Otoproteção das células ciliadas auditivas contra a ototoxicidade da amicacina

Medicações ototóxicas utilizadas no tratamento oncológico pediátrico: uma revisão sistemática

RESUMO Objetivo Fazer um levantamento dos medicamentos ototóxicos utilizados no tratamento do câncer pediátrico, apontar os danos das drogas para o sistema auditivo e os métodos utilizados na identificação destes danos nessa população. Estratégia de pesquisa: Foram utilizados periódicos nacionais e internacionais pertinentes ao assunto, acessados eletronicamente em bases de dados da Biblioteca Virtual em Saúde - MS, PubMed, Biblioteca Digital Brasileira de Teses e Dissertações, que envolvessem a população pediátrica com histórico de tratamento oncológico, publicados entre 2007 e 2016, e no Banco de Teses e Dissertações da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. Critérios de seleção Foram selecionados estudos que contemplassem os seguintes critérios: estudos observacionais nas línguas portuguesa, inglesa ou espanhola e resumos disponíveis que informassem o método de avaliação do dano auditivo. Resultados A amostra final resultou em 12 artigos. Destes, a audiometria tonal limiar foi o método de avaliação auditiva mais utilizado, estando presente em 10 (84,61%) dos estudos, seguido das emissões otoacústicas (46,15%). Todos os estudos foram desenvolvidos com pacientes que fizeram uso de cisplatina ou derivados da platina e, quanto ao dano auditivo, apenas 1 dos estudos incluídos não relatou presença de alteração na população estudada. Conclusão Os derivados da platina expressam papel importante no tratamento do câncer em diversos níveis e são os agentes ototóxicos mais citados em pesquisas. A cóclea é o local mais afetado, mais especificamente as células ciliadas externas. Os métodos de investigação da alteração auditiva mais utilizados são a audiometria tonal limiar e as emissões otoacústicas.

Cochlear epithelial of dog fetuses: a new source of multipotent stem cells

Hearing loss caused by the damage of cochlea sensory cells or neurons is a common human disease, but also affects dogs and other animals. To test their progenitor nature as potential value for future therapies, we characterized cells derived from the cochlear epithelium in dog fetuses. In total, 8 fetuses of 35-40 days of gestation, derived from castration campaigns, were investigated. Cells were analysed by the MTT colorimetric assay and in regard to cell cycle, differentiation capacities, immunophenotypes and qPCR analysis. In culture, cells had a fibroblast-like morphology. Phenotypic immunocharacterization showed positive staining for mesenchymal stem cell and pluripotency markers and were negative for hematopoietic cell markers. Cells possessed differentiation capacity for the three main cell lineages: osteogenic, adipogenic and chondrogenic, altogether indicating their nature as mesenchymal stem cells. Thus, cells derived from fetal cochlear tissues indeed may provide valuable sources of progenitor cells for cell therapy of canine deafness and other diseases.

[Lack of protection against gentamicin ototoxicity by auditory conditioning with noise]

Introduction

Auditory conditioning consists of the pre-exposure to low levels of a potential harmful agent to protect against a subsequent harmful exposure.

Objective

To confirm if conditioning with an agent different from that used to cause the trauma can also be effective.

Methods

This was an experimental study with 17 guinea pigs, divided into three groups: an ototoxic control group (Cont) that received intramuscular administration of gentamicin 160 mg/kg/day for ten consecutive days, but no sound exposure; a sound control group (Sound) that was exposed to 85 dB broadband noise centered at 4 kHz, 30 min each day for ten consecutive days, but received no ototoxic medications; and an experimental group (Expt) that received sound exposure identical to the Sound group and after each noise presentation, received gentamicin similarly to Cont group. The animals were evaluated by distortion product otoacoustic emissions (DPOAEs), brainstem auditory evoked potentials (BAEPs), and scanning electron microscopy.

Results

The animals that were conditioned with noise did not show any protective effect compared with the ones that received only the ototoxic gentamicin administration. This lack of protection was observed functionally and morphologically.

Conclusion

Conditioning with 85 dB broadband noises, 30 min a day for ten consecutive days does not protect against an ototoxic gentamicin administration of 160 mg/kg/day for ten consecutive days in the guinea pig.

Gentamicin conditioning confers auditory protection against noise trauma

Auditory conditioning consists of the pre-exposure to low levels of a potential harmful agent to protect against a subsequent harmful presentation. The agent that was first tested was noise. This paradigm was more recently successfully tested with other agents. Nonetheless, the vast majority of the studies utilize the same agent to condition and to cause the trauma. The aim of this study was to verify whether conditioning with an agent different from the agent used to cause the trauma can also be effective. Thus, the following groups were organized: group Cont, which is the noise trauma control group, was exposed to 110-dB broadband noise centered at 4 kHz for 72 h; group Gent, which is the gentamicin conditioning control group, was administered 30 mg/kg of gentamicin daily for 30 consecutive days; and group Expt was conditioned with gentamicin similarly to group Gent and then subjected to a noise trauma similarly to group Cont. The animals were functionally and morphologically evaluated through the measurement of the auditory brainstem response and scanning electron microscopy, respectively. The following variables were investigated: outer hair cell injury and auditory threshold shift. The group that was conditioned with the drug exhibited significantly less outer hair cell damage, 10.8 and 22.9%, respectively (p = 0.0146), although did not maintain the proper functioning of the auditory system. We, therefore, conclude that conditioning with a different agent from that used to cause the trauma is effective, which suggests that both agents that were used promote similar mechanisms of self-protection.

The effects of hyperbaric oxygen therapy upon ototoxic injuries produced by amikacin in guinea pigs

Hyperbaric oxygen therapy (HBOT) has enhanced the prevention and treatment of auditory ailments such as ototoxicity.

OBJECTIVE

To study the effects of HBOT upon ototoxic injuries produced by amikacin.

METHOD

This experimental study included 12 albino guinea pigs, whose auditory function was assessed through distortion product otoacoustic emissions (DPOAEs) and brainstem auditory evoked potentials (BAEPs) before and after the administration of amikacin (600 mg/kg/day) and HBOT sessions (2 ATA, 60 minutes). Morphological features were analyzed through scanning electron microscopy. Subjects were divided into four groups, as follows: group 1 - saline solution + HBOT; group 2 - amikacin for 8 days; group 3 - amikacin + seven days of rest; and group 4 - amikacin + HBOT.

RESULTS

Group 1 subjects had preserved function and morphology throughout the experiment; Group 2 subjects had statistically significant levels of hair cell injury and functional impairment; Subjects on groups 3 and 4 had statistically significant functional and morphological impairment after the administration of amikacin, which were still present after the proposed procedures had been carried out.

CONCLUSION

Hyperbaric oxygen therapy did not change the cochlear hair cell morphology or the electro-physiological thresholds of the guinea pigs given amikacin.

Spontaneous reversibility of damage to outer hair cells after sodium salicylate induced ototoxicity

BACKGROUND

High sodium salicylate doses can cause reversible hearing loss and tinnitus, possibly due to reduced outer hair cell electromotility. Sodium salicylate is known to alter outer hair cell structure and function. This study determined the reversibility and cochlear recovery time after administration of an ototoxic sodium salicylate dose to guinea pigs with normal cochlear function.

STUDY DESIGN

Prospective experimental investigation.

METHODS

All animals received a single 500 mg sodium salicylate dose, but with different durations of action. Function was evaluated before drug administration and immediately before sacrifice. Cochleae were processed and viewed using scanning electron microscopy.

RESULTS

Changes in outer hair cell function were observed to be present 2 hours after drug administration, with recovery of normal anatomy beginning after 24 hours. Subsequently, derangement and distortion of cilia reduced, with effects predominantly in row three. At 168 hours, cilia were near-normal but with mild distortions which interfered with normal cochlear physiology.

CONCLUSIONS

Ciliary changes persisted for up to 168 hours after ototoxic sodium salicylate administration.

C1494T mitochondrial DNA mutation, hearing loss, and aminoglycosides antibiotics

In view of the complex mechanism of hearing, it is not difficult to understand that hearing impairment may result from a wide variety of genetically determined anomalies and various environmental factors. Specific mutations in the mitochondrial DNA 12S rRNA gene are responsible for maternally inherited non-syndromic hearing loss, and for increased susceptibility to the ototoxicity of aminoglycoside antibiotics.

AIM

To asses the presence of C1494T mutation among individuals with normal hearing and hearing impairment who used aminoglycosides and those who had not had contact with the antibiotic.

MATERIAL AND METHOD

The study was composed of 20 patients with nonsyndromic sensorineural hearing loss without prior use of aminoglycosides and 40 premature and high-risk newborns who used ototoxic drugs, of whom 20 had good hearing and 20 had hearing loss. The samples were analyzed by PCR-RFLP with the restriction enzyme Hph I.

STUDY DESIGN

Experimental.

RESULTS

The mitochondrial 12S rRNA C1494T mutation was not detected in any of the samples analyzed.

CONCLUSION

Our data suggest that the hearing loss of the individuals we analyzed was not related to the ototoxicity of mutation C1494T, showing that this mutation is not frequent in our population.

Distortion-product otoacoustic emissions and auditory brainstem responses sensitivity assessment in cisplatin-induced ototoxicity in rats

Cisplatin (cis-diamminedicloroplatinum) is an antineoplastic drug used in the treatment of a variety of cancers, especially head-and-neck cancer. Its ototoxicity, however, has been noted as a common side-effect which limits its use and causes significant morbidity.

Aim

to assess distortion-product otoacoustic emissions (DPOAE) and brainstem evoked response audiometry (BERA) sensitivity to detect secondary ototoxicity caused by different doses and means of administration of cisplatin in rats.

Study Design

Experimental.

Materials and Methods

Male Wistar rats were intraperitoneally (i.p.) injected with 24 mg/kg cisplatin, divided into three equal doses (8mg/kg) or a single i.p. injection of 16 mg/kg. The animals were evaluated by distortion product otoacoustic emission (DPOAE) or brainstem evoked response audiometry (BERA) on the 3rd and 4th days after the cisplatin injection.

Results

Treatment with cisplatin 24 mg/kg resulted in significant DPOAE decrease and it raised the BERA electrophysiological threshold. The 16mg/kg dose could not significantly reduce the DPOAE amplitude, but it raised the animals' hearing thresholds – detected by the BERA.

Conclusion

In rats, BERA was more sensitivity than DPOAE at detecting cisplatin-induced ototoxicity in rats considering different doses and means of administration.

Light microscopy study of cisplatin-induced ototoxicity in rats

BACKGROUND

Although most studies on animal ototoxicity employ scanning electron microscopy, all cochlear structures may be identified with light microscopy. This paper describes a simple method of histological assessment of cisplatin-induced ototoxicity in rats, and relates morphological changes to functional changes in hearing detected by distortion product evoked otoacoustic emissions.

MATERIALS AND METHODS

Male Wistar rats were injected with 8 mg/kg/day cisplatin, or with an equivalent volume of saline solution, for three consecutive days. They underwent distortion product evoked otoacoustic emission testing at baseline and at 24 or 48 hours after the last administration. At the end of the experiment, the animals were sacrificed and their cochleae were retrieved and prepared for haematoxylin and eosin staining.

RESULTS

A four-point scoring system was used to grade injury to the external ciliated cells, as indicated by the number of cells absent from the basal turn of the cochlear duct. A four-point scoring system was also used to grade stria vascularis injury, as indicated by the degree of shrinkage of the intermediate cells. Scores were significantly higher in groups treated with cisplatin compared with controls. Morphological changes were confirmed by decreased distortion product evoked otoacoustic emission amplitudes in animals treated with cisplatin.

CONCLUSION

This method is simple to perform with routine histology equipment and is appropriate for the study of acute, cisplatin-induced ototoxicity in rats.

Ototoxicity and otoprotection in the inner ear of guinea pigs using gentamicin and amikacin: ultrastructural and functional aspects

Ototoxicity is still a challenge to medicine. The discovery of self-protecting endogenous mechanisms of the outer hair cells associated with their functional and ultra-structural assessment methods has opened new horizons in the understanding and controlling of these mechanisms. Aim: this paper aimed at establishing whether or not underdoses of gentamicin could protect the inner ear against the harmful effects of amikacin, based on these protection mechanisms and determine if the otoacoustic emission amplitudes could be associated with the level of hair cell integrity. Materials and Methods: Experimental study. We used 31 guinea pigs. They were injected with saline solution, gentamicin and amikacin, alone and in combinations -intramuscular injections - during 12, 30 and 42 days. The otoacoustic emissions were recorded in the beginning and at the end of the experiment, comparing it with the cochlear integrity study carried out by electron microscopy. Results: gentamicin underdoses did not protect the inner ear against amikacin toxicity; the reduction in otoacoustic emissions was strongly associated with an increase in hair cell lesions. Conclusion: these findings help understand inner ear otoprotection and ototoxicity. Establishing the correlation between the emissions amplitude an cell integrity plays an important role in the follow up of hair cell damage, with possible monitoring of ototoxicity caused by drugs in humans.

Auditory monitoring in ototoxicity

Some pharmaceutical products are capable of damaging the human auditory system. Technological progress has provided numerous resources to monitor hearing but there still is some controversy regarding the selection of the most sensitive and specific tests.

OBJECTIVE

to analyze audiological procedures used in the auditory monitoring of individuals exposed to ototoxic medication.

METHODS

we searched the MEDLINE and LILACS literature databases, using terms pertinent to audiological monitoring, ototoxicity and cancer. The pertaining literature analysis identified two procedures often used worldwide for the early detection of auditory lesions induced by ototoxic pharmaceutical drugs: high-frequency audiometry and evoked otoacoustic emissions. Both allow early identification of hearing disorders before changes are seen in conventional pure-tone audiometry and, consequently, before speech understanding is compromised.

CONCLUSION

we suggest a hearing monitoring protocol, considering the patients capability to respond to behavioral tests and monitoring timing (first test/follow up). For cancer patients, hearing monitoring should be performed in the patients treatment venue.

Amifostine otoprotection to cisplatin ototoxicity: a guinea pig study using otoacoustic emission distortion products (DPOEA) and scanning electron microscopy

Cisplatin is an antineoplastic drug for cancer treatment in children and adults. The side effects of cisplatin ototoxicity are significant: irreversible bilateral hearing damage to high frequencies (4 kHz - 8 kHz). Reports recognize some drugs that are associated with cisplatin to obtain an otoprotector effect. The ototoxicity mechanisms of cisplatin are related to injury of hair cell oxidation mechanism, especially of outer hair cells. Aim: Using otoacoustic emissions distortion products (DPOEA) and scanning electron microscopy we intended to verify the action of amifostine, a radioprotective drug that has well known antioxidant characteristics and otoprotector effects to cisplatin injury. Study design: Experimental. Material and Method: We used an experimental guinea pig model. The study was performed as follows: group 1: 6 animals, 12 ears, cisplatin 8.0 mg/Kg/day (IP), 3 days. Group 2: 6 animals, 12 ears, amifostine 100 mg/Kg/day (IP) and after 90 minutes, cisplatin 8.0 mg/Kg/day (IP), 3 days and group 3: 3 animals, 6 ears, amifostine 100 mg/Kg/day (IP), 3 days. Results: DPOEA were present before and after treatment in groups 2 and 3. The normal cilium architecture of outer hair cells was supported in all cochlear turns in groups 2 and 3. We concluded that amifostine has a potential otoprotector effect against cisplatin ototoxicity and could be used in clinical trials.