HEMOSTASIS

Hemostasis

a body mechanism to stop traumatic bleeding to prevent spontaneous bleeding to keep the fluidity of blood

Vascular injury tissue thromboplastin platelet adherent vaso constriction F XII activation ADP primary platelet aggregation PF3 ADP 5 OH tryptamin TxA2 secondary platelet aggregation (semi permeable platelet plug) fibrin non permeable platelet plug

Reactions in hemostatic process  Vascular reaction primary hemostatic barrier  Cellular reaction  Biochemical reaction / secondary hemostatic barrier

The role of vascular in hemostasis  vaso constriction  Stimulates coagulation factors and platelets  Substances synthesized by endothelial cells: –von Willebrand factor –tissue plasminogen activator (t-PA) –plasminogen activator inhibitor -1 (PAI-1) –prostacyclin (PGI 2 ) –Thrombomodulin (PC activation) –Glycosaminoglycan (heparan sulphate, dermatan sulphate)

Platelet Originated from cytoplasm of megakariocyte (fragmentation) Morphology : discoid, biconvex, Ǿ 2 – 4 μm Cytoplasm contains:   granule (PF 4,  thromboglobulin, platelet derived growth factor, vWF, fibrinogen, F V)  Dense granule (Ca, ADP, ATP)  Membrane: phospholipid bilayer, glycoprotein (receptor)

MegakaryoblastMegakaryocytesPlatelets 1/3 of platelets: stored in spleen 2/3 of plateletes: blood circulation half-lime 3-4 days 15% use daily for haemostasis normal platelet count x 10 9 /l The Platelets

Morphology of platelet

The role of platelet in hemostasis Platelet plug formation: –Platelet adherent (need von Willebrand Factor) –Platelet aggregation stimulated by ADP, thrombin, thromboxan A 2, epinephrine, collagen –Platelet release reaction (from  granule and dense granule) Stabilization of the plug : platelet factor 3 (flip flop of membrane phospholipid)

Platelet Function

phospholipid Arachidonic acid PGG2, PGH2 Thromboxan A2 Phospholipase A2, C cyclooxygenase Thromboxan synthetase Prostacyclin Prostacyclin synthetase Aspirin

Thromboxan A2 Stimulates aggregation Vaso constriction Prostacyclin Inhibits aggregation Vaso dilatation

Coagulation Factors Factor IFibrinogenprecursor of fibrin Factor IIProthrombinserine protease Factor IIITissue thromboinitiate extrinsic path. plastin Factor IVCalsium ionbridge between Gla - phospholipid Factor VProaccelerinCofactor of Xa Factor VIIProconvertinserine protease Factor VIIIAnti hemophilic f.Cofactor of IXa

Coagulation factors (cont) Factor IX Christmas factor serine protease Factor X Stuart Prower factor serine protease Factor XI Antihemophilic C serine protease Factor XII Hageman factor serine protease Factor XIII Fibrin stabilizing f. transglutaminase Prekallikrein Fletcher factor serine protease HMW kininogen Fitzgerald factor cofactor of Kall.

Characteristic of coagulation factors GroupMemberSerumAdsorb plasma Fibrinogen group I, V, VIII, XIII absentpresent Prothrombin group II, VII, IX, Xpresentabsent Contact group XI, XII, PK, HMWK present

Vitamin K Vit. K is required for carboxylation of glutamic acid →  carboxy glutamate Vitamin K dependent protein : prothrombin, VII, IX, X, protein C, protein S, protein Z Deficiency of vit. K → PIVKA (protein induced by vitamin K absence or antagonist)

Residue Glutamic acid (GLU) Precursor of II, VII, IX, X Precursor of II, VII, IX, X Prothrombin VII, IX, X Prothrombin VII, IX, X Residue  Carboxy glutamat (GLA) carboxylase Vitamin KH2 Vitamin K epoxide Vitamin K epoxide Oral Anticoagulant Oral Anticoagulant

Negative surfaceTissue thromboplastin Kal. PK HMWK XII XIIa XI XIa VIIaVII IX IXa Ca ++ Pf 3 VIII VIIIa X Xa Ca ++ Pf 3 V VaFibrinogen Prothrombin Thrombin Fibrin monomer Fibrin polimer XIII XIIIa Stabilized fibrin Ca ++ FPA FPB + F1.2 +

Mechanism of coagulation factor activation

Homeostatic mechanism  Local: fibrin, blood flow  Humoral: - Antithrombin - Protein C - Protein S - Heparin cofactor II - TFPI  Cellular : liver cell, RES

Antithrombin Synthesized in the liver Function : neutralize thrombin and other serine protease (XIIa, XIa, Xa, IXa, VIIa, Kallikrein,plasmin) Heparin cofactor Activities enhanced by heparin

Mechanism of action of AT III and heparin

Function of antithrombin

Protein C and protein S Both are vitamin K dependent protein Thrombin with thrombomodulin as cofactor activates Protein C  activated Protein C (APC) APC with Protein S as cofactor inactivates F Va and F VIIIa.

Protein C pathway

Tissue factor pathway inhibitor (TFPI) Function : inhibit F Xa and F VIIa Mechanism of action: –First F Xa + TFPI  F Xa-TFPI complex –F Xa-TFPI complex + F VIIa-TF complex  quartener complexed

Mechanism of action of TFPI

Fibrinolytic system

Fibrinolysis is a physiologic response to the deposition of intra or extra vascular fibrinFibrinolysis is a physiologic response to the deposition of intra or extra vascular fibrin Function : to destroy fibrin by enzymatic processFunction : to destroy fibrin by enzymatic process Consist of :Consist of : –Plasminogen –Plasminogen Activator –Inhibitor

Fibrinolytic system  Plasmin : proteolytic enzyme, substrates : fibrin, fibrinogen, V, VIII, hormon, complement  PLasminogen : proenzyme of plasmin, found in plasma and other body fluid  Plasminogen activator  Inhibitor

Plasminogen activator Physiologic plasminogen activators: Tissue-type plasminogen activator (t-PA) Urinary- type plasminogen activator (u-PA) Contact-phase dependent activators: F XIIa, Kallikrein Exogen: –Streptokinase (SK) –Staphylokinase (SAK) –Vampire bat plasminogen activator

Inhibitor of fibrinolysis system Antiplasmin:   2 plasmin inhibitor   2 macroglobulin  antithrombin   1 antitrypsin  TAFI  Transamin Plasminogen activator inhibitor –PAI-1 –PAI-2 –PAI-3 (?)

Coagulation and Fibrinolytic cascade

The function of PAI-1

The mechanism of fibrinolysis and inhibition of fibrinolysis

Plasminogen Free plasminogen in clot PAI Plasminogen activator Plasmin Free plasmin antiplasmin in clot Fibrin FDP Fibrinogen FDP D dimer + F V, F VIII D dimer -

Kinin kininogen XII HMWK Kallikrein XI XIIa XIa Prekallikrein Plasminogen Plasminogen Proactivator Activator Plasminogen Plasmin Complement system

Contact activation XIa IXa + VIII APC TM TF-VIIa Xa+V IIa Fibrin Fibrinolysis TFPI TM TAFI