Erythrocyte adhesiveness/aggregation: a novel biomarker for the detection of low-grade internal inflammation in individuals with atherothrombotic risk factors and proven vascular disease

Comprehensive study of the rheological status and intensity of oxidative stress during the progression of type 2 diabetes mellitus to prevent its complications

BACKGROUND

Prevention of Type 2 diabetes mellitus (T2DM) requires a modifying effect on the pathological processes inducing the β-cell dysfunction.

OBJECTIVES

the comprehensive study of the violation of rheological parameters in patients with different stages of diabetes and identification of possible links between these alterations with the intensity of the oxidative stress in the patient's body.

METHODS

60 patients with IR, prediabetes, T2DM and healthy volunteers were included. Full range of the rheological parameters of the patients' blood - the indicators of erythrocytes aggregation index (EAI), the relative deformability of the erythrocytes membranes (ERDI), blood plasma viscosity (BPV), and oxidative stress intensity (OSI) were examined.

RESULTS

In patients with insulin resistance (IR), prediabetes, and T2DM the ERDI was statistically significantly lower and BPV - higher compared to control; a significant increase in EAI was detected in the patient group with prediabetes and T2DM compared to the control.

CONCLUSION

The level of rheological disorders in patients increases with the increase of the level of carbohydrate metabolism disorders and intensity of oxidative stress and reaches a maximum during manifested diabetes. Diagnosis of hemorheological disorders and OSI in T2DM can serve as an early marker of target organ damage possibility.

The Usefulness of the Erythrocyte Sedimentation Rate and C-reactive Protein for the Differential Diagnosis of Non-Arteritic Anterior Ischemic Optic Neuropathy in the Era of Microinflammation

PURPOSE

The presence of a microinflammatory response is one of the possible pathological mechanisms related to the development of nonarteritic anterior ischemic optic neuropathy (NAAION), a common cause of optic neuropathy in old age.We tested whether individuals with NAAION harbor a heightened microinflammatory response compared to controls.

METHODS

We measured the erythrocyte sedimentation rate (ESR) and high sensitivity C-reactive protein (hs-CRP) in NAAION patients during hospital admission and in four matched controls for each patient, retrieved from a large cohort of 20,000 apparently healthy individuals.

RESULTS

We included 128 NAAION patients and 512 controls. No significant differences were found between patients and controls regarding the inflammatory biomarkers.

CONCLUSIONS

This is the first report showing a lack of difference in ESR and hs-CRP levels between NAAION patients and matched controls, suggesting NAAION is not associated with a heightened inflammatory response, such as the one associated with multiple atherothrombotic risk factors.

Biomarkers of Oxidative Stress in Metabolic Syndrome and Associated Diseases

Metabolic syndrome (MS) represents worldwide public health issue characterized by a set of cardiovascular risk factors including obesity, diabetes, dyslipidemia, hypertension, and impaired glucose tolerance. The link between the MS and the associated diseases is represented by oxidative stress (OS) and by the intracellular redox imbalance, both caused by the persistence of chronic inflammatory conditions that characterize MS. The increase in oxidizing species formation in MS has been accepted as a major underlying mechanism for mitochondrial dysfunction, accumulation of protein and lipid oxidation products, and impairment of the antioxidant systems. These oxidative modifications are recognized as relevant OS biomarkers potentially able to (i) clarify the role of reactive oxygen and nitrogen species in the etiology of the MS, (ii) contribute to the diagnosis/evaluation of the disease's severity, and (iii) evaluate the utility of possible therapeutic strategies based on natural antioxidants. The antioxidant therapies indeed could be able to (i) counteract systemic as well as mitochondrial-derived OS, (ii) enhance the endogenous antioxidant defenses, (iii) alleviate MS symptoms, and (iv) prevent the complications linked to MS-derived cardiovascular diseases. The focus of this review is to summarize the current knowledge about the role of OS in the development of metabolic alterations characterizing MS, with particular regard to the occurrence of OS-correlated biomarkers, as well as to the use of therapeutic strategies based on natural antioxidants.

Quantitative Measurement of Erythrocyte Aggregation as a Systemic Inflammatory Marker by Ultrasound Imaging: A Systematic Review

This systematic review is aimed at answering two questions: (i) Is erythrocyte aggregation a useful biomarker in assessing systemic inflammation? (ii) Does quantitative ultrasound imaging provide the non-invasive option to measure erythrocyte aggregation in real time? The search was executed through bibliographic electronic databases CINAHL, EMB Review, EMBASE, MEDLINE, PubMed and the grey literature. The majority of studies correlated elevated erythrocyte aggregation with inflammatory blood markers for several pathologic states. Some studies used "erythrocyte aggregation" as an established marker of systemic inflammation. There were limited but promising articles regarding the use of quantitative ultrasound spectroscopy to monitor erythrocyte aggregation. Similarly, there were limited studies that used other ultrasound techniques to measure systemic inflammation. The quantitative measurement of erythrocyte aggregation has the potential to be a routine clinical marker of inflammation as it can reflect the cumulative inflammatory dynamics in vivo, is relatively simple to measure, is cost-effective and has a rapid turnaround time. Technologies like quantitative ultrasound spectroscopy that can measure erythrocyte aggregation non-invasively and in real time may offer the advantage of continuous monitoring of the inflammation state and, thus, may help in rapid decision making in a critical care setup.

Protocol for Robust In Vivo Measurements of Erythrocyte Aggregation Using Ultrasound Spectroscopy

Erythrocyte aggregation is a non-specific marker of acute and chronic inflammation. Although it is usual to evaluate this phenomenon from blood samples analyzed in laboratory instruments, in vivo real-time assessment of aggregation is possible with spectral ultrasound techniques. However, variable blood flow can affect the interpretation of acoustic measures. Therefore, flow standardization is required. Two techniques of flow standardization were evaluated with porcine and equine blood samples in Couette flow. These techniques consisted in either stopping the flow or reducing it. Then, the sensibility and repeatability of the retained method were evaluated in 11 human volunteers. We observed that stopping the flow compromised interpretation and repeatability. Conversely, maintaining a low flow provided repeatable measures and could distinguish between normal and high extents of erythrocyte aggregation. Agreement was observed between in vivo and ex vivo measures of the phenomenon (R² = 82.7%, p value < 0.0001). These results support the feasibility of assessing in vivo erythrocyte aggregation in humans by quantitative ultrasound means.

Influence of erythrocyte aggregation on radial migration of platelet-sized spherical particles in shear flow

Blood platelets when activated are involved in the mechanisms of hemostasis and thrombosis, and their migration toward injured vascular endothelium necessitates interaction with red blood cells (RBCs). Rheology co-factors such as a high hematocrit and a high shear rate are known to promote platelet mass transport toward the vessel wall. Hemodynamic conditions promoting RBC aggregation may also favor platelet migration, particularly in the venous system at low shear rates. The aim of this study was to confirm experimentally the impact of RBC aggregation on platelet-sized micro particle migration in a Couette flow apparatus. Biotin coated micro particles were mixed with saline or blood with different aggregation tendencies, at two shear rates of 2 and 10s^-1 and three hematocrits ranging from 20 to 60%. Streptavidin membranes were respectively positioned on the Couette static and rotating cylinders upon which the number of adhered fluorescent particles was quantified. The platelet-sized particle adhesion on both walls was progressively enhanced by increasing the hematocrit (p<0.001), reducing the shear rate (p<0.001), and rising the aggregation of RBCs (p<0.001). Particle count was minimum on the stationary cylinder when suspended in saline at 2s^-1 (57±33), and maximum on the rotating cylinder at 60% hematocrit, 2s^-1 and the maximum dextran-induced RBC aggregation (2840±152). This fundamental study is confirming recent hypotheses on the role of RBC aggregation on venous thrombosis, and may guide molecular imaging protocols requiring injecting active labeled micro particles in the venous flow system to probe human diseases.

Hemorheological parameters better classify metabolic syndrome than novel cardiovascular risk factors and peripheral vascular disease marker

The present study compares the association of Metabolic Syndrome (MetS) with hemorheological parameters, oxidative stress, inflammation and peripheral arterial disease markers. 100 participants were recruited and participants were divided into three groups on the basis of absence or presence of MetS and its components. Odds ratio for correctly predicting MetS was highest for erythrocyte aggregation followed by erythrocyte deformability. ROC curve analysis demonstrated that all the hemorheological components significantly classified MetS participants. Area Under Curve was higher for the hemorheological parameters (erythrocyte aggregation and erythrocyte deformability) than for the oxidative stress, inflammation and peripheral arterial disease markers. The possibilities of the hemorheological components to be identified as better cardiovascular risk markers due to their strong association with MetS cannot be precluded from the present findings.

Crosstalk between red blood cells and the immune system and its impact on atherosclerosis

Atherosclerosis is a chronic multifactorial disease of the arterial wall characterized by inflammation, oxidative stress, and immune system activation. Evidence exists on a pathogenic role of oxidized red blood cells (RBCs) accumulated in the lesion after intraplaque hemorrhage. This review reports current knowledge on the impact of oxidative stress in RBC modifications with the surface appearance of senescent signals characterized by reduced expression of CD47 and glycophorin A and higher externalization of phosphatidylserine. The review summarizes findings indicating that oxidized, senescent, or stored RBCs, due to surface antigen modification and release of prooxidant and proinflammatory molecules, exert an impaired modulatory activity on innate and adaptive immune cells and how this activity contributes to atherosclerotic disease. In particular RBCs from patients with atherosclerosis, unlike those from healthy subjects, fail to control lipopolysaccharide-induced DC maturation and T lymphocyte apoptosis. Stored RBCs, accompanied by shedding of extracellular vesicles, stimulate peripheral blood mononuclear cells to release proinflammatory cytokines, augment mitogen-driven T cell proliferation, and polarize macrophages toward the proinflammatory M1 activation pathway. Collectively, literature data suggest that the crosstalk between RBCs with immune cells represents a novel mechanism by which oxidative stress can contribute to atherosclerotic disease progression and may be exploited for therapeutic interventions.

Exercise-induced changes in inflammatory processes: Implications for thrombogenesis in cardiovascular disease

Sedentary lifestyle is a risk factor and a strong predictor for chronic disease and premature death. Low-grade inflammation has been proved a key player in the pathogenesis of cardiovascular disease. Inflammatory processes have been also involved in maintaining the balance between coagulation and fibrinolysis. In addition, an inverse linear dose-response relation between physical activity and mortality risks has also been reported. However, the favorable effects of structured exercise programs and the independent contribution of physical activity to cardiovascular risk are still under investigation. In response to heavy exercise, interleukin-6 (IL-6) is secreted by contracting skeletal muscles, followed by an acute reactant release of C-reactive protein (CRP). Both CRP and IL-6 can stimulate monocyte tissue factor production, provoke platelet hyperreactivity, promote fibrinogen biosynthesis, and enhance microparticle formation and erythrocyte aggregability, thus triggering prothrombotic state. By contrast, regular exercise and physical activity are protective against all-cause mortality through suppressing pro-inflammatory cytokine production, enhancing anti-inflammatory mediators and antioxidant development, and promoting fibrinolytic activity. Low-load resistance exercise also plays an advantageous role in thrombogenesis by reducing inflammatory processes and potentiating fibrinolytic features. In the present review article, we provide an overview of the impact of different modes and intensities of physical activity on vascular inflammation and thrombogenesis.

Blood rheology and aging

The flow properties of blood play significant roles in tissue perfusion by contributing to hydrodynamic resistance in blood vessels. These properties are influenced by pathophysiological processes, thereby increasing the clinical relevance of blood rheology information. There is well-established clinical evidence for impaired blood fluidity in humans of advanced age, including enhanced plasma and whole blood viscosity, impaired red blood cell (RBC) deformability and enhanced RBC aggregation. Increased plasma fibrinogen concentration is a common finding in many studies owing to the pro-inflammatory condition of aged individuals; this finding of increased fibrinogen concentration explains the higher plasma viscosity and RBC aggregation in elderly subjects. Enhanced oxidant stress in advanced age is also known to contribute to altered blood fluidity, with RBC deformability being an important determinant of blood viscosity. Several studies have shown that physical activity may improve the hemorheological picture in elderly subjects, yet well-designed observational and mechanistic studies are required to determine the specific effects of regular exercise on hemorheological parameters in healthy and older individuals.

Role of red blood cell flow behavior in hemodynamics and hemostasis

The primary role of red blood cells (RBCs) is to transport oxygen to the tissues, which is performed predominantly in the blood capillaries. However, RBCs have unique flow-affecting properties that play a key role in blood flow in all blood vessel types and sizes. While RBCs as oxygen carriers have been studied extensively, their hemodynamic function has been examined less comprehensively. This review aims to bridge this gap, focusing on the role of RBC flow properties in hemodynamics, hemostasis and thrombosis.

Ultrasound monitoring of RBC aggregation as a real-time marker of the inflammatory response in a cardiopulmonary bypass swine model

OBJECTIVES

In many pathological conditions, including high-risk surgery, the severity of the inflammatory response is related to the patient outcome. However, determining the patient inflammatory state presents difficulties, as markers are obtained intermittently through blood testing with long delay. RBC aggregation is a surrogate marker of inflammation that can be quantified with the ultrasound Structure Factor Size and Attenuation Estimator. The latter is proposed as a real-time inflammation monitoring technique for patient care.

DESIGN

Ten swine underwent a 90-minute cardiopulmonary bypass, and surveillance was maintained during 120 minutes in the postbypass period. To promote the inflammatory reaction, lipopolysaccharide was administrated two times prior to surgery in six of those swine (lipopolysaccharide group). During the whole procedure, the Structure Factor Size and Attenuation Estimator cellular imaging method displayed a RBC aggregation index (W) computed from images acquired within the pump circuit and the femoral vein. Interleukin-6, interleukin-10, C-reactive protein, haptoglobin, immunoglobulin G, and fibrinogen concentrations were measured at specific periods.

MAIN RESULTS

Compared with controls, the lipopolysaccharide group exhibited higher W within the pump circuit (p < 0.05). In the femoral vein, W was gradually amplified in the lipopolysaccharide group during cardiopulmonary bypass and the postbypass period (p < 0.05), whereas interleukin levels were higher in the lipopolysaccharide group but only at the end of cardiopulmonary bypass and beginning of postbypass (p < 0.05).

CONCLUSIONS

Continuous RBC aggregation monitoring can characterize the evolving inflammatory response during and after cardiopulmonary bypass. The Structure Factor Size and Attenuation Estimator is proposed as a real-time noninvasive monitoring technique to anticipate inflammation-related complications during high-risk surgery or critical care situations. Because RBC aggregation promotes vascular resistance and thrombosis, W could also provide early information on vascular disorders in those clinical situations.

Influence of a moderate physical activity intervention on red cell deformability in patients suffering from chronic obstructive pulmonary disease (COPD)

The present study investigates whether a moderate physical activity intervention may alter red cell deformability (RCD) of patients suffering from chronic obstructive pulmonary disease (COPD). Subjects (n = 10; age: 62 ± 4; body-mass index (BMI): 25.8 ± 7.5) performed a training regimen for 10 weeks. In the beginning of the study and after the training period, COPD patients underwent a WHO cycle ergometry test. Venous blood samples were taken before (T0), immediately after (T1) and 30 min after (T2) the intervention. RCD was measured with the laser-assisted optical rotational cell analyzer (LORCA). Significant improvements of the RCD were detected. The semi-maximal shear stress increased significantly. Acute exhaustion had no effect on RCD. Thus, the training period of 10 weeks influenced RCD.

Red cell distribution width and risk of peripheral artery disease: Analysis of National Health and Nutrition Examination Survey 1999–2004

Red cell distribution width (RDW) is an independent predictor of the 10-year estimated risk of coronary heart disease (CHD) events. However, RDW’s association with peripheral artery disease (PAD) – a CHD risk equivalent – has not been evaluated to date. In this cross-sectional study, we examined 6950 participants of the National Health and Nutrition Examination Survey, 1999–2004. PAD was defined as an ankle–brachial index below 0.9 ( n = 618). RDW was divided into quartiles (Q) (Q1: ≤ 12.2; Q2: 12.3–12.5; Q3: 12.6–13.0; Q4: ≥ 13.1) and PAD risk was compared across these quartiles using adjusted multivariate logistic regression. A graded increase in prevalent PAD with increasing RDW quartiles was observed (4.2% in Q1 vs 13.9% in Q4; test of trend p < 0.001). Risk of PAD was significantly higher (odds ratio (OR) 1.19, 95% confidence interval (CI): 1.06–1.34; p = 0.003) after adjusting for age, sex, race, body mass index, hypertension, hyperlipidemia, diabetes, smoking, estimated glomerular filtration rate, C-reactive protein, hemoglobin, mean corpuscular volume, and nutritional factors (folate, iron and vitamin B12) deficiencies with each unit (0.1) increase in RDW. Upon receiver-operating characteristics analysis, the predictive accuracy of the American College of Cardiology / American Heart Association (ACC/AHA)-defined PAD screening criteria (for a high-risk population) was 0.657 at best, but improved significantly (0.727) after addition of RDW ( p < 0.0001). In conclusion, higher levels of RDW are independently associated with a higher risk of PAD and can significantly improve the risk prediction beyond that estimated by ACC/AHA-defined PAD screening criteria.

Exertional periodic breathing potentiates erythrocyte rheological dysfunction by elevating pro-inflammatory status in patients with anemic heart failure

BACKGROUND

Exertional periodic breathing (EPB) or anemia is associated with an adverse prognosis in advanced heart failure (HF). The disturbed rheological properties of erythrocytes may contribute to circulatory disorders. This study investigated whether EPB with/without anemia influences rheological/hemodynamic functions in patients with HF.

METHODS

According to the WHO criteria for anemia, 168 HF patients were divided into six groups: non (N)-anemic with (n=27)/without (n=56) EPB, light (L)-anemic with (n=17)/without (n=21) EPB, and moderate/several (M/S)-anemic with (n=21)/without (n=26) EPB groups. These HF patients and 30 healthy counterparts performed an incremental exercise test using a bicycle ergometer. Rheological and hemodynamic characteristics were determined by slit-flow ektacytometer and bioreactance-based device/near infrared spectrometer, respectively.

RESULTS

In the HF patients with EPB, both L- and M/S-anemic groups exhibited 1) higher plasma myeloperoxidase/interleukin-6 concentrations, 2) more blood senescent/spherical erythrocyte counts, 3) larger aggregability and smaller deformability of erythrocytes under shear flows, 4) higher systemic vascular resistance, which was accompanied by smaller amounts of blood distributed to cerebral/muscular tissues during exercise, 5) less VO(2peak) and ventilatory efficiency, and 6) lower Short Form-36 physical/mental component scores and higher Minnesota Living with HF questionnaire score than N-anemic group. Additionally, plasma myeloperoxidase/interleukin-6 levels were directly related to erythrocyte aggregability and inversely related to erythrocyte deformability. However, there were no significant differences in pro-inflammatory factors, rheological/hemodynamic properties, and aerobic capacity between L- and N-anemic groups in the HF patients without EPB.

CONCLUSION

EPB potentiates anemia-related rheological/hemodynamic dysfunctions by elevating pro-inflammatory status, reducing physical fitness in patients with HF.

Wavelength selection in measuring red blood cell aggregation based on light transmittance

The reversible aggregation of red blood cells (RBC) is of current basic science and clinical interest. Using a flow channel and light transmittance (LT) through RBC suspensions, we have examined the effects of wavelength (500 to 900 nm) on the static and dynamic aspects of RBC aggregation for normal blood and suspensions with reduced or enhanced aggregation; the effects of oxygenation were also explored. Salient observations include: 1. significant effects of wavelength on aggregation parameters reflecting the extent of aggregation (i.e., number of RBC per aggregate); 2. no significant effects of wavelength on parameters reflecting the time course of RBC aggregation; 3. a prominent influence of hemoglobin oxygen saturation on both extent and time-course related aggregation parameters measured at wavelengths less than 700 nm, but only on the time-course at 800 nm; and 4. the power of parameters in detecting a given alteration of RBC aggregation is affected by wavelength, in general being greater at higher wavelengths. It is recommended that light sources with wavelengths around 800 nm be used in instruments for measuring RBC aggregation via LT.

The red blood cell as a gender-associated biomarker in metabolic syndrome: a pilot study

In the present pilot study (56 patients), some red blood cell parameters in samples from patients with metabolic syndrome and subclinical atherosclerosis, but without any sign of coronary artery disease, have been analyzed. The main goal of this work was to determine, in this preclinical state, new peripheral gender-associated bioindicators of possible diagnostic or prognostic value. In particular, three different "indicators" of red blood cell injury and aging have been evaluated: glycophorin A, CD47, and phosphatidylserine externalization. Interestingly, all these determinants appeared significantly modified and displayed gender differences. These findings could provide novel and useful hints in the research for gender-based real-time bioindicators in the progression of metabolic syndrome towards coronary artery disease. Further, more extensive studies are, however, necessary in order to validate these findings.

A local increase in red blood cell aggregation can trigger deep vein thrombosis: evidence based on quantitative cellular ultrasound imaging

BACKGROUND

Recurrent deep vein thrombosis (DVT) risk factors include a first idiopathic DVT, strongly suggesting the existence of undiagnosed and/or unidentified prothrombotic abnormalities.

OBJECTIVES

To evaluate the impact of locally increased red blood cell (RBC) aggregation on DVT pathogenesis in a rabbit model.

METHODS

DVT presence, flow and aggregation were measured in situ with ultrasound. Greatly enhanced aggregation was achieved by covalent linkage of Pluronic F98 to the RBC surface; coating with Pluronic F68, which very mildly enhances aggregation, was used as a coating control. On day 1, endothelial damage and a partial stenosis were surgically created on the left femoral vein whereas the right femoral vein was not manipulated.

RESULTS

A thrombus was formed within 30 min in six out of seven left femoral veins of animals receiving a 30% volume blood exchange with F98-coated RBC, whereas a thrombus occurred in only one out of seven veins in F68-transfused controls. In vivo imaging using quantitative ultrasound confirmed increased aggregation in the thrombosed veins of the F98 group compared with the F68 group and the contralateral vessel. For each group, five animals were followed for 2 weeks before being killed. In F98-transfused animals, lysis of clots occurred and the presence of chronic thrombi totally occluding the vein in three out of five animals was confirmed by histology. Conversely, in the F68 group, a single disorganized blood clot was observed in one out of five animals.

CONCLUSIONS

A marked increase in RBC aggregation promotes thrombosis in rabbit femoral veins, confirming a pathophysiological role of locally altered hemorheology in the onset of DVT.

Low-grade systemic inflammation in patients with amyotrophic lateral sclerosis

OBJECTIVE

To prospectively determine the intensity of systemic low-grade inflammation in patients with amyotrophic lateral sclerosis (ALS).

PATIENTS AND METHODS

Patients with ALS and matched healthy controls underwent blood tests for inflammation-sensitive biomarkers: erythrocyte sedimentation rate (ESR), quantitative fibrinogen, wide-range C-reactive protein (wrCRP) concentrations, leukocyte count and neutrophil-to-lymphocyte ratio (NLR). The correlation between these inflammatory biomarkers and disability status of the patients, expressed by the ALS Functional Rating Scale (ALSFRS-R), was evaluated.

RESULTS

Eighty patients with ALS and 80 matched controls were included. wrCRP, fibrinogen, ESR and NLR values were significantly elevated in patients compared with controls. There was a significant correlation between the ALSFRS-R score and wrCRP, ESR and fibrinogen levels. This correlation persisted on sequential examinations.

CONCLUSIONS

A systemic low-grade inflammation was detected in patients with ALS and correlated with their degree of disability. A heightened systemic inflammatory state is apparently associated with a negative prognosis in ALS.

Low-grade inflammation in individuals with the hypertriglyceridemic waist phenotype: another feature of the atherogenic dysmetabolism

The purpose of this study was to explore the possibility that the recently described "hypertriglyceridemic waist" (HTGW) phenotype, a risk for future coronary artery disease, is associated with the presence of low-grade inflammation. This is a cross-sectional study in a cohort of apparently healthy nondiabetic employed individuals in whom the presence of low-grade inflammation was determined by using the Dade Behring high-sensitivity C-reactive protein (hs-CRP) assay. We have presently analyzed the results obtained in 9842 apparently healthy individuals, at a mean (SD) age of 44 (11) years. We identified 1249 individuals (70.0% men) with HTGW phenotype according to the cutoff points of waist girth of at least 90 cm for men and at least 85 cm for women and triglycerides levels of at least 177 mg/dL for men and at least 133 mg/dL for women. In addition, we identified 1164 individuals (69.3% men) with the metabolic syndrome (MetS) according to the updated Adult Treatment Panel III criteria. The mean (SD) of hs-CRP was 1.3 (2.9) mg/L for the 8055 individuals who had neither the HTGW phenotype nor the MetS, 2.1 (2.7) mg/L for those who had the HTGW phenotype and no MetS, and 2.5 (2.7) for 538 individuals with the MetS and no HTGW phenotype, whereas those who had both atherogenic disorders presented an hs-CRP concentration of 2.9 (2.3) mg/L. In this cohort of apparently healthy nondiabetic employed individuals, the HTGW phenotype had a similar prevalence as the MetS and was associated with the presence of low-grade inflammation. This inflammation could be a pathophysiologic link between this dysmetabolism and atherothrombosis. In addition, the HTGW phenotype is relatively prevalent and could be a simple and inexpensive way to single out individuals at risk for future coronary artery disease.

High-sensitivity C-reactive protein measurements in patients with non-arteritic anterior ischaemic optic neuropathy: a clue to the presence of a microinflammatory response

PURPOSE

To explore the possibility that individuals with non-arteritic anterior ischaemic optic neuropathy (NA-AION) harbour a heightened microinflammatory response compared to carefully matched controls.

METHODS

Diagnosis and follow-up were performed by a senior neuro-ophthalmologist (A.K.). The inflammatory biomarkers included white blood cell count, Westergren erythrocyte sedimentation rate (ESR), quantitative fibrinogen as well as high-sensitivity C-reactive protein (hs-CRP). The values of the inflammatory biomarkers of four and five matched controls were compared to patients with NA-AION.

RESULTS

We examined 33 NA-AION patients and 151 controls matched for age, gender, body mass index, oral temperature, smoking status and atherothrombotic risk factors. A significantly elevated concentration was noted for hs-CRP (P = 0.021): 3.3 mg/l for NA-AION patients and 2.1 mg/l for controls. Accelerated ESR (18.8 versus 13.5 mm/hr, P = 0.025) was noted in the NA-AION patients.

CONCLUSION

Following appropriate matching to apparently healthy controls, patients with NA-AION presented a microinflammatory response, revealed by the presence of increased hs-CRP concentrations and accelerated ESR. The finding, if confirmed in future studies, might shed more light on the eventual pathophysiological processes involved in the disease and pave the way for new therapeutic approaches.

Microinflammation in patients with Crohn's disease in clinical remission

BACKGROUND AND AIMS

It is not clear whether Crohn's disease patients in clinical remission (Crohn's disease activity index<150) display normal concentrations of inflammation sensitive biomarkers. Our goal in this work was to explore the intensity of the microinflammatory response in a group of Crohn's disease patients in clinical remission.

METHODS

High sensitivity C-reactive protein, quantitative fibrinogen, erythrocyte sedimentation rate as well as platelet and leukocyte counts were examined in a group of 76 patients with Crohn's disease in remission and in 228 matched controls.

RESULTS

Crohn's disease patients in clinical remission displayed a statistically significant (p<0.001) elevated concentration of hs-CRP (4.83±3.8 mg/l) compared to controls (1.05±2.9 mg/l). All other bio-markers were also significantly higher in Crohn's disease patients in remission compared to controls. Similar results were obtained in a subgroup of Crohn's disease patients with very low disease activity - CDAI<75.

CONCLUSIONS

Clinical remission is not equivalent to biochemical remission raising a question concerning the true definition of remission in Crohn's disease.

Exploring the usefulness of inflammation-sensitive biomarkers to reveal potential sex differences in relation to low-grade inflammation in individuals with the metabolic syndrome

Sex differences exist in the expression of different inflammation-sensitive biomarkers in relation to the metabolic syndrome (MetS). We have presently explored these differences in relation to commonly used inflammation-sensitive biomarkers including the high-sensitivity C-reactive protein (hs-CRP), quantitative fibrinogen, erythrocyte sedimentation rate (ESR), white blood cell count (WBCC), and absolute number of polymorphonuclear leukocytes. This is a cross-sectional analysis of a group of apparently healthy men (n = 5560) and women (n = 3049) in whom the results of the above-mentioned inflammation-sensitive biomarkers were analyzed in relation to the different components of MetS. The concentration of hs-CRP increased pari passu with the number of components of the MetS, the differences between the sexes being significant for any number of components of the MetS. Regarding fibrinogen, the influence of sex turned significant for waist only, similarly to the results of the ESR. None of these interactions were found to be significant for both the WBCC and the absolute number of polymorphonuclear leukocytes. Quantitative fibrinogen, ESR, WBCC, as well as the absolute number of polymorphonuclear leukocytes are not sensitive enough to reveal the potential sex differences in relation to the various components of the MetS and the expression of the low-grade inflammation. High-sensitivity CRP does have the capability to reveal these differences.

RBC NOS: regulatory mechanisms and therapeutic aspects

Nitric oxide (NO), one of the most important vascular signaling molecules, is primarily produced by endothelial NO synthase (eNOS). eNOS is tightly regulated by its substrate l-arginine, cofactors and diverse interacting proteins. Interestingly, an NO synthase (NOS) was described within red blood cells (RBC NOS), and it was recently shown to significantly contribute to the intravascular NO pool and to regulate physiologically relevant mechanisms. However, the regulatory mechanisms and clinical implications of RBC NOS are unknown. The aim of this review is to highlight intracellular RBC NOS interactions and the role of RBC NOS in RBC homeostasis. Furthermore, macro- and microvascular diseases affected by RBC-derived NO are discussed.

Glycohaemoglobin as a determinant of increased fibrinogen concentrations and low-grade inflammation in apparently healthy nondiabetic individuals

OBJECTIVE

To determine the potential role of glycohaemoglobin as a possible determinant of increased fibrinogen concentrations and low-grade inflammation in a group of apparently healthy, nondiabetic individuals not expressing clinically overt atherothrombosis.

DESIGN AND MAIN OUTCOME MEASURES

We performed a cross-sectional analysis of the concentrations of glycohaemoglobin alongside the concentrations of quantitative fibrinogen and high-sensitivity C-reactive protein (hs-CRP). In all, 1511 males and 757 apparently healthy females, without diabetes mellitus or clinically evident atherothrombotic disease, were enrolled in the study during their routine annual health check-up.

RESULTS

Glycohaemoglobin entered the linear regression models as a significant determinant of quantitative fibrinogen in both genders and of hs-CRP in men. We found this to be true even following the inclusion of multiple variables known to influence the intensity of low-grade inflammation, such as age, gender, waist circumference, body mass index, blood pressure, medications, hormone therapy, glucose levels (normal or impaired fasting glucose), smoking habits, family history of coronary artery disease, lipid profile as well as alcohol consumption and sports intensity. We found glycohaemoglobin to be a significant determinant of fibrinogen concentrations in apparently healthy nondiabetic individuals not yet presenting with evident atherothrombosis.

CONCLUSIONS

This observation supports the idea that glycohaemoglobin might have an effect on fibrinogen concentrations in both genders and on hs-CRP in men. Moreover, our results suggest that glycohaemoglobin should be perceived as a continuous variable without a 'normal' cut-off point, as it may exhibit a detrimental role even when present in relatively low levels.

Early signaling of inflammation in acute ischemic stroke: clinical and rheological implications

INTRODUCTION

Several studies have highlighted the role of interleukin-6 (IL-6) as an early signal of the inflammatory response following acute ischemic stroke. This study examines the potential advantage of employing high-sensitivity (hs)-IL-6 as a possible biomarker at the early stages of acute stroke for identifying an acute phase response and its potential rheological and clinical implications.

METHODS

Venous blood was obtained from 186 stroke patients within 24 h of hospital admission and 3-5 days thereafter in order to characterize an inflammatory and hemorheological profile (including erythrocyte aggregation). Neurological state was assessed by the National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin scale (mRs).

RESULTS

While most biomarkers displayed elevated concentrations with time, serum concentrations of hs-IL-6 declined 3-5 days following acute stroke. Initially elevated levels of hs-IL-6 at presentation further correlated with unfavorable clinical outcomes (by NIHSS and mRs) at both time points. Analysis of variance in the different quartiles identified an hs-IL-6 gradient-dependent correlation at both time points, such that the higher the initial hs-IL-6 concentration, the higher the elevation in inflammatory biomarkers and the poorer the neurological state at both time points (p<0.001 for NIHSS and p=0.001 for mRs, for trend across quartiles).

CONCLUSIONS

This study demonstrates the potential of employing hs-IL-6 as an early stage biomarker for the prognosis of acute ischemic stroke. Such an advance would provide the means to identify at an early stage the patients who would require closer clinical surveillance and/or administration of therapeutic interventions.

Heart rate and microinflammation in men: a relevant atherothrombotic link

OBJECTIVE AND BACKGROUND

To explore the possibility that increased resting heart rate (HR) is associated with a microinflammatory response. Such an association could explain, at least in part, the recently described worse cardiovascular prognosis in individuals with increased HR.

METHODS

Concentrations of fibrinogen and high-sensitivity C-reactive protein, as well as the absolute number of polymorphonuclear leucocytes, were analysed in a cohort of 4553 apparently healthy men and in those with atherothrombotic risk factors.

RESULTS

Following adjustment for age and body mass index, lipid profile and cardiovascular risk factors, a significant (p<0.001) difference was noted between individuals in the first quintile of HR (< or =58 beats/min) and those in the fifth quintile (> or =79 beats/min) regarding all the above-mentioned inflammatory biomarkers, the respective mean values being 7.38 and 8.11 micromol/l, 1.12 and 1.61 mg/l, and 4.23 and 4.74 x 10(9)/l.

CONCLUSIONS

Resting HR is associated with a microinflammatory response in apparently healthy men and in those with atherothrombotic risk factors. Sympathetic activation might be a common factor explaining such an association. If confirmed in additional studies, this association might be a relevant target for therapeutic manipulations.

The red blood cell as a biosensor for monitoring oxidative imbalance in chronic obstructive pulmonary disease: an ex vivo and in vitro study

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity in Western countries. The increased oxidative stress, caused by the release of reactive oxygen and nitrogen species (ROS/RNS) from inflammatory airways cells, contributes to the pathogenesis of the disease. The aim of the present study was to evaluate (a) whether the oxidative imbalance can lead to specific alterations of red blood cells (RBCs) from stable COPD patients; (b) whether treatment with N-acetyl-cysteine (NAC), in widespread use as mucolytic agent in clinical practice, can counteract these effects; and (c) whether an in vitro model represented by the exposure of RBC to ROS/RNS could mimic the in vivo situation. The results obtained clearly indicated that the RBC integrity and function are similarly altered in COPD patients and in ROS/RNS in vitro-treated samples and that NAC administration was capable of counteracting RBC oxidative modifications both in vivo, as detected by clinical and laboratory evaluations, and in vitro. Altogether these results point to RBC oxidative modifications as valuable bioindicators in the clinical management of COPD and indicate that in vitro RBC exposure to ROS/RNS as a useful tool in experimental studies aimed at the comprehension of the pathogenic mechanisms of the redox-associated diseases.

Leukocytosis in obese individuals: possible link in patients with unexplained persistent neutrophilia

BACKGROUND

Recently, it was shown that fat tissue produces and releases inflammatory cytokines, and that obesity may be regarded as a state of low-grade inflammation. In this regard, we aimed to establish an association between obesity and persistent leukocytosis.

PATIENTS AND METHODS

We present clinical observations of obese subjects primarily referred for further evaluation of leukocytosis without a cause and validated the link between leukocytosis and elevated body mass index (BMI) in a cross-sectional study.

RESULTS

During 1999-2005, 327 patients were referred for further investigation because of persistent leukocytosis. Of these, 15.3% were asymptomatic obese, mostly females, with mild persistent neutrophilia accompanied by elevated acute-phase reactants. After careful evaluation, no recognized cause for leukocytosis was found other than the fact that the patients were obese. During a mean follow-up of 45.6 months, the leukocytosis and the elevated acute-phase reactants persisted and no new causes for leukocytosis were evident. Furthermore, in a cross-sectional analysis of 3716 non-smoker subjects, 62 were found to have leukocytosis. Compared with the population with a normal white blood count range, these subjects with leukocytosis had higher BMI, serum C-reactive protein (CRP) levels, waist circumference, and neutrophil and platelet count (all P < 0.0005). After logistic regression analysis, only BMI was shown to be associated with leukocytosis (P < 0.0005).

CONCLUSIONS

Obesity is recognized as a possible cause for reactive leukocytosis. Awareness of this 'obesity-associated leukocytosis' may help the clinician to avoid more extensive and unnecessary diagnostic work-up, particularly in similar obese subjects.

Lack of significant effect of low doses of aspirin on the concentrations of C-reactive protein in a group of individuals with atherothrombotic risk factors and vascular events

Atherothrombosis is associated with the presence of a microinflammatory response, usually monitored by the use of C-reactive protein (CRP) measurements. In the Physician Health Study it was suggested that individuals who benefit most from the treatment are those who have enhanced concentrations of this biomarker. The possibility was suggested that one of the mechanisms of action of aspirin in thrombotic prevention is through its anti-inflammatory properties in terms of reducing the concentration of CRP. We conducted a regression analysis in a cohort of 3888 apparently healthy individuals and those with atherothrombotic risk factors and vascular events, 370 of whom were under the treatment of low doses (<or= 325 mg/day) of aspirin. The significant determinants of CRP concentrations included body mass index, oral contraceptives, hormonal replacement therapy, gender, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, physical activity, age, smoking status and the presence of diabetes mellitus but not the use of low dose of aspirin. We conclude that the use of low doses (<or= 325 mg/day) of aspirin does not have a significant role in the modulation of CRP concentrations in apparently healthy individuals and those with atherothrombotic risk factors and vascular events. The anti-atherothrombotic activity of this drug is probably not mediated through a significant reduction of the concentration of this protein.

Flow-resistant red blood cell aggregation in morbid obesity

OBJECTIVE

Enhanced red blood cell (RBC) aggregation has an adverse effect on microcirculatory blood flow and tissue oxygenation. It has been previously shown that obesity is associated with increased RBC aggregation. The objectives of the present study were to further characterize obesity-related RBC aggregation and to examine whether the enhanced aggregation is a plasma- or cellular-dependent process.

METHODS

Obese (body mass index (BMI)=40+/-6.3 kg/m2, n=22) and nonobese (BMI=24+/-3.4 kg/m2, n=18) individuals were evaluated for inflammation markers and aggregation parameters. Aggregation parameters were derived from the distribution of RBC population into aggregate sizes, and from the variation of the distribution as a function of flow-derived shear stress, using a cell flow properties analyzer. To differentiate plasmatic from cellular factors, we determined the aggregation in the presence of autologous plasma or dextran-500 kDa and calculated the plasma factor (PF) in the obese group. PF ranges from 0 to 1. When the PF=1, the aggregation is all due to plasmatic factors, when PF=0, the altered aggregation depends entirely on cellular factors, whereas 0<PF<1 reflects the joint contribution of cellular and plasmatic factors.

RESULTS

Obese subjects had relatively larger aggregates that were more resistant to dispersion by flow. The calculated PF in the obese group was 0.9, indicating a pronounced contribution of plasma to RBC aggregation in obesity.

DISCUSSION

Our results suggest that obese individuals present pathological plasma-dependent RBC aggregation, which is probably triggered by plasma macromolecules associated with the inflammatory response. These findings impact the future attempts to develop strategies aimed at attenuation of the enhanced RBC aggregation in obese individuals.