Protein Kinase C Delta Cleavage Initiates an Aberrant Signal Transduction Pathway after Cardiac Arrest and Oxygen Glucose Deprivation

Abstract

Protein kinase C (PKC) isozymes have been known to mediate a variety of complex and diverse cellular functions. dPKC has been implicated in mediating apoptosis. Using two models of cerebral ischemia, cardiac arrest in rats and oxygen glucose deprivation (OGD) in organotypic hippocampal slices, we tested whether an ischemic insult promoted dPKC cleavage during the reperfusion and whether the upstream pathway involved release of cytochrome c and caspase 3 cleavage. We showed that cardiac arrest/OGD significantly enhanced dPKC translocation and increased its cleavage at 3 h of reperfusion. Since dPKC is one of the substrates for caspase 3, we next determined caspase 3 activation after cardiac arrest and OGD. The maximum decrease in levels of procaspase 3 was observed at 3 h of reperfusion after cardiac arrest and OGD. We also determined cytochrome c release, since it is upstream of caspase 3 activation. Cytochrome c in cytosol increased at 1 h of reperfusion after cardiac arrest/OGD. Inhibition of either dPKC/caspase 3 during OGD and early reperfusion resulted in neuroprotection in CA1 region of hippocampus. Our results support the deleterious role of dPKC in reperfusion injury. We propose that early cytochrome c release and caspase 3 activation promote dPKC translocation/cleavage.

Activation of Protein Kinase C Delta following Cerebral Ischemia Leads to Release of Cytochrome C from the Mitochondria via Bad Pathway

“…This contention is supported by our earlier study where we found that suppressed rate of respiration in presence of complex IV substrates at early reperfusion (30 min) following global cerebral ischemia was due to the release of mitochondrial cytochrome c [4]. We observed similar results using a rat model of asphyxial cardiac arrest, where we found that mitochondrial cytochrome c was released at 1 h of reperfusion following 8 min of cardiac arrest [15]. The present study thus provides potential targets for δPKC whose translocation to mitochondria early after ischemia is associated with mitochondrial dysfunction and mitochondrial cytochrome c release.…”

“…In earlier studies we reported that δPKC is activated (translocated from soluble to particulate fraction) following cerebral ischemia [14], [15]. In the present study, we demonstrate that mitochondria are one of the particulate fractions to which δPKC translocates following cerebral ischemia.…”

Activation of Protein Kinase C Delta following Cerebral Ischemia Leads to Release of Cytochrome C from the Mitochondria via Bad Pathway

“…This contention is supported by our earlier study where we found that suppressed rate of respiration in presence of complex IV substrates at early reperfusion (30 min) following global cerebral ischemia was due to the release of mitochondrial cytochrome c [4]. We observed similar results using a rat model of asphyxial cardiac arrest, where we found that mitochondrial cytochrome c was released at 1 h of reperfusion following 8 min of cardiac arrest [15]. The present study thus provides potential targets for δPKC whose translocation to mitochondria early after ischemia is associated with mitochondrial dysfunction and mitochondrial cytochrome c release.…”

“…In earlier studies we reported that δPKC is activated (translocated from soluble to particulate fraction) following cerebral ischemia [14], [15]. In the present study, we demonstrate that mitochondria are one of the particulate fractions to which δPKC translocates following cerebral ischemia.…”

If Some Hypothermia Is Good, More Hypothermia Must Be Better, Right?*

“…This work corroborates work of others demonstrating the importance of these factors in ischemic/reperfusion and apoptosis (9)(10)(11). The interactions of these mechanisms are complex, yet there is evidence that release of cytochrome c from mitochondria in ischémie cells leads to caspase 3 activation, which can also increase activation of ôPKC.…”

Suppression of δ PKC Activation after Focal Cerebral Ischemia Contributes to the Protective Effect of Hypothermia

“…activated via caspase-3-mediated cleavage in hippocampal CA1 neurons after cardiac arrest in rats (Raval et al, 2005). We found a similar phenomenon after focal ischemia in this study.…”

Activation of Protein Kinase C Delta following Cerebral Ischemia Leads to Release of Cytochrome C from the Mitochondria via Bad Pathway

“…This contention is supported by our earlier study where we found that suppressed rate of respiration in presence of complex IV substrates at early reperfusion (30 min) following global cerebral ischemia was due to the release of mitochondrial cytochrome c [4]. We observed similar results using a rat model of asphyxial cardiac arrest, where we found that mitochondrial cytochrome c was released at 1 h of reperfusion following 8 min of cardiac arrest [15]. The present study thus provides potential targets for δPKC whose translocation to mitochondria early after ischemia is associated with mitochondrial dysfunction and mitochondrial cytochrome c release.…”

“…In earlier studies we reported that δPKC is activated (translocated from soluble to particulate fraction) following cerebral ischemia [14], [15]. In the present study, we demonstrate that mitochondria are one of the particulate fractions to which δPKC translocates following cerebral ischemia.…”

If Some Hypothermia Is Good, More Hypothermia Must Be Better, Right?*

“…This work corroborates work of others demonstrating the importance of these factors in ischemic/reperfusion and apoptosis (9)(10)(11). The interactions of these mechanisms are complex, yet there is evidence that release of cytochrome c from mitochondria in ischémie cells leads to caspase 3 activation, which can also increase activation of ôPKC.…”

Suppression of δ PKC Activation after Focal Cerebral Ischemia Contributes to the Protective Effect of Hypothermia

“…activated via caspase-3-mediated cleavage in hippocampal CA1 neurons after cardiac arrest in rats (Raval et al, 2005). We found a similar phenomenon after focal ischemia in this study.…”

Activation of Protein Kinase C Delta following Cerebral Ischemia Leads to Release of Cytochrome C from the Mitochondria via Bad Pathway

“…This contention is supported by our earlier study where we found that suppressed rate of respiration in presence of complex IV substrates at early reperfusion (30 min) following global cerebral ischemia was due to the release of mitochondrial cytochrome c [4]. We observed similar results using a rat model of asphyxial cardiac arrest, where we found that mitochondrial cytochrome c was released at 1 h of reperfusion following 8 min of cardiac arrest [15]. The present study thus provides potential targets for δPKC whose translocation to mitochondria early after ischemia is associated with mitochondrial dysfunction and mitochondrial cytochrome c release.…”

“…In earlier studies we reported that δPKC is activated (translocated from soluble to particulate fraction) following cerebral ischemia [14], [15]. In the present study, we demonstrate that mitochondria are one of the particulate fractions to which δPKC translocates following cerebral ischemia.…”

If Some Hypothermia Is Good, More Hypothermia Must Be Better, Right?*

“…This work corroborates work of others demonstrating the importance of these factors in ischemic/reperfusion and apoptosis (9)(10)(11). The interactions of these mechanisms are complex, yet there is evidence that release of cytochrome c from mitochondria in ischémie cells leads to caspase 3 activation, which can also increase activation of ôPKC.…”

Suppression of δ PKC Activation after Focal Cerebral Ischemia Contributes to the Protective Effect of Hypothermia

“…activated via caspase-3-mediated cleavage in hippocampal CA1 neurons after cardiac arrest in rats (Raval et al, 2005). We found a similar phenomenon after focal ischemia in this study.…”