| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Regulates Transforming Growth Factor- Expression in Regenerating Murine Liver and Isolated Hepatocytes
*
Toxicology and Molecular Biology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505; and
Tanabe Seyaku Co. Ltd. Kawagishi, Tada, Japan
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
is a pleotropic proinflammatory cytokine that has
been implicated as a contributing factor in a number of disease
processes, primarily through its ability to induce the expression of
inflammatory and cytotoxic mediators. TNF- is also involved in cell
growth accompanying the healing process in multiple organ systems and
influences liver repair following hepatotoxic damage or regeneration
following partial hepatectomy. In this respect, TNF- is a known
mitogen for hepatocytes. In this paper we describe a novel role for
TNF- in the modulation of expression of TGF-, the latter being a
complete hepatocyte mitogen. TNF- directly up-regulates TGF- mRNA
by up to 7-fold in isolated mouse hepatocytes, whereas neutralization
of TNF- significantly decreased liver mRNA and protein expression of
TGF- following chemical-induced hepatotoxicity. That TNF-
directly stimulated TGF- was suggested by the inability of either
anti-IL-6 Abs or cycloheximide to inhibit TNF--induced TGF-
expression in hepatocytes. However, in the presence of anti-TGF-
neutralizing Abs, the mitogenic activity of TNF- is abrogated. Using
cells transfected with the TGF- promoter, and an RNA polymerase
inhibitor, it was shown that TNF- modulates TGF- expression
through both pre- and posttranscriptional events. Taken together, these
data suggest that TNF- participates in liver repair and
regeneration, in part, by directly inducing the expression of
TGF-. |
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
, a 17-kDa polypeptide, was first identified as causing a
wasting syndrome in tumor-bearing mice, hemorrhage reduction in the
size of some tumors, and necrosis in normal tissues
(1, 2, 3). Originally identified in a destructive context,
TNF- is now known to provide homeostatic and physiological functions
by influencing cell proliferation and differentiation, while causing
apoptotic cell death in certain cell types. Due to the influence
chronic inflammation plays in disease processes, recent attention has
focused on its role in regulating inflammatory processes
(1, 2, 3) through its ability to regulate genes that code for
inflammatory mediators. The mechanisms by which TNF- can influence
physiological processes, such as cell proliferation, have not been well
studied but likely involves the mitogen-activating protein kinase
pathway leading to activation of transcription factors, such as AP-1,
and expression of growth factors.
The liver, unlike most organs, has the capacity to regenerate or repair
itself following injury. In experimental animals liver regeneration has
been studied using a model of physical injury (i.e., 2/3 partial
hepatectomy (PH)2),
and liver toxicity by exposure to hepatotoxins such as carbon
tetrachloride (CCl4). Although both procedures
result ultimately in restored liver mass and function, they differ in
that PH is primarily a compensatory hyperplasia, and does not
involve an inflammatory response (4), whereas
CCl4 can cause injury, necrosis, and a robust
inflammatory response that results in far more damage to the organ than
the chemical itself (5). Increasing evidence indicates
that TNF-, possibly through its ability to induce IL-6, plays an
important role in liver regeneration following PH or
CCl4 exposure (6, 7, 8, 9). Previous
studies by this laboratory (8) and elsewhere
(10) have shown that neutralization of TNF- following
CCl4 treatment or PH (6, 11) results
in a significant delay in the regenerative process. Furthermore,
administration of TNF- in the rodent increases liver weight
(12), induces hepatocyte mitosis, and stimulates liver DNA
synthesis (12, 13). In contrast to IL-1 or IL-6 (14, 15), TNF- is also a mitogen for isolated hepatocytes
(14, 15). Additionally, TNF- will induce IL-6
expression in the liver, and IL-6-deficient mice display a delay in
liver regeneration following PH, indicating that IL-6 is also important
in regeneration (7).
Cell proliferation is a complex and tightly controlled process, which
is modulated by cell-to-cell contact and various growth factors
(4). Evidence indicates that TNF- influences the
expression of several of these growth factors. For example, TNF- can
modulate hepatocyte growth factor levels in fibroblast cultures
(16) and TGF- (2) in pancreatic cell lines
(17). However, the role of TNF- in modulating
hepatocyte-derived growth factors has not been investigated. TGF-
has been identified as a mitogen for hepatocytes in culture and is one
of the major stimuli for cell proliferation during liver regeneration.
Although epidermal growth factor and hepatocyte growth factor are
produced early in the regenerative process, TGF- is induced later
and is involved in completion of the regenerative process
(4). The timing of its induction would make TGF- a
likely candidate for modulation by proinflammatory cytokines that are
induced early during liver regeneration. In this paper we describe a
novel role for TNF- in the modulation of expression of TGF- in
hepatocytes. Furthermore, we define the effects of endogenous TNF-
on TGF- induction following chemically induced hepatotoxicity, thus
indicating a distinct role for TNF- in liver regeneration.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Experimental animals were treated in accordance with the
criteria outlined in the "Guide for the Care and Use of Laboratory
Animals" (NIH publication 86-23, 1996). Female B6C3F1 (C57BL/6
x C3H) mice (The Jackson Laboratory, Bar Harbor, ME), weighing 22–28
g and 
6–8 wk old, were housed in polycarbonate cages containing
hardwood chip bedding at room temperature (21 ± 2°C) on a 12-h
light/dark cycle. Animals were assigned to groups randomly by weight
and administered a single i.p. dose of 0.1 ml/kg
CCl4 (Sigma, St. Louis, MO) or an equal volume of
corn oil vehicle as previously described (8). Euthanasia
was performed by CO2 asphyxia using National
Institute for Occupational Safety and Health-approved guidelines for
the humane treatment of laboratory rodents. Livers were flash frozen in
liquid nitrogen and stored at -70°C until assayed.
Polyclonal antiserum to murine TNF- was prepared and characterized
for specificity and titer as previously described (18).
Each mouse was injected i.v. with 0.2 ml of prefiltered, nonimmune, or
immune serum 1 h before CCl4 administration.
This dose effectively neutralizes serum TNF- activity following
endotoxin administration (18).
Hepatocyte isolation
Hepatocytes were isolated from mice and prepared by a
modification of the procedure of Seglen (19). Briefly, the
liver was retrograde perfused in situ with warmed (37°C) Liver
Perfusion Buffer (Life Technologies, Bethesda, MD) followed by
Digestion Buffer (Life Technologies). The liver was removed and the
cells were gently dispersed into William’s E medium (Life
Technologies). Viable cells were enriched using isodensity Percoll
(Pharmacia Fine Chemicals, Piscataway, NJ). Aliquots of 1 x
106 cells in 2 ml volumes were seeded into 6-well
culture dishes in William’s E medium supplemented with 10% FBS
(HyClone, Logan, UT) and 2 mM L-glutamine. The wells of the
culture dishes were preconditioned by treating with 2.6 µl/ml
Matrigel (Collaborative Biomedical Products, Bedford, MA) in William’s
E medium overnight at 37°C. Hepatocytes were allowed to adhere,
washed once with fresh medium, and incubated overnight at 37°C and
5% CO2. Following incubation, the medium was
replaced with serum-free William’s E medium containing 1 mg/ml BSA and
0.5% DMSO. The cultures were again allowed to incubate overnight,
after which fresh serum-free William’s E medium was added containing
0.2% DMSO with or without treatments. Recombinant murine (rm)IL-6,
TNF-, and anti-IL-6 neutralizing Ab were purchased from R&D
Systems (Minneapolis, MN).
Semiquantitative RT-PCR
Cells were collected and total cellular RNA was extracted using
the Qiagen RNeasy kit (Qiagen, Valencia, CA) according to the
manufacturer’s procedure. cDNA was synthesized as described previously
(20). PCR primers for mouse G3PDH and IL-6 were purchased
from Clontech (Palo Alto, CA). Primers for mouse TGF- were custom
synthesized (Life Technologies/BRL) from the following sequences:
5'-ACCTGCAGGTTTTTGGTGCAG and 3'-GGAGGGCGCTGGGCTTCTCG (266
bp).
Samples of cDNA were amplified by PCR using a GeneAmp PCR System 9600 DNA Thermal cycler (Perkin-Elmer, Foster City, CA). RNA concentrations and PCR cycles were titrated to establish standard curves, to document linearity, and to permit semiquantitative analysis of signal strength as previously described (21). For each set of primers, dilutions of cDNA were amplified for 20, 23, 25, 28, 30, 33, and 35 cycles to define optimal conditions for linearity and to permit semiquantitative analysis of signal strength (22). If necessary, the concentrations of cDNA were readjusted to normalize for G3PDH and the PCR repeated. When appropriate, the specificity of the PCR bands was confirmed by restriction site analysis of the amplified cDNA, which generated restriction fragments of the expected size (data not shown). Amplified PCR products were electrophoresed into 1.5% agarose gel (UltraPure, Sigma) and were scanned directly with an Eagle Eye II digital imaging system (Stratagene, La Jolla, CA), and the digital images were analyzed using NIH Image v1.57.
Ribonuclease protection assay (RPA)
Quantification of RNA samples was performed by RPA using the
RiboQuant kit (PharMingen, San Diego, CA) according to the
manufacturer’s instructions. The dsDNA template for GAPDH was
purchased from PharMingen, and the template for murine TGF- was
generated from a PCR product using mouse TGF- primers containing a
T7 RNA polymerase recognition site. 32P-labeled
cRNA probes were produced from dsDNA templates using the MAXIscript T7
kit from Ambion (Austin, TX) according to the manufacturer’s
instructions. Aliquots of total RNA were assayed using the RiboQuant
kit (PharMingen). Samples were electrophoresed on a sequencing gel, and
protected fragments were quantitated using a PhosphorImager system and
ImageQuant software (Storm, Molecular Dynamics, Sunnyvale,
CA).
Western blot
Liver cell membrane samples were processed for Western blot
analysis essentially as described by Paria et al. (23).
Portions of liver were homogenized, centrifuged, and the pellets were
resuspended in 10 mM Tris-HCl, 250 mM sucrose buffer containing 10
µg/ml leupeptin, 20 µg/ml PMSF, and 10 µg/ml pepstatin. The total
protein concentration was adjusted to 10 mg/ml, and 0.3 mg was
separated on a 15% reducing SDS-PAGE gel and electrophoretically
transferred to a nitrocellulose membrane as described previously
(24). The nitrocellulose membrane was incubated with a
1:200 dilution of anti-mouse TGF- mAb (Santa Cruz Biotechnology,
Santa Cruz, CA) for 16 h at 4°C, washed twice, and exposed to
goat anti-mouse alkaline phosphatase conjugate (1:500 dilution)
according to the manufacturers protocol (Santa Cruz Biotechnology). The
membrane was developed in 1Step nitroblue
tetrazolium/5-bromo-4-chloro-3-indolyl phosphate (NBT-BCIP; Pierce,
Rockford, IL) for 10–15 min until bands were apparent. The membrane
was rinsed thoroughly in dH2O and scanned
directly with an Eagle Eye II digital imaging system (Stratagene). The
digital images were analyzed using NIH Image v1.57.
Transfection of Hepa-1 cells
Hepa-1 cells (American Type Culture Collection, Manassas, VA)
were plated at 5 x 105 cells/well in
Matrigel-coated 6-well tissue culture plates in DMEM containing 10%
FBS, 100 IU/ml penicillin, 100 µg/ml streptomycin, and 2 mM
L-glutamine (DMEM + 10%). The cultures were incubated
overnight at 37°C and 5% CO2 (70–80%
confluent). The TGF- promoter plasmid (graciously provided by Dr.
D.C. Lee, University of North Carolina, Chapel Hill, NC) is a construct
of the pGL2 basic vector containing the complete murine TGF-
promoter. An aliquot of purified plasmid construct was incubated with
SuperFect reagent (Qiagen) according to the manufacture’s
instructions. The Hepa-1 cells were incubated with the plasmid for
2 h, after which the plasmid solution was aspirated and fresh
serum-free DMEM containing insulin, transferrin, selenium (ITS; Life
Technologies), 100 IU/ml penicillin, 100 g/ml streptomycin, and 2 mM
L-glutamine. Treatments were added to individual wells, and
the transfected cells were incubated overnight. After incubation, the
cells were harvested and samples were prepared for analysis with the
Luciferase Reporter Gene Assay kit (Boehringer Mannheim, Indianapolis,
IN) according to the manufacture’s instructions. Luminescence was
determined on a Wallac luminometer (Wallac, Bethesda, MD), and data
were collected in arbitrary luminescence units. Transfection efficiency
was monitored by cotransfection with the pCAT control vector.
Chloramphenicolacetyl transferase (CAT) levels were determined from
cell-free extracts using the CAT Elisa kit (Boehringer Mannheim)
according to the manufacture’s instructions.
Statistical analysis
All experiments were replicated and representative findings are shown. Statistical significance was determined by one-way ANOVA. When the F value was significant, the means were compared using Fisher post hoc analysis. In all statistical comparisons, a p value of <0.05 was used to indicate a significant difference.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
could
influence the expression of TGF- in the liver. Hepatocyte isolation
can mimic injury (19), and special culture conditions are
necessary to maintain basal activity levels following isolation (G.
Michalopoulos, unpublished data). Hepatocytes were isolated and
cultured on an extracellular matrix (Matrigel) in the presence of low
levels of an antioxidant, DMSO. Preliminary experiments found that
these conditions reduced the overexpression of growth factors that may
occur as a result of liver perfusion and isolation. Cultured
hepatocytes were treated with PMA (20 ng/ml) or various concentrations
of rmTNF- for up to 2 h, and total RNA was isolated from the
cells. RT-PCR indicated up to a 7-fold relative increase in TGF-
mRNA occurred following 10 ng/ml TNF- treatment, which was
comparable to that induce by PMA (Fig. 1
). When kinetic studies were performed,
it was found that maximum induction of TGF- by TNF- occurred
after 1–3 h of culture (data not shown). Because RT-PCR is a
semiquantitative procedure, and can be influenced by factors such as
pipetting error, or cycling beyond the linear amplification range of
the reaction, RPA was performed on mRNA from TNF--treated
hepatocytes. RPA is a quantitative measure for specific mRNA.
These studies indicated that the increase in TGF- expression was
>3-fold (Fig. 2).
|
|
to
stimulate IL-6 secretion, and that IL-6 may represent the proximal
mediator for hepatocyte growth. To explore the possibility that IL-6 is
responsible for TGF- induction, TNF-, IL-6, or Abs to IL-6 were
added to hepatocyte cultures and the expression of TGF- monitored.
According to the manufacturer, the 50% neutralization dose
(ND50) for the lot of anti-IL-6 neutralizing
Ab used was 0.001–0.003 µg/ml in the presence of 0.25 ng/ml
rmIL-6 (R&D Systems anti-mouse IL-6 Ab, lot number AHV01). To
ensure that sufficient anti-IL-6 Ab was present to neutralize any
IL-6 produced, 5000-fold excess of the ND50
was added. TNF- was capable of enhancing TGF- expression when
added to isolated mouse hepatocytes, and concomitant addition of IL-6
neutralizing Abs did not alter TGF- expression (Fig. 3). Consistent with these observations,
similar concentrations of IL-6 failed to influence TGF- expression.
To determine whether de novo protein synthesis was required for the
induction of TGF- message by TNF-, hepatocytes were stimulated
with TNF- in the presence of the protein inhibitor, cycloheximide,
and TGF- message examined by RT-PCR. As shown in Fig. 4, the ability of TNF- to stimulate
TGF- message was similar in the presence or absence of
cycloheximide, indicating that TNF- can directly induce TGF-.
Addition of cycloheximide alone had no effect on TGF- expression
(data not shown).
|
|
is a potent in vivo and in vitro hepatocyte mitogen (14, 25, 26). To help determine whether its mitogenic activity is
ultimately due to TGF- production, TNF- stimulated hepatocytes
were cultured in the presence of Abs to TGF- and proliferation was
monitored by [3H]TdR incorporation (Fig. 5). The increase in thymidine
incorporation induced by TNF- was 4-fold above medium control.
However, the addition of anti-TGF- Abs to the culture medium
completely abolished the increase in DNA synthesis, suggesting that the
stimulatory effect of TNF- is primarily due to its ability to
stimulate TGF-.
|
mRNA,
Hepa-1 cells were treated with TNF- followed by actinomycin D, and
TNF- and TGF- message degradation was evaluated as a function of
time using the RPA. As previously established (27), the
production and degradation of TNF- message occurs rapidly after
stimulation (Fig. 6). In contrast to
TNF-, the degradation of TGF- message, following identical
stimulation, proceeded considerably slower over the 2-h period,
suggesting that stabilization may contribute to the abundance of
TGF- mRNA (Fig. 6). To determine whether TNF- could also
influence TGF- transcriptional activity, Hepa-1 cells were
transiently transfected with the full-length TGF- mouse promoter
linked to a luciferase reporter gene. Transfected cells treated with
TNF- displayed a 3-fold increase in luciferase activity compared
with vehicle controls, which was similar to that observed with the
positive control, PMA (Fig. 7). Taken
together, these data suggested that elevated levels of TGF- message
are due to both transcriptional activation and mRNA stabilization.
|
|
can modulate TGF- in vivo, mice were
administered TNF- or IL-6 at concentrations known to induce an acute
phase response in the liver (28), and the expression of
TGF- was monitored by RT-PCR (Fig. 8).
Two hours following TNF- treatment, a 6-fold relative increase in
TGF- expression was observed in the liver, while administration of
rmIL-6 had no effect on its expression.
|
in chemically induced
hepatotoxicity, mice were administered an acute dose of
CCl4 (0.1 ml/kg), a concentration which has been
shown to cause temporary liver damage and TNF-dependent repair
(8), and livers were examined by RT-PCR for relative
changes in the expression of TGF-, and IL-6. We (8) and
others (29) have previously demonstrated that
CCl4 treatment induced robust TNF- expression
in the liver. In addition to TNF-, CCl4
treatment had a pronounced effect on the mRNA expression of IL-6, and
TGF- (Fig. 9) with the latter
increased maximally (3-fold) within 12–24 h after
CCl4 exposure. Furthermore, neutralizing Abs to
TNF- administered before CCl4 exposure fully
prevented the induction of IL-6 and TGF-. These observations were
verified by RPA, which also indicated that CCl4
induced a 2- to 3-fold increase in TGF- expression (Fig. 10), which could be prevented by
neutralizing Abs to TNF-. To determine whether the increase in
TGF- gene expression was associated with altered protein levels,
membrane bound pro-TGF- levels were determined by Western blot
analysis. Fig. 11 shows that
CCl4 exposure resulted in a significant increase
in pro-TGF- protein that was attenuated by pre-treatment with
neutralizing Abs to TNF-.
|
|
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
as a regulator of liver regeneration and
repair was originally demonstrated in rats in which administration of
neutralizing Abs to TNF- before PH impaired liver regeneration
(6). TNF- neutralization also prevented the activation
of "early immediate genes," such as those regulated by the
transcription factors NF-
B and AP-1, which are involved in cell
proliferation (7, 10). This is consistent with the
reported ability of TNF- to increase hepatic DNA and RNA synthesis
and hepatic mitosis (14). Repair following
CCl4-induced damage occurs through similar
processes (8, 10). However, the former is characterized
initially by marked inflammation and necrosis, where TNF- has a
suspected role (4). CCl4 is
metabolized to the highly reactive chloro-trimethyl radical which
interacts with membrane lipids and initiates lipid peroxidation
(30). Secondary liver injury following
CCl4 exposure may occur from inflammatory
processes originating from products of activated Kupffer cells such as
TNF-. TNF- can induce the production and release of
chemoattractants and activators of neutrophils. The resulting
neutrophil influx promotes extensive tissue damage, including fibrosis,
via the release of reactive nitrogen and oxygen species
(31).
To date, studies on the role of TNF- in liver repair have focused
almost exclusively on changes in early-immediate genes. In the present
studies we focused on upstream events, specifically the ability of
TNF- to modulate the complete hepatocyte mitogen TGF-. TGF-,
which is mitogenic for hepatocytes and other liver-derived cells, is
thought to be a major stimulus for liver regeneration and has been
linked to the proliferative response in the liver following PH
(32). TGF- is expressed as a 160-aa membrane-integral
precursor and a 50-aa mature form. The mature form is only detectable
after hepatocyte proliferation commences, indicating that the
membrane-bound form is responsible for the majority of the activity
during regeneration (33). Using isolated murine
hepatocytes as a model, as well as chemically induced hepatotoxicity,
we demonstrated that TNF- can directly stimulate TGF- expression
in hepatocytes. The relative increase in hepatic TGF- expression
observed in the present studies was only 3- to 4-fold following in vivo
TNF- administration, which is similar to the increase observed after
PH (33). It is thought that the low induction rate is due
in part to the fact that TGF- elicits responses in adjacent cells in
a juxtacrine fashion, primarily through membrane-bound TGF- rather
than the soluble form. Several hours following liver damage,
TGF- mRNA levels increase, peaking at approximately the same time as
the first wave of DNA synthesis (33).
As indicated earlier, increasing evidence has suggested that the
signaling pathway by which TNF- regulates liver regeneration is
through activation of the downstream events involving sequentially the
activation of NF-B, IL-6 secretion, and eventually STAT3 activation.
The importance of IL-6 in liver regeneration was demonstrated by the
ability of IL-6 injections to correct the deficiency in hepatocyte DNA
synthesis and restore STAT3 binding to normal levels in PH or
CCl4-treated TNF receptor or IL-6-deficient mice
(10, 11). As we observed that hepatic IL-6 mRNA was
increased following CCl4 administration and
reversed in animals pretreated with neutralizing TNF- Abs, it could
be assumed that IL-6, rather than TNF-, was also the proximal
mediator of TGF- induction. However, injection of IL-6, even at
concentrations as high as 1 mg/kg, failed to influence TGF-
expression, whereas injection of TNF- induced a robust response.
These data are consistent with a recent study, which demonstrated that
IL-6 injection before CCl4 treatment inhibited
DNA synthesis in livers of wild-type mice (10). In vitro
studies further demonstrated that IL-6 did not induce proliferation or
TGF- expression in isolated hepatocytes from normal mice.
Furthermore, cycloheximide did not affect the ability of TNF- to
induce TGF-, indicating that de novo protein synthesis was not a
prerequisite. These findings attest to the fact that liver regeneration
represents a complex process with numerous redundancies, which can be
exemplified by the observation that liver regeneration in TGF- null
mice occurs as rapidly as in wild-type mice following PH
(34). This is presumably due to compensation by epidermal
growth factor. Furthermore, it should be noted that liver regeneration
following CCl4 exposure is only delayed in the
absence of TNF-, suggesting that other direct acting hepatocyte
mitogens can compensate.
Multiple NF-B and an AP-1, but no STAT-3, binding sites exist in the
promoter region of the TGF- gene (35). Both NF-B and
AP-1 activation are associated with TNF--mediated signaling events
in the liver (6), and administration of TNF- increases
their DNA binding activities in hepatocytes as demonstrated by EMSA
(36). Furthermore, hepatocyte proliferation following
CCl4 exposure is preceded by NF-B
(9) and AP-1 (8) activation which can be
prevented or significantly delayed by TNF- neutralization. The
murine TGF- gene also contains several poly(A) U sites in the
3'-untranslated region that have been postulated to modulate the
stability of the transcript (37). Message
stabilization and cell transfection studies provided evidence that the
increase in TGF- message was due to both increased synthesis and
message stabilization. Consistent with our observations, it has been
postulated that the initial increase in hepatic mRNA following PH is
mediated by transcriptional activation, and within 3 h after PH,
gene regulation is switched primarily to posttranscriptional mechanisms
(38).
Although the mechanisms by which TNF- regulates liver repair are
likely quite complex, the current studies suggest that TNF--induced
TGF- expression is involved by acting upstream. There is little
doubt that other processes, including those controlled by the IL-6 and
the CCAAT/enhancer-binding protein transcription factor families, also
participate. Current studies are focusing on the specific molecular
mechanisms that control these events.
|
Footnotes |
|---|
2 Abbreviations used in this paper: CCl4, carbon tetrachloride; PH, partial hepatectomy; RPA, ribonuclease protection assay; rm, recombinant murine; NBT-BCIP, nitroblue tetrazolium/5-bromo-4-chloro-3-indolyl phosphate.
Received for publication July 12, 1999. Accepted for publication November 3, 1999.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
inhibit liver regeneration after partial hepatectomy. Am. J. Physiol. 263:G579. contribute to liver repair following chemical-induced hepatotoxicity. Hepatology 25:133.[Medline]
increases hepatic DNA and RNA and hepatocyte mitosis. Biochem. Int. 22:405.[Medline]
and interleukin 6. J. Cell. Physiol. 150:134.[Medline]
is a direct hepatocyte mitogen in the rat. Biochem. Mol. Biol. Int. 29:1.[Medline]
and -1 and tumor necrosis factor- by fibroblasts in culture. J. Biol. Chem. 268:8140. and epidermal growth factor receptor mRNA. J. Biol. Chem. 268:2762. in cadmium-induced hepatotoxicity. Toxicol. Appl. Pharmacol. 131:224.[Medline]
precursors in the mouse uterus during the periimplantation period and after steroid hormone treatments. Biol. Reprod. 50:481.[Abstract]
bifunctionally induces proliferation in primary hepatocytes: role of cell anchorage and spreading. J. Immunol. 159:4840.[Abstract]
and transforming growth factor-1 in acute liver injury. Growth Factors 1:219.[Medline]
may be a physiological regulator of liver regeneration by means of an autocrine mechanism. Proc. Natl. Acad. Sci. USA 86:1558. (TGF-) concentrations increase in regenerating rat liver: evidence for a delayed accumulation of mature TGF. Endocrinology 133:1731.[Abstract]
-targeted mice. Mol. Carcinog. 15:183.[Medline]
gene: its expression during eyelid development and in waved 1 tissues. Cell Growth Differ. 7:1271.[Abstract]
B in hepatocytes, a primary response in the regenerating liver. J. Biol. Chem. 269:30429. gene in transformed rat liver epithelial cells. Oncogene 12:1991.[Medline]
This article has been cited by other articles:
|
|
 |
|
  A. Natarajan, B. Wagner, and M. Sibilia The EGF receptor is required for efficient liver regeneration PNAS, October 23, 2007; 104(43): 17081 - 17086. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. M. Argast, J. S. Campbell, J. T. Brooling, and N. Fausto Epidermal Growth Factor Receptor Transactivation Mediates Tumor Necrosis Factor-induced Hepatocyte Replication J. Biol. Chem., August 13, 2004; 279(33): 34530 - 34536. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Bajt, T. R. Knight, A. Farhood, and H. Jaeschke Scavenging Peroxynitrite with Glutathione Promotes Regeneration and Enhances Survival during Acetaminophen-Induced Liver Injury in Mice J. Pharmacol. Exp. Ther., October 1, 2003; 307(1): 67 - 73. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 U. M. Apte, P. B. Limaye, D. Desaiah, T. J. Bucci, A. Warbritton, and H. M. Mehendale Mechanisms of Increased Liver Tissue Repair and Survival in Diet-Restricted Rats Treated with Equitoxic Doses of Thioacetamide Toxicol. Sci., April 1, 2003; 72(2): 272 - 282. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
U. M. Apte, P. B. Limaye, S. K. Ramaiah, V. S. Vaidya, T. J. Bucci, A. Warbritton, and H. M. Mehendale Upregulated Promitogenic Signaling via Cytokines and Growth Factors: Potential Mechanism of Robust Liver Tissue Repair in Calorie-Restricted Rats upon Toxic Challenge Toxicol. Sci., October 1, 2002; 69(2): 448 - 459. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. L. Lordan, F. Bucchieri, A. Richter, A. Konstantinidis, J. W. Holloway, M. Thornber, S. M. Puddicombe, D. Buchanan, S. J. Wilson, R. Djukanovic, et al. Cooperative Effects of Th2 Cytokines and Allergen on Normal and Asthmatic Bronchial Epithelial Cells J. Immunol., July 1, 2002; 169(1): 407 - 414. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Hatano and D. A. Brenner Akt protects mouse hepatocytes from TNF-alpha - and Fas-mediated apoptosis through NK-kappa B activation Am J Physiol Gastrointest Liver Physiol, December 1, 2001; 281(6): G1357 - G1368. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Dai and A. Churg Relationship of Fiber Surface Iron and Active Oxygen Species to Expression of Procollagen, PDGF-A, and TGF-{beta}1 in Tracheal Explants Exposed to Amosite Asbestos Am. J. Respir. Cell Mol. Biol., April 1, 2001; 24(4): 427 - 435. [Abstract] [Full Text]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||
, TNF-
,
CCl4, x, CCl4 + anti-TNF-
