Targeting alpha-synuclein in Parkinson's disease

Resveratrol-mediated cleavage of amyloid β1-42 peptide: potential relevance to Alzheimer's disease

Aggregation of amyloid β_1-42 (Aβ_1-42) peptide within the brain is considered one of the main causes of the neuropathological changes associated with Alzheimer's disease. Resveratrol is a well-known antioxidant but has also been reported to bind to Aβ_1-42 peptide, thereby reducing aggregation. However, little is known of the precise mechanism by which resveratrol reduces Aβ_1-42 peptide aggregation. Using the thioflavin-T assay, the ability of resveratrol to reduce the extent of Aβ_1-42 peptide aggregation was investigated. The findings of the present study demonstrate that interaction of resveratrol with Aβ_1-42 peptide resulted in the cleavage of Aβ_1-42 peptide into smaller fragments, as detected by matrix assisted laser desorption ionization-time of flight mass spectrometry. Atomic force microscopy analyses revealed Aβ_1-42 peptide, under control conditions, aggregated into oligomers, protofibrils, and fibrils, whereas there was a distinct lack of these structures when Aβ_1-42 peptide was incubated with resveratrol. Following 10 days incubation of Aβ_1-42 peptide with resveratrol, particles with a mean z-height of 1.940 nm (range 0.675-3.275 nm) were observed, which are characteristic of shorter peptide species. In cell-based studies, resveratrol significantly reduced the cytotoxicity of Aβ_1-42 peptide toward SH-SY5Y human neuroblastoma cells, suggesting a protective effect of the polyphenol. We therefore propose a novel mechanism by which resveratrol disrupts Aβ_1-42 aggregation by mediating fragmentation of Aβ_1-42 into smaller peptides, which have no propensity to aggregate further.

Structure and biomedical applications of amyloid oligomer nanoparticles

Amyloid oligomers are nonfibrillar polypeptide aggregates linked to diseases, such as Alzheimer's and Parkinson's. Here we show that these aggregates possess a compact, quasi-crystalline architecture that presents significant nanoscale regularity. The amyloid oligomers are dynamic assemblies and are able to release their individual subunits. The small oligomeric size and spheroid shape confer diffusible characteristics, electrophoretic mobility, and the ability to enter hydrated gel matrices or cells. We finally showed that the amyloid oligomers can be labeled with both fluorescence agents and iron oxide nanoparticles and can target macrophage cells. Oligomer amyloids may provide a new biological nanomaterial for improved targeting, drug release, and medical imaging.

Rifampicin improves neuronal apoptosis in LPS-stimulated co‑cultured BV2 cells through inhibition of the TLR-4 pathway

Agents inhibiting microglial activation are attracting attention as candidate drugs for neuroprotection in neurodegenerative diseases. Recently, researchers have focused on the immunosuppression induced by rifampicin. Our previous study showed that rifampicin inhibits the production of lipopolysaccharide (LPS)-induced pro-inflammatory mediators and improves neuron survival in inflammation; however, the mechanism through which rifampicin inhibits microglial inflammation and its neuroprotective effects are not completely understood. In this study, we examined the effects of rifampicin on morphological changes induced by LPS in murine microglial BV2 cells. Then we investigated, in BV2 microglia, the effects of rifampicin on two signaling pathway componentss stimulated by LPS, the Toll‑like receptor-4 (TLR-4) and the nuclear factor-κB (NF-κB). In addition, we co-cultured BV2 microglia and neurons to observe the indirect neuroprotective effects of rifampicin. Rifampicin inhibited LPS-stimulated expression of the TLR-4 gene. When neurons were co-cultured with LPS-stimulated BV2 microglia, pre-treatment with rifampicin increased neuronal viability and reduced the number of apoptotic cells. Taken together, these findings suggest that rifampicin, with its anti-inflammatory properties, may be a promising agent for the treatment of neurodegenerative diseases.

Efficacy and safety of rifampicin for multiple system atrophy: a randomised, double-blind, placebo-controlled trial

BACKGROUND

No available treatments slow or halt progression of multiple system atrophy, which is a rare, progressive, fatal neurological disorder. In a mouse model of multiple system atrophy, rifampicin inhibited formation of α-synuclein fibrils, the neuropathological hallmark of the disease. We aimed to assess the safety and efficacy of rifampicin in patients with multiple system atrophy.

METHODS

In this randomised, double-blind, placebo-controlled trial we recruited participants aged 30-80 years with possible or probable multiple system atrophy from ten US medical centres. Eligible participants were randomly assigned (1:1) via computer-generated permuted block randomisation to rifampicin 300 mg twice daily or matching placebo (50 mg riboflavin capsules), stratified by subtype (parkinsonian vs cerebellar), with a block size of four. The primary outcome was rate of change (slope analysis) from baseline to 12 months in Unified Multiple System Atrophy Rating Scale (UMSARS) I score, analysed in all participants with at least one post-baseline measurement. This study is registered with ClinicalTrials.gov, number NCT01287221.

FINDINGS

Between April 22, 2011, and April 19, 2012, we randomly assigned 100 participants (50 to rifampicin and 50 to placebo). Four participants in the rifampicin group and five in the placebo group withdrew from study prematurely. Results of the preplanned interim analysis (n=15 in each group) of the primary endpoint showed that futility criteria had been met, and the trial was stopped (the mean rate of change [slope analysis] of UMSARS I score was 0.62 points [SD 0.85] per month in the rifampicin group vs 0.47 points [0.48] per month in the placebo group; futility p=0.032; efficacy p=0.76). At the time of study termination, 49 participants in the rifampicin group and 50 in the placebo group had follow-up data and were included in the final analysis. The primary endpoint was 0.5 points (SD 0.7) per month for rifampicin and 0.5 points (0.5) per month for placebo (difference 0.0, 95% CI -0.24 to 0.24; p=0.82). Three (6%) of 50 participants in the rifampicin group and 12 (24%) of 50 in the placebo group had one or more serious adverse events; none was thought to be related to treatment.

INTERPRETATION

Our results show that rifampicin does not slow or halt progression of multiple system atrophy. Despite the negative result, the trial does provide information that could be useful in the design of future studies assessing potential disease modifying therapies in patients with multiple system atrophy.

FUNDING

National Institutes of Health, Mayo Clinic Center for Translational Science Activities, and Mayo Funds.

Rifampicin and Parkinson's disease

Rifampicin is a macrocyclic antibiotic used extensively for the treatment of Mycobacterium tuberculosis and other mycobacterial infections. Recently, it was discovered that rifampicin exhibits neuroprotective effects. It has been shown to protect PC12 cells against MPP(+)-induced apoptosis and inhibit the expression of α-synuclein multimers. In in vitro studies, rifampicin pretreatment protects PC12 cells against rotenone-induced cell death. Qualitative and quantitative analyses uncover that rifampicin significantly suppresses rotenone-induced apoptosis by ameliorating mitochondrial oxidative stress. It reduces microglial inflammation and improves neuron survival. Our results indicate that rifampicin is cytoprotective under a variety of experimental conditions, and suggest that it may be useful in PD therapeutics. It is the aim of this paper to review the experimental neuroprotection data reported using rifampicin with a focus on the molecular and cellular mechanisms of cytoprotective effect in in vitro models of PD.

What causes cell death in Parkinson's disease?

Currently, there is no proven neuroprotective or neurorestorative therapy for Parkinson's disease (PD). Several advances in the genetics of PD have created an opportunity to develop mechanistic-based therapies that hold particular promise for identifying agents that slow and even halt the progression of PD, as well as restore function. Here we review many of the advances in the last decade regarding the identification of new targets for the treatment of PD based on understanding the molecular mechanisms of how mutations in genes linked to PD cause neurodegeneration.

Rifampicin protects PC12 cells against MPP+-induced apoptosis and inhibits the expression of an alpha-Synuclein multimer

The potential cytoprotective effects of the anti-leprosy antibiotic rifampicin were investigated in rat pheochromocytoma (PC12) cells prior to intoxication with 1-Methyl-4-phenyl pyridinium (MPP(+)). MPP(+) induced both apoptotic and necrotic cell death, and increased the expression of a 57 kDa species of alpha-Synuclein. This species of alpha-Synuclein is larger than the monomer, and is therefore an oligomer or an aggregated form of the protein. Rifampicin significantly increased survival of these catecholaminergic cells in a concentration-dependent manner. The expression of the higher molecular mass alpha-Synuclein was increased by MPP(+) exposure, and its expression was inversely related to cell survival in the rifampicin-treated cells. Importantly, rifampicin suppressed apoptosis almost completely, without shifting the death cascade to necrosis, which is a problem that has been reported with caspase inhibitors of apoptosis (Hartmann, A., Troadec, J.D., Hunot, S., Kikly, K., Faucheux, B.A., Mouatt-Prigent, A., Ruberg, M. Agid, Y., Hirsch, E.C., 2001. Caspase-8 is an effector in apoptotic death of dopaminergic neurons in Parkinson's disease, but pathway inhibition results in neuronal necrosis. J. Neurosci. 21, 2247-2255). These results suggest that rifampicin improves survival of catecholamine- and alpha-Synuclein-containing cells, which degenerate in Parkinson's disease (PD), and thus may be therapeutic in this disease.