Vascular smooth muscle cells in response to cholesterol crystals modulates inflammatory cytokines release and promotes neutrophil extracellular trap formation.

BACKGROUND: The formation and accumulation of cholesterol crystals (CC) at the lesion site is a hallmark of atherosclerosis. Although studies have shown the importance of vascular smooth muscle cells (VSMCs) in the disease atherosclerosis, little is known about the molecular mechanism behind the uptake of CC in VSMCs and their role in modulating immune response. METHODS: Human aortic smooth muscle cells were cultured and treated with CC. CC uptake and CC mediated signaling pathway and protein induction were studied using flow cytometry, confocal microscopy, western blot and Olink proteomics. Conditioned medium from CC treated VSMCs was used to study neutrophil adhesion, ROS production and phagocytosis. Neutrophil extracellular traps (NETs) formations were visualized using confocal microscopy. RESULTS: VSMCs and macrophages were found around CC clefts in human carotid plaques. CC uptake in VSMCs are largely through micropinocytosis and phagocytosis via PI3K-AkT dependent pathway. The uptake of CC in VSMCs induce the release inflammatory proteins, including IL-33, an alarming cytokine. Conditioned medium from CC treated VSMCs can induce neutrophil adhesion, neutrophil reactive oxygen species (ROS) and neutrophil extracellular traps (NETs) formation. IL-33 neutralization in conditioned medium from CC treated VSMCs inhibited neutrophil ROS production and NETs formation. CONCLUSION: We demonstrate that VSMCs due to its vicinity to CC clefts in human atherosclerotic lesion can modulate local immune response and we further reveal that the interaction between CC and VSMCs impart an inflammatory milieu in the atherosclerotic microenvironment by promoting IL-33 dependent neutrophil influx and NETs formation.

Association between C10X polymorphism in the CARD8 gene and inflammatory markers in young healthy individuals in the LBA study.

BACKGROUND: The Caspase activation and recruitment domain 8 (CARD8) protein is a component of innate immunity as a negative regulator of NF- ĸB, and has been associated with regulation of proteins involved in inflammation. Expression of CARD8 mRNA and protein has been identified in human atherosclerotic lesions, and the truncated T30A variant (rs2043211) of CARD8 has been associated with lower C-reactive (CRP) and MCP-1 levels in myocardial infarction patients. The present study examines the role of a genetic variation in the CARD8 gene in relation to a selection of markers of inflammation. METHODS: In a cross-sectional study of young healthy individuals (18.0-25.9 yrs, n = 744) the association between the rs2043211 variant in the CARD8 gene and protein markers of inflammation was assessed. Genotyping of the CARD8 C10X (rs2043211) polymorphism was performed with TaqMan real time PCR on DNA from blood samples. Protein levels were studied via Olink inflammation panel ( https://olink.com/ ). Using linear models, we analyzed men and two groups of women with and without estrogen containing contraceptives separately, due to previous findings indicating differences between estrogen users and non-estrogen using women. Genotypes were analyzed by additive, recessive and dominant models. RESULTS: The minor (A) allele of the rs2043211 polymorphism in the CARD8 gene was associated with lower levels of CCL20 and IL-6 in men (CCL20, Additive model: p = 0.023; Dominant model: p = 0.016. IL-6, Additive model: p = 0.042; Dominant model: p = 0.039). The associations remained significant also after adjustment for age and potential intermediate variables. CONCLUSIONS: Our data indicate that CARD8 may be involved in the regulation of CCL20 and IL-6 in men. No such association was observed in women. These findings strengthen and support previous in vitro data on IL-6 and CCL20 and highlight the importance of CARD8 as a factor in the regulation of inflammatory proteins. The reason to the difference between sexes is however not clear, and the influence of estrogen as a possible factor important for the inflammatory response needs to be further explored.

Targeting serotonin receptor 2B inhibits TGFß induced differentiation of human vascular smooth muscle cells.

Vascular Smooth Muscle Cells (VSMCs) are known to be the key drivers of intimal thickening which contribute to early progression of atherosclerosis. VSMCs are the major producers of extracellular matrix within the vessel wall and in response to atherogenic stimuli they could modify the type of matrix proteins produced. Serotonin receptor 2B (5-HT2B receptor/HTR2B) has been implicated in several chronic fibrotic and vascular diseases. Although studies have successfully demonstrated the efficacy of HTR2B blockade in attenuating fibrotic disease, the role of 5-HT2B receptor in TGFß mediated VSMC differentiation remain largely unknown. In the present study, we investigated the potential of targeting the 5-HT2B receptor to prevent TGFß induced VSMCs differentiation. Our results showed that 5-HT2B receptors are expressed in human atherosclerotic lesion and HTR2B expression positively correlated to the VSMCs markers. We show that AM1125, a selective 5-HT2B receptor inhibitor, significantly inhibits TGFß1 induced production of collagen and CTGF. The investigation of underlying mechanisms indicated that 5-HT2B receptor antagonism blocks phospho-Smad2 mediated downstream signaling of TGFß1 in vascular smooth muscle cells. Collectively, the HTR2B/TGF-ß1/Phospho-Smad2 pathway plays a critical role in the regulation of VSMCs differentiation. Our findings might serve 5-HT2B receptor as a therapeutic target to limit TGF-ß1 induced VSMC differentiation.

Novel purine analogues regulate IL-1ß release via inhibition of JAK activity in human aortic smooth muscle cells.

Purine analogues bearing a nitrate ester motif were previously discovered as cardioprotective and anti-inflammatory agents, but the anti-inflammatory mechanism remains to be established. We therefore investigated the anti-inflammatory effect of two purine analogues, MK118 bearing a nitrate ester moiety and the methyl-substituted analogue MK196 in Aortic Smooth Muscle Cells (AoSMCs), with emphasis on IL-1ß release. The AoSMCs were stimulated with LPS with or without purine analogue, followed by ELISA, Olink proteomics, Western blot and real time PCR of NLRP3 inflammasome components. Both purine analogues inhibited the release of proteins involved in inflammation, such as TRAIL, CCL4, CSF1 and IL-1ß in AoSMCs, as well as intracellular gene and protein expression of IL-1ß and NLRP3 inflammasome components. MK196, but not MK118, also inhibited the LPS-induced release of IL-7, CXCL10, PD-L1, FLT3L and CCL20. We also showed that MK118 and possibly MK196 act via inhibition of JAKs. In silico studies showed that the purine moiety is a competent hinge binding motif and that the purine-piperazine scaffold is well accommodated in the lipophilic groove of JAK1-3. Both compounds establish interactions with catalytic amino acids in the active site of JAK1-3 and the terminal nitrate ester of MK118 was revealed as a promising pharmacophore. Our data suggest that MK118 and MK196 inhibit the release of proinflammatory proteins in AoSMCs, and targets JAK1-3 activation. Purine analogues also inhibit the expression of NLRP3 inflammasome genes and proteins and may in the future be evaluated for anti-inflammatory aspects on inflammatory diseases.

Inhibition of IL17A Using an Affibody Molecule Attenuates Inflammation in ApoE-Deficient Mice.

The balance between pro- and anti-inflammatory cytokines released by immune and non-immune cells plays a decisive role in the progression of atherosclerosis. Interleukin (IL)-17A has been shown to accelerate atherosclerosis. In this study, we investigated the effect on pro-inflammatory mediators and atherosclerosis development of an Affibody molecule that targets IL17A. Affibody molecule neutralizing IL17A, or sham were administered in vitro to human aortic smooth muscle cells (HAoSMCs) and murine NIH/3T3 fibroblasts and in vivo to atherosclerosis-prone, hyperlipidaemic ApoE-/- mice. Levels of mediators of inflammation and development of atherosclerosis were compared between treatments. Exposure of human smooth muscle cells and murine NIH/3T3 fibroblasts in vitro to αIL-17A Affibody molecule markedly reduced IL6 and CXCL1 release in supernatants compared with sham exposure. Treatment of ApoE-/- mice with αIL-17A Affibody molecule significantly reduced plasma protein levels of CXCL1, CCL2, CCL3, HGF, PDGFB, MAP2K6, QDPR, and splenocyte mRNA levels of Ccxl1, Il6, and Ccl20 compared with sham exposure. There was no significant difference in atherosclerosis burden between the groups. In conclusion, administration of αIL17A Affibody molecule reduced levels of pro-inflammatory mediators and attenuated inflammation in ApoE-/- mice.

Human Renal Fibroblasts, but Not Renal Epithelial Cells, Induce IL-1ß Release during a Uropathogenic Escherichia coli Infection In Vitro.

Understanding how uropathogenic Escherichia coli (UPEC) modulates the immune response in the kidney is essential to prevent UPEC from reaching the bloodstream and causing urosepsis. The purpose of this study was to elucidate if renal fibroblasts can release IL-1ß during a UPEC infection and to investigate the mechanism behind the IL-1ß release. We found that the UPEC strain CFT073 induced an increased IL-1ß and LDH release from renal fibroblasts, but not from renal epithelial cells. The UPEC-induced IL-1ß release was found to be NLRP3, caspase-1, caspase-4, ERK 1/2, cathepsin B and serine protease dependent in renal fibroblasts. We also found that the UPEC virulence factor α-hemolysin was necessary for IL-1ß release. Conditioned medium from caspase-1, caspase-4 and NLRP3-deficient renal fibroblasts mediated an increased reactive oxygen species production from neutrophils, but reduced UPEC phagocytosis. Taken together, our study demonstrates that renal fibroblasts, but not renal epithelial cells, release IL-1ß during a UPEC infection. This suggest that renal fibroblasts are vital immunoreactive cells and not only structural cells that produce and regulate the extracellular matrix.

Expression of CARD8 in human atherosclerosis and its regulation of inflammatory proteins in human endothelial cells.

The Caspase activation and recruitment domain 8 (CARD8) protein is a component of innate immunity and overexpression of CARD8 mRNA was previously identified in atherosclerosis. However, very little is known about the regulation of CARD8 in endothelial cells and atherosclerosis. The aim of this study was to investigate CARD8 in the regulation of cytokine and chemokine expression in endothelial cells. Sections of human atherosclerotic lesions and non-atherosclerotic arteries were immunostained for CARD8 protein. Expression of CARD8 was correlated to mediators of inflammation in atherosclerotic lesions using Biobank of Karolinska Endarterectomies microarray data. The CARD8 mRNA was knocked-down in human umbilical vein endothelial cells (HUVECs) in vitro, followed by quantitative RT-PCR analysis and OLINK Proteomics. Endothelial and smooth muscle cells in arterial tissue expressed CARD8 and CARD8 correlated with vWF, CD163 and the expression of inflammatory genes, such as CXCL1, CXCL6 and PDGF-A in plaque. Knock-down of CARD8 in HUVECs significantly altered proteins involved in inflammatory response, such as CXCL1, CXCL6, PDGF-A, MCP-1 and IL-6. The present study suggest that CARD8 regulate the expression of cytokines and chemokines in endothelial cells and atherosclerotic lesions, suggesting that CARD8 plays a significant role in endothelial activation.

A novel purine analogue bearing nitrate ester prevents platelet activation by ROCK activity inhibition.

Natural purines like ATP, ADP and adenosine have crucial roles in platelet physiology. This knowledge has been significant in drug development and today ADP receptor antagonists are widely used for prevention of thrombotic events following myocardial infarction and ischaemic stroke. Recent studies have shown that a purine analogue bearing nitrate ester group (denoted MK128) has anti-inflammatory effects probably due to its ability to donate nitric oxide (NO). However, other pharmacological mechanisms may contribute to the observed effect. The aim of the present study was to establish the anti-platelet activity and elucidate the underlying molecular mechanism(s) of the purine analogue MK128. We found that MK128 reduced aggregation and secretion induced by the thrombin receptor agonist SFLLRN and nearly abolished aggregation and secretion induced by thromboxane A2 (TxA2) and collagen receptor agonists. The inhibition took place despite blockage of the NO/cGMP signalling system. Furthermore, interaction between MK128 and platelet purinergic receptors did not explain the observed inhibition. Instead, we found that MK128 concentration-dependently inhibited Rho-associated kinase (ROCK), which led to decreased ROCK-dependent myosin phosphatase target subunit (MYPT)-1 phosphorylation and suppression of platelet functional responses.

Activation of the JAK/STAT3 and PI3K/AKT pathways are crucial for IL-6 trans-signaling-mediated pro-inflammatory response in human vascular endothelial cells.

BACKGROUND: IL-6 classic signaling is linked to anti-inflammatory functions while the trans-signaling is associated with pro-inflammatory responses. Classic signaling is induced via membrane-bound IL-6 receptor (IL-6R) whereas trans-signaling requires prior binding of IL-6 to the soluble IL-6R. In both cases, association with the signal transducing gp130 receptor is compulsory. However, differences in the downstream signaling mechanisms of IL-6 classic- versus trans-signaling remains largely elusive. METHODS: In this study, we used flow cytometry, quantitative PCR, ELISA and immuno-blotting techniques to investigate IL-6 classic and trans-signaling mechanisms in Human Umbilical Vein Endothelial Cells (HUVECs). RESULTS: We show that both IL-6R and gp130 are expressed on the surface of human vascular endothelial cells, and that the expression is affected by pro-inflammatory stimuli. In contrast to IL-6 classic signaling, IL-6 trans-signaling induces the release of the pro-inflammatory chemokine Monocyte Chemoattractant Protein-1 (MCP-1) from human vascular endothelial cells. In addition, we reveal that the classic signaling induces activation of the JAK/STAT3 pathway while trans-signaling also activates the PI3K/AKT and the MEK/ERK pathways. Furthermore, we demonstrate that MCP-1 induction by IL-6 trans-signaling requires simultaneous activation of the JAK/STAT3 and PI3K/AKT pathways. CONCLUSIONS: Collectively, our study reports molecular differences in IL-6 classic- and trans-signaling in human vascular endothelial cells; and elucidates the pathways which mediate MCP-1 induction by IL-6 trans-signaling.

Lysophosphatidic Acid Signaling in Obesity and Insulin Resistance.

Although simple in structure, lysophosphatidic acid (LPA) is a potent bioactive lipid that profoundly influences cellular signaling and function upon binding to G protein-coupled receptors (LPA1-6). The majority of circulating LPA is produced by the secreted enzyme autotaxin (ATX). Alterations in LPA signaling, in conjunction with changes in autotaxin (ATX) expression and activity, have been implicated in metabolic and inflammatory disorders including obesity, insulin resistance, and cardiovascular disease. This review summarizes our current understanding of the sources and metabolism of LPA with focus on the influence of diet on circulating LPA. Furthermore, we explore how the ATX-LPA pathway impacts obesity and obesity-associated disorders, including impaired glucose homeostasis, insulin resistance, and cardiovascular disease.

CARD8 gene encoding a protein of innate immunity is expressed in human atherosclerosis and associated with markers of inflammation.

Inflammation is a key factor in the development of atherosclerotic coronary artery disease. It is promoted through the inflammasome, a molecular machine that produces IL (interleukin)-1ß in response to cholesterol crystal accumulation in macrophages. The CARD8 (caspase recruitment domain 8) protein modulates this process by suppressing caspase 1 and the transcription factor NF-κB (nuclear factor κB). The expression of CARD8 mRNA was examined in atherosclerotic vascular tissue and the impact on MI (myocardial infarction) of a polymorphism in the CARD8 gene determined. CARD8 mRNA was analysed by microarray of human atherosclerotic tissue and compared with transplant donor arterial tissue. Microarray analysis was performed for proximal genes associated with the rs2043211 locus in plaque. The CARD8 rs2043211 polymorphism was analysed by genotyping of two Swedish MI cohorts, FIA (First Myocardial Infarction in Northern Sweden) and SCARF (Stockholm Coronary Atherosclerosis Risk Factor). The CRP (C-reactive protein) level was measured in both cohorts, but the levels of the pro-inflammatory cytokines IL-1ß, IL-18, TNF (tumour necrosis factor) and MCP-1 (monocyte chemoattractant protein) were measured in sera available from the SCARF cohort. CARD8 mRNA was highly expressed in atherosclerotic plaques compared with the expression in transplant donor vessel (P<0.00001). The minor allele was associated with lower expression of CARD8 in the plaques, suggesting that CARD8 may promote inflammation. Carriers of the minor allele of the rs2043211 polymorphism also displayed lower circulating CRP and lower levels of the pro-atherosclerotic chemokine MCP-1. However, no significant association could be detected between this polymorphism and MI in the two cohorts. Genetic alterations in the CARD8 gene therefore seem to be of limited importance for the development of MI.