The tumor suppressor gene PTEN (phosphatase and tensin homologue deleted on chromosome 10) antagonizes the pro-survival signaling of Akt and promotes cell death. Previously, we demonstrated that IL-18 induced apoptosis in human cardiac microvascular endothelial cells (HCMEC). Here we have investigated the role of PTEN in this response. Our results demonstrate that IL-18 reduced phospho-Akt and bcl-2 levels, stimulated NF-¿B activation, and induced PTEN-promoter-reporter activity, mRNA expression, and protein levels in HCMEC. IL-18-mediated PTEN transcription was enhanced by ectopic expression of wild type p65, but inhibited by dominant negative (dn) I¿B-a, dnp65, and dnIKKß. Furthermore, overexpression of constitutively active Akt and wild type bcl-2 blocked IL-18-mediated cell death. While forced expression of PTEN potentiated, expression of catalytically inactive PTEN attenuated IL-18-mediated cell death. IL-18-induced activation of NF-¿B and PTEN upregulation were mediated by p38MAPK. Together, these studies demonstrate a novel signal transduction pathway involving p38MAPK-NF-¿B-PTEN in IL-18-mediated HCMEC death, and identify IL-18 as potential therapeutic target to inhibit or reduce myocardial inflammation and injury.

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