Das Schädel-Hirn-Trauma (SHT) entsteht durch äußere Gewalteinwirkung auf den Kopf und verursacht mechanisch eine Schädigung des Hirngewebes. Zusätzlich tragen sekundäre Pathomechanismen, wie Entzündungsprozesse und die Schädigung der Blut-Hirn-Schranke (BHS), dazu bei, dass sich das initial geschädigte Läsionsareal im Laufe der Zeit vergrößert. Vor allem bei jungen Erwachsenen ist das SHT eine der häufigsten Ursachen für bleibende Behinderungen und Todesfälle. Aufgrund der schweren Auswirkungen des SHT und der bislang fehlenden Therapieoptionen ist die Identifizierung neuer Zielstrukturen für eine kausale Therapie von größter Bedeutung. Ausgehend von tierexperimentellen Studien ist das Kallikrein-Kinin-System (KKS) ein besonders erfolgversprechender Angriffspunkt zur Behandlung des SHT. Die Aktivierung des KKS über den Gerinnungsfaktor XII (FXII) und die darauf folgende Bildung von Bradykinin sind mit dem Entstehen von Hirnödemen und Entzündungsreaktionen assoziiert. Vorangegangene Studien haben weiterhin die Frage aufgeworfen, ob und in welchem Maße thrombotische Prozesse einen Einfluss auf die Pathophysiologie und die sekundären Hirnschädigungen nach SHT haben. Da FXII sowohl das KKS als auch die intrinsische plasmatische Gerinnungskaskade initiiert und somit zur Fibrinbildung beiträgt, stand FXII im Mittelpunkt der Untersuchungen dieser Dissertation. Die vorliegende Arbeit beschäftigt sich mit den Fragen, (I) inwiefern FXII eine Rolle bei der sekundären Hirnschädigung nach Trauma spielt und (II) ob thrombotische Prozesse ein pathophysiologisches Merkmal nach Trauma darstellen. In zwei unterschiedlichen Trauma-Modellen wurden FXII-defiziente Tiere und mit einem spezifischen Inhibitor des aktivierten FXII (FXIIa) behandelte Tiere gegen Kontrolltiere nach SHT verglichen. Die Analyse der funktionellen Ausfallerscheinungen und des Ausmaßes an neuronaler Degeneration zeigte, dass FXII-Defizienz und FXIIa-Inhibition vor den Auswirkungen eines SHT schützen. Als zugrundeliegende Mechanismen wurden die Reduktion von thrombotisch verschlossenen Gefäßen in der Mikrovaskulatur des Gehirns sowie der Schutz vor BHS-Störungen und verringerte inflammatorische Prozesse identifiziert. Weiterhin wurde festgestellt, dass eine Blockade der intrinsischen Gerinnungskaskade über FXII keine intrazerebralen Blutungen auslöst. In Gewebeproben von Patienten mit SHT wurde gezeigt, dass Thrombozytenaggregate auch im klinischen Verlauf auftreten und sich somit die tierexperimentellen Befunde auf die humane Situation übertragen lassen. Insgesamt tragen die Ergebnisse dazu bei, die komplexen und vielfältigen Pathomechanismen nach SHT besser zu verstehen und vor allem die Relevanz thrombo-inflammatorischer Prozesse nach SHT aufzuzeigen. Die gezielte Blockade des FXII(a) könnte als therapeutisches Prinzip zur Abschwächung der Sekundärschaden nach SHT geeignet sein. / Traumatic brain injury (TBI) is the result of an outside force causing mechanical disruption of the brain tissue. In addition, delayed pathogenic events, like inflammatory processes and blood-brain barrier damage occur, which collectively exacerbate the injury. In young adults, TBI is one of the main reasons for permanent disability and death. Because of its severe consequences and the lack of causal treatment, the identification of novel therapeutic options is of utmost importance. Based on animal studies, the kallikrein-kinin-system (KKS) is a very promising target to treat secondary injury processes following TBI. The activation of the KKS via coagulation factor XII (FXII) and the subsequent formation of bradykinin are tightly associated with the development of brain edema and inflammation. Recent studies have raised the question to what extent thrombotic processes might influence the pathophysiology and secondary injury processes following TBI. As FXII is not only the starting point of the KKS, but also the initiator of the intrinsic coagulation cascade which leads to fibrin formation, FXII was the center of interest for this dissertation. The work presented here deals with the issue, (I) whether FXII plays a role in the development and aggravation of secondary injury processes after trauma and (II) if thrombotic processes display a pathophysiological feature in TBI. In two different models of brain trauma, FXII-deficient mice and mice treated with a specific inhibitor of activated FXII (FXIIa) were compared to their respective control groups after trauma induction. The analyses of the functional outcome and the amount of neurodegenerative processes showed a distinct amelioration in favor of the genetically modified and treated animals. As underlying mechanisms, the reduction of thrombotic vessels in the brain microvasculature and additionally, protection from blood-brain barrier damages and less inflammation were identified. Moreover, it was observed that interference with the intrinsic coagulation cascade via FXII does not lead to the formation of intracerebral bleedings. The evaluation of human brain tissue surgically obtained following TBI demonstrated that platelet aggregates occur regularly in the course of brain trauma and that they seem to contribute to the secondary injury processes and the ischemia-like injury pattern. Taken together, the results contribute to the understanding of the highly complex and heterogeneous pathomechanisms following TBI, especially concerning thrombo-inflammatory processes. The targeted pharmacological blocking of FXII(a) could be a useful therapeutic principle in the treatment of TBI-associated pathologic processes.

Activated coagulation Factor XII (FXIIa) elevates blood pressure (BP) acutely by stimulating adrenomedullary catecholamine (CA) release in Brown Norway (BN) bioassay rats. These effects are absent in kininogen-deficient BN Katholiek (BNK) bioassay rats, indicating that these FXIIa-induced responses require an intact kallikrein-kinin system (KKS). In three hypertensive anephric pediatric patients, ΔFXIIa concentrations tracked peri-dialytic ΔBP. We hypothesized that FXIIa exerts a vasoconstrictor pro-hypertensive action, via the KKS, particularly evident in chronic renal failure (CRF). In CRF patients (n=11) receiving conventional hemodialysis, mean plasma FXIIa concentrations were 3-fold (p<0.05) greater than in healthy controls. Although conversion from conventional to nocturnal hemodialysis did not change mean FXIIa concentrations there was intra-session variation within individuals, such that ΔFXIIa concentrations correlated with changes in mean arterial pressure (MAP, r=0.66, p=0.026) and total peripheral resistance (TPR, r=0.75, p=0.007). In normotensive BN rats, FXIIa infusion (85 ng/min/kg for 60 mins) increased MAP (10±1 mmHg), TPR (0.5±0.1 Units), and CA, whilst left-ventricular end-diastolic volume (LVEDV) and heart rate decreased (all p<0.05). After adrenalectomy, FXIIa infusion decreased MAP (5±1 mmHg), did not raise CA or induce sustained vasoconstriction, and caused a greater fall in LVEDV (all p<0.05). In the 5/6 nephrectomized (NX) rodent CRF model, MAP and TPR were significantly greater in BN NX (n=16) than in BNK NX (n=15) (147±4 vs. 133±2 mmHg, 2.8±0.2 vs. 2.3±0.2 Units; all p<0.05). Plasma FXIIa measured using our semi-quantitive ELISA was 3-fold higher in both BN NX and BNK NX than in controls (p<0.01), but only correlated with MAP (r=0.48, p=0.01) in the BN NX. Plasma CA were elevated in the BN NX (p<0.05) but not in BNK NX. Infusion of a specific FXIIa inhibitor into BN NX decreased MAP (-12 mmHg) and TPR (-0.5 Units) proportionally to baseline FXIIa (ΔMAP: r=-0.72, p=0.002; ΔTPR: r=-0.57, p=0.021), and plasma CA fell by 40-67% (all p<0.05). No such changes occurred in the BNK NX. In summary, a significant component of the hypertension of CRF can be attributed to FXIIa-induced vasoconstriction mediated via the KKS and stimulated CA release. In normal rats, FXIIa appears also to directly or indirectly decrease preload and heart rate.

Activated coagulation Factor XII (FXIIa) elevates blood pressure (BP) acutely by stimulating adrenomedullary catecholamine (CA) release in Brown Norway (BN) bioassay rats. These effects are absent in kininogen-deficient BN Katholiek (BNK) bioassay rats, indicating that these FXIIa-induced responses require an intact kallikrein-kinin system (KKS). In three hypertensive anephric pediatric patients, ΔFXIIa concentrations tracked peri-dialytic ΔBP. We hypothesized that FXIIa exerts a vasoconstrictor pro-hypertensive action, via the KKS, particularly evident in chronic renal failure (CRF). In CRF patients (n=11) receiving conventional hemodialysis, mean plasma FXIIa concentrations were 3-fold (p<0.05) greater than in healthy controls. Although conversion from conventional to nocturnal hemodialysis did not change mean FXIIa concentrations there was intra-session variation within individuals, such that ΔFXIIa concentrations correlated with changes in mean arterial pressure (MAP, r=0.66, p=0.026) and total peripheral resistance (TPR, r=0.75, p=0.007). In normotensive BN rats, FXIIa infusion (85 ng/min/kg for 60 mins) increased MAP (10±1 mmHg), TPR (0.5±0.1 Units), and CA, whilst left-ventricular end-diastolic volume (LVEDV) and heart rate decreased (all p<0.05). After adrenalectomy, FXIIa infusion decreased MAP (5±1 mmHg), did not raise CA or induce sustained vasoconstriction, and caused a greater fall in LVEDV (all p<0.05). In the 5/6 nephrectomized (NX) rodent CRF model, MAP and TPR were significantly greater in BN NX (n=16) than in BNK NX (n=15) (147±4 vs. 133±2 mmHg, 2.8±0.2 vs. 2.3±0.2 Units; all p<0.05). Plasma FXIIa measured using our semi-quantitive ELISA was 3-fold higher in both BN NX and BNK NX than in controls (p<0.01), but only correlated with MAP (r=0.48, p=0.01) in the BN NX. Plasma CA were elevated in the BN NX (p<0.05) but not in BNK NX. Infusion of a specific FXIIa inhibitor into BN NX decreased MAP (-12 mmHg) and TPR (-0.5 Units) proportionally to baseline FXIIa (ΔMAP: r=-0.72, p=0.002; ΔTPR: r=-0.57, p=0.021), and plasma CA fell by 40-67% (all p<0.05). No such changes occurred in the BNK NX. In summary, a significant component of the hypertension of CRF can be attributed to FXIIa-induced vasoconstriction mediated via the KKS and stimulated CA release. In normal rats, FXIIa appears also to directly or indirectly decrease preload and heart rate.

Introduction: Plasma kallikrein (PK) is a cofactor in blood coagulation and modulates inflammation through the release of bradykinin (BK). Previously it was believed that plasma prekallikrein (PPK), the precursor of PK and a member of the serine protease superfamily, was synthesised exclusively by hepatocytes and secreted into circulation. However, recent studies show that various human tissues contain PPK mRNA. In this study we sought to determine in which human tissues PK is expressed. Methods: Following approval by the Ethics Committee at the University of Natal, tissue samples from the spinal cord, 13 different regions of the brain, 7 different blood vessels and various other organs were collected at autopsy within 24h of death (n =10). Sections were probed using polyclonal antibodies specific for PK. PK concentrations in extracts of these tissues were measured by competitive EllSA. Results: A Western blot analysis demonstrated the monospecificity of the antibody for the PK protein. The presence of immunoreactive PK in cells of the pancreatic islets of Langerhans served as a positive control for each immunolabeling experiment. The hepatocytes, renal distal convoluted tubules and epithelial cells lining the bronchiole and pulmonary alveoli labeled positively for PK. In the gastrointestinal tract tissue, immunoreactive PK was visualised in the acinar cells of the salivary gland, in stromal and glandular duct cells of the oesophagus, and in some chief and glandular cells in the stomach. Some of the above-mentioned tissues contained a few inflammatory cells which stained intensely for PK. Immunoreactive PK was visualised in the endothelial cells and smooth muscle cells of the all the blood vessels examined, except the renal vein. Increased immunolabeling for PK in the endothelial cells, foam cells and macrophages was observed in arteries with atheromatous plaques. In neural tissue immunoreactive PK was observed in neurons, ependymal cells, fibre tracts, and in secretory cells of the anterior pituitary gland. Immunolabeling for PK was visualised in some neurons of the spinal cord and in different brain regions viz. hypothalamus, cerebral cortex, thalamus, brain stem and hippocampus. In sections of the hypothalamus and spinal cord, we observed immunolabeling for PK in ependymal cells lining the third ventricle and central canal respectively. Positive labeling for PK was evident in fibre tracts of the pons, medulla and hippocampus. No immunoreactive PK was visualised in the choroid plexus or cerebellum. High amounts of PK were measured by competitive ELlSA in extracts of the pancreas (12.94 ± 2.04 /-lg/ml), the pons (1.67 ± 1.46 /-lg/ml) and aorta (0.44 ± 0.14 /-lg/ml). The basilar artery (0.09 ± 0.07 /-lg/ml) and spinal cord (0.09 ± 0.04 /-lg/ml) had the least PK concentrations. Discussion and Conclusions: We have shown that the PPK mRNA demonstrated in various human tissues is most likely translated into protein by the immunolocalisation of PK within specific cells in the different tissues examined. The actions of PK within these tissues may be two fold, firstly by its kininogenase activity it may release BK from high molecular weight kininogen, or alternatively, PK may act as a proteolytic enzyme on other proteins. With respect to the latter) PK may be involved in the processing of protein precursors, for example precursors of the digestive enzymes found in saliva and in gastric secretion, insulin precursors in the pancreas, and hormonal precursors in the pituitary gland. The localisation of PK and B1 and B2 kinin receptors in the kidney, lung, stomach, blood vessels and brain suggests that the effects of PK in these tissues are mediated by BK-receptor interaction. These may include the regulation of glucose uptake in the pancreas, water and ion transport in the kidney, and local and systemic blood pressure in the cardiovascular system. The presence of immunoreactive PK in neurons suggests that BK-receptor mediated interaction may regulate neurophysiological processes such as synaptic transmission. Immunolabeling for PK in polymorphonuclear leukocytes observed in some of these tissue sections suggests the potential to mediate the inflammatory process. / Thesis (M.Med.Sc.)-University of Natal, Durban, 2000

Inflammation is the normal biological response to tissue injury, and is characterised by the interactive activation of multiple mediators and cell types. One response to tissue injury is the production of pain, not only by direct trauma to sensory fibres, but also through the release of mediators from sensory nerve terminals. One such mediator is kinin which is a vasoactive peptide considered to play a primary role in inflammation by causing constriction of venules, dilation of arterioles, increasing permeability of the capillary membrane, and interacting with sensory nerve terminal transmitters to evoke pain. The kinin forming enzymes (kallikreins) reach inflammation sites either on the surface of migrating neutrophils or by transudation from plasma. The kininogen molecule which contains the kinin moiety, has been localised on the external surface of the neutrophil, and provides the substrate from which kinins can be cleaved through enzymatic action. The cellular actions of kinins are mediated through B2 receptors, which are also located on the external surface of the neutrophils. In addition, the induced effects of kinins are regulated by B1 receptors. The formation of nitric oxide (NO) from arginine released from the kinin C terminus, and receptor membrane signal transduction by nitric oxide following kinin receptor activation is discussed. A molecular response to cell injury is the formation of chemotactic mediators that attract neutrophils to sites of inflammation. The question whether neutrophils contribute to circulating levels of kinins was examined in infections and inflammatory disorders. This novel hypothesis was tested using circulating neutrophils harvested from patients with tuberculosis meningitis and pneumonia. These neutrophils showed a distinct loss of only the kinin moiety from the kininogen molecule located on the external surface. The confocal images of fixed, permeabilised neutrophils provided multi-dimensional constructs, and the intensity of fluorescence reflected the relative amounts of the molecule present in both neutrophils harvested from healthy volunteers as well as patient blood. The immunocytochemical labelling experiments using colloidal gold as markers, confirmed, at the ultrastructural level, the presence or disappearance of the kinin moiety from the kininogen molecule on the neutrophil surface. The cell component of synovial fluid in rheumatoid athritis (RA) consists mainly of neutrophils. This study demonstrates the absence of the kinin moiety from circulating and synovial fluid neutrophils from patients with RA, as well as an increased signal from immunolabelled B2 receptors in synovial fluid neutrophils. These findings support the hypothesis that in RA, kinins are released during the inflammatory response in the joints, and suggests that there is an upregulation of the B2 receptor at the site of inflammation. Neutrophils chemotactically drawn to the site of inflammation become activated to release kinin from the kininogen molecule, and thereafter re-enter the circulation where they were harvested systemically. B2 receptors may be upregulated following activation by kinins or by other mediators present in the inflammatory milieu. Interleukin-1 has been shown to upregulate kinin receptors on human synovial cells. Anti-peptide antibodies to the loops of cloned B1 and B2 receptors have provided powerful probes for the cellular identification of the two kinin receptor families. Mapping of the B2 receptors showed upregulation on the neutrophils gathered from inflamed joints. However, no activation of the Br receptors was observed in normal blood neutrophils as well as those obtained from the different disease states. / Thesis (M.Med.)-University of Natal, 1996.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 6 uppsatser.

L’angioedème (AO) à kinine est caractérisé par la survenue spontanée et récurrente d’oedèmes des tissus sous cutanés et sous muqueux, conséquence de l’accumulation des kinines sur l’endothélium vasculaire. La sévérité des AO dépend de leur localisation, ils sont déformants sur les tissus sous cutanés, douloureux au niveau de la muqueuse digestive et peuvent mettre en jeu le pronostic vital s’ils affectent le larynx. L’AO à kinine a d’abord été associé au déficit pour C1 Inhibiteur (C1Inh) puis des formes sans déficit pour C1Inh ont été décrites. L’AO est décrit comme une maladie multifactorielle pour laquelle l’ensemble des facteurs décisionnels n’est pas encore identifié. Ce travail a permis (1) de définir des paramètres stratégiques de la production des kinines pour l’AO, (2) d’identifier les paramètres impliqués et décisionnels pour la survenue des crises et leur sévérité, (3) de repérer des phénotypes biologiques des sujets atteints d’AO. / Kinin mediated angioedema (AO) is characterized by spontaneous and recurrent oedema affecting subcutaneous and submucosal tissue. Oedemas develop subsequently to kinin accumulation on vascular endothelium. AO severity is depending on localisation, they are warping on subcutaneous tissue, painful on digestive mucous and life treating when affected the larynx. Kinin mediated AO was first associated with C1 Inhibitor (C1Inh) deficiency and thereafter AO without C1Inh deficiency has been described. AO is a multifactorial disease for which all the decision-making factor(s) is(are) not yet identified. As results of this work, have emerged (1) a characterization of strategic parameters of the kinin production for AO, (2) an identification of significant and decision-making parameters for the attack onset and severity, (3) a cover of biological phenotypes of the AO patients

Le système kallicréine-kinine(s) (SKK) est un système peptidique vasomoteur avec des effets multiples et complexes qui dépendent principalement du tissu et des pathologies étudiés. Les kinines activent deux types de récepteurs : le récepteur B1 (RB1) et le récepteur B2 (RB2). L’objectif de mon travail de thèse a été d’étudier les effets de nouveaux agonistes spécifiques des RB1 ou des RB2 dans certaines complications associées au diabète chez la souris. Dans une première partie, nous avons pu montrer que l’administration chronique d’un agoniste spécifique des RB1 ou des RB2 corrige entièrement le défaut de néovascularisation post-ischémique observé chez la souris diabétique notamment en augmentant l’inflammation. Dans un deuxième modèle, nous avons pu montrer que l’activation des RB2 entraîne une désorganisation des couches cutanées et un retard important de cicatrisation chez la souris. En revanche, l’administration d’un antagoniste des RB2 accélère de façon significative la cicatrisation dans deux modèles de diabète. La dernière partie de ce travail a permis de montrer que l’administration chronique des RB2 augmente la mortalité des animaux ayant subit une ischémie cérébrale. Chez la souris diabétique, l’activation des RB1 a des effets neuroprotecteurs puisqu’elle réduit la taille de l'infarctus et les déficits neurologiques après une ischémie cérébrale transitoire. Pour conclure, nous avons pu montrer au cours de ces travaux que l’activation du SKK a des effets contradictoires en fonction des organes étudiés. Ainsi, l’étude de ces nouveaux agonistes des récepteurs des kinines ouvre des nouvelles voies thérapeutiques dans les complications du diabète. / The kallikrein-kinin(s) system (KKS) is a peptide system with various pathophysiological effects. Kinins exert their actions through activation of two different receptor subtypes: B1 receptor (B1R) and B2 receptor (B2R). The aim of my thesis was to study the role of this system in diabetic complications in mice. We used pharmacological approaches using new specific agonists of B1R or B2R, or a specific antagonist of B2R. In the first part, we showed that selective pharmacological activation of B1R or B2R overcomes the effect of diabetes on post-ischemic neovascularization and restores tissue perfusion through inflammation. In a second model, we showed that B2R agonist impairs wound repair in mice, inducing skin disorganization and epidermis thickening. Interestingly, B2R blockade improves skin wound healing in two mouse models of diabetes. In a last part, we showed that B2R activation increases mortality after transient cerebral ischemia. In diabetic mice, B1R activation has neuroprotective effects. Indeed, B1R agonist treatment decreases infarct size and improves neurological deficit at day 2 after transient cerebral ischemia. To conclude, KKS activation has contradictory effects depending on the organs studied. The study of new B1 or B2 kinin receptor agonists opens new therapeutic options in diabetic complications.

A Bradicinina, a mais importante das cininas plasmáticas, foi encontrada pela primeira vez em mamíferos. Pouco foi estudado sobre o sistema calicreína-cininas em serpentes, mas o que se sabe é que, provavelmente, são deficientes do Fator XII, um ativador da pré-calicreína em mamíferos. Com o objetivo de identificarmos novos peptídeos, submetemos plasmas das serpentes Bothrops jararaca (SBJ) e da Crotalus durissus terrificus (SCDT) tratados por duas metodologias simplificadas de determinação de bradicininogênio. O estudo com os plasmas das SBJ e da SCDT liberou uma substância com efeito semelhante à cinina de mamíferos que produziu hipotensão na serpente e no rato; esse efeito foi potencializado com o uso do captopril (0,05/0,010 mg/Kg), que inibe a cininase II, confirmando resultados diferentes das literaturas existentes sobre esse assunto. Com o resultado obtido, fracionamos este produto em aparelho de HPLC, e obtivemos seqüências peptídicas que não apresentaram homologia com a bradicinina. / The Bradykinin (BK), most important of the plasmatic kinins, was encountered for the first time in mammals. Little was studied in the kallikrein-kinin system in snakes, but it is known that, it is probably deficient of Factor XII, an activator of the daily prekallikrein in mammals. In order to identify new peptides, we submit plasma of the snakes Bothrops jararaca (SBJ) and e Crotalus durissus terrificus (SCDT) in two simplified methodologies for bradykininnogen determination, to analyze in bioassays of average arterial pressure of mammals and isolated ileum of guinea pig. The study with plasma of the SBJ and the SCDT showed that the kinin of mammals released a substance with effect similar to that producing hypotension in snakes and rats; this effect was potentiated with the use of captopril (0,05/0,010 mg/Kg), wich inhibits kininase II, confirming results different from literature?s obtained on this subject. With the obtained result, we fractioned this product in HPLC equipment and obtained peptides sequences with no homologie with the bradykinin.

No description available.