Metabolism of polyamines and oxidative stress in the brain of cholestatic rats

Spermine protects alpha-synuclein expressing dopaminergic neurons from manganese-induced degeneration

Manganese exposure is among the many environmental risk factors linked to the progression of neurodegenerative diseases, such as manganese-induced parkinsonism. In animal models, chronic exposure to manganese causes loss of cell viability, neurodegeneration, and functional deficits. Polyamines, such as spermine, have been shown to rescue animals from age-induced neurodegeneration in an autophagy-dependent manner; nonetheless, it is not understood whether polyamines can prevent manganese-induced toxicity. In this study, we used two model systems, the Caenorhabditis elegans UA44 strain and SK-MEL-28 cells, both expressing the protein alpha-synuclein (α-syn) to determine whether spermine could ameliorate manganese-induced toxicity. Manganese caused a substantial reduction in the viability of SK-MEL-28 cells and hastened neurodegeneration in the UA44 strain. Spermine protected both the SK-MEL-28 cells and the UA44 strain from manganese-induced toxicity. Spermine also reduced the age-associated neurodegeneration observed in the UA44 strain compared with a control strain without α-syn expression and led to improved avoidance behavior in a functional assay. Treatment with berenil, an inhibitor of polyamine catabolism, which leads to increased intracellular polyamine levels, also showed similar cellular protection against manganese toxicity. While both translation blocker cycloheximide and autophagy blocker chloroquine caused a reduction in the cytoprotective effect of spermine, transcription blocker actinomycin D had no effect. This study provides new insights on the effect of spermine in preventing manganese-induced toxicity, which is most likely via translational regulation of several candidate genes, including those of autophagy. Thus, our results indicate that polyamines positively influence neuronal health, even when exposed to high levels of manganese and α-syn, and supplementing polyamines through diet might delay the onset of diseases involving degeneration of dopaminergic neurons.

Progress in developing rat models of hepatic encephalopathy

Hepatic encephalopathy is a serious complication of acute and chronic liver diseases and has a high mortality rate. The pathogenesis of hepatic encephalopathy remains unclear, and there is no means of prevention or effective cure for the disease. Therefore, there is an urgent need for the basic and clinical research of hepatic encephalopathy to elucidate its pathogenesis. The development of animal models is important for elucidating the pathogenesis of hepatic encephalopathy and providing new avenues for diagnosis and therapy of the disease. Among a variety of animal models, rat model is applied most widely for similarity to humans, repeatability, reliability, applicability, controllability, simplicity and economy. In this paper, we briefly review various rat models of hepatic encephalopathy that have different origins.