N-Benzyladriamycin-14-valerate (AD 198): A Non-Cardiotoxic Anthracycline That Is Cardioprotective through PKC-ϵ Activation

Abstract

) is one of several novel anthracycline protein kinase C (PKC)-activating agents developed in our laboratories that demonstrates cytotoxic superiority over doxorubicin (Adriamycin; DOX) through its circumvention of multiple mechanisms of drug resistance. This characteristic is attributed at least partly to the principal cellular action of AD 198: PKC activation through binding to the C1b (diacylglycerol binding) regulatory domain. A significant dose-limiting effect of DOX is chronic, dose-dependent, and often irreversible cardiotoxicity ascribed to the generation of reactive oxygen species (ROS) from the semiquinone ring structure of DOX. Despite the incorporation of the same ring structure in AD 198, we hypothesized that AD 198 might also be cardioprotective through its ability to activate PKC-, a key component of protective ischemic preconditioning in cardiomyocytes. Chronic administration of fractional LD 50 doses of DOX and AD 198 to mice results in histological evidence of dose-dependent ventricular damage by DOX but is largely absent from AD 198-treated mice. The absence of significant cardiotoxicity with AD 198 occurs despite the equal ability of DOX and AD 198 to generate ROS in primary mouse cardiomyocytes. Excised rodent hearts perfused with AD 198 prior to hypoxia induced by vascular occlusion are protected from functional impairment to an extent comparable to preconditioning ischemia. AD 198-mediated cardioprotection correlates with increased PKCactivation and is inhibited in hearts from PKC-knockout mice. These results suggest that, despite ROS production, the net cardiac effect of AD 198 is protection through activation of PKC-.

Protection from Doxorubicin-Induced Cardiomyopathy Using the Modified Anthracycline N-Benzyladriamycin-14-valerate (AD 198)

“…PKC-ε activation is thought to be cardioprotective through its ability to: 1) prime sarcolemma K ATP channels to reduce action potential duration and, as such, reduce Ca 2ϩ entry and Ca 2ϩ overload, 2) open mitochondrial K ATP channels to prevent Ca 2ϩ overload and volume overload of the mitochondria and reduced mitochondrial ROS production, 3) inhibit the mitochondrial permeability transition pore opening to inhibit mitochondrial swelling, cytochrome C release, and the uncoupling of oxidative phosphorylation, 4) activate protein phosphatase 1, which decreases phospho-PLB to decrease Ca 2ϩ content and Ca 2ϩ cycling, thus attenuating any rise in cytosolic [Ca 2ϩ ], and 5) activate transcription factors that increase antioxidant expression to reduce ROS overload (Bolli et al, 2007;Budas et al, 2007). In a previous study we demonstrated that AD 198 protects from ischemia-reperfusion induced cardiac dysfunction, and this benefit is not observed in PKC-ε knockout mice (Hofmann et al, 2007). In the present study we show PKC-ε inhibition blocks the ability of AD 198 to reverse Dox-induced changes in phosphorylation of AMPK and TnI (Fig.…”

“…The chemical modifications of Dox that produce AD 198 creates a domain within AD 198 that has a structural similarity to diacyglycerol, an endogenous ligand for protein kinase C (Roaten et al, 2001). We have shown previously AD 198 binds to PKC at its diacyglycerol binding site and this activates PKC-ε in cardiomyocytes (Hofmann et al, 2007). PKC-ε activation is thought to be cardioprotective through its ability to: 1) prime sarcolemma K ATP channels to reduce action potential duration and, as such, reduce Ca 2ϩ entry and Ca 2ϩ overload, 2) open mitochondrial K ATP channels to prevent Ca 2ϩ overload and volume overload of the mitochondria and reduced mitochondrial ROS production, 3) inhibit the mitochondrial permeability transition pore opening to inhibit mitochondrial swelling, cytochrome C release, and the uncoupling of oxidative phosphorylation, 4) activate protein phosphatase 1, which decreases phospho-PLB to decrease Ca 2ϩ content and Ca 2ϩ cycling, thus attenuating any rise in cytosolic [Ca 2ϩ ], and 5) activate transcription factors that increase antioxidant expression to reduce ROS overload (Bolli et al, 2007;Budas et al, 2007).…”

“…Thus far it has been demonstrated that AD 198 overcomes drug resistance of certain tumors and has comparable tumor cytotoxicity to Dox both in vitro and in vivo (Sweatman and Israel, 1996). Furthermore, AD 198 does not have the very serious cardiotoxic effect of standard anthracyclines and even seems to protect the heart from ischemicreperfusion injury (Hofmann et al, 2007). These noncardiotoxic and cardioprotective traits are probably caused by the ability of AD 198 to induce activation of PKC-ε (Hofmann et al, 2007).…”

“…Furthermore, AD 198 does not have the very serious cardiotoxic effect of standard anthracyclines and even seems to protect the heart from ischemicreperfusion injury (Hofmann et al, 2007). These noncardiotoxic and cardioprotective traits are probably caused by the ability of AD 198 to induce activation of PKC-ε (Hofmann et al, 2007). In the present study, we wanted to expand on those studies, determine whether cotherapy of AD 198 ϩ Dox protects the heart from Dox-induced cardiotoxicity, and identify molecular factors that may contribute to any cardioprotective effects of AD 198.…”

Role of Drug Metabolism in the Cytotoxicity and Clinical Efficacy of Anthracyclines –

“…An-other anthracycline with protein kinase C-activating properties (AD 198) has also shown significant anti-tumor activity. However, unlike DOX, little ventricular damage was observed in mice administered the agent [175].…”