Activation of the complement system by recombinant tissue plasminogen activator

Area of Science:

• Cardiology
• Immunology
• Biochemistry

Background:

• Recombinant tissue plasminogen activator (rt-PA) is a key thrombolytic agent for acute myocardial infarction.
• Plasmin, generated by rt-PA, is known to activate the complement system in vitro.
• The in vivo effects of rt-PA on complement activation in patients with myocardial infarction require investigation.

Purpose of the Study:

• To test the hypothesis that rt-PA induces in vivo complement activation.
• To quantify changes in complement components C4a, C3a, and C5a following rt-PA administration in acute myocardial infarction patients.

Main Methods:

• Study involved 12 patients with acute myocardial infarction.
• Six patients received rt-PA for complete coronary occlusion; six controls had patent arteries without rt-PA.
• Blood samples were collected before and after rt-PA administration (or arteriography in controls) to measure C4a, C3a, and C5a levels.

Main Results:

• Baseline complement levels were similar between rt-PA treated and control groups.
• After rt-PA administration, but before reperfusion, significant increases were observed in C4a (p < 0.01), C3a (p < 0.05), and C5a (p < 0.05).
• Control patients showed no significant complement activation.

Conclusions:

• rt-PA administration in acute myocardial infarction patients triggers a significant in vivo activation of the complement system.
• This complement activation occurs independently of reperfusion.
• Findings suggest a potential immunomodulatory role for rt-PA beyond thrombolysis.