Premature senescence of highly proliferative endothelial progenitor cells is induced by tumor necrosis factor-alpha via the p38 mitogen-activated protein kinase pathway

Kongensin A targeting PI3K attenuates inflammation-induced osteoarthritis by modulating macrophage polarization and alleviating inflammatory signaling

The inflammatory microenvironment, polarization of macrophages towards the M1 phenotype, and consequent matrix degradation and senescence of chondrocytes are primary contributors to the degeneration of knee joint cartilage, further exacerbating the progression of osteoarthritis (OA). Kongensin A (KA) is a recently identified natural plant extract exhibiting anti-necrotic apoptosis and anti-inflammatory properties, but the potential efficacy in alleviating OA remains uncertain. The current research lucubrated the effect of KA on the inflammatory microenvironment and macrophage polarization, as well as its regulatory function in extracellular matrix (ECM) metabolism and chondrocyte senescence. Our findings demonstrated that KA can suppress inflammatory signaling, maintain homeostasis between ECM anabolism and catabolism, and suppress chondrocytes senescence. Further investigation elucidated that the mechanism involves the suppression of the PI3K/AKT/NF-κB axis in chondrocytes under inflammatory conditions. Moreover, KA impeded M1 polarization of macrophages via inhibiting PI3K/AKT/NF-κB axis. Subsequently, we treated chondrocytes with macrophages-derived conditioned medium (CM) and revealed that KA can promote ECM anabolism and alleviate chondrocytes senescence by reprogramming macrophage polarization. Consistent with in vitro experiments, in vivo administration of KA demonstrated alleviated cartilage degeneration and delayed progression of OA. Collectively, through obstructing the PI3K/AKT/NF-κB axis, KA can reprogram macrophage polarization, promote matrix metabolism equilibrium, and alleviate chondrocytes senescence, thereby attenuating the pathology of OA. In conclusion, KA may emerge as a promising therapy for OA.

LIMD2 is the Signature of Cell Aging-immune/Inflammation in Acute Myocardial Infarction

BACKGROUND

Acute myocardial infarction (AMI) is an age-dependent cardiovascular disease in which cell aging, immunity, and inflammatory factors alter the course; however, cell aging-immune/inflammation signatures in AMI have not been investigated.

METHODS

Based on the GEO database to obtain microRNA (miRNA) sequencing, mRNA sequencing and single-cell sequencing data, and utilizing the Seurat package to identify AMI-associated cellular subpopulations. Subsequently, differentially expressed miRNAs and mRNAs were screened to establish a network of competing endogenous RNAs (ceRNAs). Senescence and immunity scores were calculated by single sample gene set enrichment analysis (ssGSEA), ESTIMATE and CIBERSORT algorithms, and the Hmisc package was used to screen for genes with the highest correlation with senescence and immunity scores. Finally, protein-protein interaction (PPI) and molecular docking analyses were performed to predict potential therapeutic agents for the treatment of AMI.

RESULTS

Four cell types (Macrophage, Fibroblast, Endothelial cells, CD8 T cells) were identified in AMI, and CD8 T cells exhibited the lowest cell aging activity. A ceRNA network of miRNAs- mNRA interactions was established based on the overlapping genes in differentially expressed miRNAs (DEmiRNAs) target genes and differentially expressed mRNAs (DEmRNAs). Twenty-four marker genes of CD8 T cells were observed. LIMD2 was identified as cell aging- immune/inflammation-related hub gene in AMI. This study also identified a potential therapeutic network of DB03276-LIMD2-AMI, which showed excellent and stable binding status between DB03276-LIMD2.

CONCLUSION

This study identified LIMD2 as a cell aging-immune/inflammation-related hub gene. The understanding of the pathogenesis and therapeutic mechanisms of AMI was enriched by the ceRNA network and DB03276-LIMD2-LAMI therapeutic network.

Fetal endothelial colony-forming cells: Possible targets for prevention of the fetal origins of adult diseases

Endothelial colony-forming cells (ECFCs), a subset of circulating and resident endothelial progenitor cells, are capable of self-renewal and de novo vessel formation, and are known key regulators of vascular integrity and homeostasis. Numerous studies have found that exposure to hostile environment during the fetal development exerts a profound influence on the level and function of ECFCs, which may be the underlying factor linking endothelial dysfunction to cardiovascular disease of the offspring in later life. Herein, we focus on the latest findings regarding the effects of pregnancy-related disorders on the frequency and function of fetal ECFCs. Subsequently, we discuss about placental ECFCs and put forward some details that should be paid attention to in the process of ECFC isolation and culture. Overall, the information presented in this review highlight the potential of ECFCs as a future biomarker or even therapeutic targets for the pregnancy-related adverse maternal and fetal outcomes.

Sleeping Beauty transposon mutagenesis identified genes and pathways involved in inflammation-associated colon tumor development

Chronic inflammation promotes development and progression of colorectal cancer (CRC). To comprehensively understand the molecular mechanisms underlying the development and progression of inflamed CRC, we perform in vivo screening and identify 142 genes that are frequently mutated in inflammation-associated colon tumors. These genes include senescence and TGFβ-activin signaling genes. We find that TNFα can induce stemness and activate senescence signaling by enhancing cell plasticity in colonic epithelial cells, which could act as a selective pressure to mutate senescence-related genes in inflammation-associated colonic tumors. Furthermore, we show the efficacy of the Cdk4/6 inhibitor in vivo for inflammation-associated colonic tumors. Finally, we functionally validate that Arhgap5 and Mecom are tumor suppressor genes, providing possible therapeutic targets for CRC. Thus, we demonstrate the importance of the inactivation of senescence pathways in CRC development and progression in an inflammatory microenvironment, which can help progress toward precision medicine.

Identification and validation of senescence-related genes in circulating endothelial cells of patients with acute myocardial infarction

Background

Acute myocardial infarction (AMI) is the main clinical cause of death and cardiovascular disease and thus has high rates of morbidity and mortality. The increase in cardiovascular disease with aging is partly the result of vascular endothelial cell senescence and associated vascular dysfunction. This study was performed to identify potential key cellular senescence-related genes (SRGs) as biomarkers for the diagnosis of AMI using bioinformatics.

Methods

Using the CellAge database, we identified cellular SRGs. GSE66360 and GSE48060 for AMI patients and healthy controls and GSE19322 for mice were downloaded from the Gene Expression Omnibus (GEO) database. The GSE66360 dataset was divided into a training set and a validation set. The GSE48060 dataset was used as another validation set. The GSE19322 dataset was used to explore the evolution of the screened diagnostic markers in the dynamic process of AMI. Differentially expressed genes (DEGs) of AMI were identified from the GSE66360 training set. Differentially expressed senescence-related genes (DESRGs) selected from SRGs and DEGs were analyzed using Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and protein-protein interaction (PPI) networks. Hub genes in DESRGs were selected based on degree, and diagnostic genes were further screened by gene expression and receiver operating characteristic (ROC) curve. Finally, a miRNA-gene network of diagnostic genes was constructed and targeted drug prediction was performed.

Results

A total of 520 DEGs were screened from the GSE66360 training set, and 279 SRGs were identified from the CellAge database. The overlapping DEGs and SRGs constituted 14 DESRGs, including 4 senescence suppressor genes and 10 senescence inducible genes. The top 10 hub genes, including FOS, MMP9, CEBPB, CDKN1A, CXCL1, ETS2, BCL6, SGK1, ZFP36, and IGFBP3, were screened. Furthermore, three diagnostic genes were identified: MMP9, ETS2, and BCL6. The ROC analysis showed that the respective area under the curves (AUCs) of MMP9, ETS2, and BCL6 were 0.786, 0.848, and 0.852 in the GSE66360 validation set and 0.708, 0.791, and 0.727 in the GSE48060 dataset. In the GSE19322 dataset, MMP9 (AUC, 0.888) and ETS2 (AUC, 0.929) had very high diagnostic values in the early stage of AMI. Finally, based on these three diagnostic genes, we found that drugs such as acetylcysteine and genistein may be targeted for the treatment of age-related AMI.

Conclusion

The results of this study suggest that cellular SRGs might play an important role in AMI. MMP9, ETS2, and BCL6 have potential as specific biomarkers for the early diagnosis of AMI.

Coronary Heart Disease in Type 2 Diabetes Mellitus: Genetic Factors and Their Mechanisms, Gene-Gene, and Gene-Environment Interactions in the Asian Populations

Asians are more susceptible to type 2 diabetes mellitus (T2D) and its coronary heart disease (CHD) complications than the Western populations, possibly due to genetic factors, higher degrees of obesity, insulin resistance, and endothelial dysfunction that could occur even in healthy individuals. The genetic factors and their mechanisms, along with gene-gene and gene-environment interactions associated with CHD in T2D Asians, are yet to be explored. Therefore, the objectives of this paper were to review the current evidence of genetic factors for CHD, summarize the proposed mechanisms of these genes and how they may associate with CHD risk, and review the gene-gene and gene-environment interactions in T2D Asians with CHD. The genetic factors can be grouped according to their involvement in the energy and lipoprotein metabolism, vascular and endothelial pathology, antioxidation, cell cycle regulation, DNA damage repair, hormonal regulation of glucose metabolism, as well as cytoskeletal function and intracellular transport. Meanwhile, interactions between single nucleotide polymorphisms (SNPs) from different genes, SNPs within a single gene, and genetic interaction with environmental factors including obesity, smoking habit, and hyperlipidemia could modify the gene's effect on the disease risk. Collectively, these factors illustrate the complexities of CHD in T2D, specifically among Asians.

Mechanisms of Endothelial Regeneration and Vascular Repair and Their Application to Regenerative Medicine

Endothelial barrier integrity is required for maintaining vascular homeostasis and fluid balance between the circulation and surrounding tissues and for preventing the development of vascular disease. Despite comprehensive understanding of the molecular mechanisms and signaling pathways that mediate endothelial injury, the regulatory mechanisms responsible for endothelial regeneration and vascular repair are incompletely understood and constitute an emerging area of research. Endogenous and exogenous reparative mechanisms serve to reverse vascular damage and restore endothelial barrier function through regeneration of a functional endothelium and re-engagement of endothelial junctions. In this review, mechanisms that contribute to endothelial regeneration and vascular repair are described. Targeting these mechanisms has the potential to improve outcome in diseases that are characterized by vascular injury, such as atherosclerosis, restenosis, peripheral vascular disease, sepsis, and acute respiratory distress syndrome. Future studies to further improve current understanding of the mechanisms that control endothelial regeneration and vascular repair are also highlighted.

CD24 expression indicates healthier phenotype and less tendency of cellular senescence in human nucleus pulposus cells

Identification of specific cell markers is crucial for recognizing functionally healthy nucleus pulposus (NP) cells. The objective of this study was to investigate the role of CD24 expression in adult human NP cells. Cells were retrieved from NP tissues of 20 patients (aged 17-44) operated on for lumbar disc herniation. Based on CD24 expression, NP cells were separated by sorting and then used to examine phenotypic behavior, the effects of culture conditions and cellular senescence pathway related proteins. CD24 expression was positive in 35.5 ± 3.7% (range 9.1-65.2%) of NP cells. Consistently, normoxic expansion and serial passages in monolayers decreased percentage positivity for CD24 in NP cells. CD24^- NP cells showed a markedly decreased GSK-3β activity and increased mitogen-activated protein kinase phosphorylation accompanying by an increased β-catenin expression. Higher levels of matrix metalloproteinases, as well as lower levels of ACAN and COL2 in CD24^- cells, indicated the breakdown and reduced the formation of key extracellular matrix components. CD24⁺ NP cells presented a more favorable phenotype while CD24^- cells showed a more prominent cellular senescence fate. CD24 in NP cells may be a surrogate marker of healthy cells, in the cell-based therapeutic treatment of degenerative disc disorders.

Hyperinsulinemia impairs functions of circulating endothelial progenitor cells

AIMS

Circulating endothelial progenitor cells (EPCs) play a key role in maintaining endothelial function. Dysfunction of EPCs is associated with the cardiovascular complication of diabetes. The purpose of this study is to investigate the direct effects of hyperinsulinemia on EPCs and the underlying mechanisms.

METHODS

EPCs isolated from healthy adults were cultured with various concentrations of insulin (control group, without insulin; physiological insulin group, 10 nM insulin and hyperinsulinemia group, 100 nM insulin) with or without phosphatidylinositol-3-kinase (PI3-K) inhibitor (LY294002, 5 µM), endothelial nitric oxide synthase (eNOS) inhibitor (L-NG-nitro-arginine methyl ester (L-NAME), 100 µM), sodium nitroprusside (SNP, 25 µM), p38 mitogen-activated protein kinase(MAPK) inhibitor (SB203580, 5 µM) or extracellular signal-regulated kinases (ERK) 1/2 inhibitor (PD98059, 10 µM). Proliferation, tube formation, and apoptosis of EPCs were determined. Expressions of eNOS, PI3-K, protein kinase B (Akt), p38 MAPK, and ERK 1/2 were assessed.

RESULTS

Hyperinsulinemia caused a significant decrease in proliferation and tube formation abilities than control group. Hyperinsulinemia increased apoptosis rate of EPCs than control group. Furthermore, hyperinsulinemia downregulated phosphorylation of eNOS, PI3-K and Akt, and upregulated phosphorylation of p38 MAPK and ERK. SNP could restore impaired tube formation induced by hyperinsulinemia. P38 MAPK inhibitor but not ERK inhibitor could decrease apoptosis induced by hyperinsulinemia.

CONCLUSION

Hyperinsulinemia impaired EPCs' tube formation ability by downregulation of PI-3K/Akt/eNOS pathway. Hyperinsulinemia induced apoptosis of EPCs via upregulation of p38 MAPK.

Dysfunctional stem and progenitor cells impair fracture healing with age

Successful fracture healing requires the simultaneous regeneration of both the bone and vasculature; mesenchymal stem cells (MSCs) are directed to replace the bone tissue, while endothelial progenitor cells (EPCs) form the new vasculature that supplies blood to the fracture site. In the elderly, the healing process is slowed, partly due to decreased regenerative function of these stem and progenitor cells. MSCs from older individuals are impaired with regard to cell number, proliferative capacity, ability to migrate, and osteochondrogenic differentiation potential. The proliferation, migration and function of EPCs are also compromised with advanced age. Although the reasons for cellular dysfunction with age are complex and multidimensional, reduced expression of growth factors, accumulation of oxidative damage from reactive oxygen species, and altered signaling of the Sirtuin-1 pathway are contributing factors to aging at the cellular level of both MSCs and EPCs. Because of these geriatric-specific issues, effective treatment for fracture repair may require new therapeutic techniques to restore cellular function. Some suggested directions for potential treatments include cellular therapies, pharmacological agents, treatments targeting age-related molecular mechanisms, and physical therapeutics. Advanced age is the primary risk factor for a fracture, due to the low bone mass and inferior bone quality associated with aging; a better understanding of the dysfunctional behavior of the aging cell will provide a foundation for new treatments to decrease healing time and reduce the development of complications during the extended recovery from fracture healing in the elderly.

Resveratrol attenuates inflammation environment-induced nucleus pulposus cell senescence in vitro

Intervertebral disc degeneration is a disease identified as an inflammation response-participated pathological process. As a classical cellular feature, disc cell senescence is reported to be closely related with disc cell senescence. Resveratrol has a protective role against inflammation in some cells. However, its biological effects on disc cells remain largely unclear. The present study was aimed to study the effects of resveratrol on disc nucleus pulposus (NP) cell senescence in an inflammation environment. Isolated NP cells were cultured in cultured medium with (control group) or without (inflammation group) inflammatory cytokine TNF-α and IL-1β for 14 days. Resveratrol was added along with the NP cells treated with inflammatory cytokines to investigate its effects. NP cell senescence was analyzed by senescence-associated β-Galactosidase (SA-β-Gal) staining, cell proliferation, G0/1 cell cycle arrest, telomerase activity, gene/protein expression of senescence markers (p16 and p53) and NP matrix biosynthesis. In addition, the intracellular reactive oxygen species (ROS) was also analyzed. Compared with the control group, inflammation group significantly increased SA-β-Gal activity and ROS content, decreased cell proliferation and telomerase activity, promoted G0/1 cell cycle arrest, up-regulated gene/protein expression of senescence markers (p16 and p53) and matrix catabolism enzymes (MMP-3, MMP-13 and ADAMTS-4), and down-regulated gene/protein expression of NP matrix macromolecules (aggrecan and collagen II). However, resveratrol partly reversed the effects of inflammatory cytokine on these cell senescence-associated parameters. Together, resveratrol was effective to suppress cell senescence in an inflammatory environment. The present study shows new knowledge on how to retard inflammation response-initiated disc degeneration.

Methylome of human senescent hematopoietic progenitors

Senescence, a state of permanent cell cycle arrest, can be induced by DNA damage. This process, which was initially described in fibroblasts, is now recognized to occur in stem cells. It has been well characterized in cell lines, but there is currently very limited data available on human senescence in vivo. We recently reported that the expression of transposable elements (TE), including endogenous retroviruses, was up-regulated along with inflammatory genes in human senescent hematopoietic stem and progenitor cells (HSPCs) in vivo. The mechanism of regulation of TE expression is not completely understood, but changes in DNA methylation and chromatin modifications are known to alter their expression. In order to elucidate the molecular mechanisms for TE up-regulation after senescence of HSPCs, we employed whole-genome bisulfite sequencing in paired senescent and active human HSPCs in vivo from healthy subjects. We found that the senescent HSPCs exhibited hypomethylated regions in the genome, which were enriched for TEs. This is the first report characterizing the methylome of senescent human HSPCs.

Administration of hydrogen-rich water prevents vascular aging of the aorta in LDL receptor-deficient mice

The main cause of arteriosclerosis is atherosclerosis in the aorta. Atherosclerosis is recognized as a chronic inflammatory condition that begins with the dysfunction or activation of arterial endothelium. Low-density lipoprotein (LDL) and especially its oxidized form play a key role in endothelial dysfunction and atherogenesis. Recent studies showed that senescent cells are involved in the development and progression of atherosclerosis, and eliminating senescent cells suppresses the senescence-associated secretory phenotype. We previously reported that molecular hydrogen-rich water (HW) has antioxidant and anti-inflammatory effects in numerous diseases. Here, we used LDL receptor-deficient mice fed a high-fat diet (HFD) for 13 weeks as a model for atherosclerosis and evaluated the effects of continuous administration of HW. The numbers of endothelial cells in the atheroma expressing the senescence factors p16^INK4a and p21 decreased in HFD-fed mice given HW compared with HFD-fed mice given control water. Furthermore, macrophage infiltration and Tnfα expression in the atheroma were also suppressed. These results suggest that vascular aging can be suppressed by HW.

Featured Article: Deterioration of visual function mediated by senescence-associated endoplasmic reticulum stress in inflammatory tie2-TNF mice

Stress-associated premature senescence plays a major role in retinal diseases. In this study, we investigated the relationship between endothelial dysfunction, endoplasmic reticulum (ER) stress, and cellular senescence in the development of retinal dysfunction. We tested the hypothesis that constant endothelial activation by transmembrane tumor necrosis factor-α (tmTNF-α) exacerbates age-induced visual deficits via senescence-mediated ER stress in this model. To address this, we employed a mouse model of chronic vascular activation using endothelial-specific TNF-α-expressing (tie2-TNF) mice at 5 and 10 months of age. Visual deficits were exhibited by tie2-TNF mice at both 5 months and 10 months of age, with the older mice showing statistically significant loss of visual acuity compared with tie2-TNF mice at age 5 months. The neural defects, as measured by electroretinogram (ERG), also followed a similar trend in an age-dependent fashion, with 10-month-old tie2-TNF mice showing the greatest decrease in "b" wave amplitude at 25 cd.s.m² compared with age-matched wildtype (WT) mice and five-month-old tie2-TNF mice. While gene and protein expression from the whole retinal extracts demonstrated increased inflammatory (Icam1, Ccl2), stress-associated premature senescence (p16, p21, p53), and ER stress (Grp78, p-Ire1α, Chop) markers in five-month-old tie2-TNF mice compared with five-month-old WT mice, a further increase was seen in 10-month-old tie2-TNF mice. Our data demonstrate that tie2-TNF mice exhibit age-associated increases in visual deficits, and these data suggest that inflammatory endothelial activation is at least partly at play. Given the correlation of increased premature senescence and ER stress in an age-dependent fashion, with the loss of visual functions and increased endothelial activation, our data suggest a possible self-enhanced loop of unfolded protein response pathways and senescence in propagating neurovascular defects in this model. Impact statement Vision loss in most retinal diseases affects the quality of life of working age adults. Using a novel animal model that displays constant endothelial activation by tmTNF-α, our results demonstrate exacerbated age-induced visual deficits via premature senescence-mediated ER stress. We have compared mice of 5 and 10 months of age, with highly relevant human equivalencies of approximately 35- and 50-year-old patients, representing mature adult and middle-aged subjects, respectively. Our studies suggest a possible role for a self-enhanced loop of ER stress pathways and senescence in the propagation of retinal neurovascular defects, under conditions of constant endothelial activation induced by tmTNF-α signaling.

Endothelial Cell Aging: How miRNAs Contribute?

Endothelial cells (ECs) form monolayers and line the interior surfaces of blood vessels in the entire body. In most mammalian systems, the capacity of endothelial cells to divide is limited and endothelial cells are prone to be senescent. Aging of ECs and resultant endothelial dysfunction lead to a variety of vascular diseases such as atherosclerosis, diabetes mellites, hypertension, and ischemic injury. However, the mechanism by which ECs get old and become senescent and the impact of endothelial senescence on the vascular function are not fully understood. Recent research has unveiled the crucial roles of miRNAs, which are small non-coding RNAs, in regulating endothelial cellular functions, including nitric oxide production, vascular inflammation, and anti-thromboformation. In this review, how senescent-related miRNAs are involved in controlling the functions of ECs will be discussed.

Senescent human hematopoietic progenitors show elevated expression of transposable elements and inflammatory genes

Genomic transposable elements (TEs) constitute the majority of the genome. Expression of TEs is known to activate the double-stranded RNA recognition pathway ("viral mimicry"), leading to the activation of interferon-stimulated genes, inflammation, and immune-mediated cell death. Recently, we showed that the expression of TEs is suppressed along with immune pathways in leukemic stem cells (LSCs) in acute myeloid leukemia, suggesting a potential mechanism for immune escape of LSCs. This indicated that, during oncogenesis, where there is escape from senescence, expression of TEs is suppressed. Senescence is known to activate the interferon response and inflammatory cytokines, known as the senescence-associated secretory phenotype (SASP). We characterized the transcriptome of senescent and active human hematopoietic stem and progenitor cells (HSPCs) in vivo and showed co-occurrence of overexpression of TEs, SASP genes, and gene pathways of inflammation in senescence. The percentage of circulating senescent HSPCs (s-HSPCs) did not increase with age, indicating active clearance. Induction of senescence in human HSPCs in vitro showed increased expression of TE and SASP genes. SASP is known to mediate clearance of senescent cells and active clearance of senescent cells has been shown to increase organismal fitness. We speculate that the expression of TEs in s-HSPCs could contribute to orderly clearance of the cells via activation of immune pathways, warranting further mechanistic studies. This is the first study to characterize the transcriptome of human s-HSPCs in vivo, revealing activated expression of TEs and inflammatory genes.

TNFα-senescence initiates a STAT-dependent positive feedback loop, leading to a sustained interferon signature, DNA damage, and cytokine secretion

Cellular senescence is a cell fate program that entails essentially irreversible proliferative arrest in response to damage signals. Tumor necrosis factor-alpha (TNFα), an important pro-inflammatory cytokine secreted by some types of senescent cells, can induce senescence in mouse and human cells. However, downstream signaling pathways linking TNFα-related inflammation to senescence are not fully characterized. Using human umbilical vein endothelial cells (HUVECs) as a model, we show that TNFα induces permanent growth arrest and increases p21^CIP1, p16^INK4A, and SA-β-gal, accompanied by persistent DNA damage and ROS production. By gene expression profiling, we identified the crucial involvement of inflammatory and JAK/STAT pathways in TNFα-mediated senescence. We found that TNFα activates a STAT-dependent autocrine loop that sustains cytokine secretion and an interferon signature to lock cells into senescence. Furthermore, we show STAT1/3 activation is necessary for cytokine and ROS production during TNFα-induced senescence. However, inhibition of STAT1/3 did not rescue cells from proliferative arrest, but rather suppressed cell cycle regulatory genes and altered TNFα-induced senescence. Our findings suggest a positive feedback mechanism via the STAT pathway that sustains cytokine production and reveal a reciprocal regulatory role of JAK/STAT in TNFα-mediated senescence.

Anti-TNF-α treatment modulates SASP and SASP-related microRNAs in endothelial cells and in circulating angiogenic cells

Endothelial cell senescence is characterized by acquisition of senescence-associated secretory phenotype (SASP), able to promote inflammaging and cancer progression. Emerging evidence suggest that preventing SASP development could help to slow the rate of aging and the progression of age-related diseases, including cancer. Aim of this study was to evaluate whether and how adalimumab, a monoclonal antibody directed against tumor necrosis factor-α (TNF-α), a major SASP component, can prevent the SASP. A three-pronged approach has been adopted to assess the if adalimumab is able to: i) modulate a panel of classic and novel senescence- and SASP-associated markers (interleukin [IL]-6, senescence associated-β-galactosidase, p16/Ink4a, plasminogen activator inhibitor 1, endothelial nitric oxide synthase, miR-146a-5p/Irak1 and miR-126-3p/Spred1) in human umbilical vein endothelial cells (HUVECs); ii) reduce the paracrine effects of senescent HUVECs' secretome on MCF-7 breast cancer cells, through wound healing and mammosphere assay; and iii) exert significant decrease of miR-146a-5p and increase of miR-126-3p in circulating angiogenic cells (CACs) from psoriasis patients receiving adalimumab in monotherapy.TNF-α blockade associated with adalimumab induced significant reduction in released IL-6 and significant increase in eNOS and miR-126-3p expression levels in long-term HUVEC cultures.A significant reduction in miR-146a-5p expression levels both in long-term HUVEC cultures and in CACs isolated from psoriasis patients was also evident. Interestingly, conditioned medium from senescent HUVECs treated with adalimumab was less consistent than medium from untreated cells in inducing migration- and mammosphere- promoting effects on MCF-7 cells.Our findings suggest that adalimumab can induce epigenetic modifications in cells undergoing senescence, thus contributing to the attenuation of SASP tumor-promoting effects.

Yoder M, Majluf-Cruz A, Alvarado-Moreno JA. Reduced proliferation of endothelial colony-forming cells in unprovoked venous thromboembolic disease as a consequence of endothelial dysfunction

BACKGROUND

Venous thromboembolic disease (VTD) is a public health problem. We recently reported that endothelial colony-forming cells (ECFCs) derived from endothelial cells (EC) (ECFC-ECs) from patients with VTD have a dysfunctional state. For this study, we proposed that a dysfunctional status of these cells generates a reduction of its proliferative ability, which is also associated with senescence and reactive oxygen species (ROS).

METHODS AND RESULTS

Human mononuclear cells (MNCs) were obtained from peripheral blood from 40 healthy human volunteers (controls) and 50 patients with VTD matched by age (20-50 years) and sex to obtain ECFCs. We assayed their proliferative ability with plasma of patients and controls and supernatants of cultures from ECFC-ECs, senescence-associated β-galactosidase (SA-β-gal), ROS, and expression of ephrin-B2/Eph-B4 receptor. Compared with cells from controls, cells from VTD patients showed an 8-fold increase of ECFCs that emerged 1 week earlier, reduced proliferation at long term (39%) and, in passages 4 and 10, a highly senescent rate (30±1.05% vs. 91.3±15.07%, respectively) with an increase of ROS and impaired expression of ephrin-B2/Eph-4 genes. Proliferation potential of cells from VTD patients was reduced in endothelial medium [1.4±0.22 doubling population (DP)], control plasma (1.18±0.31 DP), or plasma from VTD patients (1.65±0.27 DP).

CONCLUSIONS

As compared with controls, ECFC-ECs from individuals with VTD have higher oxidative stress, proliferation stress, cellular senescence, and low proliferative potential. These findings suggest that patients with a history of VTD are ECFC-ECs dysfunctional that could be associated to permanent risk for new thrombotic events.

Pericardial interstitial cell senescence responsible for pericardial structural remodeling in idiopathic and postsurgical constrictive pericarditis

OBJECTIVE

Idiopathic and postsurgical constrictive pericarditis is characterized by pericardial structural remodeling that involves fibrosis, calcification, and inflammation. This study aimed to determine whether cell senescence was responsible for pericardial structural remodeling.

METHODS

Pericardial interstitial cells derived from patients with idiopathic or postsurgical pericarditis (pericarditis cells) were harvested. Timing of senescence and differences in telomere length were compared between age- and sex-matched controls (nonpericarditis cells). Pericardial interstitial cells derived from normal pericardia were serially passaged until senescence (senescent cells). Apoptosis, collagen matrix, calcium deposition, chemoattractant properties, gene expression profiles, and paracrine effects of senescent cells were compared with nonsenescent cells of passage 2 (nonsenescent cells).

RESULTS

Pericarditis cells displayed senescent changes, including short telomere length, large flattened cell sizes, positive staining for senescence-associated β-galactosidase, and limited growth capacity. These senescent cells were resistant to apoptosis, produced more collagen matrix, deposited more calcium, and attracted more monocytes/lymphocytes than the nonsenescent cells. A cluster of genes involved in extracellular matrix deposition (connective tissue growth factor, fibronectin, collagen type I, collagen type III, and tissue inhibitors of metalloproteinase-1), calcium deposition (osteopontin, bone sialoprotein, osteonectin, and matrix Gla protein), and inflammatory cell recruitment (interleukin-6, chemoattractant protein-1, and tumor necrosis factor-α) were upregulated in senescent cells, whereas extracellular matrix-degrading enzyme (metalloproteinase-1 and metalloproteinase-3) was downregulated. Furthermore, senescent cells had the ability to promote the proliferation, differentiation, and senescence of neighboring cells.

CONCLUSIONS

These findings suggest that senescent cells have characteristics promoting pericardial structural remodeling, but further work is needed to establish causation.

Vascular aging: Molecular mechanisms and potential treatments for vascular rejuvenation

Aging is the main risk factor contributing to vascular dysfunction and the progression of vascular diseases. In this review, we discuss the causes and mechanisms of vascular aging at the tissue and cellular level. We focus on Endothelial Cell (EC) and Smooth Muscle Cell (SMC) aging due to their critical role in mediating the defective vascular phenotype. We elaborate on two categories that contribute to cellular dysfunction: cell extrinsic and intrinsic factors. Extrinsic factors reflect systemic or environmental changes which alter EC and SMC homeostasis compromising vascular function. Intrinsic factors induce EC and SMC transformation resulting in cellular senescence. Replenishing or rejuvenating the aged/dysfunctional vascular cells is critical to the effective repair of the vasculature. As such, this review also elaborates on recent findings which indicate that stem cell and gene therapies may restore the impaired vascular cell function, reverse vascular aging, and prolong lifespan.

The p38 pathway, a major pleiotropic cascade that transduces stress and metastatic signals in endothelial cells

By gating the traffic of molecules and cells across the vessel wall, endothelial cells play a central role in regulating cardiovascular functions and systemic homeostasis and in modulating pathophysiological processes such as inflammation and immunity. Accordingly, the loss of endothelial cell integrity is associated with pathological disorders that include atherosclerosis and cancer. The p38 mitogen-activated protein kinase (MAPK) cascades are major signaling pathways that regulate several functions of endothelial cells in response to exogenous and endogenous stimuli including growth factors, stress and cytokines. The p38 MAPK family contains four isoforms p38α, p38β, p38γ and p38δ that are encoded by four different genes. They are all widely expressed although to different levels in almost all human tissues. p38α/MAPK14, that is ubiquitously expressed is the prototype member of the family and is referred here as p38. It regulates the production of inflammatory mediators, and controls cell proliferation, differentiation, migration and survival. Its activation in endothelial cells leads to actin remodeling, angiogenesis, DNA damage response and thereby has major impact on cardiovascular homeostasis, and on cancer progression. In this manuscript, we review the biology of p38 in regulating endothelial functions especially in response to oxidative stress and during the metastatic process.

Endothelial progenitor cells in peripheral blood may serve as a biological marker to predict severe acute pancreatitis

AIM

To investigate the significance of endothelial progenitor cells (EPCs) in predicting severe acute pancreatitis (SAP).

METHODS

We recruited 71 patients with acute pancreatitis (AP) and excluded 11 of them; finally, cases of mild acute pancreatitis (MAP) (n = 30) and SAP (n = 30), and healthy volunteers (n = 20) were internalized to investigate levels of EPCs, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), fibrinogen (FIB) and white blood cells (WBC) in peripheral blood.

RESULTS

The levels of TNF-α, WBC, FIB and CRP were higher both in SAP and MAP cases than in healthy volunteers (P < 0.05, all). Interestingly, the level of EPCs was higher in SAP than MAP (1.63% ± 1.47% vs 6.61% ± 4.28%, P < 0.01), but there was no significant difference between the MAP cases and healthy volunteers (1.63% ± 1.47% vs 0.55% ± 0.54%, P > 0.05). Receiver operating characteristics curve (ROC) showed that EPCs, TNF-α, CRP and FIB were significantly associated with SAP, especially EPCs and CRP were optimal predictive markers of SAP. When the cut-off point for EPCs and CRP were 2.26% and 5.94 mg/dL, the sensitivities were 90.0% and 73.3%, and the specificities were 83.3% and 96.7%. Although, CRP had the highest specificity, and EPCs had the highest sensitivity and highest area under the curve value (0.93).

CONCLUSION

Data suggest that EPCs may be a new biological marker in predicting SAP.

Tumor necrosis factor alpha derived from classically activated "M1" macrophages reduces interstitial cell of Cajal numbers

BACKGROUND

Delayed gastric emptying in diabetic mice and humans is associated with changes in macrophage phenotype and loss of interstitial cells of Cajal (ICC) in the gastric muscle layers. In diabetic mice, classically activated M1 macrophages are associated with delayed gastric emptying, whereas alternatively activated M2 macrophages are associated with normal gastric emptying. This study aimed to determine if secreted factors from M1 macrophages could injure mouse ICC in primary culture.

METHODS

Cultures of gastric ICC were treated with conditioned medium (CM) from activated bone marrow-derived macrophages (BMDMs) and the effect of CM was quantified by counting ICC per high-powered field.

KEY RESULTS

Bone marrow-derived macrophages were activated to a M1 or M2 phenotype confirmed by qRT-PCR. Conditioned medium from M1 macrophages reduced ICC numbers by 41.1%, whereas M2-CM had no effect as compared to unconditioned, control media. Immunoblot analysis of 40 chemokines/cytokines found 12 that were significantly increased in M1-CM, including tumor necrosis factor alpha (TNF-α). ELISA detected 0.697±0.03 ng mL^-1 TNF-α in M1-CM. Recombinant mouse TNF-α reduced Kit expression and ICC numbers in a concentration-dependent manner (EC50 = 0.817 ng mL^-1 ). Blocking M1-CM TNF-α with a neutralizing antibody preserved ICC numbers. The caspase inhibitor Z-VAD.fmk partly preserved ICC numbers (cells/field; 6.63±1.04, 9.82±1.80 w/Z-VAD.fmk, n=6, P<.05).

CONCLUSIONS & INFERENCES

This work demonstrates that TNF-α secreted from M1 macrophages can result in Kit loss and directly injure ICC in vitro partly through caspase-dependent apoptosis and may play an important role in ICC depletion in diabetic gastroparesis.

The impact of cerebrovascular aging on vascular cognitive impairment and dementia

As human life expectancy rises, the aged population will increase. Aging is accompanied by changes in tissue structure, often resulting in functional decline. For example, aging within blood vessels contributes to a decrease in blood flow to important organs, potentially leading to organ atrophy and loss of function. In the central nervous system, cerebral vascular aging can lead to loss of the integrity of the blood-brain barrier, eventually resulting in cognitive and sensorimotor decline. One of the major of types of cognitive dysfunction due to chronic cerebral hypoperfusion is vascular cognitive impairment and dementia (VCID). In spite of recent progress in clinical and experimental VCID research, our understanding of vascular contributions to the pathogenesis of VCID is still very limited. In this review, we summarize recent findings on VCID, with a focus on vascular age-related pathologies and their contribution to the development of this condition.

The inflammatory cytokine TNF-α promotes the premature senescence of rat nucleus pulposus cells via the PI3K/Akt signaling pathway

Premature senescence of nucleus pulposus (NP) cells and inflammation are two common features of degenerated discs. This study investigated the effects of the inflammatory cytokine TNF-α on the premature senescence of NP cells and the molecular mechanism behind this process. Rat NP cells were cultured with or without different concentrations of TNF-α for 1 and 3 days. The inhibitor LY294002 was used to determine the role of the PI3K/Akt pathway. NP cells that were incubated with TNF-α for 3 days followed by 3 days of recovery in the control medium were used to analyze cellular senescence. Results showed that TNF-α promoted premature senescence of NP cells, as indicated by decreased cell proliferation, decreased telomerase activity, increased SA-β-gal staining, the fraction of cells arrested in the G1 phase of the cell cycle, the attenuated ability to synthesize matrix proteins and the up-regulated expression of the senescence marker p16 and p53. Moreover, a high TNF-α concentration produced greater effects than a low TNF-α concentration on day 3 of the experiment. Further analysis indicated that the inhibition of the PI3K/Akt pathway attenuated the TNF-α-induced premature senescence of NP cells. Additionally, TNF-α-induced NP cell senescence did not recover after TNF-α was withdrawn. In conclusion, TNF-α promotes the premature senescence of NP cells, and activation of the PI3K/Akt pathway is involved in this process.

17beta-estradiol Attenuates TNF-α-Induced Premature Senescence of Nucleus Pulposus Cells through Regulating the ROS/NF-κB Pathway

Background: Accelerated cellular senescence within the nucleus pulposus (NP) region is a common feature of disc degeneration. Our previous work indicated that TNF-α promoted NP cell senescence. Although the intervertebral disc has been reported to be an estrogen-sensitive tissue, it is unclear whether estrogen can inhibit premature senescence of NP cells.

Objective: To investigate whether 17beta-estradiol (E₂) can attenuate TNF-α-induced premature senescence of NP cells and the potential mechanism behind this regulatory process.

Methods: Isolated NP cells and intact intervertebral discs from healthy rats were cultured with or without TNF-α, E₂ or their combination. The pan estrogen receptor (ER) antagonist ICI 182780 was used to investigate the role of ER. Direct and indirect indicators including cell proliferation, SA-β-Gal activity, telomerase activity, cell cycle, and the expression of matrix macromolecules (aggrecan and collagen II) and senescence markers (p16 and p53) were used to evaluate the premature senescence of NP cells. Additionally, intracellular reactive oxygen species (ROS) and NF-κB/p65 activity were also detected in the NP cell cultures.

Results: In the NP cell cultures, E₂ significantly increased cell proliferation potency, telomerase activity and the expression of matrix macromolecules but attenuated SA-β-Gal activity, senescence marker (p53 and p16) expression and G1 cycle arrest in TNF-α-treated NP cells. Furthermore, E₂ inhibited ROS generation and phospho-NF-κB/p65 expression in the TNF-α-treated NP cells. However, the ER antagonist ICI 182780 abolished the effects of E₂ on TNF-α-treated NP cells. In the disc organ cultures, E₂ also significantly increased matrix synthesis, whereas it decreased senescence marker (p53 and p16) expression, which could be abolished by the ER antagonist ICI 182780.

Conclusion: The interaction between E₂ and ER can attenuate TNF-α-induced premature senescence of rat NP cells through interfering with the ROS/NF-κB pathway.

Premature senescence of endothelial cells upon chronic exposure to TNFα can be prevented by N-acetyl cysteine and plumericin

Cellular senescence is characterized by a permanent cell-cycle arrest and a pro-inflammatory secretory phenotype, and can be induced by a variety of stimuli, including ionizing radiation, oxidative stress, and inflammation. In endothelial cells, this phenomenon might contribute to vascular disease. Plasma levels of the inflammatory cytokine tumor necrosis factor alpha (TNFα) are increased in age-related and chronic conditions such as atherosclerosis, rheumatoid arthritis, psoriasis, and Crohn's disease. Although TNFα is a known activator of the central inflammatory mediator NF-κB, and can induce the intracellular generation of reactive oxygen species (ROS), the question whether TNFα can induce senescence has not been answered conclusively. Here, we investigated the effect of prolonged TNFα exposure on the fate of endothelial cells and found that such treatment induced premature senescence. Induction of endothelial senescence was prevented by the anti-oxidant N-acetyl cysteine, as well as by plumericin and PHA-408, inhibitors of the NF-κB pathway. Our results indicated that prolonged TNFα exposure could have detrimental consequences to endothelial cells by causing senescence and, therefore, chronically increased TNFα levels might possibly contribute to the pathology of chronic inflammatory diseases by driving premature endothelial senescence.

Modulating putative endothelial progenitor cells for the treatment of endothelial dysfunction and cardiovascular complications in diabetes

Diabetes induces a decrease in the number and function of different pro-angiogenic cell types generically designated as putative endothelial progenitor cells (EPC), which encompasses cells from myeloid origin that act in a paracrine fashion to promote angiogenesis and putative "true" EPC that contribute to endothelial replacement. This not only compromises neovasculogenesis in ischemic tissues but also impairs, at an early stage, the reendotheliziation process at sites of injury, contributing to the development of endothelial dysfunction and cardiovascular complications. Hyperglycemia, insulin resistance and dyslipidemia promote putative EPC dysregulation by affecting the SDF-1/CXCR-4 and NO pathways and the p53/SIRT1/p66Shc axis that contribute to their mobilization, migration, homing and vasculogenic properties. To optimize the clinical management of patients with hypoglycemic agents, statins and renin-angiotensin system inhibitors, which display pleiotropic effects on putative EPC, is a first step to improve their number and angiogenic potential but specific strategies are needed. Among them, mobilizing therapies based on G-CSF, erythropoietin or CXCR-4 antagonism have been developed to increase putative EPC number to treat ischemic diseases with or without prior cell isolation and transplantation. Growth factors, genetic and pharmacological strategies are also evaluated to improve ex vivo cultured EPC function before transplantation. Moreover, pharmacological agents increasing in vivo the bioavailability of NO and other endothelial factors demonstrated beneficial effects on neovascularization in diabetic ischemic models but their effects on endothelial dysfunction remain poorly evaluated. More experiments are warranted to develop orally available drugs and specific agents targeting p66Shc to reverse putative EPC dysfunction in the expected goal of preventing endothelial dysfunction and diabetic cardiovascular complications.

BZLF1 Attenuates Transmission of Inflammatory Paracrine Senescence in Epstein-Barr Virus-Infected Cells by Downregulating Tumor Necrosis Factor Alpha

Recent studies have shown that inflammatory responses trigger and transmit senescence to neighboring cells and activate the senescence-associated secretory phenotype (SASP). Latent Epstein-Barr virus (EBV) infection induces increased secretion of several inflammatory factors, whereas lytic infections evade the antiviral inflammatory response. However, the changes in and roles of the inflammatory microenvironment during the switch between EBV life cycles remain unknown. In the present study, we demonstrate that latent EBV infection in EBV-positive cells triggers the SASP in neighboring epithelial cells. In contrast, lytic EBV infection abolishes this phenotype. BZLF1 attenuates the transmission of paracrine senescence during lytic EBV infection by downregulating tumor necrosis factor alpha (TNF-α) secretion. A mutant BZLF1 protein, BZLF1Δ207-210, that cannot inhibit TNF-α secretion while maintaining viral transcription, fails to block paracrine senescence, whereas a neutralizing antibody against TNF-α is sufficient to restore its inhibition. Furthermore, latent EBV infection induces oxidative stress in neighboring cells, while BZLF1-mediated downregulation of TNF-α reduces reactive oxygen species (ROS) levels in neighboring cells, and ROS scavengers alleviate paracrine senescence. These results suggest that lytic EBV infection attenuates the transmission of inflammatory paracrine senescence through BZLF1 downregulation of TNF-α secretion and alters the inflammatory microenvironment to allow virus propagation and persistence.

IMPORTANCE

The senescence-associated secretory phenotype (SASP), an important tumorigenic process, is triggered and transmitted by inflammatory factors. The different life cycles of Epstein-Barr virus (EBV) infection in EBV-positive cells employ distinct strategies to modulate the inflammatory response and senescence. The elevation of inflammatory factors during latent EBV infection promotes the SASP in uninfected cells. In contrast, during the viral lytic cycle, BZLF1 suppresses the production of TNF-α, resulting in the attenuation of paracrine inflammatory senescence. This finding indicates that EBV evades inflammatory senescence during lytic infection and switches from facilitating tumor-promoting SASP to generating a virus-propagating microenvironment, thereby facilitating viral spread in EBV-associated diseases.

Endogenous Transmembrane TNF-Alpha Protects Against Premature Senescence in Endothelial Colony Forming Cells

RATIONALE

Transmembrane tumor necrosis factor-α (tmTNF-α) is the prime ligand for TNF receptor 2, which has been shown to mediate angiogenic and blood vessel repair activities in mice. We have previously reported that the angiogenic potential of highly proliferative endothelial colony-forming cells (ECFCs) can be explained by the absence of senescent cells, which in mature endothelial cells occupy >30% of the population, and that exposure to a chronic inflammatory environment induced premature, telomere-independent senescence in ECFCs.

OBJECTIVE

The goal of this study was to determine the role of tmTNF-α in the proliferation of ECFCs.

METHODS AND RESULTS

Here, we show that tmTNF-α expression on ECFCs selects for higher proliferative potential and when removed from the cell surface promotes ECFC senescence. Moreover, the induction of premature senescence by chronic inflammatory conditions is blocked by inhibition of tmTNF-α cleavage. Indeed, the mechanism of chronic inflammation-induced premature senescence involves an abrogation of tmTNF/TNF receptor 2 signaling. This process is mediated by activation of the tmTNF cleavage metalloprotease TNF-α-converting enzyme via p38 MAP kinase activation and its concurrent export to the cell surface by means of increased iRhom2 expression.

CONCLUSIONS

Thus, we conclude that tmTNF-α on the surface of highly proliferative ECFCs plays an important role in the regulation of their proliferative capacity.

Aging and age related stresses: a senescence mechanism of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a complicated process that involves both age-related change and tissue damage caused by multiple stresses. In a degenerative IVD, cellular senescence accumulates and is associated with reduced proliferation, compromised self-repair, increased inflammatory response, and enhanced catabolic metabolism. In this review, we decipher the senescence mechanism of IVD degeneration (IVDD) by interpreting how aging coordinates with age-related, microenvironment-derived stresses in promoting disc cell senescence and accelerating IVDD. After chronic and prolonged replication, cell senescence may occur as a natural part of the disc aging process, but can potentially be accelerated by growth factor deficiency, oxidative accumulation, and inflammatory irritation. While acute disc injury, excessive mechanical overloading, diabetes, and chronic tobacco smoking contribute to the amplification of senescence-inducing stresses, the avascular nature of IVD impairs the immune-clearance of the senescent disc cells, which accumulate in cell clusters, demonstrate inflammatory and catabolic phenotypes, deteriorate disc microenvironment, and accelerate IVDD. Anti-senescence strategies, including telomerase transduction, supply of growth factors, and blocking cell cycle inhibitors, have been shown to be feasible in rescuing disc cells from early senescence, but their efficiency for disc regeneration requires more in vivo validations. Guidelines dedicated to avoiding or alleviating senescence-inducing stresses might decelerate cellular senescence and benefit patients with IVD degenerative diseases.

Significance and therapeutic implications of endothelial progenitor cells in angiogenic-mediated tumour metastasis

Cancer conveys profound social and economic consequences throughout the world. Metastasis is responsible for approximately 90% of cancer-associated mortality and, when it occurs, cancer becomes almost incurable. During metastatic dissemination, cancer cells pass through a series of complex steps including the establishment of tumour-associated angiogenesis. The human endothelial progenitor cells (hEPCs) are a cell population derived from the bone marrow which are required for endothelial tubulogenesis and neovascularization. They also express abundant inflammatory cytokines and paracrine angiogenic factors. Clinically hEPCs are highly correlated with relapse, disease progression, metastasis and treatment response in malignancies such as breast cancer, ovarian cancer and non-small-cell lung carcinoma. It has become evident that the hEPCs are involved in the angiogenesis-required progression and metastasis of tumours. However, it is not clear in what way the signalling pathways, controlling the normal cellular function of human BM-derived EPCs, are hijacked by aggressive tumour cells to facilitate tumour metastasis. In addition, the actual roles of hEPCs in tumour angiogenesis-mediated metastasis are not well characterised. In this paper we reviewed the clinical relevance of the hEPCs with cancer diagnosis, progression and prognosis. We further summarised the effects of tumour microenvironment on the hEPCs and underlying mechanisms. We also hypothesized the roles of altered hEPCs in tumour angiogenesis and metastasis. We hope this review may enhance our understanding of the interaction between hEPCs and tumour cells thus aiding the development of cellular-targeted anti-tumour therapies.

Endothelial colony-forming cells: Biological and functional abnormalities in patients with recurrent, unprovoked venous thromboembolic disease

INTRODUCTION

Endothelial cells (ECs) are an important component of the blood coagulation system because it maintains blood fluid. Because in patients with venous thromboembolic disease (VTD) a thrombophilic condition is not found sometimes, we investigated if endothelial colony-forming cells (ECFCs) from these patients have biological and functional abnormalities.

PATIENTS AND METHODS

Human mononuclear cells (MNCs) were obtained from peripheral blood from patients with VTD and controls to obtain ECFCs. These cells were assayed for their immunophenotype and electron microscopy characteristics and their ability to form capillary-like structures and to produce pro-inflammatory and pro-angiogenic cytokines and reactive oxygen species (ROS).

RESULTS

ECFCs appeared at 7 and 21 days of culture in VTD patients and controls, respectively. ECFCs increased 8-fold in patients and emerged 1 week earlier. No differences in the size of the colonies of ECFCs were found. Numbers and time of appearance of ECFCs was different between groups. ECFC-derived ECs (ECFC-ECs) of both groups expressed CD31, CD34, CD146, and CD-309 but none expressed CD45, CD14, or CD90. Interest CD34 was highly expressed in ECFC-ECs from patients. In both groups, ECFC-ECs showed similar capacity to form capillary-like structures but ECFC-ECs from patients had significant abnormalities in the mitochondrial membrane. We found a significant increase in ROS production in ECFC-ECs from patients. There were significant differences in cytokine profiles between VTD patients and controls.

CONCLUSIONS

We found a dysfunctional state in ECFC from VTD patients resembling some characteristics of dysfunctional ECs. These findings may help to understand some pathophysiological aspects of VTD.

Translational control of PML contributes to TNFα-induced apoptosis of MCF7 breast cancer cells and decreased angiogenesis in HUVECs

The tumor suppressor protein promyelocytic leukemia (PML) is a key regulator of inflammatory responses and tumorigenesis and functions through the assembly of subnuclear structures known as PML nuclear bodies (NBs). The inflammation-related cytokine tumor necrosis factor-α (TNFα) is known to induce PML protein accumulation and PML NB formation that mediate TNFα-induced cell death in cancer cells and inhibition of migration and capillary tube formation in endothelial cells (ECs). In this study, we uncover a novel mechanism of PML gene regulation in which the p38 MAPK and its downstream kinase MAP kinase-activated protein kinase 1 (MNK1) mediate TNFα-induced PML protein accumulation and PML NB formation. The mechanism includes the presence of an internal ribosome entry site (IRES) found within the well-conserved 100 nucleotides upstream of the PML initiation codon. The activity of the PML IRES is induced by TNFα in a manner that involves MNK1 activation. It is proposed that the p38–MNK1–PML network regulates TNFα-induced apoptosis in breast cancer cells and TNFα-mediated inhibition of migration and capillary tube formation in ECs.

Ageing induced vascular smooth muscle cell senescence in atherosclerosis

Atherosclerosis is a disease of ageing in that its incidence and prevalence increase with age. However, atherosclerosis is also associated with biological ageing, manifest by a number of typical hallmarks of ageing in the atherosclerotic plaque. Thus, accelerated biological ageing may be superimposed on the effects of chronological ageing in atherosclerosis. Tissue ageing is seen in all cells that comprise the plaque, but particularly in vascular smooth muscle cells (VSMCs). Hallmarks of ageing include evidence of cell senescence, DNA damage (including telomere attrition), mitochondrial dysfunction, a pro-inflammatory secretory phenotype, defects in proteostasis, epigenetic changes, deregulated nutrient sensing, and exhaustion of progenitor cells. In this model, initial damage to DNA (genomic, telomeric, mitochondrial and epigenetic changes) results in a number of cellular responses (cellular senescence, deregulated nutrient sensing and defects in proteostasis). Ultimately, ongoing damage and attempts at repair by continued proliferation overwhelm reparative capacity, causing loss of specialised cell functions, cell death and inflammation. This review summarises the evidence for accelerated biological ageing in atherosclerosis, the functional consequences of cell ageing on cells comprising the plaque, and the causal role that VSMC senescence plays in atherogenesis.

Geroconversion of aged muscle stem cells under regenerative pressure

Regeneration of skeletal muscle relies on a population of quiescent stem cells (satellite cells) and is impaired in very old (geriatric) individuals undergoing sarcopenia. Stem cell function is essential for organismal homeostasis, providing a renewable source of cells to repair damaged tissues. In adult organisms, age-dependent loss-of-function of tissue-specific stem cells is causally related with a decline in regenerative potential. Although environmental manipulations have shown good promise in the reversal of these conditions, recently we demonstrated that muscle stem cell aging is, in fact, a progressive process that results in persistent and irreversible changes in stem cell intrinsic properties. Global gene expression analyses uncovered an induction of p16(INK4a) in satellite cells of physiologically aged geriatric and progeric mice that inhibits satellite cell-dependent muscle regeneration. Aged satellite cells lose the repression of the INK4a locus, which switches stem cell reversible quiescence into a pre-senescent state; upon regenerative or proliferative pressure, these cells undergo accelerated senescence (geroconversion), through Rb-mediated repression of E2F target genes. p16(INK4a) silencing rejuvenated satellite cells, restoring regeneration in geriatric and progeric muscles. Thus, p16(INK4a)/Rb-driven stem cell senescence is causally implicated in the intrinsic defective regeneration of sarcopenic muscle. Here we discuss on how cellular senescence may be a common mechanism of stem cell aging at the organism level and show that induction of p16(INK4a) in young muscle stem cells through deletion of the Polycomb complex protein Bmi1 recapitulates the geriatric phenotype.

Epigenetic Regulation of Placenta-Specific 8 Contributes to Altered Function of Endothelial Colony-Forming Cells Exposed to Intrauterine Gestational Diabetes Mellitus

Intrauterine exposure to gestational diabetes mellitus (GDM) is linked to development of hypertension, obesity, and type 2 diabetes in children. Our previous studies determined that endothelial colony-forming cells (ECFCs) from neonates exposed to GDM exhibit impaired function. The current goals were to identify aberrantly expressed genes that contribute to impaired function of GDM-exposed ECFCs and to evaluate for evidence of altered epigenetic regulation of gene expression. Genome-wide mRNA expression analysis was conducted on ECFCs from control and GDM pregnancies. Candidate genes were validated by quantitative RT-PCR and Western blotting. Bisulfite sequencing evaluated DNA methylation of placenta-specific 8 (PLAC8). Proliferation and senescence assays of ECFCs transfected with siRNA to knockdown PLAC8 were performed to determine functional impact. Thirty-eight genes were differentially expressed between control and GDM-exposed ECFCs. PLAC8 was highly expressed in GDM-exposed ECFCs, and PLAC8 expression correlated with maternal hyperglycemia. Methylation status of 17 CpG sites in PLAC8 negatively correlated with mRNA expression. Knockdown of PLAC8 in GDM-exposed ECFCs improved proliferation and senescence defects. This study provides strong evidence in neonatal endothelial progenitor cells that GDM exposure in utero leads to altered gene expression and DNA methylation, suggesting the possibility of altered epigenetic regulation.

Long-Term Expansion in Platelet Lysate Increases Growth of Peripheral Blood-Derived Endothelial-Colony Forming Cells and Their Growth Factor-Induced Sprouting Capacity

Introduction

Efficient implementation of peripheral blood-derived endothelial-colony cells (PB-ECFCs) as a therapeutical tool requires isolation and generation of a sufficient number of cells in ex vivo conditions devoid of animal-derived products. At present, little is known how the isolation and expansion procedure in xenogeneic-free conditions affects the therapeutical capacity of PB-ECFCs.

Results

The findings presented in this study indicate that human platelet lysate (PL) as a serum substitute yields twice more colonies per mL blood compared to the conventional isolation with fetal bovine serum (FBS). Isolated ECFCs displayed a higher proliferative ability in PL supplemented medium than cells in FBS medium during 30 days expansion. The cells at 18 cumulative population doubling levels (CPDL) retained their proliferative capacity, showed higher sprouting ability in fibrin matrices upon stimulation with FGF-2 and VEGF-A than the cells at 6 CPDL, and displayed low β-galactosidase activity. The increased sprouting of PB-ECFCs at 18 CPDL was accompanied by an intrinsic activation of the uPA/uPAR fibrinolytic system. Induced deficiency of uPA (urokinase-type plasminogen activator) or uPAR (uPA receptor) by siRNA technology completely abolished the angiogenic ability of PB-ECFCs in fibrin matrices. During the serial expansion, the gene induction of the markers associated with inflammatory activation such as VCAM-1 and ICAM-1 did not occur or only to limited extent. While further propagation up to 31 CPDL proceeded at a comparable rate, a marked upregulation of inflammatory markers occurred in all donors accompanied by a further increase of uPA/uPAR gene induction. The observed induction of inflammatory genes at later stages of long-term propagation of PB-ECFCs underpins the necessity to determine the right time-point for harvesting of sufficient number of cells with preserved therapeutical potential.

Conclusion

The presented isolation method and subsequent cell expansion in platelet lysate supplemented culture medium permits suitable large-scale propagation of PB-ECFC. For optimal use of PB-ECFCs in clinical settings, our data suggest that 15–20 CPDL is the most adequate maturation stage.

Activation of Cell Surface Bound 20S Proteasome Inhibits Vascular Cell Growth and Arteriogenesis

Arteriogenesis is an inflammatory process associated with rapid cellular changes involving vascular resident endothelial progenitor cells (VR-EPCs). Extracellular cell surface bound 20S proteasome has been implicated to play an important role in inflammatory processes. In our search for antigens initially regulated during collateral growth mAb CTA 157-2 was generated against membrane fractions of growing collateral vessels. CTA 157-2 stained endothelium of growing collateral vessels and the cell surface of VR-EPCs. CTA 157-2 bound a protein complex (760 kDa) that was identified as 26 kDa α7 and 21 kDa β3 subunit of 20S proteasome in mass spectrometry. Furthermore we demonstrated specific staining of 20S proteasome after immunoprecipitation of VR-EPC membrane extract with CTA 157-2 sepharose beads. Functionally, CTA 157-2 enhanced concentration dependently AMC (7-amino-4-methylcoumarin) cleavage from LLVY (N-Succinyl-Leu-Leu-Val-Tyr) by recombinant 20S proteasome as well as proteasomal activity in VR-EPC extracts. Proliferation of VR-EPCs (BrdU incorporation) was reduced by CTA 157-2. Infusion of the antibody into the collateral circulation reduced number of collateral arteries, collateral proliferation, and collateral conductance in vivo. In conclusion our results indicate that extracellular cell surface bound 20S proteasome influences VR-EPC function in vitro and collateral growth in vivo.

Chronic heart failure and aging - effects of exercise training on endothelial function and mechanisms of endothelial regeneration: Results from the Leipzig Exercise Intervention in Chronic heart failure and Aging (LEICA) study

BACKGROUND

A reduction in number and function of endothelial progenitor cells (EPCs) occurs in both physiologic aging and chronic heart failure (CHF). We assessed whether disease and aging have additive effects on EPCs or whether beneficial effects of exercise training are diminished in old age.

METHODS

We randomized 60 patients with stable CHF and 60 referent controls to a training or a control group. To detect possible aging effects we included subjects below 55 (young) and above 65 years (older). Subjects in the training group exercised four times daily at 60% to 70% of VO2max for four weeks under supervision. At baseline and after the intervention the number and function of EPCs were assessed.

RESULTS

As compared with young referent controls, older referent controls showed at baseline a reduced EPC number (young: 190 ± 37 CD34/KDR positive cells/ml blood; older: 131 ± 26 CD34/KDR positive cells/ml blood; p < 0.05) and function (young: 230 ± 41 migrated cells/1000 plated cells; older: 185 ± 28 cells/1000 plated cells; p < 0.05). In young and older CHF patients EPC-number (young: 85 ± 21 CD34/KDR positive cells/ml blood; older: 78 ± 20 CD34/KDR positive cells/ml blood) and EPC-function (young: 113 ± 26 cells/1000 plated cells; older: 120 ± 27 cells/1000 plated cells) were impaired. As a result of exercise training, EPC function improved by 24% in older referent controls (p < 0.05), while it remained unchanged in young training referent controls and controls respectively. In young and older patients with CHF four weeks of exercise training resulted in a significant improvement in EPC numbers and EPC function (young: number +66% function +43%; p < 0.05; older: number +69% function +36%; p < 0.05). These results were accompanied by a significant increase in flow mediated dilatation in the training groups of young/older CHF patients and in older referent controls.

CONCLUSIONS

Four weeks of exercise training are effective in improving EPC number and EPC function in CHF patients. These training effects were not impaired among older patients, emphasizing the potentials of rehabilitation interventions in a patient group where CHF has a high prevalence.

Tetraspanin Family Member, CD82, Regulates Expression of EZH2 via Inactivation of p38 MAPK Signaling in Leukemia Cells

PURPOSE

We recently found that the tetraspanin family member, CD82, which is aberrantly expressed in chemotherapy-resistant CD34(+)/CD38- acute myelogenous leukemia (AML) cells, negatively regulates matrix metalloproteinase 9, and plays an important role in enabling CD34(+)/CD38(-) AML cells to adhere to the bone marrow microenvironment. This study explored novel functions of CD82 that contribute to AML progression.

MATERIALS AND METHODS

We employed microarray analysis comparing the gene expression profiles between CD34(+)/CD38(-) AML cells transduced with CD82 shRNA and CD34(+)/CD38(-) AML cells transduced with control shRNA. Real-time RT-PCR and western blot analysis were performed to examine the effect of CD82 knockdown on the expression of the polycomb group member, enhancer of zeste homolog 2 (EZH2), in leukemia cells. A chromatin immunoprecipitation assay was performed to examine the effect of CD82 expression on the amount of EZH2 bound to the promoter regions of tumor suppressor genes in leukemia cells. We also utilized methylation-specific PCR to examine whether CD82 expression influences the methylation status of the tumor suppressor gene promoter regions in leukemia cells.

RESULTS

Microarray analysis revealed that levels of EZH2 decreased after shRNA-mediated depletion of CD82 in CD34(+)/CD38(-) AML cells. Moreover, the antibody-mediated blockade of CD82 in leukemia cells lowered EZH2 expression via activation of p38 MAPK signaling, decreased the amount of EZH2 bound to the promoter regions of the tumor suppressor genes, and inhibited histone H3 lysine 27 trimethylation in these promoter regions, resulting in upregulation of the tumor suppressors at both the mRNA and protein levels.

Functional genomics of the CDKN2A/B locus in cardiovascular and metabolic disease: what have we learned from GWASs?

Genome-wide association studies (GWASs) provide an unprecedented opportunity to examine, on a large scale, the association of common genetic variants with complex diseases like type 2 diabetes (T2D) and cardiovascular disease (CVD), thus allowing the identification of new potential disease loci. Using this approach, numerous studies have associated SNPs on chromosome 9p21.3 situated near the cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) locus with the risk for coronary artery disease (CAD) and T2D. However, identifying the function of the nearby gene products (CDKN2A/B and ANRIL) in the pathophysiology of these conditions requires functional genomic studies. We review the current knowledge, from studies using human and mouse models, describing the function of CDKN2A/B gene products, which may mechanistically link the 9p21.3 risk locus with CVD and diabetes.

Activation of p38 and changes in mitochondria accompany autophagy to premature senescence-like phenotype switch upon chronic exposure to selenite in colon fibroblasts

Effects of chronic exposure to supranutritional sodium selenite (Se) were investigated in colonic fibroblasts. Initially, Se did not produce any gross changes in exposed cells; however, basal levels of autophagy were transiently increased and p38 activity was stimulated. From the 3rd week onwards, Se decreased cell proliferation, with corrensponding changes in cell cycle distribution. Also, in exposed cells oxidative stress and DNA damage slowly but gradually increased along with decreasing mitochondrial function and upon continued elevated activity of p38 kinase. Towards the end of the experiment, premature senescence features became more prominent in treated cells. Pharmacological inhibition as well as gene knockdown of these processes confirmed the involvement of p38 in balancing autophagy and premature senescence in cells exposed to Se and suggests that this element may in a given time frame compromise selected cell populations in digestive system.