CEP-1347/KT-7515, an inhibitor of c-jun N-terminal kinase activation, attenuates the 1-methyl-4-phenyl tetrahydropyridine-mediated loss of nigrostriatal dopaminergic neurons In vivo.

We have identified a bis-ethylthiomethyl analog of K-252a, CEP-1347/KT-7515, that promotes neuronal survival in culture and in vivo. The neuronal survival properties of CEP-1347/KT-7515 may be related to its ability to inhibit the activation of c-jun N-terminal kinase, a key kinase in some forms of stress-induced neuronal death and perhaps apoptosis. There is evidence that the selective nigrostriatal dopaminergic neurotoxin, MPTP, produces neuronal apoptosis in culture and in adult mice. Thus, our studies were designed to determine if CEP-1347/KT-7515 could protect dopaminergic neurons from MPTP-mediated neurotoxicity. CEP-1347/KT-7515 was assessed for neuroprotective activity in a low dose MPTP model (20 mg/kg) where there was a 50% loss of striatal dopaminergic terminals in the absence of substantia nigra neuronal loss, and a high dose (40 mg/kg) MPTP model where there was a complete loss of dopaminergic terminals and 80% loss of dopaminergic cell bodies. In the low dose MPTP model, CEP-1347/KT-7515 (0.3 mg/kg/day) attenuated the MPTP-mediated loss of striatal dopaminergic terminals by 50%. In the high dose model, CEP-1347/KT-7515 ameliorated the loss of dopaminergic cell bodies by 50% and partially preserved striatal dopaminergic terminals. CEP-1347/KT-7515 did not inhibit monoamine oxidase B or the dopamine transporter, suggesting that the neuroprotective effects of CEP-1347/KT-7515 occur downstream of the metabolic conversion of MPTP to MPP+ and accumulation of MPP+ into dopaminergic neurons. These data implicate a c-jun N-terminal kinase signaling system in MPTP-mediated dopaminergic degeneration and suggest that CEP-1347/KT-7515 may have potential as a treatment for Parkinson's disease.

Preservation of cholinergic activity and prevention of neuron death by CEP-1347/KT-7515 following excitotoxic injury of the nucleus basalis magnocellularis.

We have identified a class of small organic molecules, derived from the indolocarbazole K-252a, that promote the survival of cultured neurons. However, many of these indolocarbazoles inhibit protein kinase C and neurotrophin-activated tyrosine kinase receptors. These kinase inhibitory activities may limit the utility of these compounds for neurological disorders. A bis-ethyl-thiomethyl analogue of K-252a, CEP-1347/KT-7515, has been identified that lacks protein kinase C and tyrosine kinase receptor inhibitory activities, yet retains the ability to promote survival of cultured neurons, including cholinergic neurons derived from the basal forebrain. In the present studies, CEP-1347/KT-7515 was assessed for neurotrophic activity on basal forebrain neurons of in vivo rats following excitotoxic insult. Ibotenate infusion into the nucleus basalis magnocellularis reduced levels of choline acetyltransferase activity in the cortex, as well as reduced numbers of choline acetyltransferase-immunoreactive and retrogradely (FluoroGold)-labelled cortically-projecting neurons in the nucleus basalis. Systemically administered CEP-1347/KT-7515 attenuated the loss of cortical choline acetyltransferase activity and the loss of the number of choline acetyltransferase-immunoreactive and retrogradely-labelled FluoroGold neurons in the nucleus basalis. Moreover, CEP-1347/KT-7515 ameliorated the loss of cortical choline acetyltransferase if administration was initiated one day, but not seven days post-lesion. Together, these results demonstrate that CEP-1347/KT-7515 protects damaged cortically-projecting basal forebrain neurons from degeneration. Thus, CEP-1347/KT-7515 may have therapeutic potential in neurodegenerative diseases, such as Alzheimer's disease, in which basal forebrain cholinergic neurons degenerate.

Chronic sparing of delayed alternation performance and choline acetyltransferase activity by CEP-1347/KT-7515 in rats with lesions of nucleus basalis magnocellularis.

Peripheral injection of the indolocarbazole CEP-1347/KT-7515 into rats that have sustained ibotenic acid lesions of the nucleus basalis magnocellularis has been shown to prevent the loss of cortically-projecting neurons in that basal forebrain region. The present study tested whether this neuroprotective activity would lead to chronic sparing of a behaviour known to be impaired by that lesion, as well as to chronic maintenance of cholinergic activity in cortical target regions of the nucleus basalis. CEP-1347/KT-7515 was injected into adult rats that had sustained bilateral ibotenic acid lesions of the nucleus basalis magnocellularis; the first injection occurred 18-24 h after lesioning, with subsequent injections of CEP-1347/KT-7515 occurring every other day over 12 days. One day following the last injection the animals were tested for retention of a previously-learned delayed alternation task. Animals that received CEP-1347/KT-7515 committed significantly fewer errors than lesioned animals receiving vehicle. These same animals were tested again eight to 10 weeks later (which was 10-12 weeks post-dosing), without receiving further drug or behaviour training during the test-retest interval. The animals that had received CEP-1347/KT-7515 continued to commit significantly fewer errors than vehicle animals. Furthermore their performance at this time point was indistinguishable from normal controls. Analysis of errors showed that CEP-1347/KT-7515 prevented a lesion-induced increase in perseverative errors, suggesting the drug improved attention in the lesioned animals. Choline acetyltransferase activity in the frontal cortex of the behaviourally tested animals that received CEP-1347/KT-7515 three months previously showed a significant 40% recovery of the lesion-induced loss seen in the vehicle animals. These results demonstrate that treatment with CEP-1347/KT-7515 over 12 days following excitotoxic damage to the nucleus basalis magnocellularis produces long-term sparing of an attention-demanding behaviour.

High levels of synthesis and local effects of nerve growth factor in the septal region of the adult rat brain.

NGF found in the basal forebrain is believed to be localized to NGF-dependent cholinergic neurons and derived via retrograde axonal transport from NGF-synthesizing target hippocampal and cortical neurons. The basis for this concept of target-derived NGF is the detection of only limited amounts of NGF mRNA in the basal forebrain, despite relatively high NGF levels there. Our work, using a more sensitive and quantitative RNase protection method for detecting relative NGF mRNA levels, suggested, instead, relatively high levels of NGF mRNA synthesis in the septal region of the basal forebrain (BF-S), a region which contained primarily cells that project to the hippocampus. Similar results were obtained in analyses of a larger portion of the basal forebrain, designated "BF," that encompassed cholinergic neurons that project to both the hippocampus and the cortex. The level of NGF mRNA measured in both BF-S and BF was equivalent to approximately 50% of the amount observed in the hippocampus. Furthermore, relative NGF mRNA levels detected in the BF-S, cortex, and hippocampus were shown to be proportional to NGF protein levels quantitated in each region. The detection of relatively high amounts of NGF synthesis in the BF-S was supported in studies demonstrating rapid NGF receptor (Trk) activation in the basal forebrain by exogenous NGF and in experiments showing that NGF mRNA was inducible in the BF-S by 1,25 dihydroxyvitamin D3. The extent of NGF mRNA induction was similar (approximately twofold) in the BF-S, hippocampus, and cortex, suggesting similar regulatory mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)