Posted by michael derrida on October 05, 19103 at 23:40:39:
In Reply to: ALERT - ANTHRAX ----- Klingerman (Physical) posted by Public Info on October 01, 19103 at 14:21:07:
Trans-Resveratrol Protects Embryonic Mesencephalic Cells from
tert-Butyl Hydroperoxide:
Abstract:
In recent years, the antioxidant and other pharmacological properties of resvera
trol, a natural product present in grapes and wine, have attracted considerable i
nterest from the biomedical research community.
In an examination of the potential neuroprotective properties of the compound, w
e have investigated the ability of resveratrol to protect rat embryonic mesenceph
alic tissue,rich in opaminergic neurones, from the prooxidant tertbutyl hydropero
xide.
Using the electron paramagnetic resonance (EPR) spin-trapping technique, the mai
n radicals detected in cell suspensions were the tert-butoxyl
radical and the methyl radical, indicating the one-electron reduction of the per
oxide followed by a b-scission reaction.
The appearance of EPR signals from the trapped radicals preceded the onset of cy
totoxicity, which was almost exclusively necrotic in nature.
The inclusion of resveratrol in incubations resulted in the marked protection of
cells from tert-butyl hydroperoxide. In parallel spin-trapping experiments, we w
ere able to demonstrate the scavenging of radicals by resveratrol, which involved
direct competition between resveratrol and the spin trap for reaction with the r
adicals.
To our knowledge, this is the first example in which cytoprotection by resveratr
ol has been demonstrated by EPR spin-trapping competitionkinetics to be due to it
s scavenging of the radicals responsible for the toxicity of a prooxidant.
Discussion:
Free radicals have been implicated in the aetiology of several neurodegenerative
disorders, including Parkinson¡¯s disease . Radicals may also participate in pro
cesses responsible for the poor survival of embryonic brain tissue grafts, which
are currently being assessed as a therapy for Parkinson¡¯s disease.
Resveratrol, a naturally occurring component of red wine and grapes (Soleas et a
l., 1997), is a polyphenolic compound and may therefore act as a radical-scavengi
ng antioxidant via its chemical repair free radicals (reaction 5, in which Res-(O
H)3 represents resveratrol):Res-~OH!3 1 R• 3 Res-~OH!2O• 1 RH (5)
The unpaired electron of the resveratrol phenoxyl radical [Res-(OH)2O•] is
expected to be delocalized extensively over its two aromotic rings, resulting in
poor reactivity, which is a requirement for the effective inhibition of free-rad
ical chain reactions, such as lipid peroxidation.
Indeed, Chanvitayapongs et al. (1997) have reported recently that resveratrol ca
n protect PC12 cells from oxidative stress induced by TBHP and the Fe(II) complex
of DTPA. These authors suggested that TBHP is reduced to alkoxyl radicals by Fe(
II), as described here in the cell-free system (see Fig. 10). Although Chanvitaya
pongs et al. (1997) reported a decreased rate of TBHP-induced thiobarbituric acid
-reactive substance formation in the presence of resveratrol, no direct evidence
for radical scavenging (reaction 5) was presented.
As resveratrol has been reported to display diverse pharmacological properties (
Pace-Asciak et al., 1995; Belguendouz et al., 1997; Chanvitayapongs et al., 1997;
Jang et al., 1999; MacCarrone et al., 1999; Miloso et al., 1999;Stewart et al.,
1999; Tsai et al., 1999), we considered it timely to seek more direct evidence fo
r its radical-scavenging properties in a cellular system.
Our findings show that free-radical formation can be detected in mesencephalic c
ells at concentrations of TBHP that are well within the dose necessary to induce
cytotoxicity, as indicated by LDH leakage. Indeed, although incubation of cells f
or 1 h with 0.1 mM TBHP failed to induce a statistically significant level of LDH
leakage, a significant level of free-radical formation could be detected (Figs.
1 and 6, respectively).
In the time-course studies using TBHP at a concentration of 0.5 mM, significant
LDH leakage could not be detected before 45 min of incubation, whereas radical fo
rmation was detectable after only 15 min and maximal at 30 min (Figs. 2A and 7).
In considering the possibility that the exposed cells might be undergoing apoptos
is, and therefore that LDH leakage occurs as a late response (secondarynecrosis),
cells were costained with fluorescent dyes to allow analysis for both necrosis a
nd apoptosis.
As only very low (statistically insignificant) numbers of cells were found to ha
ve undergone apoptosis, and essentially none of the cells that did display apopto
tic nuclear morphology were positive for ethidium homodimer-1 uptake, it is clear
that the primary mechanism of TBHP-induced cell death under the conditions repor
ted here is necrosis and that this necrosis is not secondary to apoptosis.
Despite the time delay between the detection of radicals and the onset of necros
is seen in this study, it can always be argued that earlier markers of necrosis m
ight reveal cellular changes that precede radical detection. However,no matter ho
w early the marker of cell death used, it can also always be argued that radicals
are causing these changes at concentrations that are below the detection limit o
f EPR spin trapping (or indeed other, less definitive methods).
With this in mind, we consider our demonstration
that the interception of TBHP-derived radicals with the spin trap DMPO results i
n the suppression of toxicity to be extremely convincing, supportive evidence tha
t the observed radicals are indeed responsible for cytotoxicity.
Resveratrol was found to be highly protective against TBHP-induced cytotoxicity.
However, at the concentrations that were protective in the LDH-release experimen
ts, no decrease in the intensities of the EPR signals from the corresponding DMPO
-trapped radicals (primarily•CH3) was apparent. Only at much higher concent
rations was resveratrol found to suppress the EPR signal intensities.
We suggest that, rather than indicating that radical scavenging is not responsib
le for the protective effect of resveratrol, this behaviour reflects the occurren
ce of radical-scavenging competition kinetics, as reproduced in the cell-free sys
tem. It can be shown that, in a system in which the •CH3 radical can react
with either DMPO or a scavenger, the concentration of the DMPO/•CH3 adduct
is affected according to the following relationship:
in which [DMPO/•CH3]o is the concentration of DMPO/•CH3 observed in
the absence of the scavenger, [DMPO/ •CH3]s is the concentration of DMPO/&#
8226;CH3 observed in the presence of the scavenger, and kDMPO and ks are the seco
nd-order rate constants for the reaction of methyl radicals with DMPO and the sca
venger, respectively.
Using this equation, it can be shown that to achieve a 71% reduction in the conc
entration of DMPO/•CH3 due to methyl-radical scavenging by resveratrol at a
concentration of 50 mM (which gave 71% cytoprotection; see Fig. 8), in the prese
nce of 91 mM DMPO (used in the experiments shown in Figs. 4¨C7 and 9A and A9), re
sveratrol would have to react with the methyl radical at a rate constant of ;6.4
3 1010 M21 s21, which is greater than the diffusion-controlled limit and therefor
e impossible [kDMPO is 1.4 3 107 M21 s21 (Taniguchi and Madden, 1999)].
Even at a concentration of 1 mM,resveratrol would have to react with the methyl
radical with a rate constant of 3.2 3 109 M21 s21 to cause a 71%
decrease in the concentration of the DMPO/•CH3 in the presence of 91 mM DM
PO (i.e., under the conditions used in Fig. 9A and A9). From an analysis of the s
pectra obtained from the cell-free system, using 20 mM DMPO and 4 mM resveratrol
(Fig. 10B and B9), we have calculated (to a first approximation) that the rate co
nstant for the scavenging of the methyl radical by resveratrol is 8.9 3 107 M21 s
21, i.e., the radical is scavenged by resveratrol approximately six times faster
than it is trapped by DMPO. Thus, it is perfectly reasonable that the concentrati
on of DMPO radical adducts observed is suppressible by resveratrol only at the hi
gher [resveratrol]/[DMPO] values.
Therefore, that in this system resveratrol behaves as a competitive, radicalscav
engingantioxidant.
As, by definition, spin traps are radical scavengers,forming poorly reactive rad
ical adducts upon their interception of more reactive radicals, they should also
behave as protective antioxidants in systems in which radicals are responsible fo
r cytotoxicity. Our demonstration that DMPO protects mesencephalic cells from TBH
P, at the same concentration at which it was used to generate and observe radical
adducts, supports our second conclusion that the radicals reported in this study
are responsible for the toxicity of TBHP toward these cells.
To our knowledge, this is the first example in which cytoprotection by resveratr
ol has been demonstrated by EPR spintrapping competition kinetics to be due to it
s scavenging of the radicals responsible for the toxicity of a prooxi-of resverat
rol, including its recently reported inhibition of lipoxygenase, cyclooxygenase,
and protein kinase C activities and activation of extracellular signal-regulated
kinases 1 and 2 ,are also of biological significance,but clearly, in our system,
the ability of the antioxidant to scavenge free radicals appears to be the primar
y mechanism of protection.
The paradigm of using EPR to monitor TBHP-induced radical formation in embryonic
mesencephalic cells may also prove to be a powerful, novel approach for screenin
g other treatments to reduce oxidative stress in nigral transplant tissue.
and
where to source trans-resveratrol?
-----***----****----****--------------------------------------
Super Function of Trans-resveratrol as Polygonum Cuspldatum P.E.?
¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó¡ó
[Description]:Polygonum Cuspldatum P.E. Trans-resveratrol;
[Botanical Source]:Polygonum cuspidatum£¨Polygonum cuspidatum sieb. et zucc;
[Botanical Synoms]:the weed Polygon urn cuspidaturn(Polygonum Cuspldatum P.E.
);Polygonurn cuspidaturn, known as Hu-Chang and Ko-jo-kon;the roots of Polygonur
n
cuspidaturn Sieb. et Zucc.;Polygonurn multiflorurn Thumb.
[Plant Part Used]:root & stem
[Chemical Name]: 3,5,4'-trihydroxy-trans-stilbene
[Formula / M.W.]: C14H12O3/228.2
[Cas Number]: [510-36-0]
[Solubility]:Solublein diethyl ether, Chloroform,Alcohol ,Acetone, Etc.
Resveratrol is an active component extracted from Huzhang(Polygonum cuspidatu
m)
for more details, just check as following url or contact with directly:
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Polygonum Cuspldatum P.E. Trans-resveratrol98%HPLC
Polygonum Cuspldatum P.E. Trans-resveratrol95%HPLC
Polygonum Cuspldatum P.E. Trans-resveratrol90%HPLC
Polygonum Cuspldatum P.E. Trans-resveratrol50%HPLC
=======================================================
we are most famous processor of RosA,JUST contact with or check as following:
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any interesting, just transfer an email simply and we would be happy more than j
ust help.
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MDidea Group
Charger:Derrida Michael
Par e-mail derrida@vip.163.com
website; http://www.mdidea.com
-----------------------------------------------------
Reference
*trans-Resveratrol Protects Embryonic Mesencephalic Cells from
tert-Butyl Hydroperoxide: Electron Paramagnetic Resonance
Spin Trapping Evidence for a Radical Scavenging Mechanism
Jenny Karlsson, Mia Emgård, Patrik Brundin, and *Mark J. Burkitt
Section for Neuronal Survival, Wallenberg Neuroscience Center, Department of Phy
siological Sciences, Lund University, Lund,Sweden; and *Gray Laboratory Cancer Re
search Trust, Mount Vernon Hospital, Northwood, Middlesex, England
*Super Function of Trans-resveratrol as Polygonum Cuspldatum P.E.? BY Mich
ael Derrida(Pulished by Webbranch MDidea,May,2002)
[Amanuensis&Symbol trace Calligrapher: Michael Derrida]
-----------------------------------------------------
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