Phospholipase A2 and its Molecular Mechanism after Spinal Cord Injury

Phospholipases A₂ (PLA₂s) are a diverse family of lipolytic enzymes which hydrolyze the acyl bond at the sn-2 position of glycerophospholipids to produce free fatty acids and lysophospholipids. These products are precursors of bioactive eicosanoids and platelet-activating factor which have been implicated in pathological states of numerous acute and chronic neurological disorders. To date, more than 27 isoforms of PLA₂ have been found in the mammalian system which can be classified into four major categories: secretory PLA₂, cytosolic PLA₂, Ca²⁺-independent PLA₂, and platelet-activating factor acetylhydrolases. Multiple isoforms of PLA₂ are found in the mammalian spinal cord. Under physiological conditions, PLA₂s are involved in diverse cellular responses, including phospholipid digestion and metabolism, host defense, and signal transduction. However, under pathological situations, increased PLA₂ activity, excessive production of free fatty acids and their metabolites may lead to the loss of membrane integrity, inflammation, oxidative stress, and subsequent neuronal injury. There is emerging evidence that PLA₂ plays a key role in the secondary injury process after traumatic spinal cord injury. This review outlines the current knowledge of the PLA₂ in the spinal cord with an emphasis being placed on the possible roles of PLA₂ in mediating the secondary SCI.