Endotoxin-induced kinin (bradykinin) formation: activation of Hageman factor and plasma kallikrein in human plasma

Bacterial pathogenesis and mediators in apical periodontitis

Apical periodontitis is a group of inflammatory diseases caused by microorganisms (mainly bacteria) infecting the necrotic root canal system. The pathogenesis of different types of apical periodontitis and even the same type in different individuals is unlikely to follow a stereotyped fashion with regard to the involved bacterial mediators. Disease pathogenesis is rather complex and involves a multitude of bacteria- and host-related factors. This review article discusses the bacterial pathogenesis of acute and chronic apical periodontitis, with the main focus on the bacterial mediators conceivably involved in the different stages of the infectious process, including secreted products (enzymes, exotoxins, N-formyl-methionyl-leucyl-phenylalanine peptides, heat-shock proteins and metabolic end-products) and structural components (lipopolysaccharide, peptidoglycan, lipoteichoic acid, lipoproteins, fimbriae, flagella, outer membrane proteins and vesicles, DNA, and exopolysaccharides). Knowledge of the bacterial factors involved in the pathogenesis of apical periodontitis is important to the understanding of the disease process and to help establishing proper therapeutic measures to inactivate this bacterial "artillery".

Plasma contact system, kallikrein-kinin system and antiphospholipid-protein antibodies in thrombosis and pregnancy

Coagulation factor XII, prekallikrein and high molecular weight kininogen are known as plasma contact proteins in the intrinsic pathway of blood coagulation. Deficiencies of these proteins are not associated with clinical bleeding despite marked prolongation of in vitro surface-activated coagulation time. Paradoxically, studies suggest that these proteins have anticoagulant and profibrinolytic activities. In fact, association between deficiencies of these proteins as well as recurrent thrombosis has been reported. Also deficiencies of these proteins and antiphospholipid antibodies are frequent haemostasis-related abnormalities found in unexplained recurrent aborters. Recently, evidence has accumulated for the presence of the kallikrein-kinin system or plasma contact system in the fetoplacental unit. This suggests that the plasma contact system may also have an important role in pregnancy. Several studies have reported the presence of autoantibodies to the contact proteins in patients with SLE, thrombosis and recurrent pregnancy loss. These autoantibodies are often in association with antiphospholipid antibodies and lupus anticoagulants. Contact proteins may be added to the list of proteins to which autoantibodies are produced in patients assigned to antiphospholipid antibody syndrome.

The bradykinin B2 receptor antagonist Icatibant (HOE 140) corrects avid Na+ retention in rats with CCl4-induced liver cirrhosis: possible role of enhanced microvascular leakage

Avid Na+ retention is a hallmark of liver cirrhosis. The aim of this study was to investigate whether and how bradykinin is involved in Na+ retention in rats with CCl4-induced liver cirrhosis. To this end the bradykinin B2 receptor antagonist Icatibant (HOE 140) was used. On one hand, bradykinin has a renal natriuretic action. On the other hand, bradykinin is a potent mediator of both vasodilation and microvascular leakage. Both vascular mechanisms, which are reported for cirrhosis, could cause vascular underfilling and Na+ retention by activating the renin-angiotensin-aldosterone system. Icatibant normalised Na+ retention and reduced the hyperactivity of the renin-angiotensin-aldosterone system, suggesting a bradykinin-induced vascular disturbance. Icatibant had no significant effect on the mild hypotension which developed with CCl4 treatment. However, there was indirect evidence for enhanced microvascular leakage that was strongly inhibited by Icatibant. Our experimental results demonstrate that bradykinin is a key mediator of Na+ retention in liver cirrhosis and suggest that a bradykinin-induced increase in microvascular leakage is mainly responsible.

Significane of intravascular coagulation in canine endotoxin shock

The contribution of disseminated fibrin clot formation to the pathogenesis of canine endotoxin shock was explored in control dogs and in those defibrinated with a purified fraction of Malayan pit viper venom. The hemodynamic and humoral responses after the administration of an intravenous challenge dose of Escherichia coli endotoxin were comparable as was mortality. It is concluded that, although the role of the coagulation sequence in canine endotoxin shock is unclear, it does not appear to be determinative.

Studies on the interaction between collagen and a plasma kallikrein-like activity. Evidence for a surface-active enzyme system

This study has demonstrated that collagen particles, after exposure to platelet-poor human plasma and subsequent washing, generate a kinin-like agent when incubated with prekinin substrate. The binding of kinin-generating activity to collagen in the plasma collagen incubation mixture occurs rapidly, whereas the loss of this activity in the incubation mixture occurs relatively slowly. The Hageman factor appeared to be necessary for the surface-bound kinin-generating activity, as this activity was absent in collagen exposed to Hageman factor-deficient plasma. These studies have partially characterized the plasma-derived enzymatic activity bound to collagen. Incubation of collagen with plasma caused a concentration-dependent reduction in the kinin-producing activity which was generated by the addition of ellagic acid, a known activator of plasma kallikrein. The kinin-inducing activity bound to collagen is inhibited by soybean trypsin inhibitor, Trasylol, serum C1 inactivator and the plasma alpha(2)-macroglobulin, but not by lima bean trypsin inhibitor. An eluate prepared from plasma-treated collagen, when compared with purified plasma kallikrein, shared a similar inhibitor profile. Selective chemical blockage of the free carboxyl groups on the collagen molecule, or heat denaturation, inactivated the ability of the collagen to generate kinin-like activity after incubation with plasma. Removal of the collagen telopeptides or blockage of the free amino groups failed to affect the collagen-plasma interaction. The binding of partially purified plasma kallikrein to collagen was found to have similar structural and chemical requirements. These data indicate that there is a structural and chemical specificity for the activation and binding of plasma kallikrein-like activity by collagen. These studies suggest that a plasma kallikrein may function as a surface-bound enzyme system.

Coagulation changes of septic shock in the sub-human primate and their relationship to hemodynamic changes

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Blood coagulation initiation by a complement-mediated pathway

A variety of complement-activating substances, including inulin, immunoglobulin aggregates, bacterial endotoxins, and staphylococcal protein A, were found to initiate blood coagulation through a complement-mediated pathway. These substances markedly accelerated blood coagulation in normal rabbit blood. That this clot-promoting activity requires an intact complement system was demonstrated by an almost total lack of effect on blood from rabbits with an inherited deficiency of the sixth component of complement (C6). Small amounts of isolated C6 conferred to C6-deficient blood the ability to respond with accelerated coagulation upon activation of the complement system. In addition, it was determined that activation of complement through the previously described C3 activator system resulted in the initiation of blood coagulation. The participation of C1, C2, and C4 was not necessary.