Proline, ascorbic acid, or thioredoxin affect jaundice and mortality in Long Evans cinnamon rats

Animal models of Wilson disease

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism manifesting with hepatic, neurological and psychiatric symptoms. The limitations of the currently available therapy for WD (particularly in the management of neuropsychiatric disease), together with our limited understanding of key aspects of this illness (e.g. neurological vs. hepatic presentation) justify the ongoing need to study WD in suitable animal models. Four animal models of WD have been established: the Long-Evans Cinnamon rat, the toxic-milk mouse, the Atp7b knockout mouse and the Labrador retriever. The existing models of WD all show good similarity to human hepatic WD and have been helpful in developing an improved understanding of the human disease. As mammals, the mouse, rat and canine models also benefit from high homology to the human genome. However, important differences exist between these mammalian models and human disease, particularly the absence of a convincing neurological phenotype. This review will first provide an overview of our current knowledge of the orthologous genes encoding ATP7B and the closely related ATP7A protein in C. elegans, Drosophila and zebrafish (Danio rerio) and then summarise key characteristics of rodent and larger mammalian models of ATP7B-deficiency.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Chemosensitivity of U251 Cells to the Co-treatment of D-Penicillamine and Copper: Possible Implications on Wilson Disease Patients

D-Penicillamine (PA), a copper chelator, and one of the recommended drugs for treatment of Wilson disease (WD) has been reported to worsen the symptoms of patients with neurologic presentations. However, the cause of this paradoxical response has not been fully elucidated and requires further investigations. Accordingly, we have studied the in vitro effect of Copper (Cu) and/or PA treatment on human glioblastoma U251 cells as an in vitro model of Cu cytotoxicity. Treatment of U251 cells with either Cu or PA exerted no significant effect on their morphology, viability or ROS level. In contrast, co-treatment with Cu-PA caused a decrease in viability, altered glutathione and ceruloplasmin expression coupled with marked increase in ROS; depolarization of mitochondrial membrane potential; and an increase in Sub G0 phase; along with alpha-Fodrin proteolysis. These findings along with the absence of LDH release in these assays, suggest that combined Cu-PA exposure induced apoptosis in U251 cells. In addition, pre-/or co-treatment with antioxidants showed a protective effect, with catalase being more effective than N-acetyl cysteine or trolox in restoring viability and reducing generated ROS levels. By comparison, a similar analysis using other cell lines showed that rat PC12 cells were resistant to Cu and/or PA treatment, while the neuroblastoma cell line SH-SY5Y was sensitive to either compound alone, resulting in decreased viability and increased ROS level. Taken together, this study shows that glioblastoma U251 cells provide a model for Cu-PA cytotoxicity mediated by H₂O₂. We postulate that PA oxidation in presence of Cu yields H₂O₂ which in turn permeates the plasma membrane and induced apoptosis. However, other cell lines exhibited different responses to these treatments, potentially providing a model for cell type- specific cytotoxic responses in the nervous system. The sensitivity of different neural and glial cell types to Cu-PA treatment may therefore underlie the neurologic worsening occurring in some PA-treated WD patients. Our results also raise the possibility that the side effects of PA treatment might be reduced or prevented by administering antioxidants.

Effects of N-Acetylcysteine, Quercetin, and Phytic Acid on Spontaneous Hepatic and Renal Lesions in LEC Rats

The effects of anti-oxidants were examined in Long-Evans Cinnamon (LEC) rats, which develop acute hepatic injury, and subsequent hepatic and renal tumors due to accumulation of excess Cu. The rats, at the age of 15 weeks, were supplied a diet containing either 1% of N-acetylcysteine (NAC), quercetin (QC), or phytic acid (PA), or basal diet alone. At weeks 2 and 6 posttreatment, animals were sacrificed for collection of blood and tissue samples. In the NAC-treated group, the development of hepatic and renal lesions was dramatically reduced. In addition, accumulation of Cu and Fe in the liver was suppressed. Acrolein-modified protein, a new marker for lipid peroxidation, was not detected in the liver or kidney of NAC treated rats, even though deposition was evident in control. Neither QC nor PA affected the development of spontaneous hepatic lesions. These results indicate that oxidative stress was reduced by NAC in the liver and kidney, and suggest that Cu and Fe may be involved in the generation of oxidative stress in the liver. In addition, it was suggested that the different effects of the anti-oxidants on lesion development in LEC rats might be related to different mechanisms of action with regard to oxidative stress.

Dietary copper triggers onset of fulminant hepatitis in the Long-Evans cinnamon rat model

AIM: To investigate the impact of dietary copper given at different time points on the onset of fulminant hepatitis.

METHODS: The Long-Evans cinnamon (LEC) rat model of Wilson’s disease (WD) was used to study the impact of high dietary copper (hCu) on the induction of fulminant hepatitis at early or late time points of life. High Cu diet was started in rat pups or in adults (month 5) for three months. Animals that received reduced dietary copper (rCu) throughout their lifetime served as a control. Hepatitis-associated serum markers (alanine aminotransferase, aspartate transaminase, bilirubin) were analyzed in animal groups receiving hCu or rCu. Liver copper content and liver histology were revealed at sacrifice. A set of 5 marker genes previously found to be affected in injured liver and which are related to angiogenesis (Vegfa), fat metabolism (Srebf1), extracellular matrix (Timp1), oxidative stress (Hmox1), and the cell cycle (Cdkn1a) were analyzed by real-time polymerase chain reaction.

RESULTS: Regardless of the time point when hCu was started, LEC rats (35/36) developed fulminant hepatitis and died. Animals receiving rCu (36/36) remained healthy, did not develop hepatitis, and survived long term without symptoms of overt disease, although liver copper accumulated in adult animals (477 ± 75 μg/g). With regard to start of hCu, onset of fulminant hepatitis was significantly (P < 0.001) earlier in adults (35 ± 9 d) that showed pre-accumulation of liver copper as compared to the pup group (77 ± 15 d). Hepatitis-associated serum markers, liver copper and liver histology, as well as gene expression, were affected in LEC rats receiving hCu. However, except for early and rapid onset of hepatitis, biochemical and molecular markers were similar at the early and late time points of disease.

CONCLUSION: Rapid onset of fulminant hepatitis in asymptomatic LEC rats with elevated liver copper suggests that there is a critical threshold of liver copper which is important to trigger the course of WD.

Proline protects liver from D-galactosamine hepatitis by activating the IL-6/STAT3 survival signaling pathway

The oral administration of proline, one of the non-essential amino acids, has been shown to effectively protect the liver from D-galactosamine (GalN)-induced liver injury and to improve the survival rate. The aim of this study was to investigate the mechanism of this protective action of proline. We paid particular attention to the effect of proline on inflammatory activation, regenerative response, and the associated signal transduction in the liver. Male Fischer rats received intraperitoneal injections of GalN (1.4 g/kg) with or without the oral administration of proline (2 g/kg) 1 h before GalN treatment. Liver pathology, plasma indices of inflammation, and the level of proliferative marker in the liver were monitored. The hepatic activation of interleukin-6 (IL-6)/signal transducer and activator of transcription (STAT)-3 pathway, which is downstream of tumor necrosis factor (TNF)-α/nuclear factor-κB, was also studied. GalN induced massive inflammatory expansion in the liver, leading to a high death rate (60 %) more than 72 h after the treatment. Proline administration significantly suppressed inflammatory infiltration in the live after 48 h, which was accompanied by depletion of plasma TNF-α, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase. The mRNA expression of histone H3, a marker of proliferation, was significantly upregulated in the liver of proline-treated animals. Furthermore, IL-6/STAT-3 pathway, an anti-inflammatory and regenerative signaling pathway, was strongly activated prior to these observations, with the upregulated expression of downstream genes. These results suggest that the tissue-protective mechanism of proline involves the early activation of IL-6/STAT-3 pathway in the liver, with subsequent activation of the regenerative response and suppression of massive inflammatory activation.

Repeated transplantation of hepatocytes prevents fulminant hepatitis in a rat model of Wilson's disease

The outcome of consecutive hepatocyte transplants was explored in a rat model of Wilson's disease before the onset of fulminant hepatitis without preconditioning regimens. Rats received a high-copper diet in order to induce a rapid induction of liver failure. Sham-operated rats (15/15) developed jaundice and fulminant hepatitis, and they died within 4 weeks of first transplantation. Despite the continuation of a high dietary copper challenge, long-term survival was observed for a notable proportion of the transplanted animals (7/18). All survivors displayed normalized levels of hepatitis-associated serum markers and ceruloplasmin oxidase activity by posttransplant days 50 and 98, respectively. The liver copper concentrations, the liver histology, and the expression of marker genes were significantly restored within 4 months of transplantation in comparison with the control group. The high expression of a copper transporter gene (ATPase Cu++ transporting beta polypeptide) in the livers of the survivors indicated a high rate of repopulation by donor hepatocytes. Our data suggest that repeated cell transplantation can overcome the limitations of a single therapy session in rats with severe hepatic disease by functionally restoring the host liver without preconditioning.

The LEC rat: a useful model for studying liver carcinogenesis related to oxidative stress and inflammation

Growing evidence indicates oxidative stress as a mechanism of several diseases including cancer. Oxidative stress can be defined as the imbalance between cellular oxidant species production and antioxidant capability shifted towards the former. Lipid peroxidation is one of the processes that takes place during oxidative stress. Lipid peroxidation products, such as malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), are closely related to carcinogenesis as they are potent mutagens and they have been suggested as modulators of signal pathways related to proliferation and apoptosis, two processes implicated in cancer development. Mechanisms by which oxidative stress leads to tumor formation are still under investigation. The need of suitable in vivo models that could reflect that inflammation-related human carcinogenesis is evident. In this regard, the mutant strain Long Evans Cinnamon-like (LEC) rat provides a promising model for investigation of the relationship between hepatitis induced by oxidative stress and hepatocarcinogenesis because it has been demonstrated to develop spontaneous liver tumor formation related to copper accumulation and oxidative stress. In this review, the findings regarding oxidative stress and its relation with liver pathologies in LEC rats are discussed; we focus on the mechanisms proposed for HNE carcinogenesis.

Prevention of lethal hepatic injury in Long-Evans Cinnamon (LEC) rats by D-galactosamine hydrochloride

Repeated injections of D-galactosamine hydrochloride (GalN) increase the survival rate of Long-Evans Cinnamon (LEC) rats, an animal model of Wilson's disease. The aim of the present study was to investigate the mechanism of GalN for prevention of spontaneous lethal hepatic injury in LEC rats. Male LEC rats were given a single subcutaneous injection of 300 mg/kg of GalN or vehicle (0.9% NaCl) at 14 weeks, and killed at 28 weeks of age. Next, 6-week-old male LEC rats were given weekly subcutaneous injections of 300 mg/kg of GalN or vehicle for 3 or 12 weeks, and their hepatic 8-hydroxydeoxy-2'-guanosine (8-OHdG), glutathione peroxidase (GPX), and catalase activities were measured. None of GalN-treated rats died of hepatic injury (0/12), whereas the mortality rate of control rats given 0.9% NaCl was 17% (2/12). GalN administration for 12 weeks decreased the hepatic 8-OHdG, and GalN administration for either 3 or 12 weeks increased the glutathione peroxidase activity. GalN administration increased the serum level of alanine aminotransferase, and accelerated megalocytic degeneration of the hepatocytes. GalN treatment is effective in preventing lethal hepatitis in LEC rats and decrease of oxidative DNA damage by GalN plays an important role in increase of the survival rate.

Effects of D-galactosamine hydrochloride and partial hepatectomy on spontaneous hepatic injury and hepatocarcinogenesis in Long-Evans Cinnamon rats

To examine the effect of nongenotoxic chemicals on hepatocarcinogenesis in Long-Evans Cinnamon (LEC) rats, we gave 6-week-old male and female LEC rats (n = 18) weekly subcutaneous injections of D-galactosamine hydrochloride (GalN, 300 mg/kg) in 0.9% NaCl or only 0.9% NaCl for 50 weeks, and killed them in week 62. GalN-treated male rats unexpectedly showed no lethal necrotizing hepatitis. GalN treatment increased the incidence of cholangiofibrosis in males and its severity in females, but did not cause significant increases of hepatocellular tumors in either sex. GaIN treatment increased the 5-bromo-2'-deoxyuridine (BrdU)-labeling index of hepatocytes and plasma hepatocyte growth factor, and accelerated megalocytic alterations without reduction of the hepatic copper concentration. Next, male and female LEC rats were subjected to two-thirds partial hepatectomy (PH) or sham hepatectomy in week 8 (n = 12) or in week 14 (n = 9), and killed in week 62. PH in week 14 inhibited lethal hepatitis, but PH in week 8 was less effective. PH reduced the hepatic copper concentration to half that of controls. The present data suggest that induction of hepatocyte regeneration by repeated injections of GalN, or by PH just before the onset of jaundice has a significant effect in prevention of hepatic injury of LEC rats, but not enhancement of spontaneous hepatocarcinogenesis.

Benefit of a combined treatment with trientine and ascorbate in familial amyotrophic lateral sclerosis model mice

We previously reported that the common toxic gain-of-function in various mutant copper-zinc superoxide dismutases (SOD1) seen in patients with familial amyotrophic lateral sclerosis (ALS) was an abnormal copper release from the enzyme protein. In this study, trientine and ascorbate, known to have a beneficial effect in an animal model of Wilson disease, were administered to transgenic mice overexpressing a mutated human SOD1 (G93A). The onset of neurological signs in the treated group was significantly delayed compared with that in the control group, and the time to reach total paralysis in the treated group was delayed as well. Since the agents used in this study cause low toxicity in animals and humans, this treatment may be a good candidate for clinical application.