The Toxicologist - Society of Toxicology

1126 PERSISTENT DEVELOPMENTAL ARYLHYDROCARBON
RECEPTOR ACTIVATION MODULATES NOTCH1-
DEPENDENT T-CELL BUT NOT B-CELL
DIFFERENTIATION POTENTIAL.
L. Ahrenhoerster, P. Lakatos and M. Laiosa. School of Public Health, University of
Wisconsin Milwaukee, Milwaukee, WI.
Arylhydrocarbon receptor (AHR) activation in the immune system has generated
renewed interest with the findings that the AHR is an important regulator of
hematopoiesis and regulatory T-cell differentiation. In order to understand the
mechanism(s) underlying precursor cell fate decisions potentially impacted by
AHR signal transduction, our laboratory has tested the capacity of undifferentiated
mouse fetal liver progenitors to respond to signals known to drive development into
the B or T cell lineage. Specifically, lineage negative, cKit+, Sca-1+ (LSK) multipotent
hematopoietic progenitor cells obtained from gestational day (GD) 14.5
mouse fetal livers were placed in culture with either OP9-GFP cells which drives Bcell
development or OP9-DL1 stromal cells, which provide a Notch signal driving
differentiation to the T-cell lineage. To test the hypothesis that persistent AHR activation
during development modulates LSK differentiation capacity, mice were exposed
to 5μg/kg 2,3,7,8 Tetrachlorodibenzo-p-dioxin (TCDD) in olive oil on GD
0 and 7 by gavage or vehicle control. TCDD is a ubiquitous environmental contaminant
and potent AHR agonist, which humans are exposed to daily through low
level food contamination. On day 14.5, fetal livers were dissected, LSKs purified by
cell sorting, and subsequently placed into culture. At the end of the 12-day culture
period, cells were enumerated and the proportion of T-cells or B-cells obtained
from each co-culture was determined by flow cytometry. While an equivalent number
of B-cells were obtained from control or TCDD exposed mice, the number of
T-cells generated in culture was reduced by nearly 40% in the cultures derived from
TCDD exposed pregnant dams. These data suggest that early life AHR activation
reprograms a multipotent progenitor’s capacity to mediate Notch1-dependent Tcell
differentiation.
1127 THE ROLE OF THE ARYL HYDROCARBON RECEPTOR
IN WOOD SMOKE-INDUCED MACROPHAGE
SUPPRESSION.
C. T. Migliaccio, E. Kobos, V. Porter and T. Ward. Center for Environmental
Health Sciences, University of Montana, Missoula, MT.
Alveolar macrophages (AM) are part of the first line of defense against pulmonary
infections. AM are responsible for clearing particles, such as silica or bacteria, and
are key regulatory cells of the immune response in the airways. In addition to decreases
in overall AM function, including antigen presentation and bacterial clearance,
we observed a lack of classic inflammation (i.e. TNFα, neutrophil influx, increases
in total protein) following acute exposure to WS. One potential explanation
for these decreases is an observed link between polycyclic aromatic hydrocarbons
(PAH), RelB activation, and the suppression of macrophage-guided inflammation.
RelB, the non-canonical NFκB pathway, has been associated with decreases in inflammation
and apoptosis, both of which have been observed following exposure to
WS. In order to determine whether the non-canonical pathway is being activated,
AM were analyzed for RelB translocation to the nucleus using immunohistochemistry.
We observed that both WS and concentrated WS-derived particulate matter
(WS-PM) induced activation of RelB, where activation appears dependant on components
associated with the water-insoluble fraction (IF) of concentrated WS-PM.
Activation of RelB can occur in response to PAHs, via the aryl hydrocarbon receptor
(AhR), and these mechanisms have been linked to macrophage regulation. To
this end the PAH analysis of WS-PM detected 4-5 PAHs only in the IF of WS-PM.
Further analysis showed specific AhR activation by the IF, at levels significantly
higher than controls. These data suggest a role for specific AhR activation in the
WS-induced suppression of AM.
This work is supported by NIH grant RR-017670 and HEI grant 4743-RFA04-4/06-4
1128 TCDD TREATMENT ENHANCES THE M1 PHENOTYPE
IN J774 MURINE MACROPHAGES.
A. E. McCartney, R. A. Aguayo, P. V. Hamilton and K. A. Mitchell. Biological
Sciences, Boise State University, Boise, ID.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental contaminant
that elicits toxicity by activating the aryl hydrocarbon receptor. Although the
mechanism of toxicity is unclear, exposure to TCDD has been shown to enhance
inflammation in several model systems. A typical inflammatory response depends
on the production of soluble mediators by activated macrophages, which fall into
two phenotypically distinct categories: classically activated M1 (inflammatory)
macrophages and alternatively activated M2 (rebuilding) macrophages. M1
macrophages produce iNOS and soluble mediators such as TNF-α and IL-6, which
may exacerbate inflammation, whereas M2 macrophages produce mediators that
curtail inflammation and promote wound healing. In this study, we tested the hypothesis
that TCDD treatment skews macrophage activation towards the M1 phenotype.
Murine J774 macrophages were primed for 24 hr with either IFNγ, which
drives an M1 phenotype, or IL-4/IL-13, which drives an M2 phenotype, in the
presence or absence of TCDD (10 nM). Cells were then stimulated with LPS (50
ng/mL) for 24 hours. Cell lysates and supernatants were analyzed to measure TNFα,
IL-6, iNOS, and CCR7, which are characteristic of M1 macrophages. In J774
cells primed with IFNγ, TCDD had no effect on CCR7 expression or cytokine production,
but it increased iNOS expression. Treatment of J774 cells with IL-4 and
IL-13 suppressed M1 activation markers and cytokines in vehicle-treated cells but
not in TCDD-treated cells. When these cells were subsequently stimulated with
LPS, TCDD-treated cells expressed levels of IL-6 that were ten-fold higher than vehicle
controls. These results indicate that TCDD treatment may enhance the activation
of M1 macrophages and skew macrophages activated under M2 conditions
toward the M1 phenotype. Moreover, the specific cell signaling pathways in
macrophages that are enhanced by TCDD appear to be confined to those that drive
iNOS expression and IL-6 production.
1129 THE ARYL HYDROCARBON RECEPTOR MODULATES
PHENOTYPE AND FUNCTION OF DENDRITIC CELLS.
G. Jin and B. Lawrence. Environmental Medicine, University of Rochester,
Rochester, NY.
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that
is expressed in cells of the immune system. AhR activation by a variety of ligands is
profoundly immunomodulatory, with changes in CD8+ T cell function and impaired
ability to fight influenza virus infection being particularly sensitive to perturbation
by the pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a wellknown
high affinity AhR agonist. We have previously reported that AhR activation
by TCDD reduces the proliferation and differentiation of influenza virus-specific
CD8+ T cells in the mediastinal lymph nodes (MLN). However, AhR activation
does not directly affect proliferation and differentiation of CD8+ T cells, suggesting
that defects in accessory cells such as antigen presenting cells (APCs) are directly affected
by AhR activation. Dendritic cells (DCs) are professional APCs. In response
to infection, they capture antigen in the lung, migrate to the MLN and play a key
role in the priming of virus-specific naïve CD8+ T cells. In this study, we investigated
the effects of AhR activation by TCDD on the function and phenotypic profile
of DCs in influenza virus-infected mice. We show that AhR activation changes
the number of functionally distinct DC subsets in the lung and MLN, and reduces
the ability of DCs to stimulate naïve CD8+ T cells in vitro. In particular, AhR activation
reduces cell number of CD103+ DCs in the MLN. This is important because
our data and work of others indicate that CD103+ DCs are superior in priming
virus specific naïve CD8+ T cells. Our results indicate that AhR activation by
TCDD modulates DC phenotype and function, and suggest that environmental
factors may contribute to differential susceptibilities and responses to respiratory
viral infections.
(Supported by NIH Grants K02-ES012409 and R01-HL097141 to BPL).
1130 MODULATION OF NF-KB MEDIATED DENDRITIC
CELL DIFFERENTIATION AND FUNCTION BY ARYL
HYDROCARBON RECEPTOR ACTIVATION.
C. Vogel 1, 3 , S. Goth 2 , D. Wu 3 , V. Kou 3 , A. Lollies 3 , I. Pessah 2 and F.
Matsumura 1, 3 . 1 Environmental Toxicology, University of California, Davis, CA,
2 Molecular Biosciences, University of California, Davis, CA and 3 Center for Health
and the Environment, University of California, Davis, CA.
Recent findings indicate that the aryl hydrocarbon receptor (AhR) plays an important
role in the immune system including T cell and dendritic cell (DC) differentiation.
Here we show that activation of AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin
(TCDD) lead to a time-dependent induction of LPS-activated target genes in
human U937 DC like IL-8 and CCL1, in contrast expression of CCL4 and
CCL18 are antagonized by AhR activation. The DC surface marker CD86 was increased
by both LPS and TCDD and is synergistically increased after LPS/TCDD
cotreatment. The data also indicate that this synergy involves AhR and RelB. On
the other hand, the expression of CD40 and CD80 was only significantly increased
by LPS in U937 DC, but did not change by TCDD. However, the LPS-induced
expression of CD80 and CD40 was drastically suppressed in presence of TCDD.
Furthermore, TCDD induced expression of both isoforms of the regulatory enzyme
indoleamine 2,3-dioxygenase (IDO1 and IDO2) which has immunomodulatory
activity by increasing the number of regulatory T cells. Results show that in
contrast to TCDD, treatment with Interferon-(IFN)γ or 6-formylindolo[3,2-b]carbazole
(FICZ) may induce IDO1 but not the expression or promoter activity of
SOT 2011 ANNUAL MEETING 241