Background： Cognitive impairment is a severe complication caused by obstructive sleep apnea （OSA）. The mechanisms of causation are still unclear. The Wntβ-catenin signaling pathway is involved in cognition, and abnormalities in it are implicated in neurological disorders. Here, we explored the Wntβ-catenin signaling pathway abnormalities caused by chronic intermittent hypoxia （CIH）, the most characteristic pathophysiological component of OSA. Methods： We divided 32 4-week-old male C57/BL mice into four groups of eight each： a CIH ＋ normal saline （NS） group, CIH ＋ LiCI group, sham CIH ＋ NS group, and a sham CIH ＋ LiCI group. The spatial learning performance of each group was assessed by using the Morris water maze （MWM）. Protein expressions of glycogen synthase kinase-β （GSK-β） and β-catenin in the hippocampus were examined using the Western blotting test. EdU labeling and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining methods were used, respectively, to determine the proliferation and apoptosis of neurons in the hippocampal dentate gyrus region. Results： Mice exposed to CIH showed impaired spatial learning performance in the MWM, including increased mean escape latencies to reach the target platform, decreased mean times passing through the target platform and mean duration in the target quadrant. The GSK-313 activity increased, and expression of β-catenin decreased significantly in the hippocampus of the CIH-exposed mice. Besides, CIH significantly increased hippocampal neuronal apoptosis, with an elevated apoptosis index. Meanwhile, LiCI decreased the activity of GSK-β and increased the expression of β-catenin and partially reversed the spatial memory deficits in MWM and the apoptosis caused by CIH. Conclusions： Wntβ-catenin signaling pathway abnormalities possibly play an important role in the development of cognitive deficits among mice exposed to CIH and that LiCI might attenuate CIH-induced cognitive impairment via Wntβ-c
Yue-Ying PanYan DengSheng XieZhi-Hua WangYuWangJie RenHui-Guo Liu
Background：The mechanism of the neural injury caused by chronic intermittent hypoxia （CIH） that characterizes obstructive sleep apnea syndrome （OSAS） is not clearly known.The purpose of this study was to investigate whether P2X7 receptor （P2X7R） is responsible for the CIH-induced neural injury and the possible pathway it involves.Methods：Eight-week-old male C57BL/6 mice were used.For each exposure time point,eight mice divided in room air （RA） and IH group were assigned to the study of P2X7R expression.Whereas in the 21 days-Brilliant Blue G （BBG,a selective P2X7R antagonist） study,48 mice were randomly divided into CIH group,BBG-treated CIH group,RA group and BBG-treated RA group.The hippocampus P2X7R expression was determined by Western blotting and real-time polymerase chain reaction （PCR）.The spatial learning was analyzed by Morris water maze.The nuclear factor kappa B （NFκB） and NADPH oxidase 2 （NOX2） expressions were analyzed by Westem blotting.The expressions of tumor necrosis factor α,interleukin 1 β （IL-β）,IL-18,and IL-6 were measured by real-time PCR.The malondialdehyde and superoxide dismutase levels were detected by colorimetric method.Cell damage was evaluated by Hematoxylin and Eosin staining and Terminal Transferase dUTP Nick-end Labeling method.Results：The P2X7R mRNA was elevated and sustained after 3-day IH exposure and the P2X7R protein was elevated and sustained after 7-day IH exposure.In the BBG study,the CIH mice showed severer neuronal cell damage and poorer performance in the behavior test.The increased NFκB and NOX2 expressions along with the inflammation injury and oxidative stress were also observed in the CIH group.BBG alleviated CIH-induced neural injury and consequent functional deficits.Conclusions：The P2X7R antagonism attenuates the CIH-induced neuroinflammation,oxidative stress,and spatial deficits,demonstrating that the P2X7R is an important therapeutic target in the cognition deficits accompanied OSAS.
Yan Deng Xue-Ling Guo Xiao Yuan Jin Shang Die Zhu Hui-Guo Liu
Summary： Endothelial dysfunction induced by intermittent hypoxia （IH） participates in obstructive sleep apnea syndrome （OSAS）-associated cardiovascular disorders. Myeloid differentiation primary response 88 （MyD88） and tumor necrosis factor receptor-associated factor 6 （TRAF6） regulate nu- merous downstream adaptors like mitogen-activated protein kinases （MAPKs） and the subsequent oxidative stress and inflammatory responses. This study aimed to characterize the role of MyD88/TRAF6 in IH-treated cell function and its associated signaling. Human umbilical vein endo- thelial cells （HUVECs） were randomly exposed to IH or normoxia for 0, 2, 4 and 6 h. Western blot- ting was used to detect the expression pattern of target gene proteins [angiotensin 1 receptor （AT1R）, p-ERK1/2, p-p38MAPK, MyD88 and TRAF6], and the relationships among these target genes down-regulated by the corresponding inhibitors were studied. Finally, the influence of these target genes on proliferation of HUVECs was also assessed by EdU analysis. Protein levels of AT1R, TRAF6 and p-ERK1/2 were increased after IH exposure, with a slight rise in MyD88 and a dynamic change in p-p38MAPK. The down-regulation of TRAF6 by siRNA reduced ERK1/2 phosphorylation during IH without any effects on ATIR. Blockade of AT1R with valsartan decreased TRAF6 and p-ERK1/2 protein expression after IH exposure. ERK1/2 inhibition with PD98059 suppressed only AT1R expression. IH promoted HUVECs proliferation, which was significantly suppressed by the in- hibition of TRAF6, AT1R and ERK1/2. The findings demonstrate that TRAF6 regulates the prolifera- tion of HUVECs exposed to short-term IH by modulating cell signaling involving ERK1/2 down- stream of AT1R. Targeting the AT1R-TRAF6-p-ERK1/2 signaling pathway might be helpful in re- storing endothelial function.
Atorvastatin is proven to ameliorate cardiac hypertrophy induced by chronic intermittent hypoxia （CIH）. However, little is known about the mechanism by which atorvastatin modulates CIH-induced cardiac hypertrophy, and whether specific hypertrophyrelated microRNAs are involved in the modulation. MiR-31 plays key roles in the development of cardiac hypertrophy induced by ischemia/hypoxia. This study examined whether miR-31 was involved in the protective role of atorvastatin against CIH-induced myocardial hypertrophy. H9c2 cells were subjected to 8-h intermittent hypoxia per day in the presence or absence of atorvastatin for 5 days. The size of cardiomyocytes, and the expression of caspase 3 and miR-31 were determined by Western blotting and RT-PCR, respectively. MiR-31 mimic or Ro 31-8220, a specific inhibitor of protein kinase C epsilon （PKCε）, was used to determine the role of miR-31 in the anti-hypertrophic effect of atorvastatin on cardiomyocytes. PKCε in the cardiomyocytes with miR-31 upregulation or downregulation was detected using RT-PCR and Western blotting. The results showed that CIH induced obvious enlargement of cardiomyocytes, which was paralleled with increased atrial natriuretic peptide （ANP）, brain natriuretic peptide （BNP）, and slow/beta cardiac myosin heavy-chain （MYHT） mRNA levels. All these changes were reversed by the treatment with atorvastatin. Meanwhile, miR-31 was increased by CIH in vitro. Of note, the atorvastatin pretreatment significantly increased the mRNA and protein expression of PKCε and decreased that of miR-31. Moreover, overexpression of miR-31 abolished the anti-hypertrophic effect of atorvastatin on cardiomyocytes. Upregulation and downregulation of miR-31 respectively decreased and increased the mRNA and protein expression of PKCε. These results suggest that atorvastatin provides the cardioprotective effects against CIH probably via up-regulating PKCε and down-regulating miR-31.
Jie RENWei LIUGuang-cai LIMeng JINZhen-xi YOUHui-guo LIUYi HU
