Changes in the flow properties of white blood cells after acute myocardial infarction

Sterile kidney tissue injury induces neutrophil swarming in lung alveolar capillaries

Sterile tissue injury, such as by acute kidney injury, is common in the clinic and frequently associated with respiratory compromise and hypoxemia. We previously described signaling components released by the injured kidney that drive a remote inflammatory response in the lung. How this caused the resultant hypoxemia remained unclear. Here, we report that sterile kidney tissue injury induces rapid intravascular "neutrophil train" formation in lung capillaries, a novel form of neutrophil swarming. Rapid swarming is enhanced by decreased deformability of circulating neutrophils that impedes their lung capillary passage. Classical lung monocytes are required for neutrophil train formation and release CXCL2 to attract and retain stiffened neutrophils in lung capillaries which reduces capillary perfusion. We thus discovered a novel feature of kidney-lung crosstalk after sterile kidney tissue injury, capillary perfusion deficits that lead to reduced oxygenation despite proper alveolar function and ventilation, unlike in infectious inflammatory lung processes, such as bacterial pneumonia.

Numerical simulation of optical control for a soft particle in a microchannel

Technologies that use optical force to actively control particles in microchannels are a significant area of research interest in various fields. An optical force is generated by the momentum change caused by the refraction and reflection of light, which changes the particle surface as a function of the angle of incidence of light and which in turn feeds back and modifies the force on the particle. Simulating this phenomenon is a complex task. The deformation of a particle, the interaction between the surrounding fluid and the particle, and the reflection and refraction of light should be analyzed simultaneously. Herein, a deformable particle in a microchannel subjected to optical interactions is simulated using the three-dimensional lattice Boltzmann immersed-boundary method. The laser from the optical source is analyzed by dividing it into individual rays. To calculate the optical forces exerted on the particle, the intensity, momentum, and ray direction are calculated. The optical-separator problem with one optical source is analyzed by measuring the distance traveled because of the optical force. The optical-stretcher problem with two optical sources is then studied by analyzing the relation between the intensity of the optical source and particle deformation. This simulation will help the design of sorting and measuring by optical force.

Leukocyte deformability is a novel biomarker to reflect sepsis-induced disseminated intravascular coagulation

Aim

Sepsis-induced disseminated intravascular coagulopathy is associated with a high mortality rate. The function and deformability of polymorphonuclear leukocytes change in patients with sepsis. The goal of this study was to characterize the changes in polymorphonuclear leukocyte deformability in patients with sepsis-induced disseminated intravascular coagulopathy and to evaluate the relationship between the severity of disseminated intravascular coagulopathy and the deformability of polymorphonuclear leukocytes.

Methods

Thirty-five patients with sepsis-induced disseminated intravascular coagulopathy at our department were enrolled in this study. These patients were diagnosed with severe sepsis and an acute disseminated intravascular coagulopathy score ≥ 4. Blood samples were obtained from these patients on days 1, 3, and 7. Polymorphonuclear leukocyte deformability was measured with a microchannel flow analyzer, and polymorphonuclear leukocyte activity, represented as CD11b, was measured by flow cytometry. In contrast, 14 patients who fulfilled with sepsis criteria but without complicated disseminated intravascular coagulopathy were also entered in this study.

Results

In patients with sepsis-induced disseminated intravascular coagulopathy, there was a significant correlation between their Japanese Association for Acute Medicine disseminated intravascular coagulopathy score and polymorphonuclear leukocyte deformability, and CD11b expression. Polymorphonuclear leukocytes became more stiffened and CD11b expression was higher in patients with sepsis-induced disseminated intravascular coagulopathy compared to patients without the condition.

Conclusion

Polymorphonuclear leukocyte deformability correlated with the severity of sepsis-induced disseminated intravascular coagulopathy and the response to treatment.

Passive circulating cell sorting by deformability using a microfluidic gradual filter

The deformability of circulating leukocytes plays an important role in the physiopathology of several diseases like sepsis or acute respiratory distress syndrome (ARDS). We present here a microfluidic method for the passive testing, sorting and separating of non-adherent cell populations by deformability. It consists of microfluidic sieves in series with pore sizes decreasing from the upstream to the downstream. The method capabilities are demonstrated with monocytic cell lines (THP-1) treated by Jasplakinolide (a stabilizer of polymerized actin), LatrunculinA (an inhibitor of actin polymerization), and with the plasma of patients suffering from ARDS. Simple sample injection with standard syringes and pumps makes the method readily adapted for experimentation in hospitals.

Serial changes in leukocyte deformability and whole blood rheology in patients with sepsis or trauma

BACKGROUND

The objective of this study was to investigate serial changes in leukocyte deformability and rheologic properties of whole blood in patients with sepsis or trauma.

METHODS

Seventeen sepsis patients and 22 trauma patients were enrolled. Leukocyte deformability and rheologic properties of whole blood were determined with the use of a microchannel array etched on a single-crystal silicon tip, simulating the microvasculature. The number of obstructed microchannels (NOM) was used as a measure of leukocyte deformability. Transit time (TT), i.e., the time taken for 100 microL of whole blood to pass through the microchannel array was also used as rheologic measure. Oxidative activity and F-actin content of neutrophils was measured in patients with sepsis.

RESULTS

NOM and TT significantly increased in patients when sepsis was diagnosed. In survivors, NOM and TT decreased at the time of recovery from sepsis, but in non-survivors values remained high. Oxidative activity and F-actin content of neutrophils increased significantly as leukocyte deformability decreased. In patients with severe trauma, NOM and TT increased after injury and decreased by the time of recovery from the critical stage.

CONCLUSION

We conclude that leukocyte deformability decreases in patients with sepsis or severe trauma and that this change negatively affects rheologic properties of whole blood.

Flow resistance of individual neutrophils in coronary artery disease: decreased pore transit times in acute myocardial infarction

OBJECTIVE

To investigate single neutrophil flow resistance in coronary artery disease, including myocardial infarction before initiation of reperfusion therapy.

DESIGN

Neutrophil flow resistance was measured in 93 subjects in five groups: (group 1) 28 patients within 12 hours after the onset of myocardial infarction, before reperfusion therapy; (group 2) 18 with unstable angina; (group 3) 13 with stable angina; (group 4) 13 age matched patients without coronary disease, and (group 5) 21 healthy volunteers. MAIN PARAMETERS: Single neutrophil transit times through 8 microns oligopore filters determined with a modified cell transit analyser.

RESULTS

Leucocyte count (10(9)/l) was increased in coronary disease, especially in myocardial infarction and unstable angina (mean and 95% confidence intervals for groups 1 to 5: 12.6 (11.0 to 14.2), 11.3 (8.5 to 14.1), 8.5 (7.4 to 9.6), 8.0 (6.0 to 10.0), 7.0 (6.1 to 7.9)). Polymorphonuclear granulocyte (PMN) flow resistance correlated negatively with white blood cell (WBC) count and was significantly decreased in coronary artery disease (CAD), especially in myocardial infarction; mean transit times (ms) for groups 1 to 5 were: 13.6 (11.8 to 15.4), 16.9 (13.9 to 19.0), 16.9 (12.8 to 21.0), 22.0 (19.6 to 24.4), and 18.6 (15.7 to 21.5).

CONCLUSION

Neutrophil flow resistance was decreased in CAD, especially in myocardial infarction before reperfusion therapy. In contrast to previous findings in reperfused myocardial infarction, the present study showed that stiffened PMNs were not yet present in the circulating blood pool. Thus a pharmacological approach aimed at suppressing leucocyte activation before or during reperfusion therapy may be feasible.

Changes in neutrophil rheology after acute ischemia and reperfusion in the rat hindlimb

Neutrophils may contribute to the pathogenesis of ischemia-reperfusion injury by impairing microcirculatory flow and causing tissue damage. In this study neutrophil deformability and activation were studied after acute ischemia and reperfusion of the rat hindlimb. A cell transit analyzer with 8 microm pore filters was used to measure the flow resistance of individual neutrophils isolated from arterial blood drawn 30 seconds and 5 minutes after reperfusion, after 2 hours of femoral or iliac artery occlusion, in anesthetized rats. Femoral occlusion followed by 30 seconds of reperfusion resulted in a 16% rise in mean pore transit time, and iliac occlusion caused a 31% increase. Neutrophil activation (percentage of cells with nonspherical shape) rose from 6% to 23% (femoral occlusion) or from 7% to 29% (iliac occlusion). By 5 minutes of reperfusion, transit times, but not shape change, had almost returned to preischemic levels. Sham-occluded rats had no significant change in neutrophil behavior. Plasma isolated from rats after 30 seconds of reperfusion after 2 hours of iliac occlusion caused a 27% increase in mean transit time when incubated with nonautologous neutrophils, while activation rose from 32% to 55%. Thus plasma factor(s) released after ischemia and reperfusion of rat hindlimb caused transient rheologic alteration of circulating neutrophils, which may contribute to local or disseminated vascular occlusion and tissue injury.

Leukocyte flow properties, polymorphonuclear membrane fluidity, and cytosolic Ca2+ content in subjects with vascular atherosclerotic disease with and without noninsulin-dependent diabetes mellitus

The aim of this research was the evaluation of white blood cell (WBC) filtration, reflecting WBC flow properties, polymorphonuclear cell membrane fluidity, and cytosolic Ca2+ content in subjects with vascular atherosclerotic disease (VAD) and in VAD subjects with noninsulin-dependent diabetes mellitus (NIDDM), in good hemodynamic balance. The authors examined WBC filtration (unfractionated, mononuclear [MN], polymorphonuclear [PMN] cells), using the St. George Filtrometer and considering, respectively, the initial relative flow rate (IRFR) and the clogging rate (CR); the PMN membrane fluidity, employing the fluorescent probe TMA-DPH and calculating the fluorescence polarization degree; and the PMN cytosolic Ca2+ content, adopting the fluorescent probe Fura 2-AM and considering the ratio between the Fura 2-Ca2+ complex and the unchelated Fura 2 fluorescence intensity. The obtained data showed that only the filtration parameters (IRFR, CR) of unfractionated WBCs discriminated normal subjects from VAD groups, whereas the filtration parameters of MN and PMN cells did not demonstrate any distinction. PMN membrane fluidity did not distinguish normal subjects from VAD groups, whereas PMN cytosolic Ca2+ content was significantly increased in VAD groups in comparison with normal subjects. No relationship was evident between WBC filtration and plasma metabolic parameters; the correlations obtained between PMN filtration and other PMN parameters need further investigation.

Cardiac release of cytokines and inflammatory responses in acute myocardial infarction

BACKGROUND

In animal models of myocardial infarction (MI), inflammatory responses compromise microcirculation during reperfusion and restrict functional recovery. To investigate cardiac inflammatory responses in patients with acute MI, we examined the cardiac release of cytokines, the expression on neutrophils of the beta 2-integrin Mac-1 (CD11b/CD18) and L-selectin (CD62L), and the cardiac release of thrombomodulin as a marker of endothelial injury.

METHODS AND RESULTS

In 12 patients with acute anterior MI, blood samples were obtained from the coronary sinus and from the aorta immediately before and after recanalization of the coronary occlusion by balloon angioplasty. Twelve patients undergoing elective balloon angioplasty served as control subjects. Plasma concentrations of interleukin (IL)-1 beta, IL-6, IL-8, tumor necrosis factor-alpha, and thrombomodulin were determined by immunoassay, and surface expression of CD11b and CD62L was assessed by flow cytometry. Differences in coronary sinus and arterial blood were found in IL-6 before (median, 6.3 ng/L, P = .01) and after (13.4 ng/L, P = .002) recanalization and in IL-8 after recanalization (10.7 ng/L, P = .02). The cardiac release of both cytokines significantly (P < or = .03) increased with reperfusion. Cytokine release after reperfusion was associated with significant transcardiac gradients in surface expression on neutrophils of CD11b (10.1 mean channel of fluorescence intensity [mean fl], P = .01) and CD62L (-87 mean fl, P = .007) and with a thrombomodulin release (4.5 micrograms/L, P = .004). Transcardiac gradients in IL-1 beta and tumor necrosis factor-alpha were not found. None of the changes found in MI were detectable in the control group.

CONCLUSIONS

As evidence of cardiac inflammatory responses in reperfused acute MI, the study demonstrates cardiac neutrophil activation with signs of endothelial injury and a release of the proinflammatory cytokines IL-8 and IL-6. These findings may assist in the design of pharmacological interventions aimed at reducing microvascular reperfusion injury.

Neutrophils may contribute to the morbidity and mortality of claudicants

Peripheral arterial occlusive disease is a common cause of morbidity in middle-aged men; 5 per cent of those aged over 50 years suffer from intermittent claudication. While claudication itself is not fatal, claudicants have a mortality rate approximately three times that of non-claudicating men of the same age, mainly from cardiovascular disease. This review examines the evidence for involvement of the neutrophil in this increased mortality and describes the possible pathogenesis. It also discusses how treatment of claudication may modify neutrophil behaviour, reducing subsequent mortality and morbidity rates.

Pharmacological reduction of the systemically damaging effects of local ischaemia

Many patients with intermittent claudication are encouraged to exercise. However, transient exercise-induced muscle ischaemia results in systemic vascular endothelial injury associated with increased vascular permeability manifest as an increase in urinary albumin excretion. Repetitive systemic vascular endothelial injury leads to accelerated atherogenesis and may explain the high cardiovascular mortality rate of claudicants. Oxpentifylline, a haemorheological agent, has recently been shown to prevent vascular endothelial injury in animal models. A double-blind, placebo-controlled, cross-over trial was undertaken to determine the effect of oxpentifylline on exercise-induced systemic vascular endothelial injury in 20 claudicants. Urinary albumin, expressed as a creatinine ratio (ACR), was measured before and 1 and 2 hours after standardised exercise following 1 week treatment with either active drug or placebo. Oxpentifylline reduced the median (range) 1 hour post exercise increase in ACR from 0.35 (-0.46-12.72) to 0.02 (-6.00-14.10) mg/mmol. (p = 0.030, z = 2.2 Wilcoxon rank sign test). These results confirm that local ischaemia is associated with a potentially deleterious systemic effect and that it may be possible to attenuate this pharmacologically. The clinical significance of this is yet to be determined.

Abnormal neutrophil adhesion in sickle cell anaemia and crisis: relationship to blood rheology

Defects in neutrophil adhesion and migration may contribute to the susceptibility to infection seen in sickle cell anaemia (SCA). These dynamic defects may be influenced by abnormalities in blood rheology found in this disorder. A whole blood model was used to study neutrophil adhesion in SCA patients: neutrophil adhesion to protein coated glass was quantitated by measuring the rate of disappearance of neutrophils from heparinized whole blood circulating through a perfusion chamber. Twenty-three adult patients (Hb SS) were studied in asymptomatic steady state, of whom nine were also studied during pain crisis, both before and 4-7 d after conventional therapy. Red cell and granulocyte filterability and whole blood and plasma viscosity were also measured. The half-time for disappearance from the perfusion system (t1/2) of neutrophils from patients in the steady-state was 93.5 +/- 8.4 min, compared to 49.1 +/- 2.8 min in normal age-matched controls (P = 0.001). In crisis t1/2 was further prolonged to 170.0 +/- 16.1 min (P = 0.01 v. steady state). After therapy, t1/2 decreased to 57.0 +/- 4.5 min (P = 0.001 v. pre-therapy state and P = 0.009 v. steady state) and was comparable to Hb AA controls. These findings reveal a neutrophil adhesion defect in SCA which worsens in crisis but is corrected following supportive therapy. Red cell filterability (expressed as average resistance to flow and pore-clogging particles) and white cell filterability (expressed as pore-clogging particles) were also abnormal in SCA and were found to correlate with neutrophil adhesion. Plasma viscosity also correlated with adhesion t1/2. The defect appears to be related to abnormal blood flow properties in SCA but the rheological factors cannot fully explain either the steady-state defect or the marked changes in neutrophil adhesion during crisis.

Technological advances in blood rheology

The science of blood rheology (study of the flow and deformability of blood) is of increasing practical importance to the investigation of blood disorders. In diagnostic laboratories, rheological tests such as the erythrocyte sedimentation rate, zeta sedimentation ratio, and plasma viscosity are used to monitor patients with an acute-phase response of greater than 24 h duration. In sickle-cell anemia, new methods for measuring erythrocyte deformability can be used to investigate the pathogenesis of vaso-occlusion, to test potential anti-sickling drugs, and to monitor drug efficacy in clinical trials. Genetic defects in the structure of the red cell membrane can have rheological consequences, monitoring of which may be useful for diagnosis. Rheological analysis of red cells infected by Plasmodium falciparum has indicated that their abnormal flow behavior may be an important pathological factor in malaria. Finally, the flow behavior of white blood cells, particularly neutrophils, is also important, as these cells, once activated, have the potential to occlude microvessels. The authors have reviewed the laboratory methodology and clinical applications that have led to recent advances in these aspects of blood rheology.