The impact of chronic intermittent hypoxia on hematopoiesis and the bone marrow microenvironment

High Monocyte-to-Lymphocyte Ratio is Associated with Obstructive Sleep Apnea Hypopnea Syndrome

Objective

This study aims to explore the correlation between serum monocyte-to-lymphocyte ratio (MLR) and other inflammatory parameters with the occurrence of obstructive sleep apnea-hypopnea syndrome (OSAHS) in patients.

Methods

This study included 310 patients who underwent polysomnography monitoring at our hospital between January 2021 and January 2023. Routine blood inflammatory parameters and polysomnography (PSG) results were also evaluated. The differences in inflammatory markers between the OSAHS and normal groups were compared, and OSAHS independent related factors were screened.

Results

The MLR of OSAHS group was significantly higher than that of control group, and the difference was statistically significant. Multivariate logistic regression analysis suggested that MLR is an independent risk factor for OSAHS.

Conclusion

High MLR was correlated with OSAHS. The diagnostic value of MLR was better than that of the other inflammatory parameters.

Alteration in the number, morphology, function, and metabolism of erythrocytes in high-altitude polycythemia

Introduction: High-altitude polycythemia (HAPC) is a common chronic high-altitude disease characterized by significantly increased erythrocyte, hemoglobin (Hb), and hematocrit values and decreased arterial oxygen saturation. The mechanisms underlying HAPC development are unclear; we aimed to investigate this in an HAPC rat model. Methods: Twelve Sprague-Dawley rats were divided into control and HAPC groups. The HAPC group was exposed to hypobaric hypoxia. This HAPC model was assessed using routine blood tests and blood gas analyses. Bone marrow, peripheral blood reticulocytes (RETs), and peripheral blood erythrocyte apoptosis were measured using flow cytometry. Erythrocyte osmotic fragility (EOF) tests were conducted. Abnormal erythrocytes were counted using electron microscopy. Plasma-free hemoglobin, 5'-nucleotidase (CD73), adenosine, erythrocyte cytosolic adenosine, sphingosine-1-phosphate (S1P), and 2,3-bisphosphoglycerate (BPG) levels were measured using enzyme-linked immunosorbent assays. Erythrocyte metabolic pathway-related protein [adenosine A2B receptor (ADORA2B), erythrocyte equilibrative nucleoside transporter 1 (eENT1), sphingosine kinase 1 (SPHK1), phospho-SPHK1, bisphosphoglycerate mutase (BPGM), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH)] levels were assessed by Western blotting. Results: The HAPC rat model was successfully established (Hb > 210 g/L). Indices of bone marrow and peripheral blood RET proportions were significantly higher in the HAPC than the control group (p = 0.04 and p < 0.001, respectively). The proportion of peripheral blood erythrocytes in early apoptosis was significantly lower in the HAPC than the control group (p < 0.001). Vesicular erythrocyte and acanthocyte proportions were significantly higher in the HAPC than the control group (p < 0.001 and p = 0.019, respectively). The EOF tests revealed that 50% erythrocyte hemolysis occurred at 4.0-4.5 and 4.5-5.0 g/L NaCl in the control and HAPC groups, respectively. Plasma-free hemoglobin, CD73, adenosine, erythrocyte cytosolic adenosine, S1P, and 2,3-BPG levels and ADORA2B, eENT1, phospho-SPHK1, S1P, BPGM, and GAPDH erythrocyte expression levels (all p ≤ 0.02) were significantly higher in the HAPC than the control group. Conclusion: In model rats, an HAPC-related erythrocyte increase was associated with enhanced bone marrow hematopoietic function and reduced erythrocyte apoptosis, whereas numerous abnormal erythrocytes, increased EOF, and reduced hemolysis resistance were associated with erythrocyte metabolism. CD73/adenosine/S1P/2,3-BPG and eENT1/adenosine/BPGM/2,3-BPG metabolic pathways in erythrocytes were activated in HAPC rats, facilitating oxygen release. These findings further reveal the intrinsic HAPC mechanism and forms a basis for future development of preventive and therapeutic strategies for HAPC.

Sleep apnea syndrome associated with gonadal hormone imbalance (Review)

Patients with obstructive sleep apnea exhibit an increased risk of developing gonadal disorders. Because a notable number of people worldwide have sleep respiratory and reproductive disorders, it is essential to recognize the association between local upper airway dysfunction and its gonadal effects. Repeated breathing pauses cause sleep fragmentation, disorganization of sleep cycles and stages, sympathetic activation, intermittent hypoxemia and systemic inflammation. Nocturnal intermittent hypoxemia has a direct central effect on neurotransmitters, with disturbances in the normal production of hypothalamic-pituitary hormones. Awakenings and micro-awakenings at the end of apneic episodes produce a central stress responsible for hormonal changes and subsequent endocrine imbalances. The aim of the present study was to investigate the impact of obstructive sleep apnea syndrome (OSAS) on gonadal hormonal homeostasis and its consequences. Recognizing and understanding how local upper airway dysfunction causes gonadal imbalance may facilitate better care for patients with OSAS. Although there may be a direct relationship between sleep-disordered breathing and gonadal function mediated by hormones via the hypothalamic-pituitary-gonadal axis, to date, current therapies have not been effective.

Construction of Bone Hypoxic Microenvironment Based on Bone-on-a-Chip Platforms

The normal physiological activities and functions of bone cells cannot be separated from the balance of the oxygenation level, and the physiological activities of bone cells are different under different oxygenation levels. At present, in vitro cell cultures are generally performed in a normoxic environment, and the partial pressure of oxygen of a conventional incubator is generally set at 141 mmHg (18.6%, close to the 20.1% oxygen in ambient air). This value is higher than the mean value of the oxygen partial pressure in human bone tissue. Additionally, the further away from the endosteal sinusoids, the lower the oxygen content. It follows that the construction of a hypoxic microenvironment is the key point of in vitro experimental investigation. However, current methods of cellular research cannot realize precise control of oxygenation levels at the microscale, and the development of microfluidic platforms can overcome the inherent limitations of these methods. In addition to discussing the characteristics of the hypoxic microenvironment in bone tissue, this review will discuss various methods of constructing oxygen gradients in vitro and measuring oxygen tension from the microscale based on microfluidic technology. This integration of advantages and disadvantages to perfect the experimental study will help us to study the physiological responses of cells under more physiological-relevant conditions and provide a new strategy for future research on various in vitro cell biomedicines.

The Effects of Therapeutic Intermittent Hypoxia Implementation on Complete Blood Count Parameters: An Experimental Animal Model

Objective: Intermittent hypoxia (IH) implementation is a method performed by intermittently decreasing oxygen concentration in inhaled air at specific rate. This method varies between studies in terms of its application. This study aims to examine the changes in Complete Blood Count (CBC) parameters caused by IH implementation at therapeutic dose ranges with a single model. Methods: Ten Sprague Dawley type adult male rats were divided into two groups. In the study group, FiO2 level of inhaled air, was reduced to 10% in hypoxic cycle. 5 minutes normoxia-hypoxia cycle was used in each 30 minutes experiment period for study group. Control group remained in normoxic air for 30 minutes. 1 cc of blood was taken from mandibular vein from all rats at the end of 6th day. CBC analyzes were performed and differences between two groups were investigated. Results: Significant differences were detected in some CBC parameters between the two groups. It was determined that significant increase in MONO (p

Causal analysis between altered levels of interleukins and obstructive sleep apnea

Background

Inflammation proteins including interleukins (ILs) have been reported to be related to obstructive sleep apnea (OSA). The aims of this study were to estimate the levels for several key interleukins in OSA and the causal effects between them.

Method

Weighted mean difference (WMD) was used to compare the expression differences of interleukins between OSA and control, and the changed levels during OSA treatments in the meta-analysis section. A two-sample Mendelian randomization (MR) was used to estimate the causal directions and effect sizes between OSA risks and interleukins. The inverse-variance weighting (IVW) was used as the primary method followed by several other MR methods including MR Egger, Weighted median, and MR-Robust Adjusted Profile Score as sensitivity analysis.

Results

Nine different interleukins—IL-1β, IL-2, IL-4, IL-6, IL-8, IL-12, IL-17, IL-18, and IL-23—were elevated in OSA compared with control to varying degrees, ranging from 0.82 to 100.14 pg/ml, and one interleukin, IL-10, was decreased by 0.77 pg/ml. Increased IL-1β, IL-6, and IL-8 rather than IL-10 can be reduced in OSA by effective treatments. Further, the MR analysis of the IVW method showed that there was no significant evidence to support the causal relationships between OSA and the nine interleukins—IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-17, and IL-18. Among them, the causal effect of OSA on IL-5 was almost significant [estimate: 0.267 (−0.030, 0.564), p = 0.078]. These results were consistent in the sensitivity analysis.

Conclusions

Although IL-1β, IL-2, IL-4, IL-6, IL-8, IL-12, IL-17, IL-18, and IL-23 were increasing and IL-10 was reducing in OSA, no significant causal relationships were observed between them by MR analysis. Further research is needed to test the causality of OSA risk on elevated IL-5 level.

Suppression of Endothelial Cell FAK Expression Reduces Pancreatic Ductal Adenocarcinoma Metastasis after Gemcitabine Treatment

Despite substantial advances in the treatment of solid cancers, resistance to therapy remains a major obstacle to prolonged progression-free survival. Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers, with a high level of liver metastasis. Primary PDAC is highly hypoxic, and metastases are resistant to first-line treatment, including gemcitabine. Recent studies have indicated that endothelial cell (EC) focal adhesion kinase (FAK) regulates DNA-damaging therapy-induced angiocrine factors and chemosensitivity in primary tumor models. Here, we show that inducible loss of EC-FAK in both orthotopic and spontaneous mouse models of PDAC is not sufficient to affect primary tumor growth but reduces liver and lung metastasis load and improves survival rates in gemcitabine-treated, but not untreated, mice. EC-FAK loss did not affect primary tumor angiogenesis, tumor blood vessel leakage, or early events in metastasis, including the numbers of circulating tumor cells, tumor cell homing, or metastatic seeding. Phosphoproteomics analysis showed a downregulation of the MAPK, RAF, and PAK signaling pathways in gemcitabine-treated FAK-depleted ECs compared with gemcitabine-treated wild-type ECs. Moreover, low levels of EC-FAK correlated with increased survival and reduced relapse in gemcitabine-treated patients with PDAC, supporting the clinical relevance of these findings. Altogether, we have identified a new role of EC-FAK in regulating PDAC metastasis upon gemcitabine treatment that impacts outcome.

SIGNIFICANCE

These findings establish the potential utility of combinatorial endothelial cell FAK targeting together with gemcitabine in future clinical applications to control metastasis in patients with pancreatic ductal adenocarcinoma.

[Analysis of related factors in secondary erythrocytosis of obstructive sleep apnea hypopnea syndrome in Gansu province]

Objective:To analyze the related factors of secondary erythrocytosis of obstructive sleep apnea（OSA） in Gansu province. Methods:Polysomnography recording and analysis from January 2013 to January 2021, A total of 448 OSA patients of long-resident Han nationality in Gansu province. Hemoglobin（Hb） values were divided into group A（Hb 120-160 g/L） 41 cases, B（Hb 161-179 g/L） 142 cases, C（Hb 180-199 g/L） 152 cases, D（Hb 200-219 g/L） 79 cases, and E（Hb ≥220 g/L） 30 cases. General clinical data, altitude of residence, disease course, apnea hypopnea index （AHI）, and Lowest oxyhemoglobin（LSpO₂） were compared among these groups. Multivariate regression and ROC curves were used to analyze the influencing factors of OSA secondary erythrocytosis. Results:There were no significant differences in age, sex, and course of disease among groups A, B, C, D, and E （P>0.05）.The altitude of group E was higher than that of groups A, B, C, and D （P<0.05）, but there was no significant difference between groups A, B, C and D （P>0.05）.AHI was significantly different among groups A, B, C, D, and E （P<0.05）, groups C, D, and E were significantly higher than A; group D was significantly higher than B, C.LSpO₂ was significantly different among groups A, B, C, D, and E （P <0.05）, groups B, C, D, and E was significantly lower than A; group D, E was significantly lower than B, C.MSpO₂ was significantly different among groups A, B, C, D, and E （P<0.05）, groups B, C, D, and E was significantly lower A; groups D, E was significantly lower than B , C.Multivariate regression showed that the higher the altitude, the lower the MSpO₂, the more serious the secondary hyperhemoglobinemia.Age, course of the disease, AHI, and LSpO₂ were not the influencing factors of OSA secondary hemoglobin increase.The areas under the ROC curve for MSpO₂ and altitude to predict Hb≥180 g/L were 0.694（P<0.001） and 0.570（P=0.009）, with statistically significant differences（Z=3.205, P=0.001）. Conclusion:Altitude and MSpO₂ were independent risk factors for OSA secondary erythrocytosis; MSpO₂ predicted that Hb≥180 g/L in OSA patients was better than altitude.

Elucidating the combined effect of intermittent hypoxia training and acetazolamide on hypoxia induced hematological and physiological changes

As the number of people travelling to altitude increases, the risk of life threatening medical emergencies also increases. It is important that we have effective strategies to minimize the risk of altitude illness. In this study, an attempt was made to investigate the combined effect of non-pharmacological (Intermittent hypoxia training; IHT) and pharmacological (acetazolamide; ACZ) intervention as a prophylactic strategy in order to minimize the risk of high altitude hypoxic related problems using rats as an animal model. Male Sprague Dawley rats were subjected to IHT for 4 h consecutively for 5 days at 12% FiO₂ under normobaric conditions with and without oral ACZ administration at 25 mg/kg body weight. Validation of the intervention was performed by exposing the rats to extreme hypoxia (EH) at 8% FiO₂ to further assess the effect of IHT and ACZ on hypoxic acclimatization. The principal findings of this study is that the combined effect of IHT and ACZ improves the arterial oxygenation by alterations in hemodynamics and in blood gasometry, thereby resulting into an increase in the oxygen carrying capacity of the blood with increase in SpO₂ (peripheral oxygen saturation). The present study showed that the combined effect of IHT with ACZ could be refined as a prophylactic measure for better outcomes during altitude ascent and rapid altitude acclimatization rather than IHT or ACZ alone.

•

Combination of IHT with ACZ attenuates the inhibitory effect of respiratory alkalosis.

•

It also minimizes pathological changes in hematology and blood gas.

•

The strategy improved the oxygen carrying capacity of the blood by increasing SpO₂.

•

Thus, it leads to ventilatory Acclimatization.

•

The combined treatment could be refined as a prophylactic measure for altitude maladies.

Long-Term Environmental Hypoxia Exposure and Haematopoietic Prolyl Hydroxylase-1 Deletion Do Not Impact Experimental Crohn's Like Ileitis

Simple Summary

Hypoxia-induced signalling represents an important contributor to inflammatory bowel disease (IBD) pathophysiology. However, available data solely focus on colonic inflammation while the primary disease location in Crohn’s disease patients is the terminal ileum. Therefore, we explored the effects of environmental hypoxia and immune cell-specific deletion of oxygen sensor prolyl hydroxylase (PHD) 1 in a Crohn’s like ileitis mouse model. Five-week-old TNF^∆ARE/+ mice and wildtype (WT) littermates were housed in normoxia (21% O₂) or hypoxia (8% O₂) for 10 weeks. Although environmental hypoxia increased both systemic as ileal markers of hypoxia, the body weight evolution in both WT and TNF^∆ARE/+ mice was not affected. Interestingly, hypoxia did increase circulatory monocytes, ileal mononuclear phagocytes and proinflammatory cytokine expression in WT mice. However, no histological or inflammatory gene expression differences in the ileum could be identified between TNF^∆ARE/+ mice housed in hypoxia versus normoxia nor between TNF^∆ARE/+ and WT mice with additional loss of immune cell-specific Phd1 expression. This is the first study showing that long-term environmental hypoxia or haematopoietic Phd1-deletion does not impact experimental ileitis. Therefore, it strongly questions whether targeting hypoxia-induced signalling via currently available PHD inhibitors would exert an immune suppressive effect in IBD patients with ileal inflammation.

Abstract

Environmental hypoxia and hypoxia-induced signalling in the gut influence inflammatory bowel disease pathogenesis, however data is limited to colitis. Hence, we investigated the effect of environmental hypoxia and immune cell-specific deletion of oxygen sensor prolyl hydroxylase (PHD) 1 in a Crohn’s like ileitis mouse model. Therefore, 5-week-old C57/BL6 TNF^∆ARE/+ mice and wildtype (WT) littermates were housed in normoxia (21% O₂) or hypoxia (8% O₂) for 10 weeks. Systemic inflammation was assessed by haematology. Distal ileal hypoxia was evaluated by pimonidazole staining. The ileitis degree was scored on histology, characterized via qPCR and validated in haematopoietic Phd1-deficient TNF^∆ARE/+ mice. Our results demonstrated that hypoxia did not impact body weight evolution in WT and TNF^∆ARE/+ mice. Hypoxia increased red blood cell count, haemoglobin, haematocrit and increased pimonidazole intensity in the ileum. Interestingly, hypoxia evoked an increase in circulatory monocytes, ileal mononuclear phagocytes and proinflammatory cytokine expression in WT mice. Despite these alterations, no histological or ileal gene expression differences could be identified between TNF^∆ARE/+ mice housed in hypoxia versus normoxia nor between haematopoietic Phd1-deficient TNF^∆ARE/+ and their WT counterparts. Therefore, we demonstrated for the first time that long-term environmental hypoxia or haematopoietic Phd1-deletion does not impact experimental ileitis development.

Monocyte to HDL cholesterol ratio as a marker of the presence and severity of obstructive sleep apnea in hypertensive patients

This study aimed to investigate the correlation between monocyte to high-density lipoprotein cholesterol ratio (MHR) and obstructive sleep apnea (OSA) in patients with hypertension. A total of 246 hypertensive patients (67 controls, 65 mild, 51 moderate, and 63 severe OSA) were included. The relationship between MHR and OSA was analyzed. MHR correlated positively with apnea–hypopnea index (AHI), while negatively with mean SpO₂ (P < 0.01). MHR was higher in OSA group than the control group (9.2 ± 2.6 vs. 10.8 ± 3.6, P < 0.001). Moreover, MHR in severe OSA group was the highest among all groups (9.2 ± 2.6, 10.2 ± 3.2, 10.4 ± 4.0, and 11.8 ± 3.4 in control, mild, moderate, and severe OSA group, respectively, P < 0.001). Logistic regression analysis demonstrated that MHR was an independent predictor of the presence of OSA (OR = 1.152, P < 0.01) and severe OSA (OR = 1.142, P < 0.01). Area under the curve of MHR was 0.634 (P < 0.05) and 0.660 (P < 0.05) for predicting OSA and severe OSA respectively in the ROC analysis. In conclusion, MHR increased with the severity of OSA. As a practical and cost-effective test, MHR was expected to be an available marker in evaluating OSA risk and severity in hypertensive patients.

Extracellular Vesicles in Innate Immune Cell Programming

Extracellular vesicles (EV) are a heterogeneous group of bilipid-enclosed envelopes that carry proteins, metabolites, RNA, DNA and lipids from their parent cell of origin. They mediate cellular communication to other cells in local tissue microenvironments and across organ systems. EV size, number and their biologically active cargo are often altered in response to pathological processes, including infection, cancer, cardiovascular diseases and in response to metabolic perturbations such as obesity and diabetes, which also have a strong inflammatory component. Here, we discuss the broad repertoire of EV produced by neutrophils, monocytes, macrophages, their precursor hematopoietic stem cells and discuss their effects on the innate immune system. We seek to understand the immunomodulatory properties of EV in cellular programming, which impacts innate immune cell differentiation and function. We further explore the possibilities of using EV as immune targeting vectors, for the modulation of the innate immune response, e.g., for tissue preservation during sterile injury such as myocardial infarction or to promote tissue resolution of inflammation and potentially tissue regeneration and repair.

The Mystery of Red Blood Cells Extracellular Vesicles in Sleep Apnea with Metabolic Dysfunction

Sleep is very important for overall health and quality of life, while sleep disorder has been associated with several human diseases, namely cardiovascular, metabolic, cognitive, and cancer-related alterations. Obstructive sleep apnea (OSA) is the most common respiratory sleep-disordered breathing, which is caused by the recurrent collapse of the upper airway during sleep. OSA has emerged as a major public health problem and increasing evidence suggests that untreated OSA can lead to the development of various diseases including neurodegenerative diseases. In addition, OSA may lead to decreased blood oxygenation and fragmentation of the sleep cycle. The formation of free radicals or reactive oxygen species (ROS) can emerge and react with nitric oxide (NO) to produce peroxynitrite, thereby diminishing the bioavailability of NO. Hypoxia, the hallmark of OSA, refers to a decline of tissue oxygen saturation and affects several types of cells, playing cell-to-cell communication a vital role in the outcome of this interplay. Red blood cells (RBCs) are considered transporters of oxygen and nutrients to the tissues, and these RBCs are important interorgan communication systems with additional functions, including participation in the control of systemic NO metabolism, redox regulation, blood rheology, and viscosity. RBCs have been shown to induce endothelial dysfunction and increase cardiac injury. The mechanistic links between changes of RBC functional properties and cardiovascular are largely unknown. Extracellular vesicles (EVs) are secreted by most cell types and released in biological fluids both under physiological and pathological conditions. EVs are involved in intercellular communication by transferring complex cargoes including proteins, lipids, and nucleic acids from donor cells to recipient cells. Advancing our knowledge about mechanisms of RBC-EVs formation and their pathophysiological relevance may help to shed light on circulating EVs and to translate their application to clinical practice. We will focus on the potential use of RBC-EVs as valuable diagnostic and prognostic biomarkers and state-specific cargoes, and possibilities as therapeutic vehicles for drug and gene delivery. The use of RBC-EVs as a precision medicine for the diagnosis and treatment of the patient with sleep disorder will improve the prognosis and the quality of life in patients with cardiovascular disease (CVD).

Pathologic angiogenesis in the bone marrow of humanized sickle cell mice is reversed by blood transfusion

Sickle cell disease (SCD) is a monogenic red blood cell (RBC) disorder with high morbidity and mortality. Here, we report, for the first time, the impact of SCD on the bone marrow (BM) vascular niche, which is critical for hematopoiesis. In SCD mice, we find a disorganized and structurally abnormal BM vascular network of increased numbers of highly tortuous arterioles occupying the majority of the BM cavity, as well as fragmented sinusoidal vessels filled with aggregates of erythroid and myeloid cells. By in vivo imaging, sickle and control RBCs have significantly slow intravascular flow speeds in sickle cell BM but not in control BM. In sickle cell BM, we find increased reactive oxygen species production in expanded erythroblast populations and elevated levels of HIF-1α. The SCD BM exudate exhibits increased levels of proangiogenic growth factors and soluble vascular cell adhesion molecule-1. Transplantation of SCD mouse BM cells into wild-type mice recapitulates the SCD vascular phenotype. Our data provide a model of SCD BM, in which slow RBC flow and vaso-occlusions further diminish local oxygen availability in the physiologic hypoxic BM cavity. These events trigger a milieu that is conducive to aberrant vessel growth. The distorted neovascular network is completely reversed by a 6-week blood transfusion regimen targeting hemoglobin S to <30%, highlighting the plasticity of the vascular niche. A better insight into the BM microenvironments in SCD might provide opportunities to optimize approaches toward efficient and long-term hematopoietic engraftment in the context of curative therapies.

The association between circulating APRIL levels and severity of obstructive sleep apnea in Chinese adults

BACKGROUND

Obstructive sleep apnea (OSA) is the most common type of sleep breathing disorder and is characterized by chronic intermittent hypoxia, which could cause inflammation and nuclear factor kappa B (NF-KB)-dependent inflammatory pathways activation. Circulating APRIL (a proliferation-inducing ligand) play an important role in promoting inflammation and NF-KB-dependent inflammatory pathways activation. We explored the role of APRIL as a potential mechanism of inflammation in OSA patients.

METHODS

After detailed sleep evaluated, venous blood and demographic data were collected from 155 subjects with varying severity of OSA and 52 control subjects. Plasma levels of APRIL were measured by human Magnetic Luminex assay.

RESULTS

Plasma APRIL levels were significantly higher in OSA subjects compared with control subjects. Categorization of the OSA subjects into mild, moderate, and severe OSA subgroups found that plasma levels of APRIL increased with the severity of OSA. After adjusting confounding factors, found that increased plasma APRIL levels were conferred a higher odds ratio of OSA. Moreover, plasma APRIL levels were positively associated with the apnea-hypopnea index, which represents the severity of OSA. Furthermore, plasma APRIL showed higher discriminatory accuracy in predicting the presence of OSA.

CONCLUSIONS

Plasma APRIL levels were significantly associated with the occurrence of OSA and its severity. APRIL could be a plasma biomarker with a positive diagnostic value for inflammation and NF-KB-dependent inflammatory pathways activation in subjects with OSA.

TRIAL REGISTRATION

The project was approved by the Chinese Clinical Trial Registry (No. ChiCTRROC-17011027).

Endothelial cells produce angiocrine factors to regulate bone and cartilage via versatile mechanisms

Blood vessels are conduits distributed throughout the body, supporting tissue growth and homeostasis by the transport of cells, oxygen and nutrients. Endothelial cells (ECs) form the linings of the blood vessels, and together with pericytes, are essential for organ development and tissue homeostasis through producing paracrine signalling molecules, called angiocrine factors. In the skeletal system, ECs - derived angiocrine factors, combined with bone cells-released angiogenic factors, orchestrate intercellular crosstalk of the bone microenvironment, and the coupling of angiogenesis-to-osteogenesis. Whilst the involvement of angiogenic factors and the blood vessels of the skeleton is relatively well established, the impact of ECs -derived angiocrine factors on bone and cartilage homeostasis is gradually emerging. In this review, we survey ECs - derived angiocrine factors, which are released by endothelial cells of the local microenvironment and by distal organs, and act specifically as regulators of skeletal growth and homeostasis. These may potentially include angiocrine factors with osteogenic property, such as Hedgehog, Notch, WNT, bone morphogenetic protein (BMP), fibroblast growth factor (FGF), insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF). Understanding the versatile mechanisms by which ECs-derived angiocrine factors orchestrate bone and cartilage homeostasis, and pathogenesis, is an important step towards the development of therapeutic potential for skeletal diseases.

Gene Expression Profile Reveals Hematopoietic-Related Molecule Changes in Response to Hypoxic Exposure

The Qing-Tibet Plateau is characterized by low oxygen pressure, which is an important biomedical and ecological stressor. However, the variation in gene expression during periods of stay on the plateau has not been well studied. We recruited eight volunteers to stay on the plateau for 3, 7, and 30 days. Human Clariom D arrays were used to measure transcriptome changes in the mRNA expression profiles in these volunteers' blood. Analysis of variance (ANOVA) indicated that 699 genes were significantly differentially expressed in response to entering the plateau during hypoxic exposure. The genes with changes in transcript abundance were involved in the terms phosphoprotein, acetylation, protein binding, and protein transport. Furthermore, numerous genes involved in hematopoietic functions, including erythropoiesis and immunoregulation, were differentially expressed in response to hypoxia. This phenomenon may be one of reasons why the majority of people entering the plateau do not have excessive erythrocyte proliferation and are susceptible to infection.

Obstructive Sleep Apnea, Hypoxia, and Nonalcoholic Fatty Liver Disease

Recent studies have demonstrated that obstructive sleep apnea (OSA) is associated with the development and evolution of nonalcoholic fatty liver disease (NAFLD), independent of obesity or other shared risk factors. Like OSA, NAFLD is a prevalent disorder associated with major adverse health outcomes: Patients with NAFLD may develop cirrhosis, liver failure, and hepatocellular carcinoma. One major finding that has emerged from these studies is that the OSA-NAFLD association is related to the degree of nocturnal hypoxemia in OSA. Animal models have therefore largely focused on intermittent hypoxia, a key manifestation of OSA, to shed light on the mechanisms by which OSA may give rise to the complex metabolic disturbances that are seen in NAFLD. Intermittent hypoxia leads to tissue hypoxia and can result in oxidative stress, mitochondrial dysfunction, inflammation, and overactivation of the sympathetic nervous system, among many other maladaptive effects. In such models, intermittent hypoxia has been shown to cause insulin resistance, dysfunction of key steps in hepatic lipid metabolism, atherosclerosis, and hepatic steatosis and fibrosis, each of which is pertinent to the development and/or progression of NAFLD. However, many intriguing questions remain unanswered: Principally, how aggressively should the clinician screen for NAFLD in patients with OSA, and vice versa? In this review, we attempt to apply the best evidence from animal and human studies to highlight the relationship between these two disorders and to advocate for further trials aimed at defining these relationships more precisely.

Impact of Intermittent Hypoxia on Sepsis Outcomes in a Murine Model

Sleep apnea has been associated with a variety of diseases, but its impact on sepsis outcome remains unclear. This study investigated the effect of intermittent hypoxia [IH]–the principal feature of sleep apnea–on murine sepsis. 5-week-old male C57BL6 mice were assigned to groups receiving severe IH (O2 fluctuating from room air to an O2 nadir of 5.7% with a cycle length of 90 seconds), mild IH (room air to 12%, 4 minutes/cycle), or room air for 3 weeks. Sepsis was induced by cecal ligation and puncture and survival was monitored. Sepsis severity was evaluated by murine sepsis scores, blood bacterial load, plasma tumor necrosis factor-α [TNF-α]/interleukin-6 [IL-6] levels and histopathology of vital organs. Compared with normoxic controls, mice subjected to severe IH had earlier mortality, a lower leukocyte count, higher blood bacterial load, higher plasma TNF-α and IL-6 levels, more severe inflammatory changes in the lung, spleen and small intestine. Mice subjected to mild IH did not differ from normoxic controls, except a higher IL-6 level after sepsis induced. The adverse impact of severe IH was reversed following a 10-day normoxic recovery. In conclusion, severe IH, not mild IH, contributed to poorer outcomes in a murine sepsis model.

Relationship between monocyte to HDL cholesterol ratio and concomitant cardiovascular disease in Chinese Han patients with obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular disease (CVD), which is attributed to chronic intermittent hypoxia (CIH) induced inflammation. As a new inflammatory biomarker of CVD, monocyte to high-density lipoprotein cholesterol ratio (MHR) has received little attention in OSA studies to date. Therefore, we aimed to investigate the correlation between MHR and concomitant CVD in Chinese Han patients with OSA.

Methods

A total of 657 Chinese Han subjects (169 controls, 145 mild, 94 moderate, and 249 severe OSA) of both genders were enrolled in this cross-sectional study, with an average BMI of 32.35±6.56 kg/m². The relationship between MHR and concomitant CVD in OSA patients was analyzed.

Results

The level of MHR was correlated positively with apnea-hypopnea index (AHI), while negatively with lowest SpO₂ (P<0.01). Moreover, the MHR values were higher in OSA patients with CVD than those without CVD (17.64±7.16 vs. 12.73±5.06, P<0.001). Logistic regression analysis demonstrated that MHR is an independent predictor of CVD (OR =1.190, P<0.001). The ROC analysis indicated that the best cut-off value of MHR for predicting CVD in OSA patients was 15.364 (sensitivity 65.0%, specificity 74.4%), while its cutoff value for identifying CVD in severe OSA patients was 15.362 (sensitivity 67.3%, specificity 80.1%).

Conclusions

MHR is strongly correlated with the severity of OSA and the occurrence of CVD in OSA patients. As an easy and available test, MHR is expected to be a promising biomarker candidate in predicting CVD in Chinese Han patients with OSA.

Chronic intermittent hypoxia enhances disease progression in myeloma-resistant mice

Obesity is the only known modifiable risk factor for multiple myeloma (MM), an incurable cancer of bone marrow plasma cells. The mechanism linking the two is unknown. Obesity is associated with an increased risk of sleep apnea, which results in chronic intermittent hypoxia (CIH), and drives solid tumor aggressiveness. Given the link between CIH and solid tumor progression, we tested the hypothesis that CIH drives the proliferation of MM cells in culture and their engraftment and progression in vivo. Malignant mouse 5TGM1 cells were cultured in CIH, static hypoxia, or normoxia as a control in custom, gas-permeable plates. Typically MM-resistant C57BL/6J mice were exposed to 10 h/day CIH (AHI = 12/h), static hypoxia, or normoxia for 7 days, followed by injection with 5TGM1 cells and an additional 28 days of exposure. CIH and static hypoxia slowed the growth of 5TGM1 cells in culture. CIH-exposed mice developed significantly more MM than controls (67 vs. 12%, P = 0.005), evidenced by hindlimb paralysis, gammopathy, bone lesions, and bone tumor formation. Static hypoxia was not a significant driver of MM progression and did not reduce survival (P = 0.117). Interestingly, 5TGM1 cells preferentially engrafted in the bone marrow and promoted terminal disease in CIH mice, despite a lower tumor burden, compared with the positive controls. These first experiments in the context of hematological cancer demonstrate that CIH promotes MM through mechanisms distinct from solid tumors and that sleep apnea may be a targetable risk factor in patients with or at risk for blood cancer.

Nocturnal Mean Oxygen Saturation Is Associated with Secondary Polycythemia in Young Adults with Obstructive Sleep Apnea, Especially in Men

OBJECTIVE

Whether the severity of obstructive sleep apnea (OSA) contributes to clinical polycythemia is uncertain, especially in young adults. This study aimed to assess the correlation between untreated OSA and polycythemia, controlling for multiple confounders, and to observe the difference in both genders.

METHODS

All participants underwent nocturnal polysomnography. Medical comorbidities, and demographic and laboratory information were also recorded. The relationship between OSA and concomitant polycythemia in both genders was analyzed.

RESULTS

A total of 605 young participants (383 men and 222 women), aged 30.52 ± 7.21 years, were enrolled, with an average body mass index of 32.48 ± 6.06 kg/m². Although 74.4% of patients were diagnosed with OSA, less than 10% had polycythemia. The levels of hemoglobin and hematocrit increased with the severity of OSA; only men with severe OSA had significantly higher hemoglobin, hematocrit, and polycythemia compared with those in the control group (P < 0.01). Hemoglobin and hematocrit significantly correlated with mean pulse oxygen saturation (SpO₂) (P < 0.001), but the correlation coefficients were weaker in women than in men. In logistic regression analysis, mean SpO₂, but not the apnea-hypopnea index (AHI), was found to be an independent predictor of polycythemia (P < 0.05). Areas under the receive operator characteristic analysis revealed that the cutoff values of hemoglobin and hematocrit were 155.5g/L and 44.6% (P < 0.001), respectively, for assessing nocturnal hypoxemia in men with OSA.

CONCLUSION

Nocturnal mean SpO₂ was an independent predictor of polycythemia in young adults. Mean SpO₂, compared with the AHI, was more associated with polycythemia. Men were more prone to suffer from polycythemia compared with women. Hemoglobin and hematocrit values might have diagnostic utility for assessing nocturnal hypoxia severity of OSA patients, especially in men.

Prevention Is the Best Treatment: The Case for Understanding the Transition from Monoclonal Gammopathy of Undetermined Significance to Myeloma

Multiple myeloma is an invariably fatal cancer of plasma cells. Despite tremendous advances in treatment, this malignancy remains incurable in most individuals. We postulate that strategies aimed at prevention have the potential to be more effective in preventing myeloma-related death than additional pharmaceutical strategies aimed at treating advanced disease. Here, we present a rationale for the development of prevention therapy and highlight potential target areas of study.

Impairment of vascular strain in patients with obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) is an independent risk factor for the development of cardiovascular diseases. Aim of this present study was to evaluate and extend recent research on the influence of obstructive sleep apnea on vascular strain.

Methods

A total number of 98 patients were integrated in the study. Patients were grouped according to the Apnea-Hypopnea-Index (AHI) in patients with mild-to-moderate OSA (5/h ≤ AHI < 30/h), severe OSA (AHI ≥ 30/h) and controls (AHI < 5/h). Groups were matched in age, body-mass-index and cardiovascular risks. Vascular strain of common carotid arteries was assessed by ultrasound speckle-tracking. A minor group of 30 patients and controls further underwent assessment of vascular strain of brachial and femoral arteries. Additionally, all patients underwent blood testing to reveal potential influences of inflammatory markers on arterial stiffness. In additional analysis we examined the effect of statin therapy on vascular strain.

Results

Patients with OSA showed significantly reduced values of vascular strain of common carotid arteries. Radial and circumferential strains were significantly lower in both patients with mild-to-moderate (p = .05) and patients with severe OSA (p = .001) compared to control. Vascular strain parameters of brachial and femoral arteries showed no consistent results. There were no significant correlations of inflammatory markers with vascular strain parameters. No significant differences in vascular strain were detected between statin and non-statin groups.

Conclusion

Patients with OSA show significantly reduced vascular strain assessed by ultrasound-based speckle-tracking. Vascular stiffness increases with the severity of the disease. Target vessels to assess vascular strain in patients with OSA are common carotid arteries, whereas other sites of the arterial tree are not reliable. No significant impact of current statin therapy on vascular strain was found. Further studies are needed to evaluate potential benefit of statins in secondary prevention of atherosclerosis in OSA.

Abnormal Growth and Feeding Behavior in Upper Airway Obstruction in Rats

Pediatric obstructive sleep apnea (OSA) is a syndrome manifesting with snoring and increased respiratory effort due to increased upper airway resistance. In addition to cause the abnormal sleep, this syndrome has been shown to elicit either growth retardation or metabolic syndrome and obesity. Treating OSA by adenotonsillectomy is usually associated with increased risk for obesity, despite near complete restoration of breathing and sleep. However, the underlying mechanism linking upper airways obstruction (AO) to persistent change in food intake, metabolism, and growth remains unclear. Rodent models have examined the impact of intermittent hypoxia on metabolism. However, an additional defining feature of OSA that is not related to intermittent hypoxia is enhanced respiratory loading leading to increased respiratory effort and abnormal sleep. The focus of this mini review is on recent evidence indicating the persistent abnormalities in endocrine regulation of feeding and growth that are not fully restored by the chronic upper AO removal in rats. Here, we highlight important aspects related to abnormal regulation of metabolism that are not related to intermittent hypoxia per se, in an animal model that mimics many of the clinical features of pediatric OSA. Our evidence from the AO model indicates that obstruction removal may not be sufficient to prevent the post-removal tendency for abnormal growth.