ERK 1/2 Activation Mediates the Neuroprotective Effect of BpV(pic) in Focal Cerebral Ischemia-Reperfusion Injury.

Bisperoxovanadium (pyridine-2-carboxyl) [bpV(pic)] is a commercially available PTEN inhibitor. Previous studies from us and others have shown that bpV(pic) confers neuroprotection in cerebral ischemia injury. We set up to determine whether ERK 1/2 activation plays a role in bpV(pic)-induced neuroprotective effect in cerebral ischemia injury. We found that the phosphorylation levels of Akt (p-AKT) and ERK1/2 (p-ERK 1/2) were down-regulated after cerebral ischemia-reperfusion injury. The injection of bpV(pic) after injury not only increased the level of p-AKT but also the level of p-ERK 1/2. While the inhibition of PTEN mediated the up-regulatation of p-AKT and p-ERK 1/2 by bpV(pic). Interestingly, the ERK 1/2 activation induced by bpV(pic) was also independent of the inhibition of PTEN. Our results indicate that bpV(pic) protects against OGD-induced neuronal death and promotes the functional recovery of stroke animals through PTEN inhibition and ERK 1/2 activation, respectively. This study suggests that the effect of bpV(pic) on ERK 1/2 signaling should be considered while using bpV(pic) as a PTEN inhibitor.

Arginine is neuroprotective through suppressing HIF-1α/LDHA-mediated inflammatory response after cerebral ischemia/reperfusion injury.

Neuroinflammation is a secondary response following ischemia stroke. Arginine is a non-essential amino acid that has been shown to inhibit acute inflammatory reaction. In this study we show that arginine treatment decreases neuronal death after rat cerebral ischemia/reperfusion (I/R) injury and improves functional recovery of stroke animals. We also show that arginine suppresses inflammatory response in the ischemic brain tissue and in the cultured microglia after OGD insult. We further provide evidence that the levels of HIF-1α and LDHA are increased after rat I/R injury and that arginine treatment prevents the elevation of HIF-1α and LDHA after I/R injury. Arginine inhibits inflammatory response through suppression of HIF-1α and LDHA in the rat ischemic brain tissue and in the cultured microglia following OGD insult, and protects against ischemic neuron death after rat I/R injury by attenuating HIF-1α/LDHA-mediated inflammatory response. Together, these results indicate a possibility that arginine-induced neuroprotective effect may be through the suppression of HIF-1α/LDHA-mediated inflammatory response in microglia after cerebral ischemia injury.

l-lysine confers neuroprotection by suppressing inflammatory response via microRNA-575/PTEN signaling after mouse intracerebral hemorrhage injury.

l-lysine is a basic amino acid that has been shown to exert neuroprotective effect. However, the underlying mechanism remains to be elucidated. In this study, we investigate how l-lysine exerts its neuroprotective effect in hemin-insulted mouse cortical neurons in vitro and the mouse model of intracerebral hemorrhage (ICH) in vivo. We demonstrate that l-lysine treatment promotes M2 microglial polarization and reduces inflammatory response both in vitro and in vivo, suggesting that l-lysine may play a neuroprotective role in ICH injury. Indeed, we show that l-lysine treatment reduces cortical neuronal death after hemin insult in vitro and decrease the number of degenerating neurons after ICH in vivo. l-lysine also improves the functional recovery of ICH animals in neurobehavioral tests. Consistent with the role of PTEN in regulating inflammatory response, we find that PTEN inhibition promotes M2 microglial polarization and suppresses pro-inflammatory response in mouse ICH injury, which contribute to the neuroprotective effect of l-lysine. Moreover, our results reveal that microRNA-575 directly suppressed PTEN to promote M2 microglial polarization and mediate the neuroprotective effect of l-lysine in ICH injury. Together, our results suggest that l-lysine confers neuroprotection after ICH injury through enhancing M2 microglial polarization and reducing inflammatory response, which is mediated by microRNA-575 upregulation and subsequent PTEN downregulation.

DJ-1 Suppresses Cytoplasmic TDP-43 Aggregation in Oxidative Stress-Induced Cell Injury.

DJ-1 (also called PARK7) is a multifunctional redox-sensitive protein that is protective against oxidative stress-induced cell death. TAR DNA-binding protein 43 (TDP-43) is a major protein component of pathological inclusions in amyotrophic lateral sclerosis and frontotemporal dementia. Reducing aberrant aggregation of TDP-43 is a potential approach to prevent cell death. To investigate whether DJ-1 might inhibit TDP-43 aggregation to exert a protective effect in oxidative stress-induced injury, we tested the protein level and subcellular localization of TDP-43 and DJ-1 in SH-SY5Y cells transfected with wild-type DJ-1, DJ-1 mutant (L166P) cDNA, or DJ-1 siRNA. We show that oxidative stress induced by paraquat leads to the formation of cytosolic TDP-43 aggregation in SH-SY5Y cells. DJ-1 overexpression decreases paraquat-induced cytoplasmic accumulation of TDP-43 in SH-SY5Y cells and protects against paraquat-induced cell death. Transfection of DJ-1 L166P mutant or DJ-1 siRNA leads to increased cytosolic aggregation of TDP-43 in paraquat-treated SH-SY5Y cells and promotes cell death. These data suggest that DJ-1 may protect against oxidative stress-induced cell death through the suppression of cytoplasmic TDP-43 aggregation.

Glioblastoma recurrence correlates with NLGN3 levels.

Glioblastoma (GBM) is the most aggressive glioma in the brain. Recurrence of GBM is almost inevitable within a short term after tumor resection. In a retrospective study of 386 cases of GBM collected between 2013 and 2016, we found that recurrence of GBM mainly occurs in the deep brain regions, including the basal ganglia, thalamus, and corpus callosum. But the mechanism underlying this phenomenon is not clear. Previous studies suggest that neuroligin-3 (NLGN3) is necessary for GBM growth. Our results show that the levels of NLGN3 in the cortex are higher than those in the deep regions in a normal human brain, and similar patterns are also found in a normal mouse brain. In contrast, NLGN3 levels in the deep brain regions of GBM patients are high. We also show that an increase in NLGN3 concentration promotes the growth of U251 cells and U87-MG cells. Respective use of the cortex neuron culture medium (C-NCM) and basal ganglia neuron culture medium (BG-NCM) with DMEM to cultivate U251, U87-MG and GBM cells isolated from patients, we found that these cells grew faster after treatment with C-NCM and BG-NCM in which the cells treated with C-NCM grew faster than the ones treated with BG-NCM group. Inhibition of NLGN3 release by ADAM10i prevents NCM-induced cell growth. Together, this study suggests that increased levels of NLGN3 in the deep brain region under the GBM pathological circumstances may contribute to GBM recurrence in the basal ganglia, thalamus, and corpus callosum.

Bisperoxovandium (pyridin-2-squaramide) targets both PTEN and ERK1/2 to confer neuroprotection.

BACKGROUND AND PURPOSE: We and others have shown that inhibiting phosphatase and tensin homolog deleted on chromosome 10 (PTEN) or activating ERK1/2 confer neuroprotection. As bisperoxovanadium compounds are well-established inhibitors of PTEN, we designed bisperoxovandium (pyridin-2-squaramide) [bpV(pis)] and determined whether and how bpV(pis) exerts a neuroprotective effect in cerebral ischaemia-reperfusion injury. EXPERIMENTAL APPROACH: Malachite green-based phosphatase assay was used to measure PTEN activity. A western blot assay was used to measure the phosphorylation level of Akt and ERK1/2 (p-Akt and p-ERK1/2). Oxygen-glucose deprivation (OGD) was used to injure cultured cortical neurons. Cell death and viability were assessed by LDH and MTT assays. To verify the effects of bpV(pis) in vivo, Sprague-Dawley rats were subjected to middle cerebral artery occlusion, and brain infarct volume was measured and neurological function tests performed. KEY RESULTS: bpV(pis) inhibited PTEN activity and increased p-Akt in SH-SY5Y cells but not in PTEN-deleted U251 cells. bpV(pis) also elevated p-ERK1/2 in both SH-SY5Y and U251 cells. These data indicate that bpV(pis) enhances Akt activation through PTEN inhibition but increases ERK1/2 activation independently of PTEN signalling. bpV(pis) prevented OGD-induced neuronal death in vitro and reduced brain infarct volume and promoted functional recovery in stroke animals. This neuroprotective effect of bpV(pis) was blocked by inhibiting Akt and/or ERK1/2. CONCLUSIONS AND IMPLICATIONS: bpV(pis) confers neuroprotection in OGD-induced injury in vitro and in cerebral ischaemia in vivo by suppressing PTEN and activating ERK1/2. Thus, bpV(pis) is a bi-target neuroprotectant that may be developed as a drug candidate for stroke treatment.