Abstracts - Chirurgie Kongress

23.6
A20 promotes hepatocyte proliferation by enhancing IL-6 signaling
P. Studer 1,2 , C. da Silva 1 , M. Skroch 1 , S. Damrauer 1 , J. Siracuse 1 , E. Maccariello 1 , D. Inderbitzin 2 ,
E. Kaczmarek 1 , D. Candinas 2 , C. Ferran 1 ( 1 Boston/USA, 2 Bern)
Objective: Living donor liver transplantation (LDLT) has emerged as a solution to ease organ shortage
in orthotopic liver transplantation. A disadvantage of LDLT is small-for-size liver grafts that are particularly
susceptible to injury and show decreased liver regeneration. We have shown that the hepatoprotective
protein A20 promotes liver regeneration, partly through blockade of the Cyclin dependent kinase
inhibitor p21. However the impact of A20 expression in livers on the production and or signaling of the
priming cytokine IL-6 are still unknown.
Methods and Results: In this study, we demonstrate that secretion of IL-6 (ELISA) following treatment
with LPS or TNF was moderately lower in hepatocytes transduced with a recombinant A20 adenovirus
(rAd) as compared to controls. This indicates that Il-6 production in hepatocytes is not solely
NF-kB dependent (not totally blocked by the NF-kB inhibitor A20). Despite similar or lower IL-6 levels in
rAd transduced hepatocytes, IL-6 signaling as evaluated by phosphorylation of STAT3 (Western blot;
WB) was enhanced in A20 expressing hepatocytes. This was confirmed in experiments showing that
A20 increases STAT-3 phosphorylation in response to exogenous human IL-6. Accordingly, hepatocyte
proliferation was significantly higher in rAd A20 transduced hepatocytes as opposed to controls. The
balance of IL-6 signaling in hepatocytes is regulated through a negative feedback loop by the IL-6/
STAT-3 dependent induction of suppressor of cytokine signal-3 (SOCS3). Our results indicate that A20
decreased IL-6 mediated upregulation of SOCS3 (WB). Mutational analysis o A20 demonstrated that
the pro-proliferative effect of A20 co-segregate with its 7-Zinc finger (7-Zn) and not its N-terminus (Nter)
domain. Additional mutational analysis of the 7-ZN A20 domain allowed us to further narrow this
functional A20 domain to a mutant comprising the 4th and 5th Zinc fingers.
Conclusion: These results suggest that A20 enhances priming of hepatocytes by IL-6 likely through
down-regulation of SOCS3. This added to the effect of A20 on p21 would further enhance its pro-proliferative
properties in hepatocytes. The structure-function analysis indicates that A20‘s C-terminal
domain is responsible for the pro-proliferative effects of A20 and paves the way for defining small
peptides that can be potentially therapeutic in the setting of LDLT.
23.7
Higher cord blood levels of mannose-binding lectin-associated serine protease-2 (MASP-2) in infants
with necrotising enterocolitis
U. Kessler 1,2 , C. Aebi 2 , R. A. Ammann 2 , S. B. Bigler 2 , M. Nelle 2 , S. Berger 2 , L. J. Schlapbach 2 ( 1 Lausanne,
2 Bern)
Objective: Necrotising enterocolitis (NEC) causes significant morbidity and mortality in premature infants.
The role of innate immunity in the pathogenesis of NEC remains unclear. The lectin pathway of
complement activation consists of Mannose-binding lectin (MBL), H-, L- and M-Ficolins, which activate
the complement system after recognition of microorganisms via MBL-associated serine protease-2
(MASP-2). The aim of this study was to investigate whether the lectin pathway proteins are associated
with NEC.
Methods: This observational case-control study included 32 infants with radiologically confirmed NEC
and 64 controls. MBL, H-ficolin, M-Ficolin and MASP-2 were measured in cord blood using ELISA. Multivariate
logistic regression was performed.
Results: Of the 32 NEC cases (median gestational age, 30.5 weeks), 13 (41%) were operated and
5 (16%) died. MBL (p