Inhibition of neuronal nitric oxide synthase by 7-nitroindazole attenuates acute lung injury in an ovine model

The protective effect of natural medicines against excessive inflammation and oxidative stress in acute lung injury by regulating the Nrf2 signaling pathway

Acute lung injury (ALI) is a common critical disease of the respiratory system that progresses into acute respiratory distress syndrome (ARDS), with high mortality, mainly related to pulmonary oxidative stress imbalance and severe inflammation. However, there are no clear and effective treatment strategies at present. Nuclear factor erythroid 2-related factor 2(Nrf2) is a transcription factor that interacts with multiple signaling pathways and regulates the activity of multiple oxidases (NOX, NOS, XO, CYP) related to inflammation and apoptosis, and exhibits antioxidant and anti-inflammatory roles in ALI. Recently, several studies have reported that the active ingredients of natural medicines show protective effects on ALI via the Nrf2 signaling pathway. In addition, they are cheap, naturally available, and possess minimal toxicity, thereby having good clinical research and application value. Herein, we summarized various studies on the protective effects of natural pharmaceutical components such as polyphenols, flavonoids, terpenoids, alkaloids, and polysaccharides on ALI through the Nrf2 signaling pathway and demonstrated existing gaps as well as future perspectives.

Ovine model of burn wounds grafted with ovine cadaver skin

Shortage in autograft to cover burn wounds involves a frequent use of cadaver skin (CS) as a temporary cover to prevent infection, dehydration and preparation of wounds for subsequent autografting. We aimed to establish an ovine model of burn wound healing using ovine CS (OCS). Quality and efficacy of fresh and frozen OCS overlaid on to excised 3rd degree flame burn wounds in sheep were evaluated in comparison to autograft. Histologically, autografted wounds maintained normal skin structure at different time points. Wounds overlaid with fresh OCS graft showed signs of rejection starting from day 7. At day 14, the epidermis was mostly rejected. The rejection was completed by day 20 with signs of immunoreaction and presence of many immune cells. Frozen OCS was rejected in the same pattern. Immediately prior to grafting, the thickness was comparable between freshly prepared and frozen OCS for 10 or 40 days. Significant reduction in viability was detected in OCS frozen for 40 days. Both fresh or frozen ovine OCS were rejected within 10 days that mimics CS rejection time in humans (∼8.4 days), suggesting that ovine model of burn wound grafted with OCS can successfully be used in burn wound research mimicking clinical scenario.

Inhibition of neuronal nitric oxide synthase activity does not alter vasopressin secretion in septic rats

BACKGROUND/PURPOSE

During the early phase of sepsis, hypotension is accompanied by increase of plasma vasopressin hormone (AVP) levels, which decline during the late phase. This hypotension is due in part to increase of nitric oxide (NO) synthesis by nitric oxide synthase (NOS) enzyme. Neuronal isoform of this enzyme (nNOS) is present in vasopressinergics neurons of hypothalamus, but its role in vasopressin secretion during sepsis is unknown.

METHODS

We evaluated the role of nNOS in NO production and vasopressin secretion during sepsis. Wistar rats received 7-nitroindazole (50 mg/kg, i.p.), an inhibitor of nNOS activity, or vehicle and were submitted to septic stimulus by cecal ligation and puncture (CLP). At the time points 0, 4, 6, 18 and 24 h after sepsis induction the animals were decapitated and neurohypophysis and hypothalamus were removed for analysis of vasopressin content and NOS activity, respectively. Hematocrit, serum sodium, osmolality, proteins and plasmatic AVP were quantified.

RESULTS

Mortality was not affected by 7-nitroindazole (7-NI). Sodium and plasma proteins levels decreased after CLP and the treatment anticipated the protein loss, and delayed serum sodium decrease. Septic animals treated with 7-NI showed decrease of osmolality 4 h after CLP. Nitric oxide synthase activity in hypothalamus increased at 4 and 24 h after CLP and was reduced with 7-NI. Neurohypophysis content of AVP diminished after CLP and 7-NI did not alter this parameter. Plasma AVP levels increased at 6 h and decreased 18 and 24 h after CLP. Treatment with 7-NI did not alter plasma vasopressin levels.

CONCLUSION

We concluded that nNOS does not have a substantial role in vasopressin secretion during experimental sepsis.

Cardiovascular Dysfunction Following Burn Injury: What We Have Learned from Rat and Mouse Models

Severe burn profoundly affects organs both proximal and distal to the actual burn site. Cardiovascular dysfunction is a well-documented phenomenon that increases morbidity and mortality following a massive thermal trauma. Beginning immediately post-burn, during the ebb phase, cardiac function is severely depressed. By 48 h post-injury, cardiac function rebounds and the post-burn myocardium becomes tachycardic and hyperinflammatory. While current clinical trials are investigating a variety of drugs targeted at reducing aspects of the post-burn hypermetabolic response such as heart rate and cardiac work, there is still a paucity of knowledge regarding the underlying mechanisms that induce cardiac dysfunction in the severely burned. There are many animal models of burn injury, from rodents, to sheep or swine, but the majority of burn related cardiovascular investigations have occurred in rat and mouse models. This literature review consolidates the data supporting the prevalent role that β-adrenergic receptors play in mediating post-burn cardiac dysfunction and the idea that pharmacological modulation of this receptor family is a viable therapeutic target for resolving burn-induced cardiac deficits.

Heterogeneity of the effects of combined nitric oxide synthase inhibition on organ perfusion in ovine sepsis

INTRODUCTION

Previous studies demonstrated beneficial effects of early neuronal nitric oxide synthase (nNOS) and subsequent inducible NOS (iNOS) inhibition on the development of multiple organ dysfunctions in septic sheep. However, the effects of NOS inhibition on regional blood flow remained undetermined. The current study was conducted to assess the effects of combined NOS inhibition on blood flow to various organs in an ovine sepsis model.

METHODS

Eighteen adult, female sheep were randomly allocated to the following groups: (1) sham-injured, non-treated group, (2) injured (smoke inhalation and instillation of Pseudomonas aeruginosa into the lungs), non-treated group (control), and (3) injured, treated group (specific nNOS inhibition from 1 h to 12 h and iNOS inhibition from 12 h to 24 h post-injury). Fluorescent microspheres were injected at baseline and various time points post-injury. At the end of the 24-h experimental period, tissue from various organs was harvested.

RESULTS

Blood flow to the ileum was significantly increased in the control group from 12 h to 24 h versus sham (P < 0.05). This increase was attenuated in the treatment group (P < 0.05). In contrast, blood flow to the pancreas was significantly increased in the treatment group after 12 h and 24 h versus both sham and control (P < 0.05). Blood flow to the spleen was significantly lower after 24h in the control group versus sham and treatment (P < 0.05 both).

CONCLUSIONS

Combined NOS inhibition significantly influenced the pathologically altered organ perfusion during ovine sepsis. However, this treatment strategy showed heterogeneous effects on organ perfusion, perhaps dependent on the sepsis-related degree of NO production and ensuing changes in regional flow.

Time profile of oxidative stress and neutrophil activation in ovine acute lung injury and sepsis

The formation of oxidative stress in the lung and activation of neutrophils are major determinants in the development of respiratory failure after acute lung injury and sepsis. However, the time changes of these pathogenic factors have not been sufficiently described. Twenty-four chronically instrumented sheep were subjected to cotton smoke inhalation injury and instillation of live Pseudomonas aeruginosa into both lungs. The sheep were euthanized at 4, 8, 12, 18, and 24 h after injury. Additional sheep received sham injury and were euthanized after 24 h. Pulmonary function was assessed by determination of oxygenation index and pulmonary shunt fraction. In addition, lung tissue was harvested at the respective time points for the measurement of malondialdehyde, interleukin 6, poly(ADP ribose), myeloperoxidase, and alveolar polymorphonuclear neutrophil score. The injury induced severe respiratory failure that was associated with an early increase in lipid peroxidation and interleukin 6 expression. The injury further led to an increase in poly(ADP ribose) activity that reached its peak at 12 h after injury and declined afterward. In addition, progressive increases in markers of neutrophil accumulation in the lung were observed. The peak of neutrophil accumulation in the lung was associated with a severe depletion of circulating neutrophils. The results from our model may enhance the understanding of the pathophysiological alterations after acute lung injury and sepsis and thus be useful in exploring therapeutic interventions directed at modifying the expression or activation of inflammatory mediators.

Inhibitor of neuronal nitric oxide synthase improves gas exchange in ventilator-induced lung injury after pneumonectomy

BACKGROUND

Mechanical ventilation with high tidal volumes may cause ventilator-induced lung injury (VILI) and enhanced generation of nitric oxide (NO). We demonstrated in sheep that pneumonectomy followed by injurious ventilation promotes pulmonary edema. We wished both to test the hypothesis that neuronal NOS (nNOS), which is distributed in airway epithelial and neuronal tissues, could be involved in the pathogenesis of VILI and we also aimed at investigating the influence of an inhibitor of nNOS on the course of VILI after pneumonectomy.

METHODS

Anesthetized sheep underwent right pneumonectomy, mechanical ventilation with tidal volumes (VT) of 6 mL/kg and FiO2 0.5, and were subsequently randomized to a protectively ventilated group (PROTV; n = 8) keeping VT and FiO2 unchanged, respiratory rate (RR) 25 inflations/min and PEEP 4 cm H2O for the following 8 hrs; an injuriously ventilated group with VT of 12 mL/kg, zero end-expiratory pressure, and FiO2 and RR unchanged (INJV; n = 8) and a group, which additionally received the inhibitor of nNOS, 7-nitroindazole (NI) 1.0 mg/kg/h intravenously from 2 hours after the commencement of injurious ventilation (INJV + NI; n = 8). We assessed respiratory, hemodynamic and volumetric variables, including both the extravascular lung water index (EVLWI) and the pulmonary vascular permeability index (PVPI). We measured plasma nitrite/nitrate (NOx) levels and examined lung biopsies for lung injury score (LIS).

RESULTS

Both the injuriously ventilated groups demonstrated a 2-3-fold rise in EVLWI and PVPI, with no significant effects of NI. In the INJV group, gas exchange deteriorated in parallel with emerging respiratory acidosis, but administration of NI antagonized the derangement of oxygenation and the respiratory acidosis significantly. NOx displayed no significant changes and NI exerted no significant effect on LIS in the INJV group.

CONCLUSION

Inhibition of nNOS improved gas exchange, but did not reduce lung water extravasation following injurious ventilation after pneumonectomy in sheep.

Pseudomonas aeruginosa is associated with increased lung cytokines and asymmetric dimethylarginine compared with methicillin-resistant Staphylococcus aureus

The objective of the study was to investigate pulmonary responses to Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) using ovine and mice models of sepsis with emphasis on lung cytokine expression, asymmetric dimethylarginine (ADMA) concentration, and the arginase pathway. Sheep were instilled with either MRSA, P. aeruginosa, or saline under deep anesthesia; mechanically ventilated; resuscitated with fluid; and killed after 24 h. Mice were instilled with either MRSA, P. aeruginosa, or saline under deep anesthesia and killed after 8 h. Lungs were assessed for ADMA concentration, arginase activity, oxidative stress, and cytokine expression, and plasma was assessed for nitrate/nitrite concentrations. The severity of lung injury was more pronounced in P. aeruginosa sepsis compared with MRSA. The significant changes in sheep lung function after P. aeruginosa sepsis were associated with significantly increased ADMA concentrations and arginase activity compared with MRSA. However, the plasma concentration of nitrites and nitrates were significantly increased in MRSA sepsis compared with P. aeruginosa sepsis. In the mice model, P. aeruginosa significantly increased lung cytokine expression (IL-1 and IL-13), protein oxidation, and arginase activity compared with MRSA. Our data suggest that the greater expression of cytokines and ADMA concentrations may be responsible for severity of acute lung injury in P. aeruginosa sepsis. The lack of arginase activity may explain the greater nitric oxide production in MRSA sepsis.

Beneficial effects of concomitant neuronal and inducible nitric oxide synthase inhibition in ovine burn and inhalation injury

Different isoforms of nitric oxide (NO) synthase are critically involved in the development of pulmonary failure secondary to acute lung injury. Here we tested the hypothesis that simultaneous blockade of inducible and neuronal NO synthase effectively prevents the pulmonary lesions in an ovine model of acute respiratory distress syndrome induced by combined burn and smoke inhalation injury. Chronically instrumented sheep were allocated to a sham-injured group (n = 6), an injured and untreated group (n = 6), or an injured group treated with simultaneous infusion of selective inducible and neuronal NO synthase inhibitors (n = 5). The injury was induced by 48 breaths of cotton smoke and a third-degree burn of 40% total body surface area. All sheep were mechanically ventilated and fluid resuscitated. The injury induced severe pulmonary dysfunction as indicated by decreases in PaO2/FiO2 ratio and increases in pulmonary shunt fraction, ventilatory pressures, lung lymph flow, and lung wet/dry weight ratio. The treatment fully prevented the elevations in lymph and plasma nitrate/nitrite levels, pulmonary shunting, ventilatory pressures, lung lymph flow, and wet/dry weight ratio and significantly attenuated the decline in PaO2/FiO2 ratio. In conclusion, simultaneous blockade of inducible and neuronal NO synthase exerts beneficial pulmonary effects in an ovine model of acute respiratory distress syndrome secondary to combined burn and smoke inhalation injury. This novel treatment strategy may represent a useful therapeutic adjunct for patients with these injuries.

Impact of bronchial circulation on bronchial exudates following combined burn and smoke inhalation injury in sheep

We previously reported bronchial circulation contributes to pulmonary edema and increases shunt fraction following smoke inhalation, and bronchial blood flow significantly increases in inhalation injury. We hypothesized reduction of bronchial blood flow reduces exudation to the airway and ameliorates lung injury from combined burn and smoke insults (B&S injury).

METHOD

Merino ewes (n=28) randomly divided into three groups: (1) bronchial artery ligated and injured (injury+ligation group); (2) bronchial artery left intact and injured (injury+no ligation group); (3) bronchial artery ligated but not injured (no injury+ligation group) were subjected to a flame burn and inhalation injury under halothane anesthesia. Parameters were analyzed using Scheffe's post hoc test (P<0.05). All Groups were resuscitated with Ringer lactate solution and placed on a ventilator for 48h.

RESULTS

Pulmonary gas exchange (PaO(2)/FiO(2)) improved in injury+ligation group. Further, obstruction score, an index of airway cast formation, significantly changed between injury+no ligation group compared to both ligation groups.

CONCLUSION

Bronchial circulation plays a significant role in lung injury after B&S injury, and reduction of bronchial blood flow by bronchial artery ligation reduces bronchial exudates, resulting in improved gas exchange.

Specific inhibition of nitric oxide synthases at different time points in a murine model of pulmonary sepsis

Excessive production of nitric oxide (NO) by NO synthase (NOS) and a subsequent oxidative stress reaction are thought to be critically involved in the pathophysiology of sepsis. Previous studies suggested that NO production by neuronal NOS (nNOS) and inducible NOS (iNOS) is implemented in the disease process at different time points after the injury. Here we tested the roles of selective pharmacological inhibition of nNOS and iNOS at different time points in a murine model of pulmonary sepsis. The injury was induced by intranasal administration of live Pseudomonas aeruginosa (3.2×10(7) colony-forming units) in C57BL/6 wild-type mice. The animals received no treatment (control) or treatment with a specific nNOS inhibitor (4 or 8h), iNOS inhibitor (4 or 8h), or non-specific NOS inhibitor (4 or 8h). In controls, the injury was associated with excessive releases of pro-inflammatory cytokines in the plasma, enhanced tissue lipid peroxidation, and decreased survival. Non-specific NOS inhibition at either time point did not influence survival and was not further investigated. While nNOS inhibition at 4h was associated with a trend toward improved survival and significantly reduced contents of lung nitrite/nitrate (NO(x)) and liver malondialdehyde, the blockade of nNOS at 8h had no effect on these parameters. In contrast, early iNOS inhibition was associated with a trend toward decreased survival and no effects on lung NO(x) and liver malondialdehyde contents, whereas later iNOS blockade was associated with decreased malondialdehyde content in liver homogenates. In conclusion, pulmonary sepsis in mice may be beneficially influenced by specific pharmacological nNOS inhibition at an earlier time point and iNOS inhibition at a later time points post-injury. Future investigations should identify the time changes of the expression and activation of NOS isoforms.

Role of different nitric oxide synthase isoforms in a murine model of acute lung injury and sepsis

Excessive production of nitric oxide (NO) by NO synthase (NOS) with subsequent formation of peroxynitrite and poly(adenosine diphosphate ribose) is critically implemented in the pathophysiology of acute lung injury and sepsis. To elucidate the roles of different isoforms of NOS, we tested the effects of non-selective NOS inhibition and neuronal NOS (nNOS)- and inducible NOS (iNOS)-gene deficiency on the pulmonary oxidative and nitrosative stress reaction in a murine sepsis model. The injury was induced by four sets of cotton smoke using an inhalation chamber and subsequent intranasal administration of live Pseudomonas aeruginosa (3.2x10(7) colony-forming units). In wild type mice, the injury was associated with excessive releases of pro-inflammatory cytokines in the plasma, enhanced neutrophil accumulation, increased lipid peroxidation, and excessive formation of reactive nitrogen species and vascular endothelial growth factor in the lung. Both nNOS- and iNOS-gene deficiency led to significantly reduced oxidative and nitrosative stress markers in the lung, but failed to significantly improve survival. Treatment with a non-selective NOS inhibitor failed to reduce the oxidative and nitrosative stress reaction to the same extent and even tended to increase mortality. In conclusion, the current study demonstrates that both nNOS and iNOS are partially responsible for the pulmonary oxidative and nitrosative stress reaction in this model. Future studies should investigate the effects of specific pharmacological inhibition of nNOS and iNOS at different time points during the disease process.

Role of neuronal nitric oxide synthase in ovine sepsis model

Smoke inhalation injury is often complicated with pneumonia, which frequently leads to subsequent development of sepsis. Excessive NO has been shown to mediate many sepsis-related pathological responses. In the present study, we used our well-established ovine smoke inhalation and pneumonia/sepsis model to examine the hypothesis that neuronal NO synthase (NOS) may be primarily responsible for these pathological alterations. We report the beneficial effects of the specific neuronal NOS (nNOS) inhibitor ZK234238. Adult female sheep were surgically prepared for the study. After 5 to 7 days' recovery, sheep were anesthetized and given double injury: insufflation of 48 breaths of cotton smoke (<40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa (5 x 10(11) colony-forming units) into each sheep's lung via tracheostomy tube. All sheep were mechanically ventilated and fluid resuscitated by lactated Ringer's solution. Sheep were randomly allocated into groups: control (injured not treated, n = 6) and treated (injured, but treated with ZK234238, n = 4). Continuous infusion of ZK234238 (100 microg x kg(-1) x h(-1)) was started 1 h after insult. ZK234238 attenuated the hypotension (at 18 and 24 h) and fall in systemic vascular resistance (at 24 h) seen in control animals. ZK234238 significantly inhibited increased fluid accumulation as well as increased plasma nitrate/nitrite 24 h after injury. Neuronal NOS inhibition significantly reduced lung water content and attenuated inflammatory indices such as lung tissue myeloperoxidase activity, IL-6 mRNA, and reactive nitrogen species. The above results suggest that the nNOS-derived NO may be involved in the pathophysiology of sepsis-related multiorgan dysfunction.

Mechanisms of nitric oxide synthase uncoupling in endotoxin-induced acute lung injury: role of asymmetric dimethylarginine

Acute lung injury (ALI) is associated with severe alterations in lung structure and function and is characterized by hypoxemia, pulmonary edema, low lung compliance and widespread capillary leakage. Asymmetric dimethylarginine (ADMA), a known cardiovascular risk factor, has been linked to endothelial dysfunction and the pathogenesis of a number of cardiovascular diseases. However, the role of ADMA in the pathogenesis of ALI is less clear. ADMA is metabolized via hydrolytic degradation to l-citrulline and dimethylamine by the enzyme, dimethylarginine dimethylaminohydrolase (DDAH). Recent studies suggest that lipopolysaccharide (LPS) markedly increases the level of ADMA and decreases DDAH activity in endothelial cells. Thus, the purpose of this study was to determine if alterations in the ADMA/DDAH pathway contribute to the development of ALI initiated by LPS-exposure in mice. Our data demonstrate that LPS exposure significantly increases ADMA levels and this correlates with a decrease in DDAH activity but not protein levels of either DDAH I or DDAH II isoforms. Further, we found that the increase in ADMA levels cause an early decrease in nitric oxide (NO(x)) and a significant increase in both NO synthase (NOS)-derived superoxide and total nitrated lung proteins. Finally, we found that decreasing peroxynitrite levels with either uric acid or Manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin (MnTymPyp) significantly attenuated the lung leak associated with LPS-exposure in mice suggesting a key role for protein nitration in the progression of ALI. In conclusion, this is the first study that suggests a role of the ADMA/DDAH pathway during the development of ALI in mice and that ADMA may be a novel therapeutic biomarker to ascertain the risk for development of ALI.

[Pathophysiology of acute lung injury in severe burn and smoke inhalation injury]

This review article describes the pathophysiological aspects of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), induced by combined burn and smoke inhalation and examines various therapeutic approaches. The injury results in a fall in arterial oxygenation as a result of airway obstruction, increased pulmonary transvascular fluid flux and loss of hypoxic pulmonary vasoconstriction. The changes in cardiopulmonary function are mediated by reactive oxygen and nitrogen species. Nitric oxide (NO) is generated by both inducible and constitutive isoforms of nitric oxide synthase (NOS). Recently, neuronal NOS emerged as a major component within the pathogenesis of ARDS. NO rapidly combines with the oxygen radical superoxide to form reactive and highly toxic nitrogen species such as peroxynitrite. The control of NO formation involves poly(ADP-ribose) polymerase and its ability to up-regulate the activity of nuclear transcription factors through ribosylation. In addition, present data support a major role of the bronchial circulation in the injury, as blockage of bronchial blood flow will also minimize the pulmonary injury. Current data suggest that cytotoxins and activated cells are formed in the airway and carried to the parenchyma.

Inhibition of inducible nitric oxide synthase in respiratory diseases

Nitric oxide (NO) is a key physiological mediator and disturbed regulation of NO release is associated with the pathophysiology of almost all inflammatory diseases. A multitude of inhibitors of NOSs (nitric oxide synthases) have been developed, initially with low or even no selectivity against the constitutively expressed NOS isoforms, eNOS (endothelial NOS) and nNOS (neuronal NOS). In the meanwhile these efforts yielded potent and highly selective iNOS (inducible NOS) inhibitors. Moreover, iNOS inhibitors have been shown to exert beneficial anti-inflammatory effects in a wide variety of acute and chronic animal models of inflammation. In the present mini-review, we summarize some of our current knowledge of inhibitors of the iNOS isoenzyme, their biochemical properties and efficacy in animal models of pulmonary diseases and in human disease itself. Moreover, the potential benefit of iNOS inhibition in animal models of COPD (chronic obstructive pulmonary disease), such as cigarette smoke-induced pulmonary inflammation, has not been explicitly studied so far. In this context, we demonstrated recently that both a semi-selective iNOS inhibitor {L-NIL [N6-(1-iminoethyl)-L-lysine hydrochloride]} and highly selective iNOS inhibitors (GW274150 and BYK402750) potently diminished inflammation in a cigarette smoke mouse model mimicking certain aspects of human COPD. Therefore, despite the disappointing results from recent asthma trials, iNOS inhibition could still be of therapeutic utility in COPD, a concept which needs to be challenged and validated in human disease.

Activated nuclear factor kappa B and airway inflammation after smoke inhalation and burn injury in sheep

In a recent study, we have shown a rapid inflammatory cell influx across the glandular epithelium and strong proinflammatory cytokine expression at 4 hours after inhalation injury. Studies have demonstrated a significant role of nuclear factor kappa B in proinflammatory cytokine gene transcription. This study examines the acute airway inflammatory response and immunohistochemical detection of p65, a marker of nuclear factor kappa B activation, in sheep after smoke inhalation and burn injury. Pulmonary tissue from uninjured sheep and sheep at 4, 8, 12, 24, and 48 hours after inhalation and burn injury was included in the study. Following immunostaining for p65 and myeloperoxidase, the cell types and the percentage of bronchial submucosal gland cells staining for p65 and the extent of myeloperoxidase stained neutrophils in the bronchial submucosa were determined. Results indicate absence of detection of P65 before 12 hours after injury. At 12 hours after injury, strong perinuclear staining for p65 was evident in bronchial gland epithelial cells, macrophages, and endothelial cells. Bronchial submucosal gland cells showed a significant increase in the percentage of cells stained for p65 compared with uninjured animals and earlier times after injury, P < .05. At 24 and 48 hours after injury, p65 expression was evident in the bronchiolar epithelium, Type II pneumocytes, macrophages, and endothelial cells. Quantitation of the neutrophil influx into the bronchial submucosa showed a significant increase compared with uninjured tissue at 24 and 48 hours after injury, P < .05. In conclusion, immunohistochemical detection of activated p65 preceded the overall inflammatory response measured in the lamina propria. However, detection of p65 did not correlate with a recent study showing rapid emigration of neutrophils at 4 hours postinjury. Together, these results suggest that p65 immunostaining may identify cells that are activated to produce proinflammatory cytokines after injury; however, the immunoexpression may not adequately reflect the temporal activation of gene transcription that may occur with proinflammatory cytokine production with inhalation injury.

Pulmonary expression of nitric oxide synthase isoforms in sheep with smoke inhalation and burn injury

Previous studies have indicated increased plasma levels of inducible nitric oxide synthase in lung. This study further examines the pulmonary expression of nitric oxide synthase (NOS) isoforms in an ovine model of acute lung injury induced by smoke inhalation and burn injury (S+B injury). Female range bred sheep (4 per group) were sacrificed at 4, 8, 12, 24, and 48 hours after injury and immunohistochemistry was performed in tissues for various NOS isoforms. The study indicates that in uninjured sheep lung, endothelial (eNOS) is constitutively expressed in the endothelial cells associated with the airways and parenchyma, and in macrophages. Similarly, neuronal (nNOS) is constitutively present in the mucous cells of the epithelium and in neurons of airway ganglia. In uninjured lung, inducible (iNOS) was present in bronchial secretory cells and macrophages. In tissue after S+B injury, new expression of iNOS was evident in bronchial ciliated cells, basal cells, and mucus gland cells. In the parenchyma, a slight increase in iNOS immunostaining was seen in type I cells at 12 and 24 hours after injury only. Virtually no change in eNOS or nNOS was seen after injury.

Inhibition of neuronal nitric oxide synthase in ovine model of acute lung injury

OBJECTIVE

Acute respiratory distress syndrome/acute lung injury is a serious complication of burn patients with concomitant smoke inhalation injury. Nitric oxide has been shown to play a major role in pulmonary dysfunction from thermal damage. In this study, we have tested the hypothesis that inhibition of neuronal nitric oxide synthase could ameliorate the severity of acute lung injury using our well-established ovine model of cutaneous burn and smoke inhalation.

DESIGN

Prospective, randomized, controlled, experimental animals study.

SETTING

Investigational intensive care unit at university hospital.

SUBJECTS

Adult female sheep.

INTERVENTIONS

Female sheep (n = 16) were surgically prepared for the study. Seven days after surgery, all sheep were randomly allocated into three study groups: sham (noninjured, nontreated, n = 6); control (injured, treated with saline, n = 6); and neuronal nitric oxide synthase (injured, treated with specific neuronal nitric oxide synthase inhibitor, ZK 234238 (n = 4). Control and neuronal nitric oxide synthase groups were given a cutaneous burn (40% of total body surface, third degree) and insufflated with cotton smoke (48 breaths, <40 degrees C) under halothane anesthesia. Animals in sham group received fake injury also under halothane anesthesia. After injury or fake injury procedure, all sheep were placed on ventilators and resuscitated with lactated Ringer's solution. Neuronal nitric oxide synthase group was administered with continuous infusion of ZK 234238 started 1 hr postinjury with a dose of 100 microg/kg/hr. Sham and control groups received same amount of saline.

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary hemodynamics monitored during the 24-hr experimental time period was stable in the sham group. Control sheep developed multiple signs of acute lung injury. This pathophysiology included decreased pulmonary gas exchange and lung compliance, increased pulmonary edema, and inflammatory indices, such as interleukin-8. Treatment of injured sheep with neuronal nitric oxide synthase inhibitor attenuated all the observed pulmonary pathophysiology.

CONCLUSIONS

The results provide definitive evidence that inhibition of neuronal nitric oxide synthase-derived excessive nitric oxide may be a novel and beneficial treatment strategy for pulmonary pathology in burn victims with smoke inhalation injury.

Combined neuronal and inducible nitric oxide synthase inhibition in ovine acute lung injury

OBJECTIVE

Acute lung injury with subsequent pneumonia and sepsis represents a major cause of morbidity and mortality in thermally injured patients. Production of nitric oxide by the neuronal and inducible nitric oxide synthase may be critically involved in the pathophysiology of the disease process at different time points, and thus specific inhibition at different times may represent an effective treatment regimen.

DESIGN

Prospective, controlled, randomized trial.

SETTING

University research laboratory.

SUBJECTS

Eighteen chronically instrumented, adult, female sheep.

INTERVENTIONS

Following baseline measurements, the animals were allocated to either sham-injured, nontreated controls (sham), injured, nontreated controls (control), or injured animals treated with continuous infusion of 7-nitroindazole, a specific neuronal nitric oxide synthase inhibitor, during the first 12 hrs postinjury and infusion of BBS-2, a specific inducible nitric oxide synthase inhibitor, during the next 12 hrs. Injury was induced by 48 breaths of cotton smoke and subsequent instillation of Pseudomonas aeruginosa into the lungs. All sheep were mechanically ventilated and fluid resuscitated for the entire duration of the 24-hr experiment.

MEASUREMENTS AND MAIN RESULTS

The injury induced severe pulmonary dysfunction, which was associated with increases in lung edema formation, airway obstruction, and vascular endothelial growth factor, 3-nitrotyrosine, and poly(adenosine diphosphate ribose) expression in lung tissue. The treatment reduced the degree of airway obstruction and improved pulmonary gas exchange, whereas the development of lung edema was not affected. The increases in lung tissue vascular endothelial growth factor, 3-nitrotyrosine, and poly(ribose) expression were attenuated by the treatment.

CONCLUSIONS

The combination of early neuronal nitric oxide synthase and delayed inducible nitric oxide synthase inhibition shows potential benefit in ovine acute lung injury by reducing nitrosative stress in the lung and limiting the degree of airway obstruction.

gamma-Tocopherol nebulization by a lipid aerosolization device improves pulmonary function in sheep with burn and smoke inhalation injury

Fire accident victims who sustain both thermal injury to skin and smoke inhalation have gross evidence of systemic and pulmonary oxidant damage and acute lung injury. We hypothesized that gamma-tocopherol (gT), a reactive O(2) and N(2) scavenger, when delivered into the airway, would attenuate lung injury induced by burn and smoke inhalation. Acute lung injury was induced in chronically prepared, anesthetized sheep by 40% total burn surface area, third-degree skin burn and smoke insufflation (48 breaths of cotton smoke, <40 degrees C). The study groups were: (1) Sham (not injured, flaxseed oil (FO)-nebulized, n=6); (2) SA-neb (injured, saline-nebulized, n=6); (3) FO-neb (injured, FO-nebulized, n=6); and (4) gT+FO-neb (injured, gT and FO-nebulized, n=6). Nebulization was started 1 h postinjury, and 24 ml of FO with or without gT (51 mg/ml) was delivered into airways over 47 h using our newly developed lipid aerosolization device (droplet size: 2.5-5 microm). The burn- and smoke inhalation-induced pathological changes seen in the saline group were attenuated by FO nebulization; gT addition further improved pulmonary function. Pulmonary gT delivery along with a FO source may be a novel effective treatment strategy in management of patients with acute lung injury.

Novel ovine model of methicillin-resistant Staphylococcus aureus-induced pneumonia and sepsis

Methicillin-resistant Staphylococcus aureus (MRSA)-related pneumonia and/or sepsis are a frequent serious menace. The aim of the study was to establish a standardized and reproducible model of MRSA-induced septic pneumonia to evaluate new therapies. Sheep were operatively prepared for chronic study. After 5 days' recovery, tracheostomy was performed under anesthesia, and smoke injury was induced by inhalation of cotton smoke (48 breaths, <40 degrees C). Methicillin-resistant S. aureus (AW6) (approximately 2.5x10(11) colony-forming units) was instilled into the airway by a bronchoscope. After the injury, animals were awakened and maintained on mechanical ventilation by 100% oxygen for first 3 h, and thereafter, oxygen concentration was adjusted according to blood gases. The sheep were resuscitated by lactated Ringer solution with an initial rate of 2 mL kg(-1) h(-1) that was further adjusted according to hematocrit. Study groups include (1) sham (noninjured, nontreated; n=6), (2) S+MRSA (exposed to smoke inhalation and MRSA, nontreated; n=6), and (3) smoke (exposed to smoke inhalation alone; n=6). Injured (S+MRSA) animals showed the signs of severe sepsis-related multiple organ failure 3 h after insult. Cardiovascular morbidity was evidenced by severe hypotension, with increased heart rate, cardiac output, left atrial pressure and severely decreased systemic vascular resistance index, and left ventricle stroke work index. Pulmonary dysfunction was characterized by deteriorated gas exchange (PaO2/FIO2 and pulmonary shunt) and increased ventilatory pressures. The S+MRSA group showed significantly greater lung tissue water content, myeloperoxidase activity, and cytokine production compared with uninjured sham animals. Microvascular hyperpermeability was evidenced by marked fluid retention (fluid net balance), decreased plasma protein with decreased plasma oncotic pressure, and increased pulmonary microvascular pressure. All these changes were accompanied by 6- to 7-fold increase in plasma nitrite/nitrate and increased production of reactive nitrogen species in lung. The smoke inhalation alone had a little or no effect on these variables. This model closely mimics hyperdynamic human sepsis. The excessive production of NO may be extensively involved in the pathogenic process.

Assessment of vascular permeability in an ovine model of acute lung injury and pneumonia-induced Pseudomonas aeruginosa sepsis

OBJECTIVE

To assess the time changes and mechanism of pulmonary and peripheral vascular permeability in sheep with acute lung injury and sepsis.

DESIGN

Prospective, controlled, randomized trial.

SETTING

University research laboratory.

SUBJECTS

A total of 21 chronically instrumented, adult female sheep.

INTERVENTIONS

Sheep were instrumented with lung and prefemoral lymph fistulas and allocated to either an uninjured control group (n = 5) or sepsis group (n = 5). The sheep in the sepsis group received cotton smoke inhalation injury followed by instillation of Pseudomonas aeruginosa into the lungs. All sheep were mechanically ventilated and fluid resuscitated for the entire duration of the 24-hr experiment. Additional sheep (n = 11) received injury and were killed at different time points for the measurement of vascular endothelial growth factor in lung tissue.

MEASUREMENTS AND MAIN RESULTS

The injury induced a hypotensive-hyperdynamic circulation; increases in pulmonary capillary pressure, net fluid balance, lung and prefemoral lymph flow and protein content, lung water content, abdominal and thoracic fluid and protein content, neutrophil accumulation in the lung, and vascular endothelial growth factor expression in lung tissue; and decreases in PaO2/FiO2 ratio, plasma protein concentration, plasma oncotic pressure, and myocardial contractility.

CONCLUSIONS

Lung edema formation in this model was the result of marked increases in both pulmonary microvascular permeability and pressure. Pulmonary vascular hyperpermeability peaked 12 hrs postinjury and was related to vascular endothelial growth factor overexpression. Early myocardial failure was a potential contributor to the constant increase in pulmonary capillary pressure. The sepsis-induced increase in peripheral microvascular permeability was associated with significant accumulation of fluid and protein in the third space.

Neuronal nitric oxide synthase inhibition attenuates cardiopulmonary dysfunctions after combined burn and smoke inhalation injury in sheep

OBJECTIVE

We hypothesized that nitric oxide derived from the neuronal nitric oxide synthase (NOS) is responsible for much of the injury resulting from skin burn and smoke inhalation. Therefore, we aimed to examine the effects of selective neuronal NOS inhibition on cardiopulmonary functions and cellular injury in sheep with acute respiratory distress syndrome secondary to combined burn and smoke inhalation injury.

DESIGN

Prospective, randomized, controlled laboratory experiment.

SETTING

Investigational intensive care unit.

SUBJECTS

A total of 22 chronically instrumented adult ewes.

INTERVENTIONS

Sheep were randomly assigned to either healthy controls (sham), injured controls (40% third-degree flame burn; 48 breaths of cotton smoke), or an injury group treated with the specific neuronal NOS inhibitor 7-nitroindazole (1 mg x kg(-1) x hr(-1)) from 1 hr postinjury to the end of the 48-hr study period. Hypoxic pulmonary vasoconstriction was assessed as decrease in left pulmonary blood flow in response to single-lung hypoxic challenges (100% nitrogen) at baseline, 24 hrs, and 48 hrs.

MEASUREMENTS AND MAIN RESULTS

The combination injury contributed to a approximately 90% loss of hypoxic pulmonary vasoconstriction and was associated with significant pulmonary shunting and death of one animal. The increase in nitrate/nitrite plasma levels in injured controls (12 hrs: 17 +/- 2 vs. 6 +/- 1 microM in sham animals; p < .001) was linked to increases in inducible NOS messenger RNA and 3-nitrotyrosine formation in lung tissue (48 hrs: 22 +/- 1 vs. 0.8 +/- 0.3 nM in sham animals; p < .001). 7-Nitroindazole treatment prevented the injury-associated changes in inducible NOS messenger RNA, nitrate/nitrite, and 3-nitrotyrosine, thereby attenuating the loss of hypoxic pulmonary vasoconstriction and improving gas exchange. In addition, 7-nitroindazole decreased lung tissue concentrations of hemoxygenase-1 and ameliorated myocardial depression, airway obstruction, pulmonary edema, ventilatory pressures, and histopathologic changes seen in injured controls.

CONCLUSIONS

The present study provides evidence that neuronal NOS-derived nitric oxide plays a pivotal role in the pathogenesis of acute respiratory distress syndrome resulting from combined burn and smoke inhalation injury.

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.

Neuronal nitric oxide synthase deficiency decreases survival in bacterial peritonitis and sepsis

OBJECTIVE

To investigate the role of neuronal nitric oxide synthase (NOS1) in murine polymicrobial peritonitis and sepsis.

DESIGN

Randomized experimental trial.

SETTING

Animal research facility.

SUBJECTS

B6129S NOS1+/+ and B6;129S4 NOS-/- mice.

INTERVENTIONS

NOS1+/+ and NOS1-/- animals underwent cecal ligation and puncture (CLP) or sham surgery and received the NOS1 inhibitor 7-nitroindazole (7-NI) or vehicle.

MEASUREMENTS AND MAIN RESULTS

After CLP, genetic deficiency and pharmacologic inhibition of NOS1 significantly increased risk of mortality [8.69 (3.27, 23.1), p<0.0001 and 1.71 (1.00, 2.92) p=0.05, hazard ratio of death (95% confidence interval) for NOS1-/- and 7-NI-treated NOS1+/+ respectively] compared with NOS1+/+ animals. In 7-NI-treated NOS1+/+ animals, there were increases (6 h) and then decreases (24 h), whereas in NOS-/- animals persistent increases in blood bacteria counts (p=0.04 for differing effects of 7-NI and NOS1-/-) were seen compared with NOS1(+/+) animals. After CLP, NOS1(-/-) had upregulation of inducible NOS and proinflammatory cytokines and greater increases in serum tumor necrosis factor-alpha and interleukin-6 levels compared with NOS1+/+ mice (all p<0.05). Following CLP, there were similar significant decreases in circulating leukocytes and lung lavage cells (p<or=0.0008) and significant increases in peritoneal lavage cells (p=0.0045) in all groups. Over 6 h and 24 h following CLP, compared with NOS1+/+, NOS-/- mice had significantly higher peritoneal cell concentrations {respectively 0.40+/-0.09 vs 0.79+/-0.15 [log(x10(4)cells/ml)] averaged over both times p=0.038}.

CONCLUSIONS

Deficiency and inhibition of NOS1 increases mortality, possibly by increasing proinflammatory cytokine response and impairing bacterial clearance after CLP. These data suggest that NOS1 is important for survival, bacterial clearance, and regulation of cytokine response during infection and sepsis.

Burn and smoke inhalation injury in sheep depletes vitamin E: kinetic studies using deuterated tocopherols

To test the hypothesis that burn and smoke injury will deplete tissue alpha-tocopherol and cause its faster plasma disappearance, deuterium-labeled vitamin E was administered to sheep exposed to both surface skin burn and smoke insufflation, which cause injuries similar to those of human victims of fire accidents. Two different protocols were used: (1) deuterated vitamin E was administered orally with food at time 0 (just before injury) or (2) the labeled vitamin E was administered orally with food the day before injury. The animals, which had been operatively prepared seven days before, were anesthetized and then received both 40% body surface area third-degree burn and 48 breaths of cotton smoke or sham injuries. All were resuscitated with Ringer's lactate solution (4 ml/kg/% BSA burn/24 h) and mechanically ventilated. Blood samples were collected at various times after vitamin E dosing. In both studies the depletion of plasma alpha-tocopherol was faster in the injured sheep. The sheep given deuterated vitamin E 24 h before injury had similar maximum alpha-tocopherol concentrations at similar times. The exponential rates of alpha-tocopherol disappearance were 1.5 times greater and half-lives were 12 h shorter (p < 0.05) in the injured sheep. In separate studies, various tissues were obtained from sheep that were sacrificed from 4 to 48 h after injury. The liver alpha-tocopherol concentrations in sheep killed at various times after injury seem to show a linear decrease at a rate of 0.1 nmol alpha-tocopherol/g liver per hour, suggesting that the liver is supplying alpha-tocopherol to maintain the plasma and lung alpha-tocopherol concentrations, but that this injury is so severe the liver is unable to maintain lung alpha-tocopherol concentrations. These findings suggest that alpha-tocopherol should be administered to burn patients to prevent vitamin E depletion and to protect against oxidative stress from burn injury.

Cardiac molecular signaling after burn trauma

Research using mammalian burn models has defined significant cardiac deficits after burn injury. The physiologic response to burn and burn complicated by sepsis, including the cardiac dysfunction associated with these insults, remains a very complex physiologic process which, despite active study, remains unclear. The well-characterized inflammatory mediators such as tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 continue to play an active role in mediating cardiac dysfunction. However, perhaps of greater interest are the late mediators, high mobility group box 1 and macrophage migration inhibitory factor, because they offer a very realistic window for therapeutic intervention for controlling the inflammatory response. In addition, several other mediators of cardiac dysfunction have been identified and include the heat shock proteins, apoptosis, and the inflammatory caspases. These new mediators provide opportunities for therapeutic intervention, but further research is needed to clarify the importance of their mechanisms of action and the complex interactions between these various signaling pathways.

Effects of severe smoke inhalation injury and septic shock on global hemodynamics and microvascular blood flow in sheep

This prospective, randomized, controlled experimental study looks at the effects on global and regional microvascular blood flow (RMBF) in an ovine model of septic shock after severe smoke inhalation injury. Sixteen sheep were randomized into two groups, a control group (no injury, n = 8) and a smoke/sepsis (SS) group (n = 8), which received an insufflation of 4 sets of 12 breaths of cotton smoke (<40 degrees C) followed by instillation of live Pseudomonas aeruginosa into both lung lobes, according to an established protocol. All sheep were mechanically ventilated with 100% oxygen, and fluid resuscitated with lactated Ringer's solution for the entire duration of the 24-h experimental period to maintain hematocrit at baseline (BL) levels. Healthy control animals were not subjected to the injury and received only 4 x 12 breaths of room air and instillation of the vehicle (normal saline). Blood flow was analyzed using colored microspheres. Control animals remained hemodynamically stable and had no statistical changes from BL in visceral or cerebral blood flow during the entire experimental period. All SS animals developed a hypotensive, hyperdynamic circulation, characterized by a significant increase in heart rate and cardiac output with a simultaneous significant fall in mean arterial pressure, which, in combination, led to a fall in systemic vascular resistance index versus BL (P < 0.001, each). In visceral organs, the trachea showed a significant increase in RMBF (P < 0.001). In addition, skeletal muscle significantly increased versus BL and versus controls over time (P < 0.01). Whereas the pancreas displayed a significant drop in RMBF versus BL and controls (P < 0.05), no statistical differences occurred in the renal cortex, spleen, and ileum. All investigated cerebral structures, such as the cortex cerebri, basal ganglia, thalamus, hippocampus, pons, medulla oblongata, and cerebellum showed a significant increase in RMBF versus BL and versus control animals (P < 0.05, each). These data differ in areas of normal, increased, and decreased RMBF during septic shock after smoke inhalation injury and show differences to former studies of our group investigating RMBF in ovine models of either smoke inhalation or P. aeruginosa infusion. The results of this study reflect the complex pathophysiological variances of the combined injury and may provide a basis for future investigations for the treatment of this kind of injury.

Vitamin E attenuates acute lung injury in sheep with burn and smoke inhalation injury

INTRODUCTION

A decrease in alpha-tocopherol (vitamin E) plasma levels in burn patients is typically associated with increased mortality. We hypothesized that vitamin E supplementation (alpha-tocopherol) would attenuate acute lung injury induced by burn and smoke inhalation injury.

MATERIALS AND METHODS

Under deep anesthesia, sheep (33 +/- 5 kg) were subjected to a flame burn (40% total body surface area, third degree) and inhalation injury (48 breaths of cotton smoke, < 40 degrees C). Half of the injured group received alpha-tocopherol (1000 IU vitamin E) orally, 24 h prior to injury. The sham group was neither injured nor given vitamin E. All three groups (n = 5 per group) were resuscitated with Ringer's lactate solution (4 ml/kg/%burn/24 h), and placed on a ventilator (PEEP = 5 cmH2O; tidal volume = 15 ml/kg) for 48 h.

RESULTS

Plasma alpha-tocopherol per lipids doubled in the vitamin E treated sheep. Vitamin E treatment prior to injury largely prevented the increase in pulmonary permeability index and moderated the increase in lung lymph flow (52.6 +/- 6.2 ml/min, compared with 27.3 +/- 6.0 ml/min, respectively), increased the PaO2/FiO2 ratio, ameliorated both peak and pause airway pressure increases, and decreased plasma conjugated dienes and nitrotyrosine.

CONCLUSIONS

Pretreatment with vitamin E ameliorated the acute lung injury caused by burn and smoke inhalation exposure.

The inhibition of inducible nitric oxide synthase in ovine sepsis model

Excessive NO has been shown to play a major role in the pathogenesis of multiple organ dysfunctions in septic condition. Burn injury, especially if it is associated with smoke inhalation, is often complicated by subsequent development of pneumonia or sepsis that determine the outcome. In the present study, we developed an ovine sepsis model, created by exposing sheep to smoke inhalation followed by instillation of bacteria into the airway, that closely mimics human sepsis and pneumonia. We hypothesized that the inhibition of iNOS-derived excessive NO might be beneficial in treating the cardiopulmonary derangement in this model. Female sheep (n = 18) were surgically prepared for the study and given a tracheostomy. This was followed by insufflation of 48 breaths of cotton smoke (< 40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa (5 x 10(11) colony forming units) into each sheep's lung. All sheep were mechanically ventilated using 100% O2. Continuous infusion of BBS-2 (100 microg/kg/h), an iNOS inhibitor, was started 1 h after insult. The administration of BBS-2 improved pulmonary gas exchange (PaO2/FiO2 and pulmonary shunt fraction) and partially reduced airway obstruction and an increase in ventilatory pressures. The lung water content was not affected by iNOS inhibition. The hypotension seen in nontreated animals was not ameliorated either. The increase in plasma concentration of nitrate and nitrite was inhibited by BBS-2. The results of present study show that iNOS may be partially involved in the pathogenesis of acute lung injury induced by smoke inhalation followed by bacterial instillation in the airway.

Aerosolized alpha-tocopherol ameliorates acute lung injury following combined burn and smoke inhalation injury in sheep

Victims of fire accidents who sustain both thermal injury to the skin and smoke inhalation have gross evidence of oxidant injury. Therefore, we hypothesized that delivery of vitamin E, an oxygen superoxide scavenger, directly into the airway would attenuate acute lung injury postburn and smoke inhalation. Sheep (N = 17 female, 35 +/- 5 kg) were divided into 3 groups: (1) injured, then nebulized with vitamin E (B&S, Vitamin E, n = 6); (2) injured, nebulized with saline (B&S, Saline, n = 6); and (3) not injured, not treated (Sham, n = 5). While under deep anesthesia with isoflurane, the sheep were subjected to a flame burn (40% total body surface area, 3rd degree) and inhalation injury (48 breaths of cotton smoke, <40 degrees C). All groups were resuscitated with Ringer lactate solution (4 mL/kg/%burn/24 h) and placed on a ventilator [positive end-expiratory pressure (PEEP) = 5 cm H2O, tidal volume = 15 mL/kg] for 48 h. B&S injury halved the lung alpha-tocopherol concentrations (0.9 +/- 0.1 nmol/g) compared with sham-injured animals (1.5 +/- 0.3), whereas vitamin E treatment elevated the lung alpha-tocopherol concentrations (7.40 +/- 2.61) in the injured animals. B&S injury decreased pulmonary gas exchange (PaO2/FiO2 ratios) from 517 +/- 15 at baseline to 329 +/- 49 at 24 h and to 149 +/- 32 at 48 h compared with sham ratios of 477 +/- 14, 536 +/- 48, and 609 +/- 49, respectively. Vitamin E treatment resulted in a significant improvement of pulmonary gas exchange; ratios were 415 +/- 34 and 283 +/- 42 at 24 and 48 h, respectively. Vitamin E nebulization therapy improved the clinical responses to burn and smoke inhalation-induced acute lung injury.

Sepsis: emerging role of nitric oxide and selectins

Sepsis--a state of systemic bacterial infection--often leads to multiorgan failure and is associated with high mortality despite the recent advances achieved in intensive care treatment. Many of the ill effects of sepsis are attributed to an abnormally enhanced host inflammatory response that leads to neutrophil recruitment and activation involving selectins, a class of adhesion molecules, in the initial stages. Nitric oxide and its various isoforms have also been implicated in various vascular alterations and directly participate in the cellular toxicity in sepsis. This review briefly describes the role of selectins and nitric oxide in experimental and clinical sepsis as well as the therapeutic outcomes of blocking therapies.

Anti-inflammatory effect of augmented nitric oxide production in chronic lung infection

Chronic infection of the lungs with Pseudomonas aeruginosa complicates many long-term lung diseases including cystic fibrosis, bronchiectasis, chronic obstructive lung disease, and mechanical ventilation. In acute inflammatory lung diseases, increased nitric oxide synthase (NOS-2) expression leads to excess nitric oxide (NO) production, resulting in the production of reactive nitrogen intermediates, which contribute to tissue damage. In contrast, the contribution of NO to pulmonary damage in chronic Pseudomonas infection of the lung has not been directly examined and is unclear. Although NOS-2 expression is increased in this condition, NO production is not abnormally elevated. It was hypothesized that chronic infection of the airways does not cause increased NO production but, in contrast, leads to inappropriately low NO concentrations that are pro-inflammatory. A rodent model of chronic airway infection was used to examine the effects on lung damage of augmenting or inhibiting NO production after airway infection with P. aeruginosa was well established. Three days post-infection, L-arginine, which augments NO production, or L-NAME, an inhibitor of NO production, was administered in drinking water. Lung damage was assessed 12 days later. L-arginine treatment reduced tissue damage, inhibited neutrophil recruitment, and reduced the pro-inflammatory cytokine interleukin (IL)-1beta. Treatment with L-NAME caused loss of alveolar walls, greater vascular damage, and increased levels of the pro-inflammatory cytokine IL-6. Thus, in chronic airway infection, inhibition of NO production worsened lung damage, whereas augmenting NO ameliorated this damage. This is the first demonstration that augmenting endogenous NO production in chronic infective lung disease caused by P. aeruginosa is anti-inflammatory. Given that infection with this organism complicates many chronic lung diseases, most notoriously cystic fibrosis, these findings have important clinical implications.

Nitric oxide synthase inhibition in sepsis? Lessons learned from large-animal studies

Nitric Oxide (NO) plays a controversial role in the pathophysiology of sepsis and septic shock. Its vasodilatory effects are well known, but it also has pro- and antiinflammatory properties, assumes crucial importance in antimicrobial host defense, may act as an oxidant as well as an antioxidant, and is said to be a "vital poison" for the immune and inflammatory network. Large amounts of NO and peroxynitrite are responsible for hypotension, vasoplegia, cellular suffocation, apoptosis, lactic acidosis, and ultimately multiorgan failure. Therefore, NO synthase (NOS) inhibitors were developed to reverse the deleterious effects of NO. Studies using these compounds have not met with uniform success however, and a trial using the nonselective NOS inhibitor N(G)-methyl-l-arginine hydrochloride was terminated prematurely because of increased mortality in the treatment arm despite improved shock resolution. Thus, the issue of NOS inhibition in sepsis remains a matter of debate. Several publications have emphasized the differences concerning clinical applicability of data obtained from unresuscitated, hypodynamic rodent models using a pretreatment approach versus resuscitated, hyperdynamic models in high-order species using posttreatment approaches. Therefore, the present review focuses on clinically relevant large-animal studies of endotoxin or living bacteria-induced, hyperdynamic models of sepsis that integrate standard day-to-day care resuscitative measures.

In vitro identification and in silico utilization of interspecies sequence similarities using GeneChip technology

Background

Genomic approaches in large animal models (canine, ovine etc) are challenging due to insufficient genomic information for these species and the lack of availability of corresponding microarray platforms. To address this problem, we speculated that conserved interspecies genetic sequences can be experimentally detected by cross-species hybridization. The Affymetrix platform probe redundancy offers flexibility in selecting individual probes with high sequence similarities between related species for gene expression analysis.

Results

Gene expression profiles of 40 canine samples were generated using the human HG-U133A GeneChip (U133A). Due to interspecies genetic differences, only 14 ± 2% of canine transcripts were detected by U133A probe sets whereas profiling of 40 human samples detected 49 ± 6% of human transcripts. However, when these probe sets were deconstructed into individual probes and examined performance of each probe, we found that 47% of human probes were able to find their targets in canine tissues and generate a detectable hybridization signal. Therefore, we restricted gene expression analysis to these probes and observed the 60% increase in the number of identified canine transcripts. These results were validated by comparison of transcripts identified by our restricted analysis of cross-species hybridization with transcripts identified by hybridization of total lung canine mRNA to new Affymetrix Canine GeneChip^®.

Conclusion

The experimental identification and restriction of gene expression analysis to probes with detectable hybridization signal drastically increases transcript detection of canine-human hybridization suggesting the possibility of broad utilization of cross-hybridizations of related species using GeneChip technology.

Pathophysiology of acute lung injury in combined burn and smoke inhalation injury

In the U.S.A., more than 1 million burn injuries occur every year. Although the survival from burn injury has increased in recent years with the development of effective fluid resuscitation management and early surgical excision of burned tissue, the mortality of burn injury is still high. In these fire victims, progressive pulmonary failure and cardiovascular dysfunction are important determinants of morbidity and mortality. The morbidity and mortality increases when burn injury is associated with smoke inhalation. In the present review, we will describe the pathophysiological aspects of acute lung injury induced by combined burn and smoke inhalation and examine various therapeutic approaches.