Jing Feng

Effects of Varying Degrees of Intermittent Hypoxia on Proinflammatory Cytokines and Adipokines in Rats and 3T3-L1 Adipocytes

Objectives Intermittent hypoxia (IH), resulted from recurring episodes of upper airway obstruction, is the hallmark feature and the most important pathophysiologic pathway of obstructive sleep apnea (OSA). IH is believed to be the most important factor causing systemic inflammation. Studies suggest that insulin resistance (IR) is positively associated with OSA. In this study, we hypothesized that the recurrence of IH might result in cellular and systemic inflammation, which was manifested through the levels of proinflammatory cytokines and adipokines after IH exposure, and because IR is linked with inflammation tightly, this inflammatory situation may implicate an IR status. Methods We developed an IH 3T3-L1 adipocyte and rat model respectively, recapitulating the nocturnal oxygen profile in OSA. In IH cells, nuclear factor kappa B (NF-κB) DNA binding reactions, hypoxia-inducible factor-1α (HIF-1α), glucose transporter-1 (Glut-1), necrosis factor alpha (TNF-α), interleukin (IL) -6, leptin, adiponectin mRNA transcriptional activities and protein expressions were measured. In IH rats, blood glucose, insulin, TNF-α, IL-6, leptin and adiponectin levels were analyzed. Results The insulin and blood glucose levels in rats and NF-κB DNA binding activities in cells had significantly statistical results described as severe IH>moderate IH>mild IH>sustained hypoxia>control. The mRNA and protein levels of HIF-1α and Glut-1 in severe IH group were the highest. In cellular and animal models, both the mRNA and protein levels of TNF-α, IL-6 and leptin were the highest in severe IH group, when the lowest in severe IH group for adiponectin. Conclusions Oxidative stress and the release of pro-inflammatory cytokines/adipokines, which are the systemic inflammatory markers, are associated with IH closely and are proportional to the severity of IH. Because IR and glucose intolerance are linked with inflammation tightly, our results may implicate the clinical relationships between OSA and IR.

Intermittent hypoxia from obstructive sleep apnea may cause neuronal impairment and dysfunction in central nervous system: the potential roles played by microglia.

Obstructive sleep apnea (OSA) is a common condition characterized by repetitive episodes of complete (apnea) or partial (hypopnea) obstruction of the upper airway during sleep, resulting in oxygen desaturation and arousal from sleep. Intermittent hypoxia (IH) resulting from OSA may cause structural neuron damage and dysfunction in the central nervous system (CNS). Clinically, it manifests as neurocognitive and behavioral deficits with oxidative stress and inflammatory impairment as its pathophysiological basis, which are mediated by microglia at the cellular level. Microglia are dominant proinflammatory cells in the CNS. They induce CNS oxidative stress and inflammation, mainly through mitochondria, reduced nicotinamide adenine dinucleotide phosphate oxidase, and the release of excitatory toxic neurotransmitters. The balance between neurotoxic versus protective and anti- versus proinflammatory microglial factors might determine the final roles of microglia after IH exposure from OSA. Microglia inflammatory impairments will continue and cascade persistently upon activation, ultimately resulting in clinically significant neuron damage and dysfunction in the CNS. In this review article, we summarize the mechanisms of structural neuron damage in the CNS and its concomitant dysfunction due to IH from OSA, and the potential roles played by microglia in this process.

The effects of sleep hypoxia on coagulant factors and hepatic inflammation in emphysematous rats.

Objectives To develop a sleep hypoxia (SH) in emphysema (SHE) rat model and to explore whether SHE results in more severe hepatic inflammation than emphysema alone and whether the inflammation changes levels of coagulant/anticoagulant factors synthesized in the liver. Methods Seventy-five rats were put into 5 groups: SH control (SHCtrl), treated with sham smoke exposure (16 weeks) and SH exposure (12.5% O2, 3 h/d, latter 8 weeks); emphysema control (ECtrl), smoke exposure and sham SH exposure (21% O2); short SHE (SHEShort), smoke exposure and short SH exposure (1.5 h/d); mild SHE (SHEMild), smoke exposure and mild SH exposure (15% O2); standard SHE (SHEStand), smoke exposure and SH exposure. Therefore, ECtrl, SHEShort, SHEMild and SHEStand group were among emphysematous groups. Arterial blood gas (ABG) data was obtained during preliminary tests. After exposure, hepatic inflammation (interleukin -6 [IL-6] mRNA and protein, tumor necrosis factor α [TNFα] mRNA and protein) and liver coagulant/anticoagulant factors (antithrombin [AT], fibrinogen [FIB] and Factor VIII [F VIII]) were evaluated. SPSS 11.5 software was used for statistical analysis. Results Characteristics of emphysema were obvious in emphysematous groups and ABGs reached SH criteria on hypoxia exposure. Hepatic inflammation parameters and coagulant factors are the lowest in SHCtrl and the highest in SHEStand while AT is the highest in SHCtrl and the lowest in SHEStand. Inflammatory cytokines of liver correlate well with coagulant factors positively and with AT negatively. Conclusions When SH is combined with emphysema, hepatic inflammation and coagulability enhance each other synergistically and produce a more significant liver-derivative inflammatory and prothrombotic status.

Value of Autofluorescence Imaging Videobronchoscopy in Detecting Lung Cancers and Precancerous Lesions: A Review

Bronchoscopy technology is a desirable method for detecting lung cancers arising in the central airways. Most early cancers and precancerous lesions are not visible on conventional white-light bronchoscopy (WLB). Autofluorescence bronchoscopy (AFB) is a newly developed technology that exploits the difference in autofluorescence intensity between normal and tumorous tissues to detect bronchial cancers and precancerous lesions. Several types of AFB systems have been used in clinical practice, and autofluorescence imaging videobronchoscopy (AFI) is one of these AFBs. In most of the studies on AFB other than AFI, AFB has provided a much higher sensitivity but a lower specificity than WLB. Regarding AFI, recent studies have reported controversial results on the sensitivity and specificity for detecting cancers and precancerous lesions, compared with WLB. In this paper we describe the working mechanisms and characteristics of AFBs, mainly AFI, and the diagnostic performance of AFI, compared with WLB, other AFBs, and narrow-band imaging, for detecting lung cancers and precancerous lesions.

Obstructive sleep apnea and endothelial progenitor cells

Background Obstructive sleep apnea (OSA) occurs in 4% of middle-aged men and 2% of middle-aged women in the general population, and the prevalence is even higher in specific patient groups. OSA is an independent risk factor for a variety of cardiovascular diseases. Endothelial injury could be the pivotal determinant in the development of cardiovascular pathology in OSA. Endothelial damage ultimately represents a dynamic balance between the magnitude of injury and the capacity for repair. Bone marrow–derived endothelial progenitor cells (EPCs) within adult peripheral blood present a possible means of vascular maintenance that could home to sites of injury and restore endothelial integrity and normal function. Methods We summarized pathogenetic mechanisms of OSA and searched for available studies on numbers and functions of EPCs in patients with OSA to explore the potential links between the numbers and functions of EPCs and OSA. In particular, we tried to elucidate the molecular mechanisms of the effects of OSA on EPCs. Conclusion Intermittent hypoxia cycles and sleep fragmentation are major pathophysiologic characters of OSA. Intermittent hypoxia acts as a trigger of oxidative stress, systemic inflammation, and sympathetic activation. Sleep fragmentation is associated with a burst of sympathetic activation and systemic inflammation. In most studies, a reduction in circulating EPCs has emerged. The possible mechanisms underlying the decrease in the number or function of EPCs include prolonged inflammation response, oxidative stress, increased sympathetic activation, physiological adaptive responses of tissue to hypoxia, reduced EPC mobilization, EPC apoptosis, and functional impairment in untreated OSA. Continuous positive airway pressure (CPAP) therapy for OSA affects the mobilization, apoptosis, and function of EPCs through preventing intermittent hypoxia episodes, improving sleep quality, and reducing systemic inflammation, oxidative stress levels, and sympathetic overactivation. To improve CPAP adherence, the medical staff should pay attention to making the titration trial a comfortable first CPAP experience for the patients; for example, using the most appropriate ventilators or proper humidification. It is also important to give the patients education and support about CPAP use in the follow-up, especially in the early stage of the treatment.

Comparison of autofluorescence imaging bronchoscopy and white light bronchoscopy for detection of lung cancers and precancerous lesions

Background The purpose of this paper was to compare the sensitivity, specificity, and overall diagnostic performance of autofluorescence imaging bronchoscopy (AFI) versus white light bronchoscopy (WLB) in the detection of lung cancers and precancerous lesions by meta-analysis. Methods We performed a literature search using the PubMed and EMBASE databases to identify studies published between March 1991 and March 2012. Article selection, quality assessment, and data extraction were then performed. The pooled sensitivity, specificity, diagnostic odds ratio, and area under the curve of the summary receiver operating characteristic for AFI versus WLB were calculated using Stata version 12.0 software. Results Six studies were included in the meta-analysis. The pooled sensitivity of AFI and WLB was 0.89 (95% confidence interval [CI] 0.81–0.94) and 0.67 (95% CI 0.46–0.83) and the pooled specificity of AFI and WLB was 0.64 (95% CI 0.37–0.84) and 0.84 (95% CI 0.74–0.91), respectively. The diagnostic odds ratio for AFI and WLB was 14.5 (95% CI 3.76–55.63) and 10.9 (95% CI 3.12–38.21), and the area under the curve for AFI and WLB was 0.89 (95% CI 0.86–0.92) and 0.85 (95% CI 0.81–0.88), respectively. The pooled positive and negative likelihood ratios were 2.5 (95% CI 1.21–4.97) and 0.17 (95% CI 0.08–0.36) for AFI, and the corresponding values for WLB were 4.3 (95% CI 2.13–8.52) and 0.39 (95% CI 0.21–0.73). The pooled positive likelihood ratio for AFI and WLB was not higher than 10, and the pooled negative likelihood ratio for AFI and WLB was not lower than 0.1. Conclusion The sensitivity of AFI is higher than that of WLB, while the specificity of AFI is lower than that of WLB. The overall diagnostic performance of AFI is slightly better than that of WLB in detecting lung cancers and precancerous lesions. AFI should find its place in routine bronchoscopic examination and may improve the diagnostic outcome on endoscopy.

Increased oxidative stress and disrupted small intestinal tight junctions in cigarette smoke-exposed rats

Chronic obstructive pulmonary disease (COPD) is a major public health problem, and cigarette smoke (CS) is the primary risk factor. The pathology is often observed in the lung, but COPD is also associated with intestinal barrier disruption, although the underlying mechanisms are poorly understood. To address this, a CS‑exposed rat model was evaluated in the present study by analyzing small intestinal gene expression using reverse transcription‑quantitative polymerase chain reaction. CS exposure caused upregulation of the nicotinamide adenine dinucleotide phosphate‑oxidase subunits nox2 and p22phox in the small intestine, while the antioxidative enzyme superoxide dismutase was downregulated. CS exposure also increased bax expression and decreased bcl‑2 expression. This was associated with an elevation of hypoxia‑inducible factor (HIF)‑1α. Claudin‑1 was decreased and claudin‑2 increased, indicating a loosening of small intestinal tight junctions (TJs). These data suggest that during the development of COPD, HIF‑1α expression is altered in the small intestine, which may be associated with the increased oxidative stress and apoptosis, eventually resulting in disruption of the intestinal TJs.

Glucocorticoid dexamethasone regulates the differentiation of mouse conducting airway epithelial progenitor cells

Inhaled glucocorticoid dexamethasone is the most effective treatment of asthma currently available. Epithelial damage and shedding represents a clear manifestation of asthmatic pathologies. However it remains unknown if dexamethasone regulates functions of airway progenitor cells that are responsible for epithelial repair. In present study Secretoglobin1a1 (Scgb1a1) lineage tracing mice were injected intraperitoneally with tamoxifen to induce the expression of green fluorescence protein (GFP) in Scgb1a1-expressing conducting airway progenitor cells. Scgb1a1-expressing progenitor cells were isolated from lungs of Scgb1a1 lineage tracing mice via flow activated cell sorting. In vitro three-dimensional matrigel culture of these progenitor cells revealed that dexamethasone has little effect on the colony forming ability of airway epithelial progenitor cells, but exhibits significant effects on the differentiation of the progenitor cells. Compared to the untreated group, dexamethasone treatment inhibited the expression of forkhead box J1 (FoxJ1) and mucin subtype A & C (Muc5Ac), but promoted the expression of calcium activated chloride channel 3 (Clca3) and cystic fibrosis transmembrane conductance regulator (Cftr). Dexamethasone-induced effects on the expression of FoxJ1, Muc5Ac and Clca3 were abolished or even reversed in the presence of RU486, an antagonist of glucocorticoid receptor, indicating that glucocorticoid receptor plays a role in the regulation of airway epithelial progenitor cells by dexamethasone. These data suggested that, though effective to reduce airway inflammation, dexamethasone treatment alone fails to fully restore the mucociliary clearance function in the treatment of asthma patients.

Lymphocytes from intermittent hypoxia-exposed rats increase the apoptotic signals in endothelial cells via oxidative and inflammatory injury in vitro

ObjectiveObstructive sleep apnea (OSA) has been implicated as a risk factor for atherosclerosis. Intermittent hypoxia (IH) induces oxidative and immuno-inflammatory alterations that could contribute to atherosclerosis. The aim of this study was to examine the effect of lymphocytes from intermittent hypoxia-exposed rats on the apoptotic signals in endothelial cells and the interventional role of tempol.MethodMale Wistar rats were randomly distributed into three groups (n = 8 each): control group, IH group, and tempol group (exposed to IH and treated with tempol). Lymphocytes isolated from the rats were coincubated subsequently with endothelial cells under normoxia or IH condition. We analyzed endothelial apoptosis-related proteins (Bcl-2, Bax, and caspase-3) by Western blotting and measured the marks of oxidative stress (MDA, SOD, and CAT) and inflammation (TNF-α, IL-8, CRP, and ICAM-1) in cocultural supernatants by ELISA. We also determined endothelial p22phox, c-fos, and HIF-1α messenger RNA (mRNA) expressions using real time PCR.ResultsA significant decrease in the Bcl-2 level and the Bcl-2/Bax ratio and a significant increase in Bax and caspase-3 levels in endothelial cells were observed when coincubated normoxically with lymphocytes from IH-exposed rats compared to control (P < 0.01). Moreover, the oxidative stress, inflammation, and mRNA expressions of endothelial p22phox, c-fos, and HIF-1α were elevated significantly (P < 0.01). The alterations induced by lymphocytes were partially restored by tempol pretreatment while exacerbated by intermittent hypoxic coincubation.ConclusionsLymphocytes from intermittent hypoxia-exposed rats increased the apoptotic signals in endothelial cells via oxidative and inflammatory injury in vitro, which could be attenuated by tempol.

RORγt Modulates Macrophage Recruitment during a Hydrocarbon Oil-Induced Inflammation

Hydrocarbon oils are often utilized as adjuvants in vaccines. In response to naturally occurring hydrocarbon oils, inflammation is initiated and persists with the continuous recruitment of immune cells such as macrophages and neutrophils. However, the mechanism underlying the chronic inflammation in response to hydrocarbon oils is not fully defined. In this study, we revealed an essential role of retinoid-related orphan receptor gamma t (RORγt) in sustaining the recruitment of macrophages following pristane treatment. RORγt absence resulted in the incompetent formation of mesenteric oil granulomas which may associate to a reduction in the migration of macrophages into the mesentery during pristane-induced inflammation. This is at least partially dependent on the expression of the monocyte chemoattractant protein-1 (MCP-1) in the mesentery and the decrease in the macrophage reservoir in the spleen. However, the absence of RORγt had no impact on the recruitment of neutrophils to the mesentery after pristane treatment. Our data uncovered an important role of RORγt in the recruitment of macrophages during hydrocarbon oil-induced chronic inflammation.