Amok enzymes damage tissues during heart attack
CMAJ 2000;163(2):204
A team of University of Alberta researchers has discovered a cause of the tissue damage that occurs during heart attacks and, in the process, added a wrinkle to current thought on the role of bacterial infections in heart disease (Circulation 2000;101:1833).
Led by Dr. Richard Schulz, an Alberta Heritage researcher, the team has come up with striking evidence that the enzyme matrix metalloproteinase-2 (MMP) is responsible for some injuries to heart tissues in the seconds following the onset of a heart attack. What's more, the authors say a novel side effect of tetracycline-class antibiotics that inhibits the action of MMPs must be taken into consideration by researchers probing the involvement of bacteria in heart attacks.
Schulz likens the role of MMPs to a bulldozer parked in your garage — the garage being one of your cardiac muscle cells. In an experimental model of heart attack in rat hearts, the researchers discovered that MMPs, commonly associated with wound healing, were responsible for injury. Beginning mere seconds after the onset of a heart attack, MMPs run amok. It is, Schulz says, as if someone was driving the bulldozer around inside the garage, causing tremendous damage.
They discovered that tetracycline-class antibiotics block the action of MMPs during heart attacks and reduce damage. The drugs can be modified to inhibit only MMPs, so that their use for nonbacterial conditions such as this would not add to the problem of bacterial resistance to antibiotic drugs.
"The question now is for those people who are susceptible to heart attacks — for example, patients with a previous history or angina — whether this class of inhibitors could be used as a prophylactic measure." Other research has drawn links between bacteria and heart attacks. Schulz's team hasn't disproved any connection, but he says its findings cannot be ignored.
"The bacteria angle needs a lot more research," he says. "It really captures the imagination of researchers. People are saying 'Maybe we will find a bacteria that causes some forms of heart attack,' and they may be right. But we are just saying there are novel protective elements of tetracyclines that you have to consider." — Richard Cairney, Devon, Alta.
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