Therapeutic advances in Huntington’s disease

Neuroprotective effect of standardized extracts of three Lactuca sativa Linn. varieties against 3-NP induced Huntington's disease like symptoms in rats

OBJECTIVES

The study was aimed to evaluate the efficacy of three commonly consumed Lactuca sativa (LS) Linn. varieties viz., Grand rapid, Lollo rosso and Iceberg (Asteraceae) against 3-NP induced HD like symptoms in rats.

METHODS

Ethanol extracts of leaves of three LS varieties were prepared, and standardized on the basis of quercetin content using HPLC. These extracts (100 and 200 mg kg, p.o. for 20 days) were evaluated for their neuroprotective effect against 3-NP (10 mg/kg, i.p. for 14 days) induced neurotoxicity in male Wistar rats. The extract that exhibited maximum activity was successively fractionated using hexane, ethyl acetate, n-butanol and aqueous in increasing order of polarity. These fractions were also evaluated (dose equivalent to the dose of the extract of LS variety exhibiting maximum activity) for their neuroprotective effect. The protective effect of extracts and fractions was evaluated using different behavioral (rota rod, actophotometer, beam walk and Morris water maze) and biochemical (malondialdehyde, nitrite, superoxide dismutase, catalase and reduced glutathione) parameters.

RESULTS

3-NP elicit marked deterioration in motor coordination, locomotor activity and memory in comparison to control group. Standardized ethanol extract of grand rapid (200 mg/kg) exhibited maximum activity amongst the three tested varieties. Therefore, its fractions were also evaluated, and n-butanol fraction (40 mg/kg) exhibited maximum attenuation of 3-NP induced HD like symptoms which was evident from improved behavioral and biochemical parameters.

DISCUSSION

The results exhibit that LS (Grand rapid variety) prophylaxis mitigated 3-NP induced neurotoxicity and HD like symptoms in rats due to its potent antioxidant potential.

Huntington disease: new insights into molecular pathogenesis and therapeutic opportunities

Huntington disease (HD) is a neurodegenerative disease caused by CAG repeat expansion in the huntingtin gene (HTT) and involves a complex web of pathogenic mechanisms. Mutant HTT (mHTT) disrupts transcription, interferes with immune and mitochondrial function, and is aberrantly modified post-translationally. Evidence suggests that the mHTT RNA is toxic, and at the DNA level, somatic CAG repeat expansion in vulnerable cells influences the disease course. Genome-wide association studies have identified DNA repair pathways as modifiers of somatic instability and disease course in HD and other repeat expansion diseases. In animal models of HD, nucleocytoplasmic transport is disrupted and its restoration is neuroprotective. Novel cerebrospinal fluid (CSF) and plasma biomarkers are among the earliest detectable changes in individuals with premanifest HD and have the sensitivity to detect therapeutic benefit. Therapeutically, the first human trial of an HTT-lowering antisense oligonucleotide successfully, and safely, reduced the CSF concentration of mHTT in individuals with HD. A larger trial, powered to detect clinical efficacy, is underway, along with trials of other HTT-lowering approaches. In this Review, we discuss new insights into the molecular pathogenesis of HD and future therapeutic strategies, including the modulation of DNA repair and targeting the DNA mutation itself.

Emotion Recognition Correlates With Social-Neuropsychiatric Dysfunction in Huntington's Disease

OBJECTIVES

People with Huntington's disease (HD) experience poor social quality of life, relationship breakdown, and social withdrawal, which are mediated to some extent by socially debilitating neuropsychiatric symptoms, such as apathy and disinhibition. Social cognitive symptoms, such as impaired emotion recognition, also occur in HD, however, the extent of their association with these socially debilitating neuropsychiatric symptoms is unknown. Our study examined the relationship between emotion recognition and symptom ratings of apathy and disinhibition in HD.

METHODS

Thirty-two people with premanifest or symptomatic-HD completed Part 1 of The Awareness of Social Inference Test (TASIT), which is a facial emotion recognition task. In addition, we obtained severity ratings for apathy and disinhibition on the Frontal Systems Behavior Scale (FrSBe) from a close family member. Our analyses used motor symptom severity as a proxy for disease progression.

RESULTS

Emotion recognition performance was significantly associated with family-ratings of apathy, above and beyond their shared association with disease severity. We found a similar pattern for disinhibition ratings, which fell short of statistical significance. As expected, worse emotion recognition performance was correlated with higher severity in FrSBe symptom ratings.

CONCLUSIONS

Our findings suggest that emotion recognition abilities relate to key socially debilitating neuropsychiatric symptoms in HD. Our results help to understand the functional significance of emotion recognition impairments in HD, and may have implications for the development of remediation programs aimed at improving patients' social quality of life. (JINS, 2018, 24, 417-423).