Defibrotide Modulates Pulmonary Endothelial Cell Activation and Protects Against Lung Inflammation in Pre-Clinical Models of LPS-Induced Lung Injury and Idiopathic Pneumonia Syndrome.

Abstract

Background Pulmonary dysfunction remains one of the greatest challenges to the optimization of care following allogeneic blood and marrow transplantation (alloBMT). Almost half of the pneumonias that occur early after alloBMT are noninfectious, termed idiopathic pneumonia syndrome (IPS). Injury/activation to vascular endothelial cells (ECs) are believed to be directly related to several post-BMT complications, including IPS. Hence, identifying inflammatory mechanisms contributing to EC damage and strategies to protect EC integrity and function have significant merit. We have demonstrated that TNFα contributes directly to EC injury and regulates the chemokine milieu and influx of donor cells into the lung. Laboratory insights led to clinical trials of TNFα inhibition for IPS. Many, but not all, patients with IPS respond to TNFα inhibition, underscoring the need for continued research. Results Analysis of the plasma proteome from samples derived from 3 clinical studies revealed that compared to unaffected BMT controls, patients with IPS showed marked elevations in the expression of signature cytokines, including TNFα and MCP-1. Elevated expression of molecules associated with EC injury, angiopoietin (Ang)-2, VCAM-1, and E-selectin, was also noted. Ang-2 has been shown to destabilize and further sensitize ECs to the effects of TNFα, causing enhanced expression of E- and P-selectin. Serum Ang-2 levels were elevated during IPS and correlated with response to anti-TNFα therapy. In an acute lung injury (ALI) model, IV injection of LPS to naive B6 mice results in enhanced mRNA expression of TNFα, IL-6, Ang-2, E-, and P-selectin in whole lung homogenates, and the expression of Ang-2 is regulated in part by TNFα and IL-6. EC activation was associated with increased BALF total protein and cellularity. Similar findings were noted in alloBMT mice with IPS. We hypothesized that strategies to maintain EC integrity would reduce the severity of ALI and IPS. Defibrotide (DF) is FDA approved for the treatment of BMT patients with VOD and evidence of renal or pulmonary injury. DF is believed to stabilize activated ECs and protect them from further injury. The administration of DF (50 mg/kg) IV before and after LPS injection significantly reduced mRNA expression of TNFα, IL6, Ang-2, E-, and P-selectin compared to controls. BALF showed decreased cellularity, reflecting less EC damage and leak. AlloBMT mice were treated from day -1 through day 14 with DF ip (at a dose comparable to IV) either QD or BID, and lungs were harvested from D18 to 21. Compared to controls, DF treatment reduced mRNA expression of TNFα, IL6, Ang-2, E-, and P- selectin, BALF cellularity and protein content, and lung pathology score. Conclusion The administration of DF modulates EC injury in models of ALI and IPS. Combining cytokine inhibition with agents that stabilize EC integrity may represent a novel therapeutic strategy for patients with IPS.