Abstract
BackgroundCarbon monoxide (CO) poisoning is the leading cause of poisoning mortality and morbidity in the USA. Carboxyhemoglobin (COHb) levels are not predictive of severity or prognosis. At this time, the measurement of mitochondrial respiration may serve as a biomarker in CO poisoning. The primary objective of this study was to assess changes in mitochondrial function consisting of respiration and generation of reactive oxygen species (ROS) in peripheral blood mononuclear cells (PBMCs) obtained from patients with CO poisoning.MethodsPBMCs from patients having confirmed CO exposure treated with hyperbaric oxygen or HBO (CO group) and healthy controls (control group) were analyzed with high-resolution respirometry. PBMCs were placed in a 2-ml chamber at a final concentration of 3–4 × 106 cells/ml to simultaneously obtain both respiration and hydrogen peroxide (H2O2) production. In the CO group, we performed measurements before and after patients underwent their first HBO treatment.ResultsWe enrolled a total of 17 subjects, including 7 subjects with confirmed CO poisoning and 10 subjects in the control group. The CO group included five (71.4%) men and two (28.6%) women having a median COHb of 28%. There was a significant decrease in respiration as measured in pmol O2 × s− 1 × 10− 6 PBMCs in the CO group (pre-HBO) when compared to the control group: maximal respiration (18.4 ± 2.4 versus 35.4 ± 2.8, P < 0.001); uncoupled Complex I respiration (19.8 ± 1.8 versus 41.1 ± 3.8, P < 0.001); uncoupled Complex I + II respiration (32.3 ± 3.2 versus 58.3 ± 3.1, P < 0.001); Complex IV respiration (43.5 ± 2.9 versus 63.6 ± 6.31, P < 0.05). There were also similar differences measured in the CO group before and after HBO treatment with an overall increase in respiration present after treatment. We also determined the rate of H2O2 production simultaneously with the measurement of respiration. There was an overall significant increase in the H2O2 production in the CO group after HBO treatment when compared to prior HBO treatment and the control group.ConclusionsIn this study, PBMCs obtained from subjects with CO poisoning have an overall decrease in respiration (similar H2O2 production) when compared to controls. The inhibition of Complex IV respiration is from CO binding leading to a downstream decrease in respiration at other complexes. PBMCs obtained from CO-poisoned individuals immediately following initial HBO therapy displayed an overall increase in both respiration and H2O2 production. The study findings demonstrate that treatment with HBO resulted in improved cellular respiration but a higher H2O2 production. It is unclear if the increased production of H2O2 in HBO treatment is detrimental.
Highlights
Carbon monoxide (CO) poisoning is the leading cause of poisoning mortality and morbidity in the USA
The study findings demonstrate that treatment with hyperbaric oxygen (HBO) resulted in improved cellular respiration but a higher Hydrogen peroxide—one of several reactive oxygen intermediates (H2O2) production
It is unclear if the increased production of H2O2 in HBO treatment is detrimental
Summary
Carbon monoxide (CO) poisoning is the leading cause of poisoning mortality and morbidity in the USA. Carboxyhemoglobin (COHb) levels are not predictive of severity or prognosis At this time, the measurement of mitochondrial respiration may serve as a biomarker in CO poisoning. Carbon monoxide (CO) is a colorless and odorless gas that is an important cause of poisoning mortality and morbidity in the USA with approximately 15,000 intentional cases annually accounting for over two thirds of reported death. Death from CO poisoning has been reported to be between 1000 to 2000 in some years with over 50,000 CO cases seen in emergency departments in the USA annually, with approximately 10–15% requiring hospitalization [1, 2]. The standard treatment for CO poisoning recommended by the Undersea & Hyperbaric Medical Society is hyperbaric oxygen (HBO) therapy to decrease half-life and to prevent lipid peroxidation. There is a clear need for a better understanding of the interaction of HBO and mitochondrial bioenergetic function in the face of CO poisoning
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