Neocortical neurotransmitter markers in Huntington's disease

Disease-modifying effects of ganglioside GM1 in Huntington's disease models

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive and psychiatric problems. Previous studies indicated that levels of brain gangliosides are lower than normal in HD models and that administration of exogenous ganglioside GM1 corrects motor dysfunction in the YAC128 mouse model of HD In this study, we provide evidence that intraventricular administration of GM1 has profound disease-modifying effects across HD mouse models with different genetic background. GM1 administration results in decreased levels of mutant huntingtin, the protein that causes HD, and in a wide array of beneficial effects that include changes in levels of DARPP32, ferritin, Iba1 and GFAP, modulation of dopamine and serotonin metabolism, and restoration of normal levels of glutamate, GABA, L-Ser and D-Ser. Treatment with GM1 slows down neurodegeneration, white matter atrophy and body weight loss in R6/2 mice. Motor functions are significantly improved in R6/2 mice and restored to normal in Q140 mice, including gait abnormalities that are often resistant to treatments. Psychiatric-like and cognitive dysfunctions are also ameliorated by GM1 administration in Q140 and YAC128 mice. The widespread benefits of GM1 administration, at molecular, cellular and behavioural levels, indicate that this ganglioside has strong therapeutic and disease-modifying potential in HD.

GABA signalling: therapeutic targets for epilepsy, Parkinson's disease and Huntington's disease

Temporal lobe epilepsy (TLE), Parkinson's disease (PD) and Huntington's disease (HD) are neurodegenerative disorders that involve disruptions in gamma-amino butyric acid (GABA) signalling. GABA is the major inhibitory neurotransmitter in the central nervous system (CNS). TLE seizures reflect excess excitation, which may result from local inhibitory circuit dysfunction. PD devastates the input to striatal GABAergic neurones and HD destroys striatal GABAergic neurones. Controlling GABA delivery to specific brain areas should benefit each of these diseases. The molecules responsible for GABA release and signalling are ideal targets for new therapies. In this paper, we discuss the role of GABA in the circuitry affected by each of these diseases and suggest potential sites for intervention. GABA is unique among neurotransmitters because it can be synthesised by either of two related enzymes. Intracellular GABA is found throughout the cytosol and in synaptic vesicles. GABA can be released either through exocytosis, or via the plasma membrane transporter. The synthesising enzyme probably determines the intracellular location and hence the mechanism for GABA release. Directing GABA synthesis, degradation, transport or receptors can control GABA signalling. We propose that new drugs and devices aimed at GABA synthesis, release and binding will offer novel and highly effective treatments for neurodegenerative diseases.

Increased peripheral benzodiazepine binding sites in the brain of patients with Huntington's disease

Huntington's disease (HD) is a hereditary disorder associated with the development of dyskinesias and dementia, characterised by profound atrophy of the striatum and, to a lesser extent, other brain areas. A relative gliosis has been described. One marker for such inflammatory gliosis is an elevation of peripheral type benzodiazepine binding sites (PTBBS); these have also been shown to be increased following acute experimental and chronic degenerative neuronal damage. The present study investigates [3H]PK11195 binding to PTBBS in three brain areas of HD patients. We found a highly significant increase in PTBBS density in the putamen, a moderate but significant increase in the frontal cortex of HD patients and no significant change in the temporal cortex. Comparing these results to findings in other neurodegenerative diseases, e.g. Alzheimer's disease, where inflammation is discussed as a possible primary as well as a secondary pathological mechanism, our observations point to a possible involvement of inflammation in the neurodegenerative process in HD.