Ototoxicity, nephrotoxicity and pharmacokinetics of cisplatin and its monohydrated complex in the guinea pig

Oxidative Stress and Inflammation Caused by Cisplatin Ototoxicity

Hearing loss is a significant health problem that can result from a variety of exogenous insults that generate oxidative stress and inflammation. This can produce cellular damage and impairment of hearing. Radiation damage, ageing, damage produced by cochlear implantation, acoustic trauma and ototoxic drug exposure can all generate reactive oxygen species in the inner ear with loss of sensory cells and hearing loss. Cisplatin ototoxicity is one of the major causes of hearing loss in children and adults. This review will address cisplatin ototoxicity. It includes discussion of the mechanisms associated with cisplatin-induced hearing loss including uptake pathways for cisplatin entry, oxidative stress due to overpowering antioxidant defense mechanisms, and the recently described toxic pathways that are activated by cisplatin, including necroptosis and ferroptosis. The cochlea contains G-protein coupled receptors that can be activated to provide protection. These include adenosine A1 receptors, cannabinoid 2 receptors (CB2) and the Sphingosine 1-Phosphate Receptor 2 (S1PR2). A variety of heat shock proteins (HSPs) can be up-regulated in the cochlea. The use of exosomes offers a novel method of delivery of HSPs to provide protection. A reversible MET channel blocker that can be administered orally may block cisplatin uptake into the cochlear cells. Several protective agents in preclinical studies have been shown to not interfere with cisplatin efficacy. Statins have shown efficacy in reducing cisplatin ototoxicity without compromising patient response to treatment. Additional clinical trials could provide exciting findings in the prevention of cisplatin ototoxicity.

Disulfiram and Its Copper Chelate Attenuate Cisplatin-Induced Acute Nephrotoxicity in Rats Via Reduction of Oxidative Stress and Inflammation

The use of cisplatin (CP) in chemotherapy of resistant cancers is limited due to its dose-dependent nephrotoxicity. Disulfiram (DSF), the aversion therapy for alcoholism, has recently emerged as an anticancer and chemopreventive agent. Its anticancer activity is potentiated in the presence of copper. However, such use of copper leads to several adverse effects. In the present study, the protective effect of DSF and its copper chelate (Cu-DEDC) against CP-induced nephrotoxicity in rats was evaluated. Nephrotoxicity was induced by a single intraperitoneal injection of CP (5 mg/kg). The treatment groups included control (vehicle treated), CP (CP-treated), CP + DSF (CP followed by DSF), CP + DSF + Cu (CP followed by DSF and CuCl₂), CP + Cu-DEDC (CP followed by Cu-DEDC), and CP + AMF (amifostine pre-treated and CP-treated). The DSF, Cu-DEDC, and CuCl₂ were administered orally at 50 mM/kg/day dose for 5 days post CP injection. AMF served as a standard chemo protectant, administered intravenously 30 min prior to CP. The markers of oxidative stress, inflammation, and kidney function estimated on the 6th day revealed that both DSF and Cu-DEDC significantly attenuated the CP-induced rise in the serum/urine creatinine and blood urea nitrogen (BUN). The CP-induced rise in serum alkaline phosphatase (ALPase) was reversed by these drugs. Both drugs reduced the levels of malondialdehyde and nitric oxide (NO) in kidney tissues. These drugs reversed CP-induced depletion of SOD, catalase, and GSH in the kidneys. There was a significant reduction in the CP-induced TNF-α and IL-1β production along with prevention of histological alterations. Above observations indicate that DSF and Cu-DEDC may have significance as adjuvants to protect against CP-induced nephrotoxicity.

Use of the guinea pig in studies on the development and prevention of acquired sensorineural hearing loss, with an emphasis on noise

Guinea pigs have been used in diverse studies to better understand acquired hearing loss induced by noise and ototoxic drugs. The guinea pig has its best hearing at slightly higher frequencies relative to humans, but its hearing is more similar to humans than the rat or mouse. Like other rodents, it is more vulnerable to noise injury than the human or nonhuman primate models. There is a wealth of information on auditory function and vulnerability of the inner ear to diverse insults in the guinea pig. With respect to the assessment of potential otoprotective agents, guinea pigs are also docile animals that are relatively easy to dose via systemic injections or gavage. Of interest, the cochlea and the round window are easily accessible, notably for direct cochlear therapy, as in the chinchilla, making the guinea pig a most relevant and suitable model for hearing. This article reviews the use of the guinea pig in basic auditory research, provides detailed discussion of its use in studies on noise injury and other injuries leading to acquired sensorineural hearing loss, and lists some therapeutics assessed in these laboratory animal models to prevent acquired sensorineural hearing loss.

Poly (ADP-Ribose) Polymerase-1 (PARP1) Deficiency and Pharmacological Inhibition by Pirenzepine Protects From Cisplatin-Induced Ototoxicity Without Affecting Antitumor Efficacy

Cisplatin remains an indispensable drug for the systemic treatment of many solid tumors. However, a major dose-limiting side-effect is ototoxicity. In some scenarios, such as treatment of germ cell tumors or adjuvant therapy of non-small cell lung cancer, cisplatin cannot be replaced without undue loss of efficacy. Inhibition of polyadenosine diphosphate-ribose polymerase-1 (PARP1), is presently being evaluated as a novel anti-neoplastic principle. Of note, cisplatin-induced PARP1 activation has been related to inner ear cell death. Thus, PARP1 inhibition may exert a protective effect on the inner ear without compromising the antitumor activity of cisplatin. Here, we evaluated PARP1 deficiency and PARP1 pharmacological inhibition as a means to protect the auditory hair cells from cisplatin-mediated ototoxicity. We demonstrate that cisplatin-induced loss of sensory hair cells in the organ of Corti is attenuated in PARP1-deficient cochleae. The PARP inhibitor pirenzepine and its metabolite LS-75 mimicked the protective effect observed in PARP1-deficient cochleae. Moreover, the cytotoxic potential of cisplatin was unchanged by PARP inhibition in two different cancer cell lines. Taken together, the results from our study suggest that the negative side-effects of cisplatin anti-cancer treatment could be alleviated by a PARP inhibition adjunctive therapy.

N-acetylcysteine transforms necrosis into apoptosis and affords tailored protection from cisplatin cytotoxicity

Nephrotoxicity is the main limitation to the dosage and anticancer efficacy of cisplatin. Cisplatin produces tubular epithelial cell apoptosis and necrosis depending on the concentration of the drug. Protection from cisplatin nephrotoxicity must therefore tackle both cell death modes. For its ability to reduce cisplatin reactivity, in addition to its antioxidant effect, we tested and found that N-acetylcysteine (NAC) was most effective at inhibiting cisplatin cytotoxicity. NAC has no significant effect on cell death induced by either cycloheximide or Fas activation, indicating a rather selective action. Pt-DNA-binding experiments suggest that the differential effectiveness of NAC is due to its capacity to quench cisplatin reactivity inside the cell. NAC abolishes cisplatin-induced apoptosis, and transforms the necrosis induced by high concentrations of cisplatin into apoptosis. In fact, NAC allows the anti-apoptotic molecule Bcl-2 to reduce the cell death caused by pro-necrotic concentrations of cisplatin, to a significantly greater extent than in the absence of NAC. In rats, a dosage of NAC that significantly ameliorates cisplatin nephrotoxicity, has little effect on gentamicin nephrotoxicity. These characteristics provide NAC with a rationale as a potential nephroprotectant specifically tailored to and especially effective for therapeutic courses with platinated antineoplastics, which prompts to deepening into further preclinical knowledge, and to initiate clinical studies with NAC and mixed therapies composed of NAC and antiapoptotic drugs.

Electrospray ionization mass spectrometry for the hydrolysis complexes of cisplatin: implications for the hydrolysis process of platinum complexes

Non-enzyme-dependent hydrolysis of the drug cisplatin is important for its mode of action and toxicity. However, up until today, the hydrolysis process of cisplatin is still not completely understood. In the present study, the hydrolysis of cisplatin in an aqueous solution was systematically investigated by using electrospray ionization mass spectrometry coupled to liquid chromatography. A variety of previously unreported hydrolysis complexes corresponding to monomeric, dimeric and trimeric species were detected and identified. The characteristics of the Pt-containing complexes were investigated by using collision-induced dissociation (CID). The hydrolysis complexes demonstrate distinctive and correlative CID characteristics, which provides tools for an informative identification. The most frequently observed dissociation mechanism was sequential loss of NH₃ , H₂ O and HCl. Loss of the Pt atom was observed as the final step during the CID process. The formation mechanisms of the observed complexes were explored and experimentally examined. The strongly bound dimeric species, which existed in solution, are assumed to be formed from the clustering of the parent compound and its monohydrated or dihydrated complexes. The role of the electrospray process in the formation of some of the observed ions was also evaluated, and the electrospray ionization-related cold clusters were identified. The previously reported hydrolysis equilibria were tested and subsequently refined via a hydrolysis study resulting in a renewed mechanistic equilibrium system of cisplatin as proposed from our results. Copyright © 2017 John Wiley & Sons, Ltd.

Mitochondria-Targeted Antioxidant Mitoquinone Reduces Cisplatin-Induced Ototoxicity in Guinea Pigs

Objective To determine if mitoquinone (MitoQ) attenuates cisplatin-induced hearing loss in guinea pigs. Study Design Prospective and controlled animal study. Setting Academic, tertiary medical center. Subjects and Methods Guinea pigs were injected subcutaneously with either 5 mg/kg MitoQ (n = 9) or normal saline (control, n = 9) for 7 days and 1 hour before receiving a single dose of 10 mg/kg cisplatin. Auditory brainstem response thresholds were measured before MitoQ or saline administration and 3 to 4 days after cisplatin administration. Results Auditory brainstem response threshold shifts after cisplatin treatment were smaller by 28 to 47 dB in guinea pigs injected with MitoQ compared with those in the control group at all tested frequencies (4, 8, 16, and 24 kHz, P = .0002 to .04). Scanning electron microscopy of cochlear hair cells showed less outer hair cell loss and damage in the MitoQ group. Conclusion MitoQ reduced cisplatin-induced hearing loss in guinea pigs. MitoQ appears worthy of further investigation as a means of preventing cisplatin ototoxicity in humans.

The Fruit Hull of Gleditsia sinensis Enhances the Anti-Tumor Effect of cis-Diammine Dichloridoplatinum II (Cisplatin)

Lung cancer has substantial mortality worldwide, and chemotherapy is a routine regimen for the treatment of patients with lung cancer, despite undesirable effects such as drug resistance and chemotoxicity. Here, given a possible antitumor effect of the fruit hull of Gleditsia sinensis (FGS), we tested whether FGS enhances the effectiveness of cis-diammine dichloridoplatinum (II) (CDDP), a chemotherapeutic drug. We found that CDDP, when administered with FGS, significantly decreased the viability and increased the apoptosis and cell cycle arrest of Lewis lung carcinoma (LLC) cells, which were associated with the increase of p21 and decreases of cyclin D1 and CDK4. Concordantly, when combined with FGS, CDDP significantly reduced the volume and weight of tumors derived from LLC subcutaneously injected into C57BL/6 mice, with concomitant increases of phosphor-p53 and p21 in tumor tissue. Together, these results show that FGS could enhance the antitumor activity of CDDP, suggesting that FGS can be used as a complementary measure to enhance the efficacy of a chemotherapeutic agent such as CDDP.

Systemic Delivery and Biodistribution of Cisplatin in Vivo

Cisplatin is widely used to treat a variety of cancers. However, ototoxicity and nephrotoxicity remain serious side effects of cisplatin-based chemotherapy. In order to inform the study of cisplatin's off-target effects, a new drug-fluorophore conjugate was synthesized that exhibited utility as a tracer to determine the cellular uptake and in vivo distribution of cisplatin. This probe will serve as a useful tool to facilitate investigations into the kinetics and biodistribution of cisplatin and its associated side effects in preclinical models after systemic administration.

Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC/ESI-MS/MS) Study for the Identification and Characterization of In Vivo Metabolites of Cisplatin in Rat Kidney Cancer Tissues: Online Hydrogen/Deuterium (H/D) Exchange Study

In vivo rat kidney tissue metabolites of an anticancer drug, cisplatin (cis-diamminedichloroplatinum [II]) (CP) which is used for the treatment of testicular, ovarian, bladder, cervical, esophageal, small cell lung, head and neck cancers, have been identified and characterized by using liquid chromatography positive ion electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with on line hydrogen/deuterium exchange (HDX) experiments. To identify in vivo metabolites, kidney tissues were collected after intravenous administration of CP to adult male Sprague-Dawley rats (n = 3 per group). The tissue samples were homogenized and extracted using newly optimized metabolite extraction procedure which involves liquid extraction with phosphate buffer containing ethyl acetate and protein precipitation with mixed solvents of methanol-water-chloroform followed by solid-phase clean-up procedure on Oasis HLB 3cc cartridges and then subjected to LC/ESI-HRMS analysis. A total of thirty one unknown in vivo metabolites have been identified and the structures of metabolites were elucidated using LC-MS/MS experiments combined with accurate mass measurements. Online HDX experiments have been used to further support the structural characterization of metabolites. The results showed that CP undergoes a series of ligand exchange biotransformation reactions with water and other nucleophiles like thio groups of methionine, cysteine, acetylcysteine, glutathione and thioether. This is the first research approach focused on the structure elucidation of biotransformation products of CP in rats, and the identification of metabolites provides essential information for further pharmacological and clinical studies of CP, and may also be useful to develop various effective new anticancer agents.

Cisplatin-Induced Ototoxicity: Effects, Mechanisms and Protection Strategies

Cisplatin is a highly effective chemotherapeutic agent that is widely used to treat solid organ malignancies. However, serious side effects have been associated with its use, such as bilateral, progressive, irreversible, dose-dependent neurosensory hearing loss. Current evidence indicates that cisplatin triggers the production of reactive oxygen species in target tissues in the inner ear. A variety of agents that protect against cisplatin-induced ototoxicity have been successfully tested in cell culture and animal models. However, many of them interfere with the therapeutic effect of cisplatin, and therefore are not suitable for systemic administration in clinical practice. Consequently, local administration strategies, namely intratympanic administration, have been developed to achieve otoprotection, without reducing the antitumoral effect of cisplatin. While a considerable amount of pre-clinical information is available, clinical data on treatments to prevent cisplatin ototoxicity are only just beginning to appear. This review summarizes clinical and experimental studies of cisplatin ototoxicity, and focuses on understanding its toxicity mechanisms, clinical repercussions and prevention strategies.

Fortification of blood plasma from cancer patients with human serum albumin decreases the concentration of cisplatin-derived toxic hydrolysis products in vitro

While cisplatin (CP) is still one of the world's bestselling anticancer drugs, its intravenous administration is inherently associated with severe, dose limiting toxic side-effects. Although the molecular basis of the latter are not well understood, biochemical transformations of CP in blood and the interaction of the generated platinum species with plasma proteins likely play a critical role since these processes will ultimately determine which platinum-species reach the intended tumor cells as well as non-target cells. Compared to healthy subjects, cancer patients often have decreased plasma human serum albumin (HSA) concentrations. Little, however, is known about how the plasma HSA concentration will affect the metabolism of CP. To gain insight, we obtained blood plasma from healthy adults (n = 20, 42 ± 4 g HSA per L) and pediatric cancer patients (n = 11, 26 ± 7 g HSA per L). After the incubation of plasma at 37 °C, a pharmacologically relevant dose of CP was added and the Pt-distribution therein was determined by size-exclusion chromatography coupled on-line to an inductively coupled plasma atomic emission spectrometer. At the 2 h time point, a 5.9% increase of toxic CP-derived hydrolysis products was detected in pediatric cancer patient plasma, while 9.8% less platinum was protein bound compared to plasma from healthy controls. These in vitro results suggest that the elevated concentration of highly reactive free CP-derived hydrolysis products in plasma may cause the toxic side-effects in cancer patients. More importantly, the deliberate increase of the plasma HSA concentration in cancer patients prior to CP treatment would represent a simple strategy to possibly alleviate the fraction of patients that suffer from drug induced toxic side-effects.

Distribution study of cisplatin in rat kidney and liver cancer tissues by using liquid chromatography electrospray ionization tandem mass spectrometry

A sensitive and rapid liquid chromatography positive ion electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method has been developed and validated for the quantitative determination and distribution of cisplatin (CP) in kidney and liver tissues after intravenous administration of drug to adult male Sprague Dawley rats. Oxaliplatin (OXP) was used as an internal standard. The tissue samples were homogenized and extracted using conventional liquid-liquid extraction method with phosphate buffer containing ethyl acetate and then subjected to LC-MS analysis. The chromatographic separation was achieved on an Agilent ZORBAX SB C-18 column (50 × 2.1 mm, 1.8 µm) using the mobile phase consisting of 0.1% formic acid in water (Solvent A) : methanol (Solvent B) (40 : 60; v/v) in an isocratic elution followed by detection with positive ion electrospray ionization tandem mass spectrometry using the transitions of m/z 301 > 265 for CP and m/z 398 > 310 for OXP in multiple reaction monitoring mode. The calibration curve was linear in the range of 5.0-7000 and 10.0-6000 ng/ml for kidney and liver tissue homogenates, respectively. The method revealed good performances in terms of within-batch, between-batch precision (1.31-5.70%) and accuracy (97.0-102.24%) for CP in both kidney and liver tissue homogenates including lower and upper limits of quantification. The recoveries from spiked control samples were >81.0% and >87.0 % for CP and OXP, respectively. Matrix effect was found to be negligible, and the stability data were within the acceptable limits. Further, the validated LC/ES-MS/MS method was successfully applied to investigate the distribution of CP in kidney and liver tissues after intravenous administration of CP to male Sprague Dawley rats. The results showed that the higher amount of CP was distributed in kidney followed by liver, which indicated that CP mainly accumulated in kidney tissues and renal excretion might be a primary and main elimination route. This is the first research approach focused on the quantitative determination and distribution of CP in rat kidney and liver tissue homogenates by using LC/ESI-MS/MS, which could provide essential information for further pharmacological and clinical studies of CP.

A liquid chromatography electrospray ionization tandem mass spectrometric study (LC/ESI-MS/MS) of in vivo metabolites of cisplatin in rat liver and brain tissues: deuterated experiments

In vivo rat liver and brain tissue metabolites of an anticancer drug, cisplatin, have been identified and characterized by using LC/ESI-MS/MS in combination with on-line H/D exchange experiments.

Prospective longitudinal assessment of sensorineural hearing loss with hyperfractionated radiation therapy alone in patients with average-risk medulloblastoma

Background

To report on sensorineural hearing loss (SNHL) in a cohort of patients treated with hyperfractionated radiation therapy (HFRT) without upfront platinum-based chemotherapy in average-risk medulloblastoma.

Methods

Hearing thresholds were assessed by ear-specific pure-tone audiograms at stimulus frequencies of 0.25, 0.5, 1, 2, 4, and 8 kilohertz. Audiometric assessments were done serially longitudinally at baseline, between 6-12 months after HFRT, and annually thereafter. Pure-tone audiograms were analyzed and graded according to Brock pediatric ototoxicity grading criteria.

Results

Five of 20 (25%) children had communicatively and developmentally significant SNHL (Brock grade 2 or worse) even before starting radiotherapy. On follow-up, new-onset Brock grade 2 or worse ototoxicity was documented in 6 previously normal ears. Eleven patients had preserved hearing in both ears on last audiometric follow-up. Compared with baseline testing, post-HFRT audiometry at 2-3 years showed modest decline in hearing threshold across all frequencies. Age at diagnosis and sex did not significantly impact hearing, while higher cochlear doses trended towards worse hearing outcomes. Tumors that extended more towards one side expectedly showed significant worsening in the ipsilateral ear. There was a differential impact of treatment on the right and left ears with the right ear (and not the left ear) showing significantly worse hearing thresholds in the low-to-intermediate speech frequency range over time.

Conclusion

The use of HFRT for craniospinal irradiation and conformal tumor bed boost without upfront platinum-based chemotherapy in children with average-risk medulloblastoma results in preserved hearing in a large proportion of patients in the audible speech range.

Cisplatin and oxaliplatin are toxic to cochlear outer hair cells and both target thioredoxin reductase in organ of Corti cultures

Conclusion

Inhibition of thioredoxin reductase (TrxR) may be a contributing factor in cisplatin-induced ototoxicity. Direct exposure of organ of Corti to cisplatin and oxaliplatin gives equal loss of hair cells.

Objectives

Platinum-containing drugs are known to target the anti-oxidant selenoprotein TrxR in cancer cells. Two such anti-cancer, platinum-containing drugs, cisplatin and oxaliplatin, have different side effects. Only cisplatin induces hearing loss, i.e. has an ototoxic side effect that is not seen after treatment with oxaliplatin. The objective of this study was to evaluate if TrxR is a target in the cochlea. Loss of outer hair cells was also compared when cisplatin and oxaliplatin were administered directly to the organ of Corti.

Methods

Organ of Corti cell culture was used for direct exposure to cisplatin and oxaliplatin. Hair cells were evaluated and the level of TrxR was assessed. Immunohistochemical staining for TrxR was performed. An animal model was used to evaluate the effect on TrxR after treatment with cisplatin and oxaliplatin in vivo.

Results

Direct exposure of cochlear organotypic cultures to either cisplatin or oxaliplatin induced comparable levels of outer hair cell loss and inhibition of TrxR, demonstrating that both drugs are similarly ototoxic provided that the cochlea becomes directly exposed.

Assessing cisplatin-induced ototoxicity and otoprotection in whole organ culture of the mouse inner ear in simulated microgravity

Cisplatin is a widely used anti-cancer drug. Ototoxicity is a major dose-limiting side-effect. A reproducible mammalian in-vitro model of cisplatin ototoxicity is required to screen and validate otoprotective drug candidates. We utilized a whole organ culture system of the postnatal mouse inner ear in a rotating wall vessel bioreactor under "simulated microgravity" culture conditions. As previously described this system allows whole organ culture of the inner ear and quantitative assessment of ototoxic effects of aminoglycoside induced hair cell loss. Here we demonstrate that this model is also applicable to the assessment of cisplatin induced ototoxicity. In this model cisplatin induced hair cell loss was dose and time dependent. Increasing exposure time of cisplatin led to decreasing EC50 concentrations. Outer hair cells were more susceptible than inner hair cells, and hair cells in the cochlear base were more susceptible than hair cells in the cochlear apex. Initial cisplatin dose determined the final extent of hair cell loss irrespective if the drug was withdrawn or continued. Dose dependant otoprotection was demonstrated by co-administration of the antioxidant agent N-acetyl l-cysteine. The results support the use of this inner ear organ culture system as an in vitro assay and validation platform for inner ear toxicology and the search for otoprotective compounds.

Cochlear pharmacokinetics of cisplatin: an in vivo study in the guinea pig

OBJECTIVES/HYPOTHESIS

Cisplatin produces toxic lesions to outer hair cells (OHCs) in the cochlear base but not in the apex. The objective of this study was to compare the pharmacokinetic profile of cisplatin in scala tympani (ST) perilymph in the cochlear base and apex, respectively.

STUDY DESIGN

In vivo animal study.

METHODS

Forty-seven guinea pigs were given an intravenous bolus injection of an ototoxic dose of cisplatin. Ten to 240 minutes after cisplatin was given, blood, cerebrospinal fluid (CSF), and ST perilymph were aspirated within the same target time. ST perilymph was aspirated from the basal turn and from the apex of the cochlea by two different sampling techniques. Liquid chromatography with postcolumn derivatization was used for quantitative determination of the parent drug.

RESULTS

Ten minutes after administration, the concentration of cisplatin in ST perilymph was 4-fold higher in the basal turn of the cochlea than in the apex. At 30 minutes, the drug concentrations did not differ. At 60 minutes, the level of cisplatin in ST perilymph and blood UF was equivalent. The perilymph-blood ratio increased thereafter with time.

CONCLUSION

The pharmacokinetic findings of an early high concentration of cisplatin in the base of the cochlea and delayed elimination of cisplatin from ST perilymph compared to blood might correlate to the cisplatin-induced loss of OHCs in the base of the cochlea.

Cisplatin-induced ototoxicity in pediatric solid tumors: the role of glutathione S-transferases and megalin genetic polymorphisms

Cisplatin-induced ototoxicity, an important dose-limiting side effect, has proven high interindividual variability. Glutathione S-transferases (GSTs) are isoenzymes involved in cellular detoxification processes. Megalin has been demonstrated to bind aminoglycosides, known to be similar to cisplatin for their ototoxicity. The GSTs and megalin expression is genetically polymorphic, which might be responsible for the variability in cisplatin-induced ototoxicity. The genotyping of GSTM1, GSTT1 polymorphisms, and 2 nonsynonymous single nucleotide polymorphisms (SNPs) at megalin genes, rs2075252 and rs2228171, were performed in 68 children diagnosed with solid tumors who received cisplatin-based chemotherapy. After the end of treatment, audiometry demonstrated hearing loss in 79.4% of patients according to Brock classification. The cumulative cisplatin dose >400 mg/m is associated with increased risk of cisplatin-induced ototoxicity [odds ratio (OR), 17.5; 95% confidence interval (CI), 3.09-98.62]. GSTT1 wild genotype and C-allele of rs2228171 SNPs of megalin gene occurred with higher frequency in patients with ototoxicity (P=0.023; OR, 10; 95% CI, 1.80-56.00 and P=0.034; OR, 2.67; 95% CI, 1.22-5.82, respectively). In conclusion, our results suggested that GSTT1 wild genotype and C-allele of rs2228171 SNPs might be risk factors for ototoxicity. The cumulative cisplatin dose <400 mg/m should be beneficial in order to ameliorate ototoxicity.

Comparison of cochlear cell death caused by cisplatin, alone and in combination with furosemide

Establishment of appropriate animal models is an important step in exploring the mechanisms of drug-induced ototoxicity. In the present study, using guinea pigs we compared cochlear lesions induced by cisplatin administered in two regimens: consecutive application alone and in combination with furosemide. The effects of furosemide alone were also evaluated; it was found to cause temporary hearing loss and reversible damage to the stria vascularis. Consecutive application of cisplatin alone appeared to be disadvantageous because it resulted in progressive body weight loss and higher mortality compared to the combined regimen, which used a smaller cisplatin dose. The combined regimen resulted in comparable hearing loss and hair cell loss but a markedly lower mortality. However, their coadministration failed to cause similar damage to spiral ganglion neurons (SGN), as seen in animals that received cisplatin alone. This difference suggests that the combined regimen did not mimic the damage to cochlear neuronal innervation caused by the clinical application of cisplatin. The difference also suggests that the SGN lesion is not caused by cisplatin entering the cochlea via the stria vascularis.

The protective effect of recombinant human erythropoietin against cisplatin-induced renal and hepatic dysfunctions in Wistar rats

Cisplatin (Cisp) is one of the most effective chemotherapeutic drugs. However, the dose of Cisp is greatly limited by its toxicity. Recombinant human erythropoietin (rhEPO), a hormone that regulates hematopoiesis, has also been shown to exert tissue-protective effects. The purpose of this study was to explore the protective effect of rhEPO against Cisp-induced renal and liver dysfunctions. Adult male Wistar rats were divided into six groups of six each: control, rhEPO-alone group, Cisp-alone group and rhEPO + Cisp group (pretreatment, cotreatment and posttreatment conditions). Our results showed that Cisp-induced a marked renal and liver failure characterized by a significant decrease in body weight, organ weight and organ ratio and a significant increase in creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, G-glutamyl transferase, alkaline phosphatase, bilirubin conjugated and bilirubin total levels in serum. Histological examination showed that Cisp caused kidney alterations. rhEPO treatments restored body weight, organ weight and organ ratio as well as serum biochemical parameters changed due to Cisp exposure.

Carrier-based intralymphatic cisplatin chemotherapy for the treatment of metastatic squamous cell carcinoma of the head & neck

BACKGROUND

Since head and neck squamous cell carcinoma (HNSCC) preferentially metastasizes to the locoregional lymphatics, treatment of the tumor-draining cervical lymph nodes is paramount.

RESULTS

We developed a hyaluronan-cisplatin (HA-Pt) nanoconjugate with prolonged lymphatic retention and greatly improved tumor tissue deposition for the treatment of metastatic HNSCC. We also developed an orthotopic metastatic xenograft model of HNSCC to examine the efficacy of the nanoconjugate. HNSCC (1/week x 3 weeks) were completely cured for 57% of the female mice in the HA-Pt treatment group, which demonstrated greatly hindered HNSCC progression compared with the standard cisplatin therapy (p < 0.05).

CONCLUSION

With this insight, we will be able to optimize the carriers for better uptake, penetration and retention within cancer cells.

Cisplatin-induced renal salt wasting syndrome

Cisplatin was the first platinum compound to be introduced as a chemotherapeutic agent with antineoplastic activity against a wide variety of solid tumors. Renal impairment with a decline in glomerular filtration has been the classical nephrotoxicity of cisplatin. Renal salt wasting syndrome is yet another, though it is not common. Previous studies were identified by searching the Pubmed database using the following keywords: cisplatin, cisplatin nephrotoxicity, renal salt wasting, and salt loosing nephropathy. Renal salt wasting syndrome has been described in 17 case reports since 1984. It is a rare side effect of cisplatin that manifests with polyuria, hypovolemia, and hyponatremia, and, because of similarities in clinical settings and laboratory values, it is frequently misdiagnosed as a syndrome of inappropriate antidiuretic hormone. Other causes of polyuria and hyponatremia should be excluded. Treatment aims at restoring the lost water and salt. Substituting cisplatin with carboplatin depends on individual clinical settings. Prognosis is excellent, as recovery was the rule in all the reported cases.

The use of Maytenus ilicifolia to prevent cisplatin-induced ototoxicity

Maytenus ilicifolia is a native plant from South America, with several medicinal properties including antioxidant effects.

Aim

using an original cisplatin induced ototoxicity model, we evaluated a possible otoprotection caused by Maytenus ilicifolia extract.

Materials and methods

clinical and experimental study design with female albino guinea pigs divided in groups as follows: 9 animals receiving cisplatin only (three doses of 7.5mg/kg/day), 4 animals receiving the plant extract only, 10 animals receiving the cisplatin protocol and 1g/kg/day of extract for 8 days, 5 animals with cisplatin and 3g/kg/day of extract for 8 days, and 5 animals receiving extract for 3 weeks and cisplatin in the last week. The tests were distortion product otoacoustic emissions, brainstem auditory response, before and after medication and scanning electron microscopy.

Results

the animals receiving cisplatin plus plant extract, had alterations in all the tests, showing lesions on the basal cochlear region under electron microscopy.

Conclusions

Despite of the plant extract’s antioxidant effect, it was not sufficient to protect the cochlea against cisplatin ototoxicity.

Cisplatin-induced hearing loss does not correlate with intracellular platinum concentration

CONCLUSION

Inductively coupled plasma mass spectrometry (ICP-MS) can be applied to organic tissues obtained from experimental animals. Hearing loss does not correlate with the platinum (Pt) concentration found in the inner ear. Drug structure and affinity to inner ear proteins could explain ototoxicity caused by cisplatin.

OBJECTIVES

To analyse Pt affinity for brain and ear tissues (of similar embryologic origin) in the Wistar rat and clearance gradient after a single dose, and to correlate these findings with hearing changes.

MATERIALS AND METHODS

Thirty-two Wistar rats were intraperitoneally injected with cisplatin at a dose of 5 mg/kg. Animals were sacrificed after obtaining auditory brain responses (ABRs) at 3, 7, 30 and 90 days (nine, seven, seven and nine animals, respectively). Brain and both temporal bones were extracted from each animal and analysed by ICP-MS to determine the absolute concentrations of the metal. Eight non-treated animals were employed as a control group.

RESULTS

The ABR thresholds were significantly elevated in animals from all groups after cisplatin treatment. A maximum accumulation of Pt for inner ear and brain was revealed around the first week: 3.175 (57%) and 0.342 (72%), respectively. Pt significantly accumulated in greater quantities in ear than in brain (p<0.01) and was cleared at a higher rate in brain than in ear (p<0.01) following cochlea/brain ratio analysis. No statistically significant correlation was found between amounts of Pt and hearing loss in the study animals.

Augmented ototoxic effect of cisplatin in heterozygotes of the German waltzing guinea pig

It has previously been demonstrated that the carriers of the German waltzing guinea pig are less susceptible to noise trauma. To explore whether this represents a general resistance to inner ear trauma, carriers of the German waltzing guinea pig were exposed to the ototoxic agent cisplatin. Two doses of cisplatin were injected intravenously into anesthetized carriers and weight-matched control animals. Prior to and 96 h after the injections hearing thresholds were established by recording the auditory brainstem responses at 3.5, 7, 14, and 28 kHz. The cochleae were harvested to estimate hair cell loss and to analyze total platinum content. The carriers of the German waltzing guinea pig strain suffered from a more pronounced cisplatin-induced hearing loss compared to the control animals. The results suggest that mechanisms responsible for the protection against acoustic stress do not provide any protection against cisplatin in carriers of the German waltzing guinea pig.

Cisplatin Nephrotoxicity: A Review

BACKGROUND

Cisplatin is a major antineoplastic drug for the treatment of solid tumors, but it has dose-dependent renal toxicity.

METHODS

We reviewed clinical and experimental literature on cisplatin nephrotoxicity to identify new information on the mechanism of injury and potential approaches to prevention and/or treatment.

RESULTS

Unbound cisplatin is freely filtered at the glomerulus and taken up into renal tubular cells mainly by a transport-mediated process. The drug is at least partially metabolized into toxic species. Cisplatin has multiple intracellular effects, including regulating genes, causing direct cytotoxicity with reactive oxygen species, activating mitogen-activated protein kinases, inducing apoptosis, and stimulating inflammation and fibrogenesis. These events cause tubular damage and tubular dysfunction with sodium, potassium, and magnesium wasting. Most patients have a reversible decrease in glomerular filtration, but some have an irreversible decrease in glomerular filtration. Volume expansion and saline diuresis remain the most effective preventive strategies.

CONCLUSIONS

Understanding the mechanisms of injury has led to multiple approaches to prevention. Furthermore, the experimental approaches in these studies with cisplatin are potentially applicable to other drugs causing renal dysfunction.

Kinetics of Cisplatin and its monohydrated complex with sulfur-containing compounds designed for local otoprotective administration

The anticancer drug cisplatin can cause permanent inner ear damage. We have determined the second-order degradation rate constant, k(Nu), of cisplatin and its more toxic monohydrated complex (MHC) in the presence of each of the sulfur-containing nucleophiles N-acetyl-l-cysteine, l-cysteine methyl ester, 1,3-dimethyl-2-thiourea, d-methionine, and thiosulfate, compounds that are under evaluation for local administration to prevent cisplatin-induced ototoxicity. MHC was isolated from a hydrolysis solution of cisplatin using liquid chromatography (LC). The degradations were evaluated by measuring the disappearance of MHC and cisplatin at 37 degrees C and pH 7.4 in the presence of each of the nucleophiles using LC and photometric detection. The k(Nu) of MHC and of cisplatin was 0.044 M(-1)sec(-1) and 0.012 M(-1)sec(-1) with N-acetyl-l-cysteine, 0.24 M(-1)sec(-1) and 0.067 M(-1)sec(-1) with l-cysteine methyl ester, 0.16 M(-1)sec(-1) and 0.074 M(-1)sec(-1) with 1,3-dimethyl-2-thiourea, 0.070 M(-1)sec(-1) and 0.069 M(-1)sec(-1) with d-methionine, and 3.9 M(-1)sec(-1) and 0.091 M(-1)sec(-1) with thiosulfate, respectively. Our results suggest that thiosulfate, as being the strongest nucleophile, is a promising candidate for local application in order to reduce the inner ear content of MHC and cisplatin. However, otoprotection is a multifactorial event, and it remains to be established how important nucleophilicity is for the effectiveness of the protecting agent.

Future opportunities in preventing cisplatin induced ototoxicity

Cisplatin is one of the most commonly used cytotoxic agents. Ototoxicity is an important and dose-limiting side-effect of cisplatin therapy. It is believed that cisplatin suppresses the formation of endogenous anti-oxidants that normally prevent the inner ear against reactive oxygen species (ROS). These ROS affect the outer hair cells (OHCs) in the organ of Corti. Results from clinical trials with amifostine, an anti-oxidant with possible otoprotective action during cisplatin therapy, were disappointing. A variety of agents with chemoprotective action against cisplatin-induced ototoxicity were successfully tested in animal models. It is important to translate these promising results from animal models into clinical practice. The possible routes of administration are systemic and transtympanic. An important condition when using such an agent systemically is that the compound may not affect the anti-tumor effect of cisplatin. The critical step at transtympanic administration is the diffusion of the compound through the round window membrane (RWM). This diffusion depends on the characteristics of the medication as on the properties of the RWM. Positive results of an otoprotector in clinical practice may increase the effectiveness of cisplatin therapy and can improve the quality of life for a large group of patients.

High-Dose Cisplatin With Amifostine: Ototoxicity and Pharmacokinetics

OBJECTIVES/HYPOTHESIS

Ototoxicity is a common side effect of high-dose cisplatin treatment. Thiol-containing chemoprotectors ameliorate cisplatin ototoxicity under experimental conditions. The trial was initiated to test the efficacy of amifostine protection in high-dose cisplatin treatment (125-150 mg/m) for metastatic malignant melanoma, to correlate the ototoxic outcome with cisplatin pharmacokinetics, and to evaluate the importance of using a selective analytical method for the quantification of cisplatin.

STUDY DESIGN

Prospective study of 15 patients with stage IV malignant melanoma.

METHODS

Clinical follow-up of therapeutic response, pure-tone audiometry, and analysis of cisplatin and its monohydrated complex in blood ultrafiltrate by liquid chromatography with postcolumn derivatization were performed. Ultrafiltered blood platinum was analyzed by inductively coupled plasma mass spectrometry.

RESULTS

Ototoxicity and gastrointestinal toxicity were the most prominent side effects. Three patients ultimately required hearing aids. All patients had audiometric changes at one or more frequencies after the second treatment course, and all but one patient reported auditory symptoms. No correlation was found between hearing loss and blood cisplatin pharmacokinetics. Platinum levels determined by inductively coupled plasma mass spectrometry were higher than total platinum levels calculated from cisplatin and monohydrated complex concentrations obtained by liquid chromatography analysis.

CONCLUSION

Ototoxicity was unacceptable despite amifostine treatment. Cisplatin pharmacokinetics during the first treatment course were not predictive of hearing loss. Amifostine caused a lowering of dose-normalized area under the concentration-time curve for cisplatin and monohydrated complex. Use of the unselective inductively coupled plasma mass spectrometry analysis leads to an overestimation of active drug. Selective analysis of cisplatin is especially important when evaluating cisplatin pharmacokinetics during chemoprotector treatment.

Round window pH manipulation alters the ototoxicity of systemic cisplatin

The effect of manipulation of pH on the ototoxicity of systemic cisplatin was studied in Wistar rats. After control auditory brainstem responses (ABR) were performed, the auditory bullae were opened and acidic (pH 6.0), neutral (pH 7.4) or basic (pH 9.0) phosphate-buffered saline (PBS) was applied to fill the round window niche (RWN). After 30 min, 13 mg/kg cisplatin solution or saline was administered intraperitoneally. After 3 days, follow-up ABRs were performed and cochleae were processed for morphological analysis. Animals that received basic PBS on the RWN and cisplatin intraperitoneally had significantly smaller ABR threshold shifts compared to rats pretreated with neutral pH buffer (P<0.05). Animals that received acidic PBS on the RWN and systemic cisplatin showed significantly greater ABR threshold shifts compared to those pretreated with neutral pH buffer (P<0.05). No significant threshold changes were observed in animals that received buffer of any pH on the RWN, followed by saline intraperitoneally. Semiquantitative analysis of hair cell survival confirmed a protective effect by basic PBS against cisplatin and a synergistic effect by acidic PBS on cisplatin ototoxicity (P<0.05). It appears that changes in cochlear pH can modulate the ototoxic effects of systemically applied cisplatin.

Liquid chromatographic determination of oxaliplatin in blood using post-column derivatization in a microwave field followed by photometric detection

Oxaliplatin ([(1R,2R)-1,2-cyclohexanediamine-N,N']oxalato(2-)-O,O'-platinum) is the first platinum drug with significant activity for metastatic colon cancer. The analysis of oxaliplatin has previously almost exclusively been based on the determination of the platinum content in plasma or ultrafiltrate using flameless atomic absorption spectroscopy (FAAS) or inductively coupled plasma mass spectrometry (ICPMS). A new method for quantitative determination of the free fraction of the intact drug in blood ultrafiltrate is presented here. Blood was ultrafiltrated centripetally at 4 degrees C and the ultrafiltrate was analyzed by liquid chromatography. Oxaliplatin was separated on a Hypercarb column using a mobile phase of methanol/succinic acid buffer pH 7.0 (9/1, v/v). Post-column derivatization was performed by adding N,N-diethyldithiocarbamate in methanol and with microwave heating of a Teflon tubing. The derivative was quantified by photometric detection at 344 nm. The coefficient of variation of standard blood samples was 4.9 and 2.5% at 0.100 and 1.00 microg/ml, respectively. The limit of quantitation was 0.04 microg/ml.

Ototoxicity: bioprotective mechanisms

PURPOSE OF REVIEW

This review discusses current research dealing with novel approaches to the prevention of ototoxicity caused by cisplatin and aminoglycoside antibiotics.

RECENT FINDINGS

The ototoxic mechanisms of both classes of drugs appear to involve the production of reactive oxygen species. Strategies to prevent ototoxicity have involved the administration of free-radical scavengers, iron chelators, and inhibitors of cell death pathways. The potential for interference with the desired therapeutic effects of cisplatin and aminoglycoside antibiotics is examined in many of the investigations that are described.

SUMMARY

These findings provide the potential for exciting clinical trials to determine whether the animal experiments can be translated into rational therapeutic approaches to the problem of ototoxicity.