Light microscopy study of cisplatin-induced ototoxicity in rats

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.

Does Hypochlorous Acid Cause Ototoxicity? An Experimental Study

AIM

Hypochlorous acid (HOCl) is a weak acid that ionizes in water. It is an effective antiseptic exhibiting low toxicity on living tissues. We aimed to investigate the ototoxic effects of HOCl on an animal model by using electrophysiological and histological methods.

MATERIALS AND METHODS

The study comprised 32 Sprague-Dawley rats, which were separated into four groups: control group (A), saline solution group (B), 70% isopropyl alcohol + 2% chlorhexidine group (C), and HOCl group (D). After recording the auditory brainstem response (ABR) for basal hearing thresholds (8, 16, 24, and 32 kHz), 0.03 ml of the aforementioned materials was injected intratympanically three times every 2 days in groups B, C, and D. ABR measurements were repeated on the 7th and 21st days. All animals were sacrificed, and temporal bones were prepared for examinations of cochlear histology and vascular endothelial growth factor immunohistochemistry.

RESULTS

Basal hearing levels were normal across all frequencies and groups, with no statistical differentiation. On the 7th and 21st days after the ABR test, all other groups demonstrated a significant deterioration in hearing levels compared with group A. When the results from 7th and 21st days were compared within group D, a partial recovery was observed. In histopathology, groups C and D demonstrated moderate and severe cochlear degeneration, along with decreased immunoreactivity in the organ of Corti, stria vascularis, and spiral ligament.

CONCLUSION

This is the first study to evaluate the safety of using HOCl in otology. Although HOCI is less ototoxic than the disinfectant used, it may have a toxic effect on cochlea.Level of Evidence: Animal Research.

Blood Prestin Levels in Normal Hearing and in Sensorineural Hearing Loss: A Scoping Review

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Objectives:

Recently, it has been hypothesized that blood prestin concentration levels may reflect cochlear damage and thus serve as an easily measurable, early sensorineural hearing loss (HL) biomarker. This is a scoping review aiming to identify and critically appraise current evidence on prestin blood levels and their temporal variation in rodents and humans with normal hearing and with sensorineural HL.

Design:

This study was designed and held according to PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines. With no limitation with regards to study type, animal and human studies focusing on prestin blood levels in normal hearing and in sensorineural HL were sought in major databases such as Medline, Central Scopus, PROSPERO, and Clinicaltrials.gov. Results were then hand-searched. A data charting form was developed including the parameters of interest.

Results:

Seven studies focusing on measuring prestin blood levels by means of ELISA in rodents and human subjects with normal hearing and noise-induced, drug-induced, or idiopathic sudden HL were found eligible and were included in the analysis. According to these proof-of-concept studies, prestin can be detected in the circulation of subjects with no HL; however, normal ranges remain unclear. After cochlear damage, blood prestin levels seem to initially rise and then return to near or below baseline. The degree of their change relates with subjects’ degree of HL, damaged cochlear region and recovery. Prestin blood levels and their temporal variation seem to correlate with cochlear damage; however, methodological weaknesses, such as small sample size, lack of detailed phenotyping, insufficient exclusion of confounding factors, and short follow-up, do not allow for robust conclusions.

Conclusions:

Current findings support the value of studying blood prestin levels in normal hearing and HL and highlight a need for larger-scale longitudinal research.

Occurrence of tinnitus and peripheral sensory neuropathy in women during chemotherapy treatment of breast cancer

Objective: To analyze the occurrence of tinnitus and peripheral sensory neuropathy in women during breast cancer chemotherapy. Methods: This is a retrospective analytical study with a quantitative approach, performed in medical records of an oncology outpatient service between February 2014 and February 2015, using the toxicities scores of Common Terminology Criteria for Adverse Events (CTCAE). Results: Considering 181 patients with breast cancer who met the inclusion criteria, 49.2% reported tinnitus at some point of the treatment, while 65.1% peripheral sensory neuropathy. In both conditions, the predominant severity score was grade 1, with frequencies of 23.8% and 33.1%, respectively. A significant, positive and weak correlation was observed between the severity of tinnitus and peripheral sensory neuropathy (ρ = 0.325 and p = 0.001), as well as very weak between the number of complete cycles of chemotherapy and tinnitus (ρ = 0.195 and p = 0.009) and neuropathy peripheral sensory (ρ = 0.237 and p = 0.002). Conclusions: Tinnitus and peripheral sensory neuropathy were frequent toxicities during chemotherapy treatment of breast cancer, and both manifested with low severity/functional impact in most participants.

Protective Effect of Carvacrol against Paclitaxel-Induced Ototoxicity in Rat Model

Objective

This study aimed to explore whether carvacrol (CV) had a protective effect on paclitaxel-induced ototoxicity from biochemical, functional, and histopathological perspectives.

Methods

Forty Wistar albino male rats were randomly separated into five groups of eight rats. Group 1 was the control group, so Paclitaxel or CV was not administered. Group 2 was administered i.p. CV at 25 mg/kg once a week; Group 3, was administered i.p. paclitaxel at 5 mg/kg once a week; Group 4 was administered i.p. paclitaxel at 5 mg/kg followed (30 min later) by CV at 25 mg/kg once a week; and Group 5 was administered i.p. CV at 25 mg/kg followed (1 day later) by paclitaxel at 5 mg/kg. once a week. The drugs were administered intraperitoneally once a week for four consecutive weeks, and distortion product otoacoustic emissions (DPOAE) tests were performed at the beginning of the study before the first drug administration and at the end of the study after the last drug administration. All rats were sacrificed, and cochleae were removed for biochemical and histopathological analysis.

Results

Biochemical data indicated that paclitaxel caused oxidative stress in the cochlea. Histopathological findings revealed the loss of outer hair cells in the organ of Corti (CO) and moderate degenerative changes in the stria vascularis (SV). It was observed that DPOAE measurements were significantly reduced at high frequencies. In groups which CV was administered together with paclitaxel, these biochemical, histopathological, and functional changes were favorably reversed.

Conclusion

CV may have a protective effect against paclitaxel-induced ototoxicity when given.

The Protective Effect of Nigella sativa Oil against Experimentally Induced Cisplatin Ototoxicity: An Animal Study

OBJECTIVES

The objective of this study was to investigate the potential protective effect of Nigella sativa oil (NSO) against cis-diamminedichloroplatinum or cisplatin (CDDP)-induced ototoxicity.

MATERIALS AND METHODS

Twenty-four Wistar albino rats were randomly and equally divided into four groups. Groups 1 and 2 were given a total of 15 mg/kg CDDP intraperitoneally, which was divided equally into three doses on days 1, 3, and 5. Group 2 was treated via gavage feeding with 15 ml NSO that was divided into five doses on days 1, 3, 5, 7, and 9. Groups 3 and 4 received only 15 ml of NSO and 15 ml of 0.9% saline solution, respectively, which were orally administered and divided into five doses on days 1, 3, 5, 7, and 9. Baseline high-frequency (8, 12, 16, and 32 kHz) auditory brainstem response (ABR) measurements were collected in all the groups before the medical administrations and were repeated on the 14th day before sacrifice. Afterward, a histopathological evaluation of the cochlea was performed.

RESULTS

There was a significant difference in the histopathological changes between group 1 and the other groups (p<0.01). Changes in the spiral ganglion cells, the stria vascularis, and the external ciliated cells were significantly different between groups 1 and 2 (p=0.019, 0.039, and 0.045, respectively). The ABR results revealed significant differences in the 16 and 32 kHz measurements between groups 1 and 2 (p=0.013 and p<0.01, respectively).

CONCLUSION

According to the results, NSO may have a protective effect on cochlear function against the disruptive effects of CDDP in rats.

Wnt Signaling Protects against Paclitaxel-Induced Spiral Ganglion Neuron Damage in the Mouse Cochlea In Vitro

It has been reported that paclitaxel administration could cause sensorineural hearing loss, and Wnt activation is important for the development and cell protection of mouse cochlea. However, the effect of Wnt signaling in spiral ganglion neurons (SGNs) damage induced by paclitaxel has not yet been elucidated. In this study, we explored the effect of paclitaxel on SGNs in the mouse cochlea and the neuroprotective effects of Wnt signaling pathway against paclitaxel-induced SGN damage by using Wnt agonist/antagonists in vitro. We first found that paclitaxel treatment resulted in a degenerative change and reduction of cell numbers in SGNs and induced caspase-mediated apoptosis in SGNs. The expression levels of β-catenin and C-myc were increased, thus indicating Wnt signaling was activated in SGNs after paclitaxel treatment. The activation of Wnt signaling pathway protected against SGN loss after exposure to paclitaxel, whereas the suppression of Wnt signaling in SGNs made them more vulnerable to paclitaxel treatment. We also showed that activation of Wnt signaling in SGNs inhibited caspase-mediated apoptosis. Our findings demonstrated that Wnt signaling had an important role in protecting SGNs against paclitaxel-induced damage and thus might be an effective therapeutic target for the prevention of paclitaxel-induced SGN death.

Investigation of Astaxanthin Effect on Cisplatin Ototoxicity in Rats by Using Otoacoustic Emission, Total Antioxidant Capacity, and Histopathological Methods

BACKGROUND

Cisplatin-induced ototoxicity is related to oxidative stress. Astaxanthin is one of the most powerful antioxidants in nature.

AIMS/OBJECTIVES

To investigate the protective effect of astaxanthin on cisplatin-induced ototoxicity.

MATERIALS AND METHODS

Thirty-five Sprague Dawley female rats were divided into 5 groups: control, cisplatin, and cisplatin with 10, 20, and 40 mg/kg astaxanthin groups. Cisplatin group received a single intraperitoneal injection of 14 mg/kg cisplatin. While saline was administered in the control group, in the other 3 groups, 10, 20, and 40 mg/kg daily doses of astaxanthin were administered through orogastric cannula before administration of cisplatin. Baseline and 10th day otoacoustic emission tests were administered. An intracardiac blood sample was taken to measure total antioxidant capacity (TAC), and the cochleas of the animals were investigated histopathologically.

RESULTS

Hearing level of astaxanthin 40 mg/kg + cisplatin group was higher at 24 kHz and 32 kHz frequencies compared to the cisplatin group. The TAC value of the cisplatin group was lower than both the control and astaxanthin + cisplatin groups (P < .05). On histopathological examination, the other groups were deformed compared to the control group, but no statistically significant difference was observed between the astaxanthin + cisplatin and cisplatin groups.

CONCLUSIONS AND SIGNIFICANCE

Astaxanthin showed protective effect at high frequencies when it was administered at high dose. Thus, astaxanthin may have protective effect against cisplatin-induced ototoxicity.

Utilizing prestin as a predictive marker for the early detection of outer hair cell damage

PURPOSE

To evaluate prestin as a biomarker for the identification of early ototoxicity.

MATERIALS AND METHODS

Rats (n = 47) were randomly assigned to five groups: low-dose (LAG) or high-dose (HAG) amikacin (200 and 600 mg/kg/day, respectively, for 10 days), low-dose (LCIS)or high-dose (HCIS) cisplatin (single doses of 5 and 15 mg/kg, respectively, for 3 days), and control (n = 8). At the end of the experiment, measurement of distortion product-evoked otoacoustic emissions (DPOAE) were performed to evaluate hearing, then blood samples and both ear tissues were collected under anesthesia. Prestin levels were determined by ELISA. Cochlear damage was evaluated histologically using a 4-point scoring system.

RESULTS

The mean serum prestin levels were 377.0 ± 135.3, 411.3 ± 73.1, 512.6 ± 106.0, 455.0 ± 74.2 and 555.3 ± 47.9 pg/ml for control, LCIS, HCIS, LAG and HAG groups, respectively. There was significant difference between prestin levels of Control-LCIS-HCIS groups (p = 0.031) and prestin levels of Control-LAG-HAG groups (p = 0.003). There were also significant differences in prestin levels between the low- and high-dose cisplatin and amikacin groups (p = 0.028 and p = 0.011, respectively). Each group had significantly lower DPOAE results at 4, 6 and 8 kHz than control groups (p < 0.001). The LAG, HAG, LCIS and HCIS groups had significantly higher cochlear damage scores than the control group (p < 0.05).

CONCLUSIONS

Higher doses of cisplatin and amikacin were associated with the greatest increases in serum prestin level and cochlear damage score. The results of this study suggest that prestin is a promising early indicator of cochlear damage.

Effect of Remote Ischemic Preconditioning on Systemic Toxicity and Ototoxicity Induced by Cisplatin in Rats: Role of TNF-α and Nitric Oxide

BACKGROUND/AIMS

Cisplatin is a chemotherapeutic agent. The use of remote ischemic preconditioning (RIPC) was proposed after the observation that ischemic preconditioning of a cardiac vascular area could protect another completely distinctly.

METHODS

This is an experimental study. Male Wistar rats were anesthetized, and they underwent a hearing evaluation via measurement of the brainstem auditory evoked potential (BSAEP). Then, cisplatin was administered intraperitoneally (IP) at a dose of 8 mg/kg/day for 4 consecutive days to group 1, whereas saline solution was administered IP to group 2. In groups 3 and 4, ischemia of the right hind paw was performed for 10 min, followed by reperfusion for 30 min, after which cisplatin or saline was administered IP to group 3 or group 4, respectively. Afterwards, all animals were evaluated via the BSAEP. The right cochlea was dissected for immunohistochemistry.

RESULTS

RIPC lowered the increase in BSAEP of the animals treated with cisplatin (p = 0.0146). Weight loss decreased in the animals subjected to RIPC (p < 0.005). In group 3, RIPC reversed immunostaining for tumor necrosis factor-α and inducible nitric oxide synthase in the stria vascularis injured by cisplatin (p < 0.05).

CONCLUSION

RIPC protects against systemic toxicity and ototoxicity induced by cisplatin in rats.

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.

Effects of ozone (O3) therapy on cisplatin-induced ototoxicity in rats

The aim of this study is to investigate the effect of rectal ozone and intratympanic ozone therapy on cisplatin-induced ototoxicity in rats. Eighteen female Wistar albino rats were included in our study. External auditory canal and tympanic membrane examinations were normal in all rats. The rats were randomly divided into three groups. Initially, all the rats were tested with distortion product otoacoustic emissions (DPOAE), and emissions were measured normally. All rats were injected with 5-mg/kg/day cisplatin for 3 days intraperitoneally. Ototoxicy had developed in all rats, as confirmed with DPOAE after 1 week. Rectal and intratympanic ozone therapy group was Group 1. No treatment was administered for the rats in Group 2 as the control group. The rats in Group 3 were treated with rectal ozone. All the rats were tested with DPOAE under general anesthesia, and all were sacrificed for pathological examination 1 week after ozone administration. Their cochleas were removed. The outer hair cell damage and stria vascularis damage were examined. In the statistical analysis conducted, a statistically significant difference between Group 1 and Group 2 was observed in all frequencies according to the DPOAE test. In addition, between Group 2 and Group 3, a statistically significant difference was observed in the DPOAE test. However, a statistically significant difference was not observed between Group 1 and Group 3 according to the DPOAE test. According to histopathological scoring, the outer hair cell damage score was statistically significantly high in Group 2 compared with Group 1. In addition, the outer hair cell damage score was also statistically significantly high in Group 2 compared with Group 3. Outer hair cell damage scores were low in Group 1 and Group 3, but there was no statistically significant difference between these groups. There was no statistically significant difference between the groups in terms of stria vascularis damage score examinations. Systemic ozone gas therapy is effective in the treatment of cell damage in cisplatin-induced ototoxicity. The intratympanic administration of ozone gas does not have any additional advantage over the rectal administration.

Investigation of protective role of curcumin against paclitaxel-induced inner ear damage in rats

OBJECTIVES/HYPOTHESIS

The aim of this study was to investigate the potential protective effect of curcumin on paclitaxel-induced ototoxicity in rats by means of immunohistochemical and histopathological analysis and distortion product otoacoustic emissions (DPOAEs).

STUDY DESIGN

Animal study.

METHODS

Forty Sprague-Dawley rats were randomized into five groups. Group 1 was administered no paclitaxel and curcumin during the study. Groups 2, 3, 4 and 5 were administered 5 mg/kg paclitaxel; 200 mg/kg curcumin; 5 mg/kg paclitaxel, followed by 200 mg/kg curcumin; 200 mg/kg curcumin and a day later 5 mg/kg paclitaxel followed intraperitoneally by 200 mg/kg curcumin once a week for 4 consecutive weeks, respectively. After the final DPOAEs test, the animals were sacrificed and their cochlea were prepared for hematoxylin and eosin and caspase-3 staining.

RESULTS

The DPOAEs thresholds and histopathological and immunohistochemical findings were substantially correlated in all groups. The histopathologic findings in the cochlea of the paclitaxel-treated animals showed not only changes in the organ of Corti, but also damage to the stria vascularis and spiral limbus, including nuclear degeneration, cytoplasmic vacuolization, and atrophy of intermediate cells. Additionally, cochlear changes in group 2, such as intense apoptosis, were confirmed by caspase-3 immunohistochemical staining. In group 4, coreceiving curcumin could not sufficiently prevent paclitaxel-induced ototoxicity, and the results in group 5 were similar to the control group.

CONCLUSIONS

In our study, we have concluded that pre- and coreceiving curcumin can significantly protect the cochlear morphology and functions on paclitaxel-induced ototoxicity in rats. Curcumin might be considered as a potential natural product that, used as a dietary supplement, could be easily given to patients undergoing paclitaxel chemotherapy.

LEVEL OF EVIDENCE

NA

Protective role of bilberry extract against Cisplatin induced ototoxicity in rats

To investigate the potential preventive effect of bilberry extract in cisplatin-induced ototoxicity. Thirty-five 3-3.5-month healthy adult female Sprague-Dawley rats were randomly divided into three groups and treated as follows: Both, group 1 (n = 10) and group 2 (n = 15) subjects received a single dose of 12 mg/kg cisplatin intraperitoneally; while in group 2, bilberry extract was also administered via gavage feeding for 15 days. Group 3 (n = 10), received no cisplatin or bilberry extract. Baseline distortion product otoacoustic emissions testing were performed in all subjects prior to administration of any medication. The test was repeated at 15th day following administration of any medication. The distortion product otoacoustic emissions were evaluated at 1.5, 2, 3, 4, 5, 6, 7, 8, 10 and 12 kHz. Histopathological changes in the cochlea of rats were observed by light microscopy. There was no statistically significant difference in apical turn between three groups but there was a statistically significant difference in basal and mid turn external ciliated cells number. Stria vascularis changes were statistically significant between three groups. The median score for stria vascularis injury and spiral ganglion cells changes were significantly greater in group 1 than in group 2. The initial distortion product otoacoustic emissions measurement results gave similar statistically insignificant values in the three groups (p > 0.05). In contrast to initial measurements statistically significant differences were recorded between day 0 and 15 otoacoustic thresholds (p < 0.05). Bilberry extract group had a significantly higher DP-gram except for 1.5 and 2 kHz frequencies when compared to cisplatin group. The analyses of the results revealed statistically significant differences between two groups (p < 0.05), suggesting that bilberry extract had shown a protective effect against cisplatin ototoxicity. The results of our study revealed that treatment with bilberry extract affords significant protection to the cochlea from cisplatin toxicity and thus, oral experimental dose of bilberry extract administration may have a protective effect against cisplatin ototoxicity in rats.

The effects of lycopene on cisplatin-induced ototoxicity

To investigate the potential preventive effect of lycopene in cisplatin-related ototoxicity. Thirty-five healthy 3-3.5-month adult female Sprague-Dawley rats were randomly divided into three groups and treated as follows: Group 1 (n = 10), received no cisplatin or lycopene. Both group 2 (n = 10) and; Group 3 (n = 15) received a single dose of 12 mg/kg cisplatin intraperitoneally. Lycopene was administered via gavage feeding in group 2 for 15 days. Prior to any medication administration, the baseline distortion product emissions were obtained in three groups. The animals were tested again at 15th day. The resulting distortion product otoacoustic emissions (DPOAE) were evaluated at 1.5, 2, 3, 4, 5, 6, 7, 8, 10, and 12 kHz. On day 0, prior to any medications, the initial DPOAEs measurement results gave similar values in the three groups (p > 0.05). In group 2 and 3, statistically significant differences were recorded for all frequencies between day 0 and day 15 values (p < 0.05). Lycopene group demonstrated significantly higher DP-grams except for 1.5 kHz frequency when compared to cisplatin group (p < 0.05). There was a statistically significant difference in basal and mid turn external ciliated cells number (p < 0.05), but there was no statistically significant difference in apical turn between three groups (p > 0.05). Stria vascularis changes were statistically significant between the groups, and the median score for stria vascularis injury was significantly greater in group 3 than in group 2 (p < 0.05). The median scores for spiral ganglion cells changes were significantly greater in group 3 than in group 2 (p < 0.05). The analyses of the results revealed statistically significant differences between two groups (p < 0.05), suggesting lycopene's possible protective effect against cisplatin ototoxicity. The present study revealed that administration of lycopene may demonstrate a protective role against cisplatin-induced ototoxicity in rats.