Intervention in genotoxic stress-induced senescence by cordycepin through activation of EIF2α and suppression of Sp1

Abstract

In this study, we show that cordycepin (3'-deoxyadenosine), a major nucleoside isolated from Cordyceps species, attenuates genotoxic stress-induced senescence. Etoposide-or doxorubicin-treated cells exhibited senescent morphology, growth arrest, and positive staining for senescence-associated β-galactosidase. The induction of the senescent phenotype was inhibited by the treatment of cordycepin. This suppression was correlated with blunted activation of the p16INK4a and p21WAF1/CIP1 gene promoters, as well as a decreased level of p21WAF1/CIP1 mRNA. Other adenosine-related substances including ATP, ADP, and adenosine did not mimic the suppressive effect of cordycepin. The antisenescence effect of cordycepin was mediated by activation of eukaryotic translation initiation factor 2α (eIF2α) because (1) cordycepin induced phosphorylation of eIF2α, (2) selective activation of eIF2a mimicked the suppressive effect of cordycepin on senescence, and (3) functional knockdown of eIF2α reversed the effect of cordycepin. Unexpectedly, induction of p53 by etoposide was not inhibited by cordycepin, whereas (1) expression of Sp1 (required for the induction of p21WAF1/CIP1 and activation of p16INK4a by genotoxic stress) was attenuated by cordycepin, (2) DNA binding activity of Sp1 was also inhibited, and (3) selective inhibition of Sp1 reproduced the suppressive effect of cordycepin on senescence. These results suggest that cordycepin interferes with senescence signaling via activation of eIF2a and suppression of Sp1 without affecting the level of p53.©The Author 2013. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.