Limits...
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 following 6 weeks of normoxia and sustained hypoxia ± chronic antioxidant supplementation. (A) Sternohyoid protein carbonyl content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; **p < 0.05 and ***p < 0.001 vs. control, #p < 0.05 and ###p < 0.001 vs. hypoxia, Tukey's multiple comparison test; Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1); Tempol, tempol + sustained hypoxia; NAC, NAC + sustained hypoxia.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4403307&req=5

Figure 7: Sternohyoid protein carbonyl and free thiol content following 6 weeks of normoxia and sustained hypoxia ± chronic antioxidant supplementation. (A) Sternohyoid protein carbonyl content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; **p < 0.05 and ***p < 0.001 vs. control, #p < 0.05 and ###p < 0.001 vs. hypoxia, Tukey's multiple comparison test; Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1); Tempol, tempol + sustained hypoxia; NAC, NAC + sustained hypoxia.

Mentions: In the second cohort of animals, significant increases in sternohyoid protein carbonyl content were again observed after 6 weeks of CH (p < 0.001). Chronic antioxidant supplementation with either Tempol (p < 0.001) or NAC (p < 0.001) significantly ameliorated the CH-induced increase in protein carbonyl content (Figure 7A). Similarly, sternohyoid protein free thiol content was significantly lower than control after 6 weeks of CH (p < 0.01) and antioxidant treatment with Tempol (p < 0.001) and NAC (p < 0.05) ameliorated this effect (Figure 7B).


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 following 6 weeks of normoxia and sustained hypoxia ± chronic antioxidant supplementation. (A) Sternohyoid protein carbonyl content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; **p < 0.05 and ***p < 0.001 vs. control, #p < 0.05 and ###p < 0.001 vs. hypoxia, Tukey's multiple comparison test; Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1); Tempol, tempol + sustained hypoxia; NAC, NAC + sustained hypoxia.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Sternohyoid protein carbonyl and free thiol content following 6 weeks of normoxia and sustained hypoxia ± chronic antioxidant supplementation. (A) Sternohyoid protein carbonyl content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; (B) Sternohyoid protein free thiol content (mean ± SEM) expressed as normalized fluorescence intensity; n = 5–7 per group; **p < 0.05 and ***p < 0.001 vs. control, #p < 0.05 and ###p < 0.001 vs. hypoxia, Tukey's multiple comparison test; Ctrl, normoxic control; Hypoxia, sustained hypoxia (FiO2 = 0.1); Tempol, tempol + sustained hypoxia; NAC, NAC + sustained hypoxia.
Mentions: In the second cohort of animals, significant increases in sternohyoid protein carbonyl content were again observed after 6 weeks of CH (p < 0.001). Chronic antioxidant supplementation with either Tempol (p < 0.001) or NAC (p < 0.001) significantly ameliorated the CH-induced increase in protein carbonyl content (Figure 7A). Similarly, sternohyoid protein free thiol content was significantly lower than control after 6 weeks of CH (p < 0.01) and antioxidant treatment with Tempol (p < 0.001) and NAC (p < 0.05) ameliorated this effect (Figure 7B).

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