Kinin B1 receptor: a potential therapeutic target in sepsis-induced vascular hyperpermeability.

BACKGROUND: In sepsis, the endothelial barrier becomes incompetent, with the leaking of plasma into interstitial tissues. VE-cadherin, an adherens junction protein, is the gatekeeper of endothelial cohesion. Kinins, released during sepsis, induce vascular leakage and vasodilation. They act via two G-protein coupled receptors: B1 (B1R) and B2 (B2R). B1R is inducible in the presence of pro-inflammatory cytokines, endotoxins or after tissue injury. It acts at a later stage of sepsis and elicits a sustained inflammatory response. The aim of our study was to investigate the relationships between B1R and VE-cadherin destabilization in vivo in a later phase of sepsis. METHODS: Experimental, prospective study in a university research laboratory. We used a polymicrobial model of septic shock by cecal ligation and puncture in C57BL6 male mice or C57BL6 male mice that received a specific B1R antagonist (R-954). We studied the influence of B1R on sepsis-induced vascular permeability 30 h after surgery for several organs, and VE-cadherin expression in the lung and kidneys by injecting R-954 just before surgery. The 96-h survival was determined in mice without treatment or in animals receiving R-954 as a "prophylactic" regimen (a subcutaneous injection of 200 µg/kg, prior to CLP and 24 h after CLP), or as a "curative" regimen (injection of 100 µg/kg at H6, H24 and H48 post-surgery). RESULTS: B1R inactivation helps to maintain MAP above 65 mmHg but induces different permeability profiles depending on whether or not organ perfusion is autoregulated. In our model, VE-cadherin was destabilized in vivo during septic shock. At a late stage of sepsis, the B1R blockade reduced the VE-cadherin disruption by limiting eNOS activation. The survival rate for mice that received R-954 after sepsis induction was higher than in animals that received an antagonist as a prophylactic treatment. CONCLUSIONS: B1R antagonizing reduced mortality in our model of murine septic shock by limiting the vascular permeability induced by VE-cadherin destabilization through maintenance of the macrohemodynamics, consequently limiting organ dysfunctions.

Tibial post fracture pain is reduced in kinin receptors deficient mice and blunted by kinin receptor antagonists.

BACKGROUND: Tibial fracture is associated with inflammatory reaction leading to severe pain syndrome. Bradykinin receptor activation is involved in inflammatory reactions, but has never been investigated in fracture pain. METHODS: This study aims at defining the role of B1 and B2-kinin receptors (B1R and B2R) in a closed tibial fracture pain model by using knockout mice for B1R (B1KO) or B2R (B2KO) and wild-type (WT) mice treated with antagonists for B1R (SSR 240612 and R954) and B2R (HOE140) or vehicle. A cyclooxygenase (COX) inhibitor (ketoprofen) and an antagonist (SB366791) of Transient Receptor Potential Vaniloid1 (TRPV1) were also investigated since these pathways are associated with BK-induced pain in other models. The impact on mechanical and thermal hyperalgesia and locomotion was assessed by behavior tests. Gene expression of B1R and B2R and spinal cord expression of c-Fos were measured by RT-PCR and immunohistochemistry, respectively. RESULTS: B1KO and B2KO mice demonstrated a reduction in post-fracture pain sensitivity compared to WT mice that was associated with decreased c-Fos expression in the ipsilateral spinal dorsal horn in B2KO. B1R and B2R mRNA and protein levels were markedly enhanced at the fracture site. B1R and B2R antagonists and inhibition of COX and TRPV1 pathways reduced pain in WT. However, the analgesic effect of the COX-1/COX-2 inhibitor disappeared in B1KO and B2KO. In contrast, the analgesic effect of the TRPV1 antagonist persisted after gene deletion of either receptor. CONCLUSIONS: It is suggested that B1R and B2R activation contributes significantly to tibial fracture pain through COX. Hence, B1R and B2R antagonists appear potential therapeutic agents to manage post fracture pain.

Acute Bradykinin Receptor Blockade During Hemorrhagic Shock in Mice Prevents the Worsening Hypotensive Effect of Angiotensin-Converting Enzyme Inhibitor.

OBJECTIVES: Angiotensin-converting enzyme inhibitors are associated with deleterious hypotension during anesthesia and shock. Because the pharmacologic effects of angiotensin-converting enzyme inhibitors are partly mediated by increased bradykinin B2 receptor activation, this study aimed to determine the impact of acute B2 receptor blockade during hemorrhagic shock in angiotensin-converting enzyme inhibitor-treated mice. DESIGN: In vivo study. SETTING: University research unit. SUBJECTS: C57/Bl6 mice. INTERVENTIONS: The hemodynamic effect of B2 receptor blockade using icatibant (B2 receptor antagonist) was studied using a pressure-targeted hemorrhagic shock and a volume-targeted hemorrhagic shock. Animals were anesthetized with ketamine and xylazine (250 mg/kg and 10 mg/kg, respectively), intubated using intratracheal cannula, and ventilated (9 mL/kg, 150 min). Five groups were studied: 1) sham-operated animals, 2) control shocked mice, 3) shocked mice treated with ramipril for 7 days (angiotensin-converting enzyme inhibitors) before hemorrhagic shock, 4) shocked mice treated with angiotensin-converting enzyme inhibitors and a single bolus of icatibant (HOE-140) immediately before anesthesia (angiotensin-converting enzyme inhibitors + icatibant), and 5) shocked mice treated with a single bolus of icatibant. One hour after volume-targeted hemorrhagic shock, blood lactate was measured to evaluate organ failure. MEASUREMENTS AND MAIN RESULTS: During pressure-targeted hemorrhagic shock, the mean blood volume withdrawn was significantly lower in the angiotensin-converting enzyme inhibitor group than in the other groups (p < 0.001). During volume-targeted hemorrhagic shock, icatibant prevented blood pressure lowering in the angiotensin-converting enzyme inhibitor group (p < 0.001). Blood lactate was significantly higher in the angiotensin-converting enzyme inhibitor group than in the other groups, particularly the HOE groups. CONCLUSIONS: During hemorrhagic shock, acute B2 receptor blockade significantly attenuates the deleterious hemodynamic effect of angiotensin-converting enzyme inhibitor treatment in mice. This beneficial effect of B2 receptor blockade is rapidly reached and sustained with a single bolus of icatibant. This benefit could be of interest in angiotensin-converting enzyme inhibitor-treated patients during both emergency anesthesia and resuscitation.

Beneficial effects of levobupivacaine regional anaesthesia on postoperative opioid induced hyperalgesia in diabetic mice.

BACKGROUND: Diabetic neuropathy is one of the most common complications of diabetes and causes various problems in daily life. The aim of this study was to assess the effect of regional anaesthesia on post surgery opioid induced hyperalgesia in diabetic and non-diabetic mice. METHODS: Diabetic and non-diabetic mice underwent plantar surgery. Levobupivacaine and sufentanil were used before surgery, for sciatic nerve block (regional anaesthesia) and analgesia, respectively. Diabetic and non-diabetic groups were each randomly assigned to three subgroups: control, no sufentanil and no levobupivacaine; sufentanil and no levobupivacaine; sufentanil and levobupivacaine. Three tests were used to assess pain behaviour: mechanical nociception; thermal nociception and guarding behaviours using a pain scale. RESULTS: Sufentanil, alone or in combination with levobupivacaine, produced antinociceptive effects shortly after administration. Subsequently, sufentanil induced hyperalgesia in diabetic and non-diabetic mice. Opioid-induced hyperalgesia was enhanced in diabetic mice. Levobupivacaine associated to sufentanil completely prevented hyperalgesia in both groups of mice. CONCLUSION: The results suggest that regional anaesthesia can decrease opioid-induced hyperalgesia in diabetic as well as in non-diabetic mice. These observations may be clinically relevant for the management of diabetic patients.

Genetic manipulation and genetic variation of the kallikrein-kinin system: impact on cardiovascular and renal diseases.

Genetic manipulation of the kallikrein-kinin system (KKS) in mice, with either gain or loss of function, and study of human genetic variability in KKS components which has been well documented at the phenotypic and genomic level, have allowed recognizing the physiological role of KKS in health and in disease. This role has been especially documented in the cardiovascular system and the kidney. Kinins are produced at slow rate in most organs in resting condition and/or inactivated quickly. Yet the KKS is involved in arterial function and in renal tubular function. In several pathological situations, kinin production increases, kinin receptor synthesis is upregulated, and kinins play an important role, whether beneficial or detrimental, in disease outcome. In the setting of ischemic, diabetic or hemodynamic aggression, kinin release by tissue kallikrein protects against organ damage, through B2 and/or B1 bradykinin receptor activation, depending on organ and disease. This has been well documented for the ischemic or diabetic heart, kidney and skeletal muscle, where KKS activity reduces oxidative stress, limits necrosis or fibrosis and promotes angiogenesis. On the other hand, in some pathological situations where plasma prekallikrein is inappropriately activated, excess kinin release in local or systemic circulation is detrimental, through oedema or hypotension. Putative therapeutic application of these clinical and experimental findings through current pharmacological development is discussed in the chapter.

Role of kinin B2 receptors in opioid-induced hyperalgesia in inflammatory pain in mice.

Postoperative pain management is a clinical challenge that can be complicated by opioid-induced hyperalgesia (OIH). Kinin receptors could mediate both the acute and chronic phases of inflammation and pain. A few recent studies suggest that dynorphin A could maintain neuropathic pain by activating the bradykinin (BK) receptor. Thus, the effect of a single administration of sufentanil (a µ-opioid receptor agonist) was investigated in a model of carrageenan-induced inflammatory pain using three strains of mice, i.e., knockout mice for one kinin receptor, B1R or B2R (B1KO, B2KO), and wild-type C57/BL6J mice (WT) treated with either a B1R (R954) or a B2R antagonist (HOE140) or a KKS inhibitor (aprotinin). Pain was assessed and compared between the different groups using two behavioral tests exploring mechanical (von Frey filaments) and thermal (Hargreaves test) sensitivity. Pretreatment with sufentanil induced a sustained increase in pain sensitivity with a delayed return to baseline values characterizing an OIH in carrageenan-injected mice only. Sufentanil-induced OIH was not observed in B2KO but persisted in B1KO and was blunted by aprotinin and the B2R antagonist only. Collectively, our data indicate that the B2R receptor and BK synthesis or availability are essential peripheral steps in the mechanism leading to OIH in a pain context.

Bradykinin inhibits high glucose- and growth factor-induced collagen synthesis in mesangial cells through the B2-kinin receptor.

Mesangial matrix expansion is an early lesion leading to glomeruloclerosis and chronic renal diseases. A beneficial effect is achieved with angiotensin I-converting enzyme inhibitors (ACEI), which also favor bradykinin (BK) B2 receptor (B2R) activation. To define the underlying mechanism, we hypothesized that B2R activation could be a negative regulator of collagen synthesis in mesangial cells (MC). We investigated the effect of BK on collagen synthesis and signaling in MC. Inflammation was evaluated by intercellular adhesion molecule-1 (ICAM-1) expression. BK inhibited collagen I and IV synthesis stimulated by high glucose, epithelial growth factor (EGF), and transforming growth factor-ß (TGF-ß) but did not alter ICAM-1. Inhibition of collagen synthesis was B2R but not B1R mediated. PKC or phosphatidylinositol 3-kinase (PI3K) inhibitors mimicked the BK effect. B2R activation inhibited TGF-ß- and EGF-induced Erk1/2, Smad2/3, Akt S473, and EGFR phosphorylation. A phosphatase inhibitor prevented BK effects. The in vivo impact of B2R on mesangial matrix expansion was assessed in streptozotocin-diabetic rodents. Deletion of B2R increased mesangial matrix expansion and albuminuria in diabetic mice. In diabetic rats, matrix expansion and albuminuria were prevented by ACEI but not by ACEI and B2R antagonist cotreatment. Consistently, the lowered BK content of diabetic glomeruli was restored by ACEI. In conclusion, deficient B2R activation aggravated mesangial matrix expansion in diabetic rodents whereas B2R activation reduced MC collagen synthesis by a mechanism targeting Erk1/2 and Akt, common pathways activated by EGF and TGF-ß. Taken together, the data support the hypothesis of an antifibrosing effect of B2R activation.

Morphologic and functional renal impact of acute kidney injury after prolonged hemorrhagic shock in mice.

OBJECTIVE: Sparse data are available on renal consequences of hemorrhagic shock in mice. This study aimed to extend the current knowledge on functional and morphologic renal impact of hemorrhagic shock in mice and to determine its ability to stand as an accurate model of acute kidney injury. DESIGN: In vivo study. SETTING: University research unit. SUBJECTS: C57/Bl6 mice. INTERVENTIONS: A model of controlled hemorrhagic shock was adapted to determine the renal impact of hemorrhagic shock in mice. MEASUREMENTS AND MAIN RESULTS: Renal functions and kidney morphology were followed up from 3 hrs to 21 days after hemorrhagic shock. When prolonged up to 2 hrs, hypotension (35 mm Hg mean arterial blood pressure) induced by temporary blood removal was responsible for an early and lasting increase in hypoxia-inducible factor-1α and kidney-inducible molecule-1 gene expression that paralleled acute tubular necrosis and renal failure. Two-hr hypotension induced an important but reversible decrease in glomerular filtration rate up to 6 days after hemorrhagic shock. Other renal dysfunctions included a renal loss of sodium, assessed by the increase in sodium excretion, and a decrease in urine concentration that persists up to day 21. Tissular damages prevailed in the outer medulla 2 days after hemorrhagic shock, being maximal at day 6. At day 21, renal healing was associated with epithelial recovery and a significant interstitial fibrosis. CONCLUSIONS: Our data indicate that apparent recovery of renal function after acute kidney injury can mask persisting dysfunctions and tissular damages that could predispose to chronic kidney disease. Prolonged hemorrhagic shock in mice closely mimics renal effects induced by similar situation in humans, thus providing a useful tool to investigate pathophysiological mechanisms and protection strategies against acute kidney injury in situations such as hemorrhagic shock.

Kinins and Kinin Receptors in Cardiovascular and Renal Diseases.

This review addresses the physiological role of the kallikrein-kinin system in arteries, heart and kidney and the consequences of kallikrein and kinin actions in diseases affecting these organs, especially ischemic and diabetic diseases. Emphasis is put on pharmacological and genetic studies targeting kallikrein; ACE/kininase II; and the two kinin receptors, B1 (B1R) and B2 (B2R), distinguished through the work of Domenico Regoli and his collaborators. Potential therapeutic interest and limitations of the pharmacological manipulation of B1R or B2R activity in cardiovascular and renal diseases are discussed. This discussion addresses either the activation or inhibition of these receptors, based on recent clinical and experimental studies.

Kallikrein/K1, Kinins, and ACE/Kininase II in Homeostasis and in Disease Insight From Human and Experimental Genetic Studies, Therapeutic Implication.

Kallikrein-K1 is the main kinin-forming enzyme in organs in resting condition and in several pathological situations whereas angiotensin I-converting enzyme/kininase II (ACE) is the main kinin-inactivating enzyme in the circulation. Both ACE and K1 activity levels are genetic traits in man. Recent research based mainly on human genetic studies and study of genetically modified mice has documented the physiological role of K1 in the circulation, and also refined understanding of the role of ACE. Kallikrein-K1 is synthesized in arteries and involved in flow-induced vasodilatation. Endothelial ACE synthesis displays strong vessel and organ specificity modulating bioavailability of angiotensins and kinins locally. In pathological situations resulting from hemodynamic, ischemic, or metabolic insult to the cardiovascular system and the kidney K1 and kinins exert critical end-organ protective action and K1 deficiency results in severe worsening of the conditions, at least in the mouse. On the opposite, genetically high ACE level is associated with increased risk of developing ischemic and diabetic cardiac or renal diseases and worsened prognosis of these diseases. The association has been well-documented clinically while causality was established by ACE gene titration in mice. Studies suggest that reduced bioavailability of kinins is prominently involved in the detrimental effect of K1 deficiency or high ACE activity in diseases. Kinins are involved in the therapeutic effect of both ACE inhibitors and angiotensin II AT1 receptor blockers. Based on these findings, a new therapeutic hypothesis focused on selective pharmacological activation of kinin receptors has been launched. Proof of concept was obtained by using prototypic agonists in experimental ischemic and diabetic diseases in mice.

Inhibition of renin angiotensin system decreases renal protein oxidative damage in diabetic rats.

Renin angiotensin system (RAS) worsens diabetic nephropathy (DN) by increasing oxidative stress. We compared the effect of three different RAS inhibitors: the angiotensin converting enzyme inhibitor Ramipril, the vasopeptidase inhibitor AVE7688 and the angiotensin receptor (AT1) antagonist Losartan on the formation of oxidative and carbonyl stress derived protein modifications in kidney from Zucker obese hyperglycemic rats (ZDFn Gm-fa/fa). Gas chromatography-mass spectrometry was used to measure representative markers of several protein oxidative pathways: direct oxidation [dinitrophenylhydrazine reactive carbonyls (DNP), glutamic (GSA), and aminoadipic (AASA) semialdehydes], mixed glyco- and lipoxidation [N(epsilon)-carboxyethyl-lysine (CEL) and N(epsilon)-(carboxymethyl)-lysine (CML)] and lipoxidation-[N(epsilon)-(malondialdehyde)-lysine-(MDAL)], as well as renal fatty acid composition. Urinary albumin (a marker of DN), DNP, GSA, and MDAL levels, were increased in all obese rats and were dose dependently decreased by AVE7688 whereas Ramipril and Losartan were less efficient. These results show that RAS inhibition improves DN at several levels, independently of its effects on blood pressure and glycemic control, via mechanisms depending of renal oxidative stress.

Mouse model of fracture pain.

BACKGROUND: The aim of this study was to validate a model of postfracture pain in mice, which was evaluated in the presence and the absence of morphine and ketoprofen. METHODS: The study was divided into two parts: protocol A, the effects of closed fracture; and protocol B, the effects of morphine and ketoprofen on fracture pain. In protocol A, mice were assigned to three groups: group 1, sham incision; group 2, sham pinning; or group 3, fracture. In protocol B, mice were randomly assigned to four groups to receive morphine (3 or 10 mg/kg body weight), ketoprofen (50 mg/kg body weight), or placebo (vehicle). Three tests were used to assess pain behavior: von Frey filament application, hot plate test, and a subjective pain scale. RESULTS: In protocol A, thermal nociception, mechanical nociception, and subjective pain were significantly modified in group 3 (fractured) compared with control groups 1 and 2 (sham groups). In protocol B, when tests were repeated for 240 min in morphine-treated animals and in ketoprofen-treated animals, reduction of mechanical nociception, thermal nociception, and subjective pain scale score were observed. Morphine and ketoprofen administration provided the same effect on behavioral testing on postoperative days 1 and 2. CONCLUSION: This mouse model seems to be a reliable and reproducible tool to investigate the effect of closed bone fracture on several parameters, such as pain, remodeling, and recovery. Moreover, it allows studying the effects of various pharmacologic treatments as well as the involvement of various systems using different genetically modified strains of mice.

In vivo bradykinin B2 receptor activation reduces renal fibrosis.

Angiotensin-converting enzyme (ACE) inhibitors reduce the progression of various fibrotic renal diseases both in humans and in animal models. Unilateral ureteral obstruction (UUO) is an animal model of accelerated renal tubulointerstitial fibrosis that is attenuated by ACE inhibition. Although ACE inhibitors increase bradykinin concentrations in addition to their effect on angiotensin II formation, the role of bradykinin in renal fibrosis has not been studied. We show here that genetic ablation (B2(-/-) mice) or pharmacological blockade of the bradykinin B2 receptor increases UUO-induced interstitial fibrosis in mice, whereas transgenic rats expressing increased endogenous bradykinin show reduced UUO-induced interstitial fibrosis. The increased interstitial fibrosis in B2(-/-) mice was accompanied by a decreased activity of plasminogen activators (PAs) and metalloproteinase-2 (MMP-2), enzymes involved in ECM degradation, suggesting that the protective effects of bradykinin involve activation of a B2 receptor/PA/MMP-2 cascade. This ability of bradykinin to increase PA activity was confirmed in primary culture proximal tubular cells. Thus, in both mice and rats, bradykinin B2 receptor activation reduces renal tubulointerstitial fibrosis in vivo, most likely by increasing ECM degradation.

[New perspectives for bradykinin in nephroprotection]. / Bradykinine et néphroprotection: pourquoi? comment? Perspectives.

Various diseases such as arterial hypertension, diabetes and obesity result in renal diseases which are often irreversible and resistant to currently available therapies. Beside the control of glycemia in diabetic patients, only the blockade of the renin-angiotensin system is effective in reducing the occurrence of glomerulosclerosis and its development towards terminal renal failure. Inhibition of this system is based on the use of angiotensin-1 converting enzyme inhibitors (ACEI) and angiotensin AT1 receptor antagonists. For many years, the beneficial effects of these two classes of drugs were attributed mainly to their interference with angiotensin II. However, recent in vitro and in vivo evidences strongly suggest that bradykinin B2 receptor is also involved in the nephroprotective effects of these drugs. A compelling evidence is the finding that the development of glomerulosclerosis is more severe in knock-out B2 receptor mice. The nephroprotective effect of B2 receptor could be the consequence of a reduction of proteinuria, glomerular and interstitial fibrosis, cell proliferation and of the oxidative stress through the contribution of several well identified mechanisms. It is proposed that B2 receptor agonists can offer a novel therapeutic avenue in the treatment of nephropathies associated with diabetes or other vascular diseases.

Antidiabetic Effects of Aqueous and Dichloromethane/Methanol Stem Bark Extracts of Pterocarpus soyauxii Taub (Papilionaceae) on Streptozotocin-induced Diabetic Rats.

AIM OF THE STUDY: The aim is to evaluate the hypoglycemic and antidiabetic effects of aqueous and CH2Cl2/CH3OH stem bark extracts of Pterocarpus soyauxii Taub in normal and diabetic rats. MATERIALS AND METHODS: Streptozotocin (STZ)-induced diabetic and normal adult Wistar rats were orally administered with aqueous and CH2Cl2/CH3OH plant extracts of P. soyauxii at various doses (38-300 mg/kg) in a single administration. In addition, STZ-induced diabetic rats received prolonged daily administration for 14 days. Glibenclamide (GB) (10 mg/kg) was used as reference treatment. In acute test, fasting blood glucose was followed for 5 h. In subacute test, body weight, food and water intakes, and blood glucose were followed weekly and serum biochemical parameters evaluated after 14 days treatment. RESULTS: Acute administration of aqueous and CH2Cl2/CH3OH stem bark extracts moderately decreased fasting blood glucose compared to GB, significantly in normal rats (P < 0.05 to P < 0.01) but, as GB, not significantly in diabetic rats. Prolonged treatments in diabetic rats with aqueous and CH2Cl2/CH3OH extracts reduced blood glucose to an extent, respectively, superior or similar to GB. Moreover, P. soyauxii also significantly (P < 0.01) reduced weight loss, and diabetes increased serum triglycerides, total cholesterol, and transaminases (alanine aminotransferase/aspartate aminotransferase) elevations. CONCLUSION: P. soyauxii Taub stem bark extracts have possible value for antidiabetic oral medication. SUMMARY: Aqueous and Dichloromethane/Methanol stem bark extracts of Pterocarpus soyauxii Taub have potent (compared to Glibenclamide) antidiabetic effects in STZ-diabetic rats, with specific kinetics and dose-responses.Moderate hypoglycemia effects upon acute P. soyauxii administration.Potent anti-hyperglycemic effects of sub-acute P. soyauxii administration in STZ-diabetic rats.Potent anti-hyperlipidemic effects of sub-acute P. soyauxii administration in STZ-diabetic rats.Improved hepatic and renal serum parameters after sub-acute P. soyauxii administration in STZ-diabetic rats.P. soyauxii extracts may be useful for oral treatment of diabetes and related metabolic disorders. Abbreviations Used: CH2Cl2/CH3OH: Dichloromethane/Methanol; STZ: Streptozotocin; GB: Glibenclamide; AE: Aqueous extract; OE: Organic extract; FeCl3: Iron (III) chloride; NaCl: Sodium chloride; K3Fe(CN)6: Potassium ferricyanide; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; H: Hour; BW: Body weight, W1 and W2: Weeks 1 and 2; CHOD: Cholesterol oxidase; GPO: Glycerol-3 Phosphate oxidase; PAP: Phenol + Aminophenazone.

Induction of functional bradykinin b(1)-receptors in normotensive rats and mice under chronic Angiotensin-converting enzyme inhibitor treatment.

BACKGROUND: The physiological effects of ACE inhibitors may act in part through a kinin-dependent mechanism. We investigated the effect of chronic ACE-inhibitor treatment on functional kinin B(1)- and B(2)-receptor expression, which are the molecular entities responsible for the biological effects of kinins. METHODS AND RESULTS: Rats were subjected to different 6-week treatments using various mixtures of the following agents: ACE inhibitor, angiotensin AT(1)-receptor antagonist, and B(1)- and B(2)-receptor antagonists. Chronic ACE inhibition induced both renal and vascular B(1)-receptor expression, whereas B(2)-receptor expression was not modified. Furthermore, with B(1)-receptor antagonists, it was shown that B(1)-receptor induction was involved in the hypotensive effect of ACE inhibition. Using microdissection, we prepared 10 different nephron segments and found ACE-inhibitor-induced expression of functional B(1)-receptors in all segments. ACE-inhibitor-induced B(1)-receptor induction involved homologous upregulation, because it was prevented by B(1)-receptor antagonist treatment. Finally, using B(2)-receptor knockout mice, we showed that ACE-inhibitor-induced B(1)-receptor expression was B(2)-receptor independent. CONCLUSIONS: This study provides the first evidence that chronic ACE-inhibitor administration is associated with functional vascular and renal B(1)-receptor induction, which is involved in ACE-inhibitor-induced hypotension. The observed B(1)-receptor induction in the kidney might participate in the known renoprotective effects of ACE inhibition.

The protective effect of angiotensin converting enzyme inhibition in experimental renal fibrosis in mice is not mediated by bradykinin B2 receptor activation.

Unilateral ureteral obstruction (UUO) is an animal model of accelerated renal tubulointerstitial fibrosis. We have recently shown, using this model, that mice lacking the bradykinin B2-receptor (B2(-/-)) were more susceptible than control animals to the development of tubulointerstitial fibrosis. Angiotensin converting enzyme (ACE) inhibition slows down UUO-induced renal fibrosis. Since ACE-inhibition increases bradykinin and decreases angiotensin II concentrations we have verified if bradykinin is involved in the antifibrotic effects of ACE-inhibition using the UUO-model and B2(-/-) mice. Surprisingly, although ACE-inhibition significantly reduced renal fibrosis, no difference was observed between the degree of tubulointerstitial fibrosis, macrophage infiltration and cell proliferation between ACE-inhibitor treated B2(+/+) and B2(-/-) mice suggesting the absence of a role of the B2-receptor in the antifibrotic effects of ACE-inhibition. This was confirmed at the level of bradykinin-induced activity of enzymes involved in the degradation of the extracellular matrix. However in both mouse strains, ACE-inhibitors were more efficient than AT1 receptor antagonists.

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.

[Bradykinin receptors: towards new pathophysiological roles]. / Les récepteurs de la bradykinine: de nouveaux rôles physio- pathologiques.

In addition to being a pro-inflammatory mediator, bradykinin is now recognized as a neuromediator and regulator of several vascular and renal functions. New breakthroughs point to unusual and atypical signalling pathways for a G-protein coupled receptor that could explain the anti-proliferative and anti-fibrogenic effects of bradykinin. The availability of transgenic and knock out animal models for bradykinin receptors or bradykinin-synthesizing or -catabolic enzymes confirms these cardiac and renal protective roles for this peptide system. Bradykinin receptors are involved in the therapeutic action of angiotensin-1 converting enzyme inhibitors that are used in the treatment of arterial hypertension, heart failure and diabetes. Nevertheless, recent evidence highlights dissimilar mechanisms in the regulation and function of these receptors between the central nervous system and peripheral tissues. Therefore, the development of more specific bradykinin receptor agonists or antagonists devoid of central actions seems to evolve as a new therapeutic approach.