Protective effect of rasagiline in aminoglycoside ototoxicity.

Sensorineural hearing losses (SNHLs; e.g., ototoxicant- and noise-induced hearing loss or presbycusis) are among the most frequent sensory deficits, but they lack effective drug therapies. The majority of recent therapeutic approaches focused on the trials of antioxidants and reactive oxygen species (ROS) scavengers in SNHLs. The rationale for these studies was the prominent role of disturbed redox homeostasis and the consequent ROS elevation. Although the antioxidant therapies in several animal studies seemed to be promising, clinical trials have failed to fulfill expectations. We investigated the potential of rasagiline, an FDA-approved monomanine oxidase type B inhibitor (MAO-B) inhibitor type anti-parkinsonian drug, as an otoprotectant. We showed a dose-dependent alleviation of the kanamycin-induced threshold shifts measured by auditory brainstem response (ABR) in an ototoxicant aminoglycoside antibiotic-based hearing loss model in mice. This effect proved to be statistically significant at a 6-mg/kg (s.c.) dose. The most prominent effect appeared at 16kHz, which is the hearing sensitivity optimum for mice. The neuroprotective, antiapoptotic and antioxidant effects of rasagiline in animal models, all targeting a specific mechanism of aminoglycoside injury, may explain this otoprotection. The dopaminergic neurotransmission enhancer effect of rasagiline might also contribute to the protection. Dopamine (DA), released from lateral olivocochlear (LOC) fibers, was shown to exert a protective action against excitotoxicity, a pathological factor in the aminoglycoside-induced SNHL. We have shown that rasagiline enhanced the electric stimulation-evoked release of DA from an acute mouse cochlea preparation in a dose-dependent manner. Using inhibitors of voltage-gated Na(+)-, Ca(2+) channels and DA transporters, we revealed that rasagiline potentiated the action potential-evoked release of DA by inhibiting the reuptake. The complex, multifactorial pathomechanism of SNHLs most likely requires drugs acting on multiple targets for effective therapy. Rasagiline, with its multi-target action and favorable adverse effects profile, might be a good candidate for a clinical trial testing the otoprotective indication.

Vitrification of bovine blastocysts pretreated with sublethal hydrostatic pressure stress: evaluation of post-thaw in vitro development and gene expression.

Sublethal stress treatment has been reported to enhance gametes' performance in subsequent procedures, such as cryopreservation. The aim of the present study was to evaluate the effect of different equilibration times between the termination of a sublethal hydrostatic pressure (HP) stress treatment and the initiation of vitrification on the post-thaw survival, continued in vitro development, hatching rate and gene expression of selected candidate genes of in vitro-produced (IVP) expanded bovine blastocysts. Day 7 IVP blastocysts were subjected to 600 bar pressure for 60 min at 32°C. Immediately after pressure treatment (HP0h) or after 1 or 2h incubation (HP1h and HP2h groups, respectively), embryos were either vitrified and warmed using the open pulled straw method, followed by 72 h in vitro culture or were stored at -80°C until gene expression analysis. Re-expansion and hatching rates after vitrification-warming were significantly (P<0.05) higher in the HP0h (88 and 76%, respectively) and HP1h (90 and 75%, respectively) groups than in the untreated (82 and 63%, respectively) and HP2h groups (79 and 70%, respectively). Moreover, the HP1h group showed further improvement in the speed of re-expansion and resumption of normal in vitro development. Cumulative analysis of all genes (SC4MOL, HSP1A1A, SOD2 and GPX4) revealed a similar pattern of expression, with a tendency for peak transcript abundance 1h after HP treatment. Application of HP stress treatment was found to be efficient in increasing the in vitro developmental competence of vitrified bovine embryos.

Increased stress tolerance of matured pig oocytes after high hydrostatic pressure treatment.

The present paper describes a method which uses high hydrostatic pressure as a pre-treatment to in vitro matured porcine oocytes to improve their survival rates in the subsequent processes including cryopreservation, parthenogenetic activation and embryo culture. In Experiment I oocytes were treated with different pressure impulses in the range of 20-80 MPa (200-800 times greater than atmospheric pressure) for 30-120 min at 24 degrees C. For parthenogenetic activation a single dc of 12.5 kV/cm was used, to test shock tolerance of the treated vs. control oocytes and also compare their developmental competence evaluated with continued in vitro development. The upper limit of pressure tolerance was found in the 40 MPa range. In Experiment II oocytes pre-treated with pressures in the 20-40 MPa range were vitrified with the Cryotop method, and parthenogenetically activated subsequently with combined electric (single dc of 1.25 kV/cm) and chemical treatment after warming. According to our investigations performed with a total of 1980 oocytes and 3-5 replicates, pressure treatment increased cleavage and blastocyst rates after activation and cleavage rates after vitrification followed by activation. Our results indicate that the sublethal pressure treatment may induce specific responses in oocytes increasing their resistance and developmental competence. The mechanism that may lie behind the observations is the sublethal stress-induced post-transcriptional activation of shock proteins in the oocytes. Further investigations are needed to reveal the biophysical and molecular biological background of the findings and to optimize the protocol of pressure pre-treatment in both animal- and human-assisted reproductive technology (ART) to increase the efficiency of in vitro procedures.

Changes in some red blood cell and clinical laboratory parameters in young and old Beagle dogs.

Routine laboratory and lipid peroxidase parameters in the blood of Beagle dogs under 1 year of age (7 males, 7 females) and over 9 years of age (7 males, 7 females) were compared. The mean corpuscular haemoglobin (MCH) and haemoglobin (Hb) values, plasma total protein (TP) and globulin concentrations in the older dogs were significantly higher than in the younger ones by 13%, 6%, 10% and 15%, respectively. The plasma inorganic phosphate concentration, however, was 30% lower in the older dogs than in the young ones. The concentration of malondialdehyde (MDA) was 30% higher, while the glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities were around twice as high in the older dogs as in the young ones. However, in the older males the concentration of reduced glutathione (GSH) was 43% and in the older females 9% less than in the young ones. Extremely high levels of MDA and low levels of GSH were only found in the older males. GSH-Px and SOD activities were significantly higher in the older male dogs than in the young ones. The activities of these enzymes were highest in the older females. From our results, we suspect that old dogs, especially males, are particularly exposed to the harmful effects of free radicals and lipid peroxidation.