Phospholipase A2 inhibitors or platelet-activating factor antagonists prevent prion replication

A key feature of prion diseases is the conversion of the cellular prion protein (PrPC) into disease-related isoforms (PrPSc), the deposition of which is thought to lead to neurodegeneration. In this study a pharmacological approach was used to determine the metabolic pathways involved in the formation of protease-resistant PrP (PrPres) in three prion-infected cell lines (ScN2a, SMB, and ScGT1 cells). Daily treatment of these cells with phospholipase A(2) (PLA(2)) inhibitors for 7 days prevented the accumulation of PrPres. Glucocorticoids with anti-PLA(2) activity also prevented the formation of PrPres and reduced the infectivity of SMB cells. Treatment with platelet-activating factor (PAF) antagonists also reduced the PrPres content of cells, while the addition of PAF reversed the inhibitory effect of PLA(2) inhibitors on PrPres formation. ScGT1 cells treated with PLA(2) inhibitors or PAF antagonists for 7 days remained clear of detectable PrPres when grown in control medium for a further 12 weeks. Treatment of non-infected cells with PLA(2) inhibitors or PAF antagonists reduced PrPC levels suggesting that limiting cellular PrPC may restrict prion formation in infected cells. These data indicate a pivotal role for PLA(2) and PAF in controlling PrPres formation and identify them as potential therapeutic agents.