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

Microfluidic device reveals new insights into impairment of neutrophil transmigration in patients with sepsis

Neutrophils need to migrate through tight tissue spaces to eliminate pathogens, but their movement is often hindered by their large and stiff nuclei. Neutrophil migration is impaired in sepsis patients, but it is unclear whether this defect is related to the deformability of their nuclei. Herein, we designed microfluidic devices with micron-scale narrow slits to simulate biological barriers. This setup allowed us to observe and record neutrophil movement and nuclear deformation in real-time. We also developed a method for morphological analysis to quantify nucleus deformation in numerous individual cells. Our studies showed that neutrophils from healthy individuals could adjust their nuclear shape to squeeze through these constrictions, whereas those from sepsis patients demonstrated less flexibility. Neutrophils with rigid nuclei struggled to pass through narrow gaps and were more likely to rupture under pressure. These findings suggest that the migration defects of neutrophils observed in sepsis may be attributed to the inability of neutrophils to deform their nuclei, highlighting the crucial role of microfluidic technologies in offering new insights into migration defects under pathological conditions.

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.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

A Systematic Study of Size Correlation and Young's Modulus Sensitivity for Cellular Mechanical Phenotyping by Microfluidic Approaches

Cellular mechanical properties are a class of intrinsic biophysical markers for cell state and health. Microfluidic mechanical phenotyping methods have emerged as promising tools to overcome the challenges of low throughput and high demand for manual skills in conventional approaches. In this work, two types of microfluidic cellular mechanical phenotyping methods, contactless hydro-stretching deformability cytometry (lh-DC) and contact constriction deformability cytometry (cc-DC) are comprehensively studied and compared. Polymerized hydrogel beads with defined sizes are used to characterize a strong negative correlation between size and deformability in cc-DC (r = -0.95), while lh-DC presents a weak positive correlation (r = 0.13). Young's modulus sensitivity in cc-DC is size-dependent while it is a constant in lh-DC. Moreover, the deformability assessment for human breast cell line mixture suggests the lh-DC exhibits better differentiation capability of cells with different size distributions, while cc-DC provides higher sensitivity to identify cellular mechanical changes within a single cell line. This work is the first to present a quantitative study and comparison of size correlation and Young's modulus sensitivity of contactless and contact microfluidic mechanical phenotyping methods, which provides guidance to choose the most suitable cellular mechanical phenotyping platform for specific cell analysis applications.

Proinflammatory cytokines levels in sepsis and healthy volunteers, and tumor necrosis factor-alpha associated sepsis mortality: A systematic review and meta-analysis

BACKGROUND

Sepsis is a global health challenge associated with significant morbidity and mortality. Detrimental sepsis effects are attributed to excessive inflammation or a "cytokine storm." However, anti-inflammation therapies have failed to lower sepsis mortality. We aim to characterize levels of key inflammatory cytokines in patients with sepsis and compare levels with those in healthy individuals and relate tumor necrosis factor (TNF) α levels to patient characteristics and outcomes.

METHODS

We performed a systematic review and meta-analysis. Medline, Embase, Cochrane Library, and Web of Science Core Collection databases were searched between 1985 and May 2020. Analysis was restricted to studies in English. We included randomized controlled trials (RCTs), controlled trials, cohort studies, case series, and cross-sectional studies that reported mean levels of cytokines in the circulation thought to be relevant for sepsis pathogenesis. We also evaluated concentrations of these cytokines in healthy individuals. The Quality in Prognosis Studies tool was used to assess the methodological quality of included studies. We extracted summary data from published reports. Data analyses were performed using a random-effects model to estimate pooled odds ratios (OR) with 95% confidence intervals for cytokine levels and mortality. This systematic review is registered in PROSPERO (CRD42020179800).

FINDINGS

We identified 3654 records, and 104 studies were included with a total of 3250 participants. The pooled estimated mean TNFα concentration in sepsis patients was 58.4 pg/ml (95% Confidence Interval or CI 39.8-85.8 pg/ml), and in healthy individuals was 5.5 pg/ml (95% CI 3.8-8.0 pg/ml). Pooled estimate means for IL-1β and IFN-γ in sepsis patients were 21.8 pg/ml and 63.3 pg/ml, respectively. Elevated TNFα concentrations associated with increased 28-day sepsis mortality (p = 0.001). In subgroup analyses, we did not detect an association between TNFα levels and sepsis source, sepsis severity, or sequential organ failure assessment (SOFA) score. A TNF-α cutoff level ≥14.7 pg/ml separated sepsis patients from healthy individuals with a sensitivity of 82.6%, a specificity of 91.7%, and a likelihood ratio of 9.9.

INTERPRETATION

Sepsis mean TNFα concentration is increased approximately 10-fold compared to mean concentration in healthy individuals, and TNFα associated with sepsis mortality but not sepsis severity. The concept that elevated cytokines cause sepsis should be revisited in the context of these data.

FUNDING

None.

Microfluidic Impedance-Deformability Cytometry for Label-Free Single Neutrophil Mechanophenotyping

The intrinsic biophysical states of neutrophils are associated with immune dysfunctions in diseases. While advanced image-based biophysical flow cytometers can probe cell deformability at high throughput, it is nontrivial to couple different sensing modalities (e.g., electrical) to measure other critical cell attributes including cell viability and membrane integrity. Herein, an "optics-free" impedance-deformability cytometer for multiparametric single cell mechanophenotyping is reported. The microfluidic platform integrates hydrodynamic cell pinching, and multifrequency impedance quantification of cell size, deformability, and membrane impedance (indicative of cell viability and activation). A newly-defined "electrical deformability index" is validated by numerical simulations, and shows strong correlations with the optical cell deformability index of HL-60 experimentally. Human neutrophils treated with various biochemical stimul are further profiled, and distinct differences in multimodal impedance signatures and UMAP analysis are observed. Overall, the integrated cytometer enables label-free cell profiling at throughput of >1000 cells min^-1 without any antibodies labeling to facilitate clinical diagnostics.

Structural Configuration of Blood Cell Membranes Determines Their Nonlinear Deformation Properties

The ability of neutrophils and red blood cells (RBCs) to undergo significant deformations is a key to their normal functioning. Disruptions of these processes can lead to pathologies. This work studied the influence of structural configuration rearrangements of membranes after exposure to external factors on the ability of native membranes of neutrophils and RBCs to undergo deep deformation. The rearrangement of the structural configuration of neutrophil and RBC membranes under the influence of cytological fixatives caused nonlinear deformation phenomena. There were an increase in Young's modulus, a decrease in the depth of homogeneous bending, and a change in the distance between cytoskeletal junctions. Based on the results of the analysis of experimental data, a mathematical model was proposed that describes the process of deep bending of RBСs and neutrophil membranes.

Fluid Therapy in Dogs and Cats With Sepsis

Sepsis is currently defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis may occur secondary to infection anywhere in the body, and its pathogenesis is complex and not yet fully understood. Variations in the host immune response result in diverse clinical manifestations, which complicates clinical recognition and fluid therapy both in humans and veterinary species. Septic shock is a subset of sepsis in which particularly profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone. Although septic shock is a form of distributive shock, septic patients frequently present with hypovolemic and cardiogenic shock as well, further complicating fluid therapy decisions. The goals of this review are to discuss the clinical recognition of sepsis in dogs and cats, the basic mechanisms of its pathogenesis as it affects hemodynamic function, and considerations for fluid therapy. Important pathophysiologic changes, such as cellular interaction, microvascular alterations, damage to the endothelial glycocalyx, hypoalbuminemia, and immune paralysis will be also reviewed. The advantages and disadvantages of treatment with crystalloids, natural and synthetic colloids, and blood products will be discussed. Current recommendations for evaluating fluid responsiveness and the timing of vasopressor therapy will also be considered. Where available, the veterinary literature will be used to guide recommendations.

The Neutrophil: Constant Defender and First Responder

The role of polymorphonuclear neutrophils (PMNs) in biology is often recognized during pathogenesis associated with PMN hyper- or hypo-functionality in various disease states. However, in the vast majority of cases, PMNs contribute to resilience and tissue homeostasis, with continuous PMN-mediated actions required for the maintenance of health, particularly in mucosal tissues. PMNs are extraordinarily well-adapted to respond to and diminish the damaging effects of a vast repertoire of infectious agents and injurious processes that are encountered throughout life. The commensal biofilm, a symbiotic polymicrobial ecosystem that lines the mucosal surfaces, is the first line of defense against pathogenic strains that might otherwise dominate, and is therefore of critical importance for health. PMNs regularly interact with the commensal flora at the mucosal tissues in health and limit their growth without developing an overt inflammatory reaction to them. These PMNs exhibit what is called a para-inflammatory phenotype, and have reduced inflammatory output. When biofilm growth and makeup are disrupted (i.e., dysbiosis), clinical symptoms associated with acute and chronic inflammatory responses to these changes may include pain, erythema and swelling. However, in most cases, these responses indicate that the immune system is functioning properly to re-establish homeostasis and protect the status quo. Defects in this healthy everyday function occur as a result of PMN subversion by pathological microbial strains, genetic defects or crosstalk with other chronic inflammatory conditions, including cancer and rheumatic disease, and this can provide some avenues for therapeutic targeting of PMN function. In other cases, targeting PMN functions could worsen the disease state. Certain PMN-mediated responses to pathogens, for example Neutrophil Extracellular Traps (NETs), might lead to undesirable symptoms such as pain or swelling and tissue damage/fibrosis. Despite collateral damage, these PMN responses limit pathogen dissemination and more severe damage that would otherwise occur. New data suggests the existence of unique PMN subsets, commonly associated with functional diversification in response to particular inflammatory challenges. PMN-directed therapeutic approaches depend on a greater understanding of this diversity. Here we outline the current understanding of PMNs in health and disease, with an emphasis on the positive manifestations of tissue and organ-protective PMN-mediated inflammation.

Phagocytosis-Inflammation Crosstalk in Sepsis: New Avenues for Therapeutic Intervention

Phagocytosis is a complex process by which cells within most organ systems remove pathogens and cell debris. Phagocytosis is usually followed by inflammatory pathway activation, which promotes pathogen elimination and inhibits pathogen growth. Delayed pathogen elimination is the first step in sepsis development and a key factor in sepsis resolution. Phagocytosis thus has an important role during sepsis and likely contributes to all of its clinical stages. However, only a few studies have specifically explored and characterized phagocytic activity during sepsis. Here, we describe the phagocytic processes that occur as part of the immune response preceding sepsis onset and identify the elements of phagocytosis that might constitute a predictive marker of sepsis outcomes. First, we detail the key features of phagocytosis, including the main receptors and signaling hallmarks associated with different phagocytic processes. We then discuss how the initial events of phagosome formation and cytoskeletal remodeling might be associated with known sepsis features, such as a cytokine-driven hyperinflammatory response and immunosuppression. Finally, we highlight the unresolved mechanisms of sepsis development and progression and the need for cross-disciplinary approaches to link the clinical complexity of the disease with basic cellular and molecular mechanisms.

Protein Kinase C Theta Inhibition Attenuates Lipopolysaccharide-Induced Acute Lung Injury through Notch Signaling Pathway via Suppressing Th17 Cell Response in Mice

Acute lung injury (ALI)/acute respiratory distress syndrome is characterized by increased pulmonary inflammation, where T helper 17 (Th17) cells play an important regulatory role. Notch signaling critically regulates Th17 differentiation and is known to be linked with proximal T cell by protein kinase C theta (PKCθ). We hypothesized that PKCθ inhibition could attenuate ALI by suppressing Th17 response via the Notch signaling pathway. Male C57BL/6 mice were treated with phosphate-buffered saline (PBS), lipopolysaccharide (LPS), LPS and N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT, a Notch signaling inhibitor), or LPS and PKCθ inhibitor (PI), and the bronchoalveolar lavage fluid (BALF), blood, and lung tissues were harvested at 48 h after the LPS challenge. CD4⁺ T cells were treated with DAPT or PI and harvested after 72 h. PKCθ inhibition markedly attenuated pathological changes and decreased the wet to dry weight ratio of the mouse lungs. The total cell and neutrophil counts, tumor necrosis factor-α (TNF- α) in BALF, myeloperoxidase activity in lung tissue, and the leukocyte count in whole blood were markedly reduced by PKCθ inhibition. The concentration of interleukin (IL)-17 and IL-22 in BALF, and the percentage of CD4⁺IL-17A⁺ T cells in the lungs were significantly downregulated by PKCθ inhibition. A similar trend was observed for the expression of retinoic acid-related orphan receptor gamma t and IL-23 receptor after PKCθ inhibition accompanied with inactivation of the Notch signaling pathway in vivo and in vitro. Collectively, these data demonstrated that PKCθ inhibition protects against LPS-induced ALI by suppressing the differentiation and pathogenicity of Th17, at least partially, through a Notch-dependent mechanism.

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.

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.

Neutrophil Activation During Septic Shock

In addition to their well-known role as the cellular mediators of immunity, key other roles have been identified for neutrophils during septic shock. Importantly, neutrophils indeed play a critical role in the recently described immunothrombosis concept and in septic shock-induced coagulopathy. Septic shock is one of the most severe forms of infection, characterized by an inadequate host response to the pathogenic organism. This host response involves numerous defense mechanisms with an intense cellular activation, including neutrophil activation. Neutrophils are key cells of innate immunity through complex interactions with vascular cells and their activation may participate in systemic tissue damages. Their activation also leads to the emission of neutrophil extracellular traps, which take part in both pathogen circumscription and phagocytosis, but also in coagulation activation. Neutrophils thus stand at the interface between hemostasis and immunity, called immunothrombosis.The present review will develop a cellular approach of septic shock pathophysiology focusing on neutrophils as key players of septic shock-induced vascular cell dysfunction and of the host response, associating immunity and hemostasis. We will therefore first develop the role of neutrophils in the interplay between innate and adaptive immunity, and will then highlight recent advances in our understanding of immunothrombosis septic shock-induced coagulopathy.

A Comparative Review of Equine SIRS, Sepsis, and Neutrophils

The most recent definition of sepsis in human medicine can be summarized as organ dysfunction caused by a dysregulated host response to infection. In equine medicine, although no consensus definition is available, sepsis is commonly described as a dysregulated host systemic inflammatory response to infection. Defense against host infection is the primary role of innate immune cells known as neutrophils. Neutrophils also contribute to host injury during sepsis, making them important potential targets for sepsis prevention, diagnosis, and treatment. This review will present both historical and updated perspectives on the systemic inflammatory response (SIRS) and sepsis; it will also discuss the impact of sepsis on neutrophils, and the impact of neutrophils during sepsis. Future identification of clinically relevant sepsis diagnosis and therapy depends on a more thorough understanding of disease pathogenesis across species. To gain this understanding, there is a critical need for research that utilizes a clearly defined, and consistently applied, classification system for patients diagnosed with, and at risk of developing, sepsis.

Integrated automated particle tracking microfluidic enables high-throughput cell deformability cytometry for red cell disorders

Investigating individual red blood cells (RBCs) is critical to understanding hematologic diseases, as pathology often originates at the single-cell level. Many RBC disorders manifest in altered biophysical properties, such as deformability of RBCs. Due to limitations in current biophysical assays, there exists a need for high-throughput analysis of RBC deformability with single-cell resolution. To that end, we present a method that pairs a simple in vitro artificial microvasculature network system with an innovative MATLAB-based automated particle tracking program, allowing for high-throughput, single-cell deformability index (sDI) measurements of entire RBC populations. We apply our technology to quantify the sDI of RBCs from healthy volunteers, Sickle cell disease (SCD) patients, a transfusion-dependent beta thalassemia major patient, and in stored packed RBCs (pRBCs) that undergo storage lesion over 4 weeks. Moreover, our system can also measure cell size for each RBC, thereby enabling 2D analysis of cell deformability vs cell size with single cell resolution akin to flow cytometry. Our results demonstrate the clear existence of distinct biophysical RBC subpopulations with high interpatient variability in SCD as indicated by large magnitude skewness and kurtosis values of distribution, the "shifting" of sDI vs RBC size curves over transfusion cycles in beta thalassemia, and the appearance of low sDI RBC subpopulations within 4 days of pRBC storage. Overall, our system offers an inexpensive, convenient, and high-throughput method to gauge single RBC deformability and size for any RBC population and has the potential to aid in disease monitoring and transfusion guidelines for various RBC disorders.

The leukocyte-stiffening property of plasma in early acute respiratory distress syndrome (ARDS) revealed by a microfluidic single-cell study: the role of cytokines and protection with antibodies

Background

Leukocyte-mediated pulmonary inflammation is a key pathophysiological mechanism involved in acute respiratory distress syndrome (ARDS). Massive sequestration of leukocytes in the pulmonary microvasculature is a major triggering event of the syndrome. We therefore investigated the potential role of leukocyte stiffness and adhesiveness in the sequestration of leukocytes in microvessels. 

Methods

This study was based on in vitro microfluidic assays using patient sera. Cell stiffness was assessed by measuring the entry time (ET) of a single cell into a microchannel with a 6 × 9–μm cross-section under a constant pressure drop (ΔP = 160 Pa). Primary neutrophils and monocytes, as well as the monocytic THP-1 cell line, were used. Cellular adhesiveness to human umbilical vein endothelial cells was examined using the laminar flow chamber method. We compared the properties of cells incubated with the sera of healthy volunteers (n = 5), patients presenting with acute cardiogenic pulmonary edema (ACPE; n = 6), and patients with ARDS (n = 22), of whom 13 were classified as having moderate to severe disease and the remaining 9 as having mild disease. 

Results

Rapid and strong stiffening of primary neutrophils and monocytes was induced within 30 minutes (mean ET >50 seconds) by sera from the ARDS group compared with both the healthy subjects and the ACPE groups (mean ET <1 second) (p < 0.05). Systematic measurements with the THP-1 cell line allowed for the establishment of a strong correlation between stiffening and the severity of respiratory status (mean ET 0.82 ± 0.08 seconds for healthy subjects, 1.6 ± 1.0 seconds for ACPE groups, 10.5 ± 6.1 seconds for mild ARDS, and 20.0 ± 8.1 seconds for moderate to severe ARDS; p < 0.05). Stiffening correlated with the cytokines interleukin IL-1β, IL-8, tumor necrosis factor TNF-α, and IL-10 but not with interferon-γ, transforming growth factor-β, IL-6, or IL-17. Strong stiffening was induced by IL-1β, IL-8, and TNF-α but not by IL-10, and incubations with sera and blocking antibodies against IL-1β, IL-8, or TNF-α significantly diminished the stiffening effect of serum. In contrast, the measurements of integrin expression (CD11b, CD11a, CD18, CD49d) and leukocyte–endothelium adhesion showed a weak and slow response after incubation with the sera of patients with ARDS (several hours), suggesting a lesser role of leukocyte adhesiveness compared with leukocyte stiffness in early ARDS. 

Conclusions

The leukocyte stiffening induced by cytokines in the sera of patients might play a role in the sequestration of leukocytes in the lung capillary beds during early ARDS. The inhibition of leukocyte stiffening with blocking antibodies might inspire future therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1157-5) contains supplementary material, which is available to authorized users.

Decreased deformability of lymphocytes in chronic lymphocytic leukemia

This paper reports the first study of stiffness/deformability changes of lymphocytes in chronic lymphocytic leukemia (CLL) patients, demonstrating that at the single cell level, leukemic metastasis progresses are accompanied by biophysical property alterations. A microfluidic device was utilized to electrically measure cell volume and transit time of single lymphocytes from healthy and CLL patients. The results from testing thousands of cells reveal that lymphocytes from CLL patients have higher stiffness (i.e., lower deformability), as compared to lymphocytes in healthy samples, which was also confirmed by AFM indentation tests. This observation is in sharp contrast to the known knowledge on other types of metastatic cells (e.g., breast and lung cancer cells) whose stiffness becomes lower as metastasis progresses.

New strategy for sepsis: Targeting a key role of platelet-neutrophil interaction

Neutrophil and platelet are essential arms of the innate immune response. In sepsis, platelet abnormal activation as well as neutrophil paralysis are well recognized. For platelet, it is characterized by the contribution to disseminated intravascular coagulation (DIC) and the enhanced inflammation response. In terms of neutrophil, its dysfunction is manifested by the impaired recruitment and migration to the infectious foci, abnormal sequestration in the remote organs, and the delayed clearance. More recently, it has been apparent that together platelet-neutrophil interaction can induce a faster and harder response during sepsis. This article focuses on the activation of platelet, dysfunction of neutrophil, and the interaction between them during sepsis and profiles some of the molecular mechanisms and outcomes in these cellular dialogues, providing a novel strategy for treatment of sepsis.

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.

Depletion of blood neutrophils from patients with sepsis: treatment for the future?

Organ failure arising from severe sepsis accounts for nearly 6 million deaths worldwide per annum. At present there are no specific pharmacological agents available for its treatment and identifying a suitable therapeutic target is urgently needed. Neutrophils appear to be contributing directly to pulmonary damage in severe forms of lung injury and indirectly to the failure of other organs. Blood neutrophils from patients with sepsis possess a phenotype that is indicative of activation and our results show that neutrophils isolated from patients with sepsis exhibit a supranormal adherence to endothelial monolayers treated with pro-inflammatory cytokines. Additional studies reveal that the patients' cells are highly efficient at releasing IL-8. We also demonstrate that organ function is improved upon removing neutrophils from the circulation. In this article we propose that in severe sepsis there is a subpopulation of neutrophils which is actively engaged in pathological insult. The phenotypic characterisation of this subset may provide a novel therapeutic strategy for sepsis that could lead to patient benefit.

Impact of intravascular volume replacement and transfusion on outcome: where are we now?

Intravenous fluid administration is often required to counteract haemodynamic instability during emergency and elective surgeries, as well as in the intensive care unit. However, the best type and the amount of fluid required are controversial. A recent meta-analysis suggested that there is no difference among different types of colloids on outcome. Furthermore, colloids and crystalloids seem to be comparable in terms of efficiency in reverting haemodynamic instability, as well as morbidity and mortality. The interpretation of the results of different randomised controlled trials is somewhat difficult - the context must be always kept in mind. For example, results may differ in septic as compared to non-septic patient populations. Another important aspect concerns the effects on the macro- versus microcirculation. More recent studies emphasise that the microcirculation has to be taken into account when studying and interpreting the interaction between fluid therapy and the underlying disease. Nevertheless, the macrocirculation and clinical parameters have to be considered as well. Given that red blood cells remain the most important oxygen carriers, recent evidence regarding blood age may stimulate new studies according to the actual range for blood storage. Artificial oxygen carriers may play a role in specific situations, where the transfusion is indicated but the access to blood is problematic, but there is doubt that they may replace blood transfusion.

Targeting CD162 protects against streptococcal M1 protein-evoked neutrophil recruitment and lung injury

Streptococcus pyogenes of the M1 serotype can cause streptococcal toxic shock syndrome and acute lung damage. CD162 is an adhesion molecule that has been reported to mediate neutrophil recruitment in acute inflammatory reactions. In this study, the purpose was to investigate the role of CD162 in M1 protein-provoked lung injury. Male C57BL/6 mice were treated with monoclonal antibody directed against CD162 or a control antibody before M1 protein challenge. Edema, neutrophil infiltration, and CXC chemokines were determined in the lung, 4 h after M1 protein administration. Fluorescence intravital microscopy was used to analyze leukocyte-endothelium interactions in the pulmonary microcirculation. Inhibition of CD162 reduced M1 protein-provoked accumulation of neutrophils, edema, and CXC chemokine formation in the lung by >54%. Moreover, immunoneutralization of CD162 abolished leukocyte rolling and firm adhesion in pulmonary venules of M1 protein-treated animals. In addition, inhibition of CD162 decreased M1 protein-induced capillary trapping of leukocytes in the lung microvasculature and improved microvascular perfusion in the lungs of M1 protein-treated animals. Our findings suggest that CD162 plays an important role in M1 protein-induced lung damage by regulating leukocyte rolling in pulmonary venules. Consequently, inhibition of CD162 attenuates M1 protein-evoked leukocyte adhesion and extravasation in the lung. Thus, our results suggest that targeting the CD162 might pave the way for novel opportunities to protect against pulmonary damage in streptococcal infections.

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.

The function of neutrophils in sepsis

PURPOSE OF REVIEW

Neutrophils are an essential arm of the innate immune response. In patients with sepsis, reprogramming of neutrophil occurs, manifest by impaired recruitment of neutrophils to sites of infection, abnormal accumulation of neutrophils to remote sites, and dysregulation of neutrophil effector responses. This review examines the mechanisms underlying dysregulated neutrophil trafficking and function during sepsis.

RECENT FINDINGS

Mechanisms governing neutrophil function in sepsis are complex. Bacterial products, cytokines/chemokines, leukotrienes, and immunomodulatory hormones can modulate neutrophil migratory responses during sepsis via induction of cytoskeletal changes, disruption of polymorphonuclear leukocyte (PMN)-endothelial cell interactions, and alterations in G-protein-coupled receptor expression or signaling. Impaired chemotactic responses and alterations in neutrophil function can occur as a result of dysregulated PMN G-protein-coupled receptor and Toll-like receptor expression and/or signaling. As sepsis evolves, neutrophil gene expression is altered, leading to suppression of proinflammatory and immunomodulatory genes, as well as decreased production of reactive oxygen species. Neutrophil extracellular traps are produced to contain and kill invading pathogens, but can paradoxically promote further tissue damage.

SUMMARY

Neutrophil migration is a coordinated process that is altered at multiple stages during sepsis. In combination with impaired neutrophil function, these alterations culminate in defective innate immunity in septic patients. Defining the mechanisms involved and strategies to interrupt these deleterious responses requires further investigation.

Gelam honey has a protective effect against lipopolysaccharide (LPS)-induced organ failure

Gelam honey exerts anti-inflammatory and antioxidant activities and is thought to have potent effects in reducing infections and healing wounds. The aim of this study was to investigate the effects of intravenously-injected Gelam honey in protecting organs from lethal doses of lipopolysaccharide (LPS). Six groups of rabbits (N = 6) were used in this study. Two groups acted as controls and received only saline and no LPS injections. For the test groups, 1 mL honey (500 mg/kg in saline) was intravenously injected into two groups (treated), while saline (1 mL) was injected into the other two groups (untreated); after 1 h, all four test groups were intravenously-injected with LPS (0.5 mg/kg). Eight hours after the LPS injection, blood and organs were collected from three groups (one from each treatment stream) and blood parameters were measured and biochemical tests, histopathology, and myeloperoxidase assessment were performed. For survival rate tests, rabbits from the remaining three groups were monitored over a 2-week period. Treatment with honey showed protective effects on organs through the improvement of organ blood parameters, reduced infiltration of neutrophils, and decreased myeloperoxidase activity. Honey-treated rabbits also showed reduced mortality after LPS injection compared with untreated rabbits. Honey may have a therapeutic effect in protecting organs during inflammatory diseases.

Pathogenesis of indirect (secondary) acute lung injury

At present, therapeutic interventions to treat acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) remain largely limited to lung-protective strategies, as no real molecular-pathophysiologic-driven therapeutic intervention has yet become available. This is in part the result of the heterogeneous nature of the etiological processes that contribute to the state of ALI/ARDS. This article sets out to understand the development of ALI resulting from indirect pulmonary insults, such as extrapulmonary sepsis and trauma, shock, burn injury or mass transfusion, as opposed to direct pulmonary challenges, such as pneumonia, aspiration or lung contusion. Here, we consider not only the experimental and clinical data concerning the roles of various immune (neutrophil, macrophage, lymphocyte and dendritic) as well as nonimmune (epithelial and endothelial) cells in orchestrating the development of ALI resulting from indirect pulmonary stimuli, but also how these cell populations might be targeted therapeutically.

Effects of sepsis on neutrophil chemotaxis

PURPOSE OF REVIEW

Neutrophil recruitment to sites of infection is a critical element of the innate immune response. In patients with sepsis, this response is dysregulated, with exuberant inflammation being followed by a state of profound immune suppression, including inhibition of neutrophil recruitment. This review examines mechanisms underlying suppression of neutrophil migration during sepsis.

RECENT FINDINGS

Mechanisms governing neutrophil chemotactic function in sepsis are complex. Bacterial products, cytokines, and chemokines can modulate neutrophil migratory responses during sepsis via induction of cytoskeletal changes, inhibition of polymorphonuclear leukocyte (PMN)-endothelial cell interactions, and alterations in G protein-coupled receptor expression or signaling. Impaired chemotactic responses can occur as a result of dysregulated PMN Toll-like receptor signaling. Other recently identified inhibitory mechanisms include exposure to elevated temperatures, activation of the anti-inflammatory nuclear transcription factor peroxisome proliferator-activated receptor-gamma, and suppression of PMN-endothelial interactions due to nitric oxide and its metabolites. Finally, circulating microparticles released in sepsis exert important immunomodulatory effects on PMN adherence and transmigration.

SUMMARY

Neutrophil recruitment is a coordinated process that is altered at multiple stages during sepsis, culminating in defective innate immunity and increased risk of infection in these patients. Defining mechanisms involved and strategies to interrupt these deleterious responses requires further investigation.

Safe and effective devices and instruments for use in the neonatal intensive care units: NICHD Workshop summary

The neonatal intensive care unit (NICU) depends heavily on advanced biomedical devices for monitoring, diagnosis, and treatment. Developing safe and effective devices for use in the NICU requires collaborative research and testing efforts between the bioengineering and biomedical disciplines. However, no mechanism exists to match the needs of the clinical community and the efforts of the bioengineering community. To address this issue, in February 2009, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health (NIH) invited a team of experts from diverse fields of biomedicine and bioengineering to participate in a workshop. The team reviewed and summarized bioinstrumentation needs and proposed a research agenda to develop safe and effective devices and instruments. The discussants addressed topics in cardiopulmonary, cerebrovascular, metabolic, and infectious conditions of the neonate. The authors provide a summary of the workshop discussions in this paper.

The current state in the evaluation and treatment of ARdS and SIRS

Trauma, the number one cause of death until the fourth decade of life, causes an inflammatory response. This response in its extreme is associated with the development of the systemic inflammatory state, adult respiratory distress syndrome, multi-organ failure, and death. The inflammatory response is mediated via multiple pathways- the inflammatory-cytokine, immunologic, coagulation and endocrine pathways. It is countered by producing antiinflammatory mediators. This reaction is altered in elderly patients. Knowledge of the patient's prior medical problems and the differential diagnosis for the possible causes of the current condition should help direct the surgical intervention and supportive care in an attempt to stabilize the patient. With the improvement of monitoring and diagnostic technologies, understanding the significance of the inflammatory pathways in trauma patients will decrease morbidity and mortality in this group of patients.

Microfluidic investigation reveals distinct roles for actin cytoskeleton and myosin II activity in capillary leukocyte trafficking

Circulating leukocyte sequestration in pulmonary capillaries is arguably the initiating event of lung injury in acute respiratory distress syndrome. We present a microfluidic investigation of the roles of actin organization and myosin II activity during the different stages of leukocyte trafficking through narrow capillaries (entry, transit and shape relaxation) using specific drugs (latrunculin A, jasplakinolide, and blebbistatin). The deformation rate during entry reveals that cell stiffness depends strongly on F-actin organization and hardly on myosin II activity, supporting a microfilament role in leukocyte sequestration. In the transit stage, cell friction is influenced by stiffness, demonstrating that the actin network is not completely broken after a forced entry into a capillary. Conversely, membrane unfolding was independent of leukocyte stiffness. The surface area of sequestered leukocytes increased by up to 160% in the absence of myosin II activity, showing the major role of molecular motors in microvilli wrinkling and zipping. Finally, cell shape relaxation was largely independent of both actin organization and myosin II activity, whereas a deformed state was required for normal trafficking through capillary segments.

Epithelial cell apoptosis and neutrophil recruitment in acute lung injury-a unifying hypothesis? What we have learned from small interfering RNAs

In spite of protective ventilatory strategies, Acute Lung Injury (ALI) remains associated with high morbidity and mortality. One reason for the lack of therapeutic options might be that ALI is a co-morbid event associated with a diverse family of diseases and, thus, may be the result of distinct pathological processes. Among them, activated neutrophil- (PMN-) induced tissue injury and epithelial cell apoptosis mediated lung damage represent two potentially important candidate pathomechanisms that have been put forward. Several approaches have been undertaken to test these hypotheses, with substantial success in the treatment of experimental forms of ALI. With this in mind, we will summarize these two current hypotheses of ALI briefly, emphasizing the role of apoptosis in regulating PMN and/or lung epithelial cell responses. In addition, the contribution that Fas-mediated inflammation may play as a potential biological link between lung cell apoptosis and PMN recruitment will be considered, as well as the in vivo application of small interfering RNA (siRNA) as a novel approach to the inhibition of ALI and its therapeutic implications.

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.

Advanced age exacerbates the pulmonary inflammatory response after lipopolysaccharide exposure

OBJECTIVE

The aged population is at a higher risk of mortality as a result of complications of injury or infection, such as acute lung injury. The objective of this study was to analyze pulmonary inflammatory responses in young and aged mice after administration of lipopolysaccharide.

DESIGN

Prospective, controlled laboratory study.

SETTING

Animal resource facilities and research laboratory.

SUBJECTS

Young (2-3 months old) and aged (18-20 months old) female BALB/c mice.

INTERVENTIONS

Animals received intraperitoneal injection of lipopolysaccharide derived from Pseudomonas aeruginosa. Control mice received saline alone. After 24 hrs, mice were killed. Pulmonary neutrophil infiltration was assessed histologically and by myeloperoxidase activity. Pulmonary levels of the CXC chemokines, monocyte inflammatory protein-2 and KC, and cytokines, tumor necrosis factor-alpha and interleukin-1beta, were assessed by enzyme-linked immunosorbent assay.

MEASUREMENTS AND MAIN RESULTS

Lungs of aged mice given lipopolysaccharide showed a six-fold higher neutrophil infiltration and three-fold higher level of myeloperoxidase activity than lungs of young mice given lipopolysaccharide. Pulmonary levels of monocyte inflammatory protein-2 and KC were significantly higher in the lungs of aged mice given lipopolysaccharide, compared with younger mice. Levels of tumor necrosis factor-alpha and interleukin-1beta in the lung were analyzed as well. After lipopolysaccharide treatment, there was no difference in the level of tumor necrosis factor-alpha in lungs of young and aged animals, but interleukin-1beta was two-fold higher in the lungs of the aged group. These data suggest that at this time point, interleukin-1beta may contribute to the higher production of CXC chemokines observed in lungs of aged mice vs. young mice receiving lipopolysaccharide.

CONCLUSIONS

The hyperreactive systemic inflammatory response seen in aged individuals after lipopolysaccharide administration is accompanied by an exacerbated pulmonary inflammatory response, which may contribute to the higher mortality seen in the aged given an inflammatory insult.

In vitro and in vivo effects of salbutamol on neutrophil function in acute lung injury

BACKGROUND

Intravenous salbutamol (albuterol) reduces lung water in patients with the acute respiratory distress syndrome (ARDS). Experimental data show that it also reduces pulmonary neutrophil accumulation or activation and inflammation in ARDS.

AIM

To investigate the effects of salbutamol on neutrophil function.

METHODS

The in vitro effects of salbutamol on neutrophil function were determined. Blood and bronchoalveolar lavage (BAL) fluid were collected from 35 patients with acute lung injury (ALI)/ARDS, 14 patients at risk from ARDS and 7 ventilated controls at baseline and after 4 days' treatment with placebo or salbutamol (ALI/ARDS group). Alveolar-capillary permeability was measured in vivo by thermodilution (PiCCO). Neutrophil activation, adhesion molecule expression and inflammatory cytokines were measured.

RESULTS

In vitro, physiological concentrations of salbutamol had no effect on neutrophil chemotaxis, viability or apoptosis. Patients with ALI/ARDS showed increased neutrophil activation and adhesion molecule expression compared with at risk-patients and ventilated controls. There were associations between alveolar-capillary permeability and BAL myeloperoxidase (r = 0.4, p = 0.038) and BAL interleukin 8 (r = 0.38, p = 0.033). In patients with ALI/ARDS, salbutamol increased numbers of circulating neutrophils but had no effect on alveolar neutrophils.

CONCLUSION

At the onset of ALI/ARDS, there is increased neutrophil recruitment and activation. Physiological concentrations of salbutamol did not alter neutrophil chemotaxis, viability or apoptosis in vitro. In vivo, salbutamol increased circulating neutrophils, but had no effect on alveolar neutrophils or on neutrophil activation. These data suggest that the beneficial effects of salbutamol in reducing lung water are unrelated to modulation of neutrophil-dependent inflammatory pathways.

A neutrophil elastase inhibitor, sivelestat, improves leukocyte deformability in patients with acute lung injury

BACKGROUND

The objective of this study was to evaluate whether the neutrophil elastase (NE) inhibitor, sivelestat, improves leukocyte deformability and pulmonary function in patients with acute lung injury (ALI).

PATIENTS AND METHODS

Twenty-four patients with systemic inflammatory response syndrome (SIRS) were divided into two groups: those with ALI (ALI group, n = 14), and those without ALI (non-ALI group, n = 10). Within 72 hours after the diagnosis, we measured the total leukocyte count (TLC), C-reactive protein (CRP) level, NE concentration, APACHE II score, Goris multiple organ failure (MOF) index, respiratory index (RI), lung injury score (LIS), and oxygenation index (P/F ratio). Leukocyte deformability was examined with a microchannel array etched on a single-crystal silicon tip that simulates the microvasculature. The number of obstructed microchannels (NOM) because of stiffened neutrophils and transit time (TT), defined as the time needed for 100 microL of whole blood to pass through the microchannels, were determined. We then administered sivelestat (4.8 mg/kg/d) to nine ALI patients (sivelestat group) for 5 days and compared with seven ALI patients treated previously without sivelestat (conventional group). The factors described above were measured before and 5 days after treatment.

RESULTS

There were no significant differences in age, TLC, CRP, APACHE II score, and MOF index between ALI and non-ALI group. RI and LIS were higher and the P/F ratio was significantly lower in the ALI group than in the non-ALI group. NE concentration, NOM, and TT were significantly higher in the ALI group than in the non-ALI group (p < 0.05). After 5 days of treatment with sivelestat, the APACHE II score, MOF index, RI, LIS, NE concentration, TT, and NOM were lower and the P/F ratio was significantly higher than baseline values and those in the conventional group (p < 0.05).

CONCLUSION

NE concentration and neutrophil rigidity are significantly increased in SIRS patients with ALI. Sivelestat appears to reduce NE concentration and neutrophil stiffness and improve pulmonary oxygenation in patients with ALI.

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.

Endotoxin-induced acute lung injury requires interaction with the liver

Clinical and laboratory data indicate that the liver plays an important role in the incidence, pathogenesis, and outcome of acute lung injury/acute respiratory distress syndrome. To distinguish direct effects of endotoxin on the lungs from liver-dependent effects during the early phase of the response to endotoxemia, we used an in situ perfused piglet preparation in which only the ventilated lung or both the lung and liver could be included in a blood perfused circuit. We monitored pulmonary vascular resistance, oxygenation, neutrophil count, lung edema as reflected by wet-dry weights of lung tissue, perfusate concentrations of TNF-alpha, IL-6, and 8-isoprostane (a marker of oxidative stress), and activation of the transcription factor (NF-kappaB) in lung tissue before and for 2 h after endotoxin. When only the lung was perfused, endotoxin caused pulmonary hypertension and neutropenia; but oxygenation was maintained; TNF-alpha, IL-6, and 8-isoprostane levels were minimally elevated; and there was no lung edema. When both the liver and lung were perfused, endotoxin caused marked hypoxemia, large increases in perfusate TNF-alpha, IL-6, and 8-isoprostane concentrations, and severe lung edema. NF-kappaB activation in the lung was greatest when the liver was in the perfusion circuit. We conclude that the direct effects of endotoxemia on the lungs include vasoconstriction and leukocyte sequestration, but not lung injury. Intense activation of the inflammatory response and oxidative injury that results in pulmonary edema and hypoxemia (acute lung injury) requires interaction of the lungs with the liver.

Mechanisms of early pulmonary neutrophil sequestration in ventilator-induced lung injury in mice

Polymorphonuclear leukocytes (PMN) play an important role in ventilator-induced lung injury (VILI), but the mechanisms of pulmonary PMN recruitment, particularly early intravascular PMN sequestration during VILI, have not been elucidated. We investigated the physiological and molecular mechanisms of pulmonary PMN sequestration in an in vivo mouse model of VILI. Anesthetized C57/BL6 mice were ventilated for 1 h with high tidal volume (injurious ventilation), low tidal volume and high positive end-expiratory pressure (protective ventilation), or normal tidal volume (control ventilation). Pulmonary PMN sequestration analyzed by flow cytometry of lung cell suspensions was substantially enhanced in injurious ventilation compared with protective and control ventilation, preceding development of physiological signs of lung injury. Anesthetized, spontaneously breathing mice with continuous positive airway pressure demonstrated that raised alveolar pressure alone does not induce PMN entrapment. In vitro leukocyte deformability assay indicated stiffening of circulating leukocytes in injurious ventilation compared with control ventilation. PMN sequestration in injurious ventilation was markedly inhibited by administration of anti-L-selectin antibody, but not by anti-CD18 antibody. These results suggest that mechanical ventilatory stress initiates pulmonary PMN sequestration early in the course of VILI, and this phenomenon is associated with stretch-induced inflammatory events leading to PMN stiffening and mediated by L-selectin-dependent but CD18-independent mechanisms.

Acute lung injury and acute respiratory distress syndrome in pregnancy

Acute respiratory failure can be the result of a variety of clinical conditions, such as congestive heart failure, pneumonia, pulmonary embolism, exacerbation of obstructive lung diseases, and acute respiratory distress syndrome (ARDS). This article focuses on developments related to acute lung injury and ARDS and reviews epidemiology, pathogenesis and therapeutic advances with an emphasis on the obstetric population. A brief discussion of tocolytic-induced pulmonary edema, preeclampsia, venous air embolism, and aspiration-related ARDS is included. Management of pregnant women with ARDS is outlined.