The contribution of chronic intermittent hypoxia to OSAHS: From the perspective of serum extracellular microvesicle proteins

OBJECTIVE

Obstructive sleep apnea hypopnea syndrome (OSAHS) is an independent risk factor for many clinical complications. However, how OSAHS cause multiple organ injury and initiate inter-organ communication remains unclear. Moreover, despite it is well-recognized that chronic intermittent hypoxia (CIH) is a main feature of OSAHS, specific contribution of CIH to overall OSAHS-initiated pathological complications remains unclear. This study aimed to use an unbiased proteomic approach to determine whether OSAHS alters protein profiles of serum extracellular microvesicles (SEMVs) and how CIH contributes to such alterations.

METHODS

Tandem mass tag (TMT)-labeled quantitative proteomics assay was used to compare the differentially expressed proteins (DEPs) in SEMVs of OSAHS patients and non-OSAHS subjects. To evaluate the contribution of CIH to OSAHS, CIH rodent model was constructed and the same comparative proteomics study was performed in SEMVs from CIH and normoxia rats. The similarity and disparity of DEPs and DEPs-related functions predicted by bioinformatics tools were compared in above-mentioned two models, and several DEPs were selected and further verified by ELISA or Western blotting.

RESULTS

TMT-labeled quantitative proteomics assay unravels 32 DEPs in OSAHS patient SEMVs from a total of 560 human SEMV proteins identified. Four DEPs, namely C-reactive protein (CRP), Haptoglobin (HP),Fibronectin (FN1) and Platelet factor 4 (PF4), were further verified by ELISA and three of them (CRP, FN1 and Hp) showed significant difference in expression level between OSAHS and non-OSAHS groups. In SEMVs of rat CIH model, 121 DEPs out of 723 proteins were identified. By comparing the DEPs identified from the two models, 3 proteins (CRP and FN1 and F13a1) were found identical with the same alteration pattern (CRP was upregulated, FN1 and F13a1 were downregulated) in SEMVs from OSAHS patients and CIH rats, which were further verified by Western blotting. Computational functional analysis further revealed the common and distinct DEP-involved pathways under OSAHS or CIH status.

CONCLUSIONS

This study provides the first evidence that OSAHS causes significant alteration in SEMV protein composition, which may contribute to OSAHS-triggered multiple organ injury and organ-to-organ communication. Moreover, we have demonstrated that CIH is the primary contributor for increased inflammatory protein expression in SEMV. As CRP is being increasingly recognized not only as a marker but also a mediator of inflammatory response to tissue injury, increased SEMV CRP in CIH/OSAHS may play an important role in OSAHS-induced tissue injury, suggesting SEMV CRP might be a therapeutic target against OSAHS-related complications.

Decreased NAD Activates STAT3 and Integrin Pathways to Drive Epithelial-Mesenchymal Transition

Nicotinamide adenine dinucleotide (NAD) plays an essential role in all aspects of human life. NAD levels decrease as humans age, and supplementation with NAD precursors plays a protective role against aging and associated disease. Less is known about the effects of decreased NAD on cellular processes, which is the basis for understanding the relationship between cellular NAD levels and aging-associated disease. In the present study, cellular NAD levels were decreased by overexpression of CD38, a NAD hydrolase, or by treating cells with FK866, an inhibitor of nicotinamide phosphoribosyltransferase (NAMPT). Quantitative proteomics revealed that declining NAD levels downregulated proteins associated with primary metabolism and suppressed cell growth in culture and nude mice. Decreased glutathione synthesis caused a 4-fold increase in cellular reactive oxygen species levels, and more importantly upregulated proteins related to movement and adhesion. In turn, this significantly changed cell morphology and caused cells to undergo epithelial to mesenchymal transition (EMT). Secretomic analysis also showed that decreased NAD triggered interleukin-6 and transforming growth factor beta (TGFβ) secretion, which activated integrin-β-catenin, TGFβ-MAPK, and inflammation signaling pathways to sustain the signaling required for EMT. We further revealed that decreased NAD inactivated sirtuin 1, resulting in increased signal transducer and activator of transcription 3 (STAT3) acetylation and phosphorylation, and STAT3 activation. Repletion of nicotinamide or nicotinic acid inactivated STAT3 and reversed EMT, as did STAT3 inhibition. Taken together, these results indicate that decreased NAD activates multiple signaling pathways to promote EMT and suggests that age-dependent decreases in NAD may contribute to tumor progression. Consequently, repletion of NAD precursors has potential benefits for inhibiting cancer progression.

Circulating immune complexome analysis identified anti-tubulin-α-1c as an inflammation associated autoantibody with promising diagnostic value for Behcet's Disease

Background

Behcet’s disease (BD) is a chronic, multisystem-involved vasculitis and its pathogenesis remains elusive. No specific serological markers for BD diagnosis have been established. Identification of novel diagnostic biomarkers will be helpful in timely diagnostic and treatment for Behcet’s disease.

Objective

To screen novel autoantigens or autoantibodies with potential diagnostic value in circulating immune complexes (CICs) from BD patients.

Methods

A proteomic strategy for immune complexome analysis was developed, in which CICs were separated from serum sample of 10 BD patients and 10 healthy controls and then subjected to Orbitrap mass spectrometry for autoantigen profiling. Anti-tubulin-α-1c antibody levels were further determined by enzyme-linked immunosorbent assay (ELISA) in sera of patients with BD, systemic lupus erythematosus (SLE), recurrent aphthous ulcers (RAU), ANCA associated systemic vasculitis (AASV), Takayasu's arteritis (TA) and 59 healthy controls.

Result

A total of 17 potential antigens were identified in CICs from BD patients, but not in HC. The autoantibody to one of the identified antigens, tubulin-α-1c, was significantly increased in BD patients compared with that in healthy and disease controls. The sensitivity and specificity of tubulin-α-1c antibody in the diagnosis of BD in this study were 61.36% and 88.4%, respectively. Further analysis demonstrated that anti-tubulin-α-1c was associated with complications of deep venous thrombosis and erythema nodosum in BD. The levels of anti-tubulin-α-1c were also significantly correlated with the BD inflammation and disease activity markers ESR, CRP and BVAS.

Conclusion

Anti-tubulin-α-1c antibody is a promising biomarker in diagnosis and severity evaluation of BD and in indicating the risk of deep venous thrombosis and erythema nodosum. The immune complexome analysis by proteomic CIC autoantigen screening is a feasible way of identifying novel biomarkers in BD.

[Association between the ratio of early diastolic transmitral velocity to early diastolic mitral annular velocity and invasive measured left atrial pressure in patients with atrial fibrillation and preserved left ventricular ejection fraction]

Objective: To evaluate the association between the ratio of early diastolic transmitral velocity to early diastolic mitral annular velocity (E/E') and left atrial pressure (LAP) estimated from invasive catheter measurements in patients with atrial fibrillation (AF). Methods: A total of 46 consecutive patients with non-valvular AF and preserved left ventricular ejection fraction (LVEF) admitted in our department to receive the first radiofrequency ablation from May to July 2017 were included. All patients underwent echocardiography at 24-48 hours before radiofrequency ablation, and LAP was invasively measured during the ablation procedure. According to mean LAP, patients were divided into 2 groups of normal LAP (LAP≤12 mmHg(1 mmHg=0.133 kPa, n=31) and elevated LAP (LAP>12 mmHg, n=15). Linear correlation analysis was used to evaluate the relationship between E/E' and LAP. Results: E/E' correlated well with LAP (septal E/E' (E/E'(sep)), r= 0.397, P=0.006; lateral E/E' (E/E'(lat)), r=0.433, P=0.003; mean E/E' (E/E'(mean)), r=0.431, P=0.003). Using receiver operating characteristic analysis, the optimal cut-off for E/E'(sep) was 12.5 (sensitivity 73.3%, specificity 67.7%), E/E'(lat) was 10.8 (sensitivity 80.0%, specificity 77.4%), E/E'(mean) was 11.0 (sensitivity 86.7%, specificity 64.5%) to predict mean LAP>12 mmHg. Conclusion: E/E', especially the E/E'(lat), is positively correlated with LAP in patients with AF and preserved LVEF, and may be used to estimate the diastolic function in AF patients with preserved LVEF.

Nicotine inhibits osteogenic differentiation of human periodontal ligament cells under cyclic tensile stress through canonical Wnt pathway and α7 nicotinic acetylcholine receptor

BACKGROUND AND OBJECTIVES

Nicotine, the main psychoactive component of tobacco, affects cell metabolism, proliferation, adhesion and, importantly, the osteogenic differentiation of fibroblasts. Approximately 15% of all orthodontic patients are adults among who one-fifth are smokers. Hence, it is necessary to have insight into the effects of nicotine on the osteogenic differentiation of hPDLCs during orthodontic tooth movement. This study aimed to investigate the effects and mechanisms of nicotine on the osteogenic differentiation of human periodontal ligament cells (hPDLCs) under the application of cyclic tensile stress.

MATERIAL AND METHODS

hPDLCs were obtained from donor third molars. The hPDLCs were treated with nicotine and/or cyclic tensile stress that was applied with a cell stress plus unit. The effect of nicotine on cell viability was analyzed using the MTT assay. The osteogenic differentiation of hPDLCs was detected by alkaline phosphatase staining, Alizarin Red S staining, quantitative real-time polymerase chain reaction and western blotting.

RESULTS

In combination with cyclic tensile stress, nicotine prevented the tensile stress-induced increase in alkaline phosphatase activity, formation of mineralization nodules and the upregulation of mRNA and protein expression of Runt-related transcription factor 2, transcription factor Sp7 and collagen type I; however, canonical Wnt pathway was activated. Furthermore, the addition of Dickkopf-related protein 1 and α-bungarotoxin counteracted the negative effect of nicotine and rescued the osteogenic differentiation of hPDLCs, respectively.

CONCLUSION

These results indicate that nicotine prevents the increased osteogenic potential of hPDLCs induced by cyclic tensile stress by binding to an α7 nicotinic acetylcholine receptor and activating the canonical Wnt pathway.

Expression and prognostic value of CLIC1 in epithelial ovarian cancer

The clinical significance of the chloride intracellular channel 1 (CLIC1) protein in ovarian cancer is yet to be determined. The present study aimed to investigate the association between CLIC1 expression, and clinicopathological features and prognosis of patients with epithelial ovarian cancer. In this retrospective study, CLIC1 level was determined by reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemical staining. The association between CLIC1 expression and clinicopathological characteristics were evaluated. Progression-free survival and overall survival were assessed by univariate, and multivariate analyses. mRNA and protein levels of CLIC1 were significantly higher in cancerous tissues than in healthy ovarian tissues (P<0.001). CLIC1 signals in epithelial ovarian cancer tissues were significantly higher than that in healthy tissues (P<0.001). CLIC1 expression was significantly higher in higher-grade tumors than in low-grade tumors (P<0.001). Moreover, overexpression of CLIC1 was associated with cisplatin resistance (P<0.001). CLIC1 expression was an independent factor that predicted shorter progression-free survival (P=0.006) and overall survival (P=0.002) for patients with epithelial ovarian cancer. These findings indicate that CLIC1 is overexpressed and is associated with poor prognosis in patients with epithelial ovarian cancer.

Analysis of the correlation between non-alcoholic fatty liver disease and bone metabolism indicators in healthy middle-aged men

OBJECTIVE

To investigate the relationship between bone metabolic indicators and non-alcoholic fatty liver disease (NAFLD) in healthy middle-aged men.

PATIENTS AND METHODS

The bone metabolic indicators of 232 healthy middle-age men with NAFLD (NAFLD group) and 308 healthy controls without fatty liver (Control group) were measured, including non-collagenous osteocalcin, the procollagen type 1 N-terminal propeptide (P1NP), beta-C-terminal telopeptide of type I collagen (β-CTX). The Student's t-test was used to analyze the differences in the bone metabolic indicators, age, clinical data, biochemical indicators, and the indicators of glucose and lipid metabolism between the two groups. The correlation of fatty liver-related indicators was detected using the logistic regression analysis.

RESULTS

The body mass index (BMI), diastolic blood pressure, and heart rate in NAFLD group were significantly higher than those in Control group. Among the indicators of glucose and lipid metabolism in NAFLD group, the levels of blood glucose [fasting plasma glucose, postprandial blood glucose and hemoglobin A1c (HbA1c)] were significantly higher than those in Control group. In addition, the insulin resistance and secretion indexes were also significantly higher than those in Control group. The levels of lipid metabolic indicators such as triglyceride were higher, but high-density lipoprotein cholesterol was lower than that in Control group. From logistic regression analysis, the BMI, Homeostasis model assessment (HOMA)-β, HOMA-IR, HbA1c and P1NP were positively associated with the occurrence of NAFLD.

CONCLUSIONS

The bone metabolic indicator P1NP might be a potential predicator for the diagnosis of NAFLD in clinical application.

Identification and validation of differentially expressed proteins in epithelial ovarian cancers using quantitative proteomics

Ovarian cancer is the most lethal gynecological malignant tumor because of its high recurrence rate. In the present work, in order to find new therapeutic targets, we identified 8480 proteins in thirteen pairs of ovarian cancer tissues and normal ovary tissues through quantitative proteomics. 498 proteins were found to be differentially expressed in ovarian cancer, which involved in various cellular processes, including metabolism, response to stimulus and biosynthetic process. The expression levels of chloride intracellular channel protein 1 (CLIC1) and lectin galactoside-binding soluble 3 binding protein (LGALS3BP) in epithelial ovarian cancer tissues were significantly higher than those in normal ovary tissues as confirmed by western blotting and immunohistochemistry. The knockdown of CLIC1 in A2780 cell line downregulated expression of CTPS1, leading to the decrease of CTP and an arrest of cell cycle G1 phase, which results into a slower proliferation. CLIC1-knockdown can also slow down the tumor growth in vivo. Besides, CLIC1-knockdown cells showed an increased sensitivity to hydrogen peroxide and cisplatin, suggesting that CLIC1 was involved in regulation of redox and drug resistance in ovarian cancer cells. These results indicate CLIC1 promotes tumorgenesis, and is a potential therapeutic target in epithelial ovarian cancer treatment.

GATA3 acetylation at K119 by CBP inhibits cell migration and invasion in lung adenocarcinoma

GATA3 is a transcriptional factor involved in the development of multiple organs. Post translational modifications of GATA3 are critical to its function. Here, we report that GATA3 interacts with and is acetylated by the acetyltransferase CBP. Class I deacetylases HDAC1, HDAC2 and HDAC3 deacetylate GATA3. The major acetylated site of GATA3 in lung adenocarcinoma cells was determined at lysine 119 (AcK119). Functionally, GATA3-acetylation mimics K119Q mutant was found to inhibit lung adenocarcinoma cell migration and invasion with concomitant downregulation of EMT-controlling transcriptional factors Slug, Zeb1 and Zeb2. Taken together, we demonstrated that GATA3 acetylation at lysine 119 by CBP hinders the migration and invasion of lung adenocarcinoma cells.

PP5 (PPP5C) is a phosphatase of Dvl2

Dishevelled (Dvl) family proteins are key mediators of Wnt signalling and function in both canonical and noncanonical branches. Dvl2, the most studied Dvl protein, is extensively regulated by phosphorylation. Several kinases were found to be critical for Dvl2 localisation, stability control and functional segregation. For example, S143-phosphorylated Dvl2 was detected, together with CK1δ/ε, at the centrosome and basal body of primary cilia and plays pivotal roles during ciliogenesis. However, relatively less is known about Dvl dephosphorylation and the phosphatases involved. Here, we identified PP5 (PPP5C) as a phosphatase of Dvl2. PP5 interacts with and can directly dephosphorylate Dvl2. Knockdown of PP5 caused elevated Dvl2 phosphorylation both at the basal level and upon Wnt stimulation. In the Dvl2 protein, S143, the 10B5 cluster and other sites were dephosphorylated by PP5. Interestingly, comparison of PP5 with PP2A, another known Dvl2 phosphatase, revealed that PP5 and PP2A are not fully redundant in the regulation of Dvl2 phosphorylation status. In hTERT-RPE1 cells, PP5 was found at the basal body of cilia, where S143-phosphorylated Dvl2 also resides. Functional assays revealed modest effects on ciliogenesis after PP5 depletion or over-expression. Taken together, our results provided evidence to suggest PP5 as a new phosphatase for Dvl2.

Is the kernel-staples match a key-lock match?

Metal nanoclusters provide excellent references for understanding metal nanoparticle surfaces, which remain mysterious due to the difficulty of atomically precise characterization. Although some remarkable advances have been achieved for understanding the structure of metal nanoclusters, it is still unknown if the inner kernel-outer staples match is a key-lock match and how the surface staples influence some of the properties of metal nanoclusters. Herein, we have developed an acid-induction method for synthesizing a novel gold nanocluster whose composition is determined to be Au₄₂(TBBT)₂₆ (TBBT: 4-tert-butylbenzenelthiolate) by ESI-MS and single-crystal X-ray crystallography (SCXC). SCXC also reveals that Au₄₂(TBBT)₂₆ has an identical kernel but different staples with an existing gold nanocluster Au₄₄(TBBT)₂₈, indicating that the kernel-staples match is not a key-lock match and the existence of homo-ligand-homo-kernel-hetero-staples phenomenon in metal nanoclusters provides some reference for understanding the growth or transformation of metal nanoclusters. Further experiments reveal that the staples greatly contribute to the stability of gold nanoclusters and influence their photoluminescence intensity and that minute differences in the interfacial structure can lead to enhanced stability and photoluminescence.

Downregulation of HSP60 disrupts mitochondrial proteostasis to promote tumorigenesis and progression in clear cell renal cell carcinoma

In the present study, we demonstrate that HSP60 is unequivocally downregulated in clear cell renal cell carcinoma (ccRCC) tissues compared to pericarcinous tissues. Overexpression of HSP60 in ccRCC cancer cells suppresses cell growth. HSP60 knockdown increases cell growth and proliferation in both cell culture and nude mice xenografts, and drives cells to undergo epithelial to mesenchymal transition (EMT). Our results propose that HSP60 silencing disrupts the integrity of the respiratory complex I and triggers the excessive ROS production, which promotes tumor progression in the following aspects: (1) ROS activates the AMPK pathway that promotes acquisition of the Warburg phenotype in HSP60-KN cells; (2) ROS generated by HSP60 knockdown or by rotenone inhibition drives cells to undergo EMT; and (3) the high level of ROS may also fragment the Fe-S clusters that up regulates ADHFe1 expression and the 2-hydroxygluterate (2-HG) production leading to changes in DNA methylation. These results suggest that the high level of ROS is needed for tumorigenesis and progression in tumors with the low HSP60 expression and HSP60 is a potential diagnostic biomarker as well as a therapeutic target in ccRCC.

ROS-Mediated 15-Hydroxyprostaglandin Dehydrogenase Degradation via Cysteine Oxidation Promotes NAD+-Mediated Epithelial-Mesenchymal Transition

Nicotinamide adenine dinucleotide (NAD) levels decrease with aging as a result of aging-associated CD38 upregulation. Here, we established a cell model with decreased cellular NAD levels by overexpressing CD38 or treating cells with FK866, an inhibitor of nicotinamide phosphoribosyltransferase. We revealed that decreased NAD triggered reactive oxygen species (ROS)-mediated degradation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), which drove cells to undergo epithelial-mesenchymal transition (EMT). Moreover, we showed that oxidation of the Cys44 residue to sulfonic acid in 15-PGDH led to its degradation via non-canonical ubiquitination-proteasome and autophagy pathways. Mutation of Cys44 to alanine abolished ROS-induced 15-PGDH degradation. We demonstrated that 15-PGDH silencing promoted EMT, whereas supplementation with NAD precursors increased NAD and 15-PGDH stability, and reversed the EMT process. Taken together, these results suggest that declining NAD levels contribute to age-dependent increases in cancer incidence, and repletion of NAD precursors is beneficial for increasing 15-PGDH expression.