Endogenous B1 receptor mediated hypotension produced by contact system activation in the presence of endotoxemia

Multimodal strategy to counteract vasodilation in septic shock

Early initiation of a multimodal treatment strategy in the management of vasopressors during septic shock has been advocated to reduce delays in restoring adequate organ perfusion and to mitigate side effects associated with the administration of high-dose catecholamines. We provide a review that summarises the pathophysiology of vasodilation, the physiologic response to the vascular response, and the different drugs used in this situation, focusing on the need to combine early different vasopressors. Fluid loading being insufficient for counteracting vasoplegia, norepinephrine is usually the first-line vasopressor used to restore hemodynamics. Norepinephrine sparing is discussed in further detail through the concomitant use of adrenergic, vasopressinergic, and renin-angiotensin systems and the optimisation of endothelial reactivity with methylene blue. A blueprint for the construction of new studies is outlined to address the question of vasopressor selection and timing in septic shock.

Crosstalk of the plasma contact system with bacteria

Activation of the plasma contact system triggers several cascade systems such as the kallikrein-kinin system, the intrinsic pathway of coagulation, the classical complement cascade and the fibrinolytic system. Recent studies have shown a critical role of the contact system for arterial and venous thrombus formation and thromboembolic disease. In contrast, the function of the contact system for host-defense reactions and its physiological functions have remained enigmatic. Experimental animal studies and clinical data have linked the contact system to bacterial infections with implications for sepsis disease. The present review summarizes the role of the contact system and its activation for bacterial infections.

Putative roles of kinin receptors in the therapeutic effects of angiotensin 1-converting enzyme inhibitors in diabetes mellitus

The role of endogenous kinins and their receptors in diabetes mellitus is being confirmed with the recent developments of molecular and genetic animal models. Compelling evidence suggests that the kinin B(2) receptor is organ-protective and partakes to the therapeutic effects of angiotensin 1-converting enzyme inhibitors (ACEI) and angiotensin AT(1) receptor antagonists. Benefits derive primarily from vasodilatory, antihypertensive, antiproliferative, antihypertrophic, antifibrotic, antithrombotic and antioxidant properties of kinin B(2) receptor activation. Mechanisms include the formation of nitric oxide and prostacyclin and the inhibition of NAD(P)H oxidase activity involving classical and novel signalling pathways. Kinin B(2) receptor also ameliorates insulin resistance by increasing glucose uptake and supply, and by inducing glucose transporter-4 translocation either directly or through phosphorylation of insulin receptor. The kinin B(1) receptor, which is induced by the cytokine network, growth factors and hyperglycaemia, mediates hyperalgesia, vascular hyperpermeability and leukocytes infiltration in diabetic animals. However, emerging data highlight reno- and cardio-protective effects mediated by kinin B(1) receptor under chronic ACEI therapy in diabetes mellitus. Thus, the Janus-faced of kinin receptors needs to be taken into account in future drug development. For instance, locally acting kinin B(1)/B(2) receptor agonists if used in a safe therapeutic window may represent a more rationale strategy in the prevention and management of diabetic complications. Because kinin B(2) receptor antagonists may further increase insulin resistance, the persisting dogma that restricts the development of kinin receptor analogues to antagonists (that is still relevant to abrogate pain and inflammation) needs to be revisited.

Kinin B1 receptor up-regulation after lipopolysaccharide administration: role of proinflammatory cytokines and neutrophil influx

Several studies have now clearly established the ability of LPS to induce bradykinin B(1) receptor up-regulation in vivo and the functional relevance of this up-regulation for the pathophysiological effects of LPS. Using an in vivo system in which LPS is injected locally into the rat paw, we have examined the potential contribution of proinflammatory cytokines, NF-kappaB activation, and neutrophil influx for the functional and molecular up-regulation of the bradykinin B(1) receptor. Treatment with LPS resulted in a rapid and sustained functional up-regulation of B(1) receptors in the rat paw that correlated with the increase in B(1) receptor mRNA levels. B(1) receptor up-regulation is preceded by the rapid activation of the transcription factor NF-kappaB and the production of proinflammatory cytokines, including TNF-alpha and IL-1beta. More importantly, blockade of NF-kappaB translocation, TNF-alpha, or IL-1beta prevented the functional and molecular up-regulation of B(1) receptors. Injection of LPS also induced the influx of neutrophils that followed the peak of cytokine production and associated with the persistent activation of NF-kappaB and functional B(1) receptor up-regulation. Blockade of neutrophil influx with platelet-activating factor receptor antagonists or cell adhesion molecule blockers prevented B(1) receptor up-regulation. Thus, by acting in cooperation and in a coordinated, timely manner, TNF-alpha, IL-1beta, neutrophils, and the transcription factor NF-kappaB are major and essential players in the ability of LPS to induce B(1) receptor expression in vivo.

Absence of ligand-induced regulation of kinin receptor expression in the rabbit

The induction of B(1) receptors (B(1)Rs) and desensitization or down-regulation of B(2) receptors (B(2)Rs) as a consequence of the production of endogenous kinins has been termed the autoregulation hypothesis. The latter was investigated using two models based on the rabbit: kinin stimulation of cultured vascular smooth muscle cells (SMCs) and in vivo contact system activation (dextran sulphate intravenous injection, 2 mg kg(-1), 5 h). Rabbit aortic SMCs express a baseline population of B(1)Rs that was up-regulated upon interleukin-1beta treatment ([(3)H]-Lys-des-Arg(9)-BK binding or mRNA concentration evaluated by RT - PCR; 4 or 3 h, respectively). Treatment with B(1)R or B(2)R agonists failed to alter B(1)R expression under the same conditions. Despite consuming endogenous kininogen (assessed using the kinetics of immunoreactive kinin formation in the plasma exposed to glass beads ex vivo) and producing hypotension mediated by B(2)Rs in anaesthetized rabbits, dextran sulphate treatment failed to induce B(1)Rs in conscious animals (RT - PCR in several organs, aortic contractility). By contrast, lipopolysaccharide (LPS, 50 microg kg(-1), 5 h) was an effective B(1)R inducer (kidney, duodenum, aorta) but did not reduce kininogen reserve. We tested the alternate hypothesis that endogenous kinin participate in LPS induction of B(1)Rs. Kinin receptor antagonists (icatibant combined to B-9858, 50 microg kg(-1) of each) failed to prevent or reduce the effect of LPS on B(1)R expression. Dextran sulphate or LPS treatments did not persistently down-regulate vascular B(2)Rs (jugular vein contractility assessed ex vivo). The kinin receptor autoregulation hypothesis is not applicable to primary cell cultures derived from a tissue known to express B(1)Rs in a regulated manner (aorta). The activation of the endogenous kallikrein-kinin system is ineffective to induce B(1)Rs in vivo in an experimental time frame sufficient for B(1)R induction by LPS.