cytochrome-c-t and xanthurenic-acid

Xanthurenic acid is an endogenous molecule leading to caspase-9 and -3 activation. Here we report that xanthurenic acid targets signalling proteins 14-3-3 into lysosomes leading to interruption protein/protein interaction. Xanthurenic acid changed the localisation of 14-3-3 in the cells. At a concentration of 10 and 20 microM the 14-3-3 was translocated into lysosomes. At these concentrations Bad and cofilin were dephosphorylated. Translocation of dephosphorylated Bad into mitochondria and cytochrome c release were observed. Cofilin dephosphorylation in the presence of xanthurenic acid was associated with lack of the apoptotic actin cytoskeleton disintegration. In conclusion xanthurenic acid accumulation in cells abolished the regulatory function of the proteins 14-3-3 in the cell physiology and caused misfolding of the proteins leading to cell pathology.

Topics: 14-3-3 Proteins; Astrocytes; bcl-Associated Death Protein; Carrier Proteins; Cells, Cultured; Cytochromes c; Humans; Lysosomes; Mitochondria; Protein Transport; Signal Transduction; Tyrosine 3-Monooxygenase; Xanthurenates

Xanthurenic acid is an endogenous product of tryptophan degradation by indoleamine 2,3-dioxygenase (IDO). We have previously reported that IDO is present in mammalian lenses, and xanthurenic acid is accumulated in the lenses with aging. Here, we studied the involvement of xanthurenic acid in the human lens epithelial cell physiology.. Human lens epithelial cells primary cultures were used. Control cells, and cells in the presence of xanthurenic acid grow in the dark. Western blot analysis and immunofluorescence studies were performed.. In the presence of xanthurenic acid human lens epithelial cells undergo apoptosis-like cell death. In the control cells gelsolin stained the perinuclear region, whereas in the presence of 10 microM xanthurenic acid gelsolin is translocated to the cytoskeleton, but does not lead to cytoskeleton breakdown. In the same condition caspase-3 activation, and DNA fragmentation was observed. At low (5 to 10 microM) of xanthurenic acid concentration, the elongation of the cytoskeleton was associated with migration of mitochondria and cytochrome c release. At higher concentrations xanthurenic acid (20 microM and 40 microM) damaged mitochondria were observed in the perinuclear region, and nuclear DNA cleavage was observed. We observed an induction of calpain Lp 82 and an increase of free Ca2+ in the cells in a xanthurenic acid concentration-dependent manner.. The results show that xanthurenic acid accumulation in human lens epithelial cells disturbs the normal cell physiology and leads to a cascade of pathological events. Xanthurenic acid induces calpain Lp82 and caspases in the cells growing in the dark and can be involved in senile cataract development.

Topics: Apoptosis; Blotting, Western; Calcium; Calpain; Caspase 3; Caspases; Cells, Cultured; Cytochromes c; Dose-Response Relationship, Drug; Enzyme Activation; Epithelial Cells; Fluorescent Antibody Technique, Indirect; Gelsolin; Humans; Hypolipidemic Agents; Lens, Crystalline; Middle Aged; Mitochondria; Tissue Donors; Xanthurenates