Modulating the functions of neutrophils and lipid peroxidation by FK506 in a rat model of thermal injury

Neutrophil Accumulation in the Small Intestine Contributes to Local Tissue Destruction Following Combined Radiation and Burn Injury

The threat of nuclear disaster makes combined radiation and burn injury (CRI) a relevant topic when discussing modern trauma, as burn injuries are likely to occur with detonation of a conventional nuclear weapon. Previous studies in a murine model have shown that there is a breakdown of the gut epithelium and subsequent bacterial translocation into mesenteric lymph nodes after CRI. This study examines the early innate immune response of the small intestine after CRI. Using a previously established murine model of 5 to 5.5 Gy total body irradiation combined with 15% TBSA burn, the injury response of the small intestine was examined at 24, 48, and 72 hours by visual assessment, myeloperoxidase, and cytokine measurement. At 24 hours, intestinal damage as measured by villus blunting, crypt debris, and decreased mitosis, was apparent in all injury groups but the derangements persisted out to 72 hours only with CRI. The prolonged intestinal damage in CRI was accompanied by a 2-fold (P < .05) elevation in myeloperoxidase activity over sham animals at 48 hours and persisted as a 3-fold (P < .05) elevation at 72 hours after injury. Corresponding levels of KC were 8-fold (P < .05) higher than sham at 48 hours with persistent elevation at 72 hours. An enhanced innate immune response, partially mediated by the influx of neutrophils into the gastrointestinal tract is contributing to the hyperinflammatory state seen after CRI. Attenuation of the local gastrointestinal inflammatory response may play a major role in managing victims after nuclear disaster.

The Role of Hydrogen Peroxide and Other Reactive Oxygen Species in Wound Healing

Wound healing is a complex physiological process important for tissue homeostasis. An acute injury initiates massive cell migration, proliferation and differentiation, synthesis of extracellular matrix components, scar formation and remodelling. Blood flow and tissue oxygenation are parts of the complex regulation of healing. Higher organisms utilize molecular oxygen as a terminal oxidant. This way of gaining energy for vital processes such as healing leads to the production of a number of oxygen compounds that may have a defensive or informatory role. They may be harmful when present in high concentrations. Both the lack and the excess of reactive oxygen species may influence healing negatively.

Blood reflects tissue oxidative stress: a systematic review

We examined whether the levels of oxidative stress biomarkers measured in blood reflect the tissue redox status. Data from studies that measured redox biomarkers in blood, heart, liver, kidney and skeletal muscle were analyzed. In seven out of nine investigated redox biomarkers (malondialdehyde, reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase, vitamin C and E) there was generally good qualitative and quantitative agreement between the blood and tissues. In contrast, oxidized glutathione and the reduced to oxidized glutathione ratio showed poor agreement between the blood and tissues. This study suggests that most redox biomarkers measured in blood adequately reflect tissue redox status.

Tacrolimus (FK506) prevents early stages of ethanol induced hepatic fibrosis by targeting LARP6 dependent mechanism of collagen synthesis

Tacrolimus (FK506) is a widely used immunosuppressive drug. Its effects on hepatic fibrosis have been controversial and attributed to immunosuppression. We show that in vitro FK506, inhibited synthesis of type I collagen polypeptides, without affecting expression of collagen mRNAs. In vivo, administration of FK506 at a dose of 4 mg/kg completely prevented development of alcohol/carbon tetrachloride induced liver fibrosis in rats. Activation of hepatic stellate cells (HSCs) was absent in the FK506 treated livers and expression of collagen α2(I) mRNA was at normal levels. Collagen α1(I) mRNA was increased in the FK506 treated livers, but this mRNA was not translated into α1(I) polypeptide. No significant inflammation was associated with the fibrosis model used. FK506 binding protein 3 (FKBP3) is one of cellular proteins which binds FK506 with high affinity. We discovered that FKBP3 interacts with LARP6 and LARP6 is the major regulator of translation and stability of collagen mRNAs. In the presence of FK506 the interaction between FKBP3 and LARP6 is weakened and so is the pull down of collagen mRNAs with FKBP3. We postulate that FK506 inactivates FKBP3 and that lack of interaction of LARP6 and FKBP3 results in aberrant translation of collagen mRNAs and prevention of fibrosis. This is the first report of such activity of FK506 and may renew the interest in using this drug to alleviate hepatic fibrosis.

Targeting the redox balance in inflammatory skin conditions

Reactive oxygen species (ROS) can be both beneficial and deleterious. Under normal physiological conditions, ROS production is tightly regulated, and ROS participate in both pathogen defense and cellular signaling. However, insufficient ROS detoxification or ROS overproduction generates oxidative stress, resulting in cellular damage. Oxidative stress has been linked to various inflammatory diseases. Inflammation is an essential response in the protection against injurious insults and thus important at the onset of wound healing. However, hampered resolution of inflammation can result in a chronic, exaggerated response with additional tissue damage. In the pathogenesis of several inflammatory skin conditions, e.g., sunburn and psoriasis, inflammatory-mediated tissue damage is central. The prolonged release of excess ROS in the skin can aggravate inflammatory injury and promote chronic inflammation. The cellular redox balance is therefore tightly regulated by several (enzymatic) antioxidants and pro-oxidants; however, in case of chronic inflammation, the antioxidant system may be depleted, and prolonged oxidative stress occurs. Due to the central role of ROS in inflammatory pathologies, restoring the redox balance forms an innovative therapeutic target in the development of new strategies for treating inflammatory skin conditions. Nevertheless, the clinical use of antioxidant-related therapies is still in its infancy.

Role of hydrogen sulfide in severe burn injury-induced inflammation in mice

Endogenous hydrogen sulfide (H(2)S) is naturally synthesized in many types of mammalian cells from L-cysteine in the reactions catalyzed by cystathionine-β-synthase and cystathionine-γ-lyase (CSE). H(2)S has been demonstrated to play a proinflammatory role in various animal models of hindpaw edema, acute pancreatitis, lipopolysaccharide-induced endotoxemia and cecal ligation, and puncture-induced sepsis. Full-thickness burns that exceed 25% of the total body surface area (TBSA) produce a profound systemic inflammatory reaction characterized by leukocyte activation and plasma leakage in the microvasculature of tissues and organs remote from the wound. The aim of this study was to investigate the effect of local burn injury on induced distant organ endogenous H(2)S release and expression of CSE. Male BALB/c mice were subjected to 30% TBSA full-thickness burn and treated with saline (administered intraperitoneally [i.p.]); DL-propargylglycine (PAG, 50 mg/kg i.p.), which is a CSE inhibitor; or sodium hydrosulfide (NaHS, 10 mg/kg i.p.), which is an H(2)S donor. PAG was administered either 1 h before or 1 h after the burn injury, whereas NaHS was given at the same time as the burn injury. Measurements of liver myeloperoxidase (MPO) activities, liver H(2)S-synthesizing activity, plasma H(2)S level and liver and lung CSE mRNA expression and histological examination of tissues were performed after burn injury. Burn injury significantly increased the plasma H(2)S level and liver H(2)S synthesis 8 h after burn compared with the sham group. Burn injury also resulted in a significant upregulation of CSE mRNA in liver and lung. Prophylactic as well as therapeutic administration of PAG significantly reduced burn-associated systemic inflammation, as evidenced by MPO activity and histological changes in liver and lung. Injection of NaHS significantly aggravated burn-associated systemic inflammation. Therefore, our findings show for the first time the role of H(2)S in contributing to inflammatory damage after burn injury.

Tacrolimus ameliorates metabolic disturbance and oxidative stress caused by hepatitis C virus core protein: analysis using mouse model and cultured cells

Hepatic steatosis and insulin resistance are factors that aggravate the progression of liver disease caused by hepatitis C virus (HCV) infection. In the pathogenesis of liver disease and metabolic disorders in HCV infection, oxidative stress due to mitochondrial respiratory chain dysfunction plays a pivotal role. Tacrolimus (FK506) is supposed to protect mitochondrial respiratory function. We studied whether tacrolimus affects the development of HCV-associated liver disease using HCV core gene transgenic mice, which develop hepatic steatosis, insulin resistance, and hepatocellular carcinoma. Administration of tacrolimus to HCV core gene transgenic mice three times per week for 3 months led to a significant reduction in the amounts of lipid in the liver as well as in serum insulin. Tacrolimus treatment also ameliorated oxidative stress and DNA damage in the liver of the core gene transgenic mice. Tacrolimus administration reproduced these effects in a dose-dependent manner in HepG2 cells expressing the core protein. The intrahepatic level of tumor necrosis factor-alpha, which may be a key molecule for the pathogenesis in HCV infection, was significantly decreased in tacrolimus-treated core gene transgenic mice. Tacrolimus thus reversed the effect of the core protein in the pathogenesis of HCV-associated liver disease. These results may provide new therapeutic tools for chronic hepatitis C, in which oxidative stress and abnormalities in lipid and glucose metabolism contribute to liver pathogenesis.

Effect of Calendula officinalis Flower Extract on Acute Phase Proteins, Antioxidant Defense Mechanism and Granuloma Formation During Thermal Burns

Effect of Calendula officinalis flower extract was investigated against experimentally induced thermal burns in rats. Burn injury was made on the shaven back of the rats under anesthesia and the animals were treated orally with different doses of the flower extract (20 mg, 100 mg and 200 mg/kg body weight). The animals treated with the extract showed significant improvement in healing when compared with the control untreated animals. The indicators of the wound healing such as collagen-hydroxyproline and hexosamine contents were significantly increased in the treated group indicating accelerated wound healing in the treated animals. The acute phase proteins-haptoglobin and orosomucoid which were increased due to burn injury were found to be decreased significantly in 200 mg/kg body weight extract treated animals. The antioxidant defense mechanism, which was decreased in the liver during burn injury, was found to be enhanced in treated animals. The lipid peroxidation was significantly lowered in the treated group when compared to control animals. Tissue damage marker enzymes- alkaline phosphatase, alanine and aspartate transaminases were significantly lowered in the treated groups in a dose dependant manner. The histopathological analyses of skin tissue also give the evidence of the increased healing potential of the extract after burn injury.

Oxytocin ameliorates skin damage and oxidant gastric injury in rats with thermal trauma

Transient splanchnic vasoconstriction following major burns causes oxidative and/or nitrosative damage in gastrointestinal tissues due to ischemia, which is followed by reperfusion injury. Oxytocin (OT), a hypothalamic nonapeptide, possesses antisecretory and antiulcer effects, facilitates wound healing and is involved in immune and inflammatory processes. To assess the possible protective effect of oxytocin (OT) against burn-induced gastric injury, Sprague-Dawley rats (250-300g) were randomly divided into three groups as control (n=8), OT-treated burn (n=8) and saline-treated burn (n=8) groups. Under anesthesia, the shaved dorsal skin of rats was exposed to 90 degrees C water for 10s to induce burn injury covering 30% of total body surface area in a standardized manner. Either oxytocin (5microg/kg) or saline was administered subcutaneously immediately after and at 24h following burn, and the rats were decapitated at 48h. Serum samples were assayed for TNF-alpha, and stomach was taken for the determination of malondialdehyde (MDA), myeloperoxidase (MPO) activity, DNA fragmentation rate (%) and histopathological examination. MDA and MPO were assayed for products of lipid peroxidation and as an index of tissue neutrophil infiltration, respectively. When compared to control group, burn caused significant increases in gastric MDA and MPO activity and increased microscopic damage scores at 48h (p<0.001). Oxytocin treatment reversed the burn-induced elevations in MDA and MPO levels and reduced the gastric damage scores (p<0.001, p<0.01), while TNF-alpha levels, which were increased significantly at 48thh after injury (p<0.001), were abolished with OT treatment (p<0.001). The results of this study suggest that oxytocin may provide a therapeutic benefit in diminishing burn-induced gastric inflammation by depressing tissue neutrophil infiltration and decreasing the release of inflammatory cytokines, but requires further investigation as a potential therapeutic agent in ameliorating the systemic effects of severe burn.

Oxidative stress and anti-oxidative mobilization in burn injury

A severe burn is associated with release of inflammatory mediators which ultimately cause local and distant pathophysiological effects. Mediators including Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) are increased in affected tissue, which are implicated in pathophysiological events observed in burn patients. The purpose of this article is to understand the role of oxidative stress in burns, in order to develop therapeutic strategies. All peer-reviewed, original and review articles published in the English language literature relevant to the topic of oxidative stress in burns in animals and human subjects were selected for this review and the possible roles of ROS and RNS in the pathophysiology of burns are discussed. Both increased xanthine oxidase and neutrophil activation appear to be the oxidant sources in burns. Free radicals have been found to have beneficial effects on antimicrobial action and wound healing. However following a burn, there is an enormous production of ROS which is harmful and implicated in inflammation, systemic inflammatory response syndrome, immunosuppression, infection and sepsis, tissue damage and multiple organ failure. Thus clinical response to burn is dependent on the balance between production of free radicals and its detoxification. Supplementation of antioxidants in human and animal models has proven benefit in decreasing distant organ failure suggesting a cause and effect relationship. We conclude that oxidative damage is one of the mechanisms responsible for the local and distant pathophysiological events observed after burn, and therefore anti-oxidant therapy might be beneficial in minimizing injury in burned patients.

Effect of tacrolimus on the production of oxygen free radicals in hepatic mitochondria

OBJECTIVES

Cyclosporine (CsA) causes side effects that occur mainly in the kidney but also in the liver. Several reports have strongly suggested that the production of oxygen free radicals (OFRs) is a common mechanism of CsA toxicity. However, tacrolimus is believed to suppress the production of OFRs.

METHODS

We obtained the mitochondrial fraction with 96% purity from rat liver using a sucrose density gradient solution. Zero to 100 micromol/L tacrolimus was incubated with the mitochondrial fraction for 6 hours at 37 degrees C. OFRs were evaluated by measuring the fluorescent product from the oxidation of an oxidant-sensitive 2,7-dichlorefluorescein using a VICTOR3 multilabel counter.

RESULTS

The fluorescence units for OFR production were increased as the time of exposure to tacrolimus passed from 1 to 6 hours. The fluorescence units in 0.1 micromol/L tacrolimus were 6.0 x 10(5) at 1 hour, 7.8 x 10(5) at 2 hours, 9.0 x 10(5) at 3 hours, 10.0 x 10(5) at 4 hours, 11.1 x 10(5) at 5 hours, and 11.4 x 10(5) at 6 hours. However, the fluorescence units were similar although the tacrolimus concentration increases from 0.1 to 100 micromol/L.

CONCLUSIONS

The results in this experiment suggested that tacrolimus induced the production of OFRs depending on the exposure time.

Protective effect of complex antioxidant preparation containing vitamins and amino acids in rats with burn trauma complicated by endotoxemia

Burn trauma increased blood chemiluminescence, while lipopolysaccharide in a dose of 1 mg/kg potentiated this effect, activated LPO, and decreased plasma antioxidant activity. In erythrocytes, superoxide dismutase activity increased, while activity of peroxide-utilizing enzymes decreased. Myeloperoxidase content increased in the lungs and epidermis. The preparation of alpha-tocopherol, selenium aspartate, and ubiquinone abolished the effect of lipopolysaccharide, but did not modulate the increase in chemiluminescence under the influence of this agent.

Leptin ameliorates burn-induced multiple organ damage and modulates postburn immune response in rats

The present study was designed to determine whether exogenous leptin reduces remote organ injury in the rats with thermal burn trauma. Leptin (10 microg/kg) or saline was administered intraperitoneally after burn injury, and the rats were decapitated at either 6 or 24 h. Plasma samples of 24-h burn group were assayed for the determination of monocyte and neutrophil apoptosis. Thermal injury increased tissue-associated myeloperoxidase (MPO) activity and microscopic damage scores in the lung, liver, stomach, colon and kidney of both 6- and 24-h burn groups. In the 6-h burn group, leptin reduced microscopic damage score in the liver and kidney only, while damage scores in the 24-h burn group were reduced in all the tissues except the lung. Also, in both burn groups, leptin reduced elevated MPO activity in all tissues except the lung. The percentage of mononuclear cells was significantly reduced at the 24 h of burn injury, while the granulocyte percentage was increased. Leptin treatment, however, had no significant effect on burn-induced reversal of white blood cell ratios. On the other hand, burn-induced increase in the death of mononuclear cells and granulocytes was significantly reduced in leptin-treated rats. The results of the present study suggest that leptin may provide a therapeutic benefit in diminishing burn-induced inflammation and associated multiple organ failure.

Caffeic Acid Phenethyl Ester Improves Oxidative Erythrocyte Damage in a Rat Model of Thermal Injury

Oxygen-derived free radicals impair cell membrane functions and induce circulatory disturbances, and free radicals, such as superoxide anion, hydrogen peroxide, hydroxyl radicals, and peroxynitrite, have been suggested to play important roles in the pathogenesis of major burn injuries. The present study investigated the effects of thermal injury on erythrocyte lipid peroxidation and antioxidant status and investigated the effects of caffeic acid phenethyl ester (CAPE), a new antioxidant and anti-inflammatory agent, in rats subjected to thermal injury. Burn injury caused a remarkable increase in erythrocyte lipid peroxidation, levels of nitric oxide (NO), and activities of antioxidant enzymes and xanthine oxidase (XO). The treatment with CAPE decreased both activity of burn-induced XO activity and levels of NO in the erythrocytes. In conclusion, CAPE treatment resulted in decreased erythrocyte lipid peroxidation in thermal injury and helped to prevent oxidative damage by decreasing activity of XO and levels of NO.

Effects of dietary glutamine on antioxidant enzyme activity and immune response in burned mice

OBJECTIVES

We investigated the effect of dietary glutamine (Gln) on specific antibody production and antioxidant enzyme activities in burned mice vaccinated with detoxified Pseudomonas exotoxin A linked with the outer membrane proteins I and F (PEIF). We also evaluated the survival rate of vaccinated and non-vaccinated burned mice infected with Pseudomonas aeruginosa.

METHODS

There were three consecutive experiments. In experiment 1, 30 BALB/c mice were assigned to one of two groups. The control group was fed casein as the protein source; the Gln group received 4% Gln (w/w) to replace part of the casein. Mice were immunized twice with PEIF, and the production of specific antibodies against PEIF was measured every week. Eight weeks after immunization, all mice received a 30% body surface area burn injury. Mice were killed 24 h after the burn. The antioxidant enzyme activities and lipid peroxides in the tissues and specific antibody production were analyzed. In experiment 2, 12 mice were assigned to a control or a Gln group and fed with one the experimental diets for 4 wk. Then burn injury was induced, and mice were killed 24 h later. In vitro, splenocytes were cultured, and interleukin (IL)-4 and IL-10 were measured after mitogen stimulation. In experiment 3, survival rates of vaccinated and non-vaccinated burned mice complicated with P. aeruginosa infection were evaluated. The survival rate was observed for 8 d after the burn.

RESULTS

Antioxidant enzyme activities and lipid peroxides in tissues tended to be lower in the Gln group than in the control group after the burn. Specific antibody production against P. aeruginosa increased significantly in the Gln group at 4 and 7 wk after immunization and at 24 h after the burn. IL-4 concentrations in mitogen-stimulated splenocytes were significantly higher in the Gln group than in the control group. Survival rates of non-vaccinated burned mice in the Gln group were significantly higher than those in the control group, whereas there was no difference in the survival of vaccinated burned mice after bacterial infection.

CONCLUSIONS

These results suggested that vaccinated mice receiving a Gln-enriched diet may have enhanced humoral immunity and attenuated oxidative stress induced by burn injury. Also, Gln supplementation improved the survival of burned mice complicated with P. aeruginosa infection.

Protective effect of FK506 (tacrolimus) in pentylenetetrazol-induced kindling in mice

The repeated administration of otherwise subconvulsant dose of pentylenetetrazol (PTZ) is known to produce chemical kindling in animals. In our study, chronic administration of subconvulsant dose of PTZ (40 mg/kg) produced chemical kindling in mice. Pretreatment with L-arginine (50-100 mg/kg ip) potentiated the PTZ-induced kindling, whereas N(omega)-nitro-L-arginine methyl ester (L-NAME) (10-20 mg/kg ip) showed a protective effect. FK506, a potent neuroprotective agent, dose dependently (0.5-1 mg/kg po) decreased the kindling score. When given in combination, L-NAME potentiated the protective effect of lower dose of FK506 (0.5 mg/kg) on PTZ-induced kindling. L-Arginine (50-100 mg/kg) reversed the protective effect of FK506 (1 mg/kg) and L-NAME (20 mg/kg). Biochemical studies showed the potential role of free radical toxicity in the kindled mice, as there was an increased lipid peroxidation as indicated by elevated malondialdehyde (MDA) and nitrite levels and decrease in GSH and superoxide dismutase (SOD) levels. FK506 pretreatment significantly reversed the elevated MDA and nitrite levels, GSH and SOD depletion induced by PTZ treatment. In conclusion, the results of the present study suggest the possible neuroprotective action of FK506 against PTZ-induced kindling.

Effects of dietary arginine supplementation on antibody production and antioxidant enzyme activity in burned mice

This study investigated the effect of arginine (Arg) supplementation on specific antibody production and antioxidant enzyme activities in burned mice vaccinated with detoxified Pseudomonas exotoxin A linked with the outer membrane proteins I and F, named PEIF. Also, the survival rate of burned mice complicated with Pseudomonas aeruginosa was evaluated. Experiment 1: Thirty BALB/c mice were assigned to two groups. One group was fed a control diet with casein as the protein source, while the other group was supplemented with 2% Arg in addition to casein. The two groups were isonitrogenous. The mice were immunized twice with PEIF, and the production of specific antibodies against PEIF was measured every week. After 8 weeks, all mice received a 30% body surface area burn injury. Mice were sacrificed 24h after the burn. The antioxidant enzyme activities and lipid peroxides in the tissues as well as the specific antibody production were analyzed. Experiment 2: Twenty-eight mice were divided into two groups and vaccinated as described in experiment 1. After the burn the mice were infected with P. aeruginosa, and the survival rate was observed for 8 days. The results demonstrated that antioxidant enzyme activities and lipid peroxides in tissues were significantly lower in the Arg group than in the control group after the burn. The production of specific antibodies against P. aeruginosa significantly increased in the Arg group at 4 and 7 weeks after immunization, and 24h after the burn. The survival rates of vaccinated burned mice after bacterial infection did not significantly differ between the two groups. These results suggest that vaccinating mice with Arg supplementation may enhance humoral immunity and attenuate the oxidative stress induced by burn injury. However, Arg supplementation did not improve survival in vaccinated mice complicated with P. aeruginosa infection.

Octreotide improves burn-induced intestinal injury in the rat

The local thermal trauma activates a number of systemic mediator cascades, e.g. a complement activation, cytokine production, resulting in a generalized sequestration and a priming of local and systemic neutrophils and macrophages. We aimed to determine the possible protective effect of octreotide (OCT), a synthetic somatostatin analogue, against burn-induced intestinal tissue damage possibly by inhibiting neutrophil infiltration. Under brief ether anaesthesia, shaved dorsum of the rats was exposed to 90 degrees C bath for 10s to induce burn injury. Rats were decapitated either 3, 24 or 72 h after burn injury. Octreotide (10 microg/kg) or saline was administered subcutaneously (s.c.) immediately after the burn injury. In the 24- and 72-h burn groups, OCT injections were repeated three times daily. In the sham group the same protocol was applied except that the dorsum was dipped in a 25 degrees C water bath for 10 s Malondialdehyde (MDA) and glutathione (GSH) levels and myeloperoxidase (MPO) activity were determined in the intestinal tissue. The results demonstrate that burn injury results in significant neutrophil accumulation, as evidenced by increases in MPO activity. The increase in MDA and the concomitant decrease in GSH levels demonstrate the role of oxidative mechanisms in burn injury. OCT may have some beneficial therapeutic effects by reducing neutrophil-dependent injury and related lipid peroxidation following burn trauma.

Oxidative stress and antioxidative defense in the skin of rats with thermal injury

Changes in the activity and level of some antioxidative defense system components were determined in the rat skin during hypo- (ebb) and hypermetabolic (flow) phase of thermal trauma. At the same time, the effects of enzymatic (superoxide dismutase) and non-enzymatic (vitamin E and glutathione) antioxidants, as well as of L-arginine applied on the scalded skin area in different combinations in the form of a lyposomal ointment on endogenous antioxidative defense components were studied both in the injured and uninjured skin. In scalded skin during hypometabolic phase, a decrease in activity of superoxide dismutase, catalase, glutathione peroxidase glutathione reductase, as well as in the level of vitamin E was observed in comparison with the control. This decrease was accompanied by a complete loss of glutathione and the activity of glutathione-S-transferase and thioredoxin reductase. The same trend of changes was recorded in hypermetabolic phase. In the uninjured skin of scalded animals, the activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase were at the control level both in hypo- and hypermetabolic phase. Also, no changes in vitamin E content were found while the activities of thioredoxin reductase and glutathione-S-transferase were increased. Glutathione level in this group of animals was decreased the decrease being more prominent in hyper- then in hypometabolic phase. The ointments applied to the injured parts of the skin expressed protective effects observed as an increase in vitamin E level and an attenuation of glutathione reductase activity inhibition.

Effects of full-thickness burns on nociceptor sensitization in anesthetized rats

Burn-induced pain is often inadequately managed and its mechanisms, both peripheral and central, are poorly understood. To examine peripheral mechanisms, the effects of full-thickness burns on individual nociceptive fibers in sural nerve of anesthetized rats were studied. Additionally, the study investigated whether topical post-burn treatment with the mu-opioid receptor agonist loperamide ameliorated burn-induced pathologies. Receptive field (RF) properties of C-fibers were determined for 4h before and after producing burns. Burns caused profound tissue damage with edema extending beyond the injury site. Injury located within or proximal to RFs of nociceptors caused rapid decreases in mechanical responsiveness or complete desensitization at the original test site. However, post-burn, RF size frequently grew to include areas of newly sensitized skin. Transient or prolonged periods of ectopic activity was recorded from some nociceptors; this was most prevalent in fibers with RFs proximal to the injury site where burn induced background firing in 60% of the population. In most cases, loperamide significantly increased mechanical thresholds, prevented sensitization of uninjured skin, and reduced discharge.These data indicate that full-thickness burns activate and/or sensitize C-nociceptors, thus probably leading to pain. As loperamide ameliorates nociceptor activation and sensitization, it is an appropriate candidate for burn pain management.

Oxidative stress and metallothionein expression in the liver of rats with severe thermal injury

The aim of this work was to study oxidative stress and the compensating mechanisms implicated in severe thermal injury using the burned rat model. Results showed that after thermal injury glutathione (GSH) level was decreased, oxidized glutathione (GSSG) and the ratio of GSSG/GSH increased both at 24 and 48 h in the liver. The activities of GSH-reductase (GSH-Rx) in the liver and GSH-peroxidase (GSH-Px) both in the liver and erythrocytes increased at 24 h and then decreased at 48 h. The level of alpha-tocopherol in plasma was reduced at 24 h. Lipid peroxide levels increased both at 24 and 48 h in the liver. The serum zinc level decreased, reaching a minimum at 12h, whereas liver zinc level was elevated and reached the maximum at 12 h. After severe thermal injury enhancement of metallothionein (MT) expression has been discovered for the first time. MT content in the liver increased both at 24 and 48 h. Expression of MT-I mRNA was activated at 3 h and reached the top at 24 h postburn. The conclusion is that severe thermal injury gives rise to oxidative stress and dramatic enhancement of MT expression could be one of the important compensative mechanisms of natural defense system postburn.

Effects of arginine supplementation on antioxidant enzyme activity and macrophage response in burned mice

This study investigated the effect of arginine (Arg) supplementation on antioxidant enzyme activities and macrophage response in burned mice. Experiment 1: 60 male BALB/c mice were assigned to two groups. One group was fed a control diet with casein as the protein source, the other group was supplemented with 2% Arg in addition to casein. The two groups were isonitrogenous. After 4 weeks, all mice received a 30% body surface area burn injury. The antioxidant enzyme activities and lipid peroxides in the tissues were analyzed. Experiment 2: 20 mice were divided into two groups and burn injury was induced after feeding for 4 weeks as described in experiment 1. Twenty-four hours after the burn, tumor necrosis factor-alpha (TNF-alpha) secreted by cultured peritoneal macrophages was measured. The results show that antioxidant enzyme activities and lipid peroxides in tissues tended to be lower in the Arg group than in the control group after the burn. Production of TNF-alpha by peritoneal macrophages after stimulation with lipopolysacchride (LPS) was significantly elevated in the Arg group, whereas no response was observed in the control group. These results suggest that dietary Arg supplementation attenuates the oxidative stress induced by burn injury, and a better macrophage response was observed when Arg was administered.

A new technique for the analysis of endogenous mediators released following thermal injury

Few techniques today enable us to measure the complex processes taking place inside a burn wound in vivo. The present in vivo technique was based on a standardised burn model in rat skin. A partial- or full-thickness burn was induced and resulted in a gelatinous oedema located between the skin and the underlying rectus muscle. The oedema has distinct borders to the surrounding connective tissue and is separated and removed easily for further analysis. Myeloperoxidase (MPO) activity used as indicator of neutrofil infiltration was increased significantly in the burn oedema versus non-burned skin. Leukocyte metabolic activity was high as shown by significantly higher free radical formation (ESR) in the oedema than in surrounding burned and non-burned tissue. Leukocyte viability measured by Trypan blue stain was 70% in the oedema of full-thickness burns. In order to decide whether processes taking place in the oedema communicate freely with systemic circulation, we conducted a number of experiments. Results show in burned animals in vivo that intravenous administration of indomethacin induced a strong inhibition of PGE(2) in the burn oedema as compared with saline but, as expected, had no significant effect on LTB(4) synthesis. In conclusion, the present technique allows us to analyse the processes taking place inside the burn wound in vivo and to evaluate the effects of various agents on these processes.

Neutrophil depletion in rats reduces burn-injury induced intestinal bacterial translocation

OBJECTIVE

To determine whether neutrophil depletion could eradicate intestinal bacterial translocation in bum-injured rats.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

The rats were intravenously administered a rabbit anti-rat neutrophil antibody causing profound neutropenia and subjected to a 30% total body surface area scald burn.

MEASUREMENTS AND MAIN RESULTS

The depletion of neutrophils from the intestine was assessed via measurements of myeloperoxidase (MPO) activity in the intestinal homogenates. In addition, the presence of activated/extravasated neutrophils in intact intestines was determined via immunohistochemical localization of neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase component protein p47phox. Bacterial translocation was measured using agar cultures and by determining Escherichia coli beta-galactosidase gene via polymerase chain reaction/Southern blot analyses of mesenteric lymph node and spleen, liver, lung, and blood. MPO measurements demonstrated a six-fold increase above the control value in the intestinal tissue in rats on day 1 postburn. The presence of activated neutrophils (expression of p47phox protein) was also markedly increased in the intestines of these rats. The increased MPO activity and p47phox expression accompanied a translocation of indigenous E. coli into the mesenteric lymph node without a spread to other organs. The administration of anti-neutrophil antibody to burn animals prevented an increase in MPO activity and bacterial translocation.

CONCLUSION

These studies indicate that enhanced intestinal bacterial translocation caused by burn injury could be related to the increased infiltration of activated neutrophils into the intestinal tissue after bum. The release of neutrophil products such as superoxide anion may effect intestinal tissue damage leading to bacterial translocation of indigenous E. coli.

Neutrophil depletion prevents intestinal mucosal permeability alterations in burn-injured rats

Cutaneous thermal injury increases intestinal mucosal permeability. The mechanisms of this functional disturbance are not fully understood. We investigated whether accumulation of neutrophils in the intestine contributes to the increase in mucosal permeability. Labeled and unlabeled lactulose and mannitol were infused into a segment of rat ileum or jejunum. Blood concentrations of [(3)H]lactulose and [(14)C]mannitol were measured after 30, 60, and 90 min. On day 1 postburn, lactulose permeability increased fourfold in the ileum and twofold in the jejunum compared with sham-burned rats; mannitol permeability increased twofold in the ileum and 1. 5-fold in the jejunum. A greater increase in permeability occurred on day 3 postburn in the ileum, but not in the jejunum. The depletion of neutrophils in burned rats prevented the increase in permeability in both segments on day 1 postburn. Histological studies of intestines from burned, with or without neutrophil depletion, and sham-burned rats showed similar morphology. However, numerous neutrophils were found in the extravascular compartment in day 1 postburn, but not in neutrophil-depleted and sham-burned rats. These findings support the concept that the burn-induced increase in mucosal permeability is produced during the accumulation of neutrophils in the intestine and can be abrogated by the depletion of neutrophils.