ABSTRACT
To identify the core structure of 2-aminoethoxydiphenyl borate (2-APB) responsible for the anti-oxidative and protective effect on the ischemia/reperfusion (I/R)-induced heart injury, various 2-APB analogues were analyzed, and several antioxidant assays were performed. Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Myocardial infarct size was quantified using triphenyl tetrazolium chloride (TTC) staining. The levels of tumor necrosis factor-alpha (TNF-α) and cleaved-caspase-3 protein were evaluated as an indicator for the anti-inflammatory and anti-apoptotic effect, respectively. Our data show that 2-APB, diphenylborinic anhydride (DPBA) and 3-(diphenylphosphino)-1-propylamine (DP3A) all exerted the anti-oxidative activity, but only 2-APB and DPBA can scavenge H2O2. 2-APB and DPBA can potently inhibit hydrogen peroxide (H2O2)- and hypoxanthine/xanthine oxidase (HX/XOD)-induced increases in intracellular H2O2 and H9c2 cell death. 2-APB and DPBA were able to decrease the I/R-induced adult rat cardiomyocytes death, myocardial infarct size, and the levels of malondialdehyde (MDA) and creatine kinase-MB (CK-MB). Our results suggest that the two benzene rings with a boron atom comprise the core structure of 2-APB responsible for the anti-oxidative effect mediated through the reaction with H2O2 and generation of phenolic compounds, which in turn reduced the I/R-induced oxidative stress and injury in the rat heart.
ABSTRACT
Purpose: To investigate the role of sodium-hydrogen exchanger-1 (NHE-1) and exercise training on intermittent hypoxia-induced cardiac fibrosis in obstructive sleep apnea (OSA), using an animal model mimicking the intermittent hypoxia of OSA. Methods: Eight-week-old male Sprague-Dawley rats were randomly assigned to control (CON), intermittent hypoxia (IH), exercise (EXE), or IH combined with exercise (IHEXE) groups. These groups were randomly assigned to subgroups receiving either a vehicle or the NHE-1 inhibitor cariporide. The EXE and IHEXE rats underwent exercise training on an animal treadmill for 10 weeks (5 days/week, 60 min/day, 24-30 m/min, 2-10% grade). The IH and IHEXE rats were exposed to 14 days of IH (30 s of hypoxia-nadir of 2-6% O2-followed by 45 s of normoxia) for 8 h/day. At the end of 10 weeks, rats were sacrificed and then hearts were removed to determine the myocardial levels of fibrosis index, oxidative stress, antioxidant capacity, and NHE-1 activation. Results: Compared to the CON rats, IH induced higher cardiac fibrosis, lower myocardial catalase, and superoxidative dismutase activities, higher myocardial lipid and protein peroxidation and higher NHE-1 activation (p < 0.05 for each), which were all abolished by cariporide. Compared to the IH rats, lower cardiac fibrosis, higher myocardial antioxidant capacity, lower myocardial lipid, and protein peroxidation and lower NHE-1 activation were found in the IHEXE rats (p < 0.05 for each). Conclusion: IH-induced cardiac fibrosis was associated with NHE-1 hyperactivity. However, exercise training and cariporide exerted an inhibitory effect to prevent myocardial NHE-1 hyperactivity, which contributed to reduced IH-induced cardiac fibrosis. Therefore, NHE-1 plays a critical role in the effect of exercise on IH-induced increased cardiac fibrosis.
ABSTRACT
Intermittent hypoxia (IH) occurs frequently in patients with obstructive sleep apnoea and can cause ventricular dysfunction. However, whether myocardial inflammation and sodium-hydrogen exchanger-1 (NHE-1) expression play an important role in IH-induced ventricular dysfunction remains unclear. This study aimed to investigate whether short-term exercise provides a protective effect on IH-induced left ventricular (LV) function impairment. Male Sprague-Dawley rats were randomly assigned to 4 groups: control (CON), IH, exercise (EXE) or IH interspersed with EXE (IHEXE). IH rats were exposed to repetitive hypoxia/reoxygenation cycles (2%-6% O2 for 2-5 s per 75 s, followed by 21% O2 for 6 h/day) during the light phase for 12 consecutive days. EXE rats were habituated to treadmill running for 5 days, permitted 2 days of rest, and followed by 5 exercise bouts (30 m/min for 60 min on a 2% grade) on consecutive days during the dark phase. IHEXE rats were exposed to IH during the light phase interspersed with exercise programs during the dark phase on the same day. Cardiac function was quantified by echocardiographic evaluation. Myocardial levels of tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and NHE-1 were determined. IH rats showed LV dysfunction characterized by lower LV fractional shortening (LVFS%) and LV ejection fraction (LVEF%). LV dysfunction was associated with higher myocardial levels of TNF-α, IL-6 and NHE-1 mRNA and protein. These changes were not observed in IHEXE rats (P > 0.05 for all). EXE rats showed lower levels of NHE-1 protein than CON rats (P < 0.05). However, the levels of LVFS%, LVEF%, TNF-α and IL-6 protein and NHE-1 mRNA did not differ between EXE and CON rats (P > 0.05 for all). These data indicated that exercise may provide a protective effect on IH-induced LV dysfunction by attenuating IH-induced myocardial NHE-1 hyperactivity.
