Objective To develope a novel rabbit carotid body and carotid common artery model in vivo for the simulation of various intermittent hypoxia ( IH) intensities, IH durations, IH reoxygenation ( ROX) durations and continuous hypoxia ( CH) modes. Methods Forty-five adult New Zealand rabbits ( 2. 5-3. 0 kg) were anesthetized while spontaneous breathing kept intact. The tissue surrounding the right carotid common artery and carotid sinus nerve ( CSN) were cleared and " single" chemoreceptor bundle of the CSN was revealed. Then suction electrodes were placed and CSN afferent activity was monitored and recorded carefully. The right common carotid artery was exposed, cannulated to distal part and its proximal part was ligated. Preparations were challenged by changing the PO2 of the gas mixture equilibrating the perfusate. Alternatively perfusion ( 2 mL/min) of equilibrated perfusate bubbled with normoxia or hypoxia gas mixtures formed IH/ROX cycles in carotid common artery, simulating the pattern of hypoxic episodes seen in obstructive sleep apnea syndrome ( OSAS) , or with continuously perfusing hypoxia perfusate to form CH modes. All the perfusing procedures were regulated by a customized computer-controlled set and monitored using O2 gas analyzer. After the systematic exposures, carotid body, carotid common artery part distal to cannula, and carotid bifurcation were harvested as samples. Results The frequencies and average amplitudes of CSN chemoreceptor bundles afferent activities with normoxia perfusion were ( 0. 17 ±0. 03) impulse/ s and ( 46. 2 ±4. 4) μV, and with hypoxia perfusion were ( 0. 64 ±0. 09) impulse/ s and ( 87. 4 ±6. 6) μV, respectively. PO2 was ( 139 ±1. 5) mm Hg in normoxia perfusate and ( 35. 2 ±1. 3) mm Hg in hypoxia perfusate. Conclusion This new carotid body and carotid common arterymodel is a valuable tool to study neurological and biochemical changes in various IH and CH modes.
ObjectiveTo study the influence of hemin on blood pressure of intermittent hypoxic rats and investigate the mechanism of hypertension caused by intermittent hypoxia.MethodsTwenty-four male SD rats were randomly divided into a hemin group, an intermittent hypoxia group (IH group) and a normal group. Thirty minutes after intraperitoneal injection of hemin, the rats in the hemin group were exposed to intermittent normobaric hypoxic environment (8 h/d). The rats in the IH group were intraperitoneal injected with normal sodium and then exposed to the same environment (8 h/d). The rats in the normal group were intraperitoneal injected with normal sodium and placed in the glass box. The three groups were bred in the same condition. Thirty-five days later, the mean carotid artery pressure (mCAP) of the rats was measured and their plasma carbon monoxide (CO) level was measured by Chalmer’s method. Reverse transcription polymerase chain reaction was performed to detect the levels of heme oxygenase-1 (HO-1) mRNA expression in lung, liver, spleen, kidney and other organs. The expression of HO-1 protein in the organs was detected by immunohistochemistry.ResultsThe mCAP in the IH group was significantly higher than the hemin group and the normal group (P<0.05), and was higher in the hemin group than the normal group (P<0.05). The concentration of plasma CO in the hemin group was higher than the IH group and the normal group (P<0.05). There was no significant difference in plasma CO between the IH group and the normal group (P>0.05). The expression of HO-1 mRNA of lung, liver, spleen and kidney in the hemin group and the IH group was higher than the normal group (P<0.05), and was higher in the hemin group than the IH group (P<0.05). The relationship between mCAP and HO-1 mRNA showed a curvilinear trend. The quadratic curve fitting equation was Y=39.715+446.640X-334.353X2.ConclusionsIntermittent hypoxia can cause hypertension in rats. The HO-1 expression is increased in hypoxic rats, but the plasma CO does not increase significantly. As an inducer of HO-1, hemin can increase the expression of HO-1 and CO in hypoxic rats, then lower their blood pressure to some extent.
ObjectiveTo study the changes of body weight, body length, tail length, femur length, bone mineral density, serum osteocalcin content and apoptosis of bone cells in rats under intermittent hypoxia condition, so as to explore the effects of intermittent hypoxia on bone growth.MethodsForty healthy male SD rats aged 3 to 4 weeks were selected and divided into 2 groups, 20 rats in each group. Group A: normoxic control group (normal diet and normoxic environment); group B: intermittent hypoxia group (normal feeding and was put into the hypoxic chamber to establish intermittent hypoxia environment), 8 hours a day (09:00 to 17:00), 4 weeks of modeling. The body weight, body length and tail length of the two groups were measured in every morning. At the end of 4 weeks after anesthesia, the body weight, body length, tail length and right femur length were measured. The body weight growth rate, body length growth rate and tail length growth rate were calculated. Blood samples were collected from the abdominal aortic, and the content of serum osteocalcin was measured by enzyme linked immunosorbent assay; the right femur bone mineral density was measured by automatic dual-energy X-ray bone densitometer; the apoptosis of bone cells was detected by immunofluorescence staining+TUNEL.ResultsThe body weight growth rate, body length growth rate, tail length growth rate and right femur length in group A were all higher than those in group B (P<0.05); serum osteocalcin content in group A was higher than that in group B (P<0.05); bone mineral density in group A was higher than that in group B (P<0.05); the apoptotic index of bone cells in group B was higher than that in group A (P<0.05). Pearson correlation analysis showed that the serum osteocalcin content was significantly positively correlated with the growth rate of body length, femoral length and bone mineral density (P< 0.01).ConclusionIntermittent hypoxia could reduce osteocalcin secretion, inhibit bone growth and sclerosis, and induce osteocyte apoptosis, thus delay the bone growth.
ObjectiveTo investigate the mechanism of the early kidney injury in rats caused by intermittent hypoxia, and investigate the intervention effect of edaravone.MethodsEighty male Wistar rats were randomly divided into a control group (NC), an intermittent hypoxia group (IH), an intermittent hypoxia edaravone treatment group (IH+NE), and an intermittent hypoxia normal saline matched group (IH+NS). After 4 weeks of model establishment, serum urea nitrogen and creatinine concentration were determined. Pathological changes of kidney were observed under light microscope, and ultrastructural changes of glomeruli and renal tubules were observed under electron microscope. The kidney injury molecule 1 (KIM-1) protein was detected by immunohistochemistry. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), hydroxyl radical and Bcl-2 mRNA, Caspase-3 mRNA, Bax mRNA in homogenate of kidney tissue were measured.ResultsSerum urea nitrogen in each group showed no significant difference. Serum creatinine increased significantly in IH group and significantly decreased after edaravone treatment. There were no significant pathological damages in NC group under light and electron microscopy. IH group showed varying degrees of renal tubule damages compared with NC group. Compared with NC group, the mean optical density of KIM-1 protein in IH group and IH + NS group significantly increased (P<0.01), and the mean optical density of KIM-1 protein in IH+NE group significantly decreased (P<0.01). Compared with NC group, the activity of SOD in IH group and IH+NS group significantly decreased, the content of MDA and hydroxyl radical increased, the expression of Bcl-2 mRNA decreased, the expression of Caspase-3 mRNA and Bax mRNA increased, Bcl-2/Bax decreased. After edaravone intervention, the activity of SOD in kidney tissue of rats significantly increased, the content of MDA and hydroxyl radical significantly decreased, the expression of Bcl-2 mRNA increased, the expression of Caspase-3 mRNA and Bax mRNA decreased, Bcl-2/Bax increased.ConclusionsIntermittent hypoxia can cause kidney injury through oxidative stress and regulation of Bcl-2, Bax and Caspase-3. KIM-1 may be used as a sensitive indicator for monitoring early kidney injury. Edaravone can prevent kidney injury induced by intermittent hypoxia though scavenging oxygen free radical, improving antioxidant capacity, regulating cell apoptosis mediated by regulating Bcl-2/Bax and Caspase-3.
ObjectiveTo investigate the effects of smoking combined with intermittent hypoxia on the pathophysiology of lung tissue and thoracic aorta, and the endothelial injury.MethodsTwenty-four rats (SPF, female, six weeks old) were divided randomly into 4 groups (n=6). The control group was given false smoking and normal oxygen exposure, the smoking-exposed group was exposed in smoking, the intermittent hypoxia group was exposed in intermittent hypoxia environment, and the overlap group was exposed to smoking and intermittent hypoxia. After 8 weeks, body weight, right ventricular hypertrophy index (RVHI), the pathological changes of lung tissue and thoracic aorta were measured, and the level of endothelin-1 (ET-1), endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1α (SDF-1α) in serum of rats were evaluated.ResultsRVHI of rats in the smoking-exposed group, intermittent hypoxia group, overlap group were higher than that in the control group. In addition, RVHI in the overlap group was higher than that in the smoking-exposed group, intermittent hypoxia group (all P<0.05). The levels of ET-1, VEGF and SDF-1α in the serum of the smoking-exposed group, intermittent hypoxia group and overlap group were higher than those in the control group, while the level of eNOS was lower than that in the control group, (all P<0.05), the most significant difference was between control group and the overlap group. Pathological observation of lung tissue and thoracic aorta showed obvious emphysema in the smoking-exposed group and overlap group, which was more obvious in the overlap group than that in the smoking-exposed group (all P<0.05). Lung interstitial inflammatory infiltration, bronchial wall lymphocyte hyperplasia and pulmonary fibrosis were shown in different degrees in the smoking-exposed group, intermittent hypoxia group and overlap group, and the pulmonary arteriole wall showed thickening, fibrosis and peripheral inflammatory infiltration also were found in these groups. Thoracic aorta in the smoking-exposed group, intermittent hypoxia group and overlap group showed different degrees of endothelial cell injury, middle membrane thickening, and collagen fiber hyperplasia. The pathological features of the overlap group were most obvious compared to the other two groups.ConclusionsSmoking and intermittent hypoxia exposure can lead to different degrees of lung tissue and vascular endothelial injury and decrease of vascular endothelial protective factors in rats, resulting in dysfunction of vascular endothelial cells, which leads to the structural remodeling of pulmonary arterioles and aorta, such as thickening, fibrosis, etc. Combined smoking and intermittent hypoxia exposure can lead to more serious pathological damage.
ObjectiveTo explore the mechanism of renal tubular epithelial cell apoptosis induced by endoplasmic reticulum stress in rats with intermittent hypoxia (IH) and the intervention effect of losartan.MethodsSixty SPF grade healthy male SD rats were randomly divided into four groups (15 rats in each group), namely as group A (control group), group B (IH group), group C (IH+losartan group), and group D (IH+saline group). The group C and D were intraperitoneally injected with losartan 30 mg/kg and the same dose of saline 30 minutes daily before the experiment, and then the group B, C and D were placed in the intermittent hypoxia chamber. After 6 weeks of modeling, serum of the rats was sampled to detect the renal function. Hematoxylin-eosin staining was used to observe histomorphological changes of the kidney; transmission electron microscopy was used to observe ultrastructural changes of the kidney; TUNEL was used to detect apoptotic index of the renal tubular epithelial cells; and RT-PCR method was used to detect expressions of caspase-12, JNK and CHOP mRNA in the kidney.ResultsThe differences of renal function among these four groups were statistically significant (all P<0.05). Hematoxylin-eosin staining and transmission electron microscopy showed the histomorphological and ultrastructural changes of the kidneys in group B, C and D compared with group A, and the damages in group B and D were more significant. TUNEL results showed that the apoptotic index of renal tubular epithelial cells in group B and D was significantly higher than that in group A (P<0.01), while that in group C was significantly lower than that in group B and D (all P<0.01). RT-PCR results showed that caspase-12, JNK and CHOP mRNA expressions were significantly higher in group B and D than those in group A (all P<0.01); caspase-12 mRNA expression was significantly lower in group C than that in group B and D (P<0.01; P<0.05); and CHOP mRNA expression was significantly lower in group C than that in group B and D (all P<0.01).ConclusionsIH may induce apoptosis of renal tubular epithelial cells by activating endoplasmic reticulum stress through caspase-12, JNK and CHOP. Losartan has protective effects on the kidney of rats with intermittent hypoxia. Its mechanism may be related to the inhibition of apoptotic pathways mediated by endoplasmic reticulum stress.
Objective To explore the effect of total glucosides of Cistanche deserticola on oxidative stress and cognitive function in rats with intermittent hypoxia. Methods Adult male Wistar rats (n=72) were randomly divided into three groups: a blank control group, a 5% intermittent hypoxia group (IH group) and a total glucosides of Cistanche deserticola intervention group (TGs intervention group). The 5% intermittent hypoxia rat model was simulated by using the self-made cabin of intermittent hypoxia. The rats in the IH group and the TGs intervention group were given 5% intermittent hypoxia respectively, and the rats in the TGs intervention group were treated with total glucosides of Cistanche deserticola simultaneously. Learning and memory function was tested by Morris water maze in three groups at the 2nd, 4th, 6th and 8th week respectively. The expressions of superoxide dismutase (SOD) and malondialdehyde (MDA) in hippocampus were detected by test kit. Results Compared with the blank control group, the escape latency time of the rats in the IH group and the TGs intervention group was significantly prolonged at the 2nd, 4th, 6th and 8th week respectively (P<0.05). The time to cross the target quadrant in the IH group and the TGs intervention group was gradually shortened at the 2nd, 4th, 6th and 8th week respectively (P<0.05). Compared with the IH group, the escape latency gradually shortened at the 2nd, 4th, 6th and 8th week in the TGs intervention group (P<0.05), while the time to cross the target quadrant was gradually prolonged at the 2nd, 4th, 6th and 8th week (P<0.05). The expressions of MDA in hippocampal tissue in the IH group and the TGs intervention group increased at the 2nd, 4th, 6th and 8th week (P<0.05), which were significantly higher than those in the blank control group; and the expressions of SOD at the 2nd, 4th, 6th, and 8th week were all lower than those in the blank control group(P<0.05). Compared with the IH group, the expression of MDA protein in hippocampal tissue in the TGs intervention group decreased at the 2nd, 4th, 6th and 8th week, while the expression of SOD protein at the 2nd, 4th, 6th and 8th week increased, and the differences were statistically significant (P<0.05). Conclusion The total glycosides of Cistanche deserticola can improve the learning and memory function of intermittent hypoxia rats by inhibiting oxidative stress.