Olesoxime in neurodegenerative diseases: Scrutinising a promising drug candidate.

Over the last years, the experimental compound olesoxime, a mitochondria-targeting cholesterol derivative, has emerged as a promising drug candidate for neurodegenerative diseases. Numerous preclinical studies have successfully proved olesoxime's neuroprotective properties in cell and animal models of clinical conditions such as amyotrophic lateral sclerosis, Huntington disease, Parkinson disease, peripheral neuropathy and spinal muscular atrophy. The beneficial effects were attributed to olesoxime's potential impact on oxidative stress, mitochondrial permeability transition or cholesterol homoeostasis. Although no significant benefits have been demonstrated in patients of amyotrophic lateral sclerosis, and only the first 12 months of a phase II/III clinical trial showed an improvement in motor symptoms of spinal muscular atrophy, this orphan drug may still offer undiscovered potential in the treatment of neurological diseases. In our earlier preclinical studies, we demonstrated that administration of olesoxime in mouse and rat models of Huntington disease improved psychiatric and molecular phenotypes. Aside from stabilising mitochondrial function, the drug reduced the overactivation of calpains, a class of calcium-dependent proteases entangled in neurodegenerative conditions. This observation may be credited to olesoxime's action on calcium dyshomeostasis, a further hallmark in neurodegeneration, and linked to its targets TSPO and VDAC, two proteins of the outer mitochondrial membrane associated with mitochondrial calcium handling. Further research into the mode of action of olesoxime under pathological conditions, including its effect on neuronal calcium homeostasis, may strengthen the untapped potential of olesoxime or other similar compounds as a therapeutic for neurodegenerative diseases.

Correction: Further investigation of phenotypes and confounding factors of progressive ratio performance and feeding behavior in the BACHD rat model of Huntington disease.

[This corrects the article DOI: 10.1371/journal.pone.0173232.].

The BACHD rat model of Huntington disease shows slowed learning in a Go/No-Go-like test of visual discrimination.

Huntington disease is a hereditary neurodegenerative disease, in which patients display a broad range of clinical symptoms. Among these, impaired inhibitory control has been noted. The BACHD rat is a recently developed and established transgenic animal model for Huntington disease, and characterizing the presence of Huntington disease-like behavioural phenotypes in these animals is of importance. Prior studies have indicated that BACHD rats suffer from impaired inhibitory control, although further studies are necessary to fully understand the scope and specific nature of these phenotypes. In the current study, BACHD rats were trained to perform a Go/No-Go-like test of visual discrimination, akin to behavioural tests that have revealed suspected response inhibition impairments in Huntington disease patients. The results indicate that although BACHD rats showed a slow rate of learning to inhibit responses on No-Go trials, once they had learned to handle the basic discrimination, they had an unchanged ability to withhold lever responses during extended periods of time. This suggests that BACHD rats have specific impairments when applying inhibitory control to a new or changed situation. The findings are in line with previous studies of BACHD rats and support the continued use and characterization of this animal model.

Further investigation of phenotypes and confounding factors of progressive ratio performance and feeding behavior in the BACHD rat model of Huntington disease.

Huntington disease is an inherited neurodegenerative disorder characterized by motor, cognitive, psychiatric and metabolic symptoms. We recently published a study describing that the BACHD rat model of HD shows an obesity phenotype, which might affect their motivation to perform food-based behavioral tests. Further, we argued that using a food restriction protocol based on matching BACHD and wild type rats' food consumption rates might resolve these motivational differences. In the current study, we followed up on these ideas in a longitudinal study of the rats' performance in a progressive ratio test. We also investigated the phenotype of reduced food consumption rate, which is typically seen in food-restricted BACHD rats, in greater detail. In line with our previous study, the BACHD rats were less motivated to perform the progressive ratio test compared to their wild type littermates, although the phenotype was no longer present when the rats' food consumption rates had been matched. However, video analysis of food consumption tests suggested that the reduced consumption rate found in the BACHD rats was not entirely based on differences in hunger, but likely involved motoric impairments. Thus, restriction protocols based on food consumption rates are not appropriate when working with BACHD rats. As an alternative, we suggest that studies where BACHD rats are used should investigate how the readouts of interest are affected by motivational differences, and use appropriate control tests to avoid misleading results. In addition, we show that BACHD rats display distinct behavioral changes in their progressive ratio performance, which might be indicative of striatal dysfunction.

The BACHD Rat Model of Huntington Disease Shows Signs of Fronto-Striatal Dysfunction in Two Operant Conditioning Tests of Short-Term Memory.

The BACHD rat is a recently developed transgenic animal model of Huntington disease, a progressive neurodegenerative disorder characterized by extensive loss of striatal neurons. Cognitive impairments are common among patients, and characterization of similar deficits in animal models of the disease is therefore of interest. The present study assessed the BACHD rats' performance in the delayed alternation and the delayed non-matching to position test, two Skinner box-based tests of short-term memory function. The transgenic rats showed impaired performance in both tests, indicating general problems with handling basic aspects of the tests, while short-term memory appeared to be intact. Similar phenotypes have been found in rats with fronto-striatal lesions, suggesting that Huntington disease-related neuropathology might be present in the BACHD rats. Further analyses indicated that the performance deficit in the delayed alternation test might be due to impaired inhibitory control, which has also been implicated in Huntington disease patients. The study ultimately suggests that the BACHD rats might suffer from neuropathology and cognitive impairments reminiscent of those of Huntington disease patients.