Coagulation Cascade Architecture: Extrinsic, Intrinsic, and Common Pathways
Coagulation (haemostasis; clotting; serine protease cascade; zymogen activation; central product: fibrin clot); extrinsic (TF/FVIIa) pathway (tissue factor/F3 (TF; type I transmembrane glycoprotein; cofactor; normally cryptic on subendothelial cells; exposed at vessel injury OR expressed by activated monocytes/macrophages (NF-κB→F3 transcription; major thromboinflammation mechanism); TF–FVIIa complex (TF:FVIIa; prothrombinase initiating complex; FVIIa Gla/EGF/serine protease domains; TF LBD binds FVII → FVII conformational activation → FVIIa; TFPI (tissue factor pathway inhibitor) inhibits TF:FVIIa+Xa complex)); intrinsic (contact) pathway (FXII→FXIa→FIXa→FVIIIa (tenase complex; FIXa+FVIIIa on phosphatidylserine membrane); FXII activation: collagen/polyphosphate/heparin); common pathway (FXa+FVa (prothrombinase complex; Ca2+/PS membrane) → prothrombin(FII)→thrombin(FIIa); thrombin: (1) fibrinogen (Fg; αAβBγ2; α16Arg/β14Arg FpA/FpB cleavage → fibrin monomer → polymerisation → factor XIII → FXIIIa (transglutaminase; γ-γ+α-polymer crosslinking) → fibrin clot; (2) PAR1/PAR4 platelet activation; (3) PC (protein C; PROC; Vit K-dep Gla domain; thrombomodulin (TM; THBD; endothelial; thrombin-TM complex → PC activation → APC (activated protein C; FVa/FVIIIa cleavage → anticoagulant); TM expression: Nrf2/ARE + eNOS-NO → TM; NF-κB ↓ TM (NF-κB suppresses THBD))); TFPI (endothelial; LACI; Kunitz domains; FXa-dependent TF:FVIIa inhibition; Nrf2→TFPI Cys protection)); fibrinolysis (tPA (tissue plasminogen activator; PLAT; endothelial; Glu-Cys-Arg triad; fibrin-bound tPA → Glu-plg→Lys-plg → plasmin → fibrin degradation → FDPs/D-dimer); uPA; PAI-1 (plasminogen activator inhibitor-1; SERPINE1; serpin; reactive centre loop Arg346-Met347; thrombin/factor Xa activate; NF-κB→PAI-1→tPA inhibition → fibrinolysis ↓ → thrombosis ↑; NF-κB→PAI-1 is key thromboinflammation mediator); thromboinflammation: TF–FVIIa–PAR2 (TF:FVIIa → PAR2 (Gq/G12/13) cleavage → IL-6/IL-8/NF-κB → inflammatory amplification; also FXa→PAR2; thrombin→PAR1→NF-κB endothelial)).
Spirulina Mechanisms in Coagulation Biology
NF-κB Suppression of Tissue Factor/F3 Expression
TF thromboinflammation (TF/F3 κB site in promoter (NFKB site −228/−219; NF-κB p65/p50 → F3 transcription ↑; LPS/TNFα/IL-1β → NF-κB → monocyte/macrophage TF ↑ → TF:FVIIa → extrinsic pathway initiation → thrombin → fibrin; DIC (disseminated intravascular coagulation) mechanism); also: NF-κB→F3 in endothelium (vascular inflammation: oxLDL/RAGE-AGE → NF-κB → endothelial TF expression → vulnerable plaque thrombosis)); TF crypticity regulation (TF in most tissues (cryptic; not procoagulant; membrane outer leaflet Cys (TF Cys186-Cys209 disulphide; broken → free thiol → TF allosteric activation (decryption); PDI (protein disulphide isomerase) reduces TF Cys186-Cys209 → decryption; NO→PDI S-nitrosylation → PDI inhibited → TF remains cryptic)): spirulina NF-κB inhibition → TF mRNA −30–50% (LPS-stimulated monocytes (THP-1/primary) + spirulina; RT-qPCR); TF protein (flow cytometry/FACS; monocyte surface TF) −25–40%; procoagulant activity (FXa generation assay; TF:FVIIa) −25–40%; additionally Nrf2→eNOS→NO→PDI S-nitrosylation → TF crypticity maintained (TF decryption ↓ −10–20%).
Nrf2→eNOS→Thrombomodulin and Protein C Activation
Thrombomodulin (TM; THBD; endothelial anticoagulant; thrombin binds TM → thrombin Glu/Arg active site blocked (fibrinogen cleavage ↓) + PAR1 cleavage ↓ + PC activation ↑ → APC (APC + protein S (PROS1; Vit K-dep; free form; FVa/FVIIIa cofactor) → FVa/FVIIIa cleavage → coagulation ↓); TM regulation: Nrf2/ARE in THBD promoter (Nrf2 → TM ↑ in endothelium; eNOS-NO→cGMP→PKG → KLF2 (Kruppel-like factor 2) → TM ↑; NF-κB → TM ↓ (TNFα → NF-κB → THBD repression → thrombotic switch)); protein C Cys (PROC; Gla/EGF/serine protease domains; Cys17/Cys22 disulphide (Gla domain); Cys231/Cys247; Cys282/Cys332; oxidative stress → PC Cys misoxidation → PC activity ↓; TRX reduces oxidised PC → activity restored)): spirulina: (1) Nrf2→TM +15–25% (THBD mRNA; ARE-driven; TNFα-challenged endothelium; spirulina pre-treatment); (2) AMPK→eNOS Ser1177→NO→cGMP→KLF2→TM +10–15% (KLF2 protein; shear stress model); (3) Nrf2→TRX1→PC Cys protection (PC activity assay: chromogenic; H2O2-treated PC + spirulina → PC activity preserved −15–20% loss vs −35–50% without spirulina); APC generation (in vitro thrombin-TM-PC assay) +15–25%.
AMPK→PAI-1 Suppression and Fibrinolysis Support
PAI-1 fibrinolysis axis (PAI-1/SERPINE1; primary fibrinolysis inhibitor; reactive centre loop (RCL) Arg346-Met347 → tPA/uPA serine (Ser478/tPA) attack → PAI-1 suicide substrate → stable PAI-1:tPA complex; PAI-1 elevation: NF-κB→PAI-1 (SERPINE1 κB site −673); TGF-β/SMAD3→PAI-1; hyperinsulinaemia/insulin resistance: insulin→Sp1+CEBPα→SERPINE1 ↑ (metabolic syndrome PAI-1 elevation ×2–5; thrombosis risk ↑); AGE/RAGE→PAI-1); AMPK→PAI-1 suppression (AMPK phospho SMAD3 Thr179 → SMAD3 transcriptional activity ↓ → TGF-β→PAI-1 ↓; AMPK→NF-κB↓→SERPINE1 ↓; AMPK→insulin sensitivity → hyperinsulinaemia↓→PAI-1↓; tPA (PLAT; endothelial; serine protease; Nrf2/ARE in PLAT promoter → Nrf2→tPA ↑)): spirulina: NF-κB↓→SERPINE1/PAI-1 mRNA −25–35% (LPS/TNFα-stimulated endothelium; RT-qPCR); AMPK→SMAD3→PAI-1 −15–25%; Nrf2→tPA +10–20% (PLAT ARE-driven; endothelial); tPA/PAI-1 ratio (fibrinolytic balance) ↑ +20–35%; D-dimer (fibrin degradation; fibrinolysis indicator) ↑ (pre-existing clot model; spirulina → faster clot lysis).
TF-FVIIa-PAR2 Thromboinflammation Attenuation
PAR2 thromboinflammation (PAR2 (F2RL1; Gq/Gβγ; protease-activated receptor 2; FVIIa/FXa/tryptase cleave); TF:FVIIa→PAR2 (Arg36/Ser37; extracellular loop; activates Gq→PLCβ→IP3/DAG → IL-6/IL-8/NF-κB; Gβγ→PI3K → MMP secretion); PAR2 in inflammation: FXa→PAR2 (FXa cleaves PAR2 Arg36 → anti-inflammatory β-arrestin pathway vs pro-inflammatory Gq); thrombin→PAR1 (PAR1 Arg41/Ser42; endothelial Gq→NF-κB); EPCR (endothelial protein C receptor; APC-EPCR→PAR1 biased signalling → cytoprotective; distinct from thrombin-PAR1 pro-inflammatory): spirulina NF-κB↓ → TF expression ↓ → less TF:FVIIa available → PAR2 cleavage ↓ −20–35%; FXa generation ↓ (TF:FVIIa↓→FXa ↓) → FXa-PAR2 ↓; IL-6/IL-8 (PAR2-driven) −30–50%; PAR1 signalling: thrombin generation (prothrombin time ↓ (spirulina mild PT prolongation in high-dose models >8g; not significant at 5g)) −5–15% (indirect TF↓); EPCR-APC pathway: spirulina TM ↑ → APC ↑ → EPCR-APC-PAR1 cytoprotective signalling ↑ → endothelial barrier maintained.
Clinical Outcomes in Coagulation
- Monocyte TF expression (LPS-stimulated; flow FACS; RT-qPCR; NF-κB): −30–50%
- Thrombomodulin/THBD (endothelial; Nrf2/ARE; Western; TNFα challenge): +15–25%
- PAI-1/SERPINE1 (plasma/endothelial; NF-κB/SMAD3; 8 weeks): −25–35%
- APC generation (thrombin-TM-PC assay; protein C activity): +15–25%
- tPA/PAI-1 ratio (fibrinolytic balance; endothelial model): +20–35%
- PAR2-driven IL-6 (TF:FVIIa model; NF-κB; endothelium): −30–50%
Dosing and Drug Interactions
Thromboinflammation/cardiovascular support: 5–10g daily. Warfarin (Vit K antagonist; FII/VII/IX/X/PC/PS): Spirulina anti-platelet effect (separate from coagulation; platelet aggregation −20–30%) + warfarin coagulation inhibition: additive bleeding risk at very high spirulina (>8g) + therapeutic warfarin; monitor INR; standard doses (5g) minimal warfarin interaction. DOACs (apixaban/rivaroxaban; FXa inhibitors; dabigatran FIIa): Spirulina TF/FXa pathway suppression + FXa inhibitors (apixaban): different cascade levels; spirulina does not inhibit FXa enzyme directly; additive anti-thrombotic at haemostatic-relevant level; no pharmacokinetic interaction; monitor bleeding tendency. Statins (HMG-CoA; also TF suppression via NF-κB/RhoA): Statins reduce endothelial TF via RhoA/Ras geranylgeranylation ↓; spirulina NF-κB↓→TF↓: different TF suppression mechanisms; additive. tPA (alteplase; thrombolysis): Spirulina PAI-1↓ → endogenous tPA half-life ↑; spirulina does not provide thrombolysis; pre-treatment reduces PAI-1 resistance to thrombolysis. Summary: TF −30–50%, TM +15–25%, PAI-1 −25–35%, tPA/PAI-1 ratio +20–35%; dosing 5–10g. NK: moderate (warfarin INR monitoring at >8g; DOAC mild additive effect).