Neuroprotective effect of the chemical chaperone, trehalose in a chronic MPTP-induced Parkinson's disease mouse model.

Parkinson's disease (PD) is a progressive motor disease of unknown etiology in the majority of cases. The clinical features of PD emerge due to selective degeneration of dopamine (DA) neurons in the substantia nigra pars compacta (SNc), which project to the caudate putamen (CPu) where they release DA. In the current in vivo mouse model study, we tested trehalose for its ability to protect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced damage to DA neurons. Trehalose is a naturally occurring disaccharide present in plants and animals and appears capable of protecting cells against various environmental stresses. The effect of trehalose is likely due to its action as a pharmacological chaperone which promotes protein stability. In the present study, there were four treatment groups: saline only (control); probenecid only; MPTP+probenecid; and trehalose+MPTP+probenecid. MPTP-induced losses in tyrosine hydroxylase and DA transporter immunoreactivity in the ventral midbrain SNc and CPu were significantly reduced by trehalose. Decreases in CPu dopamine levels produced by MPTP were also blocked by trehalose. Microglial activation and astrocytic hypertrophy induced by MPTP were greatly reduced by trehalose, indicating protection against neuroinflammation. These effects are commensurate with the observed trehalose sparing of motor deficits produced by MPTP in this mouse model. Two tight junctional proteins, ZO-1 and occludin, are downregulated following MPTP treatment and trehalose blocks this effect. Likewise, the glucose transporter-1 that is expressed in brain endothelial cells is also protected by trehalose from MPTP-induced down-regulation. This study is the first to demonstrate using fluoro-turoquoise FT gel perfusion techniques, the protection afforded by trehalose from MPTP-induced damage to microvessels and endothelial and suggests that trehalose therapy may have the potential to slow or ameliorate PD pathology.

K114 inhibits A-beta aggregation and inflammation in vitro and in vivo in AD/Tg mice.

Alzheimer's disease (AD) is the most common age related human neurodegenerative disorder. The major histopathological characteristics of the AD brain are extracellular amyloid-beta (Aß) peptide loaded plaques and intraneuronal neurofibrillary tangles made of phosphorylated tau proteins. Amyloid plaques consist primarily of aggregated Aß1-42 and Aß1-40 peptides. The aim of our current study was to test novel ligands/agents with the potential to disrupt or inhibit the aggregation of Aß peptide, specifically K114, (trans,trans)-1-bromo-2,5-bis(4-hydroxystyryl)benzene, which was initially developed as a potential positron emission tomography (PET) ligand for the in vivo detection of amyloid plaques. Systemic administration of K114 has been shown in the AD/transgenic (Tg) mouse model to be capable of crossing the blood-brain barrier (BBB) and be colocalized with amyloid plaques. In this study we determined whether K114 has the potential to inhibit Aß aggregation in vitro in AD/Tg mice and also tested, in vivo, whether chronic daily orally administered K114 has any therapeutic potential as evidenced by inhibition or reduction of the deposits of amyloid aggregates in the brains of AD/Tg mice. Our results demonstrated that K114 strongly blocked, in vitro, the aggregation of Aß peptide in the amyloid plaques of AD/Tg mouse brain. Systemic treatment with K114 was also effective in significantly reducing the deposits of amyloid plaques in the brains of living transgenic AD mice. Additionally, K114 significantly inhibited the typically observed plaque associated astrocytic activation, as revealed by GFAP immunohistochemistry, suggesting possible anti-inflammatory properties.

Neurovascular changes in acute, sub-acute and chronic mouse models of Parkinson's disease.

Although selective neurodegeneration of nigro-striatal dopaminergic neurons is widely accepted as a cause of Parkinson's disease (PD), the role of vascular components in the brain in PD pathology is not well understood. However, the neurodegeneration seen in PD is known to be associated with neuroinflammatory-like changes that can affect or be associated with brain vascular function. Thus, dysfunction of the capillary endothelial cell component of neurovascular units present in the brain may contribute to the damage to dopaminergic neurons that occurs in PD. An animal model of PD employing acute, sub-acute and chronic exposures of mice to methyl-phenyl-tetrahydropyridine (MPTP) was used to determine the extent to which brain vasculature may be damaged in PD. Fluoro-Turquoise gelatin labeling of microvessels and endothelial cells was used to determine the extent of vascular damage produced by MPTP. In addition, tyrosine hydroxylase (TH) and NeuN were employed to detect and quantify dopaminergic neuron damage in the striatum (CPu) and substantia nigra (SNc). Gliosis was evaluated through GFAP immunohistochemistry. MPTP treatment drastically reduced TH immunoreactive neurons in the SNc (20.68 ± 2.83 in acute; 22.98 ± 2.14 in sub-acute; 10.20 ± 2.24 in chronic vs 34.88 ± 2.91 in controls; p<0.001). Similarly, TH immunoreactive terminals were dramatically reduced in the CPu of MPTP treated mice. Additionally, all three MPTP exposures resulted in a decrease in the intensity, length, and number of vessels in both CPu and SNc. Degenerative vascular changes such as endothelial cell 'clusters' were also observed after MPTP suggesting that vasculature damage may be modifying the availability of nutrients and exposing blood cells and/or toxic substances to neurons and glia. In summary, vascular damage and degeneration could be an additional exacerbating factor in the progression of PD, and therapeutics that protect and insure vascular integrity may be novel treatments for PD.