Design, synthesis and evaluation of novel 1-phenyl-pyrrolo[1,2-b]isoquinolin-3-one derivatives as antagonists for the glycine binding site of the NMDA receptor

A new series of 1-phenyl-pyrrolo[1,2-b]isoquinolin-3-one derivatives were designed, synthesized and demonstrated to act as antagonists for the glycine binding site of the NMDA receptor. These new derivatives protected PC12 cells against NMDA-induced injury and cell apoptosis in vitro, among which compound 13b exhibited excellent cytoneuroprotective potency and shown a dose-dependent prevention. The increased intracellular Ca²⁺ influx caused by NMDA in PC12 cells was reversed when pretreated with compound 13b. Furthermore, the interaction between compound 13b and the glycine binding site of the NMDA receptor was validated via MST assay. It was observed that the stereochemistry of compound 13b did not influence the binding affinity, which was consistent with the neuroprotective result. Molecular docking study confirmed the observed activity of compound 13b by virtue of their Pi-stacking, cation-Pi, H-bonding and Pi-electron interactions with the key amino acids in the glycine binding pocket. These results confirm the potential of 1-phenyl-pyrrolo[1,2-b]isoquinolin-3-one derivatives as neuroprotective agents targeting the glycine binding site of the NMDA receptor.

Honeycomb-like nickel oxide-reduced graphene oxide based sensor for the electrochemical tracking of norepinephrine in neuronal cells

Highly sensitive and specific detection and monitoring of trace norepinephrine (NE) in biological fluids and neuronal cell lines is essential for the investigation of pathogenesis of certain neurological diseases. Herein, we constructed a novel electrochemical sensor for real-time monitoring of NE released by PC12 cells based on glassy carbon electrode (GCE) modified with honeycomb-like nickel oxide (NiO)-reduced graphene oxide (RGO) nanocomposite. The synthesized NiO, RGO and the NiO-RGO nanocomposite were characterized using X-ray diffraction spectrogram (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The porous three-dimensional honeycomb-like structure of NiO and high charge transfer kinetics of RGO endowed the nanocomposite with excellent electrocatalytic activity, large surface area and good conductivity. The developed sensor exhibited superior sensitivity and specificity towards NE in a wide linear range from 20 nM to 14 μM and 14 μM-80 μM, with a low detection limit of 5 nM. The performances of the sensor in terms of excellent biocompatibility and high sensitivity allow it to be successfully employed in the tracking of NE release from PC12 cells under the stimulation of K⁺, providing an effective strategy for the real-time monitoring of cellular NE.

Dexmedetomidine protects PC12 cells from ropivacaine injury through miR-381/LRRC4 /SDF-1/CXCR4 signaling pathway

Introduction

Ropivacaine has been regularly used because of its good anesthetic and analgesic effects, but it may exert neurotoxic effects on neurocyte. Dexmedetomidine has presented special advantages in the fields of neuroprotection, and it also could improve peripheral nerve block combining with ropivacaine. However, if dexmedetomidine could repair neurocyte injury induced by ropivacaine, and the specific mechanism remain unclear.

Methods

Western blotting and qRT-PCR were applied for measuring expression of protein and mRNA, respectively. Flow cytometry was used for assessing apoptosis. Cell proliferation was detected using Cell Counting Kit-8 (CCK-8) and colony formation assays. Transwell assay was applied to measure the migration and invasion of cells. Dual luciferase reporter assay was applied for confirming the binding site between microRNA-381 (miR-381) and Leucine-rich repeat C4 protein (LRRC4).

Results

The viability of PC12 cells increased with raising the concentration of dexmedetomidine (0 μM, 10 μM, 50 μM, 100 μM). Dexmedetomidine reversed role of ropivacaine (0 mM, 0.1 mM, 0.5 mM, 1 mM) by upragulating the expression of miR-381 and suppressing the expression of LRRC4 in PC12 cells. miR-381 can directly interact with target gene LRRC4 and negatively regulate its expression. Dexmedetomidine promoted the proliferation, migration, and invasion and inhibited apoptosis of PC12 cells by suppressing LRRC4 via up-regulating the expressions of miR-381 and further activated SDF-1/CXCR4 signaling pathway.

Conclusions

Dexmedetomidine could protect PC12 cells from ropivacaine injury through miR-381/LRRC4/SDF-1/CXCR4 signaling pathway. This study may provide new therapeutic strategy targeting miR-381/LRRC4/SDF-1/CXCR4 signaling pathway about the prevention of ropivacaine induced neurocyte injury.

(-)-Syringaresinol-4-O-β-D-glucopyranoside from Cortex Albizziae inhibits corticosterone-induced PC12 cell apoptosis and relieves the associated dysfunction

The neuroprotective effects and potential mechanisms of (-)-Syringaresinol-4-O-β-D-glucopyranoside (SRG), a natural lignan glycoside extracted from Cortex Albizziae, were investigated using corticosterone (CORT)-induced PC12 cells as an in vitro anxiety model. PC12 cells were treated with 100 μM CORT and 5, 10, or 20 μM SRG for 48 h. Cell viability and lactate dehydrogenase (LDH) leakage were measured. Apoptosis were detected using FITC-coupled Annexin V (AV) and propidium iodide (PI) staining flow cytometric analyses and TUNEL assays. Rhodamine 123 and Fluo-3-AM staining flow cytometric analyses were used to detect mitochondrial membrane potential (ΔΨm) and intracellular calcium concentration ([Ca²⁺]_i), respectively. Western blot was used to detect brain-derived neurotrophic factor (BDNF), Bax, Bcl-2, cAMP-response element binding protein (CREB), cytosolic cytochrome c (Cyt c), caspase-3, and cleaved caspase-3. Experimental data showed that SRG promoted cell proliferation, reduced LDH release, inhibited apoptosis, improved ΔΨm values, decreased [Ca²⁺]_i, up-regulated CREB, BDNF, and Bcl-2, down-regulated Bax and Cyt c protein expression levels, and reduced caspase-3 activity. This suggests that SRG has neuroprotective and antiapoptotic effects in the pathogenesis of anxiety disorders, and its mechanisms are partly connecte to inhibition of the mitochondrial apoptotic pathway and activation of pathways involving CREB and BDNF.

Icariside II, a PDE5 inhibitor from Epimedium brevicornum, promotes neuron-like pheochromocytoma PC12 cell proliferation via activating NO/cGMP/PKG pathway

Icariside II (ICS II), a phosphodiesterase 5 inhibitor (PDE 5-I), is a major ingredient of Epimedium brevicornum, with wide spectrum of neuroprotective properties. However, little is known about the potential beneficial effect of ICS II on neuronal cell proliferation, and its possible underlying mechanism remains still unclear. We hypothesized that the beneficial effect of ICS II on neuron-like highly differentiated rat pheochromocytoma (PC12) cell proliferation is correlated with the nitric oxide (NO) signaling pathway and its upstream of PI3K/AKT pathway. PC12 cells were treated with ICS II alone or together with L-NMMA, H89, KT-5823, and/or LY294002 (the inhibitor of NOS, PKA, PKG, PI3K, respectively). It was found that ICS II concentration-dependently promoted PC12 cells proliferation, and cell cycle analysis showed that the proportion of ICS II-treated PC12 cells in S phase was higher than that of control. Moreover, ICS II at the appropriate concentration (100 μM) not only increased nNOS expression, NO production, but also enhanced cGMP content and PKG activity. The addition of L-NMMA and KT-5 823 significantly inhibited the effects of ICS II on nNOS expression, NO production and PKG activity. Furthermore, LY294002 significantly decreased p-AKT level, NOS activity, NO production and nNOS expression, but it did not affect iNOS expression. These findings demonstrate that the beneficial effect of ICS II on neuronal cell proliferation, and its possible underlying mechanisms are, at least partly, through activating AKT/nNOS/NO/cGMP/PKG signaling pathway.

AMP-activated protein kinase is involved in perfluorohexanesulfonate-induced apoptosis of neuronal cells

Perfluorohexanesulfonate (PFHxS), one of the major perfluoroalkyl compounds (PFCs), has been used in a variety of industrial and consumer applications and detected in serum in the general population. This raised a concern over its possible detrimental health effects, including neurotoxic effects. We have previously shown that PFHxS induced neuronal apoptosis via the NMDA receptor-mediated extracellular signal-regulated kinase (ERK) pathway. Recently, it has been reported that AMP-activated protein kinase (AMPK) acts as a key signal molecule in neuronal excitotoxicity as well as providing a neuroprotective function. In the present study, we have examined the involvement of AMPK in PFHxS-induced neuronal apoptosis using neuronal differentiated PC12 cells. PFHxS induced significant increases in intracellular [Ca(2+)] via the NMDA receptor and the L-type voltage-gated calcium channel (L-VGCC). The inhibition of Ca(2+) loading by the NMDA receptor antagonist, MK801 and the L-VGCC blockers, nifedipine and diltiazem significantly reduced PFHxS-induced apoptosis. PFHxS induced sustained activation of AMPK and the inhibition of AMPK activation by compound C and AMPK siRNA significantly reduced PFHxS-induced caspase-3 activity. These results indicate the pro-apoptotic role of AMPK. The activation of AMPK was attenuated by MK801, nifedipine and diltiazem. However, the activation of AMPK was not affected by the ERK inhibitor, PD98059. Likewise, ERK activation was not affected by compound C but was substantially reduced by MK801, nifedipine or diltiazem. This suggests that the activation of AMPK and ERK is regulated by intracellular Ca(2+) loading in distinct pathways. Taken together, PFHxS-induced neuronal apoptosis is mediated by AMPK and ERK pathways, which are distinctly regulated by increased intracellular Ca(2+) via the NMDA receptor and L-VGCC.