Attenuation of 1-methyl-4-phenylpyridinium (MPP+) neurotoxicity by deprenyl in organotypic canine substantia nigra cultures

Abstract

Systemic administration of MPTP to experimental animals induces neurodegeneration of dopaminergic neurons in the central nervous system. MPTP crosses the blood-brain barrier where it is taken up by astrocytes and converted to MPP+ by monamine oxidase-B (MAO-B). Subsequently, MPP+ is selectively taken up by dopaminergic neurons upon which it exerts intracellular neurotoxic effects. Systemic administration of the selective MAO-B inhibitor deprenyl prevents the conversion of MPTP to MPP+ and by this mechanism is able to protect against MPTP neurotoxicity. Deprenyl has also been reported to exert neuroprotective effects that are independent of its MAO-B inhibitory properties, but since MPP+ itself does not cross the blood-brain barrier it is difficult to directly study the MAO-B independent in vivo effects of MPP+ itself. One approach is to use organotypic tissue cultures of the canine substantia nigra (CSN) which permit administration of precise concentrations of pharmacological agents directly to mature, well-developed and metabolically active dopaminergic neurons. These neurons as well as other components of the cultures exhibit morphological and biochemical characteristics identical to their in vivo counterparts. This study was undertaken to evaluate the neuroprotective effects of deprenyl in MPP(+)-treated cultures by measuring changes in the levels of HVA as an indicator of dopamine release and metabolism by dopaminergic neurons and to correlate this indication of dopaminergic function with morphological evidence of survival or loss of dopaminergic neurons in mature CSN cultures. Mature CSN cultures, at 44 days in vitro (DIV), were exposed to either MPP+ alone, deprenyl alone or simultaneously to both deprenyl and MPP+ or to MPP+ following 4 day pretreatment with deprenyl. Exposure to MPP+ alone caused significant reduction in HVA levels, evidence of widespread injury and ultimate disappearance of large neurons in the cultures. These effects were attenuated by simultaneous exposure to MPP+ and deprenyl and the destructive effects of MPP+ appeared to be prevented by pretreatment with deprenyl. Thus the neuroprotective effects of deprenyl on MPP(+)-induced reduction of HVA levels in living cultures appears similar to the effects of deprenyl on dopamine levels and tyrosine hydroxylase activity reported by others in cultures previously exposed to deprenyl and MPP+. These studies also confirm that the neuroprotective effects of deprenyl against MPP+ in dopaminergic neurons are, at least in part, independent of deprenyl's inhibition of MAO-B.

Neuronal protective and rescue effects of deprenyl against MPP+ dopaminergic toxicity

“…The present findings confirm our preliminary in vivo report (Wu et al, 1993b) and agree with several in vitro studies which indicate that deprenyl can protect against spontaneous cell death and MPP + toxicity in primary cultures of midbrain dopaminergic neurons (Mytilineou and Cohen, 1985;Roy and Bedard, 1993;Schmidt et al, 1993;Vizuete et al, 1993). The present in vivo study demonstrates that deprenyl can provide significant protection against MPP + toxicity when the nigral injury caused by the toxic MPTP metabolite is less than 50% as indicated by dopamine deficiency in the striatum (Fig.…”

Dopamine release in organotypic cultures of foetal mouse mesencephalon: effects of depolarizing agents, pargyline, nomifensine, tetrodotoxin and calcium

“…, 2006). Changes of endogenous dopamine (DA) and/or DA metabolite levels in growing cultures with or without neurotrophic factors and depletion by neurotoxic treatments have also been reported in such cultures (Schmidt et al. , 1997; Gramsbergen et al.…”

Glyceraldehyde-3-phosphate dehydrogenase in neurodegeneration and apoptosis signaling

“…The study showed that (-)-deprenyl could reduce dopaminergic neuronal death at a step beyond the conversion of MPTP to MPP + by MAO-B. Subsequently, a number of investigations using a variety of approaches have unequivocally established that (-)-deprenyl can reduce neuronal death independently of MAO-B or MAO-A inhibition (Ansari et al, 1993;Finnegan et al, 1990;Gelowitz and Paterson, 1999;Le et aI., 1997a;Schmidt et al, 1997;Tatton and Chalmers-Redman, 1996;Tatton and Greenwood, 1991). According to these results, MAO-B inhibition is not necessary for (-)-deprenyl to reduce neuronal death and raises the question as to whether any of the clinical slowing found in PD patients treated with (-)-deprenyl resulted from MAO-B independent neuronal rescue.…”

“…The models have included neuronal death induced by 6-hydroxydopamine (Salonen et al, 1996), MPP + (Koutsilieri et al, 1996;Koutsilieri et al, 1994;Le et al, 1997a;Mytilineou and Cohen, 1985;Schmidt et al, 1997;Tatton and Greenwood, 1991;Vizuete et al, 1993;Wu et al, 1995); MPTP (Cohen et al, 1984;Fuller et al, 1988;Takada et al, 1993;Tatton and Greenwood, 1991), nitric oxide or peroxynitrite (Maruyama et al, 1998), DSP-4 (Finnegan et aI., 1990;Yu et al, 1994;Zhang and Yu, 1995); glutathione depletion (Mytilineou et al, 1998), peripheral nerve crush or axotomy (Ansari et al, 1993;Iwasaki et al, 1996;Ju et al, 1994;Oh et al, 1994;Salo and Tatton, 1992); optic nerve crush (Buys et al, 1995); hypoxia and/or ischemia (Knollema et al, 1995;Lahtinen et al, 1997;Paterson et al, 1997 ;Ravikumar et al, 1998;Semkova et al, 1996); cytosine arabinoside (Paterson et al, 1998); excitotoxins (Gelowitz and Paterson, 1999;Mytilineou et al, 1997;Pereira and Oliveira, 1997;Semkova et al, 1996), trophic insufficiency (Ragaiey et al, 1997;Tatton et al, 1994;Wadia et al, 1998); thiamine deficiency (Tod...…”