Sa-Ik Hong

Neuroprotective effects of chlorogenic acid on scopolamine-induced amnesia via anti-acetylcholinesterase and anti-oxidative activities in mice.

Chlorogenic acid is a major polyphenolic component of many plants and beverages, and is particularly abundant in coffee. We evaluated the neuroprotective effects of chlorogenic acid on learning and memory impairment induced by scopolamine (0.5 mg/kg, i.p.), a muscarinic antagonist, using the Y-maze, passive avoidance, and Morris water maze tests. The chlorogenic acid significantly improved the impairment of short-term or working memory induced by scopolamine in the Y-maze test, and significantly reversed cognitive impairments in mice as measured by the passive avoidance test. In addition, chlorogenic acid decreased escape latencies in the Morris water maze test. In a probe trial session, chlorogenic acid increased the latency time in the target quadrant in a dose-dependent manner. Ex vivo, chlorogenic acid inhibited acetylcholinesterase activity in the hippocampus and frontal cortex. Chlorogenic acid also decreased malondialdehyde levels in the hippocampus and frontal cortex. In vitro, chlorogenic acid was found to inhibit acetylcholinesterase activity (IC₅₀=98.17 μg/ml) and free radical scavenging activity (IC₅₀=3.09 μg/ml) in a dose-dependent manner. These results indicate that chlorogenic acid may exert anti-amnesic activity via inhibition of acetylcholinesterase and malondialdehyde in the hippocampus and frontal cortex.

Loganin protects against hydrogen peroxide-induced apoptosis by inhibiting phosphorylation of JNK, p38, and ERK 1/2 MAPKs in SH-SY5Y cells

We investigated the mechanisms underlying the protective effects of loganin against hydrogen peroxide (H(2)O(2))-induced neuronal toxicity in SH-SY5Y cells. The neuroprotective effect of loganin was investigated by treating SH-SY5Y cells with H(2)O(2) and then measuring the reduction in H(2)O(2)-induced apoptosis using 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays. Following H(2)O(2) exposure, Hoechst 33258 staining indicated nuclear condensation in a large proportion of SH-SY5Y cells, along with an increase in reactive oxygen species (ROS) production and an intracellular decrease in mitochondria membrane potential (MMP). Loganin was effective in attenuating all the above-stated phenotypes induced by H(2)O(2). Pretreatment with loganin significantly increased cell viability, reduced H(2)O(2)-induced LDH release and ROS production, and effectively increased intracellular MMP. Pretreatment with loganin also significantly decreased the nuclear condensation induced by H(2)O(2). Western blot data revealed that loganin inhibited the H(2)O(2)-induced up-regulation of cleaved poly (ADP-ribose) polymerase (PARP) and cleaved caspase-3, increased the H(2)O(2)-induced decrease in the Bcl-2/Bax ratio, and attenuated the H(2)O(2)-induced release of cytochrome c from mitochondria to the cytosol. Furthermore, pretreatment with loganin significantly attenuated the H(2)O(2)-induced phosphorylation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and extracellular signal-regulated kinase 1/2 (ERK 1/2). These results suggest that the protective effects of loganin against H(2)O(2)-induced apoptosis may be due to a decrease in the Bcl-2/Bax ratio expression due to the inhibition of the phosphorylation of JNK, p38, and ERK 1/2 MAPKs. Loganins neuroprotective properties indicate that this compound may be a potential therapeutic agent for the treatment of neurodegenerative diseases.

The neuroprotective effects of Lonicera japonica THUNB. against hydrogen peroxide-induced apoptosis via phosphorylation of MAPKs and PI3K/Akt in SH-SY5Y cells.

We investigated the neuroprotective effects of Lonicera japonica THUNB. (Caprifoliaceae) (LJ) extract against hydrogen peroxide (H(2)O(2)), a toxin created by oxidative stress and implicated in neurodegenerative diseases, in human SH-SY5Y neuroblastoma cells. We examined the effects of LJ against H(2)O(2)-induced cytotoxicity, apoptosis, the production of reactive oxygen species (ROS), the proteolysis of cleaved poly-ADP-ribose polymerase (PARP), and the expression of Bcl-2, Bcl-xL, and cleaved caspase-3. Moreover, we attempted to determine whether LJ suppressed the phosphorylation of Akt, c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and extracellular signal-regulated kinase 1/2 (ERK 1/2). We found that LJ improved cell viability, inhibited cytotoxicity and apoptosis, and attenuated elevations in ROS and nuclear condensation. In addition, LJ showed radical scavenging ability in 2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis-(3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) assays. Western blot data revealed that LJ inhibited H(2)O(2)-induced up- and down-regulation of cleaved PARP, cleaved caspase-3, Bcl-2, and Bcl-xL. Furthermore, LJ significantly attenuated the H(2)O(2)-induced phosphorylation of Akt, JNK, p38 MAPK, and ERK1/2. These results demonstrate that LJ possesses potent neuroprotective activity. Its potential to treat neurodegenerative diseases warrants further research.

Neuroprotective effects of Eucommia ulmoides Oliv. Bark on amyloid beta25–35-induced learning and memory impairments in mice

In the present study, we examined whether aqueous extract of Eucommia ulmoides Oliv. Bark (EUE) with graded doses exerted its neuroprotective effects on amyloid beta(25-35) (Aβ(25-35))-induced learning and memory impairments in mice. Mice received a single intracerebroventricular (i.c.v.) injection of Aβ(25-35) 6 nmol as the critical factor in Alzheimers disease (AD), cognition was evaluated using Y-maze, passive avoidance, and Morris water maze tests. EUE significantly improved the Aβ(25-35)-induced memory deficit in the Y-maze test. Also, EUE increased step-through latency time with Aβ(25-35)-induced learning and memory deficits in the passive avoidance test. In addition, EUE decreased the escape latencies with Aβ(25-35)-induced cognitive impairments in the Morris water maze test. In the probe trial session, EUE increased time spent in the target quadrant. In the in vitro study, EUE was found to inhibit acetylcholinesterase (AChE) activity in a dose-dependent manner (IC50 value; 172 μg/ml). Ex vivo study, EUE significantly inhibited AChE activity in the hippocampus and frontal cortex. These results demonstrate that EUE possesses potent neuroprotective effects and that its beneficial effects are mediated, in part, by AChE inhibition, and therefore, might be a potential candidate in neurodegenerative diseases such as AD.

Lonicera japonica THUNB. protects 6-hydroxydopamine-induced neurotoxicity by inhibiting activation of MAPKs, PI3K/Akt, and NF-κB in SH-SY5Y cells.

In this study, we investigated the neuroprotective effects of Lonicera japonica THUNB. extract (LJ) on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in SH-SY5Y cells. We found that LJ significantly increased cell viability decrease, lactate dehydrogenase release (LDH), morphological changes, nuclear condensation, fragmentation, and reactive oxygen species (ROS) production induced by 6-OHDA in SH-SY5Y cells. The cytoprotection afforded by pretreatment with LJ was associated with increases of the glutathione (GSH) level, superoxide dismutase (SOD) activity, and catalase (CAT) activity in 6-OHDA-induced SH-SY5Y cells. In addition, LJ strikingly inhibited 6-OHDA-induced mitochondrial dysfunctions including reduction of mitochondria membrane potential (MMP) and activation of cleaved poly-ADP-ribose polymerase (PARP), cleaved caspase-3, cleaved caspase-9, increased Bax, as well as decreased Bcl-2 and Bcl-xL. Additionally, LJ dramatically attenuated 6-OHDA-induced phosphorylation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 (ERK 1/2), and phosphoinositide 3-kinase (PI3K)/Akt. Meanwhile, LJ counteracted nuclear factor-κB (NF-κB) activation by blocking its translocation to the nucleus. These findings suggest that LJ has a potent anti-parkinsonism; this effect was mediated, at least in part, by inhibition of neurotoxicity, apoptotic cascade events, and oxidative stress via activation of MAPKs, PI3K/Akt, and NF-κB.

Eucommia ulmoides Oliv. bark. attenuates 6-hydroxydopamine-induced neuronal cell death through inhibition of oxidative stress in SH-SY5Y cells.

ETHNOPHARMACOLOGICAL RELEVANCE Eucommia ulmoides Oliv. Bark. (EUE) has commonly been used to fortify the muscles and lungs, lower blood pressure, prevent miscarriage, improve liver and kidney tone, and promote longevity as a traditional tonic medicine in Korea, China, and Japan. AIM OF THE STUDY In this study, we investigated the mechanisms by which EUE protects neuronal cells from apoptosis induced by the Parkinsons disease (PD)-related neurotoxin, 6-hydroxydopamine (6-OHDA). MATERIALS AND METHODS We determined the neuroprotective effects of EUE on 6-OHDA-induced neuronal cell death, cytotoxicity, reactive oxygen species (ROS) production, and mitochondrial membrane dysfunction. Moreover, we examined whether EUE suppressed phosphorylation of c-Jun N-terminal kinase (JNK), phosphatidylinositol 3-kinase (PI3K)/Akt, and glycogen synthase kinase-3 beta (GSK-3β). Furthermore, the neuroprotective effects of EUE on 6-OHDA-induced activation of nuclear factor-kappa B (NF-κB) was studied in SH-SY5Y cells. RESULTS Pretreatment of SH-SY5Y cells with EUE significantly reduced 6-OHDA-induced cell death and cytotoxicity. EUE inhibited 6-OHDA-induced generation of ROS, which conferred cytoprotection against 6-OHDA-induced oxidative injury. EUE treatment also strikingly inhibited 6-OHDA-induced mitochondrial dysfunction. In addition, EUE suppressed phosphorylation of JNK, PI3K/Akt, and GSK-3β. Furthermore, EUE blocked 6-OHDA-induced NF-κB nuclear translocation, an event downstream from JNK, PI3K/Akt, and GSK-3β phosphorylation. Moreover, chlorogenic acid (CGA), one of the active constituents of EUE, was also able to reduce 6-OHDA-induced toxicity in SH-SY5Y cells. CONCLUSION Taken together, these results suggest that EUE attenuates oxidative stress through activation of JNK, PI3K/Akt, GSK-3β, and NF-κB pathways, thereby protecting cells from neuronal cell death.

Strain differences in the chronic mild stress animal model of depression and anxiety in mice.

Chronic mild stress (CMS) has been reported to induce an anhedonic-like state in mice that resembles some of the symptoms of human depression. In the present study, we used a chronic mild stress animal model of depression and anxiety to examine the responses of two strains of mice that have different behavioral responsiveness. An outbred ICR and an inbred C57BL/6 strain of mice were selected because they are widely used strains in behavioral tests. The results showed that the inbred C57BL/6 and outbred ICR mice were similarly responsive to CMS treatment in sucrose intake test (SIT) and open field test (OFT). However, the two strains showed quite different responses in forced swimming test (FST) and novelty-suppressed feeding (NSF) test after 3 weeks of CMS treatment. Only C57BL/6 mice displayed the depression- and anxiety-like behavioral effects in response to CMS treatment in FST and NSF test. Our results suggest that there are differences in responsiveness to CMS according to the different types of strain of mice and behavioral tests. Therefore, these results provide useful information for the selection of appropriate behavioral methods to test depression- and anxiety-like behaviors using CMS in ICR and C57BL/6 mice.

Transient receptor potential vanilloid type 1 channel may modulate opioid reward.

Transient receptor potential vanilloid type 1 (TRPV1), a nonselective cation channel, is a well-known pain-related receptor. TRPV1 involvement in morphine-induced antinociception, tolerance, and withdrawal symptoms has been previously reported. Emerging evidence indicates that TRPV1 may be related to both the cellular and behavioral effects of addictive drugs. In the present study, we investigated the role of TRPV1 in morphine reward using the conditioned place preference (CPP) paradigm in mice. Repeated morphine treatments upregulated TRPV1 expression in the dorsal striatum (DSt). Treatment with a TRPV1 agonist potentiated morphine reward, and pretreatment with TRPV1 antagonists attenuated these effects. Microinjection of a selective TRPV1 antagonist into the DSt significantly inhibited morphine-CPP. In addition, treatment with a TRPV1 antagonist suppressed morphine-induced increases in μ-opioid receptor binding, adenylyl cyclase 1 (AC1), p38 mitogen-activated protein kinase (p38 MAPK), and nuclear factor kappa B (NF-κB) expression in the DSt. Administering a p38 inhibitor not only prevented morphine-CPP, but also prevented morphine-induced NF-κB and TRPV1 activation in the DSt. Furthermore, injecting an NF-κB inhibitor significantly blocked morphine-CPP. Our findings suggest that TRPV1 in the DSt contribute to morphine reward via AC1, p38 MAPK, and NF-κB. Brain TRPV1 may serve as a novel therapeutic target to treat morphine-addictive disorders.

Anxiolytic effects of Julibroside C1 isolated from Albizzia julibrissin in mice.

Julibroside C1 is a saponin-containing compound isolated from Albizzia julibrissin Durazz. In this study, we investigated the putative anxiolytic effects of Julibroside C1 using the elevated plus maze (EPM) in mice. Julibroside C1 at doses of 0.5 and 1 mg/kg significantly increased the time spent in the open arms and the number of entries into the open arms of the EPM compared to the control group. Moreover, the anxiolytic-like effects of Julibroside C1 (0.5 mg/kg) were blocked by WAY-100635 (5-HT1A receptor antagonist), bicuculline (GABA(A) receptor antagonist), and flumazenil (antagonist of the GABA(A) receptor benzodiazepine site). However, Julibroside C1 did not change locomotor activity or induce myorelaxant effects. We used quantitative receptor autoradiography to investigate the effects of Julibroside C1 on alterations in mouse brain receptors. After acute treatment with Julibroside C1 (0.5 mg/kg), [(3)H]-8-OH-DPAT binding was significantly decreased in the CA1 region of the hippocampus and [(3)H]-flunitrazepam binding was decreased remarkably in the cingulate cortex region. However, [(3)H]-muscimol binding did not show a significant change in any brain region. Taken together, our findings suggest that Julibroside C1 shows anxiolytic-like effects, which might be mediated by the 5-HT1A and GABA(A)-benzodiazepine receptor systems.

Dependence Potential of Propofol: Behavioral Pharmacology in Rodents

Tramadol is an opioid analgesic agent that has been the subject of a series of case reports suggesting potential for misuse or abuse. However, it is not a controlled substance and is not generally considered addictive in Korea. In this study, we examined the dependence potential and abuse liability of tramadol as well as its effect on the dopaminergic and serotonergic systems in rodents. In animal behavioral tests, tramadol did not show any positive effects on the experimental animals in climbing, jumping, and head twitch tests. However, in the conditioned place preference and self-administration tests, the experimental animals showed significant positive responses. Taken together, tramadol affected the neurological systems related to abuse liability and has the potential to lead psychological dependence.