Biology of peripheral blood cells in obstructive sleep apnea--the tip of the iceberg

The pathogenesis of OSA-related hypertension: what are the determining factors?

Sleep-disordered breathing has a relatively high prevalence, which varies from 3-7% in males and from 2-5% in females in the adult population. Studies published in the literature have shown that sleep apnea is closely related to an increased risk of developing various pathologies, among which arterial hypertension stands out. The prevalence of hypertension in patients suffering from obstructive sleep apnea (OSA) ranges from 35-80% and appears to be related to OSA severity. Approximately 40-50% of patients affected by hypertension are also affected by OSA and this association seems to be stronger in young and middle-aged adults (<50 years of age). The primary objective of this narrative review is to provide an update on what are the main contributing comorbidities to the development of a hypertensive state in patients suffering from OSA, an independent risk factor for diurnal hypertension, implicated as a risk factor for the first stroke, recurrent stroke, and post-stroke mortality. There are a lot of factors that contribute to developing a hypertensive state in OSA patients, some more decisive, others less. More evidence from longitudinal studies is needed on the impact of OSA on cardiovascular risk in females, on the causal link between OSA and arterial hypertension or metabolic diseases, like diabetes and glucose intolerance, and the effect of different kinds of OSA treatment.

Differences in selected blood parameters between brachycephalic and non-brachycephalic dogs

Introduction

Cranial and upper-airway anatomy of short-nosed, flat-faced brachycephalic dogs predisposes them to brachycephalic obstructive airway syndrome (BOAS). Periodic apnoea increased inspiratory resistance, and an inability to thermoregulate effectively are characteristic of BOAS, but internationally accepted objective markers of BOAS severity are missing. The objective of this study was to compare the selected blood parameters between non-brachycephalic (NC) and brachycephalic (BC) dogs, exploring the possibility of developing a blood test for BOAS severity grading in the future.

Methods

We evaluated blood biochemistry, complete blood cell counts, red blood cell (RBC) indices, reticulocyte counts, a blood-born marker of intermittent hypoxia (glutathione, NO production), RBC hydration, deformability, and blood markers of metabolic changes and stress between BC (n = 18) and NC (meso- and dolichocephalic, n = 22) dogs.

Results

Reticulocyte counts and the abundance of middle-fluorescence immature reticulocytes were significantly (p < 0.05) higher in BC dogs compared to NC dogs. BC dogs had significantly more NO-derived NO2 - /NO3 - in plasma than NC dogs. RBCs of BC dogs were shedding significantly more membrane, as follows from the intensity of eosin maleimide staining, and had a significantly higher mean corpuscular hemoglobin concentration than NC dogs. Intracellular reduced glutathione content in RBCs of BC dogs was significantly lower, while plasma lactate was significantly higher in BC dogs compared to NC dogs. Plasma cholesterol and triglycerides were significantly lower, and cortisol was significantly higher in BC dogs compared to NC dogs. Eosinophil counts were significantly lower and the neutrophil-to-lymphocyte ratio was higher in BC dogs compared to NC dogs.

Discussion

Taken together, our findings suggest that the brachycephalic phenotype in dogs is associated with alterations at the level of blood cells and, systemically, with oxidation and metabolic changes. The parameters identified within this study should be further investigated for their potential as objective indicators for BOAS.

Pathophysiological mechanisms and therapeutic approaches in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common breathing disorder in sleep in which the airways narrow or collapse during sleep, causing obstructive sleep apnea. The prevalence of OSAS continues to rise worldwide, particularly in middle-aged and elderly individuals. The mechanism of upper airway collapse is incompletely understood but is associated with several factors, including obesity, craniofacial changes, altered muscle function in the upper airway, pharyngeal neuropathy, and fluid shifts to the neck. The main characteristics of OSAS are recurrent pauses in respiration, which lead to intermittent hypoxia (IH) and hypercapnia, accompanied by blood oxygen desaturation and arousal during sleep, which sharply increases the risk of several diseases. This paper first briefly describes the epidemiology, incidence, and pathophysiological mechanisms of OSAS. Next, the alterations in relevant signaling pathways induced by IH are systematically reviewed and discussed. For example, IH can induce gut microbiota (GM) dysbiosis, impair the intestinal barrier, and alter intestinal metabolites. These mechanisms ultimately lead to secondary oxidative stress, systemic inflammation, and sympathetic activation. We then summarize the effects of IH on disease pathogenesis, including cardiocerebrovascular disorders, neurological disorders, metabolic diseases, cancer, reproductive disorders, and COVID-19. Finally, different therapeutic strategies for OSAS caused by different causes are proposed. Multidisciplinary approaches and shared decision-making are necessary for the successful treatment of OSAS in the future, but more randomized controlled trials are needed for further evaluation to define what treatments are best for specific OSAS patients.

Redistribution of Monocyte Subsets in Obstructive Sleep Apnea Syndrome Patients Leads to an Imbalanced PD-1/PD-L1 Cross-Talk with CD4/CD8 T Cells

Obstructive sleep apnea syndrome (OSAS) represents a substantial disease of recurrent sleep fragmentation, leading to intermittent hypoxia and subsequent diseases such as cardiovascular, metabolic, or cognitive dysfunctions. In addition, OSAS is considered as low-grade systemic inflammation, which is associated with a higher incidence of cancer, severity of infections, and an overall immune dysregulation. This research project aims to comprehensively investigate the interplay of wholesome sleep and the immune functions of circulating monocytes and T cells in OSAS patients, which are known to be affected by oxidative stress. We studied the distribution of the CD14/CD16 characterized monocyte subsets in peripheral blood as well as their PD-L1 expression and complex formation with T cells. Furthermore, a detailed analysis of T cell subsets with regard to their PD-1 and PD-L1 expression was performed. Data revealed a decrease of classical monocytes accompanied by an increase of both CD16⁺ monocyte subsets in OSAS patients that was positively correlated with the body mass index. OSAS patients revealed an increased PD-1 and PD-L1 expression in T cells and monocytes, respectively, which was linked to the severity of monocyte subset alterations. The complex formation of monocytes and T cells was also elevated in OSAS patients, which indicates a deregulated PD-1/PD-L1 cross-talk between these cells. Our data show for the first time, to our knowledge, massive alterations of peripheral monocyte subsets in response to OSAS and its accompanying phenomena.

Association between Obstructive Sleep Apnea and Cardiovascular Risk Factors: Variation by Age, Sex, and Race. The Multi-Ethnic Study of Atherosclerosis

RATIONALE

The association between obstructive sleep apnea (OSA) and cardiovascular disease (CVD) is complex, bidirectional, and may vary across groups. Understanding which cardiovascular risk factors vary in their relationship to OSA across population groups may improve knowledge of OSA-related CVD susceptibility.

OBJECTIVES

To better understand the heterogeneity of associations, we assessed whether associations of OSA with cardiovascular risk factors vary by age, sex, and race/ethnicity.

METHODS

We performed cross-sectional analyses of 1,344 Multi-Ethnic Study of Atherosclerosis participants who underwent overnight full polysomnography, assays of fasting blood, and assessments of cardiovascular risk factors. Risk factors considered were blood pressure, glucose/lipid concentrations, white blood cell (WBC) total and subset counts, and cystatin C. The outcome was the apnea-hypopnea index (AHI). Linear regression analyses with tests for interactions were conducted.

RESULTS

The sample had a mean age of 68 ± 9 years. Forty-seven percent of the sample was male, and 32% had moderate or severe OSA (AHI, ≥15). Multivariable adjusted analysis showed significant associations between higher AHI with lower high-density lipoprotein cholesterol and higher diastolic blood pressure and neutrophil counts. Significant interactions with demographic factors were observed. Stronger associations were shown between AHI and higher total WBC count (Pint = 0.006) and glucose concentrations (Pint = 0.006) in younger (<65 yr) than in older individuals, higher triglyceride concentrations in men than in women (Pint = 0.006), and higher total WBC (Pint = 0.07) and monocyte counts (Pint = 0.03) in African American individuals than in other racial groups.

CONCLUSIONS

In a multiethnic cohort, we found increased levels of cardiovascular risk factors in association with OSA, including elevated neutrophil counts, a marker of inflammation. Furthermore, several associations were stronger in men, younger individuals, and African American individuals, highlighting pathways for CVD risk that may explain heterogeneity in the associations between CVD and OSA across population groups.

Elevations in neutrophils with obstructive sleep apnea: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Obstructive sleep apnea (OSA) associates with increased risk of cardiovascular diseases (CVD). Immune abnormalities and surges in sympathetic activity accompany OSA and CVD. We hypothesized that OSA associates with leukocytosis partially by abnormalities in autonomic nervous system (ANS) function that would suggest a pathway linking OSA and CVD.

METHODS

Participants from the Multi-Ethnic Study of Atherosclerosis (MESA), a prospective cohort of individuals initially without overt CVD, underwent polysomnography and assays for white blood cells (WBC) and subsets. Heart rate (HR) and heart rate variability (HRV), indirect measurements of ANS, were obtained from overnight electrocardiography. A formal statistical mediation analysis tested the indirect effect that mean HR and HRV measures contribute to associations between OSA and leukocytosis.

RESULTS

The analytical sample consisted of 1298 participants (54% female), ages 54-93years, 14% with severe OSA (apnea-hypopnea-index, AHI≥30). Severe OSA associated with a higher prevalence of obesity, diabetes, and increased levels of WBC total and subsets. Neutrophil count associated with severe OSA after adjusting for confounders (p=0.017). Mean HR positively associated with OSA indices and neutrophils. A mediation analysis revealed an "indirect" effect of mean HR that explained an estimated 11% of the association between AHI and neutrophils. Overnight hypoxia also associated with neutrophil count (p=0.009), and mean HR explained 14% of the association between neutrophils and hypoxia.

CONCLUSIONS

In the MESA cohort, OSA measures associate with elevated neutrophil counts and increases in overnight mean HR. These data link innate immune dysregulation with OSA and provide a potential pathophysiologic pathway between CVD and OSA.

Longitudinal brain structural alterations and systemic inflammation in obstructive sleep apnea before and after surgical treatment

Background

Systemic inflammation, neurocognitive impairments, and morphologic brain changes are associated with obstructive sleep apnea (OSA). Understanding their longitudinal evolution and interactions after surgical treatment provides clues to the pathogenesis of cognitive impairment and its reversibility. In the present study, we investigate clinical disease severity, systemic inflammation, cognitive deficits, and corresponding gray matter volume (GMV) changes in OSA, and the modifications following surgery.

Methods

Twenty-one patients with OSA (apnea-hypopnea index, AHI > 5) and 15 healthy volunteers (AHI < 5) underwent serial evaluation, including polysomnography, flow cytometry for leukocyte apoptosis categorization, cognitive function evaluation, and high-resolution brain scan. Disease severity, leukocyte apoptosis, cognitive function, and imaging data were collected to assess therapeutic efficacy 3 months after surgery.

Results

Pre-operatively, patients presented with worse cognitive function, worse polysomnography scores, and higher early leukocyte apoptosis associated with increased insular GMV. There was reduced GMV in the anterior cingulate gyrus before and after surgery in the cases compared to that in controls, suggesting an irreversible structural deficit. Post-operatively, there were significant improvements in different cognitive domains, including attention, executive and visuospatial function, and depression, and in early leukocyte apoptosis. There was also a significant decrease in GMVs after treatment, suggesting recovery from vasogenic edema in the precuneus, insula, and cerebellum. Improvement in early leukocyte apoptosis post-surgery predicted better recovery of precuneus GMV.

Conclusions

In OSA, increased disease severity and systemic inflammation can alter GMV in vulnerable regions. Surgical treatment may improve disease severity and systemic inflammation, with subsequent recovery in brain structures and functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0887-8) contains supplementary material, which is available to authorized users.

Increased MCP-1 gene expression in monocytes of severe OSA patients and under intermittent hypoxia

PURPOSE

Obstructive sleep apnea (OSA) is known to be a risk factor of coronary artery disease. Monocyte chemoattractant protein-1 (MCP-1), as a critical factor for monocyte infiltration, is known to play a role in the development of atherosclerosis. This study aimed to investigate the effect of intermittent hypoxia, the hallmark of OSA, on the MCP-1 expression of monocytes.

METHODS

Peripheral blood was sampled from 61 adults enrolled for suspected OSA. RNA was prepared from the isolated monocytes for the analysis of MCP-1. The effect of in vitro intermittent hypoxia on the regulation and function of MCP-1 was investigated on THP-1 monocytic cells and human monocytes. The mRNA and secreted protein levels were investigated by RT/real-time PCR and enzyme-linked immunosorbent assay, respectively.

RESULTS

Monocytic MCP-1 gene expression was found to be increased significantly in severe OSA patients. In vitro intermittent hypoxia was demonstrated to increase the mRNA and protein expression levels of MCP-1 dose- and time-dependently in THP-1 monocytic cells. The MCP-1 mRNA expression in monocytes isolated from OSA patient was induced to a much higher level compared to that from normal control. Pre-treatment with inhibitor for p42/44 MAPK or p38 MAPK suppressed the activation of MCP-1 expression by intermittent hypoxia.

CONCLUSIONS

This is the first study to demonstrate the increase of MCP-1 gene expression in monocytes of severe OSA patients. In addition, monocytic MCP-1 gene expression can be induced under intermittent hypoxia.

Is there an effect of obstructive sleep apnea syndrome on oxidative stress and inflammatory parameters in patients with craniofacial anomalies?

The aim of this study was to test the hypothesis that obstructive sleep apnea syndrome (OSAS) exhibits oxidative stress and inflammation in patients who have a congenital, craniofacial anomaly.This prospective, cross-sectional cohort study included ambulant sleep study data to asses OSAS in patients with syndromic craniosynostosis and Treacher Collins syndrome. Laboratory analyses were performed including malondialdehyde, tumor necrosis factor α (TNF-α), interleukin 6, and high-sensitivity C-reactive protein.Forty-eight patients were included; 11 were adults; 37 were children. The patients' body mass indexes were normal, with a median (SD) of 0.7 (-1.82 to 2.48) in children and 20.5 (15.2-29.4) in adults. Obstructive sleep apnea syndrome was diagnosed in 23 of 48 patients. It was mild (median obstructive apnea-hypopnea index [oAHI], 2.3; oxygenation-desaturation index [ODI], 0.9) in 16 patients and moderate/severe in 7 patients (median oAHI, 10.8; ODI, 5.0). Neither oxidative stress nor inflammation had a correlation with the oAHI and ODI. Only TNF-α was found significantly higher in both the OSAS and non-OSAS groups compared with the reference values (median, 15.1 pg/mL and 12.3 pg/mL versus 4.05 [0.0-8.1 pg/mL], P < 0.001 and P < 0.001, respectively).Based on our findings we conclude that (mainly mild) OSAS, oxidative stress, as well as high-sensitivity C-reactive protein and interleukin 6 levels are not abnormal in the day time in a population of nonobese patients with a craniofacial anomaly. The increased level of TNF-α cannot be explained by OSAS. Future research should focus on mapping chronobiologic changes for further interpretation of the results.

Obstructive Sleep Apnoea and Vascular Disease in Patients with Type 2 Diabetes

Obstructive sleep apnoea (OSA) is common and is associated with many vascular risk factors, such as hypertension, insulin resistance, albuminuria, dyslipidaemia, increased inflammation and endothelial dysfunction. Epidemiological studies have shown that OSA is associated with increased cardiovascular disease (CVD) and that continuous positive airway pressure (CPAP) might reduce CVD events in patients with OSA. In addition, OSA has also been shown to be associated with albuminuria, chronic kidney disease, a wide range of ocular diseases and peripheral neuropathy. Considering that CVD and microvascular complications are major contributors to the morbidity, mortality and the economic burden of diabetes and that OSA is common in patients with type 2 diabetes (T2D), it is important to understand the role of OSA in the development and/or progression of vascular disease in patients with T2D and to explore the impact of CPAP on diabetes-related vascular outcomes. The purpose of this article is to review the evidence for the relationship and impact of OSA on vascular disease and vascular risk factors particularly in patients with T2D.

T, B, and NKT Cells in Systemic Inflammation in Obstructive Sleep Apnoea

Background. Obstructive sleep apnoea syndrome (OSAS) brings risk of serious complications. The study objective was to assess elements of the cellular immune response in the course of OSAS. Methods. Peripheral blood (PB) lymphocytes: T, B, NK, NKT-like, Th, Tc, and HLA DR+ T cells were evaluated by flow cytometry of 48 OSA patients; the concentration of adiponectin, interleukin 1β, and TNFα was measured by ELISA method. The OSA complication score was developed and used for statistical analysis. Results. The proportion of B cells and Th/Tc ratio were significantly lower in the BP of OSA patients when compared with control subjects (median 7.9 versus 10.9%, 0.9 versus 1.5, p < 0.05). The proportion of Tc, NK, NKT-like, and HLADR positive T cells were elevated in OSA patients when compared with healthy subjects (36.4 versus 26.8, 15.5 versus 8.5, 5.7 versus 3.0, and 8.4 versus 4.5%, p < 0.05, resp.) and were more pronounced in patients with metabolic syndrome. The grade of OSA complication score correlated with systemic inflammation markers and the proportion of B cells. The value of adiponectin/BMI ratio correlated significantly with SpO₂ (r = 0.31, p < 0.05), CRP (r = −0.35, p < 0.05), TNFα concentration (r = −0.36, p < 0.05), and proportion of B cells (r = 0.32, p < 0.05). Conclusion. Lymphocytes B, Tc, NK, NKT-like, and adiponectin are involved in systemic immune response in OSA patients possibly predisposing them to cardiovascular and metabolic complications.

Intermittent hypoxemia and OSA: implications for comorbidities

OSA is a common chronic disorder that is associated with significant morbidity and mortality including cardiovascular, metabolic, and neurocognitive disease and increased cancer-related deaths. OSA is characterized by recurrent episodes of apneas and hypopneas associated with repetitive episodes of intermittent hypoxemia, intrathoracic pressure changes, and arousals. Intermittent hypoxemia (IH) is now being recognized as a potential major factor contributing to the pathogenesis of OSA-related comorbidities. OSA-related high-frequency IH is characterized by cycles of hypoxemia with reoxygenation that is distinctly different than sustained low-frequency hypoxia and contributes to ischemia-reperfusion injury. Data from both animal and human studies support mechanistic links between IH and its adverse impact at the tissue level. IH promotes oxidative stress by increased production of reactive oxygen species and angiogenesis, increased sympathetic activation with BP elevation, and systemic and vascular inflammation with endothelial dysfunction that contributes to diverse multiorgan chronic morbidity and mortality affecting cardiovascular disease, metabolic dysfunction, cognitive decline, and progression of cancer. Data from observational studies in large population groups also support the role for hypoxia in the pathogenesis of OSA comorbidity. Treatment with CPAP to reverse OSA-related symptoms and comorbidities has been shown to provide variable benefit in some but not all patient groups. Early treatment with CPAP makes intuitive sense to promote maximal functional recovery and minimize residual injury. More studies are needed to determine the interacting effects of IH and obesity, differential effects of both short-term and long-term hypoxemia, and the effect of CPAP treatment.

White matter damage and systemic inflammation in obstructive sleep apnea

STUDY OBJECTIVES

To evaluate white matter integrity in patients with obstructive sleep apnea (OSA) using diffusion tensor imaging (DTI) and to assess its relationship with systemic inflammation.

DESIGN

Cross-sectional study.

SETTING

One tertiary medical center research institute.

PATIENTS OR PARTICIPANTS

Twenty patients with severe OSA (apnea-hypopnea index [AHI] > 30, 18 men and 2 women) and 14 healthy volunteers (AHI < 5, 11 men and 3 women).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Patients with severe OSA and healthy volunteers underwent polysomnography to determine the severity of sleep apnea, and DTI scanning to determine fiber integrity. Early or late phase changes in leukocyte apoptosis and its subsets were determined by flow cytometry. DTI-related indices (including fractional anisotropy [FA], axial diffusivity [AD], radial diffusivity [RD], and mean diffusivity [MD]) were derived from DTI. The FA maps were compared using voxel-based statistics to determine differences between the severe OSA and control groups. The differences in DTI indices, clinical severity, and leukocyte apoptosis were correlated after adjusting for age, sex, body mass index, and systolic blood pressure. Exploratory group-wise comparison between the two groups revealed that patients with OSA exhibited low FA accomplished by high RD in several brain locations, without any differences in AD and MD. The FA values were negatively correlated with clinical disease severity and leukocyte early apoptosis.

CONCLUSIONS

Obstructive sleep apnea impairs white matter integrity in vulnerable regions, and this impairment is associated with increased disease severity. The possible interactions between systemic inflammation and central nervous system microstructural damage may represent variant hypoxic patterns and their consequent processes in OSA.

Associated bone mineral density and obstructive sleep apnea in chronic obstructive pulmonary disease

BACKGROUND

Osteoporosis is an important issue for patients with chronic obstructive pulmonary disease (COPD). Worse systemic inflammation and reduced exercise capacity have been reported in COPD patients with obstructive sleep apnea (OSA), implying that OSA may be an independent factor for osteoporosis in COPD patients.

METHODS

A total of 66 patients with bone mineral density (BMD) and polysomnography results from a previous COPD cohort (January 2008 to January 2013) were retrospectively enrolled. Clinical characteristics such as medication, pulmonary function, BMD, and results of polysomnography were analyzed.

RESULTS

The BMD in those with OSA was significantly lower than in those without OSA (-1.99±1.63 versus -1.27±1.14, P=0.045). In univariate analysis, body mass index, forced expiratory volume in 1 second, percentage of predicted value, incremental shuttle walk test, apnea-hypopnea index, and oxygen desaturation index (ODI) were significantly associated with BMD. After multivariate linear regression analysis, the ODI was still an independent factor for BMD. In addition, smaller total lung capacity is significantly associated with higher ODI and lower BMD, which implies that lower BMD might cause severer OSA via decreased total lung capacity.

CONCLUSION

OSA may be an independent factor for BMD in patients with COPD, which implies a possible vicious cycle takes place in these patients.

Increased C-C chemokine receptor 2 gene expression in monocytes of severe obstructive sleep apnea patients and under intermittent hypoxia

Background

Obstructive sleep apnea (OSA) is known to be a risk factor of coronary artery disease. The chemotaxis and adhesion of monocytes to the endothelium in the early atherosclerosis is important. This study aimed to investigate the effect of intermittent hypoxia, the hallmark of OSA, on the chemotaxis and adhesion of monocytes.

Methods

Peripheral blood was sampled from 54 adults enrolled for suspected OSA. RNA was prepared from the isolated monocytes for the analysis of C-C chemokine receptor 2 (CCR2). The effect of intermittent hypoxia on the regulation and function of CCR2 was investigated on THP-1 monocytic cells and monocytes. The mRNA and protein expression levels were investigated by RT/real-time PCR and western blot analysis, respectively. Transwell filter migration assay and cell adhesion assay were performed to study the chemotaxis and adhesion of monocytes.

Results

Monocytic CCR2 gene expression was found to be increased in severe OSA patients and higher levels were detected after sleep. Intermittent hypoxia increased the CCR2 expression in THP-1 monocytic cells even in the presence of TNF-α and CRP. Intermittent hypoxia also promoted the MCP-1-mediated chemotaxis and adhesion of monocytes to endothelial cells. Furthermore, inhibitor for p42/44 MAPK or p38 MAPK suppressed the activation of monocytic CCR2 expression by intermittent hypoxia.

Conclusions

This is the first study to demonstrate the increase of CCR2 gene expression in monocytes of severe OSA patients. Monocytic CCR2 gene expression can be induced under intermittent hypoxia which contributes to the chemotaxis and adhesion of monocytes.

Melatonin attenuates intermittent hypoxia-induced lipid peroxidation and local inflammation in rat adrenal medulla

Chronic intermittent hypoxia (CIH) induces lipid peroxidation and leads to cardiovascular dysfunction, in which impaired activities of the adrenal medulla are involved. This may be caused by CIH-induced injury in the adrenal medulla, for which the mechanism is currently undefined. We tested the hypothesis that melatonin ameliorates the CIH-induced lipid peroxidation, local inflammation and cellular injury in rat adrenal medulla. Adult Sprague–Dawley rats were exposed to air (normoxic control) or hypoxia mimicking a severe recurrent sleep apnoeic condition for 14 days. The injection of melatonin (10 mg/kg) or vehicle was given before the daily hypoxic treatment. We found that levels of malondialdehyde and nitrotyrosine were significantly increased in the vehicle-treated hypoxic group, when compared with the normoxic control or hypoxic group treated with melatonin. Also, the protein levels of antioxidant enzymes (superoxide dismutase (SOD)-1 and SOD-2) were significantly lowered in the hypoxic group treated with vehicle but not in the melatonin group. In addition, the level of macrophage infiltration and the expression of inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6) and mediators (inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2)) were elevated in the vehicle-treated hypoxic group, but were significantly ameliorated by the melatonin treatment. Moreover, the amount of apoptotic cells in the hypoxic groups was significantly less in the melatonin-treated group. In conclusion, CIH-induced lipid peroxidation causes local inflammation and cellular injury in the adrenal medulla. The antioxidant and anti-inflammatory actions of melatonin are indicative of a protective agent against adrenal damage in patients with severe obstructive sleep apnea syndrome.

Alterations in circulating T-cell lymphocyte populations in children with obstructive sleep apnea

STUDY OBJECTIVES

Changes in lymphocyte phenotype and functionality have been described in adult patients with obstructive sleep apnea (OSA). We hypothesized that OSA is associated with T lymphocyte alterations in children, particularly in T regulatory lymphocytes (T regs), and aimed to characterize circulating T lymphocyte subsets in children with OSA.

DESIGN

Cross-sectional.

SETTING

Kosair Children's Hospital (Louisville, KY, USA) and Comer Children's Hospital (Chicago, IL, USA).

PARTICIPANTS

Consecutively recruited children being evaluated for habitual snoring.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Overnight polysomnography (PSG) was performed and a fasting blood sample was obtained from the patients. Flow cytometry was performed on peripheral blood mononuclear cells stained for CD3, CD4, CD8, CD25, FOXP3, interleukin-4 (IL-4), interferon-γ (IFN-γ), and IL-17. Patients were divided into three groups based on their PSG: controls (apnea-hypopnea indices [AHI] < 1/h total sleep time [TST]), mild OSA (1 ≤ AHI < 5/hTST), moderate-severe OSA (AHI ≥ 5/h TST). The percentage of CD4+ and T reg lymphocytes differed across groups. Children with moderate-severe OSA had significantly reduced T reg than control children (median [interquartile range] 4.8 [3.8-5.7% CD4+] versus 7.8 [7.0-9.2% CD4+]; P < 0.001). There were also significant differences in the percentage of T helper 1 (Th1) lymphocytes and in Th1:Th2 ratios between groups. Children with moderate-severe OSA had increased Th1 cells (P = 0.001) and Th1:Th2 ratios (P = 0.0026) compared with children with mild OSA and control children. Associations between AHI and T reg (P = 0.0003; r = -0.46), CD4+ lymphocytes (P = 0.0047; r = -0.37), and Th1:Th2 ratios (P = 0.0009; r = 0.43) emerged. In addition, the percentage of T reg was inversely correlated with Th1:Th2 ratios (P = 0.029; r = -0.29).

CONCLUSIONS

Pediatric OSA is associated with reduced T reg population and altered Th1:Th2 balance toward Th1 predominance, suggesting a shift to a proinflammatory state. The changes in lymphocytic phenotypes associated with OSA may contribute to the variance in systemic inflammation and downstream morbidities associated with this condition.

Simultaneous quantification of mitochondrial DNA damage and copy number in circulating blood: a sensitive approach to systemic oxidative stress

Systemic oxidative stress is associated with a wide range of pathological conditions. Oxidative DNA damage is frequently measured in circulating lymphocytes. Mitochondrial DNA (mtDNA) is known to be more sensitive to oxidative damage than nuclear DNA but is rarely used for direct measurement of DNA damage in clinical studies. Based on the supercoiling-sensitive real-time PCR method, we propose a new approach for the noninvasive monitoring of systemic oxidative stress by quantifying the mtDNA structural damage and copy number change in isolated lymphocytes in a single test. We show that lymphocytes have significantly less mtDNA content and relatively lower baseline levels of damage than cancer cell lines. In an ex vivo challenge experiment, we demonstrate, for the first time, that exogenous H₂O₂ induces a significant increase in mtDNA damage in lymphocytes from healthy individuals, but no repair activity is observed after 1 h recovery. We further demonstrate that whole blood may serve as a convenient alternative to the isolated lymphocytes in mtDNA analysis. Thus, the blood analysis with the multiple mtDNA end-points proposed in the current study may provide a simple and sensitive test to interrogate the nature and extent of systemic oxidative stress for a broad spectrum of clinical investigations.

DNA methylation in inflammatory genes among children with obstructive sleep apnea

BACKGROUND

Pediatric obstructive sleep apnea (OSA) leads to multiple end-organ morbidities that are mediated by the cumulative burden of oxidative stress and inflammation. Because not all children with OSA exhibit increased systemic inflammation, genetic and environmental factors may be affecting patterns of DNA methylation in genes subserving inflammatory functions.

METHODS

DNA from matched children with OSA with and without high levels of high-sensitivity C-reactive protein (hsCRP) were assessed for DNA methylation levels of 24 inflammatory-related genes. Primer-based polymerase chain reaction assays in a case-control setting involving 47 OSA cases and 31 control subjects were conducted to confirm the findings; hsCRP and myeloid-related protein (MRP) 8/14 levels were also assayed.

MEASUREMENTS AND MAIN RESULTS

Forkhead box P3 (FOXP3) and interferon regulatory factor 1 (IRF1) showed higher methylation in six children with OSA and high hsCRP levels compared with matched children with OSA and low hsCRP levels (P < 0.05). In the case-control cohort, children with OSA and high CRP levels had higher log FOXP3 DNA methylation levels compared with children with OSA and low CRP levels and control subjects. IRF1 did not exhibit significant differences. FOXP3 DNA methylation levels correlated with hsCRP and MRP 8/14 levels and with apnea-hypopnea index (AHI), BMI z score, and apolipoprotein B levels. A stepwise multiple regression model showed that AHI was independently associated with FOXP3 DNA methylation levels (P < 0.03).

CONCLUSIONS

The FOXP3 gene, which regulates expression of T regulatory lymphocytes, is more likely to display increased methylation among children with OSA who exhibit increased systemic inflammatory responses. Thus, epigenetic modifications may constitute an important determinant of inflammatory phenotype in OSA, and FOXP3 DNA methylation levels may provide a potential biomarker for end-organ vulnerability.

Effects of short term forced oral breathing in rat pups on weight gain, hydration and stress

Nasal obstruction is a risk factor in sleep-disordered breathing with a negative impact on the quality of life in humans. We investigated hydration changes produced by short term reversible, bilateral, nasal obstruction in young developing rat pups. Physiological parameters of growth (weight gain and gastric content weight) and dehydration were analyzed during two periods; during nasal obstruction at post-natal day 8 (days 9, 11 and 13), plus 7 and 90 days after recovery of nasal breathing (day 15 and adulthood). Body weight gain in oral breathing rat pups was slower compared to controls. Gastric weight was decreased significantly only in oral breathing rat pups on days 9 and 11 while plasma osmolality and vasopressin levels increased (indicators of dehydration). There were no differences between controls and treated rat pups by day 15, or at adulthood. Short term nasal obstruction-induced forced oral breathing, decreased gastric content which had a negative impact on growth and blood glucose concentration in the short term for female rat pups. Plasma corticosterone levels increased during the dehydration but were normal in males by 90 days. This could be a model for blocked nose syndrome in the newborn. Possible long term consequences on development are discussed.

Leukocyte telomere length and plasma catestatin and myeloid-related protein 8/14 concentrations in children with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is common in children and leads to multiple end-organ morbidities induced by the cumulative burden of oxidative stress and inflammation. Leukocyte telomere length (LTL) reflects not only chronologic age but also the burden of disease. We hypothesized that LTL would be decreased in children with OSA.

METHODS

Two hundred thirteen children (mean age, 7.7 +/- 1.4 years) were included after a sleep study and a morning blood sample. LTL was examined by quantitative polymerase chain reaction in a case-control setting involving 111 OSA cases and 102 controls. Myeloid-related protein (MRP) 8/14 and catestatin plasma levels also were assayed using enzyme-linked immunosorbent assay.

RESULTS

Log LTL was significantly increased and OSA severity dependently increased in children (P = .012), was positively associated with apnea-hypopnea index (AHI) (r = 0.236; P < .01), and was inversely correlated with age (r = -0.145; P < .05). In a multivariate regression model, LTL was independently associated with AHI (beta = 0.28; P = .002) after adjusting for age, sex, BMI z score, and race. Children with OSA exhibited higher BP (P < .05), lower plasma catestatin (P = .009), and higher MRP 8/14 levels (P < .001) than controls. Of note, children with the lowest plasma catestatin levels (< 1.39 ng/mL) had 5.2-fold increased odds of moderate-to-severe OSA (95% CI, 1.19-23.4 ng/mL; P < .05) after adjusting for confounding variables.

CONCLUSIONS

In pediatric OSA, LTL is longer rather than shorter. Children with OSA have reduced plasma catestatin levels and increased BP along with increased MRP 8/14 levels that exhibit AHI dependencies. Thus, catestatin and MRP 8/14 levels may serve as biomarkers for cardiovascular risk in the context of pediatric OSA. However, the implications of increased LTL in children with OSA remain to be defined.