Neuroprotective Effect of Progesterone in MPTP-Treated Male Mice

BACKGROUND

Numerous studies have reported on the neuroprotective activity of estradiol, whereas the effect of the other ovarian steroid, progesterone, is much less documented.

METHODS

This study sought to investigate neuroprotection with a low dose of progesterone (1 µg) in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated male mice to model Parkinson's disease and compare it to the effect of this steroid in intact mice (experiment 1). We also investigated if high doses of progesterone could protect dopaminergic neurons already exposed to MPTP (experiment 2). We measured progesterone effects on various dopaminergic markers [dopamine and its metabolites, dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2)] and on neuroactive steroids in both plasma and the brain.

RESULTS

For experiment 1, our results showed that progesterone completely prevented the effect of MPTP toxicity on dopamine concentrations, on the increase in the 3-methoxytyramine/dopamine ratio, as well as on VMAT2-specific binding in the striatum and the substantia nigra. Progesterone decreased MPTP effects on 3,4-dihydroxyphenylacetic acid concentrations and DAT-specific binding in the lateral part of the anterior striatum and in the middle striatum (medial and lateral parts). Progesterone treatment of intact mice had no effect on the markers investigated. For experiment 2, measures of dopaminergic markers in the striatum showed that 8 mg/kg of progesterone was the most effective dose to reduce MPTP effects, and more limited effects were observed with 16 mg/kg. We found that progesterone treatment increases the levels of brain progesterone itself as well as of its metabolites.

CONCLUSION

Our result showed that progesterone has neuroprotective effects on dopaminergic neurons in MPTP-treated male mice.

Zonisamide suppresses endoplasmic reticulum stress-induced neuronal cell damage in vitro and in vivo

Zonisamide has been reported to have protective effects on epilepsy and Parkinson׳s disease and to work via various mechanisms of action, such as inhibition of monoamine oxidase-B and enhancement of tyrosine hydroxylase. Recently, it has been suggested that zonisamide itself shows neuroprotective actions. Therefore, in the present study we investigated the neuroprotective effects of zonisamide against endoplasmic reticulum (ER) stress. We used human neuroblastoma (SH-SY5Y) cells and investigated the protective effects of zonisamide against tunicamycin- and thapsigargin-induced neuronal cell death. In addition, we investigated the effect of zonisamide against 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell death and the mechanism of protection against ER stress. In vivo, we investigated the effect of zonisamide (20 mg/kg, p.o.) in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson׳s disease. Zonisamide not only suppressed MPP⁺-induced cell death, but also inhibited ER stress-induced cell death and suppressed the expression of ER stress-related factors such as C/EBO homologous protein (CHOP) in vivo. Furthermore, zonisamide inhibited the activation of caspase-3 in vitro. These results suggest that zonisamide affected ER stress via caspase-3. We think that ER stress, particularly the mechanism via caspase-3, is involved in part of the neuroprotective effect of zonisamide against the experimental models of Parkinson׳s disease.

[Blood serum corticosterone level in modeling depression-like states in rats]

In two models of depression-like state--"behavioral despair" and experimental dopamine deficit-dependent MPTP-induced depression-like syndrome--as well as in a model of anxiety-depression-like state induced by dipeptidyl peptidase IV inhibitor methionyl-2(s)-cyanopyrrolidine administered in early postnatal period, the symptoms of behavioral depression in rats in the forced swim test were accompanied by the increase of corticosterone level in blood serum. In every model non-competitive prolyl endopeptidase (PEP) inhibitor benzyloxycarbonyl-methionyl-2(S)-cyanopyrrolidine showed antidepressant-like properties preventing the development of depressive-like behavior. PEP Inhibitor also prevented the increase of serum corticosterone level in the models of "behavioral despair" and anxiety-depressive state, but not in the model of MPTP-induced depression-like syndrome. These findings testify for the involvement of hypothalamic-pituitary-adrenal system in the implementation of depression-like behavior in the specified models of depression-like state.

[Kinetic changes of plasma IL-1 and IL-6 levels in MPTP-induced Parkinson's disease model mice and their relationship with brain asymmetry]

AIM

To set up Parkinson's disease (PD) model mice by using 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP), detect the levels of plasma IL-1 and IL-6, and to explore their relationship with brain asymmetry.

METHODS

Male C57BL/6J mice were divided into right pawed mouse group and left pawed mouse group according to paw preference test which reflects brain asymmetry. Mice were injected intraperitoneally with 25 mg/kg MPTP each day for 5 consecutive days. The mice were executed and blood samples were taken at 1, 3 and 14 days after the last time injection. Control mice were only injected with normal saline. The levels of plasma IL-6 and IL-1 were detected by ELISA.

RESULTS

Plasma IL-6 level in normal control mice was low, but elevated dramatically at 14 days after last time injection of MPTP in PD model mice. Furthermore, IL-6 level of right pawed mice was higher than that of left pawed mice. Plasma IL-1 levels also increased on day 3 after last time injection of MPTP, and the level of left pawed mice was higher than that of right pawed mice.

CONCLUSION

IL-6 and IL-1 probably participate in the occurrence and progress of MPTP-induced PD in model mice, and were related with brain asymmetry.

Sympathetic innervation in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine primate model of Parkinson's disease

Cardiac sympathetic denervation occurs commonly in Parkinson's disease. This study explored whether analogous denervation occurs in primates with Parkinsonism from systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). 6-[18F]Fluorodopamine positron emission tomographic scanning and plasma levels of catecholamines and their deaminated metabolites were used to assess sympathetic and adrenomedullary function in rhesus monkeys, in the untreated state (n = 3), 2 weeks after a series of four MPTP injections, before establishment of Parkinsonism (acute phase, n = 1); a month later, after four more MPTP doses, associated with severe Parkinsonism (subacute phase, n = 1); or more than 2 years from the last dose (remote phase, n = 3), with persistent severe Parkinsonism. A positive control received i.v. 6-hydroxydopamine 1 week before 6-[18F]fluorodopamine scanning. Acute MPTP treatment increased cardiac 6-[18F]fluorodopamine-derived radioactivity, whereas 6-hydroxydopamine markedly decreased cardiac radioactivity, despite similarly low plasma levels of catecholamines and metabolites after either treatment. Subacutely, plasma catecholamines remained decreased, but now with myocardial 6-[18F]fluorodopamine-derived radioactivity also decreased. Remotely, MPTP-treated monkeys had lower plasma catecholamines and higher myocardial 6-[18F]fluorodopamine-derived radioactivity than did untreated animals. The results indicate that in nonhuman primates, systemic MPTP administration produces multiphasic effects on peripheral catecholamine systems, with nearly complete recovery by 2 years. MPTP- and 6-hydroxydopamine-induced changes differ markedly, probably from ganglionic or preganglionic neurotoxicity with the former and more severe cardiac sympathetic neurotoxicity with the latter. Because of multiphasic sympathetic and adrenomedullary effects, without cardioselective sympathetic denervation at any time, the primate MPTP model does not mimic the changes in peripheral catecholamine systems that characterize the human disease.