RNA expression induced by cisplatin in an organ of Corti-derived immortalized cell line

Regulation of PPARγ/CPT-1 expression ameliorates cochlear hair cell injury by regulating cellular lipid metabolism and oxidative stress

This study aimed to investigate the protective effects of PPARγ/CPT-1 regulation on cisplatin-induced cochlear hair cell injury. The viability, apoptosis and mitochondrial membrane potential of cisplatin-induced HEI-OC1 cells were determined by CCK-8 assay, TUNEL and JC-1 staining, respectively. The oxidative stress and lipid metabolism were detected by the assay kits of MDA, ROS, SOD, CAT, TG and FFA. The transfection efficiency of overexpression (OV)-PPARG and OV-CPT1A was examined by RT-qPCR and the expressions of apoptosis- and lipid metabolism-related proteins were detected by western blot. As a result, cisplatin with varying concentrations (5, 10, 30 μM) suppressed the viability, promoted the apoptosis and hindered the mitochondrial function of HEI-OC1 cells, accompanied with up-regulated expressions of Bax and cleaved caspase-3 and down-regulated expression of Bcl-2. The oxidative stress was aggravated and lipid metabolism was inhibited by cisplatin (5, 10, 30 μM) induction, evidenced by the increased levels of MDA, ROS, TG, FFA and the decreased levels of SOD and CAT. Overexpression of PPARG or CPT1A could improve the viability, mitochondrial function, lipid metabolism and suppress the oxidative stress and apoptosis of cisplatin-induced HEI-OC1 cells. In conclusion, up-regulation of PPARG or CPT1A ameliorated cochlear hair cell injury by improving cellular lipid metabolism and inhibiting oxidative stress.

Detecting Novel Ototoxins and Potentiation of Ototoxicity by Disease Settings

Over 100 drugs and chemicals are associated with permanent hearing loss, tinnitus, and vestibular deficits, collectively known as ototoxicity. The ototoxic potential of drugs is rarely assessed in pre-clinical drug development or during clinical trials, so this debilitating side-effect is often discovered as patients begin to report hearing loss. Furthermore, drug-induced ototoxicity in adults, and particularly in elderly patients, may go unrecognized due to hearing loss from a variety of etiologies because of a lack of baseline assessments immediately prior to novel therapeutic treatment. During the current pandemic, there is an intense effort to identify new drugs or repurpose FDA-approved drugs to treat COVID-19. Several potential COVID-19 therapeutics are known ototoxins, including chloroquine (CQ) and lopinavir-ritonavir, demonstrating the necessity to identify ototoxic potential in existing and novel medicines. Furthermore, several factors are emerging as potentiators of ototoxicity, such as inflammation (a hallmark of COVID-19), genetic polymorphisms, and ototoxic synergy with co-therapeutics, increasing the necessity to evaluate a drug's potential to induce ototoxicity under varying conditions. Here, we review the potential of COVID-19 therapies to induce ototoxicity and factors that may compound their ototoxic effects. We then discuss two models for rapidly detecting the potential for ototoxicity: mammalian auditory cell lines and the larval zebrafish lateral line. These models offer considerable value for pre-clinical drug development, including development of COVID-19 therapies. Finally, we show the validity of in silico screening for ototoxic potential using a computational model that compares structural similarity of compounds of interest with a database of known ototoxins and non-ototoxins. Preclinical screening at in silico, in vitro, and in vivo levels can provide an earlier indication of the potential for ototoxicity and identify the subset of candidate therapeutics for treating COVID-19 that need to be monitored for ototoxicity as for other widely-used clinical therapeutics, like aminoglycosides and cisplatin.

Forensic determination of hair deposition time in crime scenes using electron paramagnetic resonance

Several types of biological samples, including hair strands, are found at crime scenes. Apart from the identification of the value and the contributor of the probative evidence, it is important to prove that the time of shedding of hair belonging to a suspect or victim matches the crime window. To this end, to estimate the ex vivo aging of hair, we evaluated time-dependent changes in melanin-derived free radicals in blond, brown, and black hairs by using electron paramagnetic resonance spectroscopy (EPR). Hair strands aged under controlled conditions (humidity 40%, temperature 20-22°C, indirect light, with 12/12 hour of light/darkness cycles) showed a time-dependent decay of melanin-derived radicals. The half-life of eumelanin-derived radicals in hair under our experimental settings was estimated at 22 ± 2 days whereas that of pheomelanin was about 2 days suggesting better stabilization of unpaired electrons by eumelanin. Taken together, this study provides a reference for future forensic studies on determination of degradation of shed hair in a crime scene by following eumelanin radicals by utilizing the non-invasive, non-destructive, and highly specific EPR technique.

Teratogenic effect of cisplatin in rats and the protective role of sodium selenate

Eighty pregnant Sprague-Dawley rats were used in this study. They were allotted to four equal groups. The first group served as a control without any treatment while the other groups were given cisplatin, sodium selenate, and cisplatin+sodium selenate, respectively. Cisplatin was injected intraperitoneally in a dose of 5mg/kgb wt. on the 12th day of gestation while sodium selenate was administered orally in a dose of 0.5mg/kgb wt throughout gestation. Animals were sacrificed on the 20th day of gestation for fetal examination. Cisplatin produced significant elevation in the percentages of late resorption sites and dead foetuses compared with the control group. The mean foetal and placental weights were significantly reduced. Dwarf foetuses and subcutaneous (s/c) haemorrhage were also recorded in cisplatin-treated group. Visceral abnormalities were revealed in the form of dilated nares, anophthalmia and/or microphthalmia, dilated brain ventricles, hypertrophy of the heart, hypoplasia of the lung, hepatomegaly and dilated renal pelvis. Skeletal examination showed wide open fontanel, incomplete ossification of parietal and interparietal bones, incomplete ossification of sternum, reduction in the number or even complete absence of phalanges, sacral and/or caudal vertebrae. Histopathological examination of placentas in cisplatin-treated group revealed severe pathological alterations. Administration of sodium selenate significantly alleviated the afore-mentioned adverse effects of cisplatin on the fetuses and their placentas so we conclude that sodium selenate as an antioxidant has an effective protective role in cisplatin teratogenic effects.

Assessing cisplatin-induced ototoxicity and otoprotection in whole organ culture of the mouse inner ear in simulated microgravity

Cisplatin is a widely used anti-cancer drug. Ototoxicity is a major dose-limiting side-effect. A reproducible mammalian in-vitro model of cisplatin ototoxicity is required to screen and validate otoprotective drug candidates. We utilized a whole organ culture system of the postnatal mouse inner ear in a rotating wall vessel bioreactor under "simulated microgravity" culture conditions. As previously described this system allows whole organ culture of the inner ear and quantitative assessment of ototoxic effects of aminoglycoside induced hair cell loss. Here we demonstrate that this model is also applicable to the assessment of cisplatin induced ototoxicity. In this model cisplatin induced hair cell loss was dose and time dependent. Increasing exposure time of cisplatin led to decreasing EC50 concentrations. Outer hair cells were more susceptible than inner hair cells, and hair cells in the cochlear base were more susceptible than hair cells in the cochlear apex. Initial cisplatin dose determined the final extent of hair cell loss irrespective if the drug was withdrawn or continued. Dose dependant otoprotection was demonstrated by co-administration of the antioxidant agent N-acetyl l-cysteine. The results support the use of this inner ear organ culture system as an in vitro assay and validation platform for inner ear toxicology and the search for otoprotective compounds.

Correlation of adverse effects of cisplatin administration in patients affected by solid tumours: a retrospective evaluation

Cisplatin is the most common antineoplastic drug used for the therapy of solid tumours. To date, researchers have focused on the dosage to be administered for each specific tumour, mainly considering the local adverse effects. The aim of this study was to correlate the severity of the adverse effects with: i) the dosage of cisplatin; ii) the specific site of the tumour; iii) the association with other drugs; and iv) the symptoms. We analysed data from 123 patients with 11 different tumour classes undergoing therapy from 2007 to 2008 at St. Anna Hospital (Ferrara, Italy), using the Spearman non-parametric correlation index. Even though significant correlations were found among the variables, the overall results showed that the main factor influencing the severity of the adverse effects was the dosage of cisplatin administered.

High throughput gene expression analysis of the inner ear

The mouse auditory and vestibular epithelia consist of a complex array of many different cell types. Over the last decade microarrays were used to characterize gene expression in the inner ear. Studies were performed on wild type mice to identify deafness genes, transcriptional networks activated during development, or identify miRNA with a functional role in the ear. Other studies focused on the molecular response of the inner ear to stimuli ranging from ototoxic medications to hypergravity and caloric restriction. Finally, microarrays were used to identify transcriptional networks activated downstream of deafness genes. As template-free high throughput gene expression profiling methods such as RNA-seq are increasingly popular, we offer a critical review of the data generated over the last decade relating to microarrays for gene expression profiling of the inner ear. Moreover, as most of the published data is available through the gene expression omnibus (GEO), we demonstrate the feasibility of integrating data from independent experiments to reach novel insights.

The role of insulin-like growth factor-I in the physiopathology of hearing

Insulin-like growth factor-I (IGF-I) belongs to the family of polypeptides of insulin, which play a central role in embryonic development and adult nervous system homeostasis by endocrine, autocrine, and paracrine mechanisms. IGF-I is fundamental for the regulation of cochlear development, growth, and differentiation, and its mutations are associated with hearing loss in mice and men. Low levels of IGF-I have been shown to correlate with different human syndromes showing hearing loss and with presbyacusis. Animal models are fundamental to understand the genetic, epigenetic, and environmental factors that contribute to human hearing loss. In the mouse, IGF-I serum levels decrease with aging and there is a concomitant hearing loss and retinal degeneration. In the Igf1(-/-) null mouse, hearing loss is due to neuronal loss, poor innervation of the sensory hair cells, and age-related stria vascularis alterations. In the inner ear, IGF-I actions are mediated by intracellular signaling networks, RAF, AKT, and p38 MAPK protein kinases modulate the expression and activity of transcription factors, as AP1, MEF2, FoxM1, and FoxP3, leading to the regulation of cell cycle and metabolism. Therapy with rhIGF-I has been approved in humans for the treatment of poor linear growth and certain neurodegenerative diseases. This review will discuss these findings and their implications in new IGF-I-based treatments for the protection or repair of hearing loss.

Effects of L-ascorbic acid on two cycles of cisplatin-induced DNA double-strand breaks and phosphorylation of p53 in the liver

Cisplatin, a commonly used anticancer drug, was studied to investigate its effects on structure, DNA damage and p53 along with the possible protective effects of L-ascorbic acid in the liver. Adult male BALB/c mice were treated with 0, 10 mg/kg L-ascorbic acid and two cycles of cisplatin 1 mg/kg/2.5 mg/kg with or without L-ascorbic acid (17 days recovery period between the cycles) and the livers were collected at 72 h after the last exposure. Structural damage was analyzed in Masson's trichrome and Hortega's silver stained liver tissues. The DNA double-strand breaks with duplex 3' overhangs and 5' P-blunt ends were labeled by in situ oligo ligation by using hairpin oligonucleotide probes. The expression of p53 and phosphorylated p53 (p-p53) was detected by immunohistochemistry. Structural changes such as vacuolization of hepatocytes, pyknosis, infiltration of leukocytes and pericentral fibrosis were observed without any protection from L-ascorbic acid. The reticular fibrous framework was affected and the incidence of Kupffer cells was decreased. Cisplatin induced the DNA double-strand breaks (p<0.001); however, the latter appeared in a p53-independent, but p-p53-dependent manner. L-ascorbic acid showed significant protective effect on cisplatin-induced DNA damage (p<0.001). Cisplatin also enhanced p53 phosphorylation in a dose-dependent manner and L-ascorbic acid reduced this biochemical change only in 1 mg/kg group. In conclusion, cisplatin-induced structural changes are not, but the DNA damage and phosphorylation of p53 are, significantly, but not completely, alleviated by L-ascorbic acid.

Effects of NSAIDs on the Inner Ear: Possible Involvement in Cochlear Protection

Cyclooxygenase and lipoxygenase, two important enzymes involved in arachidonic acid metabolism, are major targets of non-steroidal anti-inflammatory drugs (NSAIDs). Recent investigations suggest that arachidonic cascades and their metabolites may be involved in maintaining inner ear functions. The excessive use of aspirin may cause tinnitus in humans and impairment of the outer hair cell functions in experimental animals. On the other hand, NSAIDs reportedly exhibit protective effects against various kinds of inner ear disorder. The present review summarizes the effects of NSAIDs on cochlear pathophysiology. NSAIDs are a useful ameliorative adjunct in the management of inner ear disorders.

MdmX is a substrate for the deubiquitinating enzyme USP2a

It has previously been shown that ubiquitin-specific protease 2a (USP2a) is a regulator of the Mdm2/p53 pathway. USP2a binds to Mdm2 and can deubiquitinate Mdm2 without reversing Mdm2-mediated p53 ubiquitination. Overexpression of USP2a causes accumulation of Mdm2 and promotes p53 degradation. We now show that MdmX is also a substrate for USP2a. MdmX associates with USP2a independently of Mdm2. Ectopic expression of wild-type USP2a but not a catalytic mutant prevents Mdm2-mediated degradation of MdmX. This correlates with the ability of wild-type USP2a to deubiquitinate MdmX. siRNA-mediated knockdown of USP2a in NTERA-2 testicular embryonal carcinoma cells and MCF7 breast cancer cells causes destabilization of MdmX and results in a decrease in MdmX protein levels, showing that endogenous USP2a participates in the regulation of MdmX stability. The therapeutic drug, cisplatin decreases MdmX protein expression. USP2a mRNA and protein levels were also reduced after cisplatin exposure. The magnitude and time course of USP2a downregulation suggests that the reduction in USP2a levels could contribute to the decrease in MdmX expression following treatment with cisplatin. Knockdown of USP2a increases the sensitivity of NTERA-2 cells to cisplatin, raising the possibility that suppression of USP2a in combination with cisplatin may be an approach for cancer therapy.

Analysis of cochlear protein profiles of Wistar, Sprague-Dawley, and Fischer 344 rats with normal hearing function

Differences in the expression of cochlear proteins are likely to affect the susceptibility of different animal models to specific types of auditory pathology. However, little is currently known about proteins that are abundantly expressed in inner ear. Identification of these proteins may facilitate the search for biomarkers of susceptibility and intervention targets. To begin to address this issue, we analyzed cochlear protein profiles of three strains of rats, Wistar, Sprague-Dawley, and Fischer 344, using a broad spectrum antibody microarray. Normal hearing function of the animals was ascertained using distortion product otoacoustic emissions (DPOAE). Of 725 proteins screened in whole cochlea, more than 80% were detected in all three strains. However, there were striking differences in the levels at which they occur. Among 213 proteins expressed at levels>or=2 fold of actin, only 7.5% were detected at these levels in all three strains. Myosin light chain kinase (MLCK) was immunolocalized in cuticular plate of outer hair cells (OHC) while mitogen activated protein (MAP) kinase-extracellular-signal regulated kinase1/2 (ERK1/2) was detected as foci in OHC, pillar cells, strial marginal cells, and fibroblasts of spiral ligament. A review of literature indicated that the expression of 7 (44%) of these 16 proteins were detected for the first time in the inner ear, although there were implications of the presence of some of these proteins. One of these abundant, but unstudied, proteins, MAP kinase activated protein kinase2 (MAPKAPK2), shows strong immunolabeling in pillar cells and inner hair cells (IHC). There was moderate MAPKAPK2 labeling in OHC, supporting cells, neurons, and marginal, intermediate, and basal cells. The current study provides the first, large cochlear protein profile of multiple rat strains. The diversity in expression of abundant proteins in these strains may contribute to differences in susceptibility of these strains to aging, noise, or ototoxic drugs.

The effects of the glucocorticoid receptor antagonist RU486 and phospholipase A2 inhibitor quinacrine on acoustic injury of the mouse cochlea

Glucocorticoids are used clinically for the treatment of acoustic injury. However, the protective mechanism of glucocorticoid in acoustic injury has not been completely clarified. Also, the effects of phospholipase A2 (PLA2) on acoustic injury have not been examined to the best of our knowledge. The purpose of the present study was to examine the effects of methylprednisolone, a glucocorticoid receptor inhibitor (RU486) and a phospholipase A2 inhibitor (quinacrine) on cochlear injury induced by acoustic overexposure. Seventy-eight mice were exposed to a 4kHz pure tone at 128dB SPL for 4h. The auditory brainstem response (ABR) was used to examine the hearing thresholds. Cochlear morphology was examined to estimate the outer hair cell loss induced by acoustic overexposure. Methylprednisolone and quinacrine significantly alleviated the hearing threshold shift and hair cell loss induced by acoustic overexposure. RU486 antagonized the protective effect of methylprednisolone. The present findings suggest firstly that glucocorticoids exert protective effects against acoustic injury; secondly, that the protective effect of methylprednisolone was exerted by binding glucocorticoid receptors, and finally that activation of PLA2 may be involved in acoustic injury.

Dose-dependant radiation-induced apoptosis in a cochlear cell-line

Cisplatin and gentamycin are both ototoxic and they have been shown to induce cochlear cell apoptosis. Although radiation is also ototoxic, radiation-induced apoptosis in cochlear cells has not been studied. This study aimed to investigate the biophysical changes of dose-related radiation-induced cochlear cell apoptosis in an experimental model. Post gamma-irradiation apoptosis was demonstrated in the cochlear cell-line OC-k3 by flow cytometry and TUNEL assay. This was dose-dependant with enhanced apoptosis resulting after 20 than 5 Gy, and occurred predominantly at 72 h post-irradiation. Microarray analysis showed associated dose-dependant apoptotic gene regulation changes. Western blotting revealed p53 up-regulation of at 72 h and phosphorylation at 3, 24, 48 and 72 h after irradiation. Early activation of c-jun occurred at 3 h, but was not sustained with time. Associated dose-dependant intracellular generation of reactive oxygen species (ROS) was also demonstrated using 2', 7'-dichlorofluorescein diacetate. In conclusion, this study demonstrated a dose-dependant cochlear cell apoptosis and associated ROS generation after irradiation, with p53 possibly playing a key role. Based on this ROS-linked apoptotic model, anti-oxidants and anti-apoptotic factors could potentially be used to prevent radiation-induced sensori-neural hearing loss. As these medications can be delivered topically through the middle ear, their systematic side effects could therefore be minimized.

Role of cytochrome P450 in phospholipase A2- and arachidonic acid-mediated cytotoxicity

Phospholipases A2 (PLA2) comprise a set of extracellular and intracellular enzymes that catalyze the hydrolysis of the sn-2 fatty acyl bond of phospholipids to yield fatty acids and lysophospholipids. The PLA2 reaction is the primary pathway through which arachidonic acid (AA) is released from phospholipids. PLA2s have an important role in cellular death that occurs via necrosis or apoptosis. Several reports support the hypothesis that unesterified arachidonic acid in cells is a signal for the induction of apoptosis. However, most of the biological effects of arachidonic acid are attributable to its metabolism by mainly three different groups of enzymes: cytochromes P450, cyclooxygenases, and lipoxygenases. In this review we will focus on the role of cytochrome P450 in AA metabolism and toxicity. The major pathways of arachidonic acid metabolism catalyzed by cytochrome P450 generate metabolites that are subdivided into two groups: the epoxyeicosatrienoic acids, formed by CYP epoxygenases, and the arachidonic acid derivatives that are hydroxylated at or near the omega-terminus by CYP omega-oxidases. In addition, autoxidation of AA by cytochrome P450-derived reactive oxygen species produces lipid hydroperoxides as primary oxidation products. In some cellular models of toxicity, cytochrome P450 activity exacerbates PLA2- and AA-dependent injury, mainly through the production of oxygen radicals that promote lipid peroxidation or production of metabolites that alter Ca2+ homeostasis. In contrast, in other situations, cytochrome P450 metabolism of AA is protective, mainly by lowering levels of unesterified AA and by production of metabolites that activate antiapoptotic pathways. Several lines of evidence point to the combined action of phospholipase A2 and cytochrome P450 as central in the mechanism of cellular injury in several human diseases, such as alcoholic liver disease and myocardial reperfusion injury. Inhibition of specific PLA2 and cytochrome P450 isoforms may represent novel therapeutic strategies against these diseases.