Sleep apnea is a breathing disorder that results from momentary and cyclic collapse of the upper airway, leading to intermittent hypoxia (IH). IH can lead to the formation of free radicals that increase oxidative stress, and this mechanism may explain the association between central sleep apnea and nonalcoholic steatohepatitis. We assessed the level of inflammation in the lung and liver tissue from animals subjected to intermittent hypoxia and simulated sleep apnea. A total of 12 C57BL/6 mice were divided into two groups and then exposed to IH ( ) or a simulated IH (SIH) ( ) for 35 days. We observed an increase in oxidative damage and other changes to endogenous antioxidant enzymes in mice exposed to IH. Specifically, the expression of multiple transcription factors, including hypoxia inducible factor (HIF-1 ), nuclear factor kappa B (NF- B), and tumor necrosis factor (TNF- ), inducible NO synthase (iNOS), vascular endothelial growth factor (VEGF), and cleaved caspase 3 were shown to be increased in the IH group. Overall, we found that exposure to intermittent hypoxia for 35 days by simulating sleep apnea leads to oxidative stress, inflammation, and increased activity of caspase 3 in the liver and lung. 1. Introduction Obstructive sleep apnea (OSA) consists of sleep-disordered breathing. Cyclic episodes result in the momentary closure, partial or complete, of the upper airway at the level of the pharynx. The repeated pauses in breathing can lead to intermittent hypoxia (IH) and increased reactive oxygen species (ROS) [1]. The increase of ROS in OSA is likely due to the repeated oxygen depletion followed by the hyperoxia that develops to restore oxygen pressure (PO2). A similar phenomenon is observed in ischemia followed by reperfusion [2–5]. In ischemia/reperfusion, xanthine oxidase generates free radicals in the presence of oxygen, contributing to oxidative stress [6–8]. OSA is associated with chronic liver diseases, such as nonalcoholic steatohepatitis (NASH) [9–16]. Savransky and colleagues demonstrated that IH can act as a “second hit” to liver disease by amplifying the tissue damage induced by a high dose of paracetamol [17, 18]. The injury mechanism, triggered by OSA, appears to be related to the formation of peroxynitrite, depletion of glutathione, and apoptosis of hepatocytes [18]. In OSA, inflammatory factors, such as nuclear factor kappa B (NF-κB), are activated at a systemic level [17, 19]. NF-κB is a master regulator of the inflammatory process, by inhibiting its inhibitor IKK-b, and its activation leads to the increased expression of tumor
References
[1]
J. A. Dempsey, S. C. Veasey, B. J. Morgan, and C. P. O'Donnell, “Pathophysiology of sleep apnea,” Physiological Reviews, vol. 90, no. 1, pp. 47–112, 2010.
[2]
L. Lavie, “Obstructive sleep apnoea syndrome—an oxidative stress disorder,” Sleep Medicine Reviews, vol. 7, no. 1, pp. 35–51, 2003.
[3]
L. Lavie, “Sleep-disordered breathing and cerebrovascular disease: a mechanistic approach,” Neurologic Clinics, vol. 23, no. 4, pp. 1059–1075, 2005.
[4]
Y. J. Suzuki, V. Jain, A. M. Park, and R. M. Day, “Oxidative stress and oxidant signaling in obstructive sleep apnea and associated cardiovascular diseases,” Free Radical Biology and Medicine, vol. 40, no. 10, pp. 1683–1692, 2006.
[5]
L. Lavie, “Oxidative stress-A unifying paradigm in obstructive sleep apnea and comorbidities,” Progress in Cardiovascular Diseases, vol. 51, no. 4, pp. 303–312, 2009.
[6]
T. K. Aalto and K. O. Raivio, “Nucleotide depletion due to reactive oxygen metabolites in endothelial cells: effects of antioxidants and 3-aminobenzamide,” Pediatric Research, vol. 34, no. 5, pp. 572–576, 1993.
[7]
C. Szabó, B. Zingarelli, and A. L. Salzman, “Role of poly-ADP ribosyltransferase activation in the vascular contractile and energetic failure elicited by exogenous and endogenous nitric oxide and peroxynitrite,” Circulation Research, vol. 78, no. 6, pp. 1051–1063, 1996.
[8]
J. Zhang, V. L. Dawson, T. M. Dawson, and S. H. Snyder, “Nitric oxide activation of poly(ADP-ribose) synthetase in neurotoxicity,” Science, vol. 263, no. 5147, pp. 687–689, 1994.
[9]
H. Singh, R. Pollock, J. Uhanova, M. Kryger, K. Hawkins, and G. Y. Minuk, “Symptoms of obstructive sleep apnea in patients with nonalcoholic fatty liver disease,” Digestive Diseases and Sciences, vol. 50, no. 12, pp. 2338–2343, 2005.
[10]
F. Tanné, F. Gagnadoux, O. Chazouillères et al., “Chronic liver injury during obstructive sleep apnea,” Hepatology, vol. 41, no. 6, pp. 1290–1296, 2005.
[11]
K. Tatsumi and T. Saibara, “Effects of obstructive sleep apnea syndrome on hepatic steatosis and nonalcoholic steatohepatitis,” Hepatology Research, vol. 33, no. 2, pp. 100–104, 2005.
[12]
P. Jou？t, J. M. Sabaté, D. Maillard et al., “Relationship between obstructive sleep apnea and liver abnormalities in morbidly obese patients: a prospective study,” Obesity Surgery, vol. 17, no. 4, pp. 478–485, 2007.
[13]
E. R. Kallwitz, J. Herdegen, J. Madura, S. Jakate, and S. J. Cotler, “Liver enzymes and histology in obese patients with obstructive sleep apnea,” Journal of Clinical Gastroenterology, vol. 41, no. 10, pp. 918–921, 2007.
[14]
D. Zamora-Valdés and N. Méndez-Sánchez, “Experimental evidence of obstructive sleep apnea syndrome as a second hit accomplice in nonalcoholic steatohepatitis pathogenesis,” Annals of Hepatology, vol. 6, no. 4, pp. 281–283, 2007.
[15]
L. Kheirandish-Gozal, O. Sans Capdevila, E. Kheirandish, and D. Gozal, “Elevated serum aminotransferase levels in children at risk for obstructive sleep apnea,” Chest, vol. 133, no. 1, pp. 92–99, 2008.
[16]
D. Norman, W. A. Bardwell, F. Arosemena et al., “Serum aminotransferase levels are associated with markers of hypoxia in patients with obstructive sleep apnea,” Sleep, vol. 31, no. 1, pp. 121–126, 2008.
[17]
V. Savransky, A. Nanayakkara, A. Vivero et al., “Chronic intermittent hypoxia predisposes to liver injury,” Hepatology, vol. 45, no. 4, pp. 1007–1013, 2007.
[18]
V. Savransky, C. Reinke, J. Jun et al., “Chronic intermittent hypoxia and acetaminophen induce synergistic liver injury in mice: experimental physiology—research paper,” Experimental Physiology, vol. 94, no. 2, pp. 228–239, 2009.
[19]
S. Ryan, C. T. Taylor, and W. T. McNicholas, “Systemic inflammation: a key factor in the pathogenesis of cardiovascular complications in obstructive sleep apnoea syndrome?” Thorax, vol. 64, no. 7, pp. 631–636, 2009.
[20]
A. K. Htoo, H. Greenberg, S. Tongia et al., “Activation of nuclear factor κB in obstructive sleep apnea: a pathway leading to systemic inflammation,” Sleep and Breathing, vol. 10, no. 1, pp. 43–50, 2006.
[21]
H. Greenberg, X. Ye, D. Wilson, A. K. Htoo, T. Hendersen, and S. F. Liu, “Chronic intermittent hypoxia activates nuclear factor-κB in cardiovascular tissues in vivo,” Biochemical and Biophysical Research Communications, vol. 343, no. 2, pp. 591–596, 2006.
[22]
C. Selmi, N. Montano, R. Furlan, C. L. Keen, and M. E. Gershwin, “Inflammation and oxidative stress in obstructive sleep apnea syndrome,” Experimental Biology and Medicine, vol. 232, no. 11, pp. 1409–1413, 2007.
[23]
M. Yamauchi, S. Tamaki, K. Tomoda et al., “Evidence for activation of nuclear factor kappaB in obstructive sleep apnea,” Sleep and Breathing, vol. 10, no. 4, pp. 189–193, 2006.
[24]
P. Carmeliet, Y. Dor, J. M. Herbert et al., “Role of HIF-1α in hypoxia-mediated apoptosis, cell proliferation and tumour angiogenesis,” Nature, vol. 395, no. 6701, pp. 485–490, 1998.
[25]
D. Martinez, C. Z. Fiori, D. Baronio et al., “Brown adipose tissue: is it affected by intermittent hypoxia?” Lipids in Health and Disease, vol. 9, article no. 121, 2010.
[26]
[Anon], “AVMA updates its euthanasia guidelines,” Veterinary Record, vol. 161, no. 15, pp. 502–502, 2007.
[27]
[Anon], “AVMA releases updated euthanasia guidelines,” Journal of the American Veterinary Medical Association, vol. 231, no. 6, pp. 827–827, 2007.
[28]
M. M. Bradford, “A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein dye binding,” Analytical Biochemistry, vol. 72, no. 1-2, pp. 248–254, 1976.
[29]
J. A. Buege and S. D. Aust, “Microsomal lipid peroxidation,” Methods in Enzymology, vol. 52, pp. 302–310, 1978.
[30]
H. P. Misra and I. Fridovich, “The role of superoxide anion in the autoxidation of epinephrine and a simple assay for superoxide dismutase,” Journal of Biological Chemistry, vol. 247, no. 10, pp. 3170–3175, 1972.
[31]
H. Aebi, “Catalase in vitro,” Methods in Enzymology, vol. 105, pp. 121–126, 1984.
[32]
U. K. Laemmli, “Cleavage of structural proteins during the assembly of the head of bacteriophage T4,” Nature, vol. 227, no. 5259, pp. 680–685, 1970.
[33]
H. Towbin, T. Staehelin, and J. Gordon, “Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications,” Proceedings of the National Academy of Sciences of the United States of America, vol. 76, no. 9, pp. 4350–4354, 1979.
[34]
I. Shpirer, L. Copel, E. Broide, and A. Elizur, “Continuous positive airway pressure improves sleep apnea associated fatty liver,” Lung, vol. 188, no. 4, pp. 301–307, 2010.
[35]
C. P. Day and O. F. W. James, “Steatohepatitis: a tale of two “Hits”?” Gastroenterology, vol. 114, no. 4, pp. 842–845, 1998.
[36]
S. Seki, T. Kitada, and H. Sakaguchi, “Clinicopathological significance of oxidative cellular damage in non-alcoholic fatty liver diseases,” Hepatology Research, vol. 33, no. 2, pp. 132–134, 2005.
[37]
J. George, N. Pera, N. Phung, I. Leclercq, J. Y. Hou, and G. Farrell, “Lipid peroxidation, stellate cell activation and hepatic fibrogenesis in a rat model of chronic steatohepatitis,” Journal of Hepatology, vol. 39, no. 5, pp. 756–764, 2003.
[38]
D. P. Rosa, D. Martinez, J. N. Picada, J. G. Semedo, and N. P. Marroni, “Hepatic oxidative stress in an animal model of sleep apnoea: effects of different duration of exposure,” Comparative Hepatology, vol. 10, article 1, 2011.
[39]
A. M. Park and Y. J. Suzuki, “Effects of intermittent hypoxia on oxidative stress-induced myocardial damage in mice,” Journal of Applied Physiology, vol. 102, no. 5, pp. 1806–1814, 2007.
[40]
A. Dutta, K. Ray, V. K. Singh, P. Vats, S. N. Singh, and S. B. Singh, “L-carnitine supplementation attenuates intermittent hypoxia-induced oxidative stress and delays muscle fatigue in rats,” Experimental Physiology, vol. 93, no. 10, pp. 1139–1146, 2008.
[41]
S. Bertuglia and R. J. Reiter, “Melatonin reduces microvascular damage and insulin resistance in hamsters due to chronic intermittent hypoxia,” Journal of Pineal Research, vol. 46, no. 3, pp. 307–313, 2009.
[42]
L. Lavie, A. Hefetz, R. Luboshitzky, and P. Lavie, “Plasma levels of nitric oxide and L-arginine in sleep apnea patients: effects of nCPAP treatment,” Journal of Molecular Neuroscience, vol. 21, no. 1, pp. 57–63, 2003.
[43]
H. Y. Sohn, F. Krotz, T. Gloe et al., “Differential regulation of xanthine and NAD(P)H oxidase by hypoxia in human umbilical vein endothelial cells. Role of nitric oxide and adenosine,” Cardiovascular Research, vol. 58, no. 3, pp. 638–646, 2003.
[44]
G. Cairo, E. Castrusini, G. Minotti, and A. Bernelli-Zazzera, “Superoxide and hydrogen peroxide-dependent inhibition of iron regulatory protein activity: a protective stratagem against oxidative injury,” The FASEB Journal, vol. 10, no. 11, pp. 1326–1335, 1996.
[45]
W. Jordan, S. Cohrs, D. Degner et al., “Evaluation of oxidative stress measurements in obstructive sleep apnea syndrome,” Journal of Neural Transmission, vol. 113, no. 2, pp. 239–254, 2006.
[46]
S. A. Phillips, E. B. Olson, J. H. Lombard, and B. J. Morgan, “Chronic intermittent hypoxia alters NE reactivity and mechanics of skeletal muscle resistance arteries,” Journal of Applied Physiology, vol. 100, no. 4, pp. 1117–1123, 2006.
[47]
D. R. Mole, C. Blancher, R. R. Copley et al., “Genome-wide association of hypoxia-inducible factor (HIF)-1α and HIF-2α DNA binding with expression profiling of hypoxia-inducible transcripts,” Journal of Biological Chemistry, vol. 284, no. 25, pp. 16767–16775, 2009.
[48]
G. L. Semenza, “Regulation of oxygen homeostasis by hypoxia-Inducible factor 1,” Physiology, vol. 24, no. 2, pp. 97–106, 2009.
[49]
G. Yuan, S. A. Khan, W. Luo, et al., “Hypoxia-inducible factor 1 mediates increased expression of NADPH oxidase-2 in response to intermittent hypoxia,” Journal of Cellular Physiology, vol. 226, no. 11, pp. 2925–2933, 2011.
[50]
B. Nath, I. Levin, T. Csak et al., “Hepatocyte-specific hypoxia-inducible factor-1α is a determinant of lipid accumulation and liver injury in alcohol-induced steatosis in mice,” Hepatology, vol. 53, no. 5, pp. 1526–1537, 2011.
[51]
C. C. Blouin, E. L. Pagé, G. M. Soucy, and D. E. Richard, “Hypoxic gene activation by lipopolysaccharide in macrophages: implication of hypoxia-inducible factor 1α,” Blood, vol. 103, no. 3, pp. 1124–1130, 2004.
[52]
C. Peyssonnaux, P. Cejudo-Martin, A. Doedens, A. S. Zinkernagel, R. S. Johnson, and V. Nizet, “Cutting edge: essential role of hypoxia inducible factor-1α in development of lipopolysaccharide-induced sepsis,” Journal of Immunology, vol. 178, no. 12, pp. 7516–7519, 2007.
[53]
W. Moritz, F. Meier, D. M. Stroka et al., “Apoptosis in hypoxic human pancreatic islets correlates with HIF-1alpha expression,” The FASEB Journal, vol. 16, no. 7, pp. 745–747, 2002.
[54]
N. Akakura, M. Kobayashi, I. Horiuchi et al., “Constitutive expression of hypoxia-inducible factor-lα renders pancreatic cancer cells resistant to apoptosis induced by hypoxia and nutrient deprivation,” Cancer Research, vol. 61, no. 17, pp. 6548–6554, 2001.
[55]
P. van Uden, N. S. Kenneth, and S. Rocha, “Regulation of hypoxia-inducible factor-1αa by NF-κB,” Biochemical Journal, vol. 412, no. 3, pp. 477–484, 2008.
[56]
J. Rius, M. Guma, C. Schachtrup et al., “NF-κB links innate immunity to the hypoxic response through transcriptional regulation of HIF-1α,” Nature, vol. 453, no. 7196, pp. 807–811, 2008.
[57]
N. Beraza, Y. Malato, S. Vander Borght et al., “Pharmacological IKK2 inhibition blocks liver steatosis and initiation of non-alcoholic steatohepatitis,” Gut, vol. 57, no. 5, pp. 655–663, 2008.
[58]
H. L. Pahl, “Activators and target genes of Rel/NF-κB transcription factors,” Oncogene, vol. 18, no. 49, pp. 6853–6866, 1999.
[59]
N. Ferrara, “Vascular endothelial growth factor: basic science and clinical progress,” Endocrine Reviews, vol. 25, no. 4, pp. 581–611, 2004.
[60]
E. Minet, G. Michel, J. Remacle, and C. Michiels, “Role of HIF-1 as a transcription factor involved in embryonic development, cancer progression and apoptosis,” International Journal of Molecular Medicine, vol. 5, no. 3, pp. 253–259, 2000.
[61]
A. E. Greijer and E. Van Der Wall, “The role of hypoxia inducible factor 1 (HIF-1) in hypoxia induced apoptosis,” Journal of Clinical Pathology, vol. 57, no. 10, pp. 1009–1014, 2004.
