Animals, Anoxia, Antioxidants, Chronic Disease, Diaphragm, Disease Models, Animal, Glutathione, Glycerolphosphate Dehydrogenase, Male, Muscle Contraction, Muscle Fatigue, Myosin Heavy Chains, Oxidative Stress, Rats, Wistar, Reactive Oxygen Species, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Sodium-Potassium-Exchanging ATPase, Succinate Dehydrogenase, Time Factors
Health Research Board Ireland. University College Dublin.
Respiratory muscle dysfunction documented in sleep apnoea patients is perhaps due to oxidative stress secondary to chronic intermittent hypoxia (CIH). We sought to explore the effects of different CIH protocols on respiratory muscle form and function in a rodent model. Adult male Wistar rats were exposed to CIH (n = 32) consisting of 90 s normoxia-90 s hypoxia (either 10 or 5% oxygen at the nadir; arterial O2 saturation ∼ 90 or 80%, respectively] for 8 h per day or to sham treatment (air-air, n = 32) for 1 or 2 weeks. Three additional groups of CIH-treated rats (5% O2 for 2 weeks) had free access to water containing N-acetyl cysteine (1% NAC, n = 8), tempol (1 mM, n = 8) or apocynin (2 mM, n = 8). Functional properties of the diaphragm muscle were examined ex vivo at 35 °C. The myosin heavy chain and sarco(endo)plasmic reticulum Ca(2+)-ATPase isoform distribution, succinate dehydrogenase and glyercol phosphate dehydrogenase enzyme activities, Na(+)-K(+)-ATPase pump content, concentration of thiobarbituric acid reactive substances, DNA oxidation and antioxidant capacity were determined. Chronic intermittent hypoxia (5% oxygen at the nadir; 2 weeks) decreased diaphragm muscle force and endurance. All three drugs reversed the deleterious effects of CIH on diaphragm endurance, but only NAC prevented CIH-induced diaphragm weakness. Chronic intermittent hypoxia increased diaphragm muscle myosin heavy chain 2B areal density and oxidized glutathione/reduced glutathione (GSSG/GSH) ratio. We conclude that CIH-induced diaphragm dysfunction is reactive oxygen species dependent. N-Acetyl cysteine was most effective in reversing CIH-induced effects on diaphragm. Our results suggest that respiratory muscle dysfunction in sleep apnoea may be the result of oxidative stress and, as such, antioxidant treatment could prove a useful adjunctive therapy for the disorder.
Physics | Physiology
Shortt CM, Fredsted A, Chow HB, Williams R, Skelly JR, Bradford A, O’Halloran KD. Reactive oxygen species mediated diaphragm fatigue in a rat model of chronicintermittent hypoxia. Experimental Physiology. 2014;99(4):688-700.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.