Impact of NETs on vascular fibrosis, systemic inflammation and secondary organ injury after venous thrombosis
Final Report Abstract
Deep vein thrombosis (DVT) is among the leading causes of permanent disability and mortality worldwide owing to its major complication – the development of life-threatening pulmonary embolism. Post-thrombotic syndrome (PTS), characterized by vein wall fibrosis, is another widely underappreciated consequence of DVT. PTS, which is fostered by delayed or incomplete thrombus resolution, is painful and significantly reduces quality of life even in the absence of an acute thrombotic event. Importantly, therapeutic strategies aiming at resolving persistent venous thrombi and restoring blood flow to prevent PTS are limited. Currently available anticoagulants are beneficial in preventing recurrent thrombosis; however, they do not support thrombus resolution, likely because a combination treatment is necessary that targets both proteinaceous and DNA-rich parts of venous thrombi. This fellowship proposal sought to determine how neutrophil extracellular traps (NETs) fuel thrombosis and trigger subsequent vessel wall remodeling. NETs are a meshwork of decondensed chromatin lined with histones and neutrophil enzymes that are released early during venous thrombosis development and stabilize thrombi by providing an important scaffold for binding of platelets, red blood cells and coagulation factors. Venous thrombosis is a thrombo-inflammatory disease. It is now well established that resolution of self-limited inflammation is an active process, involving the endogenous synthesis of specialized proresolving mediators (SPMs). SPMs are metabolites of polyunsaturated fatty acids that facilitate resolution of inflammation and infection. In recent years, their pivotal function in dampening inflammation and in tissue remodeling, organ protection, host defense and microbial clearance has been increasingly recognized. Neutrophils from SPM-treated mice were less susceptible to stimulation-induced release of NETs and I set out to investigate if SPMs were generated during thrombus formation. First, the amount of SPMs endogenously synthesized during the natural course of venous thrombosis progression was established. Based on these results, SPM treatment was designed that consisted of mediators enriched at the onset of thrombus resolution. Repetitive delivery of SPMs significantly reduced existent thrombus burden, a key determinant of PTS development, and promoted the synthesis of other resolvins previously implicated in facilitating resolution of inflammation. These results suggest that repetitive delivery of SPMs modulates the severity of thromboinflammatory disease and accelerates thrombus resolution. Studies on the role of SPMs on accompanying vessel wall remodeling are currently under way. One of the aims in this grant proposal was to investigate how NETs as part of DVT response predispose the afflicted host to distant organ injury. In the course of this project and based on the recently published works by other investigators, this part of the project was modified as the initially proposed experimental and genetically modified mouse models did not allow to precisely address the specific scientific question. This research fellowship was also instrumental in generating experimental tools that are essential to study the role of enzymes critical for NET formation. These tools are currently used to investigate NET generation in inflammatory diseases in which the function of NETs has remained elusive.
Publications
- Peptidylarginine deiminase 4 promotes age-related organ fibrosis. J Exp Med. 2017; 214(2):439-458
Martinod K, Witsch T, Erpenbeck L, Savchenko A, Hayashi H, Cherpokova D, Gallant M, Mauler M, Cifuni SM, Wagner DD
(See online at https://doi.org/10.1084/jem.20160530) - Sirt3 deficiency does not affect venous thrombosis or NETosis despite mild elevation of intracellular ROS in platelets and neutrophils in mice. PLoS One. 2017; 12(12):e0188341
Hayashi H, Cherpokova D, Martinod K, Witsch T, Wong SL, Gallant M, Cifuni SM, Guarente LP, Wagner DD
(See online at https://doi.org/10.1371/journal.pone.0188341) - Increased neutrophil extracellular trap formation promotes thrombosis in myeloproliferative neoplasms. Sci Transl Med. 2018; 10(436)
Wolach S, Sellar RS, Martinod K, Cherpokova D, McConkey M, Chappell RJ, Silver AJ, Adams D, Castellano CA, Schneider RK, Padera RF, DeAngelo DJ, Wadleigh M, Steensma DP, Galinsky I, Stone RM, Genovese G, McCarroll SA, Iliadou B, Hultman C, Neuberg D, Mullally A, Wagner DD, Ebert BL
(See online at https://dx.doi.org/10.1126/scitranslmed.aan8292)
