Plasma tissue plasminogen activator and plasminogen activator inhibitor-1 in hospitalized COVID-19 patients

Abstract

Patients with coronavirus disease-19 (COVID-19) are at high risk for thrombotic arterial and venous occlusions. However, bleeding complications have also been observed in some patients. Understanding the balance between coagulation and fibrinolysis will help inform optimal approaches to thrombosis prophylaxis and potential utility of fibrinolytic-targeted therapies. 118 hospitalized COVID-19 patients and 30 healthy controls were included in the study. We measured plasma antigen levels of tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) and performed spontaneous clot-lysis assays. We found markedly elevated tPA and PAI-1 levels in patients hospitalized with COVID-19. Both factors demonstrated strong correlations with neutrophil counts and markers of neutrophil activation. High levels of tPA and PAI-1 were associated with worse respiratory status. High levels of tPA, in particular, were strongly correlated with mortality and a significant enhancement in spontaneous ex vivo clot-lysis. While both tPA and PAI-1 are elevated among COVID-19 patients, extremely high levels of tPA enhance spontaneous fibrinolysis and are significantly associated with mortality in some patients. These data indicate that fibrinolytic homeostasis in COVID-19 is complex with a subset of patients expressing a balance of factors that may favor fibrinolysis. Further study of tPA as a biomarker is warranted.

Figure 1

High levels of tPA and PAI-1 among patients with COVID-19. (a,b) PAI-1 and tPA were measured in individuals with COVID-19, or healthy controls. Levels of PAI-1 and tPA were compared by Mann–Whitney test as samples were not normally distributed when assessed by Shapiro–Wilk test; ****p < 0.0001 as compared with the control group. Dotted line indicates high tPA cut-off. c, The relationship between tPA and PAI-1 was assessed by Spearman’s correlation test. Statistics were calculated and the figure was produced in GraphPad Prism https://www.graphpad.com/scientific-software/prism/, using version 8.3.

Figure 2

Association between PAI-1 and tPA and clinical biomarkers in plasma. Levels of PAI-1 and tPA were compared to D-dimer (a,b), platelet counts (c,d), absolute neutrophil counts (e,f), and calprotectin (g,h). Spearman’s correlation coefficients were calculated. Statistics were calculated and the figure was produced in GraphPad Prism https://www.graphpad.com/scientific-software/prism/, using version 8.3.

Figure 3

Association between PAI-1, tPA, D-dimer and respiratory status as well as final outcomes. (a–c) COVID-19 patients were grouped by clinical status (room air vs. supplemental oxygen) and analyzed for PAI-1, tPA, and D-dimer. Level of PAI-1, tPA, and D-dimer were not normally distributed based on Shapiro–Wilk test. Groups were compared by Mann–Whitney test; *p < 0.05. (d–f) PA1-1, tPA, and D-dimer were compared to SpO2/FiO2 ratio for each patient, and correlations were determined by Spearman’s test. (g–i) COVID-19 patients were also grouped by final outcomes (death vs. discharge). Level of PAI-1, tPA and D-dimer were not normally distributed based on Shapiro–Wilk test. Thus groups were compared by Mann–Whitney test; *p < 0.05, ***p < 0.001. Statistics were calculated and the figure was produced in GraphPad Prism https://www.graphpad.com/scientific-software/prism/, using version 8.3.

Figure 4

Spontaneous lysis rate among COVID-19 patients with high and low tPA. The ability of COVID-19 patients’ plasma with high (> 100 ng/mL) and low tPA (< 20 ng/mL) to promote spontaneous lysis of an ex vivo plasma clot formed by the addition of alpha human thrombin was evaluated. (a) Lysis over time was recorded for 10 high-tPA plasma samples. (b) The rate of lysis determined from the slope of the absorbance from t_0min to t_480min was compared between COVID-19 patients with high tPA, low tPA, and healthy controls by one-way ANOVA; *p < 0.05. Statistics were calculated and the figure was produced in GraphPad Prism https://www.graphpad.com/scientific-software/prism/, using version 8.3.