A growing body of evidence suggests oxidative stress involvement in AD. However, it remains to be determined whether
oxidative stress is a cause, a result, or an epiphenomenon of the pathological processes. Several studies have indicated that
oxidative stress initially occurs in the disease-specific, site-restricted sources such as the cerebral cortex of AD brain. Subsequent
events which are common in neurons affected from this disease are represented by increased cytosolic Ca2+ levels, resulting
in activation of Ca2+- dependent and -independent enzymes. These enzymes produce reactive oxygen and nitrogen
species (ROS and RNS), which oxidatively modify nucleic acid, lipids, sugar, and proteins leading to nuclear damage, mitochondrial
damage and dysfunction, proteasome inhibition, and endoplasmic reticulum stress. In particular, Hauptmann et al.
(2008) showed that mitochondrial dysfunction, with a consequent membrane potential collapse and ATP reduction, enhanced
apoptosis and sensitivity to oxidative stress in genetic as well as in sporadic AD. Furthermore, mitochondrial stress-induced
apoptotic cell death is triggered by cytochrome c release from mitochondria and, together with Apaf-1 and dATP/ATP, forms
the apoptosome, induces processing of caspase-9, and initiates the caspase cascade that culminate with the activation of caspase
3. Interestingly, it has been shown that there is a correlation between the intracellular K+ concentration ([K+]i) and
apoptosome formation, since a fall in [K+]i triggers caspase 3 activation, thus propagating cell death signals. This effect
seems to be mainly due to an increased ROS production which, in turns, induces an increased activity of plasma-membrane
voltage-gated potassium (KV) channels(Yu et al. 1997; Lauritzen et al. 2003), in particular, we have recently demonstrated
that hippocampal neurons exposed to Ab1-42 display a selective up-regulation of KV3.4 channel subunits through the activation
of the transcriptional factor NF-kB. This activation is mediated by an early increase of a Ca2+-dependent ROS production
(Pannaccione et al. 2005; 2007). This event is associated with an increased K+ current carried by this channel. In addition,
it has been demonstrated that in neurons over-expressing KV3.4 channels an apoptotic process occurs through the activation
of caspase-3 (Pannaccione et al. 2007). The relationship between KV3.4 and apoptotic cell death is demonstrated by
the fact that the blockade of this channel by means of a specific inhibitor BDS-I prevents cell death caused by bA1-42 exposure.
In support of these data, cDNA array analysis has also demonstrated that KV3.4 gene up-regulation also occurs in cerebral
cortex of AD patients both in early and later stages (Angulo et al., 2004). Interestingly, the same up-regulation has been
found in brain extracts of Tg2576 Swedish mice, a well known pre-clinical model of the disease (Angulo et al., 2004). In order
to establish the correlation between KV3.4 channel and caspase-3 activation in a preclinical model of AD, our objectives
will be to characterize the role played by KV3.4 channel in controlling caspase-3 release in Tg2576 Swedish transgenic mice,
which overexpress KV3.4 channel (Angulo et al., 2004) and are object of investigation of Mercuri's group. This objective
will pursued by an in vivo and in vitro approach. The in vivo approach will be addressed to investigate the effect of KV3.4
knock-down, induced by siRNA, on caspase-3 release in CSF and on AD progression. The in vitro approach will be aimed to
demonstrate that knocking down Kv3.4 is able to reduce caspase-3 activation and to improve neuronal survival. This project
can have a relevant transferability to the national health service since the new information derived from the relationship existing
between Kv3.4 over-expression, caspase- 3 activation and neuronal death will help to further validate caspase-3 as AD
marker.