Hypertonic saline inhibits neutrophil (PMN) priming via attenuation of p38 MAPK signaling

The impact of hypoxic conditions on apoptosis and Toll-like receptor 4 expression in polymorphonuclear neutrophils

Many patients are admitted to the emergency department due to trauma. Trauma patients suffer from hypoxia due to massive hemorrhage, respiratory failure, and hypovolemic shock. Further damage is caused by reduced immune function and over-expression of inflammatory response. We conducted an experiment to determine the effects of hyperoxia and hypoxia on apoptosis and expression of Toll-like receptor 4 (TLR4) in polymorphonuclear neutrophils (PMNs). Initially, the PMNs were placed in normoxic and hypoxic conditions, and these PMNs were divided into two groups as stimulated or not stimulated with lipopolysaccharide (LPS). Levels of apoptosis and TLR4 expression were measured under normoxic, hypoxic, and hyperoxic conditions. Apoptosis decreased in the hypoxic group than in the normoxic group. With LPS stimulation, apoptosis was decreased in all three treatment groups and even more reduced in the hypoxic group. TLR4 expression increased in all three treatment groups with LPS stimulation, increased further in the hypoxic group, and to a lesser degree in the hyperoxic group. Unlike the cells exposed to hypoxic conditions, the cells exposed to the hyperoxic condition reacted similarly to the cells in the control (normoxic) group. Therefore, the inflammatory reactions can be stronger in the hypoxic group than in the other two groups.

Hypertonic saline protects brain endothelial cells against hypoxia correlated to the levels of epidermal growth factor receptor and interleukin-1β

OBJECTIVE

The aim of this study was to verify the protective effect of hypertonic saline (HS) on brain endothelial cells under hypoxic conditions and the relevant underlying mechanism.

METHODS

bEnd.3 cells were treated with oxygen-glucose deprivation (OGD)-induced injury. To measure HS performance, cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt assay, and cell apoptosis was assessed by flow cytometry and Terminal deoxynucleotidyl transferase UTP nick-end labeling staining. RNA-seq was performed to assess the expression profiles and screen the candidate genes that participated in OGD-induced injury and the HS protective effect. Quantitative real-time polymerase chain reaction (qPCR) and western blot analysis were used to confirm the expression of candidate genes, and enzyme-linked immunosorbent assay was used to measure the level of interleukin (IL)-1β. Overexpression analyses were performed to confirm the functions of the differentially expressed genes.

RESULTS

HS with a concentration of 40 mmol/L NaCl had an obvious protective effect on bEnd.3 cells after OGD-induced injury, resulting in increased cell viability and a smaller percentage of apoptotic cells. According to the RNA-seq results, epidermal growth factor receptor (EGFR) was chosen as the differentially expressed gene target in this study. The qPCR and western blot analyses further confirmed that the levels of EGFR/phosphorylated epidermal growth factor receptor and IL-1β were enhanced after OGD-induced injury, but attenuated after treatment with 40 mmol/L of NaCl HS. Overexpressed EGFR reversed the protective effect of HS that caused low viability and high rates of apoptosis in cells.

CONCLUSION

HS can protect endothelial cells against OGD-induced injury, but is affected by the expression of EGFR/p-EGFR and IL-1β.

Comparison of 3% and 7.5% Hypertonic Saline in Resuscitation After Traumatic Hypovolemic Shock

Hypertonic saline solutions (HSSs) (7.5%) are useful in the resuscitation of patients with hypovolemic shock because they provide immediate intravascular volume expansion via the delivery of a small volume of fluid, improving cardiac function. However, the effects of using 3% HSS in hypovolemic shock resuscitation are not well known. This study was designed to compare the effects of and complications associated with 3% HSS, 7.5% HSS, and standard fluid in resuscitation. In total, 294 severe trauma patients were enrolled from December 2008 to February 2012 and subjected to a double-blind randomized clinical trial. Individual patients were treated with 3% HSS (250 mL), 7.5% HSS (250 mL), or lactated Ringer's solution (LRS) (250 mL). Mean arterial pressure, blood pressure, and heart rate were monitored and recorded before fluid infusion and at 10, 30, 45, and 60 min after infusion, and the incidence of complications and survival rate were analyzed. The results indicate that 3% and 7.5% HSSs rapidly restored mean arterial pressure and led to the requirement of an approximately 50% lower total fluid volume compared with the LRS group (P < 0.001). However, a single bolus of 7.5% HSS resulted in an increase in heart rate (mean of 127 beats/min) at 10 min after the start of resuscitation. Higher rates of arrhythmia and hypernatremia were noted in the 7.5% HSS group, whereas higher risks of renal failure (P< 0.001), coagulopathy (P < 0.001), and pulmonary edema (P < 0.001) were observed in the LRS group. Neither severe electrolyte disturbance nor anaphylaxis was observed in the HSS groups. It is notable that 3% HSS had similar effects on resuscitation because both the 7.5% HSS and LRS groups but resulted in a lower occurrence of complications. This study demonstrates the efficacy and safety of 3% HSS in the resuscitation of patients with hypovolemic shock.

Hypertonic saline alleviates cerebral edema by inhibiting microglia-derived TNF-α and IL-1β-induced Na-K-Cl Cotransporter up-regulation

Background

Hypertonic saline (HS) has been successfully used clinically for treatment of various forms of cerebral edema. Up-regulated expression of Na-K-Cl Cotransporter 1 (NKCC1) and inflammatory mediators such as tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) has been demonstrated to be closely associated with the pathogenesis of cerebral edema resulting from a variety of brain injuries. This study aimed to explore if alleviation of cerebral edema by 10% HS might be effected through down-regulation of inflammatory mediator expression in the microglia, and thus result in decreased NKCC1 expression in astrocytes in the cerebral cortex bordering the ischemic core.

Methods

The Sprague-Dawley (SD) rats that underwent right-sided middle cerebral artery occlusion (MCAO) were used for assessment of NKCC1, TNF-α and IL-1β expression using Western blotting, double immunofluorescence and real time RT-PCR, and the model also was used for evaluation of brain water content (BWC) and infarct size. SB203580 and SP600125, specific inhibitors of the p38 and JNK signaling pathways, were used to treat primary microglia cultures to determine whether the two signaling pathways were required for the inhibition of HS on microglia expressing and secreting TNF-α and IL-1β using Western blotting, double immunofluorescence and enzyme-linked immunosorbent assay (ELISA). The effect of TNF-α and IL-1β on NKCC1 expression in primary astrocyte cultures was determined. In addition, the direct inhibitory effect of HS on NKCC1 expression in primary astrocytes was also investigated by Western blotting, double immunofluorescence and real time RT-PCR.

Results

BWC and infarct size decreased significantly after 10% HS treatment. TNF-α and IL-1β immunoexpression in microglia was noticeably decreased. Concomitantly, NKCC1 expression in astrocytes was down-regulated. TNF-α and IL-1β released from the primary microglia subjected to hypoxic exposure and treatment with 100 mM HS were decreased. NKCC1 expression in primary astrocytes was concurrently and progressively down-regulated with decreasing concentration of exogenous TNF-α and IL-1β. Additionally, 100 mM HS directly inhibited NKCC1 up-regulation in astrocytes under hypoxic condition.

Conclusions

The results suggest that 10% HS alleviates cerebral edema through inhibition of the NKCC1 Cotransporter, which is mediated by attenuation of TNF-α and IL-1β stimulation on NKCC1.

Hyperosmolarity attenuates TNF-α-mediated proinflammatory activation of human pulmonary microvascular endothelial cells

Firm neutrophil (PMN)-endothelial (EC) adhesion is crucial to the PMN-mediated hyperinflammation observed in acute lung injury. Hypertonic saline (HTS) used for resuscitation of hemorrhagic shock has been associated with a decreased incidence of PMN-mediated lung injury/acute respiratory distress syndrome. We hypothesize that physiologically accessible hypertonic incubation (170 vs. 140 mM, osmolarity ranging from 360 to 300 mOsm/L) inhibits proinflammatory activation of human pulmonary microvascular endothelial cells (HMVECs). Proinflammatory activation of HMVECs was investigated in response to tumor necrosis factor-α (TNF-α), including interleukin 8 (IL-8) release, intercellular adhesion molecule 1 (ICAM-1) surface expression, PMN adhesion, and signaling mechanisms under both isotonic (control) and hypertonic conditions. Hyperosmolarity alone had no effect on either basal IL-8 release or ICAM-1 surface expression but did lead to concentration-dependent decreases in TNF-α-induced IL-8 release, ICAM-1 surface expression, and PMN-HMVEC adhesion. Conversely, HTS activated p38 mitogen-activated protein kinase (MAPK) and enhanced TNF-α activation of p38 MAPK. Despite this basal activation, hyperosmolar incubation attenuated TNF-α-stimulated IL-8 release and ICAM-1 surface expression and subsequent PMN adherence, while p38 MAPK inhibition did not further influence the effects of hyperosmolar conditions on ICAM-1 surface expression. In addition, TNF-α induced nuclear factor-κB DNA binding, but HTS conditions attenuated this by 31% (P < 0.01). In conclusion, HTS reduces PMN-HMVEC adhesion and TNF-α-induced proinflammatory activation of primary HMVECs via attenuation of nuclear factor-κB signaling.

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.

The effects of hypertonic fluid administration on the gene expression of inflammatory mediators in circulating leucocytes in patients with septic shock: a preliminary study

Objective

This study was designed to investigate the effect of hypertonic fluid administration on inflammatory mediator gene expression in patients with septic shock.

Design and setting

Prospective, randomized, controlled, double-blind clinical study in a 15-bed mixed intensive care unit in a tertiary referral teaching hospital.

Interventions

Twenty-four patients, who met standard criteria for septic shock, were randomized to receive a bolus of hypertonic fluid (HT, 250 ml 6% HES/7.2% NaCl) or isotonic fluid (IT, 500 ml 6% HES/0.9% NaCl) administered over 15 minutes. Randomization and study fluid administration was within 24 hours of ICU admission for all patients. This trial is registered with ANZCTR.org.au as ACTRN12607000259448.

Results

Blood samples were taken immediately before and 4, 8, 12, and 24 hours after fluid administration. Real-time reverse transcriptase polymerase chain reaction (RT rtPCR) was used to quantify mRNA expression of different inflammatory mediators in peripheral leukocytes. In the HT group, compared with the IT group, levels of gene expression of MMP9 and L-selectin were significantly suppressed (p = 0.0002 and p = 0.007, respectively), and CD11b gene expression tended to be elevated (p = NS). No differences were found in the other mediators examined.

Conclusions

In septic shock patients, hypertonic fluid administration compared with isotonic fluid may modulate expression of genes that are implicated in leukocyte-endothelial interaction and capillary leakage.

The study was performed at the Intensive Care Department, Waikato Hospital, and at the Molecular Genetics Laboratory, University of Waikato, Hamilton, New Zealand.

Trial registration

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12607000259448

Understanding Intra-Abdominal Hypertension

Received November 10, 2009. Received Revised June 17, 2010. Submitted June 21, 2010. Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are highly morbid conditions that are common and underrecognized in the intensive care unit. Intra-abdominal hypertension affects the critically ill patient population and is not solely limited to the trauma and surgical subgroups. The recognition of IAH and ACS as distinct clinical states has become more apparent. Extensive bench and clinical research has shed significant light into the definition, incidence, etiology, physiology, clinical manifestations, and treatment strategies. Although further research into this morbid condition is needed, improvement in recognition is a critical first step. This review aims to scrutinize the basic science and clinical literature available on this condition in a surgically focused, organ-system-based approach.

A murine model of hypertonic saline as a treatment for acute spinal cord injury: effects on autonomic outcome

Object

Spinal cord injury (SCI) continues to be a problem without a definitive cure. Research based on improved understanding of the immunological aspects of SCI has revealed targets for treating and ameliorating the extent of secondary injury. Hypertonic saline (HTS), a substance both easy to create and to transport, has been investigated as an immunologically active material that can be used in a clinically relevant interval after injury. In this pilot study, HTS was investigated in a murine model for its abilities to ameliorate secondary injury after a severe spinal cord contusion.

Methods

Female C57Bl/6 mice with severe T8–10 contusion injuries were used as the model subjects. A group of 41 mice were studied in a blinded fashion. Mice received treatments with HTS (HTS, 7.5%) or normal saline solution (NSS, 0.9%) at 2 discreet time points (3 and 24 hours after injury.) A separate group of 9 untreated animals were also used as controls. Animals were assessed for autonomic outcome (bladder function). In a group of 33 mice, histological assessment (cellular infiltration) was also measured.

Results

Bladder function was found to be improved significantly in those treated with HTS compared with those who received NSS and also at later treatment times (24 hours) than at earlier treatment times (3 hours). Decreased cellular infiltration in each group correlated with bladder recovery.

Conclusions

The increased effectiveness of later administration time of the more osmotically active and immunomodulatory substance (HTS) suggests that interaction with events occurring around 24 hours after injury is critical. These events may be related to the invasion of leukocytes peaking at 8–24 hours postinjury and/or the peak benefit time of subject rehydration.

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 attenuates TNF-alpha-induced NF-kappaB activation in pulmonary epithelial cells

Resuscitation with hypertonic saline (HTS) attenuates acute lung injury (ALI) and modulates postinjury hyperinflammation. TNF-alpha-stimulated pulmonary epithelium is a major contributor to hemorrhage-induced ALI. We hypothesized that HTS would inhibit TNF-alpha-induced nuclear factor (NF)-kappaB proinflammatory signaling in pulmonary epithelial cells. Therefore, we pretreated human pulmonary epithelial cells (A549) with hypertonic medium (180 mM NaCl) for 30 min, followed by TNF-alpha stimulation (10 ng/mL). Key regulatory steps and protein concentrations in this pathway were assessed for significant alterations. Hypertonic saline significantly reduced TNF-alpha-induced intercellular adhesion molecule 1 levels and NF-kappaB nuclear localization. The mechanism is attenuated phosphorylation and delayed degradation of IkappaB alpha. Hypertonic saline did not alter TNF-alpha-induced p38 mitogen-activated protein kinase phosphorylation or constitutive vascular endothelial growth factor expression, suggesting that the observed inhibition is not a generalized suppression of protein phosphorylation or cellular function. These results show that HTS inhibits TNF-alpha-induced NF-kappaB activation in the pulmonary epithelium and, further, our understanding of its beneficial effects in hemorrhage-induced ALI.

Antinociception by neutrophil-derived opioid peptides in noninflamed tissue--role of hypertonicity and the perineurium

Inflammatory pain can be controlled by intraplantar opioid injection or by secretion of endogenous opioid peptides from leukocytes in inflamed rat paws. Antinociception requires binding of opioid peptides to opioid receptors on peripheral sensory nerve terminals. In the absence of inflammation, hydrophilic opioid peptides do not penetrate the perineurial barrier and, thus, do not elicit antinociception. This study was designed to examine the conditions under which endogenous, neutrophil-derived hydrophilic opioid peptides (i.e. Met-Enkephalin and beta-endorphin) can raise nociceptive thresholds in noninflamed tissue in rats. Intraplantar injection of the chemokine CXCL2/3 (macrophage inflammatory protein-2) induced selective neutrophil recruitment without overt signs of inflammation or changes in mechanical nociceptive thresholds (paw pressure threshold). Following intraplantar injection of hypertonic saline, the perineurial barrier was permeable for hours and intraplantar injection of opioid peptides increased mechanical nociceptive thresholds. While formyl-Met-Leu-Phe (fMLP) triggered opioid peptide release from neutrophils in vitro, nociceptive thresholds were unchanged in vivo. In vitro, hypertonicity interfered with fMLP-induced p38 mitogen activated kinase (MAPK) phosphorylation and opioid peptide release from neutrophils. These inhibitory effects were fully reversible by washout. In vivo, return to normotonicity occurred within 30min while the perineurium remained permeable for hours. Under these conditions, fMLP triggered MAPK phosphorylation and induced opioid peptide-mediated increases in nociceptive thresholds in the noninflamed paw. Taken together, antinociception mediated by endogenous opioids in noninflamed tissue has two important requirements: (i) opening of the perineurial barrier for opioid peptide access and (ii) opioid peptide release from neutrophils involving p38 MAPK.

Hypertonic saline reduces skeletal muscle injury and associated remote organ injury following ischemia reperfusion injury

BACKGROUND AND PURPOSE

Pharmacological modulation of skeletal muscle reperfusion injury after traumaassociated ischemia may improve limb salvage rates and prevent the associated systemic sequelae. Resuscitation with hypertonic saline restores the circulating volume and has favorable effects on tissue perfusion and blood pressure. We evaluated the effects of treatment with a bolus of hypertonic saline on skeletal muscle ischemia reperfusion (IR) injury and the associated end-organ injury.

METHODS

Adult male Sprague-Dawley rats (n = 27) were randomized into 3 groups: (1) a control group, (2) an IR group treated with normal saline, and (3) an IR group treated with hypertonic saline. Bilateral hindlimb ischemia was induced by application of a rubber band proximal to the level of the greater trochanters for 2.5 h. The treatment groups received either normal saline (4 mL/kg) or hypertonic saline (4 mL/kg) prior to tourniquet release. Following 12 h of reperfusion, the tibialis anterior muscle was dissected and muscle function was assessed electrophysiologically. The animals were then killed, and skeletal muscle and lung tissue were harvested for evaluation.

RESULTS

Hypertonic saline significantly attenuated skeletal muscle reperfusion injury, as shown by reduced myeloperoxidase content, wet-to-dry ratio, and electrical properties of skeletal muscle. There was a corresponding reduction in lung injury, as demonstrated by reduced myeloperoxidase content and reduced wet-to-dry ratio.

INTERPRETATION

Treatment with hypertonic saline attenuates skeletal muscle ischemia reperfusion injury and its associated systemic sequelae.

Effects of the dual endothelin receptor antagonist tezosentan and hypertonic saline/dextran on porcine endotoxin shock

AIM

To evaluate the haemodynamic effects of the dual endothelin receptor antagonist tezosentan, both alone and combined with hypertonic saline/dextran (HSD), on porcine endotoxin shock, with focus on cardiopulmonary circulation. The effects on gas exchange and short-term survival were also studied.

METHODS

A prospective, randomized experimental study was carried out. Thirty-two anaesthetized pigs underwent pulmonary and carotid artery catheterization. Following haemodynamic stabilization and baseline measurements, endotoxaemia was induced by an Escherichia coli-endotoxin infusion over 180 min and the animals observed another 120 min. After 60 min of endotoxaemia, directly before intervention, animals were randomized into four groups: a tezosentan group, an HSD group, a combined tezosentan/HSD group and a control group. The consequent haemodynamic effects and blood gas results were recorded.

RESULTS

The endotoxin infusion reduced mean arterial blood pressure from 111 +/- 14 (mean +/- standard deviation) to 77 +/- 27 mmHg and cardiac index from 126.9 +/- 27.2 to 109.3 +/- 22.6 mL min(-1) kg(-1) within 90 min in the control group. In addition, endotoxin simultaneously increased mean pulmonary artery pressure from 24 +/- 17 to 38 +/- 19 mmHg and reduced arterial oxygenation from 18.9 +/- 2.0 to 12.2 +/- 5.3 kPa. Tezosentan, alone and combined with HSD, reversed the pulmonary hypertension and prevented the reduction in cardiac index and arterial oxygenation, resulting in reduced metabolic acidosis. Additionally, in the tezosentan group, the mean arterial blood pressure was reduced to the same level as in controls, an effect not prevented by the addition of HSD. It was found that all three interventions improved survival rates.

CONCLUSION

Tezosentan, alone and in combination with HSD, improved cardiac index and arterial oxygenation. The addition of HSD to tezosentan treatment did not improve the endotoxin-induced hypotension, but beneficial effects on microcirculation and systemic oxygenation were seen despite low perfusion pressure, as indicated by increased SvO(2) and reduced metabolic acidosis.

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.

Infusion of Hypertonic Saline (7.5%) Does Not Change Neutrophil Oxidative Burst or Expression of Endothelial Adhesion Molecules After Abdominal Hysterectomy

BACKGROUND

Previous studies found hypertonicity to affect neutrophils in intact laboratory animals and in human blood cell cultures. We investigated whether infusion of hypertonic saline in a clinical relevant dose before hysterectomy affected peripheral blood neutrophils and their response to surgery.

METHODS

Fifteen women scheduled for open abdominal hysterectomy were randomized double-blindly to infusion of 4 mL/kg 7.5% NaCl, 4 mL/kg 0.9% NaCl, or 32 mL/kg 0.9% NaCl over 20 minutes. Blood was collected at baseline, after infusion, 1, 4, and 24 hours postoperatively for the determination of leukocyte and differential count, neutrophil membrane expression of endothelial adhesion molecules by flow cytometry, and O2- -generation by superoxide dismutase-inhibitable reduction of cytochrome C.

RESULTS

Surgery induced well-known changes in the number and distribution of white blood cells, reduced the expression of adhesion molecules, and halved the superoxide production unrelated to the tonicity or volume of the infused fluids.

CONCLUSION

Infusion of a clinically relevant dose of hypertonic saline has no detectable effect on the membrane expression of endothelial adhesion molecules or O2- -generation in circulating neutrophils after elective abdominal hysterectomy.

Beneficial effects of hypertonic saline/dextran on early survival in porcine endotoxin shock

BACKGROUND

Hypertonic saline/dextran (HSD) has been shown to have beneficial effects in haemorrhagic shock. These effects, with improved haemodynamics and organ perfusion, would in theory also be of benefit in septic shock. However, this is less studied. We have therefore further evaluated the effect of additional treatment with HSD in a porcine endotoxin shock model.

METHODS

Sixteen anaesthetized pigs were used. A continuous infusion of endotoxin (LPS EC) was increased stepwise during 30 min to a rate of 5 microg/kg/h. The infusion was discontinued after 3 h and the animals were observed for another 2 h. The animals received continuous basal fluid resuscitation with isotonic Ringer's glucose 2.5% at a rate of 20 ml/kg/h throughout the experiment. After 1 h of endotoxin infusion, the animals were randomized to additional treatment with HSD, 4 ml/kg over 5 min, or the same volume of isotonic saline. Every 30 min, haemodynamics and mixed venous saturation (SvO2) were measured via a pulmonary artery catheter. Regional blood flow rates were measured continuously by perivascular ultrasonic flow probes. The metabolic response was measured by arterial blood gas analysis.

RESULTS

The endotoxin put all animals into a progressive hypodynamic circulatory shock during the experiment. Treatment with HSD improved survival rate to 8/8 compared with controls 3/8. There was a transient circulatory recovery with improved central and regional haemodynamics, accompanied by stabilized metabolic response.

CONCLUSION

Treatment with additional HSD improves survival in an early phase of endotoxin shock. Generally improved haemodynamics and oxygenation of peripheral tissues are suggested as possible mechanisms.

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.

Small volume hypertonic resuscitation of circulatory shock

Small volume hypertonic resuscitation is a relatively new conceptual approach to shock therapy. It was originally based on the idea that a relatively large blood volume expansion could be obtained by administering a relatively small volume of fluid, taking advantage of osmosis. It was soon realized that the physiological vasodilator property of hypertonicity was a useful byproduct of small volume resuscitation in that it induced reperfusion of previously ischemic territories, even though such an effect encroached upon the malefic effects of the ischemia-reperfusion process. Subsequent research disclosed a number of previously unsuspected properties of hypertonic resuscitation, amongst them the correction of endothelial and red cell edema with significant consequences in terms of capillary blood flow. A whole set of actions of hypertonicity upon the immune system are being gradually uncovered, but the full implication of these observations with regard to the clinical scenario are still under study. Small volume resuscitation for shock is in current clinical use in some parts of the world, in spite of objections raised concerning its safety under conditions of uncontrolled bleeding. These objections stem mainly from experimental studies, but there are few signs that they may be of real clinical significance. This review attempts to cover the earlier and the more recent developments in this field.

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.

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.

The Abdominal Compartment Syndrome as a Second Insult During Systemic Neutrophil Priming Provokes Multiple Organ Injury

In our recent clinical study of damage control laparotomy, the abdominal compartment syndrome (ACS) emerged as an independent risk factor for postinjury multiple organ failure (MOF). We and others have shown previously that the ACS promotes the systemic production of proinflammatory cytokines. Our study objective was to develop a clinically relevant two-event animal model of postinjury MOF using the ACS as a second insult during systemic neutrophil priming to provoke organ dysfunction. Male adult rats underwent hemorrhagic shock (30 mmHg x 45 min) and were resuscitated with crystalloids and shed blood. The timing of postshock systemic neutrophil (PMN) priming was determined by the surface expression of CD11b via flow cytometry. Finding maximal PMN priming at 8 h, but no priming at 2 h (early) and 18 h (late), the ACS (25 mmHg x 60 min) was introduced at these time points. At 24 h postshock, lung injury was assessed by lung elastase concentration and Evans blue dye extravasation in bronchoalveolar lavage. Liver and renal injuries were determined by serum alanine aminotransferase, serum creatinine, and blood urea nitrogen. The ACS during the time of maximal systemic PMN priming (8 h) provoked lung and liver injury, but did not if introduced at 2 or 18 h postshock when there was no evidence of systemic PMN priming. The 24-h mortality of this two-event model was 33%. These findings corroborate the potential for the ACS to promote multiple organ injury when occurring at the time of systemic PMN priming. This clinically relevant two-event animal model of PMN organ injury may be useful in elucidating therapy strategies to prevent postinjury MOF.

Hypertonic saline enhances host response to bacterial challenge by augmenting receptor-independent neutrophil intracellular superoxide formation

OBJECTIVE

This study sought to determine whether hypertonic saline (HTS) infusion modulates the host response to bacterial challenge.

METHODS

Sepsis was induced in 30 Balb-C mice by intraperitoneal injection of Escherichia coli (5 x 107 organisms per animal). In 10 mice, resuscitation was performed at 0 and 24 hours with a 4 mL/kg bolus of HTS (7.5% NaCl), 10 animals received 4 mL/kg of normal saline (0.9% NaCl), and the remaining animals received 30 mL/kg of normal saline. Samples of blood, spleen, and lung were cultured at 8 and 36 hours. Polymorphonucleocytes were incubated in isotonic or hypertonic medium before culture with E. coli. Phagocytosis was assessed by flow cytometry, whereas intracellular bacterial killing was measured after inhibition of phagocytosis with cytochalasin B. Intracellular formation of free radicals was assessed by the molecular probe CM-H(2)DCFDA. Mitogen-activated protein (MAP) kinase p38 and ERK-1 phosphorylation, and nuclear factor kappa B (NFkappaB) activation were determined. Data are represented as means (SEM), and an analysis of variance test was performed to gauge statistical significance.

RESULTS

Significantly reduced bacterial culture was observed in the animals resuscitated with HTS when compared with their NS counterparts, in blood (51.8 +/- 4.3 vs. 82.0 +/- 3.3 and 78.4 +/- 4.8, P = 0.005), lung (40.0 +/- 4.1 vs. 93.2 +/- 2.1 and 80.9 +/- 4.7, P = 0.002), and spleen (56.4 +/- 3.8 vs. 85.4 +/- 4.2 and 90.1 +/- 5.9, P = 0.05). Intracellular killing of bacteria increased markedly (P = 0.026) and superoxide generation was enhanced upon exposure to HTS (775.78 +/- 23.6 vs. 696.57 +/- 42.2, P = 0.017) despite inhibition of MAP kinase and NFkappaB activation.

CONCLUSIONS

HTS significantly enhances intracellular killing of bacteria while attenuating receptor-mediated activation of proinflammatory cascades.

Effects of crystalloid and colloid resuscitation on hemorrhage-induced vascular hyporesponsiveness to norepinephrine in the rat

BACKGROUND

We have shown previously that hemorrhagic hypotension is associated with a progressive development of vascular hyporeactivity to norepinephrine (NE). The present study investigated whether select crystalloid or colloid resuscitation fluids would ameliorate this effect.

METHOD

Anesthetized male rats were hemorrhaged to and maintained at a mean arterial pressure (MAP) of 50 mm Hg for 60 minutes. Rats (n = 7 per group) were then resuscitated with lactated Ringer's (LR), 7.5% hypertonic saline (HS) for 1 hour followed by LR (HS-LR), Hespan, or Hextend to restore and maintain MAP to 70 mm Hg over 4 hours. Additional hemorrhaged groups were resuscitated with LR to the baseline MAP (LR-BL) or received no resuscitation. A sham hemorrhage group served as controls. The responses of MAP and the blood flow of the superior mesenteric, celiac, left renal, and left femoral arteries to NE (3 microg/kg administered intravenously) were measured at BL (prehemorrhage); at the end of the hypotensive period; and at 1, 2, and 4 hours after resuscitation.

RESULTS

Hemorrhagic hypotension significantly (p < 0.01) reduced the NE-induced pressor response in MAP and significantly reduced the contractile responses (reflected by the reduction of blood flow after NE administration) of the four arteries to NE. Hespan and Hextend infusion improved the NE response of MAP and the contractile responses of the observed arteries to NE significantly better than LR, HS-LR, or LR-BL. The colloids improved the vascular contractile responses to NE in the superior mesenteric and left femoral arteries and the pressor response of MAP to NE, to 80% to 90% of their basal response level compared with 40% to 60% with the crystalloid fluids (p < 0.05). LR-BL infusion resulted in hemodilution, with no added benefit to vascular responsiveness.

CONCLUSION

These data suggest that hypotensive resuscitation to 70 mm Hg with colloids was better than crystalloids in improving vascular responsiveness to the pressor effects of NE and required smaller volumes. Normotensive resuscitation with LR was not better than hypotensive resuscitation. Not all vasculatures improved equally after fluid resuscitation.

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.

Amelioration of ischemia- and reperfusion-induced myocardial injury by the selective estrogen receptor modulator, raloxifene, in the canine heart

OBJECTIVES

We sought to investigate whether raloxifene reduces ischemia-reperfusion injury and what mechanisms are involved in the cardioprotective effects.

BACKGROUND

Estradiol-17-beta reduces myocardial infarct size in ischemia-reperfusion injury. Raloxifene, a selective estrogen receptor modulator, demonstrates immediate coronary artery vasorelaxing effects.

METHODS

The myocardial ischemia-reperfusion model included anesthetized open-chest dogs after 90-min occlusion of the left anterior descending coronary artery (LAD) and subsequent 6-h reperfusion. Raloxifene and/or other drugs were infused into the LAD from 10 min before coronary occlusion to 1 h after reperfusion without an occlusion period.

RESULTS

Infarct size was reduced in the raloxifene (5 microg/kg per min) group compared with the control group (7.2 +/- 2.5% vs. 40.9 +/- 3.9% of the area at risk, p < 0.01). Either N(G)-nitro-L-arginine methyl ester (L-NAME), the inhibitor of nitric oxide (NO) synthase, or charybdotoxin, the blocker of Ca(2+)-activated K+ (K(Ca)) channels, partially attenuated the infarct size-limiting effect, and both of them completely abolished the effect. The incidence of ventricular fibrillation was also less in the raloxifene group than in the control group (11% vs. 44%, p < 0.05). Activity of p38 mitogen-activated protein (MAP) kinase increased with 15-min ischemia, and raloxifene pretreatment inhibited the activity. Myeloperoxidase activity of the 6-h reperfused myocardium was also attenuated by raloxifene.

CONCLUSIONS

These data demonstrate that raloxifene reduces myocardial ischemia-reperfusion injury by mechanisms dependent on NO and the opening of K(Ca) channels in canine hearts. Deactivation of p38 MAP kinase and myeloperoxidase by raloxifene may be involved in the cellular mechanisms of cardioprotection.

Bacterial translocation: clinical implications and prevention

The occurrence of BT has been well documented in experimental animal models of hemorrhagic shock, trauma, severe burns, cirrhosis, pancreatitis, and bacterial overgrowth. Translocation of viable bacteria and endotoxins into mesenteric lymph nodes and other gut-associated lymphatic tissue is thought to activate a complex interplay of mediators that initiates the SIRS. Multiple humoral and cellular systems cause synthesis, expression, and release of inflammatory mediators, such as toxic oxygen radicals, proteolytic enzymes, adherence molecules, and various cytokines. A massive sustained proinflammatory response can ultimately result in irreversible multiple organ dysfunction. Because BT is associated with splanchnic hypoperfusion, the cornerstone of therapy involves rapid resuscitation and restoration of tissue perfusion. If a septic focus can be identified, it should be removed. Gut protectants, promotility agents, antioxidants, and immune-enhancing diets have shown promise in improving length of survival in these critically ill patients.

Effect of medium tonicity and dextran on neutrophil function in vitro

BACKGROUND

Multiple investigations have demonstrated that hypertonic saline (HS) diminishes the response of polymorphonuclear leukocytes (PMNs) to stimulation. Recent meta-analysis suggests that hypertonic saline in dextran (HSD) is clinically superior to HS. No work to date has examined the effect of added dextran on this immunomodulatory property.

METHODS

Human PMNs were exposed to media of varying osmolarity (220-360 mOsm/L) and stimulated with f-met-leu-phe with or without dextran present in the medium. Cell volume, respiratory burst, PMN aggregation, and beta(2)-integrin (CD18) expression were measured.

RESULTS

Stimulation with f-met-leu-phe increased cell volume, respiratory burst, aggregation, and CD18 expression. The increases in cell volume, respiratory burst, and aggregation were significantly attenuated by exposure to hypertonic medium. The addition of dextran to the media did not change the results.

CONCLUSION

The alterations in PMN function associated with HS are not changed or attenuated by the addition of dextran, suggesting that the clinically superior HSD may have effects similar to HS in mitigating the tissue damage associated with activated PMNs.

Hypertonic preconditioning inhibits macrophage responsiveness to endotoxin

Hypertonic saline has been shown to modulate cell shape and the response of components of the innate immune response. However, the effect of hypertonic saline on the macrophage remains unknown. We hypothesized that hypertonic preconditioning would impair subsequent inflammatory mediator signaling through a reduction in stress fiber polymerization and mitogen-activated protein kinase activity after LPS stimulation. Rabbit alveolar macrophages were stimulated with 100 ng/ml of LPS. Selected cells were preconditioned with 40-100 mM of NaCl, mannitol, or urea for 4 h and returned to isotonic medium before LPS stimulation. Cellular protein was harvested and subjected to Western blot analysis for the dually phosphorylated active forms of p38 and extracellular signal-related kinase (ERK) 1/2. TNF production was determined by an L929 bioassay, and stress fiber polymerization was evaluated by confocal microscopy. Preconditioning of macrophages with NaCl or mannitol resulted in dose-dependent reduction in ERK 1/2 phosphorylation with no effect on p38 phosphorylation. Urea preconditioning had no effect on either mitogen-activated protein kinase. A dose-dependent attenuation of TNF production was seen with NaCl and mannitol preconditioning (p < 0.05), but not with urea. NaCl and mannitol preconditioning resulted in failure of LPS-induced stress fiber polymerization, whereas urea did not. Extracellular hypertonic conditions (i.e., NaCl and mannitol) have an immunomodulatory effect on macrophages, demonstrated through failure of optimal stress fiber polymerization, ERK 1/2 activity, and TNF production. Intracellular hypertonic conditions (i.e., urea) had no significant effect. Hypertonic saline or mannitol resuscitation, therefore, may help protect against multiple-organ dysfunction syndrome as a result of this reduced proinflammatory responsiveness.

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.

Hypertonic saline attenuation of the neutrophil cytotoxic response is reversed upon restoration of normotonicity and reestablished by repeated hypertonic challenge

BACKGROUND

Hypertonic saline (HTS) resuscitation, in addition to enhancing hemodynamic recovery, modulates postinjury hyperinflammation in the critically injured. The polymorphonuclear neutrophil (PMN) cytotoxic response, a key element in the pathogenesis of postinjury organ dysfunction, is attenuated under hypertonic conditions. Although plasma Na(+) rises to 180 mmol/L after HTS infusion, baseline levels are reestablished within 24 hours. We hypothesized that HTS attenuation of the PMN cytotoxic response (beta2-integrin expression, elastase release, and O2- production) is reversed upon return to normotonicity, but can be reestablished by repeated HTS challenge.

METHODS

Isolated human PMNs were incubated in HTS (Na(+) = 180 mmol/L) for 5 minutes at 37 degrees C then returned to normotonicity by centrifugation and resuspension in isotonic buffer. Stimulated (PAF) beta2-integrin expression was measured by flow cytometry. Stimulated (PAF/fMLP) elastase release and O2- production were measured by cleavage of N-methoxysuccinyl-Ala-Ala-Pro-Val p-nitroanilide and reduction of cytochrome c (Cyt c). Protein tyrosine phosphorylation in PMN cell lysates was assessed by Western blot.

RESULTS

Clinically relevant levels of HTS induced tyrosine phosphorylation in resting PMNs and attenuated cytotoxic responses. Reestablishment of normotonicity returned these functions to baseline. A repeated HTS challenge after restoration of normotonicity also induced tyrosine phosphorylation and suppressed the cytotoxic response.

CONCLUSIONS

HTS attenuation of the PMN cytotoxic response is reversible but can be reestablished by repeated HTS treatment. This phenomenon may provide the unique opportunity to selectively and temporarily decrease the postinjury inflammatory response when patients are at greatest risk for PMN-mediated tissue damage.

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

BACKGROUND

Recognition that hypertonic saline (HTS) modulates the inflammatory response has renewed interest in this agent for postinjury resuscitation. Changes in extracellular tonicity alter cell shape and are accompanied by cytoskeletal reorganization. Recent evidence suggests that cytoskeletal reorganization is critical for receptor-mediated signal transduction. We hypothesized that HTS-induced changes in the cytoskeleton interfere with cytotoxic signal transduction.

METHODS

Isolated neutrophils (PMNs) were incubated in HTS (Na+ = 180 mmol/L) and activated with N-formyl-methionyl-leucyl-phenylalanine (receptor-mediated) or phorbol myristate (receptor independent). Actin polymerization was assessed by digital image microscopy and flow cytometry. PMN superoxide anion (O2-) production and p38 MAPK activation was measured by reduction of cytochrome c and Western blot. Pretreatment with cytochalasin B was used to disrupt HTS-induced actin reorganization.

RESULTS

HTS inhibited receptor-mediated cytoskeletal reorganization and attenuated p38 MAPK activation and O2- production. HTS had no effect on receptor-independent O2- production. Cytoskeletal disruption (cytochalasin B) prevented HTS attenuation of receptor-mediated p38 MAPK activation.

CONCLUSION

HTS attenuates the PMN cytotoxic response by interfering with intracellular signal transduction. Changes in the actin cytoskeleton appear to modulate receptor-mediated p38 MAPK signaling.