A neuroglobin-based high-affinity ligand trap reverses carbon monoxide–induced mitochondrial poisoning

Abstract

Carbon monoxide (CO) remains the most common cause of human poisoning. The consequences of CO poisoning include cardiac dysfunction, brain injury, and death. CO causes toxicity by binding to hemoglobin and by inhibiting mitochondrial cytochrome c oxidase (CcO), thereby decreasing oxygen delivery and inhibiting oxidative phosphorylation. We have recently developed a CO antidote based on human neuroglobin (Ngb-H64Q-CCC). This molecule enhances clearance of CO from red blood cells in vitro and in vivo. Herein, we tested whether Ngb-H64Q-CCC can also scavenge CO from CcO and attenuate CO-induced inhibition of mitochondrial respiration. Heart tissue from mice exposed to 3% CO exhibited a 42 ± 19% reduction in tissue respiration rate and a 33 ± 38% reduction in CcO activity compared with unexposed mice. Intravenous infusion of Ngb-H64Q-CCC restored respiration rates to that of control mice correlating with higher electron transport chain CcO activity in Ngb-H64Q-CCC–treated compared with PBS-treated, CO-poisoned mice. Further, using a Clark-type oxygen electrode, we measured isolated rat liver mitochondrial respiration in the presence and absence of saturating solutions of CO (160 μm) and nitric oxide (100 μm). Both CO and NO inhibited respiration, and treatment with Ngb-H64Q-CCC (100 and 50 μm, respectively) significantly reversed this inhibition. These results suggest that Ngb-H64Q-CCC mitigates CO toxicity by scavenging CO from carboxyhemoglobin, improving systemic oxygen delivery and reversing the inhibitory effects of CO on mitochondria. We conclude that Ngb-H64Q-CCC or other CO scavengers demonstrate potential as antidotes that reverse the clinical and molecular effects of CO poisoning.

Sensitive quantification of carbon monoxide in vivo reveals a protective role of circulating hemoglobin in CO intoxication

“…Thus, in the last part of our study we tested the potential use of hemoCD1 as an antidote for CO intoxication considering that O 2 ventilation is the only method practically used as a therapy. Recently, a neuroglobin mutant (Ngb-H64Q-CCC) 63 , 68 , which showed much higher CO binding affinity than Hb and hemoCD1 (Table 2 ), has been proposed as an injectable type of CO antidote. Our data demonstrate that i.v.…”

Lessons from the post-genomic era: Globin diversity beyond oxygen binding and transport

“…These studies collectively illustrate that the cancer-related regulation of Ngb represents a yet-to-be-determined complex pathway, involving histological, hypoxic and epigenetic aspects, revealing Ngb to be an intriguing potential target for the development of anticancer therapies. Most recently, an additional unexpected therapeutical role of Ngb was described based on its potential function as an antidote for CO poisoning [ 256 , 257 ].…”

Carbon Monoxide Poisoning in Kuwait: A Five-Year, Retrospective, Epidemiological Study

“…Upon binding, CO displaces O 2 from Hb, thereby reducing the oxygen-carrying capacity of the erythrocytes, resulting in hypoxia. Thus, tissues and organs with a high demand for oxygen, including the brain and heart, are affected negatively due to an inadequate oxygen supply [16]; this is the primary mechanism of CO toxicity [2]. Similarly, CO decreases O 2 storage in muscle cells by binding to and displacing O 2 from the heme groups of myoglobin [5].…”