Aprotinin

Aprotinin, a naturally occurring serine protease inhibitor, saves lives and decreases the risk of stroke and repeat surgery for massive bleeding^{1, 2, 3}.

The use of aprotinin did not significantly increase the risk of renal failure or the need for postoperative renal replacement despite an increase in the proportion of patients who had a doubling of serum creatinine levels. The adjudication of death did not identify renal failure as contributing to or causing death associated with aprotinin use. A Meta analysis by Brown and colleagues showed a nonsignificant relative risk of renal failure with high-dose aprotinin⁴.

Although aprotinin is potentially more effective than other active agents in controlling hemostasis, we noted only a possible trend suggesting that it decreased massive bleeding. Only repeat surgeries and important blood losses through chest tubes, one of the main indications for surgery, were potentially improved by the use of aprotinin. Aprotinin did not appear to prevent massive bleeding or save the life of patients who had massive bleeding.

The adverse effects on mortality associated with aprotinin may also have been present among healthier patients, those under the age of 65 years, and those without coexisting illnesses at the time of surgery.

Despite the possibility of a modest reduction in the risk of massive bleeding, the strong and consistent negative mortality trend associated with aprotinin as compared with lysine analogues precludes its use in patients undergoing high-risk cardiac surgery⁵.

Reference:
1. Henry DA, Carless PA, Moxey AJ, et al. Anti-fibrinolytic use for minimising perioperative allogeneic blood transfusion. Cochrane Database Syst Rev 2007;4:CD001886.
2. Levi M, Cromheecke ME, de Jonge E, et al. Pharmacological strategies to decrease excessive blood loss in cardiac surgery: a meta-analysis of clinically relevant endpoints. Lancet 1999;354:1940-7.
3. Sedrakyan A, Treasure T, Elefteriades JA. Effect of aprotinin on clinical outcomes in coronary artery bypass graft surgery: a systematic review and meta-analysis of randomized clinical trials. J Thorac Cardiovasc Surg 2004;128:442-8.
4. Brown JR, Birkmeyer NJ, O’Connor GT. Meta-analysis comparing the effectiveness and adverse outcomes of antifibrinolytic agents in cardiac surgery. Circulation 2007;115:2801-13.
5. Dean A. Fergusson,  Paul C. Hébert et al, A Comparison of Aprotinin and Lysine Analogues in High-Risk Cardiac Surgery, N Engl J Med 2008; 358:2319-2331

Aprotinin vs. tranexamic acid in isolated coronary artery bypass surgery: A multicentre observational study.[Pubmed:28221207]

Eur J Anaesthesiol. 2017 May;34(5):280-287.

BACKGROUND: Aprotinin appears to be more efficacious than lysine analogues to reduce bleeding and transfusion of blood products in high-transfusion-risk cardiac surgical patients. However, in isolated coronary artery bypass graft (CABG) surgery, the results from head-to-head trials remain less conclusive. OBJECTIVE: Our objective was to compare the efficacies and safety of Aprotinin and tranexamic acid (TXA) in patients undergoing isolated on-pump CABG. DESIGN: A multicentre before-and-after study pooling individual data from published trials and unpublished data from three other databases. SETTING: Four tertiary care teaching hospitals (Haut-Leveque Hospital in Bordeaux, Pitie-Salpetriere Hospital and Bichat-Claude Bernard Hospital in Paris, and Laennec Hospital in Nantes). PATIENTS: We included data of 2496 isolated on-pump CABG surgery patients who received either Aprotinin between November 2003 and May 2008 (n = 1267) or TXA between November 2007 and November 2013 (n = 1229). MAIN OUTCOME MEASURES: The primary outcome was total blood loss within 24 h after operation. Secondary outcomes were transfusion of blood products, reoperation for bleeding, renal replacement therapy, ICU length of stay and in-hospital mortality. RESULTS: Adjusted mean (SEM) 24-h blood loss after surgery [483 (11) vs. 634 (11) ml, P < 0.0001] and the proportion of patients requiring intraoperative blood product transfusion (32.7 vs. 46.5%, P = 0.01) were lower in Aprotinin-treated patients. No difference was observed with regard to reoperations for bleeding, renal replacement therapy and in-hospital mortality. However, patients receiving Aprotinin had a significantly shorter adjusted ICU length of stay. CONCLUSION: In patients undergoing isolated CABG, Aprotinin was more effective than TXA in reducing postoperative blood loss, and no safety concerns were identified. The benefits of Aprotinin should be considered when evaluating the risk of major blood loss and transfusion in patients scheduled for isolated CABG surgery.

S2'-subsite variations between human and mouse enzymes (plasmin, factor XIa, kallikrein) elucidate inhibition differences by tissue factor pathway inhibitor -2 domain1-wild-type, Leu17Arg-mutant and aprotinin.[Pubmed:27797450]

J Thromb Haemost. 2016 Dec;14(12):2509-2523.

Essentials Current antifibrinolytics - aminocaproic acid and tranexamic acid-can cause seizures or renal injury. KD1L17R -KT , Aprotinin and tranexamic acid were tested in a modified mouse tail-amputation model. S2'-subsite variations between human and mouse factor XIa result in vastly different inhibition profiles. KD1L17R -KT reduces blood loss and D-dimer levels in mouse with unobserved seizures or renal injury. SUMMARY: Background Using tissue factor pathway inhibitor (TFPI)-2 Kunitz domain1 (KD1), we obtained a bifunctional antifibrinolytic molecule (KD1L17R -KT ) with C-terminal lysine (kringle domain binding) and P2'-residue arginine (improved specificity towards plasmin). KD1L17R -KT strongly inhibited human plasmin (hPm), with no inhibition of human kallikrein (hKLK) or factor XIa (hXIa). Furthermore, KD1L17R -KT reduced blood loss comparable to Aprotinin in a mouse liver-laceration model of organ hemorrhage. However, effectiveness of these antifibrinolytic agents in a model of hemorrhage mimicking extremity trauma and their inhibition efficiencies for mouse enzymes (mPm, mKLK or mXIa) remain to be determined. Objective To determine potential differences in inhibition constants of various antifibrinolytic agents against mouse and human enzymes and test their effectiveness in a modified mouse tail-amputation hemorrhage model. Methods/Results Unexpectedly, mXIa was inhibited with ~ 17-fold increased affinity by Aprotinin (Ki ~ 20 nm) and with measurable affinity for KD1L17R -KT (Ki ~ 3 mum); in contrast, KD1WT -VT inhibited hXIa or mXIa with similar affinity. Compared with hPm, mPm had ~ 3-fold reduced affinity, whereas species specificity for hKLK and mKLK was comparable for each inhibitor. S2'-subsite variations largely accounted for the observed differences. KD1L17R -KT and Aprotinin were more effective than KD1WT -VT or tranexamic acid in inhibiting tPA-induced mouse plasma clot lysis. Further, KD1L17R -KT was more effective than KD1WT -VT and was comparable to Aprotinin and tranexamic acid in reducing blood loss and D-dimer levels in the mouse tail-amputation model. Conclusions Inhibitor potencies differ between antifibrinolytic agents against human and mouse enzymes. KD1L17R -KT is effective in reducing blood loss in a tail-amputation model that mimics extremity injury.

Elastase and tryptase govern TNFalpha-mediated production of active chemerin by adipocytes.[Pubmed:23227233]

PLoS One. 2012;7(12):e51072.

Chemerin is a leukocyte chemoattractant and adipokine with important immune and metabolic roles. Chemerin, secreted in an inactive form prochemerin, undergoes C-terminal proteolytic cleavage to generate active chemerin, a ligand for the chemokine-like receptor-1 (CMKLR1). We previously identified that adipocytes secrete and activate chemerin. Following treatment with the obesity-associated inflammatory mediator TNFalpha, unknown adipocyte mechanisms are altered resulting in an increased ratio of active to total chemerin production. Based on these findings we hypothesized adipocytes produce proteases capable of modifying chemerin and its ability to activate CMKRL1. 3T3-L1 adipocytes expressed mRNA of immunocyte and fibrinolytic proteases known to activate chemerin in vitro. Following treatment with a general protease inhibitor cocktail (PIC), the TNFalpha-stimulated increase in apparent active chemerin concentration in adipocyte media was amplified 10-fold, as measured by CMKLR1 activation. When the components of the PIC were investigated individually, Aprotinin, a serine protease inhibitor, blocked 90% of the TNFalpha-associated increase in active chemerin. The serine proteases, elastase and tryptase were elevated in adipocyte media following treatment with TNFalpha and their targeted neutralization recapitulated the Aprotinin-mediated effects. In contrast, bestatin, an aminopeptidase inhibitor, further elevated the TNFalpha-associated increase in active chemerin. Our results support that adipocytes regulate chemerin by serine protease-mediated activation pathways and aminopeptidase deactivation pathways. Following TNFalpha treatment, increased elastase and tryptase modify the balance between activation and deactivation, elevating active chemerin concentration in adipocyte media and subsequent CMKLR1 activation.

Plasmin inhibitors prevent leukocyte accumulation and remodeling events in the postischemic microvasculature.[Pubmed:21364954]

PLoS One. 2011 Feb 22;6(2):e17229.

Clinical trials revealed beneficial effects of the broad-spectrum serine protease inhibitor Aprotinin on the prevention of ischemia-reperfusion (I/R) injury. The underlying mechanisms remained largely unclear. Using in vivo microscopy on the cremaster muscle of male C57BL/6 mice, Aprotinin as well as inhibitors of the serine protease plasmin including tranexamic acid and epsilon-aminocaproic acid were found to significantly diminish I/R-elicited intravascular firm adherence and (subsequent) transmigration of neutrophils. Remodeling of collagen IV within the postischemic perivenular basement membrane was almost completely abrogated in animals treated with plasmin inhibitors or Aprotinin. In separate experiments, incubation with plasmin did not directly activate neutrophils. Extravascular, but not intravascular administration of plasmin caused a dose-dependent increase in numbers of firmly adherent and transmigrated neutrophils. Blockade of mast cell activation as well as inhibition of leukotriene synthesis or antagonism of the platelet-activating-factor receptor significantly reduced plasmin-dependent neutrophil responses. In conclusion, our data suggest that extravasated plasmin(ogen) mediates neutrophil recruitment in vivo via activation of perivascular mast cells and secondary generation of lipid mediators. Aprotinin as well as the plasmin inhibitors tranexamic acid and epsilon-aminocaproic acid interfere with this inflammatory cascade and effectively prevent postischemic neutrophil responses as well as remodeling events within the vessel wall.