Edward R. Kraft

γ-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.

Gamma-Tocopherol Nebulization Decreases Oxidative Stress, Arginase Activity, and Collagen Deposition after Burn and Smoke Inhalation in the Ovine Model

ABSTRACT More than 20,000 burn injury victims suffer from smoke inhalation injury in the United States annually. In an ovine model of acute lung injury, &ggr;-tocopherol had a beneficial effect when nebulized into the airway. We hypothesize that &ggr;-tocopherol scavenges reactive oxygen species (ROS) and reactive nitrogen species resulting from burn and smoke inhalation injury and that these ROS/reactive nitrogen species activate the arginase pathway, leading to increased collagen deposition and decreased pulmonary function. To test this hypothesis, ewes were operatively prepared for chronic study, then they were randomly divided into groups (n = 8): uninjured, injured, or injured with nebulization (&ggr;-tocopherol [950 mg/g] and &agr;-tocopherol [40 mg/g] from hours 3 to 48 after the injury). The injury, under deep anesthesia, consisted of a 20% total body surface burn and 36 breaths of cotton smoke; all animals were killed after 3 weeks. Treatment increased lung &ggr;-tocopherol at 3 weeks after &ggr;-tocopherol nebulization compared with injured sheep (1.75 ± 0.62 nmol/g vs. 0.45 ± 0.06, P < 0.05). The expression of dimethylarginine dimethylaminohydrolase-2, which degrades asymmetrical dimethylarginine, a nitric oxide synthase inhibitor, significantly increases with &ggr;-tocopherol treatment compared with injured sheep (P < 0.05). Arginase activity (0.15 ± 0.02 &mgr;M urea/&mgr;g protein vs. 0.24 ± 0.009, P < 0.05), ornithine aminotransferase (11,720 ± 888 vs. 13,170 ± 1,775), and collagen deposition (0.62 ± 0.12 &mgr;M hydroxyproline/&mgr;g protein vs. 1.02 ± 0.13, P < 0.05) significantly decrease with &ggr;-tocopherol compared with injured animals without &ggr;-tocopherol. The decreases in arginase and collagen with &ggr;-tocopherol are associated with significantly increased diffusion capacity (P < 0.05) and decreased lung wet-to-dry ratio (P < 0.05). Smoke-induced chronic pulmonary dysfunction is mediated through the ROS/asymmetrical dimethylarginine/arginase pathway, and ROS scavengers such as &ggr;-tocopherol may be a potential therapeutic management of burn patients with inhalation injury.

Muscarinic receptor antagonist therapy improves acute pulmonary dysfunction after smoke inhalation injury in sheep.

Objectives:Inhalation injury contributes to the morbidity and mortality of burn victims. In humans and in an ovine model of combined smoke inhalation and burn injury, bronchospasm and acute airway obstruction contribute to progressive pulmonary insufficiency. This study tests the hypothesis that muscarinic receptor antagonist therapy with tiotropium bromide, an M1 and M3 muscarinic receptor antagonist, will decrease the airway constrictive response and acute bronchial obstruction to improve pulmonary function compared to injured animals without treatment. Design:Randomized, prospective study involving 32 sheep. Setting:Large-animal intensive care research laboratory. Interventions:The study consisted of six groups: a sham group (n = 4, instrumented noninjured), a control group (n = 6, injured and not treated), and tiotropium bromide-treated groups, including both preinjury and postinjury nebulization protocols. Treatments for these groups included nebulization with 36 &mgr;g of tiotropium bromide 1 hr before injury (n = 6) and postinjury nebulization protocols of 18 &mgr;g (n = 6), 36 &mgr;g (n = 6), and 72 &mgr;g (n = 4) administered 1 hr after injury. All treated groups received an additional 14.4 &mgr;g every 4 hrs for the 24-hr study period. Main Results:Pretreatment with tiotropium bromide significantly attenuated the increases in ventilatory pressures, pulmonary dysfunction, and upper airway obstruction that occur after combined smoke inhalation and burn injury. Postinjury treatments with tiotropium bromide were as effective as pretreatment in preventing pulmonary insufficiency, although a trend toward decreased obstruction was present only in all post-treatment conditions. There was no improvement noted in pulmonary function in animals that received a higher dose of tiotropium bromide. Conclusions:This study describes a contribution of acetylcholine to the airway constrictive and lumenal obstructive response after inhalation injury and identifies low-dose nebulization of tiotropium bromide as a potentially efficacious therapy for burn patients with severe inhalation injury.

Nebulization with γ-tocopherol ameliorates acute lung injury after burn and smoke inhalation in the ovine model.

ABSTRACT We hypothesize that the nebulization of &ggr;-tocopherol (g-T) in the airway of our ovine model of acute respiratory distress syndrome will effectively improve pulmonary function following burn and smoke inhalation after 96 h. Adult ewes (n = 14) were subjected to 40% total body surface area burn and were insufflated with 48 breaths of cotton smoke under deep anesthesia, in a double-blind comparative study. A customized aerosolization device continuously delivered g-T in ethanol with each breath from 3 to 48 h after the injury (g-T group, n = 6), whereas the control group (n = 5) was nebulized with only ethanol. Animals were weaned from the ventilator when possible. All animals were killed after 96 h, with the exception of one untreated animal that was killed after 64 h. Lung g-T concentration significantly increased after g-T nebulization compared with the control group (38.5 ± 16.8 vs. 0.39 ± 0.46 nmol/g, P < 0.01). The PaO2/FIO2 ratio was significantly higher after treatment with g-T compared with the control group (310 ± 152 vs. 150 ± 27.0, P < 0.05). The following clinical parameters were improved with g-T treatment: pulmonary shunt fraction, peak and pause pressures, lung bloodless wet-to-dry weight ratios (2.9 ± 0.87 vs. 4.6 ± 1.4, P < 0.05), and bronchiolar obstruction (2.0% ± 1.1% vs. 4.6% ± 1.7%, P < 0.05). Nebulization of g-T, carried by ethanol, improved pulmonary oxygenation and markedly reduced the time necessary for assisted ventilation in burn- and smoke-injured sheep. Delivery of g-T into the lungs may be a safe, novel, and efficient approach for management of acute lung injury patients who have sustained oxidative damage to the airway.

Photokinetic Drug Delivery: Light-Enhanced Permeation in an In Vitro Eye Model

PURPOSE To investigate light-enhanced molecular movement as a potential technology for drug delivery. To do this, we developed an in vitro eye model while representing similar concentration gradient conditions and compositions found in the eye. METHODS The eye model unit was fabricated by inserting a cross-linked type I collagen membrane in a spectrophotometer cuvette with 1% hyaluronic acid as the drug recipient medium. Photokinetic delivery was studied by illuminating 1 mg/mL methotrexate (MTX) placed in the drug donor compartment on top of the membrane, with noncoherent 450 nm light at 8.2 mW from an LED source pulsed at 25 cycles per second, placed in contact with the solution. A modified UV-visual spectrophotometer was employed to rapidly determine the concentration of MTX, at progressive 1 mm distances away from the membrane, within the viscous recipient medium of the model eye after 1 h. RESULTS A defined, progressive concentration gradient was observed within the nonagitated drug recipient media, diminishing with greater distances from the membrane. Transport of MTX through the membrane was significantly enhanced (ranging from 2 to 3 times, P < 0.05 to P ≤ 0.001) by photokinetic methods compared with control conditions by determining drug concentrations at 4 defined distances from the membrane. According to scanning electron microscopy images, no structural damage or shunts were created on the surface of the cross-linked gelatin membrane. CONCLUSION The application of pulsed noncoherent visible light significantly enhances the permeation of MTX through a cross-linked collagen membrane and hyaluronic acid recipient medium without causing structural damage to the membrane.