Pentoxifylline inhibits interleukin-2-induced leukocyte-endothelial adherence and reduces systemic toxicity

Interleukin-2 (IL-2) mediates the regression of metastatic cancer, but clinical application has been limited by the induction of dose-dependent toxicities in normal tissues. The most clinically significant toxicities occur secondary to a vascular leak syndrome and include acute respiratory failure and hemodynamic instability. Because previous studies suggested a role for pentoxifylline in attenuating the toxic effects of IL-2, we hypothesized that pentoxifylline would inhibit alterations in the microvasculature induced by IL-2 and would ultimately reduce IL-2-induced toxicity. To determine the validity of this hypothesis, we prepared four groups of rats for in vivo microvascular observation. In the first group, a bolus intravenous injection of IL-2 (1 x 10(6) units/kg) acutely induced hypotension, tachypnea, hypoxia, increased lung water, decreased microvascular blood flow, and increased leukocyte-endothelial adherence. No significant changes occurred in animals treated by pentoxifylline alone or the control IL-2 vehicle-alone group. However, pentoxifylline inhibited many of the IL-2-induced systemic and microvascular effects, such as hypotension, tachypnea, increased lung water, hypoxia, and increased leukocyte-endothelial adherence, but not tachycardia or increased microvascular protein leakage. These data support our hypothesis that systemic toxicities induced by IL-2 are associated with alterations in the microcirculation, which may be ameliorated by pentoxifylline.