Hypertonic saline activation of p38 MAPK primes the PMN respiratory burst

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.

Postinjury Inflammation and Organ Dysfunction

The development of organ dysfunction (OD) is related to the intensity and balance between trauma-induced simultaneous, opposite inflammatory responses. Early proinflammation via innate immune system activation may cause early OD, whereas antiinflammation, via inhibition of the adaptive immune system and apoptosis, may induce immunoparalysis, impaired healing, infections, and late OD. Patients discharged with low-level OD may develop the persistent inflammation-immunosuppression catabolism syndrome. Although the incidence of multiple organ failure has decreased over time, it remains morbid, lethal, and resource intensive. However, single OD, especially acute lung injury, remains frequent. Treatment is limited, and prevention remains the mainstay strategy.

The role of hypertonic saline dextran in trauma resuscitation

Modern trauma management has recognized the importance of using conservative fluid resuscitation regimes in order to prevent complications from fluid overload arising. Hypertonic/hyperoncotic fluids appear to provide an ideal means of facilitating this, requiring only small volumes to rapidly elevate blood pressure. Hypertonic saline dextran (HSD) was introduced in 1985 but its take up has been slow, a large part of this has been due to the lack of human trials and concerns about complications.

The current evidence has been reviewed and it is clear that HSD is an efficient means of correcting hypotension, doing so mainly by the mobilizing endogenous water. It is becoming apparent that early administration has the potential to modulate the inflammatory cascade in patients at risk of developing adult respiratory distress syndrome (ARDS) and multiorgan failure. This is reflected in the handful of human trials that show a trend towards increased survival (particularly for head injuries) and a possible reduction in ARDS. The side effect profile appears to be good, even in the presence of dehydration or penetrating trauma.

Published human trials have methodological problems and lack of power of study this has led to a reliance on animal studies. Clearly there is great potential, but before large-scale prehospital usage can be justified further well-conducted randomized human trials are needed.

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.

Current purpose and practice of hypertonic saline in neurosurgery: a review of the literature

OBJECTIVE

To review and summarize controversies and current concepts regarding the use of hypertonic saline during the perioperative period in neurosurgery.

METHODS

Relevant literature was searched on PubMed and Scopus electronic databases to identify all studies that have investigated the use of hypertonic saline in neurosurgery.

RESULTS

Fluid management during the course of neurosurgical practice has been debated at length, especially strategies to control intracranial pressure and small volume resuscitation. The goal of fluid therapy includes minimizing cerebral edema, preserving intravascular volume, and maintaining cerebral perfusion pressure. Mannitol is widely recognized as the gold standard for treating intracranial hypertension but can result in systemic hypotension. Thus, hypertonic saline provides volume expansion and may improve cerebral and systemic hemodynamics. Recently published prospective data, however, regarding the use of osmotic agents fails to establish clear guidelines in neurosurgical patients.

CONCLUSIONS

We suggest that hypertonic saline will emerge as an alternative to mannitol, especially for a long-term use or multiple doses are needed and lead to a great opportunity for collaborative research.

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.

Hypertonic saline and reduced peroxynitrite formation in experimental pancreatitis

OBJECTIVES

In this study, we tested the hypothesis that hypertonic saline exerts anti-inflammatory effects by modulating hepatic oxidative stress in pancreatitis.

INTRODUCTION

The incidence of hepatic injury is related to severe pancreatitis, and hypertonic saline reduces pancreatic injury and mortality in pancreatitis.

METHODS

Wistar rats were divided into four groups: control (not subjected to treatment), untreated pancreatitis (NT, pancreatitis induced by a retrograde transduodenal infusion of 2.5% sodium taurocholate into the pancreatic duct with no further treatment administered), pancreatitis with normal saline (NS, pancreatitis induced as described above and followed by resuscitation with 0.9% NaCl), and pancreatitis with hypertonic saline (HS, pancreatitis induced as described above and followed by resuscitation with 7.5% NaCl). At 4, 12, and 24 h after pancreatitis induction, liver levels of inducible nitric oxide synthase (iNOS), heat-shock protein 70, nitrotyrosine (formation of peroxynitrite), nitrite/nitrate production, lipid peroxidation, and alanine aminotransferase (ALT) release were determined.

RESULTS

Twelve hours after pancreatitis induction, animals in the HS group presented significantly lower iNOS expression (P<0.01 vs. NS), nitrite/nitrate levels (P<0.01 vs. NS), lipid peroxidation (P<0.05 vs. NT), and ALT release (P<0.01 vs. NS). Twenty-four hours after pancreatitis induction, nitrotyrosine expression was significantly lower in the HS group than in the NS group (P<0.05).

DISCUSSION

The protective effect of hypertonic saline was related to the establishment of a superoxide-NO balance that was unfavorable to nitrotyrosine formation.

CONCLUSIONS

Hypertonic saline decreases hepatic oxidative stress and thereby minimizes liver damage in pancreatitis.

Hypertonic saline reduces metalloproteinase expression in liver during pancreatitis

1. We recently demonstrated that hypertonic saline reduces inflammation and mortality in acute pancreatitis. The present study investigated the effects of hypertonic saline in metalloproteinase (MMP) regulation and pancreatitis-associated hepatic injury. 2. Wistar rats were divided into four groups: (i) control, not subjected to insult or treatment; (ii) no treatment (NT), induction of pancreatitis (retrograde infusion of 2.5% sodium taurocholate (1.0 mL/kg)), but no further treatment; (iii) normal saline (NS), induction of pancreatitis and treatment with normal saline (0.9% NaCl, 34 mL/kg, i.v. bolus, 1 h after the induction of pancreatitis); and (iv) hypertonic saline (HS), induction of pancreatitis and treatment with hypertonic saline (7.5% NaCl, 4 mL/kg administered over a period of 5 min, 1 h after the induction of pancreatitis). In all four groups, 4, 12 and 24 h after the induction of pancreatitis, liver tissue samples were assayed to determine levels of MMP-2, MMP-9, 47 kDa heat shock protein (HSP47) and collagen (Type I and III). 3. Compared with the control group, MMP-9 expression and activity was increased twofold in the NS and NT groups 4 and 12 h after the induction of pancreatitis, but remained at basal levels in the HS group. In contrast, MMP-2 expression was increased twofold 12 h after the induction of pancreatitis only in the NS group, whereas the expression of HSP47 was increased 4 h after the induction of pancreatitis in the NS and NT groups. Greater extracellular matrix remodelling occurred in the NS and NT groups compared with the HS group, probably as a result of the hepatic wound-healing response to repeated injury. However, the collagen content in hepatic tissue remained at basal levels in the HS group. 4. In conclusion, the results of the present study indicate that hypertonic saline is hepatoprotective and reduces hepatic remodelling, maintaining the integrity of the hepatic extracellular matrix during pancreatitis. Hypertonic saline-mediated regulation of MMP expression may have clinical relevance in pancreatitis-associated liver injury.

Hypertonic saline resuscitation from hemorrhagic shock does not impair the neutrophil response to intraabdominal infection

BACKGROUND

Hypertonic saline (HTS) has been proposed as a resuscitation strategy following trauma based on its ability to prevent organ dysfunction by exerting immunosuppressive effects on inflammatory cells, including neutrophils. Because these cells are central to the innate response to bacteria, we hypothesized that hypertonic treatment for hemorrhagic shock might alter the host response to bacterial contamination of the peritoneal cavity and therefore render the host more susceptible to invasive infection.

METHODS

Male Sprague-Dawley rats were subjected to hemorrhagic shock and resuscitated with either lactated Ringer solution (RL) or HTS. After intraperitoneal injection of feces, Escherichia coli, or lipopolysaccharide, peritoneal neutrophil accumulation and bacterial clearance were studied. In some studies, lipopolysaccharide as an inflammatory stimulus was injected into both the peritoneal cavity and the lungs.

RESULTS

Peritoneal neutrophil accumulation in response to each of the stimuli did not differ between RL- and HTS-resuscitated animals. Whereas emigration into the peritoneum activated neutrophils, there was no difference between resuscitation strategies, consistent with the finding that bacterial clearance did not differ between groups. Although peritoneal neutrophil sequestration was unaffected by resuscitation type, HTS still was able to prevent lung neutrophil accumulation compared to RL treatment.

CONCLUSIONS

HTS resuscitation did not impair the host response to bacterial contamination of the peritoneal cavity. However, the ability of HTS to prevent lung neutrophil accumulation in this setting persisted. These findings suggest that peritoneal bacterial contamination should not be considered a contraindication to the use of HTS in the trauma setting associated with hemorrhagic shock.

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.

Small volume of hypertonic saline as the initial fluid replacement in experimental hypodynamic sepsis

INTRODUCTION

We conducted the present study to examine the effects of hypertonic saline solution (7.5%) on cardiovascular function and splanchnic perfusion in experimental sepsis.

METHODS

Anesthetized and mechanically ventilated mongrel dogs received an intravenous infusion of live Escherichia coli over 30 minutes. After 30 minutes, they were randomized to receive lactated Ringer's solution 32 ml/kg (LR; n = 7) over 30 minutes or 7.5% hypertonic saline solution 4 ml/kg (HS; n = 8) over 5 minutes. They were observed without additional interventions for 120 minutes. Cardiac output (CO), mean arterial pressure (MAP), portal and renal blood flow (PBF and RBF, respectively), gastric partial pressure of CO2 (pCO2; gas tonometry), blood gases and lactate levels were assessed.

RESULTS

E. coli infusion promoted significant reductions in CO, MAP, PBF and RBF (approximately 45%, 12%, 45% and 25%, respectively) accompanied by an increase in lactate levels and systemic and mesenteric oxygen extraction (sO2ER and mO2ER). Widening of venous-arterial (approximately 15 mmHg), portal-arterial (approximately 18 mmHg) and gastric mucosal-arterial (approximately 55 mmHg) pCO2 gradients were also observed. LR and HS infusion transiently improved systemic and regional blood flow. However, HS infusion was associated with a significant and sustained reduction of systemic (18 +/- 2.6 versus 38 +/- 5.9%) and mesenteric oxygen extraction (18.5 +/- 1.9 versus 36.5 +/- 5.4%), without worsening other perfusional markers.

CONCLUSION

A large volume of LR or a small volume of HS promoted similar transient hemodynamic benefits in this sepsis model. However, a single bolus of HS did promote sustained reduction of systemic and mesenteric oxygen extraction, suggesting that hypertonic saline solution could be used as a salutary intervention during fluid resuscitation in septic patients.

THERMAL INJURY-INDUCED PRIMING EFFECT OF NEUTROPHIL IS TNF-α AND P38 DEPENDENT

Priming response of neutrophil in clinical-related conditions and its mechanism has not been clarified. This study is to determine if thermal injury-induced priming effect of neutrophil is TNF-alpha and p38 dependent. In Experiment 1, bone marrow neutrophil of wild-type (WT) mice and TNF receptor superfamily, member 1A (Tnfrsf1a-/-) mice were harvested and treated with TNF-alpha, platelet activating factor (PAF) first, then with or without N-formyl-Met-Leu-Phe (fMLP). Reactive oxygen species (ROS) production and p38 phosphorylation were evaluated. In Experiment 2, ROS of neutrophil from WT and Tnfrsf1a-/- mice at 3 or 15 h after thermal injury with or without fMLP treatment were assayed. In Experiment 3, p38 and p44/42 phosphorylation, CXCR2 and macrophage inflammatory protein-2 expression, apoptotic ratio, and activating protein-1 (AP-1) and nuclear factor-kappa B (NF-kappaB) activation of neutrophil from WT and Tnfrsf1a-/- mice at 3 h after thermal injury were tested. FMLP treatment after TNF-alpha or PAF incubation of neutrophil increased ROS of PAF-treated but not TNF-alpha-treated neutrophil. PAF treatment increased ROS of neutrophil in WT and Tnfrsf1a-/- mice. FMLP increased ROS of neutrophil of WT mice at 3 h after thermal but not that of Tnfrsf1a-/- mice. TNF-alpha and PAF increased p38 phosphorylation of neutrophil in WT but not that in Tnfrsf1a-/- mice. Thermal injury increased p38 phosphorylation, NF-kappaB activation, and decreased apoptosis of neutrophil at 3 h after thermal injury in WT but not in Tnfrsf1a-/- mice. Thermal injury also induced AP-1 activation and ROS production on neutrophil at 3 and 15 h after thermal injury, respectively, in WT and Tnfrsf1a-/- mice. Collectively, fMLP stimulates ROS of neutrophil through TNF-alpha signaling; PAF stimulates that of neutrophil through both TNF-alpha-dependent and TNF-alpha-independent pathway. Thermal injury induces a TNF-alpha-dependent priming effect and a TNF-alpha-independent activation effect on neutrophil at 3 and 15 h after thermal injury, respectively. NF-kappaB signaling pathway plays an important role in neutrophil activation. Thermal injury also induces TNF-alpha-dependent delay apoptosis and TNF-alpha-independent AP-1 activation of neutrophil at 3 h after thermal injury. Taken together with the TNF-alpha-dependent p38 and NF-kappaB activation in primed neutrophil, we conclude that thermal injury-induced priming effect of polymorphonuclear neutrophil is TNF-alpha and p38 dependent.

Selective inhibition of polymorphonuclear neutrophils by resuscitative concentration of hypertonic saline

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Mechanism and effect of thrombospondin-4 polymorphisms on neutrophil function

High-throughput genomic technology identified an association between a single nucleotide polymorphism (SNP), a proline (P387) rather than the predominant alanine (A387) at position 387 in thrombospondin-4 (TSP-4) and premature myocardial infarction. The inflammatory hypothesis of atherosclerosis invokes a prominent role of leukocytes and cytokines in pathogenesis. As the expression of TSP-4 by vascular cells permits its exposure to circulating leukocytes, the interactions of human neutrophils (polymorphonuclear leukocytes [PMNs]) with both TSP-4 variants were investigated. Phorbol 12-myristate 13-acetate (PMA)-stimulated PMNs adhered and migrated well and equally on the TSP-4 variants. Integrin alpha(M)beta2 was identified as the TSP-4 receptor mediating these responses, and the 3 epidermal growth factor (EGF)-like domains of TSP-4 harboring the SNPs interacted with the alpha(M)I-domain. Despite the similarity in these responses, the P387 variant induced more robust tyrosine phosphorylation of the stress-related mitogen-activated protein kinases (MAPKs): p38MAPK and c-Jun NH2-terminal kinase (JNK), as well as signal transducer and activator of transcription-1 (STAT1) and heat shock protein 27 (HSP27) than the A387 variant. Additionally, cells adherent to P387 TSP-4 variant released 4-fold more H2O2 and secreted 2-fold more interleukin 8 (IL-8) as compared with the A387. H2O2 release and p38MAPK activation were totally inhibited by blockade of alpha(M)beta2. Thus, alpha(M)beta2 plays a central role in proinflammatory activities of TSP-4 (P387) and may contribute to the prothrombotic phenotype associated with this variant.

HYPERTONIC SALINE MODULATES INNATE IMMUNITY IN A MODEL OF SYSTEMIC INFLAMMATION

We sought to determine if hypertonic saline (HTS) impacted alveolar macrophage (AM) activation and intracellular inflammatory gene signaling in a model of systemic inflammation. Rats received an intravenous administration of 4 mL/kg of 7.5% HTS or L-lactate lactated Ringer's (L-LR). They were simultaneously treated with an intraperitoneal injection of zymosan, which induces noninfectious systemic inflammation. AM were harvested by bronchoalveolar lavage 24 h after treatment. AM activation was analyzed by measurement of baseline and lipopolysaccharide (LPS)-induced TNF-alpha production. Intracellular signaling was analyzed for activation of the mitogen-activated protein kinases (MAPKs): ERK1/2, JNK, and p38. AM from HTS-treated rats produced less TNF-alpha than from L-LR-treated rats (927 +/- 335 pg/mL [SEM] vs. 3628 +/- 783 pg/mL [SEM], P = 0.001) and were also less responsive to LPS (4444 +/- 86 pg/mL [SEM] vs. 6666 +/- 91 pg/mL [SEM], P = 0.058). However, there was no difference in MAPK activation. In vivo HTS prevents excessive AM activation during systemic inflammation. This suppression is mediated through alternate pathways and does not induce the classic MAPK signaling cascade.

Increased levels of serum sulfite in patients with acute pneumonia

Sulfite, a common air pollutant, is toxic for humans, causing hypersensitivity or chronic airway diseases. We previously reported that sulfite is actively produced from neutrophils by stimulation with bacterial endotoxin, lipopolysaccharide (LPS). We also found that the serum sulfite concentration is increased in a rat model of sepsis induced by systemic injection of LPS. However, information on sulfite metabolism in human inflammatory conditions is limited. In the current study, the serum concentration of sulfite was determined in 25 patients with acute pneumonia. Serum sulfite concentration in pneumonia patients was significantly higher than that in control subjects (3.75 +/- 0.88 vs. 1.23 +/- 0.48 microM, respectively, P < 0.05). Among 20 patients, serum sulfite was serially determined before and after antibiotic therapy. The levels of serum sulfite were significantly reduced during the recovery phase compared with those during the acute phase (1.34 +/- 0.56 vs. 3.65 +/- 0.92 microM, respectively, P < 0.05). Moreover, neutrophils obtained from three patients during the acute phase of pneumonia spontaneously produced higher amounts of sulfite in vitro than those obtained after recovery. There was a close positive correlation (r = 0.71, P < 0.05) between serum sulfite and C-reactive protein (CRP) in patients with pneumonia. Taken together, the current findings suggest that serum sulfite increases during systemic inflammation in humans. Activated neutrophils might be responsible, at least in part, for the up-regulation of sulfite. Given various biological effects reported previously, sulfite may act as a mediator in inflammation.

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.

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.

Clinically relevant hypertonicity prevents stored blood- and lipid-mediated delayed neutrophil apoptosis independent of p38 MAPK or caspase-3 activation

BACKGROUND

Delayed apoptosis of primed neutrophils (PMNs) may facilitate PMN-mediated tissue injury leading to postinjury multiple organ failure. Aged (42-day-old) stored red blood cells (RBC42) delay PMN apoptosis through proinflammatory phospholipids such as platelet-activating factor (PAF) and lyso-phosphatidylcholine (LPC). Hypertonic saline (HTS) attenuates PMN cytotoxic functions. We hypothesized that clinically relevant HTS would provoke PMN apoptosis, as well as prevent stored blood- and lipid-mediated delayed PMN apoptosis through activation of p38 mitogen-activated protein kinase (MAPK) and caspase-3.

METHODS

PMNs harvested from healthy volunteers were incubated (5% CO(2), 37 degrees C, 24 hr) with RBC42 plasma, PAF (20 microM), or LPC (4.5 microM), with or without the p38 MAPK inhibitor SB 203580, the caspase-3 inhibitor zDEVD-fmk (10 micromol/L) or the pan-caspase inhibitor zVAD-fmk (20 micromol/L). Duplicate samples were preincubated in HTS (Na [180 mM]). Apoptotic index (% PMNs undergoing apoptosis) was assessed morphologically. p38 MAPK activation was assessed by Western blotting. Caspase-3 activity was measured colorimetrically.

RESULTS

PAF, LPC, and RBC42 plasma delayed apoptosis; HTS increased apoptosis compared with controls. HTS prevented PAF, LPC, and RBC42-delayed apoptosis. p38 MAPK was not activated by HTS; its inhibition had no effect on the actions of HTS. Caspase inhibition attenuated the ability of HTS to increase apoptosis, but it did not affect the ability of HTS to restore healthy PMN apoptosis in the presence of RBC42.

CONCLUSION

HTS increases PMN apoptosis and prevents stored blood- and lipid-mediated delayed PMN apoptosis. HTS may activate caspase-3, but alternative signaling pathways appear to be involved in modulating the effects of lipids on PMN apoptosis.

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

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

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.