Vulnerability of mouse cortical neurons to doxorubicin-induced apoptosis is strain-dependent and is correlated with mRNAs encoding Fas, Fas-Ligand, and metalloproteinases

Cell surface death receptor-mediated neuronal apoptosis, which is a critical component of neurodegeneration, is modulated by matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). Doxorubicin (Dox) induces neuronal death by the activation of death receptor pathways. Recently, we demonstrated that Dox-induced neuronal apoptosis is regulated by the balance of MMP-3 and TIMP-3 in rat cortical cultures. Inbred mouse strains exhibit differential susceptibility to cell death stimuli in vivo. Prior to employing transgenic approaches to further investigate the roles of TIMP-3 and MMP-3 in neuronal death, we examined whether inbred mice display strain-dependent vulnerability to Dox. We induced neuronal apoptosis with Dox in primary neuronal cultures established from cerebral cortices of embryonic day 15 C57BL/10 or C57BL/6 mice. Using fluorescence activated cell sorting for neurons, we found that C57BL/6 cortical cultures exhibit a 28% greater neuronal death following Dox treatment than C57BL/10. Real-time PCR of unstimulated cultures revealed that C57BL/10 cortical cultures have reduced basal mRNA levels encoding the pro-apoptotic proteins: Fas, FasL, and TIMP-3, but increased levels of the anti-apoptotic molecule MMP-3 as compared to C57BL/6. Furthermore, C57BL/10 cultures treated with Dox displayed an enhanced induction of mRNA transcripts that encode anti-apoptotic MMPs. These results show that C57BL/10 cortical cultures are more resistant to death receptor-mediated apoptotic cell death as compared to C57BL/6, and suggest that this difference is related to Fas, FasL, and MMP expression. Strain-dependent differences in response to apoptotic stimuli may be an important consideration for developing transgenic models of neurodegeneration.