Reduced activities of phospholipases A2 in platelets of drug-naive bipolar disorder patients

ObjectivePhospholipases A(2) (PLA(2)) comprise a family of hydrolytic enzymes that cleave membrane phospholipids and play a key role in cellular homeostasis. Alterations in enzymatic activity have been hypothesized in bipolar disorder (BD). Recent studies suggest that PLA(2) activity in platelets may reflect PLA(2) activity in the brain. The aim of this study was to determine PLA(2) activity in platelets of BD patients. MethodsWe determined the activity of PLA(2) subtypes [extracellular, calcium-dependent PLA(2) (sPLA(2)), intracellular, calcium-dependent PLA(2) (cPLA(2)), and intracellular, calcium-independent PLA(2) (iPLA(2))] by a radioenzymatic method in platelets from 20 patients with BD (15 drug-naive and five drug-free) and from 16 age- and gender-matched healthy controls. ResultsWe found that iPLA(2), cPLA(2), and sPLA(2) activities were lower in drug-naive patients with BD when compared to the control group (p=0.017, p<0.001, and p<0.001, respectively). ConclusionsReduced PLA(2) activity at the early stage of BD may disrupt brain function and increase the risk for the disease. Moreover, epidemiological studies show that patients with BD have a fivefold increased risk for developing Alzheimer's disease. Because patients with Alzheimer's disease also have reduced PLA(2) activity, the present finding of reduced PLA(2) in the BD group may be related to the risk factor for these individuals developing Alzheimer's disease in advanced age.