INTERLEUKIN-13 PROTECTS ENDOTHELIAL CELLS FROM APOPTOSIS AND ACTIVATION

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Abstract
Background. Chronic rejection is the major obstacle to long-term survival of allografts and is associated with graft endothelial cell activation and apoptosis.Recent reports have found an association between graft survival, presence of Th2 cytokines, and expression by endothelial cells of cytoplasmic “protective” molecules that prevent apoptosis and down-regulate the inflammatory process. Methods. Cultured human umbilical vein endothelial cells (HUVEC) were used. Apoptotic cells were detected by staining with FITC-annexinV followed by flow cytometry. Expression of vascular cell adhesion molecule-1, E-selectin, and intercellular adhesion molecule-1 were also measured by flow cytometry. Transcripts were detected by reverse transcription-PCR and quantitation was achieved by co-amplification of competing, internal standard RNA. Results. We demonstrate that exposure of HUVEC to interleukin (IL)-13 for 72 hr afforded partial protection from apoptosis induced by tumor necrosis factor-α/cycloheximide or serum starvation. Pretreatment with IL-13 also modulated induction of E-selectin after acute exposure to tumor necrosis factor-α or IL-1α. Protection was associated with transcription of the genes A1 and A20. Prolonged treatment with IL-13 had minimal proinflammatory effects and did not induce expression of E-selectin or vascular cell adhesion molecule-1 or increase intercellular adhesion molecule-1 above basal levels. Conclusions. Our data provide a possible explanation for the observed association between Th2 cytokines and expression of protective genes in the endothelium of long-surviving allografts and xenografts.