Hypertonic saline up-regulates A3 adenosine receptor expression of activated neutrophils and increases acute lung injury after sepsis

Therapeutic effect of yttrium oxide nanoparticles for the treatment of fulminant hepatic failure

Aim: To explore the potential therapeutic effect of yttrium oxide nanoparticles (Y₂O₃ NPs) on fulminant hepatic failure. Materials & methods: RAW264.7 cells and a lipopolysaccharide/D-galactosamine-induced hepatic failure murine model were used to assess the effects of Y₂O₃ NPs. Results: Y₂O₃ NPs exhibited anti-inflammatory activity by scavenging cellular reactive oxygen species and dampening reactive oxygen species-mediated NF-κB activation in vitro. A single intraperitoneal administration of Y₂O₃ NPs (30 mg/kg) enhanced hepatic antioxidant status and reduced oxidative stress and inflammatory response in lipopolysaccharide/galactosamine-induced mice. Y₂O₃ NPs also attenuated hepatic NF-κB activation, cell apoptosis and liver injury. Conclusion: Y₂O₃ NP administration could be used as a novel therapeutic strategy for treating fulminant hepatic failure and oxidative stress-related diseases.

The predictive value of plasma osmolality for in-hospital mortality in patients with acute pulmonary embolism

INTRODUCTION AND OBJECTIVES

Prior studies demonstrated that plasma osmolality may have a predictive value for in-hospital mortality in patients with heart failure and acute coronary syndrome. In addition, plasma glucose and blood urea nitrogen (BUN) levels, the components of plasma osmolality, have been shown to be an important contributor for in-hospital mortality in acute pulmonary embolism (APE) patients. Hence, the objective of the current study is to evaluate the effect of plasma osmolality upon admission with in-hospital mortality in patients with APE.

METHODS

A total of 245 consecutive intermediate or high risk APE patients were enrolled into the study. The study population was divided into three tertile groups (T1, T2 and T3) based on the increased plasma osmolality. The in-hospital mortality was the primary end-point.

RESULTS

After adjusting for all risk factors, in-hospital mortality was significantly higher in the T3 group compared to T1 and T2 groups (OR: 3.6, 95% CI: 1.3 to 18.8, P < .001). In addition, the incidence of asystolia, hypotension and cardiogenic shock were significantly higher in the T3 group. An area under the receiver operating characteristic curve value of plasma osmolality for the in-hospital mortality was 0.76 with sensitivity 67.2% and specificity 74.1% 95% CI: (0.66-0.87, P < .001).

CONCLUSION

This is the first study to demonstrate that elevated levels of plasma osmolality may have a predictive value for in-hospital mortality in APE patients. Our findings are novel and deserve further studies whether the treatment of higher plasma osmolality may reduce the risk of in-hospital mortality in APE patients.

Lungs donated after circulatory death and prolonged warm ischemia are transplanted successfully after enhanced ex vivo lung perfusion using adenosine A2B receptor antagonism

OBJECTIVE

The current supply of acceptable donor lungs is not sufficient for the number of patients awaiting transplantation. We hypothesized that ex vivo lung perfusion (EVLP) with targeted drug therapy would allow successful rehabilitation and transplantation of donation after circulatory death lungs exposed to 2 hours of warm ischemia.

METHODS

Donor porcine lungs were procured after 2 hours of warm ischemia postcardiac arrest and subjected to 4 hours of cold preservation or EVLP. ATL802, an adenosine A_2B receptor antagonist, was administered to select groups. Four groups (n = 4/group) were randomized: cold preservation (Cold), cold preservation with ATL802 during reperfusion (Cold + ATL802), EVLP (EVLP), and EVLP with ATL802 during ex vivo perfusion (EVLP + ATL802). Lungs subsequently were transplanted, reperfused, and assessed by measuring dynamic lung compliance and oxygenation capacity.

RESULTS

EVLP + ATL802 significantly improved dynamic lung compliance compared with EVLP (25.0 ± 1.8 vs 17.0 ± 2.4 mL/cmH₂O, P = .04), and compared with cold preservation (Cold: 12.2 ± 1.3, P = .004; Cold + ATL802: 10.6 ± 2.0 mL/cmH₂O, P = .002). Oxygenation capacity was highest in EVLP (440.4 ± 37.0 vs Cold: 174.0 ± 61.3 mm Hg, P = .037). No differences in oxygenation or pulmonary edema were observed between EVLP and EVLP + ATL802. A significant decrease in interleukin-12 expression in tissue and bronchoalveolar lavage was identified between groups EVLP and EVLP + ATL802, along with less neutrophil infiltration.

CONCLUSIONS

Severely injured donation after circulatory death lungs subjected to 2 hours of warm ischemia are transplanted successfully after enhanced EVLP with targeted drug therapy. Increased use of lungs after uncontrolled donor cardiac death and prolonged warm ischemia may be possible and may improve transplant wait list times and mortality.

Adenosine arrests breast cancer cell motility by A3 receptor stimulation

In neutrophils, adenosine triphosphate (ATP) release and autocrine purinergic signaling regulate coordinated cell motility during chemotaxis. Here, we studied whether similar mechanisms regulate the motility of breast cancer cells. While neutrophils and benign human mammary epithelial cells (HMEC) form a single leading edge, MDA-MB-231 breast cancer cells possess multiple leading edges enriched with A3 adenosine receptors. Compared to HMEC, MDA-MB-231 cells overexpress the ectonucleotidases ENPP1 and CD73, which convert extracellular ATP released by the cells to adenosine that stimulates A3 receptors and promotes cell migration with frequent directional changes. However, exogenous adenosine added to breast cancer cells or the A3 receptor agonist IB-MECA dose-dependently arrested cell motility by simultaneous stimulation of multiple leading edges, doubling cell surface areas and significantly reducing migration velocity by up to 75 %. We conclude that MDA-MB-231 cells, HMEC, and neutrophils differ in the purinergic signaling mechanisms that regulate their motility patterns and that the subcellular distribution of A3 adenosine receptors in MDA-MB-231 breast cancer cells contributes to dysfunctional cell motility. These findings imply that purinergic signaling mechanisms may be potential therapeutic targets to interfere with the motility of breast cancer cells in order to reduce the spread of cancer cells and the risk of metastasis.

Inhibition of Neutrophils by Hypertonic Saline Involves Pannexin-1, CD39, CD73, and Other Ectonucleotidases

Hypertonic saline (HS) resuscitation has been studied as a possible strategy to reduce polymorphonuclear neutrophil (PMN) activation and tissue damage in trauma patients. Hypertonic saline blocks PMNs by adenosine triphosphate (ATP) release and stimulation of A2a adenosine receptors. Here, we studied the underlying mechanisms in search of possible reasons for the inconsistent results of recent clinical trials with HS resuscitation. Purified human PMNs or PMNs in whole blood were treated with HS to simulate hypertonicity levels found after HS resuscitation (40 mmol/L beyond isotonic levels). Adenosine triphosphate release was measured with a luciferase assay. Polymorphonuclear neutrophil activation was assessed by measuring oxidative burst. The pannexin-1 (panx1) inhibitor panx1 and the gap junction inhibitor carbenoxolone (CBX) blocked ATP release from PMNs in purified and whole blood preparations, indicating that HS releases ATP via panx1 and gap junction channels. Hypertonic saline blocked N-formyl-Met-Leu-Phe-induced PMN activation by 40% in purified PMN preparations and by 60% in whole blood. These inhibitory effects were abolished by panx1 but only partially reduced by CBX, which indicates that panx1 has a central role in the immunomodulatory effects of HS. Inhibition of the ectonucleotidases CD39 and CD73 abolished the suppressive effect of HS on purified PMN cultures but only partially reduced the effect of HS in whole blood. These findings suggest redundant mechanisms in whole blood that may strengthen the immunomodulatory effect of HS in vivo. We conclude that HS resuscitation exerts anti-inflammatory effects that involve panx1, CD39, CD73, and other ectonucleotidases, which produce the adenosine that blocks PMNs by stimulating their A2a receptors. Our findings shed new light on the immunomodulatory mechanisms of HS and suggest possible new strategies to improve the clinical efficacy of hypertonic resuscitation.

Ligation of Glycophorin A Generates Reactive Oxygen Species Leading to Decreased Red Blood Cell Function

Acute, inflammatory conditions associated with dysregulated complement activation are characterized by significant increases in blood concentration of reactive oxygen species (ROS) and ATP. The mechanisms by which these molecules arise are not fully understood. In this study, using luminometric- and fluorescence-based methods, we show that ligation of glycophorin A (GPA) on human red blood cells (RBCs) results in a 2.1-fold, NADPH-oxidase-dependent increase in intracellular ROS that, in turn, trigger multiple downstream cascades leading to caspase-3 activation, ATP release, and increased band 3 phosphorylation. Functionally, using 2D microchannels to assess membrane deformability, GPS-ligated RBCs travel 33% slower than control RBCs, and lipid mobility was hindered by 10% using fluorescence recovery after photobleaching (FRAP). These outcomes were preventable by pretreating RBCs with cell-permeable ROS scavenger glutathione monoethyl ester (GSH-ME). Our results obtained in vitro using anti-GPA antibodies were validated using complement-altered RBCs isolated from control and septic patients. Our results suggest that during inflammatory conditions, circulating RBCs significantly contribute to capillary flow dysfunctions, and constitute an important but overlooked source of intravascular ROS and ATP, both critical mediators responsible for endothelial cell activation, microcirculation impairment, platelet activation, as well as long-term dysregulated adaptive and innate immune responses.

Immunomodulatory effect of hypertonic saline in hemorrhagic shock

Multiple organ dysfunction syndrome (MODS) and nosocomial infection following trauma-hemorrhage are among the most important causes of mortality in hemorrhagic shock patients. Dysregulation of the immune system plays a central role in MODS and a fluid having an immunomodulatory effect could be advantageous in hemorrhagic shock resuscitation. Hypertonic saline (HS) is widely used as a resuscitation fluid in trauma-hemorrhagic patients. Besides having beneficial effects on the hemodynamic parameters, HS has modulatory effects on various functions of immune cells such as degranulation, adhesion molecules and cytokines expression, as well as reactive oxygen species production. This article reviews clinical evidence for decreased organ failure and mortality in hemorrhagic shock patients resuscitated with HS. Despite promising results in animal models, results from pre-hospital and emergency department administration in human studies did not show improvement in survival, organ failure, or a reduction in nosocomial infection by HS resuscitation. Further post hoc analysis showed some benefit from HS resuscitation for severely-injured patients, those who received more than ten units of blood by transfusion, patients who underwent surgery, and victims of traumatic brain injury. Several reasons are suggested to explain the differences between clinical and animal models.

Effect of hypertonic saline treatment on the inflammatory response after hydrochloric acid-induced lung injury in pigs

OBJECTIVES

Hypertonic saline has been proposed to modulate the inflammatory cascade in certain experimental conditions, including pulmonary inflammation caused by inhaled gastric contents. The present study aimed to assess the potential anti-inflammatory effects of administering a single intravenous dose of 7.5% hypertonic saline in an experimental model of acute lung injury induced by hydrochloric acid.

METHODS

Thirty-two pigs were anesthetized and randomly allocated into the following four groups: Sham, which received anesthesia and were observed; HS, which received intravenous 7.5% hypertonic saline solution (4 ml/kg); acute lung injury, which were subjected to acute lung injury with intratracheal hydrochloric acid; and acute lung injury + hypertonic saline, which were subjected to acute lung injury with hydrochloric acid and treated with hypertonic saline. Hemodynamic and ventilatory parameters were recorded over four hours. Subsequently, bronchoalveolar lavage samples were collected at the end of the observation period to measure cytokine levels using an oxidative burst analysis, and lung tissue was collected for a histological analysis.

RESULTS

Hydrochloric acid instillation caused marked changes in respiratory mechanics as well as blood gas and lung parenchyma parameters. Despite the absence of a significant difference between the acute lung injury and acute lung injury + hypertonic saline groups, the acute lung injury animals presented higher neutrophil and tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-8 levels in the bronchoalveolar lavage analysis. The histopathological analysis revealed pulmonary edema, congestion and alveolar collapse in both groups; however, the differences between groups were not significant. Despite the lower cytokine and neutrophil levels observed in the acute lung injury + hypertonic saline group, significant differences were not observed among the treated and non-treated groups.

CONCLUSIONS

Hypertonic saline infusion after intratracheal hydrochloric acid instillation does not have an effect on inflammatory biomarkers or respiratory gas exchange.

Purinergic signalling and immune cells

This review article provides a historical perspective on the role of purinergic signalling in the regulation of various subsets of immune cells from early discoveries to current understanding. It is now recognised that adenosine 5'-triphosphate (ATP) and other nucleotides are released from cells following stress or injury. They can act on virtually all subsets of immune cells through a spectrum of P2X ligand-gated ion channels and G protein-coupled P2Y receptors. Furthermore, ATP is rapidly degraded into adenosine by ectonucleotidases such as CD39 and CD73, and adenosine exerts additional regulatory effects through its own receptors. The resulting effect ranges from stimulation to tolerance depending on the amount and time courses of nucleotides released, and the balance between ATP and adenosine. This review identifies the various receptors involved in the different subsets of immune cells and their effects on the function of these cells.

Prehospital hypertonic saline resuscitation attenuates the activation and promotes apoptosis of neutrophils in patients with severe traumatic brain injury

BACKGROUND

Activation of polymorphonuclear neutrophils (PMNs) is thought to contribute to traumatic brain injury (TBI). Since hypertonic fluids can inhibit PMN activation, we studied whether hypertonic fluid resuscitation can reduce excessive PMN activation in TBI patients.

METHODS

Trauma patients with severe TBI were resuscitated with 250 mL of either 7.5% hypertonic saline (HS; n = 22), HS + 6% dextran-70 (HSD; n = 22), or 0.9% normal saline (NS; n = 39), and blood samples were collected on hospital admission and 12 and 24 h after resuscitation. Polymorphonuclear neutrophil activation (CD11b, CD62L, CD64) and degranulation (CD63, CD66b, CD35) markers and oxidative-burst activity, as well as spontaneous PMN apoptosis were measured by flow cytometry.

RESULTS

Relative to healthy controls, TBI patients showed increased PMN activation and decreased apoptosis of PMNs. In the HS group, but not in the HSD group, markers of PMN adhesion (CD11b, CD64) and degranulation (CD35, CD66b) were significantly lower than those in the NS group. These effects were particularly pronounced 12 h after resuscitation. Treatment with HS and HSD inhibited PMN oxidative burst responses compared with NS-treated patients. Hypertonic saline alone partially restored delayed PMN apoptosis. Despite these differences, the groups did not differ in clinical outcome parameters such as mortality and Extended Glasgow Outcome Scale.

CONCLUSIONS

This study demonstrates that prehospital resuscitation with HS can partially restore normal PMN activity and the apoptotic behavior of PMNs, whereas resuscitation with HSD was largely ineffective. Although the results are intriguing, additional research will be required to translate these effects of HS into treatment strategies that improve clinical outcome in TBI patients.

Therapeutic applications

The current treatments offered to patients with chronic respiratory diseases are being re-evaluated based on the loss of potency during long-term treatments or because they only provide significant clinical benefits to a subset of the patient population. For instance, glucocorticoids are considered the most effective anti-inflammatory therapies for chronic inflammatory and immune diseases, such as asthma. But they are relatively ineffective in asthmatic smokers, and patients with chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF). As such, the pharmaceutical industry is exploring new therapeutic approaches to address all major respiratory diseases. The previous chapters demonstrated the widespread influence of purinergic signaling on all pulmonary functions and defense mechanisms. In Chap. 8, we described animal studies which highlighted the critical role of aberrant purinergic activities in the development and maintenance of chronic airway diseases. This last chapter covers all clinical and pharmaceutical applications currently developed based on purinergic receptor agonists and antagonists. We use the information acquired in the previous chapters on purinergic signaling and lung functions to scrutinize the preclinical and clinical data, and to realign the efforts of the pharmaceutical industry.

Effects of synthetic colloids on oxidative stress and inflammatory response in hemorrhagic shock: comparison of hydroxyethyl starch 130/0.4, hydroxyethyl starch 200/0.5, and succinylated gelatin

INTRODUCTION

This study compared the effects of hydroxyethyl starch 130/0.4, hydroxyethyl starch 200/0.5, and succinylated gelatin on oxidative stress and the inflammatory response in a rodent hemorrhagic shock model.

METHODS

Sodium pentobarbital-anesthetized adult male Wistar rats (200 g to 220 g) were subjected to a severe volume-controlled hemorrhage using arterial blood withdrawal (30 mL/kg to 33 mL/kg) and resuscitated with a colloid solution at the same volume as blood withdrawal (hydroxyethyl starch 130/0.4, hydroxyethyl starch 200/0.5, or succinylated gelatin). Arterial blood gas parameters were monitored. Malondialdehyde (MDA) content and myeloperoxidase (MPO) activity in the liver, lungs, intestine, and brain were measured two hours after resuscitation. The levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 in the intestine were also measured.

RESULTS

Infusions of hydroxyethyl starch 130/0.4, but not hydroxyethyl starch 200/0.5 or succinylated gelatin, significantly reduced MDA levels and MPO activity in the liver, intestine, lungs and brain, and it also inhibited the production of TNF-α in the intestine two hours after resuscitation. However, no significant difference between hydroxyethyl starch 200/0.5 and succinylated gelatin was observed.

CONCLUSIONS

Hydroxyethyl starch 130/0.4, but not hydroxyethyl starch 200/0.5 or succinylated gelatin, treatment after hemorrhagic shock ameliorated oxidative stress and the inflammatory response in this rat model. No significant differences were observed after hydroxyethyl starch 200/0.5 or succinylated gelatin administration at doses of approximately 33 mL/kg.

Adenosine A3 receptor activation attenuates lung ischemia-reperfusion injury

BACKGROUND

Severe ischemia-reperfusion (IR) injury leads to primary graft dysfunction after lung transplantation. Adenosine receptors modulate inflammation after IR, and the adenosine A3 receptor (A3R) is expressed in lung tissue and inflammatory cells. This study tests the hypothesis that A3R agonism attenuates lung IR injury by a neutrophil-dependent mechanism.

METHODS

Wild-type and A3R knockout (A3R-/-) mice underwent 1-hour left lung ischemia followed by 2-hours reperfusion (IR). A selective A3R agonist, Cl-IB-MECA, was administered (100 μg/kg intravenously) 5 minutes prior to ischemia. Study groups included sham, IR, and IR+Cl-IB-MECA (n = 6/group). Lung injury was assessed by measuring lung function, pulmonary edema, histopathology, and proinflammatory cytokines, and myeloperoxidase levels in bronchoalveolar lavage fluid. Parallel in vitro experiments were performed to evaluate neutrophil chemotaxis, and neutrophil activation was measured after exposure to acute hypoxia and reoxygenation.

RESULTS

Treatment of wild-type mice with Cl-IB-MECA significantly improved lung function and decreased edema, cytokine expression, and neutrophil infiltration after IR. The Cl-IB-MECA had no effects in A3R-/- mice; Cl-IB-MECA significantly decreased activation of wild-type, but not A3R-/-, neutrophils after acute hypoxia and reoxygenation and inhibited chemotaxis of wild-type neutrophils.

CONCLUSIONS

Exogenous activation of A3R by Cl-IB-MECA attenuates lung dysfunction, inflammation, and neutrophil infiltration after IR in wild-type but not A3R-/- mice. Results with isolated neutrophils suggest that the protective effects of Cl-IB-MECA are due, in part, to the prevention of neutrophil activation and chemotaxis. The use of A3R agonists may be a novel therapeutic strategy to prevent lung IR injury and primary graft dysfunction after transplantation.

Resuscitation of traumatic hemorrhagic shock patients with hypertonic saline-without dextran-inhibits neutrophil and endothelial cell activation

Posttraumatic inflammation and excessive neutrophil activation cause multiple organ dysfunction syndrome (MODS), a major cause of death among hemorrhagic shock patients. Traditional resuscitation strategies may exacerbate inflammation; thus, novel fluid treatments are needed to reduce such posttraumatic complications. Hypertonic resuscitation fluids inhibit inflammation and reduce MODS in animal models. Here we studied the anti-inflammatory efficacy of hypertonic fluids in a controlled clinical trial. Trauma patients in hypovolemic shock were resuscitated in a prehospital setting with 250 mL of either 7.5% hypertonic saline (HS; n = 9), 7.5% hypertonic saline + 6% dextran 70 (HSD; n = 8), or 0.9% normal saline (NS; n = 17). Blood samples were collected on hospital admission and 12 and 24 h after resuscitation. Multicolor flow cytometry was used to quantify neutrophil expression of cell-surface activation/adhesion (CD11b, CD62L, CD64) and degranulation (CD63, CD66b, CD35) markers as well as oxidative burst activity. Circulating concentrations of soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVACM-1), P- and E-selectins, myeloperoxidase (MPO), and matrix metalloproteinase 9 (MMP-9) were assessed by immunoassay. Multiple organ dysfunction syndrome, leukocytosis, and mortality were lower in the HS and HSD groups than in the NS group. However, these differences were not statistically significant. Hypertonic saline prevented priming and activation and neutrophil oxidative burst and CD11b and CD66b expression. Hypertonic saline also reduced circulating markers of neutrophil degranulation (MPO and MMP-9) and endothelial cell activation (sICAM-1, sVCAM-1, soluble E-selectin, and soluble P-selectin). Hypertonic saline + 6% dextran 70 was less capable than HS of suppressing the upregulation of most of these activation markers. This study demonstrates that initial resuscitation with HS, but neither NS nor HSD, can attenuate posttraumatic neutrophil and endothelial cell activation in hemorrhagic shock patients. These data suggest that hypertonic resuscitation without dextran may inhibit posttraumatic inflammation. However, despite this effect, neither HS nor HSD reduced MODS in trauma patients with hemorrhagic shock.

Impairment of adenosine A3 receptor activity disrupts neutrophil migratory capacity and impacts innate immune function in vivo

Adenosine possesses potent anti-inflammatory properties which are partly mediated by G(i) -coupled adenosine A3 receptors (A3Rs). A3R agonists have shown clinical benefit in a number of inflammatory conditions although some studies in A3R-deficient mice suggest a pro-inflammatory role. We hypothesised that, in addition to cell signalling effects, A3R compounds might inhibit neutrophil chemotaxis by disrupting the purinergic feedback loop controlling leukocyte migration. Human neutrophil activation triggered rapid upregulation of surface A3R expression which was disrupted by pre-treatment with either agonist (Cl-IB-MECA) or antagonist (MRS1220). Both compounds reduced migration velocity and neutrophil transmigration capacity without impacting the response to chemokines per se. Similar effects were observed in murine neutrophils, while cells from A3R-deficient mice displayed a constitutively impaired migratory phenotype indicating compound-induced desensitisation and genetic ablation had the same functional outcome. In a dextran sodium sulphate-induced colitis model, A3R-deficient mice exhibited reduced colon pathology and decreased tissue myeloperoxidase levels at day 8 - consistent with reduced neutrophil recruitment. However, A3R-deficient mice were unable to resolve the dextran sodium sulphate-induced inflammation and had elevated numbers of tissue-associated bacteria by day 21. Our data indicate that A3Rs play a role in neutrophil migration and disrupting this function has the potential to adversely affect innate immune responses.

Production of adenosine by ectonucleotidases: a key factor in tumor immunoescape

It is now well known that tumor immunosurveillance contributes to the control of cancer growth. Many mechanisms can be used by cancer cells to avoid the antitumor immune response. One such mechanism relies on the capacity of cancer cells or more generally of the tumor microenvironment to generate adenosine, a major molecule involved in antitumor T cell response suppression. Adenosine is generated by the dephosphorylation of extracellular ATP released by dying tumor cells. The conversion of ATP into adenosine is mediated by ectonucleotidase molecules, namely, CD73 and CD39. These molecules are frequently expressed in the tumor bed by a wide range of cells including tumor cells, regulatory T cells, Th17 cells, myeloid cells, and stromal cells. Recent evidence suggests that targeting adenosine by inhibiting ectonucleotidases may restore the resident antitumor immune response or enhance the efficacy of antitumor therapies. This paper will underline the impact of adenosine and ectonucleotidases on the antitumor response.

Increased neutrophil adenosine a3 receptor expression is associated with hemorrhagic shock and injury severity in trauma patients

Hypertonic saline (HS) has been investigated as an immune modulator following hemorrhagic shock and sepsis. The polymorphonuclear neutrophil (PMN) response to HS is regulated by the release of ATP, which is converted to adenosine and activates adenosine receptors. Binding to A3 adenosine receptors promotes PMN activation, and inhibition of A3 receptors improves the efficacy of HS resuscitation. A3 receptor expression of PMNs has not been previously evaluated in injured patients. Whole blood was obtained from 10 healthy volunteers and 60 injured patients within 2 h of injury. Inclusion criteria were blunt or penetrating injury with evidence of hypovolemic shock (systolic blood pressure [SBP] ≤90 mmHg and base deficit ≥6 mEq/L or need for blood transfusion) or evidence of severe traumatic brain injury including initial Glasgow Coma Scale score of 8 or less or evidence of traumatic brain injury on head computed tomography scan (head Abbreviated Injury Score ≥3) or intubation in the field or emergency department. A3 receptor expression was assessed by flow cytometry. Polymorphonuclear neutrophils were also exposed to fMLP or HS (20-40 mM) in vitro. Clinical data were collected including admission physiology, injury severity (Injury Severity Score [ISS]), development of multiple organ failure, and survival. In normal volunteers, less than 1% of PMNs expressed A3 receptors on the cell surface. A3 receptor expression was significantly higher in injured patients, and the level of expression correlated with the severity of injury (ISS ≥25: A3 positive PMN 36.6% vs. ISS <25: 16.2%; P = 0.019) and degree of hypovolemic shock (SBP ≤90 mmHg: A3 positive PMN 43.8% vs. SBP>90 mmHg: 20.6%; P = 0.008). Stimulation with fMLP or HS increased A3 expression in normal volunteers, but only in patients with ISS of less than 25 or without hypovolemic shock. A3 receptor expression on the surface of PMNs is upregulated by injury, and increased expression levels are associated with greater injury severity and hypovolemic shock. Hypertonic saline increases A3 expression of PMNs from healthy volunteers and less severely injured patients.

A3 adenosine receptor inhibition improves the efficacy of hypertonic saline resuscitation

We reported previously that hypertonic saline (HS) treatment can prevent or upregulate the function of polymorphonuclear neutrophils (PMNs) via A2a-type adenosine receptors or A3-type adenosine receptors (A3R), respectively. A3R translocate to the cell surface upon PMN stimulation, and thus, HS promotes PMN responses under conditions of delayed HS treatment. Here we investigated if inhibition of A3R improves the protective effects of HS resuscitation in a mouse sepsis model. We found that HS nearly triples extracellular adenosine concentrations in whole blood and that inhibition of A3R with the selective antagonist MRS-1191 dose dependently improves the inhibitory effect of HS. MRS-1191 at a concentration of 1 nM enhanced the inhibitory effect of HS and reduced stimulatory effects of delayed HS treatment. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found that MRS-1191 reduces acute lung injury and PMN accumulation in lung tissue. Whereas delayed HS treatment (4 mL/kg of 7.5% NaCl) of mice 1 h after CLP aggravated PMN accumulation, lung tissue damage, and mortality 24 h after CLP, infusion of MRS-1191 (2 ng/kg body weight) combined with HS reduced these detrimental effects of delayed HS treatment. Our data thus show that A3 receptor antagonists can strengthen the beneficial effects of HS resuscitation by avoiding stimulatory adverse effects that result from delayed HS administration.

Effects of fluid resuscitation with hypertonic saline dextrane or Ringer's acetate after nonhemorrhagic shock caused by pulmonary contusion

BACKGROUND

Injured lungs are sensitive to fluid resuscitation after trauma. Such treatment can increase lung water content and lead to desaturation. Hypertonic saline with dextran (HSD) has hyperosmotic properties that promote plasma volume expansion, thus potentially reducing these side effects. The aim of this study was to (1) evaluate whether fluid treatment counteracts hypotension and improves survival after nonhemorrhagic shock caused by lung contusion and (2) analyze whether resuscitation with HSD is more efficient than treatment with Ringer's acetate (RA) in terms of blood oxygenation, the amount of lung water, circulatory effects, and inflammatory response.

METHODS

Twenty-nine pigs, all wearing body armor, were shot with a 7.62-mm assault rifle to produce a standardized pulmonary contusion. These animals were allocated into three groups: HSD, RA, and an untreated shot control group. Exposed animals were compared with animals not treated with fluid and shot with blank ammunition. For 2 hours after the shot, the inflammatory response and physiologic parameters were monitored.

RESULTS

The impact induced pulmonary contusion, desaturation, hypotension, increased heart rate, and led to an inflammatory response. No change in blood pressure was observed after fluid treatment. HSD treatment resulted in significantly less lung water (p < 0.05) and tended to give better Pao2 (p = 0.09) than RA treatment. Tumor necrosis factor-α release and heart rate were significantly lower in animals given fluids.

CONCLUSION

Fluid treatment does not affect blood pressure or mortality in this model of nonhemorrhagic shock caused by lung contusion. However, our data indicate that HSD, when compared with RA, has advantages for the injured lung.

Out-of-hospital hypertonic resuscitation following severe traumatic brain injury: a randomized controlled trial

CONTEXT

Hypertonic fluids restore cerebral perfusion with reduced cerebral edema and modulate inflammatory response to reduce subsequent neuronal injury and thus have potential benefit in resuscitation of patients with traumatic brain injury (TBI).

OBJECTIVE

To determine whether out-of-hospital administration of hypertonic fluids improves neurologic outcome following severe TBI.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, double-blind, randomized, placebo-controlled clinical trial involving 114 North American emergency medical services agencies within the Resuscitation Outcomes Consortium, conducted between May 2006 and May 2009 among patients 15 years or older with blunt trauma and a prehospital Glasgow Coma Scale score of 8 or less who did not meet criteria for hypovolemic shock. Planned enrollment was 2122 patients.

INTERVENTION

A single 250-mL bolus of 7.5% saline/6% dextran 70 (hypertonic saline/dextran), 7.5% saline (hypertonic saline), or 0.9% saline (normal saline) initiated in the out-of-hospital setting.

MAIN OUTCOME MEASURE

Six-month neurologic outcome based on the Extended Glasgow Outcome Scale (GOSE) (dichotomized as >4 or ≤4).

RESULTS

The study was terminated by the data and safety monitoring board after randomization of 1331 patients, having met prespecified futility criteria. Among the 1282 patients enrolled, 6-month outcomes data were available for 1087 (85%). Baseline characteristics of the groups were equivalent. There was no difference in 6-month neurologic outcome among groups with regard to proportions of patients with severe TBI (GOSE ≤4) (hypertonic saline/dextran vs normal saline: 53.7% vs 51.5%; difference, 2.2% [95% CI, -4.5% to 9.0%]; hypertonic saline vs normal saline: 54.3% vs 51.5%; difference, 2.9% [95% CI, -4.0% to 9.7%]; P = .67). There were no statistically significant differences in distribution of GOSE category or Disability Rating Score by treatment group. Survival at 28 days was 74.3% with hypertonic saline/dextran, 75.7% with hypertonic saline, and 75.1% with normal saline (P = .88).

CONCLUSION

Among patients with severe TBI not in hypovolemic shock, initial resuscitation with either hypertonic saline or hypertonic saline/dextran, compared with normal saline, did not result in superior 6-month neurologic outcome or survival.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00316004.

Global end-diastolic volume, serum osmolarity, and albumin are risk factors for increased extravascular lung water

BACKGROUND

The transpulmonary thermodilution technique allows the determination of cardiac preload (global end-diastolic volume index) and quantification of pulmonary edema (extravascular lung water index [EVLWI]). Pulmonary edema commonly develops in critically ill patients; however, the underlying pathophysiology, that is, hydrostatic (cardiac) or permeability-induced (noncardiac), often remains unclear. In this study, hemodynamic and serum parameters of osmolarity and oncotic pressure were analyzed to identify risk factors for increased EVLWI.

METHODS

A retrospective, single-center analysis in an intensive care unit of a university hospital was performed. No interventions were made for the study. Forty-two critically ill patients were included, and 126 simultaneous hemodynamic measurements and serum determinations were analyzed by logistic regression and Spearman rank correlation coefficient analysis.

RESULTS

Global end-diastolic volume index (P = .001), serum albumin (P = .006), and serum osmolarity (P = .029) were significant factors for increased EVLWI (defined as >10 mL/kg).

CONCLUSION

Hypervolemia, hypoalbuminemia, and high plasma osmolarity are associated with increased EVLWI.

Cell volume regulation: physiology and pathophysiology

Cell volume perturbation initiates a wide array of intracellular signalling cascades, leading to protective and adaptive events and, in most cases, activation of volume-regulatory osmolyte transport, water loss, and hence restoration of cell volume and cellular function. Cell volume is challenged not only under physiological conditions, e.g. following accumulation of nutrients, during epithelial absorption/secretion processes, following hormonal/autocrine stimulation, and during induction of apoptosis, but also under pathophysiological conditions, e.g. hypoxia, ischaemia and hyponatremia/hypernatremia. On the other hand, it has recently become clear that an increase or reduction in cell volume can also serve as a specific signal in the regulation of physiological processes such as transepithelial transport, cell migration, proliferation and death. Although the mechanisms by which cell volume perturbations are sensed are still far from clear, significant progress has been made with respect to the nature of the sensors, transducers and effectors that convert a change in cell volume into a physiological response. In the present review, we summarize recent major developments in the field, and emphasize the relationship between cell volume regulation and organism physiology/pathophysiology.