Enhancement of endogenous fibrinolysis does not reduce local fibrin deposition, but modulates inflammation upon intestinal ischemia and reperfusion

This study investigated the contribution of endogenous suppression of fibrinolysis and increased fibrin deposition to intestinal dysfunction and injury in a rat model of intestinal ischemia/reperfusion (R), as fibrinolytic inhibition may lead to thrombotic obstructions that compromise microcirculation and promote intestinal injury. Circulatory fibrinolysis was enhanced by intravenous administration of recombinant tissue plasminogen activator (rt-PA) or by inhibition of PAI-I by administration of MA-33HIF7. Coagulation and fibrinolysis parameters obtained from portal blood were correlated to fibrin deposition (determined by anti-rat fibrin antibody staining), intestinal function (glucose/water clearance) and intestinal injury (histological evaluation by Park/Chiu score). Enhanced circulatory fibrinolytic activity, as evidenced by increased portal plasma plasminogen activator activity, elevated fibrin degradation products and decreased levels of PAI-1, did not reduce mucosal fibrin deposition and microthrombosis in postischemic intestinal tissue. Furthermore, rt-PA or anti-PAI-I antibody administration did not attenuate I/R-induced intestinal injury or dysfunction, as demonstrated by intestinal histopathology scores of 4.8 +/- 0.2 and 4.7 +/- 0.3 (control I/R group 4.7 +/- 0.2) and glucose clearances of 47 +/- 6 and 46 +/- 9 muL/min (.) g (control I/R group 30 +/- 8 muL/min (.) g) after 40 minutes of intestinal ischemia and 3 hours of reperfusion, respectively. However, both interventions resulted in decreased levels of interleukin-6, which may indicate fibrin-induced modulation of inflammation. Attempts to enhance the fibrinolytic activity (either by rt-PA or by anti-PAI-I administration), indicated by increased portal plasma levels of released FDR failed to decrease mucosal fibrin deposition and to attenuate intestinal I/R injury. Based on our observations and previous reports, the contribution of suppressed endogenous fibrinolysis to microcirculatory fibrin deposition and I/R-injury may be of limited importance