Old drug provides promising new avenue for treatment of MND

In continuation of my update on ebselen

An international study led by biochemists at the University of Liverpool has shown that the drug-molecule ebselen can correct many of the toxic characteristics of a protein that causes some cases of hereditary motor neurone disease (MND).

MND is an incurable, progressive disease that attacks the nerves controlling movement so muscles no longer work. MND affects about 5000 people in the UK at any one time and present treatment options have only a modest effect in improving the patient's quality of life.

Inherited MND is a rare form of the disease (5-10% of total cases) that runs in families. Around 20% of hereditary MND cases are caused by mutations in a gene which codes for a protein called SOD1. When the SOD1 gene is mutated, the protein assembly process malfunctions and steps are missed out. This makes the SOD1 protein structurally unstable leading to formation of protein 'clumps' in the motor neurones, causing them to die.

In a paper published in Nature Communications, scientists from the Universities of Liverpool (UK), Florence (Italy) and Wollongong (Australia) used state-of-the-art crystallography, mass-spectrometry and in-cell NMR technologies to search for a drug molecule which could 'correct' the SOD1 assembly line.

They found that ebselen, a drug which was discovered in the 1980s and has been investigated as a potential treatment for a variety of nervous system disorders, can effectively restore several important steps in the SOD1 assembly process including folding, dimerization and zinc binding.

Dr. Gareth Wright, an MND researcher at the University of Liverpool, said: "This discovery has the potential to prevent the accumulation of SOD1 into the large aggregates we see within the motor neurons of effected individuals. If we can stop that, we might be able to stop the neurons dying."

Professor Samar Hasnain, a structural biologist at the University of Liverpool, added: "The next step is to test ebselen in settings more accurately resembling human neuronal cells and optimising it so that it can become useful as a drug for motor neuron disease."

Commenting on the study, Dr Brian Dickie, Director of Research Development at the Motor Neurone Disease Association, said: "A causal link between the SOD1 gene and certain forms of hereditary motor neuron disease was established a quarter of a century ago. It is very encouraging to see new therapeutic strategies starting to emerge from the considerable advances in scientific understanding that have occurred in recent years."

Stroke drug kills bacteria that cause ulcers and tuberculosis

Now researchers  found that, a compound called ebselen (see structure) effectively inhibits the thioredoxin reductase system in a wide variety of bacteria, including Helicobacter pylori which causes gastric ulcers and Mycobacterium tuberculosis which causes tuberculosis. Thioredoxin and thioredoxin reductase proteins are essential for bacteria to make new DNA, and protect them against oxidative stress caused by the immune system. Targeting this system with ebselen, and others compounds like it, represents a new approach toward eradicating these bacteria.

Building on previous observations where ebselen has shown antibacterial properties against some bacteria, Holmgren and colleagues hypothesized that the bacteria sensitive to ebselen relied solely on thioredoxin and thioredoxin reductase for essential cellular processes. They investigated this by testing it on strains of E. coli with deletions in the genes for thioredoxin, thioredoxin reductase and the glutaredoxin system. They found that strains with deletions in the genes coding for glutaredoxin system were much more sensitive than normal bacteria. Researchers further tested ebselen againstHelicobacter pylori andMycobacterium tuberculosis, which both naturally lack the glutaredoxin system and are frequently resistant to many commonly used antibiotics, and found both to be sensitive to ebselen.

"As rapidly as these organisms evolve, we need new drugs sooner rather than later," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "The fact that these scientists have found a new target for killing some of the most resistant bacteria is great news, but the fact that we already have at least one drug which we could possibly use now makes the news even better."

Ref : http://www.fasebj.org/content/early/2012/12/17/fj.12-223305

Stroke drug kills bacteria that cause ulcers and tuberculosis