Ischemia-reperfusion of the murine testis stimulates the expression of proinflammatory cytokines and activation of c-jun N-terminal kinase in a pathway to E-selectin expression

Abstract

Ischemia-reperfusion (IR) of the testis results in germ cell-specific apoptosis and can lead to aspermatogenesis. Germ cell-specific apoptosis after IR of the testis has been shown to be correlated with and dependent on neutrophil recruitment to the testis after IR. Studies that used E-selectin-deficient mice have demonstrated that E-selectin expression is critical for neutrophil recruitment to subtunical venules in the testis after IR and for the resultant germ cell-specific apoptosis. The present study investigates the in vivo signaling pathway that exists after IR that leads to neutrophil recruitment in the murine testis. Mice were subjected to a 2-h period of testicular ischemia followed by reperfusion. Results demonstrate that the proinflammatory cytokines, tumor necrosis factor alpha (TNFalpha) and interleukin 1beta (IL-1beta), are stimulated after IR as is the phosphorylation of c-jun N-terminal kinase (JNK). The downstream transcription factors of JNK, ATF-2 and c-jun are also phosphorylated at specific times after IR of the testis. Activation of the JNK stress-related kinase pathway is correlated with an increase in E-selectin expression and neutrophil recruitment to the testis after IR. Intratesticular injection of IL-1beta also caused JNK phosphorylation and neutrophil recruitment to the testis. These results suggest that testicular IR injury stimulates IL-1beta expression, which leads to activation of the JNK signaling pathway and ultimately E-selectin expression and neutrophil recruitment to the testis. This provides the first evidence of a cytokine/stress-related kinase signaling pathway to E-selectin expression in vivo.