Hepatic injury in rats exposed to chronic intermittent hypoxia and the effect of tempol

Abstract

To investigate the mechanism of liver injury in rats exposed to chronic intermittent hypoxia (CIH) and to investigate the effect of tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl or 4-hydroxy-TEMPO). A CIH animal model of rats was established to mimic the intermittent hypoxia/re-oxygenation (IH/ROX) of obstructive sleep apnea syndrome in humans. Thirty-two healthy male Wistar rats were randomly assigned to 4 groups: conventional intermittent hypoxia group (CIH group), intermittent hypoxia Tempol treatment group (CIH + T group), intermittent hypoxia normal saline matched group (CIH + NS group), and normoxic control group (NC group), with 8 rats in each group. The frequency of every CIH group was 30 times/h, and the minimum oxygen concentration was 5%. After the experiment, sections of liver were stained with hematoxylin-eosin (HE) and the levels of nuclear factor-kappaB (NF-κB), glutathione peroxidase (GSH-PX) and malondialdehyde (MDA) in rat liver homogenate were measured. Liver histology revealed that the CIH group and the CIH + NS group showed hepatocellular swelling with rarefaction of the cytoplasm, hyperchromatosis and hepatocellular membrane disruption, but the liver histology of the CIH + T group and the NC group was normal. Compared with the NC group, the levels of NF-κB and MDA in the CIH group [(12.4 ± 2.0) ng/g, (101 ± 22) µmol/g] and the CIH + NS group [(12.2 ± 1.9) ng/g, (99 ± 18)µmol/g] were increased (all P < 0.05), but the activities of GSH-PX [(88 ± 17) U/mg, (90 ± 15) U/mg] were decreased (all P < 0.05). Compared with the CIH + NS group and the CIH group, the activity of GSH-PX in the CIH + T group [(181 ± 29) U/mg] was increased (P < 0.05), but the levels of NF-κB [(7.8 ± 1.3) ng/g] and MDA [(59 ± 10) µmol/g] were decreased (all P < 0.05). The levels of GSH-PX and MDA in the CIH + T group were not significantly different compared to the NC group (P were 0.242, 0.177 respectively), but the level of NF-κB in the CIH + T group was higher than that in the NC group (P < 0.05). The levels of NF-κB, GSH-PX, and MDA in the CIH + NS group were not significantly different as compared to those in the CIH group (all P > 0.05). The level of NF-κB was correlated negatively with GSH-PX, but positively with MDA (r = -0.754, 0.689, respectively, all P < 0.01) CIH could cause rat liver injury through oxidative stress and activating the proinflammatory transcription factors of NF-κB. Tempol could prevent CIH-induced liver injury through scavenging ROS by its anti-oxidative effect.