Biology subjects

Kroon, J.

Publications and source records attributed to Kroon, J..

8 recordsLinked to original sources

bioRxiv2025

Kynurenine and NAD+ Pathways are Associated with Macrophage Content and Polarization in Carotid Plaques

Background and AimsMetabolism dictates macrophage function and plays a central role in atherosclerotic plaque progression. The kynurenine pathway, which metabolizes the majority of the essential amino acid tryptophan, plays a pivotal role in regulating immune responses and supporting NAD+ synthesis, essential for cellular energy metabolism. Higher circulating kynurenine levels are associated with cardiovascular disease, yet their role in atherosclerotic plaques is unclear. This study aims to investigate the underlying mechanisms driving increased kynurenine concentrations in plaques and to determine whether kynurenine serves as a mere biomarker of low-grade inflammation or reflects specific macrophage-driven metabolic alterations that could position it as a potential therapeutic target. MethodsWe used histological and transcriptomic data from two biobanks: the Athero Express Biobank (AE; n=91) and Maastricht human plaque study (MaasHPS, n= 26). Macrophages were identified through CD68 staining in AE, and M1/M2-like macrophage subtypes were distinguished by iNOS/CD68 and arginase/CD68 expression in MAASHPS. Primary human monocyte-derived cultured macrophages were polarized into M1- and M2-like phenotypes for using IFN-{gamma} and IL-4, respectively. Tryptophan, kynurenine and/or NAD+ concentrations in plaques were quantified usingliquid chromatography and metabolomics analyses. ResultsKynurenine concentrations were significantly higher in plaques with greater macrophage density (p = 0.023). Transcriptomic analysis in AE revealed upregulation of IDO2, AFMID, and KYNU in plaques with increased macrophage infiltration (p < 0.05), but not IDO1 (p = 0.16). In the MAASHPS biobank, higher IDO1, KYNU, and KMO expression correlated negatively with M2 marker positive macrophages (p < 0.001), while HAAO correlated positively (p < 0.01). In vitro, M1-like macrophages showed increased IDO1 and reduced QPRT expression compared to M2-like macrophages. We found that this disruption in kynurenine pathway gene expression led to decreased NAD+ concentrations in M1-like macrophages compared to M2-like macrophages in vitro. ConclusionHigher kynurenine levels in atherosclerotic plaques are increased by the increased presence of M1 macrophages, likely driven by both an increased IDO1 activity and reduced QPRT gene expression. This leads to decreased concentrations of NAD+, potentially determining the phenotype of the macrophages. Future studies should address whether modulation of the kynurenine pathway restores NAD+ metabolism and leads to a decrease in inflammation and an increased stable plaque phenotype.

immunology↗

bioRxiv2024

Systemic inflammation is a minor contributor to remnant cholesterol atherogenicity

BackgroundBoth plasma levels of remnant cholesterol and low-density lipoprotein cholesterol (LDL-C) levels are independent risk factors for atherosclerotic cardiovascular disease. However, only remnant cholesterol has consistently been associated with systemic inflammation. The extent to which inflammation mediates the effect of remnant cholesterol on major adverse cardiovascular events (MACE) remains unclear. Methods and ResultsThis study included 16,445 participants without prior atherosclerotic cardiovascular disease from the EPIC-Norfolk cohort, with a mean age of 58.8{+/-}9.1 years, of which 9,357 (56.9%) were women. Every 1 mmol/L higher remnant cholesterol was associated with 29.5% higher hsCRP levels (95% Confidence Interval (CI): 22.1, 37.4, p<0.001), whereas LDL-C was not significantly associated with hsCRP levels in the fully adjusted model. Additionally, each 1 mmol/L higher remnant cholesterol was associated with a hazard ratio (HR) of 1.31 (95% CI: 1.14, 1.50, p<0.001) for MACE, compared to a HR of 1.21 (95% CI: 1.13, 1.31, p<0.001) for LDL-C. Mediation analysis showed that hsCRP mediated 5.9% (95% CI: 1.2, 10.6%, p<0.001) of the effect of remnant cholesterol on MACE, whereas hsCRP did not mediate the effect of LDL-C. ConclusionsPlasma remnant cholesterol levels are independently associated with systemic inflammation and cardiovascular events. Inflammation, as measured with hsCRP, contributed minorly to the association between remnant cholesterol and MACE. This underscores the need to address both remnant cholesterol and systemic inflammation separately in the clinical management of cardiovascular disease. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=186 SRC="FIGDIR/small/604203v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@bdbb4org.highwire.dtl.DTLVardef@850ea6org.highwire.dtl.DTLVardef@184f321org.highwire.dtl.DTLVardef@17616fa_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract:C_FLOATNO The study assessed the relationship between remnant cholesterol, systemic inflammation, and MACE risk in 16,445 participants free from atherosclerotic cardiovascular disease from the EPIC-Norfolk cohort. Every 1 mmol/L higher remnant cholesterol was associated with 29.5% higher hsCRP levels (95% CI: 22.1, 37.4, p<0.001), while LDL cholesterol was not significantly associated with hsCRP levels. Additionally, each 1 mmol/L higher remnant cholesterol was associated with a HR of 1.31 (95% CI: 1.14, 1.50, p<0.001) for MACE, compared to a HR of 1.21 (95% CI: 1.13, 1.31, p<0.001) for LDL-C. hsCRP mediated 5.9% (95% CI: 1.2, 10.6%, p<0.001) of the effect of remnant cholesterol on MACE, while it did not mediate the effect of LDL cholesterol. LDL: low-density lipoprotein cholesterol, HR: hazard ratio, CI: confidence interval, MACE: major adverse cardiovascular events. C_FIG

systems biology↗

bioRxiv2024

Cardiovascular risk in ANCA-associated vasculitis: monocyte phenotyping reveals distinctive signatures between serological subsets

ObjectivesAnti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV) is associated with an increased cardiovascular risk, particularly the myeloperoxidase AAV serotype (MPO-AAV). Distinct alterations in monocyte phenotypes may cause accelerated atherosclerotic disease in AAV. MethodsA cohort including 43 AAV patients and 19 healthy controls were included for downstream analyses. Extensive phenotyping of monocytes and monocyte-derived macrophages was performed using bulk RNA-sequencing and flow cytometry. An in vitro transendothelial migration assay reflecting intrinsic adhesive and migratory capacities of monocytes was employed. Subsequent sub-analyses were performed to investigate differences between serological subtypes. ResultsMonocyte subset analysis showed increased classical monocytes during active disease, whereas non-classical monocytes were decreased. RNA-sequencing revealed upregulation of distinct inflammatory pathways and lipid metabolism-related markers in monocytes of active AAV patients. No differences were detected in the intrinsic monocyte adhesion and migration capacity. Monocytes of MPO-AAV patients in remission expressed genes related to inflammation, coagulation, platelet-binding and interferon signalling, whereas the expression of chemokine receptors indicative of acute inflammation and monocyte extravasation (i.e., CCR2 and CCR5) was increased in monocytes of proteinase-3(PR3)-AAV patients. During active disease, PR3-AAV was linked with elevated serum CRP and increased platelet counts compared to MPO-AAV. ConclusionThese findings highlight changes in monocyte subset composition and activation, but not in the intrinsic migration capacity of AAV monocytes. MPO-AAV monocytes are associated with sustained upregulation of inflammatory genes, whereas PR3-AAV monocytes exhibit chemokine receptor upregulation. These molecular changes may play a role in elevating cardiovascular risk as well as in the underlying pathophysiology of AAV. Key messages- Monocytes are activated during active ANCA-associated vasculitis (AAV) and upregulate lipid metabolism-related markers - AAV monocytes have a normal intrinsic adhesion and migration capacity, although overall monocyte migration likely rises by other mechanisms - The two serological subsets MPO-AAV and PR3-AAV exhibit differences in monocyte activation and chemokine receptor expression

immunology↗

bioRxiv2023

Human inborn errors of long-chain fatty acid oxidation show impaired inflammatory responses to TLR4-ligand LPS

Stimulation of mammalian cells with inflammatory inducers such as lipopolysaccharide (LPS) leads to alterations in the activity of central cellular metabolic pathways. Interestingly, these metabolic changes seem to be important for the subsequent release of pro-inflammatory cytokines. This has become particularly clear for enzymes of the tricarboxylic acid (TCA) cycle such as succinate dehydrogenase (SDH). LPS leads to inhibition of SDH activity and accumulation of succinate to enhance the LPS-induced formation of IL-1{beta}. If enzymes involved in beta-oxidation of fatty acids are important for sufficient responses to LPS is currently not clear. Using cells from various patients with inborn fatty acid oxidation disorders, we report that disease-causing deleterious variants of Electron Transfer Flavoprotein Dehydrogenase (ETFDH) and of Very Long Chain Acyl-CoA Dehydrogenase (ACADVL), both cause insufficient responses to stimulation with LPS. The insufficiencies included reduced TLR4 expression levels, impaired TLR4 signaling, and reduced or absent induction of pro-inflammatory cytokines such as IL-6. The insufficient responses to LPS were reproduced in cells from normal healthy controls by targeted loss-of-function of either ETFDH or ACADVL, supporting that the deleterious ETFDH and ACADVL variants cause the attenuated responses to LPS. ETFDH and ACADVL encode two distinct enzymes both involved in fatty acid beta-oxidation, and patients with these deficiencies cannot sufficiently metabolize long-chain fatty acids. With this report, we therefore provide genetic evidence from two genetically distinct but phenotypically similar human metabolic diseases, that genes important for beta-oxidation of long-chain fatty acids are also important for inflammatory responses to LPS.

immunology↗

bioRxiv2022

TraB is a novel component of the ER-Mitochondria contact site (EMCS) with dual roles in ER-Mitochondrial tethering and mitophagy

ER-mitochondria contact sites (EMCSs) are important for mitochondrial function. Here, we have identified a novel eukaryotic EMCS complex, comprising a family of uncharacterised mitochondrial outer-membrane proteins, TraB1 and the ER protein, VAP27-1. In Arabidopsis, there are two TraB1 isoforms and the trab1a/trab1b double mutant exhibits abnormal mitochondrial morphology, strong starch accumulation and impaired energy metabolism, indicating that these proteins are essential for normal mitochondrial function. Moreover, TraB1 proteins also interact with ATG8 in order to regulate mitochondrial degradation (mitophagy). The turnover of depolarised mitochondria is significantly reduced in both trab1a/b and VAP27 mutants (vap27-1/3/4/6) under mitochondrial stress conditions, with an increased population of dysfunctional mitochondria present in the cytoplasm. Consequently, plant recovery after stress is significantly perturbed. A similar phenotype is found in both autophagy mutants (atg5 and atg7), suggesting that TraB1 regulated mitophagy and ER-mitochondrial tethering are two closely related processes, necessary for normal mitochondrial function. Taken together, we ascribe a dual role to TraB1 which is a novel component of the EMCS complex in eukaryotes, regulating both tethering of the mitochondria to the ER and mitophagy.

cell biology↗

bioRxiv2021

A NET4-RabG3 couple mediate the link between actin and the tonoplast and is essential for normal actin cytoskeletal remodelling in stomatal closure to flg22

Members of the NETWORKED (NET) family are involved in actin-membrane interactions. They tether the cells plasma membrane (PM) to the actin network. Moreover, in a similar manner, they are also involved in the tethering of membrane bound organelles to the actin cytoskeleton; the endoplasmic reticulum (ER) and the ER to the PM. This raises the question as to whether NET proteins are involved in actin cytoskeletal remodelling. Here we show that two members of the NET family, NET4A and NET4B, are essential for normal guard cell actin reorganization, which is a process critical for stomatal closure in plant immunity. NET4 proteins interact with F-actin and with members of the Rab7 GTPase RABG3 family through two distinct domains, allowing for simultaneous localization to actin filaments and the tonoplast. NET4 proteins interact with GTP-bound, active RABG3 members, suggesting their function as downstream effectors. We also show that RABG3b is critical for stomatal closure induced by microbial patterns. Taken together, we conclude that the actin cytoskeletal remodelling during stomatal closure depends on a molecular link between actin filaments and the tonoplast, which is mediated by the NET4-RABG3b interaction. We propose that stomatal closure to microbial patterns involves the coordinated action of immune signalling events and proper actin cytoskeletal remodelling.

plant biology↗

bioRxiv2019

Impact of a caries preventive intervention in remote Indigenous Australian children

IMPORTANCEThe burden of dental caries in remote Indigenous communities in Australia is unacceptably high.\n\nOBJECTIVESWe tested the impact of an annual caries preventive intervention, delivered by a fly-in/fly-out professional team, on Indigenous children residing in a remote Australian community, involving selective fissure sealants, topical povidone iodine and fluoride varnish application. The outcome was caries increment at 12- and 24-month follow-up.\n\nDESIGN, SETTING, PARTICIPANTSAround 600 Indigenous children aged 5 to 17 years were invited to participate at baseline, of which 408 had caregiver consent provided. Of these, 196 consented to both the study and the treatment arm and comprised the experimental group. Two hundred and twelve consented to the epidemiological examination only, and constituted the comparison group.\n\nINTERVENTIONThe Big Bang intervention, which occurred annually, comprised placement of fissure sealants, and application of povidone-iodine and fluoride varnish, following completion of each childs dental treatment plan. Standard diet and oral hygiene advice was provided.\n\nMAIN OUTCOMES AND MEASURESCaries increment (number of tooth surfaces with new dental caries) in both primary and permanent dentitions at 12- and 24-month follow-up.\n\nRESULTSAt 12-month follow-up, children in the experimental group had, on average, 5.05 ({+/-}5.47) new carious lesions compared to 7.49 ({+/-}6.94) in the comparison group (p=0.001). The preventive fraction was 33%. At 24-month follow-up, children in the experimental group had, on average, 6.47 ({+/-}6.07) new carious lesions compared to 8.43 ({+/-}5.83) in the comparison group (p=0.002). The preventive fraction was 23%.\n\nCONCLUSIONS AND RELEVANCEIndigenous children exposed to the Big Bang caries intervention had significantly less increment in dental disease than those not exposed to the intervention. Benefits were demonstrated at both 12- and 24-month follow-ups, suggesting that the intervention is likely to be sustained if delivered across a childs life. The cost-effectiveness of this approach is being evaluated.\n\nQuestionDoes a quick, intensive, Big Bang program of intervention reduce dental disease among remote Indigenous Australian children?\n\nFindingsAt 12- and 24-month follow-ups, children in the experimental group had fewer new caries surfaces. At the 24-month follow-up, the average caries increment was 6.47 ({+/-}6.07) in the experimental group compared to 8.43 ({+/-}5.83) in the comparison group; a preventive fraction of 23%.\n\nMeaningAn intensive caries intervention delivered by a peripatetic team of professionals, involving fissure sealants, topical povidone iodine and fluoride varnish application reduces experience of dental disease among this vulnerable population.

epidemiology↗

bioRxiv2018

Paralogues of the PXY and ER receptor kinases enforce radial patterning in plant vascular tissue.

Plant cell walls do not allow cells to migrate, thus plant growth and development is entirely the consequence of changes to cell division and cell elongation. Where tissues are arranged in concentric rings, expansion of inner tissue, such as that which occurs during vascular development, must be coordinated with cell division and/or expansion of the outer tissue layers, endodermis, cortex, and epidermis, in order for tissue integrity to be maintained. Little is known of how coordination between cell layers occurs, but non-cell autonomous signalling could provide an explanation. Endodermis-derived EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) ligands have been shown to signal to the ERECTA (ER) receptor kinase present in the phloem. ER interacts with PHLOEM INTERCALLATED WITH XYLEM (PXY), a receptor present in the procambium. The PXY ligand, TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF) is derived from CLE41 which is expressed in the phloem. These factors therefore represent a mechanism by which intertissue signalling could occur to control radial expansion between vascular and non-vascular tissue in plant stems. Here we show that ER regulates expression of PXY paralogues, PXL1 and PXL2, and that in turn PXY, PXL1 and PXL2 together with ER, regulate the expression of ERL1 and ERL2, genes paralogous to ER. PXY, PXL1, PXL2 and ER also regulate the expression of ER-ligands. Genetic analysis of these six receptor kinase genes demonstrated that they are required to control organisation, proliferation and cell size across multiple tissue layers. Taken together, our experiments demonstrate that ER signalling attenuates PXL expression in the stem, thus influencing vascular expansion and patterning. We anticipate that similar regulatory relationships, where tissue growth is controlled via cell signals moving across different tissue layers, will coordinate tissue layer expansion throughout the plant body.

plant biology↗