The time-dependent protective effect of hyperbaric oxygen on neuronal cell apoptosis in carbon monoxide poisoning

Introduction: The progressive clinical course with delayed neurological damage in carbon monoxide (CO) poisoning may be due to neuron apoptosis. The usefulness of hyperbaric oxygen (HBO) in different time periods after CO exposure in neuronal cell apoptosis reduction has not been evaluated thus far. The aim was to evaluate HBO efficacy in reducing neuronal apoptosis in different time periods after CO exposure. Methods: Wistar rats were exposed to 3000 ppm CO in air for 60 min and 100% oxygen at a pressure of three bar for 30 min 0-12 h after CO exposure. The apoptosis was evaluated by immunohistochemical analysis with antibodies against activated caspase-3 and the percentage of caspase-3 positive hippocampal ganglionic cells was reported. Results: It was shown that CO poisoning results in ganglionic cell apoptosis. The percentage of apoptotic cells in rats exposed to CO was the highest (32%), whereas the percentage of apoptotic cells in rats exposed to HBO 0 and 1 h after CO was similar with a lower percentage than rats exposed to CO. The percentage of apoptotic cells in rats exposed to HBO 3 and 5 h after CO was similar with a lower percentage than rats exposed to HBO 0 and 1 h after CO. The percentage of apoptotic cells in rats exposed to HBO 7-12 h after CO was similar with a higher percentage than rats exposed to HBO 5 h after CO. Conclusion: HBO has a time-dependent protective effect on CO-induced neuron apoptosis with the highest efficiency at 3 and 5 h after CO poisoning.