Indomethacin activates protein kinase C and potentiates α7 ACh receptor responses.

Background/aims: We have earlier found that indomethacin activates CaMKII, as a novel action distinct from COX inhibition. To explore further indomethacin actions, the present study focused upon PKC and examined the effect of indomethacin on α7 ACh receptor responses and hippocampal synaptic transmission through PKC.

Methods: We recorded currents through α7 ACh receptors expressed in Xenopus oocytes, quantified PKC activity in the in situ and cell-free PKC assay, and monitored field excitatory postsynaptic potentials (fEPSPs) and miniature excitatory postsynaptic currents (mEPSCs) from the CA1 region of rat hippocampal slices.

Indomethacin enhances learning and memory potential by interacting with CaMKII.

The present study examined the effect of indomethacin (IM), a cyclooxygenase inhibitor, on learning and memory functions. IM activated Ca(2+) /calmodulin-dependent protein kinase II (CaMKII) in cultured rat hippocampal neurons. IM (100 µM) significantly increased the rate of spontaneous AMPA receptor-mediated miniature excitatory postsynaptic currents elicited from CA1 pyramidal neurons of rat hippocampal slices, without affecting the amplitude, and enhanced extracellular high K(+) (20 mM)-induced glutamate release from rat hippocampal slices, indicating that IM stimulates presynaptic glutamate release.

AMID mediates adenosine-induced caspase-independent HuH-7 cell apoptosis.

Background/aims: The mechanism underlying extracellular adenosine-induced caspase-independent apoptosis in HuH-7 human hepatoma cells is not fully understood. The present study investigated the role for apoptosis-inducing factor (AIF)-homologous mitochondrion-associated inducer of death (AMID) in the pathway.

Methods: To see the implication of AMID in adenosine-induced HuH-7 cell apoptosis, real-time reverse transcription-polymerase chain reaction (RT-PCR), immunofluorescent cytochemistry, time-laps GFP monitoring, cell cycle analysis, flow cytometry, Western blotting, cell viability assay, and TUNEL staining were carried out.

DL- and PO-phosphatidylcholines as a promising learning and memory enhancer.

In the water maze test, oral administration with 1,2-dilynoleoyl-sn-glycero-3-phosphocholine (DLPhtCho)(5 mg/kg) alone or DLPhtCho (5 mg/kg) plus 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPhtCho)(5 mg/kg) significantly shortened the prolonged acquisition latency for rats intraperitoneally injected with scopolamine, with more efficient effect than (POPhtCho)(5 mg/kg) alone, arachidonic acid (AA)(5 mg/kg) alone, docosahexaenoic acid (DHA)(5 mg/kg) alone, or 1-palmitoyl-2-linoleil-sn-glycero-3-phosphoserine (PLPhtSer)(5 mg/kg) alone. POPhtCho (5 mg/kg) alone or DLPhtCho (5 mg/kg) plus POPhtCho (5 mg/kg) also significantly shortened the prolonged retention latency for rats intraperitoneally injected with scopolamine, but otherwise no significant effect was obtained with DLPhtCho (5 mg/kg) alone, AA (5 mg/kg) alone, DHA (5 mg/kg) alone, or PLPhtSer (5 mg/kg) alone. Oral co-administration with DLPhtCho (5 mg/kg) and POPhtCho (5 mg/kg) significantly shortened the acquisition latency for rats untreated with scopolamine as compared with the latency for administration with polyethylene glycol (PEG), DLPhtCho alone at doses of 5 and 10 mg/kg, or POPhtCho alone at doses of 5 and 10 mg/kg, while no efficient effect on the retention latency was obtained.

E22Δ Mutation in Amyloid β-Protein Promotes β-Sheet Transformation, Radical Production, and Synaptotoxicity, But Not Neurotoxicity.

Oligomers of 40- or 42-mer amyloid β-protein (Aβ40, Aβ42) cause cognitive decline and synaptic dysfunction in Alzheimer's disease. We proposed the importance of a turn at Glu22 and Asp23 of Aβ42 to induce its neurotoxicity through the formation of radicals. Recently, a novel deletion mutant at Glu22 (E22Δ) of Aβ42 was reported to accelerate oligomerization and synaptotoxicity.

1,2-dilinoleoyl-sn-glycero-3-phosphoethanolamine ameliorates age-related spatial memory deterioration by preventing neuronal cell death.

Background: Accumulating evidence has pointed that a variety of lipids could exert their beneficial actions against dementia including Alzheimer disease and age-related cognitive decline via diverse signaling pathways. Endoplasmic reticulum (ER) stress-induced neuronal apoptosis, on the other hand, is a critical factor for pathogenesis of neurodegenerative diseases such as Alzheimer disease and Parkinson disease, senile dementia, and ischemic neuronal damage. The present study examined the effects of 1,2-dilinoleoyl-sn-glycero-3-phosphoethanolamine (DLPhtEtn), a phospholipid, on ER stress-induced neuronal death and age-related cognitive disorders.

Regulation of AMPA receptor trafficking by O-glycosylation.

The present study investigated the role of O-linked beta-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation) in AMPA receptor trafficking. Alloxan, an inhibitor of O-GlcNAc transferase, potentiated responses of AMPA receptors composed of the GluR1 subunit expressed in Xenopus oocytes. No potentiating effect of alloxan was obtained with mutant GluR1 (S831A) receptor lacking CaMKII phosphorylation site.

Interleukin-18 regulates motor activity, anxiety and spatial learning without affecting synaptic plasticity.

Expression of Schaffer collateral-CA1 long-term potentiation (LTP) and long-term depression (LTD) was not affected in hippocampal slices from wild-type mice pretreated with lipopolysaccharide (0.25mg/kg, i.p.

DCP-LA neutralizes mutant amyloid beta peptide-induced impairment of long-term potentiation and spatial learning.

Long-term potentiation (LTP) was monitored from the CA1 region of the intact rat hippocampus by delivering high frequency stimulation (HFS) to the Schaffer collateral commissural pathway. Intraventricular injection with mutant amyloid beta(1-42) peptide lacking glutamate-22 (Abeta(1-42)E22Delta), favoring oligomerization, 10 min prior to HFS, inhibited expression of LTP, with the potency more than wild-type amyloid beta(1-42) peptide. Intraperitoneal injection with the linoleic acid derivative 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) 70 min prior to HFS neutralized mutant Abeta(1-42)E22Delta peptide-induced LTP inhibition.

DCP-LA stimulates AMPA receptor exocytosis through CaMKII activation due to PP-1 inhibition.

The linoleic acid derivative 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) activated Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) by inhibiting protein phosphatase-1 (PP-1). DCP-LA induced a transient huge facilitation of synaptic transmission monitored from the CA1 region of rat hippocampal slices, which was largely inhibited by the CaMKII inhibitor KN-93. DCP-LA potentiated kainate-evoked whole-cell membrane currents for Xenopus oocytes expressing alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors composed of the GluR1, GluR3, GluR1/GluR2, GluR1/GluR3, and GluR1/GluR2/GluR3 subunits, and the potentiation was significantly inhibited by KN-93.

1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine improves cognitive decline by enhancing long-term depression.

1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPhtCho) (1 microM) enhanced long-term depression (LTD), a synaptic plasticity relevant to learning and memory, in the CA1 region of rat hippocampal slices, where expression of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit GluR1 on the plasma membrane was decreased. In the water maze test, oral administration with POPhtCho (5 mg/kg) significantly shortened the prolonged retention latency for rats intraperitoneally injected with scopolamine (1 mg/kg), while the acquisition latency was not affected. For humans with mild cognitive impairment and dementia (average of Mini Mental State Examination score, 18), oral intake with POPhtCho (300 mg/day, once after breakfast) everyday raised the score to over 20, corresponding to normal cognitive functions, throughout 6 months after intake.

Dilinoleoylphosphatidylcholine ameliorates scopolamine-induced impairment of spatial learning and memory by targeting alpha7 nicotinic ACh receptors.

Aims: The present study was conducted to understand the role of 1,2-dilynoleoyl-sn-glycero-3-phosphocholine (DLPhtCho) in cognitive functions.

Main Methods: Two-electrode voltage-clamp was made to Xenopus oocytes expressing rat alpha7 acetylcholine (ACh) receptors. Field excitatory postsynaptic potentials (fEPSPs) were monitored from the CA1 region of rat hippocampal slices.

The phosphodiesterase III inhibitor olprinone inhibits hippocampal glutamate release via a cGMP/PKG pathway.

Olprinone, an inhibitor of cyclic nucleotide phosphodiesterase III, inhibited an increase in intracellular Ca(2+) concentrations for acutely dissociated rat hippocampal pyramidal neurons induced by extracellular high K(+) (35 mM) depolarization. Olprinone (100 microM) significantly reduced spontaneous glutamate release from rat hippocampal slices. Furthermore, olprinone significantly decreased the rate of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated miniature excitatory postsynaptic currents (AMPA-mEPSCs) monitored from CA1 pyramidal neurons of rat hippocampal slices, and the effect was blocked by KT5823, an inhibitor of protein kinase G (PKG), but not by H-89, an inhibitor of protein kinase A (PKA).

A new amyloid beta variant favoring oligomerization in Alzheimer's-type dementia.

Objective: Soluble oligomers of amyloid beta (Abeta), rather than amyloid fibrils, have been proposed to initiate synaptic and cognitive dysfunction in Alzheimer's disease (AD). However, there is no direct evidence in humans that this mechanism can cause AD. Here, we report a novel amyloid precursor protein (APP) mutation that may provide evidence to address this question.

Beneficial effect of intracellular free high-mannose oligosaccharides on cryopreservation of mammalian cells and proteins.

The cryoprotective effect of intracellular free high-mannose oligosaccharides (HMOS) on mammalian cells and proteins was examined by monitoring PC-12 cell viability and assaying protein kinase C (PKC)-epsilon activity. 1-Deoxymannojirimycin, an inhibitor of alpha-mannosidase, to cause an increase in intracellular free HMOS, significantly rescued PC-12 cells with 2-h freezing insult at -15 degrees C in a concentration (1-50mM)- and pretreatment time (48-72h)-dependent manner, as compared with unpretreated cells; full rescue from freezing injury was obtained with 1-deoxymannojirimycin at more than 25mM for 48-h pretreatment and more than 3mM for 72- and 96-h pretreatment. For PC-12 cells pretreated with 1-deoxymannojirimycin at 1mM for 72h, thawed cell viability after more than 8-w cryopreservation at -80 degrees C in 10% (v/v) dimethyl sulfoxide was much higher than that for cells without pretreatment.

The linoleic acid derivative DCP-LA selectively activates PKC-epsilon, possibly binding to the phosphatidylserine binding site.

This study examined the effect of 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA), a newly synthesized linoleic acid derivative with cyclopropane rings instead of cis-double bonds, on protein kinase C (PKC) activity. In the in situ PKC assay with reverse-phase high-performance liquid chromatography, DCP-LA significantly activated PKC in PC-12 cells in a concentration-dependent (10 nM-100 microM) manner, with the maximal effect at 100 nM, and the DCP-LA effect was blocked by GF109203X, a PKC inhibitor, or a selective inhibitor peptide of the novel PKC isozyme PKC-epsilon. Furthermore, DCP-LA activated PKC in HEK-293 cells that was inhibited by the small, interfering RNA against PKC-epsilon.

A(1) adenosine receptor signal and AMPK involving caspase-9/-3 activation are responsible for adenosine-induced RCR-1 astrocytoma cell death.

Extracellular adenosine reduced viability of RCR-1 rat astrocytoma cells in a dose (0.3-10mM)- and treatment time (24-72h)-dependent manner. In the apoptosis assay using propidium iodide (PI) and annexin V, treatment with adenosine (1mM) for 72h increased the population of PI-negative/annexin V-positive cells, that is related to early apoptosis, and that of PI-positive/annexin V-positive cells, that is related to late apoptosis/secondary necrosis.

Linoleic acid derivative DCP-LA improves learning impairment in SAMP8.

In the water-maze test, the linoleic acid derivative, 8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) (1 mg/kg, intraperitoneally), significantly shortened the prolonged latency for accelerated-senescence-prone mice 8 (SAMP8), reaching a level similar to the latency for accelerated-senescence-resistant mice 1 (SAMR1) as control. In the open-field test to assess motor activity, it was confirmed that the DCP-LA effect is not due to increased motor activity. In the passive avoidance test to assess fear memory, DCP-LA had no effect on the latency of acquisition and retention for SAMP8.

Modulation of P2X receptors via adrenergic pathways in rat dorsal root ganglion neurons after sciatic nerve injury.

The present study examined noradrenaline-induced modulation of ATP-evoked currents in dorsal root ganglion (DRG) neurons after sciatic nerve injury (transection). ATP (10 microM) generated fast/mixed type of whole-cell membrane currents, possibly as mediated via P2X(3)/P2X(3)-like receptors, and slow type of the currents, possibly as mediated via P2X(2/3) receptors, in acutely dissociated L4/5 DRG neurons, without significant difference between sham and injury group. For sham group, noradrenaline (10 microM) enhanced fast/mixed type of ATP-evoked currents in ipsilateral DRG neurons, that is not inhibited by H-7, a broad inhibitor of protein kinases, but otherwise it had no effect on slow type of the currents.

Bidirectional regulations for glutamate and GABA release in the hippocampus by alpha7 and non-alpha7 ACh receptors.

In the assay of glutamate and gamma-aminobutyric acid (GABA) with a high-performance liquid chromatography, spontaneous release of glutamate and GABA from rat hippocampal slices was significantly enhanced by mecamylamine, an inhibitor of non-alpha7 ACh receptors, or alpha-bungarotoxin, an inhibitor of alpha7 ACh receptors in the absence of tetrodotoxin (TTX), but not in the presence of TTX. Nicotine significantly enhanced glutamate and GABA release in the absence of TTX, that is abolished by mecamylamine or alpha-bungarotoxin, while it had no effect on the release in the presence of TTX. In the recording of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor-mediated excitatory postsynaptic currents (AMPA-EPSCs) and GABA(A) receptor-mediated inhibitory postsynaptic currents (GABA(A)-IPSCs) from CA1 pyramidal neurons of rat hippocampal slices, nicotine did not affect the rate and amplitude of AMPA-EPSCs and AMPA-miniature EPSCs.

8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid stimulates GABA release from interneurons projecting to CA1 pyramidal neurons in the rat hippocampus via pre-synaptic alpha7 acetylcholine receptors.

Nicotinic acetylcholine (ACh) receptors, such as alpha7, alpha3beta4 and alpha4beta2 receptors in the hippocampus, are suggested to modulate neurotransmitter release. 8-[2-(2-Pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) (100 nM), a linoleic acid derivative, potentiated responses of alpha7, alpha3beta4 and alpha4beta2 ACh receptors expressed in Xenopus oocytes that are blocked by 3-(1-[dimethylaminopropyl] indol-3-yl)-4-[indol-3-yl] maleimide (GF109203X), a selective inhibitor of protein kinase C (PKC), except for alpha3beta4 ACh receptors. DCP-LA enhanced the nicotine-triggered release of GABA from rat hippocampal slices in the presence of tetrodotoxin in a bell-shaped dose-dependent manner at concentrations ranging from 10 nM to 10 microM, although DCP-LA by itself had no effect on GABA release.

Effects of cis-unsaturated free fatty acids on PKC-epsilon activation and nicotinic ACh receptor responses.

Linoleic acid (C18:2omega6) (10 microM) depressed ACh-evoked whole-cell membrane currents followed by potentiation of the currents in Xenopus oocytes expressing Torpedo ACh receptors. The potentiation was never obtained with linoleoylamide (10 microM), which contains CONH2 instead of COOH on linoleic acid. In the assay of protein kinase C (PKC) using a reversed phase high-performance liquid chromatography, linoleic acid activated PKC-epsilon but linoleoylamide otherwise had no effect on it.

Interleukin-18 stimulates synaptically released glutamate and enhances postsynaptic AMPA receptor responses in the CA1 region of mouse hippocampal slices.

The present study examined the effects of the proinflammatory cytokine interleukin-18 (IL-18) on mouse hippocampal synaptic transmission. IL-18 (100 ng/ml) significantly increased amplitude and frequency of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor-mediated miniature excitatory postsynaptic currents (AMPA-mEPSCs), that are monitored from CA1 pyramidal neurons of mouse hippocampal slices. IL-18 (100 ng/ml) enhanced slope of basal field excitatory postsynaptic potentials (fEPSPs) that are recorded from the CA1 region of mouse hippocampal slices.

2-pyrrolidinone induces a long-lasting facilitation of hippocampal synaptic transmission by enhancing alpha7 ACh receptor responses via a PKC pathway.

2-Pyrrolidinone, a metabolite of aniracetam, potentiated currents through alpha7 receptors expressed in Xenopus oocytes, in a bell-shaped dose-dependent manner at concentrations ranged from 1 nM to 10 microM, with a maximum at 100 nM (189% of original levels 60 min after 20-min treatment). The potentiation was inhibited by GF109203X, a selective inhibitor of protein kinase C (PKC), but not by KN-93, a selective inhibitor of CaMKII, or H-89, a selective inhibitor of protein kinase A (PKA). In the PKC assay using reversed-phase high-performance liquid chromatography, 2-pyrrolidinone enhanced activity of PKC-epsilon activated by linoleic acid to about 1.