Apoptosis in Nervous Cells

Abstract

In the central nervous system both neurons and astrocytes play crucial roles. On a cellular level, brain activity involves continuous interactions within complex cellular circuits established between neural cells and glia. Despite it was initially considered that neurons were the major cell type in cerebral function, nowadays astrocytes are considered to contribute to cerebral function too. Astrocytes support normal neuronal activity, including synaptic function, by regulating the extracellular environment with respect to ions and neurotransmitters. In both cell types Ca²⁺ signalling plays a pivotal role. Normal Ca²⁺ homeostasis is required for cell activity, in either in neurons and astrocytes, and must be precisely regulated. On the other hand, mitochondria are the major cellular source for ATP, and are also central for Ca²⁺ homeostasis. Deregulation of cell cycle has devastating effects on the integrity of cells, and has been closely associated with the development of pathologies which can lead to dysfunction and cell death. Programmed cell death or apoptosis can be activated and/or initiated by different mechanisms involving cell membrane receptor activation, Ca²⁺ signal impairment, mitochondrial uncoupling or oxidative stress, and involves in its majority, caspase-mediated cleavage cascade. An alteration of normal neuronal/glial physiology and apoptotic processes could represent the basis of neurodegenerative processes. In this chapter we will pay attention on to the recent findings in neuronal-astrocyte connection and its relationship to apoptosis.