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Lens epithelial cell apoptosis and intracellular Ca2+ increase in the presence of xanthurenic acid.

Malina H, Richter C, Frueh B, Hess OM - BMC Ophthalmol (2002)

Bottom Line: 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.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.We observed an induction of calpain Lp 82 and an increase of free Ca2+ in the cells in a xanthurenic acid concentration-dependent manner.

View Article: PubMed Central - HTML - PubMed

Affiliation: Swiss Cardiovascular Research Center, Inselspital, CH-3010 Bern, Switzerland. halina.malina@dkf2.unibe.ch

ABSTRACT

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

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Cytochrome c release in HuLEC grown in the presence of xanthurenic acid for 72 hours. (A) control cells, (B) cells grown in the presence of 10 μM xanthurenic acid.
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Figure 3: Cytochrome c release in HuLEC grown in the presence of xanthurenic acid for 72 hours. (A) control cells, (B) cells grown in the presence of 10 μM xanthurenic acid.

Mentions: In the control cells mitochondria occupy the perinuclear region (Fig. 2A). In the presence of 10 μM xanthurenic acid mitochondrial migration was observed (Fig. 2B). However, at higher concentrations (20 and 40 μM) xanthurenic acid led to the destruction of mitochondria. An intrinsic apoptotic pathway is activated by cytochrome c release and apoptosome formation with APAF-1 and ATP [22]. The apoptosome leads to activation of caspase-9, which activates caspase-3. We observed that in the presence of 10 μM xanthurenic acid cytochrome c was release from mitochondria (Fig. 3). APAF-1 is present in the HuLEC and its level is independent from xanthurenic acid concentration (not shown). Thus, release of cytochrome c is responsible for the observed caspase-3 activation, and nucleus cleavage.


Lens epithelial cell apoptosis and intracellular Ca2+ increase in the presence of xanthurenic acid.

Malina H, Richter C, Frueh B, Hess OM - BMC Ophthalmol (2002)

Cytochrome c release in HuLEC grown in the presence of xanthurenic acid for 72 hours. (A) control cells, (B) cells grown in the presence of 10 μM xanthurenic acid.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC103667&req=5

Figure 3: Cytochrome c release in HuLEC grown in the presence of xanthurenic acid for 72 hours. (A) control cells, (B) cells grown in the presence of 10 μM xanthurenic acid.
Mentions: In the control cells mitochondria occupy the perinuclear region (Fig. 2A). In the presence of 10 μM xanthurenic acid mitochondrial migration was observed (Fig. 2B). However, at higher concentrations (20 and 40 μM) xanthurenic acid led to the destruction of mitochondria. An intrinsic apoptotic pathway is activated by cytochrome c release and apoptosome formation with APAF-1 and ATP [22]. The apoptosome leads to activation of caspase-9, which activates caspase-3. We observed that in the presence of 10 μM xanthurenic acid cytochrome c was release from mitochondria (Fig. 3). APAF-1 is present in the HuLEC and its level is independent from xanthurenic acid concentration (not shown). Thus, release of cytochrome c is responsible for the observed caspase-3 activation, and nucleus cleavage.

Bottom Line: 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.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.We observed an induction of calpain Lp 82 and an increase of free Ca2+ in the cells in a xanthurenic acid concentration-dependent manner.

View Article: PubMed Central - HTML - PubMed

Affiliation: Swiss Cardiovascular Research Center, Inselspital, CH-3010 Bern, Switzerland. halina.malina@dkf2.unibe.ch

ABSTRACT

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Show MeSH
Related in: MedlinePlus