Na Ning

Protective effect of (−)clausenamide against Aβ-induced neurotoxicity in differentiated PC12 cells

The neurotoxicity of aggregated beta-amyloid (Abeta) has been implicated as a critical cause in the pathogenesis of Alzheimers disease (AD). In the present study, we investigated the effect of (-)clausenamide ((-)Clau), an aqueous extract of leaves of Clausena lassium (lour) skeel, on the neurotoxicity of Abeta(25-35). The viability of differentiated PC12 cells was determined by MTT assay. Apoptosis was detected by flow cytometry. DCFH-DA was used for assessment of intracellular ROS generation, JC-1 and Rhodamine 123 for measurement of mitochondrial transmembrane potential (MMP). The intracellular calcium was determined with Fluo-3. The phosphorylation of p38 MAPK and the expression of Bcl-2, Bax, P53, Caspase 3 were examined by Western blot. The results showed that (-)Clau significantly elevated cell viability. Furthermore, (-)Clau arrested the apoptotic cascade by reversing overload of calcium, preventing ROS generation, moderated the dissipation of MMP and the misbalance of Bcl-2 and Bax, inhibiting the activation of p38 MAPK and the expression of P53 and cleaved Caspase 3. Our results suggested that (-)Clau may be a therapeutic agent for AD.

(−)Clausenamide facilitates synaptic transmission at hippocampal Schaffer collateral-CA1 synapses

Clausenamide is a chiral compound isolated from leaves of the traditional Chinese herb Clausena lansium (lour) Skeels. It has been shown that (-)clausenamide, but not (+)clausenamide, improved learning and memory in amnesia animal models. However, the precise mechanism of clausenamides actions remains unknown. Here we used an electrophysiological approach to observe the effect of (-)clausenamide on facilitating field excitatory postsynaptic potential (f-EPSP) in the CA1 area of hippocampal slices from rats. The results showed that (-)clausenamide enhanced synaptic transmission at doses 0.1, 1 and 10 μM. The increase of f-EPSP induced by (-)clausenamide was completely inhibited by preincubation with nimodipine (L-voltage-dependent calcium channel blocker, 10 μM), but there was no change when nimodipine was added after (-)clausenamide application. However, ryanodine (ryanodine receptors blocker, 100 μM) attenuated the slope of f-EPSP before or after (-)clausenamide incubation. The data suggested that (-)clausenamide promoted calcium influx to trigger intracellular calcium release which was responsible for potentiating synaptic transmission. Intracellular calcium release induced by (-)clausenamide promoted the activation of CaMKIIα at concentrations of 0.1, 1 and 10 μM, and pretreatment with KN93 (CaMKIIα inhibitor, 10 μM) completely blocked the enhancement of synaptic transmission induced by (-)clausenamide. cAMP response element-binding protein (CREB) was activated by (-)clausenamide and inhibited by KN93 preincubation, but H89 (PKA inhibitor, 10 μM) had no effect, indicating that (-)clausenamide facilitated synaptic transmission by a PKA-independent pathway. Collectively, (-)clausenamide facilitated synaptic transmission by promoting calcium influx to trigger intracellular calcium release, subsequently activating CaMKIIα-CREB signal pathway.

Claulansine F suppresses apoptosis induced by sodium nitroprusside in PC12 cells

Abstract Reactive oxygen species (ROS) are known to be involved in many neurodegenerative diseases. This study assessed the effect of Claulansine F, a new carbazole isolated from Clausena lansium, on sodium nitroprusside (SNP)-treated rat pheochromocytoma PC12 cells. First, it was found that Claulansine F showed more potential on inhibiting the programmed death of PC12 cells than edaravone by cell viability, morphologic observation, and flow cytometric analysis. Further results also showed that Claulansine F attenuated the production of total intracellular ROS formation and lipid peroxidation in PC12 cells, inhibited the mitochondrial membrane potential (MMP) loss, and prevented the programmed cell death event via the P53/Bcl-2 family pathway. Its protective effect was likely medicated by the hydroxyl radical (·OH) scavenging ability, as it appeared to be not involved in the natural antioxidant system. These results suggested a promising potential for Claulansine F as a ROS scavenger in pathologies, where an oxidative stress is involved.

(+)-epi-Clausenamide, but not (−)-epi-clausenamide, showed more potential than (−)-clausenamide on facilitating synaptic transmission in CA1 region of hippocampal synapses

Effect of (+)-epi-clausenamide and (-)-epi-clausenamide on synaptic transmission in CA1 region of hippocampal slice was compared in this study. (+)-epi-Clausenamide showed more potency than (-)-clausenamide on either induction or maintenance of long term potentiation (LTP). Effect of (+)-epi-clausenamide on potentiating basic synaptic transmission was also superior to (-)-clausenamide. However, (-)-epi-clausenamide showed only slight effects on synaptic transmission, suggesting that the effect of (+)-epi-clausenamide and (-)-epi-clausenamide on synaptic transmission depended on their chirality. Calcium influx was not involved in (+)-epi-clausenamide facilitating synaptic transmission in this study. (+)-epi-Clausenamide might promote glutamate release through the activation of Synapsin I(Ser9) to activate the downstream effectors which play a key role in synaptic plasticity. Elucidating the mechanism of each optical isomer of clausenamide by electrophysiological methods provided basis for therapeutic strategies for neurological disorders.

Ginsenoside Rg1 activated CaMKIIα mediated extracellular signal-regulated kinase/mitogen activated protein kinase signaling pathway

AbstractAim:We carried out this study to investigate the effect of ginsenoside Rg1 on the extracellular signal-regulated kinase/mitogen activated protein kinase (ERK/MAPK) pathway for understanding its effect on synaptic platicity.Methods:Western blotting and immunostaining were used to examine the phosphorylation of ERK1/2, CaMKIIα and cAMP response element binding protein (CREB) in PC12 cells and synaptosomes. The confocal microscopy and fluorescent indicator Fluo-3 was applied to observe the intracellular calcium ion flux.Results:The phosphorylation of ERK1/2 in PC12 cells and synaptosomes incubated with Rg1 was increased and reached maximum at 4 min. Rg1 also promoted the transient enhancement of upstream calcium ion and activated CaMKIIα, which reached maximum at 2 min. CREB, the downstream protein, was phosphorylated within 8 min in PC12 cells after being incubated with Rg1. Moreover, KN93 partially inhibited the activation of ERK1/2, and PD98059 also partially blocked the phosphorylation of CREB.Conclusions:Rg1 activated ERK/MAPK pathway by CaMKIIα, and the activation of CREB was not only dependent on ERK induced by Rg1, which may provide an explanation for the effect of Rg1 on long-term potentiation.

Claulansine F promotes neuritogenesis in PC12 cells via the ERK signaling pathway

Aim:To study the effects of Claulansine F (Clau F), a carbazole alkaloid isolated from the stem of Clausena lansium (Lour) Skeels, on neuritogenesis of PC12 cells, and to elucidate the mechanism of action.Methods:Neuritogenesis of PC12 cells was quantified under an inverted microscope. Expression of the neurite outgrowth marker GAP-43 was detected using immunofluorescence. GAP-43 transcription was measured using RT-PCR. Cell viability was evaluated with MTT assay. The levels of phosphor-ERK1/2, phosphor-CREB, phosphor-AKT and acetylate-p53 in the cells were examined using Western blotting analyses.Results:Clau F (10–100 μmol/L) significantly increased the percentage of PC12 cells bearing neurites. Clau F markedly increased the expression of GAP-43 in the cells. The efficiency of Clau F (10 μmol/L) in increasing neuritogenesis and GAP-43 expression was comparable to that of nerve growth factor (50 ng/mL). In addition, Clau F completely blocked the proliferation of PC12 cells within 7 d of incubation, whereas it did not cause cell death in cultured rat cortical neurons. Treatment of PC12 cells with Clau F activated both ERK and AKT signaling pathways. Co-treatment of PC12 cells with the specific ERK inhibitor PD98059, but not the specific PI3K inhibitor LY294002, blocked Clau F-induced neuritogenesis and GAP-43 upregulation.Conclusion:Clau F promotes neuritogenesis in PC12 cells specifically via activation of the ERK signaling pathway.

Activation of ERK1/2-CREB pathway during potentiating synaptic transmission of (-)clausenamide in rat dentate gyrus.

To investigate the signal mechanism of ( − )clausenamide (( − )-3-hydroxy-5-(hydroxy-phenyl-methyl)-1-methyl-4-phenyl-pyrrolidin-2-one, 1) and for understanding its effect on synaptic transmission, electrophysiological recording was done for basal synaptic transmission determination. Western blot analysis was employed to examine the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and cAMP responsive element-binding protein (CREB). Immunohistochemistry and tissue in situ hybridization were applied to detect the expression of Zif268. The results showed that ( − )clausenamide (1) increased the population spike of hippocampal dentate gyrus. The phosphorylation of ERK1/2 in hippocampus and cortex was increased and reached the maximum at 5 min and 30 min, respectively. ( − )Clausenamide (1) promoted the phosphorylation of CREB, the downstream protein of ERK1/2. The expression of Zif268 protein and mRNA increased in both hippocampal dentate gyrus and cortex. Therefore, ( − )clausenamide (1) activated the ERK1/2-CREB pathway, which may provide an explanation for its effect on potentiating synaptic transmission and improving learning and memory.

Ginsenoside Rg1 activated CaMKIIalpha mediated extracellular signal-regulated kinase/mitogen activated protein kinase signaling pathway.

AbstractAim:We carried out this study to investigate the effect of ginsenoside Rg1 on the extracellular signal-regulated kinase/mitogen activated protein kinase (ERK/MAPK) pathway for understanding its effect on synaptic platicity.Methods:Western blotting and immunostaining were used to examine the phosphorylation of ERK1/2, CaMKIIα and cAMP response element binding protein (CREB) in PC12 cells and synaptosomes. The confocal microscopy and fluorescent indicator Fluo-3 was applied to observe the intracellular calcium ion flux.Results:The phosphorylation of ERK1/2 in PC12 cells and synaptosomes incubated with Rg1 was increased and reached maximum at 4 min. Rg1 also promoted the transient enhancement of upstream calcium ion and activated CaMKIIα, which reached maximum at 2 min. CREB, the downstream protein, was phosphorylated within 8 min in PC12 cells after being incubated with Rg1. Moreover, KN93 partially inhibited the activation of ERK1/2, and PD98059 also partially blocked the phosphorylation of CREB.Conclusions:Rg1 activated ERK/MAPK pathway by CaMKIIα, and the activation of CREB was not only dependent on ERK induced by Rg1, which may provide an explanation for the effect of Rg1 on long-term potentiation.

Ginsenoside Rg1 activated CaMKII|[alpha]| mediated extracellular signal-regulated kinase/mitogen activated protein kinase signaling pathway

AbstractAim:We carried out this study to investigate the effect of ginsenoside Rg1 on the extracellular signal-regulated kinase/mitogen activated protein kinase (ERK/MAPK) pathway for understanding its effect on synaptic platicity.Methods:Western blotting and immunostaining were used to examine the phosphorylation of ERK1/2, CaMKIIα and cAMP response element binding protein (CREB) in PC12 cells and synaptosomes. The confocal microscopy and fluorescent indicator Fluo-3 was applied to observe the intracellular calcium ion flux.Results:The phosphorylation of ERK1/2 in PC12 cells and synaptosomes incubated with Rg1 was increased and reached maximum at 4 min. Rg1 also promoted the transient enhancement of upstream calcium ion and activated CaMKIIα, which reached maximum at 2 min. CREB, the downstream protein, was phosphorylated within 8 min in PC12 cells after being incubated with Rg1. Moreover, KN93 partially inhibited the activation of ERK1/2, and PD98059 also partially blocked the phosphorylation of CREB.Conclusions:Rg1 activated ERK/MAPK pathway by CaMKIIα, and the activation of CREB was not only dependent on ERK induced by Rg1, which may provide an explanation for the effect of Rg1 on long-term potentiation.