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P093 15-d-PGJ2 – a possible regulator of iron homeostasis

J. Martin*1, 2, S. Ulrich-Rueckert2, J. Stein1, 3

1Interdisciplinary Crohn Colitis Centre Rhein-Main, Frankfurt/Main, Germany, 2Goethe University Frankfurt, Insitute of Pharmaceutical Chemistry, Frankfurt/Main, Germany, 3DGD Clinics Sachsenhausen, Frankfurt/Main, Germany

Background

Hepcidin, an acute phase protein mainly produced in the liver, has been demonstrated to be a key mediator of the cytokine-induced anaemia of chronic inflammation (ACI).1 Because prostaglandins (PGs), recognised as both pro- and anti-inflammatory lipid mediators, have been shown to be involved in different pathogenic inflammatory pathways, our study was aimed to elucidate their role in iron homeostasis. Using the pro-inflammatory PG2 and the anti-inflammatory 15-Deoxy-Delta-12-14-prostaglandin J2 (15-d-PGJ2),2 the latter also a known inducer of the transcription factor Nrf-2,3 we tested whether these lipid mediators may be involved in interleukin-6 (IL-6) and oncostatin M (OSM)-induced hepcidin expression.

Methods

HepG2 cells were cultivated under standard conditions and incubated for 16 hours with IL-6 (10 ng/mL) or OSM (10 ng/mL) alone or in combination with 15-d-PGJ2 (10µM). For reporter gene assays, plasmids were transfected by lipofection and luciferase activity was measured luminometrically. Quantitative real-time polymerase chain reaction (PCR) was performed to determine mRNA expression. Proteins were detected by Western blot analysis. For gene-knockdown, HepG2 cells were transfected with Nrf-2 or nontargeting siRNA duplexes according to the protocol for reversed lipofection.

Results

Both OSM (**p < 0.01) and IL-6 (***p < 0.001) significantly induced hepcidin promoter activation and mRNA level in HepG2 cells after 6 h and 16 h. These effects were significantly counteracted by coincubation with 15-d-PGJ2 (***p < 0.001) but not with PGE2. Further, treatment with 15-d-PGJ2 leads to nuclear translocation and thus activation of transcription factor Nrf-2, which was confirmed by induction of Nrf-2 target genes HO-1 and NQO-1 (**p < 0.01). Compared with nontargeting siRNA transfection, a 50% Nrf-2 knockdown tended to reduce the 15-d-PGJ2 inhibition of IL-6-induced heparin mRNA expression. In addition, 15-d-PGJ2 significantly induced ferritin and ferroportin on mRNA level in HepG2 (**p < 0.01), both involved in iron homeostasis.

Conclusion

Our study data demonstrated an involvement of the prostaglandin 15-d-PGJ2 in the regulation of iron homeostasis. Our preliminary data also indicate that this may linked, at least in part, to the transcription factor Nrf-2. Further research will be needed confirm these data.

References:

[1] Dao MC, Meydani SN (2013), Iron biology, immunology, aging, and obesity: 4 fields connected by the small peptide hormone hepcidin. Adv Nutr 2013;4:602–17.

[2] Scher JU, Pillinger MH.15d-PGJ2: The anti-inflammatory prostaglandin? Clin Immunol 2005;114:100–09.

[3] Kim EH, Surh YJ. 15-Deoxy-D12,14-prostaglandin J2 as a potential endogenous regulator of redox-sensitive transcription factors. Biochem Pharmacol 2006:72:1516–28.