Kinins are important mediators in cardiovascular homeostasis, inflammation, and nociception. Two kinin receptors have been described, B1 and B2. The B2 receptor is constitutively expressed, and its targeted disruption leads to salt-sensitive hypertension and altered nociception. The B1 receptor is a heptahelical receptor distinct from the B2 receptor in that it is highly inducible by inflammatory mediators such as bacterial lipopolysaccharide and interleukins. To clarify its physiological function, we have generated mice with a targeted deletion of the gene for the B1 receptor. B1 receptor-deficient animals are healthy, fertile, and normotensive. In these mice, bacterial lipopolysaccharide-induced hypotension is blunted, and there is a reduced accumulation of polymorphonuclear leukocytes in inflamed tissue. Moreover, under normal noninflamed conditions, they are analgesic in behavioral tests of chemical and thermal nociception. Using whole-cell patch-clamp recordings, we show that the B1 receptor was not necessary for regulating the noxious heat sensitivity of isolated nociceptors. However, by using an in vitro preparation, we could show that functional B1 receptors are present in the spinal cord, and their activation can facilitate a nociceptive reflex. Furthermore, in B1 receptor-deficient mice, we observed a reduction in the activitydependent facilitation (wind-up) of a nociceptive spinal reflex. Thus, the kinin B1 receptor plays an essential physiological role in the initiation of inflammatory responses and the modulation of spinal cord plasticity that underlies the central component of pain. The B1 receptor therefore represents a useful pharmacological target especially for the treatment of inflammatory disorders and pain.D iseases of the cardiovascular system as well as inflammatory diseases that often lead to pain are of increasing importance for health care in aging populations. Kinins have been known for some time to be important mediators of cardiovascular homeostasis, inflammation, and nociception (1). They are probably the first mediators released in injured tissue from kininogens either by plasma kallikrein, which is activated early in the coagulation cascade, or tissue kallikrein, which is activated by proteases released at injured sites. Surprisingly, the therapeutic value of intervention in the kallikrein-kinin system has not been fully explored. The two known receptors for kinins, B1 and B2, might be suitable pharmacological targets to treat chronic inflammatory and cardiovascular diseases. The B2 receptor binds the major effector peptide of the kallikrein-kinin system, which is bradykinin (BK) in rodents and kallidin in humans. Deletion of the B2 receptor in mice leads to salt-sensitive hypertension and altered nociception (2-4). Like the B2 receptor, the B1 receptor is a heptahelical receptor, but unlike B2 receptors, it is not widely expressed in normal tissue but is highly inducible by inflammatory mediators like bacterial lipopolysaccharide (LPS) and cytokines and does not desensitize after...

SUMMARY The concentrations of angiotensin converting enzyme (ACE) activity, norepinephrine, and serotonin were measured in microdissected regions of the dog's brainstem and spinal cord. In addition, we determined the in vitro metabolism of 125 I-angiotensin I (Ang I) hi hompgenates of the same brain pnnch regions. High ACE-specific activity was found hi the monoamine-containing regions of the brainstem and in the intermediolateral column of the spinal cord. In brainstem homogenates '"I-Ang I was metabolized to angiotensin II (Ang- [l-8]) and the N-terminal heptapeptide Ang-(l-7). In the presence of MK 422 (50 fiM), Ang-(l-7) was still generated, while the production of Ang-(l-8) was inhibited. This study revealed the presence of high ACE activity in monoamine regions of dog brainstem and spinal cord, and showed that the metabolite Ang-(l-7) is the major product generated from Ang I in the presence and absence of ACE inhibition. (Ang H) in the central nervous system is limited by our lack of knowledge of the functional neurochemistry of the brain reninangiotensin system (RAS) in regions that may produce the peptide for actions on neuronal circuits engaged in autonomic function.12 Because catecholamine neuronal groups of the dorsal and ventral brainstem and the spinal cord have a major role in blood pressure regulation and the evolution of some forms of experimental hypertension, 3 we determined the distribution of the angiotensin converting enzyme (ACE) in these areas in the dog. We studied also the proteolytic hydrolysis of angiotensin I (Ang I) in brain punch homogenates obtained from these regions to evaluate the biochemical pathways that account for the generation and metabolism of angiotensins in the brain.

Post-exercise hypotension is an important event for blood pressure regulation, especially in hypertensive individuals. Although post-exercise hypotension is a well-known phenomenon, the mechanism responsible is still unclear. The kallikrein-kinin system is involved in blood pressure control, but its role in post-exercise hypotension has not yet been investigated. Thus, the purpose of this study was to investigate the involvement of the vasodilators bradykinin and des-Arg(9)-BK and kallikrein activity in post-exercise hypotension promoted by 35 min of cycle ergometer (CE) or circuit weight-training (CWT) bouts in normotensive and hypertensive individuals. A significant decrease in mean arterial pressure at 45 and 60 min after CE and 45 min after CWT was observed in normotensive individuals. Hypertensive values of mean arterial pressure were significantly reduced at 45 and 60 min after CE and at 60 min after CWT. Before exercise, plasma bradykinin concentrations and kallikrein activity were higher in hypertensive compared to normotensive volunteers. Kinin levels increased in the groups evaluated at the end of the training period and 60 min post-exercise. These data suggest that the kallikrein-kinin system may be involved in post-exercise hypotension in normotensive and hypertensive individuals subjected to CE and CWT bouts.

The administration of bradykinin may attenuate ischemia and reperfusion (I/R) injury by acting on B2Rs. Blockade of B2R has also been shown to ameliorate lesions associated with I/R injury. In an attempt to explain these contradictory results, the objective of the present work was to investigate the role of and interaction between B1 and B2 receptors in a model of intestinal I/R injury in mice. The bradykinin B2R antagonist (HOE 140) inhibited reperfusion-induced inflammatory tissue injury and delayed lethality. After I/R, there was an increase in the expression of B1R mRNA that was prevented by HOE 140. In mice that were deficient in B1Rs (B1R−/− mice), inflammatory tissue injury was abrogated, and lethality was delayed and partially prevented. Pretreatment with HOE 140 reversed the protective anti-inflammatory and antilethality effects provided by the B1R−/− phenotype. Thus, B2Rs are a major driving force for B1R activation and consequent induction of inflammatory injury and lethality. In contrast, activation of B2Rs may prevent exacerbated tissue injury and lethality, an effect unmasked in B1R−/− mice and likely dependent on the vasodilatory actions of B2Rs. Blockade of B1Rs could be a more effective strategy than B2 or B1/B2 receptor blockade for the treatment of the inflammatory injuries that follow I/R.

No abstract

No abstract

No abstract

Abstract-Angiotensin