Hypertonic saline alteration of the PMN cytoskeleton: implications for signal transduction and the cytotoxic response

The modulatory effect of high salt on immune cells and related diseases

BACKGROUND

The adverse effect of excessive salt intake has been recognized in decades. Researchers have mainly focused on the association between salt intake and hypertension. However, studies in recent years have proposed the existence of extra-renal sodium storage and provided insight into the immunomodulatory function of sodium.

OBJECTIVES

In this review, we discuss the modulatory effects of high salt on various innate and adaptive immune cells and immune-regulated diseases.

METHODS

We identified papers through electronic searches of PubMed database from inception to March 2022.

RESULTS

An increasing body of evidence has demonstrated that high salt can modulate the differentiation, activation and function of multiple immune cells. Furthermore, a high-salt diet can increase tissue sodium concentrations and influence the immune responses in microenvironments, thereby affecting the development of immune-regulated diseases, including hypertension, multiple sclerosis, cancer and infections. These findings provide a novel mechanism for the pathology of certain diseases and indicate that salt might serve as a target or potential therapeutic agent in different disease contexts.

CONCLUSION

High salt has a profound impact on the differentiation, activation and function of multiple immune cells. Additionally, an HSD can modulate the development of various immune-regulated diseases.

High Na+ Environments Impair Phagocyte Oxidase-Dependent Antibacterial Activity of Neutrophils

Infection and inflammation can augment local Na⁺ abundance. These increases in local Na⁺ levels boost proinflammatory and antimicrobial macrophage activity and can favor polarization of T cells towards a proinflammatory Th17 phenotype. Although neutrophils play an important role in fighting intruding invaders, the impact of increased Na⁺ on the antimicrobial activity of neutrophils remains elusive. Here we show that, in neutrophils, increases in Na⁺ (high salt, HS) impair the ability of human and murine neutrophils to eliminate Escherichia coli and Staphylococcus aureus. High salt caused reduced spontaneous movement, degranulation and impaired production of reactive oxygen species (ROS) while leaving neutrophil viability unchanged. High salt enhanced the activity of the p38 mitogen-activated protein kinase (p38/MAPK) and increased the interleukin (IL)-8 release in a p38/MAPK-dependent manner. Whereas inhibition of p38/MAPK did not result in improved neutrophil defense, pharmacological blockade of the phagocyte oxidase (PHOX) or its genetic ablation mimicked the impaired antimicrobial activity detected under high salt conditions. Stimulation of neutrophils with phorbol-12-myristate-13-acetate (PMA) overcame high salt-induced impairment in ROS production and restored antimicrobial activity of neutrophils. Hence, we conclude that high salt-impaired PHOX activity results in diminished antimicrobial activity. Our findings suggest that increases in local Na⁺ represent an ionic checkpoint that prevents excessive ROS production of neutrophils, which decreases their antimicrobial potential and could potentially curtail ROS-mediated tissue damage.

The Effects of Resuscitative Fluid Therapy on the Endothelial Surface Layer

The goal of resuscitative fluid therapy is to rapidly expand circulating blood volume in order to restore tissue perfusion. Although this therapy often serves to improve macrohemodynamic parameters, it can be associated with adverse effects on the microcirculation and endothelium. The endothelial surface layer (ESL) provides a protective barrier over the endothelium and is important for regulating transvascular fluid movement, vasomotor tone, coagulation, and inflammation. Shedding or thinning of the ESL can promote interstitial edema and inflammation and may cause microcirculatory dysfunction. The pathophysiologic perturbations of critical illness and rapid, large-volume fluid therapy both cause shedding or thinning of the ESL. Research suggests that restricting the volume of crystalloid, or “clear” fluid, may preserve some ESL integrity and improve outcome based on animal experimental models and preliminary clinical trials in people. This narrative review critically evaluates the evidence for the detrimental effects of resuscitative fluid therapy on the ESL and provides suggestions for future research directions in this field.

Inhaled hypertonic saline for cystic fibrosis: Reviewing the potential evidence for modulation of neutrophil signalling and function

Cystic fibrosis (CF) is a multisystem disorder with significantly shortened life expectancy. The major cause of mortality and morbidity is lung disease with increasing pulmonary exacerbations and decline in lung function predicting significantly poorer outcomes. The pathogenesis of lung disease in CF is characterised in part by decreased airway surface liquid volume and subsequent failure of normal mucociliary clearance. This leads to accumulation of viscous mucus in the CF airway, providing an ideal environment for bacterial pathogens to grow and colonise, propagating airway inflammation in CF. The use of nebulised hypertonic saline (HTS) treatments has been shown to improve mucus clearance in CF and impact positively upon exacerbations, quality of life, and lung function. Several mechanisms of HTS likely improve outcome, resulting in clinically relevant enhancement in disease parameters related to increase in mucociliary clearance. There is increasing evidence to suggest that HTS is also beneficial through its anti-inflammatory properties and its ability to reduce bacterial activity and biofilm formation. This review will first describe the use of HTS in treatment of CF focusing on its efficacy and tolerability. The emphasis will then change to the potential benefits of aerosolized HTS for the attenuation of receptor mediated neutrophil functions, including down-regulation of oxidative burst activity, adhesion molecule expression, and the suppression of neutrophil degranulation of proteolytic enzymes.

Hypertonic saline solution reduces the inflammatory response in endotoxemic rats

OBJECTIVE

Volume replacement in septic patients improves hemodynamic stability. This effect can reduce the inflammatory response. The objective of this study was to evaluate the effect of 7.5% hypertonic saline solution versus 0.9% normal saline solution for volume replacement during an inflammatory response in endotoxemic rats.

METHODS

We measured cytokines (serum and gut), nitrite, and lipid peroxidation (TBARS) as indicators of oxidative stress in the gut. Rats were divided into four groups: control group (C) that did not receive lipopolysaccharide; lipopolysaccharide injection without treatment (LPS); lipopolysaccharide injection with saline treatment (LPS +S); and lipopolysaccharide injection with hypertonic saline treatment (LPS +H). Serum and intestine were collected. Measurements were taken at 1.5, 8, and 24 h after lipopolysaccharide administration.

RESULTS

Of the four groups, the LPS +H group had the highest survival rate. Hypertonic saline solution treatment led to lower levels of IL-6, IL-10, nitric oxide, and thiobarbituric acid reactive substances compared to 0.9% normal saline. In addition, hypertonic saline treatment resulted in a lower mortality compared to 0.9% normal saline treatment in endotoxemic rats. Volume replacement reduced levels of inflammatory mediators in the plasma and gut.

CONCLUSION

Hypertonic saline treatment reduced mortality and lowered levels of inflammatory mediators in endotoxemic rats. Hypertonic saline also has the advantage of requiring less volume replacement.

Influence of preoperative 7.5% hypertonic saline on neutrophil activation after reamed intramedullary nailing of femur shaft fractures: a prospective randomized pilot study

OBJECTIVES

Femoral reaming and intramedullary nailing (IMN) primes polymorphonuclear leukocytes (PMNL) and thereby increases the posttraumatic systemic inflammatory response. Resuscitation with hypertonic saline (HTS) attenuates PMNL activation after trauma-hemorrhage. We hypothesized that preoperative administration of 7.5% HTS attenuates PMNL priming after IMN of unilateral femur shaft fractures compared with 0.9% normal saline.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Level I trauma center.

PATIENTS

Twenty patients between 18 and 80 years of age with an Injury Severity Score less than 25 and a unilateral femur shaft fracture amenable to IMN fixation within 24 hours after injury.

INTERVENTION

Patients were allocated to equally sized HTS or normal saline treatment groups (n = 10) before surgery. Solutions were administered in a blinded bag as a single bolus of 4 mL/kg body weight immediately before surgery. Whole blood samples were collected directly before saline application (t0) and at 6, 12, and 24 hours after surgery.

MAIN OUTCOME MEASUREMENTS

PMNL surface expression of CD11b and CD62L, as determined by flow cytometry analysis.

RESULTS

Demographic characteristics of both treatment groups were comparable. Baseline expression of CD11b and CD62L cell markers was in a similar range in the two cohorts. The expression levels of CD11b were comparable between the two groups throughout the observation time, whereas CD62L levels were significantly higher in the HTS group at 6 and 24 hours after surgery.

CONCLUSION AND SIGNIFICANCE

Preoperative infusion of HTS appears to exert an anti-inflammatory effect by attenuating the extent of postoperative PMNL activation after reamed IMN for femoral shaft fractures.

Current trends in resuscitation strategy for the multiply injured patient

The ideal resuscitation strategy for multiply injured patients remains a topic of ongoing debate. At present, no consensus has been reached on the ideal fluid for early resuscitation and on the threshold for blood product transfusions. The concept of "permissive hypotension" for bleeding trauma patients furthermore contributes to the controversy in the field, particularly as it relates to blunt trauma and to patients with associated head injuries. Finally, postinjury coagulopathy is a poorly defined entity, and current resuscitation strategies lack strong evidence-based scientific support. This review article provides a brief overview of the existing resuscitation protocols for multiply injured patients, including ATLS and "damage control", and will address developing controversies in the field.

Amantadine inhibits platelet-activating factor induced clathrin-mediated endocytosis in human neutrophils

Receptor signaling is integral for adhesion, emigration, phagocytosis, and reactive oxygen species production in polymorphonuclear neutrophils (PMNs). Priming is an important part of PMN emigration, but it can also lead to PMN-mediated organ injury in the host. Platelet-activating factor (PAF) primes PMNs through activation of a specific G protein-coupled receptor. We hypothesize that PAF priming of PMNs requires clathrin-mediated endocytosis (CME) of the PAF receptor (PAFr), and, therefore, amantadine, known to inhibit CME, significantly antagonizes PAF signaling. PMNs were isolated by standard techniques to >98% purity and tested for viability. Amantadine (1 mM) significantly inhibited the PAF-mediated changes in the cellular distribution of clathrin and the physical colocalization [fluorescence resonance energy transfer positive (FRET+)] of early endosome antigen-1 and Rab5a, known components of CME and similar to hypertonic saline, a known inhibitor of CME. Furthermore, amantadine had no effect on the PAF-induced cytosolic calcium flux; however, phosphorylation of p38 MAPK was significantly decreased. Amantadine inhibited PAF-mediated changes in PMN physiology, including priming of the NADPH oxidase and shape change with lesser inhibition of increases in CD11b surface expression and elastase release. Furthermore, rimantadine, an amantadine analog, was a more potent inhibitor of PAF priming of the N-formyl-methionyl-leucyl-phenylalanine-activated oxidase. PAF priming of PMNs requires clathrin-mediated endocytosis that is inhibited when PMNs are pretreated with either amantadine or rimantadine. Thus, amantadine and rimantadine have the potential to ameliorate PMN-mediated tissue damage in humans.

Hypertonic saline: a clinical review

Literature suggest that hypertonic saline (HTS) solution with sodium chloride concentration greater than the physiologic 0.9% can be useful in controlling elevated intracranial pressure (ICP) and as a resuscitative agent in multiple settings including traumatic brain injury (TBI). In this review, we discuss HTS mechanisms of action, adverse effects, and current clinical studies. Studies show that HTS administered during the resuscitation of patients with a TBI improves neurological outcome. HTS also has positive effects on elevated ICP from multiple etiologies, and for shock resuscitation. However, a prospective randomized Australian study using an aggressive resuscitation protocol in trauma patients showed no difference in amount of fluids administered during prehospital resuscitation, and no differences in ICP control or neurological outcome. The role of HTS in prehospital resuscitation is yet to be determined. The most important factor in improving outcomes may be prevention of hypotension and preservation of cerebral blood flow. In regards to control of elevated ICP during the inpatient course, HTS appears safe and effective. Although clinicians currently use HTS with some success, significant questions remain as to the dose and manner of HTS infusion. Direct protocol comparisons should be performed to improve and standardize patient care.

Hypertonic saline attenuates colonic tumor cell metastatic potential by activating transmembrane sodium conductance

Hypertonic saline (HTS) suppresses tumor cell-endothelial interactions by reducing integrin expression. This translates into reduced adhesion, migration and metastatic potential. This study determined the relative contributions of hyperosmolarity and sodium-specific hypertonicity on the inhibitory effects of HTS, the intracellular pH and sodium responses to HTS and the role of cytoskeletal remodeling in these changes. Human colonic tumor cells (LS174T) were exposed to lipopolysaccharide under isotonic, hypertonic, sodium-free (N-methyl-D-glucamine), hyperosmolar (mannitol or urea), disrupted cytoskeletal (10 microg/ml cytochalasin D) conditions or in the presence of 5-(N-ethyl-N-isopropyl)amiloride (EIPA). Beta(1) integrin expression was measured flow-cytometrically. Intracellular sodium and pH were measured with confocal laser microscopic imaging. Statistical analysis was performed with analysis of variance, and P < 0.05 was considered significant. Data are represented as mean +/- SEM. Hypertonic exposure attenuated integrin expression (62.03 +/- 4.7% of control, P < 0.04). No discernible effect was observed with sodium-free or hyperosmolar solutions. HTS evoked a cellular alkalinization (by a mean 0.2 pH units) and an increase in cytosolic sodium concentration (by a mean 12.4 mM, P < 0.001) via upregulation of sodium-hydrogen exchange. Disassembly of actin microfilaments by cytochalasin D and antiporter inhibition with EIPA abrogated the effect of hypertonicity on integrin expression and intracellular sodium and pH (P < 0.05). HTS downregulates adhesion molecule expression via a hypertonic, sodium-specific, cytoskeletally mediated mechanism that involves activation of sodium-hydrogen exchange with associated changes in intracellular pH and sodium concentrations.

Relative effects of mannitol and hypertonic saline on calpain activity, apoptosis and polymorphonuclear infiltration in traumatic focal brain injury

The purpose of this study was to compare the relative effects of mannitol and hypertonic saline (HTS) on calpain activity, apoptosis and neuroinflammatory response induced by experimental cortical contusion. Four groups of 5 Sprague-Dawley male rats were submitted to focal brain injury produced by exposing the parietal cortex to dynamic cortical deformation. Groups were defined by rescucitation fluids administered 30 min post-injury as follows: group 1-0.9% normal saline 2 ml/kg; group 2-mannitol 20% 0.5 g/kg; group 3-HTS 2 ml/kg; group 4-HTS 4 ml/kg. At 72 h, animals were sacrificed. Paraffin-mounted sections of were stained for mu-Calpain, TUNEL, active caspase 3 and myeloperoxidase. There was no difference in the lesion size between the different groups. In contrast, there was a significant reduction in calpain and apoptosis activity and in the neuroinflammatory response in animals receiving HTS. Although mannitol proved to significantly decrease the neuroinflammatory response and calpain activity, it did not affect apoptosis, and its effect was significantly less than that of HTS. Importantly, the effect of HTS was mostly independent from the infused volume. Our results show that HTS promotes cell survival and reduces secondary brain damage following TBI. This protective effect was evidenced at rather small infused volumes, proved to encompass several cellular and molecular mechanisms involved in secondary cell death and could not be related to relief of intracranial pressure. These findings suggest that the high osmolality of HTS may have protective effects besides its impact on brain edema.

Selective inhibition of polymorphonuclear neutrophils by resuscitative concentration of hypertonic saline

OBJECTIVES

This study investigated the effect of hypertonic saline on the role of polymorphonuclear neutrophils (PMNs) in the inflammatory response and the effect of hypertonic saline infused at different phases in relation to an inflammatory stimulus.

MATERIALS AND METHODS

PMNs were isolated from peripheral blood of healthy volunteers (Boyum's method) and cultured in three different media ([Na+] = 140 mmol/l, 180 mmol/l, and 200 mmol/l). PMNs were then stimulated with fMLP (N-formyl-methionyl-leucyl-phenylalanine) and H2O2 synthesis was quantified by flow cytometry at 5, 30, 60, 120, and 180 minutes. PMNs were treated with hypertonic saline before, simultaneously with, and after fMLP stimulation, and H2O2 synthesis quantified again.

RESULTS

H2O2 synthesis was two or three times higher in fMLP stimulated than in non-stimulated PMNs, and it reached maximum level at 120 minutes. In the absence of fMLP stimulation, there was no significant difference between control and hypertonic saline with regard to activity of H2O2 synthesis. In the presence of fMLP stimulation, H2O2 synthesis significantly decreased in PMNs treated with hypertonic saline. There was no significant difference between the two hypertonic saline solutions ([Na+] = 180 mmol/l and 200 mmol/l) with regard to H2O2 synthesis. However, H2O2 synthesis decreased in PMNs treated with hypertonic saline before and simultaneously with fMLP stimulation, but was not significantly decreased in the cells treated with hypertonic saline after fMLP stimulation.

CONCLUSIONS

Hypertonic saline appears to decrease H2O2 in stimulated neutrophils. This may be a further beneficial role of hypertonic saline when used clinically as an early resuscitation fluid.

HSPTX protects against hemorrhagic shock resuscitation-induced tissue injury: an attractive alternative to Ringer's lactate

BACKGROUND

Conventional fluid resuscitation with Ringer's lactated (RL) activates neutrophils and causes end-organ damage. We have previously shown that HSPTX, a combination of small volume hypertonic saline (HS) and pentoxifylline (PTX), a phosphodiesterase-inhibitor, downregulates in vitro neutrophil activation and proinflammatory mediator synthesis. Herein, we hypothesized that HSPTX decreases end-organ injury when compared with RL in an animal model of hemorrhagic shock.

METHODS

Sprague-Dawley rats were bled to a mean arterial pressure of 35 mm Hg for 1 hour. Animals were divided into 3 groups: sham (no shock, no resuscitation, n = 7), RL (32 mL/kg, n = 7), and HSPTX (7.5% NaCl 4 mL/kg + PTX 25 mg/kg; n = 7). Shed blood was infused after fluid resuscitation. Blood pressure was monitored until the end of resuscitation. Animals were sacrificed at 24 hour after resuscitation. Bronchoalveolar lavage fluid (BALF) was obtained for white cell count (total and differential) and TNF-alpha and IL-1beta levels were measured by ELISA. Lung and intestinal injury at 24 hour were evaluated by histopathology. Organ damage was graded by a pathologist and a score was created (0 = no injury; 3 = severe). Lung neutrophil infiltration was evaluated by MPO immune staining.

RESULTS

There were no differences in mean arterial pressure between groups. At 24 hours, BALF leukocyte count was decreased by 30% in HSPTX animals (p < 0.01). TNF-alpha and IL-1beta levels were markedly decreased in HSPTX-resuscitated animals compared with their RL counterparts (p < 0.01). HSPTX-resuscitated animals (lung injury score = 1.0 +/- 0.4) had markedly decreased acute lung injury compared with RL-treated animals (2.5 +/- 0.3) (p < 0.01). RL resuscitation led to a two-fold increase in lung neutrophil infiltration whereas in HSPTX-treated animals, the number of MPO + cells was similar to sham animals (p < 0.001). Intestinal injury was markedly attenuated by HSPTX (1.1 +/- 0.3) compared with RL animals (2.6 +/- 0.4) (p < 0.001).

CONCLUSIONS

HSPTX, a small volume resuscitation strategy with marked immunomodulatory potential led to a marked decrease in end-organ damage. HSPTX is an attractive alternative to RL in hemorrhagic shock resuscitation.

Effects of hypertonic (7%) saline on brain injury in experimental Escherichia coli meningitis

We sought to know whether hypertonic (7%) saline (HTS) attenuates brain injury by improving cerebral perfusion pressure (CPP) and down-modulating acute inflammatory responses in experimental bacterial meningitis in the newborn piglet. Twenty-five newborn piglets were assorted into three groups: 6 in the control group (C), 10 in the meningitis group (M), and 9 in the meningitis with HTS infusion group (H). Meningitis was induced by intracisternal injection of 10(8) colony forming units of Escherichia coli in 100 microL of saline. 10 mL/kg of HTS was given intravenously as a bolus 6 hr after induction of meningitis, thereafter the infusion rate was adjusted to maintain the serum sodium level between 150 and 160 mEq/L. HTS significantly attenuated meningitis-induced brain cell membrane disintegration and dysfunction, as indicated by increased lipid peroxidation products and decreased Na+, K+-ATPase activity in the cerebral cortex in M. HTS significantly attenuated acute inflammatory markers such as increased intracranial pressure, elevated lactate level and pleocytosis in the cerebrospinal fluid observed in M. Reduced CPP observed in M was also significantly improved with HTS infusion. These findings implicate some attenuation of the meningitis-induced alterations in cerebral cortical cell membrane structure and function with HTS, possibly by improving CPP and attenuating acute inflammatory responses.

Role of Hypertonic Saline and Pentoxifylline on Neutrophil Activation and Tumor Necrosis Factor-α Synthesis: A Novel Resuscitation Strategy

BACKGROUND

Hypertonic saline (HS) and pentoxifylline (PTX) have been shown to modulate polymorphonuclear neutrophil (PMN) functions after shock and sepsis. We hypothesized that a combination of HS and PTX (HSPTX) would down-regulate PMN functions and inflammatory mediator synthesis more effectively than each alone, possibly by acting at different steps of the signaling pathways, ultimately leading to an enhanced effect.

METHODS

Whole blood from healthy volunteers was stimulated with lipopolysaccharide (LPS) (100 microg/mL), f-methionyl-leucyl-phenylalanine (1 micromol/L), and phorbol 12-myristate 13-acetate (1 microg/mL). Baseline oxidative burst was measured by flow cytometry. Two different concentrations of NaCl to achieve increases of 10 mmol/L (HS10) and 40 mmol/L (HS40) above isotonicity, simulating increases in sodium levels seen after infusion of 3% HS and 7.5% HS, were used. PTX (2 mmol/L), HS10, HS40, HSPTX10, and HSPTX40 were added to whole blood concomitantly to the activators. PMN CD14 and CD11b expression were measured by flow cytometry and tumor necrosis factor-alpha levels by enzyme-linked immunosorbent assay in LPS-stimulated whole blood.

RESULTS

The combination of PTX with HS10 and with HS40 markedly decreased LPS- (27 +/- 7 and 23 +/- 6 vs. 100; p < 0.01), f-methionyl-leucyl-phenylalanine- (54 +/- 11 and 55 +/- 8 vs. 100; p < 0.05), and phorbol 12-myristate 13-acetate- (30 +/- 4 and 54 +/- 9 vs. 100; p < 0.01 and p < 0.05, respectively) induced PMN oxidative burst. Furthermore, a significant decrease in LPS-induced neutrophil CD11b expression after PTX treatment (79 +/- 5 vs. 100; p < 0.05) and HSPTX40 (68 +/- 7 vs. 100; p < 0.05) was observed. HSPTX10 (7 +/- 0.6; p < 0.001) or HSPTX40 (6 +/- 1.4; p < 0.001) markedly decreased tumor necrosis factor-alpha production to levels similar to those observed with PTX alone (6.5 +/- 0.5; p < 0.001) and significantly lower than HS10 (110 +/- 4.9; p < 0.001) and HS40 alone (83 +/- 1.5; p < 0.001)

CONCLUSION

HSPTX down-regulates neutrophil activation and proinflammatory mediator synthesis more effectively that HS alone. HSPTX may have significant applications as a novel fluid resuscitation strategy in hemorrhagic shock.

Clinically relevant osmolar stress inhibits priming-induced PMN NADPH oxidase subunit translocation

BACKGROUND

The plasma membrane NADPH oxidase is responsible for the external generation of superoxide by neutrophils (polymorphonucleocytes [PMNs]). The oxidase is a multicomponent enzyme, active only when all subunits are translocated to and assembled at the membrane. We have recently demonstrated that platelet-activating factor (PAF) priming of PMNs translocates the cytosolic p67 subunit to the membrane position. Osmolar stress attenuates PAF priming of the oxidase. Consequently, we hypothesized that clinically relevant osmolar stress inhibits PAF priming-induced p67 translocation.

METHODS

Isolated human PMNs were incubated at 37 degrees C for 5 minutes in buffer or 180 mmol/L hypertonic saline (HTS) followed by 3 minutes of incubation with or without 2 mumol/L PAF (resting, PAF, HTS, and HTS-PAF). Digital microscopy was used to determine p67 location in whole PMNs. Subcellular fractions were prepared and membrane translocation of p67 determined by protein electrophoresis. Resting cytosol fractions were immunodepleted of p67 and NADPH oxidase activity measured using p67-deficient sodium dodecyl sulfate cell-free oxidase assays: resting, PAF, or HTS-PAF membrane (1 mug) was combined with immunodepleted resting cytosol (25 mug).

RESULTS

By all methodologies, PAF stimulated translocation of p67 to the PMN membrane and this translocation was prevented by osmolar stress (HTS-PAF). In cell-free oxidase assays, the membrane content of p67 after PAF stimulation was increased sufficiently to induce oxidase activity, whereas resting and HTS-PAF membrane did not (0.1 +/- 0.02, 0.23 +/- 0.04, and 0.14 +/- 0.04, respectively, p < 0.01) (resting versus HTS-PAF, no difference).

CONCLUSION

PAF priming of the PMN oxidase involves translocation of p67 to the plasma membrane. Clinically relevant osmolar stress with hypertonic saline prevents this PAF-induced translocation of the p67 oxidase subunit. This finding provides new insight into the mechanisms responsible for osmolar control of PMN functional responses.

Differential expression of extracellular matrix remodeling genes in rat model of hemorrhagic shock and resuscitation1,2

BACKGROUND

Matrix metalloproteinases (MMPs) and their specific physiological inhibitors, tissue inhibitors of metalloproteinases (TIMPs), are thought to play an essential role in tissue repair, cell death and morphogenesis. We have previously discovered unexpected up-regulation of genes coding for multiple MMP/TIMP family members in a rat model of hemorrhagic shock and resuscitation. However, the effect of different resuscitation protocols at the level of protein expression and function remains unknown.

MATERIALS AND METHODS

Male Sprague-Dawley rats (n = 50; 10/group) were subjected to a three-stage volume controlled hemorrhage and resuscitated as follows: 1) lactated Ringer's solution (LR), 3:1 volume of lost blood; 2) 7.5% hypertonic saline (HTS), 9.7 ml/kg; 3) plasma, 1:1 volume. Sham hemorrhage and sham resuscitation groups were used as controls. Expression of lung and spleen MMPs (-2, -7, -9, -10, -14, and -16), and TIMPs (-1, -2, and -3) was analyzed at transcriptional, functional and protein expression level using RT-PCR, ELISA, Western blotting, and gelatin zymography techniques.

RESULTS

Spleen was affected more than lung by the resuscitation strategy and the largest number of changes was caused by HTS resuscitation. RT-PCR confirmed an increased levels of MMP-2, MMP-9, MMP-7, MMP-14, MMP-16, and TIMP-1, TIMP-2 in the spleen of HTS group compared to sham groups, whereas in lungs transcriptional levels of only TIMP-3 and TIMP-1 were significantly changed.

CONCLUSION

Expression of MMP and TIMP in lung and spleen following hemorrhage is modulated by the resuscitation strategy.

Osmotic regulation of cell function and possible clinical applications

Inflammation and immunosuppression can cause acute respiratory distress syndrome, multiple organ failure, and sepsis, all of which are lethal posttraumatic complications in trauma patients. Prevention of the inflammation and immunosuppression has been a main focus of trauma researcher for many years. Recently, hypertonic resuscitation has attracted attention as a possible therapeutic approach to counteract such deleterious immune responses in trauma patients. We have begun to understand how hypertonic fluids affect immune cell signaling, and a number of experimental and clinical studies have started to reveal valuable information on the clinical efficacy and the limitations of hypertonic resuscitation fluids. Knowledge of how osmotic cues regulate immune cell function will enable us to fully exploit the clinical potential of hypertonic resuscitation to reduce inflammatory and anergic complications in trauma patients.

Immune effect of hypertonic saline: fact or fiction?

Hypertonicity affects many parts of the immune system. Animal studies and experiments in isolated cell cultures show that hypertonicity reversibly suppresses several neutrophil functions and at the same time up-regulates T-lymphocyte function. Infusion of hypertonic saline with or without colloids may thus, besides providing efficient plasma volume expansion, ameliorate the detrimental consequences on the immune function of trauma, shock, reperfusion, and major surgery. However, the few clinical studies conducted to date, specifically addressing the immune effect of hypertonic saline infusion, have shown little, if any, effect on markers of immune function, and larger clinical trials have not demonstrated benefit in terms of morbidity or mortality. Thus, as opposed to animal and cell-culture studies, the immune-modulating properties of hypertonic saline infusion would appear to be of limited value in clinical practice. This review presents in vitro studies, animal experiments, and clinical trials which investigated the consequences of hypertonic saline on markers of immune function.

Effects of hypertonic dextran in hypovolaemic shock: a prospective clinical trial

The aim of this paper is to report the results of prospective clinical trials of hypertonic saline dextran (HSD) in the resuscitation of hypovolaemic shock in critically injured patients. There are many types of fluids, which can be administered intravenously. Recent interest in the usage of HSD solution has confirmed that they have a place in resuscitation of a patient in shock. Heart rate and arterial pressure recovered well with HSD solution. The plasma osmolarity, sodium and potassium levels were significantly elevated in patients resuscitated with HSD. Urine output recovered rapidly and was well maintained throughout.

Volume replacement and microhemodynamic changes in polytrauma

Though fluid administration is one of the most basic concepts in resuscitation, there is ongoing controversy and continuing research on the definition of the ideal fluid for resuscitation of trauma and hemorrhage and for intraoperative volume support. In general, crystalloids and colloids, as well as blood, blood substitutes and oxygen therapeutics, are available. This report briefly revisits the physiological mechanisms underlying resuscitation with crystalloids and colloids, emphasizing colloid-supplemented resuscitation with hypertonic saline. Finally, potential applications of oxygen therapeutics are briefly considered.

cDNA profiling in leukocytes exposed to hypertonic resuscitation fluids

BACKGROUND

Resuscitative fluids induce distinctive changes in leukocyte functions: incubation with colloid Dextran increases production of reactive oxygen species and adhesion, whereas exposure to hypertonic saline (HTS) inhibits "oxidative burst" and phagocytosis. In hypertonic saline Dextran (HTD), the hypertonic component determines the leukocyte functional behavior and subsequently activation response. We investigated whether leukocyte gene expression is analogously affected.

METHODS

Whole blood from eight volunteers was diluted and incubated for 30 min at 37(o)C in 6.0% Dextran-70, 7.5% HTS, and 7.5% HTD. Total leukocyte RNA was extracted and used to synthesize biotinylated cDNA probes. Each probe was individually hybridized to a cDNA array to simultaneously measure the expression of 23 genes involved in inflammation, cell migration, and apoptosis.

RESULTS

Leukocytes incubated with Dextran-70 demonstrated greater than a 6-fold (p < 0.05) increase in the expression of interleukin-8, growth-regulated oncogenes alpha and beta, L-selectin, superoxide dismutase, tumor necrosis factor-alpha (TNF-alpha), and mitogen-activated protein kinase 3. The expression profile induced by HTS was not significantly different from that of unstimulated blood, except for prominent induction of only three genes. HTD attenuated the expression of Dextran-70 upregulated genes, although the level of their expression was higher than in HTS-treated leukocytes.

CONCLUSIONS

Hypertonic resuscitation fluids diminish the expression of immune activation-associated genes. Hypertonic component of HTD determines the leukocyte gene expression profile.

Fluid resuscitation: the target from an analysis of trauma systems and patient survival

Much can be learned from studying the deaths that occur in trauma systems as they have developed. Understanding these deaths and the potential effect of trauma systems on reducing death has major implications for designing clinical trials in fluid resuscitation. The availability of new, exciting information regarding fluid composition and physiologic effects argues for new, better-designed clinical trials. By agreeing on the form of resuscitation trials in the future, we will increase our ability to see clinically significant differences in outcome as we move from animal data to clinical efficacy.

Hypertonic saline resuscitation attenuates neutrophil lung sequestration and transmigration by diminishing leukocyte-endothelial interactions in a two-hit model of hemorrhagic shock and infection

BACKGROUND

Hypertonic saline (HTS) attenuates polymorphonuclear neutrophil (PMN)-mediated tissue injury after hemorrhagic shock. We hypothesized that HTS resuscitation reduces early in vivo endothelial cell (EC)-PMN interactions and late lung PMN sequestration in a two-hit model of hemorrhagic shock followed by mimicked infection.

METHODS

Thirty-two mice were hemorrhaged (40 mm Hg) for 60 minutes and then given intratracheal lipopolysaccharide (10 microg) 1 hour after resuscitation with shed blood and either HTS (4 mL/kg 7.5% NaCl) or Ringer's lactate (RL) (twice shed blood volume). Eleven controls were not manipulated. Cremaster intravital microscopy quantified 5-hour EC-PMN adherence, myeloperoxidase assay assessed lung PMN content (2 1/2 and 24 hours), and lung histology determined 24-hour PMN transmigration.

RESULTS

Compared with RL, HTS animals displayed 55% less 5-hour EC-PMN adherence (p = 0.01), 61% lower 24-hour lung myeloperoxidase ( p= 0.007), and 57% lower mean 24-hour lung histologic score ( p= 0.027).

CONCLUSION

Compared with RL, HTS resuscitation attenuates early EC-PMN adhesion and late lung PMN accumulation in hemorrhagic shock followed by inflammation. HTS resuscitation may attenuate PMN-mediated organ damage.

Cytokine expression profiling in human leukocytes after exposure to hypertonic and isotonic fluids

BACKGROUND

Resuscitation from hemorrhagic shock causes profound immunologic changes. The tonicity of fluids used for resuscitation clearly influences the immune response. Our study was designed to determine whether isotonic and hypertonic fluids exert their differential effects on immune response by altering the cytokine gene profile of human leukocytes. The cDNA array method was used to profile transcriptional responses after exposure to hypertonic and isotonic fluids.

METHODS

Blood from seven healthy volunteers was incubated for 30 minutes with isotonic (10% dextran-40 and lactated Ringer's [LR] solution) and hypertonic (7.5% hypertonic saline and hypertonic dextran [HTD]) fluids. The volumes of isotonic fluids used were equal to the volume of blood, whereas the volumes of hypertonic fluids were adjusted to keep the salt load identical to the LR group. The cDNA array technique was used to measure the gene expression of 23 common cytokines.

RESULTS

Increased gene transcription of proinflammatory cytokines (interleukin [IL]-1alpha, IL-6, IL-10, and tumor necrosis factor-alpha) as well as others (IL-5, IL-7, and IL-16) was found after incubation with resuscitation fluids. Variances were noted depending on the type of fluid: HTD and LR solution did not induce expression of IL-5, and HTD also did not induce IL-1beta expression. Genes encoding IL-1alpha, IL-6, IL-9, and tumor necrosis factor-alpha had low level baseline expression in leukocytes isolated from unstimulated blood, and their expression increased markedly after exposure to resuscitation fluids. The inducible transcripts included IL-1beta, IL-7, IL-10, and IL-16. However, there was no difference in cytokine expression profile between isotonic and hypertonic fluids.

CONCLUSION

Exposure of human leukocytes to resuscitation fluids causes an increase in cytokine gene expressions compared with undiluted blood. This expression profile is largely independent of the type of fluid used.

Clinical review: Hypertonic saline resuscitation in sepsis

The present review discusses the hemodynamic effects of hypertonic saline in experimental shock and in patients with sepsis. We comment on the mechanisms of action of hypertonic saline, calling upon data in hemorrhagic and septic shock. Specific actions of hypertonic saline in severe sepsis and septic shock are highlighted. Data are available that support potential benefits of hypertonic saline infusion in various aspects of the pathophysiology of sepsis, including tissue hypoperfusion, decreased oxygen consumption, endothelial dysfunction, cardiac depression, and the presence of a broad array of proinflammatory cytokines and various oxidant species. The goal of research in this field is to identify reliable therapies to prevent ischemia and inflammation, and to reduce mortality.