The protective role of tetramethylpyrazine against cisplatin-induced ototoxicity

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.

Pro-Inflammatory Signalling PRRopels Cisplatin-Induced Toxicity

Cisplatin is a platinum-based chemotherapeutic that has long since been effective against a variety of solid-cancers, substantially improving the five-year survival rates for cancer patients. Its use has also historically been limited by its adverse drug reactions, or cisplatin-induced toxicities (CITs). Of these reactions, cisplatin-induced nephrotoxicity (CIN), cisplatin-induced peripheral neuropathy (CIPN), and cisplatin-induced ototoxicity (CIO) are the three most common of several CITs recognised thus far. While the anti-cancer activity of cisplatin is well understood, the mechanisms driving its toxicities have only begun to be defined. Most of the literature pertains to damage caused by oxidative stress that occurs downstream of cisplatin treatment, but recent evidence suggests that the instigator of CIT development is inflammation. Cisplatin has been shown to induce pro-inflammatory signalling in CIN, CIPN, and CIO, all of which are associated with persisting markers of inflammation, particularly from the innate immune system. This review covered the hallmarks of inflammation common and distinct between different CITs, the role of innate immune components in development of CITs, as well as current treatments targeting pro-inflammatory signalling pathways to conserve the use of cisplatin in chemotherapy and improve long-term health outcomes of cancer patients.

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.

Levosimendan ameliorates cisplatin-induced ototoxicity: Rat model

OBJECTIVES

Cisplatin is employed for chemotherapeutic purposes in several types of adult and pediatric cancer. However, side-effects including nephrotoxicity, ototoxicity, gastrointestinal effects and neuropathy restrict the use of the drug due to their adverse impacts on quality of life. This study aimed to determine whether levosimendan exhibits a protective effect against cisplatin-related ototoxicity in a rat model by means of functional, biochemical and histochemical analysis.

METHODS

The study was employed with 24 female Sprague Dawley rats. After distortion product otoacoustic emissions (DPOAE) tests applied to all rats, rats were randomly assigned into four groups of six animals each. A single intraperitoneal 15 mg/kg dose of cisplatin was administered to Cisplatin group. Levosimendan group received intraperitoneal levosimendan at a dose of 100 mg/kg for five consecutive days. Cisplatin + Levosimendan group received intraperitoneal levosimendan at a dose of 100 mg/kg for five consecutive days and a single intraperitoneal dose of 15 mg/kg cisplatin at 3rd day of the study. Control group received 8 mL/kg/day intraperitoneal saline solution for five consecutive days. The DPOAE test was repeated on the 6th day of the study. All rats were then sacrificed, the cochleas were removed and set aside for biochemical and histopathological analyses.

RESULTS

A significant increase in levels of Malondialdehyde (MDA) and significantly lower activities of superoxide dismutase (SOD) and Glutathione peroxidase (GPx) were observed at rats of cisplatin group. Administration of levosimendan showed significantly lower cochlear MDA levels, while SOD and GPx activities both increased significantly. The DPOAE test performed at 6th day of the study showed a significant impairment in the signal-noise ratio (SNR) levels of rats in Cisplatin group. The SNR levels of rats treated with levosimendan were significantly higher than those of cisplatin group and were similar to those of the control group. Cisplatin impaired the cochlear structure and a severe Caspase 3 and 8-hydroxy-2' -deoxyguanosine (8-OHdG) immunopositivity was observed at cochlea of the rats of cisplatin group. Administration of levosimendan protected the structure of cochlea and there was a mild Caspase 3 and 8OHdG immunopositivity.

CONCLUSION

Our data demonstrate that levosimendan protects hearing against cisplatin-induced ototoxicity and obviates cellular degeneration. It also significantly reduces oxidative stress and apoptosis, probable mechanisms involved in ototoxicity.