Clioquinol may slow aging

The Anti-neurodegeneration Drug Clioquinol Inhibits the Aging-associated Protein CLK-1

Ying Wang, Robyn Branicky, Zaruhi Stepanyan, Melissa Carroll, Marie-Pierre Guimond, Abdelmadjid Hihi, Steve Hayes, Kevin McBride, and Siegfried Hekimi

the press release: Old gastrointestinal drug slows aging, McGill researchers say; Clioquinol inhibits action of the CLK1 aging gene, may alleviate Alzheimer's

Recent animal studies have shown that clioquinol – an 80-year old drug once used to treat diarrhea and other gastrointestinal disorders – can reverse the progression of Alzheimer's, Parkinson's and Huntington's diseases. Scientists, however, had a variety of theories to attempt to explain how a single compound could have such similar effects on three unrelated neurodegenerative disorders.

Researchers at McGill University have discovered a dramatic possible new answer: According to Dr. Siegfried Hekimi and colleagues at McGill's Department of Biology, clioquinol acts directly on a protein called CLK-1, often informally called "clock-1," and might slow down the aging process. The advance online edition of their study was published in Oct. 2008 in the Journal of Biological Chemistry.

"Clioquinol is a very powerful inhibitor of clock-1," explained Hekimi, McGill's Strathcona Chair of Zoology and Robert Archibald & Catherine Louise Campbell Chair in Developmental Biology. "Because clock-1 affects longevity in invertebrates and mice, and because we're talking about three age-dependent neurodegenerative diseases, we hypothesize that clioquinol affects them by slowing down the rate of aging."

Once commonly prescribed in Europe and Asia for gastrointestinal problems like diarrhea and shigella, clioquinol was withdrawn from the market after being blamed for a devastating outbreak of subacute myelo-optic neuropathy (SMON) in Japan in the 1960s. However, because no rigorous scientific study was conducted at the time, and because clioquinol was used safely by millions before and after the Japanese outbreak, some researchers think its connection to SMON has yet to be proven.

The exact mechanism of how clioquinol inhibits CLK-1 is still under investigation, Hekimi said. "One possibility is that metals are involved as clioquinol is a metal chelator," he explained. Chelation is a type of binding to metal ions and is often used to treat heavy metal poisoning.

Hekimi is optimistic but cautious when asked whether clioquinol could eventually become an anti-aging treatment.

"The drug affects a gene which when inhibited can slow down aging," he said. "The implication is that we can change the rate of aging. This might be why clioquinol is able to work on this diversity of diseases that are all age-dependent."

However, he admits to being concerned about how people may interpret his results.

"The danger is that you can buy a kilogram of this compound at a chemical wholesaler, but we don't want people to start experimenting on themselves. Clioquinol can be a very toxic substance if abused, and far more research is required."

abstract

The development of neurodegenerative diseases such as Alzheimer, Parkinson, and Huntington disease is strongly age-dependent. Discovering drugs that act on the high rate of aging in older individuals could be a means of combating these diseases. Reduction of the activity of the mitochondrial enzyme CLK-1 (also known as COQ7) slows down aging in Caenorhabditis elegans and in mice. Clioquinol is a metal chelator that has beneficial effects in several cellular and animal models of neurodegenerative diseases as well as on Alzheimer disease patients. Here we show that clioquinol inhibits the activity of mammalian CLK-1 in cultured cells, an inhibition that can be blocked by iron or cobalt cations, suggesting that chelation is involved in the mechanism of action of clioquinol on CLK-1. We also show that treatment of nematodes and mice with clioquinol mimics a variety of phenotypes produced by mutational reduction of CLK-1 activity in these organisms. These results suggest that the surprising action of clioquinol on several age-dependent neurodegenerative diseases with distinct etiologies might result from a slowing down of the aging process through action of the drug on CLK-1. Our findings support the hypothesis that pharmacologically targeting aging-associated proteins could help relieve age-dependent diseases.

Source: Journal of Biological Chemistry 2009 Jan 2;284(1):314-23.