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Can gas replace protein function? CO abrogates the oxidative toxicity of myoglobin.

Sher EA, Sholto AY, Shaklai M, Shaklai N - PLoS ONE (2014)

Bottom Line: The main cause of LDL oxidation by Hb was found to be hemin which readily transfers from Hb to LDL.These reactions were fully arrested by CO.The data are interpreted to suit several circumstances, some physiological, such as high muscle activity, and some pathological, such as rhabdomyolysis, ischemia/reperfusion and skeletal muscle disuse atrophy.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.

ABSTRACT
Outside their cellular environments, hemoglobin (Hb) and myoglobin (Mb) are known to wreak oxidative damage. Using haptoglobin (Hp) and hemopexin (Hx) the body defends itself against cell-free Hb, yet mechanisms of protection against oxidative harm from Mb are unclear. Mb may be implicated in oxidative damage both within the myocyte and in circulation following rhabdomyolysis. Data from the literature correlate rhabdomyolysis with the induction of Heme Oxygenase-1 (HO-1), suggesting that either the enzyme or its reaction products are involved in oxidative protection. We hypothesized that carbon monoxide (CO), a product, might attenuate Mb damage, especially since CO is a specific ligand for heme iron. Low density lipoprotein (LDL) was chosen as a substrate in circulation and myosin (My) as a myocyte component. Using oxidation targets, LDL and My, the study compared the antioxidant potential of CO in Mb-mediated oxidation with the antioxidant potential of Hp in Hb-mediated oxidation. The main cause of LDL oxidation by Hb was found to be hemin which readily transfers from Hb to LDL. Hp prevented heme transfer by sequestering hemin within the Hp-Hb complex. Hemin barely transferred from Mb to LDL, and oxidation appeared to stem from heme iron redox in the intact Mb. My underwent oxidative crosslinking by Mb both in air and under N2. These reactions were fully arrested by CO. The data are interpreted to suit several circumstances, some physiological, such as high muscle activity, and some pathological, such as rhabdomyolysis, ischemia/reperfusion and skeletal muscle disuse atrophy. It appear that CO from HO-1 attenuates damage by temporarily binding to deoxy-Mb, until free oxygen exchanges with CO to restore the equilibrium.

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Related in: MedlinePlus

Hp attenuates heme loss while allowing oxidation of ferrous Hb.Spectrum of OxyHb (5 µM) was recorded. H2O2 (to yield 6 µM) was added and the mixture was incubated in 37°C and the spectrum recorded again. Experiment was repeated in presence of Hp1-1 (6 µM) 1: time zero (with or without Hp); 2: following 30 min in absence of Hp; 3: following 30 min in presence of Hp. Representative spectra of 3 independent experiments are shown.
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pone-0104075-g001: Hp attenuates heme loss while allowing oxidation of ferrous Hb.Spectrum of OxyHb (5 µM) was recorded. H2O2 (to yield 6 µM) was added and the mixture was incubated in 37°C and the spectrum recorded again. Experiment was repeated in presence of Hp1-1 (6 µM) 1: time zero (with or without Hp); 2: following 30 min in absence of Hp; 3: following 30 min in presence of Hp. Representative spectra of 3 independent experiments are shown.

Mentions: As seen from the spectra (Fig. 1), H2O2 oxidized oxyHb to ferric-Hb, as indicated by a shift in the Soret peak from 414 nm to 405 nm [2]. Hp thus did not prevent ferrous to ferric iron oxidation. These findings are in correlation with previous studies carried out in air and high peroxide conditions [39]. In the two cases where the heme iron was oxidized (spectra 2 and 3), since the extinction coefficient of ferric-Hb is 1.43 times higher than that of oxyHb [2], if all the oxyHb were to undergo oxidation to ferric state, we would expect the peak to be higher. However, as seen from the spectra, some of the expected absorbance was lost, indicating that a portion of heme disintegrated. Nevertheless, the Soret peak formed in the presence of Hp (spectrum 3) is higher than the one formed in its absence (spectrum 2). This implies that the heme moiety was partially shielded from oxidative disintegration by the bound Hp, in agreement with previous data [12], [33].


Can gas replace protein function? CO abrogates the oxidative toxicity of myoglobin.

Sher EA, Sholto AY, Shaklai M, Shaklai N - PLoS ONE (2014)

Hp attenuates heme loss while allowing oxidation of ferrous Hb.Spectrum of OxyHb (5 µM) was recorded. H2O2 (to yield 6 µM) was added and the mixture was incubated in 37°C and the spectrum recorded again. Experiment was repeated in presence of Hp1-1 (6 µM) 1: time zero (with or without Hp); 2: following 30 min in absence of Hp; 3: following 30 min in presence of Hp. Representative spectra of 3 independent experiments are shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128816&req=5

pone-0104075-g001: Hp attenuates heme loss while allowing oxidation of ferrous Hb.Spectrum of OxyHb (5 µM) was recorded. H2O2 (to yield 6 µM) was added and the mixture was incubated in 37°C and the spectrum recorded again. Experiment was repeated in presence of Hp1-1 (6 µM) 1: time zero (with or without Hp); 2: following 30 min in absence of Hp; 3: following 30 min in presence of Hp. Representative spectra of 3 independent experiments are shown.
Mentions: As seen from the spectra (Fig. 1), H2O2 oxidized oxyHb to ferric-Hb, as indicated by a shift in the Soret peak from 414 nm to 405 nm [2]. Hp thus did not prevent ferrous to ferric iron oxidation. These findings are in correlation with previous studies carried out in air and high peroxide conditions [39]. In the two cases where the heme iron was oxidized (spectra 2 and 3), since the extinction coefficient of ferric-Hb is 1.43 times higher than that of oxyHb [2], if all the oxyHb were to undergo oxidation to ferric state, we would expect the peak to be higher. However, as seen from the spectra, some of the expected absorbance was lost, indicating that a portion of heme disintegrated. Nevertheless, the Soret peak formed in the presence of Hp (spectrum 3) is higher than the one formed in its absence (spectrum 2). This implies that the heme moiety was partially shielded from oxidative disintegration by the bound Hp, in agreement with previous data [12], [33].

Bottom Line: The main cause of LDL oxidation by Hb was found to be hemin which readily transfers from Hb to LDL.These reactions were fully arrested by CO.The data are interpreted to suit several circumstances, some physiological, such as high muscle activity, and some pathological, such as rhabdomyolysis, ischemia/reperfusion and skeletal muscle disuse atrophy.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.

ABSTRACT
Outside their cellular environments, hemoglobin (Hb) and myoglobin (Mb) are known to wreak oxidative damage. Using haptoglobin (Hp) and hemopexin (Hx) the body defends itself against cell-free Hb, yet mechanisms of protection against oxidative harm from Mb are unclear. Mb may be implicated in oxidative damage both within the myocyte and in circulation following rhabdomyolysis. Data from the literature correlate rhabdomyolysis with the induction of Heme Oxygenase-1 (HO-1), suggesting that either the enzyme or its reaction products are involved in oxidative protection. We hypothesized that carbon monoxide (CO), a product, might attenuate Mb damage, especially since CO is a specific ligand for heme iron. Low density lipoprotein (LDL) was chosen as a substrate in circulation and myosin (My) as a myocyte component. Using oxidation targets, LDL and My, the study compared the antioxidant potential of CO in Mb-mediated oxidation with the antioxidant potential of Hp in Hb-mediated oxidation. The main cause of LDL oxidation by Hb was found to be hemin which readily transfers from Hb to LDL. Hp prevented heme transfer by sequestering hemin within the Hp-Hb complex. Hemin barely transferred from Mb to LDL, and oxidation appeared to stem from heme iron redox in the intact Mb. My underwent oxidative crosslinking by Mb both in air and under N2. These reactions were fully arrested by CO. The data are interpreted to suit several circumstances, some physiological, such as high muscle activity, and some pathological, such as rhabdomyolysis, ischemia/reperfusion and skeletal muscle disuse atrophy. It appear that CO from HO-1 attenuates damage by temporarily binding to deoxy-Mb, until free oxygen exchanges with CO to restore the equilibrium.

Show MeSH
Related in: MedlinePlus