Cell biology

Sebastian Mueller, MD, PhD

Professor of Medicine,

CAR, University of Heidelberg

VISCERA AG Bauchmedizin Bern

Based on our novel ROS models (see Biochemistry section), we were able to study how these small oxygen derived molecules such as H₂O₂, hypochlorous acid or others are involved in the communication within or between cells. These studies are important for the understanding of impaired cellular signaling has is seen during inflammation or in cancer tissues. Another interest has been, how these reactive oxygen species (ROS) are actually produced, metabolized and compartmentilized in cells. Below, some previous key findings are briefly listed.

Selected topics

1. Release and metabolsism of H2O2 from liver peroxisomes

2. Hypoxia signaling exploring a novel enzymatic hypoxia system

3. Regulation of iron metabolism by reactive oxygen species (ROS)

4. References iron

5. References hypoxia signaling

6. References cancer biology

1. Release and metabolism of H₂O₂ from liver peroxisomes

Fig. 1

Fig. 1 shows the release of H₂O₂ via very small channels (A) in the cytosol (B) of liver cells. The paper has been the first to directly demonstrate that peroxisomes which are ubiquituous and essential cell organelles are not only detoxifiers of H₂O₂ but can readily release this molecule into the surrounding cytosol where it possibly could serve as second messenger and metablic control.

2. Hypoxia signaling exploring a novel enzymatic hypoxia system

Fig. 2 Fig. 3

Using the GOX/CAT system (see Biochemistry section) we could show that the important transcription factor hypoxia inducible factor 1alpha (HIF1 alpha) is not responding to oxygen levels but to the decrease of oxygen within a certain time period. Fig. 2 shows that nuclear HIF1alpha (red) is only seen after 2 hours of hypoxia but not after 24 hours although the liver cells are alive and have actually adapted to these low oxygen levels. Fig. 3 shows directly that lowering oxygen by 50% will result in equal expression levels of HIF1 no matter what absolute degree of hypoxia is present. We have interpreted the negative feed back loop of HIF1-degrading prolyl hydroxylases (PHD) and HIF1 (see Fig. 4) as metabolic differential control. Only a disruption of this loop will result in sustained upregulation of HIF1 which will increase the metabolic turnover of tissues (for details see also ref. 27. and 36.).

Fig. 4

3. Regulation of iron metabolism by reactive oxygen species (ROS)

Iron overload is a major risk factor for liver cancer and patients with chronic liver disease or cirrhosis commonly show increased levels of iron in their liver such as alcoholic liver disease or chronica hepatitis C (see Fig. 5 below). The toxicity and carcinogenicity of iron is mainly explained by its high reactivity with reactive oxygen species (ROS) that eventually lead to extremely reactive hydroxyl radicals via the Fenton chemistry. Since the diseased liver shows a high ROS-turnover even mildly increased iron levels can be highly carcinogenic. On the other side, the molecular mechanism of the hepatic iron accumulation in chronic liver diseases are poorly understood but could provide novel targeted approaches to prevent iron-based carcinogenesis in chronic liver disease.

Fig. 5

We have a longterm research focus on how ROS regulate key proteins of iron metabolism at the cellular and systemic level. In previous studies we have shown that the central ROS metabolite hydrogen peroxide (H₂O₂) causes cellular iron accumulation via posttranscriptional (iron regulatory protein 1) and translational (transferrin receptor 1) mechanisms. Recent work from our laboratory indicates that ROS also affect the systemic control of iron. As shown in Fig. 5 above, a better understanding of the mechanisms underlying iron accumulation and toxicity could help in developing novel targeted therapies.

4. References iron studies

61. CHOP-mediated hepcidin suppression modulates hepatic iron load. Mueller K, Sunami Y, Stuetzle M, Güldiken N, Kucukoglu O, Mueller S, Kulaksiz H, Schwarz P, Strnad P. J Pathol. 2013 Jun 8. doi: 10.1002/path.4221. [Epub ahead of print] PMID: 23749468 [PubMed - as supplied by publisher] Related citations

55. Sustained submicromolar H2O2 levels induce hepcidin via Signal Transducer and Activator of Transcription 3 (STAT3).

Millonig G, Ganzleben I, Peccerella T, Casanovas G, Brodziak-Jarosz L, Breitkopf-Heinlein K, Dick TP, Seitz HK, Muckenthaler MU, Mueller S.

J Biol Chem. 2012 Aug 29. [Epub ahead of print] PMID: 22932892 PubMed - as supplied by publisher]

Free Article Related citations

53. Siderophore-mediated iron trafficking in humans is regulated by iron.

Liu Z, Lanford R, Mueller S, Gerhard GS, Luscieti S, Sanchez M, Devireddy L.

J Mol Med (Berl). 2012 Apr 15. [Epub ahead of print] PMID: 22527885 [PubMed - as supplied by publisher]

Related citations

44. Increased iron in HCV infection: Collateral damage or antiviral defense?

Mueller S.

J Hepatol. 2010 Aug 22. [Epub ahead of print] No abstract available. PMID: 20850193 [PubMed - as supplied by publisher] Related citations

43. Heme Oxygenase-1 and Iron in Liver Inflammation: a Complex Alliance.

Immenschuh S, Baumgart-Vogt E, Mueller S.

Curr Drug Targets. 2010 Aug 13. [Epub ahead of print]PMID: 20704547 [PubMed - as supplied by publisher] Related citations

42. Heme oxygenase-1 as a therapeutic target in inflammatory disorders of the gastrointestinal tract.

Vijayan V, Mueller S, Baumgart-Vogt E, Immenschuh S.

World J Gastroenterol. 2010 Jul 7;16(25):3112-9.PMID: 20593496 [PubMed - in process]Free PMC Article Free textRelated citations

29. In vitro-targeted gene identification in patients with hepatitis C using a genome-wide microarray technology.

Hagist S, Sültmann H, Millonig G, Hebling U, Kieslich D, Kuner R, Balaguer S, Seitz HK, Poustka A, Mueller S.

Hepatology. 2009 Feb;49(2):378-86.

PMID: 19177570 [PubMed - indexed for MEDLINE] Related Articles

25. Sustained hydrogen peroxide induces iron uptake by transferrin receptor-1 independent of the iron regulatory protein/iron-responsive element network.

Andriopoulos B, Hegedüsch S, Mangin J, Riedel HD, Hebling U, Wang J, Pantopoulos K, Mueller S.

J Biol Chem. 2007 Jul 13;282(28):20301-8. Epub 2007 May 21. PMID: 17517884 [PubMed - indexed for MEDLINE] Related Articles Free article at journal site

24. Compartment-dependent management of H(2)O(2) by peroxisomes.

Fritz R, Bol J, Hebling U, Angermüller S, Völkl A, Fahimi HD, Mueller S.

Free Radic Biol Med. 2007 Apr 1;42(7):1119-29. Epub 2007 Jan 12. PMID: 17349938 [PubMed - indexed for MEDLINE] Related Articles

23. Liver-homing of purified glucose oxidase: a novel in vivo model of physiological hepatic oxidative stress (H2O2).

Rost D, Welker A, Welker J, Millonig G, Berger I, Autschbach F, Schuppan D, Mueller S.

J Hepatol. 2007 Mar;46(3):482-91. Epub 2006 Nov 17. PMID: 17188390 [PubMed - indexed for MEDLINE] Related Articles

22. Iron, HCV, and liver cancer: hard metal setting the pace?

Mueller S, Afdhal NH , Schuppan D.

Gastroenterology. 2006 Jun;130(7):2229-34. No abstract available.PMID: 16762645 [PubMed - indexed for MEDLINE] Related Articles

21. Iron regulatory protein 1 as a sensor of reactive oxygen species.

Mueller S.

Biofactors. 2005;24(1-4):171-81. PMID: 16403978 [PubMed - indexed for MEDLINE] Related Articles

18. Extracellular H2O2 and not superoxide determines the compartment-specific activation of transferrin receptor by iron regulatory protein 1.

Sureda A, Hebling U, Pons A, Mueller S.

Free Radic Res. 2005 Aug;39(8):817-24. PMID: 16036361 [PubMed - indexed for MEDLINE]

16. Myeloperoxidase-derived hypochlorous acid antagonizes the oxidative stress-mediated activation of iron regulatory protein 1.

Mütze S, Hebling U, Stremmel W, Wang J, Arnhold J, Pantopoulos K, Mueller S.

J Biol Chem. 2003 Oct 17;278(42):40542-9. Epub 2003 Jul 29. Erratum in: J Biol Chem. 2003 Dec 5;278(49):49662. PMID: 12888561 [PubMed - indexed for MEDLINE]

15. Sensitive and real-time determination of H2O2 release from intact peroxisomes.

Mueller S, Weber A, Fritz R, Mütze S, Rost D, Walczak H, Völkl A, Stremmel W.

Biochem J. 2002 May 1;363(Pt 3):483-91. PMID: 11964148 [PubMed - indexed for MEDLINE]

14. Activation of iron regulatory protein-1 by oxidative stress.

Mueller S, Pantopoulos K.

Methods Enzymol. 2002;348:324-37. PMID: 11885287 [PubMed - indexed for MEDLINE]

12. IRP1 activation by extracellular oxidative stress in the perfused rat liver.

Mueller S, Pantopoulos K, Hübner CA, Stremmel W, Hentze MW.

J Biol Chem. 2001 Jun 22;276(25):23192-6. Epub 2001 Apr 10. PMID: 11297549 [PubMed - indexed for MEDLINE]

9. p21WAF1 regulates anchorage-independent growth of HCT116 colon carcinoma cells via E-cadherin expression.

Mueller S, Cadenas E, Schönthal AH.

Cancer Res. 2000 Jan 1;60(1):156-63. PMID: 10646868 [PubMed - indexed for MEDLINE]

6. Differences in the regulation of iron regulatory protein-1 (IRP-1) by extra- and intracellular oxidative stress.

Pantopoulos K, Mueller S, Atzberger A, Ansorge W, Stremmel W, Hentze MW.

J Biol Chem. 1997 Apr 11;272(15):9802-8. PMID: 9092514 [PubMed - indexed for MEDLINE]

5. References hypoxia signaling

50. The effect of low oxygen with and without steady-state hydrogen peroxide on cytokine gene and protein expression of monocyte-derived macrophages - biomed 2011.
Owegi H, Li H, Bouwens M, Egot-Lemaire S, Mueller S, Geib RW, Waite GN. Biomed Sci Instrum. 2011;47:58-63. Related citations

48. Investigation of tumor hypoxia using a two-enzyme system for in vitro generation of oxygen deficiency.

Askoxylakis V, Millonig G, Wirkner U, Schwager C, Rana S, Altmann A, Haberkorn U, Debus J, Mueller S, Huber PE.

Radiat Oncol. 2011 Apr 10;6:35. Free PMC Article PMID:21477371[PubMed - in process] Free full text Related citations

27. Hypoxia-inducible factor 1a under rapid enzymatic hypoxia: Cells sense decrements of oxygen but not hypoxia per se.

Millonig G, Hegedüsch S, Becker L, Seitz HK, Schuppan D, Mueller S.

Free Radic Biol Med. 2009 Jan 15;46(2):182-191. Epub 2008 Nov 1.

PMID: 19007879 [PubMed - as supplied by publisher] Related Articles

6. References cancer biology

45. Ethanol-mediated carcinogenesis in the human esophagus implicates CYP2E1 induction and the generation of carcinogenic DNA-lesions.

Millonig G, Wang Y, Homann N, Bernhardt F, Qin H, Mueller S, Bartsch H, Seitz HK.

Int J Cancer. 2011 Feb 1;128(3):533-40.PMID: 20715111 [PubMed - indexed for MEDLINE]Related citations

32. Alcoholic liver disease and hepatitis C: a frequently underestimated combination.

Mueller S, Millonig G, Seitz HK.

World J Gastroenterol. 2009 Jul 28;15(28):3462-71.

PMID: 19630099 [PubMed - in process] Related Articles Free article in PMC | at journal site

31. Ethanol-induced cytochrome P4502E1 causes carcinogenic etheno-DNA lesions in alcoholic liver disease.

Wang Y, Millonig G, Nair J, Patsenker E, Stickel F, Mueller S, Bartsch H, Seitz HK.

Hepatology. 2009 Aug;50(2):453-461. PMID: 19489076 [PubMed - as supplied by publisher] Related Articles

28. Alcohol and colorectal cancer: the role of alcohol dehydrogenase 1C polymorphism.

Homann N, König IR, Marks M, Benesova M, Stickel F, Millonig G, Mueller S, Seitz HK.

Alcohol Clin Exp Res. 2009 Mar;33(3):551-6. Epub 2008 Dec 19.

PMID: 19120062 [PubMed - indexed for MEDLINE] Related Articles