Direct Delivery of Low-Dose 7-Nitroindazole Into the Bronchial Artery Attenuates Pulmonary Pathophysiology After Smoke Inhalation and Burn Injury in an Ovine Model

Department of Plastic and Reconstructive Surgery, Tokyo Woman's Medical University, Tokyo, Japan.
Shock (Augusta, Ga.) (Impact Factor: 3.05). 12/2011; 36(6):575-9. DOI: 10.1097/SHK.0b013e3182360f2e
Source: PubMed


Bronchial circulation plays a critical role in the pathophysiology of burn and smoke inhalation-induced acute lung injury. A 10-fold increase in bronchial blood flow is associated with excessive production of nitric oxide (NO) following smoke inhalation and cutaneous burn. Because an increased release of neuropeptides from the airway has been implicated in smoke inhalation injury, we hypothesized that direct delivery into the bronchial artery of low-dose 7-nitroindazole (7-NI), a specific neuronal NO synthase inhibitor, would attenuate smoke/burn-induced acute lung injury. Eighteen adult female sheep were instrumented for chronic hemodynamic monitoring 5 to 7 days before the injury. The bronchial artery was cannulated via intercostal thoracotomy, while blood flow was preserved. Acute lung injury was induced by 40% total body surface area third-degree cutaneous burn and smoke inhalation (48 breaths of cotton smoke, <40°C) under deep anesthesia. Following injury, animals (35.4 ± 1.1 kg) were divided into three groups: (a) 7-NI group: 1 h after injury, 7-NI (0.01 mg · kg · h, 2 mL · h) was continuously infused into the bronchial artery, n = 6; (b) control group: 1 h after injury, same amount of saline was injected into the bronchial artery, n = 6; (c) sham group: no injury, no treatment, same operation and anesthesia, n = 6. After injury, all animals were ventilated and fluid resuscitated according to an established protocol. The experiment was conducted for 24 h. Injury induced severe pulmonary dysfunction, which was associated with increases in lung edema formation, airway obstruction, malondialdehyde, and nitrate/nitrite. 7-Nitroindazole injection into the bronchial artery reduced the degree of lung edema formation and improved pulmonary gas exchange. The increase in malondialdehyde and nitrate/nitrite in lung tissue was attenuated by treatment. Our data strongly suggest that local airway production of NO contributes to pulmonary dysfunction following smoke inhalation and burn injury. Most mechanisms that drive this pathophysiology reside in the airway.

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    • "Studies to evaluate effects of cytomix treatment demonstrated that mice developed significant acute lung inflammation (peaking at 48 h) along with transient edema (based on albumin increases in BAL fluid without LDH increase) (Table 3). Although NO changes were not assessed herein, pulmonary edema has been associated with increased NO production in animal models of acute lung injury [29,30]. Of note, both neutrophils and lymphocytes were significantly increased, consistent with MIP-2 and RANTES production, respectively. "
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    ABSTRACT: Epidemiologic studies associate childhood exposure to traffic-related air pollution with increased respiratory infections and asthmatic and allergic symptoms. The strongest associations between traffic exposure and negative health impacts are observed in individuals with respiratory inflammation. We hypothesized that interactions between nitric oxide (NO), increased during lung inflammatory responses, and reactive oxygen species (ROS), increased as a consequence of traffic exposure ─ played a key role in the increased susceptibility of these at-risk populations to traffic emissions. Diesel exhaust particles (DEP) were used as surrogates for traffic particles. Murine lung epithelial (LA-4) cells and BALB/c mice were treated with a cytokine mixture (cytomix: TNFα, IL-1β, and IFNγ) to induce a generic inflammatory state. Cells were exposed to saline or DEP (25 μg/cm2) and examined for differential effects on redox balance and cytotoxicity. Likewise, mice undergoing nose-only inhalation exposure to air or DEP (2 mg/m3 × 4 h/d × 2 d) were assessed for differential effects on lung inflammation, injury, antioxidant levels, and phagocyte ROS production. Cytomix treatment significantly increased LA-4 cell NO production though iNOS activation. Cytomix + DEP-exposed cells incurred the greatest intracellular ROS production, with commensurate cytotoxicity, as these cells were unable to maintain redox balance. By contrast, saline + DEP-exposed cells were able to mount effective antioxidant responses. DEP effects were mediated by: (1) increased ROS including superoxide anion (O2˙-), related to increased xanthine dehydrogenase expression and reduced cytosolic superoxide dismutase activity; and (2) increased peroxynitrite generation related to interaction of O2˙- with cytokine-induced NO. Effects were partially reduced by superoxide dismutase (SOD) supplementation or by blocking iNOS induction. In mice, cytomix + DEP-exposure resulted in greater ROS production in lung phagocytes. Phagocyte and epithelial effects were, by and large, prevented by treatment with FeTMPyP, which accelerates peroxynitrite catalysis. During inflammation, due to interactions of NO and O2˙-, DEP-exposure was associated with nitrosative stress in surface epithelial cells and resident lung phagocytes. As these cell types work in concert to provide protection against inhaled pathogens and allergens, dysfunction would predispose to development of respiratory infection and allergy. Results provide a mechanism by which individuals with pre-existing respiratory inflammation are at increased risk for exposure to traffic-dominated urban air pollution.
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