Hypoxia and its preconditioning on cardiac and vascular remodelling in experimental animals

Time delays between physiological signals in interpreting the body's responses to intermittent hypoxia in obstructive sleep apnea

Objective.Intermittent hypoxia, the primary pathology of obstructive sleep apnea (OSA), causes cardiovascular responses resulting in changes in hemodynamic parameters such as stroke volume (SV), blood pressure (BP), and heart rate (HR). However, previous studies have produced very different conclusions, such as suggesting that SV increases or decreases during apnea. A key reason for drawing contrary conclusions from similar measurements may be due to ignoring the time delay in acquiring response signals. By analyzing the signals collected during hypoxia, we aim to establish criteria for determining the delay time between the onset of apnea and the onset of physiological parameter response.Approach.We monitored oxygen saturation (SpO2), transcutaneous oxygen pressure (TcPO2), and hemodynamic parameters SV, HR, and BP, during sleep in 66 patients with different OSA severity to observe body's response to hypoxia and determine the delay time of above parameters. Data were analyzed using the Kruskal-Wallis test, Quade test, and Spearman test.Main results.We found that simultaneous acquisition of various parameters inevitably involved varying degrees of response delay (7.12-25.60 s). The delay time of hemodynamic parameters was significantly shorter than that of SpO2and TcPO2(p< 0.01). OSA severity affected the response delay of SpO2, TcPO2, SV, mean BP, and HR (p< 0.05). SV delay time was negatively correlated with the apnea-hypopnea index (r= -0.4831,p< 0.0001).Significance.The real body response should be determined after removing the effect of delay time, which is the key to solve the problem of drawing contradictory conclusions from similar studies. The methods and important findings presented in this study provide key information for revealing the true response of the cardiovascular system during hypoxia, indicating the importance of proper signal analysis for correctly interpreting the cardiovascular hemodynamic response phenomena and exploring their physiological and pathophysiological mechanisms.

Anti-atherosclerotic activity of aqueous extract of Ipomoea batatas (L.) leaves in high-fat diet-induced atherosclerosis model rats

OBJECTIVES

Cardiovascular diseases, especially atherosclerosis, are the leading cause of human mortality in Indonesia. Ipomoea batatas (L.) is a food plant used in Indonesian traditional medicine to treat cardiovascular diseases and related conditions. We assessed the anti-atherosclerotic activity of the aqueous extract of I. batatas leaves in a rat model of high-fat diet-induced atherosclerosis and its mechanism.

METHODS

The presence of amino acid content in the I. batatas L. purple variant was determined by liquid chromatography high-resolution mass spectrometry (LC-HRMS). Thirty male Wistar rats were divided into five groups (n=6/group), i.e., standard diet group (SD), high-fat diet group (HF), and HF plus I. batatas L. extracts orally (625; 1,250; or 2,500 mg/kg) groups. The numbers of macrophages and aortic wall thickness were analyzed histologically. Immunohistochemical analyses were performed to assess foam cells-oxidized low-density lipoprotein (oxLDL), endothelial nitric oxide synthase (eNOS), and vascular endothelial growth factor (VEGF) expression in the aorta.

RESULTS

LC-HRMS analysis showed nine amino acid content were identified from I. batatas L. In vivo study revealed that oral administration of I. batatas L. leaf extract alleviated foam cells-oxLDL formation and aortic wall thickness caused by high-fat diet atherosclerosis rats. Further, I. batatas L. leaf extract promoted the number of macrophages and modulated VEGF and eNOS expression in the aorta.

CONCLUSIONS

I. batatas L. leaf extract shows a positive anti-atherosclerosis effect. Furthermore, the mechanism may promote the macrophages, eNOS, VEGF expressions, and inhibition of foam cells-oxLDL formation and aortic wall thickness with the best dosage at 2,500 mg/kg. This could represent a novel approach to prevent cardiovascular diseases.

The Protective Effects on Ischemia–Reperfusion Injury Mechanisms of the Thoracic Aorta in Daurian Ground Squirrels (Spermophilus dauricus) over the Torpor–Arousal Cycle of Hibernation

Hibernators are a natural model of vascular ischemia–reperfusion injury; however, the protective mechanisms involved in dealing with such an injury over the torpor–arousal cycle are unclear. The present study aimed to clarify the changes in the thoracic aorta and serum in summer-active (SA), late-torpor (LT) and interbout-arousal (IBA) Daurian ground squirrels (Spermophilus dauricus). The results show that total antioxidant capacity (TAC) was unchanged, but malondialdehyde (MDA), hydrogen peroxide (H₂O₂), interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) were significantly increased for the LT group, whereas the levels of superoxide dismutase (SOD) and interleukin-10 (IL-10) were significantly reduced in the LT group as compared with the SA group. Moreover, the levels of MDA and IL-1β were significantly reduced, whereas SOD and IL-10 were significantly increased in the IBA group as compared with the SA group. In addition, the lumen area of the thoracic aorta and the expression of the smooth muscle cells (SMCs) contractile marker protein 22α (SM22α) were significantly reduced, whereas the protein expression of the synthetic marker proteins osteopontin (OPN), vimentin (VIM) and proliferating cell nuclear antigen (PCNA) were significantly increased in the LT group as compared with the SA group. Furthermore, the smooth muscle layer of the thoracic aorta was significantly thickened, and PCNA protein expression was significantly reduced in the IBA group as compared with the SA group. The contractile marker proteins SM22α and synthetic marker protein VIM underwent significant localization changes in both LT and IBA groups, with localization of the contractile marker protein α-smooth muscle actin (αSMA) changing only in the IBA group as compared with the SA group. In tunica intima, the serum levels of heparin sulfate (HS) and syndecan-1 (Sy-1) in the LT group were significantly reduced, but the serum level of HS in the IBA group increased significantly as compared with the SA group. Protein expression and localization of endothelial nitric oxide synthase (eNOS) was unchanged in the three groups. In summary, the decrease in reactive oxygen species (ROS) and pro-inflammatory factors and increase in SOD and anti-inflammatory factors during the IBA period induced controlled phenotypic switching of thoracic aortic SMCs and restoration of endothelial permeability to resist ischemic and hypoxic injury during torpor of Daurian ground squirrels.