Date of Award

3-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Medical Education

First Advisor

Sehamuddin Galadari

Second Advisor

Ernest A. Adeghate

Third Advisor

Farah Mustafa

Abstract

Dysregulation of apoptosis is a prime hallmark of leukemia. Therefore, drugs which restore the sensitivity of leukemic cells to apoptotic stimuli are promising candidates in the treatment of leukemia. The main objective of this dissertation was to examine the antileukemic effect of sanguinarine, in vitro, and to further examine the signaling mechanisms that may be involved. This study demonstrates that in human leukemic cells, sanguinarine activates a caspase-dependent apoptotic cell death pathway that is characterized by reactive oxygen species-dependent ceramide generation, and subsequent inhibition of Akt signaling pathway. In addition, sanguinarine also induces reactive oxygen species-dependent glutathione depletion and activation of extracellular signal-regulated kinase1/2. Moreover, inhibition of reactive oxygen species generation, using reactive oxygen species scavengers and antioxidants, significantly abrogates sanguinarine-induced ceramide generation, Akt dephosphorylation, extracellular signal-regulated kinase1/2 activation, and apoptosis. Sanguinarine-induced ceramide generation is mediated via reactive oxygen species-dependent activation of acid sphingomyelinase in Jurkat cells and inhibition of acid ceramidase and glucosylceramide synthase in both Jurkat and Molt-4 cells. Furthermore, the involvement of ceramide-activated protein phosphatase-1 in sanguinarine-induced Akt dephosphorylation and apoptosis is demonstrated. Altogether, this study underscores the critical role for reactive oxygen species-ceramide-Akt signaling pathway and reactive oxygen species-dependent extracellular signal-regulated kinase1/2 activation in the antileukemic action of sanguinarine. Understanding the molecular signaling mechanism of sanguinarine induced apoptosis undoubtedly should have a great impact on future sanguinarine based antileukemic drug development.

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