Selective inhibition of mitochondrial sodium-calcium exchanger protects striatal neurons from α-synuclein plus rotenone induced toxicity

Abstract

Progressive accumulation of α-synuclein (α-syn) and exposure to environmental toxins are risk factors that may both concur to Parkinson’s disease (PD) pathogenesis. Electrophysiological recordings of field postsynaptic potentials (fEPSPs) and Ca2+ measures in striatal brain slices and differentiated SH-SY5Y cells showed that co-application of α-syn and the neurotoxic pesticide rotenone (Rot) induced Ca2+ dysregulation and alteration of both synaptic transmission and cell function. Interestingly, the presence of the mitochondrial NCX inhibitor CGP-37157 prevented these alterations. The specific involvement of the mitochondrial NCX was confirmed by the inability of the plasma membrane inhibitor SN-6 to counteract such phenomenon. Of note, using a siRNA approach, we found that NCX1 was the isoform specifically involved. These findings suggested that NCX1, operating on the mitochondrial membrane, may have a critical role in the maintenance of ionic Ca2+ homeostasis in PD and that its inhibition most likely exerts a protective effect in the toxicity induced by α-syn and Rot.

Gateways for Glutamate Neuroprotection in Parkinson’s Disease (PD): Essential Role of EAAT3 and NCX1 Revealed in an In Vitro Model of PD

“…Since Rot by interacting with α-syn stimulates its aggregation and toxicity [28,29,56,57], we evaluated cell viability after exposure to α-syn plus Rot. In particular, we found that cell damage induced by syn (10 nM) plus Rot (300 nM) [22] was significantly higher than their respective experiments performed in triplicate. * Significant versus all groups (p < 0.01 versus Ctl, p < 0.05 versus 3 nM, p < 0.001 versus 30 nM); ** significant versus all groups (p < 0.0001 versus Ctl and 3 nM, p < 0.001 versus 10 nM).…”

“…Bath solution was changed with a peristaltic pump and images were acquired every 5 s. Fluo 4-AM was excited at 488 nm and the emission was time-lapsed recorded at 505-530, while Rhod 2-AM was excited at 543 nm and fluorescence emission was measured from 560 nm to 600 nm. Analysis of fluorescence was performed off-line after images acquisition, as previously described [22].…”

“…In addition, it has also been reported that reduced mitochondrial complex I activity is involved in the mechanisms leading to PD induced by oligomeric form of α-syn [22][23][24][25][26][27]. Furthermore, a direct association between mitochondrial defects and the development of PD arises from studies showing that other toxins, such as rotenone (Rot; an inhibitor of respiratory chain complex I) [3], can induce α-syn aggregation, leading to mitochondrial toxicity as well as the loss of dopaminergic neurons [22,25,28,29]. Finally, mutations in different PD-related genes can significantly affect core functions of mitochondria and ultimately disrupt mitochondrial homeostasis [30,31].…”

“…On the basis of this evidence, we investigated the ability of glutamate to recover oxidative metabolism, cell viability and intracellular Ca 2+ dysfunctions in an in vitro model of PD based on retinoic acid (RA)-differentiated SH-SY5Y neuroblastoma dopaminergic cells exposed to α-syn plus Rot treatment [22], and explored the possible involvement of NCX1 and EAAT3.…”

Modes of Calcium Regulation in Ischemic Neuron

“…In excitable cells such as neurons, mitochondria play a role in regulating intracellular calcium levels. Mitochondrial calcium concentration can be maintained either by the exchange of calcium ions through the matrix for cytosolic sodium ions mediated by mitochondrial sodium/calcium exchanger (NCXMITO), located at the inner mitochondrial membrane [30].…”