HYPOXIC INDUCTION OF INTERLEUKIN-8 GENE-EXPRESSION IN HUMAN ENDOTHELIAL-CELLS

Because leukocyte-mediated tissue damage is an important component of the pathologic picture in ischemia/reperfusion, we have sought mechani sms by which PMNs are directed into hypoxic tissue. Incubation of huma n endothelial cells (ECs) in hypoxia, PO2 similar to 14-18 Torr, led t o time-dependent release of IL-8 antigen into the conditioned medium; this was accompanied by increased chemotactic activity for PMNs, block ed by antibody to IL-8. Production of IL-8 by hypoxic ECs occurred con comitantly with both increased levels of IL-8 mRNA, based on polymeras e chain reaction analysis, and increased IL-8 transcription, based on nuclear run-on assays. Northern analysis of mRNA from hypoxic ECs also demonstrated increased levels of mRNA for macrophage chemotactic prot ein-1, another member of the chemokine superfamily of proinflammatory cytokines. IL-8 gene induction was associated with the presence of inc reased binding activity in nuclear extracts from hypoxic ECs for the N F-kB site. Studies with human umbilical vein segments exposed to hypox ia also demonstrated increased elaboration of IL-8 antigen compared wi th normoxic controls. In mice exposed to hypoxia (PO2 similar to 30-40 Torr), there was increased pulmonary leukostasis, as evidenced by inc reased myeloperoxidase activity in tissue homogenates. In parallel, in creased levels of transcripts for IP-10, a murine homologue in the che mokine family related to IL-8, mere observed in hypoxic lung tissue. T aken together, these data suggest that hypoxia constitutes a stimulus for leukocyte chemotaxis and tissue leukostasis.