J Hepatol. 2016 Mar;64(3):691-8.
Cerium oxide nanoparticles reduce steatosis, portal hypertension and display anti-inflammatory properties in rats with liver fibrosis.
- 1Biochemistry and Molecular Genetics Service, Hospital Clínic Universitari, IDIBAPS, CIBERehd, Barcelona, Spain.
- 2Institut Català de Nanociència i Nanotecnologia (ICN2), Bellaterra, Spain.
- 3Biochemistry and Molecular Genetics Service, Hospital Clínic Universitari, IDIBAPS, CIBERehd, Barcelona, Spain; Department Ciencies Fisiologiques I, University of Barcelona, Barcelona, Spain.
- 4Institut Català de Nanociència i Nanotecnologia (ICN2), Bellaterra, Spain; Institut Català de Recerca i Estudis Avançats, (ICREA), Barcelona, Spain; Vall d’Hebron Insitute of Research (VHIR), Barcelona, Spain. Electronic address: firstname.lastname@example.org.
- 5Biochemistry and Molecular Genetics Service, Hospital Clínic Universitari, IDIBAPS, CIBERehd, Barcelona, Spain; Department Ciencies Fisiologiques I, University of Barcelona, Barcelona, Spain. Electronic address: email@example.com.
BACKGROUND & AIMS: Cerium oxide nanoparticles (CeO2NPs) have proven to behave as free radical scavengers and/or anti-inflammatory agents. The aim of the study was to determine whether CeO2NPs display hepatoprotective properties in experimental chronic liver disease.
METHODS: Systemic and hepatic effects of nanoparticles were assessed in CCl4-treated rats receiving CeO2NPs or vehicle twice weekly for two weeks and CCl4 treatment was continued for 8 additional weeks. Thereafter, mean arterial pressure and portal pressure (PP) were assessed and serum samples obtained to measure standard hepatic and renal function tests. Organ and subcellular distribution of NPs were assessed using mass spectrometry (ICP-MS) and transmission electron microscopy. Liver samples were obtained to evaluate steatosis, α-SMA expression, macrophage infiltration, apoptosis and mRNA expression of oxidative stress, inflammatory or vasoactive related genes.
RESULTS: Most CeO2NPs were located in the liver and it reduced hepatic steatosis, ameliorated systemic inflammatory biomarkers and improved PP without affecting mean arterial pressure. In addition, a marked reduction in mRNA expression of inflammatory cytokines (TNFα, IL1β, COX-2, iNOS), ET-1 and messengers related to oxidative (Epx, Ncf1, Ncf2) or endoplasmic reticulum (Atf3, Hspa5) stress signaling pathways was observed in the liver of rats receiving CeO2NPs. This was associated with reduced macrophage infiltration and reduced abundance of caspase-3, α-SMA and inflammatory cytokines.
CONCLUSIONS: CeO2NPs administration to CCl4-treated rats protects against chronic liver injury by reducing liver steatosis and portal hypertension and markedly attenuating the intensity of the inflammatory response, thereby suggesting that CeO2NPs may be of therapeutic value in chronic liver disease.
KEYWORDS: Cerium oxide nanoparticles; Experimental fibrosis; Hepatic inflammation; Oxidative stress; Portal pressure
Chronic liver disease has a high prevalence in the world. Persistent liver injury induced by different factors, such as hepatitis B and C viruses, alcohol, biotransformed metabolites, among others, can result in chronic activation of inflammatory and wound healing response, which can lead to liver fibrosis and cirrhosis. Cirrhosis is currently defined as the most advanced stage of chronic liver disease, and is associated with complications, such as portal hypertension, variceal bleeding, ascites and hepatorrenal syndrome, being a major determinant of morbidity and mortality [1,2]. Sustained efforts over the past three decades to uncover the cellular and molecular basis of hepatic fibrosis have accelerated the development of novel therapeutic strategies to reverse fibrosis .
The first stage in liver disease, whatever the etiology, is dominated by persisting parenchymal injury, chronic inflammatory response and activation of fibrogenesis. It has been suggested that a molecular level, growth factors, cytokines and chemokines, changes in extracellular matrix organization and composition as well as reactive molecules originated by oxidative stress play a pathogenic role in the development of liver disease . Evidence of oxidative stress have been detected in almost all the clinical and experimental settings of chronic liver disease, often in association with decreased antioxidant defenses . Oxidative stress-related molecules may act as mediators that modulate tissue and the cellular events responsible for the progression of liver fibrosis.
In this regard, new therapeutic agents are in great need in order to palliate the effects of oxidative stress in the liver. For example, it is known that cerium oxide (CeO2) nanoparticles (NPs) have antioxidant properties. These NPs are considered to be a chemically inert ceramic with a fluorite-like structure that confers a useful capacity to be easily reduced from Ce4+ to Ce3+ and back, followed by the capture or release of oxygen . Therefore, the oxygen storage capacity of CeO2NPs becomes highly useful to remove free radicals as soon as they are generated in situations of reactive oxygen species (ROS) imbalance . We hypothesized that engineered CeO2NPs might behave as an exogenous pro-revolving mediator in liver disease thanks to their ability to uptake and neutralize free radicals.
Figure 1. Biodistribution of cerium in tissues of CCl4-treated rats 90 min after CeO2NPs administration. Cerium concentrations were evaluated using ICP-MS. Results are expressed as percentage of total cerium collected.
To answer our hypothesis, we first tested the biodistribution of CeO2NPs following their intravenous injection in an experimental model of liver fibrosis induced by carbon tetrachloride (CCl4) in rats. We found that 84 % of the total dose of cerium collected was accumulated in the liver (Figure 1), thereby confirming their highly specific local delivery in hepatic tissue.
Fibrotic rats were then treated with CeO2NPs (0.1 mg/kg bw), and induction with CCl4 was maintained for 8 additional weeks. Liver biopsies obtained from fibrotic rats receiving CeO2NPs showed a significant reduction in two key pathological alterations commonly seen in chronic liver diseases: steatosis (fat accumulation within hepatocytes) and inflammatory infiltrate. Moreover, we observed a substantial improvement in portal hypertension in rats treated with CeO2NPs (Figure 2). This effect is very interesting since increased portal pressure is a frequent clinical syndrome in cirrhotic patients, and it is a major complication of liver disease. The positive changes described above were also associated with systemic signs of attenuated liver inflammation (e.g. decreased serum transaminases), reduced activation of hepatic proinflammatory cytokines and diminished apoptosis. Since, as expected, we also observed that CeO2NPs administration reduced oxidative and ROS-mediated endoplasmatic reticulum stress, most of the beneficial effects mentioned in the article would derive from their marked antioxidant properties (Figure 3). Altogether, these results suggest that CeO2NPs may potentially have therapeutic value in chronic liver disease.
Figure 2. Portal pressure and serum transaminases results in control and CCl4-treated rats. *p<0.05, **p<0.01 compared with vehicle group.
Figure 3. Effects of CeO2NPs on rats with liver fibrosis
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This study was supported by Ministerio de Economia y Competitividad (Grant SAF12-35979). Cofinanced by FEDER, European Union, a way of making Europe, Agència de Gestió d’Ajuts Universitaris i de Recerca (SGR 2014/219) and Fundació La Maratò de TV3 (Maratò 120930). The Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd) is funded by the Instituto de Salud Carlos III.
Dr. Wladimiro Jiménez
Servicio de Bioquímica y Genética Molecular, Hospital Clinic Universitari
Villarroel 170, Barcelona 08036, Spain