Interrelationship between endothelial dysfunction and inflammation and outcomes in pulmonary embolism Free

Introduction: Acute pulmonary embolism (PE) is the third leading cause of death with a mortality rate upwards of 30% if left untreated. Although some biomarkers have been shown to be useful in the diagnosis and risk stratification of patients with acute PE, currently their clinical utility remains undefined. The interplay of endothelial damage, inflammation, and anti-PF4 antibodies have been shown to contribute to outcomes in acute PE. This study focused on the interrelationship between endothelial dysfunction and inflammatory biomarkers along with anti-PF4 antibodies and their role in acute PE pathophysiology. Additionally, the relationship of these biomarkers to blood cellular indices and clinical characteristics was investigated.

Material and Methods: Blood samples from 66 patients with confirmed PE diagnosis were collected under a pre-approved IRB project through Loyola University Medical Center's Pulmonary Embolism Response Team (PERT) registry. Control samples of normal human plasma were collected from 18 healthy individuals. Biomarker analysis included IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFN, TNF-, IL-1, IL-1ß, MCP-1 and EGF using Sandwich Chemiluminescence Biochip Array from Randox Technology. ELISA methods included Tissue Factor (TF), von Willebrand Factor (vWF), anti-PF4 antibody, and endocan. Blood cellular indices, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lyphocyte ratio (PLR), monocyte-to-lyphocyte ratio (MLR), and systemic immune-inflammation index (SII), were calculated using the complete blood count. Clinical data, including obesity and PE risk severity, were collected using EPIC chart review. Statistical analyses were performed using Excel and GraphPad Prism software.

Results: Our cohort of 66 patients with PE was comprised of 43.9% female and 56.1% male, with a median age of 66.5-years. Under AHA guidelines for PE risk severity, and combining high-intermediate and low-intermediate patients into one group, 5 were high-risk, 33 were intermediate-risk, and 28 were low-risk. In terms of obesity, 59.1% of patients had a BMI ≥30. PE patients exhibited higher inflammatory cytokines including IL-2 (p=0.0145), IL-6 (p=<0.0001), IL-8 (p=<0.0001), IL-10 (p=0.0494), MCP-1 (p=0.0054), and TNF- (p=0.0084). Markers of endothelial dysfunction were elevated in PE patients as compared to healthy controls, including vWF (p=<0.0001), anti-PF4 (p=0.0475), TF (p=0.0329), VEGF (p=0.0033), and EGF (p=<0.0001). Notable positive correlations include MCP-1 vs. IL-1ß (r=0.74), IFN vs. TNF- (r=0.50), and MCP-1 vs. TNF- (r=0.49). Notable negative correlations include endocan vs. EGF (r=-0.34) and anti-PF4 vs. TF (r=-0.30).

When stratified by PE risk severity, IL-6 was elevated in intermediate-risk patients compared to low-risk (p=0.0284). Additionally, IL-1ß was higher in intermediate-risk compared to low risk (p=0.0329) and high-risk compared to low-risk patients (p=0.0092). For biomarkers of endothelial dysfunction, vWF showed elevated levels in intermediate-risk patients as compared to low-risk (p=0.0279). An increase in both NLR (p=0.0163) and MLR (p=0.0321) was noted in the intermediate-risk patients as compared to low-risk. Interestingly, when stratified by BMI, obese patients showed a decrease in both IL-6 (p=0.0136) and IL-10 (p=0.0094).Conclusion: This study analyzed biomarkers of inflammation, endothelial dysfunction, and anti-PF4 antibodies within patients with acute PE. These results provide further evidence of the role in which endothelial damage and inflammation play in the pathophysiology of acute PE, while also highlighting their potential use as diagnostic and prognostic tools. Correlation analysis implies that there may be a coordinated pro-inflammatory response in these patients, while also indicating that distinct thromboinflammatory pathways may be activated. Elevations in IL-6 and IL-1ß in intermediate and high-risk patients, demonstrates a progressive increase in systemic inflammation with worsening PE severity. Higher inflammatory blood cellular indices (NLR, MLR) in intermediate-risk patients indicates a heightened innate immune response, while also emphasizing their potential prognostic value. Similarly, higher vWF levels in intermediate-risk patients show a possible increase in vascular stress and thrombotic burden in more severe PE cases. Lastly, lower levels of IL-6 and IL-10 in obese patients reflects a potentially dampened or dysregulated immune response.