Galanthamine treatment in Alzheimer's disease

Cloning and characterization of a tyrosine decarboxylase involved in the biosynthesis of galanthamine in Lycoris aurea

Background

Galanthamine, one kind of Amaryllidaceae alkaloid extracted from the Lycoris species, is used in the treatment of Alzheimer’s disease. In regards to medical and economic importance, the biosynthesis and regulatory mechanism of the secondary metabolites in Lycoris remain uninvestigated.

Methods

BLAST was used to identify the sequence of tyrosine decarboxylase in the transcriptome of Lycoris aurea (L’Hér) Herb. The enzyme activity of this TYDC was determined by using heterologous expressed protein in the Escherichia coli cells. The related productive contents of tyramine were detected using High Performance Liquid Chromatography (HPLC). According to the available micro RNA sequencing profiles and degradome database of L. aurea, microRNA396 were isolated, which targets to LaTYDC1 and RNA Ligase-Mediated-Rapid Amplification of cDNA Ends (RLM-RACE) were used to confirm the cleavage. The expression levels of miR396 and LaTYDC1 were measured using a quantitative real-time polymerase chain reaction (qRT-PCR).

Results

LaTYDC1 was mainly expressed in root, bulb, leaf and flower fitting the models for galanthamine accumulation. This decarboxylase efficiently catalyzes tyrosine to tyramine conversion. Under methyl jasmonate (MeJA) treatment, the expression of LaTYDC1 and the content of tyramine sharply increase. The use of RLM-RACE confirms that miR396 promotes the degradation of LaTYDC1 mRNA. Under MeJA treatment, the expression of miR396 was suppressed while the expression level of LaTYDC1 sharply increased. Following the increase of the miR396 transcriptional level, LaTYDC1 was significantly repressed.

Conclusion

LaTYDC1 participates in the biosynthesis of galanthamine, and is regulated by miR396. This finding also provides genetic strategy for improving the yield of galanthamine in the future.

Efficacy study of galantamine in possible Alzheimer's disease with or without cerebrovascular disease and vascular dementia in Thai patients: a slow-titration regimen

The objective is to evaluate the efficacy of galantamine when a slow titration regimen is employed in Thai Alzheimer's disease (AD) patients with or without cerebrovascular disease and vascular dementia (VaD). A 6-month, multicentre, open-label, uncontrolled trial was undertaken in 75 AD patients. Eligible patients received an initial galantamine dose of 8 mg/day and escalated over 5-8 weeks to maintenance doses of 16 or 24 mg/day. Primary efficacy measures were AD Assessment Scale-cognitive subscale (ADAS-cog) and the Clinician's Interview-Based Impression of Change-Plus version (CIBIC-plus). The Behavioural Pathology in AD Rating Scale (BEHAVE AD), the AD Cooperative Study Activities of Daily Living Inventory and Pittsburgh Sleep Quality Index were the secondary efficacy variables. Analyses were based on the intent-to-treat population. Treatment with galantamine showed significant improvement in cognition on the ADAS-cog and CIBIC-plus at month 6. Galantamine showed favourable effects on activities of daily living. Behavioural symptoms and sleep quality were also significantly improved (p < 0.05). Galantamine was well tolerated. The adverse events were mild-to-moderate intensity. The most frequent adverse events commonly reported were nausea (16.4%), dizziness (9.6%) and vomiting (6.8%). The results of this study may be consistent with galantamine being an effective and safe treatment for mild-to-moderate AD patients with or without cerebrovascular disease and VaD. Flexible dose escalation of galantamine was well tolerated. The daily maintenance dose of galantamine was 16 mg/day, followed by a back up dose of 24 mg/day.

Galanthamine from snowdrop--the development of a modern drug against Alzheimer's disease from local Caucasian knowledge

In recent years, galanthamine isolated from several members of the Amaryllidaceae (Leucojum spp., Narcissus species, Galanthus spp.) has become an important therapeutic options used to slow down the process of neurological degeneration in Alzheimer's disease. This review traces aspects of the history of its development from little known observational studies in the Caucasus Mountains (Southern Russia), to the use of this drug in Eastern European countries (esp. Bulgaria) in the treatment of poliomyelitis and ultimately to the recent introduction onto Western markets in the treatment of Alzheimer's disease. Of note, little is known about the early history of the drug's development and the review also points to other gaps in our knowledge about the ethnopharmacology, pharmacology and clinical use of galanthamine.

Galanthamine in Alzheimer's disease : a new alternative to tacrine?

Galanthamine (galantamine), a tertiary alkaloid derived from the bulbs of the snowdrop and various Narcissus species, is a selective, centrally active and reversible inhibitor of acetylcholinesterase that is suitable for oral therapy. After a long period during which the investigational and clinical use of the drug was limited to anaesthesia and the treatment of peripheral paralysis syndromes in Eastern Europe, the molecule has now emerged as a promising lead substance for the treatment of cognitive decline in Alzheimer's disease.Galanthamine has similar therapeutic potential to tacrine, but has a significantly more favourable pharmacokinetic and toxicity profile. A chemical synthesis process on the required industrial scale of several tons per year has become available, removing a major obstacle to the development of the drug. Clinical trials published so far are, however, rather limited in terms of both design and patient number. The main reason for this is that there has been a lack of strong support for the drug within the pharmaceutical industry. However, the available data support the notion that this molecule, if properly developed, could be a peer for any second-generation cholinergic drug currently in clinical trials for the symptomatic treatment of Alzheimer's disease.