Simple Summary The incidence of hepatocellular carcinoma (HCC) in patients with non-alcoholic fatty liver disease (NAFLD) has increased in recent years. Compared to HCC caused by other chronic... Show moreSimple Summary The incidence of hepatocellular carcinoma (HCC) in patients with non-alcoholic fatty liver disease (NAFLD) has increased in recent years. Compared to HCC caused by other chronic liver diseases, NAFLD-related HCC is often detected later, because it more commonly arises before cirrhosis has occurred. Because of this late diagnosis, NAFLD-related HCC is often more advanced at time of diagnosis, resulting in fewer curative treatment options. Most research in the pathogenesis of HCC has focused on the disease processes in hepatocytes, the most abundant type of liver cells. However, other cell types, such as cells of the immune system and cells that regulate connective tissue formation, also play an important role in the development of NAFLD-related HCC, both by contributing to the development of HCC itself and by interfering with the immune system's ability to attack cancer cells. In this paper, we review the role of different cell types in the development of NAFLD-related HCC. Hepatocellular carcinoma (HCC) in the setting of non-alcoholic fatty liver disease (NAFLD)-related cirrhosis and even in the pre-cirrhotic state is increasing in incidence. NAFLD-related HCC has a poor clinical outcome as it is often advanced at diagnosis due to late diagnosis and systemic treatment response is poor due to reduced immune surveillance. Much of the focus of molecular research has been on the pathological changes in hepatocytes; however, immune cells, hepatic stellate cells, liver sinusoidal endothelial cells and the extracellular matrix may play important roles in the pathogenesis of NAFLD-related HCC as well. Here, we review the role of non-parenchymal cells in the liver in the pathogenesis of HCC in the context of NAFLD-NASH, with a particular focus on the innate and the adaptive immune system, fibrogenesis and angiogenesis. We review the key roles of macrophages, hepatic stellate cells (HSCs), T cells, natural killer (NK) cells, NKT cells and liver sinusoidal endothelial cells (LSECs) and the role of the extracellular matrix in hepatocarcinogenesis within the steatotic milieu. Show less
Duijn, A. van; Burg, S.H. van der; Scheeren, F.A. 2022
Myeloid immune cells are frequently present in the tumor environment, and although they can positively contribute to tumor control they often negatively impact anticancer immune responses. One way... Show moreMyeloid immune cells are frequently present in the tumor environment, and although they can positively contribute to tumor control they often negatively impact anticancer immune responses. One way of inhibiting the positive contributions of myeloid cells is by signaling through the cluster of differentiation 47 (CD47)/signal regulatory protein alpha (SIRP alpha) axis. The SIRP alpha receptor is expressed on myeloid cells and is an inhibitory immune receptor that, upon binding to CD47 protein, delivers a 'don't eat me' signal. As CD47 is often overexpressed on cancer cells, treatments targeting CD47/SIRP alpha have been under active investigation and are currently being tested in clinical settings. Interestingly, the CD47/SIRP alpha axis is also involved in T cell-mediated antitumor responses. In this perspective we provide an overview of recent studies showing how therapeutic blockade of the CD47/SIRP alpha axis improves the adaptive immune response. Furthermore, we discuss the interconnection between the myeloid CD47/SIRP alpha axis and adaptive T cell responses as well as the potential therapeutic role of the CD47/SIRP alpha axis in tumors with acquired resistance to the classic immunotherapy through major histocompatibility complex downregulation. Altogether this review provides a profound insight for the optimal exploitation of CD47/SIRP alpha immune checkpoint therapy. Show less
Macrophages remodel their mechanics during differentiation toward different subtypes and drastically adapt their shapes during phagocytosis or entry to inflamed tissues. Although these functions... Show moreMacrophages remodel their mechanics during differentiation toward different subtypes and drastically adapt their shapes during phagocytosis or entry to inflamed tissues. Although these functions depend on cell mechanical properties, the mechanical behavior of macrophages is still poorly understood and accurate physiologically relevant data on basic mechanical properties of different macrophage subtypes are lacking almost entirely. By combining several complementary single-cell force spectroscopy techniques, whole cell mechanics of M1 (differentiated by granulocyte macrophage colony-stimulating factor [GM-CSF]) and M2 (differentiated by macrophage colony-stimulating factor [M-CSF]) macrophages is systematically analyzed, and it is revealed that M2 macrophages exhibit solid-like behavior, whereas M1 macrophages behave more fluid-like. In addition, the findings indicate that M2 macrophages exhibit increased dynamic motility as compared to M1 macrophages, consistent with their mechanical phenotypes. The technology presented herein can be used to distinguish macrophage subtypes based on their mechanical phenotype, and suggests that mechanical properties of macrophages are linked to their immune function. Show less
Tian, X.Z.; Aiyer, K.T.S.; Kapsenberg, J.M.; Roelen, D.L.; Hoorn, M.L. van der; Eikmans, M. 2021
Problem The embryo of an oocyte donation (OD) pregnancy is completely allogeneic to the mother, which may challenge the maternal immune system to tolerize the fetus. Decidual macrophages are... Show moreProblem The embryo of an oocyte donation (OD) pregnancy is completely allogeneic to the mother, which may challenge the maternal immune system to tolerize the fetus. Decidual macrophages are essential in maintaining a healthy pregnancy, and type 2 macrophages may exhibit immune suppressive activity. We hypothesized that the composition of decidual macrophages is different between uncomplicated OD pregnancies and non-OD in vitro fertilization (IVF) pregnancies, and is related to fetal-maternal incompatibility. Method of study Women with uncomplicated pregnancy were enrolled: 25 singleton OD pregnancies and 17 non-OD IVF pregnancies. The extent of immunohistochemical staining of CD14 (pan-macrophage marker) and CD163 (type 2 macrophage marker) in both decidua basalis and parietalis was quantitated by digital image analysis. Maternal and fetal DNA was typed for human leukocyte antigen (HLA)-A, -B, C, -DRB1, and -DQB1, and fetal-maternal HLA mismatches were calculated. Results OD pregnancies showed a higher percentage of CD163+ staining (P = .040) and higher CD163/CD14 ratio (P = .032) in the parietalis than non-OD IVF. The OD group was separated into a semi-allogeneic group (<= 5 fetal maternal HLA mismatches) and a fully allogeneic group (> 5 mismatches). The HLA-fully-allogeneic OD group, but not the HLA-semi-allogeneic OD group, showed significantly elevated CD163/CD14 ratio in the parietalis compared with the non-OD IVF group (P < .05). Conclusions Uncomplicated OD pregnancies display a higher CD163-positive cell fraction in the total decidual macrophage population compared to autologous pregnancies, which may suggest that a local type 2 macrophage-related mechanism is needed to compensate for the higher fetal-maternal HLA mismatch load. Show less
Emerging evidence suggests that immune cells not only communicatewith each other through cytokines, chemokines, and cell surface receptors, but also by releasing small membranous structures known... Show moreEmerging evidence suggests that immune cells not only communicatewith each other through cytokines, chemokines, and cell surface receptors, but also by releasing small membranous structures known as extracellular vesicles (EVs). EVs carry a variety of different molecules that can be taken up by recipient cells. Parasitic worms are well known for their immunomodulatory properties, but whether they can affect immune responses by altering EV-driven communication between host immune cells remains unclear. Here we provide evidence that stimulation of bone marrow-derived macrophages (BMDMs) with soluble products of Trichuris suis (TSPs), leads to the release of EVs with anti-inflammatory properties. Specifically, we found that EVs from TSP-pulsed BMDMs, but not those from unstimulated BMDMs can suppress TNF alpha and IL-6 release in LPS-stimulated BMDMs and BMDCs. However, no polarization toward M1 or M2 was observed in macrophages exposed to EVs. Moreover, EVs enhanced reactive oxygen species (ROS) production in the exposed BMDMs, which was associated with a deregulated redox homeostasis as revealed by pathway analysis of transcriptomic data. Proteomic analysis identified cytochrome p450 (CYP450) as a potential source of ROS in EVs from TSP-pulsed BMDMs. Finally, pharmacological inhibition of CYP450 activity could suppress ROS production in those BMDMs. In summary, we find that TSPs can modulate immune responses not only via direct interactions but also indirectly by eliciting the release of EVs from BMDMs that exert anti-inflammatory effects on recipient cells. Show less
The innate immune system displays heterologous memory characteristics, which are characterized by stronger responses to a secondary challenge. This phenomenon termed trained immunity relies on... Show moreThe innate immune system displays heterologous memory characteristics, which are characterized by stronger responses to a secondary challenge. This phenomenon termed trained immunity relies on epigenetic and metabolic rewiring of innate immune cells. As reactive oxygen species (ROS) production has been associated with the trained immunity phenotype, we hypothesized that the increased ROS levels and the main intracellular redox molecule glutathione play a role in the induction of trained immunity. Here we show that pharmacological inhibition of ROS in an in vitro model of trained immunity did not influence cell responsiveness; the modulation of glutathione levels reduced pro-inflammatory cytokine production in human monocytes. Single nucleotide polymorphisms (SNPs) in genes involved in glutathione metabolism were found to be associated with changes in pro-inflammatory cytokine production capacity upon trained immunity. Also, plasma glutathione concentrations were positively associated with ex vivo IL-1 beta production, a biomarker of trained immunity, produced by monocytes of BCG-vaccinated individuals. In conclusion, glutathione metabolism is involved in the induction of trained immunity, and future studies are warranted to explore its functional consequences in human diseases. Show less
Following the neutral results of the dal-OUTCOMES trial, a genome-wide study identified the rs1967309 variant in the adenylate cyclase type 9 (ADCY9) gene on chromosome 16 as being associated with... Show moreFollowing the neutral results of the dal-OUTCOMES trial, a genome-wide study identified the rs1967309 variant in the adenylate cyclase type 9 (ADCY9) gene on chromosome 16 as being associated with the risk of future cardiovascular events only in subjects taking dalcetrapib, a CETP (cholesterol ester transfer protein) modulator. Homozygotes for the minor A allele (AA) were protected from recurrent cardiovascular events when treated with dalcetrapib, while homozygotes for the major G allele (GG) had increased risk. Here, we present the current state of knowledge regarding the impact of rs1967309 in ADCY9 on clinical observations and biomarkers in dalcetrapib trials and the effects of mouse ADCY9 gene inactivation on cardiovascular physiology. Finally, we present our current model of the interaction between dalcetrapib and ADCY9 gene variants in the arterial wall macrophage, based on the intracellular role of CETP in the transfer of complex lipids from endoplasmic reticulum membranes to lipid droplets. Briefly, the concept is that dalcetrapib would inhibit CETP-mediated transfer of cholesteryl esters, resulting in a progressive inhibition of cholesteryl ester synthesis and free cholesterol accumulation in the endoplasmic reticulum. Reduced ADCY9 activity, by paradoxically leading to higher cyclic AMP levels and in turn increased cellular cholesterol efflux, could impart cardiovascular protection in rs1967309 AA patients. The ongoing dal-GenE trial recruited 6145 patients with the protective AA genotype and will provide a definitive answer to whether dalcetrapib will be protective in this population. Show less
The aim of this thesis was to better understand the underlying biology of tumor-immune interactions, especially in the circulation of CRC patients. The focus was primarily on the innate immune... Show moreThe aim of this thesis was to better understand the underlying biology of tumor-immune interactions, especially in the circulation of CRC patients. The focus was primarily on the innate immune system including NK cells, NKT cells, and macrophages. Show less
Zande, H.J.P. van der; Gonzalez, M.A.; Ruiter, K. de; Wilbers, R.H.P.; Garcia-Tardon, N.; Huizen, M. van; ... ; Guigas, B. 2021
Type 2 immunity plays an essential role in the maintenance of metabolic homeostasis and its disruption during obesity promotes meta-inflammation and insulin resistance. Infection with the helminth... Show moreType 2 immunity plays an essential role in the maintenance of metabolic homeostasis and its disruption during obesity promotes meta-inflammation and insulin resistance. Infection with the helminth parasite Schistosoma mansoni and treatment with its soluble egg antigens (SEA) induce a type 2 immune response in metabolic organs and improve insulin sensitivity and glucose tolerance in obese mice, yet, a causal relationship remains unproven. Here, we investigated the effects and underlying mechanisms of the T2 ribonuclease omega-1 (omega 1), one of the major S mansoni immunomodulatory glycoproteins, on metabolic homeostasis. We show that treatment of obese mice with plant-produced recombinant omega 1, harboring similar glycan motifs as present on the native molecule, decreased body fat mass, and improved systemic insulin sensitivity and glucose tolerance in a time- and dose-dependent manner. This effect was associated with an increase in white adipose tissue (WAT) type 2 T helper cells, eosinophils, and alternatively activated macrophages, without affecting type 2 innate lymphoid cells. In contrast to SEA, the metabolic effects of omega 1 were still observed in obese STAT6-deficient mice with impaired type 2 immunity, indicating that its metabolic effects are independent of the type 2 immune response. Instead, we found that omega 1 inhibited food intake, without affecting locomotor activity, WAT thermogenic capacity or whole-body energy expenditure, an effect also occurring in leptin receptor-deficient obese and hyperphagic db/db mice. Altogether, we demonstrate that while the helminth glycoprotein omega 1 can induce type 2 immunity, it improves whole-body metabolic homeostasis in obese mice by inhibiting food intake via a STAT6-independent mechanism. Show less
Nejad, E.B.; Labrie, C.; Elsas, M.J. van; Kleinovink, J.W.; Mittrucker, H.W.; Franken, K.L.M.C.; ... ; Burg, S.H. van der 2021
Background High serum interleukin (IL-6) levels may cause resistance to immunotherapy by modulation of myeloid cells in the tumor microenvironment. IL-6 signaling blockade is tested in cancer, but... Show moreBackground High serum interleukin (IL-6) levels may cause resistance to immunotherapy by modulation of myeloid cells in the tumor microenvironment. IL-6 signaling blockade is tested in cancer, but as this inflammatory cytokine has pleiotropic effects, this treatment is not always effective. Methods IL-6 and IL-6R blockade was applied in an IL-6-mediated immunotherapy-resistant TC-1 tumor model (TC-1.IL-6) and immunotherapy-sensitive TC-1.control. Effects on therapeutic vaccination-induced tumor regression, recurrence and survival as well on T cells and myeloid cells in the tumor microenvironment were studied. The effects of IL-6 signaling in macrophages under therapy conditions were studied in Il6ra(fl/fl)xLysM(cre+) mice. Results Our therapeutic vaccination protocol elicits a strong tumor-specific CD8(+) T-cell response, leading to enhanced intratumoral T-cell infiltration and recruitment of tumoricidal macrophages. Blockade of IL-6 signaling exacerbated tumor outgrowth, reflected by fewer complete regressions and more recurrences after therapeutic vaccination, especially in TC-1.IL-6 tumor-bearing mice. Early IL-6 signaling blockade partly inhibited the development of the vaccine-induced CD8(+) T-cell response. However, the main mechanism was the malfunction of macrophages during therapy-induced tumor regression. Therapy efficacy was impaired in Il6ra(fl/fl)xLysM(cre+) but not cre-negative control mice, while no differences in the vaccine-induced CD8(+) T-cell response were found between these mice. IL-6 signaling blockade resulted in decreased expression of suppressor of cytokine signaling 3, essential for effective M1-type function in macrophages, and increased expression of the phagocytic checkpoint molecule signal-regulatory protein alpha by macrophages. Conclusion IL-6 signaling is critical for macrophage function under circumstances of immunotherapy-induced tumor tissue destruction, in line with the acute inflammatory functions of IL-6 signaling described in infections. Show less
Many of the risk factors for developing severe coronavirus disease 2019 (COVID-19) are also risk factors for eye diseases such as age-related macular degeneration (AMD). During the past decades,... Show moreMany of the risk factors for developing severe coronavirus disease 2019 (COVID-19) are also risk factors for eye diseases such as age-related macular degeneration (AMD). During the past decades, macro-phages and the complement pathway (as a part of the innate immune system) have been identified as important contributors to the development of AMD, and we suggest that these mechanisms are of similar importance for the clinical course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Based on the experience with AMD, we discuss how behavioral factors such as diet, smoking and higher body mass index, as well as genetic determinants such as the complement and immune pathway genes may lead to the overactive inflammatory phenotypes seen in some patients with COVID-19, and may in part explain the heterogeneity of disease manifestations and outcomes. Based on this experience, we discuss potential genetic research projects and elaborate on preventive and treatment approaches related to COVID-19. Show less
Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major cause of end-stage kidney disease in man. The central role of cyclic adenosine monophosphate (cAMP) in ADPKD pathogenesis has been... Show moreAutosomal Dominant Polycystic Kidney Disease (ADPKD) is a major cause of end-stage kidney disease in man. The central role of cyclic adenosine monophosphate (cAMP) in ADPKD pathogenesis has been confirmed by numerous studies including positive clinical trial data. Here, we investigated the potential role of another major regulator of renal cAMP, prostaglandin E-2 (PGE(2)), in modifying disease progression in ADPKD models using selective receptor modulators to all four PGE2 receptor subtypes (EP1-4). In 3D-culture model systems utilizing dog (MDCK) and patient-derived (UCL93, OX161-C1) kidney cell lines, PGE(2) strikingly promoted cystogenesis and inhibited tubulogenesis by stimulating proliferation while reducing apoptosis. The effect of PGE(2) on tubulogenesis and cystogenesis in 3D-culture was mimicked or abolished by selective EP2 and EP4 agonists or antagonists but not those specific to EP1 or EP3. In a Pkd1 mousemodel (Pkd1(nl/nl)), kidney PGE(2) and COX-2 expression were increased by two-fold at the peak of disease (week four). However, Pkd1(nl/nl) mice treated with selective EP2 (PF-04418948) or EP4 (ONO-AE3-208) antagonists from birth for three weeks had more severe cystic disease and fibrosis associated with increased cell proliferation and macrophage infiltration. A similar effect was observed for the EP4 antagonist ONO-AE3-208 in a second Pkd1 model (Pax8rtTA-TetO-Cre-Pkd1(f/f)). Thus, despite the positive effects of slowing cyst growth in vitro, the more complex effects of inhibiting EP2 or EP4 in vivo resulted in a worse outcome, possibly related to unexpected pro-inflammatory effects. Show less
Atherosclerosis-related CVD causes nearly 20 million deaths annually. Most patients are treated after plaques develop, so therapies must regress existing lesions. Current therapies reduce plaque... Show moreAtherosclerosis-related CVD causes nearly 20 million deaths annually. Most patients are treated after plaques develop, so therapies must regress existing lesions. Current therapies reduce plaque volume, but targeting all apoB-containing lipoproteins with intensive combinations that include alirocumab or evinacumab, monoclonal antibodies against cholesterol-regulating proprotein convertase subtilisin/kexin type 9 and angiopoietin-like protein 3, may provide more benefit. We investigated the effect of such lipid-lowering interventions on atherosclerosis in APOE*3-Leiden.CETP mice, a well-established model for hyperlipidemia. Mice were fed a Western-type diet for 13 weeks and thereafter matched into a baseline group (euthanized at 13 weeks) and five groups that received diet alone (control) or with treatment [atorvastatin; atorvastatin and alirocumab; atorvastatin and evinacumab; or atorvastatin, alirocumab, and evinacumab (triple therapy)] for 25 weeks. We measured effects on cholesterol levels, plaque composition and morphology, monocyte adherence, and macrophage proliferation. All interventions reduced plasma total cholesterol (37% with atorvastatin to 80% with triple treatment; all P < 0.001). Triple treatment decreased non-HDL-C to 1.0 mmol/l (91% difference from control; P < 0.001). Atorvastatin reduced atherosclerosis progression by 28% versus control (P < 0.001); double treatment completely blocked progression and diminished lesion severity. Triple treatment regressed lesion size versus baseline in the thoracic aorta by 50% and the aortic root by 36% (both P < 0.05 vs. baseline), decreased macrophage accumulation through reduced proliferation, and abated lesion severity. Thus, high-intensive cholesterol-lowering triple treatment targeting all apoB-containing lipoproteins regresses atherosclerotic lesion area and improves lesion composition in mice, making it a promising potential approach for treating atherosclerosis. Show less
The embryo of an oocyte donation (OD) pregnancy is completely allogeneic to the mother, which leads to a more serious challenge for the maternal immune system to tolerize the fetus. It is thought... Show moreThe embryo of an oocyte donation (OD) pregnancy is completely allogeneic to the mother, which leads to a more serious challenge for the maternal immune system to tolerize the fetus. It is thought that macrophages are essential in maintaining a healthy pregnancy, by acting in immunomodulation and spiral arterial remodeling. OD pregnancies represent an interesting model to study complex immunologic interactions between the fetus and the pregnant woman since the embryo is totally allogeneic compared to the mother. Here, we describe a narrative review on the role of macrophages and pregnancy and a systematic review was performed on the role of macrophages in OD pregnancies. Searches were made in different databases and the titles and abstracts were evaluated by three independent authors. In total, four articles were included on OD pregnancies and macrophages. Among these articles, some findings are conflicting between studies, indicating that more research is needed in this area. From current research, we could identify that there are multiple subtypes of macrophages, having diverse biological effects, and that the ratio between subtypes is altered during gestation and in aberrant pregnancy. The study of macrophages' phenotypes and their functions in OD pregnancies might be beneficial to better understand the maternal-fetal tolerance system. Show less
Unstable atherosclerotic plaques frequently show plaque angiogenesis which increases the chance of rupture and thrombus formation leading to infarctions. Hypoxia plays a role in angiogenesis and... Show moreUnstable atherosclerotic plaques frequently show plaque angiogenesis which increases the chance of rupture and thrombus formation leading to infarctions. Hypoxia plays a role in angiogenesis and inflammation, two processes involved in the pathogenesis of atherosclerosis. We aim to study the effect of resolution of hypoxia using carbogen gas (95% O-2, 5% CO2) on the remodeling of vein graft accelerated atherosclerotic lesions in ApoE3*Leiden mice which harbor plaque angiogenesis. Single treatment resulted in a drastic decrease of intraplaque hypoxia, without affecting plaque composition. Daily treatment for three weeks resulted in 34.5% increase in vein graft patency and increased lumen size. However, after three weeks intraplaque hypoxia was comparable to the controls, as were the number of neovessels and the degree of intraplaque hemorrhage. To our surprise we found that three weeks of treatment triggered ROS accumulation and subsequent Hif1a induction, paralleled with a reduction in the macrophage content, pointing to an increase in lesion stability. Similar to what we observed in vivo, in vitro induction of ROS in bone marrow derived macrophages lead to increased Hif1a expression and extensive DNA damage and apoptosis. Our study demonstrates that carbogen treatment did improve vein graft patency and plaque stability and reduced intraplaque macrophage accumulation via ROS mediated DNA damage and apoptosis but failed to have long term effects on hypoxia and intraplaque angiogenesis. Show less
Myeloid cells, including macrophages and dendritic cells, represent an important first line of defense against infections. Upon recognition of pathogens, these cells undergo a metabolic... Show moreMyeloid cells, including macrophages and dendritic cells, represent an important first line of defense against infections. Upon recognition of pathogens, these cells undergo a metabolic reprogramming that supports their activation and ability to respond to the invading pathogens. An important metabolic regulator of these cells is mammalian target of rapamycin (mTOR). During infection, pathogens use host metabolic pathways to scavenge host nutrients, as well as target metabolic pathways for subversion of the host immune response that together facilitate pathogen survival. Given the pivotal role of mTOR in controlling metabolism and DC and macrophage function, pathogens have evolved strategies to target this pathway to manipulate these cells. This review seeks to discuss the most recent insights into how pathogens target DC and macrophage metabolism to subvert potential deleterious immune responses against them, by focusing on the metabolic pathways that are known to regulate and to be regulated by mTOR signaling including amino acid, lipid and carbohydrate metabolism, and autophagy. Show less
Thiem, K.; Hoeke, G.; Zhou, E.C.; Hijmans, A.; Houben, T.; Boels, M.G.; ... ; Diepen, J.A. van 2019
Background: C-type lectin receptors, including Dectin-2, are pattern recognition receptors on monocytes and macrophages that mainly recognize sugars and sugar-like structures present on fungi.... Show moreBackground: C-type lectin receptors, including Dectin-2, are pattern recognition receptors on monocytes and macrophages that mainly recognize sugars and sugar-like structures present on fungi. Activation of C-type lectin receptors induces downstream CARD9 signalling, leading to the production of cytokines. We hypothesized that under hyperglycaemic conditions, as is the case in diabetes mellitus, glycosylated protein (sugar-like) structures activate C-type lectin receptors, leading to immune cell activation and increased atherosclerosis development. Methods: Low-density lipoprotein receptor-deficient mice were lethally irradiated and transplanted with bone marrow from control wild-type, Dectin-2(-/-) or Card9(-/-) mice. After 6 weeks of recovery, mice received streptozotocin injections (50 mg/g BW; 5 days) to induce hyperglycaemia. After an additional 2 weeks, mice were fed a Western-type diet (0.1% cholesterol) for 10 weeks. Results and Conclusion: Deletion of haematopoietic Dectin-2 reduced the number of circulating Ly6C(hi) monocytes, increased pro-inflammatory cytokine production, but did not affect atherosclerosis development. Deletion of haematopoietic CARD9 tended to reduce macrophage and collagen content in atherosclerotic lesions, again without influencing the lesion size. Deletion of haematopoietic Dectin-2 did not influence atherosclerosis development under hyperglycaemic conditions, despite some minor effects on inflammation. Deletion of haematopoietic CARD9 induced minor alterations in plaque composition under hyperglycaemic conditions, without affecting lesion size. Show less
Antigen-presenting cells (APCs) such as dendritic cells (DCs) are crucial for initiation of adequate inflammatory responses, which critically depends on the cooperated engagement of different... Show moreAntigen-presenting cells (APCs) such as dendritic cells (DCs) are crucial for initiation of adequate inflammatory responses, which critically depends on the cooperated engagement of different receptors. In addition to pattern recognition receptors (PRRs), Fc gamma receptors (Fc gamma Rs) have recently been identified to be important in induction of inflammation by DCs. Fc gamma Rs that recognize IgG immune complexes, which are formed upon opsonization of pathogens, induce pro-inflammatory cytokine production through cross-talk with PRRs such as Toll-like receptors (TLRs). While the physiological function of Fc gamma R-TLR cross-talk is to provide protective immunity against invading pathogens, undesired activation of Fc gamma R-TLR cross-talk, e.g., by autoantibodies, also plays a major role in the development of chronic inflammatory disorders such as rheumatoid arthritis (RA). Yet, the molecular mechanisms of Fc gamma R-TLR cross-talk are still largely unknown. Here, we identified that Fc gamma R-TLR cross-talk-induced cytokine production critically depends on activation of the transcription factor interferon regulatory factor 5 (IRF5), which results from induction of two different pathways that converge on IRF5 activation. First, TLR stimulation induced phosphorylation of TBK1/IKK epsilon, which is required for IRF5 phosphorylation and subsequent activation. Second, Fc gamma R stimulation induced nuclear translocation of IRF5, which is essential for gene transcription by IRF5. We identified that IRF5 activation by Fc gamma R-TLR cross-talk amplifies pro-inflammatory cytokine production by increasing cytokine gene transcription, but also by synergistically inducing glycolytic reprogramming, which is another essential process for induction of inflammatory responses by DCs. Combined, here we identified IRF5 as a pivotal component of Fc gamma R-TLR cross-talk in human APCs. These data may provide new potential targets to suppress chronic inflammation in autoantibody-associated diseases that are characterized by undesired or excessive Fc gamma R-TLR cross-talk, such as RA, systemic sclerosis, and systemic lupus erythematous. Show less
