But minocycline must first be tested for toxicity in humans, Friedlander cautioned, noting that the drug appeared slightly more toxic in mice with their form of Huntington's Disease than it did in normal mice. Minocycline is a form of tetracycline currently used in humans to treat acne, rheumatoid arthritis and other diseases. Unlike the better known tetracycline, minocycline can cross the blood-brain barrier that blocks most chemicals from entering the brain. In the brain, minocycline blocks the production of some of the enzymes called caspases that cause brain cells to commit suicide. Production of caspases in adult brains has been associated with Huntington's Disease, Lou Gehrig's Disease, Parkinson's Disease and strokes, Friedlander said.
Caspases help eliminate unneeded cells in the developing fetus.
But victims of Huntington's Disease inherit a gene that causes changes in the brain, usually beginning in middle age, that include the activation of caspases. Friedlander previously succeeded in delaying the onset of Lou Gehrig's Disease in mice using a different chemical to inhibit the action of caspases. After a 1998 study found that minocycline reduced the size of the injury following a stroke by limiting caspases, Friedlander decided to see if it had affect in Huntington's. It prolonged the life of the mice, which was the most important thing. But, he said, the mice eventually went on to die, indicating that the disease is complex and this was treating only one part of it.