Sleep apnea syndrome increases the risk of cardiovascular morbidity and mortality. We previously reported that intermittent hypoxia increases superoxide production in a manner dependent on nicotinamide adenine dinucleotide phosphate and accelerates adverse left ventricular (LV) remodeling. Recent studies have suggested that hydrogen (H(2)) may have an antioxidant effect by reducing hydroxyl radicals. In this study, we investigated the effects of H(2) gas inhalation on lipid metabolism and LV remodeling induced by intermittent hypoxia in mice. Male C57BL/6J mice (n = 62) were exposed to intermittent hypoxia (repetitive cycle of 1-min periods of 5 and 21% oxygen for 8 h during daytime) for 7 days. H(2) gas (1.3 vol/100 vol) was given either at the time of reoxygenation, during hypoxic conditions, or throughout the experimental period. Mice kept under normoxic conditions served as controls (n = 13). Intermittent hypoxia significantly increased plasma levels of low- and very low-density cholesterol and the amount of 4-hydroxy-2-nonenal-modified protein adducts in the LV myocardium. It also upregulated mRNA expression of tissue necrosis factor-α, interleukin-6, and brain natriuretic peptide, increased production of superoxide, and induced cardiomyocyte hypertrophy, nuclear deformity, mitochondrial degeneration, and interstitial fibrosis. H(2) gas inhalation significantly suppressed these changes induced by intermittent hypoxia. In particular, H(2) gas inhaled at the timing of reoxygenation or throughout the experiment was effective in preventing dyslipidemia and suppressing superoxide production in the LV myocardium. These results suggest that inhalation of H(2) gas was effective for reducing oxidative stress and preventing LV remodeling induced by intermittent hypoxia relevant to sleep apnea.

We have reported previously that intermittent hypoxia related to sleep apnea induces cardiovascular remodeling secondary to the oxidative stress. The aim of this study was to examine the effect of pitavastatin as an antioxidant to prevent intermittent hypoxia-induced left ventricular (LV) remodeling in mice without hypercholesterolemia. Eight-week-old male C57BL/6J mice (n¼35) were exposed to intermittent hypoxia (30 s exposure to 5% oxygen, followed by 30 s exposure to 21% oxygen) for 8 h per day during the daytime or maintained under normoxic conditions; in addition, they were either treated with pitavastatin (3 mg kg À1 per day) or vehicle for 10 days. After cardiac catheterization and blood sampling, the LV myocardium was examined. The systemic blood pressure and plasma level of total cholesterol were similar among the four groups. Intermittent hypoxia significantly increased the expression levels of 4-hydroxy-2-nonenal (4-HNE) proteins, TNF-a and TGF-b mRNA, and also the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling (TUNEL)-positive myocardial cells in the LV myocardium. In addition, enhanced hypertrophy of the cardiomyocytes, perivascular fibrosis and histological degeneration were observed in the mice exposed to hypoxic stress. Treatment with pitavastatin significantly suppressed the expression levels of the 4-HNE proteins, cytokines, superoxide production and TUNEL-positive myocardial cells in the LV myocardium, consequently attenuating the hypoxia-induced histological changes. Pitavastatin preserved, at least partially, the morphological structure of the LV myocardium in lean mice exposed to intermittent hypoxia, through its antioxidant effect.

We have previously reported that intermittent hypoxic stress, which is relevant to sleep apnea syndrome (SAS), increases oxidative stress and induces left ventricular (LV) remodeling. Celiprolol, a β1-selective adrenoreceptor blocker, is known to have not only an antihypertensive effect but also an antioxidant effect through releasing nitric oxide. The aim of this study was to examine the hypothesis that celiprolol might ameliorate the LV remodeling induced by intermittent hypoxia through its antioxidant effect. Male C57BL/6J mice (8 weeks old) were exposed to intermittent hypoxia (30 s of 5% oxygen followed by 30 s of 21% oxygen) for 8 h day(-1) during the daytime for 10 consecutive days or were maintained under normoxic conditions. Animals were treated with either celiprolol (100 mg kg(-1) day(-1) by gavage) or vehicle. Hypoxic stress caused fluctuations in blood pressure (BP), an increase in the mean cardiomyocyte diameter, perivascular fibrosis and a decrease in endothelial nitric oxide synthase (eNOS) expression. These changes were associated with increased levels of 4-hydroxy-2-nonenal protein, superoxide, tumor necrosis factor-α mRNA and brain natriuretic peptide mRNA in the LV myocardium. Celiprolol significantly suppressed BP fluctuation, restored eNOS expression and reduced oxidative stress and superoxide production, thus ameliorating hypoxia-induced LV remodeling in mice. These findings suggest that treatment with celiprolol might prevent cardiovascular events in borderline hypertensive patients with SAS.

Postprandial hyperglycemia (PPH) and intermittent hypoxia related to the sleep apnea syndrome are important predictors of cardiovascular disease. We investigated the effects of intermittent hypoxia on pathological changes in the left ventricular (LV) myocardium caused by PPH in lean mice and evaluated the influence of acarbose, an α-glucosidase inhibitor. Male C57BL/6J mice aged 8 weeks were exposed to intermittent hypoxia (8 h/day during the daytime) or kept under normoxia. PPH was induced by restriction of feeding to 1-h periods twice a day, with the restricted diet (RD) mice receiving either standard chow or chow containing 0.02% acarbose. Another group of mice were fed standard chow ad libitum (AL). Plasma glucose levels after food intake were significantly elevated in RD but not in AL mice, and glucose levels were suppressed by acarbose. Intermittent hypoxia exacerbated cardiomyocyte hypertrophy and interstitial fibrosis in the LV myocardium of RD mice. Superoxide production and expression of 4-hydroxy-2-nonenal in the LV myocardium with intermittent hypoxia were increased in RD mice, but not AL mice. In addition, expression of tumor necrosis factor α (TNF-α) mRNA was increased in hypoxic RD mice. Treatment with acarbose inhibited oxidative stress and TNF-α mRNA expression and preserved the histological architecture of the LV myocardium.

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