al 2001 . In isolated rat liver mitochondria, we also detected that 6 OHDA induces cytochrome c release via a CMPT mechanism, which showed mitochondrial swelling and membrane depolarization with a CsA sensitive mechanism data not shown . Within the whole PC12 cells, nonetheless, 6 OHDA induced mitochondrial membrane depolarization Ganetespib and chromatin condensation had been not inhibited by CsA Inhibitor 4 . These final results indicate that CMPT, which characterized by depolarization and swelling in a CsA sensitive mechanism, is just not involved in the mechanism of apoptosis Di Paola et al 2006 . Presumably, the decrease in mitochondrial membrane potential was rather a result of cell death. In this context, we observed that tiron, that is a superoxide scavenger, but not pCPT cAMP, suppressed the 6 OHDA induced mitochondrial membrane depolarization and superoxide generation Figs.
10B and 11B and D . Furthermore, it has been reported that 6 OHDA induced lipid peroxidation, which induces the depolarization from the mitochondrial membrane in a CsA insensitive mechanism Chaloupka et al 1999; Nobre et al 2003; Ogawa et al 1994 . These final results may possibly indicate that the 6 OHDA induced superoxide and or products Ganetespib of its chain reaction, for instance lipid peroxide, trigger mitochondrial membrane depolarization in a CsA insensitive mechanism. Hence, we presented a feasible mechanism from the 6 OHDA induced apoptosis in Inhibitor 12. Caspase 8 activation and tBid appear to be early events in our apoptosis model. It's typically accepted that Bax and tBid trigger the release of cytochrome c independently from the CMPT mechanism.
The activation of caspase 8 leads to Bid cleavage and facilitates mitochondria mediated downstream apoptotic events Li et al 1998 . Within the present experiments, we demonstrated Imatinib that 6 OHDA activated caspase 8 in a timedependent manner Inhibitor 2 , and that tBid was detected soon after the addition of 6 OHDA Inhibitor 8A . Furthermore, we demonstrated that Ac IETD CHO, which was an inhibitor of caspase 8, suppressed caspase 9 activity Inhibitor 8B . These final results indicate that the cleavage of Bid by Protein biosynthesis activated caspase 8 triggers the activation Imatinib from the caspase cascade in 6 OHDAtreated PC12 cells. Cyclic AMP protected neuronal cells Neame et al 1998 and PC12 cells Rideout et al 2001; Yamada et al 1997 from apoptosis induced by numerous stimulations.
Cyclic AMP induced the transactivation from the receptors for nerve growth factor, thereby the modulating activation of Akt in PC12 cells Piiper et al 2002 and regulated the cellular level Ganetespib of p Akt via a PI3 kinase dependent pathway Tsygankova et al 2001 . In this experiment, we found that 6 OHDA induced the downregulation dephosphorylation of Akt Inhibitor 9 and that pCPT cAMP induced Akt phosphorylation and suppressed the 6 OHDA induced caspase activation and chromatin condensation Figs. 5 and 6 . Moreover, we found that LY294002, which was an inhibitor of PI3 kinase Akt pathway, promoted 6 OHDA induced chromatin condensation Inhibitor 5 . These final results indicated that the PI3 kinase Akt pathway promoted cell survival against 6 OHDA induced apoptosis, and that pCPT cAMP suppressed the apoptosis of PC12 cells via this pathway Inhibitor 12 .
Akt is localized upstream of caspase 8 activation and is activated by phosphorylation and protects cells from apoptosis Suhara et al 2001 . Recent studies indicated that p Akt increases the expression of FLICE inhibitory protein FLIP , which inhibits caspase 8 activation Panka et al 2001; Suhara et al 2001 . In this experiment, Imatinib we found that pCPT cAMP suppressed the 6 OHDA induced caspase 8 activation and chromatin condensation Figs. 5 and 6 , but not mitochondrial membrane depolarization Inhibitor 7 . These final results indicate that pCPT cAMP acts at upstream of caspase 8 activation. Within the 6 OHDA induced apoptosis pathway, the oxidative tension induced phosphorylation of p38 was linked to the activation of caspase 8 and 9 in MN9D cell and major cultures of mesencephalic neurons Ganetespib Choi et al 2004 .
The protein kinase activity of p38 was needed for the apoptosis of PC12 cells in some models Jenkins and Barone, 2004 . Additionally, PI3 kinase Akt signaling promotes cell survival by inhibiting the p38 mitogen activated protein kinase dependent apoptosis Gratton et al 2001 . Within the present experiment, we found that pCPT cAMP worked as an Akt activator, and suppressed the 6 OHDA Imatinib induced p38 phosphorylation Inhibitor 9 , but not superoxide generation Inhibitor 10 . These final results suggest that p38 phosphorylation is involved in 6 OHDAinduced apoptosis, and that pCPT cAMP acts upstream from the activation of p38 too as caspase 8, and downstream of superoxide generation in PC12 cells Inhibitor 12 . Accumulated evidence indicates that 6 OHDA induces neuronal cell apoptosis via ROS generation from oxidation of 6 OHDA and this ROS acts as a second messenger in cellular signaling Berman and Hastings, 1999; Choi et al 1999; Graham, 1978; He et al 2000; Kumar et al 1995
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