Protein Kinase C Delta Modulates Endothelial Nitric Oxide Synthase after Cardiac Arrest

Abstract

We previously showed that inhibition of protein kinase C delta (PKCd) improves brain perfusion 24 hours after asphyxial cardiac arrest (ACA) and confers neuroprotection in the cortex and CA1 region of the hippocampus 7 days after arrest. Therefore, in this study, we investigate the mechanism of action of PKCd-mediated hypoperfusion after ACA in the rat by using the two-photon laser scanning microscopy (TPLSM) to observe cortical cerebral blood flow (CBF) and laser Doppler flowmetry (LDF) detecting regional CBF in the presence/absence of dV1-1 (specific PKCd inhibitor), nitric oxide synthase (NOS) substrate (L-arginine, L-arg) and inhibitor (N o -Nitro-L-arginine, NLA), and nitric oxide (NO) donor (sodium nitroprusside, SNP). There was an increase in regional LDF and local (TPLSM) CBF in the presence of dV1-1 þ L-arg, but only an increase in regional CBF under dV1-1 þ SNP treatments. Systemic blood nitrite levels were measured 15 minutes and 24 hours after ACA. Nitrite levels were enhanced by pretreatment with dV1-1 30 minutes before ACA possibly attributable to enhanced endothelial NOS protein levels. Our results suggest that PKCd can modulate NO machinery in cerebral vasculature. Protein kinase C delta can depress endothelial NOS blunting CBF resulting in hypoperfusion, but can be reversed with dV1-1 improving brain perfusion, thus providing subsequent neuroprotection after ACA. Keywords: asphyxial cardiac arrest; middle cerebral artery occlusion; neuroprotection; palmitic acid methyl ester; stearic acid methyl ester INTRODUCTIONWe previously showed that inhibition of protein kinase C delta (PKCd) via dV1-1 can increase perfusion 24 hours after asphyxial cardiac arrest (ACA). Global cerebral ischemia (via ACA) causes derangement of cerebral blood flow (CBF) responsible for neuronal cell death in the CA1 region of the hippocampus as well as the cortex.1 Owing to the overall decrease in CBF after ischemia, neuronal cell death 1 can occur in major regions of the brain responsible for learning, memory, and cognitive function.2 It is thought that during global ischemia, PKCd (a novel PKC) levels are elevated causing PKCd to translocate to the nucleus (activation) resulting in cellular damage. In the normal brain, PKCd levels are nominal whereas global ischemia can cause activation/translocation of PKCd.3 Inhibition of PKCd (via specific inhibitor of PKCd, dV1-1) can cause a revival of CBF 24 hours after ischemia to counteract hypoperfusion or low CBF found to be suppressed after cardiac arrest from 38% to 65%. 1,4 We previously showed that pretreatment of dV1-1 before ACA can enhance perfusion 24 hours after ischemia, resulting in improved neuronal survival in the hippocampal CA1 and cortex regions in our rat model of ACA.1 Here, we sought out to define the specific mechanism(s) of how inhibition of PKCd can alleviate these pathologies. The possible endothelium and endothelial-mediated nitric oxide synthase (eNOS) involvement as a target for PKCd relating to general circulation was first reported by Monti et al.

Effect of Cardiac Arrest on Cognitive Impairment and Hippocampal Plasticity in Middle-Aged Rats

“…In our study, the seven day survival following ACA in nine month old Fischer 344 rats was significantly reduced from 95% in the sham group to 38% in the ACA group ( Fig 1 ). This decline in survival is greatly reduced compared to our previous studies in Sprague Dawley rats, where the seven day survival rates were around 80–90% at seven days [ 46 , 47 ]. Ischemic events may be increasingly detrimental as an individual ages as compared to their younger counterparts, a trend that has been previously suggested [ 48 , 49 ].…”

Global and regional differences in cerebral blood flow after asphyxial versus ventricular fibrillation cardiac arrest in rats using ASL-MRI

“…[14, 30, 37–39] The exact underlying mechanisms and consequences, however, remain unknown. The reperfusion pattern is a net result of multiple factors, including dysregulation of the vascular tone by agents such as nitric oxide,[45] oxygen radical species,[46] and others. It was also postulated that the perturbations are a result of vasoconstriction, since blood volume was decreased while mean transit time of blood through the brain was increased.…”

Reduced Apoptotic Injury by Phenothiazine in Ischemic Stroke through the NOX-Akt/PKC Pathway

“…Additionally, PKC has been studied for its role in ischemic tolerance and reperfusion injury [19,20]. Molecular events during ischemia and reperfusion, including caspase-mediated damage, reduced cerebral blood flow, and increased free radical formation, are at least partially modulated by PKC [21][22][23]. Importantly, one study highlighted that Akt modulates NOX activation and that PKC may act in a pathway upstream from the Akt regulation of NOX [24].…”