Blood clotting plays an important role in the body. We depend on clotting to help close wounds and keep us from bleeding too much. But when we clot more than normal, it can lead to heart attack, stroke or other diseases of the cardiovascular system.
We look not only at blood itself but also the way it interacts with the inside lining of the blood vessels, called the endothelium. This thin layer of cells works with the blood so it knows when to clot—or not. In particular, we study the process that controls the start of blood clotting at the point where the blood and vessel walls interact.
We also observe the changes that lead to the formation of blood clots during sepsis. Sepsis is a serious blood infection that kills approximately 500,000 people worldwide each year. It occurs when the body must fight a severe infection that has spread through the body via the bloodstream. If a patient contracts sepsis, they will likely develop widespread blood clotting coupled with a state of low blood pressure called “shock.” This condition can develop either as a result of the body’s own defense system or from toxic substances made by an infectious agent, such as a bacteria, virus or fungus.
One line of research in our lab focuses on what triggers the normal blood-clotting system. We study a protein on the surface of cells that is responsible for telling the blood to clot. This protein, known as tissue factor, is strictly regulated by a natural inhibitor called tissue factor pathway inhibitor (TFPI). By looking at the ways that TFPI is regulated in the vessels, we hope to identify new proteins involved in the process and increase our understanding of blood clotting.
We also look at the steps involved in the progression of sepsis and how they lead to organ damage and, many times, death. Our group studies bacterial sepsis that occurs from exposure to E. coli or anthrax and the sequence of overlapping disease conditions involved, any one of which can be lethal. By learning more about the way sepsis infection develops and spreads, we hope to find ways to diagnose the condition earlier and develop more effective ways to treat it.
Our research focuses on the investigation of the cell surface mechanisms of tissue factor-factor VIIa (TF-FVIIa) inhibition by tissue factor pathway inhibitor (TFPI). TF is a transmembrane protein that triggers blood coagulation in vivo. Among other effects, TF elicits thrombogenic responses in septicemia, cancer and atherosclerosis. Formation of the TF-FVIIa-FXa-TFPI complex provides sustained repression of the TF pathway. In vivo, most TFPI associates with caveolae in EC. The mechanism of this association and the anticoagulant role of caveolar TFPI are not yet known. By using HEK 293, a cell system where we controlled the expression of both TFPI and caveolin-1 by transfection, we observed that caveolin/caveolae keep TFPI exposed on the plasmalemma surface, decrease the membrane lateral mobility of TFPI and increase the TFPI-dependent inhibition of TF-FVIIa. Caveolae-associated TFPI supports the co-localization of the quaternary complex with caveolae. Further, we used RNA interference technology to deplete EC of caveolin-1 and thus to test the possible physiological significance of these observations for EC. Functional assays and fluorescence microscopy revealed that the inhibitory properties of TFPI diminished in EC lacking caveolin-1, apparently through deficient assembly of the quaternary complex. Our studies identified caveolin-1 as an active regulator of TFPI-dependent inhibition of TF-FVIIa activity, therefore adding the haemostatic dimension as a novel dimension to the biological significance of caveolae.
On a parallel line of investigation, we study the alteration of EC hemostatic properties in severe sepsis in relationship to the expression and function of TF and TFPI. The hallmark of sepsis is represented by EC dysfunction, characterized as an excessive, sustained and generalized activation of the endothelium. Accordingly, we investigated whether localized changes of endothelial function in areas of the arterial tree exposed to perturbed flow may contribute to the severe sepsis phenotype. To verify our hypothesis, we compared the expression and function of various pro- and antithrombotic proteins in straight versus branched segments of arteries in healthy and septic baboons. Confocal microscopy and 3D rendering were used to obtain en-face images of whole-mount arterial segments after immunostaining with fluorescent markers for coagulation-specific proteins. We observed that the endothelial responses to E. coli differ according to the spatial geometry of the arteries, showing increased TF- dependent coagulant function at branches, when compared to the straight segments of arteries. These data suggest that site-dependent endothelial heterogeneity and rheological factors possibly contribute to a focally enhanced procoagulant response to E. coli.
In the long term, our studies should facilitate the understanding of the patho-physiology of blood clotting associated with sepsis and may provide clues for the development of new therapeutic approaches.
M.S., Faculty of Biology, University of Cluj, Romania, 1975
Ph.D., Institute of Cellular Biology and Pathology, Bucharest, Romania, 1986
Honors and Awards
1983 Fulbright Fellow, US Council for International Exchange of Scholars
1994 Young Investigator Award of American Health Association
Serves on the editorial board of the journal Pathophysiology of Haemostasis and Thrombosis
Reviews articles submitted to Thrombosis & Haemostasis, Arteriosclerosis Thrombosis and Vascular Biology, Haemostasis, Blood Coagulation and Fibrinolysis, Fibrinolysis and Proteolysis, and Gene Therapy
Reviews grants submitted to British Heart Foundation, Wellcome Trust, Austrian National Science Foundation, and European Union.
Member, OMRF Institutional Review Board
Histochemical Society – 2003
American Society for Investigative Pathology – 2003
American Society of Hematology – 2002
European Immunocytochemistry Club – 1994
Royal Microscopial Society – 1994
International Society for Fibrinolysis and Thrombolysis – 1992
International Society for Haemostasis and Thrombosis – 1991
European Vascular Biology Organization – 1986
Romanian Society for Cell Biology – 1982
Joined OMRF Scientific Staff in 2001.
Menendez MT, Ong EC, Shepherd BT, Muthukumar V, Silasi-Mansat R, Lupu F, Griffin CT. BRG1 (Brahma-Related Gene 1) Promotes Endothelial Mrtf Transcription to Establish Embryonic Capillary Integrity. Arterioscler Thromb Vasc Biol. 2017 Jul 20. pii: ATVBAHA.117.309785. [Epub ahead of print] PMID: 28729363
Keshari RS, Silasi R, Popescu NI, Patel MM, Chaaban H, Lupu C, Coggeshall KM, Mollnes TE, DeMarco SJ, Lupu F. Inhibition of complement C5 protects against organ failure and reduces mortality in a baboon model of Escherichia coli sepsis. Proc Natl Acad Sci U S A. 2017 Jul 18. pii: 201706818. PMID: 28720697
Healy LD, Puy C, Fernández JA, Mitrugno A, Keshari RS, Taku NA, Chu TT, Xu X, Gruber A, Lupu F, Griffin JH, McCarty OJT. Activated protein C inhibits neutrophil extracellular trap formation in vitro and activation in vivo. J Biol Chem. 2017 May 26;292(21):8616-8629. PMCID: PMC5448091
Fuentes-Mattei E, Giza DE, Shimizu M, Ivan C, ..., Lupu F, Ferrajoli A, Keating MJ, Vasilescu C, Yeung SJ, Calin GA. Plasma Viral miRNAs Indicate a High Prevalence of Occult Viral Infections. EBioMedicine. 2017 Apr 19. pii: S2352-3964(17)30162-7. [Epub ahead of print] [Abstract]
*Dong Y, Wu H, Rahman HN, Liu Y, Pasula S, Tessneer KL, Cai X, Liu X, Chang B, McManus J, Hahn S, Dong J, Brophy ML, Yu L, Song K, Silasi-Mansat R, Saunders D, Njoku C, Song H, Mehta-D’Souza P, Towner R, Lupu F, McEver RP, Xia L, Boerboom D, Srinivasan RS, Chen H. Motif mimetic of epsin perturbs tumor growth and metastasis. J Clin Invest. 2016 Mar 21. pii: 87344. [Abstract] [Epub ahead of print] PMID: 26999611
Geng X, Cha B, Mahamud MR, Lim KC, Silasi-Mansat R, Uddin MK, Miura N, Xia L, Simon AM, Engel JD, Chen H, Lupu F, Srinivasan RS. Multiple mouse models of primary lymphedema exhibit distinct defects in lymphovenous valve development. Dev Biol. 2016 Jan 1;409(1):218-33. Epub 2015 Nov 2. [Abstract] PMCID: PMC4688075
* De Souza PC, Smith N, Pody R, He T, Njoku C, Silasi-Mansat R, Lupu F, Meek B, Chen H, Dong Y, Saunders D, Orock A, Hodges E, Colijn S, Mamedova N, Towner RA. OKN-007 decreases VEGFR-2 levels in a preclinical GL261 mouse glioma model. Am J Nucl Med Mol Imaging 5:363-378, 2015. [Abstract]
* Towner RA, Smith N, Saunders D, Carrizales J, Lupu F, Silasi-Mansat R, Ehrenshaft M, Mason RP. In Vivo targeted molecular magnetic resonance imaging of free radicals in diabetic cardiomyopathy within mice. Free Radic Res 1-17, 2015. [Abstract]
Mastellos DC, Yancopoulou D, Kokkinos P, Huber-Lang M, Hajishengallis G, Biglarnia AR, Lupu F, Nilsson B, Risitano AM, Ricklin D, Lambris JD. Compstatin: a C3-targeted complement inhibitor reaching its prime for bedside intervention. Eur J Clin Invest 2015. [Abstract] EPub
Cardiovascular Biology Research Program, MS 45
Oklahoma Medical Research Foundation
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