Stimulus-Specific Effects of Pentoxifylline on Neutrophil CR3 Expression, Degranulation, and Superoxide Production

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Abstract
The effects of pentoxifylline (Trental) on human neutrophil CR3 up-modulation, degranulation, and superoxide production were studied. We used the chemotactic peptide fMLP and the phorbol ester PMA as soluble stimuli, and β-glucan particles as a CR3-specific solid phase stimulus of neutrophil superoxide production. Since neutrophils have adenosine A2 receptors, we compared effects of pentoxifylline to effects of adenosine, and we also looked at the effect of cytochalasin B, which breaks up actin filaments. Pentoxifylline inhibited both CR3 up-modulation and degranulation of myeloperoxidase and lysozyme. Pentoxifylline is a more potent inhibitor of fMLP- compared to PMA-induced degranulation, and is especially potent against superoxide production. While pentoxifylline is less potent than adenosine in its inhibiton of fMLP-induced superoxide production, it is more potent in its inhibition of PMA- and β-glucan particle-stimulated superoxide production. Cytochalasin B, which enhances degranulation and fMLP-stimulated superoxide production, was found to inhibit β-glucan particle-stimulated superoxide production. These findings are consistent with the hypothesis that pentoxifylline can affect both the cytoskeletal architecture of unstimulated neutrophils and the activation and responses of neutrophils which involve actin polymerization and receptor-cytoskeletal interactions.