Hypoxia inducible factor-1α accumulation in steatotic liver preservation: role of nitric oxide

AIM: To examine the relevance of hypoxia inducible factor (HIF-1) and nitric oxide (NO) on the preservation of fatty liver against cold ischemia-reperfusion injury (IRI). METHODS: We used an isolated perfused rat liver model and we evaluated HIF-1α in steatotic and non-steatotic livers preserved for 24 h at 4°C in University of Wisconsin and IGL-1 solutions, and then subjected to 2 h of normothermic reperfusion. After normoxic reperfusion, liver enzymes, bile production, bromosulfophthalein clearance, as well as HIF-1α and NO [endothelial NO synthase (eNOS) activity and nitrites/nitrates] were also measured. Other factors associated with the higher susceptibility of steatotic livers to IRI, such as mitochondrial damage and vascular resistance were evaluated. RESULTS: A significant increase in HIF-1α was found in steatotic and non-steatotic livers preserved in IGL-1 after cold storage. Livers preserved in IGL-1 showed a significant attenuation of liver injury and improvement in liver function parameters. These benefits were enhanced by the addition of trimetazidine (an anti-ischemic drug), which induces NO and eNOS activation, to IGL-1 solution. In normoxic reperfusion, the presence of NO favors HIF-1α accumulation, promoting also the activation of other cytoprotective genes, such as heme-oxygenase-1. CONCLUSION: We found evidence for the role of the HIF-1α/NO system in fatty liver preservation, especially when IGL-1 solution is used

Olprinone protects liver from ischemia reperfusion injury through oxidative stress prevention and protein kinase Akt activation

Liver ischemia reperfusion (IR) injury is inevitable in surgical procedures such as hepatic resection and liver transplantation. It represents a leading cause of liver graft dysfunction and primary non function after transplantation. Phosphodiesterase (PDE) inhibitors are emerging as effective drugs able to reduce IR damage. The aim of this study was to investigate the effect of selective PDE-3 inhibitor olprinone (Olp) against liver IR injury. Male Wistar rats were subjected to one hour of partial warm ischemia (70%) followed by six hours of reperfusion. Before ischemia, rats were treated with saline (IR group), Olp (Olp group) or Olp with Akt inhibitor LY294002 (Olp + LY group). After reperfusion, hepatic injury (transaminase activities), mitochondrial damage (glutamate dehydrogenase activity), oxidative stress (malondialdehyde and glutathione concentrations and catalase and superoxide dismutase activities) as well as protein kinase Akt activation were evaluated. Rat treatment with Olp reduced liver injury, prevented mitochondrial damage, decreased lipid peroxidation and enhanced antioxidant enzymes. Also, Olp induced a significant activation in protein kinase Akt. Inhibition of Akt with LY294002 abolished all the protective effects of Olp. In conclusion, Olp treatment may be an effective strategy in reducing liver IR injury through oxidative stress prevention and Akt activation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Trimetazidine and liver preservation against ischaemia-reperfusion injury

Trimetazidine is an anti-ischaemic drug used for angina pectoris treatment. Recently, it has been shown that trimetazidine protects against hepatic ischaemia reperfusion injury. Several hypotheses have been proposed to explain the exact hepatoprotective mechanisms but they still remain unclear. This review assesses the possible mechanisms responsible for the increase of the liver's tolerance against ischaemia-reperfusion injury with special emphasis on: (1) the prevention of oxidative stress and protection of mitochondrial function; (2) the generation of vasoactive mediators such as nitric oxide and endothelins; and finally (3) the preservation of liver energy metabolism. Copyright © 2007 Termedia & Banach.This work was supported by the Ministerio de Educación y Ciencia (project grant SAF 2005-00385), Ministerio de Sanidad y Consumo (project grant PIO60021) and Ministerio de Asuntos Exteriores y de Cooperación Internacional/Agencia Española De Cooperación Internacional.Peer Reviewe

Thymoquinone protects rat liver after partial hepatectomy under ischemia/reperfusion through oxidative stress and endoplasmic reticulum stress prevention

International audienceIschemia reperfusion (I/R) is associated with liver injury and impaired regeneration during partial hepatectomy (PH). The aim of this study was to investigate the effect of thymoquinone (TQ), the active compound of essential oil obtained from Nigella sativa seeds, on rat liver after PH. Male Wistar rats were equally divided into four groups (n=6) receiving an oral administration of either vehicle solution (Sham and PH groups) or TQ at 30 mg/kg (TQ and TQ+PH groups) for ten consecutive days. Then, rats underwent PH (70%) with 60 min of ischemia followed by 24h of reperfusion (PH and TQ+PH groups). Alanine aminotransferase (ALT) activity and histopathological damage were determined. Also, antioxidant parameters, liver regeneration index, hepatic adenosine triphosphate (ATP) content, endoplasmic reticulum (ER) stress and apoptosis were assessed. In response to PH under I/R, liver damage was significantly alleviated by TQ treatment as evidenced by the decrease in ALT activity (P < 0.01) and histological findings (P < 0.001). In parallel, TQ preconditioning increased hepatic antioxidant capacities. Moreover, TQ improved mitochondrial function (ATP, P < 0.05), attenuated ER stress parameters and repressed the expression of apoptotic effectors. Taken together, our results suggest that TQ preconditioning could be an effective strategy to reduce liver injury after PH under I/R. The protective effects were mediated by the increase of antioxidant capacities and the decrease of ER stress and apoptosis

How to protect liver graft with nitric oxide

Organ preservation and ischemia reperfusion injury associated with liver transplantation play an important role in the induction of graft injury. One of the earliest events associated with the reperfusion injury is endothelial cell dysfunction. It is generally accepted that endothelial nitric oxide synthase (e-NOS) is cell-protective by mediating vasodilatation, whereas inducible nitric oxide synthase mediates liver graft injury after transplantation. We conducted a critical review of the literature evaluating the potential applications of regulating and promoting e-NOS activity in liver preservation and transplantation, showing the most current evidence to support the concept that enhanced bioavailability of NO derived from e-NOS is detrimental to ameliorate graft liver preservation, as well as preventing subsequent graft reperfusion injury. This review deals mainly with the beneficial effects of promoting “endogenous” pathways for NO generation, via e-NOS inducer drugs in cold preservation solution, surgical strategies such as ischemic preconditioning, and alternative “exogenous” pathways that focus on the enrichment of cold storage liquid with NO donors. Finally, we also provide a basic bench-to-bed side summary of the liver physiology and cell signalling mechanisms that account for explaining the e-NOS protective effects in liver preservation and transplantation

Fucoidan alleviates the mitochondria and endoplasmic reticulum stresses in ischemic rat livers

International audienceBackgroundHepatic ischemia reperfusion (I/R) injury remains a major problem for liver surgery leading to graft dysfunction. The use of compounds of natural origin as fucoidan, a sulfated polysaccharide from brown seaweed, could have a potential clinical benefit in the treatment of ischemic diseases. Nevertheless, the accurate mechanisms of action of fucoidan on endoplasmic reticulum (ER) stress response and mitochondria after warm hepatic ischemia have not been yet investigated. Thus, the present study focused on the modulation of fucoidan effects on the signaling pathways involving the mitochondria and the ER in ischemic rat liver.MethodsMale Wistar rats were subjected to either sham operation or one hour of partial warm ischemia (70%) followed by two hours of reperfusion. Before ischemia, rats were treated with 0.9% NaCl (I/R group), fucoidan (100 mg/kg body weight) orally for 7 consecutive days (I/R-Fuc group), TUDCA (tauroursodeoxycholic acid, inhibitor of ER stress) (100 mg / kg body weight, i.v.) 10 min before ischemia (I/R-TUDCA group) or fucoidan with TUDCA (I/R-Fuc-TUDCA group).ResultsOur results showed that fucoidan and TUDCA reduced cytolysis and induced a significant improvement in antioxidant status, as compared to I/R. Interestingly, preconditioning with fucoidan resulted in significant decreased ER stress, as reflected by GRP78, p-PERK, ATF-6, XBP-1 and TRAF2. Furthermore, the phosphorylation of MAPKs (ERK, JUNK and P38) significantly diminished after fucoidan treatment. Rats undergoing fucoidan treatment protected liver against mitochondrial stress, which was correlated with low induction of apoptosis (caspase-3). Inhibition of ER stress by TUDCA administration boosted all the protective effects of fucoidan.ConclusionIn conclusion, fucoidan treatment may represent an effective strategy in reducing liver I/R injury through mitochondrial stress attenuation and ER inhibition

Thymoquinone prevents endoplasmic reticulum stress and mitochondria-induced apoptosis in a rat model of partial hepatic warm ischemia reperfusion

International audienceThis study was undertaken to evaluate the protective effect of thymoquinone (TQ), the bioactive compound of Nigella sativa seeds, against warm ischemia-reperfusion (I/R) injury in liver. Rats were given an oral administration of a vehicle solution (sham group) or TQ at the appropriate dose (10, 20, 30 and 40mg/kg) for ten days consecutively. Following, they were subjected to 60min of partial hepatic ischemia followed by 24h of reperfusion. .Transaminase activities, histopathological changes, TNFα and antioxidant parameters were evaluated. Also, endoplasmic reticulum (ER) stress, mitochondrial damage and apoptosis were studied. In addition, ERK and P38 phosphorylation was determined by Western blot technique. We found that TQ at 30mg/kg is the effective dose to protect rat liver against I/R injury. Moreover, 30mg/kg of TQ prevented histological damages, inflammation and oxidative stress. Interestingly, it decreased the expression of ER stress parameters including GRP78, CHOP and caspase-12. In parallel, it improved mitochondrial function and attenuated the expression of apoptotic parameters. Furthermore, TQ significantly enhanced ERK and P38 phosphorylation. In conclusion, we demonstrated the potential of TQ to protect the rat liver against I/R injury through the prevention of ER stress and mitochondrial dysfunction. These effects implicate the prevention of oxidative stress

Effectiveness of a single versus repeated administration of trimetazidine in the protection against warm ischemia/reperfusion injury of rat liver

[Background/aim] The aim of this study was to compare the effects of single and repeated trimetazidine (TMZ) administration against warm hepatic ischemia/reperfusion (I/R) injury and to explore the possible mechanisms affected by TMZ. [Materials and methods] Wistar rats were divided into 4 groups (n = 6). Sham: rats were subjected to dissection. I/R: rats were subjected to 60 min of partial hepatic ischemia followed by 24 h of reperfusion. TMZ1: Same as I/R group but rats were pretreated with a single dose of TMZ (10 mg/kg, intraperitoneal injection) 30 min before warm ischemia. TMZ3: Same as I/R but rats were treated with 10 mg/ kg TMZ for 3 successive days. [Results] TMZ treatment decreased liver injury, lipid peroxidation, and apoptosis. The repeated administration of TMZ conferred more protection than the single dose treatment concerning all studied parameters. In parallel, we noted a significant increase in phosphorylated adenosine monophosphate activated protein kinase (p-AMPK) and endothelial nitric oxide synthase (eNOS) levels in TMZ3 as compared to TMZ1. [Conclusion] Repeated administration of TMZ for 3 days was more efficient than a single dose of TMZ in protecting the liver against I/R induced apoptosis and lipid peroxidation. These effects implicate AMPK and eNOS activation.This study was funded by the Tunisian Ministry of Higher Education and Scientific Research.Peer Reviewe

Identification of mutations that causes glucose-6-phosphate transporter defect in tunisian patients with glycogenosis type 1b

Abstract Background Glycogen storage disease type 1b (GSD1b) is an autosomal recessive lysosomal storage disease caused by defective glucose-6-phosphate transporter encoded by SLC37A4 leading to the accumulation of glycogen in various tissues. The high rate of consanguineous marriages in Tunisian population provides an ideal environment to facilitate the identification of homozygous pathogenic mutations. We aimed to determine the clinical and genetic profiles of patients with GSD1b to evaluate SLC37A4 mutations spectrum in Tunisian patients. Methods All exons and flanking intron regions of SLC37A4 gene were screened by direct sequencing to identify mutations and polymorphisms in three unrelated families with GSD1b. Bioinformatics tools were then used to predict the impacts of identified mutations on the structure and function of protein in order to propose a function-structure relationship of the G6PT1 protein. Results Three patients (MT, MB and SI) in Families I, II and III who had the severe phenotype were homoallelic for the two identified mutations: p.R300H (famillies I, II) and p.W393X (Family III), respectively. One of the alterations was a missense mutation p.R300H of exon 6 in SLC37A4 gene. The analysis of the protein structure flexibility upon p.R300H mutation using DynaMut tool and CABS-flex 2.0 server showed that the reported mutation increase the molecule flexibility of in the cytosol region and would probably lead to significant conformational changes. Conclusion This is the first Tunisian report of SLC37A4 mutations identified in Tunisia causing the glycogenosis type Ib disease. Bioinformatics analysis allowed us to establish an approximate structure-function relationship for the G6PT1 protein, thereby providing better genotype/phenotype correlation knowledge