Osmotic regulation of cell function and possible clinical applications

Sex disparities in adverse outcomes after surgically managed isolated traumatic spinal injury

BACKGROUND

Traumatic spinal injury (TSI) encompasses a wide range of injuries affecting the spinal cord, nerve roots, bones, and soft tissues that result in pain, impaired mobility, paralysis, and death. There is some evidence suggesting that women may have different physiological responses to traumatic injury compared to men; therefore, this study aimed to investigate if there are any associations between sex and adverse outcomes following surgically managed isolated TSI.

METHODS

Using the 2013-2019 TQIP database, all adult patients with isolated TSI, defined as a spine AIS ≥ 2 with an AIS ≤ 1 in all other body regions, resulting from blunt force trauma requiring spinal surgery, were eligible for inclusion in the study. The association between the sex and in-hospital mortality as well as cardiopulmonary and venothromboembolic complications was determined by calculating the risk ratio (RR) after adjusting for potential confounding using inverse probability weighting.

RESULTS

A total of 43,756 patients were included. After adjusting for potential confounders, female sex was associated with a 37% lower risk of in-hospital mortality [adjusted RR (95% CI): 0.63 (0.57-0.69), p < 0.001], a 27% lower risk of myocardial infarction [adjusted RR (95% CI): 0.73 (0.56-0.95), p = 0.021], a 37% lower risk of cardiac arrest [adjusted RR (95% CI): 0.63 (0.55-0.72), p < 0.001], a 34% lower risk of deep vein thrombosis [adjusted RR (95% CI): 0.66 (0.59-0.74), p < 0.001], a 45% lower risk of pulmonary embolism [adjusted RR (95% CI): 0.55 (0.46-0.65), p < 0.001], a 36% lower risk of acute respiratory distress syndrome [adjusted RR (95% CI): 0.64 (0.54-0.76), p < 0.001], a 34% lower risk of pneumonia [adjusted RR (95% CI): 0.66 (0.60-0.72), p < 0.001], and a 22% lower risk of surgical site infection [adjusted RR (95% CI): 0.78 (0.62-0.98), p < 0.032], compared to male sex.

CONCLUSION

Female sex is associated with a significantly decreased risk of in-hospital mortality as well as cardiopulmonary and venothromboembolic complications following surgical management of traumatic spinal injuries. Further studies are needed to elucidate the cause of these differences.

Sperm preparedness and adaptation to osmotic and pH stressors relate to functional competence of sperm in Bos taurus

The adaptive ability of sperm in the female reproductive tract micromilieu signifies the successful fertilization process. The study aimed to analyze the preparedness of sperm to the prevailing osmotic and pH stressors in the female reproductive tract. Fresh bovine sperm were incubated in 290 (isosmotic-control), 355 (hyperosmotic-uterus and oviduct), and 420 (hyperosmotic-control) mOsm/kg and each with pH of 6.8 (uterus) and 7.4 (oviduct). During incubation, the changes in sperm functional attributes were studied. Sperm kinematics and head area decreased significantly (p < 0.05) immediately upon exposure to hyperosmotic stress at both pH. Proportion of sperm capacitated (%) in 355 mOsm/kg at 1 and 2 h of incubation were significantly (p < 0.05) higher than those in 290 mOsm media. The magnitude and duration of recovery of sperm progressive motility in 355 mOsm with pH 7.4 was correlated with the ejaculate rejection rate (R² = 0.7). Using this information, the bulls were divided into good (n = 5) and poor (n = 5) osmo-adapters. The osmo-responsive genes such as NFAT5, HSP90AB1, SLC9C1, ADAM1B and GAPDH were upregulated (p < 0.05) in the sperm of good osmo-adapters. The study suggests that sperm are prepared for the osmotic and pH challenges in the female reproductive tract and the osmoadaptive ability is associated with ejaculate quality in bulls.

Hypertonic Saline Solution Reduces Microcirculatory Dysfunction and Inflammation in a Rat Model of Brain Death

BACKGROUND

Brain death (BD) induces hemodynamic instability with microcirculatory hypoperfusion, leading to increased organ inflammation and dysfunction. This study investigated the effects of 7.5% hypertonic saline solution (HSS) on mesenteric microcirculatory dysfunction and inflammation in a rat model of BD.

METHODS

Male Wistar rats were anesthetized and mechanically ventilated. BD was induced by rapidly inflating an intracranial balloon catheter. The rats were randomly divided into: SH, sham-operated rats subjected to trepanation; NS, rats treated with NaCl 0.9%, 4 mL/kg immediately after BD; T1, rats treated with HSS (NaCl 7.5%, 4 mL/kg) immediately or 60 min after BD, T60. All groups were analyzed 180 min after the start of the experiment.

RESULTS

Rats in BD groups presented with a similar hypertensive peak, followed by hypotension. Proportion of perfused small vessels was decreased in the NS group (46%) compared with the SH group (74%, P = 0.0039). HSS restored the proportion of perfused vessels (T1 = 71%, P = 0.0018). The anti-endothelial nitric oxide synthase (eNOS) protein expression significantly increased in rats given HSS (T1, and T60, P = 0.0002). Similar results were observed regarding endothelin-1 (P < 0.0001). Increased numbers of rolling (P = 0.0015) and migrated (P = 0.0063) leukocytes were observed in the NS group compared with the SH group. Rats given HSS demonstrated an overall reduction in leukocyte-endothelial interactions. The ICAM-1 levels increased in the NS group compared with the SH group, and decreased in the HSS-treated groups (P = 0.0002).

CONCLUSIONS

HSS may improve the density of mesenteric perfused small vessels due to its effects on eNOS and endothelin-1 protein expression, and reduces inflammation by decreasing leukocyte adhesion and migration in a rat model of BD.

Gender differences in trauma, shock and sepsis

Despite efforts in prevention and intensive care, trauma and subsequent sepsis are still associated with a high mortality rate. Traumatic injury remains the main cause of death in people younger than 45 years and is thus a source of immense social and economic burden. In recent years, the knowledge concerning gender medicine has continuously increased. A number of studies have reported gender dimorphism in terms of response to trauma, shock and sepsis. However, the advantageous outcome following trauma-hemorrhage in females is not due only to sex. Rather, it is due to the prevailing hormonal milieu of the victim. In this respect, various experimental and clinical studies have demonstrated beneficial effects of estrogen for the central nervous system, the cardiopulmonary system, the liver, the kidneys, the immune system, and for the overall survival of the host. Nonetheless, there remains a gap between the bench and the bedside. This is most likely because clinical studies have not accounted for the estrus cycle. This review attempts to provide an overview of the current level of knowledge and highlights the most important organ systems responding to trauma, shock and sepsis. There continues to be a need for clinical studies on the prevailing hormonal milieu following trauma, shock and sepsis.

200mM hypertonic saline resuscitation attenuates intestinal injury and inhibits p38 signaling in rats after severe burn trauma

BACKGROUND

An overabundant discharge of inflammatory mediators plays a significant role in intestinal injury throughout the early stages of critical burns. The present study aims to explore the outcome of 200mM hypertonic saline (HS) resuscitation on the intestinal injury of critically burned rats.

MATERIALS AND METHODS

Fifty-six Sprague-Dawley rats were randomized into three groups: sham group (group A), burn plus lactated Ringer's group (group B), and burn plus 200mM HS group (group C). Samples from the intestine were isolated and assayed for wet-weight-to-dry-weight (W/D) ratio, histopathology analyses, and p38 mitogen-activated protein kinase (MAPK) activity. Serum interleukin 1β (IL-1β) and high mobility group protein box 1 (HMGB1) concentrations were also examined.

RESULTS

Initial resuscitation with 200mM Na⁺ HS significantly decreased the intestinal W/D ratio and improved intestinal histopathology caused by severe burn. HS resuscitation also inhibited the increase of serum IL-1β and HMGB1 concentrations, and p38 MAPK activity in the intestine of critically burned rats.

CONCLUSIONS

The overall findings of this study suggest that preliminary resuscitation with 200mM HS after severe thermal injury reduces intestinal edema, inhibits systemic inflammatory response, and attenuates intestinal p38 MAPK activation, thus reduces burns-induced intestinal injury.

Hypertonic Saline Primes Activation of the p53-p21 Signaling Axis in Human Small Airway Epithelial Cells That Prevents Inflammation Induced by Pro-inflammatory Cytokines

Uncontrolled inflammatory responses underlie the etiology of acute lung injury and acute distress respiratory syndrome, the most common late complications in trauma, the leading cause of death under the age of 59. Treatment with HTS decreases lung injury in clinical trials, rat models of trauma and hemorrhagic shock and inflammation in lung cell lines, although the mechanisms underlying these responses are still incompletely understood. Transcriptomics (RNaseq), proteomics, and U-¹³C-glucose tracing metabolomics experiments were performed to investigate the mechanisms of cellular responses to HTS treatment in primary small airway epithelial cells in the presence or absence of inflammatory injury mediated by a cocktail of cytokines (10 ng/mL of IFNγ, IL-1β, and TNFα). Modestly hyperosmolar HTS has an anti-inflammatory effect, triggers the p53-p21 signaling axis, and deregulates mitochondrial metabolism while inducing minimal apoptosis in response to a second hit by cytokines. Decreased transcription of pro-inflammatory cytokines suggested a role for the tumor suppressor protein p53 in mediating the beneficial effects of the HTS treatment. The anti-inflammatory mechanisms induced by HTS involves p53 gene regulation, promotes cell cycle arrest, and prevents ROS formation and mitochondria depolarization. Pharmaceutical targeting of the p53-p21 axis may mimic or reinforce the beneficial effects mediated by HTS when sustained hypertonicity cannot be maintained.

Hyperosmolarity invokes distinct anti-inflammatory mechanisms in pulmonary epithelial cells: evidence from signaling and transcription layers

Hypertonic saline (HTS) has been used intravenously to reduce organ dysfunction following injury and as an inhaled therapy for cystic fibrosis lung disease. The role and mechanism of HTS inhibition was explored in the TNFα and IL-1β stimulation of pulmonary epithelial cells. Hyperosmolar (HOsm) media (400 mOsm) inhibited the production of select cytokines stimulated by TNFα and IL-1β at the level of mRNA translation, synthesis and release. In TNFα stimulated A549 cells, HOsm media inhibited I-κBα phosphorylation, NF-κB translocation into the nucleus and NF-κB nuclear binding. In IL-1β stimulated cells HOsm inhibited I-κBα phosphorylation without affecting NF-κB translocation or nuclear binding. Incubation in HOsm conditions inhibited both TNFα and IL-1β stimulated nuclear localization of interferon response factor 1 (IRF-1). Additional transcription factors such as AP-1, Erk-1/2, JNK and STAT-1 were unaffected by HOsm. HTS and sorbitol supplemented media produced comparable outcomes in all experiments, indicating that the effects of HTS were mediated by osmolarity, not by sodium. While not affecting MAPK modules discernibly in A549 cells, both HOsm conditions inhibit IRF-1 against TNFα or IL-1β, but inhibit p65 NF-kB translocation only against TNFα but not IL-1β. Thus, anti-inflammatory mechanisms of HTS/HOsm appear to disrupt cytokine signals at distinct intracellular steps.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Hypertonic saline solution reduces mesenteric microcirculatory dysfunctions and bacterial translocation in a rat model of strangulated small bowel obstruction

We examined the effects of hypertonic saline (HS) on inflammatory, metabolic variables, and bacterial translocation (BT) in rats submitted to intestinal obstruction and ischemia (IO). Male Wistar rats were submitted to IO and treated, 2 h thereafter, with lactated Ringer's (LR) (4 mL/kg per 5 min, i.v.) or HS (7.5% NaCl, 4 mL/kg per 5 min, i.v.). Twenty-four hours after IO, rats were also submitted to enterectomy/enteroanastomosis to resection of necrotized small bowel. Leukocyte-endothelial interactions were investigated by intravital microscopy and the expression of P-selectin and intercellular adhesion molecule 1 by immunohistochemistry. Bacterial cultures of mesenteric lymph nodes, liver, spleen, and blood were used to evaluate BT. Levels of chemokines (cytokine-induced neutrophil chemoattractants 1 and 2), insulin, and corticosterone were determined by enzyme-linked immunosorbent assay. Intestinal histology, serum urea and creatinine levels, and hepatic enzymes activities were performed to evaluate local and remote damage. Relative to IO and LR-treated rats, which exhibited increases in the number of rolling (1.5-fold), adhered (3.5-fold) and migrated (9.0-fold) leukocytes, and increased expression of P-selectin (3-fold) and intercellular adhesion molecule 1 (3-fold) on mesenteric microcirculation, treatment with HS followed by enterectomy reduced leukocyte-endothelial interactions and expression of both adhesion molecules to values attained in sham rats. Serum chemokines were normalized after treatment with both solutions followed by enterectomy. Hypertonic saline-treated rats demonstrated a significant reduction in BT to 50% in liver and spleen samples and bacteremia (14%), compared with 82% of BT in liver and spleen samples of IO and LR-treated rats and bacteremia (57%). Local intestinal damage was attenuated, and renal and hepatic function preserved by treatment with HS followed by enterectomy. Survival rate increased to 86% up to 15 days. Data presented suggest that HS solution followed by enterectomy reduces mesenteric microcirculatory dysfunctions and BT, attenuating local and remote damage in a model of strangulated small bowel obstruction.

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

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

Intestinal injury can be reduced by intra-arterial postischemic perfusion with hypertonic saline

AIM: To investigate the effect of local intestinal perfusion with hypertonic saline (HTS) on intestinal ischemia-reperfusion injury (IRI) in both ex vivo and in vivo rat models.

METHODS: All experiments were performed on male Wistar rats anesthetized with pentobarbital sodium given intraperitoneally at a dose of 60 mg/kg. Ex vivo vascularly perfused rat intestine was subjected to 60-min ischemia and either 30-min reperfusion with isotonic buffer (controls), or 5 min with HTS of 365 or 415 mOsm/L osmolarity (HTS^365mOsm or HTS^415mOsm, respectively) followed by 25-min reperfusion with isotonic buffer. The vascular intestinal perfusate flow (IPF) rate was determined by collection of the effluent from the portal vein in a calibrated tube. Spontaneous intestinal contraction rate was monitored throughout. Irreversible intestinal injury or area of necrosis (AN) was evaluated histochemically using 2.3.5-triphenyltetrazolium chloride staining. In vivo, 30-min ischemia was followed by either 30-min blood perfusion or 5-min reperfusion with HTS^365mOsm through the superior mesenteric artery (SMA) followed by 25-min blood perfusion. Arterial blood pressure (BP) was measured in the common carotid artery using a miniature pressure transducer. Histological injury was evaluated in both preparations using the Chui score.

RESULTS: Ex vivo, intestinal IRI resulted in a reduction in the IPF rate during reperfusion (P < 0.05 vs sham). The postischemic recovery of the IPF rate did not differ between the controls and the HTS^365mOsm group. In the HTS^415mOsm group, postischemic IPF rates were lower than in the controls and the HTS^365mOsm group (P < 0.05). The intestinal contraction rate was similar at baseline in all groups. An increase in this parameter was observed during the first 10 min of reperfusion in the control group as compared to the sham-treated group, but no such increase was seen in the HTS^365mOsm group. In controls, AN averaged 14.8% ± 5.07% of the total tissue volume. Administration of HTS^365mOsm for 5 min after 60-min ischemia resulted in decrease in AN (5.1% ± 1.20% vs controls, P < 0.01). However, perfusion of the intestine with the HTS of greater osmolarity (HTS^415mOsm) failed to protect the intestine from irreversible injury. The Chiu score was lower in the HTS^365mOsm group in comparison with controls (2.4 ± 0.54 vs 3.2 ± 0.44, P = 0.042), while intestinal perfusion with HTS^415mOsm failed to improve the Chiu score. Intestinal reperfusion with HTS^365mOsm in the in vivo series secured rapid recovery of BP after its transient fall, whereas in the controls no recovery was seen. The Chiu score was lower in the HTS^365mOsm group vs controls (3.1 ± 0.26 and 3.8 ± 0.22, P = 0.0079 respectively,), although the magnitude of the effect was lower than in the ex vivo series.

CONCLUSION: Brief intestinal postischemic perfusion with HTS^365mOsm through the SMA followed by blood flow restoration is a protective procedure that could be used for the prevention of intestinal IRI.

Effects of trauma-hemorrhage and IL-6 deficiency on splenic immune function in a murine trauma model

Splenic immune function is known to be depressed following hemorrhage. The present study investigates the effects of femoral shaft fracture, isolated or in combination with hemorrhage, on early stage cytokine production capacity of splenocytes and observes the role of IL-6 under these conditions. Male IL-6 knockout (IL-6^−/−) and wild-type mice (WT) were randomly divided into three groups: sham (S), isolated femoral fracture (Fx), and femoral fracture + volume controlled hemorrhage (TH-Fx) (n = 6 per group). Animals were sacrificed four hours after induction of hemorrhage and fracture. Cytokine release (TNF-α, IL-6, and IL-10) of isolated and LPS-stimulated splenocytes was determined by cytometric bead array. Femoral fracture with or without hemorrhage caused a suppression of in vitro cytokine production capacity of splenocytes at an early posttraumatic stage in WT and IL-6^−/−. In the absence of IL-6, the profile of splenic cytokine secretion is significantly altered, identifying this cytokine as a potential therapeutic target to modulate the posttraumatic immune response.

Hypertonic saline enhances host defense and reduces apoptosis in burn mice by increasing toll-like receptors

Hypertonic saline (HTS) is useful in the management of intracranial hypertension and shock patients. The aim of this study was to investigate whether HTS enhances host defense in burn mice through the increase of Toll-like receptors (TLRs) and nuclear factor κB (NF-κB) activation. C57BL/6, TLR4, C3H/HeN, and C3H/HeJ (nonfunctional TLR4 mutant) mice underwent burn and were given 10 mL/kg HTS (7.5% NaCl, 1.28 mol/L), 10 mL/kg saline (154 mmol/L), or 80 mL/kg saline (154 mmol/L) at 8 h after burn. At 24 h after burn, mesenteric lymph nodes were harvested and assayed for bacterial translocation (BT). Next, animals received i.p. Escherichia coli challenge, and bacterial clearance was measured. Finally, peritoneal cells were isolated for assay of bacterial killing activity, phagocytic activity, apoptotic ratio, NF-κB DNA binding activity, and expression of TLR4, MyD88, p-Akt, pp38, macrophage inflammatory protein 2, and Bcl-xL. Hypertonic saline decreased BT in C57BL/6 and C3H/HeN mice but not in TLR4 mutant mice. Also, HTS increased bacterial clearance and bacterial killing activity and decreased apoptotic ratio of peritoneal cells from C57BL/6 and C3H/HeN mice but not TLR4 or C3H/HeJ mice. Finally, HTS increased NF-κB activity and expression of TLR4, MyD88, p-Akt, pp38, macrophage inflammatory protein 2, and Bcl-xL in C57BL/6 but not in TLR4 mice. Hypertonic saline increases bacterial clearance and bacterial killing activity and decreases thermal injury-induced BT in wild-type but not in TLR4 mutant mice. Given that HTS induces NF-κB activity and TLR4, MyD88, and pp38 expression but decreases the apoptosis of inflammatory cells, we conclude that HTS resuscitation enhances host defense against bacterial challenge and reduces apoptosis of inflammatory cells in burn mice by increasing TLR4 expression and NF-κB activation.

Hypertonicity-enhanced TNF-α release from activated human monocytic THP-1 cells requires ERK activation

BACKGROUND

Hypertonic stress enhances tumor necrosis factor (TNF)-α expression in activated monocytes. However, the underlying mechanism is unknown. The produced TNF-α is primarily cleaved and released by TNF-α-converting enzyme (TACE), and the surface expression of TACE is down-regulated by endocytosis. As hypertonicity inhibits endocytosis, we evaluated the mechanism of hypertonicity-induced TNF-α release from activated human monocytic THP-1 cells.

METHODS

THP-1 cells were stimulated with lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) in the presence or absence of hypertonic agents (150 mM sucrose or 150-300 mM NaCl). The amount of TNF-α mRNA and protein, surface expression of TACE and activation of signaling pathways (mitogen-activated protein kinase, Akt and NF-κB) were assayed.

RESULTS

Hypertonic sucrose and NaCl significantly enhanced TNF-α release from THP-1 cells upon LPS or PMA stimulation. Hypertonic sucrose and other endocytosis inhibitors increased surface expression of TACE, but their effects on TNF-α release were inconsistent. This enhancement effect by hypertonicity was not attenuated by inhibition of TACE or IκB kinase, but it was blocked by cycloheximide and a MAP/ERK kinase inhibitor. The LPS- or PMA-induced TNF-α mRNA expression was not increased; rather, it was inhibited by hypertonicity. ERK1/2 was re-activated after sucrose treatment in LPS-stimulated THP-1 cells.

CONCLUSIONS

Hypertonicity-enhanced TNF-α protein synthesis from LPS- or PMA-activated THP-1 cells requires ERK activation and may proceed without TACE.

GENERAL SIGNIFICANCE

A vast amount of TNF-α production was regulated by a crucial post-transcriptional manner in activated human monocytic leukemia cells, and it may possibly be contributed to the cachexia condition.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Hypertonic stress regulates T cell function via pannexin-1 hemichannels and P2X receptors

Hypertonic saline (HS) resuscitation increases T cell function and inhibits posttraumatic T cell anergy, which can reduce immunosuppression and sepsis in trauma patients. We have previously shown that HS induces the release of cellular ATP and enhances T cell function. However, the mechanism by which HS induces ATP release and the subsequent regulation of T cell function by ATP remain poorly understood. In the present study, we show that inhibition of the gap junction hemichannel pannexin-1 (Panx1) blocks ATP release in response to HS, and HS exposure triggers significant changes in the expression of all P2X-type ATP receptors in Jurkat T cells. Blocking or silencing of Panx1 or of P2X1, P2X4, or P2X7 receptors blunts HS-induced p38 MAPK activation and the stimulatory effects of HS on TCR/CD28-induced IL-2 gene transcription. Moreover, treatment with HS or agonists of P2X receptors overcomes T cell suppression induced by the anti-inflammatory cytokine IL-10. These findings indicate that Panx1 hemichannels facilitate ATP release in response to hypertonic stress and that P2X1, P2X4, and P2X7 receptor activation enhances T cell function. We conclude that HS and P2 receptor agonists promote T cell function and thus, could be used to improve T cell function in trauma patients.

Resuscitation with hypertonic saline-dextran reduces serum biomarker levels and correlates with outcome in severe traumatic brain injury patients

In the treatment of severe traumatic brain injury (TBI), the choice of fluid and osmotherapy is important. There are practical and theoretical advantages to the use of hypertonic saline. S100B, neuron-specific enolase (NSE), and myelin-basic protein (MBP) are commonly assessed biomarkers of brain injury with potential utility as diagnostic and prognostic indicators of outcome after TBI, but they have not previously been studied in the context of fluid resuscitation. This randomized controlled trial compared serum concentrations of S100B, NSE, and MBP in adult severe TBI patients resuscitated with 250 mL of 7.5% hypertonic saline plus 6% dextran70 (HSD; n = 31) versus 0.9% normal saline (NS; n = 33), and examined their relationship with neurological outcome at discharge. Blood samples drawn on admission (<or=3 h post-injury), and at 12, 24, and 48 h post-resuscitation were assayed by ELISA for the selected biomarkers. Serial comparisons of biomarker concentrations were made by ANOVA, and relationships between biomarkers and outcome were assessed by multiple regression. On admission, mean (+/-SEM) S100B and NSE concentrations were increased 60-fold (0.73 +/- 0.08 microg/L) and sevenfold (37.0 +/- 4.8 microg/L), respectively, in patients resuscitated with NS, compared to controls (0.01 +/- 0.01 and 6.2 +/- 0.6, respectively). Compared with NS resuscitation, S100B and NSE were twofold and threefold lower in HSD-treated patients and normalized within 12 h. MBP levels were not significantly different from controls in either treatment arm until 48 h post-resuscitation, when a delayed increase (0.58 +/- 0.29 microg/L) was observed in NS-treated patients. Biomarkers were elevated in the patient group showing an unfavorable outcome. HSD-resuscitated patients with favorable outcomes exhibited the lowest serum S100B and NSE concentrations, while maximal levels were found in NS-treated patients with unfavorable outcomes. The lowest biomarker levels were seen in survivors resuscitated with HSD, while maximal levels were in NS-resuscitated patients with fatal outcome. Pre-hospital resuscitation with HSD is associated with a reduction in serum S100B, NSE, and MBP concentrations, which are correlated with better outcome after severe TBI.

Pentoxifylline modulates p47phox activation and downregulates neutrophil oxidative burst through PKA-dependent and -independent mechanisms

BACKGROUND AND AIM

Pentoxifylline (PTX) has been proven to be an inhibitor of fMLP-induced neutrophil (PMN) oxidative burst and is thought to function by increasing cAMP and Protein kinase A (PKA). We hypothesized that PTX diminishes production of the neutrophil respiratory burst by both PKA-dependent and independent mechanisms.

MATERIAL AND METHODS

Human neutrophils were isolated and stimulated with fMLP (1microM) alone or in combination with PTX (2mM). PMN activation was determined by the cytochrome C reduction method in the presence and absence of p38 MAPK (SB203580), ERK (PD98059), and PKA inhibitors (H89). Western blot analysis of Ras, Raf, p38 MAPK, ERK, and Akt was performed in PMNs exposed to fMLP and PTX. Cell membranes were fractionated to measure membrane-associated p47 phox. Treated cells were imaged using confocal microscopy to examine changes in localization of Akt and p47phox.

RESULTS

PTX produced a decrease in oxidative burst that was diminished but not abrogated by H89 exposure. The reduction in Ras, Raf, and Akt activation seen with PTX was not effected by the presence of H89. The ability of PTX to attenuate phosphorylation of p38 MAPK and ERK was significantly decreased in the presence of H89, suggesting a PKA-dependent mechanisms. Membrane fractions of neutrophils demonstrate that PTX decreased membrane-associated p47phox, thus diminishing the ability to generate oxidative burst. PTX also decreased membrane localization of Akt and p47phox by confocal microscopy.

CONCLUSIONS

PTX attenuates activation of signaling molecules involved in activation of p47phox and suppress the subsequent assembly of the NADPH machinery through both PKA-dependent and PKA-independent mechanisms.

Salutary effects of 17beta-estradiol on Peyer's patch T cell functions following trauma-hemorrhage

Although 17beta-estradiol (E2) administration following trauma-hemorrhage (T-H) improves immune functions in male rodents, it remains unclear whether E2 has salutary effects on Peyer's patch (PP) T cell functions. We hypothesized that T-H induces PP T cell dysfunction and E2 administration following T-H will improve PP T cell function. T-H was induced in male C3H/HeN mice (6-8weeks) by midline laparotomy and approximately 90min of hemorrhagic shock (blood pressure 35mmHg), followed by fluid resuscitation (4x the shed blood volume in the form of Ringer's lactate). Estrogen receptor (ER)-alpha agonist propyl pyrazole triol (PPT; 5microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5microg/kg), E2 (50microg/kg), or vehicle was injected subcutaneously at resuscitation onset. Two hours later, mice were sacrificed and PP T cells isolated. PP T cell capacity to produce cytokines in response to in vitro stimulation, PP T cell proliferation and MAPK (p38, ERK-1/2, JNK) activation were measured. Results indicate PP T cell proliferation, cytokine production and MAPK activation decreased significantly following T-H. E2, PPT or DPN administration normalized these parameters. Since PPT or DPN administration following T-H was effective in normalizing PP T cell functions, the salutary effects of E2 are mediated via ER-alpha and ER-beta.

Fluid replacement with hypertonic or isotonic solutions guided by mixed venous oxygen saturation in experimental hypodynamic sepsis

BACKGROUND

Splanchnic perfusion is prone to early injury and persists despite normalization of global hemodynamic variables in sepsis. Volume replacement guided by oxygen derived variables has been recommended in the management of septic patients. Our hypothesis was that a hypertonic isoncotic solution would improve the benefits of crystalloids replacement guided by mixed venous oxygen saturation.

METHODS

Seventeen anesthetized and mechanically ventilated mongrel dogs received an intravenous infusion of live E. coli in 30 minutes. They were then randomized into three groups: control group (n = 3) bacterial infusion without treatment; normal saline (n = 7), initial fluid replacement with 32 mL/kg of normal saline during 20 minutes; hypertonic solution (n = 7), initial fluid replacement with 4 mL/kg of hypertonic solution during 5 minutes. After 30 and 60 minutes, additional boluses of normal saline were administered when mixed venous oxygen saturation remained below 70%. Mean arterial pressure, cardiac output; regional blood flows, systemic and regional oxygen-derived variables, and lactate levels were assessed. Animals were observed for 90 minutes and then killed. Hystopathological analysis including apoptosis detection using terminal deoxynucleotidil transferase mediated dUTP-biotin nick end labeling was performed.

RESULTS

A hypodynamic septic shock was observed after bacterial infusion. Both the fluid-treated groups presented similar transient benefits in systemic and regional variables. A greater degree of gut epithelial cells apoptosis was observed in normal saline-treated animals.

CONCLUSIONS

Although normalization of mixed venous oxygen saturation was not associated with restoration of markers of splanchnic or other systemic perfusion variables, the initial fluid savings with hypertonic saline and its latter effect on gut apoptosis may be of interest in sepsis management.

Peripheral osmotic stimulation inhibits the brain's innate immune response to microdialysis of acidic perfusion fluid adjacent to supraoptic nucleus

During the brain's innate immune response microglia, astroglia and ependymal cells resolve/repair damaged tissue and control infection. Released interleukin-1beta (IL-1beta) reaching cerebroventricles stimulates circumventricular organs (CVOs; subfornical organ, SFO; organum vasculosum lamina terminalis, OVLT), the median preoptic nucleus (MePO), and magnocellular and parvocellular neurons in the supraoptic (SON) and paraventricular (PVN) nuclei. Hypertonic saline (HS) also activates these osmosensory CVOs and neuroendocrine systems, but, in contrast to IL-1beta, inhibits the peripheral immune response. To examine whether the brain's innate immune response is attenuated by osmotic stimulation, sterile acidic perfusion fluid was microdialyzed (2 microl/min) in the SON area of conscious rats for 6 h with sterile HS (1.5 M NaCl) injected subcutaneously (15 ml/kg) at 5 h. Immunohistochemistry identified cytokine sources (IL-1beta(+); OX-42(+) microglia) and targets (IL-1R(+); inducible cyclooxygenase, COX-2(+); c-Fos(+)) near the probe, in CVOs, MePO, ependymal cells, periventricular hypothalamus, SON, and PVN. Inserting the probe stimulated magnocellular neurons (c-Fos(+); SON; PVN) via the MePO (c-Fos(+)), a response enhanced by HS. Microdialysis activated microglia (OX-42(+); amoeboid/hypertrophied; IL-1beta(+)) in the adjacent SON and bilaterally in perivascular areas of the PVN, periventricular hypothalamus and ependyma, coincident with c-Fos expression in ependymal cells and COX-2 in the vasculature. These microglial responses were attenuated by HS, coincident with activating parvocellular and magnocellular neuroendocrine systems and elevating circulating IL-1beta, oxytocin, and vasopressin. Acidosis-induced cellular injury from microdialysis activated the brain's innate immune response by a mechanism inhibited by peripheral osmotic stimulation.

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

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

Effect of interleukin-15 on depressed splenic dendritic cell functions following trauma-hemorrhage

Although trauma-hemorrhage (T-H) induces suppressed splenic dendritic cell (DC) maturation and antigen presentation capacity, it remains unclear whether IL-15 modulates splenic DC functions. The aim of this study therefore was to investigate the effect of IL-15 on splenic DC functions after T-H. Male C3H/HeN mice (6-8 wk old) were randomly assigned to T-H or sham operation. T-H was induced by midline laparotomy and approximately 90 min of hemorrhagic shock (blood pressure 35 mmHg), followed by fluid resuscitation (4x the shed blood volume in the form of Ringer lactate). Two hours later, mice were killed, splenic DCs were isolated, and the effects of exogenous IL-15 on their costimulatory factors, major histocompatibility class II expression, ability to produce cytokines, and antigen presentation were measured. The results indicate that IL-15 production capacity of splenic DCs was reduced following T-H. Ex vivo exposure to IL-15 attenuated the suppressed production of TNF-alpha, IL-6, and IFN-gamma from splenic DCs following T-H. In addition, expression of surface antigen studies demonstrate that exogenous IL-15 attenuated T-H-induced downregulation of the activation of DC. The suppressed splenic DC antigen presentation function following T-H was also attenuated by IL-15 treatment. Moreover, IL-15 enhanced IL-12-induced IFN-gamma production and antigen presentation by splenic DCs. These data suggest that ex vivo treatment with IL-15 following T-H provides beneficial effects on splenic DCs. The depression in IL-15 production by splenic DCs could contribute to the host's enhanced susceptibility to infections following T-H.

Hyperglycemia may alter cytokine production and phagocytosis by means other than hyperosmotic stress

In the previous issue of Critical Care, Otto and colleagues used in vitro studies to explore the theory that immunomodulation, by correction of hyperglycemia, may be a contributing factor to the reported efficacy of intensive insulin therapy (IIT) in critically ill patients. They suggested that hyperglycemia via hyperosmolarity at supra-physiological levels potentiates the production of cytokines by peripheral blood mononuclear cells in response to lipopolysaccharide (LPS) stimulation and that it also reduces the responses of phagocytosis and oxidative burst in human granulocytes. The efficacy of IIT, they concluded, may be partially due to the correction of hyperosmolality. Other studies, however, have suggested that immunological responses to LPS in the presence of hyperglycemia are mediated by a mechanism other than hyperosmolality.

Hypertonic saline reduces neutrophil-epithelial interactions in vitro and gut tissue damage in a mouse model of colitis

Transepithelial migration of polymorphonuclear neutrophils (PMN) plays a crucial role in inflammatory conditions of the intestine, such as inflammatory bowel diseases. Hypertonic saline (HS) exerts various inhibitory effects on PMN function. We hypothesized that HS could inhibit transepithelial migration of PMN and thereby prevent inflammatory events in experimental colitis. Isolated human PMN were treated with HS (40 mM), and their transmigration across a monolayer of T84 epithelial cells was induced by N-formyl-methionyl-leucyl-phenylalanine. Monolayer disruption was assessed by monitoring changes in transepithelial conductance in an Ussing chamber. Colitis in mice was induced by oral administration of dextran sulfate sodium (DSS). Animals were treated with 4 or 8 ml/kg of 7.5% saline intraperitoneally two times daily for 7 days. Controls received equivalent volumes of normal saline (NS, n = 6) or no intraperitoneal treatment (DSS, n = 12). The severity of inflammation was evaluated based on disease activity index and histology score. HS treatment of PMN in vitro significantly reduced cell migration and the disruption of T84 monolayers compared with untreated control cells (n = 5, P < 0.05). This effect of HS was dose dependent. HS treatment in vivo also reduced colitis-induced gut tissue damage, as indicated by an improved histology score compared with the NS and DSS groups. We conclude that HS inhibits transepithelial migration of PMN in vitro and gut tissue damage in vivo in a mouse model of colitis. Thus HS may have clinical value to reduce PMN-mediated intestinal damage.

Sex steroids/receptor antagonist: their use as adjuncts after trauma-hemorrhage for improving immune/cardiovascular responses and for decreasing mortality from subsequent sepsis

Studies in human as well as animal models demonstrate that females in the proestrus cycle (i.e., with high estrogen) tolerate trauma-hemorrhage and sepsis far better than males. The female sex steroid, estrogen, is the significant factor contributing to this observed gender difference in outcome. One reason for the lack of significant gender association in some clinical studies is the possibility of heterogeneity of the population in terms of their hormonal status at the time of injury. Several experimental investigations have revealed that androgens produce immune and cardiovascular depression after trauma-hemorrhage. However, the use of an androgen receptor antagonist after trauma-hemorrhage has salutary effects of immune and cardiovascular function. Likewise, estrogen produces beneficial effects on immune and cardiovascular function after trauma-hemorrhage and significantly decreases mortality rates from subsequent sepsis. The salutary effects of estrogen after trauma-hemorrhage have been shown to be due to both genomic and nongenomic effects. Thus, the use of an estrogen or androgen receptor antagonist as an adjunct after trauma-hemorrhage is a safe and novel approach for restoring immune and cardiovascular function after trauma-hemorrhage and for decreasing the mortality from subsequent sepsis.

Estradiol's salutary effects on keratinocytes following trauma-hemorrhage are mediated by estrogen receptor (ER)-alpha and ER-beta

Although administration of 17beta-estradiol (estrogen) following trauma-hemorrhage attenuates the elevation of cytokine production and mitogen-activated protein kinase (MAPK) activation in epidermal keratinocytes, whether the salutary effects of estrogen are mediated by estrogen receptor (ER)-alpha or ER-beta is not known. To determine which estrogen receptor is the mediator, we subjected C3H/HeN male mice to trauma-hemorrhage (2-cm midline laparotomy and bleeding of the animals to a mean blood pressure of 35 mmHg and maintaining that pressure for 90 min) followed by resuscitation with Ringer's lactate (four times the shed blood volume). At the middle of resuscitation we subcutaneously injected ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), estrogen (50 microg/kg), or ER antagonist ICI 182,780 (150 microg/kg). Two hours after resuscitation, we isolated keratinocytes, stimulated them with lipopolysaccharide for 24 h (5 microg/mL for maximum cytokine production), and measured the production of interleukin (IL)-6, IL-10, IL-12, and TNF-alpha and the activation of MAPK. Keratinocyte cytokine production markedly increased and MAPK activation occurred following trauma-hemorrhage but were normalized by administration of estrogen, PPT, and DPN. PPT and DPN administration were equally effective in normalizing the inflammatory response of keratinocytes, indicating that both ER-alpha and ER-beta mediate the salutary effects of estrogen on keratinocytes after trauma-hemorrhage.

Purinergic regulation of neutrophil chemotaxis

Chemotaxis allows polymorphonuclear neutrophils (PMN) to rapidly reach infected and inflamed sites. However, excessive influx of PMN damages host tissues. Better knowledge of the mechanisms that control PMN chemotaxis may lead to improved treatments of inflammatory diseases. Recent findings suggest that ATP and adenosine are involved in PMN chemotaxis. Therefore, these purinergic signaling processes may be suitable targets for novel therapeutic approaches to ameliorate host tissue damage.

Estrogen: a novel therapeutic adjunct for the treatment of trauma-hemorrhage-induced immunological alterations

Trauma-hemorrhage leads to prolonged immune suppression, sepsis, and multiple organ failure. The condition affects all compartments of the immune system, and extensive studies have been carried out elucidating the immunological events following trauma-hemorrhage. The immune alteration observed following trauma-hemorrhage is gender dependent in both animal models and humans, though some studies in humans are contradictory. Within 30 min after trauma-hemorrhage, splenic and peritoneal macrophages, as well as T-cell function, are depressed in male animals, but not in proestrus females. Studies have also shown that the mortality [corrected] rate and the induction of subsequent sepsis following trauma-hemorrhage are significantly higher in males and ovariectomized females compared with proestrus females. These and other investigations show that sex hormones form the basis of this gender dichotomy, and administration of estrogen can ameliorate the immune depression and increase the survival rate after trauma-hemorrhage. This review specifically elaborates the studies carried out thus far demonstrating immunological alteration after trauma-hemorrhage and its modulation by estrogen. Also, estrogen was shown to produce its salutary effects through nuclear as well as extranuclear receptors. Estrogen rapidly activates several protein kinases and phosphatases, as well as the release of calcium in different cell types. The results of the studies exemplify the promise of estrogen as a therapeutic adjunct in treating adverse pathophysiological conditions following trauma-hemorrhage.

The role of estrogen receptor subtypes on hepatic neutrophil accumulation following trauma-hemorrhage: direct modulation of CINC-1 production by Kupffer cells

Although 17beta-estradiol (E2) administration following trauma-hemorrhage (T-H) reduces liver injury by decreasing neutrophil accumulation via estrogen receptor (ER)-alpha, it remains unclear whether cytokine-induced neutrophil chemoattractant (CINC)-1 production by Kupffer cells (KC) is directly modulated by ER-alpha under such condition. Male rats underwent laparotomy and hemorrhagic shock (40 mmHg for 90 min), followed by resuscitation with four times the shed blood volume in the form of Ringer's lactate. ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), E2 (50 microg/kg), or vehicle (10% DMSO) was administered subcutaneously during resuscitation; rats were sacrificed 24h thereafter. KC were isolated and cultured with ER agonists to examine if they directly affect CINC-1 production. T-H increased plasma alanine aminotransferase (ALT; hepatic injury) and hepatic myeloperoxidase (MPO) activity. E2, PPT and DPN administration reduced increased ALT; however, PPT was more effective than DPN. PPT and E2, but not DPN significantly attenuated increased hepatic MPO activity and CINC-1 levels. PPT addition in vitro (10(-7) and 10(-6)M) significantly reduced KC CINC-1 production. In summary, the salutary effects of E2 against hepatic injury are mediated predominantly via ER-alpha which directly modulates KC CINC-1 production and hepatic neutrophil accumulation following T-H.

Mitogen activated protein kinase (MAPK) mediates non-genomic pathway of estrogen on T cell cytokine production following trauma-hemorrhage

Although studies have shown 17beta-estradiol (E2) administration following trauma-hemorrhage (T-H) attenuates alterations in T cell cytokine production, it remains unknown whether such effects of E2 are mediated via genomic or non-genomic pathways. In this study, we determined the non-genomic effects of E2 on splenic T cell cytokine production and the role of MAPK following T-H. Male Sprague-Dawley rats underwent T-H (mean BP 40 mmHg for 90 min, then resuscitation). E2, E2 conjugated with BSA (E2-BSA, 1 mg/kg E2) with or without an estrogen receptor antagonist (ICI 182 780), or vehicle was administered during resuscitation. Two hours thereafter, T cell production of IL-2 and IFN-gamma and activation of MAPK (p38, ERK-1/2 and JNK) were determined. The effect of selective MAPK inhibitors on cytokine production was also examined in vitro. IL-2 and IFN-gamma production capacity and MAPK activation decreased in T cells following T-H. However, E2 administration normalized these parameters. Although E2-BSA administration also attenuated suppression in cytokine production, the values were lower compared to sham. In contrast, E2-BSA prevented T-H-induced suppression in MAPK activation to the same extent as E2. Co-administration of ICI 182 780 abolished E2-BSA effects. These findings suggest E2 effects on T cell cytokine production following T-H are mediated at least in part via non-genomic pathway and these non-genomic effects are likely mediated via MAPK pathways.

Trauma-hemorrhage inhibits splenic dendritic cell proinflammatory cytokine production via a mitogen-activated protein kinase process

Although splenic dendritic cell (DC) functions are markedly altered following trauma-hemorrhage, the mechanism(s) responsible for the altered DC functions remains unknown. We hypothesized that trauma-hemorrhage inhibits DC function via suppressing toll-like receptor 4 (TLR4) expression and mitogen-activated protein kinases (MAPKs). To examine this, male C3H/HeN (6–8 wk) mice were randomly assigned to sham operation or trauma-hemorrhage. Trauma-hemorrhage was induced by midline laparotomy and ∼90 min of hypotension [blood pressure (BP) 35 mmHg], followed by fluid resuscitation (4× the shed blood volume in the form of Ringer lactate). Two hours later, mice were euthanized, splenic DCs were isolated, and the changes in their MAPK activation, TLR4-MD-2 expression, and ability to produce cytokines were measured. The results indicate that trauma-hemorrhage downregulated the lipopolysaccharide (LPS)-induced MAPK activation in splenic DCs. In addition to the decrease in MAPK activation, surface expression of TLR4-MD-2 was suppressed following trauma-hemorrhage. Furthermore, LPS-induced cytokine production from splenic DCs was also suppressed following trauma-hemorrhage. These findings thus suggest that the decrease in TLR4-MD-2 and MAPK activation may contribute to the LPS hyporesponsiveness of splenic DCs following trauma-hemorrhage. Hyporesponsiveness of splenic DCs was also found after stimulation with the TLR2 agonist zymosan. Our results may thus explain the profound immunosuppression that is known to occur under those conditions.

Trauma and immune response--effect of gender differences

A major consequence of traumatic injury is immunosuppression. Findings from previous studies suggest that the depression of immune functions is severe in young males, ovariectomised and aged females. In contrast, the immune functions in proestrus females following trauma-haemorrhage are maintained. Studies have also shown that the survival rate in proestrus females following trauma-haemorrhage and the induction of subsequent sepsis is significantly higher than in age-matched males and ovariectomised females. Furthermore, administration of female sex hormone 17beta-oestradiol in males and ovariectomised females after trauma-haemorrhage prevents the suppression of immune response. Thus, these findings suggest that sex hormones play a significant role in shaping the host response following trauma. This article reviews studies delineating the mechanism by which sex hormones regulate immune cell functions in the experimental model of trauma-haemorrhage. The findings from the studies reviewed in this article suggest that sex steroids can be synthesised by the immune cell. The findings further indicate that T cell and macrophages express receptors for androgen and oestrogen. Since these cells are also the cells that produce cytokines, local synthesis of active steroids in these cells may become the significant factor in modulating their cytokine production.

17beta-Estradiol: a novel hormone for improving immune and cardiovascular responses following trauma-hemorrhage

17beta-Estradiol (i.e., estrogen or E2) is a female sex steroid, which plays an essential role in female reproductive physiology. However, several lines of evidence indicate that in addition to its role in reproductive physiology, E2 is critical for maintaining many other organ functions in stress conditions. These include immune, cardiovascular, and neuronal functions, as well as regulation of skin, bone, and lipid metabolism. Studies have examined the role of E2 as an adjunct in post-trauma responses, and this article will review whether E2 as an adjunct to fluid resuscitation following trauma-hemorrhage plays any role in improving/restoring immune and cardiovascular functions.

Sodium chloride inhibits cytokine production by lipopolysaccharide-stimulated human neutrophils and mononuclear cells

Hypertonic sodium chloride (NaCl) solution has been shown to have beneficial effects on patients with hypovolemic shock. Therapy with hypertonic saline seems to neutralize or minimize the deleterious immune responses in these patients. In this study, we addressed how hypertonic NaCl solution affects the release of cytokines by isolated human blood cells. We examined the effect of NaCl on tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, IL-1beta, and IL-1 receptor antagonist released by human neutrophils and mononuclear cells under nonstimulated and LPS-stimulated conditions. Cells isolated from healthy donors were cultured in the presence or absence of lipopolysaccharide (LPS). Cytokine concentrations were measured by enzyme-linked immunosorbent assay in culture supernatants. The addition of NaCl lowered the production of IL-8, TNF-alpha, and IL-1 receptor antagonist by neutrophils, and IL-8 and IL-1beta by mononuclear cells stimulated with LPS. This effect was not observed when NaCl solution was replaced by a solution of potassium iodide in the same conditions. The decreased production of cytokines in the presence of hypertonic saline was not caused by cell death. Our findings support the proposal that the modulation of leukocyte inflammatory response by NaCl occurs by an electrolyte-specific effect in addition to the hyperosmolarity. Furthermore, the results of this study support the therapeutic use of appropriate doses of i.v. NaCl solutions to minimize tissue injury characterized by neutrophil and mononuclear cell infiltration into tissues in post-traumatic patients.

The effects of a novel resuscitation strategy combining pentoxifylline and hypertonic saline on neutrophil MAPK signaling

BACKGROUND

The combination of hypertonic saline (HS) and pentoxifylline (PTX) has been shown to synergistically downregulate neutrophil oxidative burst in vitro. We investigated the effects of HS/PTX on human neutrophil mitogen-activated protein kinase (MAPK) signaling and the role of Protein kinase A (PKA) in this process.

METHODS

Isolated neutrophils were treated with PTX (2 mmol/L), HS10 (10 mmol/L above isotonicity), and HS40 (40 mmol/L above isotonicity) alone or in combination for determination of intracellular cyclic adenosine monophosphate (cAMP) concentrations. Human neutrophils were stimulated with f-methionyl-leucyl-phenylalanine (fMLP) (1 micromol/L) before the treatments above in both the presence and the absence of PKA inhibition for Western blot analysis of MAPK p38 and extracellular signal-related kinase 1/2 (ERK 1/2) phosphorylation.

RESULTS

Concomitant exposure to HS/PTX results in an additive increase in intracellular cAMP. fMLP-induced ERK 1/2 phosphorylation was synergistically attenuated by HS/PTX. Both PTX and HS reduced p38MAPK phosphorylation. No additive effect was observed with combined treatment. Although PKA inhibition abrogated the effects of PTX, HS retained some capacity to attenuate MAPK phosphorylation.

CONCLUSION

HS/PTX is more effective in attenuating neutrophil ERK signaling than either component alone, whereas both components alone or in combination produced comparable results with p38MAPK. Although PTX functions primarily through PKA activation, HS may suppress neutrophils through a partially PKA-independent mechanism.

17beta-Estradiol's salutary effects on splenic dendritic cell functions following trauma-hemorrhage are mediated via estrogen receptor-alpha

Although 17beta-estradiol administration following trauma-hemorrhage attenuates Kupffer cell, splenic and peritoneal macrophage functions, it remains unknown whether 17beta-estradiol has any salutary effects on splenic dendritic cell (DC) functions and if so, whether such effects are mediated via the estrogen receptors (ER). We hypothesized that 17beta-estradiol administration following trauma-hemorrhage has salutary effects on splenic DC functions. Male C3H/HeN (6-8 weeks) mice were randomly assigned to sham operation or trauma-hemorrhage. Trauma-hemorrhage was induced by midline laparotomy and approximately 90 min of hemorrhagic shock (blood pressure [BP] 35 mmHg), followed by fluid resuscitation (4x the shed blood volume in the form of Ringer's lactate). Estrogen receptor (ER)-alpha agonist propyl pyrazole triol (PPT; 5microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5microg/kg), 17beta-estradiol (50microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Two hours later, the mice were sacrificed, splenic DCs were isolated and the changes in their apoptosis, co-stimulating factors and MHC class II expression, ability to produce cytokines, and antigen presentation capacity were measured. Apoptosis of splenic DC increased following trauma-hemorrhage; however, 17beta-estradiol administration after trauma-hemorrhage normalized the rate of apoptosis. Moreover, splenic DC cytokines production, co-stimulating factors and MHC class II expression, and antigen presentation capacity were significantly decreased following trauma-hemorrhage; however, 17beta-estradiol as well as PPT also prevented these depressions. In contrast, DPN did not attenuate splenic DC functions following trauma-hemorrhage. Since PPT administration following trauma-hemorrhage was more effective in normalizing splenic DC functions than DPN, the salutary effects of 17beta-estradiol on splenic DC functions are mediated predominantly via ER-alpha.

Actin filaments mediate mechanical gating during osmosensory transduction in rat supraoptic nucleus neurons

Osmosensory transduction is a bidirectional process displayed by neurons involved in the control of thirst and antidiuretic hormone release, and is therefore crucial for body fluid homeostasis. Although this mechanism is known to involve the activation of nonselective cation channels during hypertonicity-evoked shrinking, and the inhibition of these channels during hypotonicity-evoked swelling, the basis for this regulation is unknown. Here, we investigated this process using whole-cell patch-clamp recordings from neurons acutely isolated from the supraoptic nucleus of adult rats. The mechanosensitivity index, defined as the ratio of conductance change to normalized volume change, was quantitatively equivalent whether cell volume was increased or decreased by changes in extracellular fluid osmolality, or by changes in pipette pressure. Moreover, responses induced by hyperosmotic or hypo-osmotic media could be reversed by increasing or decreasing pipette pressure, respectively. The mechanosensitivity index was significantly reduced in neurons treated with cytochalasin-D, a compound that promotes the depolymerization of actin filaments. Conversely, cells treated with jasplakinolide, a compound that promotes actin polymerization, showed a significant increase in mechanosensitivity index. Finally, the depolarizing and excitatory effects of hypertonic stimuli were significantly enhanced by jasplakinolide and reduced by cytochalasin-D. We conclude that osmosensory transduction in these neurons is a reversible mechanical process that depends on an intact actin cytoskeleton, and the sensitivity of the transducer appears to vary in proportion with the density of actin filaments.

Salutary effects of 17beta-estradiol on T-cell signaling and cytokine production after trauma-hemorrhage are mediated primarily via estrogen receptor-alpha

Although 17beta-estradiol (E2) administration following trauma-hemorrhage prevents the suppression in splenocyte cytokine production, it remains unknown whether the salutary effects of 17beta-estradiol are mediated via estrogen receptor (ER)-alpha or ER-beta. Moreover, it is unknown which signaling pathways are involved in 17beta-estradiol's salutary effects. Utilizing an ER-alpha- or ER-beta-specific agonist, we examined the role of ER-alpha and ER-beta in E2-mediated restoration of T-cell cytokine production following trauma-hemorrhage. Moreover, since MAPK, NF-kappaB, and activator protein (AP)-1 are known to regulate T-cell cytokine production, we also examined the activation of MAPK, NF-kappaB, and AP-1. Male rats underwent trauma-hemorrhage (mean arterial pressure 40 mmHg for 90 min) and fluid resuscitation. ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), 17beta-estradiol (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Twenty-four hours thereafter, splenic T cells were isolated, and their IL-2 and IFN-gamma production and MAPK, NF-kappaB, and AP-1 activation were measured. T-cell IL-2 and IFN-gamma production was decreased following trauma-hemorrhage, and this was accompanied with a decrease in T-cell MAPK, NF-kappaB, and AP-1 activation. PPT or 17beta-estradiol administration following trauma-hemorrhage normalized those parameters, while DPN administration had no effect. Since PPT, but not DPN, administration following trauma-hemorrhage was as effective as 17beta-estradiol in preventing the T-cell suppression, it appears that ER-alpha plays a predominant role in mediating the salutary effects of 17beta-estradiol on T cells following trauma-hemorrhage, and that such effects are likely mediated via normalization of MAPK, NF-kappaB, and AP-1 signaling pathways.

Hypertonic Saline Resuscitation: Efficacy May Require Early Treatment in Severely Injured Patients

BACKGROUND

Activation of polymorphonuclear neutrophils (PMN) is a critical event leading to host tissue injury and organ damage after trauma. Hypertonic saline (HS) resuscitation prevents PMN activation in vitro and in animal models. Here, we studied how clinical parameters and timing requirements influence the efficacy of HS in suppressing PMN activation.

MATERIALS AND METHODS

Twenty-six injured patients and 16 healthy volunteers were included as study subjects. To study how clinical parameters affect the efficacy of HS, whole blood samples from patients were collected 24 hours after admission, treated with HS and N-formyl-methionyl-leucyl-phenylalanine (fMLP), and PMN oxidative burst and degranulation were measured using flow cytometry. We studied the effect of timing on the ability of HS to inhibit PMN function by exposing blood of healthy volunteers to plasma samples from trauma patients before or after the addition of fMLP and HS.

RESULTS

Age and gender did not significantly influence the effect of HS on PMN function. The suppressive effect of clinically relevant HS concentrations (20 mmol/L) on PMN oxidative burst correlated weakly with Sepsis Severity Score (SSS) and Acute Physiology and Chronic Health Evaluation II (APACHE II) score but not with the Injury Severity Score (ISS) or Multiple Organ Failure score (MOF). There was no correlation between any of these clinical scores and degranulation. HS was significantly less effective in suppressing oxidative burst of PMN from patients with ISS >10, APACHE II >5, MOF >0, or SSS >1 compared with patients with ISS < or =10, APACHE II < or =5, MOF = 0, or SSS < or =1. HS more effectively suppressed PMN activation when PMN were pretreatment with HS, whereas it was less effective on PMN previously primed in vivo or in vitro by adding trauma plasma. HS was ineffective on PMN previously stimulated in vitro with fMLP.

CONCLUSIONS

Our data suggest that HS resuscitation may prevent PMN activation most effectively when patients are treated with HS early in the field.

Effects of 17beta-estradiol and flutamide on splenic macrophages and splenocytes after trauma-hemorrhage

Since splenic immune functions are depressed in metestrus females following trauma-hemorrhage, we hypothesized that administration of the androgen receptor antagonist flutamide at the onset of resuscitation will maintain the immune function of the spleen following trauma-hemorrhage. Female C57BL6/J mice (metestrus state, 8-12 weeks old), underwent laparotomy and hemorrhagic shock (35.0+/-5.0 mm Hg for 90 min) and received 17beta-estradiol (50 microg/25 g), flutamide (625 microg/25 g) or 17beta-estradiol+flutamide. Four hours after resuscitation, the in vitro productive capacity of different cytokines (TNF-alpha, IL-6, IL-10, and IFN-gamma) by splenic MPhi and splenocytes were determined by flow cytometry. A significantly decreased cytokine production by both splenocytes and splenic MPhi was observed following trauma-hemorrhage compared to shams. Administration of 17beta-estradiol, flutamide and 17beta-estradiol+flutamide following trauma-hemorrhage resulted in a significant increase in the in vitro IL-6 release by splenic MPhi. The TNF-alpha productive capacity, however, was only restored by 17beta-estradiol and 17beta-estradiol+flutamide administration following trauma-hemorrhage. No significant effect of either treatment was observed with regard to the suppressed splenic MPhi IL-10 release. Anti-CD3 stimulation, administration of 17beta-estradiol and 17beta-estradiol+flutamide, but not the administration of flutamide alone resulted in a significant increased release of TNF-alpha, IL-6 and IFN-gamma compared to vehicle-treated animals. No significant effect of either treatment was found on IL-10 productive capacity. These results collectively suggest that flutamide administration following trauma-hemorrhage in females has beneficial effects on splenic immune function. However, flutamide administration in combination with estrogen does not provide any significant, additional effects over 17beta-estradiol administration alone.

Liver cytokine production and ICAM-1 expression following bone fracture, tissue trauma, and hemorrhage in middle-aged mice

Although studies have indicated that hemorrhagic shock and resuscitation produces hepatic damage by mechanisms involving adhesion molecules in endothelial cells and hepatocytes, it is not known if there is any difference in the extent of hepatic damage following bone fracture, soft tissue trauma, and hemorrhage (Fx-TH) between young and middle-aged animals. To study this, young (6-8 wk) and middle-aged (approximately 12 mo) C3H/HeN male mice were subjected to a right lower leg fracture, soft tissue trauma, (i.e., midline laparotomy), and hemorrhage (blood withdrawal to decrease the blood pressure to 35 +/- 5 mmHg for 90 min) followed by resuscitation with four times the shed blood volume in the form of lactated Ringer solution. Mice were euthanized 24 h later, and liver tissues were harvested. Total bilirubin levels in the hepatocyte extract increased markedly following Fx-TH in both groups of mice; however, the increase in middle-aged mice was significantly higher compared with young mice. TNF-alpha and IL-6 levels in the hepatocyte extract following Fx-TH increased significantly in middle-aged mice but remained unchanged in young mice. IL-10 levels significantly decreased in middle-aged mice following Fx-TH but remained unchanged in young mice. Kupffer cells from middle-aged mice produced significantly higher IL-6 and IL-10 levels compared with young mice. Protein levels and mRNA expression of ICAM-1 in hepatocytes were also significantly higher in middle-aged mice compared with young mice following Fx-TH. These results collectively suggest that the extent of hepatic damage following Fx-TH is dependent on the age of the subject.

Hypertonicity triggers RhoA-dependent assembly of myosin-containing striated polygonal actin networks in endothelial cells

Endothelial cells respond to mechanical stresses of the circulation with cytoskeletal rearrangements such as F-actin stress fiber alignment along the axis of fluid flow. Endothelial cells are exposed to hypertonic stress in the renal medulla or during mannitol treatment of cerebral edema. We report here that arterial endothelial cells exposed to hypertonic stress rearranged F-actin into novel actin-myosin II fibers with regular 0.5-microm striations, in which alpha-actinin colocalizes with actin. These striated fibers assembled over hours into three-dimensional, irregular, polygonal actin networks most prominent at the cell base, and occasionally surrounding the nucleus in a geodesic-like structure. Hypertonicity-induced assembly of striated polygonal actin networks was inhibited by cytochalasin D, blebbistatin, cell ATP depletion, and intracellular Ca(2+) chelation but did not require intact microtubules, regulatory volume increase, or de novo RNA or protein synthesis. Striated polygonal actin network assembly was insensitive to inhibitors of MAP kinases, tyrosine kinases, or phosphatidylinositol 3-kinase, but was prevented by C3 exotoxin, by the RhoA kinase inhibitor Y-27632, and by overexpressed dominant-negative RhoA. In contrast, overexpression of dominant-negative Rac or of dominant-negative cdc42 cDNAs did not prevent striated polygonal actin network assembly. The actin networks described here are novel in structure, as striated actin-myosin structures in nonmuscle cells, as a cellular response to hypertonicity, and as a cytoskeletal regulatory function of RhoA. Endothelial cells may use RhoA-dependent striated polygonal actin networks, possibly in concert with cytoskeletal load-bearing elements, as a contractile, tension-generating component of their defense against isotropic compressive forces.

MyD88 and Src are differentially regulated in Kupffer cells of males and proestrus females following hypoxia

Hypoxia produces sex dimorphic immune responses in males and proestrus females. Because Kupffer cells are the major source of proinflammatory cytokines, studies were conducted to discern IL-6 production in mouse Kupffer cells following hypoxia. Hypoxia enhances TLR4 expression in Kupffer cells irrespective of sex. However, MyD88 and Src expression in Kupffer cells decreased significantly after hypoxia in proestrus females, whereas Src protein expression and phosphorylation increased in males in concurrence with differences in IL-6 production. 17beta-estradiol administration elevated MyD88 and Src expression in males to levels in normoxic proestrus females. Administration of Src inhibitor in hypoxic males prevented increased IL-6 production. Thus, differential regulation of MyD88 and Src in males and females plays an important role in sex-specific immune response following hypoxia.