In this context, it is important to note that click here release of cytochrome c from mitochondria plays critical roles in the apoptotic cascade, activating caspase-9 which, in turn, activates executioner caspase-3 and ‐7 ( Slee et al., 1999). However, more experiments will be needed to clarify the pathways involved in the activation of caspase 3 in the striatum of (PhTe)2-treated rats. Additional evidence of the pro-apoptotic mechanism of action of (PhTe)2 comes
from our results showing decreased Akt phosphorylation/activity in striatal slices from injected animals. The PI3K-Akt signaling pathway plays a critical role in mediating survival signals in a wide range of neuronal cell types (Cardone et al., 1998). The identification of a number of substrates for the serine/threonine kinase Akt suggests that it blocks cell death by both impinging on the cytoplasmic cell death machinery and by regulating the expression of genes involved in cell death and survival (Koh et al., 2004). This is in line with Zhou et al. (2000) who described that activated Akt may inhibit activation of caspase-9 and − 3 by posttranslational modification of a cytosolic factor downstream of cytochrome c and before activation of caspase-9 ( Cardone et al., 1998). Therefore, inhibited PI3K-Akt pathway, that was found in (PhTe)2, could be consistent with the apoptotic insult
observed in the striatum. Otherwise, GSK3β is a critical downstream element of the PÌ3K/Akt pathway and its activity can be inhibited by Akt-mediated Everolimus in vitro phosphorylation at Ser9 ( Srivastava and Pandey, 1998). GSK3β has been implicated in multiple cellular processes and linked with the pathogenesis and neuronal loss in several neurodegenerative diseases ( Petit-Paitel, 2010). In his context, Takashima (2006) described that GSK-3β activation through impairment of PI3K/Akt signaling was involved in amyloid-beta (Abeta)-induced neuronal death in rat hippocampal cultures. many However, in our experimental model of (PhTe)2-induced neurodegeneration, Akt inhibition is apparently not implicated
in GSK3β (Ser9) hyperphosphorylation, supporting different signaling pathways downstream of different stressor events. In the CNS, following injury, astrocytes become reactive, a prominent process leading to the formation of the glial scar that inhibits axon regeneration after CNS injury. Upon becoming reactive, astrocytes undergo various molecular and morphological changes including upregulation of their expression of GFAP, vimentin and chondroitin sulfate proteoglycans as well as other molecules that are inhibitory to axon growth (Yu et al., 2012). However, upregulation of IFs is a hallmark of astrogliosis and a well-accepted indicator of structural damage in the CNS (Sofroniew and Vinters, 2010).