Proteasomes are eukaryotic ring-shaped or cylindrical particles with multicatalytic protease activities. To clarify the involvement of proteasomes in tumorigenesis of human blood cells, we compared their expression in human hematopoietic malignant tumor cells with that in normal peripheral blood mononuclear cells. Immunohistochemical staining showed considerably increased concentrations of proteasomes in leukemic cells from the bone marrow of patients with various types of leukemia and the predominant localization of these proteasomes in the nuclei. Moreover, enzyme immunoassay and Northern blot analysis indicated that the concentrations of proteasomes and their mRNA levels were consistently much higher in a variety of malignant human hematopoietic cell lines than in resting peripheral lymphocytes and monocytes from healthy adults. Proteasome expression was also greatly increased in normal blood mononuclear cells during blastogenic transformation induced by phytohemagglutinin; their expression increased in parallel with induction of DNA synthesis and returned to the basal level with progress of the cell cycle. Thus, abnormally high expression of proteasomes may play an important role in transformation and proliferation of blood cells and in specific functions of hematopoietic tumor cells.named C2 (12) and C3 (13), from rat liver proteasomes and one component of 35 kDa of Drosophila proteasomes (14) have been determined by cDNA cloning. The overall amino acid sequence of rat C2 closely resembles that of the Drosophila 35-kDa protein, suggesting that these two components function similarly in most eukaryotes and that they evolved from the same ancestral gene. In contrast, no significant homologies of these components with any other known proteins were found by computer analysis, indicating that proteasomes are a novel type of enzyme complex.Proteasomes are ubiquitous in cells of eukaryotes ranging from humans to yeast (1,15,16). Moreover, proteasomes or the related 20S particles have been found in both the cytoplasm and the nuclei of a variety of mammalian cells (8,17,18) and also various lower eukaryotes (14,(19)(20)(21)(22)(23)(24)(25), suggesting that their diverse roles depend on their differential localizations in the cells. However, the exact function of proteasomes is still unknown. One way to obtain information on their physiological role(s) is to study their expression in cells in abnormal states. In this work, we examined the expression of proteasomes in resting and growth-stimulated normal peripheral blood mononuclear cells and in a variety of human hematopoietic tumor cell lines.Proteasomes are multicatalytic proteinase complexes that are thought to be major intracellular proteolytic enzyme complexes responsible for certain types of nonlysosomal pathways of protein breakdown that requires metabolic energy (1). They were found to catalyze the degradation of various proteins in an ATP-dependent fashion (2-4). Moreover, 20S proteasomes were demonstrated to assemble into 26S proteolytic complexes t...

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Aims/hypothesis. We investigated the role played by sorbitol accumulation in the kidney in the development of diabetic albuminuria. Methods. We created mice (hAR-Tg:SDH null) with transgene-derived human aldose reductase and sorbitol dehydrogenase (SDH) deficiency, and analysed (i) the contribution of accumulated sorbitol to urinary albumin excretion rate, and (ii) the effect of the aldose reductase inhibitor, epalrestat, on the diabetic redox state, including decreased renal reduced glutathione concentrations or increased lactate to pyruvate ratios in the diabetic kidney. Results. Compared to littermates, non-diabetic transgenic mice had a 2.6-fold increase in aldose reductase mRNA. In a diabetic group, aldose reductase mRNA in hAR-Tg mice was 2.7-fold higher than in littermates. In the diabetic and non-diabetic groups, hARTg:SDH null mice had the highest sorbitol content among all four genetic types including hAR-Tg:SDH null, SDH null, hAR-Tg and littermates. The urinary albumin excretion rate in non-diabetic groups was similar in the four genetic types of mouse. In diabetic groups it was greater than in non-diabetic groups, but did not correlate with the sorbitol content among the four genetic types of mouse. When aldose reductase inhibitor and streptozotocin were given simultaneously at 6 weeks of age, epalrestat prevented diabetic increases in urinary albumin excretion rate and completely prevented diabetic decreases in reduced glutathione concentrations and diabetic increases in lactate to pyruvate ratios, even in the presence of transgenic aldose reductase. Conclusions/interpretation. The degree of diabetic albuminuria in genetically modified mice is dependent on the redox state and independent of polyol accumulation; aldose reductase inhibitor can prevent diabetic albuminuria by normalising diabetic redox changes.[Diabetologia (2004) Abbreviations: AR, Aldose reductase · SDH, sorbitol dehydrogenase · UAE, urinary albumin excretion rate · GSH, reduced glutathione · hAR-Tg, human aldose reductase-transgenic mouse · L/P, lactate/pyruvate Diabetologia (2004) 47:541-548

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This two-site immunoassay measures erythrocyte aldose reductase by using monoclonal and polyclonal antibodies to recombinant human enzyme. Total incubation time is 2.5 h, and the limit of detection is < 0.05 microgram/L. Analytical recovery tested with blood samples from healthy and diabetic individuals was 101-106%. Average CVs within and between assays were 3.7% and 4.8%, respectively. The enzyme content determined by this system correlated well with the activity of aldose reductase isolated from the same erythrocyte preparations. The amount of erythrocyte aldose reductase per milligram of hemoglobin was higher in women than in men (P < 0.001), but no significant correlation was observed between the amount of enzyme and the age of the individuals. This assay method should provide useful clinical information to optimize administration of aldose reductase inhibitors for effective prevention and treatment of diabetic complications.