The effect of endotoxin and tumour necrosis factor on erythrocyte and leucocyte deformability in vitro

Inter-α inhibitor proteins maintain neutrophils in a resting state by regulating shape and reducing ROS production

The plasma levels of inter-α inhibitor proteins (IAIPs) are decreased in patients with sepsis and the reduced levels correlate with increased mortality. In the present study, we examined the effects of IAIPs on human neutrophils to better understand the beneficial effects of IAIPs in the treatment of sepsis. We demonstrated that IAIPs induced a spherical shape that was smaller in size with a smooth cellular surface in a concentration-dependent manner. These changes were inhibited by a specific antibody against IAIPs. In contrast, bikunin, light chain of IAIP, had no effect on neutrophil morphology. The neutrophils treated with IAIPs could easily pass through the artificial microcapillaries and were prevented from entrapment inside the capillaries. Coincubation of human blood neutrophils with a confluent human vascular endothelial monolayer showed that adhesion of neutrophils on endothelial cells was suppressed by treatment with IAIPs. IAIPs inhibited the spontaneous release of reactive oxygen species (ROS) in a concentration-dependent fashion. ROS inhibition was associated with reductions in p47^phox phosphorylation on Ser328. These results suggest that IAIP-induced morphological changes that render neutrophils quiescent, facilitate passage through the microvasculature, and reduce adhesion to vascular endothelial cells and production of ROS. Thus, IAIP plays a key role in controlling neutrophil activation.

Effect of yeast biomass with high content of carotenoids on erythrocyte deformability, NO production and Na,K-ATPase activity in healthy and LPS treated rats

Measurements of red blood cell (RBC) deformability together with estimation of NO-synthase activity and Na,K-ATPase activity were used for characterization of RBC functionality in rats subjected to single dose of Escherichia coli lipopolysaccharides (LPS) at a dose of 1 mg/kg. We hypothesized that LPS might initiate a malfunction of RBC. We also investigated the potential effect of carotenoids (10 mg/kg/day) produced in red yeast biomass of Rhodotorula glutinis on RBC in LPS-challenged rats. LPS significantly reduced the deformability of RBC (by 14%) together with decrease of NO-synthase activity by 20%. Daily supplementation of carotenoids for 10 days attenuated the LPS-induced injury, as observed by 22% increase of RBC deformability and 23% increase of NO-synthase activity. The activity of Na,K-ATPase was also improved probably due to increased number of active enzyme molecules as indicated by 66% enhancement of Vmax value, hence maintaining the activity of erythrocyte Na,K-ATPase to the level even higher as compared with healthy control animals. It may be concluded that administration of yeast biomass with high content of carotenoids resulted in advanced function of erythrocytes as concerns their ability to squeeze through narrow capillaries of the circulation, better intrinsic production of NO and improvement of intracellular homeostasis of sodium.

From the Cradle to the Grave: The Role of Macrophages in Erythropoiesis and Erythrophagocytosis

Erythropoiesis is a highly regulated process where sequential events ensure the proper differentiation of hematopoietic stem cells into, ultimately, red blood cells (RBCs). Macrophages in the bone marrow play an important role in hematopoiesis by providing signals that induce differentiation and proliferation of the earliest committed erythroid progenitors. Subsequent differentiation toward the erythroblast stage is accompanied by the formation of so-called erythroblastic islands where a central macrophage provides further cues to induce erythroblast differentiation, expansion, and hemoglobinization. Finally, erythroblasts extrude their nuclei that are phagocytosed by macrophages whereas the reticulocytes are released into the circulation. While in circulation, RBCs slowly accumulate damage that is repaired by macrophages of the spleen. Finally, after 120 days of circulation, senescent RBCs are removed from the circulation by splenic and liver macrophages. Macrophages are thus important for RBCs throughout their lifespan. Finally, in a range of diseases, the delicate interplay between macrophages and both developing and mature RBCs is disturbed. Here, we review the current knowledge on the contribution of macrophages to erythropoiesis and erythrophagocytosis in health and disease.

Cellular softening mediates leukocyte demargination and trafficking, thereby increasing clinical blood counts

Leukocytes normally marginate toward the vascular wall in large vessels and within the microvasculature. Reversal of this process, leukocyte demargination, leads to substantial increases in the clinical white blood cell and granulocyte count and is a well-documented effect of glucocorticoid and catecholamine hormones, although the underlying mechanisms remain unclear. Here we show that alterations in granulocyte mechanical properties are the driving force behind glucocorticoid- and catecholamine-induced demargination. First, we found that the proportions of granulocytes from healthy human subjects that traversed and demarginated from microfluidic models of capillary beds and veins, respectively, increased after the subjects ingested glucocorticoids. Also, we show that glucocorticoid and catecholamine exposure reorganizes cellular cortical actin, significantly reducing granulocyte stiffness, as measured with atomic force microscopy. Furthermore, using simple kinetic theory computational modeling, we found that this reduction in stiffness alone is sufficient to cause granulocyte demargination. Taken together, our findings reveal a biomechanical answer to an old hematologic question regarding how glucocorticoids and catecholamines cause leukocyte demargination. In addition, in a broader sense, we have discovered a temporally and energetically efficient mechanism in which the innate immune system can simply alter leukocyte stiffness to fine tune margination/demargination and therefore leukocyte trafficking in general. These observations have broad clinically relevant implications for the inflammatory process overall as well as hematopoietic stem cell mobilization and homing.

Red cell physiology and signaling relevant to the critical care setting

PURPOSE OF REVIEW

Oxygen (O2) delivery, the maintenance of which is fundamental to supporting those with critical illness, is a function of blood O2 content and flow. Here, we review red blood cell (RBC) physiology relevant to disordered O2 delivery in the critically ill.

RECENT FINDINGS

Flow (rather than content) is the focus of O2 delivery regulation. O2 content is relatively fixed, whereas flow fluctuates by several orders of magnitude. Thus, blood flow volume and distribution vary to maintain coupling between O2 delivery and demand. The trapping, processing and delivery of nitric oxide (NO) by RBCs has emerged as a conserved mechanism through which regional blood flow is linked to biochemical cues of perfusion sufficiency. We will review conventional RBC physiology that influences O2 delivery (O2 affinity & rheology) and introduce a new paradigm for O2 delivery homeostasis based on coordinated gas transport and vascular signaling by RBCs.

SUMMARY

By coordinating vascular signaling in a fashion that links O2 and NO flux, RBCs couple vessel caliber (and thus blood flow) to O2 need in tissue. Malfunction of this signaling system is implicated in a wide array of pathophysiologies and may be explanatory for the dysoxia frequently encountered in the critical care setting.

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.

Red blood cell clearance in inflammation

SUMMARY

Anemia is a frequently encountered problem in the critically ill patient. The inability to compensate for anemia includes several mechanisms, collectively referred to as anemia of inflammation: reduced production of erythropoietin, impaired bone marrow response to erythropoietin, reduced iron availability, and increased red blood cell (RBC) clearance. This review focuses on mechanisms of RBC clearance during inflammation. We state that phosphatidylserine (PS) expression in inflammation is mainly enhanced due to an increase in ceramide, caused by an increase in sphingomyelinase activity due to either platelet activating factor, tumor necrosis factor-α, or direct production by bacteria. Phagocytosis of RBCs during inflammation is mediated via RBC membrane protein band 3. Reduced deformability of RBCs seems an important feature in inflammation, also mediated by band 3 as well as by nitric oxide, reactive oxygen species, and sialic acid residues. Also, adherence of RBCs to the endothelium is increased during inflammation, most likely due to increased expression of endothelial adhesion molecules as well as PS on the RBC membrane, in combination with decreased capillary blood flow. Thereby, clearance of RBCs during inflammation shows similarities to clearance of senescent RBCs, but also has distinct entities, including increased adhesion to the endothelium.

Pentoxifylline in preterm neonates: a systematic review

Sepsis, necrotizing enterocolitis (NEC), and chronic lung disease (CLD) in preterm neonates are associated with significant mortality and morbidity, including long-term neurodevelopmental impairment and socioeconomic burden. Safe and effective drugs for the prevention and treatment of these conditions are urgently needed. Pentoxifylline, a synthetic theobromine derivative, is a non-steroidal immunomodulating agent with unique hemorrheologic effects which has been used in a range of infectious, vascular, and inflammatory conditions in adults and children. The unique properties of pentoxifylline explain its potential benefits in preterm neonates with sepsis, NEC, and CLD, conditions characterized by activation of the inflammatory cytokine cascade, free radical toxicity, and impaired microcirculation. Pentoxifylline has anti-inflammatory properties resulting from inhibition of erythrocyte phosphodiesterase. It lowers blood viscosity and improves microcirculation and tissue perfusion. As a phosphodiesterase inhibitor, pentoxifylline downregulates pro-inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-6, and interferon-gamma. Methylxanthines, including caffeine, theophylline, and theobromine are relatively non-toxic drugs; of these, theobromine is the least toxic. Pentoxifylline-related significant adverse events are thus very rare. Unlike other methylxanthines, pentoxifylline does not have significant cardiac and bronchodilating effects at therapeutic doses. Although it is contraindicated in adults with recent cerebral hemorrhage due to its effect on platelets, red blood cells, and plasma fibrinogen levels, no significant adverse effects including thrombocytopenia and bleeding have been reported in critically ill preterm neonates with sepsis or NEC after treatment with pentoxifylline. Based on data from pilot randomized trials and observational studies, our systematic review suggests that pentoxifylline may reduce mortality and/or morbidity in preterm neonates with sepsis, NEC, and CLD. Results of experimental studies also indicate that pentoxifylline may potentially be beneficial in meconium aspiration syndrome and hypoxic ischemic encephalopathy. Given the substantial burden of sepsis, NEC, and CLD in high-risk preterm neonates, and the findings of this systematic review, pentoxifylline needs to be evaluated urgently as a preventative and therapeutic agent for these conditions in randomized controlled trials that can detect minimal clinically significant effect sizes. Further clinical and experimental studies are also necessary to evaluate whether pentoxifylline is safe and effective in meconium aspiration syndrome and hypoxic ischemic encephalopathy.

Analyzing cell mechanics in hematologic diseases with microfluidic biophysical flow cytometry

Pathological processes in hematologic diseases originate at the single-cell level, often making measurements on individual cells more clinically relevant than population averages from bulk analysis. For this reason, flow cytometry has been an effective tool for single-cell analysis of properties using light scattering and fluorescence labeling. However, conventional flow cytometry cannot measure cell mechanical properties, alterations of which contribute to the pathophysiology of hematologic diseases such as sepsis, diabetic retinopathy, and sickle cell anemia. Here we present a high-throughput microfluidics-based 'biophysical' flow cytometry technique that measures single-cell transit times of blood cell populations passing through in vitro capillary networks. To demonstrate clinical relevance, we use this technique to characterize biophysical changes in two model disease states in which mechanical properties of cells are thought to lead to microvascular obstruction: (i) sepsis, a process in which inflammatory mediators in the bloodstream activate neutrophils and (ii) leukostasis, an often fatal and poorly understood complication of acute leukemia. Using patient samples, we show that cell transit time through and occlusion of microfluidic channels is increased for both disease states compared to control samples, and we find that mechanical heterogeneity of blood cell populations is a better predictor of microvascular obstruction than average properties. Inflammatory mediators involved in sepsis were observed to significantly affect the shape and magnitude of the neutrophil transit time population distribution. Altered properties of leukemia cell subpopulations, rather than of the population as a whole, were found to correlate with symptoms of leukostasis in patients-a new result that may be useful for guiding leukemia therapy. By treating cells with drugs that affect the cytoskeleton, we also demonstrate that their transit times could be significantly reduced. Biophysical flow cytometry offers a low-cost and high-throughput diagnostic and drug discovery platform for hematologic diseases that affect microcirculatory flow.

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.

Deformability of passive and activated neutrophils in children with Gram-negative septicemia

Animal experiments suggest that obstruction of small vessels by polymorphonuclear neutrophils (PMNs) may contribute to the disturbed microcirculation in septic shock. The purpose of this investigation was to study deformability and volume of passive and activated PMNs and immature neutrophils in 15 children with Gram-negative septicemia and in 20 healthy children. Membrane cytoplasm tongues of neutrophils were aspirated by means of a micropipette system into 2.5-microm (diameter) pipettes for 60 s. Tongue growth was used as an indicator of deformability and the cell volume was calculated from the cell circumference before aspiration. Septicemic children showed higher percentages of immature neutrophils (38+/-13%) and activated PMN (12+/-5%) than healthy children (3+/-2% and 3+/-2%). In septicemic children, cellular volume of passive neutrophils decreased progressively with increasing maturity from myeloblasts (493+/-105 fL) to mature PMNs (346+/-29 fL) and the final tongue length in the micropipette increased from 2.7+/-1.1 to 8.5+/-1.8 microm during maturation. The final tongue length of activated PMNs was decreased by 60% compared with that of passive PMNs. The increased number of rigid activated and immature neutrophils may contribute to impaired microcirculation in septicemic patients.

Linoleic acid increases monocyte deformation and adhesion to endothelium

Fatty acids have been implicated in having both anti- or pro-inflammatory actions, which may contribute to the progression and severity of atherosclerosis. Linoleic acid has been shown by others to decrease CD18 expression and leukocyte adhesion under static conditions. We investigated the effect of steric acid (18:0), oleic acid (18:1), and linoleic acid (18:2) on the cortical tension (a measure of cell membrane deformability) and adhesion characteristics of the monocytic cell line Mono Mac 6 (MM6) cells to TNF-alpha activated HUVEC under fluid flow. Linoleic acid concentrations up to 23 microM decreased cortical tension and increased adhesion frequencies. Increased adhesion was not due to altered cell morphology or adhesion kinetics and occurred despite decreases in receptor expression (CD18 and CD11a). At higher levels of linoleic acid (> or = 46 microM), cell dissociation constants significantly increased. Results show that decreasing cortical tension increased the probability that contact between MM6 cells and endothelium would produce an adhesive interaction, possibly due to increased deformation of the microvilli and the cell membrane cortex. However, more deformable cells rolled more erratically at low shear rates. The different behavior during initial contact and rolling suggest that adhesion is influenced by two force-dependent mechanisms, deformation of microvilli and a steric barrier. Incubation of MM6 with 23 microM steric or oleic acid did not significantly affect cortical tension. However, cells incubated with steric acid greatly increased their adherence to HUVEC and cells incubated with oleic acid showed no significant effect, indicating factors other than deformability may dominate.

Effects of storage on efficacy of red cell transfusion: When is it not safe?

OBJECTIVE

To review the literature on red blood cell storage and its relationship to the efficacy of transfusion.

RESULTS

Well-documented changes occur to the red blood cell product during ex vivo storage. These changes include a reduction in red blood cell deformability, altered red blood cell adhesiveness and aggregability, and a reduction in 2,3-diphosphoglycerate and ATP. Bioactive compounds with proinflammatory effects also accumulate in the storage medium. These changes reduce posttransfusion viability of red blood cells. The clinical effects beyond posttransfusion viability are uncertain, but a growing body of evidence suggests that the storage lesion may reduce tissue oxygen availability, have proinflammatory and immunomodulatory effects, and influence morbidity and mortality. There are no published randomized, control trials examining the effect of storage duration on morbidity and mortality. Leukoreduction improves the quality of stored red blood cell products and in some studies has been shown to reduce morbidity and mortality.

CONCLUSION

Although storage duration influences the quality of red blood cell product, there is currently insufficient evidence to advocate shorter storage periods for red blood cell products.

Red blood cell rheology in sepsis

Changes in red blood cell (RBC) function can contribute to alterations in microcirculatory blood flow and cellular dysoxia in sepsis. Decreases in RBC and neutrophil deformability impair the passage of these cells through the microcirculation. While the role of leukocytes has been the focus of many studies in sepsis, the role of erythrocyte rheological alterations in this syndrome has only recently been investigated. RBC rheology can be influenced by many factors, including alterations in intracellular calcium and adenosine triphosphate (ATP) concentrations, the effects of nitric oxide, a decrease in some RBC membrane components such as sialic acid, and an increase in others such as 2,3 diphosphoglycerate. Other factors include interactions with white blood cells and their products (reactive oxygen species), or the effects of temperature variations. Understanding the mechanisms of altered RBC rheology in sepsis, and the effects on blood flow and oxygen transport, may lead to improved patient management and reductions in morbidity and mortality.

Endotoxin binding to erythrocyte membrane and erythrocyte deformability in human sepsis and in vitro

OBJECTIVE

Several studies have shown that lipopolysaccharide and lipid A impair red blood cell deformability and. However, it is unclear whether impaired red blood cell deformability is associated with binding of lipopolysaccharide to the red blood cell membrane.

DESIGN

Analysis of hydroxymyristic acid content in red blood cell membranes and red blood cell deformation in patients with Gram-negative septicemia and after incubation of red blood cells from healthy adults with 100 microg of lipid A or 1 mg of lipopolysaccharide per milliliter of red blood cell in buffer solution and in whole blood. Hydroxymyristic acid is a fatty acid of the lipid A part of lipopolysaccharide in most Gram-negative bacteria.

SETTING

University research laboratories.

SUBJECTS

Ten healthy adults and four patients with clinical and laboratory signs of septicemia.

INTERVENTIONS

Blood sampling.

MEASUREMENTS AND MAIN RESULTS

Red blood cell deformation was measured with a laser-diffraction shearing device (Rheodyn) and a computerized micropore filtration system (CTA). Lipopolysaccharide and lipid A binding to red blood cell membranes was studied by measuring the amide-linked hydroxymyristic acid by gas chromatography. The detection rates of hydroxymyristic acid were 82% for lipopolysaccharide and 79% for lipid A in buffer solution. In membranes of washed red blood cell, the detection rates of lipopolysaccharide and lipid A were 0.26 +/- 0.03% (2.6 +/- 0.3 microg/mL) and 1.3 +/- 0.5% (1.3 +/- 0.5 microg/mL), and in red blood cell membranes of whole blood the detection rates were 2.6% (25.5 microg/mL) and 4.1% (4.1 microg/mL), respectively. The lipopolysaccharide content in red blood cell membranes of septic patients ranged from 47 to 103 microg/mL of red blood cell. Red blood cell deformation in the Rheodyn and in the CTA were not influenced by lipopolysaccharide incubated with washed red blood cells. In the Rheodyn, red blood cell deformation was significantly decreased by 18% after lipid A incubation in washed red blood cells, by 26% after lipopolysaccharide incubation in whole blood, and by 31% in septic patients. Similar effects were observed when we used the CTA.

CONCLUSIONS

Red blood cell deformation is decreased in septic patients, after incubation of washed red blood cells with lipid A and of whole blood with lipopolysaccharide. Lipopolysaccharide did not influence red blood cell deformation after incubation with washed red blood cells. The decrease of red blood cell deformation was related to the amount of hydroxymyristic acid measured in red blood cell membranes, suggesting that endotoxin binding directly affects mechanical properties of red blood cells.

Potential role of IL-8, platelet-activating factor and TNF-alpha in the sequestration of neutrophils in the lung: effects on neutrophil deformability, adhesion receptor expression, and chemotaxis

The microvasculature of the normal lung contains a pool of sequestered neutrophils, which is markedly enhanced in acute lung inflammation. Lung neutrophil sequestration is determined by the cells' deformability and adhesivity to capillary endothelium, and is a pre-requisite for emigration into the airspaces. We assessed the effect of several pro-inflammatory mediators associated with acute lung inflammation on these factors. Platelet-activating factor, IL-8 and formyl-Met-Leu-Phe (fMLP) induced a marked, but transient reduction in neutrophil deformability. Also, increased surface expression of the beta(2)-integrin and CD11b, and shedding of L-selectin (CD62L) was observed for these stimuli. TNF-alpha in contrast caused a small decrease in cell deformability only after 30 min, and shedding of L-selectin, but no change in CD11b levels. However, TNF-alpha-pretreatment markedly enhanced the fMLP response for cell deformability, CD11b expression and CD62L loss. Moreover, all pre-treatments were found to induce chemokinesis, and all except fMLP, enhanced fMLP-directed chemotaxis. We were able to demonstrate, using specific TNF-alpha receptor antagonists, that the TNF-alpha-induced changes in chemotaxis were mediated through the 55-kDa receptor. Also, inhibitors of the mitogen activated protein (MAP) kinase signaling pathway showed that the p38 MAP kinase pathway was involved for fMLP-directed chemotaxis of TNF-pretreated neutrophils, although activation of the extracellular signal-regulated kinase (ERK) pathway was also seen. These data demonstrate the differential role of pro-inflammatory mediators in controlling neutrophil sequestration and migration, which may orchestrate the severity of the inflammatory response in such respiratory diseases as chronic obstructive pulmonary disease and asthma.

Effects of pentoxifylline on the different steps during adhesion and transendothelial migration of flowing neutrophils

We used a flow system to observe the stepwise adhesion and migration of neutrophils on cultured human umbilical vein endothelial cells (HUVEC) stimulated with tumour necrosis factor-alpha (TNF) for 4 h, and to evaluate the effects of pentoxifylline (PTX) at each step. When HUVEC had been stimulated with 100 U ml(-1) TNF, treatment of neutrophils with PTX did not reduce the number captured from flow but did cause nearly all adherent cells ( > 90%) to roll, whereas most untreated cells became immobilized and approximately 30% transmigrated within minutes. On washout of the PTX, many rolling cells halted and started to migrate. Treatment of the HUVEC with PTX at the same time as 100 U ml(-1) TNF did not affect the number of neutrophils adhering, but there was a significant increase in the percentage of cells rolling even though PTX was no longer present. Thus PTX reduced presentation of activating agents by HUVEC, as well as inhibiting the response by neutrophils to surface-presented activating agent(s). If HUVEC were stimulated with 10 U ml(-1) TNF with PTX, the adhesion of flowing neutrophils was greatly inhibited compared to TNF alone. Surface ELISA indicated that PTX reduced TNF-induced upregulation of E-selectin. This reduction was only sufficient to reduce capture of neutrophils at the low dose of TNF. Thus, by using a flow-based model, we have been able to separate the effects of a multipotent agent such as pentoxifylline, which acts on leucocytes and endothelial cells, at each stage of migration.

Erythrocyte deformability is a nitric oxide-mediated factor in decreased capillary density during sepsis

Erythrocyte deformability has been recognized as a determinant of microvascular perfusion. Because nitric oxide (NO) is implicated in the modulation of red blood cell (RBC) deformability and NO levels increase during sepsis, we tested the hypothesis that a NO-mediated decrease in RBC deformability contributes to decreased functional capillary density (CD) in remote organs. With the use of a peritonitis model of sepsis in the rat [cecal ligation and perforation (CLP)] and aminoguanidine (AG) to prevent increases in NO, we measured CD in skeletal muscle (intravital microscopy), mean erythrocyte membrane deformability (; micropipette aspiration), systemic NO production [plasma nitrite/nitrate (NO(x)) chemiluminescence], and NO accumulation in RBC [NO bound to hemoglobin (HbNO) detected by electron paramagnetic resonance spectroscopy]. In untreated CLP animals relative to sham, NO(x) increased 254% (P < 0.05), stopped flow capillaries increased 149% (P < 0.05), and decreased 12.7% (P < 0.05), with a subpopulation (5%) of RBC with deformabilities below the normal range. AG prevented increases in NO(x), accumulation of HbNO, and decreases in both and functional CD. We found no evidence of leukocyte plugging postcapillary venules. Our findings suggest that decreased functional CD during sepsis resulted from a NO-mediated decrease in erythrocyte deformability.

Effect of cytokines and colony-stimulating factors on passive polymorphonuclear leukocyte deformability in vitro

Cytokines are potent polymorphonuclear leukocyte (PMN) activators and can decrease their deformability. We evaluated passive PMN deformability using the micropipette method after incubation with different concentrations of lipopolysaccharide (LPS), interleukins (IL-) 1, 6, 8 and 10, tumour necrosis factor (TNF), granulocyte (G) and granulocyte-macrophage (GM) colony-stimulating factors (CSF). TNF, IL-1, G-CSF, GM-CSF and, to a lesser degree, IL-6 significantly and in a dose-dependent fashion decrease PMN deformability. LPS had no direct effect on PMN deformability. When cytokines at concentrations with no effect on deformability were combined they increased PMN rigidity. The findings suggest that several cytokines and CSF impair directly, and not by activation alone, PMN deformability.

Polymorphonuclear leukocyte rigidity is defective in patients with chronic renal failure

BACKGROUND

The purpose of the study was to investigate the rigidity of polymorphonuclear leukocytes (PMNs) in non-dialysed chronic renal failure (CRF) and haemodialysis (HD) patients.

METHODS

PMN rigidity as well as tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) plasma levels were assessed in 10 early-stage CRF, 10 late-stage non-HD, and 10 HD patients, before and during dialysis. In HD patients both cellulose acetate and polysulphone membranes were used. Ten healthy subjects served as controls. Rigidity was tested by counting the deformability in morphologically passive PMNs by the micropipette method. Cytokine levels were measured by enzyme-linked immunosorbent assay.

RESULTS

PMN rigidity was significantly increased in end-stage CRF patients regardless of HD but not in early-stage CRF. In HD patients PMN rigidity increased significantly 60 min after initiation of HD. There was an increase of TNF-alpha and IL-1beta levels in end-stage non-HD and HD patients and a further increase at 60 min after initiation of HD. The percentage of morphologically activated PMNs was increased only during dialysis. The nature of the HD membrane had no influence on rigidity, PMN activation, or cytokine production.

CONCLUSIONS

The results indicate that PMN rigidity is defective in end-stage chronic CRF patients and is further increased 60 min after initiation of HD, regardless of the nature of the HD membrane used. PMN activation, increased TNF-alpha and IL-1beta levels, or a direct PMN impairment may cause the observed cell rigidity.

Neutrophil deformability in patients with sepsis, septic shock, and adult respiratory distress syndrome

OBJECTIVE

To investigate the deformability of morphologically active and passive neutrophils in patients with sepsis (SP), septic shock (SS), and adult respiratory distress syndrome (ARDS).

DESIGN

Prospective, observational study.

SETTING

A university hospital intensive care unit and research laboratory.

PATIENTS

Six patients with sepsis, six patients with septic shock, and six patients with ARDS. Eight healthy volunteers and eight ventilated but noninfected patients served as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Morphologically passive and active neutrophil deformability as defined by the micropipette method was significantly decreased in patients with SP, SS, and ARDS associated with sepsis as compared with both control groups. Neutrophils from SS and ARDS patients were significantly more rigid as compared with neutrophils from SP patients but they did not differ from each other. The percentage of activated neutrophils was significantly higher in SP, SS, and ARDS patients. Increased passive neutrophil rigidity was significantly attenuated after coincubation with cytochalasin D. Tumor necrosis factor-alpha and interleukin-1beta serum levels were significantly higher in SP, SS, and ARDS patients.

CONCLUSIONS

The entire neutrophil population is less deformable in SP, SS, and ARDS patients. The decreased deformability of passive neutrophils suggests that a direct mechanism involving actin polymerization, distinct from cell activation, is involved. These observations may be important in the mechanism of impaired vascular flow in patients with sepsis.

Increased rigidity and priming of polymorphonuclear leukocytes in sepsis

It has been proposed that abnormal mechanical properties may contribute to capillary retention of polymorphonuclear leukocytes (PMN) in sepsis, leading to the development of organ dysfunction. The present study was designed to determine whether PMN rigidity is increased in severe sepsis, and whether changes in the rheologic behavior of PMN correlate with the clinical course in sepsis. Eighteen adults with severe sepsis were studied over a period of 14 d; 11 survived and seven died. PMN deformation behavior was investigated via micropore filtration, using the cell transit analyzer. On Day 0, PMN rigidity was 2.5-fold greater for sepsis patients than for five normal controls (p < 0.001). PMN rigidity progressively improved over the 14 d study period for patients who recovered, but not for those who died; clinical indicators correlated with PMN rigidity. Patient PMN also exhibited a 5-fold greater increase in rigidity in response to formyl-methionylleucylphenylalanine (fMLP) than did control PMN. Both the increased rigidity and enhanced response to fMLP could be simulated in vitro by incubation of normal PMN with tumor necrosis factor-alpha (TNF-alpha). We conclude that circulating PMN are more rigid in severe sepsis, and are "primed" for an augmented response to chemotactic stimuli. These findings support the hypothesis that cytokine-mediated increases of PMN rigidity may lead to sequestration of these cells in capillaries and to the consequent impairment of microvascular perfusion in sepsis.

Effects of proinflammatory cytokines and bacterial toxins on neutrophil rheologic properties

OBJECTIVE

To examine the changes in neutrophil deformability, aggregation, and adherence in response to stimulation with proinflammatory cytokines and bacterial toxins.

DESIGN

Prospective, randomized trial.

SETTING

Research laboratory.

SUBJECTS

Neutrophils isolated from healthy volunteers.

INTERVENTIONS

Neutrophils were exposed to tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-8, their combination, endotoxin (LPS), lipoteichoic acid (LTA), and staphyloccocal enterotoxin B (SEB). Neutrophil deformability was measured as percent neutrophils filtered through 5-microm diameter filters. Aggregation was measured using a platelet aggregometer. Adherence was determined by examining the binding of neutrophils to albumin-coated latex beads.

MEASUREMENTS AND MAIN RESULTS

Exposure to TNF-alpha and IL-1beta led to significant decreases in neutrophil filterability, which was attenuated by cytochalasin D pretreatment. LPS and LTA also decreased deformability, suggesting that these toxins directly stimulated neutrophils independent of cytokines. IL-8 and SEB did not significantly affect neutrophil deformability. TNF-alpha and LPS were associated with significant neutrophil aggregation, which was inhibited by pretreatment with anti-CD18 antibodies. Neutrophil aggregation was not affected by IL-1beta, LTA, or SEB. TNF-alpha, IL-8, and LPS increased neutrophil adherence, which also was attenuated by pretreatment with anti-CD18 antibodies. IL-1beta, LTA, and SEB did not significantly affect neutrophil adherence.

CONCLUSIONS

Cytokines and bacterial toxins differ in their effects on neutrophil deformability, aggregation, and adherence. Of the cytokines examined, TNF-alpha appears to have the greatest direct effects on neutrophil rheology. Similarly, endotoxin appears to have greater direct effects on neutrophil rheology than the Gram-positive bacterial toxins, LTA, and staphylococcal enterotoxins.

Treatment of endotoxic shock: glucocorticoids, lazaroids, nonsteroidals, others

Review of the literature would indicate that a therapy inhibiting a single step in the inflammatory mediator cascade, although potentially beneficial, cannot serve as the "magic bullet" in endotoxic shock. Thus, combination therapy using drugs that target multiple steps in the mediator cascade may prove useful in the future. Until controlled clinical studies have been performed in veterinary medicine using the agents discussed in this manuscript (or others), many questions will remain regarding the best possible pharmacologic therapies to use in supplementing traditional supportive care (e.g., fluids, broad-spectrum antimicrobials) measures. Many of the therapies discussed in this manuscript hold tremendous potential, but must be administered before endotoxic shock occurs or early in the course of endotoxic shock to elicit a beneficial response. Unfortunately this is not usually possible in the clinical situation. Further, the possibility of eliciting a detrimental response by use of drugs at inappropriate dosages or too late in the course of the disease must be considered. In time, therapies may be grouped into those that hold promise for being beneficial in the patient at risk for endotoxic shock and those that are beneficial for treatment of established endotoxic shock. Therapies that may hold promise for the patient with established endotoxic shock possibly include the lazaroids, certain NSAIDs, pentoxifylline, and selective inhibitors of iNOS activity. Although still controversial, methylprednisolone and other glucocorticoids are probably best reserved for the patient at risk for endotoxic shock, or those identified very early in the course of endotoxemia and endotoxic shock, and should never be used in conjunction with NSAIDs. Since no one therapy is likely to provide the "magic bullet" for the patient in endotoxic shock, treatment may ultimately involve combination therapy using some of these drugs that target different pathways and mediators and may also include antibodies against endotoxin or its mediators.

Sepsis/septic shock: participation of the microcirculation: an abbreviated review

OBJECTIVE

An overview of the importance of understanding mechanisms occurring in the microcirculation during septic and endotoxic shock. The thesis of the paper is to place emphasis on this important vascular network to ultimately benefit the patient.

DATA SOURCES

Early descriptions of vascular reactions to endotoxin which suggest that the microcirculation is a major site of attack during shock. More recent studies were sought out and examined as to their possible impacts on the microcirculation.

STUDY SELECTION

Early comprehensive studies concerning vascular reactions in the microcirculation during shock were selected. Subsequent studies identified from the mainstream scientific medical literature describe the actions of blood, cells, and the emerging significant role of the vascular endothelium among other factors. A consensus view is identified, pointing to the causes of a malfunctioning microcirculation during shock.

DATA EXTRACTION

Data gathered from reports in the mainstream, well-established basic and clinical literature, from reviews and forum reports, from studies by well-established investigators, and from more recent reports of excellent quality.

DATA SYNTHESIS

The microcirculation undergoes massive alterations during sepsis/septic shock. There are numerous changes, including slowing of capillary blood flow due to depressed perfusion pressure as a result of systemic pressure reduction and local arteriolar constriction. Observations suggest that the microcirculation is shut off early in severe sepsis, allowing the effects of hypoperfusion and attacks by microorganisms to prevail in their destructive capabilities. Widespread capillary dilation may ultimately occur. However, with blood flow diverted through some arteriovenous channels, important areas of capillary exchange are bypassed. Decreased capillary blood flow during shock results from failure to allow normal passage of cellular elements, including erythrocytes and neutrophils. This defect occurs, in part, because of decreased perfusion pressure, decreased deformability of red and white cells, constricted arterioles, circulating obstructive fragments (including hemoglobin), and plugging of microvessels with "sludge." Other factors are adherence of cells to capillary and venular epithelial membranes creating increased resistance to flow, loss of fluid through abnormal transcapillary exchange, differential vascular resistance changes between various beds (e.g., intestinal vs. muscle), and the relative absence of regulatory neurohumoral control of small vessel segments of the circulation. During sepsis/septic shock, endothelial cells are reported to modulate vascular tone, control local blood flow, influence the rate of leakage of fluids and plasma proteins into tissues, modulate the accumulation and extravasation of white cells into tissues, and influence white cell activation. As a result of the predominance of many destructive factors, a subsequent round of tissue damage may occur. Because of prolonged capillary vascular stasis, deficient flow, and factors released from injured cells, the microcirculation becomes a trap for uncontrolled bacterial growth enhanced by sustained hypoxemia, acidosis and toxemia. These events may combine to contribute to the loss of normal cell integrity and death of the host.

CONCLUSIONS

The purpose of this review is to draw the readers' attention to the growing list of adverse factors occurring in the microcirculation during sepsis/septic shock. A further aim is to point to the realization of the complexity of factors which may contribute to the importance of a well-functioning microcirculation.

Effects of pentoxifylline on circulating cytokine concentrations and hemodynamics in patients with septic shock: results from a double-blind, randomized, placebo-controlled study

OBJECTIVE

To determine whether a continuous intravenous infusion of pentoxifylline, a methylxanthine derivative, alters the serum cytokine concentrations and/or hemodynamic measurements in patients with septic shock.

DESIGN

A prospective, randomized, double-blind, placebo-controlled study.

SETTING

Medical intensive care unit in a university hospital.

PATIENTS

Sixteen patients with septic shock.

INTERVENTIONS

Patients were randomly assigned to receive either pentoxifylline (1 mg/kg) followed by an infusion of 1.5 mg/kg/hr for 24 hrs (n = 8), or placebo (n = 8).

MEASUREMENTS AND MAIN RESULTS

Tumor necrosis factor (TNF) and interleukin (IL)-6 concentrations were measured by radioimmunoassays; IL-8 concentrations by an enzyme-linked immunosorbent assay (ELISA) and pentoxifylline concentrations by high-performance liquid chromatography at 0, 3, 6, 12, 18, 24 and 48 hrs after study entry. Pulmonary artery catheter-derived hemodynamics were measured at 0, 0.75, 3, 6, 12, 18, and 24 hrs. In pentoxifylline-treated patients, at 24 hrs, serum concentrations of TNF were significantly lower compared with controls (12 +/- 2 vs. 42 +/- 12 pg/mL, respectively, p = .04). Serum concentrations of IL-6 and IL-8 did not differ between the two treatment groups. There were also no significant differences in any hemodynamic and oxygenation measurements comparing the two treatment groups. Pentoxifylline concentrations were 1,544 +/- 241 ng/mL after the initial dose, and 5,776 +/- 1,781 ng/mL at the end of the 24-hr infusion. Five patients in the pentoxifylline group and four patients in the placebo group died.

CONCLUSIONS

Pentoxifylline is able to decrease serum TNF but not IL-6 or IL-8 serum concentrations during septic shock. Pentoxifylline was well tolerated by all eight patients with no adverse effect. Further studies are needed to determine if pentoxifylline's ability to lower circulating TNF concentration without altering hemodynamics will improve outcome in septic shock.

Effect of endotoxin on lipid order and motion in erythrocyte membranes

Electron paramagnetic resonance employing a lipid-specific spin label has been used to investigate the molecular effects of endotoxin on the physical state of bilayer lipids in rat erythrocyte membranes. When added at a concentration as low as 40 micrograms/ml to whole blood (plasma plus leukocytes present), decreased membrane lipid motion was found in subsequently washed and spin-labeled intact erythrocytes (P < 0.02). However, if endotoxin were added to washed, plasma plus leukocyte-free intact erythrocytes, no change in the motion of the spin label was found, suggesting that plasma-soluble substances and/or leukocytes are required to produce the change in the physical state of lipids. The decreased lipid motion found in these studies is discussed with reference to the known decreased deformability of endotoxin-treated red cells and to the pathogenesis of sepsis.