Signaling of apoptotic lung injury by liquid hydroperoxides

Background: Acute lung injury is common after shock and sepsis, but the pathophysiology is unclear. Lipid hydroperoxide products including 4-hydroxynonenal (HNE) increase significantly during these insults and may induce apoptosis. This study investigates the role of pathophysiologic concentrations of HNE on isolated lung biophysical function and apoptosis. Methods: Male Sprague-Dawley rat lungs were isolated and perfused with Krebs-Henseleit buffered solution for 120 minutes, Hydroxynonenal (50 mu mol/L) or vehicle was added to the perfusate at 60 minutes. Lung elastance and perfusion pressure were determined. Perfusate glutathione and lactate dehydrogenase were determined at 30-minute intervals. Genomic DNA was extracted for electrophoretic determination of apoptotic laddering. Results: There were no differences in any parameter measured before HNE infusion. Lung edema increased significantly with HNE infusion; a trend increase in lung elastance and perfusion pressure was noted. DNA laddering characteristic of apoptosis was noted in HNE-treated lungs that was absent in control animals. Conclusion: Lipid hydroperoxide products formed during shock or sepsis may be causally related to lung injury. Low concentrations of a candidate metabolite, HNE, appear to induce significant lung injury and apoptosis, which may partially mediate lung injury during shock and sepsis.