C-reactive protein adversely alters the protein-protein interaction of the endothelial isoform of nitric oxide synthase

Compartmentalized nitric oxide signaling in the resistance vasculature

Nitric oxide (NO) was first described as a bioactive molecule through its ability to stimulate soluble guanylate cyclase, but the revelation that NO was the endothelium derived relaxation factor drove the field to its modern state. The wealth of research conducted over the past 30 years has provided us with a picture of how diverse NO signaling can be within the vascular wall, going beyond simple vasodilation to include such roles as signaling through protein S-nitrosation. This expanded view of NO's actions requires highly regulated and compartmentalized production. Importantly, resistance arteries house multiple proteins involved in the production and transduction of NO allowing for efficient movement of the molecule to regulate vascular tone and reactivity. In this review, we focus on the many mechanisms regulating NO production and signaling action in the vascular wall, with a focus on the control of endothelial nitric oxide synthase (eNOS), the enzyme responsible for synthesizing most of the NO within these confines. We also explore how cross talk between the endothelium and smooth muscle in the microcirculation can modulate NO signaling, illustrating that this one small molecule has the capability to produce a plethora of responses.

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.

Regulation of endothelial nitric oxide synthase activity by protein-protein interaction

Endothelial nitric oxide synthase (eNOS) is expressed in vascular endothelial cells and plays an important role in the regulation of vascular tone, platelet aggregation and angiogenesis. Protein-protein interactions represent an important posttranslational mechanism for eNOS regulation. eNOS has been shown to interact with a variety of regulatory and structural proteins which provide fine tuneup of eNOS activity and eNOS protein trafficking between plasma membrane and intracellular membranes in a number of physiological and pathophysiological processes. eNOS interacts with calmodulin, heat shock protein 90 (Hsp90), dynamin-2, β-actin, tubulin, porin, high-density lipoprotein (HDL) and apolipoprotein AI (ApoAI), resulting in increases in eNOS activity. The negative eNOS interacting proteins include caveolin, G protein-coupled receptors (GPCR), nitric oxide synthase-interacting protein (NOSIP), and nitric oxide synthase trafficking inducer (NOSTRIN). Dynamin-2, NOSIP, NOSTRIN, and cytoskeleton are also involved in eNOS trafficking in endothelial cells. In addition, eNOS associations with cationic amino acid transporter-1 (CAT-1), argininosuccinate synthase (ASS), argininosuccinate lyase (ASL), and soluble guanylate cyclase (sGC) facilitate directed delivery of substrate (L-arginine) to eNOS and optimizing NO production and NO action on its target. Regulation of eNOS by protein-protein interactions would provide potential targets for pharmacological interventions in NO-compromised cardiovascular diseases.

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.

Asymmetric dimethylarginine as a surrogate marker of endothelial dysfunction and cardiovascular risk in patients with systemic rheumatic diseases

The last few decades have witnessed an increased life expectancy of patients suffering with systemic rheumatic diseases, mainly due to improved management, advanced therapies and preventative measures. However, autoimmune disorders are associated with significantly enhanced cardiovascular morbidity and mortality not fully explained by traditional cardiovascular disease (CVD) risk factors. It has been suggested that interactions between high-grade systemic inflammation and the vasculature lead to endothelial dysfunction and atherosclerosis, which may account for the excess risk for CVD events in this population. Diminished nitric oxide synthesis—due to down regulation of endothelial nitric oxide synthase—appears to play a prominent role in the imbalance between vasoactive factors, the consequent impairment of the endothelial hemostasis and the early development of atherosclerosis. Asymmetric dimethylarginine (ADMA) is one of the most potent endogenous inhibitors of the three isoforms of nitric oxide synthase and it is a newly discovered risk factor in the setting of diseases associated with endothelial dysfunction and adverse cardiovascular events. In the context of systemic inflammatory disorders there is increasing evidence that ADMA contributes to the vascular changes and to endothelial cell abnormalities, as several studies have revealed derangement of nitric oxide/ADMA pathway in different disease subsets. In this article we discuss the role of endothelial dysfunction in patients with rheumatic diseases, with a specific focus on the nitric oxide/ADMA system and we provide an overview on the literature pertaining to ADMA as a surrogate marker of subclinical vascular disease.

The Fcγ receptor IIA R131H gene polymorphism is associated with endothelial function in patients with hypercholesterolaemia

OBJECTIVE

A gene polymorphism substituting arginine (R) for histidine (H) at position 131 has been described within the Fcγ receptor IIa (FcγRIIa). The R allele is associated with increased binding of CRP and enhanced activation of monocytes. FcγRIIa is also expressed on endothelial cells, and we hypothesized this polymorphism would be associated with alterations of endothelial function.

METHODS

Genomic DNA was extracted and allele-specific PCR reactions were used to determine the FcγRIIa H131R polymorphism in 78 hypercholesterolaemic subjects. Using strain gauge plethysmography, forearm blood flow (FBF) responses were determined to intra-arterial infusion of acetylcholine (ACH), for endothelium-dependent vasodilatation (EDV), to nitroprusside (NP), for endothelium-independent vasodilatation (EIV), to NG-monomethyl-l-arginine (l-NMMA), for basal NO activity, and to ACH in the presence of l-NMMA, to assess the contribution of NO release to EDV.

RESULTS

Homozygous carriers of the H allele (n=30) had significantly better EDV than homozygous carriers of the R allele (n=15), while heterozygotes showed an intermediate phenotype (n=33) (e.g. % increase of FBF to ACH 48μg/min: 527±359% in H/H versus 452±262% in H/R versus 332±413% in R/R, p=0.0012 by 2-way ANOVA). EIV and basal NO activity were not affected by genotype, and co-infusion of l-NMMA abolished the differences in EDV.

CONCLUSIONS

The R allele of the FcγRIIa polymorphism is associated with impaired EDV and reduced NO activity during endothelial cell stimulation. These data suggest that the functional effects of the FcγRIIa H131R gene polymorphism previously observed in vitro translate into clinically relevant alterations of endothelial function in vivo.

Modulating endothelial nitric oxide synthase: a new cardiovascular therapeutic strategy

The pathogenesis of many cardiovascular diseases is associated with reduced nitric oxide (NO) bioavailability and/or increased endothelial NO synthase (eNOS)-dependent superoxide formation. These findings support that restoring and conserving adequate NO signaling in the heart and blood vessels is a promising therapeutic intervention. In particular, modulating eNOS, e.g., through increasing the bioavailability of its substrate and cofactors, enhancing its transcription, and interfering with other modulators of eNOS pathway, such as netrin-1, has a high potential for effective treatments of cardiovascular diseases. This review provides an overview of the possibilities for modulating eNOS and how this may be translated to the clinic in addition to describing the genetic models used to study eNOS modulation.

Rosuvastatin attenuates the elevation in blood pressure induced by overexpression of human C-reactive protein

C-reactive protein (CRP) has been shown to function as an inflammatory factor to induce endothelial dysfunction and hypertension in rats. The anti-inflammatory effects of statins suggest that they may attenuate CRP-induced endothelial dysfunction and hypertension in Sprague-Dawley rats. Male Sprague-Dawley rats were injected with an adeno-associated virus (AAV) to induce overexpression of human CRP (AAV-hCRP) or green fluorescent protein (GFP) control (AAV-GFP). At 2 months after injection, rats were administered rosuvastatin by daily oral gavage (10 mg kg(-1)) for 2 additional months. Rosuvastatin administration attenuated the increased blood pressure and loss of vascular endothelial nitric oxide synthase expression in AAV-hCRP-treated rats, and N-nitro-L-arginine methyl ester blocked its hypotensive effect. Rosuvastatin also activated phosphoinositide 3-kinases/Akt, and inhibited Rho kinase activity in aorta. Rosuvastatin reduced the production of reactive oxygen species through downregulation of nicotinamide adenine dinucleotide phosphate oxidase subunits, p22 phox and gp91 phox, and upregulation of superoxide dismutase 1 expression. Rosuvastatin attenuated the increase in blood pressure in AAV-hCRP-treated rats through endothelial protection and antioxidant effects. Our data reveals a novel mechanism through which statins may lower blood pressure.

Inflammatory pathways in children with insufficient or disordered sleep

Sleep is not only an essential physiological function, but also serves important roles in promoting growth, maturation, and overall health of children and adolescents. There is increasing interest regarding the impact of sleep and its disorders on the regulation of inflammatory processes and end-organ morbidities, particularly in the context of metabolic and cardiovascular diseases (CVD) and their complications. Obstructive sleep apnea syndrome (OSAS) is an increasingly common health problem in children, and in the last decade, the emergence of increasing obesity rates has further led to remarkable increases in the prevalence of OSAS, along with more prominent neurocognitive, behavioral, cardiovascular and metabolic morbidities. Although the underlying mechanisms leading to OSAS-induced morbidities are likely multi-factorial, and remain to be fully elucidated, activation of inflammatory pathways by OSAS has emerged as an important pathophysiological component of the end-organ injury associated with this disorder. To this effect, it would appear that OSAS could be viewed as a chronic, low-grade inflammatory disorder. Furthermore, the concurrent presence of obesity and OSAS poses a theoretically increased risk of OSAS-related complications. In this review, we will critically review the current state of research regarding the impact of insufficient and disrupted sleep and OSAS on the immune processes and inflammatory pathways that underlie childhood OSAS as a distinctive systemic inflammatory condition in children, and will explore potential interactions between OSAS and obesity.

Statin therapy in metabolic syndrome and hypertension post-JUPITER: what is the value of CRP?

Much evidence supports a pivotal role for inflammation in atherosclerosis. C-reactive protein (CRP), the prototypic marker of inflammation in humans, is a cardiovascular risk marker and may also promote atherogenesis. CRP levels are increased in metabolic syndrome and hypertension and confer increased risk of cardiovascular events in patients in these subgroups. Statins have been shown to lower low-density lipoproteins and CRP independently, and reduce cardiovascular events in subjects with and without metabolic syndrome and hypertension. In this review, we focus on the results from the primary prevention statin trial, Justification for the Use of statins in Primary prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER), which showed reductions in LDL, CRP, and cardiovascular events. Post-JUPITER, the new guidelines will now need to consider recommending high-sensitivity CRP testing to intermediate-risk metabolic syndrome patients and those with hypertension and intermediate risk so that we can better identify candidates at greater risk and reduce cardiovascular burden in these subjects with statin therapy.

C-reactive protein polarizes human macrophages to an M1 phenotype and inhibits transformation to the M2 phenotype

OBJECTIVE

Inflammation is pivotal in atherosclerosis. Monocyte-macrophages are crucial in atherosclerosis. Monocytes can develop into subsets: classically (M1) or alternatively (M2) activated cells. Several studies point to a proinflammatory role for C-reactive protein (CRP). Because there is a paucity of data on the effects of CRP on macrophage phenotype, we tested effects of CRP on macrophage polarization.

METHODS AND RESULTS

Monocytes were incubated with CRP (0 to 50 μg/mL) and differentiated into macrophages for 7 days. Phenotypic characterization of M1 and M2 macrophages was performed using flow cytometry. CRP treatment resulted in increased population of M1 macrophages (tumor necrosis factor [TNF]/interleukin [IL]-12/C-C chemokine receptor 2, TNF/IL-12/monocyte chemotactic protein-1, or TNF/IL-1/IL-12). These effects were not abrogated by polymixin B or small interfering RNA to Toll-like receptor-4, but they were abrogated by boiled CRP. Administration of human CRP to rats in vivo increased polarization of macrophages to M1 phenotype compared with human serum albumin. When macrophages were primed to the M2 phenotype with IL-4, addition of CRP resulted in significantly increased secretion of TNF-α, MCP-1, and IL-1 and conversion of macrophages from the M2 to the M1 phenotype. CRP failed to prime macrophages to the M1 phenotype in presence of CD32/CD64 small interfering RNA or dominant-negative nuclear factor kappa B.

CONCLUSION

Collectively, these results further support a role for CRP in promoting differentiation of human monocytes toward a proinflammatory M1 phenotype.