טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMullokandov Michael
SubjectInvestigation of Mitochondrial Function in CNS Oxygen
Toxicity by Means of Repeated Exposure to
Non-Convulsive Hyperbaric Oxygen and
Following Administration of
DepartmentDepartment of Medicine
Supervisors Professor Emeritus Moshe Gavish
Dr. Yehuda Arieli
Full Thesis textFull thesis text - English Version


Abstract

Background: We have previously shown that hyperbaric oxygen preconditioning (HBO-PC) results in increased latency to CNS-oxygen toxicity (CNS-OT), associated with alterations in the activity of hippocampal ROS scavenger enzymes. In the present study, we examined the effect of HBO-PC on isolated mitochondrial function. Additionally we have tested the effect of PK 11195 the specific ligand of 18 kDa traslocator protein (TSPO) on CNS-OT. Methods: Male Sprague-Dawley rats were divided into six groups. The animals of untreated control group (UC) were not exposed to hyperbaric oxygen (HBO). Another group of animals was exposed to HBO at 6 ATA until the appearance of grand mal convulsions (6 ATA). Two groups of rats were preconditioned to HBO by three 1-hour exposures to pure oxygen at 2 ATA, one session every other day. At the end of the preconditioning process, one of these groups (Prec 6 ATA) was exposed to HBO at 6 ATA. The second group (Prec) was not exposed further to HBO. The last two groups were rats administered whether with DMSO or PK 11195 and exposed to HBO at 6 ATA (DMSO 6 ATA and PK 11195 6 ATA respectively). Samples were extracted from the frontal cortex and hippocampus of the animals in all six groups to evaluate mitochondrial membrane potential and to assess ATP production. Grp75 and TSPO levels were evaluated by Western blot. Results: The HBO-PC as applied in this study had no effect on latency to CNS-OT. On the other hand the administration of PK 11195 (15 mg/kg) increased the latency to CNS-OT (p<0.05). The mitochondrial membrane potential in the hippocampus was increased following exposure to HBO at 6 ATA (p<0.05), representing a hyperpolarized state of the mitochondria. The same hyperpolarization was observed in the HBO-PC group that wasn’t exposed to HBO at 6 ATA (Prec). In addition, membrane potential in the Prec 6 ATA and PK 11195 6 ATA groups was slightly reduced when compared with their control groups.  ATP production was highest in the cortex of the preconditioned rats; however, following HBO exposure it decreased in the preconditioned rats and increased in the rats exposed to 6 ATA. No significant change in ATP production was found in the hippocampus of HBO-PC groups. The PK 11195 had a trend of inhibitory effect on ATP production in hippocampus as well in the cortex.  Measurements of the stress-induced chaperone Grp75 showed decreased levels in the hippocampus in the Prec 6 ATA group (p<0.05). The PK 11195 administration resulted in reduction of TSPO levels both in hippocampus and cortex (p<0.05). Conclusions: We observed that mitochondrial parameters such as ATP production in cortex, mitochondrial membrane potential in the hippocampus and mitochondrial Grp75 levels following HBO preconditioning were altered. Administration of PK 11195 to rats had an effect on latency to CNS-OT as well as on mitochondrial function in rats’ brain.