Activation of the Nuclear Factor Kappa B Pathway Following Ischemia‐Reperfusion of the Murine Testis

Abstract

ABSTRACT: Ischemia‐reperfusion (IR) of the testis results in testicular oxidative stress and germ cell‐specific apoptosis. Nuclear factor kappa B (NF‐κB) is a nuclear transcription factor involved in the control of a number of cellular processes, and its activation is part of the cellular stress response to a variety of factors including cytokine stimulation, irradiation, and IR. The present study investigates NF‐κB activation after IR of the murine testis and potential downstream target genes of that activation. Mice were subjected to a period of testicular ischemia followed by 0–4 hours of reperfusion. Activation of NF‐κB was assessed by 1) Western blot analysis of the NF‐κB inhibitory protein, IκBα; 2) immunohistochemistry for IκBα; and 3) TranSignal NF‐κB target gene array (107 genes) analysis. Results demonstrate that IκBα is phosphorylated on serine 32 reaching a peak by 2 hours after IR of the testis. A decrease in total IκBα was also noted at 2 hours after IR, consistent with the rapid degradation of the phosphorylated protein. Phosphorylation and degradation of IκBα is indicative of NF‐κB activation. Imunnolocalization revealed IκBα specifically in Sertoli cells of the murine testis. Results of the TranSignal target gene array revealed that the expression of 9 genes was consistently changed 2 hours after IR of the testis, 3 of which increased in expression and 6 of which were down‐regulated. Most notably, high‐mobility group nucleosomal binding domain 1 increased in expression while platelet‐derived growth factor B and Wilms tumor homolog decreased. These results suggest that testicular IR releases the suppression of NF‐κB by IκBα in Sertoli cells. Activation of the NF‐κB pathway in the testis resulted in an alteration of expression of potential NF‐κB target genes, some increased while others decreased. The specific roles of these genes in the testicular response to IR remains to be determined.