E-ISSN 2146-8362
 

Original Research 


Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study

Ganka Bekyarova, Maria Tzaneva, Minka Hristova.

Abstract
Objective: Generation of reactive oxygen metabolites (ROM) and oxidative stress are crucial in pathogenesis of thermal skin injury. Heat shock proteins such as HSP32 known as heme oxygenase-1 (HO-1) possesses antioxidant, anti-inflammatory, and vasodilative properties and play an important role in the protecting of tissues from several stresses. In this immunohistochemical study, we have assessed the constitutive expression of HO-1 in normal gastric mucosa and liver and tested the hypothesis that its expression in these tissues is upregulated in thermal skin injury characterized by increased production of ROMs and other pro-inflammatory mediators. We used malondialdehyde (MDA) as a marker of oxidative stress and tumor necrosis factor (TNF) α as a marker of inflammatory response in burn rat model.
Methods: HO-1 expression in formalin-fixed sections was assessed by peroxidase anti-peroxidase immunohistochemistry using a polyclonal rabbit anti-HO-1 as primary antibody. TNF-α in plasma was quantified using enzyme-linked immunosorbent assay (ELISA) kit. Spectrometric method was used for plasma and tissue MDA assay.
Results:Immunohistochemical staining revealed HO-1 expression in all groups. Staining scores for HO-1 in endothelial cells in both gastric mucosa and liver were increased with 32% (p <0.001) and 51 % (p< 0.001), compared to that of controls. The levels of MDA in the gastric mucosa were increased by 43% (p<0.05) and in liver in 126% (p<0.001). Plasma concentration of TNF α was also elevated by 111 % (p<0.001) and MDA level in plasma was increased by 37% (p<0.05).
Conclusion: Our data suggest that HO-1 induction following burn is an adaptive response which can protect gastric mucosal and liver against further oxidative damage. HO-1 system may represent a target and an effective and cooperative strategy to intervene in the protection against inflammatory processes and oxidative tissue injury.

Key words: Heme oxygenase-1; gastric mucosa; liver; burns; inflammatory response; oxidative stress


 
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REFERENCES
Pintaudi AM, Tesoriere L, D'Arpa N, D'Amelio L, D'Arpa D, Bongiorno A,Masellis M, Livrea MA. Oxidative stress after moderate to extensive burning in humans. Free Radic Res 2000; 33: 139-46.

http://dx.doi.org/10.1080/10715760000300691

[Pubmed]   

Ieri SO, Gedik IE, Erzik C, Uslu B, Arbak S, Gedik N, Yeen BC. Oxytocin ameliorates skin damage and oxidant gastric injury in rats with thermal trauma. Burns 2008; 34: 361-9.

http://dx.doi.org/10.1016/j.burns.2007.03.022

[Pubmed]   

Ding, HQ, Zhou, BJ, Liu, L, Cheng, S. Oxidative stress and methallothionein expression in the liver of rats with severe thermal injury. Burns 2002; 28: 215-21.

http://dx.doi.org/10.1016/S0305-4179(02)00018-9

Sehirli O, Sener E, Sener G, Cetinel S, Erzik C, Yeen BC. Ghrelin improvesburn-induced multiple organ injury by depressing neutrophil infiltration and the release of pro-inflammatory cytokines. Peptides 2008; 29: 1231-40.

http://dx.doi.org/10.1016/j.peptides.2008.02.012

[Pubmed]   

Barton SGRG, Rampton DS, Winrow VR, Domizio P, Feakins RM. Expression of heat shock protein 32 (hemoxygenase-1) in the normal and inflamed human stomach and colon: an immunohistochemical study. Cell Stress & Chaperones 2003; 8: 329–34.

http://dx.doi.org/10.1379/1466-1268(2003)008<0329:EOHSPH>2.0.CO;2

Applegate LA, Luscher P, Tyrrell RM. Induction of heme oxygenase: a general response to oxidant stress in cultured mammalian cells. Cancer Res 1991; 51: 974-78.

[Pubmed]   

Ryter SW, Alam J, Choi AM. Heme oxygenase-1/carbon monoxide: from basic science to therapeutic applications. Physiol Rev 2006; 86: 583-650.

http://dx.doi.org/10.1152/physrev.00011.2005

[Pubmed]   

Bach FH. Heme oxygenase-1 as a protective gene.Wien Klin Wochenschr 2002; 114, Suppl 4, 1-3.

[Pubmed]   

Gomes AS, Gadelha GG, Lima SJ, Garcia JA, Medeiros JV, Havt A, Lima AA, Ribeiro RA, Brito GA, Cunha FQ, Souza MH. Gastroprotective effect of heme-oxygenase 1/biliverdin/CO pathway in ethanol-induced gastric damage in mice. Eur J Pharmacol 2010; 642: 140-45.

http://dx.doi.org/10.1016/j.ejphar.2010.05.023

[Pubmed]   

Uc A, Zhu X, Wagner BA, Buettner GR, Berg DJ. Heme oxygenase-1 is protective against nonsteroidal anti-inflammatory drug-induced gastric ulcers. J Pediatr Gastroenterol Nutr 2012; 54: 471-76.

http://dx.doi.org/10.1097/MPG.0b013e3182334fdf

[Pubmed]   

Nakahira K, Takahashi T, Shimizu H, Maeshima K, Uehara K, Fujii H, Nakatsuka H, Yokoyama M, Akagi R, Morita K. Protective role of heme oxygenase-1 induction in carbon tetrachloride-induced hepatotoxicity. Biochem Pharmacol 2003; 66: 1091-105.

http://dx.doi.org/10.1016/S0006-2952(03)00444-1

Farombi EO, Surh YJ. Heme oxygenase-1 as a potential therapeutic target for hepatoprotection. J Biochem Mol Biol 2006; 39:479-91.

http://dx.doi.org/10.5483/BMBRep.2006.39.5.479

[Pubmed]   

Devey L, Ferenbach D, Mohr E, Sangster K, Bellamy CO, Hughes J, Wigmoren SJ. Tissue-resident macrophages protect the liver from ischemia reperfusion injury via a heme oxygenase-1-dependent mechanism. Mol Ther 2009; 17: 65-72.

http://dx.doi.org/10.1038/mt.2008.237

[Pubmed]    [PMC Free Fulltext]   

Zhu X, Fan WG, Li DP, Kung H, Lin MC Heme oxygenase-1 system and gastrointestinal inflammation: a short review. World J Gastroenterol 2011; 17: 4283-88.

http://dx.doi.org/10.3748/wjg.v17.i38.4283

[Pubmed]    [PMC Free Fulltext]   

Porter NA, Nixon JR, Isaac R. Cyclic peroxidase and thiobarbituric assay. Biochem Biophys Acta 1976; 441: 596-99.

Tzaneva M. Electron microscopic immunohistochemical investigation of chromogranin A in endocrine cells in human oxyntic gastric mucosa. Acta histochem 2001; 103: 179-94.

http://dx.doi.org/10.1078/0065-1281-00585

[Pubmed]   

Sener G, Sehirli O, Velioglu Ogune A, Erean F, Erkainli G, Gedik N, Yegen BC. Propylthiouracil (PTU)-induced hypothyroidism alleviates burn-induced multiple organ injury. Burns 2006; 32: 728–36.

http://dx.doi.org/10.1016/j.burns.2006.01.002

[Pubmed]   

Tilg H, Moschen AR, Kaneider NC. Pathways of liver injury in alcoholic liver disease. J Hepatol 2011; 55: 1159-61.

http://dx.doi.org/10.1016/j.jhep.2011.05.015

[Pubmed]   

Otterbein LE, Choi AM. Heme oxygenase: colors of defense against cellular stress. Am J Physiol Lung Cell Mol Physiol 2000; 279: L1029-37.

[Pubmed]   

Sammut IA, Foresti R, Clark JE, Exon DJ, Vesely MJ, Sarathchandra P, Green CJ, Motterlini R. Carbon monoxide is a major contributor to the regulation of vascular tone in aortas expressing high levels of haeme oxygenase-1. Br J Pharmacol 1998; 125: 1437-44.

http://dx.doi.org/10.1038/sj.bjp.0702212

[Pubmed]    [PMC Free Fulltext]   

Vile GF, Tyrrell RM. Oxidative stress resulting from ultraviolet A irradiation of human skin fibroblasts leads to a heme oxygenase-dependent increase in ferritin. J Biol Chem 1993; 268: 14678-81.

[Pubmed]   

Kim HP, Ryter SW, Choi AM. CO as a cellular signaling molecule. Annu Rev Pharmacol Toxicol 2006; 46: 411-49

http://dx.doi.org/10.1146/annurev.pharmtox.46.120604.141053

[Pubmed]   

Otterbein LE, Bach FH, Alam J, Soares M, Tao Lu H, Wysk M, Davis RJ, FlavellRA, Choi AM. Carbon monoxide has anti-inflammatory effects involving themitogen-activated protein kinase pathway. Nat Med 2000; 6: 422-28.

http://dx.doi.org/10.1038/74680

[Pubmed]   

Ueda K, Ueyama T, Oka M, Ito T, Tsuruo Y, Ichinose M. Polaprezinc (ZincL-carnosine) is a potent inducer of anti-oxidative stress enzyme, heme oxygenase (HO)-1 - a new mechanism of gastric mucosal protection. J Pharmacol Sci 2009; 110: 285-94.

http://dx.doi.org/10.1254/jphs.09056FP

[Pubmed]   

Shibuya A, Onda K, Kawahara H, Uchiyama Y, Nakayama H, Omi T, Nagaoka M, Matsui H, Hirano T. Sofalcone, a gastric mucosa protective agent, increases vascular endothelial growth factor via the Nrf2-heme-oxygenase-1 dependent pathway in gastric epithelial cells. Biochem Biophys Res Commun 2010; 398: 581-84.

http://dx.doi.org/10.1016/j.bbrc.2010.06.124

[Pubmed]   


How to Cite this Article
Pubmed Style

Bekyarova G, Tzaneva M, Hristova M. Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. J Interdiscip Histopathol. 2013; 1(5): 246-251. doi:10.5455/jihp.20130417103023


Web Style

Bekyarova G, Tzaneva M, Hristova M. Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. http://www.ejmjih.com/?mno=33942 [Access: August 16, 2018]. doi:10.5455/jihp.20130417103023


AMA (American Medical Association) Style

Bekyarova G, Tzaneva M, Hristova M. Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. J Interdiscip Histopathol. 2013; 1(5): 246-251. doi:10.5455/jihp.20130417103023



Vancouver/ICMJE Style

Bekyarova G, Tzaneva M, Hristova M. Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. J Interdiscip Histopathol. (2013), [cited August 16, 2018]; 1(5): 246-251. doi:10.5455/jihp.20130417103023



Harvard Style

Bekyarova, G., Tzaneva, M. & Hristova, M. (2013) Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. J Interdiscip Histopathol, 1 (5), 246-251. doi:10.5455/jihp.20130417103023



Turabian Style

Bekyarova, Ganka, Maria Tzaneva, and Minka Hristova. 2013. Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. Journal of Interdisciplinary Histopathology, 1 (5), 246-251. doi:10.5455/jihp.20130417103023



Chicago Style

Bekyarova, Ganka, Maria Tzaneva, and Minka Hristova. "Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study." Journal of Interdisciplinary Histopathology 1 (2013), 246-251. doi:10.5455/jihp.20130417103023



MLA (The Modern Language Association) Style

Bekyarova, Ganka, Maria Tzaneva, and Minka Hristova. "Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study." Journal of Interdisciplinary Histopathology 1.5 (2013), 246-251. Print. doi:10.5455/jihp.20130417103023



APA (American Psychological Association) Style

Bekyarova, G., Tzaneva, M. & Hristova, M. (2013) Heme Oxygenase-1 Expresion in Gastric Mucosa and Liver after Burns: Preliminary Immunohistochemical Study. Journal of Interdisciplinary Histopathology, 1 (5), 246-251. doi:10.5455/jihp.20130417103023





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