Roles have been suggested for brain-derived neurotrophic factor (BDNF) – which helps to support neurons and also stimulates and controls neurogenesis – in preventing or treating degenerative diseases such amyotrophic lateral sclerosis, Parkinson’s disease, and Alzheimer’s disease. The use of BDNF itself in therapy is limited by a poor pharmokinetic profile including rapid metabolism and poor CNS penetration. BDNF elicits at least some of its effects through binding to the high affinity tyrosine kinase receptor B, TrkB, and investigators at Emory University School of Medicine have now identified a small, high-affinity molecule that can also activate signalling through TrkB.
7,8-Dihydroxyflavone was shown to protect wild-type, but not TrkB-deficient, neurons from apoptosis. Following intraperitoneal administration, the compound was also found to activate TrkB in the brain and to be protective in animal models of seizure, stroke and Parkinson’s disease. The compound was also found to have low toxicity on chronic dosing. Although favonoids such as 7,8-dihydroxyflavone occur in a wide range of foodstuffs, levels obtained from a normal diet are believed to be insufficient for a sustained effect.
The study is published in the online early edition of PNAS.
Photo credit: NASA Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is one of the most common neuromuscular diseases worldwide and attacks the neurons responsible for controlling voluntary muscles. Few treatment options are currently available for ALS patients but researchers at UT Southwestern Medical Center and Harvard University have shown that microRNA-206 (miR-206) plays a crucial role in the progression of ALS. miRNAs are small non-coding RNA molecules which down-regulate gene expression and dysfunction of miRNAs has been associated with a number of diseases. In ALS, as the affected neurons stop signalling to muscle cells, the muscles atrophy. Although the skeletal muscles attempt to reinnervate themselves by signalling to healthy neurons via miRNA-206, eventually the surviving neurons are unable to cope, the muscle cells die and the ability of the brain to control voluntary movement is lost.
Mice that are genetically deficient in miRNA-206 form normal neuromuscular synapses during development but, in the ALS mouse model, disease progression is faster in mice that are deficient in miRNA-206. miRNA-206 is required for efficient regeneration of neuromuscular synapses after acute nerve injury and is dramatically induced in the mouse model of ALS. The effects of miRNA-206 in slowing ALS were suggested to be mediated, at least in part, through histone deacetylase 4 and fibroblast growth factor signalling pathways. miRagen Therapeutics hope to exploit the newly discovered role for miRNA-206 in neuromuscular maintenance to develop treatments for patients suffering from ALS and other neuromuscular diseases. Because miR-206 is only produced by skeletal muscles, such treatments may have a limited risk of side effects.