Polymorphonuclear leukocytes are activated during atelectasis before lung reexpansion in rat

Area of Science:

• Pulmonary Medicine
• Cellular Biology
• Inflammation Research

Background:

• Reexpansion pulmonary edema is a known complication of lung collapse, but its underlying mechanisms remain unclear.
• Inflammatory processes in the pulmonary circulation during atelectasis and reexpansion are not fully understood.

Purpose of the Study:

• To investigate inflammatory changes during lung atelectasis and reexpansion.
• To elucidate the mechanism of reexpansion pulmonary edema, focusing on polymorphonuclear leukocytes (PMNs) and reactive oxygen species (ROS) production.

Main Methods:

• Utilized a rat model with 1-hour bronchial occlusion to induce lung collapse, followed by 1-hour reexpansion and ventilation.
• Employed fluorescent imaging to assess PMN accumulation and ROS production.
• Used confocal laser scanning microscopy and image analysis to evaluate p47-phox translocation in sequestered PMNs.

Main Results:

• PMNs accumulated in the lung during atelectasis, with p47-phox translocation to the plasma membrane, but no ROS production was observed.
• Significant PMN ROS production occurred after reexpansion with air, but minimal ROS was detected upon reexpansion with nitrogen.
• These findings suggest PMNs are primed during atelectasis and undergo respiratory bursting upon reoxygenation.

Conclusions:

• PMN accumulation and priming occur during lung atelectasis.
• Reoxygenation following lung collapse triggers PMN respiratory bursting and ROS production, contributing to reexpansion pulmonary edema.
• Understanding this mechanism may lead to new therapeutic strategies for reexpansion pulmonary edema.