Hypertonic saline activates protein tyrosine kinases and mitogen-activated protein kinase p38 in T-cells

Hyperosmotic Stress Induces Inflammation and Excessive Th17 Response to Blunt T-Cell Immunity in Tilapia

Despite the advances in study on osmotic physiology in bony fish, the mechanism by which the immune system, especially T-cell immunity, adapts and responds to osmotic stress remains unknown. In the current study, we investigated the response of T cells to hyperosmotic stress in the bony fish Nile tilapia (Oreochromis niloticus). As a euryhaline fish, tilapia was able to adapt to a wide range of salinities; however, hypertonic stress caused inflammation and excessive T-cell activation. Furthermore, hypertonic stress increased the expression of IL-17A in T cells, upregulated the transcription factor RORα, and activated STAT3 signaling, along with IL-6- and TGF-β1-mediated pathways, revealing an enhanced Th17 response in this early vertebrate. These hypertonic stress-induced events collectively resulted in an impaired antibacterial immune response in tilapia. Hypertonic stress elevated the intracellular ROS level, which in turn activated the p38-MK2 signaling pathway to promote IL-17A production by T cells. Both ROS elimination and the p38-MK2 axis blockade diminished the increased IL-17A production in T cells under hypertonic conditions. Moreover, the produced proinflammatory cytokines further amplified the hypertonic stress signaling via the MKK6-p38-MK2 axis-mediated positive feedback loop. To our knowledge, these findings represent the first description of the mechanism by which T-cell immunity responds to hypertonic stress in early vertebrates, thus providing a novel perspective for understanding the adaptive evolution of T cells under environmental stress.

Effect of Hypertonic Saline Solution on the Ventilatory Mechanics of Lungs Donated After Brain Death

INTRODUCTION

Brain death (BD) compromises the viability of the lung for donation. Hypertonic saline solution (HSS) induces rapid intravascular volume expansion and immunomodulatory action. We investigated its role in ventilatory mechanics (VMs) and in the inflammatory activity of the lungs of rats subjected to BD.

METHODS

Wistar rats were divided into four groups: control, n = 10: intact rats subjected to extraction of the heart-lung block; BD, n = 8 (BD): rats treated with isotonic saline solution (4 mL/kg) immediately after BD; hypertonic saline 0 h, n = 9 (Hip.0'): rats treated with HSS (4 mL/kg) immediately after BD; and hypertonic saline 1 h, n = 9 (Hip.60'), rats treated with HSS (4 mL/kg) 60 min after BD. The hemodynamic characteristics, gas exchange, VMs, inflammatory mediators, and histopathological evaluation of the lung were evaluated over 240 min of BD.

RESULTS

In VMs, we observed increased airway resistance, tissue resistance, tissue elastance, and respiratory system compliance in the BD group (P < 0.037), while the treated groups showed no impairment over time (P > 0.05). In the histological analysis, the BD group showed a greater area of perivascular edema and a higher neutrophil count than the control group and the Hip.60' group (P < 0.05).

CONCLUSIONS

Treatment with HSS was effective in preventing changes in the elastic and resistive pulmonary components, keeping them at baseline levels. Late treatment reduced perivascular and neutrophilic edema in lung tissue.

A new immune disease: systemic hypertension

Systemic hypertension is the most common medical comorbidity affecting the adult population globally, with multiple associated outcomes including cerebrovascular diseases, cardiovascular diseases, vascular calcification, chronic kidney disease, metabolic syndrome and mortality. Despite advancements in the therapeutic field approximately one in every five adult patients with hypertension is classified as having treatment-resistant hypertension, indicating the need for studies to provide better understanding of the underlying pathophysiology and the need for more therapeutic targets. Recent pre-clinical studies have demonstrated the role of the innate and adaptive immune system including various cell types and cytokines in the pathophysiology of hypertension. Moreover, pre-clinical studies have indicated the potential beneficial effects of immunosuppressant medications in the control of hypertension. Nevertheless, it is unclear whether such pathophysiological mechanisms and therapeutic alternatives are applicable to human subjects, while this area of research is undoubtedly a rapidly growing field.

Genome-wide identification and expression analysis of mitogen-activated protein kinase (MAPK) genes in response to salinity stress in channel catfish (Ictalurus punctatus)

The mitogen-activated protein kinase (MAPK) gene family has been systematically described in several fish species, but less so in channel catfish (Ictalurus punctatus), which is an important global aquaculture species. In this study, 16 MAPK genes were identified in the channel catfish genome and classified into three subfamilies based on phylogenetic analysis, including six extracellular signal regulated kinase (ERK) genes, six p38-MAPK genes and four C-Jun N-terminal kinase (JNK) genes. All MAPK genes were distributed unevenly across 10 chromosomes, of which three (IpMAPK8, IpMAPK12 and IpMAPK14) underwent teleost-specific whole genome duplication during evolution. Gene expression profiles in channel catfish during salinity stress were analysed using transcriptome sequencing and qRT-PCR (quantitative reverse transcription PCR). Results from reads per kilobase million (RPKM) analysis showed IpMAPK13, IpMAPK14a and IpMAPK14b genes were differentially expressed when compared with other genes between treatment and control groups. Furthermore, three of these genes were validated by qRT-PCR, of which IpMAPK14a expression levels were significantly upregulated in treatment groups (high and low salinity) when compared with the control group, with the highest expression levels in the low salinity group (P < 0.05). Therefore, IpMAPK14a may have important response roles to salinity stress in channel catfish.

The impacts of oxygen and pentoxifylline in hypoxic condition

Introduction:Among major trauma patients in the emergency department, the leading cause of morbidity and mortality is a hemorrhagic shock. The low oxygen flow with hypovolemia in trauma patients is believed to play a significant role. Hence, oxygen supply is essential in severe trauma patients with massive hemorrhage. This study aimed to investigate the effect of oxygen supply in hypoxic condition and variable treatments such as pentoxifylline (PTX), glycerol, hypertonic saline (HTS), protease inhibitor, and dexamethasone (DEXA) in macrophage and T cells. Method:Nitric oxide synthase (iNOS) and macrophage migration inhibitory factor (MIF) were measured for macrophage. MIF, interleukin (IL)-2, and IL-8 were measured for T cells. T cell viability was measued by MTT assay. Results: Pentoxifylline decreased iNOS expression mostly followed by glycerol under hypoxia. Under the hyperoxia, PTX and other treatments decreased iNOS expressions in macrophage. MIF expression was lowered with PTX under hypoxia. PTX, glycerol, HTS, and protease inhibitor were effective under hyperoxia in macrophage. PTX increased T cell survival under hypoxia. Under the hyperoxia, IL-2 expressions were upregulated with PTX, glycerol, and HTS. PTX and other treatments were effective for IL-8. Our results indicate that the PTX and the other agents tested reversed the effects of stimulation of lipopolysaccharide, PGE2 in hypoxia or hypoxia. Conclusion:Our study demonstrated potential usefulness in improving immune systems during severe inflammatory conditions similar to septic shock possibly caused by massive hemorrhage.

Traumatic Brain Injury-A Review of Intravenous Fluid Therapy

This manuscript will review intravenous fluid therapy in traumatic brain injury. Both human and animal literature will be included. Basic treatment recommendations will also be discussed.

Sodium Chloride Aggravates Arthritis via Th17 Polarization

PURPOSE

Sodium chloride (NaCl) has been proposed as a driving factor in autoimmune diseases through the induction of pathogenic CD4⁺ T helper cells that produce interleukin-17 (Th17 cells). This study investigated the effects of NaCl on inflammatory arthritis in mice and humans.

MATERIALS AND METHODS

Collagen-induced arthritis (CIA) mice were fed a normal or high-salt diet ad libitum, and clinical and histologic features of arthritis were evaluated. The proportion of Th17 cells in the spleens of CIA mice fed a normal or high-salt diet was evaluated by flow cytometry, and the expression of IL-17 in joints and intestines was determined by immunohistochemical staining. We also analyzed the effect of NaCl on Th17 differentiation from peripheral blood monocytes of patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and evaluated the contents of sodium and IL-17 in the synovial fluid of RA and OA patients.

RESULTS

NaCl increased murine and human Th17 cell differentiation in a dose-dependent manner. Clinical and histological arthritis was more severe in the high-salt-fed CIA mice, compared to control CIA mice. The proportion of Th17 cells among splenocytes was higher in CIA mice fed a high-salt diet. Expression of synovial and intestinal IL-17 was also higher in high-salt-fed CIA mice. Comparison of synovial fluid between RA patients and OA patients revealed that Na⁺ and IL-17 were more abundant in RA synovial fluid.

CONCLUSION

This study suggests that NaCl can aggravate arthritis by affecting Th17 differentiation. Accordingly, limiting salt intake may be helpful for treating inflammatory arthritis, such as RA.

Chloride Content of Fluids Used for Large-Volume Resuscitation Is Associated With Reduced Survival

OBJECTIVE

We sought to investigate if the chloride content of fluids used in resuscitation was associated with short- and long-term outcomes.

DESIGN

We identified patients who received large-volume fluid resuscitation, defined as greater than 60 mL/kg over a 24-hour period. Chloride load was determined for each patient based on the chloride ion concentration of the fluids they received during large-volume fluid resuscitation multiplied by the volume of fluids. We compared the development of hyperchloremic acidosis, acute kidney injury, and survival among those with higher and lower chloride loads.

SETTING

University Medical Center.

PATIENTS

Patients admitted to ICUs from 2000 to 2008.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 4,710 patients receiving large-volume fluid resuscitation, hyperchloremic acidosis was documented in 523 (11%). Crude rates of hyperchloremic acidosis, acute kidney injury, and hospital mortality all increased significantly as chloride load increased (p < 0.001). However, chloride load was no longer associated with hyperchloremic acidosis or acute kidney injury after controlling for total fluids, age, and baseline severity. Conversely, each 100 mEq increase in chloride load was associated with a 5.5% increase in the hazard of death even after controlling for total fluid volume, age, and severity (p = 0.0015) over 1 year.

CONCLUSIONS

Chloride load is associated with significant adverse effects on survival out to 1 year even after controlling for total fluid load, age, and baseline severity of illness. However, the relationship between chloride load and development of hyperchloremic acidosis or acute kidney injury is less clear, and further research is needed to elucidate the mechanisms underlying the adverse effects of chloride load on survival.

Elementary immunology: Na+ as a regulator of immunity

The skin can serve as an interstitial Na+ reservoir. Local tissue Na+ accumulation increases with age, inflammation and infection. This increased local Na+ availability favors pro-inflammatory immune cell function and dampens their anti-inflammatory capacity. In this review, we summarize available data on how NaCl affects various immune cells. We particularly focus on how salt promotes pro-inflammatory macrophage and T cell function and simultaneously curtails their regulatory and anti-inflammatory potential. Overall, these findings demonstrate that local Na+ availability is a promising novel regulator of immunity. Hence, the modulation of tissue Na+ levels bears broad therapeutic potential: increasing local Na+ availability may help in treating infections, while lowering tissue Na+ levels may be used to treat, for example, autoimmune and cardiovascular diseases.

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

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

Implications of dietary salt intake for multiple sclerosis pathogenesis

In recent years it has become increasingly clear that, alongside genetic risk factors, environmental factors strongly influence the incidence and severity of multiple sclerosis (MS). Based on observations from epidemiological studies, the potential contribution of dietary habits has lately been a matter of debate. Recently it was shown that high salt conditions promote pathogenic T-cell responses and aggravate autoimmunity in an animal model of MS, suggesting that high dietary salt intake might promote central nervous system (CNS) autoimmunity. However, so far, not much is known about the influence of dietary salt intake on MS disease pathology. Here, we discuss the association of dietary salt levels and MS with a special focus on the mechanisms of salt-mediated modulation of the different cell types critically involved in the pathophysiology of MS.

Hypertonic saline reduces vascular leakage in a mouse model of severe dengue

Dengue (DEN) is a mosquito-borne viral disease and represents a serious public health threat and an economical burden throughout the tropics. Dengue clinical manifestations range from mild acute febrile illness to severe DEN hemorrhagic fever/DEN shock syndrome (DHF/DSS). Currently, resuscitation with large volumes of isotonic fluid remains the gold standard of care for DEN patients who develop vascular leakage and shock. Here, we investigated the ability of small volume of hypertonic saline (HTS) suspensions to control vascular permeability in a mouse model of severe DEN associated with vascular leakage. Several HTS treatment regimens were considered and our results indicated that a single bolus of 7.5% NaCl at 4 mL per kg of body weight administered at the onset of detectable vascular leakage rapidly and significantly reduced vascular leak for several days after injection. This transient reduction of vascular leakage correlated with reduced intestine and liver damage with restoration of the hepatic functions, and resulted in delayed death of the infected animals. Mechanistically, we showed that HTS did not directly impact on the viral titers but resulted in lower immune cells counts and decreased systemic levels of soluble mediators involved in vascular permeability. In addition, we demonstrated that neutrophils do not play a critical role in DEN-associated vascular leakage and that the therapeutic effect of HTS is not mediated by its impact on the neutrophil counts. Together our data indicate that HTS treatment can transiently but rapidly reduce dengue-associated vascular leakage, and support the findings of a recent clinical trial which evaluated the efficacy of a hypertonic suspension to impact on vascular permeability in DSS children.

A dormant state modulated by osmotic pressure controls clonogenicity of prostate cancer cells

Cell dormancy constitutes a limiting step of the metastatic process by preventing the proliferation of isolated cancer cells disseminated at distant sites from the primary tumor. The study of cancer cell dormancy is severely hampered by the lack of biological samples so that the mechanisms that regulate cell dormancy have not been extensively explored. In this work, we describe the rapid induction in vitro of a dormant state in prostate cancer cells by exposure to a slightly hypertonic growth medium. This quiescence is observed only when cells are seeded at low density and, once established, requires additional stimuli besides osmotic pressure to be reversed. Media conditioned by cells grown at high density can partially prevent or reverse dormancy, a phenomenon which can be reproduced with citric acid. In addition to this role of small metabolites, inactivation of the p53 and smad pathways also counters the entry into dormancy, whereas exposure to activin A induces it to some extent. Thus, this easily inducible dormancy reproduces several features associated with the dormancy of stem cells and cancer cells in vivo.

Use of hypertonic saline injection in trauma

PURPOSE

The use of hypertonic saline injection in trauma patients is discussed.

SUMMARY

Patients with hemorrhage, burns, and traumatic brain injury (TBI) may develop hypovolemic shock and require resuscitation. Compared with conventional isotonic crystalloids, hypertonic saline has several advantages, including hemodynamic, immune-modulating, and antiinflammatory effects, for use in trauma patients for resuscitation. In addition, hypertonic saline is also used in patients with TBI to reduce intracranial pressure (ICP). Overall, studies have not shown a difference in mortality or other clinically important outcomes with the use of hypertonic saline for resuscitation in trauma patients; however, most of these studies were not adequately powered to show significant differences. A recent Cochrane review concluded that there is no evidence that hypertonic crystalloids are better than isotonic or near-isotonic crystalloids for fluid resuscitation in trauma patients. Two recent trials that were adequately powered to investigate a mortality endpoint were halted for futility. A few small randomized controlled studies found that hypertonic saline was more effective than mannitol as a hyperosmolar agent for ICP reduction. Recent guidelines from the American Burn Association have suggested that hypertonic saline may be used for burn shock resuscitation by experienced providers with close monitoring to avoid excessive hypernatremia. One of the main concerns with the use of hypertonic saline is its potential to cause central pontine myelinolysis due to a rapid increase in serum sodium levels.

CONCLUSION

There is no evidence that hypertonic saline provides any additional benefit over isotonic crystalloid solutions for trauma resuscitation. Hypertonic saline may be more effective than mannitol at reducing ICP in patients with TBI.

Hypertonic saline resuscitation maintains a more balanced profile of T-lymphocyte subpopulations in a rat model of hemorrhagic shock

OBJECTIVE

To investigate the potential and early effect of hypertonic saline resuscitation on T-lymphocyte subpopulations in rats with hemorrhagic shock.

METHODS

A model of rat with severe hemorrhagic shock was established in 18 Sprague-Dawley (SD) rats. The rats were randomly divided into Sham group, HTS group (hypertonic saline resuscitation group) and NS group (normal saline resuscitation group). Each group contained 6 rats. The CD4(+) and CD8(+) subpopulations of T-lymphocytes in peripheral blood were detected respectively before shock and after resuscitation by double antibody labelling and flow cytometry.

RESULTS

In the early stage after hemorrhagic shock, fluid resuscitation and emergency treatment, the CD4(+) lymphocytes of peripheral blood in HTS and NS groups markedly increased. Small volume resuscitation with HTS also induced peripheral CD8(+) lymphocytes to a certain extent, whereas NS resuscitation showed no effect in this respect. Consequently, compared with Sham and HTS groups, CD4(+)/CD8(+) ratio of peripheral blood in NS group was obviously increased, and showed statistically differences.

CONCLUSION

In this model of rat with severe hemorrhagic shock, small volume resuscitation with HTS is more effective than NS in reducing immunologic disorders and promoting a more balanced profile of T-lymphocyte subpopulations regulating network.

Hypertonic saline dextran after burn injury decreases inflammatory cytokine responses to subsequent pneumonia-related sepsis

The present study examined the hypothesis that hypertonic saline dextran (HSD), given after an initial insult, attenuates exaggerated inflammation that occurs with a second insult. Adult rats (n = 15 per group) were divided into groups 1 (sham burn), 2 [40% total body surface area burn + 4 ml/kg isotonic saline (IS) + 4 ml.kg(-1).% burn(-1) lactated Ringer solution (LR)], and 3 (burn + 4 ml/kg HSD + LR), all studied 24 h after burns. Groups 4 (sham burn), 5 (burn + IS + LR), and 6 (burns + HSD + LR) received intratracheal (IT) vehicle 7 days after burns; groups 7 (burn + IS + LR) and 8 (burn + HSD + LR) received IT Streptococcus pneumoniae (4 x 10(6) colony-forming units) 7 days after burn. Groups 4-8 were studied 8 days after burn and 24 h after IT septic challenge. When compared with sham burn, contractile defects occurred 24 h after burn in IS-treated but not HSD-treated burns. Cardiac inflammatory responses (pg/ml TNF-alpha) were evident with IS (170 +/- 10) but not HSD (45 +/- 5) treatment vs. sham treatment (80 +/- 15). Pneumonia-related sepsis 8 days after IS-treated burns (group 7) exacerbated TNF-alpha responses/contractile dysfunction vs. IS-treated burns in the absence of sepsis (P < 0.05). Sepsis that occurred after HSD-treated burns (group 8) had less myocyte TNF-alpha secretion/better contractile function than IS-treated burns given septic challenge (group 7, P < 0.05). We conclude that an initial burn injury exacerbates myocardial inflammation/dysfunction occurring with a second insult; giving HSD after the initial insult attenuates myocardial inflammation/dysfunction associated with a second hit, suggesting that HSD reduces postinjury risk for infectious complications.

Clinical review: Acid-base abnormalities in the intensive care unit -- part II

Acid-base abnormalities are common in the critically ill. The traditional classification of acid-base abnormalities and a modern physico-chemical method of categorizing them will be explored. Specific disorders relating to mortality prediction in the intensive care unit are examined in detail. Lactic acidosis, base excess, and a strong ion gap are highlighted as markers for increased risk of death.

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.

Activation of Dendritic Cells and Induction of T Cell Responses by Hpv 16 L1/E7 Chimeric Virus-Like Particles are Enhanced by Cpg ODN or Sorbitol

Chimeric human papillomavirus-like particles, consisting of human papillomavirus (HPV) 16 L1-E7 fusion proteins [HPV 16 L1/E7 chimeric virus-like particles (CVLP)], are a vaccine candidate for treatment and prevention of cervical cancer. Although in preclinical studies CVLPs were shown to induce neutralizing antibodies and L1-and E7-specific T cell responses, the results of a recent clinical trial emphasized the need of improved immunogenicity of CVLPs. Here we studied the interaction of HPV 16 L1/E7 CVLPs with mouse bone marrow-derived dendritic cells (BMDCs) activated with different immune adjuvants. We found that lipopolysaccharides (LPS), unmethylated CpG motifs (CpG ODN) and sorbitol enhanced CVLP-induced stimulation of C57BL/6 mouse BMDCs as revealed by increased levels of CD40, CD80, MHC II and CD54 at the cell surface. CpG ODN and sorbitol also enhanced the presentation of Db-restricted cytotoxic T lymphocyte epitopes to HPV 16 L1- or E7-specific T lymphocytes after loading of CVLPs onto BMDCs. Treatment of BMDCs with CpG ODN in combination with CVLPs improved in vitro priming of naive T lymphocytes by CVLP-loaded BMDCs. In vivo, CVLP-loaded BMDCs were more immunogenic as compared with injection of CVLPs alone. CpG ODN and sorbitol further enhanced priming of antigen-specific T cell responses. Our data demonstrate that CpG ODN- or sorbitol-activated BMDCs substantially increase the immunogenicity of CVLPs. Implementing our results in clinical trial protocols may lead to improved activity of therapeutic HPV vaccines for the treatment of HPV-induced cancer.

Salt of the earth or a drop in the ocean? A pathophysiological approach to fluid resuscitation

The evolved endocrine response after injury leads to sodium, chloride, and water retention at a time when large volumes of sodium containing fluids are given to maintain the circulation and preserve tissue oxygenation. Sodium, chloride, and water are also retained because of increased systemic vascular permeability to plasma proteins, especially albumin, which sequesters fluid in the interstitial space and causes oedema. Excessive fluid and electrolyte retention and interstitial oedema are associated with the systemic inflammatory response syndrome and multiple organ dysfunction, and failure. This review attempts an overview of these processes and addresses the question, "Can manipulation of fluid resuscitation influence the inflammatory response to injury and organ function". Results of randomised controlled prospective clinical studies suggest that limiting the sodium and chloride input and optimal use of synthetic colloids, which are well retained in the vascular space, can reduce the inflammatory response to injury and improve organ function.

Activation of p38 plays a pivotal role in the inhibitory effect of lipopolysaccharide and interleukin-1 beta on long term potentiation in rat dentate gyrus

Lipopolysaccharide (LPS), a component of the cell wall of Gram-negative bacteria, has been shown to induce profound changes both peripherally and centrally. It has recently been reported that intraperitoneal injection of LPS inhibited long term potentiation (LTP) in perforant path-granule cell synapses and that this effect was coupled with an increase in the concentration of the proinflammatory cytokine, interleukin-1 beta (IL-1 beta). The LPS-induced effects were abrogated by inhibition of caspase-1, suggesting that IL-1 beta may mediate the effects of LPS. Here we report that the inhibition of LTP induced by LPS and IL-1 beta was coupled with stimulation of the stress-activated protein kinase p38 in hippocampus and entorhinal cortex and that this effect was abrogated by the p38 inhibitor SB203580, while the effect of LPS was markedly attenuated in C57BL/6 IL-1RI-/- mice. The data also indicate that activation of the transcription factor, nuclear factor kappa B (NF kappa B), may play a role, since the inhibitory effect of LPS and IL-1 beta on LTP was attenuated by the NF kappa B inhibitor, SN50; consistently, LPS and IL-1 beta led to activation of NF kappa B in entorhinal cortex. We suggest that one consequence of these LPS and IL-1 beta-induced changes is a compromise in glutamate release in dentate gyrus, which was coupled with the inhibition of LTP. The evidence is consistent with the idea that the LPS-induced impairment in LTP is mediated by IL-1 beta and is a consequence of activation of p38.

Hypertonic stress increases T cell interleukin-2 expression through a mechanism that involves ATP release, P2 receptor, and p38 MAPK activation

Hypertonic stress (HS) can alter the function of mammalian cells. We have reported that HS enhances differentiated responses of T cells by increasing their ability to produce interleukin (IL)-2, a finding of clinical interest because hypertonic infusions may modulate immune function in patients. HS shrinks cells and mechanically deforms membranes, which results in ATP release from many cell types. Here we investigate if ATP release is an underlying mechanism through which HS augments T cell function. We found that mechanical stress and HS induced rapid ATP release from Jurkat T cells. HS and exogenous ATP mobilized intracellular Ca(2+), activated p38 MAPK, and increased IL-2 expression. Ca(2+) mobilization was attenuated in the presence of EGTA or by removal of extracellular ATP with apyrase. Adenosine did not increase IL-2 expression, as did ATP. Apyrase, inhibition of P2 receptors, or inhibition of p38 MAPK with SB203580 reduced the stimulatory effects of HS, indicating that HS enhances IL-2 expression through a mechanism that involves ATP release, P2 (perhaps P2X7) receptors, and p38 MAPK activation. We conclude that release of and response to ATP plays a key role in the mechanism through which hypertonic stress regulates the function of T cells.

Reduced rate of bacterial translocation and improved variables of natural killer cell and T-cell activity in rats surviving controlled hemorrhagic shock and treated with hypertonic saline

OBJECTIVE

To examine the effect of hypertonic saline on bacterial translocation and the number and function of natural killer and T cells in controlled hemorrhagic shock.

DESIGN

Randomized controlled study. Duration of follow-up was 24 hrs.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats, weighing 310-390 g.

INTERVENTIONS

Controlled hemorrhagic shock was induced by blood withdrawal (mean arterial pressure, 30-40 mm Hg) and maintained for 30 mins. The animals were randomly divided into three groups: group 1 (n = 10) was sham-operated, group 2 (n = 10) was untreated, and group 3 was treated with 5 mL/kg hypertonic saline (n = 10). The rats were killed after 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Infusion of hypertonic saline in group 3 was followed by reduced bacterial translocation rate (5.0 +/- 2.2% vs. 18.3 +/- 5.3%, p <.033). The total mass of bacteria isolated from hypertonic saline-treated animals with bacterial translocation was 7.8- to 10.4-fold less than that from untreated rats. Controlled hemorrhagic shock resulted in a low percentage of CD4+ cells in blood (35.2 +/- 3.9%, p <.05) and lymph nodes (44.4 +/- 4.5%, p <.05) and depressed CD4 expression on blood (82 +/- 13 arbitrary units, p <.005) and lymph node (168 +/- 24 arbitrary units, p <.03) cells. A compensatory mobilization of NKR-P1+ cells from lymph nodes (8.6 +/- 2.3%, p <.05) to blood (21.2 +/- 5.2%, p <.01) with down-regulated NKR-P1 expression on blood cells (59 +/- 10 arbitrary units, p <.005) was observed. Natural killer cell-mediated cytotoxicity was decreased (67.9 +/- 9.7%, p <.05). Hypertonic saline treatment greatly stimulated CD4 expression on blood (419 +/- 113 arbitrary units, p <.005) and lymph node (553 +/- 115 arbitrary units, p <.03) cells. Also, normalization of NKR-P1 expression (160 +/- 19 arbitrary units, p <.005) and restoration of natural killer cell-mediated cytotoxicity to near normal values (88.6 +/- 7.4%, p <.05) were demonstrated.

CONCLUSION

Controlled hemorrhagic shock was accompanied by CD4+ cells suppression and excessive recruitment of natural killer cells with abnormally low NKR-P1 expression and suppressed cytolytic activity into circulation. Infusion of hypertonic saline reversed these changes and reduced bacterial translocation.

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.

Chronic exposure of human mesangial cells to high glucose environments activates the p38 MAPK pathway

BACKGROUND

High glucose (HG) environments activate several protein kinase pathways in mesangial cells, including the mitogen-activated protein kinase (MAPK) pathway, ERK. The p38 MAPK pathway is activated by events that occur in the setting of diabetes, such as protein kinase C (PKC) up-regulation and cellular stresses (osmotic stress and redox changes). Substrates of activated p38 MAPK include transcription factors that are involved in the microvascular complications of diabetes. This current study investigated the mechanisms of HG-mediated activation of p38 MAPK in cultured human mesangial cells (HMCs) and the effects of p38 MAPK activation on the transcription factor activator protein-1 (AP-1).

METHODS

HMCs were cultured in 5 mmol/L D-glucose [normal glucose (NG)] or 30 mmol/L D-glucose (HG) for seven days. Cells were also treated with HG for brief periods of time (0.5 to 4 hours) to assess the acute effects of HG on p38 MAPK. Using Western blotting of HMC lysates, changes in the tyrosine and threonine phosphorylation of p38 MAPK were measured. The kinase activity of immunoprecipitated p38 MAPK was determined by an in vitro assay that measured the phosphorylation and activation of MAPKAP kinase-2, an intermediary signaling protein downstream of p38 MAPK. To investigate the role of osmotic stress in HG activation of p38 MAPK, cells were acutely treated with mannitol (25 to 250 mOsm/L x 5 to 60 min) or were grown seven days in media supplemented with mannitol at concentrations iso-osmotic to HG media. To investigate the role of PKC in HG-mediated p38 MAPK activation, HMCs were treated with the PKC inhibitors GF 109203X, Ro 32-0432, or rottlerin during the last several hours of HG treatment. HG conditioned cells were also treated with the antioxidants L-N-acetylcysteine (L-NAC) or diphenyliodonium (DPI) prior to harvest. To determine a functional significance of HG-mediated p38 MAPK activation, the DNA binding of the transcription factor complex AP-1 was measured by electrophoretic mobility shift assay.

RESULTS

The p38 MAPK pathway was not activated by the acute addition of HG to the HMCs. However, activation of p38 MAPK in HMCs grown seven days in HG was demonstrated by increased tyrosine and threonine phosphorylation of p38 MAPK proteins and increased kinase activity of immunoprecipitated p38 MAPK. As assessed by a kinase assay, p38 MAPK activity in cells grown in HG for seven days exceeded that of NG cells by more than 250%. This difference was not due to differences in the amount of p38 MAPK protein between the treatment groups. Acute osmotic activation of p38 MAPK occurred at extremely high mannitol concentrations (250 mOsm/L) that exceeded the osmotic stress of acute HG. Furthermore, in cells grown for seven days in mannitol at concentrations similar to HG, p38 MAPK activity was similar to control values. Phorbol ester (PMA) treatment stimulated a twofold increase in p38 MAPK activity. The addition of GFX or Ro 32-0432 to HG cells, at concentrations that inhibited PMA activation of p38 MAPK, did not inhibit the glucose-mediated p38 MAPK activation. Rottlerin, a PKC delta inhibitor, also failed to reverse the HG-mediated p38 MAPK activation. Treatment of HG cells with L-NAC or DPI inhibited the HG-mediated p38 MAPK phosphorylation. As we have previously shown, DNA binding of the transcription factor complex AP-1 was increased in HG cells. This binding was reversed by treatment of the HG cells with the p38 MAPK inhibitor SB 203580.

CONCLUSIONS

Chronic exposure of HMC to HG concentrations activates the p38 MAPK pathway. This activation appears to be independent of changes in the amount of total p38 MAPK produced by the cells, independent of chronic osmotic stress and independent of PKC activation. The reversal of p38 MAPK by L-NAC and DPI suggests the glucose-mediated p38 MAPK activation may occur via reactive oxygen species. The activity of AP-1, a transcription factor complex that regulates several genes involved in diabetic nephropathy, is reversed when the p38 MAPK pathway is inhibited. These findings suggest the p38 MAPK pathway may be an important pathway involved in diabetic complications.

Hypertonicity rescues T cells from suppression by trauma-induced anti-inflammatory mediators

Trauma causes the release of anti-inflammatory factors thought to cause infections by inhibiting T cells. We have found that hypertonic saline (HS) enhances functions of normal T cells. Here we studied if HS can rescue T cells from suppression by costimulating interleukin (IL)-2 production. Human peripheral blood mononuclear cells were treated with the immunosuppressive factors IL-4, IL-10, transforming growth factor (TGF)-beta(1), and PGE(2) and with serum of trauma patients and stimulated with phytohemagglutinin, and IL-2 production was measured. Costimulation with HS tripled IL-2 production of normal cells. IL-4, IL-10, TGF-beta(1), and PGE(2) suppressed IL-2 production with IC(50) of 500, 1, 36,000, and 0.01 pg/ml, respectively. Costimulation of suppressed cells with HS restored IL-2 production and increased IC(50) values >70-fold. Serum from trauma patients could completely suppress normal cells; however, costimulation with HS restored IL-2 production by up to 80% of the control response. These findings show that HS can restore the function of suppressed T cells, suggesting that HS resuscitation of trauma patients could reduce posttraumatic sepsis.

Hypertonic saline-dextran suppresses burn-related cytokine secretion by cardiomyocytes

Whereas hypertonic saline-dextran (HSD, 7.5% NaCl in 6% D70) improves cardiac contractile function after burn trauma, the mechanisms of HSD-related cardioprotection remain unclear. We recently showed that cardiomyocytes secrete tumor necrosis factor-alpha (TNF-alpha), a response that was enhanced by burn trauma. This study addressed the question: does HSD modulate cardiac contraction/relaxation by altering cardiomyocyte TNF-alpha secretion? Wistar-Furth rats (325 g) were given a burn injury over 40% of the total body surface area and were then randomized to receive a bolus of either isotonic saline or HSD (4 ml/kg, n = 14 rats/group). Sham burn rats were given either isotonic saline or HSD (n = 14 rats/group) to provide appropriate controls for the two burn groups. Hearts were isolated 24 h postburn for either Langendorff perfusion (n = 8 hearts/group) or to prepare cardiomyocytes (n = 6 hearts/group). Myocytes were stimulated with lipopolysaccharide (LPS) (0, 10, 25, or 50 microg for 18 h) to measure cytokine secretion. Burn trauma increased myocyte TNF-alpha and interleukin-1 beta and -6 secretion, exacerbated cytokine response to LPS stimulus, and impaired cardiac contraction. HSD treatment of burns decreased cardiomyocyte cytokine secretion, decreased responsiveness to LPS challenge with regard to cytokine secretion, and improved ventricular function. These data suggest that HSD mediates cardioprotection after burn trauma, in part, by downregulating cardiomyocyte secretion of inflammatory cytokines.

Interleukin-1beta-dependent changes in the hippocampus following parenteral immunization with a whole cell pertussis vaccine

Neurological side effects are a major cause of concern following immunization with a number of vaccines, especially the whole cell pertussis vaccine (Pw). In this study we report that IL-1beta concentrations were significantly increased in the hippocampus following subcutaneous (s.c.) injection of Pw, and that this was accompanied by increased activity of the stress-activated kinase, c-Jun-N-terminal kinase (JNK) and a decrease in glutamate release. These effects were mimicked by s.c injection of active pertussis toxin (PT) or lipopolysaccharide (LPS). Incubation of hippocampal synaptosomes in the presence of Pw, PT or LPS also resulted in increased JNK activation and decreased glutamate release, effects which were mimicked by IL-1beta and blocked by the IL-1 receptor antagonist (IL-ra). Our observations are consistent with the hypothesis that IL-1beta induced by active bacterial toxins present in vaccine preparations, mediate the neurochemical and perhaps the neurological effects of Pw.

The inhibitory effect of interleukin-1beta on long-term potentiation is coupled with increased activity of stress-activated protein kinases

Long-term potentiation (LTP) in perforant path-granule cell synapses is decreased in aged rats, stressed rats, and rats injected intracerebroventricularly with the proinflammatory cytokine interleukin-1beta (IL-1beta). One factor that is common to these experimental conditions is an increase in the concentration of IL-1beta in the dentate gyrus, suggesting a causal relationship between the compromise in LTP and increased IL-1beta concentration. In this study, we have investigated the downstream consequences of an increase in IL-1beta concentration and report that the reduced LTP in rats injected intracerebroventricularly with IL-1beta was accompanied by a decrease in KCl-stimulated glutamate release in synaptosomes prepared from dentate gyrus, although unstimulated glutamate release was increased. These changes were paralleled by increased activity of the stress-activated kinases, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase. Intracerebroventricular injection of IL-1beta increased reactive oxygen species production in hippocampal tissue, whereas IL-1beta and H(2)O(2) increased activities of both JNK and p38 in vitro. Dietary manipulation with antioxidant vitamins E and C blocked the increase in reactive oxygen species production, the stimulation of JNK and p38 activity, the attenuation of glutamate release, and the IL-1beta-induced inhibitory of LTP. We propose that IL-1beta stimulates activity of stress-activated kinases, which in turn may inhibit glutamate release and result in compromised LTP and that these actions are a consequence of increased production of reactive oxygen species.

Use of hypertonic saline solutions in treatment of cerebral edema and intracranial hypertension

OBJECTIVES

To review the literature on the use of hypertonic saline (HS) in treating cerebral edema and intracranial hypertension.

DATA SOURCES

Review of scientific and clinical literature retrieved from a computerized MEDLINE search from January 1965 through November 1999.

STUDY SELECTION

Pertinent literature is referenced, including clinical and laboratory investigations, to demonstrate principles and efficacy of treatment with HS in patients with intracranial space-occupying pathology.

DATA EXTRACTION

The literature was reviewed to summarize the mechanisms of action, efficacy, adverse effects, systemic effects, and comparisons with standard treatments in both clinical and laboratory settings.

DATA SYNTHESIS

HS has an osmotic effect on the brain because of its high tonicity and ability to effectively remain outside the bloodbrain barrier. Numerous animal studies have suggested that fluid resuscitation with HS bolus after hemorrhagic shock prevents the intracranial pressure (ICP) increase that follows resuscitation with standard fluids. There may be a minimal benefit in restoring cerebral blood flow, which is thought to be mitigated through local effects of HS on cerebral microvasculature. In animal models with cerebral injury, the maximum benefit is observed in animals with focal injury associated with vasogenic edema (cryogenic injury). The ICP reduction is seen for < or =2 hrs and may be maintained for longer periods by using a continuous infusion of HS. The ICP reduction is thought to be caused by a reduction in water content in areas of the brain with intact blood-brain barrier such as the nonlesioned hemisphere and cerebellum. Most comparisons with mannitol suggest almost equal efficacy in reducing ICP, but there is a suggestion that mannitol may have a longer duration of action. Human studies published to date reporting on the use of HS in treating cerebral edema and elevated ICP include case reports, case series, and small controlled trials. Results from studies directly comparing HS with standard treatment in regard to safety and efficacy are inconclusive. However, the low frequency of side effects and a definite reduction of ICP observed with use of HS in these studies are very promising. Systemic effects include transient volume expansion, natriuresis, hemodilution, immunomodulation, and improved pulmonary gas exchange. Adverse effects include electrolyte abnormalities, cardiac failure, bleeding diathesis, and phlebitis. Although unproven, a potential for central pontine myelinolysis and rebound intracranial hypertension exists with uncontrolled administration.

CONCLUSIONS

HS demonstrates a favorable effect on both systemic hemodynamics and intracranial pressure in both laboratory and clinical settings. Preliminary evidence supports the need for controlled clinical trials evaluating its use as resuscitative fluid in brain-injured patients with hemorrhagic shock, as therapy for intracranial hypertension resistant to standard therapy, as firstline therapy for intracranial hypertension in certain intracranial pathologies, as small volume fluid resuscitation during spinal shock, and as maintenance intravenous fluid in neurocritical care units.

Age-related impairment in LTP is accompanied by enhanced activity of stress-activated protein kinases: analysis of underlying mechanisms

The age-related impairment in long-term potentiation in the rat dentate gyrus is coupled with an increase in the proinflammatory cytokine, interleukin-1beta (IL-1beta). It is possible that this increase in IL-1beta might be a consequence of the age-related increase in reactive oxygen species production in hippocampal tissue. In this study we set out to identify the underlying cause of the age-related increase in reactive oxygen species production and to establish whether any consequences of such a change might impact on the ability of aged rats to sustain long-term potentiation (LTP). We report that there was an age-related increase in the activity of superoxide dismutase but no parallel increases in activities of glutathione peroxidase or catalase, while age-related decreases in the concentration of the scavengers, vitamins E and C and glutathione were also observed. We propose that these compromises in antioxidative strategies may result in an increase in reactive oxygen species production. The data described indicate that IL-1beta and H2O2 increase the activity of two stress-activated mitogen-activated protein kinases, c-Jun NH2-terminal kinase (JNK) and p38 in vitro, while age-related increases in both kinases were observed. We propose that the endogenous increase in these parameters which occurs with age induces the increase in activity of the stress-activated kinases, which in turn impacts on the ability of the aged rat to sustain LTP.

Genetic evidence that stress-activated p38 MAP kinase is necessary but not sufficient for UV activation of HIV gene expression

We have examined the role of stress-activated p38 MAP kinase in regulating human immunodeficiency virus (HIV) gene expression in response to ultraviolet light (UV). We found that UV activated p38 in HeLa cells harboring stably integrated copies of an HIVcat plasmid to levels similar to those obtained by hyperosmotic shock. However, hyperosmotic shock resulted in one order of magnitude smaller increase in CAT activity than treatment with UV. The specific p38 inhibitor SB203580 significantly decreased (>80%) UV activation of HIV gene expression whereas PD98059, a specific MEK-1 inhibitor did not, suggesting that p38 is specifically involved in the HIV UV response and little to no contribution is provided by MEK-1 and the p42/p44 MAP kinase pathway. Whereas increased binding of NF-kappaB to an oligonucleotide spanning the HIV enhancer was observed after UV, as expected, this binding was not affected by SB203580. Furthermore, UV activation of HIV gene expression in cells having the cat reporter gene under control of an HIV promoter deleted of the enhancer (-69/+80) produced results indistinguishable from those using HIVcat/HeLa cells with an intact HIV promoter (-485/+80), suggesting that SB203580 acts through the basal transcription machinery. Northern blot analysis of steady-state RNA from HIVcat/HeLa cells revealed an almost complete inhibition of UV activation with SB203580 at the RNA level. Similarly, the UV response was almost completely obliterated at the CAT and RNA levels in HIVcat/HeLa cells stably transfected with a plasmid expressing a kinase-inactive mutant of p38 (isoform alpha), without affecting NF-kappaB activation, providing strong genetic evidence that p38, at least the alpha isoform, is necessary for UV activation of HIV gene expression and that NF-kappaB activation alone is insufficient. These results firmly establish p38 MAP kinase as a key modulator of HIV gene expression in response to UV that acts independently of NF-kappaB.

Splenic immune suppression in sepsis: A role for IL-10-induced changes in P38 MAPK signaling

BACKGROUND

Studies have indicated that following the induction of sepsis, there is a late (24 h) generalized suppression of the immune response which is associated with increased anti-inflammatory mediator release (e.g., IL-10). However, the mechanisms by which this occurs are unknown. In this regard, recent studies indicate that p38 mitogen-activated protein kinase (p38 MAPK) may play a central role in transducing the signals from immunosuppressive agents which in turn may alter lymphoid cytokine release. The aim of this study, therefore, was to determine whether the anti-inflammatory mediator IL-10 alters splenocyte IL-2 and IFN-gamma release, as well as the expression and activation of p38 MAPK in septic animals.

MATERIALS AND METHODS

Splenocytes (SPL) (or for some experiments purified T cells) were harvested from mice subjected 24 h earlier to either sepsis by cecal ligation and puncture (CLP) or Sham-CLP and stimulated with 2.5 microg concanavalin A (ConA)/ml in the presence or absence of either monoclonal antibody (Mab) to IL-10 (4 microg/ml) or IgG control. In subsequent studies, sepsis was induced in C57BL/6J and C57BL/6 IL-10 knockout mice, and SPL harvested and stimulated with ConA. SPL cytokine release was measured by ELISA, and the expression and phosphorylation of p38 MAPK were measured by Western analysis.

RESULTS

The results indicate that Th1 cytokine (IL-2, IFN-gamma) release was depressed by sepsis, while p38 MAPK expression and activity were increased in SPL as well as in T-cells. Neutralization of IL-10 by in vitro use of anti-IL-10 Mab and in the IL-10 knockout animal restored the Th1 response and caused a downregulation of p38 MAPK expression and activity after CLP. Thus, IL-10 appears to contribute to the increase in p38 MAPK activity and expression and the corresponding suppression of Th1 response seen in late sepsis.

Hypertonicity regulates the function of human neutrophils by modulating chemoattractant receptor signaling and activating mitogen-activated protein kinase p38

Excessive neutrophil activation causes posttraumatic complications, which may be reduced with hypertonic saline (HS) resuscitation. We tested if this is because of modulated neutrophil function by HS. Clinically relevant hypertonicity (10-25 mM) suppressed degranulation and superoxide formation in response to fMLP and blocked the activation of the mitogen activated protein kinases (MAPK) ERK1/2 and p38, but did not affect Ca2+ mobilization. HS did not suppress oxidative burst in response to phorbol myristate acetate (PMA). This indicates that HS suppresses neutrophil function by intercepting signal pathways upstream of or apart from PKC. HS activated p38 by itself and enhanced degranulation in response to PKC activation. This enhancement was reduced by inhibition of p38 with SB203580, suggesting that p38 up-regulation participates in HS-induced enhancements of degranulation. HS had similar effects on the degranulation of cells that were previously stimulated with fMLP, but had no effect on its own, suggesting that HS enhancement of degranulation requires another signal. We conclude that depending on other stimuli, HS can suppress neutrophil activation by intercepting multiple receptor signals or augment degranulation by enhancing p38 signaling. In patients HS resuscitation may reduce posttraumatic complications by preventing neutrophil activation via chemotactic factors released during reperfusion.

Hypertonic saline activates lipid-primed human neutrophils for enhanced elastase release

BACKGROUND

Ongoing clinical trials have revived interest in hypertonic saline (HTS) for postinjury resuscitation; these studies have documented serum Na+ concentrations > or = 170 mmol/L. Recent animal studies have shown that HTS enhances T-cell and monocyte function, but effects on the polymorphonuclear neutrophil (PMN) remain unclear. The postinjury lipid mediators platelet-activating factor (PAF) and leukotriene B4 (LTB4) have been implicated in PMN priming for cytotoxicity, which is believed to be important in the pathogenesis of multiple organ failure. We hypothesized that HTS would stimulate PMN superoxide (O2-) and elastase release from PAF- and LTB4-primed PMNs.

METHODS

Isolated PMNs from five donors were primed for 5 minutes with 200 nmol/L PAF or 1 micromol/L LTB4 in Kreb's-Ringer's phosphate with dextrose at a Na+ concentration of 140 mmol/L (normal serum Na+ concentration), pelleted, and resuspended in Kreb's-Ringer's phosphate with dextrose for 10 minutes at a Na+ concentration of 130 to 170 mmol/L. O2- generation was measured by superoxide dismutase-inhibitable reduction of cytochrome c and elastase release by cleavage of N-methoxysuccinyl-Ala-Ala-Pro-Val p-nitroanilide.

RESULTS

HTS with Na+ concentration up to 170 mmol/L had no significant effect on O2- production or elastase release from quiescent cells. Na+ concentration of 160 and 170 mmol/L, however, activated PAF- and LTB4-primed PMNs for enhanced elastase release with no effect on O2- production.

CONCLUSION

In clinically relevant concentrations, elevated Na+ activates lipid-primed neutrophils for enhanced elastase degranulation. Consequently, the administration of HTS in the early postinjury resuscitation period, when PMNs are maximally primed, may activate PMN elastase release and thereby promote the development of multiple organ failure.