Mechanisms of Neuronal Death and Neuroprotection

Project: Research project

Project Details

Description

The use of platinum compounds is increasing in the treatment of cancer. Cisplatin, carboplatin and
oxaliplatin produce a dose-related and dose-limiting sensory neuropathy. We have demonstrated that
cisplatin binds to neuronal DNA, activates DMA-damage recognition pathways, initiates aberrant cell cycle
entry, and induces apoptosis in vitro and in vivo. We now propose to test the hypothesis that platinum
compounds produce neuronal injury by a common mechanism that involves separate nuclear (n-DNA) and
mitochondrial DNA (mt-DNA) binding followed by synergistic activation of parallel death pathways. A new
approach to measuring mt-DNA platination has been developed using inhibition of the polymerase chain
reaction. We will determine whether the number of platinum adducts in mt-DNA of DRG neurons is sufficient
to prevent replication and transcription of the mitochondrial genome. Function of respiratory chain
components will be measured. Inability to repair Pt-DNA lesions in mt-DNA would result in attrition of
mitochondria and chronic neuronal death explaining the clinical phenomenon of "coasting" or progression of
neuropathy after drug cessation. We will use DRG neurons from Bax and cyclin D1 knockout mice to
determine whether platinum-induced inhibition of mitochondrial function is sufficient to cause neuronal death.
We will use the mitochondrial DNA synthesis inhibitor dideoxycytidine (ddC) to determine whether inhibition
of mitochondrial DNA replication is independently sufficient to cause cell death.
The mitochondrial genome will be protected by selectively increasing mitochondrial glutathione. The
modifier and catalytic subunits ofglutamate cysteine ligase (GCL) andglutathione synthetase (GS) willbe
targeted to mitochondria in an adeno-viral vector to reduce formation of mt-DNA adducts. Both nerve growth
factor (NGF) and pigment epithelium derived growth factor (PEDF) have been demonstrated to partially
protect DRG from cisplatin-induced apoptosis. We will determine whether a combination of therapeutic
strategies that block n-DNA induced apoptosis and protect mt-DNA promote long-term survival of cisplatin
treated DRG in vitro. If the combination strategy is effective,we will test it in an animal model by developing
methods to provide long-term delivery of growth factors and viral targeting of GCL and GS to DRG in vivo.
The goal is to develop a mechanism-based therapy that will prevent the major dose-limiting side effect of the
platinum compounds.
StatusNot started

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