The signalling axis mediating neuronal apoptosis in response to [Pt(O,O′-acac)(γ-acac)(DMS)

Abstract

It was previously shown that [Pt(O,O′-acac)(γ-acac)(DMS)] induces apoptosis in various cancer cells and exerts antimetastatic responses in vitro. In rats, [Pt(O,O′-acac)(γ-acac)(DMS)] reaches the central nervous system in quantities higher than cisplatin causing less excitotoxicity. The aim of the present paper was to investigate whether [Pt(O,O′-acac)(γ-acac)(DMS)] is able to exert cytotoxic effects on SH-SY5Y human neuroblastoma cell line, and to study the intracellular transduction mechanisms underlying these effects. Here we have demonstrated that [Pt(O,O′-acac)(γ-acac)(DMS)] was more effective than cisplatin in provoking apoptosis characterized by: (a) mitochondria depolarization, (b) decrease of Bcl-2 expression and increase of BAX expressions with cytosol-to-mitochondria translocation, (c) activation of caspase-7 and -9 and (d) generation of reactive oxygen species (ROS). [Pt(O,O′-acac)(γ-acac)(DMS)] provoked the activation of the following signalling kinases that were interacting with each other: PKC-δ and -ɛ, ERK1/2, p38MAPK, JNK1/2, NF-κB, c-src and FAK. We found that ROS generated by NADPH oxidase was responsible for the [Pt(O,O′-acac)(γ-acac)(DMS)]-mediated PKC-δ and -ɛ activation and consequential phosphorylation of all MAPKs. [Pt(O,O′-acac)(γ-acac)(DMS)]-induced mitochondrial apoptosis was blocked when p38MAPK and JNK1/2 were inhibited, whilst the effects on Bax/Bcl-2 mRNA and protein levels were blocked inhibiting NF-κB. NF-κB nuclear translocation was blocked inhibiting MEK1/2 activity. In addition to the induction of apoptosis [Pt(O,O′-acac)(γ-acac)(DMS)] downregulated pro-survival pathway. Survival inhibition started from mitochondrial ROS generation which induced c-src, FAK and Akt activation. In conclusion, our results suggest that [Pt(O,O′-acac)(γ-acac)(DMS)] may be considered a promising compound for the treatment of neuroblastoma. Further studies are warranted to explore in detail the therapeutic potential of this compound.