Matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1 and tumour necrosis factor alpha release during cardiopulmonary bypass

An inflammatory response occurs during cardiac surgery involving cardiopulmonary bypass. Matrix metalloproteinase-9 is an enzyme involved in cytokine processing and leucocyte extravasation. It is secreted as a pro-enzyme in response to several inflammatory mediators and is inhibited by endogenous tissue inhibitor of metalloproteinase-1. The interaction between matrix metalloproteinase-9 and its inhibitor during cardiopulmonary bypass is not known. We measured tumour necrosis factor alpha, and matrix metalloproteinase-9 and its inhibitor using enzyme immunoassay at three time points in 20 patients undergoing elective coronary artery bypass grafting with cardiopulmonary bypass. Tumour necrosis factor and matrix metalloproteinase concentrations increased in all patients during bypass (both p < 0.0001), whereas the inhibitor in contrast, decreased (p < 0.0001). We conclude that matrix metalloproteinase-9 is released as part of the inflammatory response during cardiac surgery. Levels of the endogenous inhibitor of metalloproteinase, however, show a different pattern of release, suggesting independent regulation.