Attenuation of Streptomycin Ototoxicity by Tetramethylpyrazine in Guinea Pig Cochlea

Tetramethylpyrazine Attenuates Radiation-Induced Ototoxicity in a Rat Model

INTRODUCTION

Tetramethylpyrazine (TMP) is a chemical compound, which has been shown to possess numerous biological features such as anticoagulation, inhibition of platelet aggregation, anti-inflammation, capillary dilatation, improvement in microcirculation, and protection against reactive oxygen radicals. The aim of the present study was to investigate the protective effect of TMP against radiation-induced ototoxicity.

MATERIALS AND METHODS

40 rats were divided into four groups. The first group was irradiated for 5 days. The second group received a single dose of 140 mg/kg/day intraperitoneal TMP given to the rats 30 min before radiotherapy (RT) for 5 days. The third group received a single dose of 140 mg/kg/day i.p. TMP for 5 days, whereas the fourth group was administered saline. All rats underwent distortion product otoacoustic emission (DPOAE) and auditory brainstem response measurements before and after the application. The temporal bulla of animals was removed for immunohistopathological examination.

RESULTS

Signal-noise ratio values were significantly decreased in the RT group for the frequencies of 2-32 kHz after RT (p < 0.05), whereas the difference was not significant in terms of pre- and posttreatment values for the other groups. Also in the RT group, the ABR thresholds were significantly increased after treatment. In H&E staining, the mean scores for outer hair cells (OHCs), stria vascularis (SV), and spiral ganglion (SG) injuries were significantly higher in RT and RT + TMP groups than in the other groups. The mean OHCs and SV injury scores were also significantly higher in the RT group than in the RT + TMP group (p < 0.05). The number of cochleas that showed cytoplasmic caspase-3 immunoreactivity in the OHC, SV, and SG was significantly higher in RT and RT + TMP groups than in the other groups.

CONCLUSION

The findings of the present study suggest that TMP may have a therapeutic potential for preventing sensorineural hearing loss (SNHL) related to RT.

β-Cyclodextrin and Oligoarginine Peptide-Based Dendrimer-Entrapped Gold Nanoparticles for Improving Drug Delivery to the Inner Ear

Here, we developed a safe and highly effective nanocarrier using β-cyclodextrin (β-CD) and oligoarginine peptide (Arg8)-modified dendrimer-entrapped gold nanoparticles (Au@CD-PAMAM-Arg8), with a diameter of 5 nm, for improved delivery of dexamethasone (Dex) to the inner ear. The properties and in vivo distribution of the Au@CD-PAMAM-Arg8 were assessed in vitro, and a streptomycin (SM) ototoxicity model was used in vivo. Flow cytometry analysis of HEIOC1 cells treated with Au@CD-PAMAM-Arg8 and Au @CD-PAMAM at different time intervals indicated that cell uptake efficiency of the drug delivery carrier Au@CD-PAMAM-Arg8 was higher than that of Au @CD-PAMAM. Au@CD-PAMAM-Arg8 carrying Dex (Au@CD-PAMAM-Arg8/Dex) were mainly distributed in hair cells, the spiral ganglion, lateral wall, and nerve fibers and had stronger protective effects on the inner ear than Dex administration alone. In vivo tracer tests revealed that tympanic injection was significantly more effective than posterior ear injection, muscle injection, and tail vein injection, whereas clinical retro-auricular injection could not increase the efficiency of drug delivery into the ear. Electrocochleography results showed that Au@CD-PAMAM-Arg8/Dex significantly improved hearing in C57/BL6 mice after SM exposure. These findings indicate that Au@CD-PAMAM-Arg8 may be the useful drug carriers for the treatment of inner ear diseases.

Identifying the mechanisms underlying the protective effect of tetramethylpyrazine against cisplatin‑induced in vitro ototoxicity in HEI‑OC1 auditory cells using gene expression profiling

Sensorineural hearing loss is prevalent in patients receiving cisplatin therapy. Tetramethylpyrazine (Tet) and tanshinone IIA (Tan IIA) have protective roles against hearing impairment or ototoxicity. The present study aimed to investigate the molecular mechanisms underlying cisplatin-induced ototoxicity and the protective effect of Tet and Tan IIA against it. House Ear Institute-Organ of Corti 1 auditory cells were treated with titrating doses of Tan IIA, Tet, and cisplatin. In a cell viability assay, cisplatin, Tan IIA and Tet had IC₅₀ values of 42.89 µM, 151.80 and 1.04×10³ mg/l, respectively. Tan IIA augmented cisplatin-induced cytotoxicity. However, Tet concentrations <75 mg/l attenuated cisplatin-induced cytotoxicity and apoptosis. Moreover, RNA sequencing analysis was carried out on auditory cells treated for 30 h with 30 µM cisplatin alone for 48 h or combined with 37.5 mg/l Tet for 30 h. Differentially expressed genes (DEGs) induced in these conditions were identified and examined using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis. Cisplatin increased the expression of genes related to the p53 and FoxO pathways, such as Fas, p21/CDKN1A, and Bcl-2 binding component 3, but decreased the expression of insulin-like growth factor 1 (IGF1), as well as genes in the histone (Hist)1 and Hist2 clusters. Treatment with Tet downregulated FOXO3 and Bcl-2 binding component 3, and increased the expression of IGF1. Moreover, Tet upregulated genes associated with Wnt signaling, but not p53-related genes. Thus, the otoprotective properties of Tet might be mediated by activation of Wnt and IGF1 signaling, and inhibition of FoxO signaling.

Long-Term Protective Effect of N-Acetylcysteine against Amikacin-Induced Ototoxicity in End-Stage Renal Disease: A Randomized Trial

BACKGROUND

The aim of the study is to evaluate the long-term protective effect of N-acetylcysteine (NAC), an antioxidant agent, against aminoglycoside (AG)-induced ototoxicity.

METHODS

A total of 40 patients receiving continuous ambulatory peritoneal dialysis (CAPD) and having their first peritonitis attacks and planned to be treated with AGs were enrolled in the study. They were randomized into 2 groups: 1 group received additional NAC and the other did not. All patients underwent hearing tests with pure tone audiometry (PTA) after the diagnosis, at 1 month and 12 months and at the same time the tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels were measured.

RESULTS

Patients taking NAC had better hearing test results in both ears at 1 month except 2,000 Hz for the left ear, which wasn't significantly different between the 2 groups. Although patients taking NAC had generally better PTA results at 12 months, differences between the 2 groups were not statistically significant. Baseline IL-6 level was significantly higher in the NAC group than the control group. Both TNF-α and IL-6 levels at 1 month were significantly lower in the NAC group than in the control group. On the other hand, there was no significant difference between the 2 groups in terms of TNF-α and IL-6 levels at 12 months.

CONCLUSIONS

The results of the current study showed that NAC, a potent anti-inflamatory drug, may be otoprotective, but that the effect is not long-lasting.

The protective role of tetramethylpyrazine against cisplatin-induced ototoxicity

OBJECTIVES

The aim of the present study was to investigate the protective effect of tetramethylpyrazine (TMP) on cisplatin-induced ototoxicity in rats.

METHODS

Forty healthy, female, 24-week-old, Sprague-Dawley rats (n = 40) were randomly assigned to four groups as follows: group one (n = 10) received intraperitoneal (i.p.) physiological saline at daily doses of 3 mg/kg for seven days; group two (n = 10) received a single dose of i.p. 15 mg/kg cisplatin; group three (n = 10) received i.p. 140 mg/kg TMP daily for seven days plus a single dose of i.p. 15 mg/kg cisplatin on the fourth day; group four (n = 10) received i.p. 140 mg/kg TMP daily for seven days. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) measurements were obtained from the animals (40 rats, 80 ears) under general anesthesia before and after drug administration. The temporal bulla of animals were bilaterally removed for immunohistopathological examination.

RESULTS

In group two, DPOAE and ABR values were significantly deteriorated after drug administration, whereas there was no statistically significant difference between the pre- and posttreatment DPOAE and ABR values for all frequencies for groups one, three and four. The mean scores for external ciliated cells (ECCs), stria vascularis (SV) and spiral ganglion (SG) injuries in hematoxylin and eosin (H&E) staining, and also caspase-3 immunoreactivity were significantly higher in group two than in the other groups.

CONCLUSION

In the present study, the protective effect of TMP on cisplatin ototoxicity was demonstrated through studies of electrophysiology and immunohistopathology. Co-administration of TMP may have potential protective effects against cisplatin-induced ototoxicity.

Clinical predictors of aminoglycoside-induced ototoxicity in drug-resistant Tuberculosis patients on intensive therapy

OBJECTIVE

The study objectives were to determine the incidence of aminoglycoside-induced ototoxicity in institutionalized patients on intensive phase of therapy for drug-resistant Tuberculosis (DR Tb) and also to assess clinical factors which could predict the ototoxicity.

METHODS

The study was a prospective analytical study among consecutive DR Tb patients who were admitted for intensive phase of therapy (of 4 months) at the DR-Tb center over a 12-month period. Patients were diagnosed as DR Tb using the Gene Xpert machine to confirm Rifampicin resistance. All eligible 70 out of 87 consenting patients were consecutively recruited into the study. Patients had baseline (admission) and serial pure tone audiometries (PTAs) performed at 4 weekly intervals until discharge after 4 months of admission. Audiometric confirmation of aminoglycoside-induced ototoxicity was done by comparing serial with baseline PTA.

RESULTS

Among the 70 patients the male:female ratio was 1.7:1. Nine patients (12.9%) were retroviral-positive, and 16 patients (22.9%) were confirmed to have ototoxicity by audiometric criteria. The duration of treatment when ototoxicity was detected in the patients ranged 4-17 (Mean±SD; 9.4±3.4) weeks. Ototoxicity was detected in the audiometric low frequency ranges in 7 (43.8%) and at the high frequencies in 4 (25.0%) of the patients. Univariate analyses of clinical parameters found that age, underlying diabetes mellitus, deranged baseline PTAv >25dB HL, BMI on admission and retroviral status were significantly associated, while sex and previous drug regimen failure were not associated with ototoxicity. Multivariate adjusted logistic regression analyses, controlling for sex, revealed age (OR=1.068, p=0.018), BMI on admission (OR=0.673, p=0.012) and retroviral positivity (OR=8.822, p=0.014) of patients could significantly predict aminoglycoside-induced ototoxicity.

CONCLUSION

Incidence of aminoglycoside-induced ototoxicity in DR Tb patients was 22.9%. The clinical predictors for ototoxicity were age, BMI on admission, and co-existing retroviral infection in the patients. Clinicians should consider these factors in making choices of aminoglycosides to be used during intensive phase of treatment with second line anti-Tuberculous therapy.