Morphological, physiological and biochemical alterations in livers of rodents induced by protease inhibitors: a comparison with old livers

Distinct types of lipofuscin pigment in the hippocampus and cerebellum of aged cheirogaleid primates

The formation of autofluorescent lipopigment or lipofuscin is a highly consistent and reliable cytological change that correlates with cellular aging in postmitotic cells. One causal factor of lipofuscinogenesis involves free radical-induced lipid peroxidation. In mammals, dentate gyrus neurons and Purkinje cells are usually affected widely. In this study, we investigated the ultrastructure of lipofuscin deposits in large neurons of the dentate gyrus and in Purkinje cells of aged fat-tailed dwarf lemurs (Cheirogaleus medius Geoffroy, 1812) with electron and confocal microscopy and compared it with previous observations in other species. Cheirogaleid primates such as mouse and dwarf lemurs are archaic primates that provide interesting nonhuman models of aging. Our study revealed region-specific as well as species-specific characteristics of lipofuscin ultrastructure. This suggests differences in cellular metabolism and/or in organelles involved in lipofuscin production in cerebellar Purkinje cells and in hippocampal dentate gyrus neurons.

Didemnin binds to the protein palmitoyl thioesterase responsible for infantile neuronal ceroid lipofuscinosis

The marine natural product didemnin B, currently in clinical trials as an antitumor agent, has several potent biological activities apparently mediated by distinct mechanisms. Our initial investigation of didemnin B resulted in the discovery of its GTP-dependent binding of the translation elongation factor EF1 alpha. This finding is consistent with the protein synthesis inhibitory activity of didemnin B observed at intermediate concentrations. To begin to dissect the mechanisms involved in the cytostatic and immunosuppressive activities of didemnin B, observed at low concentrations, additional didemnin-binding proteins were sought. Here we report the purification of a 36-kDa glycosylated didemnin-binding protein from bovine brain lysate. Cloning of the human cDNA encoding this protein revealed a strong sequence similarity with palmitoyl protein thioesterase (PPT), an enzyme that removes palmitate from H-Ras and the G alpha s subunits of heterotrimeric GTP-binding proteins in vitro. Mutations in PPT have recently been shown to be responsible for infantile neuronal ceroid lipofuscinosis, which is a severe brain disorder characterized by progressive loss of brain function and early death.

Evidence for lipase abnormality: high levels of free and triacylglycerol forms of unsaturated fatty acids in neuronal ceroid-lipofuscinosis tissue

Total lipid obtained from normal and different forms of neuronal ceroid-lipofuscinoses (NCL) tissues was analyzed by high performance thin layer chromatography (HPTLC). We observed a large (greater than 6-fold) increase in a lipid band corresponding to triolein for NCL dog pancreas and spleen and juvenile human NCL brain and infantile NCL spleen. The accumulation was less pronounced for the brain samples but apart from increased dolichol-monophosphate levels, other lipids appeared normal. Normal dog, goat, or human spleen contained virtually no triacylglycerol, and of the pathological controls, beta-mannosidosis goat spleen showed no triacylglycerol band at all. A sample of human spleen from a patient with lymphoma-associated splenomegaly displayed a strong triacylglycerol band, but gas chromatography-mass spectrometry (GC/MS) of the bands showed an equal increase in both saturated and unsaturated fatty acid containing triacylglycerols in the splenomegaly sample, in keeping with the notion of non-specific fat deposition in damaged tissue. In contrast, in all the NCL samples (spleen, pancreas, and brain) a prominent increase in the proportion of unsaturated fatty acids was observed in both free fatty acid and/or triacylglycerol bands following GC/MS. The NCL-English setter dog pancreas showed a major presence of oleic acid (18:1) (twofold increase) as compared to normal, while dog and infantile human NCL spleen samples and juvenile Batten brain (human) displayed a robust increase in linoleic acid (18:2) and sometimes in oleic acid and arachidonic acid (20:4) (for infantile human NCL spleen). For the infantile human NCL spleen sample an increase in linoleic acid in both free fatty acid (3.2-fold) and triacylglycerol (10-fold) was observed.(ABSTRACT TRUNCATED AT 250 WORDS)