Acute inflammation in a sheep model of unilateral lung ischemia: the role of interleukin-8 recruitment of polymorphonuclear leukocytes

ACUTE BRONCHIAL OBSTRUCTION IN SHEEP: HISTOPATHOLOGY AND GLAND CYTOKINE EXPRESSION

An ovine model of smoke inhalation and burn (S+B) injury models the pathophysiology of these injuries in humans. This study examines the degree of airway obstruction, associated histopathology, and bronchial gland cell expression of cytokines during the first 24 hours after S+B injury in sheep. Changes in the mean degree of obstruction were limited to the bronchial airways, showing significant increases in obstruction with time, P<.05. At 4 hours after injury, the obstructive material was predominantly mucus, with neutrophils clustered around and within gland acini. At 8 to 24 hours, bronchial obstruction was characterized by increased inflammatory cell accumulation. Immunohistochemical results showed that gland cells constitutively express and secrete interleukin (IL)-1beta, and that after injury there is an increase in the percentage of gland cells staining for IL-1alpha, IL-8, and tumor necrosis factor (TNF)-alpha, P<.05.

Lung ischemia-reperfusion injury: implications of oxidative stress and platelet-arteriolar wall interactions

Pulmonary ischemia-reperfusion (IR) injury may result from trauma, atherosclerosis, pulmonary embolism, pulmonary thrombosis and surgical procedures such as cardiopulmonary bypass and lung transplantation. IR injury induces oxidative stress characterized by formation of reactive oxygen (ROS) and reactive nitrogen species (RNS). Nitric oxide (NO) overproduction via inducible nitric oxide synthase (iNOS) is an important component in the pathogenesis of IR. Reaction of NO with ROS forms RNS as secondary reactive products, which cause platelet activation and upregulation of adhesion molecules. This mechanism of injury is particularly important during pulmonary IR with increased iNOS activity in the presence of oxidative stress. Platelet-endothelial interactions may play an important role in causing pulmonary arteriolar vasoconstriction and post-ischemic alveolar hypoperfusion. This review discusses the relationship between ROS, RNS, P-selectin, and platelet-arteriolar wall interactions and proposes a hypothesis for their role in microvascular responses during pulmonary IR.

MOB-1 and TNF-alpha interact to induce microvascular lung injury

We have recently identified the alpha-chemokine mob-1 as a highly inducible gene in several rat models of microvascular lung injury, whose expression was suppressed by inhibition of tumor necrosis TNF-alpha (TNF-alpha). This work provides further insight into the relationship between mob-1 and TNF-alpha in the development of lung injury assessed by pulmonary edema and leukosequestration. First, pulmonary mob-1 and TNF-alpha were upregulated in animals subjected to lung injury produced by the intratracheal administration of recombinant TNF-alpha and recombinant mob-1, respectively. Second, mob-1 inhibition by intratracheal anti-mob-1 antibody attenuated lung injury induced by recombinant TNF-alpha. Third, pretreatment with anti-TNF-alpha monoclonal antibody administered intratracheally abrogated recombinant mob-1-induced microvascular lung injury. In vitro, mob-1 and TNF-alpha increased each other's production in RAW 264.7 cells and mob-1 or TNF-alpha inhibition prevented endotoxin-induced upregulation of TNF-alpha or mob-1, respectively, from these cells. Together, these data suggest that mob-1 and TNF-alpha interact to promote lung inflammation.

Amelioration of lung reperfusion injury by L- and E- selectin blockade

OBJECTIVE

Reperfusion injury is the main reason for early graft failure after lung transplantation. Inhibition of the adherence of polymorphonuclear leukocytes to activated endothelium by blocking L- and E-selectins (antibody EL-246) could potentially inhibit reperfusion injury.

METHODS

Reperfusion injury was induced in a left lung autotransplant model in sheep. After hilar stripping the left lung was flushed with Euro-Collins solution and preserved for 2 h in situ at 15 degrees C. After reperfusion right main bronchus and pulmonary artery were occluded leaving the animal dependent on the reperfused lung (control, n = 6). Pulmonary function was assessed by alveolo-arterial oxygen difference (AaDO2) and pulmonary vascular resistance (PVR), the chemiluminescence of isolated neutrophils, as well as the release of beta-N-acetyl-glucosaminidase (beta-NAG) served as indicator of neutrophilic activation. Extravascular lung water was an indicator for pulmonary edema formation. EL-246 group animals (n = 6) were treated additionally with 1 mg/kg BW of EL-246 given prior and during reperfusion.

RESULTS

After 3 h of reperfusion five control animals developed alveolar edema compared to one animal in the EL-246 group (P = 0.08). AaDO2 (mm Hg) was significantly higher in the control compared to the EL-246 group (510 +/- 148 vs. 214 +/- 86). PVR (dyn x s x cm(-5)) was significantly increased in the control compared to the EL-246 group (656 +/- 240 vs. 317 +/- 87). Neutrophilic activation was significantly lower in the EL-246 group. Extravascular lung water was significantly lower compared to control (6.88 +/- 1.0 vs. 13.4 +/- 2.8 g/g blood-free lung weight).

CONCLUSIONS

Treatment with EL-246 results in improved pulmonary function and less in vivo PMN activation in this experimental model. Further studies are necessary to evaluate the possible role of selectin blockade in amelioration of reperfusion injury in human lung transplantation.

Ischemia-reperfusion lung injury in rabbits: mechanisms of injury and protection

To study the mechanisms responsible for ischemia-reperfusion lung injury, we developed an anesthetized rabbit model in which the effects of lung deflation, lung inflation, alveolar gas composition, hypothermia, and neutrophils on reperfusion pulmonary edema could be studied. Rabbits were anesthetized and ventilated, and the left pulmonary hilum was clamped for either 2 or 4 h. Next, the left lung was reperfused and ventilated with 100% oxygen. As indexes of lung injury, we measured arterial oxygenation, extravascular lung water, and the influx of a vascular protein (131I-labeled albumin) into the extravascular space of the lungs. The principal results were that 1) all rabbits with the deflation of the lung during ischemia for 4 h died of fulminant pulmonary edema within 1 h of reperfusion; 2) inflation of the ischemic lung with either 100% oxygen, air, or 100% nitrogen prevented the reperfusion lung injury; 3) hypothermia at 6-8 degreesC also prevented the reperfusion lung injury; 4) although circulating neutrophils declined during reperfusion lung injury, there was no increase in interleukin-8 levels in the plasma or the pulmonary edema fluid, and, furthermore, neutrophil depletion did not prevent the reperfusion injury; and 5) ultrastructural studies demonstrated injury to both the lung endothelium and the alveolar epithelium after reperfusion in deflated lungs, whereas the inflated lungs had no detectable injury. In summary, ischemia-reperfusion injury to the rabbit lung can be prevented by either hypothermia or lung inflation with either air, oxygen, or nitrogen.