Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 14, 2015; 21(26): 8021-8031
Published online Jul 14, 2015. doi: 10.3748/wjg.v21.i26.8021
Losartan activates sirtuin 1 in rat reduced-size orthotopic liver transplantation
Eirini Pantazi, Mohamed Bejaoui, Mohamed Amine Zaouali, Emma Folch-Puy, Anabela Pinto Rolo, Arnau Panisello, Carlos Marques Palmeira, Joan Roselló-Catafau
Eirini Pantazi, Mohamed Bejaoui, Mohamed Amine Zaouali, Emma Folch-Puy, Arnau Panisello, Joan Roselló-Catafau, Experimental Pathology Department, Experimental Hepatic Ischemia-Reperfusion Unit, Institute of Biomedical Research of Barcelona (IIBB-CSIC), Barcelona, 08036 Catalonia, Spain
Anabela Pinto Rolo, Carlos Marques Palmeira, Department of Life Sciences, Faculty of Science and Technology, University of Coimbra, 3004-517 Coimbra, Portugal
Anabela Pinto Rolo, Carlos Marques Palmeira, Portugal and Center for Neurosciences and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
Author contributions: Pantazi E carried out the experimental work; Pantazi E, Bejaoui M and Folch-Puy E provided protocols and analyzed data; Zaouali MA, Bejaoui M and Panisello A established the animal experimental model and injury parameters; Rolo AP and Palmeira CM determinated NAD+, NAMPT levels and contributed to critical analysis of the data and discussion; Pantazi E, Folch-Puy E and Roselló-Catafau J designed the study, coordinated the experiments and wrote the paper.
Supported by Grants from Fondo de Investigaciones Sanitarias, No. FIS PI12/00519; fellowship from Agència de Gestió d’Ajuts Universitaris i de Recerca, No. 2012FI_B00382; Generalitat de Catalunya, Barcelona, Catalonia, Spain (to Pantazi E).
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Ethics Committees for Animal Experimentation (CEEA, Directive 400/12), University of Barcelona and all procedures complied with European Union regulations for animal experiments (EU guideline 86/609/EEC).
Conflict-of-interest statement: The authors declare that they have no conflict of interest or any financial interests.
Data sharing statement: Any further information related to technical appendix, statistical code and dataset are available from the corresponding author at jrcbam@iibb.csic.es. The authors gave informed consent for data sharing.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Joan Roselló-Catafau, Professor, Experimental Pathology Department, Experimental Hepatic Ischemia-Reperfusion Unit, Institute of Biomedical Research of Barcelona (IIBB-CSIC), C/Rosello 161, 7th floor, 08036 Barcelona, Spain. jrcbam@iibb.csic.es
Telephone: +34-933-638300 Fax: +34-933-638301
Received: January 15, 2015
Peer-review started: January 16, 2015
First decision: February 10, 2015
Revised: February 25, 2015
Accepted: April 3, 2015
Article in press: April 3, 2015
Published online: July 14, 2015
Abstract

AIM: To investigate a possible association between losartan and sirtuin 1 (SIRT1) in reduced-size orthotopic liver transplantation (ROLT) in rats.

METHODS: Livers of male Sprague-Dawley rats (200-250 g) were preserved in University of Wisconsin preservation solution for 1 h at 4 °C prior to ROLT. In an additional group, an antagonist of angiotensin II type 1 receptor (AT1R), losartan, was orally administered (5 mg/kg) 24 h and 1 h before the surgical procedure to both the donors and the recipients. Transaminase (as an indicator of liver injury), SIRT1 activity, and nicotinamide adenine dinucleotide (NAD+, a co-factor necessary for SIRT1 activity) levels were determined by biochemical methods. Protein expression of SIRT1, acetylated FoxO1 (ac-FoxO1), NAMPT (the precursor of NAD+), heat shock proteins (HSP70, HO-1) expression, endoplasmic reticulum stress (GRP78, IRE1α, p-eIF2) and apoptosis (caspase 12 and caspase 3) parameters were determined by Western blot. Possible alterations in protein expression of mitogen activated protein kinases (MAPK), such as p-p38 and p-ERK, were also evaluated. Furthermore, the SIRT3 protein expression and mRNA levels were examined.

RESULTS: The present study demonstrated that losartan administration led to diminished liver injury when compared to ROLT group, as evidenced by the significant decreases in alanine aminotransferase (358.3 ± 133.44 vs 206 ± 33.61, P < 0.05) and aspartate aminotransferase levels (893.57 ± 397.69 vs 500.85 ± 118.07, P < 0.05). The lessened hepatic injury in case of losartan was associated with enhanced SIRT1 protein expression and activity (5.27 ± 0.32 vs 6.08 ± 0.30, P < 0.05). This was concomitant with increased levels of NAD+ (0.87 ± 0.22 vs 1.195 ± 0.144, P < 0.05) the co-factor necessary for SIRT1 activity, as well as with decreases in ac-FoxO1 expression. Losartan treatment also provoked significant attenuation of endoplasmic reticulum stress parameters (GRP78, IRE1α, p-eIF2) which was consistent with reduced levels of both caspase 12 and caspase 3. Furthermore, losartan administration stimulated HSP70 protein expression and attenuated HO-1 expression. However, no changes were observed in protein or mRNA expression of SIRT3. Finally, the protein expression pattern of p-ERK and p-p38 were not altered upon losartan administration.

CONCLUSION: The present study reports that losartan induces SIRT1 expression and activity, and that it reduces hepatic injury in a ROLT model.

Keywords: Losartan, Sirtuin 1, Endoplasmic reticulum stress, Liver ischemia reperfusion injury, Angiotensin II

Core tip: Losartan is an angiotensin II type 1 receptor (AT1R) antagonist known to protect livers against ischemia-reperfusion injury (IRI). However, the mechanisms underlying this hepatoprotective effect are not fully understood, especially in case of reduced-size orthotopic liver transplantation (ROLT). SIRT1 has recently emerged as an important target to modulate for alleviating IRI. In our study, we describe that AT1R antagonism enhances SIRT1 activity and prevents endoplasmic reticulum stress and liver apoptosis in a rat model of ROLT. Consequently, losartan increases the resistance of ROLT grafts against IRI.