Young Jin Jang

Caffeinated coffee, decaffeinated coffee, and the phenolic phytochemical chlorogenic acid up-regulate NQO1 expression and prevent H2O2-induced apoptosis in primary cortical neurons

Neurodegenerative disorders are strongly associated with oxidative stress, which is induced by reactive oxygen species including hydrogen peroxide (H₂O₂). Epidemiological studies have suggested that coffee may be neuroprotective, but the molecular mechanisms underlying this effect have not been clarified. In this study, we investigated the protective effects of caffeinated coffee, decaffeinated coffee, and the phenolic phytochemical chlorogenic acid (5-O-caffeoylquinic acid), which is present in both caffeinated and decaffeinated coffee, against oxidative neuronal death. H₂O₂-induced apoptotic nuclear condensation in neuronal cells was strongly inhibited by pretreatment with caffeinated coffee, decaffeinated coffee, or chlorogenic acid. Pretreatment with caffeinated coffee, decaffeinated coffee, or chlorogenic acid inhibited the H₂O₂-induced down-regulation of anti-apoptotic proteins Bcl-2 and Bcl-X(L) while blocking H₂O₂-induced pro-apoptotic cleavage of caspase-3 and pro-poly(ADP-ribose) polymerase. We also found that caffeinated coffee, decaffeinated coffee, and chlorogenic acid induced the expression of NADPH:quinine oxidoreductase 1 (NQO1) in neuronal cells, suggesting that these substances protect neurons from H₂O₂-induced apoptosis by up-regulation of this antioxidant enzyme. The neuroprotective efficacy of caffeinated coffee was similar to that of decaffeinated coffee, indicating that active compounds present in both caffeinated and decaffeinated coffee, such as chlorogenic acid, may drive the effects.

Attenuation of oxidative neuronal cell death by coffee phenolic phytochemicals.

Neurodegenerative disorders such as Alzheimers disease (AD) are strongly associated with oxidative stress, which is induced by reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)). Recent studies suggest that moderate coffee consumption may reduce the risk of neurodegenerative diseases such as AD, but the molecular mechanisms underlying this effect remain to be clarified. In this study, we investigated the protective effects of chlorogenic acid (5-O-caffeoylquinic acid; CGA), a major phenolic phytochemical found in instant decaffeinated coffee (IDC), and IDC against oxidative PC12 neuronal cell death. IDC (1 and 5 microg/ml) or CGA (1 and 5 microM) attenuated H(2)O(2)-induced PC12 cell death. H(2)O(2)-induced nuclear condensation and DNA fragmentation were strongly inhibited by pretreatment with IDC or CGA. Pretreatment with IDC or CGA also inhibited the H(2)O(2)-induced cleavage of poly(ADP-ribose) polymerase (PARP), and downregulation of Bcl-X(L) and caspase-3. The accumulation of intracellular ROS in H(2)O(2)-treated PC12 cells was dose-dependently diminished by IDC or CGA. The activation of c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) by H(2)O(2) in PC12 cells was also inhibited by IDC or CGA. Collectively, these results indicate that IDC and CGA protect PC12 cells from H(2)O(2)-induced apoptosis by blocking the accumulation of intracellular ROS and the activation of MAPKs.

Cocoa procyanidins attenuate 4-hydroxynonenal-induced apoptosis of PC12 cells by directly inhibiting mitogen-activated protein kinase kinase 4 activity

Neurodegenerative disorders such as Alzheimers disease (AD) are associated with oxidative stress, and it has been suggested that apoptosis is a crucial pathway in neuronal cell death in AD patients. 4-Hydroxynonenal (HNE), one of the aldehydic products of membrane lipid peroxidation, is reported to be elevated in the brains of AD patients and mediates the induction of neuronal apoptosis in the presence of oxidative stress. In this study, we investigated the HNE-induced apoptosis mechanism and the protective effects of the cocoa procyanidin fraction (CPF) and its major antioxidant procyanidin B2 against the apoptosis induced by HNE in rat pheochromocytoma (PC12) cells. HNE-induced nuclear condensation and increased sub-G1 fraction, both of which are markers of apoptotic cell death, were inhibited by CPF and procyanidin B2. Intracellular reactive oxygen species (ROS) accumulation was attenuated by pretreatment with CPF and procyanidin B2. CPF and procyanidin B2 also prevented HNE-induced poly(ADP-ribose) polymerase cleavage, antiapoptotic protein (Bcl-2 and Bcl-X(L)) down-regulation, and caspase-3 activation. Activation of c-Jun N-terminal protein kinase (JNK) and mitogen-activated protein kinase kinase 4 (MKK4) was attenuated by CPF and procyanidin B2. Moreover, CPF and procyanidin B2 bound directly to MKK4 and inhibited its activity. Data obtained with SP600125, a selective inhibitor of JNK, revealed that JNK is involved in HNE-induced apoptosis through the inhibition of PARP cleavage and caspase-3 activation in PC12 cells. Collectively, these results indicate that CPF and procyanidin B2 protect PC12 cells against HNE-induced apoptosis by blocking MKK4 activity as well as ROS accumulation.

Piceatannol Attenuates 4‐Hydroxynonenal‐Induced Apoptosis of PC12 Cells by Blocking Activation of c‐Jun N‐Terminal Kinase

Alzheimers disease (AD) is an age‐related neurodegenerative disorder in which apoptosis plays a potentially important role. 4‐Hydroxynonenal (HNE) is a major lipid peroxidation product produced by oxidative stress, and its level is elevated in the AD brain. In the present study, piceatannol (but not resveratrol) at the concentration of 20 μmol/L inhibited HNE‐induced PC12 cell death. Treatment with HNE induced nuclear condensation in PC12 cells, and this was attenuated by piceatannol treatment. HNE induced poly(ADP‐ribose) polymerase cleavage and decreased Bcl‐2 expression, with both of these effects being attenuated by piceatannol. Piceatannol also inhibited the phosphorylation of c‐Jun N‐terminal kinase, which is a key regulator of HNE‐induced PC12 cell death. These results indicate that piceatannol has therapeutic potential in the prevention of AD.

Transcription factor Nrf2 suppresses LPS-induced hyperactivation of BV-2 microglial cells

Microglial hyperactivation is a hallmark of neurodegenerative diseases and the suppression of microglial hyperactivation is being investigated as a means to treat inflammation-mediated neurodegenerative disorders. Here we report that transcription factor Nrf2 in BV-2 microglia, which regulates the expression of phase II antioxidant enzyme genes, decreased the levels of LPS-induced inflammatory cytokines and mediators. These anti-inflammatory effects were not due to Nrf2-mediated up-regulation of phase II enzymes, since over-expression of these enzymes failed to suppress LPS-mediated microglial hyperactivation. However, Nrf2 inhibited LPS-derived increases in p38 MAPK phosphorylation and NF-κB activation. This suggests that Nrf2 inhibits microglial hyperactivation by suppressing p38 MAPK and NF-κB signaling pathway.

Decaffeinated coffee prevents scopolamine-induced memory impairment in rats.

INTRODUCTION Several human studies have reported that coffee consumption improves cognitive performance. In the present study, we investigated whether instant decaffeinated coffee also ameliorates cognitive performance and attenuates the detrimental effects of scopolamine on memory. METHODS Memory performance was evaluated in Morris water maze test and passive avoidance test. Instant decaffeinated coffee (p.o.) at 120 or 240 mg/kg in Sprague-Dawley rats, which is equivalent to approximately three or six cups of coffee, respectively, in a 60 kg human, was administered for two weeks. RESULTS Oral gavage administration of instant decaffeinated coffee inhibited scopolamine-induced memory impairment, which was measured by Morris water maze test and passive avoidance test. Instant decaffeinated coffee suppressed scopolamine-mediated elevation of tumor necrosis factor-α (TNF-α) and stimulation of nuclear factor-κB (NF-κB) pathway (i.e., phosphorylation of IκBα and p65) in the rat hippocampus. DISCUSSION These findings suggest that caffeine-free decaffeinated coffee may prevent memory impairment in human through the inhibition of NF-κB activation and subsequent TNF-α production.

Gallic acid induces neuronal cell death through activation of c-Jun N-terminal kinase and downregulation of Bcl-2.

Oxidative stress induced by reactive oxygen species (ROS) is strongly associated with the pathogenesis of various neurodegenerative disorders, including Alzheimers disease. We investigated the possible combined effects of gallic acid and resveratrol, which are major antioxidants present in fruit, including grapes, on PC12 rat pheochromocytoma (PC12) cell death. Gallic acid did not protect against H2O2‐induced PC12 cell death; it reduced the viability of PC12 cells in a dose‐dependent manner. Gallic acid also induced cleavage of poly (ADP‐ribose) polymerase, which is strongly related to apoptosis in neurons. Gallic acid induced the phosphorylation of c‐Jun N‐terminal protein kinase (JNK) and the downregulation of Bcl‐2 in PC12 cells. Treatment of PC12 cells with resveratrol increased their viability in a dose‐dependent manner by blocking the activation of JNK and the downregulation of Bcl‐2. Furthermore, gallic acid led to a progressive reduction in the viability of vector‐transfected PC12 cells, which was delayed in PC12 cells that overexpressed Bcl‐2. The JNK inhibitor SP600125 protected against gallic acid‐induced PC12 cell death. Collectively, these findings suggest that the combined effects of dietary phenolic phytochemicals on oxidative neuronal cell death and antioxidants differ in ROS‐mediated neuronal cell death.

Protective Effects of Red Wine Flavonols on 4‐Hydroxynonenal‐Induced Apoptosis in PC12 Cells

There is accumulating evidence that a moderate consumption of red wine has health benefits, such as the inhibition of neurodegenerative diseases. Although this is generally attributed to resveratrol, the protective mechanisms and the active substance(s) remain unclear. We examined whether and how red wine extract (RWE) and red wine flavonols quercetin and myricetin inhibited 4‐hydroxynonenal (HNE)‐induced apoptosis of rat pheochromocytoma PC12 cells. RWE attenuated HNE‐induced PC12 cell death in a dose‐dependent manner. HNE induced cleavage of poly(ADP‐ribose) polymerase, which is involved in DNA repair in the nucleus, and this was inhibited by RWE treatment. Treatment with RWE also inhibited HNE‐induced nuclear condensation in PC12 cells. Data of 2′,7′‐dichlorofluorescin diacetate showed that RWE protected against apoptosis of PC12 cells by attenuating intracellular reactive oxygen species. The cytoprotective effects on HNE‐induced cell death were stronger for quercetin and myricetin than for resveratrol. HNE‐induced nuclear condensation was attenuated by quercetin and myricetin. These results suggest that the neuroprotective potential of red wine is attributable to flavonols rather than to resveratrol.

Dehydroglyasperin C Suppresses TPA-Induced Cell Transformation Through Direct Inhibition of MKK4 and PI3K

Bioactive natural compounds from plant‐derived sources have received substantial interest due to their potential therapeutic and preventive effects toward various human diseases. Licorice (Glycyrrhiza), a frequently‐used component in traditional oriental medicines, has been incorporated into recipes not only to enhance taste, but also to treat various conditions including inflammation, chronic fatigue syndrome, and even cancer. Dehydroglyasperin C (DGC) is a major isoflavone found in the root of licorice. In the present study, we investigated the cancer chemopreventive effect of DGC and the underlying molecular mechanisms involved, by analyzing its effects on 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA)‐induced neoplastic cell transformation and cyclooxygenase (COX)‐2 expression in JB6 P+ mouse epidermal cells. DGC treatment attenuated TPA‐induced activator protein‐1 (AP‐1) and nuclear factor‐κB (NF‐κB) transcriptional activation, two major regulators of TPA‐induced cell transformation, and COX‐2 expression. TPA‐induced phosphorylation of p38, JNK1/2 and Akt was also suppressed by DGC. Kinase assay data revealed that DGC inhibited the kinase activity of MKK4 and PI3K and this outcome was due to direct physical binding with DGC. Notably, DGC bound directly to MKK4 and PI3K in an ATP‐competitive manner. Taken together, these results suggest that DGC exhibits cancer chemopreventive potential via its inhibitory effect on TPA‐induced neoplastic cell transformation and COX‐2 modulation through regulation of the MKK4 and PI3K pathways.