A cell-permeable peptide inhibitor TAT-JBD reduces the MPP super(+)-induced caspase-9 activation but does not prevent the dopaminergic degeneration in substantia nigra of rats

• Published in: Toxicology (Amsterdam) Vol. 243; no. 1-2; pp. 124 - 137
• Main Authors: Pain, S, Barrier, L, Deguil, J, Milin, S, Piriou, A, Fauconneau, B, Page, G
• Format: Journal Article
• Language: English
• Published: 14.01.2008
• ISSN: 0300-483X
• DOI: 10.1016/j.tox.2007.09.033

Many studies showed that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which was widely used to produce Parkinson's disease (PD)-like models in animals can elicit apoptosis with increase of caspase activity via its neurotoxic metabolite 1-methyl-4-phenylpyridinium ion (MPP super(+)). Another pathway shown in MPTP-mediated nigrostriatal dopaminergic cell death involved the c-Jun-N-terminal kinases (JNKs) which are stress-activated protein kinases (SAPKs). Activation of the JNKs leads to the activation of transcription factors such as c-Jun that regulates its own expression. However, it is not known whether the activation of c-Jun is crucial in the stimulation of caspases leading to apoptosis observed in PD-like models. The aim of this study was to investigate the cellular expression and phosphorylation of c-Jun and the caspase-9 activity in rat injured with an intranigral injection of MPP super(+). Furthermore, we determined the effects of a cell-permeable peptide TAT-JBD, inhibiting selectively JNKs, on apoptosis markers and on the expression of tyrosine hydroxylase (TH). Our results showed that MPP super(+) induced not only an activation of c-Jun but also an early and robust stimulation of caspase-9 in midbrain of rats. Furthermore, a preliminary intravenous injection of TAT-JBD reduced the caspase-9 activation specifically induced by MPP super(+) suggesting a control of the JNKs pathway on the intrinsic way of apoptosis in MPP super(+)-toxicity. However, the inhibition of the JNK pathway did not prevent TH inhibition, DNA fragmentation and Bad expression in MPP super(+)-lesioned substantia nigra of rats. Therefore, the possibility of intervention on the JNK pathway as a therapeutic strategy in Parkinson's disease is questionable. nick-end labelling