Apoptotic Mode of Cell Death in Substantia Nigra Following Intranigral Infusion of the Parkinsonian Neurotoxin, MPP+ in Sprague-Dawley Rats: Cellular, Molecular and Ultrastructural Evidences

Abstract

The potent parkinsonian neurotoxin 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) is known to cause dopaminergic neurodegeneration in nigrostriatal system. In the present study we investigated the nuclear morphology of cells in the substantia nigra pars compacta (SNpc) region of rats following unilateral intranigral infusion of the active metabolite, 1-methyl-4-phenyl pyridinium ion (MPP(+)), which resulted in a dose-dependent and prolonged dopamine depletion in the ipsilateral striatum. There appeared a substantial loss of tyrosine hydroxylase immunoreactive neurons in the SNpc that received the neurotoxin. Specific nuclear staining with Hoechst 33342 or acridine orange revealed bright pyknotic, shrunken, distorted nuclei and condensed chromatin with perinuclear nucleolus respectively following visualization with the former and latter dyes in the ipsilateral SNpc, as compared to the round, intact nuclei and centrally positioned nucleolus in the contralateral side. Ultrastructural details of the nucleus under transmission electron microscope confirmed distorted nuclear organization with shrunken or condensed nuclei and disrupted nuclear membrane. These features are typical of nucleus undergoing apoptosis, and suggest that MPP(+) causes dopaminergic neuronal death through an apoptotic mode. Typical laddering pattern of genomic DNA isolated from the ipsilateral SN in agarose gel electrophoresis conclusively established apoptosis following intranigral administration of MPP(+) in rats.

Triptolide protects against 1-methyl-4-phenyl pyridinium-induced dopaminergic neurotoxicity in rats: Implication for immunosuppressive therapy in Parkinson’s disease

“…Activated microglia not only bring damage to neurons through releasing a variety of noxious compounds [42,43] , but also recruit and activate more microglial cells, forming a vicious cycle that leads to more dopaminergic neuronal death. In the present study, after MPP + intoxication to SN, we observed a progressive TH-positive cell loss and behavioral defects in rats, which were consistent with previous studies [23,31,44] . Activation of microglia was seen from the third day after MPP + injection and lasted throughout our experiment.…”

“…1C) Our results are broadly in accordance with previous study by Banerjee R et al who showed that intranigral MPP + infusion cause long-lasting damage to the nigrostriatal dopamine pathway, and did not show any sign of recovery in striatal dopamine content even after 90 d [31] .…”

Melatonin enhances L‐DOPA therapeutic effects, helps to reduce its dose, and protects dopaminergic neurons in 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐induced parkinsonism in mice

“…However, the apparent increase in the number of TH‐positive neurons in SNc could be an observational artifact, if we consider the distorted, shrunken perikarya of SNc TH‐positive neurons and the significantly increased number of small‐sized (30–50 μ m 2 ) and medium‐sized (50–80 μ m 2 ) neurons, but significantly decreased large (>80 μ m 2 ) neurons in the SN of MPTP and MPTP‐ plus melatonin‐treated group, as compared to the control. Therefore, it is a strong possibility that there is a general increase in the small‐sized neurons along the whole length of the SN, as MPTP treatment causes cerebral atrophy extending to the striatum, SN, and other parts of the brain and the increased number of TH‐positive neurons in the sections 18–30 could be resulting from the atrophy. In short, the present study features the unusual differential sensitivity of SNc dopaminergic neurons to MPTP treatment, which has not been heretofore reported.…”

Embryonic Stem Cells Derived Neuron Transplantation Recovery in Models of Parkinsonism in Relation to Severity of the Disorder in Rats

“…15 Similarly, increasing doses of parkinsonian neurotoxins can cause a proportional reduction in striatal DA levels, thereby modeling PD with increased severity. 14,[16][17][18] There are several behavioral tests for animal models of PD that display the onset and progression of the disease. 19,20 Some of the well-established behavioral tests in unilaterally lesioned animal models of PD include amphetamine-or apomorphine-induced unilateral rotations, cylinder test, elevated body swing test, skilled-forelimb use test, beam balancing test, etc.…”