Media Release
12 November 2003
UniSA researchers unlocking the channels to treat bone disease
Australia spends about $6 billion a year directly and indirectly on
osteoporosis and related fractures. Breakthroughs by researchers at the
University of South Australia in understanding the basis of this disease
could lead to dramatic improvements for the nation’s two million
sufferers.
UniSA’s Centre for Biomolecular Studies led by Professor Allan Bretag
has made one of the biggest contributions worldwide to understanding how
chloride channels work, and how chloride ions permeate the channels.
Chloride channels are proteins that occur in the membranes of all cells,
allowing chloride, part of common salt, in and out of cells, according
to Professor Bretag.
“In all people, osteoblast cells deposit bone, while osteoclast cells
dissolve it in a continuously balanced fashion that favours bone
deposition while growing but frequently favours dissolution of bone
(osteoporosis) during ageing. Bone is dissolved because osteocytes
secrete hydrogen ions and chloride ions (through chloride channels) and,
when combined, these make hydrochloric acid,” Professor Bretag said.
“The opposite happens in a disease called osteopetrosis, where bones
become so dense that blood vessels cannot pass through. It occurs
because the chloride channels don’t work and so osteoclasts are unable
to produce hydrochloric acid or to dissolve bone.”
Armed with his unique knowledge of chloride channel proteins, of how to
produce them by genetic engineering and of the kinds of drugs that block
or open the channels, Professor Bretag believes he will be able to slow
down the rate of dissolving bone to treat osteoporosis. He anticipates
that this research will also help to find solutions for a range of other
medical conditions involving abnormal chloride channel function that are
already known to include epilepsy, several different kidney and muscle
diseases, as well as being implicated in infertility, brain
abnormalities, at least one kind of blindness and some very aggressive
brain tumours.
“Interestingly, the importance of ion channels, of their structure and
of their involvement in disease has been recognised this year by the
award of the Nobel Prize in Chemistry to Professor Roderick MacKinnon of
the Rockefeller University, New York,” he said. “Rod and I have been
sharing our discoveries on ion channels for several years.
“Our group at the University of South Australia has a wealth of
knowledge on how to produce channels in cells, so we can study the kinds
of drugs that might block or open them. We can work out where in the DNA
is the part of a gene known as the promoter region, which has to be
activated in order for the gene to make protein. By interfering with the
promoter region, we can interfere with how a gene makes a channel
protein and how much is made, adjusting the levels up or down - down to
treat osteoporosis and up to treat osteopetrosis, for example.”
Professor Bretag is leading the study with UniSA researchers Associate
Professor Bernie Hughes,
Dr Paul Bartley, three PhD students and one honours student, along with
colleagues at IMVS, the Hanson Centre and Adelaide University, and
internationally, in Genoa and Hamburg.
Media contact
-
Geraldine Hinter (08) 8302 0963 or 0417 861832