[Pulmonary apoptosis and necrosis in hyperoxia-induced acute mouse lung injury]

Abstract

Objective: To investigate the pathways to cell death in hyperoxia-induced lung injury and the functional significance of apoptosis in vivo in response to hyperoxia.

Methods: Seventy-two mice were exposed in sealed cages > 98% oxygen (for 24 - 72 h) or room air, and the severity of lung injury and epithelium sloughing was evaluated. The extent and location of apoptosis in injured lung tissues were studied by terminal transferase dUTP end labeling assay (TUNEL), reverse transcript-polymerase chain reaction (RT-PCR) and immunohistochemistry.

Results: Hyperoxia caused acute lung injury; the hyperoxic stress resulted in marked epithelium sloughing. TUNEL assay exhibited increased apoptosis index both in alveolar epithelial cells and bronchial epithelial cells in sections from mice after 48 h hyperoxia compared with their control group (0.51 +/- 0.10, 0.46 +/- 0.08 verse 0.04 +/- 0.02, 0.02 +/- 0.01). This was accompanied by increased expression of caspase-3 mRNA in lung tissues after 48 h hyperoxia compared with their control group (0.53 +/- 0.09 verse 0.34 +/- 0.07), the expression was higher at 72 h of hyperoxia (0.60 +/- 0.08). Immunohistochemistry study showed caspase-3 protein was located in cytoplasm and nuclei of airway epithelial cells, alveolar epithelial cells and macrophage in hyperoxia mice. The expression of caspase-3 protein in airway epithelium significantly increased at 24 h of hyperoxia compared with their control group (41.62 +/- 3.46 verse 15.86 +/- 1.84), the expression level was highest at 72 h of hyperoxia (55.24 +/- 6.80).

Conclusions: Both apoptosis and necrosis contribute to cell death during hyperoxia. Apoptosis plays an important role in alveolar damage and cell death from hyperoxia.