Pantothenic acid and coenzyme A in experimental cisplatin-induced ototoxia

Specific antioxidant compounds differentially modulate cytotoxic activity of doxorubicin and cisplatin: in vitro and in vivo study

Aim

To use the antioxidant compounds (sodium selenite, selenomethionine, D-pantethine) for modulation of cytotoxic effect of doxorubicin and cisplatin toward wild type and drug-resistant mutants of several human tumor cells. Similar treatments were applied in vivo toward adult male Wistar rats.

Methods

Human tumor cells of different lines (HCT-116, Jurkat and HL-60) with various mechanisms of drug-resistance were treated with doxorubicin or cisplatin, alone or in combination with sodium selenite, selenomethionine, or D-pantethine. Cell viability, induction of apoptosis, and production of O₂^- radicals were measured. Activity of redox potential modulating enzymes was measured in the liver and blood plasma of adult male Wistar rats subjected to similar treatments.

Results

All antioxidants used in physiologically harmless concentration inhibited cytotoxic action of doxorubicin toward tumor cells sensitive to chemotherapy treatment by 15%-30%, and slightly enhanced cytotoxic effect of this medicine toward drug-resistant malignant cells. At the same time, there was no significant effect of these antioxidants on cisplatin action. Such effects were accompanied by a complete inhibition of production of superoxide radicals induced by doxorubicin. The results of in vivo study in adult male Wistar rats were in agreement with the results of in vitro study of human tumor cells.

Conclusion

Protective effect of specific antioxidant agents during cytotoxic action of doxorubicin was demonstrated in vitro in drug-sensitive human tumor cells and in adult male Wistar rats, while there was no protective effect in drug-resistant sub-lines of these tumor cells during action of doxorubicin and cisplatin.

The protective role of tiopronin in cisplatin ototoxicity in Wistar rats

The purpose of this study was to evaluate cisplatin-induced ototoxicity and the protective effects of tiopronin. Twenty-four adult Wistar rats served as subjects and were divided into three groups. Eight rats receiving only saline (group A) were used as controls. Eight rats received cisplatin (2 mg/kg) injections (group B) and eight rats received cisplatin and tiopronin (300 mg/kg) (group C) for 8 consecutive days. Both ears of all animals were tested by DPOAE before treatment and on the 4th and 9th days. Seventy-two hours after the final recording session, all animals were killed, and the left cochleas were prepared for electron microscopy and analysed. DPOAE responses were significantly reduced in group B compared to controls (p<0.05). When tiopronin was added, DPOAE responses were significantly increased compared to those obtained with the administration of cisplatin alone (p<0.05). The cochleogram showed that tiopronin had a significant protective effect in the basal half and in the lower half of the middle turn. We conclude that tiopronin, a drug effective in protecting against cisplatin nephrotoxicity, is also effective in protecting against cisplatin ototoxicity.

Ototoxicity and noise trauma: electron transfer, reactive oxygen species, cell signaling, electrical effects, and protection by antioxidants: practical medical aspects

Ototoxins are substances of various structures and classes. This review provides extensive evidence for involvement of electron transfer (ET), reactive oxygen species (ROS) and oxidative stress (OS) as a unifying theme. Successful application is made to the large majority of ototoxins, as well as noise trauma. We believe it is not coincidental that these toxins generally incorporate ET functionalities (quinone, metal complex, ArNO(2), or conjugated iminium) either per se or in metabolites, potentially giving rise to ROS by redox cycling. Some categories, e.g., peroxides and noise, appear to operate via non-ET routes in generating OS. These highly reactive entities can then inflict injury via OS upon various constituents of the ear apparatus. The theoretical framework is supported by the extensive literature on beneficial effects of antioxidants, both for toxins and noise. Involvement of cell signaling and electrical effects are discussed. This review is the first comprehensive one based on a unified mechanistic approach. Various practical medical aspects are also addressed. There is extensive documentation for beneficial effects of antioxidants whose use might be recommended clinically for prevention of ototoxicity and noise trauma. Recent research indicates that catalytic antioxidants may be more effective. In addition to ototoxicity, a widespread problem consists of ear infections by bacteria which are demonstrating increasing resistance to conventional therapies. A recent, novel approach to improved drugs involves use of agents which inhibit quorum sensors that play important roles in bacterial functioning. Prevention of ear injury by noise trauma is also discussed, along with ear therapeutics.

Effects of Piracetam Supplementation on Cochlear Damage Occuring in Guinea Pigs Exposed to Irradiation

In this study we aimed to determine the role of piracetam (PIR) in preventing radiation induced cochlear damage after total-cranium irradiation (radiotherapy; RT). Male albino guinea pigs used in the study were randomly divided into three groups. Group 1 (Control group) (n=11) received neither PIR nor irradiation, but received saline solution intraperitoneally (i.p.) and received sham irradiation. Group 2 (RT group) (n=32) was exposed to total cranium irradiation of 33 Gy in 5 fractions of 6.6 Gy/d for five successive days, with a calculated (alpha/beta=3.5) biological effective dose of fractionated irradiation equal to 60 Gy conventional fractionation, then received saline solution for five successive days i.p. Group 3 (PIR+RT group) (n=33) received total cranium irradiation, plus 350 mg/kg per day PIR for five successive days i.p. After the last dose of RT, the guinea pigs were all sacrificed at the 4th, 24th and 96th hours, respectively. Their cochleas were enucleated for histopathologic examination. It was observed that total cranium irradiation (RT group) promoted degeneration in stria vascularis (SV), spiral ganglion cells (SG), outer hair cells (OHC) and inner hair cell (IHC) of cochleas at these times (p<0.05). While in the PIR+RT group, there was no statistically significant difference on radiation-induced cochlear degeneration in SV and OHC at 4th (p>0.05) and IHC at 4th, 24th hours (p>0.05), there was a significant difference on radiation-induced cochlear degeneration in SV and OHC at 24th and 96th hours (p<0.05), IHC at 96th hour (p<0.05) and SG at 4th, 24th and 96th hours (p<0.05). There was no any cochlear degeneration in the control group. Piracetam might reduce radiation-induced cochlear damage in the guinea pig. These results are pioneer to studies that will be performed with PIR for radiation toxicity protection.

[Cochlear cytotoxic activity of cisplatin in experimentation animals. A study using scanning electron microscopy]

Cisplatin is an antitumoral agent commonly used in the treatment of different solid tumors. Its use induces adverse effects like oto- and nephrotoxicity due to acute renal failure. This makes it a suitable drug when creating an experimental model of ototoxicity. Our aim is to study the cellular lesions induced in the cochlea of the rat and the guinea pig by variable doses of cisplatin injected intraperitoneally, after short, middle, and long term survival, by means of scanning electronic microscopy. Results show the global effect of the cells of the organ of Corti with a more intense initial damage of the supporting cells, continuing with the late effect of the sensorial cells.

[Vestibular and oculomotor changes in subjects treated with cisplatin]

Cisplatin is an agent used in the treatment of distinct oncologic diseases. We present the electrooculographic (EOG) findings of 6 patients which were seen at our Department under the diagnosis of chronic toxicity for cisplatin and associated vestibular alterations. Mean of age was 45 years. Three subjects were female (50%). The most frequent pathologic finding was ataxic pursuit tracking (100%). Additionally, spontaneous nystagmus, alterations in positional test, and vestibulo-ocular reflex suppression were also found. These results are discussed and the main literature concerning this matter is reviewed.

TEOAE monitoring of Cisplatin induced ototoxicity in guinea pigs: the protective effect of vitamin B treatment

OBJECTIVE

To evaluate Cisplatin (CP) induced ototoxicity and the effects of vitamin B treatment on ototoxicity in guinea pigs by using the Transient Evoked Otoacoustic Emission (TEOAE) technique.

METHODS

Eleven guinea pigs were divided into two groups and they were tested by TEOAE before and after the experiment. A TEOAE response was regarded as positive when all of the following criteria were met: 1. The mean amplitude of the cochlear response in dB pe SPL should be greater than that of the noise in the external auditory canal; 2. The reproducibility rate of the response should be greater than 50%; 3. The stimulus stability rate should be greater than 65%; 4. The signal to noise ratio of the response in 1, 2, 3, 4 and 5 kHz band frequencies should be greater than 3 dB pe SPL in at least two bands. The first group included five animals that had only CP injections. Six animals in the second group received additional 0.2 ml/kg combined vitamin B preparations for 7 consecutive days. Thereafter, the right and left ears of all animals in both groups were tested by TEOAE.

RESULTS

TEOAE responses recorded from 22 ears of 11 guinea pigs before drug administrations showed that the responses with maximum amplitude were originated from the mid-frequency region. Positive TEOAE responses were significantly reduced after CP administrations in both groups when compared with their respective pretreatment results (P<0.01). However, vitamin B injections, in addition to a single large dose of CP, resulted in significantly better TEOAE responses than those obtained after only CP injections (P<0.05).

CONCLUSIONS

The routine use of TEOAE monitoring is recommended in clinical CP treatment protocols for the early detection and follow up of ototoxicity. Also, prospective clinical trials are needed in order to validate the protective effects of vitamin B treatment against ototoxicity.

Histological effects of co-administration of an ACTH((4-9)) analogue, ORG 2766, on cisplatin ototoxicity in the albino guinea pig

Cisplatin is one of the most potent antineoplastic drugs presently known, but its therapeutic efficacy is seriously limited by several side effects such as ototoxicity. Several compounds that are known for their nephroprotective effects also seem to reduce the incidence and severity of cisplatin-induced ototoxicity. Hamers et al. (1994) and De Groot et al. (1997) investigated the possibly protective effect of concomitant administration of the ACTH((4-9)) analogue ORG 2766 upon cisplatin ototoxicity in guinea pigs. Animals were treated with cisplatin at a daily dose of 2.0 mg/kg for 8 consecutive days and ORG 2766 at a daily dose of 75 mcg/kg for 9 days. Concomitant administration of cisplatin plus ORG 2766 resulted in a bimodal distribution of the electrophysiological data (compound action potential and cochlear microphonics amplitudes) and the histological data (outer hair cell (OHC) counts). It was surmised that this dichotomy might occur at a certain cisplatin dose. We investigated whether this protective effect of ORG 2766 could be enhanced by reducing the daily dose of cisplatin while maintaining the same dose of ORG 2766. Thirty-six animals were treated with daily i.p. injections of cisplatin at a dose of 1.0 mg/kg (n=18) or 1.5 mg/kg (n=18) for 8 consecutive days. When comparing the mean OHC counts of the different experimental groups, treatment with cisplatin at a daily dose of 1.5 mg/kg for 8 consecutive days resulted in a considerable loss of OHCs, which was significantly reduced after co-administration of ORG 2766. Co-treatment with ORG 2766 did not result in a change in the volume of the scala media. The present results are in agreement with the electrophysiological results published earlier (Stengs et al., 1998b).