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

Protective Effect of Nebulized Heparin in the Animal Models of Smoke Inhalation Injury: A Meta-analysis and Systematic Review of Experimental Studies

The pathophysiological mechanism of abnormal coagulation can result from smoke inhalation injury (SII). Heparin nebulization is a common treatment for lung disorders. This study aimed to use meta-analysis in animal models to examine the effectiveness of atomized heparin on SII. For our online searches, we used the Cochrane Central Register of Controlled Trials, PubMed, Web of Science, Chinese National Knowledge Infrastructure, Chinese BioMedical Literature Database, and Wanfang Database up to January 2022. Data for SII were retrieved and compared to control animals. The studies' findings were determined by combining standardized mean difference (SMD) analysis with 95% confidence intervals (CIs). The findings showed that as compared to the control group, the heparin-treated group had a lower death rate (relative risk 0.42; 95% CI 0.22, 0.80; p < .05). The meta-analysis demonstrated favorable changes in lung physiology, including PaO2/FiO2 (SMD 1.04; 95% CI 0.65, 1.44; p < .001), lung wet-to-dry weight ratio (SMD -1.83; 95% CI -2.47, -1.18; p < .001), and pulmonary shunt Qs/Qt (SMD -0.69; 95% CI -1.29, -0.08; p < .05) after heparin nebulization for lung injury. The present data indicated that pulmonary artery mean pressure in the heparin therapy group was significantly lowered after 24 and 48 hours of therapy, suggesting that the cardiovascular system could recover following heparin treatment. As a result, heparin nebulization appeared to be more effective against SII and improved cardiopulmonary function compared to the control group. Graphical Abstract.

The Role of Vitamin E in Thermal Burn Injuries, Infection, and Sepsis: A Review

Thermal burn injuries are still a serious public health concern in the United States, due to the initial insult and resulting comorbidities. Burned patients are increasingly susceptible to colonization by endogenous and exogenous microorganisms after having lost skin, which acts as the primary protective barrier to environmental contaminants. Furthermore, the onset of additional pathophysiologies, specifically sepsis, becomes more likely in burned patients compared to other injuries. Despite improvements in the early care of burn patients, infections, and sepsis, these pathophysiologies remain major causes of morbidity and mortality and warrant further investigation of potential therapies. Vitamin E may be one such therapy. We aimed to identify publications of studies that evaluated the effectiveness of vitamin E as it pertains to thermal burn injuries, infection, and sepsis. Several investigations ranging from in vitro bench work to clinical studies have examined the impact on, or influence of, vitamin E in vitro, in vivo, and in the clinical setting. To the benefit of subjects it has been shown that enteral or parenteral vitamin E supplementation can prevent, mitigate, and even reverse the effects of thermal burn injuries, infection, and sepsis. Therefore, a large-scale prospective observational study to assess the potential benefits of vitamin E supplementation in patients is warranted and could result in clinical care practice paradigm changes.

The black summer bushfires: impacts and risk factors for livestock bushfire injury in south-eastern Australia

Background

The 2019/2020 Australian bushfires were the largest bushfire event in modern Australian history. While actions to mitigate risk to homes from bushfires are well reported, there is very little research reported on the impacts of bushfires on livestock. With an increasing incidence of bushfires predicted, there is an urgent need to identify how farmers can best protect their livestock.

Objectives

Compare bushfire affected farms with and without injured livestock to identify associations between risk factors and bushfire injury. Infer management approaches that can be used to reduce bushfire injury in livestock.

Method

A case‐control study using a structured interview questionnaire, delivered in late 2020 to cattle and sheep farmers in south‐eastern Australia (New South Wales and Victoria) whose farmland was burnt in the 2019/2020 Australian bushfires. Case farms were farms with bushfires injured or killed livestock. Control farms were farms that had no bushfire injured livestock but that still had fire present on the farm. Interview responses were summarised and information theoretical approaches were used to identify potential risk factors for livestock bushfire injury and protective actions that could inform future fire‐preparation recommendations.

Results and discussion

Of 46 farms in the case‐control study, 21 (46%) reported bushfire injured or killed livestock. Apparent protective factors identified included: preparation (having a bushfire plan and more than two farm bushfire fighting units), backburning and receiving assistance from fire authorities. Combined beef and sheep grazing enterprises appeared to have an increased risk of bushfire injury to livestock.

The Australian 2019/2020 Black Summer Bushfires: Analysis of the Pathology, Treatment Strategies and Decision Making About Burnt Livestock

In 2019/2020, Australia experienced a severe bushfire event, with many tens of thousands of livestock killed or euthanized. Little systematic research has occurred to understand livestock bushfire injuries, risk factors for injury, or how to make decisions about management of bushfire-injured livestock. Addressing this research gap is important as there is an increasing bushfire incidence globally. This paper presents qualitative research findings about bushfire-injured and killed livestock in the south-east of Australia after the 2019/2020 Australian bushfires. We describe observed pathology, treatments used, and risk factors for injury, then use thematic analysis to understand decision making about managing fire-injured livestock. Livestock injured by the fires showed pathology predominantly associated with the common integument (feet, hooves and skin) and signs of acute respiratory damage. It could take several days for the full extent of burns to become apparent, leaving prognostic doubt. Treatment strategies included immediate euthanasia, salvage slaughter, retention for later culling, treatment and recovery on farm, hospitalization and intensive treatment, or no intervention. Risk factors reported for livestock injury included lack of warnings about an impending fire, the type and amount of vegetation around livestock and the weather conditions on the day the fire reached livestock. Moving stock to an area with little vegetation before fire arrived was seen as protective. Decision making regarding injured livestock appeared influenced by three main themes: (1) observations on the severity of pathology, clinical signs and level of prognostic doubt, (2) pre-existing beliefs about animal welfare (responsibility to minimize unnecessary suffering) and (3) assumptions about the future. The management of livestock was largely appropriate due to the rapid provision of veterinary expertise. However, it is likely that some injured livestock were euthanized due to conservative veterinary advice driven by a lack of opportunity to re-assess stock, with impacts on farmers. In future, resourcing regular revisits of injured livestock to manage risks of gradual progression of burn pathology may facilitate more accurate prognostic assessment, provided injured animals can receive appropriate pain relief. In addition, a more comprehensive burns classification system linked to prognosis that can be rapidly applied in the field may assist assessments.

Metal chelation attenuates oxidative stress, inflammation, and vertical burn progression in a porcine brass comb burn model

Oxidative stress and inflammation may mediate cellular damage and tissue destruction as the burn wound continues to progress after the abatement of the initial insult. Since iron and calcium ions play key roles in oxidative stress, this study tested whether topical application of a metal chelator proprietary lotion (Livionex Formulation (LF) lotion), that contains disodium EDTA as a metal chelator and methyl sulfonyl methane (MSM) as a permeability enhancer, would prevent progression or reduce burn wound severity in a porcine model. We have reported earlier that in a rat burn model, LF lotion reduces thermal injury progression. Here, we used the porcine brass comb burn model that closely mimics the human condition for contact burns and applied LF lotion every 8 h starting 15 min after the injury. We found that LF lotion reduces the depth of cell death as assessed by TUNEL staining and blood vessel blockage in the treated burn sites and interspaces. The protein expression of pro-inflammatory markers IL-6, TNF-a, and TNFα Converting Enzyme (TACE), and lipid aldehyde production (protein-HNE) was reduced with LF treatment. LF lotion reversed the burn-induced decrease in the aldehyde dehydrogenase (ALDH-1) expression in the burn sites and interspaces. These data show that a topically applied EDTA-containing lotion protects both vertical and horizontal burn progression when applied after thermal injury. Curbing burn wound conversion and halting the progression of second partial burn to third-degree full-thickness burn remains challenging when it comes to burn treatment strategies during the acute phase. Burn wound conversion can be reduced with targeted treatments to attenuate the oxidative and inflammatory response in the immediate aftermath of the injury. Our studies suggest that LF lotion could be such a targeted treatment.

Monophosphoryl Lipid a Attenuates Multiorgan Dysfunction During Post-Burn Pseudomonas Aeruginosa Pneumonia in Sheep

BACKGROUND

Monophosphoryl lipid A (MPLA) is a TLR4 agonist that has potent immunomodulatory properties and modulates innate immune function to improve host resistance to infection with common nosocomial pathogens in mice. The goal of this study was to assess the safety and efficacy of MPLA in a sheep model of burn injury and Pseudomonas aeruginosa pneumonia. The sheep provides a favorable model for preclinical testing as their response to TLR4 agonists closely mimics that of humans.

METHODS

Twelve chronically instrumented adult female Merino sheep received 20% total body surface area, third-degree cutaneous burn under anesthesia and analgesia. At 24 h after burn, sheep were randomly allocated to receive: MPLA (2.5 μg/kg i.v., n = 6), or vehicle (i.v., n = 6). At 24 h after MPLA or vehicle treatment, Pseudomonas aeruginosa pneumonia was induced. Sheep were mechanically ventilated, fluid resuscitated and cardiopulmonary variables were monitored for 24 h after induction of pneumonia. Cytokine production, vascular barrier function, and lung bacterial burden were also measured.

RESULTS

MPLA infusion induced small and transient alterations in core body temperature, heart rate, pulmonary artery pressure, and pulmonary vascular resistance. Pulmonary mechanics were not altered. Vehicle-treated sheep developed severe acute lung injury during Pseudomonas aeruginosa pneumonia, which was attenuated by MPLA as indicated by improved PaO2/FiO2 ratio, oxygenation index, and shunt fraction. Sheep treated with MPLA also exhibited less vascular leak, lower blood lactate levels, and lower modified organ injury score. MPLA treatment attenuated systemic cytokine production and decreased lung bacterial burden.

CONCLUSIONS

MPLA was well tolerated in burned sheep and attenuated development of acute lung injury, lactatemia, cytokinemia, vascular leak, and hemodynamic changes caused by Pseudomonas aeruginosa pneumonia.

Micronutrients after burn injury: a review

Supplementation of micronutrients after burn injury is common practice in order to fight oxidative stress, support the immune system, and optimize wound healing. Assessing micronutrient status after burn injury is difficult because of hemodilution in the resuscitation phase, redistribution of nutrients from the serum to other organs, and decreases in carrier proteins such as albumin. Although there are many preclinical data, there are limited studies in burn patients. Promising research is being conducted on combinations of micronutrients, especially via the intravenous route.

Vitamin E inadequacy in humans: causes and consequences

It is estimated that >90% of Americans do not consume sufficient dietary vitamin E, as α-tocopherol, to meet estimated average requirements. What are the adverse consequences of inadequate dietary α-tocopherol intakes? This review discusses health aspects where inadequate vitamin E status is detrimental and additional vitamin E has reversed the symptoms. In general, plasma α-tocopherol concentrations <12 μmol/L are associated with increased infection, anemia, stunting of growth, and poor outcomes during pregnancy for both the infant and the mother. When low dietary amounts of α-tocopherol are consumed, tissue α-tocopherol needs exceed amounts available, leading to increased damage to target tissues. Seemingly, adequacy of human vitamin E status cannot be assessed from circulating α-tocopherol concentrations, but inadequacy can be determined from “low” values. Circulating α-tocopherol concentrations are very difficult to interpret because, as a person ages, plasma lipid concentrations also increase and these elevations in lipids increase the plasma carriers for α-tocopherol, leading to higher circulating α-tocopherol concentrations. However, abnormal lipoprotein metabolism does not necessarily increase α-tocopherol delivery to tissues. Additional biomarkers of inadequate vitamin E status are needed. Urinary excretion of the vitamin E metabolite α-carboxy-ethyl-hydroxychromanol may fulfill this biomarker role, but it has not been widely studied with regard to vitamin E status in humans or with regard to health benefits. This review evaluated the information available on the adverse consequences of inadequate α-tocopherol status and provides suggestions for avenues for research.

Higher serum concentrations of dietary antioxidants are associated with lower levels of inflammatory biomarkers during the year after hip fracture

BACKGROUND & AIMS

Chronic inflammation impairs recovery among the 1.6 million people who suffer from hip fracture annually. Vitamin E and the carotenoids are two classes of dietary antioxidants with profound anti-inflammatory effects, and the goal of this study was to assess whether higher post-fracture concentrations of these antioxidants were associated with lower levels of interleukin 6 (IL-6) and the soluble receptor for tumor necrosis factor-alpha (sTNF-αR1), two common markers of inflammation.

METHODS

Serum concentrations of the dietary antioxidants and inflammatory markers were assessed at baseline and 2, 6, and 12 month follow-up visits among 148 hip fracture patients from The Baltimore Hip Studies. Generalized estimating equations modeled the relationship between baseline and time-varying antioxidant concentrations and inflammatory markers.

RESULTS

Higher post-fracture concentrations of vitamin E and the carotenoids were associated with lower levels of inflammatory markers. Associations were strongest at baseline, particularly between the α-tocopherol form of vitamin E and sTNF-αR1 (p = 0.05) and total carotenoids and both sTNF-αR1(p = 0.01) and IL-6 (p = 0.05). Higher baseline and time-varying α-carotene and time-varying lutein concentrations were also associated with lower sTNF-αR1 at all post-fracture visits (p ≤ 0.05).

CONCLUSIONS

These findings suggest that a clinical trial increasing post-fracture intake of vitamin E and the carotenoids may be warranted.

Acute lung injury-induced collagen deposition is associated with elevated asymmetric dimethylarginine and arginase activity

Evidence suggests that lung structure and function are partly maintained by a balance between the competing arginine-metabolizing enzymes arginase and nitric oxide (NO) synthase. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthase. It is metabolized by dimethylarginine dimethylaminohydrolase 2 (DDAH-2), which is oxidant-sensitive. The mechanism that induces excess lung collagen deposition in burned patients has not yet been explored. Our objective was to investigate the role of ADMA and the arginase pathway in acute lung injury. An ovine model for burn and smoke inhalation injury was used to assess excess lung collagen deposition. Sheep were deeply anesthetized during the injury, mechanically ventilated, resuscitated with fluid, and killed after either 2 or 3 weeks. Lungs were assessed histologically and biochemically for collagen content, arginase activity, lipid peroxidation product and antioxidant concentration, and protein concentrations. Plasma was assessed for amino acid and nitrate/nitrite concentrations. Burn and inhalation injury resulted in significantly reduced pulmonary function and increased lung collagen deposition. These physiological changes were associated with significantly increased lung arginase activity, collagen synthesis precursor ornithine aminotransferase, and ornithine decarboxylase, which is associated with cell proliferation. Significant decreases in plasma nitrate/nitrite after injury were associated with increased lung ADMA concentrations and decreased DDAH-2 expression. The decreased DDAH-2 expression was associated with significantly increased lipid peroxidation product and decreased antioxidant content in the lung. These data support that excess lung collagen deposition and reduced pulmonary function in acute lung injury after burn and inhalation injury are mediated through the arginase pathway.

Effect of antioxidants on the incidence of wound infection in burn patients

Background. Thermal injury causes the destruction of the physical skin barrier that normally protects the body from invasion by micro-organisms and induces an immunocompromised state that predisposes burn patients to infection, sepsis, and multiple organ failure. Reactive oxygen species contribute to burn-mediated immune suppression, and as the use of antioxidants has a positive effect on immune function, this may reduce the incidence of wound infection and related complications in burn patients. Patients and methods. One hundred and eighty burn patients of either sex and different ages, suffering from burns of varying percentage, were involved in the study. They were allocated to six groups: A, B, C, D, E, and F, each of 30 patients. Groups B, C, D, E, and F were treated with antioxidants (vitamins E and C, zinc sulphate, allopurinol, melatonin, and N-acetylcysteine, respectively) while group A was treated without antioxidants, according to our hospital policy. Thirty healthy subjects (group G) were also involved in the study as a control group for comparison. In each group, serum malondialdehyde and serum glutathione levels, microbiological values, healing time, and the mortality rate were measured using standard methods. Results. Administering antioxidants to burn patients produced significant improvements in the parameters studied compared with burn patients not given antioxidants. Conclusion. The study clearly showed the beneficial effect of antioxidants in the treatment of burn patients, as evidenced by the reduced incidence of wound infection and the shortening of healing time, in addition to the lower mortality rate. It is therefore recommended to add antioxidants to the treatment list of burn patients.

α-Tocopherol adipose tissue stores are depleted after burn injury in pediatric patients

BACKGROUND

We previously showed that thermal injury depletes plasma vitamin E in pediatric burn patients; however, plasma changes may reflect immediate alterations in vitamin E nutriture. Adipose tissue α-tocopherol concentrations are generally accepted to reflect long-term vitamin E status.

OBJECTIVE

To test the hypothesis that thermal injury depletes body stores of vitamin E, α-tocopherol concentrations were measured in adipose tissue samples.

DESIGN

Pediatric patients (n = 8) were followed up to 1 y after burn injury. Surgically obtained samples were collected at various intervals and stored at -80°C in a biorepository. α- and γ-Tocopherols, cholesterol, and triglycerides were measured in the same tissue aliquot.

RESULTS

During the first week after injury, adipose tissue α-tocopherol concentrations were within the expected normal range of 199 ± 40 nmol/g adipose tissue but were substantially lower at weeks 2 and 3 (133 ± 13 and 109 ± 8 nmol/g adipose tissue, respectively). Individual rates of decrease, estimated by linear regression, showed that adipose tissue α-tocopherol decreased by an average of 6.1 ± 0.6 nmol/g daily. During the first month after injury, adipose tissue triglyceride concentrations also decreased, whereas no changes in cholesterol concentrations occurred.

CONCLUSIONS

These data emphasize that the burn injury experienced by these pediatric patients altered their metabolism such that vitamin E status diminished during the month after injury. Further studies are needed to evaluate the mechanism and consequences of the observed vitamin E depletion. This trial was registered at clinicaltrials.gov as NCT00675714.

Modulation of ozone-sensitive genes in alpha-tocopherol transfer protein null mice

Alpha-tocopherol transfer protein (ATTP) null mice (ATTP-/-) have a systemic alpha-tocopherol (AT) deficiency, with their lung AT levels being < 10% of those in AT-replete ATTP(+/+) mice when fed a standard rodent chow diet. ATTP(+/+) and ATTP(-/-) mice (4 wk old male mice, n = 16 per group) were fed a standard diet (35 IU AT/kg diet) for 8-12 wk, exposed 6 h/day for 3 days to either to O(3) (0.5 ppm) or filtered air, then sacrificed. No significant differences in plasma or lung AT concentrations were observed in response to this level of O(3) exposure. Lung genomic responses of the lungs to O(3) were determined using Affymetrix 430A 2.0 arrays containing over 22,600 probe sets representing 14,000 well-characterized mouse genes. As compared with filtered air exposure, O(3) exposure resulted in 99 genes being differentially expressed in ATTP(-/-) mice, as compared to 52 differentially expressed genes in ATTP(+/+) mice. The data revealed an O(3)-induced upregulation of genes related to cell proliferation/DNA repair and inflammatory-immune responses in both ATTP(+/+) and ATTP(-/-) mice, with the expression of 22 genes being common to both, whereas 30 and 77 genes were unique to ATTP(+/+) and ATTP(-/-) mice, respectively. The expressions of O(3) sensitive genes-Timp1, Areg, Birc5 and Tnc-were seen to be further modulated by AT status. The present study reveals AT modulation of adaptive response of lung genome to O(3) exposure.

Molecular biological effects of selective neuronal nitric oxide synthase inhibition in ovine lung injury

Neuronal nitric oxide synthase is critically involved in the pathogenesis of acute lung injury resulting from combined burn and smoke inhalation injury. We hypothesized that 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, blocks central molecular mechanisms involved in the pathophysiology of this double-hit insult. Twenty-five adult ewes were surgically prepared and randomly allocated to 1) an uninjured, untreated sham group (n = 7), 2) an injured control group with no treatment (n = 7), 3) an injury group treated with 7-nitroindazole from 1-h postinjury to the remainder of the 24-h study period (n = 7), or 4) a sham-operated group subjected only to 7-nitroindazole to judge the effects in health. The combination injury was associated with twofold increased activity of neuronal nitric oxide synthase and oxidative/nitrosative stress, as indicated by significant increases in plasma nitrate/nitrite concentrations, 3-nitrotyrosine (an indicator of peroxynitrite formation), and malondialdehyde lung tissue content. The presence of systemic inflammation was evidenced by twofold, sixfold, and threefold increases in poly(ADP-ribose) polymerase, IL-8, and myeloperoxidase lung tissue concentrations, respectively (each P < 0.05 vs. sham). These molecular changes were linked to tissue damage, airway obstruction, and pulmonary shunting with deteriorated gas exchange. 7-Nitroindazole blocked, or at least attenuated, all these pathological changes. Our findings suggest 1) that nitric oxide formation derived from increased neuronal nitric oxide synthase activity represents a pivotal reactive agent in the patho-physiology of combined burn and smoke inhalation injury and 2) that selective neuronal nitric oxide synthase inhibition represents a goal-directed approach to attenuate the degree of injury.

Role of antioxidants in the treatment of burn lesions

Burns are a major health problem worldwide, with high mortality and morbidity in addition to causing changes in the quality of life of burn patients. Utilizing antioxidant therapeutic strategies depending on new mechanisms involved in the pathogenesis of burns-related "oxidative stress" may be considered a promising step in burns management. This study involved 180 burn patients of varying age and either sex and with varying burns percentages. The patients were subdivided into six groups (A, B, C, D, E, and F); each group thus included 30 patients. Patients in groups B, C, D, E, and F were treated with antioxidants (vitamin E with vitamin C, zinc sulphate, allopurinol, melatonin, and N-acetylcysteine respectively) while group A was treated according to hospital policy, without any antioxidant; also, healthy subjects (group G) were involved in the study as a control group for comparison.In each group we examined serum malondialdehyde and serum glutathione levels, serum zinc and copper levels, liver function, renal function, mortality rate, and healing time, using standard methods. It was found that the administration of antioxidants to burn patients produced significant improvement in the parameters studied compared with group A (no antioxidant given). This study clearly shows the importance of the therapeutic targeting of oxidative stress in the treatment of burns. It is important to consider antioxidant a most effective weapon that must be added to the arsenal available in the combating of burn complications.

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.