Cyclooxygenase-inhibition enhances the effects of rSP-C surfactant therapy in a rat lavage model of acute respiratory distress syndrome (ARDS)

Peripheral leukocytapheresis attenuates acute lung injury induced by lipopolysaccharide in vivo

The mortality of acute lung injury and acute respiratory distress syndrome (ALI/ARDS) remains high and efforts for prevention and treatments have shown little improvement over the past decades. The present study investigated the efficacy and mechanism of leukocytapheresis (LCAP) to partially eliminate peripheral neutrophils and attenuate lipopolysaccharide (LPS)-induced lung injury in dogs. A total of 24 healthy male mongrel dogs were enrolled and randomly divided into LPS, LCAP and LCAP-sham groups. All animals were injected with LPS to induce endotoxemia. The serum levels of leucocytes, neutrophil elastase, arterial blood gas, nuclear factor-kappa B (NF-κB) subunit p65 in lung tissues were measured. The histopathology and parenchyma apoptosis of lung tissues were examined. We found that 7, 3, and 7 animals in the LPS, LCAP, and sham-LCAP groups, respectively, developed ALI 36 h after LPS infusion. The levels of NF-κB p65 in lung tissue, neutrophils and elastase in blood, decreased significantly following LCAP. LCAP also alleviated apoptosis, and NF-κB p65 in lung tissues. Collectively, our results show that partial removal of leucocytes from peripheral blood decreases elastase level in serum. This, in turn, attenuates lung injuries and may potentially decrease the incidence of ALI.

Evolution of treatments for patients with acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are acute life-threatening forms of hypoxemic respiratory failure. ALI/ARDS patients require intensive care with prolonged mechanical ventilation. Despite advances in our understanding of the pathophysiology of ALI/ARDS, mortality rates remain > 30% and survivors suffer significant decrements in their quality of life. The evolving understanding of ALI/ARDS and the complex interactions involved in ALI/ARDS open the door for many potential targets for treatment. The condition is characterised by an acute inflammatory state that leads to increased capillary permeability and accumulation of proteinaceous pulmonary oedema. The changes that occur as a result of this inflammation clinically manifest themselves as hypoxemia, infiltrates on chest radiograph and reduced lung compliance. Many years have been dedicated to analysing the complexities involved in ALI/ARDS in order to improve current and future possibilities for treatment, with the aim of improving patient outcomes. Although some therapies have demonstrated benefits of improved oxygenation, such as surfactant and nitric oxide, these benefits have not translated into reductions in the duration of mechanical ventilation or mortality. Inflammatory mediator-targeted therapies were promising early on; however, larger trials have found therapies such as cytokine modulation, platelet-activating factor inhibition and neutrophil elastase inhibitors to be ineffective in the treatment of ALI/ARDS. Preclinical studies with beta2-agonists and granulocyte macrophage colony-stimulating factor have shown promise for restoring alveolar capillary barrier integrity or reducing pulmonary oedema, and further studies are being conducted to test for true clinical benefit. Despite previous therapeutic failures, newer surfactant formulations have shown promise, particularly in patients with direct forms of lung injury, and are currently in Phase III trials. Anticoagulant therapy with activated protein C has been shown to improve survival in sepsis, the most common risk factor for the development of ALI/ARDS, and is now being studied in ALI/ARDS. Until new data emerge, the focus must remain on supportive care, including optimised mechanical ventilation, nutritional support, manipulation of fluid balance and prevention of intervening medical complications.