To Örebro University

Inflammatory signaling is a major contributor to cardiac dysfunction in diseases such as sepsis, myocarditis, and heart failure, yet existing in vitro models lack the multicellular complexity and physiological relevance needed to accurately recapitulate human cardiac pathology. In this study, we used human cardiac spheroids, three dimensional microtissues composed of cardiomyocytes, fibroblasts, and endothelial cells to study lipopolysaccharide induced inflammation. High resolution confocal microscopy confirmed a radial distribution of cell types within the spheroids. Following 24 h LPS stimulation, the spheroids exhibited no significant increase in lactate dehydrogenase release, indicating preserved membrane integrity and absence of overt cytotoxicity. Nevertheless, a robust inflammatory response was observed at both transcriptional and protein levels, including significant upregulation and secretion of TLR2, IL6, TNF, CXCL8, and CCL2. Mitochondrial stress testing revealed significantly reduced basal respiration, ATP production, and maximal respiratory capacity. Functional analyses showed impaired contractility characterized by reduced beat rate, delayed time to peak contraction, and prolonged relaxation time. Together, these findings demonstrate that human cardiac spheroids mount a physiologically relevant, multicellular inflammatory response that compromises both mitochondrial metabolism and mechanical performance. The model offers a powerful platform for investigating innate immune activation and for screening therapeutic interventions targeting inflammation induced cardiac dysfunction.

Background: Endothelial dysfunction profoundly compromises the barrier function that precludes trans-endothelial entry of low-density lipoprotein cholesterol (LDL-C) into the vessel wall. LDL-C retention in the vessel wall is atherogenic and its flux involves several mechanisms including LDL-receptor (LDL-R) mediated transcytosis, a process that is facilitated by inflammatory stressors. In this study, we aimed to investigate the role of interleukin-6 (IL-6) in regulating LDL-R and LDL-C uptake by vascular endothelial cells.

Method: We used commercially available Human umbilical vein endothelial cells (HUVECs) in this study. Flow cytometry, western blotting, qRT-PCR and ELISA were used to investigate expression of LDL-R and Mylip/IDOL. LDL-C uptake and free cholesterol levels in HUVECs was assessed using flowcytometry and mass-spectrometry respectively.

Results: We show that HUVECs treated with a combination of IL-6 and soluble IL-6 receptor (sIL-6R) result in a significant reduction in surface expression of LDL-R, an effect that is reversed by soluble gp130Fc - an antagonist of IL-6 trans-singling. Using pharmacological inhibitors and gene silencing techniques, we demonstrate that IL-6 trans-signaling induced downregulation of LDL-R is attained through lysosomal degradation mediated by the E3 ubiquitin ligase Mylip. Conversely, HUVECs treated with IL-6 in combination with sIL-6R exhibit markedly increased uptake of native LDL-C which is also inhibited by sgp130Fc, the actin inhibitor Cytochalasin D and the macropinocytosis inhibitor EIPA. Although stimulation of HUVECs upregulated the expression of scavenger receptors CD36 and CXCL16, their contribution to native LDL-C uptake turned out to be negligible.

Conclusion: Collectively, this study highlights the role of IL-6 in the regulation of LDL-R expression and cholesterol homeostasis in vascular ECs. IL-6 trans-signaling downregulates LDL-R yet increases LDL-C uptake via an LDL-R-independent, actin-dependent macropinocytosis pathway.

Endothelial dysfunction is an early driver of atherosclerosis, yet the direct impact of endogenous crystals such as cholesterol crystals and monosodium urate on endothelial activation remains incompletely understood. In this study, we examine how crystalline stimuli modulate human umbilical vein endothelial cells by assessing inflammatory signaling, mitochondrial respiration, and neutrophil recruitment. Using dose- and time-controlled experiments, we show that CC and MSU are internalized by endothelial cells, activating NF-κB and STAT3 signaling pathways and inducing a robust pro-inflammatory cytokine profile. Notably, CC caused marked mitochondrial dysfunction, evidenced by impaired respiratory capacity and loss of membrane potential, revealing a novel bioenergetic vulnerability in endothelial cells. Both direct crystal stimulation and exposure to crystal-primed conditioned media triggered endothelial adhesion molecule expression and promoted neutrophil adhesion, indicating that soluble mediators released upon crystal stimulation can propagate vascular inflammation. These findings demonstrate that crystalline stimuli are potent vascular danger signals capable of driving endothelial inflammation, mitochondrial impairment, and immune cell engagement, which are hallmarks of early atherogenesis. By elucidating these multifaceted endothelial responses, this study provides important mechanistic insights into how crystal-induced signals may contribute to vascular dysfunction and the early stages of atherogenesis.

BACKGROUND: Blockade of IL1RAP (interleukin 1 receptor associated protein) was recently shown to reduce atherosclerosis in mice, but the effect on human vascular cells is largely unknown. Targeting the IL1RAP coreceptor represents a novel strategy to block the IL1RAP-dependent cytokines IL (interleukin)-1, IL-33, and IL-36. In the present study, we aimed to evaluate the role of novel antibodies targeting IL1RAP to reduce the effects of IL-1β, IL-33, or IL-36γ in human vascular cells.

METHODS: Expression of IL1RAP was observed in human atherosclerotic plaques by immunohistochemistry and microarray and in endothelial cells by flow cytometry. Endothelial cells were cultured with IL-1β, IL-33, or IL-36γ cytokines with or without IL1RAP antibodies and analyzed with Olink proteomics, ELISA, Western blot, and real-time quantitative polymerase chain reaction. The functional effect of IL1RAP antibodies on endothelial cells were analyzed with adhesion and permeability assays.

RESULTS: Olink proteomics showed inhibition of the inflammatory proteins LIF (leukemia inhibitory factor), OPG (osteoprotegerin), CCL4 (C-C motif chemokine ligand 4), and MCP-3 (monocyte chemoattractant protein 3) by IL1RAP-blockade in endothelial cells after IL-1β stimulation. In addition, the IL1RAP antibodies inhibited IL-1β, and IL-33 induced IL-6 and IL-8 secretion. Secretion of MCP-1 (monocyte chemoattractant protein 1) was induced by IL-1β, IL-33, and IL-36γ, and subsequently was inhibited by IL1RAP antibodies. Similar effects were found on mRNA expression level. Endothelial expression of the adhesion markers ICAM1, VCAM1, and SELE were significantly reduced by IL1RAP antibodies, and neutrophil adhesion to endothelial cells induced by IL-1β and IL-33 was reduced by IL1RAP blockade. In human atherosclerotic lesions, IL1RAP expression correlated with markers of inflammation like IL6, IL8, and MCP1.

CONCLUSIONS: IL1RAP-targeting antibodies can reduce the expression of inflammatory cytokines and markers of adhesion in endothelial cells, which may be of importance for future putative targeted treatments against cardiovascular disease.

INTRODUCTION: Studies suggest that immune checkpoints play a role in accelerating the formation of atherosclerosis. We aimed to assess the expression of soluble and membrane-bound immune checkpoints in patients with peripheral artery disease (PAD).

METHODS: The levels of 14 soluble immune checkpoints were assessed in blood plasma of PAD patients (n= 37) and healthy controls (HCs, n=39) by Multiplex protein assay. The surface expression of immune checkpoints on peripheral blood immune cells was determined by flow cytometry. Cytokine production capacity was measured by flow cytometry in TIM-3+ T cells to determine immune exhaustion.

RESULTS: Soluble levels of PD-L2 were decreased in female PAD patients, whereas soluble levels of TIM-3 showed a trend towards an increased concentration in female PAD patients. PD-L2+ frequencies were higher within all monocyte subsets in PAD patients. CD4+ T cells from PAD patients had increased frequencies of TIM-3+ cells, showing little overlap with other immune exhaustion markers. TIM-3+ CD4+ T cells from both PAD patients and HCs, had a low capacity to produce pro-inflammatory cytokines, but a higher capacity to produce IL-10 compared to TIM-3- CD4+ T cells.

CONCLUSION: PAD patients show differences in the expression of membrane-bound and soluble immune checkpoints. Some of these differences might be caused by prolonged immune activation, although immune exhaustion markers did not always overlap.

In atherosclerotic lesions, monocyte-derived macrophages are major source of interferon gamma (IFN-γ), a pleotropic cytokine known to regulate the expression of numerous genes, including the antiviral gene RSAD2. While RSAD2 was reported to be expressed in endothelial cells of human carotid lesions, its significance for the development of atherosclerosis remains utterly unknown. Here, we harnessed publicly available human carotid atherosclerotic data to explore RSAD2 in lesions and employed siRNA-mediated gene-knockdown to investigate its function in IFN-γ-stimulated human aortic smooth muscle cells (hAoSMCs). Silencing RSAD2 in IFN-γ-stimulated hAoSMCs resulted in reduced expression and secretion of key CXCR3-chemokines, CXCL9, CXCL10, and CXCL11. Conditioned medium from RSAD2-deficient hAoSMCs exhibited diminished monocyte attraction in vitro compared to conditioned medium from control cells. Furthermore, RSAD2 transcript was elevated in carotid lesions where it was expressed by several different cell types, including endothelial cells, macrophages and smooth muscle cells. Interestingly, RSAD2 displayed significant correlations with CXCL10 (r =  0.45, p = 0.010) and CXCL11 (r = 0.53, p = 0.002) in human carotid lesions. Combining our findings, we uncover a novel role for RSAD2 in hAoSMCs, which could potentially contribute to monocyte recruitment in the context of atherosclerosis.

Laminins are essential components of the basement membranes, expressed in a tissue- and cell-specific manner under physiological conditions. During inflammatory circumstances, such as atherosclerosis, alterations in laminin composition within vessels have been observed. Our study aimed to assess the influence of tumor necrosis factor-alpha (TNF), a proinflammatory cytokine abundantly found in atherosclerotic lesions, on endothelial laminin gene expression and the effects of laminin-332 (LN332) on endothelial cells' behavior. We also evaluated the expression of LN332-encoding genes in human carotid atherosclerotic plaques. Our findings demonstrate that TNF induces upregulation of LAMB3 and LAMC2, which, along with LAMA3, encode the LN332 isoform. Endothelial cells cultured on recombinant LN332 exhibit decreased claudin-5 expression and display a loosely connected phenotype, with an elevated expression of chemokines and leukocyte adhesion molecules, enhancing their attractiveness and adhesion to leukocytes in vitro. Furthermore, LAMB3 and LAMC2 are upregulated in human carotid plaques and show a positive correlation with TNF expression. In summary, TNF stimulates the expression of LN332-encoding genes in human endothelial cells and LN332 promotes an endothelial phenotype characterized by compromised junctional integrity and increased leukocyte interaction. These findings highlight the importance of basement membrane proteins for endothelial integrity and the potential role of LN332 in atherosclerosis.

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.

Background and Aims: Peripheral arterial disease (PAD) is a clinical manifestation of atherosclerosis, affecting arteries in the leg. Based on their symptoms and severity, PAD patients are characterized into three sub-groups: asymptomatic, intermittent claudication (IC) and critical limb ischemia (CLI). Despite its high prevalence, PAD remains under diagnosed and the role of immune cells in PAD pathophysiology remains poorly understood. In this study, we characterized the innate immune responses in PAD patients compared to healthy controls.

Methods: Blood samples were collected from 14 patients with PAD (IC) and 30 healthy controls, to assess the phenotype of monocytes and neutrophils by using 10-colour flow cytometry. Phagocytosis assay was performed with labelled E.coli particles. Mann-Whitney U non-parametrical test was used for statistical comparison between PAD patients and healthy controls.

Results: A significant higher proportion of leukocytes (p<0.05) and neutrophils (p<0.01) was observed in PAD patients compared to healthy controls, whereas monocyte subsets showed no significant differences. Interestingly, neutrophils showed a significantly impaired phagocytosis capability (p<0.05) and reduced expression of myeloperoxidase (MPO) (p<0.05) in PAD patients compared to healthy controls.

Conclusions: Taken together these results, suggest that PAD patients have an increased proportion of neutrophils in circulation, with impaired phagocytosis capability, compared to healthy controls.