Differential gene expression following early renal ischemia/reperfusion

Background. Acute renal failure from ischemia/reperfusion injury is associated with tubule cell apoptosis, the molecular mechanisms of which remain under active investigation. The purpose of this study was to identify apoptosis-related genes that are differentially expressed in the early periods following renal ischemia. Methods. Mice underwent unilateral renal artery clamping for 45 minutes and were sacrificed at 0, 3, 12, or 24 hours of reperfusion. Tubule cell apoptosis was confirmed by DNA laddering and terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end labeling (TUNEL) assay. We employed cDNA microarrays to define global changes in renal gene expression. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry were used as confirmatory tools. Results. By microarray analysis, we identified consistent patterns of altered gene expression, including transcription factors, growth factors, signal transduction molecules, and apoptotic factors. Prominent among the last category included FADD, DAXX, BAD, BAK, and p53. Up-regulation of these proapoptotic genes was confirmed by semiquantitative RT-PCR and immunohistochemistry. Conclusion. The results indicate that apoptosis may represent an important mechanism for the early loss of tubule cells following ischemia/reperfusion injury. Both the death receptor-dependent (FADD-DAXX) and mitochondrial (BAD-BAK) pathways are activated. The results also provide a molecular basis for the previous findings that significant intrarenal mechanisms exist to enable tubule cell repair and regeneration, as evidenced by the up-regulation of genes such as growth, proliferation, transcription, and cytoskeletal factors.