Grant: Operating Grant

Ischemic heart disease is a major health problem in Canada which affects millions of people worldwide. It is caused by either the constriction or blockade of arteries which supply heart muscle. When blocked, heart muscle is starved of oxygen and nutrients required for contraction, and harmful metabolic by-products accumulate. Further injury occurs when blood flow is restored by either drug or mechanical means (as cardiologists are able to do), a term called 'reperfusion' as reactive oxygen metabolites are synthesized in heart cells which damages them. Ischemia and reperfusion (I/R) together causes heart muscle to contract more poorly, and this is due in part to reactive oxygen metabolites activating an enzyme we found to be located inside heart muscle cells, matrix metalloproteinase-2 (MMP-2). We found that MMP-2 is found near certain proteins which are part of the contraction and structural machinery of these cells. MMP-2 damages by acting as a molecular scissors, cutting certain target proteins into smaller pieces. Here we wish to study the molecular structure of intracellular MMP-2 as its shape and function should be distinct from that of extracellular MMP-2. Knowing its precise shape will help us to understand which of the current drugs which are known to block MMP activity in general may be specific for the intracellular MMP-2. We will also make artificial proteins which should be cut by MMP-2 and could be used in tests of MMP-2 activity, to help us find new drugs to inhibit it. We will also determine which of the contractile and structural proteins is most susceptible to MMP-2 in I/R injury and whether a hormone known to be elevated in persons with cardiovascular disease increases MMP-2's damage to these proteins. We will test MMP-2 inhibitor drugs to see if we can protect mouse or rat hearts, or heart muscle cells, from I/R injury. Our research may identify new drugs useful to treat ischemic heart disease, and which have fewer side effects.