Effects of intermittent hypoxia stimulation with different frequencies on HT22 cell viability and expression of Hif-1α and p-NF-κB / 生理学报

Intermittent hypoxia (IH) could induce cognitive impairment through oxidative stress and inflammation. However, the degree of cell damage is closely related to the IH stimulus frequency. IH stimulation with different frequencies also induces opposite results on neuronal cell lines. Therefore, this study was aimed to compare the effects of IH stimulation with three different frequencies on murine hippocampal neuronal HT22 cell activity, and to explore the molecular mechanism of the IH stimulus frequency-related neuron injury. HT22 cells were cultured and divided into control group and three IH stimulation groups with different frequencies. Oxygen concentration in the chamber was circulated between 21% and 1% (IH1 group, 6 cycles/h; IH2 group, 2 cycles/h; IH3 group, 0.6 cycle/h). Cell morphology was observed at 6, 12, 24 and 48 h of IH treatment. Cell viability was determined by the CCK-8 kit, lactate dehydrogenase (LDH) content in cell supernatant was determined by LDH kit, oxidative stress level was detected by the reactive oxygen species (ROS) probe, and protein expression levels of hypoxia inducible factor-1α (Hif-1α) and phosphorylated nuclear factor κB (p-NF-κB) were detected by Western blot. The results showed that, compared with control group, cell number and activity in the three IH groups were decreased, LDH content and ROS levels were increased with the prolongation of IH stimulation time, and the changes were most obvious in the IH1 group among those of the three IH groups. Hif-1α expression and the p-NF-κB/NF-κB ratio were also up-regulated with the prolongation of IH stimulation time, and the changes of IH1 group were the most significant. These results suggest that IH stimulation induces oxidative stress injury in HT22 cells, which is related to increased Hif-1α expression and NF-κB phosphorylation. Moreover, the higher frequency of IH stimulation induces more serious cell injury.

The effects of Xiaotan Huayu Liqiao formula on mesenteric artery function in rats exposed to chronic intermittent hypoxia / 中国应用生理学杂志

OBJECTIVE@#To investigate the effects of Xiaotan Huayu Liqiao formula (the Chinese Medicine) on mesenteric artery function in rats exposed to chronic intermittent hypoxia (CIH), and to explore the related mechanism.@*METHODS@#Forty-eight male SD rats were randomly divided into four groups as Normoxia, CIH, Formula+CIH and formula group. Rats were exposed to normoxia in the Normoxia and Formula group, or intermittent hypoxia in CIH or Formula+CIH group. Xiaotan Huayu Liqiao formula was given at 24g/kg by intragastric administration before intermittent hypoxia exposure. The pathological changes of mesenteric artery were determined by HE staining, and the relaxation of mesenteric artery (induced by acetylcholine(ACh) and L-arginine(L-Arg)) was recorded by microvascular ring technique. Serums of all rats were collected (0 d and 21 d) and the content of NO was detected by ELISA. The levels of endothelial nitric oxide synthase (eNOS) and p-eNOS were measured by Western blot.@*RESULTS@#Compared with Normoxia group, the mesenteric arterial endothelial injury and media thickening were observed and the relaxation of mesenteric artery was significantly reduced in rats exposed to CIH. The level of NO in serum and the ratio of p-eNOS/eNOS were also decreased in the CIH group. Xiaotan Huayu Liqiao formula administration improved the pathologic changes and dilatation function of mesenteric artery, increased the levels of NO and p-eNOS. Compared with Normoxia group,all the results were not observed significant difference in Formula group.@*CONCLUSION@#Xiaotan Huayu Liqiao formula increased the bioavailability of NO, and ameliorated the CIH induced mesenteric artery function injury.

Improvement of hydrogen on liver oxidative stress injury in chronic intermittent hypoxia rats / 中国应用生理学杂志

OBJECTIVE@#To explore the effects of hydrogen on liver injury in chronic intermittent hypoxia rats and the related oxidative stress mechanism.@*METHODS@#Twenty-four male adult SD rats were randomly divided into 3 groups(=8):the normoxia group (Norm), the chronic intermittent hypoxia group (CIH), the chronic intermittent hypoxia and hydrogen group (H + CIH). Rats in Norm group were exposed in air, those in the other 2 groups suffered from chronic intermittent hypoxia conditions for 5 weeks. Before the CIH treatment, rats in H+CIH group inhaled hydrogen gas at 67% concentration for 1 hour. The serum biochemical indicators of oxidative stress, pro-inflammatory cytokine, liver enzyme and blood lipid were inspected after five weeks treatment, the pathological changes of liver tissue were also observed in the transmission electron microscope.@*RESULTS@#Compared with Norm group, the microstructure of liver cells was severely injured, and the serum levels of glutamic-pyruvic transaminase(ALT),glutamic-oxalacetic transaminase (AST) were significantly higher in CIH group (<0.05); the serum level of 8-hydroxy-2 deoxyguanosine(8-OHdG) and interleukin-6(IL-6) was significantly higher, the serum level of superoxide dismutase (SOD) was significantly lower. Compared with CIH group, the pathology of liver microstructure were significantly improved and the serum levels of ALT, AST were significantly lower in H+CIH group (<0.05); the serum levels of 8-OHdG and IL-6 were significantly lower, the serum level of SOD was significantly higher. Compared with Norm group, the serum level of IL-1 was higher, the serum level of TC, TG, and low density lipoprotein(LDL) were lower, but there was no statistical difference with those in CIH group. There was no statistical difference in the serum level of high density lipoprotein (HDL)among the three groups.@*CONCLUSIONS@#Pre-treatment with hydrogen could improve the liver injury caused by chronic intermittent hypoxia, and reducing oxidative stress level for protecting the liver cells damage.

Early cardiac injury in patients with obstructive sleep apnea / 中国应用生理学杂志

OBJECTIVE@#To evaluate the early cardiac injury caused by obstructive sleep apnea (OSA) before the development of cardiovascular symptoms of OSA.@*METHODS@#Ninety-two patients without any known cardiovascular disorders who underwent polysomnography (PSG) were enrolled in the study. Subjects were divided into mild, moderate, and severe OSA groups by their apnea hypopnea index (AHI), and 25 healthy individuals were identified as controls. After PSG examination, fasting blood samples for the evaluation of N-terminal pro-brain natriuretic peptide (NT-proBNP) and heart-type fatty acid binding protein (h-FABP) were collected in the morning, and left ventricular(LV) functions were assessed by using echocardiographic methods. Thirty moderate and severe OSA patients were treated with continuous positive airway pressure respectively (CPAP).@*RESULTS@#The levels of h-FABP and NT-proBNP were obviously higher in all OSA groups than those in the control group (<0.01), and were positively correlated with AHI (<0.01). The Em/Am values of all OSA groups and E/A values of the moderate and severe OSA groups were significantly reduced (<0.01). The difference in Em/Am values among the groups was statistically significant (<0.01). Compared with those before treatment, h-FABP and NT-BNP levels in serum of OSA patients after CPAP treatment were significantly reduced (<0.01), and Em/Am and E/A values were significantly increased (<0.01).@*CONCLUSIONS@#Left ventricular diastolic dysfunction and early myocardial microtrauma are major manifestations of early heart damage in patients with OSA. CPAP therapy could significantly improve early cardiac damage in OSA patients.

The role of adventitia in hypoxic vascular remodeling / 生理学报

As an important site for the production, storage and release of key regulators for vascular function, the vascular adventitia is thought to be a damage sensing tissue in the vascular wall under certain conditions. The adventitial cells are usually the first ones to respond to vascular stress or injury, and consequently affect the structure and function of blood vessel wall. Growing lines of evidence have shown that the vascular adventitia exhibits the earliest and most prominent changes in vascular remodeling due to hypoxia and related pulmonary hypertension and atherosclerosis. In particular, fibroblasts play an important role in the adaptation and regulation to local microenvironmental changes. This review focuses on the role of vascular adventitia in hypoxia-induced vascular remodeling and the underlying molecular mechanisms.

Bosentan ameliorates hypertension in rats exposed to chronic intermittent hypoxia through inhibiting renal sympathetic nerve activity / 生理学报

The purpose of this study is to investigate the effect of the oral endothelin antagonist Bosentan on blood pressure and renal sympathetic nerve activity (RSNA) in rats exposed to chronic intermittent hypoxia (CIH), and to explore the sympathoexcitation mechanism of endothelin-1 (ET-1) in CIH-induced hypertension. Twenty-four male SD rats were randomly divided into normoxia, CIH and Bosentan groups. Rats in the normoxia group were exposed to normoxic environment, and rats in CIH or Bosentan group were exposed to intermittent hypoxia for 3 weeks. Bosentan was given at 50 mg/kg by intragastric administration before intermittent hypoxia exposure in Bosentan group. Systolic blood pressure (SBP) was measured by BP-2000, and the change of RSNA to sodium nitroprusside (SNP) or phenylephrine (PE) was recorded by PowerLab signal acquisition system. Serums of all rats were collected and the contents of ET-1 and norepinephrine (NE) were measured by ELISA. Results showed that blood pressure was gradually increased following CIH exposure compared with the normoxia group during the 3 weeks (P < 0.01, P < 0.01, P < 0.001). The basal RSNA was increased and baroreflex sensitivity was decreased in rats exposed to CIH. Furthermore, the blood pressure was positively correlated with the level of ET-1 in serum in rats exposed to CIH (r = 0.833, P = 0.01). Bosentan administration significantly decreased SBP and basal RSNA, increased the baroreflex sensitivity, and decreased serum NE level in rats exposed to CIH. These results suggest that ET-1 is related with blood pressure elevation in rats exposed to CIH, and Bosentan reverses CIH-induced hypertension by decreasing RSNA.

Adenosine reduces intracellular free calcium concentration in guinea pig ventricular myocytes / 中国应用生理学杂志

<p><b>AIM</b>To observe the effects of adenosine on intracellular calcium concentration ([Ca2+]i) level in guinea pig ventricular myocytes and to define the possible mechanisms involved.</p><p><b>METHODS</b>The effects of adenosine on [Ca2+]i were investigated in guinea pig ventricular myocytes. [Ca2+]i was detected by laser confocal microscopy and represented by relative fluorescent intensity ((FI-FI0)/FI0, %, FIo: control, FI: administration of drugs).</p><p><b>RESULTS</b>(1) Adenosine (10, 50, 100 micromol/L) reduced [Ca2+]i of ventricular myocytes in both normal Tyrode's solution and Ca(2+) -free Tyrode's solution in a concentration-dependent manner. (2) Tyrode's solution containing 30 mmol/L KCl (high K+ Tyrode's solution) induced [Ca2+]i elevation in ventricular myocytes, while adenosine (10, 50, 100 micromol/L) markedly inhibited the increase in [Ca2+]i induced by KCl. (3) Pretreatment with DPCPX (1 micromol/L) significantly reduced the effects of adenosine (100 micromol/L) in high K+ Tyrode's solution. The effects of adenosine (100 micromol/L) on [Ca2+]i in high K+ Tyrode's solution were also partially attenuated by pretreatment with L-NAME (1 mmol/L). (4) Adenosine (100 micromol/L) markedly inhibited the low concentration of ryanodine-induced [Ca2+]i increase in Ca(2+) -free Tyrode's solution. (5) When the propagating waves of elevated [Ca2+]i (Ca2+ waves) were produced by increasing extracellular Ca2+ concentration from 1 mmol/L to 10 mmol/L, adenosine (100 micromol/L) could block the propagating waves of elevated [Ca2+]i, reduce the frequency and duration of propagating waves, and reduce [Ca2+]i as well.</p><p><b>CONCLUSION</b>Adenosine may reduce the [Ca2+]i in isolated guinea pig ventricular myocytes via inhibiting Ca2+ influx and alleviating Ca2+ release from sarcoplasmic reticulum(SR). The reduction of Ca2+ influx might be due to the inhibition of voltage-dependent Ca2+ channel via adenosine A1 receptor, and NO might be involved in this process.</p>

Effects of genistein on intracellular free-calcium concentration in guinea pig ventricular myocytes / 生理学报

The effects of genistein (GST) on intracellular calcium concentration ([Ca(2+)](i)) were investigated in guinea pig ventricular myocytes. [Ca(2+)](i) was detected by confocal microscopy and represented by relative fluorescent intensity (FI-F(0)) /FI(0), %). The results showed that GST (10-40 micromol/L) reduced [Ca(2+)](i) in normal Tyrode's solution, Ca(2+)-free Tyrode's solution and normal Tyrode's solution containing 3 mmol/L EGTA in a concentration-dependent manner. The effects of GST on [Ca(2+)](i) in normal Tyrode's solution were partially inhibited by pretreatment with sodium orthovanadate, a potent inhibitor of protein tyrosine phosphatase, or L-type Ca(2+) channel agonist Bay K8644. GST also markedly inhibited the ryanodine-induced [Ca(2+)](i) responses in Ca(2+)-free Tyrode's solution. When Ca(2+) waves were produced by increasing extracellular Ca(2+) concentration from 1 to 10 mmol/L, GST (40 micromol/L) could block the propagating waves of elevated [Ca(2+)](i), and reduce the velocity and duration of propagating waves. These results suggest that GST may reduce the [Ca(2+)](i) in isolated guinea pig ventricular myocytes. The inhibition of voltage-dependent Ca(2+) channel, tyrosine kinase inhibition, and alleviation of Ca(2+) release from SR are possibly involved in the GST effect.

Effect of genistein on L-type calcium current in guinea pig ventricular myocytes / 生理学报

This paper was aimed to study the effect of genistein (GST) on L-type calcium current (I(Ca,L)) in isolated guinea pig ventricular myocytes using whole cell patch-clamp recording technique. The results are as follows. (1) GST (10, 50, 100 micromol/L) reduced the voltage-activated peak amplitude of I(Ca,L) in a concentration-dependent manner. Daidzein (100 micromol/L), a structural analogue of GST which has little or no inhibitory effect on tyrosine kinase, produced no effect over the same concentration range on I(Ca,L) (n=5, P>0.05). (2) GST up- shifted the current-voltage (I-V) curve, but the characteristics of I-V relationship were not significantly altered, and the maximal activation voltage of I(Ca,L) was not different from that of control. GST did not affect the activation kinetics of I(Ca,L). (3) GST markedly shifted the steady-state inactivation curve of I(Ca,L) to the left, and accelerated the voltage-dependent steady-state inactivation of I(Ca,L). V(0.5) value was -28.6 +/-0.6 mV in the control and -32.8 +/-1.1 mV in the presence of GST. The kappa values were 5.8 +/-0.5 mV and 6.5 +/-0.9 mV, respectively (n=6, P<0.05). (4) GST markedly shifted the curve of time-dependent recovery of I(Ca,L) from the steady-state inactivation to the right, and slowed down the recovery of I(Ca,L) from inactivation (n=7, P<0.01). (5) Sodium orthovanadate (1 mmol/L), a potent inhibitor of tyrosine phosphatase, significantly inhibited GST-induced inhibition (n=6, P<0.01). From the results obtained it is concluded that genistein inhibits I(Ca,L) and acts on the inactivated state of L-type calcium channel. This inhibitory effect of GST involves protein tyrosine kinase inhibition in guinea pig ventricular myocytes.

Limb ischemic preconditioning reduces infarct size following myocardial ischemia-reperfusion in rats / 生理学报

The effect of limb ischemic preconditioning (LIP) on ischemia-reperfused myocardium was examined in the urethane-anesthetized rats to determine whether LIP produces cardioprotection and to observe the roles of adenosine and neural reflex in this effect. The area at risk (AR) and infarct area (IA) were determined using Evans blue and nitro-blue tetrazolium staining respectively. Infarct size (IS) was defined as 100xIA/AR (%). The results obtained are as follows: (1) During 30 min myocardial ischemia and subsequent 120 min reperfusion, the myocardial infarct size occupied 51.48+/-0.82% of the area at risk. (2) LIP significantly reduced the myocardial infarct size to 35.14+/-0.88% (p<0.01 ), indicating the cardioprotective effect of such an intervention. (3) Femoral nerve section (FNS) completely abolished the cardioprotection afforded by LIP. (4) Intrafemoral artery injection of adenosine (10 nmol/kg) produced a similar effect to that of LIP, reducing the myocardial infarct size to 37.28+/-1.68%, while intrafemoral vein injection of the same dose of adenosine showed no effect. (5) Pretreatment with a selective adenosine A(1) receptor antagonist 8-cyclopentyl-1,diproylxanthine (DPCPX ) (32 nmol/kg) partially abolished the cardioprotection of LIP on myocardium. Taken together, it is concluded that LIP reduces infarct size following myocardial ischemia-reperfusion, and that the locally released adenosine and thereby the activated relevant neural pathway play an important role in the cardioprotection provided by LIP.

Effects of taurine on rabbit cardiomyocyte apoptosis during ischemia/reperfusion injury / 中国应用生理学杂志

<p><b>AIM</b>To study the effect of taurine (Tau) on rabbit cardiomyocyte apoptosis during ischemia/reperfusion (I/R) injury.</p><p><b>METHODS</b>Rabbit heart I/R injury was induced by occluding the left anterior descending coronary artery for 45 min and reperfusion for 180 min. taurine (200 mg/kg) was intravenously injected 5 min before heart ischemia. Cardiomyocyte apoptosis was measured by using terminal deoxynucleotidyl transferase--mediated dUTP nick end labeling method (TUNEL), flow cytometry (FCM) and DNA agarose gel electrophoresis.</p><p><b>RESULTS</b>DNA ladder pattern of DNA in myocardium was revealed by agarose gel electrophoresis in I/R group while was not found in Tau + I/R group. Apoptotic cardiomyocytes were sparse within ischemic myocardium at risk in Tau + I/ R group as compared with that in I/R group (TUNEL stain). Apoptosis rate in ischemic myocardium from I/R and Tau + I/R groups detected by flow cytometry was 17.66% +/- 1.54% and 4.86% +/- 1.23%, respectively. Fas and Bax protein expressions in ischemic myocardium of I/R group were higher than that in nonischemic myocardium group (P < 0.01), Bcl-2/Bax ratio in I/R group was lower than that in nonischemic myocardium (P < 0.01); while in Tau + I/R group, Fas and Bax protein expressions were lower than that in I/R group (P < 0.01), the Bcl-2/Bax ratio was higher than that in I/R group (P < 0.01).</p><p><b>CONCLUSION</b>Taurine reduced apoptosis of myocytes in I/R rabbit heart; its mechanism may involve Fas, Bax and Bcl-2 proteins expression.</p>

Responses of regional vascular beds to local injection of genistein in rats / 生理学报

The effects of local injection of genistein on femoral, renal, and mesenteric vascular beds were investigated respectively by constant flow perfusion method in 72 anaesthetized rats. The results are as follows: (1) genistein (0.4, 0.8, 1.2 mg/kg) decreased the perfusion pressure (PP) of femoral vascular bed in a dose-dependent manner. The effect of genistein (0.8 mg/kg) was partially inhibited by L-NAME, or by sodium orthovanadate (50 microg/kg), a potent inhibitor of protein tyrosine phosphatase; (2) genistein also decreased the PP of renal vascular bed in a dose-dependent manner and the effect of genistein was completely inhibited by pretreatment with sodium orthovanadate, but unaffected by L-NAME; and (3) genistein decreased the PP of mesenteric vascular bed in a dose-dependent manner, an effect which was partially inhibited by sodium orthovanadate, but unaffected by L-NAME. From the results obtained, it is concluded that genistein can decrease the vascular tone in the femoral, renal, and mesenteric vascular beds with the underlying mechanism that involves tyrosine kinase inhibition, while in femoral arterial beds, it also involves NO release.

Action of genistein on tension of isolated rabbit femoral artery and its mechanism / 生理学报

The phytoestrogen genistein has been shown to relax agonist-preconstricted arteries in vitro, the mechanism of this relaxation remains incompletely understood. The present study aimed to investigate the effect of phytoestrogen genistein on the tension of rabbit femoral arteries in vitro and to determine the mechanism of such relaxation. The results are as follows: (1) genistein (10~40 micromol/L) relaxed femoral arterial rings in a concentration-dependent manner under the condition of precontraction induced by phenylephrine (PE, 1 micromol/L); (2) removal of the endothelium significantly inhibited genistein-induced relaxation; (3) pretreatment with NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 100 micromol/L) also significantly inhibited this relaxation by genistein, implying that the concentration-dependent vasorelaxation caused by genistein is endothelium-dependent and involved nitric oxide; and (4) pretreatment with an L-type calcium channel agonist, Bay K 8644 (0.5 micromol/L), also significantly inhibited the genistein-induced relaxation in both endothelium-intact and endothelium-denuded rings. The results suggest that the genistein-induced vascular relaxation of these rabbit arteries is partially endothelium-dependent and involves calcium antagonistic mechanism.