Sung-Oh Huh

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.

Srg3, a Mouse Homolog of Yeast SWI3, Is Essential for Early Embryogenesis and Involved in Brain Development

ABSTRACT Srg3 (SWI3-related gene product) is a mouse homolog of yeast SWI3,Drosophila melanogaster MOIRA (also named MOR/BAP155), and human BAF155 and is known as a core subunit of SWI/SNF complex. This complex is involved in the chromatin remodeling required for the regulation of transcriptional processes associated with development, cellular differentiation, and proliferation. We generated mice with a null mutation in theSrg3 locus to examine its function in vivo. Homozygous mutants develop in the early implantation stage but undergo rapid degeneration thereafter. An in vitro outgrowth study revealed that mutant blastocysts hatch, adhere, and form a layer of trophoblast giant cells, but the inner cell mass degenerates after prolonged culture. Interestingly, about 20% of heterozygous mutant embryos display defects in brain development with abnormal organization of the brain, a condition known as exencephaly. Histological examination suggests that exencephaly is caused by the failure in neural fold elevation, resulting in severe brain malformation. Our findings demonstrate that Srg3 is essential for early embryogenesis and plays an important role in the brain development of mice.

Behavioral and Neuropathologic Changes Induced by Central Injection of Carboxyl-Terminal Fragment of β-Amyloid Precursor Protein in Mice

Abstract: Expression of the carboxyl‐terminal fragment (CT) of the β‐amyloid precursor protein (APP) in transgenic animals has been linked with neurotoxicity. However, it remains to be clarified whether the neurotoxicity is caused by β‐amyloid proteins (Aβs) derived from CT or by CT itself. To study the in vivo neurotoxicity of CT, mice were given a single intracerebroventricular injection of a recombinant 105‐amino acid CT (CT105; 68.5–685 pmol, intracerebroventricularly), and changes in behavior and in brain histology were examined. Animals given CT105 (410 or 685 pmol, intracerebroventricularly) showed a dose‐dependent impairment in the passive avoidance performance, whereas boiled CT105 had no effect. CT105 (685 pmol, intracerebroventricularly) induced reactive gliosis in neocortex and hippocampus and neurodegeneration in neocortex. These results indicate that centrally administered CT105 induces behavioral impairment and neuropathologic changes, suggesting a direct toxic effect of CT105 per se.

SIRT1 regulates tyrosine hydroxylase expression and differentiation of neuroblastoma cells via FOXO3a

To examine the function of SIRT1 in neuronal differentiation, we employed all‐trans retinoic acid (ATRA)‐induced differentiation of neuroblastoma cells. Nicotinamide inhibited neurite outgrowth and tyrosine hydroxylase (TH) expression. Inhibition of PARP or histone deacetylase did not inhibit TH expression, showing the effect to be SIRT1 specific. Expression of FOXO3a and its target proteins were increased during the differentiation and reduced by nicotinamide. FOXO3a deacetylation was increased by ATRA and blocked by nicotinamide. SIRT1 and FOXO3a siRNA inhibited ATRA‐induced up‐regulation of TH and differentiation. Taken together, these results indicate that SIRT1 is involved in ATRA‐induced differentiation of neuroblastoma cells via FOXO3a.

Effects of histamine receptor antagonists injected intrathecally on antinociception induced by opioids administered intracerebroventricularly in the mouse.

The present study was designed to investigate the modulatory effects of blockade of spinal histamine receptors on antinociception induced by supraspinally administered mu-epsilon-, delta-, and kappa-opioid receptor agonists. The effects of intrathecal (i.t.) injections with cyproheptadine [a histamine-1 (H1) receptor antagonist], ranitidine (a H2 receptor antagonist), or thioperamide (a H3 receptor antagonist) injected i.t., on the antinociception induced by morphine (a mu-receptor antagonist), beta-endorphin (an epsilon-receptor agonist), D-Pen(2,5)-enkephalin (DPDPE, a delta-receptor agonist) or trans-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohxyl] benzeocetamide (U50,488H, a kappa-receptor agonist) injected intracerebroventricularly (i.c.v.) were studied. The antinociception was assayed using the tail-flick test. The i.t. injection of cyproheptadine (from 0.31 to 62 nmole), ranitidine (from 0.28 to 56 nmole), or thioperamide (from 0.24 to 48 nmole) alone did not show any antinociceptive effect. The i.t. pretreatment with cyproheptadine or thioperamide dose-dependently attenuated the inhibition of the tail-flick response induced by i.c.v. administered morphine (0.6 nmole), b-endorphin (0.03 nmole), DPDPE (1.5 nmole), and U50,488H (130 nmole). In addition, the i.t. pretreatment with ranitidine dose-dependently attenuated the inhibition of the tail-flick response induced by morphine, b-endorphin and U50,488H without affecting DPDPE-induced response. Our results suggest that spinal histamine H1 and H3 receptors may involved in the production of antinociception induced by supraspinally applied morphine, b-endorphin, DPDPE and U50,488H. Spinal H2 receptors appear to be involved in supraspinally administered morphine, b-endorphin- and U50,488H-induced antinociception but not DPDPE-induced antinociception.

Lysophosphatidic acid stimulates CREB through mitogen- and stress-activated protein kinase-1.

Lysophosphatidic acid (LPA) is a growth factor-like phospholipid that elicits a variety of cellular responses in numerous cell types, including neurons, immune cells, and fibroblasts. In this report, we investigated the possibility that LPA activates the transcription factor cAMP response element-binding protein, CREB, in Rat-2 fibroblast cells. CREB is activated in many cells downstream of signaling events, such as growth factor and neurotrophin stimulation. We found that LPA rapidly stimulated phosphorylation of CREB at Ser133 in a time- and dose-dependent manner, as revealed by immunoblot analysis with a phospho-specific antibody recognizing CREB on Ser133. LPA-induced phosphorylation of CREB was dependent on the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK). Inhibition of ERK1/2 with PD98059 and of p38 MAPK with SB203580 efficiently blocked LPA-mediated phosphorylation of CREB. The LPA-induced CREB phosphorylation was abolished by H89, an inhibitor of mitogen- and stress-activated protein kinase-1 (MSK1). Together, these data suggest that LPA stimulates nuclear transcription factor CREB via mitogen-activated protein kinase signaling components, ERK1/2, p38 MAPK, and MSK1 in Rat-2 fibroblast cells.

Differential involvement of central and peripheral norepinephrine in the central lipopolysaccharide-induced interleukin-6 responses in mice.

Abstract: Intracerebroventricular injection of lipopolysaccharide (LPS) induces a marked increase in circulating interleukin (IL)‐6 levels and in IL‐6 mRNA expression in brain and peripheral organs. Recently, it was reported that intraperitoneal administration of α‐adrenoceptor antagonists inhibits centrally injected LPS‐induced increases in plasma IL‐6 levels, suggesting the involvement of the norepinephrine (NE) system in the central LPS‐induced IL‐6 response. However, the localization (either central or peripheral) of NE involvement in the central LPS‐induced IL‐6 response has not been characterized. In the present study, mice were pretreated with 6‐hydroxydopamine (6‐OHDA) administered intracerebroventricularly or intraperitoneally to deplete central or peripheral stores of NE, respectively. Intracerebroventricular LPS (50 ng/mouse) markedly increased plasma IL‐6 levels and IL‐6 mRNA expression in choroid plexus, hypothalamus, pituitary, adrenals, heart, liver, spleen, and lymph nodes, but with minimal effect in lung, kidney, and testis, as revealed by RT‐PCR. Pretreatment, with intracerebroventricular 6‐OHDA (50 μg/mouse) decreased the LPS‐induced plasma IL‐6 levels by 39% and the LPS‐induced IL‐6 mRNA expression in liver, spleen, and lymph nodes, but not in choroid plexus, hypothalamus, pituitary, adrenals, and heart. Pretreatment with intraperitoneal 6‐OHDA (100 mg/kg) decreased the LPS‐induced plasma IL‐6 levels by 36% and the LPS‐induced IL‐6 mRNA expression in all the peripheral organs displaying increased IL‐6 mRNA. Central LPS‐induced increase in plasma corticosterone levels was decreased slightly by central but not by peripheral NE depletion. These results suggest that central NE and peripheral NE are differentially involved in the central LPS‐induced IL‐6 mRNA expression in peripheral organs.

Antinociceptive mechanisms of Dipsacus saponin C administered intrathecally in mice.

Dipsacus saponin C (DSC) administered intrathecally (i.t.) showed antinociceptive effect in a dose-dependent (from 3.75 to 30 microg) manner as measured by the tail-flick assay. The antinociception induced by DSC at the dose of 30 microg reached at peak 7.5 min and almost returned to the control level after 60 min. 5-Amino-valeric acid (5-AVA, a GABA(A) receptor antagonist, from 1 to 20 microg) and SR 95531 (a GABA(B) receptor antagonist, from 0.1 to 2 ng) dose-dependently attenuated i.t. administered DSC-induced increase of the inhibition of the tail-flick response. The i.t. injection of yohimbine (an alpha(2)-adrenergic receptor antagonist, from 1 to 20 microg) and methysergide (a serotonin receptor antagonist, from 1 to 20 microg), but not naloxone (from 2 to 8 microg), significantly attenuated inhibition of the tail-flick response induced by DSC (30 microg) administered i.t. Sulfated cholecystokinin (CCK, from 0.05 to 0.5 ng) injected i.t. significantly reduced the inhibition of the tail-flick response induced by DSC (30 microg) administered i.t. Our results suggest that DSC shows an antinociceptive effect when it is administered spinally and GABA(A), GABA(B), alpha(2)-adrenergic and serotonin receptors located at the spinal cord level, but not opioid receptors, may be involved in DSC-induced antinociception. Furthermore, CCK may play an important role for the modulation of i. t. injected DSC-induced antinociception.

Central injection of nicotine increases hepatic and splenic interleukin 6 (IL-6) mRNA expression and plasma IL-6 levels in mice: involvement of the peripheral sympathetic nervous system

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. Nicotine, one of the major drugs abused by humans, has been shown to affect immunological functions. In the present study, effects of intracere‐broventricular (i.c.v.) injection of nicotine on plasma IL‐6 levels were investigated in mice. Nicotine administered i.c.v. dose‐dependently increased plasma IL‐6 levels; the lowest effective dose was 0.3 ng/mouse and the maximal effect was attained with the dose of 105 ng/mouse. The nicotine (105 ng/mouse, i.c.v.)‐induced plasma IL‐6 levels peaked at 3 h and approached basal levels 6 h after injection. Mecamylamine, a nicotinic receptor antagonist, blocked nicotine‐induced plasma IL‐6 levels. Depletion of peripheral norepinephrine with 6‐hydroxydo‐pamine [100 mg/kg, intraperitoneal (i.p.)] inhibited the nicotine‐induced plasma IL‐6 levels by 57%, whereas central norepinephrine depletion with 6‐hydroxydopamine (50 µg/mouse, i.c.v.) had no effect. Pretreatment with prazosin (α1‐adrenergic antagonist; 1 mg/kg, i.p.), yohimbine (α2‐adrenergic antagonist; 1 mg/kg, i.p.), and ICI‐118,551 (β2‐adrenergic antagonist; 2 mg/kg, i.p.), but not with betaxolol (β1‐adrenergic antagonist; 2 mg/kg, i.p.), inhibited nicotine‐induced plasma IL‐6 levels. Among the peripheral organs, including the pituitary, adrenals, heart, lung, liver, spleen, and lymph nodes, nicotine (105 ng/mouse, i.c.v.) increased IL‐6 mRNA expression only in the liver and spleen, which was inhibited by peripheral norepinephrine depletion. These results suggest that stimulation of central nicotinic receptors induces plasma IL‐6 levels and IL‐6 mRNA expression in the liver and spleen via the peripheral sympathetic nervous system, α1‐, α2‐, and β2‐adreno‐receptors being involved.—Song, D.‐K., Im, Y.‐B., Jung, J.‐S., Suh, H.‐W., Huh, S.‐O., Song, J.‐H., Kim, Y.‐H. Central injection of nicotine increases hepatic and splenic interleukin 6 (IL‐6) mRNA expression and plasma IL‐6 levels in mice: involvement of the peripheral sympathetic nervous system. FASEB J. 13, 1259–1267 (1999)