Effects of E-selectin and P-selectin blockade on neutrophil sequestration in tissues and neutrophil oxidative burst in burned rats

Cinnamaldehyde-Based Self-Nanoemulsion (CA-SNEDDS) Accelerates Wound Healing and Exerts Antimicrobial, Antioxidant, and Anti-Inflammatory Effects in Rats’ Skin Burn Model

Cinnamaldehyde, the main phytoconstituent of the cinnamon oil, has been reported for its potential wound healing activity, associated to its antimicrobial and anti-inflammatory effects. In this study, we are reporting on the cinnamaldehyde-based self-nanoemulsifying drug delivery system (CA-SNEDDS), which was prepared and evaluated for its antimicrobial, antioxidant, anti-inflammatory, and wound healing potential using the rat third-degree skin injury model. The parameters, i.e., skin healing, proinflammatory, and oxidative/antioxidant markers, were evaluated after 3 weeks of treatment regimens with CA-SNEDDS. Twenty rats were divided randomly into negative control (untreated), SNEDDS control, silver sulfadiazine cream positive control (SS), and CA-SNEDDS groups. An aluminum cylinder (120 °C, 10-s duration) was used to induce 3rd-degree skin burns (1-inch square diameter each) on the rat’s dorsum. At the end of the experiment, skin biopsies were collected for biochemical analysis. The significantly reduced wound size in CA-SNEDDS compared to the negative group was observed. CA-SNEDDS-treated and SS-treated groups demonstrated significantly increased antioxidant biomarkers, i.e., superoxide dismutase (SOD) and catalase (CAT), and a significant reduction in the inflammatory marker, i.e., NAP-3, compared to the negative group. Compared to SNEDDS, CA-SNEDDS exhibited a substantial antimicrobial activity against all the tested organisms at the given dosage of 20 µL/disc. Among all the tested microorganisms, MRSA and S. typhimurium were the most susceptible bacteria, with an inhibition zone diameter (IZD) of 17.0 ± 0.3 mm and 19.0 ± 0.9 mm, respectively. CA-SNEDDS also exhibited strong antifungal activity against C. albicans and A. niger, with IZD of 35.0 ± 0.5 mm and 34.0 ± 0.5 mm, respectively. MIC and MBC of CA-SNEDDS for the tested bacteria ranged from 3.125 to 6.25 µL/mL and 6.25 to 12.5 µL/mL, respectively, while the MIC and MBC for C. albicans and A. niger were 1.56 µL/mL and 3.125 µL/mL, respectively. The MBIC and MBEC of CA-SNEDDS were also very significant for the tested bacteria and ranged from 6.25 to 12.5 µL/mL and 12.5 to 25.0 µL/mL, respectively, while the MBIC and MBEC for C. albicans and A. niger were 3.125 µL/mL and 6.25 µL/mL, respectively. Thus, the results indicated that CA-SNEDDS exhibited significant wound healing properties, which appeared to be attributed to the formulation’s antimicrobial, antioxidant, and anti-inflammatory effects.

Burn-Induced Local and Systemic Immune Response: Systematic Review and Meta-Analysis of Animal Studies

As burn injuries are often followed by a derailed immune response and excessive inflammation, a thorough understanding of the occurring reactions is key to prevent secondary complications. This systematic review, that includes 247 animal studies, shows the post-burn response of 14 different immune cell types involved in immediate and long-term effects, in both wound tissue and circulation. Peripheral blood neutrophil and monocyte numbers increased directly after burns, whereas thrombocyte numbers increased near the end of the first week. Lymphocyte numbers, however, were decreased for at least two weeks. In burn wound tissue, neutrophil and macrophage numbers accumulated during the first three weeks. Burns also altered cellular functions as we found increased migratory potential of leukocytes, impaired antibacterial activity of neutrophils and enhanced inflammatory mediator production by macrophages. Neutrophil surges were positively associated with burn size and were highest in rats. Altogether, this comprehensive overview of the temporal immune cell dynamics shows that unlike normal wound healing, burn injury induces a long-lasting inflammatory response. It provides a fundamental research basis to improve experimental set-ups, burn care and outcome.

Reduction of burn progression with topical delivery of (antitumor necrosis factor-α)-hyaluronic acid conjugates

In this study, we explored whether topical application of antibodies targeting tumor necrosis factor-α (TNF-α) or interleukin-6 (IL-6) conjugated to hyaluronic acid (HA) could reduce the extension of necrosis by modulating inflammation locally in a partial-thickness rat burn model. Partial-thickness to deep partial-thickness burn injuries present significant challenges in healing, as these burns often progress following the initial thermal insult, resulting in necrotic expansion and increased likelihood of secondary complications. Necrotic expansion is driven by a microenvironment with elevated levels of pro-inflammatory mediators, and local neutralization of these using antibody conjugates could reduce burn progression. Trichrome-stained tissue sections indicated the least necrotic tissue in (anti-TNF-α)-HA-treated sites, while (anti-IL-6)-HA-treated sites displayed similar outcomes to saline controls. This was confirmed by vimentin immunostaining, which demonstrated that HA treatment alone reduced burn progression by nearly 30%, but (anti-TNF-α)-HA reduced it by approximately 70%. At all time points, (anti-TNF-α)-HA-treated sites showed reduced tissue levels of IL-1β compared to controls, suggesting inhibition of a downstream mediator of inflammation. Decreased macrophage infiltration in (anti-TNF-α)-HA-treated sites compared to controls was elucidated by immunohistochemical staining of macrophages, suggesting a reduction in overall inflammation in all time points. These results suggest that local targeting of TNF-α may be an effective strategy for preventing progression of partial-thickness burns.

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.

Dissimilar hepatic protein expression profiles during the acute and flow phases following experimental thermal injury

The liver plays a major role in the early hypometabolic and later hypermetabolic phases after severe burn injury. Proteomic analysis was used to identify altered proteins in liver during these two phases. Sprague-Dawley rats were subjected to a full-thickness dorsal burn injury covering 40% of the total body surface area. Controls consisted of sham-treated animals. Liver tissues were collected on postburn days 1 and 7. The proteomic data show greater production of positive acute phase proteins on day 1 than on day 7. Many antioxidant enzymes were coordinately downregulated on day 1, including the potent biliverdin reductase. These antioxidants were restored and in some cases upregulated on day 7. This opposite trend in the change of antioxidant proteins corroborated our finding of more pronounced oxidative stress on day 1 than on day 7 as measured via protein carbonyl content. The changes of metabolic enzymes on days 1 and 7 were consistent with hypo- and hyper-metabolic states, respectively. Furthermore, a previously unreported decrease in ornithine aminotransferase on day 7 may be a key contributor to the observed increased urinary urea excretion during the hypermetabolic phase. Overall, the many differences in protein expression observed on postburn days 1 and 7 reflect the dissimilar hepatic metabolic patterns during the acute and flow phases following burn injury.

Phagocyte migration and cellular stress induced in liver, lung, and intestine during sleep loss and sleep recovery

Sleep is understood to possess recuperative properties and, conversely, sleep loss is associated with disease and shortened life span. Despite these critical attributes, the mechanisms and functions by which sleep and sleep loss impact health still are speculative. One of the most consistent, if largely overlooked, signs of sleep loss in both humans and laboratory rats is a progressive increase in circulating phagocytic cells, mainly neutrophils. The destination, if any, of the increased circulating populations has been unknown and, therefore, its medical significance has been uncertain. The purpose of the present experiment was to determine the content and location of neutrophils in liver and lung tissue of sleep-deprived rats. These are two principal sites affected by neutrophil migration during systemic inflammatory illness. The content of neutrophils in the intestine also was determined. Sleep deprivation in rats was produced for 5 and 10 days by the Bergmann-Rechtschaffen disk method, which has been validated for its high selectivity under freely moving conditions and which was tolerated and accompanied by a deep negative energy balance. Comparison groups included basal conditions and 48 h of sleep recovery after 10 days of sleep loss. Myeloperoxidase (MPO), an enzyme constituent of neutrophils, was extracted from liver, lung, and intestinal tissues, and its activity was determined by spectrophotometry. Leukocytes were located in vasculature and interstitial spaces in the liver and the lung by immunohistochemistry. Heme oxygenase-1, also known as heat shock protein-32 and a marker of cellular stress, and corticosterone also were measured. The results indicate neutrophil migration into extravascular liver and lung tissue concurrent with cell stress and consistent with tissue injury or infection induced by sleep loss. Plasma corticosterone was unchanged. Recovery sleep was marked by increased lung heme oxygenase-1, increased intestinal MPO activity, and abnormally low corticosterone, suggesting ongoing reactive processes as a result of prior sleep deprivation.

Burn injury reveals altered phenotype in mannan-binding lectin-deficient mice

Burn injury destroys skin, the second largest innate immune organ in the body, and triggers chaotic immune and inflammatory responses. The pattern recognition molecule, mannan-binding lectin (MBL), plays an important role in the first-line host defense against infectious agents. MBL initiates the lectin complement pathway and acts as an opsonin. Recent studies suggest that MBL also modulates inflammatory responses. We report that local responses after burn in MBL null mice differ from those found in wild-type (WT) mice in the following important biological markers: spontaneous eschar separation, thinned epidermis and dermis, upregulation of soluble factors including cytokines, chemokines, cell adhesion molecules, a growth factor-binding protein, and matrix metalloproteinases. Mice lacking C1q, C4, or C3 did not show the lack of eschar separation seen in MBL null-burn phenotype. These findings implicate MBL as an important molecule in the maintenance of the homeostatic balance.

Hypertonic saline enhances host defense to bacterial challenge by augmenting Toll-like receptors*

OBJECTIVE

To determine whether hypertonic saline infusion modulates thermal injury-induced bacterial translocation and host response to bacterial challenge through the augmentation of Toll-like receptors (TLRs).

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Thermal injury models in the mice.

INTERVENTIONS

In experiment 1, mice underwent burn were given with 10 mL/kg hypertonic saline (7.5% NaCl), 10 mg/kg saline (N/S1), or 80 mL/kg saline (N/S2) at 4 or 8 hrs after burn. At 24 hrs after burn, mesenteric lymph nodes were harvested for bacterial translocation assay. In experiment 2, mice receiving hypertonic saline or saline after thermal injury received peritoneal challenge with Escherichia coli, and bacterial clearance was measured. In experiment 3, peritoneal cells from mice receiving hypertonic saline or saline after thermal injury were incubated with E. coli, and bacterial count, TLR2, TLR4, MIP2, CXCR2, pp38, and ERK expression were evaluated. In experiment 4, reactive oxygen species production, CXCR2, MIP2, TLR2, and TLR4 expression of bone marrow neutrophil from mice receiving hypertonic saline or saline treatment after thermal injury were evaluated. In experiment 5, neutrophil were cultured with hypertonic saline or N/S and incubated with E. coli. TLR2 and TLR4 expression and bacterial count were evaluated. In experiment 6, mice were fed with oral antibiotics with or without lipopolysaccharide, a TLR ligand, supplements. At 24 hrs after burn, mesenteric lymph nodes were harvested for bacterial translocation assay, and neutrophils were harvested for TLR2 and TLR4 protein assay.

MEASUREMENTS AND MAIN RESULTS

Hypertonic saline decreased thermal injury-induced bacterial translocation. Hypertonic saline increased bacterial clearance, phagocytic activity, and TLR2, TLR4, CXCR2, pp38, and p44/42 expression of peritoneal cells. Hypertonic saline treatment at 4 or 8 hrs after thermal injury decreased reactive oxygen species production of neutrophil. Hypertonic saline injection increased TLR2, TLR4, and pp38 expression of neutrophil. In vitro treatment of neutrophil with hypertonic saline increased phagocytic activity and TLR2 and TLR4 expression. Commensal depletion with oral antibiotics decreased TLR2 and TLR4 expression of neutrophil; lipopolysaccharide increased TLR4 expression of neutrophil and decreased thermal injury-induced bacterial translocation.

CONCLUSIONS

Restoration of extracellular fluid in burn shock with hypertonic saline decreased thermal injury-induced bacterial translocation. Hypertonic saline increased the phagocytic activity and TLR2, TLR4, CXCR2, pp38, and P44/42 expression of peritoneal cells. Hypertonic saline decreased reactive oxygen species but increased TLR2, TLR4, and pp38 expression and phagocytic activity of bone marrow neutrophil. Stimulation of the TLRs with lipopolysaccharide in commensal depleted mice increased TLRs expression of neutrophil and decreased thermal injury-induced bacterial translocation. Taken together with the fact that stimulation of TLRs with hypertonic saline increases phagocytic activity of systemic inflammatory cells, we conclude that TLRs play a critical role in the innate immunity by recognizing bacteria and that hypertonic saline enhances host response to bacterial challenge by increasing TLRs of inflammatory cells.

Early Excision of a Full-Thickness Burn Prevents Peripheral Nerve Conduction Deficits in Mice

BACKGROUND

A full-thickness 20 percent body surface area burn in mice produces a significant decrease in tibial motor nerve conduction velocity within 6 hours of the burn and in sensory conduction velocity within 7 days. This suggests that cutaneous burn injury produces a systemic response that affects peripheral motor and sensory nerve function at a distance from the burn site. The authors tested the hypothesis that burn wound excision either 30 minutes or 3 hours after burn would prevent neuropathy.

METHODS

A 20 percent body surface area third-degree burn was applied to the backs of anesthetized mice using procedures that followed National Institutes of Health guidelines. Motor nerve conduction velocity and sensory conduction velocity were determined in intact, anesthetized mice by percutaneous nerve stimulation. Burn wounds were excised and closed at 30 minutes or 3 hours after burn. Motor nerve conduction velocity and sensory conduction velocity were measured before burn and 1, 3, 7, 14, and 21 days after a burn or sham procedure. The number of circulating neutrophils and serum concentrations of tumor necrosis factor-alpha, nitrite, and electrolytes were also determined in each group.

RESULTS

Motor nerve conduction velocity and sensory conduction velocity in the 30-minute excision (n = 10) and sham group (n = 5) were not significantly different. Motor nerve conduction velocity and sensory conduction velocity in the nonexcised group (n = 10) and 3-hour excision group (n = 10) were significantly decreased. Serum tumor necrosis factor-alpha concentration was elevated 6 hours after burn in nonexcised animals (n = 9) and in 3-hour excision mice (n = 8) but was not significantly different in the sham (n = 8) and the 30-minute excision group (n = 7).

CONCLUSION

The authors conclude that burn wound excision at 30 minutes but not at 3 hours prevents the nerve conduction deficits measured in mice with 20 percent body surface area burns. The cellular basis of burn-induced neuropathy is unknown, but nitric oxide and tumor necrosis factor alpha-alpha appear to play a role.

Inhibition of nitric oxide synthase reverses the effect of albumin on lung damage in burn

BACKGROUND

Early colloid resuscitation in major burn patients has been stopped because of its deteriorating effect on thermal injury-induced vascular hyperpermeability. We hypothesized that inhibition of inducible nitric oxide synthase (iNOS) to stabilize endothelial permeability and to retain colloid solution in the vascular space will reverse its effect on lung damage.

STUDY DESIGN

In experiment 1, specific pathogen free rats underwent 35% total-body surface area burn or sham burn and were given equal volumes (7.5 mL/kg) of normal saline or albumin from femoral veins for fluid resuscitation immediately after burn. In experiment 2, S-methylisothiourea (SMT, 7.5 mg/kg, IP) was given immediately after burn to rats from different groups, as in experiment 1. At 8 hours after burn, blood was assayed for peroxynitrite-mediated dihydrorhodamine 123 (DHR 123) oxidation, and lung tissues were harvested for myeloperoxidase (MPO) determination and histologic studies. Pulmonary microvascular dysfunction was quantified by measuring the extravasations of Evans blue dye.

RESULTS

Blood peroxynitrite level and iNOS expression, MPO activity, permeability, and inflammatory cell infiltration of lungs were significantly induced after thermal injury. Albumin resuscitation after burn without iNOS inhibition enhanced thermal injury-induced lung damage with 10%, 14%, and 5% increases in blood DHR oxidation level, lung MPO activity, and lung permeability, respectively, compared with saline injection. In contrast, burn + SMT rats with albumin injection showed significant, 23%, 37%, and 20%, decreases, respectively, in blood DHR 123 oxidation level, lung MPO activity, and lung permeability compared with burn + SMT + saline rats.

CONCLUSIONS

Thermal injury induced lung damage. Restoration of extracellular fluid in early burn shock with albumin markedly augmented the lung neutrophil deposition, lung permeability increase, and blood peroxynitrite level. Inhibition of iNOS before albumin supplementation reversed its damaging effects on thermal injury-induced lung dysfunction to beneficial ones.

Hypertonic saline-enhanced postburn gut barrier failure is reversed by inducible nitric oxide synthase inhibition

OBJECTIVE

To determine whether inhibition of inducible nitric oxide synthase to stabilize endothelial permeability and to retain hypertonic saline in the vascular space will ameliorate burn-induced gut barrier dysfunction.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Thermal injury models in the rat.

INTERVENTIONS

In experiment 1, specific pathogen free rats underwent 3% total body surface area burn or sham burn and were given 7.5 mL/kg hypertonic saline (7.5% NaCl), 7.5 mg/kg saline, or 50 mL/kg saline (nearly equal sodium load with hypertonic saline) in the right femoral vein for 15 mins for fluid resuscitation at 0, 4, or 8 hrs after burn. In experiment 2, S-methylisothiourea (7.5 mg/kg, intraperitoneally), a specific inducible nitric oxide synthase inhibitor, was given immediately after burn to rats from different groups as in experiment 1. At 24 hrs after burn, the intestinal mucosa was assayed for myeloperoxidase activity and lipid peroxidation, the distribution of fluorescein isothiocyanate-dextran across the lumen of the small intestine was determined, and bacterial translocation to the mesenteric lymph nodes and ileum histology were also examined.

MEASUREMENTS AND MAIN RESULTS

Burn induced significant increases in intestinal mucosa inducible nitric oxide synthase expression, myeloperoxidase activity, lipid peroxidation, intestinal permeability, bacterial translocation to mesenteric lymph nodes, and villi sloughing in rats. Hypertonic saline administration at 0 or 4 hrs after burn worsened intestinal mucosa lipid peroxidation, neutrophil sequestration, intestinal permeability, and villi sloughing compared with those of burn + 7.5 mg/kg saline and burn + 50 mL/kg saline rats. To the contrary, burn + S-methylisothiourea rats with hypertonic saline injection at 4 or 8 hrs after burn showed an improvement of gut barrier function compared with burn + S-methylisothiourea + 7.5 mg/kg saline and burn + S-methylisothiourea + 50 mL/kg saline rats. Administration of hypertonic saline at 8 hrs after burn and S-methylisothiourea injection also significantly attenuated the bacterial translocation to mesenteric lymph nodes and villi sloughing.

CONCLUSIONS

Using hypertonic saline as a resuscitation fluid in early burn shock markedly augmented the thermal injury-induced intestinal mucosa neutrophil deposition, lipid peroxidation, and intestinal hyperpermeability. Inhibition of inducible nitric oxide synthase not only significantly attenuated neutrophil deposition and mucosa lipid peroxidation but also reversed the deteriorating effects of hypertonic saline on thermal injury-induced gut barrier dysfunction and bacterial translocation.

Peripheral axon caliber and conduction velocity are decreased after burn injury in mice

Peripheral neuropathies are reported to arise as a result of the systemic inflammatory response produced by a full-thickness cutaneous burn injury. This study was designed to characterize the magnitude and time course of functional and morphological changes in peripheral axons that arise after a full-thickness dermal burn injury in an animal model. A 20% body surface area (20% BSA) full-thickness dermal burn was applied to the back of C57BL6 female mice. Longitudinal H- and M-wave recordings were used to determine the conduction velocities (CV) of large myelinated motor and sensory axons in the tibial nerve of sham control and burn-injured mice. Motor CVs were significantly reduced from 6 h to 28 days after the burn, and sensory CVs were significantly reduced from 7 to 14 days after the burn. Morphological evaluation also showed that the mean caliber of large axons in tibial nerves and L5 ventral and dorsal roots in burned mice was significantly decreased. The results demonstrate that both functional and morphological deficits may be produced in peripheral nerve axons at sites well removed from a full-thickness dermal burn injury. The neural deficits may contribute to changes in neuromuscular transmission and the development of limb and respiratory muscle weakness that also accompany burn injury.

INDUCIBLE NITRIC OXIDE SYNTHASE INHIBITOR REVERSES EXACERBATING EFFECTS OF HYPERTONIC SALINE ON LUNG INJURY IN BURN

The use of hypertonic saline (HTS) resuscitation in major trauma patients is still controversial. The objective of this study is to determine if inhibition of inducible nitric oxide synthase (iNOS) to stabilize the endothelial permeability and to retain HTS in the vascular space will reverse its exacerbating effect on burn-induced lung damage. In Experiment 1, specific pathogen-free (SPF) rats underwent 35% total body surface area (TBSA) burn and were resuscitated with 7.5 mL/kg HTS (7.5% NaCl), 7.5 mL/kg saline, or 50 mL/kg saline (nearly equal sodium load as HTS) via femoral veins for 15 min immediately after the burn. In Experiment 2, S-methylisothiourea (SMT) (7.5 mg/kg, i.p.) was given immediately after the burn to rats from the different groups of Experiment 1. At 8 h after the burn, the permeability and myeloperoxidase (MPO) activity of lung tissues were determined, and plasma samples were assayed for peroxynitrite levels. Burn significantly induced lung MPO activity, lung permeability, and blood dihydrorhodamine 123 (DHR 123) oxidation in rats. HTS administration after burn significantly increased the blood DHR 123 oxidation level, lung MPO activity, lung permeability, and inflammatory cell infiltration in comparison with those of burn plus 7.5 mg/kg saline and burn plus 50 mL/kg saline rats. In contrast, burn plus SMT rats with HTS injection showed significant 54%, 11%, and 35% decreases in blood DHR 123 oxidation level, lung MPO activity, and lung permeability, respectively, in comparison with burn plus SMT plus 7.5 mg/kg saline rats. In conclusion, restoration of extracellular fluid in early burn shock with HTS supplementation significantly exacerbates burn-induced lung neutrophil deposition, lung hyperpermeability, and blood peroxynitrite production. Inhibition of iNOS before HTS supplementation reverses the deteriorating effects of HTS on thermal injury-induced lung damage to beneficial ones. Using HTS in thermal injury resuscitation without the inhibition of iNOS is dangerous.

Effect of different resuscitation strategies on neutrophil activation in a swine model of hemorrhagic shock

Activated neutrophils play a pivotal role in resuscitation injury. The strategies used for resuscitation (types of fluids and methods of administration) can affect the degree of neutrophil activation. The aim of this study was to test the commonly available resuscitation fluids in a large animal model of hemorrhagic shock to determine the strategy associated with the least degree of neutrophil activation.

METHODS

Female swine (n=63, weight 45-60 kg) were anesthetized using isoflurane and catheters were placed for hemodynamic monitoring. After 120 min, they were subjected to a volume controlled hemorrhage (28 ml/kg) over 15 min, kept in shock for 60 min, and then resuscitated. The resuscitation groups were as follows: (1) anesthesia only (n=5); (2) hemorrhage, sham resuscitation (n=5); (3) LR-fast rate 3x blood loss (n=6); (4) LR slow rate-3x blood loss (n=6); (5) LR low volume-1x blood loss (n=6); (6) Dextran 40-1x blood loss (n=6); (7) 6% hetastarch-1x blood loss (n=6); (8) 5% albumin-1x blood loss (n=6); (9) 25% albumin-1/5x blood loss (n=6); (10) whole blood resuscitation-1x blood loss (n=6); (11) 7.5% hypertonic saline (HTS)-0.3x blood loss (n=5). Resuscitation fluids were infused over 1 h in all groups except group 4 (LR slow rate, which was over 3 h). Animals were observed for 180 min following the resuscitation period. Neutrophil oxidative burst activity was determined in whole blood using flow cytometery.

RESULTS

Animals resuscitated with dextran and hetastarch showed significantly (P<0.05) higher neutrophil burst activity. Resuscitation with LR also caused neutrophil activation (P<0.05), and the highest degree of activation was seen when a large volume of LR was given at a fast rate (group 8). However, all LR infusion protocols were associated with significant neutrophil activation compared with anesthesia (group 1) or sham resuscitation (group 2). No significant activation was seen in the animals resuscitated with albumin or fresh whole blood.

CONCLUSION

Artificial colloids and LR (independent of rate or volume of infusion) caused significant neutrophil activation, which was not seen with albumin and whole blood resuscitation. These findings suggest that the type of resuscitation fluid and method of infusion can influence neutrophil function.

Enhanced Production of Endothelial Microparticles With Increased Binding to Leukocytes in Patients With Severe Systemic Inflammatory Response Syndrome

BACKGROUND

The vascular endothelium sustains substantial damage after severe insult. Recently, activated endothelial cells have been reported to produce microparticles in vitro. The objective of this study was to evaluate endothelial microparticle formation and microparticle-leukocyte interaction among patients with severe systemic inflammatory response syndrome (SIRS).

METHODS

The participants in this study were 28 patients with severe SIRS (SIRS criteria and serum C-reactive protein > 10 mg/dL) and 18 healthy volunteers. Endothelial microparticles in the blood, microparticle-polymorphonuclear leukocyte (PMNL) binding, and PMNL oxidative activity were measured by flow cytometry. Soluble E-selectin, thrombomodulin, and plasminogen activator inhibitor-1 levels in the blood, variables representing systemic vascular endothelial cell activation and damage, and coagulative activity in the blood also were measured.

RESULTS

Endothelial microparticle levels in the blood, microparticle binding to PMNLs, and oxidative activity in PMNLs increased significantly in patients with severe SIRS, as compared with the values in healthy volunteers. Soluble E-selectin, thrombomodulin, plasminogen activator inhibitor-1, and procoagulant activity in the blood also increased in these patients.

CONCLUSIONS

Activated vascular endothelial cells with increased procoagulant activity enhance production of microparticles with increased binding to leukocytes in patients with severe SIRS. Endothelial microparticles may be involved in the pathogenesis of endothelial injury after severe insult.

Mesenteric lymph from burned rats induces endothelial cell injury and activates neutrophils

OBJECTIVE

Our previous studies indicated that mesenteric lymph duct ligation prevented burn-induced lung injury. Thus, the goal of the present study was to begin to investigate potential mechanisms of this protective effect.

DESIGN

Prospective animal study with concurrent control.

SETTING

Small animal laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Mesenteric lymph and portal vein plasma were collected from male rats subjected to a 40% third-degree scald burn or sham burn. The biological effects of these lymph and plasma samples were tested for their ability to kill human umbilical vein endothelial cells (HUVECs), increase HUVEC monolayer permeability, and activate polymorphonuclear leukocytes (PMNs), as reflected in CD11b adhesion molecule expression and superoxide production. Additionally, ileal specimens were harvested at the end of the experiment (6 hrs postburn) for histologic analysis.

MEASUREMENTS AND MAIN RESULTS

Postburn mesenteric lymph produced during the first 2 hrs after burn injury and tested at a 5% concentration, but not sham-burn lymph or portal plasma from burned rats, was toxic for HUVECs resulting in cell death after an 18-hr incubation period. Similarly, only postburn lymph increased HUVEC monolayer permeability. Postburn lymph activated both rat and human PMNs as reflected in increased CD11b expression and augmentation of the phorbol myristate acetate-induced superoxide response. Neither sham-burn lymph nor postburn portal vein plasma activated PMNs. Both the burn and sham-burn lymph samples were sterile, indicating that the effects of burn lymph on the HUVECs or PMNs were not due to translocating bacteria. Last, an association was found between burn-induced gut injury and the production of toxic burn lymph.

CONCLUSIONS

Burn-induced gut injury results in the production of biologically active factors that are carried in the mesenteric lymph, but not the portal plasma, which injure endothelial cells and activate PMNs and thus could contribute to distant organ injury.

Neutrophil CD11b, L-selectin and Fc IgA receptors in patients with dermatitis herpetiformis

BACKGROUND

The skin lesions found in patients with dermatitis herpetiformis (DH) are characterized by the presence of neutrophils at the dermal papillary tips in areas where the diagnostic cutaneous IgA deposits are found. Although the presence of the skin lesions of DH is known to be associated with gluten-sensitive enteropathy, the mechanisms that control the development of skin lesions are not known.

OBJECTIVES

To determine if circulating neutrophils from patients with DH have evidence of priming as shown by increased expression of CD11b, decreased expression of L-selectin and increased function of neutrophil Fc IgA receptor.

METHODS

Neutrophils from 12 normal subjects and 10 DH patients with active, ongoing disease and 14 DH patients with quiescent disease activity were examined by fluorescence-activated cell sorter for expression of cell surface CD11b, L-selectin expression, Fc IgA expression (CD89) and for the function of the Fc IgA receptor by determining the binding capacity of neutrophils for monoclonal human IgA.

RESULTS

Neutrophils from patients with active, ongoing DH had increased expression of CD11b when compared with patients with inactive DH or normal subjects [mean net geometric mean channel fluorescence (GMCF): active DH, 403.3; inactive DH, 237.8; normal subjects, 290.5; P < 0.05]. L-selectin expression in both groups of DH patients was significantly lower than that seen in normal subjects (mean net GMCF: active DH, 363.2; inactive DH, 375.2; normal subjects, 432.7; P < 0.05). No difference in CD89 expression was seen in any of the groups; however, the function of Fc IgA receptor was increased in patients with active DH when compared with patients with inactive DH and normal subjects.

CONCLUSIONS

Neutrophils from patients with active, ongoing DH show an increased expression of CD11b, decreased expression of L-selectin and increased ability to bind IgA, consistent with a pattern of priming of the neutrophils. This priming may occur in the gut as a result of the ongoing mucosal immune response that is present in patients with DH on a gluten-containing diet and may predispose neutrophils to localize in the skin of patients with DH.

Acquired disorders of phagocyte function complicating medical and surgical illnesses

There is evidence that acquired dysfunction of neutrophils, monocytes, or macrophages is an important cause of infection in patients with diabetes mellitus, renal or hepatic failure, alcoholism, autoimmune diseases, influenza or human immunodeficiency virus infection, burns, and trauma. Distinguishable mechanisms of acquired phagocyte dysfunction include inhibitory effects of metabolic disturbances (e.g., hyperglycemia, uremia), chemical toxins (e.g., ethanol), viral proteins on phagocyte activation, and pathologic activation of phagocytes in the circulation (e.g., after hemodialysis, burns, or cardiopulmonary bypass). Although the burden of morbidity and mortality resulting from acquired phagocyte dysfunction appears to be vast, research in this area has been hampered by the complexity of the underlying illnesses and by limitations of laboratory assays and clinical study methodology. Given the advent of improved assays of phagocyte functions and treatments that can enhance these functions, there is a pressing need for more prospective studies of acquired phagocyte dysfunction.

E- and P-selectin expression depends on the resuscitation fluid used in hemorrhaged rats

BACKGROUND

E- and P-selectins are adhesion molecules that effect neutrophil-mediated reperfusion injury. Our hypothesis was that the expression of E- and P-selectins is dependent on the type of fluid used for resuscitation and that lactated Ringer's (LR) solution would result in an early upregulation of these molecules.

METHODS

Male Sprague-Dawley rats (n = 36) were subjected to a 27 ml/kg hemorrhage over 5 min followed by a 1-h shock period and 1-h of resuscitation. The animals were randomized into the following resuscitation groups: (1) sham; (2) hemorrhage, no resuscitation; (3) whole blood (27 ml/kg); (4) 3:1 lactated Ringer's (81 ml/kg); (5) sham hemorrhage, infusion of lactated Ringer's (81 ml/kg); (6) 7. 5% hypertonic saline (9.7 ml/kg). Immediately after resuscitation, the spleen and lung were harvested for measurement of E- and P-selectin mRNA expression with reverse transcriptase- polymerase chain reaction (RT-PCR), and protein expression with immunostaining.

RESULTS

LR resuscitation and LR infusion without prior hemorrhage significantly increased the E- and P-selectin mRNA in the lung and spleen. Immunostaining demonstrated that the adhesion molecule expression was mainly located in perivascular/peribronchial areas in the lung, and the marginal and trabecular areas in the spleen. Pulmonary edema and inflammatory cell infiltration were observed only in the animals that were hemorrhaged and resuscitated with LR. No resuscitation and resuscitation with whole blood caused no significant increase in selectin expression.

CONCLUSION

LR resuscitation and LR infusion without hemorrhage are associated with early increased expression of E- and P-selectin molecules in the lung and spleen.

Dynamics of tissue neutrophil sequestration after cutaneous burns in rats

BACKGROUND

Neutrophil recruitment in organs after burns may cause local vascular damage, which can be reduced by agents blocking neutrophil adhesion to the vascular wall. Because these agents may increase susceptibility to infection, it is important to characterize the dynamics of neutrophil sequestration in order to optimize an eventual anti-adhesion therapy.

MATERIALS AND METHODS

Rats were scald burned over 20 or 40% of their total body surface area (TBSA) and saline resuscitated. Sham controls were used. Myeloperoxidase (MPO) activity was measured in lungs, liver, kidney, gut, and burned skin up to 1 week postburn. Extravascular accumulation of (125)I-labeled bovine serum albumin ((125)I-BSA) was measured at 12 h postburn.

RESULTS

MPO activity in lungs, liver, and kidney was increased within 3 h postburn and returned to normal within 24-48 h. Peak MPO levels occurred at 6-12 h postburn and were similar for both burn sizes. No MPO increase was observed in gut. MPO levels in burned skin did not increase before 6 h, peaked at 24 h, decreased at 48 h, but remained elevated for up to 7 days. Neutrophil recruitment in lungs and liver was confirmed histochemically. No neutrophils were found in kidneys. Extravascular (125)I-BSA was increased in lungs, liver, kidneys, and gut, in the 40% TBSA group only.

CONCLUSIONS

Neutrophil sequestration in remote organs is a transient phenomenon while neutrophil homing into the wound site is sustained. Neutrophil accumulation dynamics are independent of burn size, although a minimum size is required to trigger vascular damage. Temporary early anti-adhesion therapy to reduce lung and liver neutrophil sequestration with little impact on neutrophil homing into the burn wound may be possible.

The use of cylexin (CY-1503) in prevention of reperfusion lung injury in patients undergoing pulmonary thromboendarterectomy

Pulmonary thromboendartectomy (PTE) for chronic thromboembolic pulmonary hypertension may be complicated by reperfusion lung injury. This has previously been demonstrated to be neutrophil-mediated. We postulated that blocking selectin-mediated adhesion of neutrophils to the endothelium with Cylexin (CY-1503) would prevent reperfusion lung injury in this patient population. In this double-blind, randomized, placebo-controlled, parallel study, 26 patients received Cylexin the day of surgery and 25 received placebo. Significantly fewer patients in the treated group (31%) compared with the placebo group (60%) developed lung injury (p = 0.036). However, the average number of days of mechanical ventilation, days in the intensive care unit (ICU) and hospital, as well as mortality were not significantly different between the treatment groups. Those with reperfusion lung injury had significantly elevated percent neutrophils, total protein, and soluble P-selectin in bronchoalveolar lavage fluid compared with those without lung injury. We conclude that reperfusion lung injury after PTE is a high-permeability lung injury and its incidence can be reduced by the administration of Cylexin on the day of surgery.

Role of L-selectin in physiological manifestations after burn and smoke inhalation injury in sheep

The effects of a monoclonal antibody against L-selectin [leukocyte adhesion molecule (LAM)1-3] on microvascular fluid flux were determined in conscious sheep subjected to a combined injury of 40% third-degree burn and smoke inhalation. This combined injury induced a rapid increase in systemic prefemoral lymph flow (sQlymph) from the burned area and a delayed-onset increase in lung lymph flow. The initial increase in sQlymph was associated with an elevation of the lymph-to-plasma oncotic pressure ratio; consequently, it leads to a predominant increase in the systemic soft tissue permeability index (sPI). In an untreated control group, the increased sPI was sustained beyond 24 h after injury. Pretreatment with LAM1-3 resulted in earlier recovery from the increased sPI, although the initial responses in sQlymph and sPI were identical to those in the nontreatment group. The delayed-onset lung permeability changes were significantly attenuated by pretreatment with LAM1-3. These findings indicate that both leukocyte-dependent and -independent mechanisms are involved in the pathogenesis that occurs after combined injury with burn and smoke inhalation.

Systemic thermal injury in anesthetized rabbits causes early pulmonary vascular injury that is not ablated by lazaroids

PURPOSE

To study the effects of a systemic thermal injury on the pulmonary vasculature with and without inhibitors of lipid peroxidation (U74389G).

METHODS

In a prospective, placebo control, randomized, and blinded multi-group study, burn shock was induced by scalding thermal injury (65C) to 35% body surface area in rabbits (n = 28). Hemodynamics and gas exchange were followed for 240 min post burn in four groups: No Burn, Burn-Control, Burn-U74 (10 mg.Kg-1 U74389G), No Burn-U74 (10 mg.Kg-1 U74389G).

RESULTS

Scald resulted in early pulmonary injury as measured by increased pulmonary vascular resistance in the pooled Burn group compared with the No Burn groups (942 +/- 358 vs 605 +/- 255 dynes.sec-1.cm-5 respectively, P < 0.05). These pulmonary changes were associated with alveolar sequestration of leukocytes (4.8 +/- 2.9 vs 17.7 +/- 6.0 cells x 10(9).L-1, P < 0.05) in the No Burn and Burn groups respectively. Histological evidence of decreased neutrophil sequestration after scald injury was present in U74 treated animals (3+ vs 2+, P < 0.05 in the Burn and No Burn groups respectively and 2+ vs 2+, P > 0.05 in the Burn-U74 and No Burn-U74 groups respectively) although bronchial alveolar lavage still demonstrated neutrophil sequestration (5.3 +/- 2.5 vs 12.2 +/- 3.3 cell 10(9).L-1, P < 0.05 in No Burn-U74 and Burn-U74 groups respectively). Similarly, circulating white blood cells were increased in the Burn group but not Burn-U74 group four hours post burn. The increase in pulmonary vascular resistance after burn was not altered by administration of U74.

CONCLUSIONS

Systemic burn results in early pulmonary vascular changes associated with leukocyte sequestration. After scald injury administration of lazaroids (U744389G) did not lessen pulmonary vascular resistance changes but did reduce neutrophil sequestration.

Posttranslational modifications of cardiac and skeletal muscle proteins by reactive oxygen species after burn injury in the rat

OBJECTIVE

To determine the involvement of oxidative damage in muscle wasting after burn injury.

SUMMARY BACKGROUND DATA

Burn injury damages tissue at the site of the burn and also affects peripheral tissue. There is evidence to suggest that reactive oxygen species may be generated in increased amounts after burn, and these may contribute to wound healing and to posttranslational modifications of tissue constituents distant from the wound site.

METHODS

The oxidation of muscle proteins was assessed, using the dinitrophenylhydrazine assay for carbonyl content, in muscles of rats after a full-thickness skin scald burn covering 20% of the total body surface area, over a 6-week period. In this model, rats failed to incur normal body weight or muscle weight gain.

RESULTS

Soleus, extensor digitorum longus, diaphragm, and heart ventricle proteins were oxidatively damaged after injury. The extent of tissue protein oxidation, however, differed depending on the time points studied. In general, higher levels of protein carbonyl group formation, an indicator of oxidative damage, were found to occur within 1 to 5 days after injury, and the oxidized protein content of the various tissues decreased during the later stages. Both sarcoplasmic and myofibrillar carbonyl-containing proteins accumulated in diaphragm 3 days after burn injury and were rapidly removed from the tissue during a 2-hour in vitro incubation. This coincided with increased proteolytic activity in diaphragm.

CONCLUSIONS

These observations suggest that the loss of proteins modified by reactive oxygen species may contribute to the burn-induced protein wasting in respiratory and other muscles by a proteolytically driven mechanism.