studies

302A AASLD ABSTRACTS HEPATOLOGY, October, 2015
In contrast, IL-4Rα ∆LysM mice displayed retarded fibrosis resolution
as evidenced by slower clearance of hydroxyproline
and Sirius-Red stained collagen at 2 weeks off CCL 4
. This was
accompanied by a reduction of Ly-6c lo restorative and M2
macrophages and an increase of M1 macrophages. In a therapeutic
approach, we applied an ASO targeting IL-4Rα (IL-4Rα
ASO) to CCL 4
-treated mice. IL-4Rα ASO strongly attenuated
fibrosis progression but mitigated fibrosis resolution after CCL 4
withdrawal. Conclusion: Our studies demonstrate that IL-4Rα
modulates fibrosis progression and reversal in discordant ways
through macrophages. During progression, IL-4Rα signaling
increases inflammation and fibrosis by activating Ly6c hi macrophages;
during reversal, IL-4Rα potentiates restorative (M2,
Ly6c lo ) macrophage signaling. Accordingly, IL-4Rα ASO treatment
attenuates fibrosis progression, but retards reversal.
Disclosures:
Jeff R. Crosby - Employment: ISIS Pharmaceuticals
Michael L. McCaleb - Employment: Isis Pharmaceuticals; Stock Shareholder: Isis
Pharmaceuticals
The following authors have nothing to disclose: Shih-Yen Weng, Santosh Vijayan,
Xiaoyu Wang, Yilang Tang, Kornelius Padberg, Yong Ook Kim, Brombacher
Frank, Ari Waisman, Ernesto Bockamp, Detlef Schuppan
184
Liver sinusoidal endothelial cells induce neutrophil
extracellular traps in liver sterile inflammation via
IL-33/ST2 axis
Hai Huang, Hamza Yazdani, Patricia Loughran, Heth R. Turnquist,
Allan Tsung; Department of Suegery, University of Pittsburgh Medical
Center, Pittsburgh, PA
Both liver sinusoidal endothelial cells (LSECs) and neutrophils
are involved and interact in liver ischemia/reperfusion (I/R)
injury. Damaged LSECs, as the major sources of IL-33, play
important role in neutrophil infiltration during liver I/R. We
recently found that in response to damage associated molecular
patterns (DAMPs), infiltrated neutrophils forming neutrophil
extracellular traps (NETs), exacerbate sterile inflammatory
injury during liver I/R. We here sought to determine the role
of IL-33 released from LSECs in NET formation during liver I/R.
WT or IL-33 KO mice were subjected to a non-lethal warm liver
I/R model. Recombinant IL-33 (rIL-33) or soluble ST2 (sST2,
decoy receptor of IL-33) was administered in select groups.
IL-33 KO mice or sST2-treated WT mice were significantly protected
from I/R injury, having significantly less serum sALT and
hepatic necrosis, lower levels of systemic cytokines, abrogation
of proinflammatory signaling pathways compared to WT mice.
rIL-33 administered during I/R exacerbated hepatotoxicity and
systemic inflammation. Although significant neutrophils infiltration
was found in both IL-33 KO and WT mice, NETs formation
decreased in IL-33 KO mice during liver I/R compared
with WT mice, associated with significant less serum level of
myeloperoxidase (MPO)-DNA complexes and tissue level of
citrullinated-histone H3 (NET markers). In addition, treatment
of sST2 reduced NET formation whereas significant increased
NETs were found in rIL-33 treated mice after liver I/R. In vitro,
IL-33 released from LSECs that were subjected to hypoxia (1%
O 2
) promotes NET formation. Directly using rIL-33 stimulates
neutrophils confirmed IL-33/ST2-MyD88 signaling pathway in
NET formation. Using either IL-33 KO LSECs, or co-stimulated
neutrophil with IL-33 neutralizing antibody or sST2 blocked
NET formation. Our study demonstrates IL-33 from LSECs initiates
a feed-forward mechanism to neutrophils inducing NETs
formation in excessive inflammation and hepatotoxicity during
liver I/R.
Disclosures:
The following authors have nothing to disclose: Hai Huang, Hamza Yazdani,
Patricia Loughran, Heth R. Turnquist, Allan Tsung
185
15-PGDH prevents LPS/GalN-induced acute liver injury
through inhibiting Kupffer cell activation
Lu Yao, Chang Han, Tong Wu; pathology and laboratory medicine,
tulane university, New Orleans, USA Minor Outlying Islands
The NAD+-dependent 15-hydroxyprostaglandin dehydrogenase
(15-PGDH) catalyzes the oxidation of the 15(S)-hydroxyl
group of Prostaglandin E 2
(PGE 2
), converting the pro-inflammatory
PGE 2
to the anti-inflammatory 15-keto-PGE 2
(an
endogenous ligand for peroxisome proliferator-activated receptor-gamma
[PPAR-γ]). PPAR-γ is a ligand-dependent transcriptional
factor, which plays an important role in regulation of
inflammatory cell activation. To evaluate the significance of
15-PGDH/PPAR-γ cascade in liver inflammation, we generated
transgenic mice with targeted expression of 15-PGDH in the
liver (15-PGDH Tg) and the animals were subjected to lipopolysaccharide
(LPS)/Galactosamine (GalN) induced acute liver
inflammation and tissue damage. Compared to the wild type
mice, the 15-PGDH Tg mice showed lower levels of alanine
aminotransferase (ALT) and aspartate aminotransferase (AST),
less liver tissue damage, less hepatic apoptosis/necrosis, less
macrophage activation, and lower inflammatory cytokine production.
In cultured Kupffer cells, treatment with 15-keto-PGE 2
or the conditioned medium (CM) from 15-PGDH Tg hepatocyes
inhibited LPS-induced cytokine production. Both 15-keto-PGE 2
and the CM from15-PGDH Tg hepatocyes also significantly
up-regulated the expression of PPAR-γ down-stream genes in
Kupffer cells. On the other hand, 15-PGDH overexpression
or 15-keto-PGE 2
treatment of hepatocytes did not influence
TNF-α-induced hepatocyte apoptosis. These results suggest
that the resistance of 15-PGDH Tg mice to LPS/GalN-induced
liver injury is mediated through 15-keto-PGE 2
, which activates
PPAR-γ in Kupffer cells and inhibited inflammatory cytokine
production. Consistent with this assertion, we observed that the
PPAR-γ antagonist, GW9662, reversed the effect of 15-keto-
PGE 2
in Kupffer cell (in vitro) and restored the susceptibility
of 15-PGDH Tg mice to LPS/GalN-induced acute liver injury
(in vivo). Taken together, our findings provide novel evidence
that hepatic overexpression of 15-PGDH protects against
LPS/GalN-induced acute liver injury by inhibiting Kupffer cell
inflammatory response. Thus, 15-keto-PGE 2
is an endogenous
PPAR-γ ligand that may be utilized as a pharmacological agent
to ameliorate liver inflammation and tissue damage.