Macrophage uptake of oxidized and acetylated low-density lipoproteins and generation of reactive oxygen species are regulated by linear stiffness of the growth surface

Mechanosensitivity of macrophage polarization: comparing small molecule leukadherin-1 to substrate stiffness

Macrophages sustain tissue homeostasis through host defense and wound repair. To promote host defense, macrophages upregulate surface markers associated with antigen processing and secrete pro-inflammatory mediators such as IL-6 and IL-1β. After pathogen clearance, macrophages shift phenotype to promote wound repair. Shifts in phenotypes are termed "polarization" and have historically been modeled by exposure to soluble mediators such as LPS+IFNγ (host defense) or IL-4+IL-13 (tissue repair). Greater emphasis is now being placed on understanding how the mechanical environment of macrophages, such as tissue compliance, regulates macrophages responses. Here, we compare incubation of primary macrophages on collagen-coated silica gels of varying stiffness to treatment with the small molecule integrin activator, leukadherin-1 (LA1), to examine how substrate stiffness alters macrophage polarization in response to multiple stimuli. LA1 was developed as an immunomodulator to treat inflammatory diseases by impairing trafficking of inflammatory cells. A recent clinical trial examining LA1 as an immunomodulator in solid tumors was terminated early because no benefit was observed. We hypothesized that LA1 treatment may exert additional, unexpected effects on macrophage polarization by replicating mechanotransduction. Specifically, we hypothesized that LA1 would mimic effects of incubation on stiffer substrates, as both conditions would be predicted to activate integrins. Our results show that soft substrate (0.2 kPa) trends towards upregulation of host defense molecules, in contrast to prior reports using different experimental systems. We further show that soft substrates enhance NLRP3-mediated IL-1β production, compared to stiff, in both primary mouse and human macrophages. LA1 mimicked incubation on stiff substrates in inhibiting NLRP3 activation and in regulating expression of several surface markers but differed by reducing IL-6 production. Our results show that macrophage inflammatory responses are regulated by adhesion-based, integrin-mediated mechanical signaling. Modulation of NLRP3-mediated IL-1β production by LA1 supports the possibility of repurposing LA1 to treat NLRP3-dependent inflammatory diseases.

Exploring the comorbidity mechanisms between atherosclerosis and hashimoto's thyroiditis based on microarray and single-cell sequencing analysis

Atherosclerosis (AS) is a chronic vascular disease characterized by inflammation of the arterial wall and the formation of cholesterol plaques. Hashimoto's thyroiditis (HT) is an autoimmune disorder marked by chronic inflammation and destruction of thyroid tissue. Although previous studies have identified common risk factors between AS and HT, the specific etiology and pathogenic mechanisms underlying these associations remain unclear. We obtained relevant datasets for AS and HT from the Gene Expression Omnibus (GEO). By employing the Limma package, we pinpointed common differentially expressed genes (DEGs) and discerned co-expression modules linked to AS and HT via Weighted Gene Co-expression Network Analysis (WGCNA). We elucidated gene functions and regulatory networks across various biological scenarios through enrichment and pathway analysis using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Core genes were identified using Cytoscape software and further validated with external datasets. We also conducted immune infiltration analysis on these core genes utilizing the CIBERSORT method. Lastly, Single-cell analysis was instrumental in uncovering common diagnostic markers. Based on differential analysis and WGCNA, we identified 119 candidate genes within the cohorts for AS and HT. KEGG and GO enrichment analyses indicate that these genes are significantly involved in antigen processing and presentation, along with various immune-inflammatory pathways. Two pivotal genes, PTPRC and TYROBP, were identified using five algorithms from the cytoHubba plugin. Validation through external datasets confirmed their substantial diagnostic value for AS and HT. Moreover, the results of Gene Set Enrichment Analysis (GSEA) indicated that these core genes are significantly enriched in various receptor interactions and signaling pathways. Immune infiltration analysis revealed a strong association of lymphocytes and macrophages with the pathogenesis of AS and HT. Single-cell analysis demonstrated predominant expression of the core genes in macrophages, monocytes, T cells and Common Myeloid Progenitor (CMP). This study proposes that an aberrant immune response might represent a shared pathogenic mechanism in AS and HT. The genes PTPRC and TYROBP are identified as critical potential biomarkers and therapeutic targets for these comorbid conditions. Furthermore, the core genes and their interactions with immune cells could serve as promising targets for future diagnostic and therapeutic strategies.

Functional and Multi-Omics Effects of an Optimized CRISPR-Mediated FURIN Depletion in U937 Monocytes

The pro-protein convertase FURIN (PCSK3) is implicated in a wide range of normal and pathological biological processes such as infectious diseases, cancer and cardiovascular diseases. Previously, we performed a systemic inhibition of FURIN in a mouse model of atherosclerosis and demonstrated significant plaque reduction and alterations in macrophage function. To understand the cellular mechanisms affected by FURIN inhibition in myeloid cells, we optimized a CRISPR-mediated gene deletion protocol for successfully deriving hemizygous (HZ) and nullizygous (NZ) FURIN knockout clones in U937 monocytic cells using lipotransfection-based procedures and a dual guide RNA delivery strategy. We observed differences in monocyte and macrophage functions involving phagocytosis, lipid accumulation, cell migration, inflammatory gene expression, cytokine release patterns, secreted proteomics (cytokines) and whole-genome transcriptomics between wild-type, HZ and NZ FURIN clones. These studies provide a mechanistic basis on the possible roles of myeloid cell FURIN in cardiovascular disorders.

The lack of association between different LDL-C levels and oxidized LDL in patients with type 2 diabetes

Background

High concentrations of low-density lipoprotein cholesterol (LDL-C) have been a known risk factor for cardiovascular diseases. Also, the role of oxidized LDL (ox-LDL) in forming atherosclerosis plaque has been proven. However, it has not yet been proven that atherogenic LDL-C by-products like ox-LDL will decrease by keeping the LDL levels at the desired level. This study aimed to examine the relationship between LDL-C and ox-LDL in different LDL-C values in patients with type 2 diabetes (T2D).

Methods

In this cross-sectional study, 347 patients with T2D who received statins were enrolled. LDL-C values were defined into four groups as LDL-C < 55 mg/dL, 55 mg/dL ≤ to <70 mg/dL, 70 mg/dL ≤ to <100 mg/dL and LDL-C ≥ 100 mg/dL. Total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and ox-LDL were studied in the four defined groups.

Results

Ox-LDL levels were not different among the four groups (p = 0.30). In addition, LDL-C and ox-LDL levels had no significant correlation (r = 0.480, p = 0.376). Additionally, based on this study analysis, ox-LDL levels were significantly correlated with TG levels (r = 0.119, p < 0.05) and TG/HDL ratio (r = 0.390, p < 0.01).

Conclusions

It is concluded that ox-LDL levels were not associated with different LDL-C level categories from <55 mg/dL to >100 mg/dL in patients with T2D. However, the revealed association of ox-LDL with TG level and TG/HDL ratio may be considered in the clinic.

Exosomes-regulated lipid metabolism in tumorigenesis and cancer progression

Increasing evidence highlights the role of lipid metabolism in tumorigenesis and tumor progression. Targeting the processes of lipid metabolism, including lipogenesis, lipid uptake, fatty acid oxidation, and lipolysis, is an optimal strategy for anti-cancer therapy. Beyond cell-cell membrane surface interaction, exosomes are pivotal factors that transduce intercellular signals in the tumor microenvironment (TME). Most research focuses on the role of lipid metabolism in regulating exosome biogenesis and extracellular matrix (ECM) remodeling. The mechanisms of exosome and ECM-mediated reprogramming of lipid metabolism are currently unclear. We summarize several mechanisms associated with the regulation of lipid metabolism in cancer, including transport of exosomal carriers and membrane receptors, activation of the PI3K pathway, ECM ligand-receptor interactions, and mechanical stimulation. This review aims to highlight the significance of these intercellular factors in TME and to deepen the understanding of the functions of exosomes and ECM in the regulation of lipid metabolism.

Modulation of macrophages by biophysical cues in health and beyond

Macrophages play a key role in tissue development and homeostasis, innate immune defence against microbes or tumours, and restoring homeostasis through tissue regeneration following infection or injury. The ability to adopt such diverse functions is due to their heterogeneous nature, which is driven largely by their developmental origin and their response to signals they encounter from the microenvironment. The most well-characterized signals driving macrophage phenotype and function are biochemical and metabolic. However, the way macrophages sense and respond to their extracellular biophysical environment is becoming increasingly recognized in the field of mechano-immunology. These biophysical cues can be signals from tissue components, such as the composition and charge of extracellular matrix or topography, elasticity, and stiffness of the tissue surrounding cells; and mechanical forces such as shear stress or stretch. Macrophages are important in determining whether a disease resolves or becomes chronic. Ageing and diseases such as cancer or fibrotic disorders are associated with significant changes in the tissue biophysical environment, and this provides signals that integrate with those from biochemical and metabolic stimuli to ultimately dictate the overall function of macrophages. This review provides a brief overview of macrophage polarization, followed by a selection of commonly recognized physiological and applied biophysical stimuli impacting macrophage activity, and the potential signalling mechanisms driving downstream responses. The effects of biophysical cues on macrophages' function in homeostasis and disease and the associated clinical implications are also highlighted.

Transcriptional analysis reveals that the intracellular lipid accumulation impairs gene expression profiles involved in insulin response-associated cardiac functionality

Cardiovascular disease (CVD) is a multisystemic and multicellular pathology that is generally associated with high levels of atherogenic lipoproteins in circulation. These lipoproteins tend to be retained and modified, for example, aggregated low-density lipoprotein (aggLDL), in the extracellular matrix of different tissues, such as the vascular wall and heart. The uptake of aggLDL generates a significant increase in cholesteryl ester (CE) in these tissues. We previously found that the accumulation of CE generates alterations in the insulin response in the heart. Although the insulin response is mainly associated with the uptake and metabolism of glucose, other studies have shown that insulin would fulfill functions in this tissue, such as regulating the calcium cycle and cardiac contractility. Here, we found that aggLDL induced-lipid accumulation altered the gene expression profile involved in processes essential for cardiac functionality, including insulin response and glucose uptake (Insr, Ins1, Pik3ip1, Slc2a4 gene expression), calcium cycle (Cacna1s and Gjc2 gene expression) and calcium-dependent cardiac contractility (Myh3), and cholesterol efflux (Abca1), in HL-1 cardiomyocytes. These observations were recapitulated using an in vivo model of hypercholesterolemic ApoE-KO mice. Altogether, these results may explain the deleterious effect of lipid accumulation in the myocardium, with important implications for lipid-overloaded associated CVD, including impaired insulin response, disrupted lipid metabolism, altered cardiac structure, and increased susceptibility to cardiovascular events.

Transcriptional analysis reveals that the intracellular lipid accumulation impairs gene expression profiles involved in insulin response-associated cardiac functionality

Cardiovascular disease (CVD) is a multisystemic and multicellular pathology that is generally associated with high levels of atherogenic lipoproteins in circulation. These lipoproteins tend to be retained and modified, for example, aggregated low-density lipoprotein (aggLDL), in the extracellular matrix of different tissues, such as the vascular wall and heart. The uptake of aggLDL generates a significant increase in cholesteryl ester (CE) in these tissues. We previously found that the accumulation of CE generates alterations in the insulin response in the heart. Although the insulin response is mainly associated with the uptake and metabolism of glucose, other studies have shown that insulin would fulfill functions in this tissue, such as regulating the calcium cycle and cardiac contractility. Here, we found that aggLDL induced-lipid accumulation altered the gene expression profile involved in processes essential for cardiac functionality, including insulin response and glucose uptake ( Insr , Ins1 , Pik3ip1 , Slc2a4 gene expression), calcium cycle ( Cacna1s and Gjc2 gene expression) and calcium-dependent cardiac contractility ( Myh3 ), and cholesterol efflux ( Abca1 ), in HL-1 cardiomyocytes. These observations were recapitulated using an in vivo model of hypercholesterolemic ApoE-KO mice. Altogether, these results may explain the deleterious effect of lipid accumulation in the myocardium, with important implications for lipid-overloaded associated CVD.

Identification of potential M2 macrophage-associated diagnostic biomarkers in coronary artery disease

BACKGROUND

M2 macrophages have been reported to be important in the progression of coronary artery disease (CAD). Thus, the present study aims at exploring the diagnostic value of M2 macrophage-associated genes in CAD.

METHODS

Transcriptome profile of CAD and control samples were downloaded from Gene Expression Omnibus database. The proportion of immune cells was analyzed using cell type identification by estimating relative subsets of RNA transcripts. Weighted Gene Co-expression Network Analysis (WGCNA) was carried out to screen the relevant module associated with M2 macrophages. Differential CAD and control samples of expressed genes (DEGs) were identified by the limma R package. Functional enrichment analysis by means of the clusterProfiler R package. Least absolute shrinkage and selection operator (LASSO) and random forest (RF) algorithms were carried out to select signature genes. Receiver operating curves (ROC) were plotted to evaluate the diagnostic value of selected signature genes. The expressions of potential diagnostic markers were validated by RT-qPCR. The ceRNA network of diagnostic biomarkers was constructed via miRwalk and Starbase database. CMap database was used to screen candidate drugs in the treatment of CAD by targeting diagnostic biomarkers.

RESULTS

A total of 166 M2 macrophage-associated genes were identified by WGCNA. By intersecting those genes with 879 DEGs, 53 M2 macrophage-associated DEGs were obtained in the present study. By LASSO, RF, and ROC analyses, C1orf105, CCL22, CRYGB, FRK, GAP43, REG1P, CALB1, and PTPN21 were identified as potential diagnostic biomarkers. RT-qPCR showed the consistent expression patterns of diagnostic biomarkers between GEO dataset and clinical samples. Perhexiline, alimemazine and mecamylamine were found to be potential drugs in the treatment of CAD.

CONCLUSION

We identified eight M2 macrophage-associated diagnostic biomarkers and candidate drugs for the CAD treatment.

cGAS-STING Pathway Performance in the Vulnerable Atherosclerotic Plaque

The important role of Ca2+ in pathogenic store-operated calcium entry (SOCE) is well-established. Among the proteins involved in the calcium signaling pathway, Stromal interacting molecule 1 (STIM1) is a critical endoplasmic reticulum transmembrane protein. STIM1 is activated by the depletion of calcium stores and then binds to another calcium protein, Orai1, to form a channel through which the extracellular Ca2+ can enter the cytoplasm to replenish the calcium store. Multiple studies have shown that increased STIM1 facilitates the aberrant proliferation and apoptosis of vascular smooth cells (VSMC) and macrophages which can promote the formation of rupture-prone plaque. Together with regulating the cytosolic Ca2+ concentration, STIM1 also activates STING through altered intracellular Ca2+ concentration, a critical pro-inflammatory molecule. The cGAS-STING pathway is linked with cellular proliferation and phenotypic conversion of VSMC and enhances the progression of atherosclerosis plaque. In summary, we conclude that STIM1/cGAS-STING is involved in the progression of AS and plaque vulnerability.

The involvement of oxysterol-binding protein related protein (ORP) 6 in the counter-transport of phosphatidylinositol-4-phosphate (PI4P) and phosphatidylserine (PS) in neurons

Oxysterol-binding protein (OSBP)-related protein (ORP) 6, a member of subfamily III in the ORP family, localizes to membrane contact sites between the endoplasmic reticulum (ER) and other organelles and functions in non-vesicular exchange of lipids including phosphatidylinositol-4-phosphate (PI4P) in neurons. In this study, we searched for the lipid counter-transported in exchange for PI4P by using molecular cell biology techniques. Deconvolution microscopy revealed that knockdown of ORP6 partially shifted localization of a phosphatidylserine (PS) marker but not filipin in primary cultured cerebellar neurons. Overexpression of ORP6 constructs lacking the OSBP-related ligand binding domain (ORD) resulted in the same shift of the PS marker. A PI4KⅢα inhibitor specifically inhibiting the synthesis and plasma membrane (PM) localization of PI4P, suppressed the localization of ORP6 and the PS marker at the PM. Overexpression of mutant PS synthase 1 (PSS1) inhibited transport of the PS marker to the PM and relocated the PI4P marker to the PM in Neuro-2A cells. Introduction of ORP6 but not the dominant negative ORP6 constructs, shifted the localization of PS back to the PM. These data collectively suggest the involvement of ORP6 in the counter-transport of PI4P and PS.

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Knockdown of ORP6 changed localization of PS marker.

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Localization of PS marker and ORP6 at the PM was suppressed by PI4K inhibitor.

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ORP6 restored PS from the ER to PM when mutant PSS1 is expressed.