Apoptosis induced by Aß25-35 peptide is Ca(2+) -IP3 signaling-dependent in murine astrocytes.

Although the accumulation of the neurotoxic peptide ß-amyloid (Aß) in the central nervous system is a hallmark of Alzheimer's disease, whether Aß acts in astrocytes is unclear, and downstream functional consequences have yet to be defined. Here, we show that cytosolic Ca(2+) dysregulation, induced by a neurotoxic fragment (Aß25-35), caused apoptosis in a concentration-dependent manner, leading to cytoplasmic Ca(2+) mobilization from extra- and intracellular sources, mainly from the endoplasmic reticulum (ER) via IP3 receptor activation. This mechanism was related to Aß-mediated apoptosis by the intrinsic pathway because the expression of pro-apoptotic Bax was accompanied by its translocation in cells transfected with GFP-Bax. Aß-mediated apoptosis was reduced by BAPTA-AM, a fast Ca(2+) chelator, indicating that an increase in intracellular Ca(2+) was involved in cell death. Interestingly, the Bax translocation was dependent on Ca(2+) mobilization from IP3 receptors because pre-incubation with xestospongin C, a selective IP3 receptor inhibitor, abolished this response. Taken together, these results provide evidence that Aß dysregulation of Ca(2+) homeostasis induces ER depletion of Ca(2+) stores and leads to apoptosis; this mechanism plays a significant role in Aß apoptotic cell death and might be a new target for neurodegeneration treatments.

The role of mitochondrial function in glutamate-dependent metabolism in neuronal cells.

Glutamate is an important neurotransmitter in neurons and glial cells and it is one of the keys to the neuron-glial interaction in the brain. Glutamate transmission is strongly dependent on calcium homeostasis and on mitochondrial function. In the present work we presented several aspects related to the role of mitochondria in glutamate signaling and in brain diseases. We focused on glutamateinduced calcium signaling and its relation to the organelle dysfunction with cell death processes. In addition, we have discussed how alterations in this pathway may lead or aggravate a variety of neurodegenerative diseases. We compiled information on how mitochondria can influence cell fate during glutamate stimulation and calcium signaling. These organelles play a pivotal role in neuron and glial exchange, in synaptic plasticity and several pathological conditions related to Aging, Alzheimer's, Parkinson's and Huntington's diseases. We have also presented autophagy as a mechanism activated during mitochondrial dysfunction which may function as a protective mechanism during injury. Furthermore, some new perspectives and approaches to treat these neurodegenerative diseases are offered and evaluated.