Dysregulation of intracellular calcium homeostasis is responsible for neuronal death in an experimental model of selective hippocampal degeneration induced by trimethyltin

Abstract

Trimethyltin (TMT) intoxication is considered a suitable experimental model to study the molecular basis of selective hippocampal neurodegeneration as that occurring in several neurodegenerative diseases. We have previously shown that rat hippocampal neurons expressing the Ca2+‐binding protein calretinin (CR) are spared by the neurotoxic action of TMT hypothetically owing to their ability to buffer intracellular Ca2+ overload. The present study was aimed at determining whether intracellular Ca2+ homeostasis dysregulation is involved in the TMT‐induced neurodegeneration and if intracellular Ca2+‐buffering mechanisms may exert a protective action in this experimental model of neurodegeneration. In cultured rat hippocampal neurons, TMT produced time‐ and concentration‐dependent [Ca2+]i increases that were primarily due to Ca2+ release from intracellular stores although Ca2+ entry through Cav1 channels also contributed to [Ca2+]i increases in the early phase of TMT action. Cell pre‐treatment with the Ca2+ chelator, 1,2‐bis(2‐aminophenoxy)ethane‐N,N,N′,N′‐tetraacetic acid tetrakis(acetoxymethyl ester) (2 μM) significantly reduced the TMT‐induced neuronal death. Moreover, CR+ neurons responded to TMT with smaller [Ca2+]i increases. Collectively, these data suggest that the neurotoxic action of TMT is mediated by Ca2+ homeostasis dysregulation, and the resistance of hippocampal neurons to TMT (including CR+ neurons) is not homogeneous among different neuron populations and is related to their ability to buffer intracellular Ca2+ overload.

Intracellular Accumulation of Amyloid- (A ) Protein Plays a Major Role in A -Induced Alterations of Glutamatergic Synaptic Transmission and Plasticity

“…MO exhibited soluble small-oligomer distribution similar to that of wtA␤ but very limited neurotoxicity (Piacentini et al, 2008a;. This A␤ variant scarcely crossed the neuronal membrane: after 20 min application most of the labeled…”

“…Apoptosis was evaluated in hippocampal cultures with the APO-BrdU TUNEL assay Kit (Invitrogen) according to the manufacturer's instructions, as described in Podda et al (2014). Briefly, the cell cultures were exposed to 200 nM A␤42 or vehicle for 1 h. Cells exposed for 3 h to 100 M H 2 O 2 were used as positive control of apoptosis.…”

“…Hippocampal neurons from P0 to P2 C57BL/6 mice, eGFP-expressing mice (Okabe et al, 1997) or B6.129S7-App tm1Dbo /J mice (APP knock-out mice purchased from The Jackson Laboratory) brains were prepared according to standard procedure as previously described (Piacentini et al, 2008b; with some modifications. Briefly, hippocampi were incubated for 10 min at 37°C in PBS containing trypsin-EDTA (0.025%/0.01% w/v; Biochrom AG), and the tissue was mechanically dissociated at RT with a firepolished Pasteur pipette.…”

“…Freeze-dried purified A␤40, A␤42, A␤42-1, and A␤42 variant harboring oxidized methionine at position 35 (A␤42 MO ) and human amylin were purchased from AnaSpec. Protein solutions were prepared as previously described (Piacentini et al, 2008a;De Chiara et al, 2010;Maiti et al, 2011;Attar et al, 2012; according to standard procedures. Briefly, peptides were diluted to 1 mM in 1,1,1,3,3,3,-hexafluoro-2-propanol to disassemble preformed aggregates and stored as dry films at Ϫ20°C before use.…”

“…The slices were allowed to recover at 32°C for 1 h before being equilibrated at RT. For electrophysiological recordings, slices were transferred to a submerged recording chamber constantly perfused with heated ACSF (32°C) and bubbled with 95% O 2 /5% CO 2 (Podda et al, 2008;Fusco et al, 2012).…”