Polymorphonuclear neutrophils promote endothelial apoptosis by enhancing adhesion upon stimulation by intermittent hypoxia.

PURPOSE: This study explored the interactive effects between polymorphonuclear neutrophils (PMNs) and vascular endothelial cells under intermittent hypoxia (IH) and investigated the mechanisms underlying these effects. METHODS: Endothelial cells were co-cultured with PMNs isolated from rats exposed to normoxia or IH. The PMN apoptotic rate was determined using flow cytometry. Expression of apoptosis-related proteins in the endothelial cells were evaluated using Western blotting, and the levels of intercellular adhesion molecules in the co-culture supernatants were measured using enzyme-linked immunosorbent assay. RESULTS: The PMN apoptotic rate in the IH-exposed rat group was significantly lower than that of the normoxia control group. There was a positive relationship between the PMN apoptotic rate and IH exposure time. In endothelial cells co-cultured with PMNs isolated from IH-exposed rats, a significant increase in the protein expression levels of Bax, Bcl-2, and caspase-3 and a significant decrease in the Bcl-2/Bax ratio were observed. Furthermore, the intercellular cell adhesion molecule-1(ICAM-1) and E-select element (E-S) levels were elevated significantly in the co-cultured supernatants of endothelial cells and PMNs from IH-exposed rats compared to that from controls. The above IH-induced alterations were partially restored by tempol pretreatment. CONCLUSIONS: The apoptotic rate was low in PMNs from IH-exposed rats, which consequently increased the apoptotic signals in endothelial cells in vitro. This may be associated with the increased levels of intercellular adhesion molecules. Further, tempol partially attenuates the PMN-mediated pro-apoptotic effects on endothelial cells under IH.

The Impact of Programmed Death-Ligand 1 Expression on the Prognosis of Early Stage Resected Non-Small Cell Lung Cancer: A Meta-Analysis of Literatures.

INTRODUCTION: Previous studies have demonstrated that programmed cell death-ligand 1 (PD-L1) serves as biomarker for poor prognosis and survival in advanced-stage non-small cell lung cancer (NSCLC) patients. However, the merit of PD-L1 expression to predict the prognosis of early stage NSCLC patients who underwent complete resection remains controversial. In the present study, we performed a meta-analysis to investigate the relationship between PD-L1 expression and prognosis in patients with early stage resected NSCLC. METHODS: Electronic databases, including PubMed, EMBASE, and the Cochrane Library, were searched until July 23 2020 for studies evaluating the expression of PD-L1 and the prognosis of resected NSCLCs. Hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival (OS) and disease-free survival (DFS) were pooled and analyzed. Heterogeneity and publication bias analyses were also assessed. RESULTS: A total of 15 studies involving 3,790 patients were considered in the present meta-analysis. The pooled HR indicated that PD-L1 expression related to a much shorter DFS (HR = 1.56, 95% CI: 1.18-2.05, p < 0.01), as well a significantly worse OS (HR = 1.68, 95% CI: 1.29-2.18, p < 0.01). Furthermore, our analysis indicated that PD-L1 expression was significantly associated with gender (male vs. female: OR = 1.27, 95% CI:1.01-1.59, p = 0.038), histology (ADC vs. SCC: OR = 0.54, 95% CI:0.38-0.77, p = 0.001), TNM stage (I vs. II-III: OR = 0.45, 95% CI:0.34-0.60, p = 0.000), smoking status (Yes vs No: OR = 1.43, 95% CI:1.14-1.80, p = 0.002) and lymph node metastasis (N+ vs N-: OR = 1.97, 95% CI:1.26-3.08, p = 0.003). CONCLUSIONS: The results of this meta-analysis suggest that PD-L1 expression predicts an unfavorable prognosis in early stage resected NSCLCs. The role of personalized anti-PD-L1/PD-1 immunotherapy in the adjuvant settings of resected NSCLC warrants further investigation.

Quercetin induces pro-apoptotic autophagy via SIRT1/AMPK signaling pathway in human lung cancer cell lines A549 and H1299 in vitro.

BACKGROUND: Quercetin, a natural flavonoid compound, is a potent cancer therapeutic agent widely found in fruit and vegetables. It has been reported to induce growth inhibition and apoptosis in both A549 and H1299 human lung cancer cells. However, the effect of quercetin-induced autophagy on apoptosis and the possible autophagy mechanism in A549 and H1299 cells have not yet been critically examined. METHODS: A549 and H1299 cells were treated with different concentrations of quercetin for 24 hours. Cell growth was measured by cell counting kit-8 (CCK-8) assay, whereas apoptosis was assessed by western blotting analysis of apoptotic proteins. The levels of proteins and genes involved in autophagy were determined by western blotting and reverse transcription polymerase chain reaction (RT-PCR), respectively. Autophagosomes were also observed by transmission electron microscopy (TEM) and LC3 immunofluorescence. RESULTS: Quercetin inhibited cell viability and induced mitochondria-dependent apoptosis in both A549 and H1299 cells in a dose-dependent. Moreover, quercetin also promoted the expression of LC3-II and beclin 1 and suppressed the expression of p62. The mRNA levels of LC3-II, beclin 1, Atg5, Atg7, and Atg12 were upregulated by quercetin treatment. Autophagy inhibition with 3-methyladenine could effectively inhibit quercetin-induced apoptosis. In addition, quercetin dose-dependently elevated the levels of SIRT1 protein and the pAMPK-AMPK ratio. Quercetin-induced autophagy was attenuated by SIRT1 inhibitor EX527 and SirT1 knockdown by small interfering RNA (siRNA). CONCLUSIONS: Quercetin-induced autophagy contributes to apoptosis in A549 and H1299 lung cancer cells, which involved the SIRT1/AMPK signaling pathway.

Intermittent hypoxia-induced autophagy via AMPK/mTOR signaling pathway attenuates endothelial apoptosis and dysfunction in vitro.

PURPOSE: The aim of this study was to examine whether or not intermittent hypoxia (IH) upregulated autophagy and the contributions of autophagy to endothelial apoptosis and dysfunction in human umbilical vein endothelial cells (HUVECs). METHOD: HUVECs were incubated under normoxia and IH conditions. After 3-, 6-, 12-, and 24-h exposure, the autophagic vacuoles and autophagosomes were observed by transmission electron microscopy and monodansylcadaverine staining. The protein levels of autophagy-related biomarkers and AMPK/mTOR pathway were measured by Western blot. The apoptosis-related proteins and the percentage of apoptotic cells were evaluated by Western blot and flow cytometry, respectively, while the levels of endothelial function biomarkers were assessed by ELISA. RESULTS: IH induced autophagy, as determined by the increased numbers of the autophagic vacuoles, autophagosomes, and by the elevated levels of Beclin-1 protein, the LC3II/LC3I ratio, and p62 degradation. IH-induced autophagic flux peaked at 12-h duration and weakened at 24 h. IH increased the ratio of p-AMPK/AMPK and decreased the ratio of p-mTOR/mTOR, while compound C restored the alteration. A significant decrease in the Bcl-2 level and the Bcl-2/Bax ratio and a significant increase in the protein expression levels of Bax and cleaved caspase 3 and in the percentage of apoptosis were observed under IH exposure. Moreover, the NO level was reduced, while the ET-1 and VEGF levels were raised under IH condition. These alterations were suppressed by the pretreatment of 3-methyladenine. CONCLUSIONS: IH upregulates autophagy through AMPK/mTOR pathway in HUVECs in vitro, which might be protective against endothelial apoptosis and dysfunction caused by IH.

The importance of autophagy regulation in obstructive sleep apnea.

PURPOSE: Autophagy, the self-renewal process of cells, is dependent on lysosomes to degrade damaged organelles and proteins. The increased or damaged level of autophagy is proven to relate to a number of disorders, including metabolic disorders, malignant tumors, pulmonary diseases, and neurodegenerative disorders. This review aims to examine the effects of autophagy on the pathogenic mechanism of obstructive sleep apnea (OSA) in order to guide relevant disease treatment. METHODS: We conducted a search of the literature using the electronic database, focusing on articles that explored the association between OSA and autophagy. CONCLUSION: OSA can induced autophagy through hypoxia, oxidative stress, endoplasmic reticulum stress, endothelial dysfunction, miRNA, etc. We propose that the mechanism of the autophagy in patients with OSA should be eclucidated in further studies.

Obstructive sleep apnea and respiratory center regulation abnormality.

PURPOSE: Obstructive sleep apnea (OSA) is a complex disease in which phenotypic analysis and understanding pathological mechanisms facilitate personalized treatment and outcomes. However, the pathophysiology responsible for this robust observation is incompletely understood. The objective of the present work was to review how respiratory center regulation varies during sleep and wakeness in patients with OSA. DATA SOURCES: We searched for relevant articles up to December 31, 2019 in PubMed database. METHODS: This review examines the current literature on the characteristics of respiratory center regulation during wakefulness and sleep in OSA, detection method, and phenotypic treatment for respiratory center regulation. RESULTS: Mechanisms for ventilatory control system instability leading to OSA include different sleep stages in chemoresponsiveness to hypoxia and hypercapnia and different chemosensitivity at different time. One can potentially stabilize the breathing center in sleep-related breathing disorders by identifying one or more of these pathophysiological mechanisms. CONCLUSIONS: Advancing mechanism research in OSA will guide symptom research and provide alternate and novel opportunities for effective treatment for patients with OSA.

Treatment-emergent central sleep apnea: a unique sleep-disordered breathing.

Treatment-emergent central sleep apnea (TECSA) is a specific form of sleep-disordered breathing, characterized by the emergence or persistence of central apneas during treatment for obstructive sleep apnea. The purpose of this review was to summarize the definition, epidemiology, potential mechanisms, clinical characteristics, and treatment of TECSA. We searched for relevant articles up to January 31, 2020, in the PubMed database. The prevalence of TECSA varied widely in different studies. The potential mechanisms leading to TECSA included ventilatory control instability, low arousal threshold, activation of lung stretch receptors, and prolonged circulation time. TECSA may be a self-limited disorder in some patients and could be resolved spontaneously over time with ongoing treatment of continuous positive airway pressure (CPAP). However, central apneas persist even with the regular CPAP therapy in some patients, and new treatment approaches such as adaptive servo-ventilation may be necessary. We concluded that several questions regarding TECSA remain, despite the findings of many studies, and it is necessary to carry out large surveys with basic scientific design and clinical trials for TECSA to clarify these irregularities. Further, it will be vital to evaluate the baseline demographic and polysomnographic data of TECSA patients more carefully and comprehensively.

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

OBJECTIVE: Obstructive 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. METHOD: Male 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 p22(phox), c-fos, and HIF-1α messenger RNA (mRNA) expressions using real time PCR. RESULTS: A 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 p22(phox), 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. CONCLUSIONS: Lymphocytes 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.