Ji-Jing Yan

Protection against β‐amyloid peptide toxicity in vivo with long‐term administration of ferulic acid

β‐Amyloid peptide (Aβ), a 39 – 43 amino acid peptide, is believed to induce oxidative stress and inflammation in the brain, which are postulated to play important roles in the pathogenesis of Alzheimers disease. Ferulic acid is an antioxidant and anti‐inflammatory agent derived from plants; therefore, the potential protective activity of ferulic acid against Aβ toxicity in vivo was examined. Mice were allowed free access to drinking water (control) or water containing ferulic acid (0.006%). After 4 weeks, Aβ1‐42 (410 pmol) was administered via intracerebroventricular injection. Injection of control mice with Aβ1‐42 impaired performance on the passive avoidance test (35% decrease in step‐through latency), the Y‐maze test (19% decrease in alternation behaviour), and the water maze test (32% decrease in percentage time in platform‐quadrant). In contrast, mice treated with ferulic acid prior to Aβ1‐42 administration were protected from these changes (9% decrease in step‐through latency; no decrease in alternation behaviour; 14% decrease in percentage time in platform‐quadrant). Aβ1‐42 induced 31% decrease in acetylcholine level in the cortex, which was tended to be ameliorated by ferulic acid. In addition, Aβ1‐42 increased immunoreactivities of the astrocyte marker glial fibrillary acidic protein (GFAP) and interleukin‐1β (IL‐1β) in the hippocampus, effects also suppressed by pretreatment with ferulic acid. Administration of ferulic acid per se unexpectedly induced a transient and slight increase in GFAP and IL‐1β immunoreactivity in the hippocampus on day 14, which returned to basal levels on day 28. A slight (8%) decrease in alternation behaviour was observed on day 14. These results demonstrate that long‐term administration of ferulic acid induces resistance to Aβ1‐42 toxicity in the brain, and suggest that ferulic acid may be a useful chemopreventive agent against Alzheimers disease.

Therapeutic effects of lysophosphatidylcholine in experimental sepsis.

Sepsis represents a major cause of death in intensive care units. Here we show that administration of lysophosphatidylcholine (LPC), an endogenous lysophospholipid, protected mice against lethality after cecal ligation and puncture (CLP) or intraperitoneal injection of Escherichia coli. In vivo treatment with LPC markedly enhanced clearance of intraperitoneal bacteria and blocked CLP-induced deactivation of neutrophils. In vitro, LPC increased bactericidal activity of neutrophils, but not macrophages, by enhancing H2O2 production in neutrophils that ingested E. coli. Incubation with an antibody to the LPC receptor, G2A, inhibited LPC-induced protection from CLP lethality and inhibited the effects of LPC in neutrophils. G2A-specific antibody also blocked the inhibitory effects of LPC on certain actions of lipopolysaccharides (LPS), including lethality and the release of tumor necrosis factor-α (TNF-α) from neutrophils. These results suggest that LPC can effectively prevent and treat sepsis and microbial infections.

Lysophosphatidylcholine as a death effector in the lipoapoptosis of hepatocytes

The pathogenesis of nonalcoholic steatohepatitis (NASH) is unclear, despite epidemiological data implicating FFAs. We studied the pathogenesis of NASH using lipoapoptosis models. Palmitic acid (PA) induced classical apoptosis of hepatocytes. PA-induced lipoapoptosis was inhibited by acyl-CoA synthetase inhibitor but not by ceramide synthesis inhibitors, suggesting that conversion products other than ceramide are involved. Phospholipase A2 (PLA2) inhibitors blocked PA-induced hepatocyte death, suggesting an important role for PLA2 and its product lysophosphatidylcholine (LPC). Small interfering RNA for Ca2+-independent phospholipase A2 (iPLA2) inhibited the lipoapoptosis of hepatocytes. PA increased LPC content, which was reversed by iPLA2 inhibitors. Pertussis toxin or dominant-negative Gαi mutant inhibited hepatocyte death by PA or LPC acting through G-protein-coupled receptor (GPCR)/Gαi. PA decreased cardiolipin content and induced mitochondrial potential loss and cytochrome c translocation. Oleic acid inhibited PA-induced hepatocyte death by diverting PA to triglyceride and decreasing LPC content, suggesting that FFAs lead to steatosis or lipoapoptosis according to the abundance of saturated/unsaturated FFAs. LPC administration induced hepatitis in vivo. LPC content was increased in the liver specimens from NASH patients. These results demonstrate that LPC is a death effector in the lipoapoptosis of hepatocytes and suggest potential therapeutic values of PLA2 inhibitors or GPCR/Gαi inhibitors in NASH.

Protection against β-amyloid peptide-induced memory impairment with long-term administration of extract of Angelica gigas or decursinol in mice

We investigated the effect of long-term oral administration of ethanolic extract of Angelica gigas Nakai (Umbelliferae) (EAG) or decursinol, a coumarin isolated from A. gigas, on beta-amyloid peptide 1-42 (Abeta(1-42))-induced memory impairment in mice. Mice were allowed free access to drinking water (control) or water containing different concentrations of EAG. After 4 weeks, Abeta(1-42) (410 pmol) was administered via intracerebroventricular injection. Pretreatment of mice with EAG (0.1%) for 4 weeks significantly blocked the Abeta(1-42)-induced impairment in passive avoidance performance. Next, mice were fed with chow mixed with various doses of decursinol for 4 weeks before intracerebroventricular injection of Abeta(1-42) (410 pmol). Pretreatment of mice with decursinol (0.001%, 0.002%, and 0.004%) for 4 weeks significantly attenuated the Abeta(1-42)-induced impairment in passive avoidance performance. Decursinol (0.004%) also significantly blunted the Abeta(1-42)-induced decrease in alternation behavior (spatial working memory) in the Y-maze test without change in general locomotor activity. These findings suggest that EAG or decursinol may have preventive effect against memory impairment related with Abeta of Alzheimers disease.

Lysophosphatidylcholine, Oxidized Low-Density Lipoprotein and Cardiovascular Disease in Korean Hemodialysis Patients: Analysis at 5 Years of Follow-up

Although oxidized low-density lipoprotein (LDL) and lysophosphatidylcholine (LPC) have been proposed as important mediators of the atherosclerosis, the long-term contribution to the risk of cardiovascular disease (CVD) in hemodialysis patients has not been evaluated. This study investigated the relation between oxidized LDL and LPC levels with long term risk of CVD. Plasma oxidized LDL and LPC levels were determined in 69 Korean hemodialysis patients as a prospective observational study for 5 yr. During the observation period, 18 cardiovascular events (26.1%) occurred including 6 deaths among the hemodialysis patients. The low LPC level group (≤ 254 µM/L, median value) had much more increased risk of CVD compared to the high LPC level group (> 254 µM/L) (P = 0.01). However, serum levels of oxidized LDL were not significantly different between groups with and without CVD. In adjusted Cox analysis, previous CVD, (hazard ratio [HR], 5.68; 95% confidence interval [CI], 1.94-16.63, P = 0.002) and low LPC level (HR, 3.45; 95% CI, 1.04-11.42, P = 0.04) were significant independent risk factors for development of CVD. It is suggested that low LPC, but not oxidized LDL, is associated with increased risk of CVD among a group of Korean hemodialysis patients.

Protective Effect of Decursinol on Mouse Models of Sepsis: Enhancement of Interleukin-10

The effects of decursinol on various models of sepsis were investigated. Intra-peritoneal pretreatment of mice with various doses of decursinol (1~100 mg/kg) effectively suppressed lethality induced in three mouse models of experimental sepsis, i.e., lipopolysaccharide (LPS)/D-galactosamine (GalN), high-dose LPS (20 mg/kg), and cecal ligation and puncture (CLP). Intra-peritoneal pretreatment of mice with decursinol (50 mg/kg) markedly enhanced the LPS/GalN-induced increase of plasma interleukin-10 (IL-10) levels, without affecting plasma TNF-alpha, IL-6 and IL-12 levels. These results suggest that decursinol could be effective for prevention or treatment of sepsis.

Protective effects of a dimeric derivative of ferulic acid in animal models of Alzheimer's disease

Ferulic acid is a compound with potent anti-oxidant and anti-inflammatory activities. We previously reported the protective effects of ferulic acid administration against two animal models of Alzheimers disease (AD): intracerebroventricular (i.c.v.) injection of Aß1-42 in mice and APP/PS1 mutant transgenic mice. In this study using the same AD animal models, we examined the effect of KMS4001, one of dimeric derivatives of ferulic acid. Intragastric pretreatment of mice with KMS4001 (30mg/kg/day) for 5 days significantly attenuated the Aß1-42 (i.c.v.)-induced memory impairment both in passive avoidance test and in Y-maze test. APP/PS1 mutant transgenic mice at KMS4001 doses of 3 and 30mg/kg/day via drinking water showed the significantly enhanced novel-object recognition memory at both 1.5 and 3 months after the start of KMS4001 treatment. Treatment of APP/PS1 mutant transgenic mice with KMS4001 for 3 months at the doses of 3 and 30mg/kg/day markedly decreased Aβ1-40 and Aβ1-42 levels in the frontal cortex. The KMS4001 dose-response relationships for Aβ decrease and for improvement in novel-object recognition test corresponded to each other. Taken together, these results suggest that KMS4001 could be an effective drug candidate against AD.

Central injection of nitric oxide synthase inhibitors increases peripheral interleukin-6 and serum amyloid A: involvement of adrenaline from adrenal medulla

Accumulating evidence suggests that plasma levels of interleukin‐6 (IL‐6), a major cytokine stimulating the synthesis of acute phase proteins, are intimately regulated by the central nervous system (CNS). In the present study, effects of intracerebroventricular (i.c.v) injection of NG‐nitro‐L‐arginine methyl ester (L‐NAME) or 7‐nitroindazole, nitric oxide synthase (NOS) inhibitors, on plasma IL‐6 levels and peripheral IL‐6 mRNA expression were examined in mice. L‐NAME (0.1–2 μg per mouse i.c.v.) and 7‐nitroindazole (0.2–2 μg per mouse i.c.v.) induced a dose‐dependent increase in plasma IL‐6 levels and a subsequent increase in circulating serum amyloid A, a liver acute‐phase protein. In contrast, an intraperitoneal (i.p.) injection of L‐NAME up to the dose of 25 μg per mouse had no effect. Pretreatment with yohimbine (α2‐adrenergic antagonist; 1 mg kg−1 i.p.), or ICI‐118,551 (β2‐adrenergic antagonist; 2 mg kg−1 i.p.), but not with prazosin (α1‐adrenergic antagonist; 1 mg kg−1 i.p.), nor betaxolol (β1‐adrenergic antagonist; 2 mg kg−1 i.p.), significantly inhibited the central L‐NAME‐induced plasma IL‐6 levels. I.c.v. (50 μg per mouse) or i.p. (100 mg kg−1) pretreatment with 6‐hydroxydopamine had no effect on central L‐NAME‐induced plasma IL‐6 levels. However, intrathecal (i.t.) pretreatment with 6‐hydroxydopamine (20 μg per mouse) markedly inhibited central L‐NAME‐induced plasma IL‐6 levels. Both yohimbine (1.5 μg per mouse i.t.) and ICI‐118,551 (1.5 μg per mouse i.t.) were effective in inhibition of central L‐NAME‐induced plasma IL‐6 levels. There was an elevation of base‐line plasma IL‐6 levels in adrenalectomized animals. The adrenalectomy‐enhanced levels were not further increased by central L‐NAME. L‐NAME (2 μg per mouse i.c.v.) induced an increase in IL‐6 mRNA expression in liver, spleen, and lymph node. These results suggest that NOS activity in the brain tonically down‐regulates peripheral IL‐6 by inhibiting adrenaline release from the adrenal medulla.

Increased plasma corticosterone, aggressiveness and brain monoamine changes induced by central injection of pertussis toxin.

The effects of intracerebroventricular (i.c.v.) injection of pertussis toxin, a specific inhibitor of G(i)/G(o) proteins, on plasma corticosterone levels, aggressiveness, and hypothalamic and hippocampal monoamines and their metabolites levels were examined in mice. Plasma corticosterone level was markedly increased at 3 h after pertussis toxin injection (0.03 and 0.2 microg/mouse), peaked at 6 h and was still increased for up to 6 days after injection. Mice injected with pertussis toxin (0.2 microg/mouse) did not show weight gain between day 0 and day 6 after injection. In addition, pertussis toxin (0.2 microg/mouse) induced a progressive increase in aggressiveness, i.e. a decrease in attack latency and an increase in number of attacks, on day 1 and 6 after injection. Brain monoamines and their metabolites levels were changed on day 1 and 6 after pertussis toxin injection (0.2 microg/mouse): in the hypothalamus, levels of dopamine and 3,4-dihydroxyphenylacetic acid were increased, norepinephrine level decreased, and 5-hydroxyindole acetic acid (5-HIAA) level was markedly increased, with no changes in 5-hydroxytryptamine (5-HT) level, whereas in the hippocampus, 5-HT level was significantly decreased, with no changes in 5-HIAA and catecholamines. These results suggest that signal transduction through G(i)/G(o) proteins in the brain is involved in the modulation of hypothalamo-pituitary-adrenal axis, aggressiveness, and monoamine levels in vivo.

Protective effects of Acanthopanax divaricatus extract in mouse models of Alzheimer's disease

BACKGROUND Acanthopanax divaricatus var. albeofructus (ADA) extract has been reported to have anti-oxidant, immunomodulatory, and anti-mutagenic activity. MATERIALS/METHODS We investigated the effects of ADA extract on two mouse models of Alzheimers disease (AD); intracerebroventricular injection of β-amyloid peptide (Aβ) and amyloid precursor protein/presenilin 1 (APP/PS1)-transgenic mice. RESULTS Intra-gastric administration of ADA stem extract (0.25 g/kg, every 12 hrs started from one day prior to injection of Aβ1-42 until evaluation) effectively blocked Aβ1-42-induced impairment in passive avoidance performance, and Aβ1-42-induced increase in immunoreactivities of glial fibrillary acidic protein and interleukin (IL)-1α in the hippocampus. In addition, it alleviated the Aβ1-42-induced decrease in acetylcholine and increase in malondialdehyde levels in the cortex. In APP/PS1-transgenic mice, chronic oral administration of ADA stem extract (0.1 or 0.5 g/kg/day for six months from the age of six to 12 months) resulted in significantly enhanced performance of the novel-object recognition task, and reduced amyloid deposition and IL-1β in the brain. CONCLUSIONS The results of this study suggest that ADA stem extract may be useful for prevention and treatment of AD.