Secretory PLA2-IIA and ROS generation in peripheral mitochondria are critical for neuronal death

Abstract

In this study the role of mitochondrial secretory PLA2-IIA in glutamate-induced cell death in cultured cerebellar granule neurons has been investigated. Inhibition of secretory PLA2-IIA blocked glutamate-induced cell death. Since PLA2 may generate reactive oxygen species (ROS), we have investigated ROS production, detected as dihydrorhodamine 123 oxidation and nitrotyrosine modifications of proteins, following glutamate treatment in the absence or presence of an inhibitor of secretory PLA2-IIA. There was an increased generation of ROS in both glutamate- and buffer-treated neurons compared to untreated neurons. Scavenging with dihydrorhodamine 123 reduced glutamate-induced death (60%), showing that ROS detected in glutamate-treated neurons were associated with cell death. However, ROS detected in buffer-treated neurons were not associated with toxicity. Glutamate treatment led to ROS production predominantly in peripheral mitochondria, whereas buffer treatment led to ROS production in somal mitochondria. Inhibition of secretory PLA2-IIA (i) reduced the generation of ROS after glutamate treatment, (ii) reduced the ROS production in peripheral mitochondria in glutamate-treated neurons, consistent with the fact that calcium entry through glutamate (NMDA) receptors has a privileged access to peripheral mitochondria, and (iii) did not reduce the generation of ROS after buffer treatment. In conclusion, activation of NMDA receptors induces ROS, which is critical for neuronal death, due to secretory PLA2-IIA associated with peripheral mitochondria.

Small‐Molecule Targeting of the Mitochondrial Compartment with an Endogenously Cleaved Reversible Tag

“…Mitochondria were loaded with the nonfluorescent dye MitoTracker CM-H2XROS, which selectively accumulates within mitochondria and subsequently oxidized to a fluorescent chromophore, as repeatedly demonstrated in the past. [20][21][22] Free LipAc did not reduce the fluorescence of the redox-sensitive probe at 1 mm concentration (Figure 4 A). At higher concentrations (10 mm), LipAc had significantly elevated endogenous ROS levels after 12 h. In contrast, reversibly targeted LipAc (revMitoLipAc) protected mitochondria from endogenous ROS at 1 mm and 10 mm concentrations.…”

Low Molecular Weight Phospholipases A2 in Mammalian Brain and Neural Cells: Roles in Functions and Dysfunctions

“…Commercially available c(2NapA)LS(2NapA)R (sPLA 2 -IIA inhibitor I) protected cerebellar granule neuron death induced by glutamate and inhibited ROS production in peripheral neuronal mitochondria [105]. A recent study also demonstrated that this pentapeptide could abolish NMDAinduced increase in PLA 2 activity and apoptotic cell death of cortical primary neurons [19].…”

“…However, the presence of sPLA 2 in intracellular compartments of neural cells [9,48] suggests that endogenous enzymes might also participate in apoptotic cell death. Indeed, inhibition of GIIA by a cell permeable specific inhibitor could reduce glutamate-induced death of cerebellar granule neurons [105]. In addition, GIIA was also involved in the generation of ROS in peripheral mitochondria.…”

Upregulation of Fas and FasL in Taiwan cobra phospholipase A2‐treated human neuroblastoma SK‐N‐SH cells through ROS‐ and Ca2+‐mediated p38 MAPK activation

“…This revealed that ROS was at the upstream of activation of p38 MAPK. Given that oxidative stress arising from activation of NADPH oxidase has been reported to be associated with neurodegenerative disorders [Mathisen et al, 2007;Sun et al, 2007], the effect of DPI (inhibitor of NADPH oxidase) on p38 MAPK activation was assessed. Co-incubation of DPI with PLA 2 or BPB-PLA 2 abolished p38 MAPK activation and upregulation of Fas and FasL (Fig.…”