Activation of PLA2 in Spinal Cord Injury

High levels of calcium-dependent cytosolic phospholipase A2 (CPLA2) activity have been reported to occur in rat and monkey spinal cords. At the cellular level, dense immunoreactivity is present in motor neurons from cervical, thoracic, lumbar, and sacral regions (Ong et al., 1999). Traumatic injury to spinal cord stimulates activities of lipases and phospholipases (Taylor et al., 1988). SCI significantly stimulates CPLA2 activity and its expression in injured spinal cord. This increase in CPLA2 activity can be blocked by the PLA2 inhibitor, mepacrine (Liu et al., 2006). 

At the injury site, PLA2 catalyzed reaction product, arachidonate (ARA), is metabolized to neuroactive pro-inflammatory compounds such as prostaglandin E2 (PGE2), which facilitates macrophage and microglial recruitment at the injury site (see below). In addition, PGE2 also increases local blood flow and leukocyte infiltration and enhances vascular permeability and proinflammatory cytokine production (Amar and Levy, 1999). 

Annexin Al (ANXAl), a family of structurally related calcium- and phospholipid-binding and PLA2 inhibitory protein, is known to facilitate antiinflammatory action of glucocorticoids. SCI upregulates the expression of annexins I, II, and V in the injured spinal cord. Thus, annexin I expression increases at 3 days after SCI, peaks at 7 days, start to decline at 14 days, and return to the baseline level at and beyond 28 days post-injury (Liu et al., 2004). Similarly, the expression of annexin II begins to increase at 3 days, reaches 

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