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RNA velocity provides an approach for inferring cellular state transitions from single-cell RNA sequencing (scRNA-seq) data. Conventional RNA velocity models infer universal kinetics from all cells in an scRNA-seq experiment, resulting in unpredictable performance in experiments with multi-stage and/or multi-lineage transition of cell states where the assumption of the same kinetic rates for all cells no longer holds. Here we present cellDancer, a scalable deep neural network that locally infers velocity for each cell from its neighbors and then relays a series of local velocities to provide single-cell resolution inference of velocity kinetics. In the simulation benchmark, cellDancer shows robust performance in multiple kinetic regimes, high dropout ratio datasets and sparse datasets. We show that cellDancer overcomes the limitations of existing RNA velocity models in modeling erythroid maturation and hippocampus development. Moreover, cellDancer provides cell-specific predictions of transcription, splicing and degradation rates, which we identify as potential indicators of cell fate in the mouse pancreas.

Osteoprotegerin (OPG), also known as osteoclastogenesis inhibitory factor or tumor necrosis factor receptor superfamily member 11B, is well known as a modulator of bone remodeling. The contribution of OPG to cardiovascular disease (CVD) has been suggested, but its molecular mechanism is complex and remains unclear. In the present study, Alves-Lopes et al. (Clin. Sci. (Lond.) (2021) 135(20): https://doi.org/10.1042/CS20210643) reported the critical role of syndecan-1 (SDC-1, also known as CD138), a surface protein part of the endothelial glycocalyx, in OPG-induced vascular dysfunction. The authors found that in endothelial cells (ECs), through SDC-1, OPG increased eNOS Thr495 phosphorylation, thereby inhibiting eNOS activity. Furthermore, the OPG–SDC-1 interaction increased reactive oxygen species (ROS) production through NOX1/4 activation. Both the reduced eNOS activity and induced ROS production inhibited NO production and impaired EC function. In vascular smooth muscle cells (VSMCs), the OPG–SDC-1 interaction increased ROS production through NOX1/4 activation, subsequently increased MLC phosphorylation-mediated Rho kinase-MYPT1 regulation, leading to increased vascular contraction. Ultilizing wire myography and mechanistic studies, the authors nicely provide the evidence that SDC-1 plays a crucial role in OPG-induced vascular dysfunction. As we mentioned above, the molecular mechanism and roles of OPG in cardiovascular system are complex and somewhat confusing. In this commentary, we briefly summarize the OPG-mediated signaling pathways in cardiovascular system.

When influenza virus infects cells, it changes cellular metabolism in such a way that allows virus particles to replicate efficiently. This metabolic engineering takes place soon after virus infects cells, for which the PSD95/DiscLarge/ZO-1 (PDZ) domain of certain proteins is known to play a role. Membrane-associated guanylate kinase with inverted domain structure-1 (MAGI1) is a scaffold protein with 6 PDZ domains, and we have shown that it is involved in the regulation of endothelial cell (EC) activation and atherosclerosis in mice. Since recent studies indicate that the vascular endothelium can be infected by influenza A virus (IAV) and plays a role in the influenza-induced pathogenesis and cardiovascular disease (CVD), we investigated the role of MAGI1 in IAV infection using cultured human umbilical vein endothelial cells (HUVECs) as well as human lung microvascular endothelial cells (HULECs). We found increased MAGI1 mRNA expression in IAV-infected cells. Conversely, when MAGI1 depleted ECs were infected with IAV, virus infection and replication was greatly suppressed. Our microarray studies revealed that depletion of MAGI1 in HUVECs increased the protein expression and signaling networks involved in interferon production. Specifically, we found that the MAGI1 null condition induced expression of anti-viral response genes including interferon-induced GTP-binding protein MX1, an antiviral protein, interferon beta1, a cytokine promotor STAT1 (signal transducer and activator of transcription 1), and also increased protein expression levels of STAT1, phosphorylated STAT5 and MX1. Co-transfection of HUVECs with siMX1 and siMAGI1 impaired MAGI1 depletion-induced suppression of IAV infection. Furthermore, we found nuclear localization of interferon regulatory factor 3 (IRF3) in MAGI1 depleted cells, indicating that MAGI1 depletion elicits the interferon production and signaling. Taken together, we conclude that IAV infection and replication occurs in ECs in a MAGI1 expression dependent manner. Thus, MGAI1 depletion in ECs suppresses IAV replication, and this suppression is due to increased MX1 expression, which induces IRF3 activation and interferon production. MAGI1 can be a potential therapeutic target for influenza-induced CVD.

The central role of ERK5 S496 phosphorylation in promoting senescence has been reported. Recently the conventional model of senescence as an event of cell cycle arrest has been challenged, given that senescence induced by various stresses reprograms cancer cells to acquire senescence-associated stemness (SAS), which allows them to escape senescence-induced cell cycle arrest with enhanced growth potential. To determine the role of ERK5 S496 phosphorylation in SAS, we utilized imaging mass cytometry (IMC) by using antibodies against various cell surface markers, senescence, and proliferation. We prepared tissue sections from the plaques in wild-type (WT) and ERK5 S496A knock-in (KI) mice, and the ablated plaque materials were evaluated by the CyTOF mass cytometer. We used the VISIOPHARM program, and single-cell features were computationally segmented using a watershed algorithm. Nine clusters were detected in WT (total 7903 cells) and ERK5 S496A KI (total 6166 cells) plaques. Single-cell analysis of p53 and Ki67 revealed three groups of the cells with different pattern of p53 and Ki67 expression (Fig.A). We calculated log scaled ratio of Ki67 and p53 of selected cells by log 10 (expression of Ki67/ expression of p53), and further calculated one-dimension density of this log scaled ratio to cluster cells into three groups by using cutoff of ration with log 10 (-1.01) and log 10 (-0.024) (Fig.B). Group 2 myeloid cells showed that p53 and Ki67 were co-expressed lineally, suggesting that this group of cells escaped from the growth-suppression effects of p53, which is also known as a senescence marker. Of note, the % of ERK5 S496A KI cells in group 2 were significantly lower than those in WT (Fig.C). Also, in vitro oxidized LDL remarkably increase β-gal + Ki67 + cells, which was significantly inhibited in ERK5 S496A KI macrophage compared to those in WT. Collectively, these data implicates ERK5 S496 phosphorylation in a unique role-regulation of SAS during atherogenesis.

The crucial role of ERK5 S496 phosphorylation in reprogramming macrophage phenotype to pro-inflammatory senescent phenotype (PISP) has been reported, but the exact molecular mechanism remains unclear. This study focused on identifying the dysregulated molecular pathways and core genes that are differentially regulated in bone marrow derived macrophage (BMDMs) isolated from wild type and ERK5 S549A knock-in (KI) mice under normal or hypercholesterolemia (HC) after high-fat diet (HFD) and AAV-PCSK9 injection. The extent of atherosclerosis was inhibited in ERK5 S496A KI mice. We sequenced RNA-seq for wild type and ERK5 S549A KI mice and used Top Hat program (v2.0.12) with default parameters to map all reads to the mouse genome (Mus musculus GRCm38). Gene expression and significance of differential expression were calculated by Cuffdiff (v2.0.12). Differentially expressed genes (DEGs) were defined by Cuffdiff according to Q value ≤0.05 as a threshold. Hallmark analysis was performed by Gene Set Enrichment Analysis (GSEA v4.2.1). We used the R package “GOplot” to perform GO bubble plot, GO circle plot, and GO chord plot. We identified 784 DEGs regulated by HC-induced ERK5 S496 phosphorylation, and the GO analysis revealed that they are involved in critical senescent processes including cell cycle, cellular response to DNA damage stimulus, protein transport, and negative regulation of apoptotic process. Gene-annotation enrichment analysis (GOCircle) showed that Z-scores of both cell cycle and cellular response to DNA damage stimulus were negative in ERK5 S496A KI mice, suggesting the role of cell cycle and DNA damage response in inducing PISP. Interestingly, we only found 40 DEGs in BMDMs isolated from normal chow diet and HFD-fed wild type mice, and 15 out of 40 DEGs were significantly regulated by ERK5 S496 phosphorylation, supporting the critical role of ERK5 S496 phosphorylation in HC-mediated macrophage reprogramming. Our study identified 10 core genes (Ahr, Gclm, H3C3, H4c11, Lpar1, Megf9, Nfe2, Ppih, Rpl22l1, and Tpt1) that are regulated by HC-mediated ERK5 S496 phosphorylation, which might be crucial for HC-induced PISP. However, functional analysis is further needed to validate their roles in PISP induction.

ERK5 is a dual kinase-transcription factor, which contains two transcriptional transactivation domains in the C-terminus and a kinase domain in the N-terminus. Many ERK5 kinase inhibitors have been developed, and are being tested in clinical studies for cancer and inflammatory diseases. Recent data has raised questions regarding the functional role of these ERK5 kinase inhibitors. Specifically, the possible link between blockade of pro-inflammatory ERK5 S496 phosphorylation and the anti-inflammatory effects of ERK5-specific kinase inhibitors has largely been neglected. In this study, we aimed to study the role and regulatory mechanisms of ERK5 S496 phosphorylation on macrophage inflammation and the impact of ERK5-specific kinase inhibitors. ATP binding site deletion mutant of ERK5b (a kinase-dead mutant) inhibited KLF2 induction but not oxidized LDL (oxLDL)-induced ERK5 S496 phosphorylation and TNFα expression. In contrast, both specific ERK5 kinase inhibitors (AX15836 and XMD8-92) and a dual phosphorylation site mutant of ERK5 (AEF) inhibited not only KLF2 but also oxLDL-induced ERK5 S496 phosphorylation and TNFα induction. These data suggested that ERK5 S496 phosphorylation, but not ERK5 kinase activity, plays a crucial role in ERK5-mediated pro-inflammatory effects. We also discovered a key effect of ERK5 S496 phosphorylation on SUMOylation at a novel site of NRF2 (i.e., K518), which inhibited NRF2 transcriptional activity without affecting ERK5 kinase activity, and antagonized oxLDL-induced macrophage inflammation. The role of NRF2 activation on the efficiency of oxidative phosphorylation (OXPHOS) and ATP synthesis had previously been reported, and we found that both ERK5 S496A and NRF2 K518R mutants abolished oxLDL-induced reduction of OXPHOS, ATP, and NAD + levels. In summary, we discovered a novel mechanism in which ERK5 S496 phosphorylation directly inhibited NRF2 activity via SUMOylation of NRF2 at K518 and thereby induced macrophage inflammation and mitochondrial dysfunction. The often-neglected role of ERK S496 signaling should be carefully considered in the interpretation of prior reports of ERK5 knockdown and pharmacological kinase inhibition relative to cellular inflammation and mitochondrial dysfunction.

Cancer Radiation therapy (RT) induces cardiovascular disease (CVD) even when the heart is shealed or not irradiated, but there is a paucity of available preventive measures for RT-induced CVD. Ionizing radiation (IR) induces senescence, which was originally discovered to suppress tumorigenesis by inducing cell cycle blockade and necrosis, and positioned IR as pro-senescence cancer therapy. IR-induced senescence cells secrete cytokines, growth factors, and reactive oxygen species (ROS), becoming so called senescence associated secretory phenotype (SASP), and we hypothesize that SASP induction in immune cells cause CVD after RT. Although the involvement of DNA damage response (DDR), efferocytosis, and clonal hematopoiesis drivers (CHD) to SASP induction has been suggested, the exact mechanisms through which RT induces SASP in a specific cell type remains unclear. We characterize most of the major human immune cell lineages in a single assay using mass cytometery (CyTOF). We generated a CyTOF panel which includes antibodies against various senescence phenotype, DDR, efferocytosis, and CHD. We isolated peripheral blood mononuclear cells (PBMCs) before and 3 month after RT from 16 thoracic cancer patients. First, we found the frequency of only B cell subtype was decreased after RT. Second, we obtained 138 functional profiling subsets by unsupervised clustering with our antibody set, and found that T-bet expression was increased in the largest B cell subset of naïve B Cell (CD27 - ) Ki67 lo CD38 lo DNMT3a hi after RT, which showed the good correlation with p-p90RSK expression in the samples from pre-RT and post-RT. Lastly, the significant increase of CD38 expression in the subsets of naïve B cell (CD27 - ) and CD8 + T cell (EMRA) was detected. These data suggest the unique response of naïve B cell (CD27-) to RT with the increase of CD38 expression, and T-bet in the subset of B Cell (CD27 - ) Ki67 lo CD38 lo DNMT3a hi , and also the potential role of p90RSK activation in IR-induced T-bet expression. T-bet plays a role in developing the age-associated B cell (ABC), and the increase of CD38 expression promotes aging-related events. Therefore, the induction of T-bet and CD38 in naïve B (CD27 - ) cell after RT supports the novel role of naïve B cell in IR-induced SASP and subsequent CVD.

Atherosclerosis (AthS) tends to form at arterial regions exposed to disturbed (DF) but not laminar (LF) flow. Previously, we reported the significant role of SUMOylation in DF-induced endothelial (EC) activation and subsequent AthS formation via upregulating p53 and ERK5 SUMOylation. LF can inhibit the basal levels of p53 and ERK5 SUMOylation, but how LF inhibits SUMOylation remains unknown. A chemical genetics approach with high-resolution mass spectrometry revealed that the cell-cycle checkpoint kinases CHK1 can phosphorylate SENP2 S344 site, but the functional role remains largely unknown. We aimed to study the functional role of CHK1 in SENP2 function and subsequent AthS. First, we generated phospho-specific SENP2 S344 antibody, and found that LF, but not DF, increases SENP2 S344 phosphorylation. We found the increase of CHK1 S280 phosphorylation (related to nuclear translocation) after LF, suggesting LF-induced nuclear translocation of CHK1. The CHK1 specific inhibitor of GDC0575 and the depletion of CHK1 inhibited LF-induced SENP2 S344 phsophorylation and increased both p53 and ERK5 SUMOylation in ECs. These data suggested the crucial role of CHK1 in LF-induced SENP2 S344 phosphorylation and upregulating de-SUMOylation activity. Next, we generated CRISPR/Cas9-induced Senp2 S344A knock-in (KI) and found that the mutation of SENP2 S344A accelerated p53 and ERK5 SUMOylation. LF-induced reduction of p21, cleaved caspase 3, and ICAM-1 were all reversed by SENP2 S344A mutation. Lastly, we found that the significant acceleration of AthS formation in both ascending aorta/arch (DF area) and descending aorta (LF area) in KI mice compared to wild type (WT) mice after receiving AAV-PCSK9 and high fat diet. We also performed bone marrow transplantation (BMT) after 13 Gy whole body radiation, and larger AthS but only in the aortic arch was observed in BMT mice from WT donor to KI recipient, but not in BMT mice from WT donor to WT recipient, supporting the role of endothelial SENP2 S344 phosphorylation on AthS. The radiation reduced CHK1 expression in ECs, which may explain the different regulatory pattern under BMT or non-BMT. Taken together, these results suggest the critical role of CHK1-mediated SENP2 S344 phosphorylation on LF-induced anti-AthS effects.

Purpose of Review As both a cholesterol acceptor and carrier in the reverse cholesterol transport (RCT) pathway, high-density lipoprotein (HDL) is putatively atheroprotective. However, current pharmacological therapies to increase plasma HDL cholesterol (HDL-c) concentration have paradoxically failed to prevent or reduce atherosclerosis and cardiovascular disease (CVD). Given that free cholesterol (FC) transfer between surfaces of lipoproteins and cells is reversible, excess plasma FC can be transferred to the cells of peripheral tissue sites resulting in atherosclerosis. Here, we summarize potential mechanisms contributing to this paradox and highlight the role of excess free cholesterol (FC) bioavailability in atherosclerosis vs. atheroprotection. Recent Findings Recent findings have established a complex relationship between HDL-c concentration and atherosclerosis. Systemic scavenger receptor class B type 1 (SR-B1) knock out (KO) mice exhibit with increased diet-induced atherosclerosis despite having an elevated plasma HDL-c concentration compared to wild type (WT) mice. The greater bioavailability of HDL-FC in SR-B1 vs. WT mice is associated with a higher FC content in multiple cell types and tissue sites. These results suggest that dysfunctional HDL with high FC bioavailability is atheroprone despite high HDL-c concentration. Summary Past oversimplification of HDL-c involvement in cholesterol transport has led to the failures in HDL targeted therapy. Evidence suggests that FC-mediated functionality of HDL is of higher importance than its quantity; as a result, deciphering the regulatory mechanisms by which HDL-FC bioavailability can induce atherosclerosis can have far-reaching clinical implications.

Cellular metabolic dysregulation is a consequence of COVID-19 infection that is a key determinant of disease severity. To understand the mechanisms underlying these cellular changes, we performed high-dimensional immune cell profiling of PBMCs from COVID-19-infected patients, in combination with single cell transcriptomic analysis of COVID-19 BALFs. Hypoxia, a hallmark of COVID-19 ARDS, was found to elicit a global metabolic reprogramming in effector lymphocytes. In response to oxygen and nutrient-deprived microenvironments, these cells shift from aerobic respiration to increase their dependence on anaerobic processes including glycolysis, mitophagy, and glutaminolysis to fulfill their bioenergetic demands. We also demonstrate metabolic dysregulation of ciliated lung epithelial cells is linked to significant increase of proinflammatory cytokine secretion and upregulation of HLA class 1 machinery. Augmented HLA class-1 antigen stimulation by epithelial cells leads to cellular exhaustion of metabolically dysregulated CD8 and NK cells, impairing their memory cell differentiation. Unsupervised clustering techniques revealed multiple distinct, differentially abundant CD8 and NK memory cell states that are marked by high glycolytic flux, mitochondrial dysfunction, and cellular exhaustion, further highlighting the connection between disrupted metabolism and impaired memory cell function in COVID-19. Our findings provide novel insight on how SARS-CoV-2 infection affects host immunometabolism and anti-viral response during COVID-19.Graphical AbstractHighlightsHypoxia and anaerobic glycolysis drive CD8, NK, NKT dysfunctionHypoxia and anaerobic glycolysis impair memory differentiation in CD8 and NK cellsHypoxia and anaerobic glycolysis cause mitochondrial dysfunction in CD8, NK, NKT cells

Background: Endothelial cells (ECs) predominantly govern vascular tone and homeostasis. Activation of ECs is the central pathophysiological process in the initiation of atherosclerosis (AS). Interferon signaling (IFN Type I and II) is activated in ECs under inflammatory conditions such as systemic lupus erythematosus and is implicated in EC activation. Yet, the underlying mechanisms are still unknown. Through RNA sequencing and pathway analysis we have identified, TNIK, a Ste20 family of MAP kinases (MAP4K) to regulate IFN signaling in ECs. Our study is the first to report the role and function of TNIK in IFN and EC activation. Hypothesis: TNIK regulates IFNs through focal adhesion kinase (FAK) mediated STAT signaling in EC activation (Fig 1A). Methods: Cultured human aortic endothelial cells (HAECs) were treated with control or TNIK-targeted siRNA. Later cells were subjected to static, laminar or disturbed flow conditions. Total RNA was isolated and then RNA-sequencing was performed. The differential expression data were analyzed using CLC genomics and Ingenuity Pathway Analysis (IPA). Western blotting and qRT-PCR were performed to validate STAT activation and interferon-stimulated genes (ISGs) Results: We found >450 genes differentially expressed in siTNIK vs siCTRL treated ECs (fold change>2, FDR11) and upregulation of eukaryotic transcription elongation factor signaling (eIF2, -log P-value >7) (Fig 1B, C). In addition, under DF, TNIK depletion led to downregulation of hypercytokinemia/hyperchemokinemia (-log P-value >8, Fig 1B). Validation through western blotting and qRT-PCR (Fig 1D, E) confirmed that TNIK regulates FAK and STAT phosphorylation and IFN stimulated gene targets. Conclusions: Our study elucidates the unique role of TNIK in regulating FAK-STAT mediated IFN signaling and subsequently EC activation.

Overlapping risks for cancer and cardiovascular diseases (CVD), the two leading causes of mortality worldwide, suggest a shared biology between these diseases. The role of senescence in the development of cancer and CVD has been established. However, its role as the intersection between these diseases remains unclear. Senescence was originally characterized by an irreversible cell cycle arrest after a high number of divisions, namely replicative senescence (RS). However, it is becoming clear that senescence can also be instigated by cellular stress, so-called stress-induced premature senescence (SIPS). Telomere shortening is a hallmark of RS. The contribution of telomere DNA damage and subsequent DNA damage response/repair to SIPS has also been suggested. Although cellular senescence can mediate cell cycle arrest, senescent cells can also remain metabolically active and secrete cytokines, chemokines, growth factors, and reactive oxygen species (ROS), so-called senescence-associated secretory phenotype (SASP). The involvement of SASP in both cancer and CVD has been established. In patients with cancer or CVD, SASP is induced by various stressors including cancer treatments, pro-inflammatory cytokines, and ROS. Therefore, SASP can be the intersection between cancer and CVD. Importantly, the conventional concept of senescence as the mediator of cell cycle arrest has been challenged, as it was recently reported that chemotherapy-induced senescence can reprogram senescent cancer cells to acquire “stemness” (SAS: senescence-associated stemness). SAS allows senescent cancer cells to escape cell cycle arrest with strongly enhanced clonogenic growth capacity. SAS supports senescent cells to promote both cancer and CVD, particularly in highly stressful conditions such as cancer treatments, myocardial infarction, and heart failure. As therapeutic advances have increased overlapping risk factors for cancer and CVD, to further understand their interaction may provide better prevention, earlier detection, and safer treatment. Thus, it is critical to study the mechanisms by which these senescence pathways (SAS/SASP) are induced and regulated in both cancer and CVD.

Significance: Inflammasomes are cytosolic multi-protein complexes that mediate innate immune pathways. Inflammasomes activate inflammatory caspases and regulate inflammatory cytokines IL-1β and IL-...

Healthy kidney structure and environment rely on epithelial integrity and interactions between epithelial cells and other kidney cells. The Ser/Thr kinase 90 kDa ribosomal protein S6 kinase 1 (p90RSK) belongs to a protein family that regulates many cellular processes, including cell motility and survival. p90RSK is predominantly expressed in the kidney, but its possible role in chronic kidney disease (CKD) remains largely unknown. Here, we found that p90RSK expression is dramatically activated in a classic mouse obstructive chronic kidney disease model, largely in the interstitial FSP-1–positive fibroblasts. We generated FSP-1–specific p90RSK transgenic mouse (RSK-Tg) and discovered that these mice, after obstructive injury, display significantly increased fibrosis and enhanced tubular epithelial damage compared with their wt littermates (RSK-wt), indicating a role of p90RSK in fibroblast–epithelial communication. We established an in vitro fibroblast–epithelial coculture system with primary kidney fibroblasts from RSK-Tg and RSK-wt mice and found that RSK-Tg fibroblasts consistently produce excessive H(2)O(2) causing epithelial oxidative stress and inducing nuclear translocation of the signaling protein β-catenin. Epithelial accumulation of β-catenin, in turn, promoted epithelial apoptosis by activating the transcription factor forkhead box class O1 (FOXO1). Of note, blockade of reactive oxygen species (ROS) or β-catenin or FOXO1 activity abolished fibroblast p90RSK-mediated epithelial apoptosis. These results make it clear that p90RSK promotes kidney fibrosis by inducing fibroblast-mediated epithelial apoptosis through ROS-mediated activation of β-catenin/FOXO1 signaling pathway.

Background: The incidence of cardiovascular disease is higher in HIV-positive (HIV + ) patients than it is in the average population, and combination antiretroviral therapy (cART) is a recognized risk factor for cardiovascular disease. However, the molecular mechanisms that link cART and cardiovascular disease are currently unknown. Our study explores the role of the activation of p90RSK, a reactive oxygen species-sensitive kinase, in engendering senescent phenotype in macrophages and accelerating atherogenesis in patients undergoing cART. Methods: Peripheral whole blood from cART-treated HIV + individuals and nontreated HIV-negative individuals was treated with H 2 O 2 (200 µmol/L) for 4 minutes, and p90RSK activity in CD14 + monocytes was measured. Plaque formation in the carotids was also analyzed in these individuals. Macrophage senescence was determined by evaluating their efferocytotic ability, antioxidation-related molecule expression, telomere length, and inflammatory gene expression. The involvement of p90RSK-NRF2 signaling in cART-induced senescence was assessed by p90RSK-specific inhibitor (FMK-MEA) or dominant-negative p90RSK (DN-p90RSK) and NRF2 activator (NRF2A). Further, the severity of atherosclerosis was determined in myeloid cell-specific wild-type and DN-p90RSK transgenic mice. Results: Monocytes from HIV + patients exhibited higher levels of p90RSK activity and were also more sensitive to reactive oxygen species than monocytes from HIV-negative individuals. A multiple linear regression analysis involving cART, Reynolds cardiovascular risk score, and basal p90RSK activity revealed that cART and basal p90RSK activity were the 2 significant determinants of plaque formation. Many of the antiretroviral drugs individually activated p90RSK, which simultaneously triggered all components of the macrophage senescent phenotype. cART inhibited antioxidant response element reporter activity via ERK5 S496 phosphorylation. NRF2A reversed the H 2 O 2 -induced overactivation of p90RSK in cART-treated macrophages by countering the induction of senescent phenotype. Last, the data obtained from our gain- or loss-of-function mice conclusively showed the crucial role of p90RSK in inducing senescent phenotype in macrophages and atherogenesis. Conclusions: cART increased monocyte/macrophage sensitivity to reactive oxygen species- in HIV + individuals by suppressing NRF2-ARE activity via p90RSK-mediated ERK5 S496 phosphorylation, which coordinately elicited senescent phenotypes and proinflammatory responses. As such, our report underscores the importance of p90RSK regulation in monocytes/macrophages as a viable biomarker and therapeutic target for preventing cardiovascular disease, especially in HIV + patients treated with cART.

Previously, we reported that post-translational modifications (PTMs) of MAGI1, including S741 phosphorylation and K931 de-SUMOylation, both of which are regulated by p90RSK activation, lead to endothelial cell (EC) activation. However, roles for p90RSK and MAGI1-PTMs in regulating EC permeability remain unclear despite MAGI1 being a junctional molecule. Here, we show that thrombin (Thb)-induced EC permeability, detected by the electric cell-substrate impedance sensing (ECIS) based system, was decreased by overexpression of dominant negative p90RSK or a MAGI1-S741A phosphorylation mutant, but was accelerated by overexpression of p90RSK, siRNA-mediated knockdown of magi1, or the MAGI1-K931R SUMOylation mutant. MAGI1 depletion also increased the mRNA and protein expression of the large tumor suppressor kinases 1 and 2 (LATS1/2), which inhibited YAP/TAZ activity and increased EC permeability. Because the endothelial barrier is a critical mediator of tumor hypoxia, we also evaluated the role of p90RSK activation in tumor vessel leakiness by using a relatively low dose of the p90RSK specific inhibitor, FMK-MEA. FMK-MEA significantly inhibited tumor vessel leakiness at a dose that does not affect morphology and growth of tumor vessels in vivo. These results provide novel insights into crucial roles for p90RSK-mediated MAGI1 PTMs and the Hippo pathway in EC permeability, as well as p90RSK activation in tumor vessel leakiness.

Allogeneic bone marrow transplantation (BMT) is an effective therapy for hematological malignancies due to the graft-versus-leukemia (GVL) effect to eradicate tumors. However, its application is limited by the development of graft-versus-host disease (GVHD), a major complication of BMT. GVHD is evoked when T-cells in the donor grafts recognizealloantigen expressed by recipient cells and mount unwanted immunological attacks against recipient healthy tissues. Thus, traditional therapies are designed to suppress donor T-cell alloreactivity. However, these approaches substantially impair the GVL effect so that the recipient's survival is not improved. Understanding the effects of therapeutic approaches on BMT, GVL, and GVHD, is thus essential. Due to the antigen-presenting and cytokine-secreting capacities to stimulate donor T-cells, recipient dendritic cells (DCs) play a significant role in the induction of GVHD. Therefore, targeting recipient DCs becomes a potential approach for controlling GVHD. This work provides a description of a novel BMT platform to investigate how host DCs regulate GVH and GVL responses after transplantation. Also presented is an effective BMT model to study the biology of GVHD and GVL after transplantation.

Focal adhesion kinase (FAK) activation plays a crucial role in vascular diseases. In endothelial cells, FAK activation is involved in the activation of pro-inflammatory signaling and the progression of atherosclerosis. Disturbed flow (D-flow) induces endothelial activation and senescence, but the exact role of FAK in D-flow-induced endothelial activation and senescence remains unclear. The objective of this study is to investigate the role of FAK SUMOylation in D-flow-induced endothelial activation and senescence. The results showed that D-flow induced reactive oxygen species (ROS) production via NADPH oxidase activation and activated a redox-sensitive kinase p90RSK, leading to FAK activation by upregulating FAK K152 SUMOylation and the subsequent Vav2 phosphorylation, which in turn formed a positive feedback loop by upregulating ROS production. This feedback loop played a crucial role in regulating endothelial activation and senescence. D-flow-induced endothelial activation and senescence were significantly inhibited by mutating a FAK SUMOylation site lysine152 to arginine. Collectively, we concluded that FAK K152 SUMOylation plays a key role in D-flow-induced endothelial activation and senescence by forming a positive feedback loop through ROS production.

Numerous studies have revealed the critical role of premature senescence induced by various cancer treatment modalities in the pathogenesis of aging-related diseases. Senescence-associated secretory phenotype (SASP) can be induced by telomere dysfunction. Telomeric DNA damage response induced by some cancer treatments can persist for months, possibly accounting for long-term sequelae of cancer treatments. Telomeric DNA damage-induced mitochondrial dysfunction and increased reactive oxygen species production are hallmarks of premature senescence. Recently, we reported that the nucleus-mitochondria positive feedback loop formed by p90 ribosomal S6 kinase (p90RSK) and phosphorylation of S496 on ERK5 (a unique member of the mitogen-activated protein kinase family that is not only a kinase but also a transcriptional co-activator) were vital signaling events that played crucial roles in linking mitochondrial dysfunction, nuclear telomere dysfunction, persistent SASP induction, and atherosclerosis. In this review, we will discuss the role of NAD+ depletion in instigating SASP and its downstream signaling and regulatory mechanisms that lead to the premature onset of atherosclerotic cardiovascular diseases in cancer survivors.

The incidence of cardiovascular disease (CVD) is higher in cancer survivors than in the general population. Several cancer treatments are recognized as risk factors for CVD, but specific therapies are unavailable. Many cancer treatments activate shared signaling events, which reprogram myeloid cells (MCs) towards persistent senescence-associated secretory phenotype (SASP) and consequently CVD, but the exact mechanisms remain unclear. This study aimed to provide mechanistic insights and potential treatments by investigating how chemo-radiation can induce persistent SASP. We generated ERK5 S496A knock-in mice and determined SASP in myeloid cells (MCs) by evaluating their efferocytotic ability, antioxidation-related molecule expression, telomere length, and inflammatory gene expression. Candidate SASP inducers were identified by high-throughput screening, using the ERK5 transcriptional activity reporter cell system. Various chemotherapy agents and ionizing radiation (IR) up-regulated p90RSK-mediated ERK5 S496 phosphorylation. Doxorubicin and IR caused metabolic changes with nicotinamide adenine dinucleotide depletion and ensuing mitochondrial stunning (reversible mitochondria dysfunction without showing any cell death under ATP depletion) via p90RSK-ERK5 modulation and poly (ADP-ribose) polymerase (PARP) activation, which formed a nucleus-mitochondria positive feedback loop. This feedback loop reprogramed MCs to induce a sustained SASP state, and ultimately primed MCs to be more sensitive to reactive oxygen species. This priming was also detected in circulating monocytes from cancer patients after IR. When PARP activity was transiently inhibited at the time of IR, mitochondrial stunning, priming, macrophage infiltration, and coronary atherosclerosis were all eradicated. The p90RSK-ERK5 module plays a crucial role in SASP-mediated mitochondrial stunning via regulating PARP activation. Our data show for the first time that the nucleus-mitochondria positive feedback loop formed by p90RSK-ERK5 S496 phosphorylation-mediated PARP activation plays a crucial role of persistent SASP state, and also provide preclinical evidence supporting that transient inhibition of PARP activation only at the time of radiation therapy can prevent future CVD in cancer survivors., Graphical abstract Image 1, Highlights • High-throughput screening detects chemo-radiation as p90RSK-ERK5 modulator, which induces senescence-associated secretory phenotype (SASP). • Chemo-radiation instigates mitochondrial (mt) stunning (reversible mt dysfunction without showing any cell death under ATP depletion). • Mt stunning is provoked by p90RSK-ERK5 modulation and PARP activation, which forms a nucleus-mitochondria positive feedback loop. • This feedback loop reprogramed myeloid cells (MCs) to induce a sustained SASP state, and ultimately prime MCs to be more sensitive to reactive oxygen species. • When PARP activity is transiently inhibited at the time of IR, mitochondrial stunning, priming, macrophage infiltration, and coronary atherosclerosis are all eradicated.

The interplay among signaling events for endothelial cell (EC) senescence, apoptosis, and activation and how these pathological conditions promote atherosclerosis in the area exposed to disturbed flow (d-flow) in concert remain unclear. The aim of this study was to determine whether telomeric repeat-binding factor 2-interacting protein (TERF2IP), a member of the shelterin complex at the telomere, can regulate EC senescence, apoptosis, and activation simultaneously, and if so, by what molecular mechanisms. We found that d-flow induced p90RSK and TERF2IP interaction in a p90RSK kinase activity-dependent manner. An in vitro kinase assay revealed that p90RSK directly phosphorylated TERF2IP at the serine 205 (S205) residue, and d-flow increased TERF2IP S205 phosphorylation as well as EC senescence, apoptosis, and activation by activating p90RSK. TERF2IP phosphorylation was crucial for nuclear export of the TERF2IP-TRF2 complex, which led to EC activation by cytosolic TERF2IP-mediated NF-κB activation and also to senescence and apoptosis of ECs by depleting TRF2 from the nucleus. Lastly, using EC-specific TERF2IP-knockout (TERF2IP-KO) mice, we found that the depletion of TERF2IP inhibited d-flow-induced EC senescence, apoptosis, and activation, as well as atherosclerotic plaque formation. These findings demonstrate that TERF2IP is an important molecular switch that simultaneously accelerates EC senescence, apoptosis, and activation by S205 phosphorylation.

The possible association between the membrane-associated guanylate kinase with inverted domain structure-1 (MAGI1) and inflammation has been suggested, but the molecular mechanisms underlying this link, especially during atherogenesis, remain unclear. In endothelial cells (ECs) exposed to disturbed flow (d-flow), p90 ribosomal S6 kinase (p90RSK) bound to MAGI1, causing MAGI1-S741 phosphorylation and sentrin/SUMO-specific protease 2 T368 phosphorylation-mediated MAGI1-K931 deSUMOylation. MAGI1-S741 phosphorylation upregulated EC activation via activating Rap1. MAGI1-K931 deSUMOylation induced both nuclear translocation of p90RSK-MAGI1 and ATF-6-MAGI1 complexes, which accelerated EC activation and apoptosis, respectively. Microarray screening revealed key roles for MAGI1 in the endoplasmic reticulum (ER) stress response. In this context, MAGI1 associated with activating transcription factor 6 (ATF-6). MAGI1 expression was upregulated in ECs and macrophages found in atherosclerotic-prone regions of mouse aortas as well as in the colonic epithelia and ECs of patients with inflammatory bowel disease. Further, reduced MAGI1 expression in Magi1(–/+) mice inhibited d-flow–induced atherogenesis. In sum, EC activation and ER stress–mediated apoptosis are regulated in concert by two different types of MAGI1 posttranslational modifications, elucidating attractive drug targets for chronic inflammatory disease, particularly atherosclerosis.

Objective- Members of the microRNA (miR)-199a family, namely miR-199a-5p and miR-199a-3p, have been recently identified as potential regulators of cardiac homeostasis. Also, upregulation of miR-199a expression in cardiomyocytes was reported to influence endothelial cells. Whether miR-199a is expressed by endothelial cells and, if so, whether it directly regulates endothelial function remains unknown. We investigate the implication of miR-199a products on endothelial function by focusing on the NOS (nitric oxide synthase)/NO pathway. Approach and Results- Bovine aortic endothelial cells were transfected with specific miRNA inhibitors (locked-nucleic acids), and potential molecular targets identified with prediction algorithms were evaluated by Western blot or immunofluorescence. Ex vivo experiments were performed with mice treated with antagomiRs targeting miR-199a-3p or -5p. Isolated vessels and blood were used for electron paramagnetic resonance or myograph experiments. eNOS (endothelial NO synthase) activity (through phosphorylations Ser1177/Thr495) is increased by miR-199a-3p/-5p inhibition through an upregulation of the PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B) and calcineurin pathways. SOD1 (superoxide dismutase 1) and PRDX1 (peroxiredoxin 1) upregulation was also observed in locked-nucleic acid-treated cells. Moreover, miR-199a-5p controls angiogenesis and VEGFA (vascular endothelial growth factor A) production and upregulation of NO-dependent relaxation were observed in vessels from antagomiR-treated mice. This was correlated with increased circulated hemoglobin-NO levels and decreased superoxide production. Angiotensin infusion for 2 weeks also revealed an upregulation of miR-199a-3p/-5p in vascular tissues. Conclusions- Our study reveals that miR-199a-3p and miR-199a-5p participate in a redundant network of regulation of the NOS/NO pathway in the endothelium. We highlighted that inhibition of miR-199a-3p and -5p independently increases NO bioavailability by promoting eNOS activity and reducing its degradation, thereby supporting VEGF-induced endothelial tubulogenesis and modulating vessel contractile tone.

Ponatinib is a multi-targeted third generation tyrosine kinase inhibitor (TKI) used in the treatment of chronic myeloid leukemia (CML) patients harboring the Abelson (Abl)-breakpoint cluster region (Bcr) T315I mutation. In spite of having superb clinical efficacy, ponatinib triggers severe vascular adverse events (VAEs) that significantly limit its therapeutic potential. On vascular endothelial cells (ECs), ponatinib promotes EC dysfunction and apoptosis, and inhibits angiogenesis. Furthermore, ponatinib-mediated anti-angiogenic effect has been suggested to play a partial role in systemic and pulmonary hypertension via inhibition of vascular endothelial growth factor receptor 2 (VEGFR2). Even though ponatinib-associated VAEs are well documented, their etiology remains largely unknown, making it difficult to efficiently counteract treatment-related adversities. Therefore, a better understanding of the mechanisms by which ponatinib mediates VAEs is critical. In cultured human aortic ECs (HAECs) treated with ponatinib, we found an increase in nuclear factor NF-kB/p65 phosphorylation and NF-kB activity, inflammatory gene expression, cell permeability, and cell apoptosis. Mechanistically, ponatinib abolished extracellular signal-regulated kinase 5 (ERK5) transcriptional activity even under activation by its upstream kinase mitogen-activated protein kinase kinase 5α (CA-MEK5α). Ponatinib also diminished expression of ERK5 responsive genes such as Krüppel-like Factor 2/4 (klf2/4) and eNOS. Because ERK5 SUMOylation counteracts its transcriptional activity, we examined the effect of ponatinib on ERK5 SUMOylation, and found that ERK5 SUMOylation is increased by ponatinib. We also found that ponatibib-mediated increased inflammatory gene expression and decreased anti-inflammatory gene expression were reversed when ERK5 SUMOylation was inhibited endogenously or exogenously. Overall, we propose a novel mechanism by which ponatinib up-regulates endothelial ERK5 SUMOylation and shifts ECs to an inflammatory phenotype, disrupting vascular homeostasis.

Background: Adverse cardiovascular events are a leading nonmalignant cause of morbidity and mortality among cancer survivors who have been exposed to ionizing radiation (IR), but the exact mechanism of the cardiovascular complications induced by IR remains unclear. In this study we investigated the potential role of the p90RSK-ERK5 module in regulating IR-induced endothelial cell inflammation and apoptosis. Methods and Results: Whole body radiation of mice with 2 Gy γ-ray significantly increased endothelial VCAM-1 expression; especially in the disturbed flow area in vivo . In vitro studies showed that IR increased p90RSK activation as well as subsequent ERK5 S496 phosphorylation in cultured human endothelial cells (ECs). A specific p90RSK inhibitor, FMK-MEA, significantly inhibited both p90RSK activation and ERK5 S496 phosphorylation, but it had no effect on IR-induced ERK5 TEY motif phosphorylation, suggesting that p90RSK regulates ERK5 transcriptional activity, but not its kinase activity. In fact, we found that IR-induced NF-kB activation and VCAM-1 expression in ECs were significantly inhibited by the over-expression of S496 phosphorylation site mutant of ERK5 (ERK5 S496A) compared to overexpression of wild type ERK5. Furthermore, when ECs were exposed to IR, the number of annexin V positive cells increased, and overexpression of ERK5 S496A, but not wild type ERK5, significantly inhibited this increase. Conclusions: Our results demonstrate that IR augmented disturbed flow-induced VCAM-1 expression in vivo. Endothelial p90RSK was robustly activated by IR and subsequently up-regulated ERK5 S496 phosphorylation, inflammation, and apoptosis in ECs. The EC p90RSK-ERK5 signaling axis can be a good target to prevent cardiovascular events after radiation therapy in cancer patients.

Atherosclerosis is a multifactorial disease mainly caused by endothelial cell (EC) dysfunction resulting from EC senescence. Both EC inflammation and senescence are increased by disturbed flow (d-flow) but the exact mechanism is still unknown. The potential role of TERF2IP in regulating inflammation has been reported, but it has been controversial, especially in ECs. We found that d-flow-induced NF-kB activation was significantly inhibited by the depletion of TERF2IP, but TNF-induced NF-kB activation under laminar flow (l-flow) was not inhibited by TERF2IP depletion. TERF2IP S205 phosphorylation was increased by d-flow, but not by s-flow. This TERF2IP S205 phosphorylation was crucial for d-flow-induced TERF2IP nuclear export, which also caused nuclear export of its binding partner TERF2 in a piggy-back manner. Both the depletion of TERF2IP (TERF2IP siRNA) and overexpression of TERF2IP S205A mutant inhibited d-flow-induced TERF2 nuclear export as well as subsequent EC senescence. In addition, we found the key role of p90RSK activation in regulating EC inflammation and senescence via TERF2IP S205 phosphorylation. To determine the role of TERF2IP and TERF2 cellular localization in vivo, we performed in vivo en face immunostaining of mouse aortic arch in EC specific TERF2IP knock out (EC-TERF2IP-KO) and control mice using anti-TERF2IP or TEFR2 and anti-VE-cadherin antibodies. In control mice TERF2IP expression was very low in the l-flow area. In contrast we found a significant increase of TERF2IP expression, especially in the extra-nuclear region of ECs in the d-flow area. More nuclear localization of TERF2 was observed in EC-TERF2IP-KO mice than those in wild type, which supports our finding in vitro. Significant decreases of VCAM-1 expression and apoptosis were found in the d-flow area in EC-TERF2IP-KO mice compared to control mice. Lastly, we found a significant decrease in d-flow-induced atherosclerotic plaque formation after partial carotid ligation in EC-TERF2IP-KO mice crossed with Ldlr-/- mice compared to control Ldlr-/- mice. These data suggest the key role of nuclear export of TERF2IP in up-regulating EC inflammation and senescence via p90RSK-mediated TERF2IP S205 phosphorylation.

Increased cardiovascular (CV) events in HIV patients and cancer survivors and the fact that combination antiretroviral therapy (cART) and chemotherapy induce similar unwanted CV effects are becoming evident, but the reason for this is unclear. In this study, we examined the role of p90RSK in the CV toxicity of cART and anti-cancer drugs. The level of p90RSK activation by H2O2 was higher in peripheral monocytes from cART-treated patients than in those from untreated patients. Multiple linear regression analysis involving HIV+/-, Reynolds CV risk score, and basal p90RSK activation revealed HIV+/- and basal p90RSK activation to be strong determinants for plaque formation when adjusted for other independent variables. In murine macrophages most of the cART and several chemotherapy agents activated p90RSK and reduced antioxidant molecule expression and telomere (TL) lengths. p90RSK-mediated ERK5 S496 phosphorylation inhibited transcriptional activity of ERK5 and NRF2, decreasing efferocytosis, antioxidant production and TL lengths. NRF2 activator normalized cART-induced sensitization of p90RSK to H2O2. Lastly, we generated myeloid cells-specific wild type (WT) and dominant negative (DN) p90RSK transgenic mice, and ERK5 S496A knock-in mice, crossed with Ldlr-/- mice or treated with a single injection of adeno-associated virus vector (AAV) encoding a gain-of-function mutant of PCSK9 and fed a high fat diet. Our animal studies showed the crucial role of p90RSK-mediated ERK5 S496 phosphorylation in suppressing effecrocytosis and antioxidant production, and up-regulating senescence and inflammation-related molecules expression, leading to atherogenesis. Our results taken together show that p90RSK is activated by anti-HIV and anti-cancer drugs, and this activation sensitizes the monocyte/macrophages to the secondary oxidative insult by reducing NRF2 transcriptional activity and TL length. The p90RSK activation also reduces macrophage efferocytosis and antioxidant capacity, and increases inflammation and senescence via up-regulating ERK5 S496 phosphorylation, thereby accelerating atherosclerosis. Monocyte/macrophage p90RSK-ERK5 S496 phosphorylation could be a good target to prevent drugs-induced CV diseases.

Upregulation of both inflammation and senescence (Sen) of endothelial cells (ECs) in the disturbed flow area within the aortic arch is well established, but the exact mechanisms and the relationship between inflammation and senescence remain unclear. TERF2IP is involved in regulation of DNA double strand break (DSB) repair of telomeres (TLs) as a component of the shelterin complex and in IκB kinase (IKK)-NF-kB signaling in the cytosol. TERF2IP and TERF2 form a stable heterodimer to protect the duplex region of TLs. Recent studies showed that TERF2IP or TERF2 deficiency caused TL shortening in mice. We studied how TERF2IP SUMOylation is regulated in ECs and what role it may play in EC inflammation and Sen. We found that disturbed flow (d-flow) activated p90RSK and increased TERF2IP S205 phosphorylation and subsequently K240 SUMOylation. Overexpression of dominant negative p90RSK inhibited d-flow-induced TERF2IP S205 phosphorylation and K240 SUMOylation, and also inhibited EC inflammation and Sen provoked by d-flow. TERF2IP S205 phosphorylation induced TERF2IP nuclear export, which then caused EC inflammation and Sen. In contrast, TERF2IP K240 SUMOylation had no effect on TERF2IP nuclear export, and the TERF2IP K240R SUMOylation site mutant failed to inhibit d-flow-induced NF-kB activation. Interestingly, this point mutation inhibited d-flow-induced Sen with reduced d-flow-induced TL shortening, 8-OHdG level, and apoptosis. Overexpression of a de-SUMOylation enzyme SENP2 and SENP2 T368 mutant significantly inhibited d-flow-induced TERF2IP SUMOylation, suggesting that SENP2 regulates nuclear TERF2IP SUMOylation. Lastly, EC Sen increased when SENP2 was specifically knocked out in ECs in mice, suggesting that TERF2IP K240 SUMOylation may play a role in d-flow-induced EC Sen. These data suggest that TERF2IP post-translational modifications play roles in regulating EC inflammation and Sen, which are differentially regulated by S205 phosphorylation and K240 SUMOylation. TERF2IP K240R knock-in mice will be used to determine the role of TERF2IP K240 SUMOylation in d-flow-induced atherogenesis. We suggest that TERF2IP SUMOylation promotes TL dysfunction, but it does not interfere with TERF2IP-mediated IKK-NF-kB activation in the cytosol.