Immobilized transition metal ions stimulate contact activation and drive factor XII-mediated coagulation

Plasma kallikrein supports FXII-independent thrombin generation in mouse whole blood

ABSTRACT

Plasma kallikrein (PKa) is an important activator of factor XII (FXII) of the contact pathway of coagulation. Several studies have shown that PKa also possesses procoagulant activity independent of FXII, likely through its ability to directly activate FIX. We evaluated the procoagulant activity of PKa using a mouse whole blood (WB) thrombin-generation (TG) assay. TG was measured in WB from PKa-deficient mice using contact pathway or extrinsic pathway triggers. PKa-deficient WB had significantly reduced contact pathway-initiated TG compared with that of wild-type controls and was comparable with that observed in FXII-deficient WB. PKa-deficient WB supported equivalent extrinsic pathway-initiated TG compared with wild-type controls. Consistent with the presence of FXII-independent functions of PKa, targeted blockade of PKa with either small molecule or antibody-based inhibitors significantly reduced contact pathway-initiated TG in FXII-deficient WB. Inhibition of activated FXII (FXIIa) using an antibody-based inhibitor significantly reduced TG in PKa-deficient WB, consistent with a PKa-independent function of FXIIa. Experiments using mice expressing low levels of tissue factor demonstrated that persistent TG present in PKa- and FXIIa-inhibited WB was driven primarily by endogenous tissue factor. Our work demonstrates that PKa contributes significantly to contact pathway-initiated TG in the complex milieu of mouse WB, and a component of this contribution occurs in an FXII-independent manner.

Biochemical Approach to Poly(Lactide)-Copper Composite-Impact on Blood Coagulation Processes

The paper presents the investigation of the biological properties of Poly(Lactide)-Copper composite material obtained by sputter deposition of copper onto Poly(lactide) melt-blown nonwoven fabrics. The functionalized composite material was subjected to microbial activity tests against colonies of Gram-positive (Staphylococcus aureus), Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, Chaetomium globosum and Candida albicans fungal mold species and biochemical-hematological tests including the evaluation of the Activated Partial Thromboplastin Time, Prothrombin Time, Thrombin Time and electron microscopy fibrin network imaging. The substantial antimicrobial and antifungal activities of the Poly(Lactide)-Copper composite suggests potential applications as an antibacterial/antifungal material. The unmodified Poly(Lactide) fabric showed accelerated human blood plasma clotting in the intrinsic pathway, while copper plating abolished this effect. Unmodified PLA itself could be used for the preparation of wound dressing materials, accelerating coagulation in the case of hemorrhages, and its modifications with the use of various metals might be applied as new customized materials where blood coagulation process could be well controlled, yielding additional anti-pathogen effects.

Blood Coagulation Activities of Cotton-Alginate-Copper Composites

Alginate-based materials have gained significant attention in the medical industry due to their biochemical properties. In this article, we aimed to synthesize Cotton-Alginate-Copper Composite Materials (COT-Alg(-)Cu(2+)). The main purpose of this study was to assess the biochemical properties of new composites in the area of blood plasma coagulation processes, including activated partial thromboplastin time (aPTT), prothrombin time (PT), and thrombin time (TT). This study also involved in vitro antimicrobial activity evaluation of materials against representative colonies of Gram-positive and Gram-negative bacteria and antifungal susceptibility tests. The materials were prepared by immersing cotton fibers in an aqueous solution of sodium alginate, followed by ionic cross-linking of alginate chains within the fibers with Cu(II) ions to yield antimicrobial activity. The results showed that the obtained cotton-alginate-copper composites were promising materials to be used in biomedical applications, e.g., wound dressing.

Titanium is a potent inducer of contact activation: implications for intravascular devices

BACKGROUND

Titanium (Ti) and its alloys are widely used in manufacturing medical devices because of their strength and resistance to corrosion. Although Ti compounds are considered compatible with blood, they appear to support plasma contact activation and may be thrombogenic.

OBJECTIVES

The objective of this study was to compare Ti and titanium nitride (TiN) with known activators of contact activation (kaolin and silica) in plasma-clotting assays and to assess binding and activation of factor XII, (FXII), factor XI (FXI), prekallikrein, and high-molecular-weight kininogen (HK) with Ti/TiN.

METHODS

Ti-based nanospheres and foils were compared with kaolin, silica, and aluminum in plasma-clotting assays. Binding and activation of FXII, prekallikrein, HK, and FXI to surfaces was assessed with western blots and chromogenic assays.

RESULTS

Using equivalent surface amounts, Ti and TiN were comparable with kaolin and superior to silica, for inducing coagulation and FXII autoactivation. Similar to many inducers of contact activation, Ti and TiN are negatively charged; however, their effects on FXII are not neutralized by the polycation polybrene. Antibodies to FXII, prekallikrein, or FXI or coating Ti with poly-L-arginine blocked Ti-induced coagulation. An antibody to FXII reduced FXII and PK binding to Ti, kallikrein generation, and HK cleavage.

CONCLUSION

Titanium compounds induce contact activation with a potency comparable with that of kaolin. Binding of FXII with Ti shares some features with FXII binding to soluble polyanions but may have unique features. Inhibitors targeting FXII or FXI may be useful in mitigating Ti-induced contact activation in patients with titanium-based implants that are exposed to blood.

Systematic Evaluation of Copper(II)-Loaded Immobilized Metal Affinity Chromatography For Selective Enrichment of Copper-Binding Species in Human Serum and Plasma

Copper is essential in a host of biological processes, and disruption of its homeostasis is associated with diseases including neurodegeneration and metabolic disorders. Extracellular copper shifts in its speciation between healthy and disease states, and identifying molecular components involved in these perturbations could widen the panel of biomarkers for copper status. While there have been exciting advances in approaches for studying the extracellular proteome with mass-spectrometry-based methods, the typical workflows disrupt metal-protein interactions due to the lability of these bonds either during sample preparation or in gas-phase environments. We sought to develop and apply a workflow to enrich for and identify protein populations with copper-binding propensities in extracellular fluids using an immobilized metal affinity chromatography (IMAC) resin. The strategy was optimized using human serum to allow for maximum quantity and diversity of protein enrichment. Protein populations could be differentiated based on protein load on the resin, likely on account of differences in abundance and affinity. The enrichment workflow was applied to plasma samples from patients with Wilson disease (WD) and protein IDs and differential abundancies compared to healthy subjects were compared to those yielded from a traditional proteomic workflow. While the IMAC workflow preserved differential abundance and protein ID information from the traditional workflow, it identified several additional proteins being differentially abundant including those involved in lipid metabolism, immune system, and antioxidant pathways. Our results suggest the potential for this IMAC workflow to identify new proteins as potential biomarkers in copper-associated disease states.

An update on factor XII-driven vascular inflammation

The plasma protein factor XII (FXII) is the liver-derived zymogen of the serine protease FXIIa that initiates an array of proteolytic cascades. Zymogen activation, enzymatic FXIIa activity and functions are regulated by interactions with cell receptors, negatively charged surfaces, other serine proteases, and serpin inhibitors, which bind to distinct protein domains and regions in FXII(a). FXII exerts mitogenic activity, while FXIIa initiates the pro-inflammatory kallikrein-kinin pathway and the pro-thrombotic intrinsic coagulation pathway, respectively. Growing evidence indicates that FXIIa-mediated thrombo-inflammation plays a crucial role in various pathological states besides classical thrombosis, such as endothelial dysfunction. Consistently, increased FXIIa levels are associated with hypercholesterolemia and hypertriglyceridemia. In contrast, FXII deficiency protects from thrombosis but is otherwise not associated with prolonged bleeding or other adverse clinical manifestations. Here, we review current concepts for FXII(a)-driven vascular inflammation focusing on endothelial hyperpermeability, receptor signaling, atherosclerosis and immune cell activation.

Coagulation factor XII contributes to hemostasis when activated by soil in wounds

Bleeding is a common contributor to death and morbidity in animals and provides strong selective pressure for the coagulation system to optimize hemostasis for diverse environments. Although coagulation factor XII (FXII) is activated by nonbiologic surfaces, such as silicates, which leads to blood clotting in vitro, it is unclear whether FXII contributes to hemostasis in vivo. Humans and mice lacking FXII do not appear to bleed more from clean wounds than their counterparts with normal FXII levels. We tested the hypothesis that soil, a silicate-rich material abundant in the environment and wounds of terrestrial mammals, is a normal and potent activator of FXII and coagulation. Blood loss was compared between wild-type (WT) and FXII-knocked out (FXII-/-) mice after soil or exogenous tissue factor was applied to transected tails. The activation of FXII and other components of the coagulation and contact system was assessed with in vitro coagulation and enzyme assays. Soils were analyzed by time-of-flight secondary ionization mass spectrometry and dynamic light scattering. Soil reduced blood loss in WT mice, but not FXII-/- mice. Soil accelerated clotting of blood plasma from humans and mice in a FXII-dependent manner, but not plasma from a cetacean or a bird, which lack FXII. The procoagulant activity of 13 soils strongly correlated with the surface concentration of silicon, but only moderately correlated with the ζ potential. FXII augments coagulation in soil-contaminated wounds of terrestrial mammals, perhaps explaining why this protein has a seemingly minor role in hemostasis in clean wounds.

Penicillin causes non-allergic anaphylaxis by activating the contact system

Immediate hypersensitivity reaction (IHR) can be divided into allergic- and non-allergic-mediated, while “anaphylaxis” is reserved for severe IHR. Clinically, true penicillin allergy is rare and most reported penicillin allergy is “spurious”. Penicillin-initiated anaphylaxis is possible to occur in skin test- and specific IgE-negative patients. The contact system is a plasma protease cascade initiated by activation of factor XII (FXII). Many agents with negative ion surface can activate FXII to drive contact system. Our data showed that penicillin significantly induced hypothermia in propranolol- or pertussis toxin-pretreated mice. It also caused a rapid and reversible drop in rat blood pressure, which did not overlap with IgE-mediated hypotension. These effects could be countered by a bradykinin-B2 receptor antagonist icatibant, and consistently, penicillin indeed increased rat plasma bradykinin. Moreover, penicillin not only directly activated contact system FXII-dependently, but also promoted bradykinin release in plasma incubated-human umbilical vein endothelial cells. In fact, besides penicillin, other beta-lactams also activated the contact system in vitro. Since the autoactivation of FXII can be affected by multiple-factors, plasma from different healthy individuals showed vastly different amidolytic activity in response to penicillin, suggesting the necessity of determining the potency of penicillin to induce individual plasma FXII activation. These results clarify that penicillin-initiated non-allergic anaphylaxis is attributed to contact system activation, which might bring more effective diagnosis options for predicting penicillin-induced fatal risk and avoiding costly and inappropriate treatment clinically.

Factor XII and uPAR upregulate neutrophil functions to influence wound healing

Coagulation factor XII (FXII) deficiency is associated with decreased neutrophil migration, but the mechanisms remain uncharacterized. Here, we examine how FXII contributes to the inflammatory response. In 2 models of sterile inflammation, FXII-deficient mice (F12-/-) had fewer neutrophils recruited than WT mice. We discovered that neutrophils produced a pool of FXII that is functionally distinct from hepatic-derived FXII and contributes to neutrophil trafficking at sites of inflammation. FXII signals in neutrophils through urokinase plasminogen activator receptor-mediated (uPAR-mediated) Akt2 phosphorylation at S474 (pAktS474). Downstream of pAkt2S474, FXII stimulation of neutrophils upregulated surface expression of αMβ2 integrin, increased intracellular calcium, and promoted extracellular DNA release. The sum of these activities contributed to neutrophil cell adhesion, migration, and release of neutrophil extracellular traps in a process called NETosis. Decreased neutrophil signaling in F12-/- mice resulted in less inflammation and faster wound healing. Targeting hepatic F12 with siRNA did not affect neutrophil migration, whereas WT BM transplanted into F12-/- hosts was sufficient to correct the neutrophil migration defect in F12-/- mice and restore wound inflammation. Importantly, these activities were a zymogen FXII function and independent of FXIIa and contact activation, highlighting that FXII has a sophisticated role in vivo that has not been previously appreciated.

Platelet-Derived Short-Chain Polyphosphates Enhance the Inactivation of Tissue Factor Pathway Inhibitor by Activated Coagulation Factor XI

Introduction

Factor (F) XI supports both normal human hemostasis and pathological thrombosis. Activated FXI (FXIa) promotes thrombin generation by enzymatic activation of FXI, FIX, FX, and FV, and inactivation of alpha tissue factor pathway inhibitor (TFPIα), in vitro. Some of these reactions are now known to be enhanced by short-chain polyphosphates (SCP) derived from activated platelets. These SCPs act as a cofactor for the activation of FXI and FV by thrombin and FXIa, respectively. Since SCPs have been shown to inhibit the anticoagulant function of TFPIα, we herein investigated whether SCPs could serve as cofactors for the proteolytic inactivation of TFPIα by FXIa, further promoting the efficiency of the extrinsic pathway of coagulation to generate thrombin.

Methods and Results

Purified soluble SCP was prepared by size-fractionation of sodium polyphosphate. TFPIα proteolysis was analyzed by western blot. TFPIα activity was measured as inhibition of FX activation and activity in coagulation and chromogenic assays. SCPs significantly accelerated the rate of inactivation of TFPIα by FXIa in both purified systems and in recalcified plasma. Moreover, platelet-derived SCP accelerated the rate of inactivation of platelet-derived TFPIα by FXIa. TFPIα activity was not affected by SCP in recalcified FXI-depleted plasma.

Conclusions

Our data suggest that SCP is a cofactor for TFPIα inactivation by FXIa, thus, expanding the range of hemostatic FXIa substrates that may be affected by the cofactor functions of platelet-derived SCP.

The factor XIIa blocking antibody 3F7: a safe anticoagulant with anti-inflammatory activities

The plasma protein factor XII (FXII) is the initiating protease of the procoagulant and proinflammatory contact system. FXII activates both the bradykinin (BK) producing kallikrein-kinin system and the intrinsic pathway of coagulation. Contact with negatively charged surfaces induces auto-activation of zymogen FXII that results in activated FXII (FXIIa). Various in vivo activators of FXII have been identified including heparin, misfolded protein aggregates, nucleic acids and polyphosphate. Murine models have established a central role of FXII in arterial and venous thromboembolic diseases. Despite the central function of FXII in pathologic thrombosis, its deficiency does not impair hemostasis in animals or humans. The selective role of FXIIa in thrombosis, but not hemostasis, offers an exciting novel strategy for safe anticoagulation based on interference with FXIIa. We have generated the recombinant fully human FXIIa-blocking antibody 3F7, which abolished FXIIa enzymatic activity and prevented thrombosis in a cardiopulmonary bypass system in large animals, in the absence of increased therapy-associated bleeding. Furthermore, 3F7 also interfered with BK-driven edema in the severe swelling disorder hereditary angioedema (HAE) type III. Taken together, targeting FXIIa with 3F7 appears to be a promising approach to treat edema disorders and thrombosis.

New agents for thromboprotection. A role for factor XII and XIIa inhibition

Blood coagulation is essential for hemostasis, however excessive coagulation can lead to thrombosis. Factor XII starts the intrinsic coagulation pathway and contact-induced factor XII activation provides the mechanistic basis for the diagnostic aPTT clotting assay. Despite its function for fibrin formation in test tubes, patients and animals lacking factor XII have a completely normal hemostasis. The lack of a bleeding tendency observed in factor XII deficiency states is in sharp contrast to deficiencies of other components of the coagulation cascade and factor XII has been considered to have no function for coagulation in vivo. Recently, experimental animal models showed that factor XII is activated by an inorganic polymer, polyphosphate, which is released from procoagulant platelets and that polyphosphate-driven factor XII activation has an essential role in pathologic thrombus formation. Cumulatively, the data suggest to target polyphosphate, factor XII, or its activated form factor XIIa for anticoagulation. As the factor XII pathway specifically contributes to thrombosis but not to hemostasis, interference with this pathway provides a unique opportunity for safe anticoagulation that is not associated with excess bleeding. The review summarizes current knowledge on factor XII functions, activators and inhibitors.