FcγRIIB Mediates C-Reactive Protein Inhibition of Endothelial NO Synthase

Genetic variants in FCGR2A, PTPN2, VDR as predictive signatures of aggressive phenotypes in cerebral cavernous malformation

OBJECTIVE

The biological behavior of Cerebral Cavernous Malformation (CCM) is still controversial, lacking a clear-cut signature for a mechanistic explanation of lesion aggressiveness. In this study, we evaluated the predictive capacity of genetic variants concerning the aggressive behavior of CCM and their implications in biological processes.

METHODS

We genotyped the variants in VDRrs7975232, VDRrs731236, VDRrs11568820, PTPN2rs72872125 and FCGR2Ars1801274 genes using TaqMan Genotyping Assays in a cohort study with 103 patients, 42 of whom had close follow-up visits for 4 years, focusing on 2 main aspects of the disease: (1) symptomatic events, which included both intracranial bleeding or epilepsy, and (2) the onset of symptoms. The genotypes were correlated with the levels of several cytokines quantified in peripheral blood, measured using the x-MAP method.

RESULTS

We report a novel observation that the PTPN2rs72872125 CT and the VDRrs7975232 CC genotype were independently associated with an asymptomatic phenotype. Additionally, PTPN2rs72872125 CC genotype and serum level of GM-CSF could predict a diagnostic association with symptomatic phenotype in CCM patients, while the FCGR2Ars1801274 GG genotype could predict a symptomatic event during follow-up. The study also found a correlation between VDRrs731236 AA and VDRrs11568820 CC genotype to the time to the first symptomatic event.

CONCLUSIONS

These genetic markers could pave the way for precision medicine strategies for CCM, enhancing patient outcomes by enabling customized therapeutic approaches.

Blocking FcγRIIB in Smooth Muscle Cells Reduces Hypertension

[Figure: see text].

Clinically relevant high levels of human C-reactive protein induces endothelial dysfunction and hypertension by inhibiting the AMPK-eNOS axis

Successful treatment of resistant hypertension accompanied by elevated human C-reactive protein (hCRP) remains a key challenge in reducing the burden of cardiovascular diseases. It is still unclear whether clinically relevant high-level hCRP is merely a marker or a key driver of hypertension. Here, we investigated the role and mechanism of clinically relevant high level of hCRP in hypertension. Elevated blood pressure was observed in all three hCRP overexpression models, including adeno-associated virus 9 (AAV9)-transfected mice, AAV9-transfected rats and hCRP transgenic (hCRPtg) rats. hCRPtg rats expressing clinically relevant high-level hCRP developed spontaneous hypertension, cardiac hypertrophy, myocardial fibrosis and impaired endothelium-dependent relaxation. Mechanistically, studies in endothelial nitric oxide (NO) synthase (eNOS) knockout mice transfected with AAV9-hCRP and phosphoproteomics analysis of hCRP-treated endothelial cells revealed that hCRP inhibited AMP-activated protein kinase (AMPK)-eNOS phosphorylation pathway. Further, activation of AMPK by metformin normalized endothelial-dependent vasodilation and decreased the blood pressure of hCRPtg rats. Our results show that clinically relevant high-level hCRP induces hypertension and endothelial dysfunction by inhibiting AMPK-eNOS signaling, and highlight hCRP is not only an inflammatory biomarker but also a driver of hypertension. Treatment with metformin or a synthetic AMPK activator may be a potential strategy for vaso-dysfunction and hypertension in patients with high hCRP levels.

Protein Glycosylation in Diabetes

Diabetes mellitus is a group of metabolic disorders characterized by the presence of hyperglycaemia. Due to its high prevalence and substantial heterogeneity, many studies have been investigating markers that could identify predisposition for the disease development, differentiate between the various subtypes, establish early diagnosis, predict complications or represent novel therapeutic targets. N-glycans, complex oligosaccharide molecules covalently linked to proteins, emerged as potential markers and functional effectors of various diabetes subtypes, appearing to have the capacity to meet these requirements. For instance, it has been shown that N-glycome changes in patients with type 2 diabetes and that N-glycans can even identify individuals with an increased risk for its development. Moreover, genome-wide association studies identified glycosyltransferase genes as candidate causal genes for both type 1 and type 2 diabetes. N-glycans have also been suggested to have a major role in preventing the impairment of glucose-stimulated insulin secretion by modulating cell surface expression of glucose transporters. In this chapter we aimed to describe four major diabetes subtypes: type 1, type 2, gestational and monogenic diabetes, giving an overview of suggested role for N-glycosylation in their development, diagnosis and management.

Immunoglobulins G modulate endothelial function and affect insulin sensitivity in humans

BACKGROUND AND AIMS

Data from animals suggest that immunoglobulins G (IgG) play a mechanistic role in atherosclerosis and diabetes through endothelial dysfunction and insulin resistance. Patients with common variable immunodeficiency (CVID), who have low circulating levels of IgG and are treated with intravenous polyclonal IgG (IVIgG), may provide an ideal model to clarify whether circulating IgG modulate endothelial function and affect insulin sensitivity in humans.

METHODS AND RESULTS

We studied 24 patients with CVID and 17 matched healthy controls (HC). Endothelial function was evaluated as flow mediated dilation (FMD) of the brachial artery at baseline and 1, 7, 14, and 21 days after IVIgG infusion in the CVID patients. We measured also plasma glucose, insulin, and calculated the HOMA-IR index. We also investigated the role of human IgG on the production of Nitric Oxide (NO) in vitro in Human Coronary Artery Endothelial Cells (HCAEC). Compared to HC, FMD of CVID patients was significantly impaired at baseline (9.4 ± 0.9 and 7.6 ± 0.6% respectively, p < 0.05) but rose above normal levels 1 and 7 days after IVIgG infusion to return at baseline at 14 and 21 days. Serum insulin concentration and HOMA-IR index dropped by 50% in CVID patients after IVIgG (p < 0.002 vs. baseline). In vitro IgG stimulated NO production in HCAEC.

CONCLUSIONS

Reduced IgG levels are associated with endothelial dysfunction and IVIgG stimulates endothelial function directly while improving insulin sensitivity. The current findings may suggest an anti-atherogenic role of human IgG.

N-glycans as functional effectors of genetic and epigenetic disease risk

N-glycosylation is a frequent modification of proteins, essential for all domains of life. N-glycan biosynthesis is a dynamic, complex, non-templated process, wherein specific glycoforms are modulated by various microenvironmental cues, cellular signals and local availability of dedicated enzymes and sugar precursors. This intricate regulatory network comprises hundreds of proteins, whose activity is dependent on both sequence of implicated genes and the regulation of their expression. In this regard, variation in N-glycosylation patterns stems from either gene polymorphisms or from stable epigenetic regulation of gene expression in different individuals. Moreover, epigenome alters in response to various environmental factors, representing a direct link between environmental exposure and changes in gene expression, that are subsequently reflected through altered N-glycosylation. N-glycosylation itself has a fundamental role in numerous biological processes, ranging from protein folding, cellular homeostasis, adhesion and immune regulation, to the effector functions in multiple diseases. Moreover, specific modification of the glycan structure can modulate glycoprotein's biological function or direct the faith of the entire cell, as seen on the examples of antibodies and T cells, respectively. Since immunoglobulin G is one of the most profoundly studied glycoproteins in general, the focus of this review will be on its N-glycosylation changes and their functional implications. By deepening the knowledge on the mechanistic roles that certain glycoforms exert in differential pathological processes, valuable insight into molecular perturbations occurring during disease development could be obtained. The prospect of resolving the exact biological pathways involved offers a potential for the development of new therapeutic interventions and molecular tools that would aid in prognosis, early referral and timely treatment of multiple disease conditions.

Common transcriptome, plasma molecules, and imaging signatures in the aging brain and a Mendelian neurovascular disease, cerebral cavernous malformation

Brain senescence is associated with impaired endothelial barrier function, angiogenic and inflammatory activity, and propensity to brain hemorrhage. The same pathological changes occur in cerebral cavernous malformations (CCM), a genetic neurovascular anomaly. We hypothesized common transcriptomic and plasma cytokine signatures in the aging brain and CCM. We identified 320 genes [fold change ≥1.5; p < 0.05; false discovery rate (FDR) corrected] commonly dysregulated in the aging brain and CCM. Ontology and pathway analyses of the common differentially expressed genes were related to inflammation and extracellular matrix organization. Plasma levels of C-reactive protein and angiopoietin-2 were significantly greater in older compared to younger healthy non-CCM subjects and were also greater in CCM (Sporadic and Familial) subjects regardless of age (all: p < 0.05; FDR corrected). Plasma levels of vascular endothelial growth factor were significantly greater in older compared to younger subjects, in both healthy non-CCM and Sporadic-CCM groups (all: p_adj < 0.05). Plasma levels of vascular endothelial growth factor were also significantly greater in Familial-CCM cases with germ line mutations regardless of age (all: p_adj < 0.05) compared to both healthy non-CCM and Sporadic-CCM subjects. Brain white matter vascular permeability assessed by MRI followed the same pattern as vascular endothelial growth factor across all groups. In addition, quantitative susceptibility mapping of brain white matter, a measure of iron deposition, was increased in older compared to younger healthy non-CCM subjects. Genetic aberrations, plasma molecules, and imaging biomarkers in a well characterized Mendelian neurovascular disease may also be applicable in the aging brain. Graphical abstract.

Adaptation of the balanced scorecard model to measure performance of the departments at Dr Zainoel Abidin Regional General Hospital, Banda Aceh

Purpose

This paper aims to determine the performance of the departments at Dr Zainoel Abidin Regional General Hospital, Banda Aceh, Indonesia, in 2016, based on the targets and realization of their work programs using balanced scorecard.

Design/methodology/approach

This study adopted qualitative and quantitative approaches.

Findings

The overall results of the performance appraisal using the balanced scorecard approach seen from the financial, internal business, customer and training and learning perspectives are good. Dr Zainoel Abidin Regional General Hospital has provided good services, and performance of its departments have generated the expected outcome, realized by the Hospital.

Originality/value

The novelty of the present study lies in its research model, where human resources (transformational leadership, organizational commitment and resource uniqueness) and financial management (business plans, budget and performance).

C-Reactive Protein Promotes the Expansion of Myeloid Derived Cells With Suppressor Functions

Previously we established that human C-reactive protein (CRP) exacerbates mouse acute kidney injury and that the effect was associated with heightened renal accumulation of myeloid derived cells with suppressor functions (MDSC). Herein we provide direct evidence that CRP modulates the development and suppressive actions of MDSCs in vitro. We demonstrate that CRP dose-dependently increases the generation of MDSC from wild type mouse bone marrow progenitors and enhances MDSC production of intracellular reactive oxygen species (iROS). When added to co-cultures, CRP significantly enhanced the ability of MDSCs to suppress CD3/CD28-stimulated T cell proliferation. Experiments using MDSCs from FcγRIIB deficient mice (FcγRIIB^-/-) showed that CRP's ability to expand MDSCs and trigger their increased production of iROS was FcγRIIB-independent, whereas its ability to enhance the MDSC T cell suppressive action was FcγRIIB-dependent. Importantly, CRP also enabled freshly isolated primary human neutrophils to suppress proliferation of autologous T cells. These findings suggest that CRP might be an endogenous regulator of MDSC numbers and actions in vivo.

Biomarkers of cavernous angioma with symptomatic hemorrhage

BACKGROUNDCerebral cavernous angiomas (CAs) with a symptomatic hemorrhage (CASH) have a high risk of recurrent hemorrhage and serious morbidity.METHODSEighteen plasma molecules with mechanistic roles in CA pathobiology were investigated in 114 patients and 12 healthy subjects. The diagnostic biomarker of a CASH in the prior year was derived as that minimizing the Akaike information criterion and validated using machine learning, and was compared with the prognostic CASH biomarker predicting bleeding in the subsequent year. Biomarkers were longitudinally followed in a subset of cases. The biomarkers were queried in the lesional neurovascular unit (NVU) transcriptome and in plasma miRNAs from CASH and non-CASH patients.RESULTSThe diagnostic CASH biomarker included a weighted combination of soluble CD14 (sCD14), VEGF, C-reactive protein (CRP), and IL-10 distinguishing CASH patients with 76% sensitivity and 80% specificity (P = 0.0003). The prognostic CASH biomarker (sCD14, VEGF, IL-1β, and sROBO-4) was confirmed to predict a bleed in the subsequent year with 83% sensitivity and 93% specificity (P = 0.001). Genes associated with diagnostic and prognostic CASH biomarkers were differentially expressed in CASH lesional NVUs. Thirteen plasma miRNAs were differentially expressed between CASH and non-CASH patients.CONCLUSIONShared and unique biomarkers of recent symptomatic hemorrhage and of future bleeding in CA are mechanistically linked to lesional transcriptome and miRNA. The biomarkers may be applied for risk stratification in clinical trials and developed as a tool in clinical practice.FUNDINGNIH, William and Judith Davis Fund in Neurovascular Surgery Research, Be Brave for Life Foundation, Safadi Translational Fellowship, Pritzker School of Medicine, and Sigrid Jusélius Foundation.

L-sepiapterin restores SLE serum-induced markers of endothelial function in endothelial cells

OBJECTIVE

SLE serves as an independent risk factor` for endothelial dysfunction (ED) not explained by Framingham risk factors. We sought to understand the development of SLE-induced ED on a cellular level in order to develop strategies aimed at reversing cellular abnormalities. This study assessed the impact of SLE patient serum on endothelial nitric oxide synthase (eNOS), nitric oxide (NO) production and functional changes in the cell.

METHODS

Human umbilical vein endothelial cells (HUVECs) cultured in serum of either SLE (n=25) or healthy patients (n=14) or endothelial basal medium 2 (EBM-2) culture media supplemented with fetal bovine serum with or without L-sepiapterin were used for our studies. We applied the fluorescent probe DAF-FM diacetate for intracellular NO detection using flow cytometry. Total RNA isolates were analysed using reverse transcription PCR for eNOS mRNA expression. Oxygen consumption rate was determined using seahorse analysis. Neutrophil adhesion and migration were determined using a calcein AM microscopy assay.

RESULTS

The mRNA expression of eNOS was increased in SLE cultured HUVECs compared with healthy control (p<0.05). The SLE eNOS mRNA level correlated with SLE patient age (p=0.008); however, this trend was not observed with healthy patients. SLE serum reduced NO production in HUVECs compared with EBM-2 cultured cells (p<0.05). Co-treatment of endothelial cells with L-sepiapterin preserved HUVEC capacity to produce NO in SLE conditions (p<0.01). SLE serum enhanced neutrophil migration (p<0.01) but not neutrophil adhesion compared with healthy controls. The bioenergetic health index was not different.

CONCLUSIONS

SLE likely causes disruption of endothelial cell eNOS function and NO modulated pathways.

RhoB antibody alters retinal vascularization in models of murine retinopathy

Neovascularization in cancer or retinopathy is driven by pathological changes that foster abnormal sprouting of endothelial cells. Mouse genetic studies indicate that the stress-induced small GTPase RhoB is dispensable for normal physiology but required for pathogenic angiogenesis. In diabetic retinopathy, retinopathy of prematurity (ROP) or age-related wet macular degeneration (AMD), progressive pathologic anatomic changes and ischemia foster neovascularization are characterized by abnormal sprouting of endothelial cells. This process is driven by the angiogenic growth factor VEGF, which induces and supports the formation of new blood vessels. While injectable biologics targeting VEGF have been used to treat these pathological conditions, many patients respond poorly, prompting interest in other types of mechanism-based therapy. Here we report the preclinical efficacy of a monoclonal antibody that specifically targets RhoB, a signaling molecule that is genetically dispensable for normal physiology but required for pathogenic retinal angiogenesis. In murine models of proliferative retinal angiogenesis or oxygen-induced retinopathy, administering a monoclonal RhoB antibody (7F7) was sufficient to block neoangiogenesis or avascular pathology, respectively. Our findings offer preclinical proof of concept for antibody targeting of RhoB to limit diabetic retinopathy, ROP or wet AMD and perhaps other diseases of neovasculogenesis such as hemangioma or hemangiosarcoma nonresponsive to existing therapies.

Inverse association between serum antioxidant levels and inflammatory markers is moderated by adiposity: a report based on a large representative population sample of American adults

We examined the association between plasma antioxidant levels and markers of inflammation, including C-reactive protein (CRP) and fibrinogen (FG) in US adults. National Health and Nutrition Examination Survey participants examined between 2001 and 2002 were included, if data on CRP or FG levels. Serum vitamins A and E, two retinyl esters, and six carotenoids were measured using HPLC with photodiode array detection. Multivariable-adjusted linear regression analyses accounted for the survey design and sample weights. A total of 784 eligible participants were included; 47·5 % (n 372) were men. In multivariable linear regression models, serum α-carotene, trans-β-carotene, cis-β-carotene, β-cryptoxanthin, combined lutein/zeaxanthin, trans-lycopene, retinyl palmitate, α-tocopherol, retinol and 25-hydroxy vitamin D were negatively associated with serum CRP (P3 mg/l, decreased with increasing levels of antioxidants (α-carotene, trans-β-carotene, cis-β-carotene, vitamins A and E). Furthermore, we found a moderate impact of adiposity on the link between antioxidants and CRP. Our results suggest that the lower the antioxidants levels, the higher the inflammatory burden, based on CRP and FG levels. Adiposity moderately affects this association. Furthermore, an inverse relationship between CVD risk and antioxidant levels was observed. This finding suggests that reduced levels of vitamins with antioxidant properties may predispose to increased CVD risk.

Antiphospholipid antibodies induce thrombosis by PP2A activation via apoER2-Dab2-SHC1 complex formation in endothelium

In the antiphospholipid syndrome (APS), antiphospholipid antibody (aPL) recognition of β2 glycoprotein I promotes thrombosis, and preclinical studies indicate that this is due to endothelial nitric oxide synthase (eNOS) antagonism via apolipoprotein E receptor 2 (apoER2)-dependent processes. How apoER2 molecularly links these events is unknown. Here, we show that, in endothelial cells, the apoER2 cytoplasmic tail serves as a scaffold for aPL-induced assembly and activation of the heterotrimeric protein phosphatase 2A (PP2A). Disabled-2 (Dab2) recruitment to the apoER2 NPXY motif promotes the activating L309 methylation of the PP2A catalytic subunit by leucine methyl transferase-1. Concurrently, Src homology domain-containing transforming protein 1 (SHC1) recruits the PP2A scaffolding subunit to the proline-rich apoER2 C terminus along with 2 distinct regulatory PP2A subunits that mediate inhibitory dephosphorylation of Akt and eNOS. In mice, the coupling of these processes in endothelium is demonstrated to underlie aPL-invoked thrombosis. By elucidating these intricacies in the pathogenesis of APS-related thrombosis, numerous potential new therapeutic targets have been identified.

New revelations from an old receptor: Immunoregulatory functions of the inhibitory Fc gamma receptor, FcγRIIB (CD32B)

The Fc gamma receptor IIB (FcγRIIB/CD32B) was generated million years ago during evolution. It is the sole inhibitory receptor for IgG, and has long been associated with the regulation of humoral immunity and innate immune homeostasis. However, new and surprising functions of FcγRIIB are emerging. In particular, FcγRIIB has been shown to perform unexpected activatory roles in both immune-signaling and monoclonal antibody (mAb) immunotherapy. Furthermore, although ITIM signaling is an integral part of FcγRIIB regulatory activity, it is now clear that inhibition/activation of immune responses can occur independently of the ITIM. In light of these new findings, we present an overview of the established and noncanonical functions of FcγRIIB and discuss how this knowledge might be exploited therapeutically.

Redox modification of caveolar proteins in the cardiovascular system- role in cellular signalling and disease

Rapid and coordinated release of a variety of reactive oxygen species (ROS) such as superoxide (O₂^.-), hydrogen peroxide (H₂O₂) and peroxynitrite, in specific microdomains, play a crucial role in cell signalling in the cardiovascular system. These reactions are mediated by reversible and functional modifications of a wide variety of key proteins. Dysregulation of this oxidative signalling occurs in almost all forms of cardiovascular disease (CVD), including at the very early phases. Despite the heavily publicized failure of "antioxidants" to improve CVD progression, pharmacotherapies such as those targeting the renin-angiotensin system, or statins, exert at least part of their large clinical benefit via modulating cellular redox signalling. Over 250 proteins, including receptors, ion channels and pumps, and signalling proteins are found in the caveolae. An increasing proportion of these are being recognized as redox regulated-proteins, that reside in the immediate vicinity of the two major cellular sources of ROS, nicotinamide adenine dinucleotide phosphate oxidase (Nox) and uncoupled endothelial nitric oxide synthase (eNOS). This review focuses on what is known about redox signalling within the caveolae, as well as endogenous protective mechanisms utilized by the cell, and new approaches to targeting dysregulated redox signalling in the caveolae as a therapeutic strategy in CVD.

C-reactive protein can upregulate VEGF expression to promote ADSC-induced angiogenesis by activating HIF-1α via CD64/PI3k/Akt and MAPK/ERK signaling pathways

Background

Proliferation of the vasa vasorum has been implicated in the pathogenesis of atherosclerosis, and the vasa vasorum is closely associated with resident stem cells within the vasculature. C-reactive protein (CRP) is positively correlated with cardiovascular disease risk, and our previous study demonstrated that it induces inflammatory reactions of perivascular adipose tissue by targeting adipocytes.

Methods

Here we investigated whether CRP affected the proliferation and proangiogenic paracrine activity of adipose-derived stem cells (ADSCs), which may contribute to vasa vasorum angiogenesis.

Results

We found that CRP did not affect ADSC apoptosis, cell cycle, or proliferation but did increase their migration by activating the PI3K/Akt pathway. Our results demonstrated that CRP can upregulate vascular endothelial growth factor-A (VEGF-A) expression by activating hypoxia inducible factor-1α (HIF-1α) in ADSCs, which significantly increased tube formation on Matrigel and functional vessels in the Matrigel plug angiogenesis assay. The inhibition of CRP-activated phosphorylation of ERK and Akt can suppress CRP-stimulated HIF-1α activation and VEGF-A expression. CRP can also stimulate proteolytic activity of matrix metalloproteinase-2 in ADSCs. Furthermore, CRP binds activating CD64 on ADSCs, rather than CD16/32.

Conclusion

Our findings implicate that CRP might play a role in vasa vasorum growth by activating the proangiogenic activity of ADSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0377-1) contains supplementary material, which is available to authorized users.

Development of a high sensitivity C-reactive protein immunoassay and comparison with a commercial kit

C-reactive protein (CRP) is intricately sensitive marker of inflammation, infection, and tissue damage. Role in the prognosis of heart diseases has been recently discovered. This study aimed to develop a cost-effective and high-sensitivity CRP immunoassay for use in cardiac risk assessment. Assay was optimized for coating, blocking of capturing antibody, dilution, and reaction time of the conjugate and sample volume. For normal reference range, CRP was determined in serum samples from apparently healthy volunteers. For clinical validation, CRP was determined in samples of acute coronary syndrome patients by in-house and commercial assays. The lower detection limit of in-house assay was 0.16 µg/L. Intra and inter assay imprecision was 4.39%, 4.6% and 8.6%, 9.3%, respectively. The correlation between the CRP levels by the two assays was r = 0.861. Sensitivity, specificity, predictive value for a positive test, and a negative test of in-house assay was 95.3%, 92.8%, 95.3%, and 92.8%, respectively. At lower-end CRP levels of both kits correlated very well but showed variation at upper end. In-house assay showed high sensitivity and reliability at lower end and it is hoped that will help to evaluate cardiac risk assessment (after improvement at upper end) in clinically poor settings.

Endothelial Fcγ Receptor IIB Activation Blunts Insulin Delivery to Skeletal Muscle to Cause Insulin Resistance in Mice

Modest elevations in C-reactive protein (CRP) are associated with type 2 diabetes. We previously revealed in mice that increased CRP causes insulin resistance and mice globally deficient in the CRP receptor Fcγ receptor IIB (FcγRIIB) were protected from the disorder. FcγRIIB is expressed in numerous cell types including endothelium and B lymphocytes. Here we investigated how endothelial FcγRIIB influences glucose homeostasis, using mice with elevated CRP expressing or lacking endothelial FcγRIIB. Whereas increased CRP caused insulin resistance in mice expressing endothelial FcγRIIB, mice deficient in the endothelial receptor were protected. The insulin resistance with endothelial FcγRIIB activation was due to impaired skeletal muscle glucose uptake caused by attenuated insulin delivery, and it was associated with blunted endothelial nitric oxide synthase (eNOS) activation in skeletal muscle. In culture, CRP suppressed endothelial cell insulin transcytosis via FcγRIIB activation and eNOS antagonism. Furthermore, in knock-in mice harboring constitutively active eNOS, elevated CRP did not invoke insulin resistance. Collectively these findings reveal that by inhibiting eNOS, endothelial FcγRIIB activation by CRP blunts insulin delivery to skeletal muscle to cause insulin resistance. Thus, a series of mechanisms in endothelium that impairs insulin movement has been identified that may contribute to type 2 diabetes pathogenesis.

A Pilot Study to Determine if Vitamin D Repletion Improves Endothelial Function in Lupus Patients

BACKGROUND

The endothelium is important not only in regulating vascular tone but also in modulating inflammation. Patients with systemic lupus erythematosus (SLE) have deficits in these endothelial functions. Vitamin D is a nuclear hormone that regulates vascular endothelial nitric oxide synthase activity and expression. Many SLE patients have insufficient levels of vitamin D. The effect of this hormone on vascular endothelial function in SLE patients is not known. This study was designed to determine the effect size of repleting vitamin D levels on endothelial function in patients with SLE and vitamin D deficiency.

METHODS

SLE patients with 25(OH) vitamin D (25(OH)D) levels <20 ng/mL were randomized to oral vitamin D3 (D3) doses that did or did not raise 25(OH)D levels to ≥32 ng/mL. Endothelial function was measured with flow-mediated dilation (FMD) before and after 16 weeks of vitamin D3 supplementation.

RESULTS

Half of those who achieved 25(OH)D levels of ≥32 ng/mL experienced increases in FMD, whereas none of those with continued low 25(OH)D levels did. Those with increases in FMD had significantly higher final 25(OH)D levels. Using the effect size from this study, future studies designed to test the effect of repleting 25(OH)D on FMD in vitamin D-deficient SLE patients will require 35 patients in each group.

CONCLUSIONS

These results suggest a potential role for vitamin D in SLE-related endothelial dysfunction and that an adaptive, multi-arm, treat-to-target, serum-level trial design may increase the efficiency and likelihood of success of such a study.

Hepatic but Not CNS-Expressed Human C-Reactive Protein Inhibits Experimental Autoimmune Encephalomyelitis in Transgenic Mice

We recently demonstrated that human C-reactive protein (CRP), expressed hepatically in transgenic mice (CRPtg), improved the outcome of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS). The liver is the primary site of CRP synthesis in humans and in CRPtg mice but is also expressed by both at low levels in the CNS. To determine if CNS expression of human CRP is sufficient to impact EAE, we generated neuronal CRP transgenic mice (nCRPtg) wherein human CRP expression is driven by the neuron-specific Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) gene promoter. We found that hepatically expressed/blood-borne CRP, but not CNS expressed CRP, lessened EAE severity. These outcomes indicate that the protective actions of human CRP in EAE are manifested in the periphery and not in the CNS and reveal a previously unappreciated site specificity for the beneficial actions of CRP in CNS disease.

Fcγ receptors and ligands and cardiovascular disease

Fcγ receptors (FcγRs) classically modulate intracellular signaling on binding of the Fc region of IgG in immune response cells. How FcγR and their ligands affect cardiovascular health and disease has been interrogated recently in both preclinical and clinical studies. The stimulation of activating FcγR in endothelial cells, vascular smooth muscle cells, and monocytes/macrophages causes a variety of cellular responses that may contribute to vascular disease pathogenesis. Stimulation of the lone inhibitory FγcR, FcγRIIB, also has adverse consequences in endothelial cells, antagonizing NO production and reparative mechanisms. In preclinical disease models, activating FcγRs promote atherosclerosis, whereas FcγRIIB is protective, and activating FcγRs also enhance thrombotic and nonthrombotic vascular occlusion. The FcγR ligand C-reactive protein (CRP) has undergone intense study. Although in rodents CRP does not affect atherosclerosis, it causes hypertension and insulin resistance and worsens myocardial infarction. Massive data have accumulated indicating an association between increases in circulating CRP and coronary heart disease in humans. However, Mendelian randomization studies reveal that CRP is not likely a disease mediator. CRP genetics and hypertension warrant further investigation. To date, studies of genetic variants of activating FcγRs are insufficient to implicate the receptors in coronary heart disease pathogenesis in humans. However, a link between FcγRIIB and human hypertension may be emerging. Further knowledge of the vascular biology of FcγR and their ligands will potentially enhance our understanding of cardiovascular disorders, particularly in patients whose greater predisposition for disease is not explained by traditional risk factors, such as individuals with autoimmune disorders.

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.

IgG receptor FcγRIIB plays a key role in obesity-induced hypertension

There is a well-recognized association between obesity, inflammation, and hypertension. Why obesity causes hypertension is poorly understood. We previously demonstrated using a C-reactive protein (CRP) transgenic mouse that CRP induces hypertension that is related to NO deficiency. Our prior work in cultured endothelial cells identified the Fcγ receptor IIB (FcγRIIB) as the receptor for CRP whereby it antagonizes endothelial NO synthase. Recognizing known associations between CRP and obesity and hypertension in humans, in the present study we tested the hypothesis that FcγRIIB plays a role in obesity-induced hypertension in mice. Using radiotelemetry, we first demonstrated that the hypertension observed in transgenic mouse-CRP is mediated by the receptor, indicating that FcγRIIB is capable of modifying blood pressure. We then discovered in a model of diet-induced obesity yielding equal adiposity in all study groups that whereas FcγRIIB(+/+) mice developed obesity-induced hypertension, FcγRIIB(-/-) mice were fully protected. Levels of CRP, the related pentraxin serum amyloid P component which is the CRP-equivalent in mice, and total IgG were unaltered by diet-induced obesity; FcγRIIB expression in endothelium was also unchanged. However, whereas IgG isolated from chow-fed mice had no effect, IgG from high-fat diet-fed mice inhibited endothelial NO synthase in cultured endothelial cells, and this was an FcγRIIB-dependent process. Thus, we have identified a novel role for FcγRIIB in the pathogenesis of obesity-induced hypertension, independent of processes regulating adiposity, and it may entail an IgG-induced attenuation of endothelial NO synthase function. Approaches targeting FcγRIIB may potentially offer new means to treat hypertension in obese individuals.

Selective Activation of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Mediates C-Reactive Protein–Evoked Endothelial Vasodilator Dysfunction in Coronary Arterioles

Rationale :

Studies in cultured endothelium implicate that lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) or Fcγ receptor II (CD32) contributes to the proatherogenic effects of C-reactive protein (CRP). However, the identity of the receptors linking to deleterious actions of CRP in vasomotor regulation remains unknown.

Objective :

We tested the hypothesis that LOX-1 contributes to adverse effects of CRP on endothelium-dependent vasomotor function in resistance arterioles.

Methods and Results :

Porcine coronary arterioles were isolated for vasoreactivity study, dihydroethidium fluorescence staining of superoxide, immunohistochemical localization of receptors, immunoprecipitation of receptor/CRP interaction, and protein blot. Intraluminal treatment of pressurized arterioles with a pathophysiological level of CRP (7 µg/mL; 60 minutes) attenuated endothelium-dependent nitric oxide–mediated and prostacyclin-mediated dilations to serotonin and arachidonic acid, respectively. LOX-1 and CD32 were detected in the endothelium of arterioles. Blockade of LOX-1 with either pharmacological antagonist κ-carrageenan or anti–LOX-1 antibody prevented the detrimental effect of CRP on vasodilator function, whereas anti-CD32 antibody treatment was ineffective. Denudation of endothelium and blockade of LOX-1 but not CD32 prevented CRP-induced elevation of superoxide in the vessel wall. CRP was coimmunoprecipitated with LOX-1 and CD32 from CRP-treated arterioles. Similarly, LOX-1 and CD32 blockade prevented CRP-induced arteriolar expression of plasminogen activator inhibitor-1, a thrombogenic protein.

Conclusions :

CRP elicits endothelium-dependent oxidative stress and compromises nitric oxide–mediated and prostacyclin-mediated vasomotor function via LOX-1 activation. In contrast, both LOX-1 and CD32 mediate plasminogen activator inhibitor-1 upregulation in arterioles by CRP. Thus, activation of LOX-1 and CD32 may contribute to vasomotor dysfunction and proatherogenic actions of CRP, respectively.

Inhibition of nitric oxide and antiphospholipid antibody-mediated thrombosis

The antiphospholipid syndrome (APS) is characterized by recurrent vascular thrombosis, thrombocytopenia, and fetal loss occurring in the presence of antiphospholipid antibodies (aPL). Along with arterial and venous thrombosis and pregnancy complications, patients with APS have an increased risk of myocardial infarction, stroke, and coronary artery disease, resulting from vascular cell dysfunction induced by aPL. Accumulating evidence to date indicates that interactions between circulating aPL and cell surface molecules of target cells, primarily endothelial cells and platelets, underlie the vascular disease phenotypes of APS. However, the molecular basis of APS is poorly understood. Nitric oxide produced by endothelial cells is a key determinant of vascular health that regulates several physiologic processes, including thrombosis, endothelial-leukocyte interaction, vascular cell migration, and the modulation of vascular tone. This review will discuss recent findings that indicate a novel mechanism by which aPL antagonize endothelial cell production of nitric oxide and thereby promote thrombosis.

Gene Deficiency in Activating Fcγ Receptors Influences the Macrophage Phenotypic Balance and Reduces Atherosclerosis in Mice

Immunity contributes to arterial inflammation during atherosclerosis. Oxidized low-density lipoproteins induce an autoimmune response characterized by specific antibodies and immune complexes in atherosclerotic patients. We hypothesize that specific Fcγ receptors for IgG constant region participate in atherogenesis by regulating the inflammatory state of lesional macrophages. In vivo we examined the role of activating Fcγ receptors in atherosclerosis progression using bone marrow transplantation from mice deficient in γ-chain (the common signaling subunit of activating Fcγ receptors) to hyperlipidemic mice. Hematopoietic deficiency of Fcγ receptors significantly reduced atherosclerotic lesion size, which was associated with decreased number of macrophages and T lymphocytes, and increased T regulatory cell function. Lesions of Fcγ receptor deficient mice exhibited increased plaque stability, as evidenced by higher collagen and smooth muscle cell content and decreased apoptosis. These effects were independent of changes in serum lipids and antibody response to oxidized low-density lipoproteins. Activating Fcγ receptor deficiency reduced pro-inflammatory gene expression, nuclear factor-κB activity, and M1 macrophages at the lesion site, while increasing anti-inflammatory genes and M2 macrophages. The decreased inflammation in the lesions was mirrored by a reduced number of classical inflammatory monocytes in blood. In vitro, lack of activating Fcγ receptors attenuated foam cell formation, oxidative stress and pro-inflammatory gene expression, and increased M2-associated genes in murine macrophages. Our study demonstrates that activating Fcγ receptors influence the macrophage phenotypic balance in the artery wall of atherosclerotic mice and suggests that modulation of Fcγ receptor-mediated inflammatory responses could effectively suppress atherosclerosis.

C-reactive protein causes insulin resistance in mice through Fcγ receptor IIB-mediated inhibition of skeletal muscle glucose delivery

Elevations in C-reactive protein (CRP) are associated with an increased risk of insulin resistance. Whether CRP plays a causal role is unknown. Here we show that CRP transgenic mice and wild-type mice administered recombinant CRP are insulin resistant. Mice lacking the inhibitory Fcγ receptor IIB (FcγRIIB) are protected from CRP-induced insulin resistance, and immunohistochemistry reveals that FcγRIIB is expressed in skeletal muscle microvascular endothelium and is absent in skeletal muscle myocytes, adipocytes, and hepatocytes. The primary mechanism in glucose homeostasis disrupted by CRP is skeletal muscle glucose delivery, and CRP attenuates insulin-induced skeletal muscle blood flow. CRP does not impair skeletal muscle glucose delivery in FcγRIIB(-/-) mice or in endothelial nitric oxide synthase knock-in mice with phosphomimetic modification of Ser1176, which is normally phosphorylated by insulin signaling to stimulate nitric oxide-mediated skeletal muscle blood flow and glucose delivery and is dephosphorylated by CRP/FcγRIIB. Thus, CRP causes insulin resistance in mice through FcγRIIB-mediated inhibition of skeletal muscle glucose delivery.

C-reactive protein reduces protein S-nitrosylation in endothelial cells

C-reactive protein (CRP) emerges as an important mediator of cardiovascular lesions. In this study, we aimed to assess the role of CRP in the S-nitrosylation of proteins in endothelial cells and elucidate the potential mechanisms. Our results showed that CRP reduced protein S-nitrosylation in human umbilical vein endothelial cells (HUVECs). NO donor S-nitrosoglutathione antagonized CRP-mediated reduction of protein S-nitrosylation. Neutralizing antibody to Fcγ receptor II remarkably attenuated these changes. In addition, CRP increased NF-κB activation via the reduction of S-nitrosylation of p65, but not p50 in HUVECs, and induced the upregulation of NF-kB target gene vascular cell adhesion molecule-1. Furthermore, we confirmed that CRP reduced S-nitrosylated proteins in the rat aorta. Taken together, these data suggest that CRP-induced decline of protein S-nitrosylation by activating NF-κB via reduction of S-nitrosylation of p65, which may contribute to the endothelial dysfunction.

The role of Fcγ receptors in atherosclerosis

Atherosclerosis is widely considered to be an immune-mediated process. Fcγ receptors (Fcγ Rs) contribute to the regulation of a multitude of immune and inflammatory responses and are implicated in human atherosclerotic lesions. Major cell types involved in the pathogenesis of atherosclerosis express Fcγ Rs and their proatherogenic ligands such as immune complexes and C-reactive protein, which act to activate Fcγ R signaling pathways. This review summarizes recent significant progress addressing the multifaceted roles of Fcγ Rs in atherogenesis which comes from the studies of Fcγ R-deficient animal models, clinical investigations and in vitro molecular and cellular studies. These new findings help us appreciate the emerging role of Fcγ Rs in atherosclerosis, and suggest Fcγ Rs as a potential therapeutic target for atherosclerosis.

Tackling endothelial dysfunction by modulating NOS uncoupling: new insights into its pathogenesis and therapeutic possibilities

Endothelial nitric oxide synthase (eNOS) serves as a critical enzyme in maintaining vascular pressure by producing nitric oxide (NO); hence, it has a crucial role in the regulation of endothelial function. The bioavailability of eNOS-derived NO is crucial for this function and might be affected at multiple levels. Uncoupling of eNOS, with subsequently less NO and more superoxide generation, is one of the major underlying causes of endothelial dysfunction found in atherosclerosis, diabetes, hypertension, cigarette smoking, hyperhomocysteinemia, and ischemia/reperfusion injury. Therefore, modulating eNOS uncoupling by stabilizing eNOS activity, enhancing its substrate, cofactors, and transcription, and reversing uncoupled eNOS are attractive therapeutic approaches to improve endothelial function. This review provides an extensive overview of the important role of eNOS uncoupling in the pathogenesis of endothelial dysfunction and the potential therapeutic interventions to modulate eNOS for tackling endothelial dysfunction.

C-reactive protein induces interleukin-6 and thrombospondin-1 protein and mRNA expression through activation of nuclear factor-ĸB in HK-2 cells

BACKGROUND

Although C-reactive protein (CRP) is significantly increased in patients with diabetic nephropathy, whether CRP exerts direct proinflammatory effects on human renal tubular epithelial cells (HK-2 cells) is still unclear.

METHODS

HK-2 cells were incubated with purified CRP at clinically relevant concentrations (0, 5, 10, 20 and 40 μg/ml). The protein and transcript levels of thrombospondin-1 (TSP-1) and interleukin-6 (IL-6) were determined by ELISA and RT-PCR. Phosphorylation of p38MAPK was investigated through Western blot analysis in HK-2 cells induced by CRP. The activation of nuclear factor-kappa B (NF-κB) was studied via EMSA. A specific p38MAPK inhibitor (SB203580) and an NF-κB inhibitor (PDTC; pyrrolidine dithiocarbamate) were used to analyze the signal transduction in CRP induction. To explore the direct or indirect role of CRP in HK-2 cells, IL-6 or TSP-1 antibodies were used. The expression of IL-6, TSP-1 and transforming growth factor-β(1 )(TGF-β(1)) were determined through Western blot analysis in HK-2 cells.

RESULTS

In HK-2 cells, purified CRP significantly induced protein release and mRNA expression of IL-6 and TSP-1 in a dose- and time-dependent manner. TGF-β(1) protein was overexpressed in HK-2 cells induced by CRP, which cannot be inhibited by IL-6 or TSP-1 antibodies. CRP triggered phosphorylation of p38MAPK and activation of NF-κB-mediated signal transduction. SB203580 (5 μM) and PDTC (50 μM) efficiently suppressed those effects of CRP in HK-2 cells.

CONCLUSIONS

CRP induces IL-6 and TSP-1 protein release and mRNA expression from HK-2 cells via activation of the p38MAPK and NF-κB signaling pathways and TGF-β(1) was highly expressed in HK-2 cells, suggesting that CRP plays an important role in the propagation and prolongation of inflammation in renal fibrosis.

Regulation of eNOS in caveolae

Caveolae are a specialized subset of lipid domains that are prevalent on the plasma membrane of endothelial cells. They compartmentalize signal transduction molecules which regulate multiple endothelial functions including the production of nitric oxide (NO) by the caveolae resident enzyme endothelial NO synthase (eNOS). eNOS is one of the three isoforms of the NOS enzyme which generates NO upon the conversion of L-arginine to L-citrulline and it is regulated by multiple mechanisms. Caveolin negatively impact eNOS activity through direct interaction with the enzyme. Circulating factors known to modify cardiovascular disease risk also influence the activity of the enzyme. In particular, high density lipoprotein cholesterol (HDL) maintains the lipid environment in caveolae, thereby promoting the retention and function of eNOS in the domain and it also causes direct activation of eNOS via scavenger receptor class B, Type I (SR-BI)-induced kinase signaling. Estrogen binding to estrogen receptors (ER) in caveolae also activates eNOS and this occurs through G protein coupling and kinase activation. Discrete domains within SR-BI and ER mediating signal initiation in caveolae have been identified. Counteracting the promodulatory actions of HDL and estrogen, C-reactive protein (CRP) antagonizes eNOS through FcγRIIB, which is the sole inhibitory receptor for IgG. Through their actions on eNOS, estrogen and CRP also regulate endothelial cell growth and migration. Thus, signaling events in caveolae invoked by known circulating cardiovascular disease risk factors have major impact on eNOS and endothelial cell phenotypes of importance to cardiovascular health and disease.

Coupling of Fcγ receptor I to Fcγ receptor IIb by SRC kinase mediates C-reactive protein impairment of endothelial function

RATIONALE

Elevations in C-reactive protein (CRP) are associated with increased cardiovascular disease risk and endothelial dysfunction. CRP antagonizes endothelial nitric oxide synthase (eNOS) through processes mediated by the IgG receptor Fcγ receptor IIB (FcγRIIB), its immunoreceptor tyrosine-based inhibitory motif, and SH2 domain-containing inositol 5'-phosphatase 1. In mice, CRP actions on eNOS blunt carotid artery re-endothelialization.

OBJECTIVE

How CRP activates FcγRIIB in endothelium is not known. We determined the role of Fcγ receptor I (FcγRI) and the basis for coupling of FcγRI to FcγRIIB in endothelium.

METHODS AND RESULTS

In cultured endothelial cells, FcγRI-blocking antibodies prevented CRP antagonism of eNOS, and CRP activated Src via FcγRI. CRP-induced increases in FcγRIIB immunoreceptor tyrosine-based inhibitory motif phosphorylation and SH2 domain-containing inositol 5'-phosphatase 1 activation were Src-dependent, and Src inhibition prevented eNOS antagonism by CRP. Similar processes mediated eNOS antagonism by aggregated IgG used to mimic immune complex. Carotid artery re-endothelialization was evaluated in offspring from crosses of CRP transgenic mice (TG-CRP) with either mice lacking the γ subunit of FcγRI (FcRγ(-/-)) or FcγRIIB(-/-) mice. Whereas re-endothelialization was impaired in TG-CRP vs wild-type, it was normal in both FcRγ(-/-); TG-CRP and FcγRIIB(-/-); TG-CRP mice.

CONCLUSIONS

CRP antagonism of eNOS is mediated by the coupling of FcγRI to FcγRIIB by Src kinase and resulting activation of SH2 domain-containing inositol 5'-phosphatase 1, and consistent with this mechanism, both FcγRI and FcγRIIB are required for CRP to blunt endothelial repair in vivo. Similar mechanisms underlie eNOS antagonism by immune complex. FcγRI and FcγRIIB may be novel therapeutic targets for preventing endothelial dysfunction in inflammatory or immune complex-mediated conditions.

New Insights into the Molecular Basis of the Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disease characterized by the presence of circulating antiphospholipid antibodies (aPL) that promote thrombosis, pregnancy complications and cardiovascular diseases. Alterations in the function of vascular cells induced by aPL underlie these outcomes. This review will discuss recent findings that indicate a novel mechanism by which aPL antagonize endothelial cell production of nitric oxide and thereby promote thrombosis.

Antiphospholipid antibodies promote leukocyte-endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via β2GPI and apoER2

In antiphospholipid syndrome (APS), antiphospholipid antibodies (aPL) binding to β2 glycoprotein I (β2GPI) induce endothelial cell-leukocyte adhesion and thrombus formation via unknown mechanisms. Here we show that in mice both of these processes are caused by the inhibition of eNOS. In studies of cultured human, bovine, and mouse endothelial cells, the promotion of monocyte adhesion by aPL entailed decreased bioavailable NO, and aPL fully antagonized eNOS activation by diverse agonists. Similarly, NO-dependent, acetylcholine-induced increases in carotid vascular conductance were impaired in aPL-treated mice. The inhibition of eNOS was caused by antibody recognition of domain I of β2GPI and β2GPI dimerization, and it was due to attenuated eNOS S1179 phosphorylation mediated by protein phosphatase 2A (PP2A). Furthermore, LDL receptor family member antagonism with receptor-associated protein (RAP) prevented aPL inhibition of eNOS in cell culture, and ApoER2-/- mice were protected from aPL inhibition of eNOS in vivo. Moreover, both aPL-induced increases in leukocyte-endothelial cell adhesion and thrombus formation were absent in eNOS-/- and in ApoER2-/- mice. Thus, aPL-induced leukocyte-endothelial cell adhesion and thrombosis are caused by eNOS antagonism, which is due to impaired S1179 phosphorylation mediated by β2GPI, apoER2, and PP2A. Our results suggest that novel therapies for APS can now be developed targeting these mechanisms.

Functional expression of IgG-Fc receptors in human airway smooth muscle cells

IgE-Fc receptors and IgG-Fc receptors are expressed on hematopoietic cells, but some evidence suggests that these receptors are also found on nonhematopoietic cells, including human airway smooth muscle (hASM) cells. Our study characterizes the expression of IgE-Fc receptors (FcεRI/CD23) and IgG-Fc receptors (FcγRs-I, -II, and -III) in cultured hASM cells by flow cytometry and Western blotting, and the functional activity of receptors was determined through quantification of cell proliferation and released cytokines. Expression of Fc receptor-linked intracellular signaling proteins and phosphorylation of the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase 1/2 and p38(MAPK) in hASM cells was examined by Western blotting. Expression of FcεRI and CD23 was not detectable in hASM cells. However, FcγRI and FcγRII were shown to be expressed on these cells. Specific antibodies, validated using transfected cell lines, revealed that the inhibitory IgG receptor, FcγRIIb, was the most abundant Fc receptor subtype expressed. Although cross-linking FcγR with heat-aggregated γ globulin (HAGG) did not induce detectable cell stimulation, pretreating hASM cells with HAGG significantly inhibited IL-1α-induced increases in cytokine levels and basic fibroblast growth factor-induced cell proliferation. This inhibitory effect of HAGG was abrogated by preincubation of cells with an anti-FcγRIIb antigen-binding fragment (Fab). Expression of proteins involved in the canonical FcγRIIb inhibitory signaling pathway was established in hASM cells. Pretreatment of hASM cells with HAGG significantly inhibited IL-1α- and basic fibroblast growth factor-induced extracellular signal-regulated kinase 1/2 and p38(MAPK) phosphorylation. This study identifies functional expression of FcγRIIb in hASM cells, with the potential to suppress their remodeling and immunomodulatory roles.

Non-nuclear estrogen receptor alpha signaling promotes cardiovascular protection but not uterine or breast cancer growth in mice

Steroid hormone receptors function classically in the nucleus as transcription factors. However, recent data indicate that there are also non-nuclear subpopulations of steroid hormone receptors, including estrogen receptors (ERs), that mediate membrane-initiated signaling of unclear basis and significance. Here we have shown that an estrogen-dendrimer conjugate (EDC) that is excluded from the nucleus stimulates endothelial cell proliferation and migration via ERalpha, direct ERalpha-Galphai interaction, and endothelial NOS (eNOS) activation. Analysis of mice carrying an estrogen response element luciferase reporter, ER-regulated genes in the mouse uterus, and eNOS enzyme activation further indicated that EDC specifically targets non-nuclear processes in vivo. In mice, estradiol and EDC equally stimulated carotid artery reendothelialization in an ERalpha- and G protein-dependent manner, and both agents attenuated the development of neointimal hyperplasia following endothelial injury. In contrast, endometrial carcinoma cell growth in vitro and uterine enlargement and MCF-7 cell breast cancer xenograft growth in vivo were stimulated by estradiol but not EDC. Thus, EDC is a non-nuclear selective ER modulator (SERM) in vivo, and in mice, non-nuclear ER signaling promotes cardiovascular protection. These processes potentially could be harnessed to provide vascular benefit without increasing the risk of uterine or breast cancer.

C-reactive protein at the interface between innate immunity and inflammation

C-reactive protein (CRP), the prototypic acute-phase protein, increases rapidly in response to infection and inflammation. Although CRP was thought to be a passive, nonspecific marker of inflammation, recent studies indicate that CRP plays a key role in the innate immune system by recognizing pathogens and altered self determinants. Activation of complement and interaction with Fcgamma receptors by CRP provides a link between the innate and adaptive immune systems. Recent evidence suggests that CRP is a marker of atherosclerotic disease and may play a role in its induction. However, CRP has an anti-inflammatory role in autoimmune diseases, such as systemic lupus erythematosus. In this article, we review the biological mechanisms by which CRP exerts its effects on the immune system and discuss its role in infection, cardiovascular disease, malignancy and systemic lupus erythematosus.

Induction of interleukin-8 gene expression and protein secretion by C-reactive protein in ARPE-19 cells

C-reactive protein (CRP) is an acute phase reactant and its level rises rapidly during inflammation. Recent studies have suggested the potential involvement of CRP in the pathogenesis of age-related macular degeneration (AMD). To delineate the functional roles of CRP in inflammatory response by the ocular posterior segments, the effects of CRP on ARPE-19, an immortalized human retinal pigment epithelia (hRPE) cell line, were investigated in the present study. Treatment of ARPE-19 cells with CRP resulted in enhanced NF-kB nuclear translocation and dose-dependent transient induction of IL-8 mRNA synthesis and protein secretion. Stimulated expression of VEGF, but not MCP-1 by CRP was also observed. The induced IL-8 expression was transient and peaked at 12h post stimulation. In the presence of inhibitors for NF-kB, p38, MEK and JNK, the CRP-induced IL-8 production was abolished by 99.5+/-2.3, 97.8+/-2.1, 55.3+/-2.5 and 37.3+/-1.3%, respectively. Neutralization of Fc gamma receptors by anti-CD32 and CD64 antibodies produced 39.9+/-1.6 and 59.5+/-2.6% reduction, respectively, of CRP-stimulated IL-8 secretion, whereas that by anti-CD16 antibody had no effect. This study suggests that the pro-inflammatory effects of CRP in ARPE-19 cells may contribute to the inflammatory retinal diseases by induction of pro-inflammatory cytokines such as IL-8. This induction is mediated by NF-kB and multiple MAPK pathways through Fc gamma receptors.

Monomeric C-Reactive Protein Decreases Acetylated LDL Uptake in Human Endothelial Cells

Background: C-reactive protein (CRP) is a risk marker for cardiovascular disease and has been implicated in atherogenesis. In atherosclerotic plaques, it colocalizes with oxidized LDL (oxLDL) and promotes oxLDL uptake by macrophages, suggesting an important cross-talk between CRP and lipid processing. A growing body of evidence indicates the existence of distinct configurations of human CRP, native pentameric (nCRP) and structurally modified monomeric (mCRP), that elicit opposing bioactivities in vitro and in vivo. Here, we tested the impact of mCRP and nCRP on the uptake of acetylated LDL (acLDL), which is internalized by receptors similar to those of oxLDL in human endothelial cells.

Methods: We cultured human umbilical vein endothelial cells (HUVECs) for 8 h with mCRP or nCRP (10–100 mg/L) and measured the uptake of acLDL (10–100 mg/L) over a 20-h period by FACS analysis. To assess the receptors involved, we used function-blocking antibodies against Fc γ receptor CD16 (FcγRIII) and CD32 (FcγRII), and RT-PCR analysis of CD16, CD32, and the receptor for oxidized LDL (LOX-1). Uptake of acLDL and CRP isoforms was visualized by immunofluorescence.

Results: Culture of HUVECs with mCRP, but not nCRP, decreased uptake of acLDL, which was not prevented by anti-CD16 or anti-CD32 antibodies. LOX-1, CD16, and CD32 were undetectable by RT-PCR. Immunofluorescence showed decreased cytoplasmic acLDL staining in human umbilical vein endothelial cells (HUVECs) treated with mCRP, but not with nCRP.

Conclusions: Monomeric CRP, but not nCRP, decreased acLDL uptake in human endothelial cells independent of CD16, CD32, or LOX-1. Our data support a protective role of mCRP in cardiovascular disease.