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

Abstract

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.

Beneficial pulmonary effects of a metalloporphyrinic peroxynitrite decomposition catalyst in burn and smoke inhalation injury

“…PARP activates NF-B (9), which upregulates IL-8 and inducible NOS, setting into motion a positive-feedback loop. We have confirmed much of this hypothesis by blocking calcitonin gene-related peptide (17), different isoforms of NOS (5,24), PARP (25), and now RNS.…”

“…Combined burn and smoke inhalation injury in sheep closely reflects the pathophysiological changes in humans with these injuries (10), and previous studies with our model demonstrated that reactive nitrogen species (RNS) are critically involved in this process (5,24,28,36). We have also reported the presence of reactive oxygen species (ROS) in patients with burn and smoke inhalation injury (20).…”

“…The chemicals in toxic smoke stimulate the release of neuropeptides, such as calcitonin gene-related peptide, which then activate NO synthase (NOS) to cause the release of RNS (17,24). RNS, in turn, damage DNA to cause the activation of PARP (24). PARP activates NF-B (9), which upregulates IL-8 and inducible NOS, setting into motion a positive-feedback loop.…”

Effects of Early Neuronal and Delayed Inducible Nitric Oxide Synthase Blockade on Cardiovascular, Renal, and Hepatic Function in Ovine Sepsis

“…13 The chosen dosage of 7-NI has been established in previous studies using the same and a similar animal model. 6,14,15 It has previously been demonstrated that infusion of 7-NI in sheep at a dose of 1 mg ⅐ kg Ϫ1 ⅐ h Ϫ1 effectively suppresses plasma nitrate/nitrite levels 6,14,15 and establishes plasma concentrations of 7-NI 15 far below the IC 50 reported for endothelial and inducible NOS. 16 All sheep were mechanically ventilated (Servo Ventilator 900C; Siemens, Elema, Sweden) with a tidal volume of 12-15 ml/kg and a positive-end expiratory pressure of 5 cm H 2 O during the entire study period of 24 h. The fraction of inspired oxygen was set at 1.0 for the first 3 h postinjury and was then adjusted to maintain sufficient oxygenation (arterial oxygen saturation more than 90%, partial arterial oxygen pressure 80 -100 mmHg) whenever possible.…”

Review of Burn Research for the Year 2010

“…Administration of 7-nitroindazole attenuated all of these responses, implicating neuronal nitric oxide synthase as having a key role in the pathology of inhalation injuries. 22 These studies offer the possibility of potential future therapies for the treatment of inhalation injuries.…”