Mesenchymal stem cells induce resistance to chemotherapy through the release of platinum-induced fatty acids

The development of resistance to chemotherapy is a major obstacle for lasting effective treatment of cancer. Here, we demonstrate that endogenous mesenchymal stem cells (MSCs) become activated during treatment with platinum analogs and secrete factors that protect tumor cells against a range of chemotherapeutics. Through a metabolomics approach, we identified two distinct platinum-induced polyunsaturated fatty acids (PIFAs), 12-oxo-5,8,10-heptadecatrienoic acid (KHT) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)), that in minute quantities induce resistance to a broad spectrum of chemotherapeutic agents. Interestingly, blocking central enzymes involved in the production of these PIFAs (cyclooxygenase-1 and thromboxane synthase) prevents MSC-induced resistance. Our findings show that MSCs are potent mediators of resistance to chemotherapy and reveal targets to enhance chemotherapy efficacy in patients.

Adipose tissue-resident immune cells: key players in immunometabolism

Adipose tissue (AT) plays a pivotal role in whole-body lipid and glucose homeostasis. AT exerts metabolic control through various immunological mechanisms that instigated a new research field termed immunometabolism. Here, we review AT-resident immune cells and their role as key players in immunometabolism. In lean subjects, AT-resident immune cells have housekeeping functions ranging from apoptotic cell clearance to extracellular matrix remodeling and angiogenesis. However, obesity provides bacterial and metabolic danger signals that mimic bacterial infection, and drives a shift in immune-cell phenotypes and numbers, classified as a prototypic T helper 1 (Th1) inflammatory response. The resulting AT inflammation and insulin resistance link obesity to its metabolic sequel, and suggests that targeted immunomodulatory interventions may be beneficial for obese patients.

Natural killer T cells in adipose tissue prevent insulin resistance

Lipid overload and adipocyte dysfunction are key to the development of insulin resistance and can be induced by a high-fat diet. CD1d-restricted invariant natural killer T (iNKT) cells have been proposed as mediators between lipid overload and insulin resistance, but recent studies found decreased iNKT cell numbers and marginal effects of iNKT cell depletion on insulin resistance under high-fat diet conditions. Here, we focused on the role of iNKT cells under normal conditions. We showed that iNKT cell-deficient mice on a low-fat diet, considered a normal diet for mice, displayed a distinctive insulin resistance phenotype without overt adipose tissue inflammation. Insulin resistance was characterized by adipocyte dysfunction, including adipocyte hypertrophy, increased leptin, and decreased adiponectin levels. The lack of liver abnormalities in CD1d-null mice together with the enrichment of CD1d-restricted iNKT cells in both mouse and human adipose tissue indicated a specific role for adipose tissue-resident iNKT cells in the development of insulin resistance. Strikingly, iNKT cell function was directly modulated by adipocytes, which acted as lipid antigen-presenting cells in a CD1d-mediated fashion. Based on these findings, we propose that, especially under low-fat diet conditions, adipose tissue-resident iNKT cells maintain healthy adipose tissue through direct interplay with adipocytes and prevent insulin resistance.

Human adipocyte extracellular vesicles in reciprocal signaling between adipocytes and macrophages

OBJECTIVE

Extracellular vesicles (EVs) released by human adipocytes or adipose tissue (AT)-explants play a role in the paracrine interaction between adipocytes and macrophages, a key mechanism in AT inflammation, leading to metabolic complications like insulin resistance (IR) were determined.

METHODS

EVs released from in vitro differentiated adipocytes and AT-explants ex vivo were characterized by electron microscopy, Western blot, multiplex adipokine-profiling, and quantified by flow cytometry. Primary monocytes were stimulated with EVs from adipocytes, subcutaneous (SCAT) or omental-derived AT (OAT), and phenotyped. Macrophage supernatant was subsequently used to assess the effect on insulin signaling in adipocytes.

RESULTS

Adipocyte and AT-derived EVs differentiated monocytes into macrophages characteristic of human adipose tissue macrophages (ATM), defined by release of both pro- and anti-inflammatory cytokines. The adiponectin-positive subset of AT-derived EVs, presumably representing adipocyte-derived EVs, induced a more pronounced ATM-phenotype than the adiponectin-negative AT-EVs. This effect was more evident for OAT-EVs versus SCAT-EVs. Furthermore, supernatant of macrophages pre-stimulated with AT-EVs interfered with insulin signaling in human adipocytes. Finally, the number of OAT-derived EVs correlated positively with patients HOMA-IR.

CONCLUSIONS

A possible role for human AT-EVs in a reciprocal pro-inflammatory loop between adipocytes and macrophages, with the potential to aggravate local and systemic IR was demonstrated.

Systemic inflammation in childhood obesity: circulating inflammatory mediators and activated CD14++ monocytes

AIMS/HYPOTHESIS

In adults, circulating inflammatory mediators and activated CD14(++) monocytes link obesity to its metabolic and cardiovascular complications. However, it is largely unknown whether these inflammatory changes already occur in childhood obesity. To survey inflammatory changes during the early stages of obesity, we performed a comprehensive analysis of circulating inflammatory mediators, monocyte populations and their function in childhood obesity.

METHODS

In lean and obese children aged 6 to 16 years (n = 96), 35 circulating inflammatory mediators including adipokines were measured. Hierarchical cluster analysis of the inflammatory mediator profiles was performed to investigate associations between inflammatory mediator clusters and clinical variables. Whole-blood monocyte phenotyping and functional testing with the toll-like receptor 4 ligand, lipopolysaccharide, were also executed.

RESULTS

First, next to leptin, the circulating mediators chemerin, tissue inhibitor of metalloproteinase 1, EGF and TNF receptor 2 were identified as novel inflammatory mediators that are increased in childhood obesity. Second, cluster analysis of the circulating mediators distinguished two obesity clusters, two leanness clusters and one mixed cluster. All clusters showed distinct inflammatory mediator profiles, together with differences in insulin sensitivity and other clinical variables. Third, childhood obesity was associated with increased CD14(++) monocyte numbers and an activated phenotype of the CD14(++) monocyte subsets.

CONCLUSIONS/INTERPRETATION

Inflammatory mediator clusters were associated with insulin resistance in obese and lean children. The activation of CD14(++) monocyte subsets, which is associated with increased development of atherosclerosis in obese adults, was also readily detected in obese children. Our results indicate that inflammatory mechanisms linking obesity to its metabolic and cardiovascular complications are already activated in childhood obesity.

A Multiplex Immunoassay for Human Adipokine Profiling

BACKGROUND

Adipose tissue secretory proteins, called adipokines, play pivotal roles in the pathophysiology of obesity and its associated disorders such as metabolic syndrome, type 2 diabetes, and cardiovascular disease. Because methods for comprehensive adipokine profiling in patient plasma and other biological samples are currently limited, we developed a multiplex immunoassay for rapid and high-throughput measurement of 25 adipokines in only 50 μL of sample.

METHODS

(Pre)adipocyte and ex vivo cultured adipose tissue supernatants were generated and together with plasma from 5 morbidly obese patients and 5 healthy and normal weight controls used to develop the adipokine multiplex immunoassay and test its usefulness in biological samples. We assessed adipokine dynamic ranges, lower limits of detection and quantification, cross-reactivity, intra- and interassay variation, and correlation with adipokine ELISAs.

RESULTS

The limits of quantification and broad dynamic ranges enabled measurement of all 25 adipokines in supernatants and patient plasmas, with the exception of TNF-α in plasma samples. Intraassay variation was <10% for all adipokines; interassay variation was <15%. The multiplex immunoassay results correlated significantly with ELISA measurements. Plasma adipokine profiling showed significantly higher concentrations of the novel adipokines cathepsin S (5.1 × 104 vs 4.3 × 104 ng/L, P = 0.003) and chemerin (4.1 × 105 vs 2.7 × 105 ng/L, P = 0.0008) in morbidly obese patients than normal weight controls, besides the established differences in adiponectin and leptin concentrations.

CONCLUSIONS

Our findings underscore the relevance of the novel adipokines cathepsin S and chemerin, but foremost the potential of this novel method for both comprehensive adipokine profiling in large patient cohorts and for biological discovery.

Altered plasma adipokine levels and in vitro adipocyte differentiation in pediatric type 1 diabetes

CONTEXT

Type 1 diabetes (T1D) is considered a proinflammatory condition. Adipose tissue involvement seems evident because adiponectin levels correlate with disease remission and administration of leptin suppresses the low-grade systemic inflammation in mice with T1D. Whether adipose tissue involvement in T1D already occurs at a young age is yet unknown.

OBJECTIVE

The aim was to explore the extent of adipokine alterations in pediatric T1D and gain more insight into the mechanisms underlying the involvement of adipose tissue.

DESIGN AND PARTICIPANTS

First, plasma adipokine profiling (24 adipokines) of 20 children with onset T1D, 20 children with long-standing T1D, and 17 healthy controls was performed using a recently developed and validated multiplex immunoassay. Second, the effects of diabetic plasma factors on preadipocyte proliferation and differentiation were studied in vitro.

RESULTS

In children with onset and long-standing T1D, plasma adipokine profiling showed increased levels of various adipokines acting at the crossroads of adipose tissue function and inflammation, including CCL2/monocyte chemoattractant protein-1 and the novel adipokines cathepsin S, chemerin, and tissue inhibitor of metalloproteinase-1 (P < 0.05). Furthermore, onset and long-standing diabetic plasma significantly induced preadipocyte proliferation and adipocyte differentiation in vitro (P < 0.05). Two candidate plasma factors, glucose and the saturated fatty acid palmitic acid, did not affect proliferation or adipocyte differentiation in vitro but were found to increase CCL2 (monocyte chemoattractant protein-1) secretion by adipocytes.

CONCLUSIONS

The adipogenic effects of diabetic plasma in vitro and the altered adipokine levels in vivo suggest adipose tissue involvement in the low-grade inflammation associated with T1D, already in pediatric patients.

CD1d-mediated presentation of endogenous lipid antigens by adipocytes requires microsomal triglyceride transfer protein

Obesity-induced adipose tissue (AT) dysfunction results in a chronic low-grade inflammation that predisposes to the development of insulin resistance and type 2 diabetes. During the development of obesity, the AT-resident immune cell profile alters to create a pro-inflammatory state. Very recently, CD1d-restricted invariant (i) natural killer T (NKT) cells, a unique subset of lymphocytes that are reactive to so called lipid antigens, were implicated in AT homeostasis. Interestingly, recent data also suggest that human and mouse adipocytes can present such lipid antigens to iNKT cells in a CD1d-dependent fashion, but little is known about the lipid antigen presentation machinery in adipocytes. Here we show that CD1d, as well as the lipid antigen loading machinery genes pro-saposin (Psap), Niemann Pick type C2 (Npc2), α-galactosidase (Gla), are up-regulated in early adipogenesis, and are transcriptionally controlled by CCAAT/enhancer-binding protein (C/EBP)-β and -δ. Moreover, adipocyte-induced Th1 and Th2 cytokine release by iNKT cells also occurred in the absence of exogenous ligands, suggesting the display of endogenous lipid antigen-D1d complexes by 3T3-L1 adipocytes. Furthermore, we identified microsomal triglyceride transfer protein, which we show is also under the transcriptional regulation of C/EBPβ and -δ, as a novel player in the presentation of endogenous lipid antigens by adipocytes. Overall, our findings indicate that adipocytes can function as non-professional lipid antigen presenting cells, which may present an important aspect of adipocyte-immune cell communication in the regulation of whole body energy metabolism and immune homeostasis.

Endogenous lipid antigens for invariant natural killer T cells hold the reins in adipose tissue homeostasis

The global obesity epidemic and its associated co-morbidities, including type 2 diabetes, cardiovascular disease and certain types of cancers, have drawn attention to the pivotal role of adipocytes in health and disease. Besides their 'classical' function in energy storage and release, adipocytes interact with adipose-tissue-resident immune cells, among which are lipid-responsive invariant natural killer T (iNKT) cells. The iNKT cells are activated by lipid antigens presented by antigen-presenting cells as CD1d/lipid complexes. Upon activation, iNKT cells can rapidly secrete soluble mediators that either promote or oppose inflammation. In lean adipose tissue, iNKT cells elicit a predominantly anti-inflammatory immune response, whereas obesity is associated with declining iNKT cell numbers. Recent work showed that adipocytes act as non-professional antigen-presenting cells for lipid antigens. Here, we discuss endogenous lipid antigen processing and presentation by adipocytes, and speculate on how these lipid antigens, together with 'environmental factors' such as tissue/organ environment and co-stimulatory signals, are able to influence the fate of adipose-tissue-resident iNKT cells, and thereby the role of these cells in obesity and its associated pathologies.

Immunometabolic Activation of Invariant Natural Killer T Cells

Invariant natural killer T (iNKT) cells are lipid-reactive T cells with profound immunomodulatory potential. They are unique in their restriction to lipid antigens presented in CD1d molecules, which underlies their role in lipid-driven disorders such as obesity and atherosclerosis. In this review, we discuss the contribution of iNKT cell activation to immunometabolic disease, metabolic programming of lipid antigen presentation, and immunometabolic activation of iNKT cells. First, we outline the role of iNKT cells in immunometabolic disease. Second, we discuss the effects of cellular metabolism on lipid antigen processing and presentation to iNKT cells. The synthesis and processing of glycolipids and other potential endogenous lipid antigens depends on metabolic demand and may steer iNKT cells toward adopting a Th1 or Th2 signature. Third, external signals such as toll-like receptor ligands, adipokines, and cytokines modulate antigen presentation and subsequent iNKT cell responses. Finally, we will discuss the relevance of metabolic programming of iNKT cells in human disease, focusing on their role in disorders such as obesity and atherosclerosis. The critical response to metabolic changes places iNKT cells at the helm of immunometabolic disease.

Adipocytes harbor a glucosylceramide biosynthesis pathway involved in iNKT cell activation

BACKGROUND

Natural killer T (NKT) cells in adipose tissue (AT) contribute to whole body energy homeostasis.

RESULTS

Inhibition of the glucosylceramide synthesis in adipocytes impairs iNKT cell activity.

CONCLUSION

Glucosylceramide biosynthesis pathway is important for endogenous lipid antigen activation of iNKT cells in adipocytes.

SIGNIFICANCE

Unraveling adipocyte-iNKT cell communication may help to fight obesity-induced AT dysfunction. Overproduction and/or accumulation of ceramide and ceramide metabolites, including glucosylceramides, can lead to insulin resistance. However, glucosylceramides also fulfill important physiological functions. They are presented by antigen presenting cells (APC) as endogenous lipid antigens via CD1d to activate a unique lymphocyte subspecies, the CD1d-restricted invariant (i) natural killer T (NKT) cells. Recently, adipocytes have emerged as lipid APC that can activate adipose tissue-resident iNKT cells and thereby contribute to whole body energy homeostasis. Here we investigate the role of the glucosylceramide biosynthesis pathway in the activation of iNKT cells by adipocytes. UDP-glucose ceramide glucosyltransferase (Ugcg), the first rate limiting step in the glucosylceramide biosynthesis pathway, was inhibited via chemical compounds and shRNA knockdown in vivo and in vitro. β-1,4-Galactosyltransferase (B4Galt) 5 and 6, enzymes that convert glucosylceramides into potentially inactive lactosylceramides, were subjected to shRNA knock down. Subsequently, (pre)adipocyte cell lines were tested in co-culture experiments with iNKT cells (IFNγ and IL4 secretion). Inhibition of Ugcg activity shows that it regulates presentation of a considerable fraction of lipid self-antigens in adipocytes. Furthermore, reduced expression levels of either B4Galt5 or -6, indicate that B4Galt5 is dominant in the production of cellular lactosylceramides, but that inhibition of either enzyme results in increased iNKT cell activation. Additionally, in vivo inhibition of Ugcg by the aminosugar AMP-DNM results in decreased iNKT cell effector function in adipose tissue. Inhibition of endogenous glucosylceramide production results in decreased iNKT cells activity and cytokine production, underscoring the role of this biosynthetic pathway in lipid self-antigen presentation by adipocytes.

Differential adipokine receptor expression on circulating leukocyte subsets in lean and obese children

BACKGROUND

Childhood obesity prevalence has increased worldwide and is an important risk factor for type 2 diabetes (T2D) and cardiovascular disease (CVD). The production of inflammatory adipokines by obese adipose tissue contributes to the development of T2D and CVD. While levels of circulating adipokines such as adiponectin and leptin have been established in obese children and adults, the expression of adiponectin and leptin receptors on circulating immune cells can modulate adipokine signalling, but has not been studied so far. Here, we aim to establish the expression of adiponectin and leptin receptors on circulating immune cells in obese children pre and post-lifestyle intervention compared to normal weight control children.

METHODS

13 obese children before and after a 1-year lifestyle intervention were compared with an age and sex-matched normal weight control group of 15 children. Next to routine clinical and biochemical parameters, circulating adipokines were measured, and flow cytometric analysis of adiponectin receptor 1 and 2 (AdipoR1, AdipoR2) and leptin receptor expression on peripheral blood mononuclear cell subsets was performed.

RESULTS

Obese children exhibited typical clinical and biochemical characteristics compared to controls, including a higher BMI-SD, blood pressure and circulating leptin levels, combined with a lower insulin sensitivity index (QUICKI). The 1-year lifestyle intervention resulted in stabilization of their BMI-SD. Overall, circulating leukocyte subsets showed distinct adipokine receptor expression profiles. While monocytes expressed high levels of all adipokine receptors, NK and iNKT cells predominantly expressed AdipoR2, and B-lymphocytes and CD4+ and CD8+ T-lymphocyte subsets expressed AdipoR2 as well as leptin receptor. Strikingly though, leukocyte subset numbers and adipokine receptor expression profiles were largely similar in obese children and controls. Obese children showed higher naïve B-cell numbers, and pre-intervention also higher numbers of immature transition B-cells and intermediate CD14++CD16+ monocytes combined with lower total monocyte numbers, compared to controls. Furthermore, adiponectin receptor 1 expression on nonclassical CD14+CD16++ monocytes was consistently upregulated in obese children pre-intervention, compared to controls. However, none of the differences in leukocyte subset numbers and adipokine receptor expression profiles between obese children and controls remained significant after multiple testing correction.

CONCLUSIONS

First, the distinct adipokine receptor profiles of circulating leukocyte subsets may partly explain the differential impact of adipokines on leukocyte subsets. Second, the similarities in adipokine receptor expression profiles between obese children and normal weight controls suggest that adipokine signaling in childhood obesity is primarily modulated by circulating adipokine levels, instead of adipokine receptor expression.

Systemic and local interferon-gamma production following Mycobacterium ulcerans infection

Buruli ulcer disease (BUD) is an emerging predominantly tropical disease caused by Mycobacterium ulcerans. The initial pre-ulcerative skin lesion often breaks down into an ulcer with undermined edges. Healing is common but may require considerable time, and scarring often results in functional limitations. Considerable evidence has now emerged that patients with early BUD cannot mount a sufficient protective T helper 1 (Th1) cell response to M. ulcerans, but uncertainty remains as to whether immune protection is restored over time. This study investigates the Th1 cell response of patients with various stages of BUD on mycobacterial antigens. We measured interferon (IFN)-gamma levels after ex vivo whole blood stimulation with tuberculin purified protein derivative (PPD), and compared the Th1 cell response of individuals with pre-ulcerative, ulcerative and healed BUD as well as healthy controls. Moreover, the systemic Th1 cell response was related to histopathological features in the various stages of surgically resected BUD lesions. We show that patients with ulcerative and healed BUD produce significantly higher IFN-gamma levels after mycobacterial ex vivo whole blood stimulation than healthy controls, and that patients with a granulomatous tissue response produce higher IFN-gamma levels than individuals without. We therefore suggest that the mounted Th1 cell response in ulcerative BUD patients might be related to their histopathological tissue response.

Monocyte gene expression in childhood obesity is associated with obesity and complexity of atherosclerosis in adults

Childhood obesity coincides with increased numbers of circulating classical CD14⁺⁺CD16^- and intermediate CD14⁺⁺CD16⁺ monocytes. Monocytes are key players in the development and exacerbation of atherosclerosis, which prompts the question as to whether the monocytosis in childhood obesity contributes to atherogenesis over the years. Here, we dissected the monocyte gene expression profile in childhood obesity using an Illumina microarray platform on sorted monocytes of 35 obese children and 16 lean controls. Obese children displayed a distinctive monocyte gene expression profile compared to lean controls. Upon validation with quantitative PCR, we studied the association of the top 5 differentially regulated monocyte genes in childhood obesity with obesity and complexity of coronary atherosclerosis (SYNTAX score) in a cohort of 351 adults at risk for ischemic cardiovascular disease. The downregulation of monocyte IMPDH2 and TMEM134 in childhood obesity was also observed in obese adults. Moreover, downregulation of monocyte TMEM134 was associated with a higher SYNTAX atherosclerosis score in adults. In conclusion, childhood obesity entails monocyte gene expression alterations associated with obesity and enhanced complexity of coronary atherosclerosis in adults.

Lipoproteins act as vehicles for lipid antigen delivery and activation of invariant natural killer T-cells

Invariant Natural Killer T (iNKT) cells act at the interface between lipid metabolism and immunity, due to their restriction to lipid antigens presented on CD1d by antigen presenting cells (APC). How foreign lipid antigens are delivered to APC remains elusive. Since lipoproteins routinely bind glycosylceramides structurally similar to lipid antigens, we hypothesized that circulating lipoproteins form complexes with foreign lipid antigens. In this study, we used 2-color fluorescence correlation spectroscopy to show, for the first time, stable complex formation of lipid antigens α-galactosylceramide (αGalCer), Isoglobotrihexosylceramide (iGb3) and OCH, a sphingosine-truncated analogue of αGalCer, with very-low-density (VLDL) and/or low-density (LDL) lipoproteins in vitro and in vivo. We demonstrate LDL receptor (LDLR)-mediated uptake of lipoprotein-αGalCer complexes by APCs, leading to potent complex-mediated activation of iNKT cells in vitro and in vivo. Finally, LDLR-mutant PBMCs of patients with familial hypercholesterolemia showed impaired activation and proliferation of iNKT cells upon stimulation, underscoring the relevance of lipoproteins as a lipid antigen delivery system in humans. Taken together, circulating lipoproteins form complexes with lipid antigens to facilitate their transport and uptake by APCs, leading to enhanced iNKT cell activation. This study thereby reveals a novel mechanism of lipid antigen delivery to APCs, and provides further insight in the immunological capacities of circulating lipoproteins.

Cardiovascular Risk Assessment and Management for Pediatricians

Childhood and adolescence provide a unique window of opportunity to prevent atherosclerotic cardiovascular disease later in life, especially for pediatric groups at risk. The growing list of pediatric groups at risk includes individuals with chronic inflammatory disorders, organ transplants, familial hypercholesterolemia, endocrine disorders, childhood cancer, chronic kidney diseases, congenital heart diseases, and premature birth, as well as increasing numbers of children and adolescents with traditional risk factors such as obesity, hypertension, hyperlipidemia, and hyperglycemia. Here, we focus on recent advances in cardiovascular risk assessment and management and their implications for pediatric practice. First, hyperlipidemia and hyperglycemia are highly prevalent in the young, with hyperlipidemia occurring in 14.6% and hyperglycemia in 16.4% of children and adolescents with a normal weight. Implementation of nonfasting lipid and glycated hemoglobin screening in youth at risk is emerging as a promising avenue to improve testing compliance and lipid and glucose management. Second, blood pressure, lipid, and glucose management in youth at risk are reviewed in depth. Third, multisite and multimodal assessment of early atherosclerosis is discussed as a way to capture the complexity of atherosclerosis as a systemic disease. In addition to conventional carotid intima-media thickness measurements, the measurement of aortic pulse wave velocity and peripheral arterial tonometry can advance the assessment of early atherosclerosis in pediatrics. Finally, we make a plea for lifetime atherosclerotic cardiovascular disease risk stratification that integrates disease-associated risk factors and traditional risk factors and could facilitate tailored cardiovascular risk management in growing numbers of children and adolescents at risk.

Atherosclerotic Cardiovascular Risk as an Emerging Priority in Pediatrics

Over the last decades, childhood and adolescence have emerged as an important window of opportunity to prevent atherosclerotic cardiovascular disease (ASCVD) later in life. Here, we discuss the underlying advances in the field. First, atherosclerosis development starts as early as childhood. Atherogenesis initiates in the iliac arteries and abdominal aorta and subsequently develops in higher regions of the arterial tree, as has been demonstrated in nonhuman primate studies and human autopsy studies. Obesity, hypertension, hyperlipidemia, and hyperglycemia at a young age can accelerate atherogenesis. Children and adolescents with obesity have a relative risk of ∼ 2.5 for ASCVD mortality later in life, compared to peers with a normal weight. Conversely, early prevention improves long-term cardiovascular outcomes. Second, we review disease-associated factors that add to the traditional risk factors. Various pediatric disorders carry similar or even higher risks of ASCVD than obesity, including chronic inflammatory disorders, organ transplant recipients, familial hypercholesterolemia, endocrine disorders, childhood cancer survivors, chronic kidney diseases, congenital heart diseases, and premature birth, especially after fetal growth restriction. The involved disease-associated factors that fuel atherogenesis are diverse and include inflammation, vascular, and endothelial factors. The diverse and growing list of pediatric groups at risk underscores that cardiovascular risk management has solidly entered the realm of general pediatrics. In a second review in this series, we will, therefore, focus on recent advances in cardiovascular risk assessment and management and their implications for pediatric practice.

Dyslipidaemia as a target for atherosclerotic cardiovascular disease prevention in children with type 1 diabetes: lessons learned from familial hypercholesterolaemia

In the last few decades, atherosclerotic cardiovascular disease (ASCVD) risk has decreased dramatically among individuals affected by familial hypercholesterolaemia (FH) as a result of the early initiation of statin treatment in childhood. Contemporaneously important improvements in care for people with diabetes have also been made, such as the prevention of mortality from acute diabetic complications. However, individuals with type 1 diabetes still have a two to eight times higher risk of death than the general population. In the last 20 years, a few landmark studies on excess mortality in people with type 1 diabetes, in particular young adults, have been published. Although these studies were carried out in different populations, all reached the same conclusion: individuals with type 1 diabetes have a pronounced increased risk of ASCVD. In this review, we address the role of lipid abnormalities in the development of ASCVD in type 1 diabetes and FH. Although type 1 diabetes and FH are different diseases, lessons could be learned from the early initiation of statins in children with FH, which may provide a rationale for more stringent control of dyslipidaemia in children with type 1 diabetes.

Targeted inhibition of glycogen synthase kinase-3 using 9-ING-41 (elraglusib) enhances CD8 T-cell-reactivity against neuroblastoma cells

The prognosis of patients with high-risk neuroblastoma remains poor, partly due to inadequate immune recognition of the tumor. Neuroblastomas display extremely low surface MHC-I, preventing recognition by cytotoxic T lymphocytes (CTLs) and contributing to an immunosuppressive tumor microenvironment. Glycogen synthase kinase-3 beta (GSK-3β) is involved in pathways that may affect the MHC-I antigen processing and presentation pathway. We proposed that therapeutic inhibition of GSK-3β might improve the surface display of MHC-I molecules on neuroblastoma cells, and therefore tested if targeting of GSK-3β using the inhibitor 9-ING-41 (Elraglusib) improves MHC-I-mediated CTL recognition. We analyzed mRNA expression data of neuroblastoma tumor datasets and found that non-MYCN-amplified neuroblastomas express higher GSK-3β levels than MYCN-amplified tumors. In non-MYCN-amplified cells SH-SY5Y, SK-N-AS and SK-N-SH 9-ING-41 treatment enhanced MHC-I surface display and the expression levels of a subset of genes involved in MHC-I antigen processing and presentation. Further, 9-ING-41 treatment triggered increased STAT1 pathway activation, upstream of antigen presentation pathways in two of the three non-MYCN-amplified cell lines. Finally, in co-culture experiments with CD8 + T cells, 9-ING-41 improved immune recognition of the neuroblastoma cells, as evidenced by augmented T-cell activation marker levels and T-cell proliferation, which was further enhanced by PD-1 immune checkpoint inhibition. Our preclinical study provides experimental support to further explore the GSK-3β inhibitor 9-ING-41 as an immunomodulatory agent to increase tumor immune recognition in neuroblastoma.

Immunometabolic factors in adolescent chronic disease are associated with Th1 skewing of invariant Natural Killer T cells

Invariant Natural Killer T (iNKT) cells respond to the ligation of lipid antigen-CD1d complexes via their T-cell receptor and are implicated in various immunometabolic diseases. We considered that immunometabolic factors might affect iNKT cell function. To this end, we investigated iNKT cell phenotype and function in a cohort of adolescents with chronic disease and immunometabolic abnormalities. We analyzed peripheral blood iNKT cells of adolescents with cystic fibrosis (CF, n = 24), corrected coarctation of the aorta (CoA, n = 25), juvenile idiopathic arthritis (JIA, n = 20), obesity (OB, n = 20), and corrected atrial septal defect (ASD, n = 25) as controls. To study transcriptional differences, we performed RNA sequencing on a subset of obese patients and controls. Finally, we performed standardized co-culture experiments using patient plasma, to investigate the effect of plasma factors on iNKT cell function. We found comparable iNKT cell numbers across patient groups, except for reduced iNKT cell numbers in JIA patients. Upon ex-vivo activation, we observed enhanced IFN-γ/IL-4 cytokine ratios in iNKT cells of obese adolescents versus controls. The Th1-skewed iNKT cell cytokine profile of obese adolescents was not explained by a distinct transcriptional profile of the iNKT cells. Co-culture experiments with patient plasma revealed that across all patient groups, obesity-associated plasma factors including LDL-cholesterol, leptin, and fatty-acid binding protein 4 (FABP4) coincided with higher IFN-γ production, whereas high HDL-cholesterol and insulin sensitivity (QUICKI) coincided with higher IL-4 production. LDL and HDL supplementation in co-culture studies confirmed the effects of lipoproteins on iNKT cell cytokine production. These results suggest that circulating immunometabolic factors such as lipoproteins may be involved in Th1 skewing of the iNKT cell cytokine response in immunometabolic disease.

Preclinical Aortic Atherosclerosis in Adolescents With Chronic Disease

Background

Adolescents with chronic disease are often exposed to inflammatory, metabolic, and hemodynamic risk factors for early atherosclerosis. Since postmortem studies have shown that atherogenesis starts in the aorta, the CDACD (Cardiovascular Disease in Adolescents with Chronic Disease) study investigated preclinical aortic atherosclerosis in these adolescents.

Methods and Results

The cross‐sectional CDACD study enrolled 114 adolescents 12 to 18 years old with chronic disorders including juvenile idiopathic arthritis, cystic fibrosis, obesity, corrected coarctation of the aorta, and healthy controls with a corrected atrial septal defect. Cardiovascular magnetic resonance was used to assess aortic pulse wave velocity and aortic wall thickness, as established aortic measures of preclinical atherosclerosis. Cardiovascular magnetic resonance showed a higher aortic pulse wave velocity, which reflects aortic stiffness, and higher aortic wall thickness in all adolescent chronic disease groups, compared with controls ( P <0.05). Age (β=0.253), heart rate (β=0.236), systolic blood pressure (β=−0.264), and diastolic blood pressure (β=0.365) were identified as significant predictors for aortic pulse wave velocity, using multivariable linear regression analysis. Aortic wall thickness was predicted by body mass index (β=0.248) and fasting glucose (β=0.242), next to aortic lumen area (β=0.340). Carotid intima‐media thickness was assessed using ultrasonography, and was only higher in adolescents with coarctation of the aorta, compared with controls ( P <0.001).

Conclusions

Adolescents with chronic disease showed enhanced aortic stiffness and wall thickness compared with controls. The enhanced aortic pulse wave velocity and aortic wall thickness in adolescents with chronic disease could indicate accelerated atherogenesis. Our findings underscore the importance of the aorta for assessment of early atherosclerosis, and the need for tailored cardiovascular follow‐up of children with chronic disease.

Abstract 705: Interfering with mesenchymal stem cell-induced chemoresistance via COX-1 and thromboxane synthase inhibition

Background: Environment-mediated resistance to chemotherapy is emerging as a cause of treatment failure. We showed that mesenchymal stem cells (MSCs) induce resistance to a broad spectrum of chemotherapies. Upon platinum stimulation, two unique polyunsaturated fatty acids (PIFAs), 12-oxo-5,8,10-heptadecatrienoic acid (KHT(n-6)) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)) are produced by MSCs, which, via a paracrine mechanism, induce chemoresistance in tumors.

Aim: Here, we aim to prevent MSC-induced chemoresistance by blocking PIFA production.

Method: Various mouse models were established in which recruitment of MSCs to tumors was mimicked by iv administration of MSCs. Furthermore, cultured MSCs were treated with various drugs in order to block their chemo-protective capacity. Conditioned media were subsequently analyzed in vivo.

Results: Conditioned medium of platinum-stimulated, cultured MSCs induced chemoresistance in tumor-bearing mice. However, the capacity to secrete the chemo-protective PIFAs was only retained by mesenchymal cells with multi-lineage differentiation potential: MSCs and mouse embryonic fibroblasts (MEFs). More differentiated progeny from the mesenchymal lineage including 3T3 Fibroblasts, pre-adipocytes (3T3-L1), differentiated adipocytes, pre-osteoblasts (MC3T3) and differentiated osteoblasts were not capable of PIFA production upon platinum stimulation. Furthermore, this cytoprotective response was specific for multipotent cells from the mesenchymal lineage, since administration of hematopoietic stem cells did not influence the tumor response to chemotherapy.

One of the identified PIFAs, KHT(n-6), is known to be a by-product of thromboxane A2 synthesis, which is a downstream product of the cyclooxygenase (COX)-1 and thromboxane synthase (TxS) pathway. Interestingly, conditioned media from MSCs pre-treated with SC-560, a highly selective COX-1 inhibitor, indomethacin, a relatively selective COX-1 inhibitor or one of two specific TxS inhibitors (ozagrel and furegrelate) did not induce chemoresistance in vivo. Of note, selective COX-2 inhibition in MSC by celecoxib did not affect their capacity to induce chemoresistance, suggestive of a specific COX-1/TxS-dependent PIFA production. When mice were treated with either indomethacin or ozagrel as single agents no anti-tumor effect was observed. However, combining these drugs with cisplatin in vivo had an additive anti-tumor effect compared to cisplatin alone.

Conclusion: We show a novel mechanism of chemoresistance mediated by PIFA released from early, multipotent cells of the mesenchymal lineage. The production of these PIFAs is dependent on COX-1 and TxS, and blocking these enzymes enhanced the antitumor effects of cisplatin in vivo, making these enzymes drugable targets to prevent PIFA-induced chemoresistance.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 705. doi:10.1158/1538-7445.AM2011-705