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Chronic sustained hypoxia-induced redox remodeling causes contractile dysfunction in mouse sternohyoid muscle.

Lewis P, Sheehan D, Soares R, Varela Coelho A, O'Halloran KD - Front Physiol (2015)

Bottom Line: There was no change in redox-sensitive proteasome activity or HIF-1α content, but CH decreased phospho-JNK content independent of antioxidant supplementation.We conclude that CH causes upper airway dilator muscle dysfunction due to redox modulation of proteins key to function and homeostasis.Such changes could serve to further disrupt respiratory homeostasis in diseases characterized by CH such as chronic obstructive pulmonary disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, School of Medicine, University College Cork Cork, Ireland.

ABSTRACT
Chronic sustained hypoxia (CH) induces structural and functional adaptations in respiratory muscles of animal models, however the underlying molecular mechanisms are unclear. This study explores the putative role of CH-induced redox remodeling in a translational mouse model, with a focus on the sternohyoid-a representative upper airway dilator muscle involved in the control of pharyngeal airway caliber. We hypothesized that exposure to CH induces redox disturbance in mouse sternohyoid muscle in a time-dependent manner affecting metabolic capacity and contractile performance. C57Bl6/J mice were exposed to normoxia or normobaric CH (FiO2 = 0.1) for 1, 3, or 6 weeks. A second cohort of animals was exposed to CH for 6 weeks with and without antioxidant supplementation (tempol or N-acetyl cysteine in the drinking water). Following CH exposure, we performed 2D redox proteomics with mass spectrometry, metabolic enzyme activity assays, and cell-signaling assays. Additionally, we assessed isotonic contractile and endurance properties ex vivo. Temporal changes in protein oxidation and glycolytic enzyme activities were observed. Redox modulation of sternohyoid muscle proteins key to contraction, metabolism and cellular homeostasis was identified. There was no change in redox-sensitive proteasome activity or HIF-1α content, but CH decreased phospho-JNK content independent of antioxidant supplementation. CH was detrimental to sternohyoid force- and power-generating capacity and this was prevented by chronic antioxidant supplementation. We conclude that CH causes upper airway dilator muscle dysfunction due to redox modulation of proteins key to function and homeostasis. Such changes could serve to further disrupt respiratory homeostasis in diseases characterized by CH such as chronic obstructive pulmonary disease. Antioxidants may have potential use as an adjunctive therapy in hypoxic respiratory disease.

No MeSH data available.


Related in: MedlinePlus

Sternohyoid protein carbonyl and free thiol content after 1, 3, and 6 weeks of sustained hypoxia compared to normoxic controls. (A) Sternohyoid protein carbonyl content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 5–8 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 7–8 per group; *p < 0.05, **p < 0.01, ***p < 0.001, ns, not significant; Student t-test or Mann-Whitney test as appropriate. Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1).
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Figure 2: Sternohyoid protein carbonyl and free thiol content after 1, 3, and 6 weeks of sustained hypoxia compared to normoxic controls. (A) Sternohyoid protein carbonyl content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 5–8 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 7–8 per group; *p < 0.05, **p < 0.01, ***p < 0.001, ns, not significant; Student t-test or Mann-Whitney test as appropriate. Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1).

Mentions: Significant increases in sternohyoid carbonyl content were observed after 3 (p < 0.001) and 6 (p < 0.001) weeks of CH (Figure 2A)—indicative of increased sternohyoid protein oxidation. Sternohyoid protein free thiol content changes were bi-phasic (Figure 2B). There was a significant increase in sternohyoid protein free thiol content after 1 (p < 0.05) and 3 (p < 0.01) weeks of CH; however free thiol content was significantly lower than control after 6 weeks of CH (p < 0.001). For comparison, two limb muscles, namely soleus, and extensor digitorum longus (EDL) were also studied. Unlike the sternohyoid, there were no significant changes to the carbonyl content of the EDL proteome after CH exposure (Figure 3A). There was, however, significant increases in EDL free thiol content after 1 (p < 0.01), 3 (p < 0.001), and 6 (p < 0.001) weeks of CH—though the magnitude of the increase is seen to decrease over time (Figure 3B). Similar to the sternohyoid muscle, but unlike the EDL, significant increases in soleus protein carbonyl content were observed after 3 (p < 0.05), and 6 (p < 0.01) weeks of CH (Figure 4A). Soleus protein free thiol content was significantly increased after 1 (p < 0.001), 3 (p < 0.01), and 6 (p < 0.001) weeks of CH compared to controls (Figure 4B). Consistent with EDL, there was a decline in increased free thiol content in the soleus with progressive CH.


Chronic sustained hypoxia-induced redox remodeling causes contractile dysfunction in mouse sternohyoid muscle.

Lewis P, Sheehan D, Soares R, Varela Coelho A, O'Halloran KD - Front Physiol (2015)

Sternohyoid protein carbonyl and free thiol content after 1, 3, and 6 weeks of sustained hypoxia compared to normoxic controls. (A) Sternohyoid protein carbonyl content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 5–8 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 7–8 per group; *p < 0.05, **p < 0.01, ***p < 0.001, ns, not significant; Student t-test or Mann-Whitney test as appropriate. Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4403307&req=5

Figure 2: Sternohyoid protein carbonyl and free thiol content after 1, 3, and 6 weeks of sustained hypoxia compared to normoxic controls. (A) Sternohyoid protein carbonyl content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 5–8 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) after 1, 3, and 6 weeks of normoxia or sustained hypoxia expressed as normalized fluorescence intensity; n = 7–8 per group; *p < 0.05, **p < 0.01, ***p < 0.001, ns, not significant; Student t-test or Mann-Whitney test as appropriate. Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1).
Mentions: Significant increases in sternohyoid carbonyl content were observed after 3 (p < 0.001) and 6 (p < 0.001) weeks of CH (Figure 2A)—indicative of increased sternohyoid protein oxidation. Sternohyoid protein free thiol content changes were bi-phasic (Figure 2B). There was a significant increase in sternohyoid protein free thiol content after 1 (p < 0.05) and 3 (p < 0.01) weeks of CH; however free thiol content was significantly lower than control after 6 weeks of CH (p < 0.001). For comparison, two limb muscles, namely soleus, and extensor digitorum longus (EDL) were also studied. Unlike the sternohyoid, there were no significant changes to the carbonyl content of the EDL proteome after CH exposure (Figure 3A). There was, however, significant increases in EDL free thiol content after 1 (p < 0.01), 3 (p < 0.001), and 6 (p < 0.001) weeks of CH—though the magnitude of the increase is seen to decrease over time (Figure 3B). Similar to the sternohyoid muscle, but unlike the EDL, significant increases in soleus protein carbonyl content were observed after 3 (p < 0.05), and 6 (p < 0.01) weeks of CH (Figure 4A). Soleus protein free thiol content was significantly increased after 1 (p < 0.001), 3 (p < 0.01), and 6 (p < 0.001) weeks of CH compared to controls (Figure 4B). Consistent with EDL, there was a decline in increased free thiol content in the soleus with progressive CH.

Bottom Line: There was no change in redox-sensitive proteasome activity or HIF-1α content, but CH decreased phospho-JNK content independent of antioxidant supplementation.We conclude that CH causes upper airway dilator muscle dysfunction due to redox modulation of proteins key to function and homeostasis.Such changes could serve to further disrupt respiratory homeostasis in diseases characterized by CH such as chronic obstructive pulmonary disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, School of Medicine, University College Cork Cork, Ireland.

ABSTRACT
Chronic sustained hypoxia (CH) induces structural and functional adaptations in respiratory muscles of animal models, however the underlying molecular mechanisms are unclear. This study explores the putative role of CH-induced redox remodeling in a translational mouse model, with a focus on the sternohyoid-a representative upper airway dilator muscle involved in the control of pharyngeal airway caliber. We hypothesized that exposure to CH induces redox disturbance in mouse sternohyoid muscle in a time-dependent manner affecting metabolic capacity and contractile performance. C57Bl6/J mice were exposed to normoxia or normobaric CH (FiO2 = 0.1) for 1, 3, or 6 weeks. A second cohort of animals was exposed to CH for 6 weeks with and without antioxidant supplementation (tempol or N-acetyl cysteine in the drinking water). Following CH exposure, we performed 2D redox proteomics with mass spectrometry, metabolic enzyme activity assays, and cell-signaling assays. Additionally, we assessed isotonic contractile and endurance properties ex vivo. Temporal changes in protein oxidation and glycolytic enzyme activities were observed. Redox modulation of sternohyoid muscle proteins key to contraction, metabolism and cellular homeostasis was identified. There was no change in redox-sensitive proteasome activity or HIF-1α content, but CH decreased phospho-JNK content independent of antioxidant supplementation. CH was detrimental to sternohyoid force- and power-generating capacity and this was prevented by chronic antioxidant supplementation. We conclude that CH causes upper airway dilator muscle dysfunction due to redox modulation of proteins key to function and homeostasis. Such changes could serve to further disrupt respiratory homeostasis in diseases characterized by CH such as chronic obstructive pulmonary disease. Antioxidants may have potential use as an adjunctive therapy in hypoxic respiratory disease.

No MeSH data available.


Related in: MedlinePlus