Current therapeutic advances in patients and experimental models of Huntington's disease.

Huntington's disease (HD) clinical manifestations begin insidiously and are progressively incapacitating. Symptomatic therapies, in particular dopamine blockers and neuroleptics, are presently the only treatment for HD. Identification of neuropathological mechanisms that underlie the selective striatal and cortical neurodegeneration has allowed for the development of novel neuroprotective therapies that may improve HD patients' quality of life and enhance their survival. In this review we describe the symptomatic and neuroprotective therapies in HD that are currently in a preclinical or clinical stage. Neuroprotective therapies can act at several stages of HD, namely through: i) transcription modulation, ii) regulation of neurotrophic factors levels, iii) inhibition of metabolic dysfunction through metabolic enhancers, iv) apoptosis inhibition, v) autophagy regulation, vi) transglutaminase inhibition, and/or vii) modulation of neurotransmitter receptors. Moreover, emerging therapies in HD, including gene therapy using siRNA and shRNA to silence CAG repeats or deep brain stimulation, have shown promising results. Although most of the therapies are at a pre-clinical stage, phase II-III clinical trials have been performed for each pathophysiological mechanism of the disease. Thus, efforts should continue to ensure that effective therapies are studied and tested to help mitigate HD.

Caspase-dependent and -independent cell death induced by 3-nitropropionic acid in rat cortical neurons.

Mitochondria play a critical role in cell death by releasing apoptogenic factors, such as cytochrome c and apoptosis-inducing factor (AIF), from the intermembrane space into the cytoplasm. Because mitochondrial dysfunction has been shown to be involved in several neurodegenerative diseases, mitochondrial toxins are largely used to model these disorders. These include 3-nitropropionic acid (3-NP), an irreversible inhibitor of succinate dehydrogenase, which has been used to model Huntington's disease and was previously reported by us to induce apoptotic cell death through caspase activation. In the present study, we evaluated the involvement of caspase-independent neuronal cell death induced by 3-NP (1 mM) and the effect of z-VDVAD-fmk, an inhibitor of caspase-2, using cortical neurons in culture. Our results highly suggest that 3-NP induces both caspase-dependent and -independent cell death. We showed that z-VDVAD-fmk prevented both caspase-2 and -3-like activities evoked by 3-NP, but only partly prevented chromatin fragmentation/condensation. However, z-VDVAD-fmk did not avoid 3-NP-induced release of cytochrome c or AIF from mitochondria nor did it affect the levels of mitochondrial Bax. Furthermore, 3-NP-mediated decrease in plasma membrane integrity was not affected by z-VDVAD-fmk. Under these conditions, the inhibitor prevented the caspase-dependent cell death.