The effect of N-acetylcysteine on oxidative stress in intestine and bacterial translocation after thermal injury

Ischemia due to transient splanchnic vasoconstriction following major burns causes oxidative and/or nitrosative damage in intestinal tissue followed by reperfusion injury. Thus, burn injury leads to breakdown in the intestinal mucosal barrier which can induce bacterial translocation (BT). As an antioxidant and anti-inflammatory agent the protective effects of N-acetylcysteine (NAC) are documented in several studies. This study was designed to determine the effect of NAC treatment on the oxidative stress in the intestine and BT after burn injury. To evaluate this, 32 Wistar rats were randomly divided into four groups as sham (n = 8), burn (n = 8), pre-burn, NAC injection (150 mg kg⁻¹, intraperitoneally) 15 min before thermal injury (n = 8), post-burn, NAC injection (150 mg kg⁻¹, intraperitoneally) 2 h after thermal injury. Under anesthesia, the shaved dorsal skin of rats was exposed to boiling water for 12 s to induce burn injury in a standardized manner. Twenty-four hours later, tissue samples from mesenteric lymph nodes (MLN), spleen, and liver were obtained under sterile conditions for microbiological analysis and ileum samples were harvested for biochemical analysis. In the burn group, the incidence of isolating bacteria in MLN, spleen, and liver specimens was significantly higher than other groups. NAC treatment prevented burn-induced BT in both pre- and post-burn groups. Thermal injury caused a significant decrease in glutathione (GSH) level, significant increases in malondialdehyde (MDA) and myeloperoxidase (MPO) activity at post-burn 24th hour. Treatment of rats with NAC significantly elevated the reduced GSH levels while decreasing MDA levels and MPO activity. These data suggested that NAC has a crucial cytoprotective role in intestinal mucosal barrier and preventive effects against burn injury-induced BT.     

The role of poly(ADP-ribose) synthetase inhibition on the intestinal mucosal barrier after thermal injury

Oxidative and nitrosative stressor agents can trigger DNA strand breakage, which then activates the nuclear enzyme poly(ADP-ribose) synthetase (PARS). Activation of the enzyme depletes the intracellular concentration of energetic substrates such as nicotinamide adenine dinucleotide (NAD). This process can result in cell dysfunction and cell death. PARS inhibitors have been successfully used in ischemia–reperfusion injury, inflammation and sepsis in several experimental models. In our experimental study, we investigated the role of 3-aminobeanzamide (3-AB), a non-specific PARS inhibitor, on the intestinal mucosal barrier after burn injury. Twenty-four Wistar rats were randomly divided into three groups. The sham group (n = 8) was exposed to 21 °C water while the burn group (n = 8) and the burn + 3-AB group (n = 9) were exposed to boiling water for 12 s to produce a full thickness burn in 35–40% of total body surface area. In the burn + 3-AB group, 10 mg/kg of 3-AB was given intraperitoneally 10 min before thermal injury. Twenty-four hours later, tissue samples from mesenteric lymph nodes (MLN), spleen and liver were obtained under sterile conditions for microbiological analysis and ileum samples were obtained for biochemical and histopathological analysis. In burn group, the incidence of bacteria isolated from MLN and spleen was significantly higher than other groups (P < 0.05). 3-AB pre-treatment prevented burn induced bacterial translocation and it significantly reduced burn induced intestinal injury. Tissue malondialdehyde and 3-nitrotyrozine levels were found significantly lower than that of the burn group. These data suggest that the relationship between PARS pathway and lipid peroxidation in intestinal tissue and PARS has a role in intestinal injury caused by thermal injury.     

Reversal of the effect of albumin on gut barrier function in burn by the inhibition of inducible isoform of nitric oxide synthase

HYPOTHESIS: The use of albumin in the early resuscitation formula after major burn has been forbidden because of its damaging effect on the gut barrier function. We hypothesize that inhibition of the inducible isoform of nitric oxide synthase to stabilize endothelial permeability and to retain albumin in the vascular space will ameliorate the major trauma-induced gut barrier dysfunction. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES: In experiment 1, specific pathogen-free rats undergoing 35% total body surface area burn or sham burn were given equal volumes (7.5 mL/kg) of isotonic sodium chloride solution or albumin from femoral veins for fluid resuscitation at 0, 4, or 8 hours after burn. In experiment 2, intraperitoneal S-methylisothiourea sulfate (7.5 mg/kg) was given immediately after burn to rats from different groups, as in experiment 1 (SMT groups). At 24 hours after burn, the intestinal mucosa was assayed for myeloperoxidase activity as an index for neutrophil sequestration, the distribution of fluorescein isothiocyanate-dextran across the lumen of small intestine was determined to evaluate the intestinal permeability, and bacterial translocation (BT) to the mesenteric lymph nodes (MLNs) and histological findings in the ileum were also examined. RESULTS: Compared with sham burn, burn induced significant increases in intestinal mucosa myeloperoxidase activity, intestinal permeability, BT to the MLNs, and villi sloughing in rats. Albumin administration at 0 or 4 hours after burn enhanced the increases in neutrophil sequestration, permeability, and villi sloughing compared with saline injection at the same times. In contrast, injection of albumin in the burn-SMT group did not aggravate these changes in intestinal myeloperoxidase activity, intestinal permeability, BT to the MLNs, and villi edema. Burn-SMT rats with albumin injections at 4 or 8 hours after burn showed significant 35% and 52% decreases, respectively, in intestinal permeability compared with burn-SMT-saline rats. Use of albumin at 8 hours after burn in combination with S-methylisothiourea significantly attenuated BT to the MLNs and reduced villi edema. CONCLUSIONS: Early albumin resuscitation aggravated the burn-induced gut damage. Albumin administration and inhibition of the inducible isoform of nitric oxide synthase in combination decreased burn-induced gut barrier dysfunction and reversed the damaging effect of albumin on gut barrier function and decreased BT.     

The effects of ketamine and propofol on bacterial translocation in rats after burn injury

BACKGROUND: Bacterial translocation (BT) occurs after thermal injury and may result from an ischemic intestinal insult. The aim of the study was to investigate the effects of ketamine and propofol as anesthetic agents on BT in an animal model of burn injury. METHODS: Sixty male Wistar Albino rats were randomly assigned to six groups of 10 rats each. Anesthesia was induced and maintained with ketamine in groups 1, 2 and 3 and with propofol in groups 4, 5 and 6 during 6 h. Groups 2, 3, 5 and 6 received 30% total body surface area (TBSA) third-degree burns. Groups 1 and 4 had no burn injury. Then, they were allowed to recover from the anesthesia at the end of 6 h. Mean arterial pressure (MAP) was monitored continuously and maintained within 10% of baseline (before burn injury) levels in all animals. Animals in groups 3 and 6 had a laparotomy to obtain a tissue sample from the terminal ileum for determination of intestinal lipid peroxidation by-product malondialdehyde (MDA) before (baseline) and 6 and 24 h after burn injury (ABI). So these animals were not included in the BT studies. At postburn 24 h, animals in groups 1, 2 and 4, 5 were sacrified and samples were taken from the mesenteric lymph nodes (MLN), liver and spleen for bacteriologic cultures. RESULTS: The incidence of BT was found to be significantly higher in group 2 than in all the other groups. Bacterial translocation incidence of group 5 was not significantly different from that of groups 4 and 1. Group 5 was associated with a significantly reduced number of enteric organisms per gram of tissue compared to group 2. Baseline MDA contents of groups 3 and 6 were similar. Ileal MDA levels were increased in group 3, but there were no significant changes in group 6 at 6 and 24 h ABI compared to baseline. CONCLUSION: Our results suggest that propofol as an anesthetic agent may prevent BT by scavenging reactive oxygen species and inhibiting lipid peroxidation in an animal model of burn injury.     

Changes in lymphocyte number and phenotype in seven lymphoid compartments after thermal injury.

Thermal injury is associated with dysfunction of host defense systems. The present study used flow cytometric immunofluorescence analyses to investigate changes in number and phenotype of lymphocytes in seven different lymphoid compartments at 2, 6, 12, 24, 48, and 60 days after 50% total body-surface area thermal injury in the rat. Relative to sham-injured control rats, at postburn day 2, significant lymphopenia was observed in the peripheral blood along with depletion of lymphocytes from the spleen and thymus. By day 6 after injury, lymphocytes in the bone marrow and cervical lymph nodes decreased significantly while numbers in the spleen and thymus remained depressed. Splenic and cervical node lymphocyte numbers normalized by day 12, the bone marrow and thymus numbers still were significantly lower than control, and a 6.5-fold increase in number of lymphocytes was observed in the nodes draining the burn wound, pooled axillary, brachial, inguinal, and lumbar lymph nodes. At day 24 after injury, the thymus and bone marrow virtually were depleted of lymphocytes, the mesenteric lymph nodes manifested a significant decrease, and lymphocytes in the nodes draining the burn wound continued to increase in number. This same pattern was maintained on day 48, but numbers of lymphocytes in the mesenteric nodes normalized. At day 60 after injury, lymphocyte numbers in all tissues were normalized, but the spleen and nodes draining the burn wound where increased numbers compared to control persisted. Cell-surface phenotyping was performed on all lymphoid tissues at all time intervals to determine the percentages of lymphocytes comprising the following subsets: Ia+ cells (B cells and activated T cells), T cells, T-Helper/Inducer cells (T-H/I), and T-Suppressor/Cytotoxic (T-S/C) cells. Although changes in lymphocyte subset percentages were complex, they could be divided grossly into two phases. First, all compartments showed significant phenotypic changes in the first six days after burn. With the exception of the nodes draining the burn wound and the blood, this was followed by a return towards normal on day 12. The second phase then ensued with significant phenotypic changes again occurring in most tissues from days 24 to 60 after injury. These studies demonstrate that burn injury results in dramatic alterations in lymphocyte numbers and subset percentages in different lymphoid compartments. Immune alterations observed following thermal injury may be due, in part, to a redistribution of the cellular elements responsible for generation of the immune response.     

Portal Hypertension Promotes Bacterial Translocation in Rats Mono- and Non Mono-Associated with Escherichia Coli C25

The basis for the high incidence of infectious complications in portal hypertension (PHT) remains unclear. The hypothesis that PHT induces bacterial translocation (BT) was tested in a rat model with or without mono-association with streptomycin resistant Escherichia coli C25 and with or without hypovolemic shock. PHT was achieved by partial portal vein ligation and three weeks later hypovolemic shock (HS) was induced. Blood, liver, spleen and mesenteric lymph nodes cultures were performed twenty-four hours later.PHT promoted BT to mesenteric lymph nodes in indigenous flora (4/6 [67%]) and mono-associated animals (7/9 [78%]) compared to sham laparotomy and sham shock (SL + SS) animals (0/6 [0%] and 2/9 [22%] respectively) (p = 0.03). The combination of PHT and HS resulted in increased mortality in mono-associated (7/15 [47%]) and non mono-associated animals (8/15 [53%]). No significant translocation was noted in liver and spleen and bacteremia was found only in the PHT + HS mono-associated animals (4/8 [50%]).PHT induces BT to mesenteric lymph nodes and this may account for the high incidence of septic complications associated witti PHT. In this model, the addition of HS to PHT leads to an increased mortality but without uniform translocation of the gut flora beyond mesenteric lymph nodes.     

N-acetylcysteine attenuates bacterial translocation after partial hepatectomy in rats

BACKGROUND: Translocating enteric bacteria have been suggested as playing a major role in the development of infections after partial hepatectomy. We investigated the effect of N-acetylcysteine (NAC) on bacterial translocation (BT) and intestinal mucosa as the first line of defense against BT. MATERIALS AND METHODS: We compared four groups of eight Sprague-Dawley male rats each: sham, control (partially hepatectomized), partial hepatectomy plus preoperative single-dose NAC, and a fourth that received partial hepatectomy with a preoperative single-dose NAC plus treatment with NAC for 2 days. Microorganism counts of tissues, lung injury score, lung tissue glutathione, and malondialdehyde levels and microscopy of intestinal mucosa were studied at the end of 48 h. RESULTS: Microorganism count in the lung and mesenteric lymph node cultures and lung injury score were significantly higher in the control group when compared with the sham, third, and fourth groups (lung: 9919.6 versus 0.0, 2912.9, 1550.0 cfu/g tissue; mesenteric lymph nodes: 8458.3 versus 0.0, 89.0, 88.9 cfu/g tissue; lung injury score: 3.25 versus 0.5, 1.13, 1.75). In the control group, the villous height of the distal ileal mucosa was significantly shorter than the sham group (65.25 versus 75.25 microm) and the difference from groups 3 and 4 was not statistically significant. Neutrophil infiltration in the distal ileal mucosa of the control group was significantly higher than the sham, third and fourth groups (3.13 versus 0.25, 0.38 and 1.0). CONCLUSIONS: The parenteral use of NAC attenuates bacterial translocation after partial hepatectomy in rats. Attenuation of the lung injury after partial hepatectomy in NAC-treated groups might be attributable to both anti-inflammatory effect and the effect on BT.     

A comparison of effects of thermal injury and smoke inhalation on bacterial translocation

Thermal injury as well as smoke inhalation injury results in serious morbidity and high mortality. In a chronic ovine model, we studied the development of bacterial translocation to the mesenteric lymph node, liver, spleen, kidney, and lung following: 1) sham injury (N = 6), 2) cutaneous thermal injury (N = 5), 3) cotton smoke inhalation injury (N = 4), 4) combined thermal injury and smoke inhalation injury (N = 7). Cardiac output, mean arterial pressure, and plasma protein concentration were maintained within 10% of preinjury values. Urine output was maintained above 1 ml/kg/hour with fluid and plasma resuscitation. A wide-beam ultrasonic flow probe was chronically implanted to allow serial measurement of cephalic mesenteric arterial blood flow throughout the 48-hour experimental period. Sheep were sacrificed 48 hours following injury for quantitative organ culture of mesenteric lymph node, liver, spleen, kidney, and lung. Measurements of mesenteric blood flow demonstrated a decrease to 48 +/- 8%, 80 +/- 5%, and 64 +/- 9% of preinjury levels in sheep receiving thermal injury, smoke inhalation injury, and combination injury, respectively. The sham animals maintained mesenteric blood flow at 102 +/- 7% of control levels. Thermal injury, as well as combination thermal and smoke inhalation injury, resulted in higher levels of translocation than smoke inhalation injury alone.     

Mesenteric lymphadenectomy prevents postburn systemic spread of translocated bacteria.

We investigated the role of mesenteric lymph nodes in postburn systemic spread of intestinal bacteria. Group 1 minipigs (n=8) had a 40% third-degree burn. Group 2 minipigs (n=7) had the same burn injury, but their mesenteric lymph nodes were removed immediately after burn. Group 3 minipigs (n=8) had sham burn, and group 4 minipigs (n=6) had mesenteric lymph node removal under anesthesia. All minipigs were killed at 48 hours, and tissues were harvested for bacteriological culture. Group 1 showed a large number of positive cultures from several of the systemic organs. Group 2 demonstrated no positive cultures in any of the tissues except the peritoneal fluid. These data suggest that bacterial translocation occurs mainly via mesenteric lymphatics to mesenteric lymph nodes and, thence, into other systemic tissue. After major burns, mesenteric lymph nodes may become an additional focus of infection.     

Beneficial effects of recombinant platelet-activating factor acetylhydrolase and BN 52021 on bacterial translocation in cerulein-induced pancreatitis

BACKGROUND: Bacterial translocation (BT) has been suggested to be responsible for the high incidence of infections occurring after acute pancreatitis (AP). The aim of this study was to investigate the effects of the platelet-activating factor (PAF) inactivator, recombinant PAF-acetylhydrolase (rPAF-AH), and the PAF receptor antagonist, BN 52021, in AP. METHODS: Forty-eight male Wistar rats were divided into 4 groups: the sham group received saline intraperitoneally every hour for 6 h; the control group received cerulein 50 g/kg i.p. every hour for 6 h; the rPAF-AH group received AP plus rPAF-AH (5 mg/kg i.v. bolus), and the BN52021 group received AP plus BN 52021 (5 mg/kg i.v. bolus). The animals were sacrificed 12 h after the first cerulein injection. RESULTS: Supramaximal cerulein stimulation induced an increase in serum pancreatic enzymes, interleukin (IL)-6, pancreatic edema, and produced histologic evidence of AP. Compared with the control group, the addition of PAF receptor antagonists had a significant effect on serum pancreatic enzymes, pancreatic edema, and the histologic score of the pancreatitis. AP caused significant increases in BT in mesenteric lymph nodes (MLNs), pancreas, liver, spleen and blood. Compared with the control group, both rPAF-AH and BN 52021 decreased BT in the pancreas and blood. In addition, rPAF-AH decreased BT in the MLNs. We also found that PAF receptor antagonists suppressed the elevation in IL-6 levels. CONCLUSION: PAF antagonists attenuated the severity of experimental AP and reduced pancreatitis-induced BT to distant sites.     

Effect of steroid on mitochondrial oxidative stress enzymes, intestinal microflora, and bacterial translocation in rats subjected to temporary liver inflow occlusion

Protective effects of steroids against ischemia-reperfusion (I/R) injury are well known, but there is little information about the influence of temporary inflow occlusion on intestinal barrier function or bacterial translocation. The aim of this experimental study was to investigate the effects on liver, kidney, spleen, ileal mitochondrial stress enzymes, and bacterial translocation of methylprednisolone (MP) in rats undergoing temporary liver inflow occlusion. Twenty-seven pathogen-free Wistar albino rats were randomized into three groups: group A: I/R (n = 10); group B: I/R + MP (n = 10); and group C: sham (n = 7). Rats in groups A and B were subjected to 20 minutes of portal vein and hepatic artery occlusion with 3 mg/kg MP injected into group B animals intraperitoneally during the occlusion. Twenty-two hours later, all rats were sacrificed to measure mitochondrial oxidative stress enzymes in liver, kidney, spleen, and ileum. We evaluated intestinal bacterial counts, intestinal mucosal histopathology, bacterial translocation to mesenteric lymph nodes (MLN), liver, spleen, and kidney. Decreased levels of malondialdehyde and increased levels of glutathione were observed in all examined tissues of group B compared to those of group A rats. Statistically significant increases in the intestinal counts of Klebsiella spp and Proteus spp and of bacterial translocation to liver, kidney, spleen, and MLN were measured in group B with respect to group A.     

Specific inhibition of iNOS decreases the intestinal mucosal peroxynitrite level and improves the barrier function after thermal injury

Failure of GI tract mucosa to act as a barrier against bacterial translocation (BT) has been proposed as a potential source of sepsis and subsequent multiple organ failure post thermal injury. Nitric oxide (NO) is an inorganic radical produced by NO synthase (NOS) from -arginine. Gut mucosal constitutive NOS (cNOS) provides protection for itself. In contrast to cNOS, inducible NOS (iNOS) releases far greater amounts of NO, promotes oxidative reactions and is responsible for tissue injury. Peroxynitrite formed by the rapid reaction between superoxide and NO, is a toxic substance that contributes to tissue injury in a number of biological systems. This study was designed to investigate the effect of iNOS specific inhibitor S-methylisothiourea (SMT) on the postburn intestinal mucosal barrier function and the possible mechanism of SMT's action. Female SPF Sprague–Dawley rats underwent 35% total body surface area (TBSA) or sham burn. Either SMT or the same volume of saline was given (5 mg/kg, i.p. q 12 h) for 2 days to assess the effect of iNOS inhibition. On postburn day 2, the intestinal mucosal cNOS and iNOS activity were assayed by using Griess' reagent, the mesenteric lymph node (MLN), spleen and liver were collected and cultured for BT assay and the cellular localization of nitrotyrosine, a marker for peroxynitrite activity, was examined by immunostaining. After thermal injury in rats, administration of SMT for 2 days decreased the intestinal mucosal iNOS activity/tNOS activity ratio and the BT incidence. Nitrotyrosine immunostaining of the intestinal mucosa showed a decrease in the SMT-treated group. These findings suggest that SMT, a specific inhibitor for iNOS improves the barrier function after burn by suppression of the intestinal mucosal iNOS activity. The decrease in NO production resulted in decreased formation of peroxynitrite and subsequently decreased damage of mucosal tissue.     

Administration of nitric oxide with caspase inhibitors minimizes bacterial translocation in experimental intestinal transplantation

BACKGROUND: Bacterial translocation (BT) has been suggested to be responsible for the high incidence of infections occurring after small-bowel transplantation (Trp). Nitric oxide (NO) and apoptosis could affect cell demise. The aim of this study was to asses whether supplementation of University of Wisconsin (UW) solution with NO donors and apoptosis inhibitors can abolish BT in Trp. METHODS: The following experimental groups were studied: sham, Trp, intestinal transplantation, Trp+spermine NONOate (NONOs), and Trp+NONOs+caspase inhibitor Z-Val-Ala-Asp(Ome)-fluoromethylketone(Z-VAD-fmk). Histologic analysis, caspase-3 activity, DNA fragmentation, and BT from graft to mesenteric lymph nodes, liver, and spleen were measured in tissue samples after transplantation. RESULTS: During intestinal transplantation, apoptosis and necrosis were increased, showing graft injury and high levels of BT. The rats treated with NONOs showed a histologic protection of transplanted graft and a decrease in BT despite caspase-3 and DNA fragmentation-inducing effects. Administration of caspase inhibitor Z-VAD to NONOs-treated rats reversed the NO apoptosis-inducing effects and showed the lowest levels of BT in all tissues. CONCLUSIONS: Exogenous administration of NO associated with the inhibition of apoptosis maintains the graft in optimal conditions in terms of BT and improves the histology of the graft after intestinal transplantation in rats.     

N-acetylcysteine improves intestinal barrier in partially hepatectomized rats

BACKGROUND: Translocating enteric bacteria play an important role in the development of infections following partial hepatectomy. The intestine itself is the first line of defence against bacterial translocation (BT). We investigated the effect of N-acetylcysteine (NAC) on BT and the intestinal wall. METHODS: We compared four groups of Sprague-Dawley male rats (eight in each group): sham, sham plus preoperative single dose of NAC, partial hepatectomy and partial hepatectomy plus preoperative single dose of NAC. Microorganism count in the tissues and the glutathione and malondialdehyte contents of the intestinal wall were studied at the end of the 24th hour. RESULTS: Bacterial growth was observed in the spleen and mesenteric lymph nodes in the sham group. There was bacterial growth in all the samples of the partial hepatectomy group. Differences were significant except in atrial and portal blood counts. In the partial hepatectomy plus NAC treatment group, counts were significantly low in all, except atrial and portal blood samples. The malondialdehyte level in the intestinal wall was 35.38 +/- 10.27 in the sham group, increasing significantly in the partial hepatectomy group (69.50 +/- 21.48), and decreasing in the partial hepatectomy plus NAC treatment group (35.63 +/- 14.12). Glutathione levels decreased significantly in the partial hepatectomy group and increased with preoperative single-dose NAC. CONCLUSION: Partial hepatectomy resulted in oxidative disturbances in intestinal wall, which in turn gave rise to BT. Parenteral NAC protects the intestinal wall from oxidative injury and attenuates BT.     

Bacterial translocation and intestinal atrophy after thermal injury and burn wound sepsis.

Bacterial translocation (BT) occurs after thermal injury in rodents in association with intestinal barrier loss. Infection complicating thermal injury may also affect the intestine producing bowel atrophy. To study these relationships, Wistar rats received either 30% scald followed by wound inoculation with Pseudomonas; 30% scald with pair feeding to infected animals; or sham injury as controls. On days 1, 4, and 7 after injury animals were killed with examination of the bowel and culture of the mesenteric lymph nodes (MLN), livers, spleens, and blood. All burned animals demonstrated BT to the MLN on day 1 after injury, but only burn-infected animals had continued BT on days 4 and 7, with progression of BT to the abdominal organs and blood. Burn injury and infection also resulted in significant atrophy of small bowel mucosa temporally associated with continued BT. Thus injury complicated by infection results in prolonged and enhanced bacterial translocation, perhaps due to failure to maintain the mucosal barrier.     

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.     

Antibiotic prophylaxis diminishes bacterial translocation but not mortality in experimental burn wound sepsis

Pseudomonas (PSA) burn wound sepsis results in prolonged bacterial translocation (BT) of enteric organisms such as E. coli to the mesenteric lymph nodes (MLN) and organs in rats. Intestinal decontamination with oral antibiotics may improve mortality after burn injury, perhaps due to decreased BT. To determine the effect of oral antibiotic prophylaxis effective against E. coli but not PSA on BT and subsequent mortality in a model of PSA burn wound sepsis, rats were given a 30% scald burn and wound inoculation with 10(8) PSA followed by randomization to either ampicillin (50 mg/kg/d) or saline gavage. Cultures of MLN, organs, blood, and cecal contents were obtained on days 1, 4, and 7 after injury, with additional animals observed for 14-day mortality. Although oral antibiotic prophylaxis resulted in increased cecal colony counts, the incidence of BT was unchanged. The number of organisms present in both the MLN and organs, however, was significantly reduced with prophylaxis, indicating cecal overgrowth by non-translocating bacteria. Reduction of the number of translocating organisms did not result in improved mean survival time after injury, suggesting that mortality from PSA burn wound sepsis occurs independently of bacterial translocation.     

Two-Day Fasting Prior to Intestinal Ischemia-Reperfusion Injury on Bacterial Translocation in Rats

ABSTRACT

Purpose: The aim of this study is to verify the effect of two-day fasting prior to intestinal ischemia-reperfusion (I/R) injury on bacterial translocation (BT). Materials and Methods: Mail Sprague–Dawley rats were divided into four groups: group 1, control rats that underwent sham operation only; group 2, rats fasted for two days prior to sham operation; group 3, rats that underwent occlusion of mesenteric vessels for 30 min followed by reperfusion for 4 hr; and group 4, rats fasted for two days prior to the same intestinal I/R injury as in group 3. In all groups, E. coli labeled with ^99mTc were inoculated into the terminal ileum. Two hr after inoculation of E. coli, the rats were killed. A segment of ileum was obtained for histological examination and samples of mesenteric lymph nodes (MLNs), liver, lung, blood, and spleen were obtained for radioactivity determination. Results: There were no significant differences in the intestinal mucosa and radioactivity of all samples between groups 1 and 2. Group 3 showed significantly shorter mucosa and villi, and higher radioactivity of samples, except for MLNs, compared to group 1. Group 4 showed similar mucosa and villi, but significantly higher radioactivity of samples, except for MLNs, compared to group 3. Conclusion: Two-day fasting without I/R injury does not cause mucosal change and BT, but in cases following intestinal I/R injury, two-day fasting increases the susceptibility of BT to systemic organs in rats.     

Effect of Probiotic Supplementation on Bacterial Translocation in Thermal Injury

Purpose To examine the effects of probiotic supplementation and enteral solutions containing glutamine and arginine on bacterial translocation (BT) and intestinal villous atrophy in thermal injury.Methods Forty male Sprague-Dawley rats weighing 200–250 g were divided into four groups of ten. Group 1 served as control group without thermal injury and was fed standard chow. Thermal injury was inflicted as a 30% scald burn in the other three groups. Group 2 was fed standard chow and group 3 was fed standard chow supplemented with a probiotic (Acidophilus plus) containing Bifidobacterium bifidum, Lactobacillus acidophilus, and Lactobacillus bulgaricus (2 × 10⁹ CFU/day) via an orogastric tube. Group 4 was fed only an enteral diet (Stresson multifiber) containing glutamine, arginine, and medium chain triglyceride, at 1 g/kg per day amino acid and 230 kcal/kg, for 7 days before thermal injury. All the animals were killed 24 h after thermal injury, and ileal segments were resected and examined histopathologically. To evaluate BT, samples from blood, mesenteric lymph nodes, and cecal content were cultured under aerobic and anaerobic conditions. Terminal ileum specimens were histologically examined to evaluate mucosal integrity.Results Significantly less BT was seen in groups 3 and 4 than in group 2 (P < 0.001). No significant difference was found between groups 3 and 4. Histological evaluation showed significant reduction in villous atrophy in groups 3 and 4.Conclusion Probiotic supplementation seems to reduce bacterial translocation and decrease intestinal mucosal atrophy in rats with thermal injury, as do enteral solutions with arginine and glutamine.     

Effects of granulocyte colony-stimulating factor on bacterial translocation due to burn wound sepsis

The presence of certain defects in both cellular and humoral immunity after thermal injury has been established. Likewise, the translocation of enteric bacteria to the mesenteric lymph nodes and to distant organs has also been observed following serious thermal injury. The effects of granulocyte colony-stimulating factor (G-CSF) on bacterial translocation, the small bowel mucosa, and cecal bacterial content were investigated in a rat model of burn wound sepsis in which albino Wistar rats were scalded over 30% of their bodies, after which the lesions were infected by 1×10⁸ colony-forming units (cfu)Pseudomonas aeruginosa. The control group was treated with 5% dextrose solution subcutaneously starting 2 days preburn, while the treatment group received 100μg/kg human G-CSF subcutaneously. On the 4th day post burn all animals were killed to examine the bowel and culture of the mesenteric lymph nodes (MLN), livers, and spleens. No significant differences were observed between the groups regarding the cecal bacterial content and small bowel; however, a difference was seen in the ratio of translocation in the MLN liver and spleen and quantitative MLN cultures. Based on these findings, G-CSF was thus found to be significantly effective in reducing bacterial translocation due to burn wound sepsis.