| 1. |
- Amara, Umme, et al.
(författare)
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Molecular Intercommunication between the Complement and Coagulation Systems
- 2010
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 185:9, s. 5628-5636
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Tidskriftsartikel (refereegranskat)abstract
- The complement system as well as the coagulation system has fundamental clinical implications in the context of life-threatening tissue injury and inflammation. Associations between both cascades have been proposed, but the precise molecular mechanisms remain unknown. The current study reports multiple links for various factors of the coagulation and fibrinolysis cascades with the central complement components C3 and C5 in vitro and ex vivo. Thrombin, human coagulation factors (F) XIa, Xa, and IXa, and plasmin were all found to effectively cleave C3 and C5. Mass spectrometric analyses identified the cleavage products as C3a and C5a, displaying identical molecular weights as the native anaphylatoxins C3a and C5a. Cleavage products also exhibited robust chemoattraction of human mast cells and neutrophils, respectively. Enzymatic activity for C3 cleavage by the investigated clotting and fibrinolysis factors is defined in the following order: FXa > plasmin > thrombin > FIXa > FXIa > control. Furthermore, FXa-induced cleavage of C3 was significantly suppressed in the presence of the selective FXa inhibitors fondaparinux and enoxaparin in a concentration-dependent manner. Addition of FXa to human serum or plasma activated complement ex vivo, represented by the generation of C3a, C5a, and the terminal complement complex, and decreased complement hemolytic serum activity that defines exact serum concentration that results in complement-mediated lysis of 50% of sensitized sheep erythrocytes. Furthermore, in plasma from patients with multiple injuries (n = 12), a very early appearance and correlation of coagulation (thrombin-antithrombin complexes) and the complement activation product C5a was found. The present data suggest that coagulation/fibrinolysis proteases may act as natural C3 and C5 convertases, generating biologically active anaphylatoxins, linking both cascades via multiple direct interactions in terms of a complex serine protease system. The Journal of Immunology, 2010, 185: 5628-5636.
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| 2. |
- Burk, Anne-Maud, et al.
(författare)
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Early Complementopathy After Multiple Injuries in Humans.
- 2012
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Ingår i: Shock. - 1540-0514. ; 37:4, s. 348-354
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: After severe tissue injury, innate immunity mounts a robust systemic inflammatory response. However, little is known about the immediate impact of multiple trauma on early complement function in humans. In the present study we hypothesized that multiple trauma results in immediate activation, consumption and dysfunction of the complement cascade and that the resulting severe "complementopathy" may be associated with morbidity and mortality.Therefore a prospective multicenter study with 25 healthy volunteers and 40 polytrauma patients (mean injury severity score [ISS] = 30.3 ± 2.9) was performed. After polytrauma serum was collected as early as possible at the scene, upon admission to the emergency room and 4, 12, 24, 120 and 240 hours post trauma and analysed for the complement profile. Complement hemolytic activity (CH-50) was massively reduced within the first 24 h after injury, recovered only 5 days after trauma and discriminated between lethal and non-lethal 28-day outcome. Serum levels of the complement activation products C3a and C5a were significantly elevated throughout the entire observation period and correlatedwith the severity of traumatic brain injury and survival. The soluble terminal complement complex SC5b-9 and mannose-binding lectin (MBL) showed a biphasic response after trauma. Key fluid phase inhibitors of complement, such as C4b-binding protein (C4BP) and factor I, were significantly diminished early after trauma.The present data indicate an almost synchronically rapid activation and dysfunction of complement suggesting a trauma-induced "complementopathy" early after injury. These events may participate to the impairment of the innate immune response observed after severe trauma.
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| 3. |
- Denk, Stephanie, et al.
(författare)
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Complement C5a Functions as a Master Switch for the pH Balance in Neutrophils Exerting Fundamental Immunometabolic Effects
- 2017
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 198:12, s. 4846-4854
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Tidskriftsartikel (refereegranskat)abstract
- During sepsis, excessive activation of the complement system with generation of the anaphylatoxin C5a results in profound disturbances in crucial neutrophil functions. Moreover, because neutrophil activity is highly dependent on intracellular pH (pH(i)), we propose a direct mechanistic link between complement activation and neutrophil pHi. In this article, we demonstrate that in vitro exposure of human neutrophils to C5a significantly increased pHi by selective activation of the sodium/hydrogen exchanger. Upstream signaling of C5a-mediated intracellular alkalinization was dependent on C5aR1, intracellular calcium, protein kinase C, and calmodulin, and downstream signaling regulated the release of antibacterial myeloperoxidase and lactoferrin. Notably, the pH shift caused by C5a increased the glucose uptake and activated glycolytic flux in neutrophils, resulting in a significant release of lactate. Furthermore, C5a induced acidification of the extracellular micromilieu. In experimental murine sepsis, pHi of blood neutrophils was analogously alkalinized, which could be normalized by C5aR1 inhibition. In the clinical setting of sepsis, neutrophils from patients with septic shock likewise exhibited a significantly increased pHi. These data suggest a novel role for the anaphylatoxin C5a as a master switch of the delicate pHi balance in neutrophils resulting in profound inflammatory and metabolic changes that contribute to hyperlactatemia during sepsis.
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| 4. |
- Ehrnthaller, Christian, et al.
(författare)
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Complement C3 and C5 deficiency affects fracture healing.
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:11
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Tidskriftsartikel (refereegranskat)abstract
- There is increasing evidence that complement may play a role in bone development. Our previous studies demonstrated that the key complement receptor C5aR was strongly expressed in the fracture callus not only by immune cells but also by bone cells and chondroblasts, indicating a function in bone repair. To further elucidate the role of complement in bone healing, this study investigated fracture healing in mice in the absence of the key complement molecules C3 and C5. C3(-/-) and C5(-/-) as well as the corresponding wildtype mice received a standardized femur osteotomy, which was stabilized using an external fixator. Fracture healing was investigated after 7 and 21 days using histological, micro-computed tomography and biomechanical measurements. In the early phase of fracture healing, reduced callus area (C3(-/-): -25%, p=0.02; C5(-/-): -20% p=0.052) and newly formed bone (C3(-/-): -38%, p=0.01; C5(-/-): -52%, p=0.009) was found in both C3- and C5-deficient mice. After 21 days, healing was successful in the absence of C3, whereas in C5-deficient mice fracture repair was significantly reduced, which was confirmed by a reduced bending stiffness (-45%; p=0.029) and a smaller callus volume (-17%; p=0.039). We further demonstrated that C5a was activated in C3(-/-) mice, suggesting cleavage via extrinsic pathways. Our results suggest that the activation of the terminal complement cascade in particular may be crucial for successful fracture healing.
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| 5. |
- Halbgebauer, Rebecca, et al.
(författare)
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Thirty-Eight-Negative Kinase 1 Is a Mediator of Acute Kidney Injury in Experimental and Clinical Traumatic Hemorrhagic Shock
- 2020
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Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 11, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Trauma represents a major socioeconomic burden worldwide. After a severe injury, hemorrhagic shock (HS) as a frequent concomitant aspect is a central driver of systemic inflammation and organ damage. The kidney is often strongly affected by traumatic-HS, and acute kidney injury (AKI) poses the patient at great risk for adverse outcome. Recently, thirty-eight-negative kinase 1 (TNK1) was proposed to play a detrimental role in organ damage after trauma/HS. Therefore, we aimed to assess the role of TNK1 in HS-induced kidney injury in a murine and apost hocanalysis of a non-human primate model of HS comparable to the clinical situation. Mice and non-human primates underwent resuscitated HS at 30 mmHg for 60 min. 5 h after the induction of shock, animals were assessed for systemic inflammation and TNK1 expression in the kidney.In vitro, murine distal convoluted tubule cells were stimulated with inflammatory mediators to gain mechanistic insights into the role of TNK1 in kidney dysfunction. In a translational approach, we investigated blood drawn from either healthy volunteers or severely injured patients at different time points after trauma (from arrival at the emergency room and at fixed time intervals until 10 days post injury; identifier: NCT02682550,). A pronounced inflammatory response, as seen by increased IL-6 plasma levels as well as early signs of AKI, were observed in mice, non-human primates, and humans after trauma/HS. TNK1 was found in the plasma early after trauma-HS in trauma patients. Renal TNK1 expression was significantly increased in mice and non-human primates after HS, and these effects with concomitant induction of apoptosis were blocked by therapeutic inhibition of complement C3 activation in non-human primates. Mechanistically,in vitrodata suggested that IL-6 rather than C3 cleavage products induced upregulation of TNK1 and impaired barrier function in renal epithelial cells. In conclusion, these data indicate that C3 inhibitionin vivomay inhibit an excessive inflammatory response and mediator release, thereby indirectly neutralizing TNK1 as a potent driver of organ damage. In future studies, we will address the therapeutic potential of direct TNK1 inhibition in the context of severe tissue trauma with different degrees of additional HS.
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