Bee venom reduces neuroinflammation in the MPTP-induced model of Parkinson's disease.

AIM: This study was designed to investigate the anti-inflammatory effects of bee venom (BV) in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson's disease (PD). METHOD: MPTP was administered by intraperitoneal (IP) injection at 2-hr intervals over an 8-hr period. Mice were then subjected to BV subcutaneous injection and sacrificed on days 1 and 3 following the final MPTP injection. The loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) was assessed by tyrosine hydroxylase (TH) immunohistochemistry. Microglial activation was measured by immunohistochemistry for macrophage antigen complex-1 (MAC-1) and inducible nitric oxide synthase (iNOS). The staining intensities of MAC-1 and iNOS were quantified with respect to optical density. RESULT: In animals treated with MPTP, the survival percentages of TH+ cells in the SNpc were 32% on day 1 and 46% on day 3 compared with normal mice. In BV-treated mice, the survival percentages of TH+ cells improved to 70% on day 1 and 78% on day 3 compared with normal mice. BV treatment also resulted in reduced expression of the inflammation markers MAC-1 and iNOS in the SNpc. CONCLUSION: These data suggest that BV injection may have a neuroprotective effect that attenuates the activation of the microglial response, which has implications for the treatment of PD.

Novel multifunctional neuroprotective iron chelator-monoamine oxidase inhibitor drugs for neurodegenerative diseases. In vivo selective brain monoamine oxidase inhibition and prevention of MPTP-induced striatal dopamine depletion.

Several multifunctional iron chelators have been synthesized from hydroxyquinoline pharmacophore of the iron chelator, VK-28, possessing the monoamine oxidase (MAO) and neuroprotective N-propargylamine moiety. They have iron chelating potency similar to desferal. M30 is a potent irreversible rat brain mitochondrial MAO-A and -B inhibitor in vitro (IC50, MAO-A, 0.037 +/- 0.02; MAO-B, 0.057 +/- 0.01). Acute (1-5 mg/kg) and chronic [5-10 mg/kg intraperitoneally (i.p.) or orally (p.o.) once daily for 14 days]in vivo studies have shown M30 to be a potent brain selective (striatum, hippocampus and cerebellum) MAO-A and -B inhibitor. It has little effects on the enzyme activities of the liver and small intestine. Its N-desmethylated derivative, M30A is significantly less active. Acute and chronic treatment with M30 results in increased levels of dopamine (DA), serotonin(5-HT), noradrenaline (NA) and decreases in DOPAC (dihydroxyphenylacetic acid), HVA (homovanillic acid) and 5-HIAA (5-hydroxyindole acetic acid) as determined in striatum and hypothalamus. In the mouse MPTP (N-methy-4-phenyl-1,2,3,6-tetrahydropyridine) model of Parkinson's disease (PD) it attenuates the DA depleting action of the neurotoxin and increases striatal levels of DA, 5-HT and NA, while decreasing their metabolites. As DA is equally well metabolized by MAO-A and -B, it is expected that M30 would have a greater DA neurotransmission potentiation in PD than selective MAO-B inhibitors, for which it is being developed, as MAO-B inhibitors do not alter brain dopamine.

Neuroprotective effect of dextromethorphan in the MPTP Parkinson's disease model: role of NADPH oxidase.

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by a progressive loss of dopaminergic neurons in the substantia nigra and depletion of the neurotransmitter dopamine in the striatum. Progress in the search for effective therapeutic strategies that can halt this degenerative process remains limited. Mechanistic studies using animal systems such as the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) rodent PD model have revealed the involvement of the brain's immune cells and free radical-generating processes. We recently reported that dextromethorphan (DM), a widely used anti-tussive agent, attenuated endotoxin-induced dopaminergic neurodegeneration in vitro. In the current study, we investigated the potential neuroprotective effect of DM and the underlying mechanism of action in the MPTP rodent PD model. Mice (C57BL/6J) that received daily MPTP injections (15 mg free base/kg body weight, s.c.) for 6 consecutive days exhibited significant degeneration of the nigrostriatal dopaminergic pathway. However, the MPTP-induced loss of nigral dopaminergic neurons was significantly attenuated in those mice receiving DM (10 mg/kg body weight, s.c.). In mesencephalic neuron-glia cultures, DM significantly reduced the MPTP-induced production of both extracellular superoxide free radicals and intracellular reactive oxygen species (ROS). Because NADPH oxidase is the primary source of extracellular superoxide and intracellular ROS, we investigated the involvement of NADPH oxidase in the neuroprotective effect of DM. Indeed, the neuroprotective effect of DM was only observed in the wild-type but not in the NADPH oxidase-deficient mice, indicating that NADPH oxidase is a critical mediator of the neuroprotective activity of DM. More importantly, due to its proven safety record of long-term clinical use in humans, DM may be a promising agent for the treatment of degenerative neurological disorders such as PD.

Neuroprotective effects of oral administration of triacetyluridine against MPTP neurotoxicity.

Administration of triacetyluridine (TAU) is a means of delivering exogenous pyrimidines to the brain, which may help to compensate for bioenergetic defects. TAU has previously been shown to be neuroprotective in animal models of Huntington's and Alzheimer's diseases. We examined whether oral administration of TAU in the diet could exert significant neuroprotective effects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity model of Parkinson's disease. Administration of TAU significantly attenuated MPTP-induced depletion of striatal dopamine and loss of tyrosine-hydroxylase-positive neurons in the substantia nigra. These findings suggest that administration of TAU may be a novel approach for treating neurodegenerative diseases associated with impaired mitochondrial function.

Neuroprotective actions of the ginseng extract G115 in two rodent models of Parkinson's disease.

The herbal remedy, ginseng, has recently been demonstrated to possess neurotrophic and neuroprotective properties, which may be useful in preventing various forms of neuronal cell loss including the nigrostriatal degeneration seen in Parkinson's disease (PD). In these studies, we examine the potential neuroprotective actions of the ginseng extract, G115, in two rodent models of PD. Animals received oral administration of G115 prior to and/or following exposure to the parkinsonism-inducing neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), in mice, or its toxic metabolite, 1-methyl-4-phenylpyridinium (MPP(+)), in rats. Such treatment significantly and dramatically blocked tyrosine hydroxylase-positive cell loss in the substantia nigra and reduced the appearance of locomotor dysfunction. Thus, oral administration of ginseng appears to provide protection against neurotoxicity in rodent models of PD. Further examination of the neuroprotective actions of ginseng and its various elements may provide a potential means of slowing the progress of PD.

Prevention of nitric oxide-mediated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease in mice by tea phenolic epigallocatechin 3-gallate.

In animal models of Parkinson's disease (PD), the toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is mediated by oxidative stress, especially by nitric oxide (NO). Inhibition of NO synthase (NOS) activity in the brain produces a neuroprotective effect against PD induced by MPTP Green tea containing high levels of (-)-epigallocatechin 3-gallate (EGCG) was administered to test whether EGCG attenuates MPTP-induced PD in mice through the inhibition of NOS expression. Both tea and the oral administration of EGCG prevented the loss of tyrosine hydroxylase (TH)-positive cells in the substantia nigra (SN) and of TH activity in the striatum. These treatments also preserved striatal levels of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid (HVA). Both tea and EGCG decreased expressions of nNOS in the substantia nigra. Also tea plus MPTP and EGCG plus MPTP treatments decreased expressions of neuronal NO synthase (nNOS) at the similar levels of EGCG treatment group. Therefore, the preventive effects of tea and EGCG may be explained by the inhibition of nNOS in the substantia nigra.

Nerve growth factor prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced cell death via the Akt pathway by suppressing caspase-3-like activity using PC12 cells: relevance to therapeutical application for Parkinson's disease.

Nerve growth factor (NGF) mediates a variety of nerve cell actions through receptor tyrosine kinase TrkA. It has been revealed that the Akt pathway contributes to the prevention of apoptosis. It is thought that Parkinson's disease involves apoptosis, and NGF prevents apoptosis in an in vivo model system. However, there is no evidence that the Akt pathway helps to prevent parkinsonism. Here, we report that NGF prevents apoptosis induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in PC12 cells as an in vitro model system of parkinsonism and that this survival effect diminishes on addition of LY294002, a specific inhibitor of phosphatidylinositol 3-kinase. Immunocytochemical analysis revealed that 1 mM MPTP-treated cells or dominant negative Akt-expressing cells, to which were added NGF and MPTP, undergo apoptosis. Moreover, the caspase-3-like activity is increased by addition of MPTP or MPTP with NGF and LY294002. The importance of another signal pathway is shown by PD98059, a specific inhibitor of MAP kinase (MAPK) kinase, but PD98059 does not alter the survival effect in this model system. These results indicate that the Akt pathway helps to prevent parkinsonism by suppressing caspase-3-like activity, but the MAPK pathway is not involved in the NGF-dependent survival enhancing effect in this model system.

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.

L-Deprenyl and MDL72974 do not improve the recovery of dopaminergic cells following systemic administration of MPTP in mouse.

L-Deprenyl, a monoamine oxidase B (MAO-B) inhibitor, administered prior to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) protects dopaminergic neurons against degeneration in several animal species including mice. L-Deprenyl inhibits MPP+ formation, the mediator of MPTP toxicity. In addition, L-deprenyl, administered 72 h following MPTP, improves the recovery of tyrosine hydroxylase (TH) immunopositive neurons in the substantia nigra (SN) of mice. This observation lead to the proposal that L-deprenyl exerts a 'neurorescue' effect. However, clinical trials failed to demonstrate that L-deprenyl can effectively 'rescues' degenerating dopaminergic neurons in early untreated Parkinson's disease (PD) patients. These observations prompted us to reevaluate the long-term impact of L-deprenyl on MPTP-induced dopaminergic cell loss in mice. In addition, we made use of another MAO-B inhibitor, MDL72974, to assess MAO-B participation in this paradigm. Our results suggest that L-deprenyl does not improve the recovery of TH immunopositive neurons in MPTP-treated mice. An apparent reduction in TH+ neurons is observed in the SN of MDL72974 and L-deprenyl/MPTP-treated mice at 30 days post-treatment. The possible implication of these findings in relation to the used of MAO-B inhibitors in PD is discussed.

Prevention by a Ginkgo biloba extract (GBE 761) of the dopaminergic neurotoxicity of MPTP.

In mice implanted subcutaneously with osmotic minipumps releasing the neurotoxic agent N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 7 days (105 micrograms h-1/mouse) (approximately 100 mg kg-1 day-1) a significant reduction (approximately 25%) in the striatal dopaminergic nerve endings was observed. This neurotoxic effect was prevented by the semi-chronic ingestion of a Ginkgo biloba extract for 17 days (GBE 761, approximately 100 mg kg-1 day-1). The high concentrations (approximately 1 g L-1) at which GBE 761 in-vitro either prevented the uptake of [3H]dopamine by synaptosomes prepared from striatum, or prevented the specific binding of the pure dopamine uptake inhibitor [3H]GBR 12783 to membranes prepared from striatum suggests that the prevention of the MPTP neurotoxicity does not depend on an inhibition of the MPTP uptake by dopamine neurons. This is also suggested by the lack of prevention of the in-vitro striatal binding of [3H]GBR 12783 administered i.v. at a tracer dose, in mice pretreated for 8 days with GBE 761 (100 mg kg-1 p.o.) and receiving a supplementary gastric administration of GBE 761 (100 mg kg-1) 1 h before testing. Similar treatment with GBE 761 did not modify the toxicity for dopamine neurons of 6-hydroxydopamine (20 micrograms) directly injected into the striatum of rats.