| Summary: | <p>Abstract</p> <p>Background</p> <p>The enzyme cytosolic phospholipase A<sub>2 </sub>alpha (cPLA<sub>2</sub>α) has been implicated in the progression of cerebral injury following ischemia and reperfusion. Previous studies in rodents suggest that cPLA<sub>2</sub>α enhances delayed injury extension and disruption of the blood brain barrier many hours after reperfusion. In this study we investigated the role of cPLA<sub>2</sub>α in early ischemic cerebral injury.</p> <p>Methods</p> <p>Middle cerebral artery occlusion (MCAO) was performed on cPLA<sub>2</sub>α<sup>+/+ </sup>and cPLA<sub>2</sub>α<sup>-/- </sup>mice for 2 hours followed by 0, 2, or 6 hours of reperfusion. The levels of cPLA<sub>2</sub>α, cyclooxygenase-2, neuronal morphology and reactive oxygen species in the ischemic and contralateral hemispheres were evaluated by light and fluorescent microscopy. PGE<sub>2 </sub>content was compared between genotypes and hemispheres after MCAO and MCAO and 6 hours reperfusion. Regional cerebral blood flow was measured during MCAO and phosphorylation of relevant MAPKs in brain protein homogenates was measured by Western analysis after 6 hours of reperfusion.</p> <p>Results</p> <p>Neuronal cPLA<sub>2</sub>α protein increased by 2-fold immediately after MCAO and returned to pre-MCAO levels after 2 hours reperfusion. Neuronal cyclooxygenase-2 induction and PGE<sub>2 </sub>concentration were greater in cPLA<sub>2</sub>α<sup>+/+ </sup>compared to cPLA<sub>2</sub>α<sup>-/- </sup>ischemic cortex. Neuronal swelling in ischemic regions was significantly greater in the cPLA<sub>2</sub>α<sup>+/+ </sup>than in cPLA<sub>2</sub>α<sup>-/- </sup>brains (+/+: 2.2 ± 0.3 fold vs. -/-: 1.7 ± 0.4 fold increase; <it>P </it>< 0.01). The increase in reactive oxygen species following 2 hours of ischemia was also significantly greater in the cPLA<sub>2</sub>α<sup>+/+ </sup>ischemic core than in cPLA<sub>2</sub>α<sup>-/- </sup>(+/+: 7.12 ± 1.2 fold vs. -/-: 3.1 ± 1.4 fold; <it>P </it>< 0.01). After 6 hours of reperfusion ischemic cortex of cPLA<sub>2</sub>α<sup>+/+</sup>, but not cPLA<sub>2</sub>α<sup>-/-</sup>, had disruption of neuron morphology and decreased PGE<sub>2 </sub>content. Phosphorylation of the MAPKs-p38, ERK 1/2, and MEK 1/2-was significantly greater in cPLA<sub>2</sub>a<sup>+/+ </sup>than in cPLA<sub>2</sub>α<sup>-/- </sup>ischemic cortex 6 hours after reperfusion.</p> <p>Conclusions</p> <p>These results indicate that cPLA<sub>2</sub>α modulates the earliest molecular and injury responses after cerebral ischemia and have implications for the potential clinical use of cPLA<sub>2</sub>α inhibitors.</p>
|
|---|