Functional significance of inducible nitric oxide synthase induction and protein nitration in the thermally injured cutaneous microvasculature

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.

Protective effect of snail secretion filtrate against ethanol-induced gastric ulcer in mice

Gastric ulcer or peptic ulcer is a common disease worldwide. Basically, it develops when there is an imbalance between the protective and aggressive factors, especially at the luminal surface of epithelial cells. Thus, there is a constant interest in research new drugs for treatment of gastric ulcer. The snail secretion is a dense mucous, that covers the external surface of the snails, with important functions for the survival of snails. The biological proprieties of snail Helix Aspersa Muller mucus it has been known for centuries to treat human disorders in particular for skin disease. Recently the use of snail mucus has seen a worldwide increase, as a component in cosmetic product and it has been used in particular for the management of wound and skin disorders. In this study we use a murine model of ethanol intragastric administration which has been widely used to test the drugs efficacies and to explore the underlying mechanism for gastric ulcer development. The intragastric ethanol administration causes several mucosal damages and an induction of a severe inflammatory response. Our results show a significant protective effect of snail secretion filtrate in reducing macroscopic and histological lesions, as well the protective effect on mucus content, oxidative stress and inflammatory response. In conclusion this study demonstrate the protective effect of intragastrical snail secretion filtrate, in a model of ethanol-induced gastric ulcer in mice, suggesting its possible useful use in the treatment or prevention of gastric ulcer.

Targeting the NO/superoxide ratio in adipose tissue: relevance to obesity and diabetes management

Insulin sensitivity and metabolic homeostasis depend on the capacity of adipose tissue to take up and utilize excess glucose and fatty acids. The key aspects that determine the fuel-buffering capacity of adipose tissue depend on the physiological levels of the small redox molecule, nitric oxide (NO). In addition to impairment of NO synthesis, excessive formation of the superoxide anion (О2•- ) in adipose tissue may be an important interfering factor diverting the signalling of NO and other reactive oxygen and nitrogen species in obesity, resulting in metabolic dysfunction of adipose tissue over time. Besides its role in relief from superoxide burst, enhanced NO signalling may be responsible for the therapeutic benefits of different superoxide dismutase mimetics, in obesity and experimental diabetes models. This review summarizes the role of NO in adipose tissue and highlights the effects of NO/О2•- ratio 'teetering' as a promising pharmacological target in the metabolic syndrome.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Influence of ISDN, L-NAME and selenium on microcirculation, leukocyte endothelium interaction and angiogenesis after frostbite

BACKGROUND

The body of knowledge regarding the different facets of frostbite injury continues to expand. However, beside the administration of physiological saline, local rewarming, local disinfection and symptomatic medications, today no causal therapy is known which would accelerate angiogenesis and wound healing. The aim of this study was to investigate the influences of dilative acting drugs on microcirculation, angiogenesis and leukocyte behavior.

MATERIALS AND METHODS

Ears of male hairless mice (n=40) were inflicted with full thickness frostbites using a cold air jet. Then the affects of four intraperitoneal injections of isosorbitdinitrate (ISDN, n=10), l-nitroarginine-methyl-ester (l-NAME, n=10), selenium (n=10) or sodium chloride (n=10; each administered to one of four corresponding study groups), on microcirculation, leukocyte-endothelial interaction and angiogenesis were investigated over a 12-day period using intravital fluorescent microscopy.

RESULTS

Angiogenesis was most improved by ISDN (36.8 vs. 54.5% non-perfused area on day 3, 3.9 vs. 17.0% on day 7 compared to selenium, p<0.006). Venular diameter was most significantly dilated in the ISDN-group, l-NAME showed significantly decreased diameter over the complete time of 12 days. ISDN had positive influences on edema formation, which was significantly reduced compared to control (27% lower values compared to control; p=0.007 on day 3). The l-NAME-group showed the significant highest leukocyte-adhesion compared to control on days 7 and 12 (53% resp. 58% higher, p<0.006).

CONCLUSION

Overall, out of all the drugs tested, ISDN improved angiogenesis, dilated venules and decreased edema formation and therefore seems to have the greatest positive impact on these crucial parameters after frostbite injury.

Repetitive extracorporeal shock wave applications are superior in inducing angiogenesis after full thickness burn compared to single application

OBJECTIVE

Burn wounds remain a challenge due to subsequent wound infection and septicemia, which can be prevented by acceleration of wound healing. The aim of the study was to analyze microcirculation and leukocyte endothelium interaction with particular focus on angiogenesis after full-thickness burn using three different repetitions of low energy shock waves.

METHODS

Full-thickness burns were inflicted to the ears of hairless mice (n=44; area: 1.6±0.05 mm2 (mean±SEM)). Mice were randomized into four groups: the control group received a burn injury but no shock waves; group A received ESWA (0.03 mJ/mm2) on day one after burn injury; group B received shock waves on day one and day three after burn injury; group C ESWA on day one, three and seven after burn injury. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte interaction. Values were obtained before burn (baseline value) immediately after and on days 1, 3, 7 and 12 after burn.

RESULTS

Shock-wave treated groups showed significantly accelerated angiogenesis compared to the control group. The non-perfused area (NPA) is regarded as a parameter for angiogenesis and showed the following data on day 12 2.7±0.4% (group A, p=0.001), 1.4±0.5% (group B, p<0.001), 1.0±0.3% (group C, p<0.001), 6.1±0.9% (control group). Edema formation is positively correlated with the number of shock wave applications: day 12: group A: 173.2±9.8%, group B: 184.2±6.6%, group C: 201.1±6.9%, p=0.009 vs. control: 162.3±8.7% (all data: mean±SEM).

CONCLUSION

According to our data shock waves positively impact the wound healing process following burn injury. Angiogenesis showed significantly improved activity after shock wave application. In all three treatment groups angiogenesis was higher compared to the control group. Within the ESWA groups, double applications showed better results than single application and three applications showed better results than single or double applications.

Activated skin γδ T-cells regulate T-cell infiltration of the wound site after burn

Burn induces an immunopathological response involving multiple immune cell types that includes γδ T-cells. Nonetheless, the role of γδ T-cells at the wound site after burn is not clearly defined. Wild type and γδ T-cell receptor deficient (δ TCR(-/-)) mice were subjected to a major burn or sham procedure. At 1-7 d thereafter, skin samples were collected and T-cell populations analyzed. The majority of T-cells in the skin of sham mice were γδ T-cells. After burn, however, an increase in the total T-cells was observed at the wound site and these cells were predominantly αβ T-cells. Their influx was γδ T-cell dependent, as it was markedly reduced in injured δ TCR(-/-) mice. Burn wound γδ T-cells were activated with increased expression of TLRs and CD69. In contrast, the infiltrating αβ T-cells TLR and CD69 expressions were attenuated after burn. Thus, burn is associated with of γδ T-cell activation at the injury site, which initiates a massive infiltration of the wound with αβ T-cells that likely facilitate the transition from the inflammatory to the proliferative phase of healing.

Liver sinusoidal endothelial cells link hyperinsulinemia to hepatic insulin resistance

Insulin signaling in vascular endothelial cells (ECs) is critical to maintain endothelial function but also to mediate insulin action on peripheral glucose disposal. However, gene knockout studies have reached disparate conclusions. Thus, insulin receptor inactivation in ECs does not impair insulin action, whereas inactivation of Irs2 does. Previously, we have shown that endothelial ablation of the three Foxo genes protects mice from atherosclerosis. Interestingly, here we show that mice lacking FoxO isoforms in ECs develop hepatic insulin resistance through excessive generation of nitric oxide (NO) that impairs insulin action in hepatocytes via tyrosine nitration of insulin receptors. Coculture experiments demonstrate that NO produced in liver sinusoidal ECs impairs insulin's ability to suppress glucose production in hepatocytes. The effects of liver sinusoidal ECs can be mimicked by NO donors and can be reversed by NO inhibitors in vivo and ex vivo. The findings are consistent with a model in which excessive, rather than reduced, insulin signaling in ECs predisposes to systemic insulin resistance, prompting a reevaluation of current approaches to insulin sensitization.

Gamma delta (γδ) T-cells are critical in the up-regulation of inducible nitric oxide synthase at the burn wound site

BACKGROUND

The high incidence of morbidity and mortality following major burn can in part be attributed to immune derangements and wound healing complications. Inflammation plays an important role in wound healing, of which inducible nitric oxide synthase (iNOS) derived nitric oxide is a central mediator. T-cells of the γδ TCR lineage have also been shown to be important in healing of the burn wound site. Nonetheless, the role of γδ T-cells in the regulation of the burn wound iNOS expression is unknown.

METHODS

Wildtype (WT) and δ TCR(-/-) male C57BL/6 mice were subjected to burn (3rd degree, 12.5% TBSA) or sham treatment. Three days after injury, skin samples from non-injured and the burn wound were collected and analyzed for the expression of iNOS and cytokines and chemokine levels. In a second series of experiments, WT mice were subjected to burn and left untreated or treated with the iNOS inhibitor, L-Nil. Skin cytokine and chemokine levels were assessed 3days thereafter.

RESULTS

Burn induced an 18-fold increase in iNOS expression at the wound site as compared to the uninjured skin of WT sham mice. In δ TCR(-/-) mice iNOS expression at the wound site was significantly lower than that of the WT group. Burn also induced increased levels of IL-1β, IL-6, G-CSF, TNF-α, KC, MCP-1, MIP-1α and MIP-1β at the wound site in WT and δ TCR(-/-) mice, but G-CSF, TNF-α, and MIP-1β levels were greater in δ TCR(-/-) mice. Inhibition of iNOS activity in WT mice with L-Nil suppressed burn wound levels of IL-1β, G-CSF, and MIP-1α, whereas IL-6, TNF-α, KC, MCP-1 and MIP-1β were unaffected.

CONCLUSIONS

T-cells of the γδ TCR lineage significantly contribute to the up-regulation of iNOS expression which contributes to wound inflammation.

Extracorporeal shock waves improve angiogenesis after full thickness burn

OBJECTIVE

Extensive wounds of burn patients remain a challenge due to wound infection and subsequent septicemia. We wondered whether extracorporeal shock wave application (ESWA) accelerates the healing process. The aim of the study was to analyze microcirculation, angiogenesis and leukocyte endothelium interaction after burns by using ESWA with two types of low intensity.

METHODS

Full-thickness burns were inflicted to the ears of hairless mice (n=51; area: 1.3 mm(2)). The mice were randomized into five groups: (A) low-energy shock waves after burn injury (0.04 mJ/mm(2)); (B) very low-energy shock waves after burn injury (0.015 mJ/mm(2)); (C) mice received burns but no ESWA (control group); (D) mice without burn were exposed to low-energy shock waves; (E) mice without burns and with no shock wave application. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte behavior. ESWA was performed on day 1, 3 and 7 (500 shoots, 1 Hz). Values were obtained straight after and on days 1, 3, 7 and 12 post burn.

RESULTS

Group A showed accelerated angiogenesis (non-perfused area at day 12: 5.3% vs. 9.1% (group B) and 12.6% (group C), p=0.005). Both shock wave groups showed improved blood flow after burn compared to group C. Shock waves significantly increased the number of rolling leukocytes compared to the non-ESWA-treated animals (group D: 210.8% vs. group E: 83.3%, p=0.017 on day 7 and 172.3 vs. 90.9%, p=0.01 on day 12).

CONCLUSION

Shock waves have a positive effect on several parameters of wound healing after burns, especially with regard to angiogenesis and leukocyte behaviour. In both ESWA groups, angiogenesis and blood flow outmatched the control group. Within the ESWA groups the higher intensity (0.04 mJ/mm(2)) showed better results than the lower intensity group. Moreover, shock waves increased the number of rolling and sticking leukocytes as a part of an improved metabolism.

Multiple antioxidants and L-arginine modulate inflammation and dyslipidemia in chronic renal failure rats

The kidney is an important source of L-arginine, the endogenous precursor of nitric oxide (NO). Surgical problems requiring extensive renal mass reduction (RMR) decrease renal NO production, leading to multiple hemodynamic and homeostatic disorders manifested by hypertension, oxidative stress, and increased inflammatory cytokines. Using the RMR model of chronic renal failure (CRF), we assessed the effects of twelve weeks' administration of L-arginine and/or a mixture of antioxidants (L-carnitine, catechin, vitamins E and C) on plasma cytokines, soluble intercellular adhesion molecule-1 (sICAM-1), nitrate and nitrites (NO(2)/NO(3)), lipid profile, blood pressure, and renal function. CRF rats showed increased plasma IL-1 alpha, IL1-beta, IL-6, TNF-alpha, and sICAM-1 levels and decreased anti-inflammatory cytokines IL-4 and 10 levels, hypertension, and dyslipidemia. L-arginine treatment improved kidney functions, decreased systolic blood pressure, and decreased inflammatory cytokines levels. Antioxidants administration decreased inflammatory cytokines and sICAM-1 levels and increased IL-4 levels. Combined use of both L-arginine and the antioxidant mixture were very effective in their tendency to recover normal values of kidney functions, plasma cytokines, sICAM-1, blood pressure, NO(2)/NO(3), cholesterol, and triglycerides concentrations. Indeed, the effects of L-arginine and the antioxidants on the reduction of proinflammatory cytokines may open new perspectives in the treatment of uremia.

Inducible nitric oxide synthase induction underlies lipid-induced hepatic insulin resistance in mice: potential role of tyrosine nitration of insulin signaling proteins

OBJECTIVE

The present study was undertaken to assess the contribution of inducible nitric oxide (NO) synthase (iNOS) to lipid-induced insulin resistance in vivo.

RESEARCH DESIGN AND METHODS

Wild-type and iNOS(-/-) mice were infused for 6 h with a 20% intralipid emulsion, during which a hyperinsulinemic-euglycemic clamp was performed.

RESULTS

In wild-type mice, lipid infusion led to elevated basal hepatic glucose production and marked insulin resistance as revealed by impaired suppression of liver glucose production and reduced peripheral glucose disposal (R(d)) during insulin infusion. Liver insulin resistance was associated with a robust induction of hepatic iNOS, reduced tyrosine phosphorylation of insulin receptor (IR) beta, insulin receptor substrate (IRS)-1, and IRS-2 but elevated serine phosphorylation of IRS proteins as well as decreased Akt activation. The expression of gluconeogenic enzymes Pepck and G6Pc was also increased in the liver of wild-type mice. In contrast to their wild-type counterparts, iNOS(-/-) mice were protected from lipid-induced hepatic and peripheral insulin resistance. Moreover, neither the phosphorylation of insulin signaling intermediates nor expression of gluconeogenic enzymes were altered in the lipid-infused iNOS(-/-) mice compared with their saline-infused controls. Importantly, lipid infusion induced tyrosine nitration of IRbeta, IRS-1, IRS-2, and Akt in wild-type mice but not in iNOS(-/-) animals. Furthermore, tyrosine nitration of hepatic Akt by the NO derivative peroxynitrite blunted insulin-induced Akt tyrosine phosphorylation and kinase activity.

CONCLUSIONS

These findings demonstrate that iNOS induction is a novel mechanism by which circulating lipids inhibit hepatic insulin action. Our results further suggest that iNOS may cause hepatic insulin resistance through tyrosine nitration of key insulin signaling proteins.

The effect of post-burn local hyperthermia on the reducing burn injury: The possible role of opioids

PURPOSE

This paper studied the effect of post-burn local hyperthermia on burn induced injury.

METHODS

A second-degree burn injury was induced on the right and left flanks of Balb/c mice. Thirty-two burn wounds were divided into four groups. Opioid receptor blocking was done for groups 3 and 4 by intra-peritoneal administration of Naloxone (NLX) 30 min before the thermal injury. Local hyperthermia (45 degrees C, 30 s) was applied only for the burn wounds of groups 2 and 4. Twenty-four hours after burn injury, the burned wounds were assessed for the level of iNOS (by immunohistochemistry) and the number of hair follicles (as an indicator of tissue injury).

RESULTS

The wounds that received hyperthermia (group 2) had significantly more hair follicles (p < 0.001) compared to the control wounds (group 1). There was no significant difference between the number of hair follicles and acute inflammation of group 1 and group 3 (NLX + burn). Group 4 (NLX + burn + hyperthermia) had significantly fewer hair follicles compared to group 1 (p < 0.001), group 2 (p < 0.001) and group 3 (p < 0.001). The level of iNOS in groups 1, 3 and 4 was not significantly different but significantly more than group 2 (p < 0.001, p < 0.001 and p < 0.001, respectively).

CONCLUSIONS

The results showed that local hyperthermia after second degree burn decreased the tissue injury and iNOS expression. It is also concluded that endogenous opioid response may have a key role in the above mentioned effects of post-burn local hyperthermia.

Bench-to-bedside review: Burn-induced cerebral inflammation--a neglected entity?

Severe burn injury remains a major burden on patients and healthcare systems. Following severe burns, the injured tissues mount a local inflammatory response aiming to restore homeostasis. With excessive burn load, the immune response becomes disproportionate and patients may develop an overshooting systemic inflammatory response, compromising multiple physiological barriers in the lung, kidney, liver, and brain. If the blood–brain barrier is breached, systemic inflammatory molecules and phagocytes readily enter the brain and activate sessile cells of the central nervous system. Copious amounts of reactive oxygen species, reactive nitrogen species, proteases, cytokines/chemokines, and complement proteins are being released by these inflammatory cells, resulting in additional neuronal damage and life-threatening cerebral edema. Despite the correlation between cerebral complications in severe burn victims with mortality, burn-induced neuroinflammation continues to fly under the radar as an underestimated entity in the critically ill burn patient. In this paper, we illustrate the molecular events leading to blood–brain barrier breakdown, with a focus on the subsequent neuroinflammatory changes leading to cerebral edema in patients with severe burns.

Burn model for in vivo investigations of microcirculatory changes

OBJECTIVE

The treatment of burns remains a challenge due to the associated high morbidity and mortality. Besides the administration of physiologic saline, local disinfection, and symptomatic medications, no causal therapy is known to reduce the tissue damage and accelerate wound healing. The aim of the study was to develop a reliable burn model that allows for reproducible quantitative in vivo analysis of the microcirculation, angiogenesis, and leukocyte endothelium interaction after burn injury.

METHODS

Experiments were carried out on male hairless mice (n = 9). Full-thickness burns were inflicted with a hot air jet without any contact to the tissue (117 +/- 2.1 degrees C for 1 second; burn area: 1.3 mm(2)). Intravital fluorescent microscopy, in combination with FITC-dextran as plasma marker, was used to assess microcirculatory standard parameters; leukocytes were stained with rhodamine 6G. Values were obtained before, immediately after, as well as at days 1, 3, 7, and 14 postburn.

RESULTS

The nonperfused area decreased during the observed period and perfusion was almost completely due to angiogenesis at day 14. No posttraumatic expansion of the nonperfused area after 24 hours could be observed. Leukocyte endothelium interaction showed its maximum 24 hours postburn. The formation of edema occurred immediately postburn and decreased during the following observation time.

CONCLUSION

The developed burn model allows a reproducible assessment with significant results of the microcirculation, angiogenesis, and leukocyte endothelium interaction without causing mechanical damage to the tissue; therefore, this model qualifies for the further investigations of interventional drugs to decrease the effects of burn injury.

Gammadelta T-cells: potential regulators of the post-burn inflammatory response

Severe burn induces an immunopathological response that contributes to the development of a systemic inflammatory response (SIRS) and subsequent multiple organ failure. While, multiple immune cells type (T-cells, macrophages, neutrophils) are involved in this response, recent evidence suggests that a unique T-cell subset, gammadelta T-cells are central in the response to injury. While gammadelta T-cells represent only a small percentage of the total T-cell population, they display specific functional characteristics that uniquely position them in the immune/inflammatory axis to influence a number of important aspects of the body's response to burn. This review will focus on the potential regulator role of gammadelta T-cells in immunopathological response following burn and thereby their potential as therapeutic targets for affecting inflammation and healing.

T cells of the gammadelta T-cell receptor lineage play an important role in the postburn wound healing process

Although gammadelta T cells have been implicated in various aspects of the dermal wound healing process, their role in postburn wound healing processes has not been investigated. To study this, we subjected mice deficient in gammadelta T cells (ie, T-cell receptor delta gene [delta TCR]) and wild-type (WT; C57BL6J) mice to burn injury (25% TBSA) or sham treatment; skin samples were isolated 3 days later. Marked inflammation of the injury site was observed in WT mice but was markedly reduced in delta TCR mice. Postinjury fibroblast growth factor, platelet-derived growth factor granulocyte-colony stimulating factor levels, and nitrite/nitrate were elevated in skin samples from injured WT mice, whereas skin tissue levels of these growth factors and inflammatory mediators was significantly atteunuated in delta TCRmice. In conclusion, these findings support the concept that gammadelta T cells are important to postburn wound healing via the production of growth factors and, potentially, regulation of inducible nitric oxide synthase activation.

How important are NK1 receptors for influencing microvascular inflammation and itch in the skin? Studies using Phoneutria nigriventer venom

Pain and itch sensations are induced by depolarization of C-fibre nerves and possibly other types of fibres. We have evidence from several species, including mice, that skin plasma extravasation induced by the Phoneutria nigriventer spider venom (PNV) is dependent on tachykinin NK(1) receptors. We have now investigated the itching measured as bouts of scratching in response to intradermal (i.d.) PNV in wildtype (NK(1)(+/+)) and NK(1) receptor knockout (NK(1)(-/-)) mice. Mice, either NK(1)(+/+) or NK(1)(-/-), were given a single i.d. injection (0.05 ml) of test agent or vehicle into the shaved dorsal skin, in the intercostal region, in a randomized way. The bouts of scratching were recorded in a blinded manner for 60 min. Oedema formation was concomitantly assessed by the extravascular accumulation of i.v. injected (125)I-albumin. The i.d. injection of either substance P (at a high dose of 100 nmol/site), or PNV (0.3-10 microg/site) induced oedema formation in NK(1)(+/+) but substantially less was observed in NK(1)(-/-) mice, as previously reported. PNV also induced scratching, but significantly less scratching was observed in NK(1)(-/-) compared with NK(1)(+/+) mice. In contrast, SP did not induce significant scratching at amounts up to 100 nmol in NK(1)(+/+) mice. Experiments with an NK(1) receptor antagonist SR140333 (at doses that blocked PNV-induced oedema) revealed that whilst a local co-injection i.d. (1 nmol) in NK(1)(+/+) mice had no effect on PNV (3 microg/site)-induced scratching (18.5+/-3.7 vs. 14.4+/-3.5 bouts, mean+/-S.E.M., n=5-7), systemic treatment with SR140333 (120 nmol/kg, i.v.) significantly inhibited scratching (14+/-3.5 vs. 3.1+/-1.2 bouts, n=4-6; P<0.05). These results indicate that NK(1) receptors are involved in mediating PNV-induced scratching and that the location of the receptors is unlikely to be skin. Thus, a distinct separation between endogenous microvascular and PNV nociceptive NK(1)-dependent effects is suggested.

Nitric oxide contributes to the development of a post-injury Th2 T-cell phenotype and immune dysfunction

Severe injury induces immune dysfunction resulting in increased susceptibility to opportunistic infections. Previous studies from our laboratory have demonstrated that post-burn immunosuppression is mediated by nitric oxide (NO) due to the increased expression of macrophage inducible nitric oxide synthase (iNOS). In contrast, others suggest that injury causes a phenotypic imbalance in the regulation of Th1- and Th2 immune responses. It is unclear whether or not these apparently divergent mediators of immunosuppression are interrelated. To study this, C57BL/6 mice were subjected to major burn injury and splenocytes were isolated 7 days later and stimulated with antiCD3. Burn injury induced NO-mediated suppression of proliferative responses that was reversed in the presence of the NOS inhibitor L-monomethyl-L-arginine and subsequently mimicked by the addition of the NO donor, S-nitroso-N-acetyl-penicillamine (SNAP). SNAP also dose-dependently suppressed IFN-gamma and IL-2 (Th1), but not IL-4 and IL-10 (Th2) production. Delaying the addition of SNAP to the cultures by 24 h prevented the suppression of IFN-gamma production. The Th2 shift in immune phenotype was independent of cGMP and apoptosis. The addition of SNAP to cell cultures also induced apoptosis, attenuated mitochondrial oxidative metabolism and induced mitochondrial membrane depolarization. However, these detrimental cellular effects of NO were observed only at supra-physiologic concentrations (>250 microM). In conclusion, these findings support the concept that NO induces suppression of cell-mediated immune responses by selective action on Th1 T cells, thereby promoting a Th2 response.

Poly (adp-ribose) synthetase inhibition reduces oxidative and nitrosative organ damage after thermal injury

Poly (ADP-ribose) synthetase (PARS) is a nuclear enzyme activated by DNA single-strand breakage, which can be triggered by reactive oxygen and nitrogen species. Activation of this enzyme depletes the intracellular concentration of energetic substrates such as nicotinamide adenine dinucleotide (NAD). Eventually, this process results in cell dysfunction and cell death. PARS inhibitors have successfully shown benefits in several experimental models of ischemia-reperfusion injury, inflammation, and sepsis. In our experimental study, we investigated the role of 3-aminobenzamide (3-AB), a nonspecific PARS inhibitor, in systemic organ damage after burn. Twenty-four Wistar rats were randomly divided into three groups. The sham group (n=8) was exposed to 21 degrees C water, and the burn group (n=8) and the burn-plus-3-AB group (n=8) were exposed to boiling water for 12 s to produce a full-thickness burn of 35-40% of total body surface area. In the burn-plus-3-AB group, 3-AB 10 mg/kg was given intraperitoneally 10 min before thermal injury. Twenty-four hours later, tissue samples were obtained for biochemical analysis from lung, intestine, and kidney. In the burn group, tissue malondialdehyde, myeloperoxidase, and 3-nitrotyrosine levels in all organs were significantly increased compared with the sham group (p<0.05). Pretreatment with 3-AB significantly reduced burn-induced organ damage (p<0.05). These data provide evidence of the relationship between the PARS pathway and lipid peroxidation in systemic organ damage after thermal injury.

The role of γδ T cells in the regulation of neutrophil-mediated tissue damage after thermal injury

Thermal injury induces an inflammatory response that contributes to the development of secondary tissue damage. Neutrophil recruitment and activation are in part responsible for this tissue damage. Although gammadelta T cells have been shown to regulate the inflammatory responses in tissues that are prone to neutrophil-mediated injury post-burn, their role in the induction of secondary tissue injury post-burn remains unknown. To study this, gammadelta T cell-deficient (gammadelta TCR-/-) and wild-type (WT) mice were subjected to thermal injury or sham procedure, and tissue samples were isolated 1-24 h thereafter. Burn injury induced neutrophil accumulation in the lung and small intestines of WT mice at 1-3 h post-injury. No such increase in neutrophil tissue content was observed in gammadelta TCR-/- mice. An increase in tissue wet/dry weight ratios was also observed in these organs at 3 h post-burn in WT but not in gammadelta TCR-/- mice. A parallel increase in plasma and small intestine levels of the chemokines macrophage-inflammatory protein-1beta (chemokine ligand 4) and keratinocyte-derived chemokine (CXC chemokine ligand 1) were observed in injured WT mice but not in injured gammadelta TCR-/- mice. Increased activation (CD120b expression) of the circulating gammadelta T cell population was also observed at 3 h post-burn in WT mice. These results indicate the gammadelta T cells, through the production of chemokines, play a central role in the initiation of neutrophil-mediated tissue damage post-burn.

Nitric oxide, inflammation and acute burn injury

Nitric oxide (NOz.rad;) is a diatomic mediator liberated on oxidation of L-arginine by the nitric oxide synthase (NOS) family of enzymes. It has complex and wide ranging functions in vivo and has been implicated in the development of the profound inflammatory response that occurs as a result of cutaneous burn injury. In addition, dysregulation of NOS activity has been associated with multiple organ failure in human burn patients and may therefore represent a novel therapeutic target in such circumstances. This review focuses on the role of NOz.rad; in inflammation, with particular emphasis on the acute post-burn inflammatory response. Specific areas of discussion include the maintenance of microvascular haemostasis, leukocyte recruitment and remote organ dysfunction following thermal injury.