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Diterpenoids From Germander, an Herbal Medicine, Induce Apoptosis in Isolated Rat Hepatocytes
source: http://www.gastrojournal.org/abs113_4/v113n4p1334.html
DANIEL FAU,* MOUNIA LEKEHAL,* GEOFFREY FARRELL,* ALAIN MOREAU,‡
CLAUDE MOULIS,§ GERARD FELDMANN,‡ DELPHINE HAOUZI,*
and DOMINIQUE PESSAYRE*
*INSERM Unité 24 and Centre de Recherche de Physiopathologie
Hépatique, Association Claude Bernard, Hôpital Beaujon,
Clichy; ‡INSERM Unité 327, Faculté de Médecine
Xavier Bichat, Paris; and §Laboratoire de Pharmacognosie,
Faculté des Sciences Pharmaceutiques, Toulouse, France
See editorial on page 1408.
Background & Aims: Germander was withdrawn from the market
after its use for weight control caused an epidemic of hepatitis.
Its toxicity was shown to be caused by diterpenoids and their
cytochrome P4503A-mediated metabolic activation into electrophilic
metabolites that deplete cellular thiols. The aim of the present
study was to determine the mechanisms of cell death.
Methods: Isolated rat hepatocytes were incubated for 2 hours with
germander diterpenoids (100 µg/mL).
Results: Diterpenoids decreased cell glutathione, increased cytosolic
[Ca2+], activated Ca2+-dependent tissue transglutaminase forming
a cross-linked protein scaffold, and caused internucleosomal DNA
fragmentation and the ultrastructural features of apoptosis. Cell
death was prevented by decreasing metabolic activation (with troleandomycin),
preventing depletion of glutathione (with cystine), blocking activation
of Ca2+-modulated enzymes (with calmidazolium), or inhibiting
internucleosomal DNA fragmentation (with aurintricarboxylic acid).
Apoptosis was increased and diterpenoids caused overexpression
of p53 and interleukin 1<Picture: beta>-converting enzyme
in rats treated with dexamethasone (cytochrome P4503A inducer).
Apoptosis was also increased by a diet deficient in sulfur amino
acids.
Conclusions: The germander furano diterpenoids cause apoptosis
within 2 hours in isolated rat hepatocytes. Electrophilic metabolites
may stimulate apoptosis by decreasing thiols, increasing [Ca2+],
and activating Ca2+-dependent transglutaminase and endonucleases.
Address requests for reprints to: Daniel Fau, INSERM Unité
24, Hôpital Beaujon, 92118 Clichy, France. Fax: (33) 1-47-30-94-40.
1997 by the American Gastroenterological Association
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MASATAKA OKUNO,1 HISATAKA MORIWAKI,1 SHOKO IMAI,1 YASUTOSHI MUTO,1
NORIFUMI KAWADA,2 YASUHIRO SUZUKI,3 AND SOICHI KOJIMA3
SEE EDITORIAL ON PAGE 1072
Liver stellate cells (SCs) play central roles in both the storage
of retinol and the development of liver fibrosis. The present
study is aimed to understand the mechanism by which retinoic acid
(RA, an active metabolite of retinol) enhances hepatic fibrosis
in rats. We tested the effect of 9-cis-RA on several aspects in
vitro rat SC cultures, including the activity of cellular plasminogen
activator (PA), messenger RNA (mRNA), and protein levels of transforming
growth factor-<Picture: beta> (TGF-<Picture: beta>)
mRNA level of type-I procollagen, and the activity of type-I collagenase.
Employing the rat liver fibrosis model produced by porcine serum,
we also estimated the effect of oral administration of a stable
RA analog on the progression of the fibrosis, as well as on hepatic
TGF-<Picture: beta> contents. In vitro SC cultures, 9-cis-RA
enhanced cellular PA and plasmin levels thereby induced plasmin-mediated
activation of latent TGF-<Picture: beta>. Active TGF-<Picture:
beta> generated self-stimulated its synthesis as well as that
of collagen and suppressed the production of collagenase in an
autocrine manner. In in vivo rat models, an RA analog accelerated
the porcine serum-induced fibrosis by enhancing TGF-<Picture:
beta> contents and, thus, collagen levels in the liver, although
the RA analog alone was not fibrogenic. These results suggest
that RA exacerbated liver fibrosis, at least in part, by inducing
the activation and production of latent TGF-<Picture: beta>
in liver SCs.
Address reprint requests to: Soichi Kojima, Ph.D., Laboratory
of Gene Technology and Safety, Tsukuba Life Science Center, The
Institute of Physical and Chemical Research (RIKEN), Koyadai,
Tsukuba, Ibaraki 305, Japan. Fax: 81-298-36-9050.
Copyright © 1997 by the American Association for the Study of Liver Diseases.
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