Dodecylglycerol provides partial protection against glutamate toxicity in neuronal cultures derived from different regions of embryonic rat brain

Glyceryl 1,3-Dipalmitate Produced from Lactobacillus paracasei subspecies. paracasei NTU 101 Inhibits Oxygen-Glucose Deprivation and Reperfusion-Induced Oxidative Stress via Upregulation of Peroxisome Proliferator-Activated Receptor γ in Neuronal SH-SY5Y Cells

Glyceryl 1,3-dipalmitate (GD) purified from Lactobacillus paracasei subsp. paracasei NTU 101-fermented products has been demonstrated to possess neuroprotective properties. We determined the effect of GD on oxygen-glucose deprivation and reperfusion (OGD/R)-induced SH-SY5Y neuroblastoma cell death. GD ameliorated OGD/R-induced apoptosis by elevating the protein expression of nuclear peroxisome proliferator-activated receptor γ (PPARγ) and nuclear factor erythroid 2-related factor 2 (Nrf2), thereby attenuating reactive oxygen species (ROS) generation. Pretreatment with GD reduced nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) expression from 1.54 ± 0.27 to 0.84 ± 0.46, thereby attenuating the induction of pro-inflammatory mediators, and increased the plasma membrane Ca²⁺ ATPase (PMCA) levels from 0.81 ± 0.02 to 1.08 ± 0.06, thus reducing the levels of cytosolic Ca²⁺; this also correlated with reduced cell death. We conclude that GD prevents SH-SY5Y cells from injury after OGD/R insult, possibly by modulating oxidative stress and inflammatory response.

Forskolin, an inducer of cAMP, up-regulates acetylcholinesterase expression and protects against organophosphate exposure in neuro 2A cells

Bioscavenger prophylactic therapy using purified human acetylcholinesterase (AChE) or butylcholinesterase (BChE) is a promising treatment for future protection against chemical warfare nerve agent exposure. Potential immune response due to the complex structure of cholinesterases, mutations, post-translational modifications, and genetic variation is a limiting factor against purified enzyme therapy. We investigated an alternative bioscavenger approach using forskolin, an inducer of intracellular cyclic AMP (cAMP), which activates AChE promoter and up-regulates its expression. A mouse neuronal cell line, Neuro 2A, was treated with various doses of forskolin and analysis of the expressed enzyme indicates that the AChE activity was significantly increased in cells exposed to repeated administration of the drug every other day for 7-10 days. Cholinesterase enzyme assays showed that the enzyme activity was increased approximately 2-fold for the extracellular enzyme and 3-fold for the intracellular enzyme. The optimal dose found for extracellular enzyme production was 12-24 microM forskolin, while the optimal dose for intracellular was 12 microM. In parallel with the rise in the AChE level, the morphology of forskolin-treated cells showed neurite growth with increasing doses. Forskolin treatment protects Neuro 2A cells from diisopropylflurophophate (DFP), a surrogate of the organophosphate chemical warfare agents soman and sarin, induced toxicity in Neuro 2A cells. These results indicate that transcriptional inducers, such as forskolin, can sufficiently up-regulate cellular AChE production and protect cells against organophosphate toxicity.

Histone acetylase inhibitor trichostatin A induces acetylcholinesterase expression and protects against organophosphate exposure

The biological effects of organophosphorous (OP) chemical warfare nerve agents (CWNAs) are exerted by inhibition of acetylcholinesterase (AChE), which prevents the hydrolysis of the neurotransmitter acetylcholine, leading to hypercholinergy, seizures/status epilepticus, respiratory/cardiovascular failure, and potentially death. Current investigations show that bioscavenger therapy using purified fetal bovine AChE in rodents and non-human primates and the more recently tested human butyrylcholinesterase, is a promising treatment for protection against multiple LD(50) CWNA exposures. Potential impediments, due to the complex structure of the enzyme, purification effort, resources, and cost have necessitated alternative approaches. Therefore, we investigated the effects of transcriptional inducers to enhance the expression of AChE to achieve sufficient protection against OP poisoning. Trichostatin A (TSA), an inhibitor of histone deacetylase that de-condenses the chromatin, thereby increasing the binding of transcription factors and mRNA synthesis, was evaluated for induction of AChE expression in various neuronal cell lines. Dose-response curves showed that a concentration of 333 nM TSA was optimal in inducing AChE expression. In Neuro-2A cells, TSA at 333 nM increased the extracellular AChE activity approximately 3-4 fold and intracellular enzyme activity 10-fold. Correlating with the AChE induction, TSA pre-treatment significantly protected the cells against exposure to the organophosphate diisopropylfluorophosphate, a surrogate for the chemical warfare agents soman and sarin. These studies indicate that transcriptional inducers such as TSA up-regulate AChE, which then can bioscavenge any organophosphates present, thereby protecting the cells from OP-induced cytotoxicity. In conclusion, transcriptional inducers are prospective new methods to protect against CWNA exposure.

(34) Transcriptional induction of cholinesterase expression and protection against chemical warfare nerve agents

We investigated whether transcriptional inducers could enhance the expression of acetylcholinesterase (AChE) in cell lines to achieve protection against organophosphate (OP) poisoning. Trichostatin A (TSA), an inhibitor of histone deacetylase that de-condenses chromatin and increases the binding of transcription factors and mRNA synthesis, induced three- to four-fold extracellular and 8-10-fold intracellular AChE expression at the optimal dose of 165-333 nM in Neuro 2A cells. Pre-treatment with TSA protected against OP exposure. Thus, transcriptional inducers, such as TSA, up-regulate AChE, which then can scavenge the OP and protect the cells from OP-induced toxicity, and are potential novel ways to treat chemical warfare nerve agent (CWNA) exposure.

Celastrus paniculatus seed water soluble extracts protect against glutamate toxicity in neuronal cultures from rat forebrain

Aqueous extracts of Celastrus paniculatus (CP) seed have been reported to improve learning and memory in rats. In addition, these extracts were shown to have antioxidant properties, augmented endogenous antioxidant enzymes, and decreased lipid peroxidation in rat brain. However, water soluble extracts of CP seed (CP-WSE) have not been evaluated for their neuroprotective effects. In the study reported here, we used enriched forebrain primary neuronal cell (FBNC) cultures to study the neuroprotective effects of three CP-WSE extracts (a room temperature, WF; a hot water, HF; and an acid, AF) on glutamate-induced toxicity. FBNC were pre-treated with the CP-WSE and then with glutamate to evaluate the protection afforded against excitatory amino acid-induced toxicity. The criteria for neuroprotection were based on the effects of CP-WSE on a mitochondrial function test following glutamate-induced neurotoxicity. Pre-treatment of neuronal cells with CP-WSE significantly attenuated glutamate-induced neuronal death. To understand the molecular mechanism of action of CP-WSE, we conducted electrophysiological studies using patch-clamp techniques on N-methyl-D-aspartate (NMDA)-activated whole-cell currents in FBNC. WSE significantly and reversibly inhibited whole-cell currents activated by NMDA. The results suggest that CP-WSE protected neuronal cells against glutamate-induced toxicity by modulating glutamate receptor function.

RS-100642-198, a novel sodium channel blocker, provides differential neuroprotection against hypoxia/hypoglycemia, veratridine or glutamate-mediated neurotoxicity in primary cultures of rat cerebellar neurons

The present study investigated the effects of RS-100642-198 (a novel sodium channel blocker), and two related compounds (mexiletine and QX-314), in in vitro models of neurotoxicity. Neurotoxicity was produced in primary cerebellar cultures using hypoxia/hypoglycemia (H/H), veratridine or glutamate where, in vehicle-treated neurons, 65%, 60% and 75% neuronal injury was measured, respectively. Dose-response neuroprotection experiments were carried out using concentrations ranging from 0.1-500 micro M. All the sodium channel blockers were neuroprotective against H/H-induced injury, with each exhibiting similar potency and efficacy. However, against veratridine-induced neuronal injury only RS-100642-198 and mexiletine were 100% protective, whereas QX-314 neuroprotection was limited (i.e. only 54%). In contrast, RS-100642-198 and mexiletine had no effect against glutamate-induced injury, whereas QX-314 produced a consistent, but very limited (i.e. 25%), neuroprotection. Measurements of intraneuronal calcium [Ca(2+)]i) mobilization revealed that glutamate caused immediate and sustained increases in [Ca(2+)]i which were not affected by RS-100642-198 or mexiletine. However, both drugs decreased the initial amplitude and attenuated the sustained rise in [Ca(2+)]i mobilization produced by veratridine or KCl depolarization. QX-314 produced similar effects on glutamate-, veratridine- or KCl-induced [Ca(2+)]i dynamics, effectively decreasing the amplitude and delaying the initial spike in [Ca(2+)]i, and attenuating the sustained increase in [Ca(2+)]i mobilization. By using different in vitro models of excitotoxicity, a heterogeneous profile of neuroprotective effects resulting from sodium channel blockade has been described for RS-100642-198 and related drugs, suggesting that selective blockade of neuronal sodium channels in pathological conditions may provide therapeutic neuroprotection against depolarization/excitotoxicity via inhibition of voltage-dependent Na(+) channels.

Studies on neuronal apoptosis in primary forebrain cultures: neuroprotective/anti-apoptotic action of NR2B NMDA antagonists

While the role of apoptosis in neuronal injury is continually being re-defined, approaches to intervene in the progression of apoptotic injury have been documented to provide neuroprotection against a variety of insults. The present studies were undertaken to systematically study the effects of certain neuroprotective agents against neuronal apoptosis mediated by staurosporine (ST). ST (0.01-5 micro M) produced a dose-related apoptotic injury (as characterized by cellular morphology, 'Comet' assay analysis [single cell gel electrophoresis] and caspase-3 activation) in primary cultures of forebrain neurons. ST significantly increased caspase-3 activity. The NMDA receptor subtype non-selective antagonist dizocilpine [(+) MK-801; 0.1-50 micro M] and a novel sodium channel blocker RS100642 (1.0-250 micro M) had no significant effects against ST-induced neurotoxicity. Conversely, NR2B-selective NMDA receptor antagonists CGX-1007 (0.01-50 micro M) and ifenprodil (0.01-50 micro M) provided dose-dependent neuroprotection against ST-induced neurotoxicity (as measured by neuronal viability and comet assay analysis). CGX-1007 had no significant effect on ST-induced caspase-3 activity; however, ifenprodil did block activation of caspase-3. These studies demonstrate that NR2B NMDA receptor antagonists are anti-apoptotic and may mediate their action via mechanism(s) that are dependent or independent of caspase-3 activation.

Neuroprotection produced by the NAALADase inhibitor 2-PMPA in rat cerebellar neurons

The present study examined the neuroprotective actions of the N-acetylated-alpha-linked-acidic dipeptidase (NAALADase) inhibitor 2-(phosphonomethyl)pentanedioic acid (2-PMPA) in four in vitro models of neurotoxicity. Using neuron-enriched primary cultures derived from rat embryo (E15) cerebellum, 2-PMPA afforded 100% neuroprotection from injuries induced by hypoxia (EC(50)=8.4 microM). In contrast, against glutamate or N-methyl-D-aspartate (NMDA) injury, 2-PMPA was less potent and its efficacy limited to a maximum of 46% and 16%, respectively. 2-PMPA was not effective against veratridine-induced injury. Also, the less potent analog of 2-PMPA, 2-[phosphonomethyl]succinic acid (2-PMSA), was ineffective. Unlike 2-PMPA, the endogenous NAALADase substrate and mGlu(3) receptor agonist N-acetyl-aspartyl-glutamate (NAAG) was neuroprotective against all four injury mechanisms and compared to 2-PMPA, exhibited a different "phosphate effect" on neuroprotection. These results confirm the superior efficacy of 2-PMPA to protect against injury caused by cellular anoxia, and are discussed relative to upstream modulation of hyperglutamatergic activity vs. downstream modulation of metabotropic receptors as possible targets for ischemia/stroke therapy.