Effect of melatonin on otoprotection in rodents: a systematic review with meta-analysis

Abstract Objectives: To determinate the otoprotective efficacy of melatonin.in experimental models of rodents through a systematic review of the literature. Methods: Altogether, 154 articles were found in four databases. The PICOS strategy (Population, Intervention, Comparison, and Outcome) was used to define the eligibility criteria. Studies that met the inclusion criteria for the second step were included in a qualitative synthesis. Each study type was analyzed with the CAMARADES quality of assessment's checklist and the SYRCLE RoBS risk of bias. Results: Seven articles were selected, and four were included in the meta-analysis. It was possible to obtain seven outcomes according to the standard auditory frequencies presented among the studies, considering a minimum of three standard frequencies. The outcomes analyzed were for the frequencies of 1500, 2000, 3000, 4000, 5000, 6000, and 8000 Hz. Conclusion: Melatonin can provide protection against the ototoxic effects of cisplatin and aminoglycosides at 5000 Hz, 6000 Hz, and 8000 Hz, thereby minimizing the reduction in Otoacustic Emissions (OAE) amplitude. The same effect was not observed in the lower frequencies. Despite the limited number of studies that were evaluated, the results appeared consistent in higher frequencies. However, the methodology of the available studies did not meet the necessary methodological rigor that promotes the safe replicability of these studies.

Effect of melatonin on otoprotection in rodents: a systematic review with meta-analysis.

OBJECTIVES: To determinate the otoprotective efficacy of melatonin.in experimental models of rodents through a systematic review of the literature. METHODS: Altogether, 154 articles were found in four databases. The PICOS strategy (Population, Intervention, Comparison, and Outcome) was used to define the eligibility criteria. Studies that met the inclusion criteria for the second step were included in a qualitative synthesis. Each study type was analyzed with the CAMARADES quality of assessment's checklist and the SYRCLE RoBS risk of bias. RESULTS: Seven articles were selected, and four were included in the meta-analysis. It was possible to obtain seven outcomes according to the standard auditory frequencies presented among the studies, considering a minimum of three standard frequencies. The outcomes analyzed were for the frequencies of 1500, 2000, 3000, 4000, 5000, 6000, and 8000 Hz. CONCLUSION: Melatonin can provide protection against the ototoxic effects of cisplatin and aminoglycosides at 5000 Hz, 6000 Hz, and 8000 Hz, thereby minimizing the reduction in Otoacustic Emissions (OAE) amplitude. The same effect was not observed in the lower frequencies. Despite the limited number of studies that were evaluated, the results appeared consistent in higher frequencies. However, the methodology of the available studies did not meet the necessary methodological rigor that promotes the safe replicability of these studies.

Melatonin prevents age-related hearing loss in the murin experimental model

Abstract Objective: The present study aimed to perform a morphological and morphometric analysis of cochlear structures of C57BL/6J mice receiving oral melatonin for a 12-month period. Methods: 32 male C57BL/6J were divided into control and melatonin groups. Control received saline and ethanol solution and melatonin group, 50 μL of 10 mg of melatonin/kg/day orally for a 12-month period. After de experiment the animals were sacrificed into a 40% concentration of CO2 chamber, and the blades were morphological and morphometrically analyzed. Results: The melatonin group revealed a higher median density of viable cells (45 ± 10.28 cells/100 μm2, 31-73, vs. 32 ± 7.47 cells/100 μm2, 25-48). The median area of stria vascularis was 55.0 ± 12.27 cells/100 μm2 (38-80) in the control, and 59.0 ± 16.13 cells/100 μm2 (40-134) in the melatonin group. The morphometric analysis of the spiral ligament reveals a higher median of total viable neurons in the melatonin (41 ± 7.47 cells/100 μm2, 27-60) than in the control group (31 ± 5.68 cells/100 μm2, 21-44). Conclusion: Although melatonin is a potent antioxidant, it does not completely neutralize the occurrence of presbycusis; however, it may delay the onset of this condition. Level of evidence: 3.

Melatonin prevents age-related hearing loss in the murin experimental model.

OBJECTIVE: The present study aimed to perform a morphological and morphometric analysis of cochlear structures of C57BL/6J mice receiving oral melatonin for a 12-month period. METHODS: 32 male C57BL/6J were divided into control and melatonin groups. Control received saline and ethanol solution and melatonin group, 50 µL of 10 mg of melatonin/kg/day orally for a 12-month period. After de experiment the animals were sacrificed into a 40% concentration of CO2 chamber, and the blades were morphological and morphometrically analyzed. RESULTS: The melatonin group revealed a higher median density of viable cells (45 ±â€¯10.28 cells/100 µm2, 31-73, vs. 32 ±â€¯7.47 cells/100 µm2, 25-48). The median area of stria vascularis was 55.0 ±â€¯12.27 cells/100 µm2 (38-80) in the control, and 59.0 ±â€¯16.13 cells/100 µm2 (40-134) in the melatonin group. The morphometric analysis of the spiral ligament reveals a higher median of total viable neurons in the melatonin (41 ±â€¯7.47 cells/100 µm2, 27-60) than in the control group (31 ±â€¯5.68 cells/100 µm2, 21-44). CONCLUSION: Although melatonin is a potent antioxidant, it does not completely neutralize the occurrence of presbycusis; however, it may delay the onset of this condition.

Role of melatonin in prevention of age-related hearing loss.

INTRODUCTION: Age-related hearing loss (ARHL) is a consequence of aging of the auditory system. The best known mechanism of cell death in ARHL is apoptosis due to increased production of reactive oxygen species. In this context, it is hypothesized that melatonin, owing to its high antioxidant potential and its action in the mitochondria, helps prevent or delay outer hair cell dysfunction (HCD). AIMS: To evaluate the effect of melatonin on the prevention of HCD dysfunction in the ARHL process in a susceptible murine C57BL/6J model. METHOD: C57BL/6J animals were divided into two groups: control (CG) and melatonin (MG). The CG received a saline and ethanol solution and the MG, melatonin (10 mg/kg/day). The solutions were offered daily (50 µl) orally over a 10-month period. Distortion Product Otoacoustic Emissions (DPOAE) measurements were conducted once a month. RESULTS: There was a decrease in DPOAE values in both groups over time and a differentiation between them from the 10th month of life onwards. At 10 months, the MG maintained higher DPOAE values than the CG at all frequencies tested. CONCLUSION: The use of melatonin has otoprotective effects on HCD in the ARHL process in the C57BL/6J model.

[Sugarcane biopolymer membrane: experimental evaluation in the middle ear]. / Membrana do biopolímero da cana-de-açúcar: avaliação experimental na orelha média.

UNLABELLED: New developments on biomaterials are important in surgery. The behavior of a new membrane produced from sugarcane will be evaluated in the middle ear of rats. AIM: This study analyzed the results from the interaction of the sugarcane-base biopolymer membrane in the middle ear of a rat. MATERIALS AND METHODS: We ran an experimental, prospective, paired study with 24 Wistar rats. The sugarcane-base polymer membrane was inoculated in the right ear; and an autologous fascia in the left ear. The rats were divided in 3 groups of 8, and slaughtered at 4, 8 and 12 weeks after surgery. Histological analyses were performed on the rats' middle ear mucosa and their tympanic membranes. RESULTS: There was an inflammatory reaction on the experimental group and middle ear subacute exudate in 50%of the cases; 30% chronic exudate; and 20% was normal. In the control group there was only one case of exudate. The inflammation was initially described as intense, but it decreased over time. Myringosclerosis was observed in both groups. The sugarcane biopolymer membrane was absorbed later when compared with fascia. CONCLUSION: The sugarcane biopolymer membrane induced an inflammatory reaction in the middle ear which decreased over time, and mild fibrosis. Future studies can indicate its use in otolaryngology.

Membrana do biopolímero da cana-de-açúcar: avaliação experimental na orelha média / Sugarcane biopolymer membrane: experimental evaluation in the middle ear

O desenvolvimento dos biomateriais é importante na cirurgia. O comportamento de uma nova membrana derivada da cana-de-açúcar será avaliado na orelha média do rato. OBJETIVOS: Analisar a interação da membrana do biopolímero da cana-de-açúcar na mucosa da orelha do rato. MATERIAL E MÉTODO: Estudo experimental, prospectivo e pareado com 24 ratos Wistar. A membrana do biopolímero da cana-de-açúcar foi inoculada na orelha média direita e a fáscia autóloga na orelha esquerda. Os ratos foram subdivididos em 3 grupos de 8 e sacrificados com 4, 8 e 12 semanas após a cirurgia. Foi realizada uma análise histológica da mucosa da orelha média e da membrana timpânica. RESULTADOS: Houve reação inflamatória no grupo experimental com exsudato subagudo em 50 por cento dos casos e 30 por cento exsudato crônico; 20 por cento estava normal. A inflamação foi intensa inicialmente, mas diminuiu no decorrer do tempo. No grupo controle houve apenas um caso de exsudato. Miringoesclerose na membrana timpânica foi observada em ambos os grupos. A biomembrana foi absorvida tardiamente em comparação com a fáscia. CONCLUSÕES: A membrana do biopolímero da cana-de-açúcar causou reação inflamatória na orelha média, com regressão no tempo tardio do experimento e fibrose leve. Futuros estudos podem direcionar seu uso na otorrinolaringologia.

New developments on biomaterials are important in surgery. The behavior of a new membrane produced from sugarcane will be evaluated in the middle ear of rats. AIM: This study analyzed the results from the interaction of the sugarcane-base biopolymer membrane in the middle ear of a rat. MATERIALS AND METHODS: We ran an experimental, prospective, paired study with 24 Wistar rats. The sugarcane-base polymer membrane was inoculated in the right ear; and an autologous fascia in the left ear. The rats were divided in 3 groups of 8, and slaughtered at 4, 8 and 12 weeks after surgery. Histological analyses were performed on the rats' middle ear mucosa and their tympanic membranes. RESULTS: There was an inflammatory reaction on the experimental group and middle ear subacute exudate in 50 percentof the cases; 30 percent chronic exudate; and 20 percent was normal. In the control group there was only one case of exudate. The inflammation was initially described as intense, but it decreased over time. Myringosclerosis was observed in both groups. The sugarcane biopolymer membrane was absorbed later when compared with fascia. CONCLUSION: The sugarcane biopolymer membrane induced an inflammatory reaction in the middle ear which decreased over time, and mild fibrosis. Future studies can indicate its use in otolaryngology.