PB1379 - The physicochemical signature of lipopolysaccharides regulates FXII and contact system activation

Tuesday, June 25, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

Andre Luis Lira da Silva, PhD

Postdoctoral Scholar
OREGON HEALTH & SCIENCE UNIVERSITY
Portland, Oregon (EUA), Oregon, United States

Co-Author(s)

TL

Ting Liu

PhD Student
Oregon health & science university
Portland, Oregon, United States
JA

Joe Aslan, PhD

Oregon Health & Science University, United States
Cristina Puy

Instructor
Oregon health & science university
Portland, Oregon, United States
cL

christina Lorentz

Researcher
Oregon health & science university
Portland, Oregon, United States
Alvin H. Schmaier

Professor
Department of Medicine, University Hospitals Cleveland Medical Center and Case Western Reserve University
Cleveland, Ohio, United States
FL

Florea Lupu, n/a

Professor
Oklahoma Medical Research Foundation
Oklahoma City, Oklahoma, United States
David Gailani, MD

Professor of Pathology, Microbiology & Immunology
Vanderbilt University Medical Center
Nashville, Tennessee, United States
Owen McCarty

Professor
Oregon Health & Science University
Portland, Oregon, United States

Background: Lipopolysaccharide (LPS) is the primary pathogenic factor in Gram-negative sepsis. While the presence of LPS in the bloodstream during infection is associated with the development of disseminated intravascular coagulation, the mechanistic link between LPS and thrombin generation remains ill-defined. The coagulation factor (F)XII of the contact activation pathway has been shown to be activated in Gram-negative septic patients.

Aims: Define the pathways by which LPS chemotypes that form anionic aggregates with distinct properties bind and activate members of the contact pathway of coagulation.

Methods: The physical characteristics of E.coli LPS (chemotypes O111:B4, O26:B6, Rd2) aggregates were determined by dynamic light scattering and zeta potential (ZP). Chromogenic substrate and plasma clotting assays were used to study the effects of LPS on FXII, FXI, and plasma prekallikrein (PK) activation in the presence or absence of high molecular weight kininogen (HK).

Results: The LPS O111:B4, O26:B6, Rd2 chemotypes produced aggregates with sizes of 95, 196 and 211nm, and ZP of −6.2, −23.5, and −55.1mV, respectively. The LPS chemotypes showed procoagulant activity by reducing the clotting time from 552 seconds to 385 seconds for O111:B4, 338 seconds for O26:B6, and 297 seconds for Rd2. FXII, PK, or FXI were incubated in HEPES buffer, in the presence of LPS. The reaction for PK or FXI was analyzed in the presence or absence of HK. Only the chemotype O26:B6 was able to promote FXIIa generation. All the LPS were able to promote the direct activation of PK in the presence of HK. Conversely, they did not directly stimulate FXI activation either in the presence or absence of HK.

Conclusion(s): Dependent on their physicochemical properties, LPS may be able to initiate coagulation by a direct and independent activation of both FXII and PK. A deeper understanding of these processes can assist in better targeting infection-mediated thrombosis.