Phospholipases A2: distinctive roles in the regulation of α-synuclein biology and neuronal redox response?.

IGLESIAS GONZÁLEZ, PABLO A.; CONDE, MELISA A.; URANGA, ROMINA M.; SALVADOR, GABRIELA A.

Salta

Congreso; Joint LV annual SAIB meeting and XIV PABMB congress, 5 al 9 de noviembre de 2019, Salta, Argentina.; 2019

SAIB

Iron (Fe) accumulation and α-synuclein (α-syn) overexpression are hallmarks of several neurodegenerative disorders. We have previously reported that Fe-induced oxidative stress activates fatty acid release catalyzed by different phospholipase A2 (PLA2) isoforms in the nervous system (Rodriguez Diez, 2012, 2013; Sanchez Campos, 2015; Mateos 2012). In this work, our aim was to study the involvement of PLA2s in the regulation of α-syn biology and in the neuronal redox response to Fe overload. We also investigate the role of glia in the neuronal outcome. For this purpose, we exposed human IMR-32 neuroblastoma cells to increasing ferric ammonium citrate concentrations (300-1000 μM) or vehicle for different incubation times (24-72 h). To study the role of glia in the neuronal response conditionated media derived from C6 astroglioma cells, previously challenged with Fe or vehicle, was added to neuronal cultures. Using these experimental conditions, redox status, α-syn expression and phosphorylation, and the participation of the PLA2 isoforms in the regulation of these events were studied. IMR-32 neurons exposed to Fe overload showed increased expression levels of calcium- independent PLA2 isoform (iPLA2) concomitantly with an increase in oxidative stress markers such as: lipid peroxides and plasma membrane permeability. The pharmacological blockage of iPLA2 activity increased even more the levels of lipid peroxides and the content of reactive oxygen species. On the contrary, the inhibition of cytosolic calcium ?dependent PLA2 (cPLA2) showed the opposite effect by promoting a decrease in oxidative stress markers associated with increased neuronal viability. Fe-challenged neurons also displayed increased α-syn expression and phosphorylation. The phosphorylation of α-syn was blocked by the inhibition of iPLA2 activity. Astrocytes were positive for the rate- limiting step enzyme for glutathione biosynthesis and when exposed to Fe showed an increase in the glia marker S100B and in lipid peroxidation levels, thus indicating reactivity to oxidative stress. Neurons incubated with astrocytes- derived media previously exposed to Fe displayed lower levels of oxidative injury than neurons exposed to metal injury. All toghether our resuts show specific roles for the different PLA2 isoforms in the neuronal response to Fe-induced injury: whereas iPLA2 showed to be neuroprotective and also to be involved in the regulation of α-syn phosphorylation, cPLA2 appeared to act as a damage promoter. To ascertain the nature of the effect exerted by astrocytes on neuronal response to oxidative stress we are currently studying glutathione synthesis and how isoform- specific PLA2s inhibition could be involved.