Hypoxia inducible factor 1-alpha (HIF-1 alpha) is induced during reperfusion after renal ischemia and is critical for proximal tubule cell survival.

Acute tubular necrosis (ATN) caused by ischemia/reperfusion (I/R) during renal transplantation delays allograft function. Identification of factors that mediate protection and/or epithelium recovery could help to improve graft outcome. We studied the expression, regulation and role of hypoxia inducible factor 1-alpha (HIF-1 α), using in vitro and in vivo experimental models of I/R as well as human post-transplant renal biopsies. We found that HIF-1 α is stabilized in proximal tubule cells during ischemia and unexpectedly in late reperfusion, when oxygen tension is normal. Both inductions lead to gene expression in vitro and in vivo. In vitro interference of HIF-1 α promoted cell death and in vivo interference exacerbated tissue damage and renal dysfunction. In pos-transplant human biopsies, HIF-1 α was expressed only in proximal tubules which exhibited normal renal structure with a significant negative correlation with ATN grade. In summary, using experimental models and human biopsies, we identified a novel HIF-1 α induction during reperfusion with a potential critical role in renal transplant.

Multiple cis-acting elements regulate the expression of the early T cell activation antigen CD69.

CD69 is the earliest activation antigen expressed on T lymphocytes upon stimulation through the TCR, or with stimuli that mimic TCR triggering. Here we describe that the phorbol ester PMA and a calcium ionophore had a synergistic effect on both CD69 antigen expression and promoter activity in Jurkat cells, that was sensitive to cyclosporin A (CsA). CD69 promoter analysis indicated that the sequence -78 to +16 contained the elements responsible for PMA and PMA plus calcium ionophore induction, as well as CsA inhibition. Mutagenesis of two previously described AP-1 motifs did not affect either the basal or the inducible promoter activities. Electrophoretic mobility shift assays allowed the identification of three novel inducible complexes composed by Egr-1/Egr-3, Egr-1, and ATF-3/Fos. Mutation of each sequence resulted in a partial reduction of the basal promoter activity, whereas the inducibility by PMA plus calcium ionophore remained almost unaffected. It was necessary to combine at least two mutations to obtain a significative or complete reduction of the response to the mitogenic stimulus. These results indicate that the inducible expression of CD69 gene by mitogenic signals is regulated by multiple cis-acting elements and by the interplay of transcription factors of the AP-1, EGR and ATF/CREB families.