Apoptosis Of Polymorphonuclear Neutrophils Research Articles

Neutrophil apoptosis during the development and resolution of oleic acid-induced acute lung injury in the rat.

The oleic acid (OA) model of acute lung injury in rats is characterized by a massive and rapid influx of polymorphonuclear neutrophils (PMN) within 1 h, with a peak inflammatory response at 4 h and resolution by 72 h. We hypothesized that PMN apoptosis is involved in the resolution of OA-induced acute lung injury. To test this hypothesis, healthy adult Fischer 344 rats were given 30 microl OA in 0.1% bovine serum albumin (BSA) intravenously; controls were given BSA alone and killed at 1, 4, 24, and 72 h after OA to obtain bronchoalveolar lavage fluid (BALF) and lung tissue. Cell pellets from BALF and formalin-fixed, paraffin-embedded tissue section samples were processed for terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) to identify apoptotic cells. Propidium iodide was used to counterstain nuclei. Percentage of nuclei undergoing apoptosis was counted under a fluorescent microscope. Control rats showed only resident alveolar macrophages (AM) in the BALF with no apoptosis. At the peak of injury, 1 h and 4 h after OA injection, we observed a massive PMN response without any evidence of apoptosis. At 24 h, when the OA injury is clinically and histologically in early resolution, we observed intense apoptosis of PMN nuclei along with evidence of apoptotic bodies in the cytoplasm of AM. Some of the AM also showed apoptotic nuclei at 72 h. Similar observations were made in the lung tissue sections. The results of the TUNEL assay were confirmed by DNA ladders and electron microscopy. We conclude that apoptosis of PMN and clearance by AM is an important mechanism in resolution of OA- induced acute lung injury.

Effect of pentoxifylline on apoptosis of cultured cells.

Apoptosis or programmed cell death (PCD) was measured in two human cell models by flow cytometric analysis. Blood neutrophils underwent spontaneous apoptosis in short-term culture. Pentoxifylline (PTX) inhibited spontaneous neutrophil PCD. We confirmed that granulocyte/macrophage colony-stimulating factor (GM-CSF) inhibited apoptosis of polymorphonuclear neutrophils. Treatment with both GM-CSF and PTX did not increase the inhibition of PCD by either GM-CSF or PTX alone. Because apoptosis could be due to the accumulation of H2O2 in the culture medium, and because PTX has been described to reduce peroxide production, we studied the effect of adding catalase to the medium. Catalase reduced the neutrophil apoptosis and this effect was cumulative with the effect of PTX. Camptothecin, an inhibitor of topoisomerase I, induces a block in the S-phase of the cell cycle followed by apoptosis of the U937 cell line. This drug-induced apoptosis was partially inhibited by PTX, whereas the S-phase cell block was not affected. In conclusion, PTX was found to inhibit apoptosis in two different human cell types. In neutrophils, this effect appears to occur regardless of the inhibition of phosphodiesterase activity and inhibition of H2O2 release.