May 19 — Scientists have found a way to delay the onset of Huntington’s disease and slow its progress in mice by targeting an enzyme that is believed to trigger cell death. Experts say the finding, published in Thursday’s issue of the journal Nature, is a promising lead for drug researchers working to extend the lives of Huntington’s sufferers.

       “I think this is important and exciting. This is the first demonstration of a drug that can slow the progress of HD in an animal model,” said Dr. Christopher Ross, a Johns Hopkins Medical School professor and a scientific adviser to the Huntington’s Disease Society of America. “It says this goal of slowing progress probably can be accomplished.”
       Huntington’s disease is caused by a genetic disorder which usually affects people between the ages of 35 and 40. The disease kills nerve cells in the region of the brain that controls movement.
       Victims cannot control their limbs and suffer from dementia. There is no cure and each child of a parent with the disorder has a 50-50 chance of getting it.
       As the disease worsens and symptoms appear, an enzyme called caspase-1 goes into action and cuts the mutant Huntington protein. Fragments of the protein cause cells to self-destruct and die.
       “Specifically, our research provides solid evidence that by blocking caspase-1 from cutting the mutant Huntington protein, onset of HD was delayed and lifespan was prolonged in mice,” said study author Dr. Robert M. Friedlander of Harvard University.

Drugs that block caspase-1 could delay the symptoms of Huntington’s and other diseases that affect cells in the brain.
       “Since this process of cell death appears to be shared by a variety of neurological diseases, including stroke, amyotrophic lateral sclerosis (ALS), head trauma and Parkinson’s disease, successful strategies for the treatment of HD may apply to other diseases as well,” Friedlander said.
       “Caspase inhibition may turn out to be the magic bullet against neurodegenerative disease,” University of Munich biochemist Christian Haass said in an accompanying editorial.
       
STUDY DETAILS
       In the new study, the researchers blocked caspase in mice that had been genetically engineered to contract the disease. These mice developed Huntington’s symptoms about 10 percent later in life and lived about 20 percent longer.
       How the enzyme works is unclear, but scientists think that it slices up the so-called Huntington gene, and that the fragments then kill the cell.
       The Harvard researchers slowed that process by breeding mice with a mutant protein that counteracts caspase-1.
       The mice showed Huntington’s symptoms — walking trouble, weight loss and seizures — after 84 days, on average, compared with 77 days in the other mice. The mice with the caspase blocker lived an average of 121 days, compared with 101 days for the other mice.
       
       The Associated Press and Reuters contributed to this report.