Caspase‐dependent and caspase‐independent signalling of apoptosis in the penumbra following middle cerebral artery occlusion in the adult rat

Abstract

Transient focal ischaemia by middle cerebral artery occlusion (MCAO) may produce cell death, but the mechanisms leading to cell death differ in the infarct core and in the penumbra, the immediate zone surrounding the infarct core. In the present study, transient focal ischaemia to adult rats was produced by intraluminal occlusion of the middle cerebral artery for 1 h followed by 0 h (n=6), 1 h (n=10), 4 h (n=8), 6 h (n=2) and 12 h (n=3) of reperfusion. The present model of ischaemia causes a large cortico-striatal infarct extending through the mediolateral cortex and dorsolateral striatum at 12 h. The expression and subcellular distribution of several proteins involved in apoptosis have been examined in the penumbra and in the infarct core by using combined methods of immunohistochemistry, cell subfractionation and Western blotting. Transient focal ischaemia by MCAO results in activation of complex signal pathways for cell death in the penumbra. Increased expression of Bcl-2 and Bax, but not of Bcl-x, occurs in the penumbra at the time when Bax translocates from the cytosol to the mitochondria, cytochrome c is released to the cytoplasm and active caspase-3 is expressed. Bax translocation, cytochrome c release and active caspase-3 are observed at 4 h, but not at 1 h, following reperfusion, and together indicate activation of the caspase-dependent pathway of apoptosis in the penumbra. In contrast, reduced Bax expression but not Bax translocation and cytochrome c release occurs in the infarct core, thus suggesting apoptosis signals restricted to the penumbra. In addition, increased expression of an apoptosis-inducing factor in the cytoplasm and nuclei of selected cells shows, for the first time, activation of the caspase-independent mitochondrial pathway in the penumbra following transient focal ischaemia and reperfusion.

Influence of duration of focal cerebral ischemia and neuronal nitric oxide synthase on translocation of apoptosis-inducing factor to the nucleus

“…This finding with AIF immunoblotting is consistent with immunohistochemical detection of nuclear AIF in a small percent of cells by 1 hour of reperfusion and a larger increase that occurs by 4-8 hours of reperfusion after 45 minutes of MCAO in the mouse (Plesnila et al, 2004). Nuclear staining for AIF has also been reported in the rat brain at 4 hours of reperfusion after 1 hour of MCAO (Ferrer et al, 2003). An increase in the production of reactive oxygen species (ROS) leads to DNA damage and activation of PARP after MCAO (Zhang et al, 1994;Eliasson et al, 1999).…”

“…This design permitted evaluation at early reperfusion, at a mid-range of reperfusion, when many neurons show ischemic morphologic changes, and at late reperfusion, when cell death is widespread throughout the maturing infarct. These timepoints spanned the 1-8 hour range for AIF translocation reported by others (Ferrer et al, 2003;Plesnila et al, 2004;Zhao et al, 2004;Culmsee et al, 2005). Two hemispheres were used per lane.…”

“…Translocation of AIF has also been demonstrated with focal cerebral ischemia (Ferrer et al, 2003;Komjati et al, 2004). After permanent occlusion of the distal middle cerebral artery (MCA) in rats, significant increases in AIF in nuclear subcellular fractions occurred at 48 hours, although localized increases in cortical border regions were evident at 8 hours (Zhao et al, 2004).…”

A candidate gene for developmental dyslexia encodes a nuclear tetratricopeptide repeat domain protein dynamically regulated in brain

“…Examination of DYX1C1 expression in ischemic brain tissue suggested that it is involved dynamically in the functional cell state, changing in the face of metabolic challenge. Similar changes in protein distribution in ischemia have been observed for the Elk-1 transcription factor (39). These results from human cerebral ischemia warrant more systematic studies on the role of DYX1C1 in cell stress and ischemia as well as dyslexia.…”

5,7-Dimethoxycoumarin inhibits neuronal apoptosis by targeting caspase-3 expression in rats with acute cerebral infarction

“…Caspase-3 is considered to be the significant target for prevention of acute cerebral infarction because of its major role in ischemia and induction of apoptosis [23,24]. In the current Figure 3: 5,7-Dimethoxycoumarin prevents increase in apoptosis index in the rats with acute cerebral infarction.…”