Erythropoietin promotes functional recovery via anti-apoptotic mechanisms in mouse unilateral ureteral obstruction

The purpose of the work was to investigate mechanisms of erythropoietin-induced protection and accelerated recovery of kidneys and ureters from obstructive injury. Unilateral ureteral obstruction was established for 24, 48, and 72 h in C57BL/6 mice using a non-traumatic micro-clip followed by the microscopic quantification of ureteral peristalsis pre- and post-obstruction. Expression of erythropoietin, erythropoietin receptor, beta-common receptor, and downstream apoptosis-related markers was assessed by RT-PCR and immunohistochemistry in ureters and kidneys and compared to the respective organs on the contralateral side within each animal. Expression of genes in kidneys and ureters from mice treated with 20 IU of erythropoietin daily for 72 h prior to obstruction was compared to that of untreated mice following obstruction. Apoptosis in ureteral tissues after 72-h obstruction was assessed via TUNEL assay. Ureteral obstruction increased apoptosis in affected ureters, with peristaltic function halted following all periods of obstruction. Erythropoietin treatment suppressed apoptosis in obstructed tissues and increased the percentage of mice retaining ureteral function immediately following obstruction reversal. Erythropoietin, erythropoietin receptor, Bcl-2, and Bcl-xl mRNA expression were down-regulated, while phospho-Nf-b p65 was up-regulated in ureteral epithelia following obstruction. Erythropoietin treatment induced anti-apoptotic signaling via down-regulated Bax mRNA expression and abrogated phospho-Nf-b p65. Erythropoietin-induced protection of ureteral function and accelerated recovery post-obstruction removal is mediated via anti-apoptotic mechanisms. Ureteral function is disrupted even following obstruction removal, negatively affecting renal function due to delayed recovery. Thus, our results represent a potential target for the development of safe therapeutic agents aimed at improving functional recovery from obstructive injury.