Opposing effects of monomeric and pentameric C-reactive protein on endothelial progenitor cells

Comprehensive analysis of shared risk genes and immunity-metabolisms between non-alcoholic fatty liver disease and atherosclerosis via bulk and single-cell transcriptome analyses

Objective

and design: Considering the clinical link between non-alcoholic fatty liver disease (NAFLD) and atherosclerosis (AS), we performed bioinformatics analysis to uncover their pathogenic interrelationship.

Methods and results

Data from the U.S. National Health and Nutritional Examination Survey (NHANES) 1999-2018 were included. Among 4851 participants in NHANES, NAFLD was significantly associated with atherosclerotic cardiovascular disease risk (ASCVD risk) (OR = 2.32, 95%CI: 2.04-2.65, P < 0.0001). We conducted WGCNA analysis for NAFLD (GSE130970) and AS (GSE28829) and identified three modules positively related to NAFLD severity and two modules accelerating atherosclerosis plaque progression. 198 key-modules genes were obtained via overlapping these modules. Next, we mined the disease-controlled differentially expressed genes (DEGs) from NAFLD (GSE89632) and AS (GSE100927), respectively. The final common risk genes (ACP5, TP53I3, RPS6KA1, TYMS, TREM2, CA12, and IFI27) were defined by intersecting the upregulated DEGs with 198 genes and validated in new datasets (GSE48452 and GSE43292). Importantly, they showed good diagnostic ability for NAFLD and AS. Immune infiltration analysis showed both illnesses have dysregulated immunity. Analysis of single-cell sequencing datasets NAFLD (GSE179886) and AS (GSE159677) uncovered different abnormal expressions of seven common genes in different immune cells while highlighting metabolic disturbances including upregulation of fatty acid biosynthesis, downregulation of fatty acid degradation and elongation.

Conclusion

We found 7 shared hub genes with good diagnostic ability and depicted the landscapes of immune and metabolism involved in NAFLD and AS. Our results provided a comprehensive association between them and may contribute to developing potential intervention strategies for targeting both disorders based on these risk factors.

C-Reactive Protein in Atherosclerosis-More than a Biomarker, but not Just a Culprit

C-reactive protein (CRP) is a pentraxin that is mainly synthesized in the liver in response to inflammatory cytokines. It exists in two functionally and structurally distinct isoforms. The first is a highly pro-inflammatory and mostly tissue-bound monomeric isoform (mCRP). The second is circulating pentameric CRP (pCRP), which also serves as a substrate for the formation of mCRP. CRP is elevated during inflammatory conditions and is associated with a higher risk of cardiovascular disease. The aim of this review is to examine the current state of knowledge regarding the role of these two distinct CRP isoforms on atherogenesis. This should allow further evaluation of CRP as a potential therapeutic target for atherosclerosis. While it seems clear that CRP should be used as a therapeutic target for atherosclerosis and cardiovascular disease, questions remain about how this can be achieved. Current data suggests that CRP is more than just a biomarker of atherosclerosis and cardiovascular disease. Indeed, recent evidence shows that mCRP in particular is strongly atherogenic, whereas pCRP may be partially protective against atherogenesis. Thus, further investigation is needed to determine how the two CRP isoforms contribute to atherogenesis and the development of cardiovascular disease.

C-Reactive Protein: Pathophysiology, Diagnosis, False Test Results and a Novel Diagnostic Algorithm for Clinicians

The current literature provides a body of evidence on C-Reactive Protein (CRP) and its potential role in inflammation. However, most pieces of evidence are sparse and controversial. This critical state-of-the-art monography provides all the crucial data on the potential biochemical properties of the protein, along with further evidence on its potential pathobiology, both for its pentameric and monomeric forms, including information for its ligands as well as the possible function of autoantibodies against the protein. Furthermore, the current evidence on its potential utility as a biomarker of various diseases is presented, of all cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions and neoplasms, including other possible factors that have been linked with elevated concentrations of that protein. Moreover, data on molecular diagnostics on CRP are discussed, and possible etiologies of false test results are highlighted. Additionally, this review evaluates all current pieces of evidence on CRP and systemic inflammation, and highlights future goals. Finally, a novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated.

Current Position on the Role of Monomeric C-reactive Protein in Vascular Pathology and Atherothrombosis

C-reactive Protein (CRP) is an acute phase reactant, belonging to the pentraxin family of proteins. Its level rises up to 1000-fold in response to acute inflammation. High sensitivity CRP level is utilized as an independent biomarker of inflammation and cardiovascular disease. The accumulating data suggests that CRP has two distinct forms. It is predominantly produced in the liver in a native pentameric form (nCRP). At sites of local inflammation and tissue injury it may bind to phosphocholine-rich membranes of activated and apoptotic cells and their microparticles, undergoing irreversible dissociation to five monomeric subunits, termed monomeric CRP (mCRP). Through dissociation, CRP deposits into tissues and acquires distinct proinflammatory properties. It activates both classic and alternative complement pathways, binding complement component C1q and factor H. mCRP actively participates in the development of endothelial dysfunction. It activates leukocytes, inducing cytokine release and monocyte recruitment. It may also play a role in the polarization of monocytes and T cells into proinflammatory phenotypes. It may be involved in low-density lipoproteins (LDL) opsonization and uptake by macrophages. mCRP deposits were detected in samples of atherosclerotic lesions from human aorta, carotid, coronary and femoral arteries. mCRP may also induce platelet aggregation and thrombus formation, thus contributing in multiple ways in the development of atherosclerosis and atherothrombosis. In this mini-review, we will provide an insight into the process of conformational rearrangement of nCRP, leading to dissociation, and describe known effects of mCRP. We will provide a rationalization for mCRP involvement in the development of atherosclerosis and atherothrombosis.

Emerging roles for human glycolipid transfer protein superfamily members in the regulation of autophagy, inflammation, and cell death

Glycolipid transfer proteins (GLTPs) were first identified over three decades ago as ~24kDa, soluble, amphitropic proteins that specifically accelerate the intermembrane transfer of glycolipids. Upon discovery that GLTPs use a unique, all-α-helical, two-layer 'sandwich' architecture (GLTP-fold) to bind glycosphingolipids (GSLs), a new protein superfamily was born. Structure/function studies have provided exquisite insights defining features responsible for lipid headgroup selectivity and hydrophobic 'pocket' adaptability for accommodating hydrocarbon chains of differing length and unsaturation. In humans, evolutionarily-modified GLTP-folds have been identified with altered sphingolipid specificity, e. g. ceramide-1-phosphate transfer protein (CPTP), phosphatidylinositol 4-phosphate adaptor protein-2 (FAPP2) which harbors a GLTP-domain and GLTPD2. Despite the wealth of structural data (>40 Protein Data Bank deposits), insights into the in vivo functional roles of GLTP superfamily members have emerged slowly. In this review, recent advances are presented and discussed implicating human GLTP superfamily members as important regulators of: i) pro-inflammatory eicosanoid production associated with Group-IV cytoplasmic phospholipase A₂; ii) autophagy and inflammasome assembly that drive surveillance cell release of interleukin-1β and interleukin-18 inflammatory cytokines; iii) cell cycle arrest and necroptosis induction in certain colon cancer cell lines. The effects exerted by GLTP superfamily members appear linked to their ability to regulate sphingolipid homeostasis by acting in either transporter and/or sensor capacities. These timely findings are opening new avenues for future cross-disciplinary, translational medical research involving GLTP-fold proteins in human health and disease. Such avenues include targeted regulation of specific GLTP superfamily members to alter sphingolipid levels as a therapeutic means for combating viral infection, neurodegenerative conditions and circumventing chemo-resistance during cancer treatment.

Monomeric C-reactive protein inhibits renal cell-directed complement activation mediated by properdin

Previous studies have shown that complement activation on renal tubular cells is involved in the induction of interstitial fibrosis and cellular injury. Evidence suggests that the tubular cell damage is initiated by the alternative pathway (AP) of complement with properdin having an instrumental role. Properdin is a positive regulator of the AP, which can bind necrotic cells as well as viable proximal tubular epithelial cells (PTECs), inducing complement activation. Various studies have indicated that in the circulation there is an unidentified inhibitor of properdin. We investigated the ability of C-reactive protein (CRP), both in its monomeric (mCRP) and pentameric (pCRP) form, to inhibit AP activation and injury in vitro on renal tubular cells by fluorescent microscopy, ELISA, and flow cytometry. We demonstrated that preincubation of properdin with normal human serum inhibits properdin binding to viable PTECs. We identified mCRP as a factor able to bind to properdin in solution, thereby inhibiting its binding to PTECs. In contrast, pCRP exhibited no such binding and inhibitory effect. Furthermore, mCRP was able to inhibit properdin-directed C3 and C5b-9 deposition on viable PTECs. The inhibitory ability of mCRP was not unique for viable cells but also demonstrated for binding to necrotic Jurkat cells, a target for properdin binding and complement activation. In summary, mCRP is an inhibitor of properdin in both binding to necrotic cells and viable renal cells, regulating complement activation on the cell surface. We propose that mCRP limits amplification of tissue injury by controlling properdin-directed complement activation by damaged tissue and cells.

The Relationship Between High-Sensitivity C-Reactive Protein Levels and Left Ventricular Hypertrophy in Patients With Newly Diagnosed Hypertension

The authors aimed to evaluate the relationship between high-sensitivity C-reactive protein (hs-CRP) and presence of left ventricular hypertrophy and diastolic dysfunction in patients with hypertension. A total of 95 newly diagnosed hypertensive patients (mean age, 54±10 years) and 20 controls were included in this study. Patients were divided into four groups according to relative wall thickness as normal, concentric remodeling, concentric, and eccentric hypertrophy. hs-CRP was measured in all patients and serum hs-CRP level was shown to be increased in patients with hypertension compared with controls (0.57 mg/dL vs 0.25 mg/dL, respectively; P<.001). The hs-CRP level was highest in patients with concentric hypertrophy. When compared with controls, serum hs-CRP level was significantly higher in patients with concentric remodeling (0.61±0.3 mg/dL vs 0.43±0.5 mg/dL, P<.030) and concentric hypertrophy (0.69±0.3 mg/dL vs 0.43±0.5 mg/dL, P<.032). The present study shows that serum hs-CRP is significantly associated with left ventricular diastolic function and concentric hypertrophy in patients with hypertension.

Oxidized high-density lipoprotein impairs endothelial progenitor cells' function by activation of CD36-MAPK-TSP-1 pathways

AIMS

High-density lipoprotein (HDL) levels inversely correlate with cardiovascular events due to the protective effects on vascular wall and stem cells, which are susceptible to oxidative modifications and then lead to potential pro-atherosclerotic effects. We proposed that oxidized HDL (ox-HDL) might lead to endothelial progenitor cells (EPCs) dysfunction and investigated underlying mechanisms.

RESULTS

ox-HDL was shown to increase apoptosis and intracellular reactive oxygen species levels, but to reduce migration, angiogenesis, and cholesterol efflux of EPCs in a dose-dependent manner. p38 mitogen-activated protein kinase (MAPK) and NF-κB were activated after ox-HDL stimulation, which also upregulated thrombospondin-1 (TSP-1) expression without affecting vascular endothelial growth factor. Effects caused by ox-HDL could be significantly attenuated by pretreatment with short hairpin RNA-mediated CD36 knockdown or probucol. Data of in vivo experiments and the inverse correlation of ox-HDL and circulating EPC numbers among patients with coronary artery diseases (CAD) or CAD and type 2 diabetes also supported it. Meanwhile, HDL separated from such patients could significantly increase cultured EPC's caspase 3 activity, further supporting our proposal.

INNOVATION

This is the most complete study to date of how ox-HDL would impair EPCs function, which was involved with activation of CD36-p38 MAPK-TSP-1 pathways and proved by not only the inverse relationship between ox-HDL and circulating EPCs in clinic but also pro-apoptotic effects of HDL separated from patients' serum.

CONCLUSION

Activation of CD36-p38 MAPK-TSP-1 pathways contributes to the pathological effects of ox-HDL on EPCs' dysfunction, which might be one of the potential etiological factors responsible for the disturbed neovascularization in chronic ischemic disease.

C-Reactive Protein: An In-Depth Look into Structure, Function, and Regulation

Cardiovascular disease is the leading cause of morbidity and mortality in the adult population worldwide, with atherosclerosis being its key pathophysiologic component. Atherosclerosis possesses a fundamental chronic inflammatory aspect, and the involvement of numerous inflammatory molecules has been studied in this scenario, particularly C-reactive protein (CRP). CRP is a plasma protein with strong phylogenetic conservation and high resistance to proteolysis, predominantly synthesized in the liver in response to proinflammatory cytokines, especially IL-6, IL-1β, and TNF. CRP may intervene in atherosclerosis by directly activating the complement system and inducing apoptosis, vascular cell activation, monocyte recruitment, lipid accumulation, and thrombosis, among other actions. Moreover, CRP can dissociate in peripheral tissue—including atheromatous plaques—from its native pentameric form into a monomeric form, which may also be synthesized de novo in extrahepatic sites. Each form exhibits distinct affinities for ligands and receptors, and exerts different effects in the progression of atherosclerosis. In view of epidemiologic evidence associating high CRP levels with cardiovascular risk—reflecting the biologic impact it bears on atherosclerosis—measurement of serum levels of high-sensitivity CRP has been proposed as a tool for assessment of cardiovascular risk.

Obesity associated molecular forms of C-reactive protein in human

Objective

To describe novel C-reactive protein (CRP) molecular forms (mf) in human plasma.

Design and Methods

Five novel CRP-mfs, disctinct from the previously described native (nCRP) and modified (mCRP) C-reactive proteins, were separated from human plasma by polyacrylamide gel electrophoresis and immunodetected by western blot in subjects with or without increased BMI, cardiovascular disease (CVD), and diabetes (n = 1800).

Results

Three of the five CRP-mfs were present in all samples. One, CRPmf-4, was present in a subgroup of subjects and its presence was associated with elevated body mass index (BMI). CRP-mf-5 was present in about 2% of the subjects and was not associated with any other parameters. The presence or distribution of the 5 CRP-mfs were not Ca²⁺-dependent. Crossed immuno-localization experiments indicated that none of the CRP-mfs were complexed with any of the lipoprotein classes or with signature proteins of the complement-factor. Moreover, the distribution of CRP-mfs were not significantly correlated with plasma CRP levels. CRP-mf-4 was significantly associated with increased BMI, but not with other parameters of the metabolic syndrome (HDL-C and triglyceride levels, and diabetes).

Conclusions

We have identified five new CRP-mfs out of which CRP-mf-4 was significantly associated with obesity. We have shown that oligomerization of CRP was not calcium dependent. We hypothesize that adipose tissue produces a factor which influences the formation of CRP mf-4. CRP-mfs might be used as an obesity-associated inflammatory marker.

A significant correlation between C - reactive protein levels in blood monocytes derived macrophages versus content in carotid atherosclerotic lesions

Background

Atherosclerosis is a complex disease involving different cell types, including macrophages that play a major role in the inflammatory events occurring in atherogenesis. C-Reactive Protein (CRP) is a sensitive systemic marker of inflammation and was identified as a biomarker of cardiovascular diseases. Histological studies demonstrate CRP presence in human atherosclerotic lesions, and we have previously shown that macrophages express CRP mRNA. CRP could be locally secreted in the atherosclerotic lesion by arterial macrophages and local regulation of CRP could affect its pro-atherogenic effects. Moreover, human blood derived macrophages (HMDM) expression of CRP could reflect atherosclerotic lesion secretion of CRP.

Methods

Ten type 2 diabetic patients and ten non-diabetic patients scheduled to undergo carotid endarterectomy were enrolled in this study, and their blood samples were used for serum CRP, lipid determination, and for preparation of HMDM further analyzed for their CRP mRNA expression and CRP content. Carotid lesions obtained from the patients were analyzed for their CRP and interleukin 6 (IL-6) content by immunohistochemistry.

Results

Lesions from diabetic patients showed substantially higher CRP levels by 62% (p = 0.05) than lesions from non diabetic patients, and CRP staining that co-localized with arterial macrophages. CRP carotid lesion levels positively correlated with CRP mRNA expression (r² = 0.661) and with CRP content (r² = 0.611) in the patient’s HMDM.

Conclusions

Diabetes up-regulated carotid plaques CRP levels and CRP measurements in HMDM could reflect atherosclerotic lesion macrophages secretion of CRP. Understanding the regulation of locally produced macrophage CRP in the arterial wall during atherogenesis could be of major importance in identifying the underlying mechanisms of inflammatory response pathways during atherogenesis.

Influence of elevated levels of C-reactive protein on circulating endothelial progenitor cell function

In vitro, C-reactive protein (CRP) impairs endothelial progenitor cell (EPC) function; however, the influence of CRP on EPCs in vivo is unclear. We determined whether EPC function is impaired in adults with elevated plasma CRP concentrations, independent of other risk factors. EPCs were harvested from 75 adults (43 males, 32 females): 25 with low CRP (<1.0 mg/L); 25 with moderate CRP (1.0-3.0 mg/L); and 25 with high CRP (>3.0 mg/L). The capacity of EPCs to form colonies (colony assay), migrate (Boyden chamber), release angiogenic growth factor (ELISA) and resist apoptosis (active caspase-3) was determined. There were no significant differences between the CRP groups in EPC colony formation (CFU), migration (AU) or the ability to release vascular endothelial growth factor (VEGF; pg/mL): low (13 ± 3 CFU; 1255 ± 100 AU; 126 ± 24 pg/mL); moderate (11 ± 3 CFU; 1137 ± 85 AU; 97 ± 14 pg/mL); and high (13 ± 4 CFU; 1071 ± 80 AU; 119 ± 22 pg/mL) CRP. Staurosporine-stimulated activation of caspase-3 was also similar between the low (2.3 ± 0.2 ng/mL), moderate (2.1 ± 0.3 ng/mL), and high (2.2 ± 0.2 ng/mL) CRP groups. These results indicate that elevations in plasma CRP are not associated with impaired EPC function. EPC dysfunction may not play a role in CRP-related cardiovascular risk.

Pathologic endothelial response and impaired function of circulating angiogenic cells in patients with Fabry disease

Fabry disease is an X-chromosomal recessive deficiency of the lysosomal hydrolase alpha-galactosidase A (alpha-Gal). This results in an accumulation of globotriaosylceramide (GL-3) in a variety of cells often with subsequent functional impairment. Here, the impact of Fabry disease on the biology of circulating angiogenic cells (CACs) and the endothelial response to transient ischemia was investigated. Untreated patients with Fabry disease (n = 26), patients after initiation of alpha-Gal enzyme replacement therapy (ERT) (n = 16) and healthy controls (n = 26) were investigated. Endothelial function was assessed by the EndoPAT2000 device. CAC numbers were assessed by flow-cytometry, CAC function by a modified Boyden chamber assay. Fabry patients showed a pathologic endothelial response, which normalized after ERT. CACs were increased in number, but functionally impaired. Immunofluorescence and electron microscopy identified an accumulation of GL-3 in Fabry CACs. ERT attenuated CAC dysfunction and improved markers of oxidative stress response in Fabry patients via a reduction in GL-3 accumulation in vitro and in vivo. Silencing of alpha-Gal in healthy CACs impaired their migratory capacity underlining a key role of this enzyme for CAC function. CAC supernatant as well as CACs from Fabry patients impaired angiogenesis and migratory capacity of HUVECs providing a mechanistic link between CAC and endothelial dysfunction. CAC adhesion to TNF-α pre-stimulated HUVECs and tube formation was impaired by alpha-Gal knockdown. Fabry patients show a dysfunction of CAC and a pathologic endothelial response. ERT improves CAC and endothelial function and thus may attenuate development of cardiovascular disease in the long term in this patient population.

Moutan Cortex Radicis inhibits inflammatory changes of gene expression in lipopolysaccharide-stimulated gingival fibroblasts

Moutan Cortex Radicis (MCR), the root bark of Paeonia suffruticosa Andrews (Paeoniaceae), is found in the traditional Chinese medicinal formulae which were used to treat periodontal diseases. This study investigated the changes in gene expression by MCR treatment when stimulated with lipopolysaccharide (LPS) in cultured human gingival fibroblasts (HGFs). A genome-wide expression GeneChip was used for the gene array analysis, and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis was also performed to confirm the gene expression. It was shown that 42 of the 643 genes up-regulated by LPS, when compared to the control, were down-regulated by the MCR treatment. Of these 42 genes, the inflammation and immune response-related genes were especially noted, which indicates that MCR inhibits the induction of inflammation by LPS stimulation. In addition, 33 of the 519 genes down-regulated by LPS, when compared to the control, were up-regulated by the MCR treatment. The expression patterns of some representative genes by real-time RT-PCR correlated with those of the genes shown in the microarray. In addition, the MCR extract contained paeonol and paeoniflorin, which are known to have the anti-inflammatory effect as the major phenolic components of MCR. This study showed that the MCR extract could comprehensively inhibit a wide variety of activations of inflammation-related genes, which may be due to paeonol and paeoniflorin. It is, thus, suggested that MCR may be applied to alleviate the inflammation of periodontal diseases.

Endothelial progenitor cells in cardiovascular disease and chronic inflammation: from biomarker to therapeutic agent

The discovery of endothelial progenitor cells in the 1990s challenged the paradigm of angiogenesis by showing that cells derived from hematopoietic stem cells are capable of forming new blood vessels even in the absence of a pre-existing vessel network, a process termed vasculogenesis. Since then, the majority of studies in the field have found a strong association between circulating endothelial progenitor cells and cardiovascular risk. Several studies have also reported that inflammation influences the mobilization and differentiation of endothelial progenitor cells. In this review, we discuss the emerging role of endothelial progenitor cells as biomarkers of cardiovascular disease as well as the interplay between inflammation and endothelial progenitor cell biology. We will also review the challenges in the field of endothelial progenitor cell-based therapy.

Presence of endothelial colony-forming cells is associated with reduced microvascular obstruction limiting infarct size and left ventricular remodelling in patients with acute myocardial infarction

Endothelial colony-forming cells (ECFCs) are known to increase after acute myocardial infarction (AMI). We examined whether the presence of ECFCs is associated with preserved microvascular integrity in the myocardium at risk by reducing microvascular obstruction (MVO). We enrolled 88 patients with a first ST elevation AMI. ECFC colonies and circulating progenitor cells were characterized at admission. MVO was evaluated at 5 days and infarct size at 5 days and at 6-month follow-up by magnetic resonance imaging. ECFC colonies were detected in 40 patients (ECFC(pos) patients). At 5 days, MVO was of greater magnitude in ECFC(neg) versus ECFC(pos) patients (7.7 ± 5.3 vs. 3.2 ± 5%, p = 0.0002). At 6 months, in ECFC(pos) patients, there was a greater reduction in infarct size (-32.4 ± 33 vs. -12.8 ± 24%; p = 0.003) and a significant improvement in left ventricular (LV) volumes and ejection fraction. Level of circulating CD34+/VEGF-R2+ cells was correlated with the number of ECFC colonies (r = 0.54, p < 0.001) and relative change in infarct size (r = 0.71, p < 0.0001). The results showed that the presence of ECFC colonies is associated with reduced MVO after AMI, leading to reduced infarct size and less LV remodelling and can be considered a marker of preserved microvascular integrity in AMI patients.