Evaluating the Molecular Properties and Function of ANKHD1, and Its Role in Cancer.

Ankyrin repeat and single KH domain-containing protein 1 (ANKHD1) is a large, scaffolding protein composed of two stretches of ankyrin repeat domains that mediate protein-protein interactions and a KH domain that mediates RNA or single-stranded DNA binding. ANKHD1 interacts with proteins in several crucial signalling pathways, including receptor tyrosine kinase, JAK/STAT, mechanosensitive Hippo (YAP/TAZ), and p21. Studies into the role of ANKHD1 in cancer cell lines demonstrate a crucial role in driving uncontrolled cellular proliferation and growth, enhanced tumorigenicity, cell cycle progression through the S phase, and increased epithelial-to-mesenchymal transition. Furthermore, at a clinical level, the increased expression of ANKHD1 has been associated with greater tumour infiltration, increased metastasis, and larger tumours. Elevated ANKHD1 resulted in poorer prognosis, more aggressive growth, and a decrease in patient survival in numerous cancer types. This review aims to gather the current knowledge about ANKHD1 and explore its molecular properties and functions, focusing on the protein's role in cancer at both a cellular and clinical level.

ß1 integrin is a sensor of blood flow direction.

Endothelial cell (EC) sensing of fluid shear stress direction is a critical determinant of vascular health and disease. Unidirectional flow induces EC alignment and vascular homeostasis, whereas bidirectional flow has pathophysiological effects. ECs express several mechanoreceptors that respond to flow, but the mechanism for sensing shear stress direction is poorly understood. We determined, by using in vitro flow systems and magnetic tweezers, that ß1 integrin is a key sensor of force direction because it is activated by unidirectional, but not bidirectional, shearing forces. ß1 integrin activation by unidirectional force was amplified in ECs that were pre-sheared in the same direction, indicating that alignment and ß1 integrin activity has a feedforward interaction, which is a hallmark of system stability. En face staining and EC-specific genetic deletion studies in the murine aorta revealed that ß1 integrin is activated and is essential for EC alignment at sites of unidirectional flow but is not activated at sites of bidirectional flow. In summary, ß1 integrin sensing of unidirectional force is a key mechanism for decoding blood flow mechanics to promote vascular homeostasis.This article has an associated First Person interview with the first author of the paper.

A genome-wide RNAi screen identifies MASK as a positive regulator of cytokine receptor stability.

Cytokine receptors often act via the Janus kinase and signal transducer and activator of transcription (JAK/STAT) pathway to form a signalling cascade that is essential for processes such as haematopoiesis, immune responses and tissue homeostasis. In order to transduce ligand activation, cytokine receptors must dimerise. However, mechanisms regulating their dimerisation are poorly understood. In order to better understand the processes regulating cytokine receptor levels, and their activity and dimerisation, we analysed the highly conserved JAK/STAT pathway in Drosophila, which acts via a single receptor, known as Domeless. We performed a genome-wide RNAi screen in Drosophila cells, identifying MASK as a positive regulator of Domeless dimerisation and protein levels. We show that MASK is able to regulate receptor levels and JAK/STAT signalling both in vitro and in vivo We also show that its human homologue, ANKHD1, is also able to regulate JAK/STAT signalling and the levels of a subset of pathway receptors in human cells. Taken together, our results identify MASK as a novel regulator of cytokine receptor levels, and suggest functional conservation, which may have implications for human health.This article has an associated First Person interview with the first author of the paper.

The Controversial Role of Fibrosis in Autosomal Dominant Polycystic Kidney Disease.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is characterized by the progressive growth of cysts but it is also accompanied by diffuse tissue scarring or fibrosis. A number of recent studies have been published in this area, yet the role of fibrosis in ADPKD remains controversial. Here, we will discuss the stages of fibrosis progression in ADPKD, and how these compare with other common kidney diseases. We will also provide a detailed overview of some key mechanistic pathways to fibrosis in the polycystic kidney. Specifically, the role of the 'chronic hypoxia hypothesis', persistent inflammation, Transforming Growth Factor beta (TGFß), Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT) and microRNAs will be examined. Evidence for and against a pathogenic role of extracellular matrix during ADPKD disease progression will be provided.

Ankyrin repeat and single KH domain 1 (ANKHD1) drives renal cancer cell proliferation via binding to and altering a subset of miRNAs.

Clear cell renal cell carcinoma (ccRCC) represents the most common kidney cancer worldwide. Increased cell proliferation associated with abnormal microRNA (miRNA) regulation are hallmarks of carcinogenesis. Ankyrin repeat and single KH domain 1 (ANKHD1) is a highly conserved protein found to interact with core cancer pathways in Drosophila; however, its involvement in RCC is completely unexplored. Quantitative PCR studies coupled with large-scale genomics data sets demonstrated that ANKHD1 is significantly up-regulated in kidneys of RCC patients when compared with healthy controls. Cell cycle analysis revealed that ANKHD1 is an essential factor for RCC cell division. To understand the molecular mechanism(s) utilized by ANKHD1 to drive proliferation, we performed bioinformatics analyses that revealed that ANKHD1 contains a putative miRNA-binding motif. We screened 48 miRNAs with tumor-enhancing or -suppressing activities and found that ANKHD1 binds to and regulates three tumor-suppressing miRNAs (i.e. miR-29a, miR-205, and miR-196a). RNA-immunoprecipitation assays demonstrated that ANKHD1 physically interacts with its target miRNAs via a single K-homology domain, located in the C terminus of the protein. Functionally, we discovered that ANKHD1 positively drives ccRCC cell mitosis via binding to and suppressing mainly miR-29a and to a lesser degree via miR-196a/205, leading to up-regulation in proliferative genes such as CCDN1. Collectively, these data identify ANKHD1 as a new regulator of ccRCC proliferation via specific miRNA interactions.

Mechanical Activation of Hypoxia-Inducible Factor 1α Drives Endothelial Dysfunction at Atheroprone Sites.

OBJECTIVE: Atherosclerosis develops near branches and bends of arteries that are exposed to low shear stress (mechanical drag). These sites are characterized by excessive endothelial cell (EC) proliferation and inflammation that promote lesion initiation. The transcription factor HIF1α (hypoxia-inducible factor 1α) is canonically activated by hypoxia and has a role in plaque neovascularization. We studied the influence of shear stress on HIF1α activation and the contribution of this noncanonical pathway to lesion initiation. APPROACH AND RESULTS: Quantitative polymerase chain reaction and en face staining revealed that HIF1α was expressed preferentially at low shear stress regions of porcine and murine arteries. Low shear stress induced HIF1α in cultured EC in the presence of atmospheric oxygen. The mechanism involves the transcription factor nuclear factor-κB that induced HIF1α transcripts and induction of the deubiquitinating enzyme Cezanne that stabilized HIF1α protein. Gene silencing revealed that HIF1α enhanced proliferation and inflammatory activation in EC exposed to low shear stress via induction of glycolysis enzymes. We validated this observation by imposing low shear stress in murine carotid arteries (partial ligation) that upregulated the expression of HIF1α, glycolysis enzymes, and inflammatory genes and enhanced EC proliferation. EC-specific genetic deletion of HIF1α in hypercholesterolemic apolipoprotein E-defecient mice reduced inflammation and endothelial proliferation in partially ligated arteries, indicating that HIF1α drives inflammation and vascular dysfunction at low shear stress regions. CONCLUSIONS: Mechanical low shear stress activates HIF1α at atheroprone regions of arteries via nuclear factor-κB and Cezanne. HIF1α promotes atherosclerosis initiation at these sites by inducing excessive EC proliferation and inflammation via the induction of glycolysis enzymes.

STAT5 drives abnormal proliferation in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) leads to renal failure. The hallmark of ADPKD is increased epithelial proliferation, which has been proposed to be due to atypical signaling including abnormal JAK-STAT activity. However, the relative contribution of JAK-STAT family members in promoting proliferation in ADPKD is unknown. Here, we present siRNA JAK-STAT-focused screens discovering a previously unknown proliferative role for multiple JAK-STAT components (including STAT1, STAT2, STAT4, STAT5a, and STAT5b). Amongst these, we selected to study the growth hormone/growth hormone receptor/STAT5-axis because of its known role as a regulator of growth in nonrenal tissues. Loss of STAT5 function, facilitated by pharmacological inhibition or siRNAs, significantly reduced proliferation with an associated reduction in cyst growth in vitro. To study whether STAT5 is abnormally activated in vivo, we analyzed its expression using two independent mouse models of ADPKD. STAT5 was nuclear, thus activated, in renal epithelial cyst lining cells in both models. To test whether forced activation of STAT5 can modulate proliferation of renal cells in vivo, irrespective of the Pkd1 status, we overexpressed growth hormone. These mice showed increased STAT5 activity in renal epithelial cells, which correlated with de novo expression of cyclin D1, a STAT5 target gene. Chromatin immunoprecipitation experiments revealed that STAT5 transcriptionally activated cyclin D1 in a growth hormone-dependent fashion, thus providing a mechanism into how STAT5 enhances proliferation. Finally, we provide evidence of elevated serum growth hormone in Pkd1 mutant mice. Thus, the growth hormone/STAT5 signaling axis is a novel therapeutic target in ADPKD.

Cezanne regulates inflammatory responses to hypoxia in endothelial cells by targeting TRAF6 for deubiquitination.

RATIONALE: Hypoxia followed by reoxygenation promotes inflammation by activating nuclear factor κB transcription factors in endothelial cells (ECs). This process involves modification of the signaling intermediary tumor necrosis factor receptor-associated factor 6 with polyubiquitin chains. Thus, cellular mechanisms that suppress tumor necrosis factor receptor-associated factor 6 ubiquitination are potential therapeutic targets to reduce inflammation in hypoxic tissues. OBJECTIVE: In this study, we tested the hypothesis that endothelial activation in response to hypoxia-reoxygenation can be influenced by Cezanne, a deubiquitinating enzyme that cleaves ubiquitin from specific modified proteins. METHODS AND RESULTS: Studies of cultured ECs demonstrated that hypoxia (1% oxygen) induced Cezanne via p38 mitogen-activated protein kinase-dependent transcriptional and post-transcriptional mechanisms. Hypoxia-reoxygenation had minimal effects on proinflammatory signaling in unmanipulated ECs but significantly enhanced Lys63 polyubiquitination of tumor necrosis factor receptor-associated factor 6, activation of nuclear factor κB, and expression of inflammatory genes after silencing of Cezanne. Thus, although hypoxia primed cells for inflammatory activation, it simultaneously induced Cezanne, which impeded signaling to nuclear factor κB by suppressing tumor necrosis factor receptor-associated factor 6 ubiquitination. Similarly, ischemia induced Cezanne in the murine kidney in vascular ECs, glomerular ECs, podocytes, and epithelial cells, and genetic deletion of Cezanne enhanced renal inflammation and injury in murine kidneys exposed to ischemia followed by reperfusion. CONCLUSIONS: We conclude that inflammatory responses to ischemia are controlled by a balance between ubiquitination and deubiquitination, and that Cezanne is a key regulator of this process. Our observations have important implications for therapeutic targeting of inflammation and injury during ischemia-reperfusion.

Investigation of Perception of Quality of Life and Psychological Burden of Patients Undergoing Hemodialysis-Quality of Life of Hemodialysis Patients.

Chronic kidney disease (CKD) has a significant impact on the life of patients undergoing chronic periodic hemodialysis. It negatively affects their social, economic and family status, and particularly their psychological well-being. The aim of this study was to investigate the perception of the quality of life (QoL) and psychological burden of patients undergoing hemodialysis. A cross-sectional study was conducted with 63 patients. Τhe majority were men (63.5%), and the mean age of the patients was 66.7 years (±12.9) with 61.9% aged 65-89 years. Data collection was performed in 2021 using the Hospital Anxiety and Depression Scale (HADS) and the Kidney Disease and Quality of Life-Short Form (KDQOL-SF™) research tools, and their relationships were assessed using parametric and non-parametric methods. Moderate to mild levels of Anxiety and Depression were found. Physical and Mental Composite Scores were mild to moderate, with the Mental Composite Score being significantly higher (p < 0.05). Anxiety and Depression were significantly correlated with lower QoL (p < 0.05), while a higher educational level was correlated with lower Depression Symptom Levels and higher QoL for Disease Symptoms, Disease Effects, Physical Functioning, Vitality and Overall Health (p < 0.05). A higher number of years of hemodialysis was correlated with lower levels of Anxiety and higher levels of Quality of Sleep (p < 0.05). Ease of Access to the Hemodialysis Unit was correlated with lower levels of Social Support (p < 0.05). The highest Mental Composite Scores were also correlated with a higher level of education, with patients living in urban areas, and with a higher monthly income (p < 0.05). Patients with moderate or severe levels of Anxiety and Depression had a lower QoL in the Physical and Mental Composite Scores, indicating their dependence on the appropriate medical, nursing and social environment in order to attain higher levels of well-being, leading to the improvement of patients' health. This study was not registered.

Lessons from microRNA biology: Top key cellular drivers of Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: Numerous microRNAs (miRs), small RNAs targeting several pathways, have been implicated in the development of Autosomal Dominant Polycystic Kidney Disease (ADPKD), which is the most common genetic cause of Chronic Kidney Disease. The hallmark of ADPKD is tissue overgrowth and hyperproliferation, eventually leading to kidney failure. SCOPE OF THE REVIEW: Many miRs are dysregulated in disease, yet the intracellular pathways regulated by these are less well described in ADPKD. Here, I summarise all the differentially expressed miRs and highlight the top miR-regulated cellular driver of ADPKD. MAJOR CONCLUSIONS: Literature review has identified 35 abnormally expressed miRs in ADPKD. By performing bioinformatics analysis of their target genes I present 10 key intracellular pathways that drive ADPKD progression. The top key drivers are divided into three main areas: (i) hyperproliferation and the role of JAK/STAT and PI3K pathways (ii) DNA damage and (iii) inflammation and NFκB. GENERAL SIGNIFICANCE: The description of the 10 top cellular drivers of ADPKD, derived by analysis of miR signatures, is of paramount importance in better understanding the key processes resulting in pathophysiological changes that underlie disease.

Quality of Life and Psychological Burden of Parents of Children, Adolescents, and Young Adults with Type 1 Diabetes: A Cross-Sectional Study during the Lockdown Period of COVID-19.

The current study aimed to investigate how parents of children, adolescents, and young adults with DM1 perceived quality of life and psychological burden during the lockdown period of COVID-19. A cross-sectional study was carried out on 110 parents in Greece in spring 2021. Perceived quality of life was measured using the Parent Diabetes Distress Scale, and psychological burden was measured using the Spielberger State/Trait Anxiety Inventory, and both were assessed with correlational analysis. Overall, 79.1% of the parents were females ,while the mean age of all was 44.4 years (±5.8). PDDS was found to be moderate (mean 2.42 ± 0.76): 63.6% of respondents had moderate/high distress. The highest mean score was for Teen Management Distress and the lowest for Healthcare Team (3.02 vs. 1.49, p < 0.001). STAI was found to be moderate to high, with a higher mean score for state versus trait anxiety (49.8 vs. 48.0, p = 0.006). Increased distress or poorer parents' quality of life was related with the highest number of hyperglycemic episodes (ß = 0.25, p = 0.002), the fewest hypoglycemic episodes (ß = −0.18, p = 0.024), and the highest parental trait anxiety (ß = 0.04, p < 0.001). Parents were found with moderate-to-high distress and anxiety, and their correlation also shows that there is an urgent need for suitable education of parents on managing the disease to improve quality of life and eliminate health risks to all involved.

JAG1-NOTCH4 mechanosensing drives atherosclerosis.

Endothelial cell (EC) sensing of disturbed blood flow triggers atherosclerosis, a disease of arteries that causes heart attack and stroke, through poorly defined mechanisms. The Notch pathway plays a central role in blood vessel growth and homeostasis, but its potential role in sensing of disturbed flow has not been previously studied. Here, we show using porcine and murine arteries and cultured human coronary artery EC that disturbed flow activates the JAG1-NOTCH4 signaling pathway. Light-sheet imaging revealed enrichment of JAG1 and NOTCH4 in EC of atherosclerotic plaques, and EC-specific genetic deletion of Jag1 (Jag1ECKO) demonstrated that Jag1 promotes atherosclerosis at sites of disturbed flow. Mechanistically, single-cell RNA sequencing in Jag1ECKO mice demonstrated that Jag1 suppresses subsets of ECs that proliferate and migrate. We conclude that JAG1-NOTCH4 sensing of disturbed flow enhances atherosclerosis susceptibility by regulating EC heterogeneity and that therapeutic targeting of this pathway may treat atherosclerosis.

Epithelial-mesenchymal transition in renal fibrosis - evidence for and against.

Epithelial to mesenchymal transition (EMT) is a well established biological process in metazoan embryological development. Over the past 15 years, investigators have sought to establish whether EMT also occurs in renal epithelial cells, following kidney injury, and to show that the mesenchymal cells formed could give rise to myofibroblasts which populate the renal interstitium, causing fibrosis within it. There is no doubt that proximal tubular epithelial cells (PTECs) can undergo EMT in vitro in response to TGFß-1 and other inflammatory stimuli. Moreover, the results of experiments with animal models of renal fibrosis and examination of biopsies from patients with chronic kidney disease have lent support to the hypothesis that EMT occurs in vivo. This review discusses some of the key evidence underlying that idea and summarises recent advances in understanding the molecular mechanism underlying the process. Early experiments using mice which were genetically engineered to mark PTECs with the LacZ gene to trace their fate following kidney injury provided evidence supporting the occurrence of EMT. Recently, however, cell lineage tracking experiments using the red fluorescent protein (RFP) as a high-resolution marker for cells of renal epithelial origin did not replicate this result; the interstitial space following kidney injury was devoid of RFP expressing cells, leading the investigators to reject the renal EMT hypothesis.

In position 7 L- and D-Tic-substituted oxytocin and deamino oxytocin: NMR study and conformational insights.

Incorporation of L- or D-Tic into position 7 of oxytocin (OT) and its deamino analogue ([Mpa(1)]OT) resulted in four analogues, [L-Tic(7)]OT (1), [D-Tic(7)]OT (2), [Mpa(1),L-Tic(7)]OT (3) and [Mpa(1),D-Tic(7)]OT (4). Their biological properties were described by Fragiadaki et al. (Eur J Med Chem 42:799-806, 2007). Their NMR study (NOESY, TOCSY, (1)H-(13)C HSQC spectra) is presented here. Analogues 1, 3 and 4 showed partial agonistic activity, analogue 2 was pure antagonist, suggesting that a cis conformation between residues 6 and 7 of the molecule does not result in antagonistic activity. However, the reduction in agonistic activity of analogues 1, 3 and 4 in comparison to oxytocin is consistent with the reduction of the trans conformation form. Binding affinity for the human oxytocin receptor with IC(50) value of 130, 730, 103, and 380 nM for peptides 1, 2, 3, and 4, respectively, showed lower affinity in the case of D analogues. Deamination slightly increased the affinity. The existence of both cis and trans configurations of the Cys(6)-D-Tic(7) bond is supported by observation of two sets of cross-peaks for (1)H and (13)C nuclei for most of the residues of the peptide not only in NOESY and TOCSY but also in (1)H-(13)C HSQC spectra. The MS and HPLC indicate the presence of a single molecule/peptide, and NMR data thus suggest that this second set of peaks is due to the cis conformation.

Diabetic atherosclerosis: is there a role for the hypoxia-inducible factors?

Atherosclerosis is a major cause of mortality worldwide and is driven by multiple risk factors, including diabetes. Diabetes is associated with either an insulin deficiency in its juvenile form or with insulin resistance and obesity in Type 2 diabetes mellitus, and the latter is clustered with other comorbidities to define the metabolic syndrome. Diabetes and metabolic syndrome are complex pathologies and are associated with cardiovascular risk via vascular inflammation and other mechanisms. Several transcription factors are activated upon diabetes-driven endothelial dysfunction and drive the progression of atherosclerosis. In particular, the hypoxia-inducible factor (HIF) transcription factor family is a master regulator of endothelial biology and is raising interest in the field of atherosclerosis. In this review, we will present an overview of studies contributing to the understanding of diabetes-driven atherosclerosis, integrating the role of HIF in this disease with the knowledge of its functions in metabolic syndrome and diabetic scenario.

Endothelial responses to shear stress in atherosclerosis: a novel role for developmental genes.

Flowing blood generates a frictional force called shear stress that has major effects on vascular function. Branches and bends of arteries are exposed to complex blood flow patterns that exert low or low oscillatory shear stress, a mechanical environment that promotes vascular dysfunction and atherosclerosis. Conversely, physiologically high shear stress is protective. Endothelial cells are critical sensors of shear stress but the mechanisms by which they decode complex shear stress environments to regulate physiological and pathophysiological responses remain incompletely understood. Several laboratories have advanced this field by integrating specialized shear-stress models with systems biology approaches, including transcriptome, methylome and proteome profiling and functional screening platforms, for unbiased identification of novel mechanosensitive signalling pathways in arteries. In this Review, we describe these studies, which reveal that shear stress regulates diverse processes and demonstrate that multiple pathways classically known to be involved in embryonic development, such as BMP-TGFß, WNT, Notch, HIF1α, TWIST1 and HOX family genes, are regulated by shear stress in arteries in adults. We propose that mechanical activation of these pathways evolved to orchestrate vascular development but also drives atherosclerosis in low shear stress regions of adult arteries.

Endothelial dysfunction in COVID-19: a position paper of the ESC Working Group for Atherosclerosis and Vascular Biology, and the ESC Council of Basic Cardiovascular Science.

The COVID-19 pandemic is an unprecedented healthcare emergency causing mortality and illness across the world. Although primarily affecting the lungs, the SARS-CoV-2 virus also affects the cardiovascular system. In addition to cardiac effects, e.g. myocarditis, arrhythmias, and myocardial damage, the vasculature is affected in COVID-19, both directly by the SARS-CoV-2 virus, and indirectly as a result of a systemic inflammatory cytokine storm. This includes the role of the vascular endothelium in the recruitment of inflammatory leucocytes where they contribute to tissue damage and cytokine release, which are key drivers of acute respiratory distress syndrome (ARDS), in disseminated intravascular coagulation, and cardiovascular complications in COVID-19. There is also evidence linking endothelial cells (ECs) to SARS-CoV-2 infection including: (i) the expression and function of its receptor angiotensin-converting enzyme 2 (ACE2) in the vasculature; (ii) the prevalence of a Kawasaki disease-like syndrome (vasculitis) in COVID-19; and (iii) evidence of EC infection with SARS-CoV-2 in patients with fatal COVID-19. Here, the Working Group on Atherosclerosis and Vascular Biology together with the Council of Basic Cardiovascular Science of the European Society of Cardiology provide a Position Statement on the importance of the endothelium in the underlying pathophysiology behind the clinical presentation in COVID-19 and identify key questions for future research to address. We propose that endothelial biomarkers and tests of function (e.g. flow-mediated dilatation) should be evaluated for their usefulness in the risk stratification of COVID-19 patients. A better understanding of the effects of SARS-CoV-2 on endothelial biology in both the micro- and macrovasculature is required, and endothelial function testing should be considered in the follow-up of convalescent COVID-19 patients for early detection of long-term cardiovascular complications.

Homeobox B9 integrates bone morphogenic protein 4 with inflammation at atheroprone sites.

AIMS: Atherosclerosis develops near branches and bends of arteries that are exposed to disturbed blood flow which exerts low wall shear stress (WSS). These mechanical conditions alter endothelial cells (EC) by priming them for inflammation and by inducing turnover. Homeobox (Hox) genes are developmental genes involved in the patterning of embryos along their anterior-posterior and proximal-distal axes. Here we identified Hox genes that are regulated by WSS and investigated their functions in adult arteries. METHODS AND RESULTS: EC were isolated from inner (low WSS) and outer (high WSS) regions of the porcine aorta and the expression of Hox genes was analysed by quantitative real-time PCR. Several Hox genes (HoxA10, HoxB4, HoxB7, HoxB9, HoxD8, HoxD9) were significantly enriched at the low WSS compared to the high WSS region. Similarly, studies of cultured human umbilical vein EC (HUVEC) or porcine aortic EC revealed that the expression of multiple Hox genes (HoxA10, HoxB9, HoxD8, HoxD9) was enhanced under low (4 dyn/cm2) compared to high (13 dyn/cm2) WSS conditions. Gene silencing studies identified Hox genes (HoxB9, HoxD8, HoxD9) that are positive regulators of inflammatory molecule expression in EC exposed to low WSS, and others (HoxB9, HoxB7, HoxB4) that regulated EC turnover. We subsequently focused on HoxB9 because it was strongly up-regulated by low WSS and, uniquely, was a driver of both inflammation and proliferation. At a mechanistic level, we demonstrate using cultured EC and murine models that bone morphogenic protein 4 (BMP4) is an upstream regulator of HoxB9 which elicits inflammation via induction of numerous inflammatory mediators including TNF and downstream NF-κB activation. Moreover, the BMP4-HoxB9-TNF pathway was potentiated by hypercholesterolaemic conditions. CONCLUSIONS: Low WSS induces multiple Hox genes that control the activation state and turnover of EC. Notably, low WSS activates a BMP4-HoxB9-TNF signalling pathway to initiate focal arterial inflammation, thereby demonstrating integration of the BMP and Hox systems in vascular pathophysiology.