Atherosclerosis-related functions of C-reactive protein

Dynamic Resistance Exercise Alters Blood ApoA-I Levels, Inflammatory Markers, and Metabolic Syndrome Markers in Elderly Women

Combined endurance and dynamic-resistance exercise has important anti-inflammatory effects, altering vascular endothelial function, and helping to prevent and treat aging-related metabolic syndrome (MS). We studied changes in 40 elderly women aged ≥ 65 years (control group (no MS), n = 20, mean age: 68.23 ± 2.56 years; MS group, n = 19, mean age: 71.42 ± 5.87 years; one left). The exercise program comprised dynamic-resistance training using elastic bands, three times weekly, for six months. We analyzed body composition, blood pressure, physical fitness, and MS-related blood variables including ApoA-I, antioxidant factors, and inflammatory markers. After the program, the MS group showed significant reductions in waist-hip ratio, waist circumference, diastolic blood pressure, blood insulin, and HOMA-IR, and a significant increase in HSP70 (p < 0.05). Both groups showed significant increases in ApoA-I levels, ApoA-I/HDL-C ratio, SOD2, IL-4, and IL-5 levels (p < 0.05). Active-resistance training-induced changes in ApoA-I were significantly positively correlated with changes in HDL-C and HSP70, and significantly negatively correlated with changes in triglycerides, C-reactive protein, and TNF-α (p < 0.05). Active-resistance training qualitatively altered HDL, mostly by altering ApoA-I levels, relieving vascular inflammation, and improving antioxidant function. This provides evidence that dynamic-resistance exercise can improve physical fitness and MS risk factors in elderly women.

Monomeric C-reactive protein affects cell injury and apoptosis through activation of p38 mitogen-activated protein kinase in human coronary artery endothelial cells

C-reactive protein (CRP) is an important predictor of cardiovascular events and plays a role in vascular inflammation and vessel damage. The aim of this study was to investigate the effect of pentameric CRP (pCRP) and monomeric CRP (mCRP) on the production of atherosclerosis-re-lated factors in cultured human coronary artery endothelial cells (HCAECs). HCAECs were treated with pCRP, mCRP, p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580, or transfected with p38 MAPK siRNA. Western blotting was performed to detect the expression of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2), intercellular adhesion molecule-2 (ICAM-2) and vascular cell adhe-sion molecule-1 (VCAM-1). Proliferation, damage, and apoptosis of HCAECs were examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, lactate dehydrogenase (LDH), and flow cytometry, respectively. mCRP suppressed VEGF and COX-2 expression and enhanced ICAM-2 and VCAM-1 expression in HCAECs, in both dose-dependent and time-dependent manner. Except at 100 μg/ml concen-tration and 20-hour or 24-hour incubation, pCRP had no apparent effects. mCRP but not pCRP induced HCAEC injury and phosphorylation of p38 MAPK, and the inhibitor SB203580 reversed the effects of mCRP. mCRP promotes injury and apoptosis of HCAECs through a p38 MAPK-dependent mechanism, which provides a new therapy for the injury of HCAECs in atherosclerosis.

Can Active Aerobic Exercise Reduce the Risk of Cardiovascular Disease in Prehypertensive Elderly Women by Improving HDL Cholesterol and Inflammatory Markers?

This study aims to verify the efficacy of exercise programs designed to prevent and treat hypertension-induced cardiovascular disease (CVD) by analyzing the effects of a 6-month active aerobic exercise program, administered to prehypertensive elderly women, on reducing the risk of developing CVD by enhancing their physical fitness level and improving the detailed markers of high-density lipoprotein cholesterol (HDL-C) and inflammatory markers. We assigned the elderly women (≥65 years) recruited into normal blood pressure (120–129/80–84; NBP, n = 18) and high-normal blood pressure (130–139/85–89; HNBP, n = 12) groups according to the European guidelines for the management of arterial hypertension. The exercise program was made up of combined workouts of elastic band resistance exercise and aerobics with dance music. The program took place three times a week for six months, with each session lasting 60 min. We measured pre- and post-intervention body composition, blood pressure, physical fitness level, blood lipids profile, HDL-C, SAA, TNF-α, IL-6, IL-4, IL-15, CRP, and HSP70 and calculated the Framingham risk scores for comparison. A significant post-intervention reduction in the mean systolic blood pressure (SBP) was observed in the HNBP group (p < 0.001), with significant increase in HDL-C (p < 0.01) and significant decrease in serum amyloid A (SAA) concentration (p < 0.01). A significant improvement in physical fitness factors such as physical efficiency index (PEI) was also observed in the HNBP group (p < 0.05). The post-intervention TNF-α, IL-6, and SAA concentrations were more significantly lower in the HNBP than in the NBP group (p < 0.05). Compared to the baseline values, a significant decrease in SAA concentration (p < 0.01) and significant increase in HSP70 concentration (p < 0.001) were observed in the HNBP group. The HNBP group’s 10-year CVD risk was also significantly reduced (p < 0.05). The pre–post differences in SBP and DBP were significantly correlated with those in the anti-inflammatory markers IL-4 and IL-15 (p < 0.01). In conclusion, the 6-month active aerobic exercise program of moderate intensity administered to prehypertensive elderly women (≥65 years) had the effect of reducing the 10-year CVD risk through a substantial reduction in SBP, overall physical fitness improvement, increase in HDL-C, decrease in SAA concentration, and substantial decrease in inflammatory biomarkers. It was also confirmed that an increase in anti-inflammatory markers, which showed a small range of increase with respect to the decrease in blood pressure, may have a major effect.

Conformationally Altered C-Reactive Protein Capable of Binding to Atherogenic Lipoproteins Reduces Atherosclerosis

The aim of this study was to test the hypothesis that C-reactive protein (CRP) protects against the development of atherosclerosis and that a conformational alteration of wild-type CRP is necessary for CRP to do so. Atherosclerosis is an inflammatory cardiovascular disease and CRP is a plasma protein produced by the liver in inflammatory states. The co-localization of CRP and low-density lipoproteins (LDL) at atherosclerotic lesions suggests a possible role of CRP in atherosclerosis. CRP binds to phosphocholine-containing molecules but does not interact with LDL unless the phosphocholine groups in LDL are exposed. However, CRP can bind to LDL, without the exposure of phosphocholine groups, if the native conformation of CRP is altered. Previously, we reported a CRP mutant, F66A/T76Y/E81A, generated by site-directed mutagenesis, that did not bind to phosphocholine. Unexpectedly, this mutant CRP, without any more conformational alteration, was found to bind to atherogenic LDL. We hypothesized that this CRP mutant, unlike wild-type CRP, could be anti-atherosclerotic and, accordingly, the effects of mutant CRP on atherosclerosis in atherosclerosis-prone LDL receptor-deficient mice were evaluated. Administration of mutant CRP into mice every other day for a few weeks slowed the progression of atherosclerosis. The size of atherosclerotic lesions in the aorta of mice treated with mutant CRP for 9 weeks was ~40% smaller than the lesions in the aorta of untreated mice. Thus, mutant CRP conferred protection against atherosclerosis, providing a proof of concept that a local inflammation-induced structural change in wild-type CRP is a prerequisite for CRP to control the development of atherosclerosis.

Systemic inflammation is associated with incident stroke and heart disease in East Asians

Systemic inflammation, reflected by increased plasma concentrations of C-reactive protein (CRP) and fibrinogen, is associated with increased risk of coronary heart disease, but its relevance for stroke types remains unclear. Moreover, evidence is limited in non-European populations. We investigated associations of CRP and fibrinogen with risks of incident major coronary events (MCE), ischemic stroke (IS) and intracerebral hemorrhage (ICH) in a cohort of Chinese adults. A nested case-control study within the prospective China Kadoorie Biobank included 1,508 incident MCE cases, 5,418 IS cases, 4,476 ICH cases, and 5,285 common controls, aged 30–79 years. High-sensitivity CRP and low-density lipoprotein cholesterol (LDL-C) were measured in baseline plasma samples from all participants, and fibrinogen in a subset (n = 9,380). Logistic regression yielded adjusted odds ratios (ORs) per SD higher usual levels of log-transformed CRP and fibrinogen. The overall mean (SD) baseline LDL-C was 91.6 mg/dL (24.0) and geometric mean (95% CI) CRP and fibrinogen were 0.90 mg/L (0.87–0.93) and 3.01 g/L (2.98–3.03), respectively. There were approximately log-linear positive associations of CRP with each outcome, which persisted after adjustment for LDL-C and other risk factors, with adjusted ORs (95% CI) per SD higher CRP of 1.67 (1.44–1.94) for MCE and 1.22 (1.10–1.36) for both IS and ICH. No associations of fibrinogen with MCE, IS, or ICH were identified. Adding CRP to prediction models based on established risk factors improved model fit for each of MCE, IS, and ICH, with small improvements in C-statistic and correct reclassification of controls to lower risk groups. Among Chinese adults, who have low mean LDL-C, CRP, but not fibrinogen, was independently associated with increased risks of MCE and stroke.

Functionality of C-Reactive Protein for Atheroprotection

C-reactive protein (CRP) is a pentameric molecule made up of identical monomers. CRP can be seen in three different forms: native pentameric CRP (native CRP), non-native pentameric CRP (non-native CRP), and monomeric CRP (mCRP). Both native and non-native CRP execute ligand-recognition functions for host defense. The fate of any pentameric CRP after binding to a ligand is dissociation into ligand-bound mCRP. If ligand-bound mCRP is proinflammatory, like free mCRP has been shown to be in vitro, then mCRP along with the bound ligand must be cleared from the site of inflammation. Once pentameric CRP is bound to atherogenic low-density lipoprotein (LDL), it reduces both formation of foam cells and proinflammatory effects of atherogenic LDL. A CRP mutant, that is non-native CRP, which readily binds to atherogenic LDL, has been found to be atheroprotective in a murine model of atherosclerosis. Thus, unlike statins, a drug that can lower only cholesterol levels but not CRP levels should be developed. Since non-native CRP has been shown to bind to all kinds of malformed proteins in general, it is possible that non-native CRP would be protective against all inflammatory states in which host proteins become pathogenic. If it is proven through experimentation employing transgenic mice that non-native CRP is beneficial for the host, then using a small-molecule compound to target CRP with the goal of changing the conformation of endogenous native CRP would be preferred over using recombinant non-native CRP as a biologic to treat diseases caused by pathogenic proteins such as oxidized LDL.

Evolution of C-Reactive Protein

C-reactive protein (CRP) is an evolutionarily conserved protein. From arthropods to humans, CRP has been found in every organism where the presence of CRP has been sought. Human CRP is a pentamer made up of five identical subunits which binds to phosphocholine (PCh) in a Ca²⁺-dependent manner. In various species, we define a protein as CRP if it has any two of the following three characteristics: First, it is a cyclic oligomer of almost identical subunits of molecular weight 20–30 kDa. Second, it binds to PCh in a Ca²⁺-dependent manner. Third, it exhibits immunological cross-reactivity with human CRP. In the arthropod horseshoe crab, CRP is a constitutively expressed protein, while in humans, CRP is an acute phase plasma protein and a component of the acute phase response. As the nature of CRP gene expression evolved from a constitutively expressed protein in arthropods to an acute phase protein in humans, the definition of CRP became distinctive. In humans, CRP can be distinguished from other homologous proteins such as serum amyloid P, but this is not the case for most other vertebrates and invertebrates. Literature indicates that the binding ability of CRP to PCh is less relevant than its binding to other ligands. Human CRP displays structure-based ligand-binding specificities, but it is not known if that is true for invertebrate CRP. During evolution, changes in the intrachain disulfide and interchain disulfide bonds and changes in the glycosylation status of CRP may be responsible for different structure-function relationships of CRP in various species. More studies of invertebrate CRP are needed to understand the reasons behind such evolution of CRP. Also, CRP evolved as a component of and along with the development of the immune system. It is important to understand the biology of ancient CRP molecules because the knowledge could be useful for immunodeficient individuals.

Conformational Changes in C-Reactive Protein Affect Binding to Curved Membranes in a Lipid Bilayer Model of the Apoptotic Cell Surface

C-reactive protein (CRP) is a serum protein that binds to damaged membranes through a phosphatidylcholine binding site. The membrane binding process can initiate the complement immune response and facilitates the clearance of apoptotic cells, likely aiding in the protection of autoimmunity. The initiation of an immune response relies on a conformation change from a native, pentameric form to a modified form, where the modified form binds complement proteins (i.e., C1q) and regulatory proteins substantially better than the native form. In vitro, this reactivity is observed when CRP is monomeric, and a modified form has also been observed at sites of inflammation. Despite evidence that the monomeric form has much higher affinities for almost all proteinaceous binding partners, the role of CRP conformation on lipid binding is yet unknown. In this work, we mimic the outer leaflet of apoptotic cell membranes using a nanopatterned substrate to create curved, supported lipid bilayers and then characterize how CRP conformation affects the interactions between CRP and target membranes. In this assay, the chemical composition and shape are separately tunable parameters. The lipids consisted primarily of palmitoyloleoylphosphatidylcholine, with and without lysophosphatidylcholine, and the curvature had a radius of 27-55 nm. Using this model system combined with quantitative fluorescence microscopy methods, CRP binding to lipid membranes was measured as a function of different conformations of CRP. The modified form of CRP bound curved membranes, but the pentameric form did not for the range of curvatures measured. Unlike most other curvature-sensing proteins, modified CRP accumulated more at a moderate curvature, rather than highly curved or flat regions, suggesting that the membrane bound form does not solely depend on a defect binding mechanism. The presence of lysophosphatidylcholine, a component of apoptotic membranes, increased CRP binding to all types of membranes. Overall, our results show that CRP interactions vary with protein form, lipid composition, and membrane shape. The mechanism by which CRP recognizes damaged membranes depends on the combination of all three.

Functional Transformation of C-reactive Protein by Hydrogen Peroxide

C-reactive protein (CRP) is present at sites of inflammation including amyloid plaques, atherosclerotic lesions, and arthritic joints. CRP, in its native pentameric structural conformation, binds to cells and molecules that have exposed phosphocholine (PCh) groups. CRP, in its non-native pentameric structural conformation, binds to a variety of deposited, denatured, and aggregated proteins, in addition to binding to PCh-containing substances. In this study, we investigated the effects of H2O2, a prototypical reactive oxygen species that is also present at sites of inflammation, on the ligand recognition function of CRP. Controlled H2O2 treatment of native CRP did not monomerize CRP and did not affect the PCh binding activity of CRP. In solid phase ELISA-based ligand binding assays, purified pentameric H2O2-treated CRP bound to a number of immobilized proteins including oxidized LDL, IgG, amyloid β peptide 1-42, C4b-binding protein, and factor H, in a CRP concentration- and ligand concentration-dependent manner. Using oxidized LDL as a representative protein ligand for H2O2-treated CRP, we found that the binding occurred in a Ca2+-independent manner and did not involve the PCh-binding site of CRP. We conclude that H2O2 is a biological modifier of the structure and ligand recognition function of CRP. Overall, the data suggest that the ligand recognition function of CRP is dependent on the presence of an inflammatory microenvironment. We hypothesize that one of the functions of CRP at sites of inflammation is to sense the inflammatory microenvironment, change its own structure in response but remain pentameric, and then bind to pathogenic proteins deposited at those sites.

Purification of recombinant C-reactive protein mutants

C-reactive protein (CRP) is an evolutionarily conserved protein, a component of the innate immune system, and an acute phase protein in humans. In addition to its raised level in blood in inflammatory states, CRP is also localized at sites of inflammation including atherosclerotic lesions, arthritic joints and amyloid plaque deposits. Results of in vivo experiments in animal models of inflammatory diseases indicate that CRP is an anti-pneumococcal, anti-atherosclerotic, anti-arthritic and an anti-amyloidogenic molecule. The mechanisms through which CRP functions in inflammatory diseases are not fully defined; however, the ligand recognition function of CRP in its native and non-native pentameric structural conformations and the complement-activating ability of ligand-complexed CRP have been suggested to play a role. One tool to understand the structure-function relationships of CRP and determine the contributions of the recognition and effector functions of CRP in host defense is to employ site-directed mutagenesis to create mutants for experimentation. For example, CRP mutants incapable of binding to phosphocholine are generated to investigate the importance of the phosphocholine-binding property of CRP in mediating host defense. Recombinant CRP mutants can be expressed in mammalian cells and, if expressed, can be purified from the cell culture media. While the methods to purify wild-type CRP are well established, different purification strategies are needed to purify various mutant forms of CRP if the mutant does not bind to either calcium or phosphocholine. In this article, we report the methods used to purify pentameric recombinant wild-type and mutant CRP expressed in and secreted by mammalian cells.

CARDIOPROTECTIVE ROLES OF THE CHINESE MEDICINAL FORMULA BAO-XIN-TANG ON ACUTE MYOCARDIAL INFARCTION IN RATS

Background:

Bao-Xin-Tang (BXT) is a traditional Chinese medicinal formula used for the treatment of coronary heart disease and known to have favorable therapeutic benefits. The current study was designed to determine whether BXT has a cardioprotective role for acute myocardial infarction. The underlying mechanisms were also explored.

Materials and Methods:

The Sprague-Dawley rat model of acute myocardial infarction was established by occluding the left anterior descending branch of the coronary artery. After a 3-h ischemic period, we determined the myocardial infarction size, inflammatory components, and antioxidant activities.

Results:

The data showed that BXT could reduce the infarction size and lower the levels of C-reactive protein, interleukin-6, and myeloperoxidase, and increase the activities of superoxide dismutase and the anti-inflammatory cytokine, interleukin-10. These results indicate that administration of BXT, following acute myocardial infarction, could reduce infarct size.

Conclusion:

The effects of BXT may be related to its anti-inflammatory and anti-oxidative properties.

Action mechanism and cardiovascular effect of anthocyanins: a systematic review of animal and human studies

Cardiovascular diseases (CVD) are an important cause of death worldwide. Anthocyanins are a subgroup of flavonoids found in berries, flowers, fruits and leaves. In epidemiological and clinical studies, these polyphenols have been associated with improved cardiovascular risk profiles as well as decreased comorbidities. Human intervention studies using berries, vegetables, parts of plants and cereals (either fresh or as juice) or purified anthocyanin-rich extracts have demonstrated significant improvements in low density lipoproteins oxidation, lipid peroxidation, total plasma antioxidant capacity, and dyslipidemia as well as reduced levels of CVD molecular biomarkers. This review discusses the use of anthocyanins in animal models and their applications in human medicine, as dietary supplements or as new potent drugs against cardiovascular disease.

Possible mechanisms of C-reactive protein mediated acute myocardial infarction

Myocardial infarction is a relevant cardiovascular event worldwide for morbidity and mortality. It has been theorized that acute myocardial infarctions (AMIs) and other acute coronary events that are precipitated by atherosclerosis are due to arterial blockage from fat deposits. It is now known, however, that atherosclerosis involves more than just lipids. Inflammation has also been studied extensively to play a substantial role in myocardial infarction. There have been debates and conflicting reports over the past few years about the value of assessing levels of C-reactive protein and other biomarkers of inflammation for the prediction of cardiovascular events. Several studies have shown that CRP is not only an inflammatory marker, but also involved in the pathogenesis of myocardial infarction. Studies have linked atherogenesis and rupture of atherosclerotic lesion to endothelial dysfunction. CRP directly inhibits endothelial cell nitric oxide (NO) production via destabilizing endothelial NO synthase (eNOS). Decreased NO release causes CRP mediated inhibition of angiogenesis, stimulating endothelial cell apoptosis. CRP can also activate the complement system through the classical pathway. Complement activation plays an important role in mediating monocyte and neutrophil recruitment in an injured myocardium and may therefore lead to increase in infarct size. This article discusses the possible roles of CRP in complement activation, endothelial dysfunction and its impact on the development of myocardial infarction. We also reviewed the possible therapeutic approaches to myocardial infarction.

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.

Recognition functions of pentameric C-reactive protein in cardiovascular disease

C-reactive protein (CRP) performs two recognition functions that are relevant to cardiovascular disease. First, in its native pentameric conformation, CRP recognizes molecules and cells with exposed phosphocholine (PCh) groups, such as microbial pathogens and damaged cells. PCh-containing ligand-bound CRP activates the complement system to destroy the ligand. Thus, the PCh-binding function of CRP is defensive if it occurs on foreign pathogens because it results in the killing of the pathogen via complement activation. On the other hand, the PCh-binding function of CRP is detrimental if it occurs on injured host cells because it causes more damage to the tissue via complement activation; this is how CRP worsens acute myocardial infarction and ischemia/reperfusion injury. Second, in its nonnative pentameric conformation, CRP also recognizes atherogenic low-density lipoprotein (LDL). Recent data suggest that the LDL-binding function of CRP is beneficial because it prevents formation of macrophage foam cells, attenuates inflammatory effects of LDL, inhibits LDL oxidation, and reduces proatherogenic effects of macrophages, raising the possibility that nonnative CRP may show atheroprotective effects in experimental animals. In conclusion, temporarily inhibiting the PCh-binding function of CRP along with facilitating localized presence of nonnative pentameric CRP could be a promising approach to treat atherosclerosis and myocardial infarction. There is no need to stop the biosynthesis of CRP.

Computational analysis of C-reactive protein for assessment of molecular dynamics and interaction properties

Serum C-reactive protein (CRP) is used as a marker of inflammation in several diseases including autoimmune disease and cardiovascular disease. CRP, a member of the pentraxin family, is comprised of five identical subunits. CRP has diverse ligand-binding properties which depend upon different structural states of CRP. However, little is known about the molecular dynamics and interaction properties of CRP. In this study, we used SAPS, SCRATCH protein predictor, PDBsum, ConSurf, ProtScale, Drawhca, ASAView, SCide and SRide server and performed comprehensive analyses of molecular dynamics, protein-protein and residue-residue interactions of CRP. We used 1GNH.pdb file for the crystal structure of human CRP which generated two pentamers (ABCDE and FGHIJ). The number of residues involved in residue-residue interactions between A-B, B-C, C-D, D-E, F-G, G-H, H-I, I-J, A-E and F-J subunits were 12, 11, 10, 11, 12, 11, 10, 11, 10 and 10, respectively. Fifteen antiparallel β sheets were involved in β-sheet topology, and five β hairpins were involved in forming the secondary structure. Analysis of hydrophobic segment distribution revealed deviations in surface hydrophobicity at different cavities present in CRP. Approximately 33 % of all residues were involved in the stabilization centers. We show that the bioinformatics tools can provide a rapid method to predict molecular dynamics and interaction properties of CRP. Our prediction of molecular dynamics and interaction properties of CRP combined with the modeling data based on the known 3D structure of CRP is helpful in designing stable forms of CRP mutants for structure-function studies of CRP and may facilitate in silico drug design for therapeutic targeting of CRP.

Not only immunoglobulins, C-reactive protein too

The purpose of this letter is to expand a discussion, published recently in Molecular Immunology, on the post-secretion gain of function by immunoglobulins. It was reported that some circulating IgG molecules in all healthy individuals acquire novel antigen-binding specificity after exposure to conditions that change protein conformation, such as acidic pH. Another protein, C-reactive protein, also acquires novel ligand-binding specificity post-secretion after a switch from its native pentameric conformation to non-native pentameric conformation. Thus, that the functions of a protein depend upon its alternate structural states, and therefore on the surrounding milieu, is a more general phenomenon for some ancient molecules of the immune system than previously thought.

Oxytocin administration attenuates atherosclerosis and inflammation in Watanabe Heritable Hyperlipidemic rabbits

Oxytocin (OT) is a neurohypophyseal peptide traditionally associated with female reproductive functioning, and more recently with prosocial behavior. OT and its receptor are also expressed in the heart and vascular tissue and play a role in cardiovascular homeostasis. In vitro, it has been demonstrated that OT decreases NADPH-dependent superoxide production and pro-inflammatory cytokine release from vascular endothelial cells and macrophages, suggesting that OT may attenuate pathophysiological processes involved with atherosclerotic lesion formation. The present study sought to determine the effect of chronic exogenous OT administration on inflammation and atherosclerosis in an animal model of dyslipidemia and atherosclerosis, the Watanabe Heritable Hyperlipidemic (WHHL) rabbit. Twenty-two, 3-month-old WHHLs were surgically implanted with osmotic mini-pumps containing OT (n=11) or vehicle (n=11), and then were individually housed for the entire study. Blood and 24-h urine samples were taken at baseline and after 8 (midpoint) and 16 (endpoint) weeks of treatment. At endpoint, the aortas and visceral fat samples were dissected and stored for analyses. There were no group differences in body weight, serum lipids, plasma/urinary measures of oxidative stress, plasma cortisol or urinary catecholamines over the 16-week treatment. OT-treated animals exhibited significantly lower plasma C-reactive protein levels at midpoint and endpoint and developed significantly less atherosclerosis in the thoracic aorta relative to vehicle control animals at endpoint (p<0.05). Cytokine gene expression from visceral adipose tissue samples suggested that there was a decrease in adipose tissue inflammation in the OT-treated group compared to the vehicle control group, however these differences were not statistically significant. These results suggest that chronic peripheral OT administration can inhibit inflammation and atherosclerotic lesion development.

C-reactive protein/oxidised low-density lipoprotein/β2-glycoprotein I complex promotes atherosclerosis in diabetic BALB/c mice via p38mitogen-activated protein kinase signal pathway

Background

The aim of this study was to investigate the effect of C-reactive protein/oxidised low-density lipoprotein/β2-glycoprotein I (CRP/oxLDL/β2GPI) complex on atherosclerosis (AS) in diabetic BALB/c mice.

Methods

BALB/c mice were fed high-fat and normal diet. Eight weeks later, the mice fed with high-fat diet were injected with streptozotocin (STZ) to induce diabetes. The diabetic mice were respectively injected twice monthly with 20 μg oxLDL, 20 μg β2GPI, 40 μg oxLDL/β2GPI complex, 44 μg CRP/oxLDL/β2GPI complex, and PBS. Aortas were stained with Sudan IV to investigate lipid plaque formation. The infiltration condition of smooth muscle cells (SMCs), macrophages, and T cells in the aortas were determined by immunohistochemistry (IH). The mRNA expressions of receptors associated with lipid metabolism were quantified by real-time PCR. The phosphorylation of p38 mitogen-activated protein kinase (p38MAPK) and MKK3/6 in aorta tissues were assessed by Western blot. The expression of inflammation cytokines was evaluated by protein chip.

Results

The lipid plaques were more extensive, the lumen area was obviously narrower, the ratio of intima and media thickness were increased, and the normal internal elastic lamia structure and endothelial cell disappeared (P < 0.05) in the oxLDL and CRP/oxLDL/β2GPI groups (P < 0.05). CRP/oxLDL/β2GPI complex dramatically promoted infiltration of SMCs, macrophages, and T cells, improved the mRNA expression of ABCA1 and ABCG1, but reduced the mRNA expression of SR-BI and CD36 and increased the phosphorylation of p38MAPK and MKK3/6 (all P < 0.05). The highest expression levels of IL-1, IL-9, PF-4, bFGF, and IGF-II were detected in the CRP/oxLDL/β2GPI group (P < 0.05).

Conclusions

CRP/oxLDL/β2GPI complex aggravated AS in diabetic BALB/c mice by increasing lipid uptake, the mechanism of which may be mediated by the p38MAPK signal pathway.

The association between subclinical atherosclerosis and uterine fibroids

Objective(s)

To explore the atherogenic hypothesis of uterine fibroids among Chinese women.

Methods

In a case-control study, 335 patients confirmed by ultrasound or hysterectomy surgery and 539 controls were enrolled between October 1, 2009 and April 1, 2012. Unconditional logistic regressions were used to calculate the odds ratios (ORs) for the associations of subclinical atherogenic and cardiovascular risk parameters with uterine fibroids in the overall case group and hysterectomy-confirmed case group, respectively.

Results

Higher level of ankle-brachial index (ABI) was independently associated with increased odds of uterine fibroids. The odds of UF among women in the highest tertile of ABI were 1.88 times higher (95%CI: 1.17, 3.02, P_trend = 0.008) compared to those in the lowest tertile. The serum concentration of homocysteine was inversely related to fibroids (middle vs. low: OR 0.56, 95%CI: 0.36, 0.85; high vs. low: OR 0.50, 95% CI: 0.32, 0.79; P_trend = 0.002). In the hysterectomy-confirmed group, an inverse association was suggested between high-density lipoprotein cholesterol (HDL-C) and fibroids (OR 0.46, 95% CI: 0.25, 0.84, P_trend = 0.014). Moreover, the effect of homocysteine concentration was not observed in this group.

Conclusion(s)

These findings suggest that women with uterine fibroids might have an increased risk of subclinical atherosclerosis.

Does Apolipoprotein E genotype affect cardiovascular risk in subjects with acromegaly?

Acromegaly is a syndrome that results when the pituitary gland produces excess growth hormone after epiphyseal closure at puberty. Usually, subjects with acromegaly exhibit a 2- to 3-fold higher mortality rate from diseases that are associated with cardiovascular complications when compared to the normal population. In this study, we therefore aimed to evaluate whether a well-established cardiovascular risk factor, the Apolipoprotein E (Apo E) genotype, contributes to increased risk of cardiovascular complications in subjects with acromegaly. A total of 102 unrelated acromegaly subjects were prospectively included into this case-control association study and constituted our study group. The study group was comparable by age and gender with 200 unrelated healthy subjects constituting our control group. Genomic DNA was isolated from the peripheral blood leukocytes of all subjects and Apo E genotype (codon 112/158) was assessed by melting temperature analyses after using a real-time PCR protocol. The Apolipoprotein E4 allele was found at a significantly higher frequency in the study group when compared with the control group (P = 0.032). Subjects with the E2 allele, on the other hand, had significantly increased values in body mass index (P = 0.004), waist circumference (P = 0.001), C-reactive protein (CRP) (P < 0.001), and left-side carotid intima media thickness (P = 0.025). The Apolipoprotein E2 genotype might contribute to increased risk of cardiovascular complications in subjects with acromegaly since it is concurrently present with other cardiovascular risk factors such as the left-side carotid intima media thickness and CRP.

Novel phytonutrient contributors to antioxidant protection against cardiovascular disease

The associations linking endothelial inflammation, endothelial oxidative stress, and atherogenesis and the potential for dietary phytonutrients to decrease the impact of these associations were assessed. A detailed literature review was conducted and summarized. A large body of scientific evidence describes the interactions among endothelial inflammation, endothelial oxidative stress, and atherogenesis. A growing body of research indicates that several dietary phytonutrients (astaxanthin, lycopene, lutein, and glabridin) can decrease the risk for atherosclerosis by decreasing endothelial inflammation and oxidative stress. The consumption of foods or dietary supplements that provide astaxanthin, lycopene, lutein, and glabridin can ameliorate endothelial inflammation and oxidative stress, retard atherogenesis, and decrease the risk for atherogenic cardiovascular disease.

Exposing a hidden functional site of C-reactive protein by site-directed mutagenesis

C-reactive protein (CRP) is a cyclic pentameric protein whose major binding specificity, at physiological pH, is for substances bearing exposed phosphocholine moieties. Another pentameric form of CRP, which exists at acidic pH, displays binding activity for oxidized LDL (ox-LDL). The ox-LDL-binding site in CRP, which is hidden at physiological pH, is exposed by acidic pH-induced structural changes in pentameric CRP. The aim of this study was to expose the hidden ox-LDL-binding site of CRP by site-directed mutagenesis and to generate a CRP mutant that can bind to ox-LDL without the requirement of acidic pH. Mutation of Glu(42), an amino acid that participates in intersubunit interactions in the CRP pentamer and is buried, to Gln resulted in a CRP mutant (E42Q) that showed significant binding activity for ox-LDL at physiological pH. For maximal binding to ox-LDL, E42Q CRP required a pH much less acidic than that required by wild-type CRP. At any given pH, E42Q CRP was more efficient than wild-type CRP in binding to ox-LDL. Like wild-type CRP, E42Q CRP remained pentameric at acidic pH. Also, E42Q CRP was more efficient than wild-type CRP in binding to several other deposited, conformationally altered proteins. The E42Q CRP mutant provides a tool to investigate the functions of CRP in defined animal models of inflammatory diseases including atherosclerosis because wild-type CRP requires acidic pH to bind to deposited, conformationally altered proteins, including ox-LDL, and available animal models may not have sufficient acidosis or other possible modifiers of the pentameric structure of CRP at the sites of inflammation.

Probing the phosphocholine-binding site of human C-reactive protein by site-directed mutagenesis

Human C-reactive protein (CRP) can activate the classical pathway of complement and function as an opsonin only when it is complexed to an appropriate ligand. Most known CRP ligands bind to the phosphocholine (PCh)-binding site of the protein. In the present study, we used oligonucleotide-directed site-specific mutagenesis to investigate structural determinants of the PCh-binding site of CRP. Eight mutant recombinant (r) CRP, Y40F; E42Q; Y40F, E42Q; K57Q; R58G; K57Q, R58G; W67K; and K57Q, R58G, W67K were constructed and expressed in COS cells. Wild-type and all mutant rCRP except for the W67K mutants bound to solid-phase PCh-substituted bovine serum albumin (PCh-BSA) with similar apparent avidities. However, W67K rCRP had decreased avidity for PCh-BSA and the triple mutant, K57Q, R58G, W67K, failed to bind PCh-BSA. Inhibition experiments using PCh and dAMP as inhibitors indicated that both Lys-57 and Arg-58 contribute to PCh binding. They also indicated that Trp-67 provides interactions with the choline group. The Y40F and E42Q mutants were found to have increased avidity for fibronectin compared to wild-type rCRP. We conclude that the residues Lys-57, Arg-58, and Trp-67 contribute to the structure of the PCh-binding site of human CRP. Residues Tyr-40 and Glu-42 do not appear to participate in the formation of the PCh-binding site of CRP, however, they may be located in the vicinity of the fibronectin-binding site of CRP.