Neuroprotective effect of 2-hydroxy arachidonic acid in a rat model of transient middle cerebral artery occlusion.

Stroke modifies the composition of cell membranes by eliciting the breakdown of membrane phospholipids whose products, such as arachidonic acid (AA), are released in the cytosol. The action of enzymes such as cyclooxygenases on AA leads to inflammatory stimuli and increases the cell oxidative stress. We report here the neuroprotective effect of 2-hydroxyarachidonic acid (2OAA), a cyclooxygenase inhibitor derived from AA, as a promising neuroprotective therapy against stroke. The effect of a single dose of 2OAA, administered intragastrically 1h after the ischaemic insult, in a rat model of transient middle cerebral artery occlusion (tMCAO) was tested after 24h of reperfusion. Infarct volume was measured by TTC method to evaluate the neuroprotective effect. Levels of phospholipids and neutral lipids were measured by thin-layer chromatography. The expression of cPLA2 and sPLA2 phospholipases responsible for the cleavage of membrane phospholipids, as well as the expression of antioxidant enzymes, was measured by qPCR. Lipid peroxidation was measured as the concentration of malondialdehyde and 4-hydroxynonenal. The treatment with 2OAA reduced the infarct volume and prevented ischaemia-induced increases in transcription levels of free fatty acid (FFAs), as well as in both phospholipases A2 (cPLA2 and sPLA2). The lipid peroxidation and the transcription levels of antioxidant enzymes induced by ischaemia were also decreased by this treatment. We conclude that 2OAA treatment results in a strong neuroprotective effect that seems to rely on a decrease in PLA2 transcriptional activity. This would reduce their action on the membrane phospholipids reducing reactive oxygen and nitrogen species generated by FFAs. Based on the transcriptional activity of the antioxidant enzymes, we conclude that the treatment prevents oxidative stress rather than promoting the antioxidant response. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Ischemic insults induce necroptotic cell death in hippocampal neurons through the up-regulation of endogenous RIP3.

Global cerebral ischemia induces selective acute neuronal injury of the CA1 region of the hippocampus. The type of cell death that ensues may include different programmed cell death mechanisms namely apoptosis and necroptosis, a recently described type of programmed necrosis. We investigated whether necroptosis contributes to hippocampal neuronal death following oxygen-glucose deprivation (OGD), an in vitro model of global ischemia. We observed that OGD induced a death receptor (DR)-dependent component of necroptotic cell death in primary cultures of hippocampal neurons. Additionally, we found that this ischemic challenge upregulated the receptor-interacting protein kinase 3 (RIP3) mRNA and protein levels, with a concomitant increase of the RIP1 protein. Together, these two related proteins form the necrosome, the complex responsible for induction of necroptotic cell death. Interestingly, we found that caspase-8 mRNA, a known negative regulator of necroptosis, was transiently decreased following OGD. Importantly, we observed that the OGD-induced increase in the RIP3 protein was paralleled in an in vivo model of transient global cerebral ischemia, specifically in the CA1 area of the hippocampus. Moreover, we show that the induction of endogenous RIP3 protein levels influenced neuronal toxicity since we found that RIP3 knock-down (KD) abrogated the component of OGD-induced necrotic neuronal death while RIP3 overexpression exacerbated neuronal death following OGD. Overexpression of RIP1 also had deleterious effects following the OGD challenge. Taken together, our results highlight that cerebral ischemia activates transcriptional changes that lead to an increase in the endogenous RIP3 protein level which might contribute to the formation of the necrosome complex and to the subsequent component of necroptotic neuronal death that follows ischemic injury.