Targeting the ROS-HIF-1-endothelin axis as a therapeutic approach for the treatment of obstructive sleep apnea-related cardiovascular complications

Intermittent Hypoxia Mediates Caveolae Disassembly That Parallels Insulin Resistance Development

Repetitive complete or incomplete pharyngeal collapses are leading to chronic intermittent hypoxia (CIH), a hallmark feature of obstructive sleep apnea (OSA) syndrome responsible for many metabolic disorders. In humans, an association between OSA and insulin resistance has been found independently of the degree of obesity. Based on our previous work showing that hypoxia applied to adipocytes led to cellular insulin resistance associated with caveolae flattening, we have investigated the effects of CIH on caveolae structuration in adipose tissue. Original exploratory experiences demonstrate that 6 weeks-exposure of lean mice to CIH is characterized by systemic insulin resistance and translates into adipocyte insulin signaling alterations. Chronic intermittent hypoxia also induces caveolae disassembly in white adipose tissue (WAT) illustrated by reduced plasma membrane caveolae density and enlarged caveolae width, concomitantly to WAT insulin resistance state. We show that CIH downregulates caveolar gene and protein expressions, including cavin-1, cavin-2, and EHD2, underlying molecular mechanisms responsible for such caveolae flattening. Altogether, we provide evidences for adipose tissue caveolae disassembly following CIH exposure, likely linked to cavin protein downregulation. This event may constitute the molecular basis of insulin resistance development in OSA patients.

Oxidative stress and diabetic retinopathy: Molecular mechanisms, pathogenetic role and therapeutic implications

Oxidative stress, a cytopathic outcome of excessive generation of ROS and the repression of antioxidant defense system for ROS elimination, is involved in the pathogenesis of multiple diseases, including diabetes and its complications. Retinopathy, a microvascular complication of diabetes, is the primary cause of acquired blindness in diabetic patients. Oxidative stress has been verified as one critical contributor to the pathogenesis of diabetic retinopathy. Oxidative stress can both contribute to and result from the metabolic abnormalities induced by hyperglycemia, mainly including the increased flux of the polyol pathway and hexosamine pathway, the hyper-activation of protein kinase C (PKC) isoforms, and the accumulation of advanced glycation end products (AGEs). Moreover, the repression of the antioxidant defense system by hyperglycemia-mediated epigenetic modification also leads to the imbalance between the scavenging and production of ROS. Excessive accumulation of ROS induces mitochondrial damage, cellular apoptosis, inflammation, lipid peroxidation, and structural and functional alterations in retina. Therefore, it is important to understand and elucidate the oxidative stress-related mechanisms underlying the progress of diabetic retinopathy. In addition, the abnormalities correlated with oxidative stress provide multiple potential therapeutic targets to develop safe and effective treatments for diabetic retinopathy. Here, we also summarized the main antioxidant therapeutic strategies to control this disease.

•

Oxidative stress can both contribute to and result from hyperglycemia-induced metabolic abnormalities in retina.

•

Genes important in regulation of ROS are epigenetically modified, increasing ROS accumulation in retina.

•

Oxidative stress is closely associated with the pathological changes in the progress of diabetic retinopathy.

•

Antioxidants ameliorate retinopathy through targeting multiple steps of oxidative stress.

HIF-1α-Mediated, NADPH Oxidase-Derived ROS Contributes to Laryngeal Airway Hyperreactivity Induced by Intermittent Hypoxia in Rats

Obstructive sleep apnea, similar to intermittent hypoxia (IH) during sleep, is associated with laryngeal airway hyperreactivity (LAH). IH-induced laryngeal oxidative stress may contribute to LAH, but the underlying mechanism remains unknown. Conscious rats were subjected to repetitive 75 s cycles of IH for 7 or 14 consecutive days. Reflex apneic responses to laryngeal provocations with chemical stimulants were measured to reflect laryngeal reflex reactivity. Compared with control rats, rats exposed to IH for 14 days, but not for 7 days, displayed enhanced apneic response to laryngeal chemical stimulants. The apneic response to chemical stimulants, but not to mechanical stimulation, was totally abolished by perineural capsaicin treatment of superior laryngeal nerves (SLNs) or by the sectioning of the SLNs, suggesting that the reflex was mediated through capsaicin-sensitive SLNs. Daily intraperitoneal administration of N-acetyl-L-cysteine [NAC, a reactive oxygen species (ROS) scavenger], apocynin (an inhibitor of NADPH oxidase) or YC-1 (an inhibitor of HIF-1α), but not their vehicles, largely attenuated this augmented apneic response in 14 days IH rats. Laryngeal lipid peroxidation (an index of oxidative stress) was elevated in 7 days IH rats and 14 days IH rats, and was abolished by any of these three pharmacologic interventions. The protein expression of HIF-1α (an index of HIF-1 activation) and p47^phox subunit in the membrane fraction (an index of NADPH oxidase activation) in the laryngeal tissues increased in 14 days IH rats; the former was reduced by NAC, whereas the latter was inhibited by YC-1. These results suggest that 14 days of IH exposure may sensitize capsaicin-sensitive SLNs and result in exaggerated apneic reflex response to laryngeal chemical stimulants. This phenomenon depends on the action of HIF-1α-mediated, NADPH oxidase-derived ROS.

Guanxinshutong Alleviates Atherosclerosis by Suppressing Oxidative Stress and Proinflammation in ApoE-/- Mice

Atherosclerosis (AS) is a chronic progressive disease related to dyslipidemia, inflammation, and oxidative stress. Guanxinshutong capsule (GXST), a traditional Chinese medicine, has been widely used in treating coronary atherosclerotic heart disease, while its mechanism actions on AS are still not to be well addressed. Our present study is aimed to examine the effect of GXST on AS and elucidate the multitarget mechanisms of GXST on AS. Network pharmacology analysis was employed to screen the multitarget mechanisms of GXST on AS. ApoE^−/− mice were used to validate these effects. Circulating lipid profile and oxidative stress-related factors were measured by the Elisa kit. Furthermore, the aortic trunk and aortic root were excised for oil red O staining, histopathological and immunohistochemical analysis. We first discovered that GXST was clued to exert synergistically antiatherosclerosis properties including lipid-lowering, anti-inflammation, and antioxidation through the computational prediction based on a network pharmacology simulation. Next, the validation experiments in atherosclerosis mice provided evidence that GXST significantly reduced atherosclerotic lesions, increased collagen deposition, and attenuated LV remodeling to some extent. Mechanistically, GXST modulated lipid profile, downregulated the level of inflammatory cytokines and NF-κBp65. GXST also reduced the activity of oxidative parameter MDA and upregulated the activities of antioxidant enzymes (SOD and GSH) compared with the AS model group. In conclusion, GXST intervention might attenuate atherosclerosis by mechanisms involving reducing lipid deposition, modulating oxidative stress and inflammatory responses, but a larger controlled trial is necessary for confirmation.

Intermittent Hypoxia Triggers Early Cardiac Remodeling and Contractile Dysfunction in the Time-Course of Ischemic Cardiomyopathy in Rats

BACKGROUND Sleep-disordered breathing is associated with a poor prognosis (mortality) in patients with ischemic cardiomyopathy. The understanding of mechanisms linking intermittent hypoxia (IH), the key feature of sleep-disordered breathing, to ischemic cardiomyopathy progression is crucial for identifying specific actionable therapeutic targets. The aims of the present study were (1) to evaluate the impact of IH on the time course evolution of cardiac remodeling and contractile dysfunction in a rat model of ischemic cardiomyopathy; and (2) to determine the impact of IH on sympathetic activity, hypoxia inducible factor-1 activation, and endoplasmic reticulum stress in the time course of ischemic cardiomyopathy progression. METHODS AND RESULTS Ischemic cardiomyopathy was induced by a permanent ligature of the left coronary artery in male Wistar rats (rats with myocardial infarction). Rats with myocardial infarction were then exposed to either IH or normoxia for up to 12 weeks. Cardiac remodeling and function were analyzed by Sirius red and wheat germ agglutinin staining, ultrasonography, and cardiac catheterization. Sympathetic activity was evaluated by spectral analysis of blood pressure variability. Hypoxia-inducible factor-1α activation and burden of endoplasmic reticulum stress were characterized by Western blots. Long-term IH exposure precipitated cardiac remodeling (hypertrophy and interstitial fibrosis) and contractile dysfunction during the time course evolution of ischemic cardiomyopathy in rodents. Among associated mechanisms, we identified the early occurrence and persistence of sympathetic activation, associated with sustained hypoxia-inducible factor-1α expression and a delayed pro-apoptotic endoplasmic reticulum stress. CONCLUSIONS Our data provide the demonstration of the deleterious impact of IH on post-myocardial infarction remodeling and contractile dysfunction. Further studies are needed to evaluate whether targeting sympathetic nervous system or HIF-1 overactivities could limit these effects and improve management of coexisting ischemic cardiomyopathy and sleep-disordered breathing.

Dexmedetomidine Attenuates LPS-Induced Monocyte-Endothelial Adherence via Inhibiting Cx43/PKC-α/NOX2/ROS Signaling Pathway in Monocytes

Dexmedetomidine is widely used for sedating patients in operation rooms or intensive care units. Its protective functions against oxidative stress, inflammation reaction, and apoptosis have been widely reported. In present study, we explored the effects of dexmedetomidine on monocyte-endothelial adherence. We built lipopolysaccharide- (LPS-) induced monocyte-endothelial adherence models with U937 monocytes and human umbilical vein endothelial cells (HUVECs) and observed the effects of dexmedetomidine on U937-HUVEC adhesion. Specific siRNA was designed to knock-down Connexin43 (Cx43) expression in U937 monocytes. Gö6976, GSK2795039, and NAC were used to inhibit PKC-α, NOX2, and ROS, respectively. Then, we detected whether dexmedetomidine could downregulate Cx43 expression and its downstream PKC-α/NOX2/ROS signaling pathway activation and ultimately result in the decrease of U937-HUVEC adhesion. The results showed that dexmedetomidine, at its clinically relevant concentrations (0.1 nM and 1 nM), could inhibit adhesion of molecule expression (VLA-4 and LFA-1) and U937-HUVEC adhesion. Simultaneously, it also attenuated Cx43 expression in U937 monocytes. With the downregulation of Cx43 expression, the activity of PKC-α and its related NOX2/ROS signaling pathway were reduced. Inhibiting PKC-α/NOX2/ROS signaling pathway with Gö6976, GSK2795039, and NAC, respectively, VLA-4, LFA-1 expression, and U937-HUVEC adhesion were all decreased. In summary, we concluded that dexmedetomidine, at its clinically relevant concentrations (0.1 nM and 1 nM), decreased Cx43 expression in U937 monocytes and PKC-α associated with carboxyl-terminal domain of Cx43 protein. With the downregulation of PKC-α, the NOX2/ROS signaling pathway was inhibited, resulting in the decrease of VLA-4 and LFA-1 expression. Ultimately, U937-HUVEC adhesion was reduced.

Curcumin prevents chronic intermittent hypoxia-induced myocardial injury

Background:

Chronic intermittent hypoxia (IH), the hallmark feature of obstructive sleep apnoea syndrome, contributes to infarct size enhancement after myocardial ischemia–reperfusion (I/R). Curcumin (Curc), the natural pigment of Curcuma longa, has been demonstrated to be beneficial in the context of myocardial injury. In this study, we assessed the effects of Curc on the maladaptive cardiac response to IH, and particularly on IH-induced hypoxia inducible factor-1 (HIF-1) expression, oxidative stress, inflammation, endoplasmic reticulum (ER) stress and apoptosis.

Methods:

Swiss/SV129 mice were exposed to normoxia or IH (21–5% FiO₂, 60 s cycles, 8 h per day, for 21 days) and treated orally with Curc (100 mg kg⁻¹ day⁻¹, oral gavage) or its vehicle. Mice were then either euthanised for heart sampling in order to perform biochemical and histological analysis, or subjected to an in vivo ischemia-reperfusion protocol in order to measure infarct size.

Results:

IH increased nuclear HIF-1α expression and superoxide anion (O₂^.–) production as well as nuclear factor kappa B (NF-kB) p65, glucose-regulated protein (Grp78) and C/EBP homologous protein (CHOP) expression. IH also induced apoptosis and increased infarct size after I/R . The IH-induced HIF-1 activation, oxidative stress, inflammation, ER stress and apoptosis were abolished by chronic Curc treatment. Curc also significantly decreased infarct size only in mice exposed to IH.

Conclusion:

Curc prevents IH-induced myocardial cell death signalling. Curc might be used as a combined therapy with continuous positive airway pressure in sleep apnoea patients with high cardiovascular risk.

TWEAK/Fn14 axis in respiratory diseases

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a well known multifunctional cytokine extensively distributed in cell types and tissues. Accumulating evidence has shown that TWEAK binding to the receptor factor-inducible 14 (Fn14) participates in diverse pathologic processes including cell proliferation and death, angiogenesis, carcinogenesis and inflammation. Interestingly, alterations of intracellular signaling cascades are correlated to the development of respiratory disease. Recently, a several lines of evidence suggests that TWEAK in lung tissues are closely associated with these signaling pathways. In this review, we explore if TWEAK could provide a novel therapeutic strategy for managing respiratory disease in general and pulmonary arterial hypertension (PAH), obstructive sleep apnea syndrome (OSAS), asthma, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and non-small cell lung cancer (NSCLC), specifically.

TGF-β1 attenuates mitochondrial bioenergetics in pulmonary arterial endothelial cells via the disruption of carnitine homeostasis

Transforming growth factor beta-1 (TGF-β1) signaling is increased and mitochondrial function is decreased in multiple models of pulmonary hypertension (PH) including lambs with increased pulmonary blood flow (PBF) and pressure (Shunt). However, the potential link between TGF-β1 and the loss of mitochondrial function has not been investigated and was the focus of our investigations. Our data indicate that exposure of pulmonary arterial endothelial cells (PAEC) to TGF-β1 disrupted mitochondrial function as determined by enhanced mitochondrial ROS generation, decreased mitochondrial membrane potential, and disrupted mitochondrial bioenergetics. These events resulted in a decrease in cellular ATP levels, decreased hsp90/eNOS interactions and attenuated shear-mediated NO release. TGF-β1 induced mitochondrial dysfunction was linked to a nitration-mediated activation of Akt1 and the subsequent mitochondrial translocation of endothelial NO synthase (eNOS) resulting in the nitration of carnitine acetyl transferase (CrAT) and the disruption of carnitine homeostasis. The increase in Akt1 nitration correlated with increased NADPH oxidase activity associated with increased levels of p47^phox, p67^phox, and Rac1. The increase in NADPH oxidase was associated with a decrease in peroxisome proliferator-activated receptor type gamma (PPARγ) and the PPARγ antagonist, GW9662, was able to mimic the disruptive effect of TGF-β1 on mitochondrial bioenergetics. Together, our studies reveal for the first time, that TGF-β1 can disrupt mitochondrial function through the disruption of cellular carnitine homeostasis and suggest that stimulating carinitine homeostasis may be an avenue to treat pulmonary vascular disease.

Revealing the Common Mechanisms of Scutellarin in Angina Pectoris and Ischemic Stroke Treatment via a Network Pharmacology Approach

OBJECTIVE

To investigate the shared mechanisms of scutellarin in angina pectoris (AP) and ischemic stroke (IS) treatment.

METHODS

A network pharmacology approach was used to detect the potential mechanisms of scutellarin in AP and IS treatment by target prediction, protein-protein interaction (PPI) data collection, network construction, network analysis, and enrichment analysis. Furthermore, molecular docking simulation was employed to analyze the interaction between scutellarin and core targets.

RESULTS

Two networks were established, including a disease-target network and a PPI network of scutellarin targets against AP and IS. Network analysis showed that 14 targets, namely, AKT1, VEGFA, JUN, ALB, MTOR, ESR1, MAPK8, HSP90AA1, NOS3, SERPINE1, FGA, F2, FOXO3, and STAT1, might be the therapeutic targets of scutellarin in AP and IS. Among them, NOS3 and F2 were recognized as the core targets. Additionally, molecular docking simulation confifirmed that scutellarin exhibited a relatively high potential for binding to the active sites of NOS3 and F2. Furthermore, enrichment analysis indicated that scutellarin might exert a therapeutic role in both AP and IS by regulating several important pathways, such as coagulation cascades, mitogen-activated protein kinase (MAPK) signaling pathway, phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway, Toll-like receptor signaling pathway, hypoxia inducible factor-1 (HIF-1) signaling pathway, forkhead box O (FoxO) signaling pathway, tumor necrosis factor (TNF) signaling pathway, adipocytokine signaling pathway, insulin signaling pathway, insulin resistance, and estrogen signaling pathway.

CONCLUSIONS

The shared underlying mechanisms of scutellarin on AP and IS treatment might be strongly associated with its vasorelaxant, anticoagulant, anti-inflammatory, and antioxidative effects as well as its effect on improving lipid metabolism.

Mechanical forces alter endothelin-1 signaling: comparative ovine models of congenital heart disease

The risk and progression of pulmonary vascular disease in patients with congenital heart disease is dependent on the hemodynamics associated with different lesions. However, the underlying mechanisms are not understood. Endothelin-1 is a potent vasoconstrictor that plays a key role in the pathology of pulmonary vascular disease. We utilized two ovine models of congenital heart disease: (1) fetal aortopulmonary graft placement (shunt), resulting in increased flow and pressure; and (2) fetal ligation of the left pulmonary artery resulting in increased flow and normal pressure to the right lung, to investigate the hypothesis that high pressure and flow, but not flow alone, upregulates endothelin-1 signaling. Lung tissue and pulmonary arterial endothelial cells were harvested from control, shunt, and the right lung of left pulmonary artery lambs at 3–7 weeks of age. We found that lung preproendothelin-1 mRNA and protein expression were increased in shunt lambs compared to controls. Preproendothelin-1 mRNA expression was modestly increased, and protein was unchanged in left pulmonary artery lambs. These changes resulted in increased lung endothelin-1 levels in shunt lambs, while left pulmonary artery levels were similar to controls. Pulmonary arterial endothelial cells exposed to increased shear stress decreased endothelin-1 levels by five-fold, while cyclic stretch increased levels by 1.5-fold. These data suggest that pressure or an additive effect of pressure and flow, rather than increased flow alone, is the principal driver of increased endothelin signaling in congenital heart disease. Defining the molecular drivers of the pathobiology of pulmonary vascular disease due to differing mechanical forces will allow for a more targeted therapeutic approach.

Cooperation Between Hypoxia-Inducible Factor 1α and Activating Transcription Factor 4 in Sleep Apnea-Mediated Myocardial Injury

Chronic intermittent hypoxia (CIH) occurring during sleep apnea amplifies infarct size owing to ischemia-reperfusion. CIH activates hypoxia-inducible factor 1 (HIF-1) and activating transcription factor 4 (ATF4). However, whether HIF-1 and ATF4 interact to promote cardiomyocyte death remains unexplored. For the first time, we observed that in myocardium from apneic patients, CCAAT enhancer-binding protein homologous protein (CHOP) expression is increased and HIF-1α expression is correlated with sleep apnea severity. In mice, single-allele deletion of HIF-1α prevents CIH increase in CHOP expression and infarct size. We uncovered a physical interaction between HIF-1α and ATF4 in CIH that may represent a novel cardiomyocyte death complex.

Hypoxia-Induced ROS Contribute to Myoblast Pyroptosis during Obstructive Sleep Apnea via the NF-κB/HIF-1α Signaling Pathway

Tissue hypoxia caused by upper airway collapse is a main cause of excessive oxidative stress and systemic inflammation in obstructive sleep apnea (OSA) patients. Increased reactive oxygen species (ROS) and inflammatory responses affect cell survival and ultimately contribute to tissue injury. In the present study, we proposed that the induction of ROS by hypoxia, as an intrinsic stress, activates myoblast pyroptosis in OSA. We found increased cell death and abnormal expression of pyroptosis markers in the skeletal muscle of OSA mice. In vitro studies showed hypoxia-induced pyroptotic death of C2C12 myoblasts, as evidenced by the activation of caspase-1 and gasdermin D (GSDMD). Hypoxia induced ROS overproduction and accumulation in myoblasts. More importantly, applying N-acetylcysteine (NAC), an ROS scavenger, rescued cell swelling, downregulated the inflammatory response, and prevented pyroptotic death in hypoxia-cultured myoblasts. Hypoxia stimulation promoted NF-κB P65 phosphorylation and HIF-1α nuclear translocation. Moreover, hypoxia increased the nuclear level of cleaved caspase-1 and GSDMD. NAC inhibited hypoxia-induced variations in the HIF-1α and NF-κB signaling pathway. Taken together, our results determined that hypoxia-induced ROS contribute to myoblast pyroptosis. Therefore, our findings suggest that ROS may be a potential therapeutic target for ameliorating hypoxia-induced cell death and tissue injury, especially in OSA and hypoxia-related diseases.

Explorating the Involvement of Plasma Sestrin2 in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) can lead to serious complications such as coronary heart disease and hypertension due to oxidative stress. Sestrin2 expression is upregulated under conditions of oxidative stress. This study aimed to explore whether Sestrin2 was involved in OSA. OSA and healthy control subjects were recruited and matched with age, gender, and body mass index (BMI). Plasma Sestrin2 levels were measured and compared. A multivariate stepwise regression model was used to detect the relationship between Sestrin2 and other variable factors. The Sestrin2 levels were compared between before and after four weeks treatment by nasal continuous positive airway pressure (nCPAP) in severe OSA patients. Fifty-seven subjects were divided into two groups: control group (39.33 ± 9.40 years, n = 21) and OSA group (38.81 ± 7.84 years, n = 36). Plasma Sestrin2 levels increased in the OSA group (control group 2.06 ± 1.76 ng/mL, OSA group 4.16 ± 2.37 ng/mL; P = 0.001). Sestrin2 levels decreased after four-week nCPAP treatment (pre-nCPAP 5.21 ± 2.32 ng/mL, post-nCPAP 4.01 ± 1.54 ng/mL; P = 0.004). Sestrin2 was positively correlated with apnea/hypopnea index (AHI) oxygen desaturation index, while negatively correlated with mean oxygen saturation. Moreover, these correlations remained unchanged after adjusting for gender, age, waist-to-hip ratio, and body mass index. Multiple regression analysis showed that there was an association between Sestrin2 and AHI. Our findings suggest that Sestrin2 is involved in OSA. The increase of plasma Sestrin2 is directly related to the severity of OSA. To some extent, Sestrin2 may be useful for determining the severity of OSA and monitoring the effect of CPAP. In addition, since some complications of OSA such as coronary heart disease and diabetes are usually related with oxidative stress, the role of Sestrin2 in those OSA complications needs further study.

1,25-Vitamin D3 protects against cooking oil fumes-derived PM2.5-induced cell damage through its anti-inflammatory effects in cardiomyocytes

The functional role of 1,25-vitamin D3 in cooking oil fumes (COFs)-derived PM2.5-induced cell damage is largely unexplored. The present study investigated the protective role of 1,25-vitamin D3 against cell injury by possible involvement of JAK/STAT and NF-κB signaling pathways in cardiomyocytes. Cell viability was measured using CCK-8 assay, and cell apoptosis was analyzed by flow cytometry, qRT-PCR and Western blot in cultured rat neonatal cardiomyocytes treated with 1,25-vitamin D3 and COFs-derived PM2.5. Expressions of JAK/STAT and NF-κB signaling pathway were measured by Western blot. The results suggested that treatment with COFs-derived PM2.5 significantly decreased cell viability and increased apoptosis and oxidative stress in cultured rat neonatal cardiomyocytes. 1,25-vitamin D3 pretreatment alleviated the cell injury by increasing cell viability and decreasing apoptosis in the cardiomyocytes. 1,25-vitamin D3 pretreatment also decreased the ROS level and inflammation in the cardiomyocytes. Furthermore, 1,25-vitamin D3 pretreatment alleviated COFs-derived PM2.5-evoked elevation of JAK/STAT and NF-κB signaling pathways. Our study showed that 1,25-vitamin D3 pretreatment protected cardiomyocytes from COFs-derived PM2.5-induced injury by decreasing ROS, apoptosis and inflammation level via activations of the JAK/STAT and NF-κB signaling pathways.

Dual Effects of Chinese Herbal Medicines on Angiogenesis in Cancer and Ischemic Stroke Treatments: Role of HIF-1 Network

Hypoxia-inducible factor-1 (HIF-1)-induced angiogenesis has been involved in numerous pathological conditions, and it may be harmful or beneficial depending on the types of diseases. Exploration on angiogenesis has sparked hopes in providing novel therapeutic approaches on multiple diseases with high mortality rates, such as cancer and ischemic stroke. The HIF-1 pathway is considered to be a major regulator of angiogenesis. HIF-1 seems to be involved in the vascular formation process by synergistic correlations with other proangiogenic factors in cancer and cerebrovascular disease. The regulation of HIF-1-dependent angiogenesis is related to the modulation of HIF-1 bioactivity by regulating HIF-1α transcription or protein translation, HIF-1α DNA binding, HIF-1α and HIF-1α dimerization, and HIF-1 degradation. Traditional Chinese herbal medicines have a long history of clinical use in both cancer and stroke treatments in Asia. Growing evidence has demonstrated potential proangiogenic benefits of Chinese herbal medicines in ischemic stroke, whereas tumor angiogenesis could be inhibited by the active components in Chinese herbal medicines. The objective of this review is to provide comprehensive insight on the effects of Chinese herbal medicines on angiogenesis by regulating HIF-1 pathways in both cancer and ischemic stroke.

Epigenetics: A Potential Mechanism Involved in the Pathogenesis of Various Adverse Consequences of Obstructive Sleep Apnea

Epigenetics is defined as the heritable phenotypic changes which do not involve alterations in the DNA sequence, including histone modifications, non-coding RNAs, and DNA methylation. Recently, much attention has been paid to the role of hypoxia-mediated epigenetic regulation in cancer, pulmonary hypertension, adaptation to high altitude, and cardiorenal disease. In contrast to sustained hypoxia, chronic intermittent hypoxia with re-oxygenation (IHR) plays a major role in the pathogenesis of various adverse consequences of obstructive sleep apnea (OSA), resembling ischemia re-perfusion injury. Nevertheless, the role of epigenetics in the pathogenesis of OSA is currently underexplored. This review proposes that epigenetic processes are involved in the development of various adverse consequences of OSA by influencing adaptive potential and phenotypic variability under conditions of chronic IHR. Improved understanding of the interaction between genetic and environmental factors through epigenetic regulations holds great value to give deeper insight into the mechanisms underlying IHR-related low-grade inflammation, oxidative stress, and sympathetic hyperactivity, and clarify their implications for biomedical research.

Zinc deficiency promotes endothelin secretion and endothelial cell migration through nuclear hypoxia-inducible factor-1 translocation

Zinc is involved in the expression and function of various transcription factors, including the hypoxia-inducible factor-1 (HIF-1). HIF-1 and its target gene endothelin-1 (ET-1) are activated by intermittent hypoxia (IH), one of the main consequences of obstructive sleep apnea (OSA), and both play a key role in the cardiovascular consequences of IH. Because OSA and IH are associated with zinc deficiency, we investigated the effect of zinc deficiency caused by chelation on the HIF-1/ET-1 pathway and its functional consequences in endothelial cells. Primary human microvascular endothelial cells (HMVEC) were incubated with submicromolar doses of the zinc-specific membrane-permeable chelator N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylene diamine (TPEN, 0.5 µM) or ET-1 (0.01 µM) with or without bosentan, a dual ET-1-receptor antagonist. HIF-1α expression was silenced by transfection with specific siRNA. Nuclear HIF-1 content was assessed by immunofluorescence microscopy and Western blot. Migratory capacity of HMVEC was evaluated with a wound-healing scratch assay. Zinc chelation by TPEN exposure induced the translocation of the cytosolic HIF-1α subunit of HIF-1 to the nucleus as well as an HIF-1-mediated ET-1 secretion by HMVEC. Incubation with either TPEN or ET-1 increased endothelial wound-healing capacity. Both HIF-1α silencing or bosentan abolished this effect. Altogether, these results suggest that zinc deficiency upregulates ET-1 signaling through HIF-1 activation and stimulates endothelial cell migration, suggesting an important role of zinc in the vascular consequences of IH and OSA mediated by HIF-1-ET- signaling.

Obstructive sleep apnea syndrome promotes the progression of aortic dissection via a ROS- HIF-1α-MMPs associated pathway

Aims: Obstructive sleep apnea syndrome (OSAS) has been increasingly recognized as an independent risk factor for aortic dissection (AD) and it is strongly associated with the extent of intermittent hypoxia and re-oxygenation (IH). This study aimed to clarify role of ROS- HIF-1α-MMPs pathway in the pathogenesis of AD and whether the HIF-1α inhibitor attenuates AD formation. Methods and results: 8-week-old male ApoE-/- mice were given β-aminopropionitrile at a concentration of 0.1 % for 3 weeks and infused via osmotic mini pumps with either saline or 2,500 ng/min/kg angiotensin II (Ang II) for 2 weeks. To mimic the OSAS, one group was exposed to IH, which consisted of alternating cycles of 20.9% O2/8% O2 FiO2 (30 episodes per hour) with 20 s at the nadir FiO2 during the 12-h light phase, 2 weeks before Ang II infusion. After Ang II infusion, we assessed remodeling in the aorta by echocardiography, histological and immunohistochemical analysis. IH treatment resulted in significant enlargement of the luminal area, destruction of the media, marked thickening of the adventitia, higher incidence of AD formation and lower survival rate in compared with the Ang II only group. Moreover, IH exposure markedly increased the aortic ROS production and subsequent HIF-1α expression, which in turn promoted the expressions of VEGF, MMP2 and MMP9 and finally leading to the progression of AD. Besides, in vitro study confirmed that IH induced HIF-1α expression plays an important role in the induction of MMPs and that is regulated by the PI3K/AKT/FRAP pathway. Intriguingly, a selective HIF-1α inhibitor KC7F2 could significantly ameliorate IH exposure induced aforementioned deleterious effects in vitro and in vivo.Conclusion: OSAS induced IH can promote the occurrence and progression of AD via a ROS- HIF-1α-MMPs associated pathway. The selective HIF-1α inhibitor KC7F2 could be a novel therapeutic agent for AD patient with OSAS.

Prognostic impact of lactic dehydrogenase to albumin ratio in hepatocellular carcinoma patients with Child-Pugh I who underwent curative resection: a prognostic nomogram study

Background

Radical resection is the treatment of choice for hepatocellular carcinoma (HCC). However, even with this treatment, HCC prognosis and the efficacy of current predictive models for such patients remain unsatisfactory. Here, we describe an accurate and easy-to-use prognostic index for patients with HCC who have undergone curative resection.

Methods

The study population comprised of 1,041 patients with HCC who underwent curative resection at Zhongshan Hospital. This population was reduced to 768 patients who were treated in 2012 analyzed as the training cohort and 273 patients treated in 2007 who were used as a validation cohort.

Results

The lactic dehydrogenase to albumin ratio (LAR) was identified as a significant prognostic index for both overall survival and recurrence-free survival in two independent cohorts. The optimal cutoff value for LAR was determined to be 5.5. The C-index of LAR was superior to other inflammatory scores and serum parameters. This biomarker was also shown to be a stable predictive index in the validation cohort. The new nomogram combining LAR with the Barcelona Clinic Liver Cancer staging system had an improved ability to discriminate overall survival and recurrence-free survival. Nomogram predictions were consistent with observations based on calibration and decisive curve analysis in both independent cohorts.

Conclusion

LAR is a novel, convenient, reliable, and accurate prognostic predictor in patients with HCC undergoing curative resection. Our results suggest the recommendation of LAR to be used in routine clinical practice.

Models of intermittent hypoxia and obstructive sleep apnea: molecular pathways and their contribution to cancer

Obstructive sleep apnea (OSA) is common and linked to a variety of poor health outcomes. A key modulator of this disease is nocturnal intermittent hypoxia. There is striking epidemiological evidence that patients with OSA have higher rates of cancer and cancer mortality. Small-animal models demonstrate an important role for systemic intermittent hypoxia in tumor growth and metastasis, yet the underlying mechanisms are poorly understood. Emerging data indicate that intermittent hypoxia activates the hypoxic response and inflammatory pathways in a manner distinct from chronic hypoxia. However, there is significant heterogeneity in published methods for modeling hypoxic conditions, which are often lacking in physiological relevance. This is particularly important for studying key transcriptional mediators of the hypoxic and inflammatory responses such as hypoxia-inducible factor (HIF) and NF-κB. The relationship between HIF, the molecular clock, and circadian rhythm may also contribute to cancer risk in OSA. Building accurate in vitro models of intermittent hypoxia reflective of OSA is challenging but necessary to better elucidate underlying molecular pathways.

Intermittent Hypoxia Is Associated With High Hypoxia Inducible Factor-1α but Not High Vascular Endothelial Growth Factor Cell Expression in Tumors of Cutaneous Melanoma Patients

Epidemiological associations linking between obstructive sleep apnea and poorer solid malignant tumor outcomes have recently emerged. Putative pathways proposed to explain that these associations have included enhanced hypoxia inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) cell expression in the tumor and altered immune functions via intermittent hypoxia (IH). Here, we examined relationships between HIF-1α and VEGF expression and nocturnal IH in cutaneous melanoma (CM) tumor samples. Prospectively recruited patients with CM tumor samples were included and underwent overnight polygraphy. General clinical features, apnea–hypopnea index (AHI), desaturation index (DI4%), and CM characteristics were recorded. Histochemical assessments of VEGF and HIF-1α were performed, and the percentage of positive cells (0, <25, 25–50, 51–75, >75%) was blindly tabulated for VEGF expression, and as 0, 0–5.9, 6.0–10.0, >10.0% for HIF-1α expression, respectively. Cases with HIF-1α expression >6% (high expression) were compared with those <6%, and VEGF expression >75% of cells was compared with those with <75%. 376 patients were included. High expression of VEGF and HIF-1α were seen in 88.8 and 4.2% of samples, respectively. High expression of VEGF was only associated with increasing age. However, high expression of HIF-1α was significantly associated with age, Breslow index, AHI, and DI4%. Logistic regression showed that DI4% [OR 1.03 (95% CI: 1.01–1.06)] and Breslow index [OR 1.28 (95% CI: 1.18–1.46)], but not AHI, remained independently associated with the presence of high HIF-1α expression. Thus, IH emerges as an independent risk factor for higher HIF-1α expression in CM tumors and is inferentially linked to worse clinical CM prognostic indicators.

Reduction of the Oxidative Stress Status Using Steviol Glycosides in a Fish Model (Cyprinus carpio)

Steviol glycosides are sweetening compounds from the Stevia rebaudiana Bertoni plant. This product is considered safe for human consumption and was approved as a food additive by the Food and Drugs Administration (FDA) and European Food Safety Authority (EFSA). Its effects on the ecosystem have not been studied in depth; therefore, it is necessary to carry out ecotoxicological studies in organisms such as Cyprinus carpio. The present study aimed to evaluate the antioxidant activity by SGs on diverse tissues in C. carpio using oxidative stress (OS) biomarkers. To test the antioxidant activity, carps were exposed to four systems: (1) SGs free control, (2) CCl₄ 0.5 mL/kg, (3) SGs 1 g/L, and (4) CCl₄ 0.5 mL/kg + SGs 1 g/L at 96 h. The following biomarkers were analyzed: lipoperoxidation (LPX), hydroperoxide content (HPC), and protein carbonyl content (PCC), as well as antioxidant activity of superoxide dismutase (SOD) and catalase (CAT). It was found that both (3 and 4) systems' exposure decreases LPX, CHP, PCC, SOD, and CAT with respect to the CCl₄ system. The results of this study demonstrate that the concentrations of SGs used are not capable of generating oxidative stress and, on the contrary, would appear to induce an antioxidant effect.

Chronic intermittent hypoxia promotes myocardial ischemia-related ventricular arrhythmias and sudden cardiac death

We investigated the effects of intermittent hypoxia (IH), such as that encountered in severe obstructive sleep apnea (OSA) patients, on the development and severity of myocardial ischemia-related ventricular arrhythmias. Rats were exposed to 14 days of IH (30 s at 5%O₂ and 30 s at 21%O₂, 8 h·day⁻¹) or normoxia (N, similar air-air cycles) and submitted to a 30-min coronary ligature. Arterial blood pressure (BP) and ECG were recorded for power spectral analysis, ECG interval measurement and arrhythmia quantification. Left ventricular monophasic action potential duration (APD) and expression of L-type calcium (LTCC) and transient receptor potential (TRPC) channels were assessed in adjacent epicardial and endocardial sites. Chronic IH enhanced the incidence of ischemic arrhythmias, in particular ventricular fibrillation (66.7% vs. 33.3% in N rats, p < 0.05). IH also increased BP and plasma norepinephine levels along with increased low-frequency (LF), decreased high-frequency (HF) and increased LF/HF ratio of heart rate and BP variability. IH prolonged QTc and Tpeak-to-Tend intervals, increased the ventricular APD gradient and upregulated endocardial but not epicardial LTCC, TRPC1 and TRPC6 (p < 0.05). Chronic IH, is a major risk factor for sudden cardiac death upon myocardial ischemia through sympathoactivation and alterations in ventricular repolarization, transmural APD gradient and endocardial calcium channel expression.

Which place of pharmacological approaches beyond continuous positive airway pressure to treat vascular disease related to obstructive sleep apnea?

Obstructive sleep apnea (OSA) is characterized by recurrent episodes of partial or complete upper airway obstruction, occurring during sleep, leading to chronic intermittent hypoxia (IH), which harms the cardiovascular system. OSA is associated with both functional and structural vascular alterations that contribute to an increased prevalence of fatal and non-fatal cardiovascular events. OSA is a heterogeneous disease with respect to the severity of hypoxia, the presence of daytime symptoms, obesity, and cardiovascular comorbidities. Various clusters of OSA phenotypes have been described leading to more highly personalized treatment. The aim of this review is to describe the various therapeutic strategies including continuous positive airway pressure (CPAP), oral appliances, surgery, weight loss, and especially pharmacological interventions that have been evaluated to reduce vascular alterations in both OSA patients and preclinical animal models. Conventional therapies, predominantly CPAP, have a limited impact on vascular alterations in the presence of co-morbidities. A better knowledge of pharmacological therapies targeting IH-induced vascular alterations will facilitate the use of combined therapies and is crucial for designing clinical trials in well-defined OSA phenotypes.