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Is Necessary in Thymic Development and Estradiol-Induced Thymic Alterations1
*
Department of Microbiology and Immunology, State University of New York Health Science Center, Syracuse, NY 13210;
Environmental Health Science Center, Department of Environmental Medicine, University of Rochester School of Medicine, Rochester, NY 14642;
Department of Biochemistry, University of Missouri, Columbia, MO 65211; and
§
Receptor Biology Section, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental and Health Sciences, Research Triangle Park, NC 27709
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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(ER) knockout
(ERKO) mice were examined. ERKO mice have significantly smaller thymi
than their wild-type (WT) littermates. Construction of ER radiation
bone marrow chimeras indicated that the smaller thymi were due to a
lack of ER in radiation-resistant tissues rather than hemopoietic
elements. ERKO mice were also susceptible to estradiol-induced thymic
atrophy, but the extent of their atrophy was less than what was seen in
WT mice. The estradiol-treated ERKO mice failed, however, to manifest
alterations in their thymic CD4/CD8 phenotypes compared with WT mice.
Therefore, ER is essential in nonhemopoietic cells to obtain a
full-sized thymus, and ER also mediates some of the response of the
thymus to elevated estrogen levels. Finally, these results suggest that
in addition to ER, another receptor pathway is involved in
estradiol-induced thymic atrophy. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The thymus is the major organ responsible for the maturation and education of T cells. Prothymocytes enter the thymus from the bloodstream after originating in the bone marrow and/or fetal liver. Once in the thymus these cells develop through multiple stages that can be delineated by cell surface markers, including CD4 and CD8. In the earliest stage, cells do not express either of these markers and are referred to as double negative (DN)3 (3) cells. Subsequently, these markers are up-regulated to give rise to CD4+CD8+, double-positive (DP) cells. These cells undergo a rigorous process of selection and then down-regulate either their CD4 or CD8 molecules to become single-positive (SP) cells before migrating into the periphery. The overall process of maturation and education of T cells is orchestrated, to a degree, by the supporting cells of the stroma, including epithelial cells, dendritic cells, and macrophages (10).
It is generally believed that estrogens exert most if not all of their
biological effects by binding to a specific nuclear protein, the
estrogen receptor (ER). Once estrogen is bound to the ER, the complex
dimerizes and binds to specific estrogen response elements in
estrogen-regulated genes (11). In the thymus both the
stromal elements and the thymocytes have been found to contain ER
(12), and thus could serve as targets in estrogen-induced
thymic alterations. Recently, a second isoform of the ER was
discovered, ERß (13, 14). Although the expression level
of ERß mRNA is variable between species and has not yet been found in
mouse thymic tissue (15, 16), ERß has been found in the
thymus at low levels in rats and high levels in humans (13, 17, 18).
Because estrogen has many effects on T cell function and development,
ER knockout (ERKO) mice were examined to determine what role ER
might play in thymic development and estradiol-induced thymic
alterations. Furthermore, ER radiation bone marrow chimeras were
constructed, lacking ER either in radiation-sensitive hemopoietic
elements or radiation-insensitive stromal elements, to examine the role
of the receptor in each compartment.
The results demonstrate that ER is essential in nonhemopoietic cells
for the development of a full-sized thymus in mice, and that ER is
also necessary for the maximum response to atrophy induced by elevated
levels of estradiol. Additionally, the results suggest that either
another ER-dependent or -independent pathway is working in combination
with the ER to contribute to thymic atrophy induced by
estradiol.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Strains used. C57BL/6 Ly5.1 congenic mice were
originally obtained from Dr. E. A. Boyse (Memorial Sloan-Kettering
Cancer Center, New York, NY) and maintained at our own facility. The
129/SV x C57BL/6N (Ly5.2) ER+/+ (WT) and
ER-/- (ERKO) male mice were obtained from
the breeding colonies located at the National Institute of
Environmental and Health Sciences (Research Triangle Park, NC). Mice
were obtained from the mating of heterozygote
(ER+/-) male and female mice. The genotype of
the mice was confirmed by PCR analysis of tail-derived DNA as
previously described (19). All mice were housed and cared
for according to The Guide for the Care and Use of Laboratory
Animals (20), in isolation cages at constant
temperature and humidity on a 12-h light, 12-h dark cycle with food and
water provided ad libitum.
Chimeric mice.
Radiation bone marrow chimeras were created as previously described
(21). Briefly, 4-wk-old male B6Ly5.1 or B6Ly5.2 ERKO mice
were irradiated in two doses of 550 rad spaced at a 4-h interval. A
half-hour after their second irradiation the mice were given 1 x
106 bone marrow cells from B6Ly5.1
(ER+/+), B6Ly5.2 WT, or B6Ly5.2 ERKO mice.
B6Ly5.2 WT or B6 Ly5.2 ERKO bone marrow was used to reconstitute the
B6Ly5.2 ERKO hosts to avoid a graft-vs-host reaction that could have
resulted from B6Ly5.1 bone marrow cells recognizing the 129/SV
component of the B6Ly5.2 ERKO mice. The reconstituted mice were allowed
to recover for 4 wk before they were treated to ensure that the thymus
was fully reconstituted (22) and releasing mature cells of
donor origin (23). Radiation bone marrow chimeras are
designated as bone marrow donor
irradiated host.
Treatment protocol. Eight-week-old ERKO, WT, or ER chimeric mice were injected s.c. with either 5 mg/kg of ß-estradiol 17-valerate (Sigma, St. Louis, MO) in olive oil (F. Berio, Hackensack, NJ) or olive oil alone (0.1 ml/20 g). This is the minimum single dose of estradiol found to induce substantial atrophy (>50%) after 10 days (data not shown). All mice were killed 10 days after receiving an injection. Each experiment was performed with randomized, age-matched litters (±3 days). Male mice were used in most experiments to avoid confounding by the excess levels of estradiol seen in the ERKO females (24). A minimum of four mice were used per treatment group, although the chimera studies were performed with at least five mice per group. Mice were analyzed individually.
Cell preparation
Cell counting and flow cytometry. Mice were euthanized by CO2 asphyxiation, and the thymi were removed and dissected free of lymph nodes and blood vessels. Cell suspensions were made as previously described (21). The cell yield was enumerated by diluting the cells and counting at least two samples for each cell preparation with a Neubauer hemocytometer. Cell viability was determined to be >90% from all animals by trypan blue dye (0.08%) exclusion.
For reconstitution. Bone marrow was isolated by flushing the marrow cavity of femurs and tibias with MEM containing 5% FBS and penicillin (100 U/ml) and streptomycin (100 µg/ml). It was then suspended by passing the cells successively through 22- and 25-gauge needles. The cell suspension was finally passed through 80-gauge nylon mesh, and cells were pelleted by centrifugation. After the initial pelleting, the cells were resuspended in 1 ml of ACK buffer (0.17 M NH4Cl, 10 mM KHCO3, and 1 mM EDTA) and incubated for 4 min at room temperature to lyse RBC. The preparation was then washed once and counted as described above. After the cells were counted, they were resuspended in MEM and penicillin (100 U/ml) and streptomycin (100 µg/ml) without FBS at a concentration of 5 x 106 cells/ml. Irradiated recipients received 1 x 106 cells (0.2 ml) by tail vein injection.
Antibodies.
The following mAbs were used at predetermined saturating levels: FITC-
and biotin-conjugated anti-CD8 (clone 53-6.7, rat IgG2a), FITC-
and PE-conjugated anti-CD4 (clone RM4-5, rat IgG2a),
biotin-conjugated anti-CD3
(clone 500A2, hamster IgG),
PE-conjugated anti-CD44 (clone IM7, rat IgG2b), biotin-conjugated
anti-CD25 (IL-2R, clone 7D4, rat IgM), and FITC-conjugated
anti-CD45.1 (Ly5.1, clone A20, mouse IgG2a) (PharMingen, San Diego,
CA). Biotin-conjugated anti-CD45.2 was made in our laboratory using
Ly5.2 hybridoma clone, 104.2.1 (mouse IgG2a), obtained from Dr. Shoji
Kimura (Memorial Sloan-Kettering Cancer Center, New York, NY).
Flow cytometric staining and analysis. Freshly isolated thymocytes were pelleted by centrifugation and rinsed in wash buffer (1x PBS, 0.5% BSA, and 0.1% sodium azide). One hundred thousand cells were then incubated simultaneously with a FITC- and biotin-conjugated mAb in 50 µl for 30 min at 4°C. Cells were washed twice with 1 ml of wash buffer and were then incubated with a PE-conjugated mAb and streptavidin-Red 670 (Life Technologies) for 30 min at 4°C. After two more washes the cells were fixed in 1% paraformaldehyde in PBS. Ten thousand or more fixed cells were analyzed on a Becton Dickinson FACStarPlus flow cytometer (Mountain View, CA) using the Becton Dickinson LYSYS II program. Single and dual stainings of fresh thymocytes from untreated young adults were used in assorted combinations to set compensation. Negative staining was performed with either isotype or total Ig controls conjugated appropriately.
Statistics
Two-tailed Student’s t test, for paired and unpaired variables, was used to evaluate differences between treatment groups and their respective vehicle-treated controls. Results were considered statistically significant at p < 0.05.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To determine whether ER played a role in the development of the
thymus, body weights, thymic weights, thymic cell numbers, and thymic
phenotypes were analyzed in 10-wk-old male ERKO and WT littermates.
Although the body weights of the ERKO and WT mice were identical, the
average weight of the thymi from the ERKO mice was 50% less than that
in the WT mice (Fig. 1
). An even larger
difference was seen in the overall thymocyte number of ERKO mice
compared with WT mice (9.7 ± 1.8 x
107 for WT and 3.4 ± 0.6 x
107 for ERKO mice). ERKO and WT thymocytes were
also analyzed for their CD4/CD8 expression by flow cytometry to
determine whether there was a preferential loss of one or more of the
major thymic subpopulations or any subset within these subpopulations
in the ERKO mice (Fig. 2). Table I shows that the CD4/CD8 phenotypic
profile of the ERKO thymocytes was not significantly different from
that of the WT cells. To further explore whether different stages of
maturation were affected in the ERKO mice vs the WT mice, thymocytes
were stained with CD3, for maturity, and with CD44/CD25, for the stem
cell compartment. Table I shows that the CD3 expression pattern was
similar between WT and ERKO mice. Additionally, the distribution of
CD4/CD8 cells within each of the CD3 subpopulations was not
significantly different between ERKO and WT mice (data not shown).
Table I shows the CD44 vs CD25 pattern within the
CD3-CD4-CD8-
population. Again, there was no significant difference between these
subgroups for ERKO vs WT mice.
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Elevated levels of estrogen have been shown to have a significant
impact on the thymus and T cell development, causing both atrophy and
phenotypic shifts in the CD4/CD8 expression patterns (6, 25, 26). To examine the role of ER in estrogen-induced thymic
alterations, age-matched, 8-wk-old male ERKO and WT littermates were
treated with 5 mg/kg of estradiol or oil and sacrificed 10 days later
at the approximate point of maximum thymic atrophy (26, 27). Measurements of thymic weight (not shown) and thymic cell
number (Fig. 3A) indicated
that both estradiol-treated WT and ERKO mice underwent significant
thymic atrophy compared with their oil-treated controls. However, the
estradiol-treated ERKO mice had less of a reduction in cell number than
estradiol-treated WT mice when expressed as a percentage of their
respective control value (Fig. 3B). Because the thymi of the
ERKO mice were smaller to begin with, it was plausible that the ERKO
thymi were not able to undergo the amount of atrophy that was seen in
WT mice. To explore this possibility, 4.5-wk-old male ERKO mice with
larger thymi (23.8 ± 3.2 x 107 cells)
were treated with 5 mg/kg of estradiol. After 10 days, the number of
thymocytes from estradiol-treated ERKO mice was only reduced by 51%
(11.6 ± 5.3 x 107). Body weights were
not significantly altered in any group of mice (data not shown).
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). In contrast, the ERKO mice
failed to have any significant alterations in the ratio of their thymic
phenotypes after estradiol treatment. These results suggested that
ER mediates estradiol-induced thymic phenotype alterations and that
ER mediates some, but not all, of the thymic atrophy caused by
estradiol.
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was necessary in the stromal elements, but not in the
hemopoietic elements, to obtain a full-sized thymus
Given that male ERKO mice have smaller thymi than their WT
littermates, the presence of ER appeared to be important in
establishing the physiological size of the thymus. Because previous
studies have localized ER in both stromal and hemopoietic
populations in the thymus (12), it is possible that the
receptor is necessary in both elements or, alternatively, in only one
to produce a full-sized thymus. To determine this, ER chimeric mice
were created. B6Ly5.1 congenic male mice whose cells contained WT ER
were irradiated to eliminate their endogenous hemopoietic elements and
then reconstituted with the bone marrow cells from B6Ly5.2 ERKO male
mice. Using this approach, mice were created that did not have ER in
their hemopoietic elements, but had ER in their radioresistant
stromal elements. To verify that the process of irradiation and
reconstitution was successful, thymocytes from these chimeric mice were
stained with anti-Ly5.1 (host) and anti-Ly5.2 (donor) and
analyzed by flow cytometry. Greater than 98% of the thymocytes from
mice that had undergone irradiation and reconstitution contained
thymocytes that expressed only Ly5.2, the donor phenotype (data not
shown) (21). The reverse construct was also created, yielding mice that
had ER in hemopoietic elements but lacked it in stromal
elements.
When the weight and cellularity of the ER chimeric thymi were measured,
both chimeric mice containing ER-positive stroma (WTWT and
KOWT), regardless of the ER content of the hemopoietic elements,
had larger thymi and were comparable in size to age-matched B6Ly5.1
mice that had not been irradiated and reconstituted (Fig. 4). In contrast, mice that lacked ER
in their stromal elements had thymi that were smaller and similar in
size to those in ERKO mice. The body weights of all the chimeric mice
were not significantly different (data not shown). These data indicated
that the ER was essential in nonhemopoietic cells, but not in
hemopoietic cells, to obtain a full-sized thymus.
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Because the thymi of ERKO mice underwent atrophy when treated with
exogenous estradiol, ER appeared to be mediating some, but not all,
of the thymic atrophy induced by estradiol. To locate which elements in
the thymus were targeted by estradiol to produce thymic atrophy, ER
chimeric mice were treated with estradiol, and the degree of thymic
atrophy was examined. Furthermore, since ERKO mice failed to undergo
significant shifts in their thymic CD4/CD8 phenotypes after estradiol
treatment, the phenotypes of estradiol-treated chimeric mice were
examined to determine whether these effects were mediated by ER in
stromal elements, hemopoietic elements, or both. Before the chimeras
were treated with estradiol, a control experiment was performed to
ensure that radiation did not alter the responsiveness of the ER
chimeric mice to estradiol treatment. B6Ly5.1 male mice were divided
into two groups; one group underwent irradiation and reconstitution
with B6Ly5.1 bone marrow, while the second group was unmanipulated.
These mice were then further divided into two groups; one group
received 5 mg/kg of estradiol, while the other group was injected with
oil and served as controls. Results from the experiment indicated that
mice that underwent irradiation/reconstitution responded to estradiol
treatment similarly to mice that were unmanipulated (77% atrophy in
thymic cell number for unmanipulated B6Ly5.1 mice compared with their
controls vs 75% atrophy in B6Ly5.1B6Ly5.1). Therefore, the process
of irradiation and reconstitution did not alter the sensitivity of the
thymus to estradiol.
When the ER chimeric mice were treated with estradiol, a significant
decline in both their thymic weights and cellularities was observed for
all chimeras (Table III). When the amount
of atrophy in the estradiol-treated ER chimeras was examined and
expressed as a percentage of their respective control values, a larger
percent decline was seen in the thymic weight of mice containing ER
in their stromal elements than in those that lacked ER in these
elements. Conversely, a larger percent decline was seen in thymic
cellularity in mice containing ER in their hemopoietic elements
compared with those that did not. These results indicated that ER in
both stromal and hemopoietic elements were triggered to cause thymic
atrophy.
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). Only mice that
lacked ER in both stromal and hemopoietic elements had few or no
alterations in the proportions of the thymic subpopulations. All the
other chimeric mice had a significant decline in the percentage of DP
cells and an increased percentage of SP cells. These phenotypic results
suggested that ER was mediating estradiol-induced shifts in the
CD4/CD8 subpopulations by being activated in stromal or hemopoietic
elements, or both.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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WT littermates
(Fig. 1
), but their CD4/CD8, CD3, and CD44/CD25 phenotypes
and size distributions are similar (Table I and Fig. 2, and data not
shown). Although the male ERKO mice lacked ER and had smaller thymi,
they still underwent thymic atrophy when treated with exogenous
estradiol, but to a lesser degree than the WT mice. ERKO mice did not,
however, manifest changes in the ratio of their CD4/CD8 thymic
subpopulations that are observed in WT mice with estradiol. Experiments
using ER chimeras indicated that the presence of ER in stromal
elements was essential for the development of a normal-sized thymus,
while it did not matter whether the hemopoietic elements contained or
lacked the receptor.
The finding that male ERKO mice have smaller thymi than their WT
littermates was surprising and suggested that ER was essential in
male mice to establish a normal-sized thymus. This was not the first
observation that suggested that ER had a significant physiological
role in males. For instance, ERKO male mice have been found to be
infertile and to have behavioral alterations (28, 29).
Additionally, abnormalities in bone structure were noted in a man that
lacked a functional ER (30). Although our reported
studies were performed exclusively in male ERKO mice, preliminary
observations of female ERKO mice show a similar reduction in thymic
size compared with their WT female littermates (K. S. Korach and
S. W. Curtis, unpublished observations). Ovariectomized ERKO
female mice, however, have the same size thymus as ovariectomized WT
littermates (K. S. Korach and S. W. Curtis, unpublished
observations), suggesting that perhaps the elevated production of
estrogen in the ERKO females may be responsible for causing atrophy by
an ER-independent mechanism. Male ERKO mice do not have elevated
levels of estradiol or other hormones such as cortisol or progesterone
(K. S. Korach, unpublished observations), but they do have a
slight, but significant, increase in the level of testosterone compared
with their WT littermates (28). Because administration of
exogenous androgens has been shown to cause atrophy in thymi of
castrated male mice (3), and testosterone can cause thymic
atrophy in adrenalectomized mice (31), dysregulation of
testosterone levels in male ERKO mice could be the cause of their
smaller thymi. In the male ERKO mouse, however, the levels of androgens
are increased <2-fold (28) and are therefore not as high
as the levels that are required to cause significant thymic atrophy in
castrated or unmanipulated adult mice (31, 32).
Besides an indirect role in controlling thymic size by regulating
hormone production, ER may also have a more direct role in the male
thymus by regulating the production of local thymic factors that may be
necessary for full thymic development. ER protein has been found in
the thymus, localized mostly in the stromal elements at the
cortico-medullary junction and in the subcapsular region (33, 34), although ER mRNA has also been found in thymocytes
(35). ER being found primarily in the epithelial cells
agrees well with the ER chimera studies indicating that the receptor’s
presence in stromal tissues is necessary to obtain a full-sized thymus
(Fig. 4). Because the cortico-medullary junction is where T cell
progenitors enter the thymus, and the subcapsular region is where they
begin to proliferate and differentiate (reviewed in 36), ER may
be needed in the stromal cells to regulate signals supporting the entry
and maturation of early thymocytes. There are multiple factors produced
by ER-containing stromal cells that aid in the growth and
differentiation of thymocytes that could serve as targets for estrogen
regulation, including thymulin (33, 37), thymosin ,
thymopoietin, IL-7, and IL-1 (38). However, since there is
no significant difference between CD44/CD25 cell distribution in the DN
cells between ERKO and WT mice (Table I), ER in nonhemopoietic
tissues may be affecting the development of progenitor T cells at an
earlier stage of development, i.e., in the bone marrow, or may be
affecting all stages of development equally.
Thymi from male ERKO mice were still susceptible to estradiol-induced
atrophy (Fig. 3). ERKO mice lost 
50% of their thymocytes after
estradiol treatment regardless of their age and, hence, the size of
their thymi. Meanwhile, WT mice lost 80% of their thymocytes after
estradiol treatment, indicating that ERKO mice fail to undergo full
atrophy and that ER was needed to obtain full estradiol-induced
thymic atrophy. It was plausible, however, that the ERKO male mice did
not undergo full thymic atrophy when given estradiol because their
thymi were already partially decreased in size and that elements that
were reduced or lacking could not be targeted to obtain full atrophy.
This does not appear to be the case, since ER chimeras that had KO
stroma and WT hemopoietic elements underwent the same percentage of
atrophy by cell number as mice that had WT stroma and WT hemopoietic
elements (Table III), even though their size when untreated was as
small as that in ERKO mice. The studies of ER chimeric mice treated
with estradiol additionally indicated that there was a correlation
between the degree of atrophy and the expression pattern of ER in
the thymic stromal and hemopoietic elements. Mice with ER in their
stromal elements had more of a decline in thymic weight than those that
lacked it, and alternatively, mice with ER in their hemopoietic
elements had more of a decline in thymic cell number than those that
did not have the receptor in their hemopoietic elements. In general,
the largest percent atrophy was seen in cell numbers for mice with
ER in the hemopoietic elements. These data indicate that
ER-mediated estradiol-induced thymic atrophy is due to signaling in
both stromal and hemopoietic cells, but is probably associated more
with the hemopoietic elements. Overall, the finding of less atrophy in
ERKO mice suggests that either the atrophy kinetics of estradiol are
different in ERKO mice vs WT mice or there are other pathways, besides
ER, that are mediating the effects of estradiol-induced thymic
atrophy.
The recent discovery of a second ER, ERß, could provide another
potential signaling pathway for the atrophy found in ERKO mice.
However, while ERß has been found at high levels in human thymic
tissue (13, 17) and at low levels in rat thymic tissue
(18), it surprisingly has not been found in mouse thymic
tissue (15, 16). ERß has also not been found in the bone
marrow of mice (16). However, it is possible that ERß
might be produced in thymus and bone marrow to compensate for the loss
of ER. Studies of ERß levels in ERKO mice do not support this,
because ERß RNA does not appear to be up-regulated in any of the
tissues of the ERKO mice, including bone marrow precursor cells or
thymus (16). All these findings suggest that there is
either another ER in thymus or bone marrow or there is a
receptor-independent pathway through which estradiol is working.
Multiple recent studies support the idea of alternative estradiol
signaling pathways. One study found that estradiol bound to the cell
membrane of T cells and raised the cytosolic free calcium level in the
cells by triggering a Ca2+ influx and releasing
Ca2+ from intracellular stores (39).
A second study found that natural estrogens such as
4-hydroxyestradiol-17ß and xenoestrogens such as kepone were able to
trigger uterine lactoferrin expression even when ICI-182,780 was given
to block ER and ERß signaling (40). Finally,
estradiol at high doses has been found to activate the androgen
receptor to induce transcription (41). Overall, these
findings suggest that alternative signaling, through membrane ER,
alternatively spliced forms of ER (24), or other
response proteins, such as the orphan family of estrogen-related
receptors (42) or the androgen receptor (41)
could be responsible for mediating estrogenic signals that do not go
through the classical receptor pathway.
Although ER is not solely responsible for mediating
estradiol-induced thymic atrophy, it appears to be solely responsible
for mediating estradiol-induced phenotypic shifts. Estradiol-treated
ERKO mice failed to undergo any significant shifts in their CD4/CD8
thymocyte phenotypic profile, although their WT littermates have
significant alterations (Table II). The phenotypic shifts observed in
WT mice agree with other studies of estradiol’s effect on the thymus
using different murine strains and different treatment protocols
(6, 27, 35, 43). However, the degrees of atrophy of the
various subpopulations are not identical between our current study and
previous studies (6, 35, 43), most likely due to the
substantially decreased dose of estradiol used in our experiments (3
mg/mouse in previous studies vs 0.125 mg/mouse in our current study).
Additionally, the other investigators have used different murine
strains, which could have different overall sensitivities to estradiol.
Studies of phenotypic alterations in estradiol-treated ER chimeric mice
found that all chimeric mice that contained ER in either their
stromal or hemopoietic cells had statistically significant shifts in
their thymic phenotypes (Table IV). In contrast, chimeric mice that
lacked ER in all cell types had only a slight percent increase in
one of its four thymic subpopulations,
CD4-CD8+. These results
indicate that ER is necessary for the shifts seen in the phenotypic
profile of the thymocytes after estradiol administration and that ER
can be in either the stromal or the hemopoietic elements to mediate
these shifts.
This study is one of the first to suggest a role for ER in the
normal physiological development of the thymus. Future studies should
be performed in ERKO male mice to determine whether the role of ER
in thymic development is in the thymus, in the bone marrow, or in
hormone regulation. Additionally, further studies are needed to
validate the role ER has in female thymic development and
estradiol-induced atrophy.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Allen E. Silverstone, Department of Microbiology and Immunology, State University of New York Health Science Center, Syracuse, NY 13210. E-mail address:
3 Abbreviations used in this paper: DN, double negative; DP, double positive; SP, single positive; ER, estrogen receptor; ERKO, estrogen receptor knockout; WT, wild type.
Received for publication March 29, 1999. Accepted for publication July 29, 1999.
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References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
.
Gustafsson. 1996. Cloning of a novel estrogen receptor
expressed in rat prostate and ovary. Proc. Natl. Acad. Sci. USA
93:5925.
. Gustafsson, and K. S.
Korach. 1997. Tissue distribution and quantitative analysis of
estrogen receptor- (ER) and estrogen receptor-ß (ERß)
messenger ribonucleic acid in the wild-type and ER-knockout mouse.
Endocrinology 138:4613.
(ER-) and ß (ER-ß) in the midgestational human fetus. J. Clin. Endocrinol. Metab. 82:3509.. Gustafsson. 1997. Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors and ß. Endocrinology 138:863. deficient mice reveal a distinct estrogen signaling pathway. Proc. Natl. Acad. Sci. USA 94:12786.This article has been cited by other articles:
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  C. Wang, B. Dehghani, I. J. Magrisso, E. A. Rick, E. Bonhomme, D. B. Cody, L. A. Elenich, S. Subramanian, S. J. Murphy, M. J. Kelly, et al. GPR30 Contributes to Estrogen-Induced Thymic Atrophy Mol. Endocrinol., March 1, 2008; 22(3): 636 - 648. [Abstract] [Full Text] [PDF]
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 D. Jane-wit, C. Z. Altuntas, J. Monti, J. M. Johnson, T. G. Forsthuber, and V. K. Tuohy Sex-Defined T-Cell Responses to Cardiac Self Determine Differential Outcomes of Murine Dilated Cardiomyopathy Am. J. Pathol., January 1, 2008; 172(1): 11 - 21. [Abstract] [Full Text] [PDF]
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 R. H. Straub The Complex Role of Estrogens in Inflammation Endocr. Rev., August 1, 2007; 28(5): 521 - 574. [Abstract] [Full Text] [PDF]
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 L. J Ma, E. A Guzman, A. DeGuzman, H K. Muller, A. M Walker, and L. B Owen Local cytokine levels associated with delayed-type hypersensitivity responses: modulation by gender, ovariectomy, and estrogen replacement J. Endocrinol., May 1, 2007; 193(2): 291 - 297. [Abstract] [Full Text] [PDF]
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 S. L. Tilley, M. Jaradat, C. Stapleton, D. Dixon, X. Hua, C. J. Erikson, J. G. McCaskill, K. D. Chason, G. Liao, L. Jania, et al. Retinoid-Related Orphan Receptor {gamma} Controls Immunoglobulin Production and Th1/Th2 Cytokine Balance in the Adaptive Immune Response to Allergen J. Immunol., March 1, 2007; 178(5): 3208 - 3218. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. OFFNER and M. POLANCZYK A Potential Role for Estrogen in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis Ann. N.Y. Acad. Sci., November 1, 2006; 1089(1): 343 - 372. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. L. Zoller and G. J. Kersh Estrogen Induces Thymic Atrophy by Eliminating Early Thymic Progenitors and Inhibiting Proliferation of beta-Selected Thymocytes. J. Immunol., June 15, 2006; 176(12): 7371 - 7378. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Selvaraj, D. Bunick, C. Finnigan-Bunick, R. W. Johnson, H. Wang, L. Liu, and P. S. Cooke Gene Expression Profiling of 17{beta}-Estradiol and Genistein Effects on Mouse Thymus Toxicol. Sci., September 1, 2005; 87(1): 97 - 112. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Nancy and S. Berrih-Aknin Differential Estrogen Receptor Expression in Autoimmune Myasthenia Gravis Endocrinology, May 1, 2005; 146(5): 2345 - 2353. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
U A KAYISLI, O GUZELOGLU-KAYISLI, and A ARICI Endocrine-Immune Interactions in Human Endometrium Ann. N.Y. Acad. Sci., December 1, 2004; 1034(1): 50 - 63. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. C. Lambert, E. M. Curran, B. M. Judy, D. B. Lubahn, and D. M. Estes Estrogen receptor-{alpha} deficiency promotes increased TNF-{alpha} secretion and bacterial killing by murine macrophages in response to microbial stimuli in vitro J. Leukoc. Biol., June 1, 2004; 75(6): 1166 - 1172. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Polanczyk, S. Yellayi, A. Zamora, S. Subramanian, M. Tovey, A. A. Vandenbark, H. Offner, J. F. Zachary, P. D. Fillmore, E. P. Blankenhorn, et al. Estrogen Receptor-1 (Esr1) and -2 (Esr2) Regulate the Severity of Clinical Experimental Allergic Encephalomyelitis in Male Mice Am. J. Pathol., June 1, 2004; 164(6): 1915 - 1924. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Polanczyk, A. Zamora, S. Subramanian, A. Matejuk, D. L. Hess, E. P. Blankenhorn, C. Teuscher, A. A. Vandenbark, and H. Offner The Protective Effect of 17{beta}-Estradiol on Experimental Autoimmune Encephalomyelitis Is Mediated through Estrogen Receptor-{alpha} Am. J. Pathol., October 1, 2003; 163(4): 1599 - 1605. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. P. Gilleran, O. Putz, M. DeJong, S. DeJong, L. Birch, Y. Pu, L. Huang, and G. S. Prins The Role of Prolactin in the Prostatic Inflammatory Response to Neonatal Estrogen Endocrinology, May 1, 2003; 144(5): 2046 - 2054. [Abstract] [Full Text] [PDF]
|
|
|
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|
Y. Do, S. Ryu, M. Nagarkatti, and P. S. Nagarkatti Role of Death Receptor Pathway in Estradiol-Induced T-Cell Apoptosis in Vivo Toxicol. Sci., November 1, 2002; 70(1): 63 - 72. [Abstract] [Full Text] [PDF]
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5).
