Model Of Smoke Inhalation Injury Research Articles

Effects of nebulized adipose-derived mesenchymal stem cells on acute lung injury following smoke inhalation in sheep

IntroductionTreatment of ARDS caused by smoke inhalation is challenging with no specific therapies available. The aim of this study was to test the efficacy of nebulized adipose-derived mesenchymal stem cells (ASCs) in a well-characterized, clinically relevant ovine model of smoke inhalation injury. Material and MethodsFourteen female Merino sheep were surgically instrumented 5–7 days prior to study. After induction of acute lung injury (ALI) by cooled cotton smoke insufflation into the lungs (under anesthesia and analgesia), sheep were placed on a mechanical ventilator for 48 hrs and monitored for cardiopulmonary hemodynamics in a conscious state. ASCs were isolated from ovine adipose tissue. Sheep were randomly allocated to two groups after smoke injury: 1) ASCs group (n = 6): 10 million ASCs were nebulized into the airway at 1 hr post-injury; and 2) Control group (n = 8): Nebulized with saline into the airways at 1 hr post-injury. ASCs were labeled with green fluorescent protein (GFP) to trace cells within the lung. ASCs viability was determined in bronchoalveolar lavage fluid (BALF). ResultsPaO2/FiO2 in the ASCs group was significantly higher than in the control group (p = 0.001) at 24 hrs. Oxygenation index: (mean airway pressure × FiO2/PaO2) was significantly lower in the ASCs group at 36 hr (p = 0.003). Pulmonary shunt fraction tended to be lower in the ASCs group as compared to the control group. GFP-labelled ASCs were found on the surface of trachea epithelium 48 hrs after injury. The viability of ASCs in BALF was significantly lower than those exposed to the control vehicle solution. ConclusionNebulized ASCs moderately improved pulmonary function and delayed the onset of ARDS.

The expression profile of lung long non-coding RNAs and mRNAs in a mouse model of smoke inhalation injury

ABSTRACT To study the potential expression of lung long non-coding RNAs (lncRNAs) and mRNAs during smoke inhalation injury (SII), using a SII mouse model that we created in our previous work. Microarray was used to investigate the lncRNAs and mRNAs profiles. A bioinformatics analysis was performed. Changes in the top 10 down-regulated and 10 up-regulated lncRNAs were validated using Quantitative Reverse Transcription-PCR (RT-qPCR). The acute lung injury (ALI) mouse model was successfully induced by smoke inhalation, as confirmed by the aberrantly modified cell numbers of red blood cells and neutrophils counts, increased levels of TNF-α, IL-1β, Bax, caspase-7, caspase-3, and decreased Bcl-2 content in lung tissues. When compared to the control mice, 577 lncRNAs and 517 mRNAs were found to be aberrantly expressed in the SII mice. According to the Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, the altered mRNAs were enriched in acute-phase response, oxidoreductase activity, oxidation-reduction process, glutathione metabolism, the wnt signaling pathway, and ferroptosis. A lncRNA-related competitive endogenous RNA (ceRNA) network, including 383 lncRNAs, 318 MicroRNAs (miRNAs), and 421 mRNAs specific to SII, was established. The changes in NONMMUT026843.2, NONMMUT065071.2, ENSMUST00000235858.1, NONMMUT131395.1, NONMMUT122516.1, NONMMUT057916.2, and NONMMUT013388.2 in the lung matched the microarray results. Our findings help to provide a more comprehensive understanding of the pathogenesis of SII as well as new insights into potential therapeutic targets.

Effects of simvastatin on iNOS and caspase‑3 levels and oxidative stress following smoke inhalation injury.

The overexpression of inducible nitric oxide synthase (iNOS) induces cell apoptosis through various signal transduction pathways and aggravates lung injury. Caspase-3 is an important protein in the apoptotic pathway and its activation can exacerbate apoptosis. Simvastatin, a hydroxymethyl glutaryl-A reductase inhibitor, protects against smoke inhalation injury by inhibiting the synthesis and release of inflammatory factors and decreasing cell apoptosis. Following the establishment of an animal model of smoke inhalation injury, lung tissue and serum were collected at different time points and the protein and mRNA expression of iNOS and caspase-3 in lung tissue by immunochemistry, western blot and reverse transcription-quantitative polymerase chain reaction, the malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in lung tissue and serum were analyzed using thiobarbituric acid method and the WST-1 method. The results were statistically analyzed. The lung tissues of the rats in the saline group and the low-, middle- and high-dose groups exhibited clear edema and hemorrhage, and had significantly higher pathological scores at the various time points compared with the rats in the control group (P<0.05). Furthermore, lung tissue and serum samples obtained from these four groups had significantly higher mRNA and protein expression levels of iNOS and caspase-3 (P<0.05), significantly lower SOD activity and higher MDA content (P<0.05). Compared with the saline group, the low-, middle- and high-dose groups had significantly lower pathological scores (P<0.05), significantly lower mRNA and protein expression levels of iNOS, caspase-3 and MDA content in lung tissues (P<0.05) and significantly higher SOD activity in lung tissues and serum. The middle- and high-dose groups had significantly lower pathological scores (P<0.05), significantly decreased iNOS and caspase-3 mRNA and protein expression in lung tissues, significantly higher SOD activity in lung tissues and serum and a significantly lower MDA content (P<0.05) compared with the low-dose group. With the exception of SOD activity in lung tissues at 24 and 72 h and MDA content in serum at 48 h, no significant differences were observed between the middle- and high-dose groups. The present study demonstrated that there was an association between the therapeutic effect and dosage of simvastatin within a definitive range. In rats with smoke inhalation injury, simvastatin inhibited iNOS and caspase-3 expression in lung tissues and mitigated oxidative stress, thereby exerting a protective effect. In addition, the effect and dose were associated within a definitive range.

Blood carboxyhemoglobin elimination curve, half-lifetime, and arterial-venous differences in acute phase of carbon monoxide poisoning in ovine smoke inhalation injury model

Smoke inhalation injury (SII) affects more than 50,000 people annually causing carbon monoxide (CO) poisoning. Although the increased blood level of carboxyhemoglobin (CO-Hb) is frequently used to confirm the diagnosis of SII, knowledge of its elimination in the acute phase is still limited. The aim of this study is to determine CO-Hb elimination rates and their differences in arterial (aCO-Hb) and mixed-venous (vCO-Hb) blood following severe SII in a clinically relevant ovine model. Forty-three chronically instrumented female sheep were subjected to SII (12 breaths, 4 sets) through tracheostomy tube under anesthesia and analgesia. After the SII, sheep were awakened and placed on a mechanical ventilator (FiO2 = 1.0, tidal volume 12 mL/kg, and PEEP = 5cmH2O) and monitored. Arterial and mixed-venous blood samples were withdrawn simultaneously for blood gas analysis at various time points to determine CO-HB half-lifetime and an elimination curve. The mean of highest aCO-Hb level during SII was 70.8 ± 13.9%. The aCO-Hb elimination curve showed an approximated exponential decay during the first 60 min. Per mixed linear regression model analysis, aCO-Hb significantly (p < 0.001) declined (4.3%/minute) with a decay constant lambda of 0.044. With this lambda, mean lifetime and half-lifetime of aCO-Hb were 22.7 and 15.7 min, respectively. The aCO-Hb was significantly lower compared to vCO-Hb at all-time points (0–180 min). To our knowledge, this is the first report describing CO-Hb elimination curve in the acute phase after severe SII in the clinically relevant ovine model. Our data shows that CO-Hb is decreasing in linear manner with supportive mechanical ventilation (0–60 min). The results may help to understand CO-Hb elimination curve in the acute phase and improvement of pre-hospital and initial clinical care in patients with CO poisoning.

Expression profile of microRNAs in bronchoalveolar lavage fluid of rats as predictors for smoke inhalation injury

Smoke inhalation injury (SII) is an independent risk factor for morbidity and mortality in patients with severe burns, however, the underlying mechanisms of SII are still not fully understood. In our study, we established an advanced rat model of SII based on the previous work, and explored the dynamic changes of pathophysiology and inflammatory factors during 28days post SII. We also measured the different expressions of miRNAs in bronchoalveolar lavage fluid (BALF) between SII and normal control rats by miRNA microarray. At 1day after smoke inhalation, the histopathological results exhibited inflammatory exudates in the lung tissue with significant edema. As time went on, the lung injuries gradually appeared at alveolar septum thickening and alveolar collapse, which suggested that it further induced damage to lung parenchyma by smoke inhalation. Particularly, the collagen deposition indicating pulmonary fibrosis happened at 28days post-injury. Plasma IL-6 and TNF-a were significantly increased after 1day of smoke inhalation. Plasma IL-10, BALF TNF-α and IL-10 were significantly increased after 2days of smoke inhalation. By extending the observation time, the levels of plasma IL-6, BALF TNF-a and IL-10 appeared a second peak again after 14days of injury. Compared with the normal control group, there were 23 upregulated miRNAs and 2 downregulated miRNAs in BALF of SII group at 1day post-injury. RT-qPCR validation assay confirmed that the changes of miR-34c-5p, miR-92b-3p, miR-205, miR-34b-3p, miR-92a-3p, let-7b-5p, let-7c-5p in BALF were consistent with the conclusion of the miRNA microarray. In summary, we showed the dynamic changes of pathologic changes and inflammatory factors in rats with SII, and a subset of seven miRNAs changed in BALF after SII which may be used for diagnosis and potential therapeutic targets.

Effects of non-muscle myosin ⅡA silenced bone marrow mesenchymal stem cells on lung damage of rats at early stage of smoke inhalation injury

Objective: To investigate the effects of non-muscle myosin ⅡA (NMⅡA) silenced bone marrow mesenchymal stem cells (BMSCs) on the lung damage of rats at early stage of smoke inhalation injury. Methods: Forty Sprague-Dawley rats were divided into control, simple injury, NMⅡA-BMSCs, and BMSCs groups according to the completely random method, with 10 rats in each group. Rats in control group inhaled air normally, while rats in the latter 3 groups inhaled smoke to reproduce model of smoke inhalation injury. At 30 min post injury, rats in simple injury group were injected with 1 mL normal saline via caudal vein, and rats in group BMSCs were injected with 1 mL the fifth passage of BMSCs (1×10(7)/mL), and rats in group NMⅡA-BMSCs were injected with 1 mL NMⅡA silenced BMSCs (1×10(7)/mL). At post injury hour (PIH) 24, abdominal aorta blood and right lung of rats in each group were harvested, and then arterial partial pressure of oxygen (PaO(2)), arterial partial pressure of carbon dioxide (PaCO(2)), and pH value were detected by blood gas analyzer. Ratio of wet to dry weight of lung was determined by dry-wet weight method. Pathological changes of lung were observed with HE staining. Bronchoalveolar lavage fluid (BALF) were collected, and then tumor necrotic factor-α (TNF-α) and interleukin-10 (IL-10) content of BALF was determined by enzyme-linked immunosorbent assay. Data were processed with one-way analysis of variance, Kruskal-Wallis H test, and least-significant difference test. Results: (1) At PIH 24, compared with those in control group, PaO(2) values of rats in simple injury, BMSCs, and NMⅡA-BMSCs groups were obviously decreased (with P values below 0.05), and PaCO(2) values were obviously increased (with P values below 0.05). Compared with those in simple injury group, PaO(2) values of rats in groups NMⅡA-BMSCs and BMSCs were obviously increased (with P values below 0.05), while PaCO(2) values were obviously decreased (with P values below 0.05). PaO(2) value of rats in group NMⅡA-BMSCs was obviously increased as compared with that in group BMSCs (P<0.05). The pH value of arterial blood of rats in simple injury group was obviously lower than that in control group (P<0.05). (2) At PIH 24, ratios of wet to dry weight of lung of rats in control, simple injury, BMSCs, and NMⅡA-BMSCs groups were 4.36±0.15, 7.79±0.42, 5.77±0.18, and 5.11±0.20, respectively. Compared with that in control group, ratio of wet to dry weight of lung of rats was obviously increased in the other 3 groups (with P values below 0.05). Compared with that in simple injury group, ratio of wet to dry weight of lung of rats was obviously decreased in groups BMSCs and NMⅡA-BMSCs (with P values below 0.05). Compared with that in group BMSCs, ratio of wet to dry weight of lung of rats in group NMⅡA-BMSCs was obviously decreased (P<0.05). (3) At PIH 24, alveolar structure of rats in control group was complete without abnormality. Compared with those in simple injury group, lung injury and infiltration of inflammatory cells of rats in groups BMSCs and NMⅡA-BMSCs were obviously alleviated, and alveolar structure was relatively complete with no thickening of alveolar wall. (4) At PIH 24, compared with that in control group, TNF-α content of BALF of rats in simple injury and BMSCs groups was obviously increased (with P values below 0.05). Compared with that in simple injury group, TNF-α content of BALF in groups BMSCs and NMⅡA-BMSCs was obviously decreased (with P values below 0.05). Compared with that in control group, IL-10 content of BALF in simple injury, NMⅡA-BMSCs and BMSCs groups were obviously increased (with P values below 0.05). Compared with that in simple injury group, IL-10 content of BALF in groups BMSCs and NMⅡA-BMSCs was obviously increased (with P values below 0.05). Compared with that in group BMSCs, IL-10 content of BALF in group NMⅡA-BMSCs was obviously increased (P<0.05). Conclusions: NMⅡA silenced BMSCs can alleviate lung damage of rats at early stage of smoke inhalation injury, showing better effectiveness than using BMSCs only.

Smoke inhalation injury repaired by a bone marrow-derived mesenchymal stem cell paracrine mechanism: Angiogenesis involving the Notch signaling pathway.

Smoke inhalation injury is an acute lung injury induced by smoke exposure characterized by vascular endothelial injury and increased permeability. Cell therapy is an attractive new therapeutic approach, although its underlying mechanism and signaling pathway remain poorly understood. We investigated the effect of systemic transplantation of preconditioned bone marrow-derived mesenchymal stem cells (BMSCs) on angiogenesis in rat model of smoke inhalation injury and explored the underlying mechanism and possible signaling pathway. After the establishment of a smoke inhalation injury rat model, the animals were further randomized into subgroups that received either a tail vein injection of 2 × 10(6) preconditioned or nonpreconditioned BMSCs in 5-mL phosphate-buffered saline to explore the characteristics of preconditioned BMSCs, pulmonary microvessel quantities in smoke inhalation injury, and its Notch1 expression. BMSCs preconditioned by 60Co γ-ray radiation at an appropriate dose were inhibited differentiation potential in vitro without significantly affecting the paracrine activity, the ability of cell proliferation, viability, and homing. Systemic preconditioned BMSC transplantation significantly increased the quantities of microvessels in rat with smoke inhalation injury, improved the lung wet-dry weight ratio, and alleviated lung injury simply through paracrine activity. Immunofluorescence staining and Western blot analysis confirmed that the expression level of Notch microvessel and Notch1 protein increased significantly after systemic transplantation. Our findings indicate that systemic transplantation of preconditioned BMSCs promotes angiogenesis through paracrine activity after smoke inhalation injury and that the Notch signaling pathway is involved in the angiogenesis process.

A dynamic smoke generation and nose-only inhalation exposure system for rats: preliminary results from studies of selected transportation materials

Context: Smoke inhalation injury is the main cause of fatalities for fire victims. Understanding in the pathophysiology of the injury has not been fully explored in recent years. To further explore the pathophysiological mechanism, a dynamic and controllable animal model is necessary.Objective: To develop a rat model of smoke inhalation injury to simulate human victims in air-restricted vehicle cabin fires.Materials and methods: Smoke concentration, including CO, O2, VOCs and smoke temperature under different combustion conditions, were detected. Levels of COHb, respiratory function, lung wet-to-dry weight ratio and protein concentration in BALF and blood were measured. Pathological evaluations of lung in tissues were conducted at 1, 6, 24 and 48 h post-exposure.Results: Smoke concentration rose with the increase of combustion temperature and decrease of oxygen flow. Further, 215 kinds of VOCs in the smoke were detected, and the concentrations of benzene, methylbenzene, ethylbenzene, dimethylbenzene, phenylethylene and trimethylbenzene was 32.93, 402.06, 764.03, 113.73, 1006.61 and 89.28 mg/m3, respectively. Significant hypoxemia and CO poisoning occurred in rats. The FCOHb after exposure for 14 min immediately rose to (44.2 ± 12.3) % and then gradually decrease to a normal level at 300 min post-exposure. At 24 h post-exposure, Penh increased significantly (p < 0.05), and high pulmonary vascular permeability and significant lung edema (p < 0.05) were observed in the smoke inhalation group.Discussion and conclusion: In summary, the novel rat model of smoke inhalation injury system used in the study is dynamic and controllable, and appropriate for use in smoke inhalation injury studies of air-restricted cabins in vehicles.

A rat model of smoke inhalation injury

Context: Smoke inhalation injury is the leading cause of acute respiratory failure in critical burn victims. Advances in the treatment of smoke inhalation injury have been limited in the past years. To further explore the pathogenesis, stable and practical animal models are necessary.Objective: To develop a rat model of smoke inhalation injury.Materials and methods: The smoke composition including the particulate matters, irritant gases, chemical carcinogens was measured. The blood gas values, pro-inflammatory and protein concentration in bronchoalveolar lavage fluid and lung wet to dry weight ratio were assayed. Pathological evaluations of pulmonary were performed at 24 h, 96 h, 7 days and 28 days post-injury. Masson–Goldner trichrome staining was performed on day 7 and 28 post-injury, along with the measurement of hydroxyproline and collagen I and III.Results: In our present animal model, smoke inhalation caused a significant hypoxemia and CO poisoning. A surge of pro-inflammatory response and microvascular hyperpermeability with neutrophils accumulations were also found in our animal model. At 24 h post-smoke inhalation, the hematoxylin and eosin results exhibited that there were inflammatory exudates and diffuse hemorrhage in the lung tissue with significant edema. With the time going, the lung injuries appeared at alveolar collapse and alveolar septum thickening, which indicated that smoke inhalation further induced damage to lung parenchyma. Specially, the markedly collagen deposition appeared at 28 days post-injury indicated that pulmonary fibrosis happened.Discussion and conclusion: In conclusion, this rat smoke inhalation injury model induced by our novel self-made smoke generator could be used for acute and chronic lung injury experiments.

The effect of bone marrow mesenchymal stem cells engraftment on lung tissue at early stage of smoke inhalation injury in rabbits

To explore the effect of bone marrow mesenchymal stem cells (MSCs) engraftment on lung tissue at early stage of smoke inhalation injury in rabbits. MSCs were proliferated by the method of whole marrow culture and identified by flow cytometry. Forty-eight rabbits were randomly divided into smoke inhalation group (S group) and MSCs group (M group) after reproduction of rabbit smoke inhalation injury model. 10 ml of phosphate buffer saline (PBS) containing 1×10(7)/ml MSCs was intravenously injected in M group, meanwhile 10 ml PBS was injected intravenously in S group. Eight rabbits were sacrificed at 2, 6 and 24 hours after intervention, and the lung tissue was harvested for morphological and pathological observation, and lung injury score was used to evaluate smoke inhalation injury. Cultured cells were confirmed to be MSCs with flow cytometry. Lung injury in rabbits of M group was less serious in morphology and histopathology than that in S group. Though there was no significance in lung injury score between M group and S group at 2 hours after injury (4.0±0.7 vs. 4.5±0.6, P>0.05), the lung injury scores in M group at 6 hours and 24 hours after injury were significantly lower than those in S group (6 hours: 6.1±0.9 vs. 8.2±0.9, 24 hours: 4.6±0.9 vs. 10.4±0.8, both P<0.01). Intravenous engraftment of MSCs could ameliorate lung injury induced by smoke inhalation, and improve lung injury score significantly.

A novel antibiotic based long-term model of ovine smoke inhalation injury and septic shock

We modified our established and clinically relevant ARDS model of smoke inhalation injury and septic shock by administration of combined antibiotics (AB) such as piperacillin and ciprofloxacin, to more closely mimic the clinical intensive care setting. Twenty-three sheep were subjected to the injury, and allocated to four groups for a 96 h study period: sham ( n = 5 non-injured); control ( n = 6: injured); AB6h ( n = 6: injured, antibiotics started 6 h post-injury); AB12h ( n = 6: injured, antibiotics started 12 h post-injury). All sham animals survived 96 h. Control, AB6h, AB12h groups reached criteria of septic shock within 12 h post-injury. All controls died within 36 h. Eighty three percent of AB6h and fifty percent of AB12h survived 96 h. Median survival times were significantly improved in the treated groups compared with the control group: 24 h in control vs. 80.5 h in AB6h, and 65 h in AB12h animals. Combined ciprofloxacin and piperacillin therapy was effective, reduced nitric oxide production and mortality, and will allow future long-term studies in this model.

A rat model of smoke inhalation injury: Influence of combustion smoke on gene expression in the brain

Acute smoke inhalation causes death and injury in victims of home and industrial fires as well as victims of combat situations. The lethal factors in combustion smoke inhalation are toxic gases and oxygen deficiency, with carbon monoxide (CO) as a primary cause of death. In survivors, inhalation of smoke can result in severe immediate and delayed neuropathologies. To gain insight into the progression of molecular events contributing to smoke inhalation sequelae in the brain, we developed a smoke inhalation rat model and conducted a genome-wide analysis of gene expression. Microarray analysis revealed a modified brain transcriptome with changes peaking at 24 h and subsiding within 7 days post-smoke. Overall, smoke inhalation downregulated genes associated with synaptic function, neurotransmission, and neurotrophic support, and upregulated genes associated with stress responses, including nitric oxide synthesis, antioxidant defenses, proteolysis, inflammatory response, and glial activation. Notably, among the affected genes, many have been previously implicated in other types of brain injury, demonstrating the usefulness of microarrays for analysis of changes in gene expression in complex insults. In accord with previously described modulations of nitric oxide homeostasis in CO poisoning, microarray analysis revealed increased brain expression of nitric oxide synthase (NOS) and NOS ligand after inhalation of smoke. Furthermore, immunostaining showed significant elevations in perivascular NOS and in protein nitration, corroborating the involvement of nitric oxide perturbations in post-smoke sequelae in the brain. Thus, the new rat model, in combination with microarray analyses, affords insight into the complex molecular pathophysiology of smoke inhalation in the brain.

EFFECTS OF MANGANESE SUPEROXIDE DISMUTASE NEBULIZATION ON PULMONARY FUNCTION IN AN OVINE MODEL OF ACUTE LUNG INJURY

Smoke inhalation injury is a major cause of morbidity and mortality in thermally injured individuals. There is evidence of increased oxygen free radical activity, e.g., superoxide, in association with smoke inhalation injury. Because superoxide dismutase converts the reactive superoxide radical to peroxide, we hypothesized that nebulization of manganese superoxide dismutase (Mn-SOD) into the airway might attenuate pulmonary dysfunction secondary to smoke inhalation injury. The present study was designed as a prospective, controlled, and randomized laboratory experiment to determine the effects of aerosolized Mn-SOD on lung fluid balance, as indexed by changes in pulmonary microvascular permeability, lung lymph flow (Q(L)), and gas exchange in an established and clinically relevant ovine model of smoke inhalation injury. Fifteen female Merino sheep were chronically instrumented with a femoral arterial, a Swan-Ganz, and a left atrial catheter. In addition, the right caudal mediastinal lymph node was cannulated to measure Q(L) (mL.h(-1)). Pneumatic occluders were placed around the right pulmonary veins for the determination of the reflection coefficient (sigma). After 7 days of recovery, sheep were randomly allocated to (a) an untreated control group (4 groups of 12 breaths of cotton smoke), (b) an injured group treated with nebulized Mn-SOD (5 mg/kg), and (c) an injured group that received only the vehicle (nebulized saline). Nebulization was performed 1 h and 12 h after smoke inhalation. Mn-SOD nebulization attenuated the increase in both filtration coefficient and sigma and significantly decreased lung tissue conjugated dienes. However, there were no differences in Q(L), PaO2/FiO2 ratio, and bloodless lung wet/dry weight ratio between groups. Although Mn-SOD nebulization attenuated the loss of protein, it failed to improve lung edema and pulmonary gas exchange, thereby limiting its clinical use.

Drotrecogin Alfa (activated) Prevents Smoke-Induced Increases in Pulmonary Microvascular Permeability and Proinflammatory Cytokine IL-1β in Rats

In an established rat model of smoke inhalation injury, we conducted a dose-response study to examine the protective effects of Xigris [drotrecogin alfa (activated) (DrotAA)], a recombinant form of human activated protein C (APC). DrotAA is a serine protease (approximately 55 kD molecular weight) with the same amino acid sequence and the glycosylation site as human plasma-derived APC. A total of 120 F344/NH rats (half each gender, approximately 175 g body weight) were randomly divided into five groups and exposed nose-only to air or diesel fuel smoke for 20 min. These rats were then i.v. administered with DrotAA in 0, 5, 10, and 20 mg/kg body weight, respectively, immediately following smoke exposure. Treatment with DrotAA significantly attenuated smoke inhalation injury in a dose-dependent manner at 2 hours after insult, as indicated by preserving microvascular permeability and proinflammatory cytokine IL-1beta (but not TNF-alpha and neuropeptide substance P) in bronchoalveolar lavage fluid (BALF). Moreover, the rats treated with 20 mg/ kg of DrotAA had an improvement of the expiration phase of pulmonary dynamic compliance. At all dosages, however, DrotAA also significantly increased all phases of pulmonary resistance compared with either the controls or to smoke inhalation alone. Generally, these data suggest that DrotAA may exert an anti-inflammatory effect by inhibiting cytokine-mediated inflammatory amplification. However, additional studies following a clinical course are needed to confirm the maximum efficiency and possible side effects of this recombined human activated protein C.

The effects of inhaled nitric oxide on cardiac pathology and energy metabolism in a canine model of smoke inhalation injury

Objective: The effects of inhaled nitric oxide (NO) on cardiac pathology and energy metabolism were studied in a canine model of smoke inhalation injury. Material and method: Twenty-one dogs were randomly divided into three groups: four dogs constituted the normal control group (group N), eight dogs subjected to smoke inhalation followed by O 2 inhalation (FiO 2=0.45) constituted the injury control group (group C), and nine dogs inhaling a mixture of O 2 and 45 ppm nitric oxide after smoke exposure served as the treatment group (group T). Myocardial zymograms were continuously measured, and ventricular muscles were examined for histopathology in the end of the experiment. Results: Lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (alpha-HBD), creatine kinase (CK) and glutamic oxalacetic transaminase (GOT) in group T were less than those in group C( P<0.05, or P<0.01). ATP content and energy charge (EC) in group T were higher significantly than those in group C( P<0.01). Light microscopy and electron microscopy indicated that the ventricular pathologic changes in group T were milder than in control group. Conclusion: Nitric oxide inhalation relieved myocardial damage and improved energy metabolism.

Carboxyhemoglobin formation following smoke inhalation injury in sheep is interrelated with pulmonary shunt fraction

Carboxyhemoglobin (COHb) formation is triggered by the inducible isoform of heme oxygenase (HO-1) catalyzing carbon monoxide (CO) production through breakdown of heme molecules, exposure to CO or both. In the setting of CO poisoning, COHb is regarded as a reliable marker characterizing both severity of injury and efficacy of treatment strategies. This study was designed as a prospective laboratory experiment to elucidate potential interdependencies between COHb generation, oxygenation, and pulmonary shunt fraction (Qs/Qt) in an ovine model of smoke inhalation injury. Chronically instrumented ewes (n=15) were repeatedly subjected to cotton smoke (4×12 breaths) according to an established protocol. This approach resulted in a progressive increase in COHb formation that was interrelated with the degree of Qs/Qt (P<0.001) and inversely correlated with both arterial and mixed venous HbO2 saturation (r=−0.96 and −0.93). Although the arteriovenous COHb gradient successively decreased over time, COHb determined in venous blood underestimated the arterial content.

Effects of exogenous surfactant supplementation and partial liquid ventilation on acute lung injury induced by wood smoke inhalation in newborn piglets.

To investigate the beneficial effects of exogenous surfactant supplementation (ESS) and partial liquid ventilation (PLV) in treating acute lung injury induced by wood smoke inhalation. A prospective, randomized, controlled, multigroup study. An animal research laboratory at a medical center. Newborn piglets (n = 29; 1.80 +/- 0.06 kg) of either sex. Animals were ventilated with a tidal volume of 15 mL/kg, a rate of 30 breaths/min, a positive end-expiratory pressure of 5 cm H(2)O, and an Fio(2) of 1.0. After the induction of acute lung injury by wood smoke inhalation, animals were randomly assigned to receive either conventional mechanical ventilation (CMV) or PLV with or without ESS pretreatment. Animals were grouped as CMV, ESS-CMV, PLV, and ESS-PLV. Arterial blood gases, cardiovascular hemodynamics, dynamic lung compliance, and total lung injury scores were measured. After smoke inhalation, all four groups displayed similar high arterial carboxyhemoglobin levels, low Pao(2) (<150 mm Hg), and low dynamic lung compliance (<66% of its baseline). In the CMV group, these deleterious conditions remained during the 4-hr observation period, and severe lung injury was noted histologically. All treatment groups demonstrated a significant increase in Pao(2) compared with the CMV group. In addition, both the PLV and ESS-PLV groups displayed significant improvements in dynamic lung compliance and in their histologic outcomes. Nevertheless, none of the variables measured in the PLV group differed from those measured in the ESS-PLV group. In a newborn piglet model of smoke inhalation injury, PLV or ESS improved oxygenation. PLV compared favorably with ESS in its greater improvements in lung compliance and lung pathology. However, the combined therapy of ESS and PLV was not clearly superior to PLV alone during the observation period.

The effects of inhaled nitric oxide on the levels of cGMP plasma and lung tissue in a canine model of smoke inhalation injury

The effects of inhaled nitric oxide (NO) on pulmonary hypertension and their mechanisms were studied in a canine model of smoke inhalation injury. Twenty-one dogs were randomly divided into three groups: four dogs constituted the normal control group, eight dogs subjected to smoke inhalation followed by O 2 inhalation (FiO 2=0.45) constituted the injury control group, and nine dogs inhaling a mixture of O 2 and 45 ppm nitric oxide after smoke exposure served as the treatment group. The levels of cyclic guanosine monophosphate (cGMP) in arterial plasma of the treatment group were higher than that of the control group at 5, 8, and 12 h after smoke exposure, while the levels of cGMP in lung tissue were also significantly higher compared with that of the control group ( P<0.01). The levels of cGMP of injury control group were decreased significantly compared with normal controls ( P<0.05). Pulmonary vasoconstriction following smoke inhalation was significantly attenuated by inhalation of NO ( P<0.05), which exerted no apparent effect on the systemic circulation ( P>0.05). Inhalation of NO may lower pulmonary hypertension induced by smoke inhalation injury in dogs. The selective effect of NO on pulmonary circulation may be attributed to an increase in level of cGMP in smooth muscle cells of the lung tissue after inhalation of NO.

Enhanced pulmonary expression of endothelin-1 in an ovine model of smoke inhalation injury.

Recent studies suggest a role of endothelin-1 (ET-1) in mediating airway inflammation and lung injury. The aim of this study was to assess the immunohistochemical expression of ET-1 in the lung following smoke inhalation injury. ET-1 immunoreactivity was assessed in normal sheep (N = 4) and in sheep at 1 (N = 2), 6 (N = 3), 12 (N = 3), and 24 (N = 3) hours after inhalation injury. In normal animals, ET-1 expression was limited to the basal cell layer of the tracheal epithelium, main bronchi, and associated mucous glands. One hour after injury, ET-1 immunoreactivity was enhanced in upper airway epithelium and mucus glands with new expression in bronchioles. Airway smooth muscle, vascular tissue, and alveolar duct smooth muscle cells expressed moderate levels of ET-1 at 12 and 24 hours. ET-1 immunoreactivity was absent in areas of parenchymal edema and inflammation. The pattern of ET-1 expression following inhalation injury suggests that this peptide may contribute to the airway inflammation, mucus secretion, pulmonary hypertension, increased airway resistance, and decreased lung compliance, which are evident in our ovine model of inhalation injury.

Delayed partial liquid ventilation shows no efficacy in the treatment of smoke inhalation injury in swine.

In an earlier neonatal porcine model of smoke inhalation injury (SII), immediate postinjury application of partial liquid ventilation (PLV) had dramatic beneficial effects on lung compliance, oxygenation, and survival over a 24-h period. To explore the efficacy of PLV following SII, we treated animals at 2 and 6 h after SII and followed them for 72 h. Pigs weighing 8-12 kg were sedated and pharmacologically paralyzed, given a SII, and placed on volume-cycled, pressure-limited ventilation. Animals were randomized to three groups: group I (+SII, no PLV, n = 8), group II (+SII, PLV at 2 h, n = 6), and group III (+SII, PLV at 6 h, n = 7). Ventilatory parameters and arterial blood gasses were obtained at scheduled intervals. The PLV animals (groups II and III) followed a worse course than group I (no PLV); PLV groups had higher peak and mean airway pressures, oxygenation index, and rate-pressure product (a barotrauma index) and lower lung compliance and arterial partial pressure of oxygen-to-inspired oxygen fraction ratio (all P < 0.05). PLV conferred no survival advantage. The reported beneficial effects of PLV with other models of acute lung injury do not appear to extend to the treatment of SII when PLV is instituted in a delayed manner. This study was not able to validate the previously reported beneficial effects of PLV in SII and actually found deleterious effects, perhaps reflecting the predominance of airway over alveolar disease in SII.