP, irrespective of co-treatment, i.e., addition of MTBA did not accelerate the EP decrease. In contrast to MTBA, STS ameliorated the ototoxic effect of cisplatin. In conclusion, local application of anti-oxidants can ameliorate cisplatin ototoxicity but this is not a feature of all anti-oxidants.     

Assessment of the protective effects of amifostine against cisplatin-induced toxicity

OBJECTIVE: The goals of this study were to determine whether the toxicity of cisplatin, a chemotherapeutic alkylating agent, could be reduced by the use of amifostine and to determine whether amifostine alone could cause ototoxicity. STUDY DESIGN: Prospective, animal study. METHODS: Auditory brainstem response click threshold, latencies, and blood work were used to measure ototoxicity, nephrotoxicity, and myelotoxicity before and 4 weeks after treatment. Groups of guinea pigs received either cisplatin alone (30 mg/kg), amifostine (1000 mg/kg), cisplatin plus amifostine (1000 mg/kg), or no agent. RESULTS: Amifostine reduced the hearing loss caused by cisplatin for many animals. Amifostine partially protected against cisplatin-induced ototoxicity and renal toxicity. We did not find evidence for myelotoxicity owing to cisplatin in this sample. CONCLUSION: Amifostine may have a role in reducing toxicity or permitting larger doses of cisplatin to be given, but toxicity can still be significant even with protection.     

Intracochlear administration of thiourea protects against cisplatin-induced outer hair cell loss in the guinea pig

Amelioration of cisplatin-induced side-effects is of great clinical importance. Local administration of a cytoprotective agent to the inner ear offers a possibility to prevent cisplatin-induced ototoxicity without risk of interference with the antitumour effect. The ideal substance for local administration has yet to be identified. Thiourea (TU) has unique properties that make it an interesting candidate. This study was initiated to test the hypothesis that TU given by local administration protects against cisplatin ototoxicity in the guinea pig. After baseline auditory brainstem response (ABR) assessment, the left cochlea was implanted with a microtip catheter connected to an osmotic pump filled with either 27 mg/ml TU in artificial perilymph (AP), or AP administered for the full duration of the study. Three days post-implant, animals with normal ABRs received an intravenous injection of 8 mg/kg body-weight cisplatin. Five days after the cisplatin treatment ABRs were reassessed, animals decapitated and bilateral cytocochleograms prepared. TU-treated ears demonstrated significantly lower outer hair cell (OHC) loss as compared to contralateral untreated ears, and significantly lower OHC loss compared to AP-treated ears. ABR threshold shift did not differ significantly between the two groups. It can be postulated that TU demonstrates partial protection against cisplatin-induced ototoxicity.     

Effects of cisplatin and thiosulfate upon auditory brainstem responses of guinea pigs

Two side effects which limit the use of cisplatin in cancer chemotherapy are severe nephrotoxicity and ototoxicity. The concurrent administration of sodium thiosulfate with cisplatin reportedly protects from cisplatin nephrotoxicity, however, protection from ototoxicity has not been documented. The purpose of this study was to examine the efficacy of using thiosulfate to ameliorate the ototoxic effects of cisplatin. Toward this end, the effects of cisplatin alone, cisplatin administered concurrently with sodium thiosulfate (CIS/THIO), and sodium thiosulfate alone on the auditory brainstem response (ABR) of guinea pigs were compared. ABR waveforms, comparing latencies, amplitudes and response thresholds, were monitored before, immediately after, and 30 days post treatment. Sodium thiosulfate administered with cisplatin (CIS/THIO) consistently protected animals from hearing loss and surprisingly yielded significant increases in amplitude when compared to baseline and saline controls. However, ABRs of CIS/THIO animals returned toward baseline values after 30 days.     

Mechanisms of cisplatin ototoxicity and progress in otoprotection

PURPOSE OF REVIEW: This review presents exciting new data published in the past year that help to elucidate the mechanisms of cisplatin ototoxicity. Recent research findings on otoprotection could lead to the development of novel protective agents. Cisplatin ototoxicity is a frequent and serious problem in patients. Strategies to ameliorate ototoxicity without interfering with the desired therapeutic effects are urgently needed. RECENT FINDINGS: Cisplatin ototoxicity appears to involve the production of reactive oxygen species in target tissues in the inner ear by activating an enzyme unique to the cochlea. This leads to a cascade resulting in oxidation of lipids and cell death. The upregulation of endogenous protective mechanisms in the cochlea or treatment with exogenous compounds reduces ototoxicity in cisplatin-treated animals. The only clinical trials reported to date with the putative protective agent, amifostine, have been disappointing. SUMMARY: The data summarized in this paper could lead to important clinical trials to determine whether the findings in experimental animals can translate into effective treatments to prevent cisplatin ototoxicity.     

Protection against cisplatin-induced ototoxicity by adeno-associated virus-mediated delivery of the X-linked inhibitor of apoptosis protein is not dependent on caspase inhibition.

HYPOTHESIS: Gene therapy with an adeno-associated viral (AAV) vector encoding the X-linked inhibitor of apoptosis protein (XIAP) in an animal model of cisplatin-induced ototoxicity can elucidate apoptotic pathways in the inner ear. BACKGROUND: Cisplatin is limited clinically by ototoxicity associated with apoptosis in the inner ear. The relevant intracellular apoptotic pathways, however, are unknown. XIAP is an antiapoptotic protein that both inhibits caspases and reciprocally regulates the proapoptotic Smac/Omi proteins. AAV-mediated delivery of various XIAP mutants could distinguish between these antiapoptotic pathways in the ear and further the development of specific reagents for gene therapy- mediated prevention of cisplatin-induced ototoxicity. METHODS: We administered unilaterally through the round-window AAV-harboring genes encoding wild-type dXIAP, yellow fluorescent protein, or either of two dXIAP point mutants-one deficient in caspase inhibition (dXIAP-d) and the other additionally deficient in the binding of Smac/Omi (dXIAP-t). All rats received a 3-day systemic course of cisplatin. Functional hearing loss was measured by shifts in auditory brainstem response (ABR) thresholds after cisplatin treatment, and hair-cell loss was assessed by whole-mount phalloidin staining of cochlear turns. RESULTS: Uninjected ears universally displayed high-frequency-specific hair-cell loss and ABR threshold shifts upon cisplatin treatment. Although yellow fluorescent protein had no effect, ears injected with dXIAP exhibited 68% less ABR threshold shift at 32 kHz and 50% less basal-turn outer-hair-cell loss compared with contralateral untreated ears. This protection was maintained in ears injected with dXIAP-d but was abolished in those expressing dXIAP-t, which is incapable of blocking Smac/Omi. CONCLUSIO: Hair-cell apoptosis induced by cisplatin involves the Smac/Omi pathway. Thus, gene therapy with either wild-type dXIAP or Smac/Omi-selective dXIAP-d may be effective to protect against cisplatin-mediated ototoxicity.     

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.     

AAV-mediated delivery of the caspase inhibitor XIAP protects against cisplatin ototoxicity.

HYPOTHESIS: Delivery of the gene encoding X-linked inhibitor of apoptosis (XIAP) using an adeno-associated viral (AAV) vector can protect against cisplatin-mediated ototoxicity. BACKGROUND: Cisplatin is a widely used chemotherapeutic agent with significant ototoxic side effects. One possible mechanism of toxicity is apoptotic death of many cochlear cell types. Acute treatment with inhibitors of caspases- enzymes critical for apoptosis- has been shown to prevent hearing loss in vivo, but is too short-acting for therapeutic use. Gene therapy provides a specific and chronic means of delivering potential therapeutic gents. Introducing an anti-apoptotic gene into the cochlea could provide long-term prophylaxis against the ototoxic effects of cisplatin. METHOD: Two groups of rats were treated with unilateral injection into the round window of AAV harboring a gene encoding either XIAP or green fluorescent protein (GFP). After at least two months of gene expression, auditory-brainstem-response (ABR) threshold shifts and outer-hair-cell (OHC) number were measured in these two groups of animals after 72-hour treatment with cisplatin. RESULTS: Consistent with previous reports, uninjected and AAV.GFP-injected ears displayed profound ABR threshold elevations and OHC loss after cisplatin treatment. Ears that had been injected with AAV encoding XIAP, however, were significantly protected from these effects: cisplatin-induced ABR-threshold shift and hair-cell loss were attenuated by as much as 78% and 45%, respectively, when compared with contralateral (untreated) ears. CONCLUSION: XIAP delivery to the cochlea can protect against the audiometric changes and hair-cell loss associated with cisplatin ototoxicity. The efficacy, specificity, and duration of the protective effects make this a potentially attractive therapeutic paradigm.     

Ginkgo biloba extract (EGb 761) protects against cisplatin-induced ototoxicity in rats.

HYPOTHESIS: A standardized Ginkgo biloba extract, EGb 761, may have protective effect against cisplatin-induced ototoxicity in rats. BACKGROUND: Cisplatin-induced ototoxicity is a major dose-limiting side effect in anticancer chemotherapy. Cisplatin-induced ototoxicity has been correlated to depletion of the cochlear antioxidant system and increased lipid peroxidation. EGb 761 contains potent antioxidants capable of scavenging free radicals, inhibiting nitric oxide synthesis, reducing lipid peroxidation, and protecting against apoptosis. The purpose of this study was to investigate the effect of EGb 761 on cisplatin-induced ototoxicity in rats. METHODS: Male Wistar rats were divided into four groups and were treated as follows: 1) vehicle control; 2) cisplatin (13 mg/kg, intraperitoneally) plus vehicle; 3) EGb 761 (200 mg/kg, intraperitoneally); and 4) EGb 761 plus cisplatin. Auditory brainstem responses (ABRs) were measured pretreatment and 72 hours posttreatment, and threshold shifts were analyzed. Endocochlear potentials (EPs) were also obtained at 72 hours posttreatment. Cochleae were harvested and processed for scanning electron microscopy after completion of auditory testing. RESULTS: Cisplatin-treated rats showed significant ABR threshold shifts across all frequencies (click, and 2-, 4-, 8-, 16-, and 32-kHz tones) compared with each of the other groups (p < 0.001). Rats treated with EGb 761 plus cisplatin did not show significant ABR threshold shifts (p > 0.05). Similarly, the EPs of cisplatin-treated rats were decreased significantly approximately 50% in comparison with the other groups (p < 0.001). The EPs of EGb 761 plus cisplatin-treated rats were decreased less than 20% compared with vehicle control group or the EGb 761 only group (p < 0.01). The scanning electron microscopy observation indicated severe outer hair cell loss in the basal turn of cochleae of cisplatin-treated rats, whereas outer hair cells remained intact in the rats treated with EGb 761 plus cisplatin. CONCLUSION: These results demonstrate that EGb 761 protects against cisplatin-induced ototoxicity.