Inhibition of neuronal nitric oxide synthase by 7-nitroindazole attenuates acute lung injury in an ovine model

Abstract

Nitric oxide (NO) has been shown to play a major role in acute lung injury (ALI) after smoke inhalation. In the present study, we developed an ovine sepsis model, created by exposing sheep to smoke inhalation followed by instillation of bacteria into the airway, that mimics human sepsis and pneumonia. We hypothesized that the inhibition of neuronal NO synthase (nNOS) might be beneficial in treating ALI associated with this model. Female sheep (n = 26) were surgically prepared for the study and given a tracheostomy. This was followed by insufflation of 48 breaths of cotton smoke (40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa [5 x 10(11) colony forming units (CFU)] into each sheep's lung. All sheep were mechanically ventilated using 100% O2. Continuous infusion of 7-nitroindazole (7-NI), an nNOS inhibitor, NG-monomethyl-l-arginine (l-NMMA), a nonspecific NOS inhibitor, or aminoguanidine (AG), an inducible NOS inhibitor, was started 1 h after insult. The administration of 7-NI improved pulmonary gas exchange (PaO2/FiO2; where PaO2 is arterial PO2 and FiO2 is fractional inspired oxygen concentration) and pulmonary shunt fraction and attenuated the increase in lung wet-to-dry weight ratio seen in the nontreated sheep. Histologically, 7-NI prevented airway obstruction. The increase in airway blood flow after injury in the nontreated group was significantly inhibited by 7-NI. The increase in plasma concentration of nitrate and nitrite (NOx) was inhibited by 7-NI as well. Posttreatment with l-NMMA improved the pulmonary gas exchange, but AG did not. The results of the present study show that nNOS may be involved in the pathogenesis of ALI after smoke inhalation injury followed by bacterial instillation in the airway.

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

“…Sheep were surgically prepared for chronic study, as described previously (19)(20)(21). Briefly, a Swan-Ganz thermal dilution catheter (model 93A-1317-F, Edwards Critical Care Division; Irvine, CA) was inserted through the right external jugular vein for the measurement of cardiac output and the core body temperature and measure the central venous pressure to evaluate fluid resuscitation.…”

“…ID, 0.047 in, OD, Dow Corning; Midland, MI) according to a modification of the technique described by Staub and colleagues (22). The contribution to the node was removed by ligation of the tail of the caudal mediastinal lymph node and cauterization of the systemic diaphragmatic lymph vessels (20). After the operation, the sheep were allowed 5-7 days to recover from the operative procedure and given food and water ad libitum.…”

“…The smoke and burn injury protocol was described previously (19)(20)(21). Briefly, under induction of anesthesia with 10 mg/kg ketamine (Ketalar; Parke-Davis; Morris Plains, NJ), a tracheotomy was performed, and a cuffed tracheostomy tube (10-mm diameter, Sheiley; Irvine, CA) was inserted.…”

“…The resuscitation protocol was described previously (19)(20)(21). Immediately after the injury, anesthesia was discontinued and the animals were allowed to awaken and were mechanically ventilated with a Servo ventilator (model 900C, Simens-Elena; Solna, Sweden) throughout the next 48 h experimental period.…”

“…During the experiment, fluid resuscitation was performed with Ringer's lactate solution following the formula (4 ml/%burn surface area / kg body wt for the first 24h and 2 ml / % burned surface area /kg body wt per day for the next 48 h) (20). During this experimental period, the animals were allowed free access to food, but not to water, to allow accurate determination of fluid balance.…”