Inhibitory effect of a novel bradykinin B1 receptor antagonist, R-954, on enhanced vascular permeability in type 1 diabetic mice

Genetic Ablation and Pharmacological Blockade of Bradykinin B1 Receptor Unveiled a Detrimental Role for the Kinin System in Chagas Disease Cardiomyopathy

Chagas disease, the parasitic infection caused by Trypanosoma cruzi, afflicts about 6 million people in Latin America. Here, we investigated the hypothesis that T. cruzi may fuel heart parasitism by activating B1R, a G protein-coupled (brady) kinin receptor whose expression is upregulated in inflamed tissues. Studies in WT and B1R^-/- mice showed that T. cruzi DNA levels (15 days post infection-dpi) were sharply reduced in the transgenic heart. FACS analysis revealed that frequencies of proinflammatory neutrophils and monocytes were diminished in B1R^-/- hearts whereas CK-MB activity (60 dpi) was exclusively detected in B1R^+/+ sera. Since chronic myocarditis and heart fibrosis (90 dpi) were markedly attenuated in the transgenic mice, we sought to determine whether a pharmacological blockade of the des-Arg⁹-bradykinin (DABK)/B1R pathway might alleviate chagasic cardiomyopathy. Using C57BL/6 mice acutely infected by a myotropic T. cruzi strain (Colombian), we found that daily treatment (15-60 dpi) with R-954 (B1R antagonist) reduced heart parasitism and blunted cardiac injury. Extending R-954 treatment to the chronic phase (120-160 dpi), we verified that B1R targeting (i) decreased mortality indexes, (ii) mitigated chronic myocarditis, and (iii) ameliorated heart conduction disturbances. Collectively, our study suggests that a pharmacological blockade of the proinflammatory KKS/DABK/B1R pathway is cardioprotective in acute and chronic Chagas disease.

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.

Expression, distribution and function of kinin B1 receptor in the rat diabetic retina

BACKGROUND AND PURPOSE

The kinin B₁ receptor contributes to vascular inflammation and blood-retinal barrier breakdown in diabetic retinopathy (DR). We investigated the changes in expression, cellular localization and vascular inflammatory effect of B₁ receptors in retina of streptozotocin diabetic rats.

EXPERIMENTAL APPROACH

The distribution of B₁ receptors on retinal cell types was investigated by immunocytochemistry. Effects of B₁ receptor agonist, R-838, and antagonist, R-954, on retinal leukocyte adhesion, gene expression of kinin and VEGF systems, B₁ receptor immunoreactivity, microgliosis and capillary leakage were measured. Effect of B₁ receptor siRNA on gene expression was also assessed.

KEY RESULTS

mRNA levels of the kinin and VEGF systems were significantly enhanced at 2 weeks in streptozotocin (STZ)-retina compared to control-retina and were further increased at 6 weeks. B₁ receptor mRNA levels remained increased at 6 months. B₁ receptor immunolabelling was detected in vascular layers of the retina, on glial and ganglion cells. Intravitreal R-838 amplified B₁ and B₂ receptor gene expression, B₁ receptor levels (immunodetection), leukostasis and vascular permeability at 2 weeks in STZ-retina. Topical application (eye drops) of R-954 reversed these increases in B₁ receptors, leukostasis and vascular permeability. Intravitreal B₁ receptor siRNA inhibited gene expression of kinin and VEGF systems in STZ-retina. Microgliosis was unaffected by R-838 or R-954 in STZ-retina.

CONCLUSION AND IMPLICATIONS

Our results support the detrimental role of B₁ receptors on endothelial and glial cells in acute and advanced phases of DR. Topical application of the B₁ receptor antagonist R-954 seems a feasible therapeutic approach for the treatment of DR.

Kinin B1 receptors as a therapeutic target for inflammation

INTRODUCTION

Kinins are peptide mediators exerting their pro-inflammatory actions by the selective stimulation of two distinct G-protein coupled receptors, termed BKB1R and BKB2R. While BKB2R is constitutively expressed in a multitude of tissues, BKB1R is hardly expressed at baseline but highly inducible by inflammatory mediators. In particular, BKB1R was shown to be involved in the pathogenesis of numerous inflammatory diseases. Areas covered: This review intends to evaluate the therapeutic potential of substances interacting with the BKB1R. To this purpose we summarize the published literature on animal studies with antagonists and knockout mice for this receptor. Expert Opinion: In most cases the pharmacological inhibition of BKB1R or its genetic deletion was beneficial for the outcome of the disease in animal models. Therefore, several companies have developed BKB1R antagonists and tested them in phase I and II clinical trials. However, none of the developed BKB1R antagonists was further developed for clinical use. We discuss possible reasons for this failure of translation of preclinical findings on BKB1R antagonists into the clinic.

Radiolabeled R954 Derivatives for Imaging Bradykinin B1 Receptor Expression with Positron Emission Tomography

Peptide receptors have emerged as promising targets for diagnosis and therapy. The aberrant overexpression of these receptors in different cancer subtypes allows for the adoption of new treatment strategies that complement conventional chemotherapies. Bradykinin B1 receptor (B1R) is a G protein-coupled receptor that is overexpressed in many cancers, with limited expression in healthy tissues. Previously, we developed ⁶⁸Ga- and ¹⁸F-labeled derivatives of B1R antagonist peptides B9858 and B9958, and successfully targeted B1R-expressing tumor xenografts in vivo. R954 (Ac-Orn-Arg-Oic-Pro-Gly-αMePhe-Ser-d-2-Nal-Ile), a potent B1R antagonist, is reportedly more stable than B9858 against peptidase degradation. We evaluated two radiolabeled derivatives of R954 (⁶⁸Ga-HTK01083 and ¹⁸F-HTK01146) for B1R PET imaging. Peptides were synthesized via solid phase strategy. Nonradioactive standards were obtain by reacting GaCl₃ with DOTA-dPEG2-R954 and by clicking N-propargyl-N,N-dimethylammoniomethyl-trifluoroborate with azidoacetyl-dPEG2-R954. Binding affinity for B1R was determined by an in vitro competition binding assay. ⁶⁸Ga-HTK01083 was obtained by incubating DOTA-dPEG2-R954 with ⁶⁸GaCl₃ under acidic conditions, while ¹⁸F-HTK01146 was prepared via an ¹⁸F-¹⁹F isotope exchange reaction. Biodistribution and imaging studies were conducted at 1 h postinjection (p.i.) in mice inoculated with B1R-expressing (B1R+) and B1R-nonexpressing (B1R-) cells. HTK01083 and HTK01146 bound B1R with good affinity (K_i = 30.5 and 24.8 nM, respectively). ⁶⁸Ga/¹⁸F-labeled R954 were obtained on average in ≥10% decay-corrected radiochemical yield with >99% radiochemical purity and ≥52 GBq/μmol specific activity. For both tracers, clearance was predominantly renal with minimal involvement of the hepatobiliary system. For PET images, B1R+ tumors, kidneys, and bladder were visible. At 1 h p.i., uptake in B1R+ tumor was comparable between ⁶⁸Ga-HTK01083 (8.46 ± 1.44%ID/g) and ¹⁸F-HTK01146 (9.25 ± 0.69%ID/g). B1R+ tumor-to-blood and B1R+ tumor-to-muscle ratios were 6.32 ± 1.44 and 20.7 ± 3.58 for ⁶⁸Ga-HTK01083, and 7.24 ± 2.56 and 19.5 ± 4.29 for ¹⁸F-HTK01146. Our results indicate R954 is a good lead sequence for optimization of B1R tracers for cancer imaging.

Regardless of etiology, progressive renal disease causes ultrastructural and functional alterations of peritubular capillaries

Progressive renal diseases are associated with rarefaction of peritubular capillaries, but the ultrastructural and functional alterations of the microvasculature are not well described. To study this, we analyzed different time points during progressive kidney damage and fibrosis in 3 murine models of different disease etiologies. These models were unilateral ureteral obstruction, unilateral ischemia-reperfusion injury, and Col4a3-deficient mice, we analyzed ultrastructural alterations in patient biopsy specimens. Compared with kidneys of healthy mice, we found a significant and progressive reduction of peritubular capillaries in all models analyzed. Ultrastructurally, compared with the kidneys of control mice, focal widening of the subendothelial space and higher numbers of endothelial vacuoles and caveolae were found in fibrotic kidneys. Quantitative analysis showed that peritubular capillary endothelial cells in fibrotic kidneys had significantly and progressively reduced numbers of fenestrations and increased thickness of the cell soma and lamina densa of the capillary basement membrane. Similar ultrastructural changes were also observed in patient's kidney biopsy specimens. Compared with healthy murine kidneys, fibrotic kidneys had significantly increased extravasation of Evans blue dye in all 3 models. The extravasation could be visualized using 2-photon microscopy in real time in living animals and was mainly localized to capillary branching points. Finally, fibrotic kidneys in all models exhibited a significantly greater degree of interstitial deposition of fibrinogen. Thus, peritubular capillaries undergo significant ultrastructural and functional alterations during experimental progressive renal diseases, independent of the underlying injury. Analyses of these alterations could provide read-outs for the evaluation of therapeutic approaches targeting the renal microvasculature.

Vascular endothelial growth factor-A165b prevents diabetic neuropathic pain and sensory neuronal degeneration

Diabetic peripheral neuropathy affects up to half of diabetic patients. This neuronal damage leads to sensory disturbances, including allodynia and hyperalgesia. Many growth factors have been suggested as useful treatments for prevention of neurodegeneration, including the vascular endothelial growth factor (VEGF) family. VEGF-A is generated as two alternative splice variant families. The most widely studied isoform, VEGF-A165a is both pro-angiogenic and neuroprotective, but pro-nociceptive and increases vascular permeability in animal models. Streptozotocin (STZ)-induced diabetic rats develop both hyperglycaemia and many of the resulting diabetic complications seen in patients, including peripheral neuropathy. In the present study, we show that the anti-angiogenic VEGF-A splice variant, VEGF-A165b, is also a potential therapeutic for diabetic neuropathy. Seven weeks of VEGF-A165b treatment in diabetic rats reversed enhanced pain behaviour in multiple behavioural paradigms and was neuroprotective, reducing hyperglycaemia-induced activated caspase 3 (AC3) levels in sensory neuronal subsets, epidermal sensory nerve fibre loss and aberrant sciatic nerve morphology. Furthermore, VEGF-A165b inhibited a STZ-induced increase in Evans Blue extravasation in dorsal root ganglia (DRG), saphenous nerve and plantar skin of the hind paw. Increased transient receptor potential ankyrin 1 (TRPA1) channel activity is associated with the onset of diabetic neuropathy. VEGF-A165b also prevented hyperglycaemia-enhanced TRPA1 activity in an in vitro sensory neuronal cell line indicating a novel direct neuronal mechanism that could underlie the anti-nociceptive effect observed in vivo. These results demonstrate that in a model of Type I diabetes VEGF-A165b attenuates altered pain behaviour and prevents neuronal stress, possibly through an effect on TRPA1 activity.

Preclinical pharmacology, metabolic stability, pharmacokinetics and toxicology of the peptidic kinin B1 receptor antagonist R-954

We previously showed that R-954 (AcOrn[Oic(2),(αMe)Phe(5),dβNal(7),Ile(8)]desArg(9)-bradykinin) is a potent, selective and stable peptide antagonist of the inducible GPCR kinin B1 receptor. This compound shows potential applications for the treatment of several diseases, including cancer and neurological disturbances of diabetes. To enable clinical translation, more information regarding its pharmacological, pharmacokinetics (PK) and toxicological properties at preclinical stage is warranted. This was the principal objective of the present study. Herein, specificity of R-954 was characterized in binding studies on 133 human molecular targets to reveal minor cross-reactivities against the angiotensin AT2 and the bombesin receptors (110- and 330-fold lower affinity than for B1R, respectively). The pharmacokinetic of R-954 was studied in both normal and streptozotocin-diabetic anaesthetized rats providing half-lives of 1.9-2.7h. R-954 does not appear to be metabolized in the rat circulation and in several rat tissue homogenates, as the kidney, lung and liver. It appears to be excreted as parent drug in the bile (21%) and in urine. A preliminary toxicological profile of R-954 was obtained in rats under various administration routes. R-954 appears to be well tolerated. Overall, these results indicate that R-954 exhibits favorable preclinical pharmacological/PK characteristics and encouraging safety profiles, suitable for early studies in humans.

The kallikrein-kinin system in diabetic retinopathy

Diabetic retinopathy (DR) is a major microvascular complication associated with type 1 and type 2 diabetes mellitus, which can lead to visual impairment and blindness. Current treatment strategies for DR are mostly limited to laser therapies, steroids, and anti-VEGF agents, which are often associated with unwanted side effects leading to further complications. Recent evidence suggests that kinins play a primary role in the development of DR through enhanced vascular permeability, leukocytes infiltration, and other inflammatory mechanisms. These deleterious effects are mediated by kinin B1 and B2 receptors, which are expressed in diabetic human and rodent retina. Importantly, kinin B1 receptor is virtually absent in sane tissue, yet it is induced and upregulated in diabetic retina. These peptides belong to the kallikrein-kinin system (KKS), which contains two separate and independent pathways of regulated serine proteases, namely plasma kallikrein (PK) and tissue kallikrein (TK) that are involved in the biosynthesis of bradykinin (BK) and kallidin (Lys-BK), respectively. Hence, ocular inhibition of kallikreins or antagonism of kinin receptors offers new therapeutic avenues in the treatment and management of DR. Herein, we present an overview of the principal features and known inflammatory mechanisms associated with DR along with the current therapeutic approaches and put special emphasis on the KKS as a new and promising therapeutic target due to its link with key pathways directly associated with the development of DR.

MAPK/NF-κB-dependent upregulation of kinin receptors mediates airway hyperreactivity: a new perspective for the treatment

Airway hyperreactivity (AHR) is a major feature of asthmatic and inflammatory airways. Cigarette smoke exposure, and bacterial and viral infections are well-known environmental risk factors for AHR, but knowledge about the underlying molecular mechanisms on how these risk factors lead to the development of AHR is limited. Activation of intracellular mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) and their related signal pathways including protein kinase C (PKC), phosphoinositide 3-kinase (PI3K) and protein kinase A (PKA) signaling pathways may result in airway kinin receptor upregulation, which is suggested to play an important role in the development of AHR. Environmental risk factors trigger the production of pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and interleukins (ILs) that activate intracellular MAPK- and NF-κB-dependent inflammatory pathways, which subsequently lead to AHR via kinin receptor upregulation. Blockage of intracellular MAPK/NF-κB signaling prevents kinin B₁ and B₂ receptor expression in the airways, resulting in a decrease in the response to bradykinin (kinin B₂ receptor agonist) and des-Arg⁹-bradykinin (kinin B₁ receptor agonist). This suggests that MAPK- and NF-κB-dependent kinin receptor upregulation can provide a novel option for treatment of AHR in asthmatic as well as in other inflammatory airway diseases.

Alternative pathways in the development of diabetic retinopathy: the renin-angiotensin and kallikrein-kinin systems

Diabetic retinopathy is a common complication of both type 1 and type 2 diabetes and is the leading cause of blindness in people of working age. Current treatment strategies are mostly limited to laser photocoagulation, which restricts proliferative retinopathic changes but also causes irreversible damage to the retina. This review examines two important pathways involved in regulating vascular function and their role in the development of diabetic retinopathy. One, the renin-angiotensin system, is well known and has established angiogenic effects on the retina that increase in diabetic retinopathy. The other, the kallikrein-kinin system, has recently been found to be important in the development of diabetic retinal complications. This review describes the components of the two signalling networks, examines the current animal model studies investigating the role of these pathways in diabetic retinopathy and reviews the clinical studies that have been undertaken examining systemic inhibition of different points in these pathways. These systems are promising targets for therapies aimed at inhibiting the development of diabetic retinopathy and in the future, combination therapies that take advantage of both pathways might result in new treatment options for this debilitating complication of diabetes.

Induction of selective blood-tumor barrier permeability and macromolecular transport by a biostable kinin B1 receptor agonist in a glioma rat model

Treatment of malignant glioma with chemotherapy is limited mostly because of delivery impediment related to the blood-brain tumor barrier (BTB). B1 receptors (B1R), inducible prototypical G-protein coupled receptors (GPCR) can regulate permeability of vessels including possibly that of brain tumors. Here, we determine the extent of BTB permeability induced by the natural and synthetic peptide B1R agonists, LysdesArg⁹BK (LDBK) and SarLys[dPhe⁸]desArg⁹BK (NG29), in syngeneic F98 glioma-implanted Fischer rats. Ten days after tumor inoculation, we detected the presence of B1R on tumor cells and associated vasculature. NG29 infusion increased brain distribution volume and uptake profiles of paramagnetic probes (Magnevist and Gadomer) at tumoral sites (T₁-weighted imaging). These effects were blocked by B1R antagonist and non-selective cyclooxygenase inhibitors, but not by B2R antagonist and non-selective nitric oxide synthase inhibitors. Consistent with MRI data, systemic co-administration of NG29 improved brain tumor delivery of Carboplatin chemotherapy (ICP-Mass spectrometry). We also detected elevated B1R expression in clinical samples of high-grade glioma. Our results documented a novel GPCR-signaling mechanism for promoting transient BTB disruption, involving activation of B1R and ensuing production of COX metabolites. They also underlined the potential value of synthetic biostable B1R agonists as selective BTB modulators for local delivery of different sized-therapeutics at (peri)tumoral sites.

Blockade of early and late retinal biochemical alterations associated with diabetes development by the selective bradykinin B1 receptor antagonist R-954

The chronic hyperglycemia measured alongside diabetes development is associated with significant long-term damage and failure of various organs. In the present study it was shown that hyperglycemia induced early and long term increases in nitric oxide (NO) levels, kallikrein activity and vascular capillary permeability measured as plasma extravasation, and decreases of Na/K ATPase activity in diabetic rat retina 4 and 12 weeks after streptozotocin (STZ) injection. Treatment of the animals for 5 consecutive days with a novel selective bradykinin B(1) receptor (BKB(1)-R) antagonist R-954 (2mg/kg s.c) at the end of the 4 and 12 week periods highly reduced NO, kallikrein and capillary permeability and increased Na/K ATPase activity in the retina. These results suggest that the BKB(1)-R receptor subtype is over-expressed during the streptozotocin-induced development of diabetes in rat retina as evidenced by the inhibitory effects of the BKB(1)-R antagonist R-954 on NO, kallikrein and vascular permeability increases as well as Na/K ATPase decreases. The beneficial role of the BKB(1)-R antagonist R-954 for the treatment of the diabetic retinopathy is also suggested.

Ocular application of the kinin B1 receptor antagonist LF22-0542 inhibits retinal inflammation and oxidative stress in streptozotocin-diabetic rats

PURPOSE

Kinin B(1) receptor (B(1)R) is upregulated in retina of Streptozotocin (STZ)-diabetic rats and contributes to vasodilation of retinal microvessels and breakdown of the blood-retinal barrier. Systemic treatment with B(1)R antagonists reversed the increased retinal plasma extravasation in STZ rats. The present study aims at determining whether ocular application of a water soluble B(1)R antagonist could reverse diabetes-induced retinal inflammation and oxidative stress.

METHODS

Wistar rats were made diabetic with STZ (65 mg/kg, i.p.) and 7 days later, they received one eye drop application of LF22-0542 (1% in saline) twice a day for a 7 day-period. The impact was determined on retinal vascular permeability (Evans blue exudation), leukostasis (leukocyte infiltration using Fluorescein-isothiocyanate (FITC)-coupled Concanavalin A lectin), retinal mRNA levels (by qRT-PCR) of inflammatory (B(1)R, iNOS, COX-2, ICAM-1, VEGF-A, VEGF receptor type 2, IL-1β and HIF-1α) and anti-inflammatory (B(2)R, eNOS) markers and retinal level of superoxide anion (dihydroethidium staining).

RESULTS

Retinal plasma extravasation, leukostasis and mRNA levels of B(1)R, iNOS, COX-2, VEGF receptor type 2, IL-1β and HIF-1α were significantly increased in diabetic retinae compared to control rats. All these abnormalities were reversed to control values in diabetic rats treated with LF22-0542. B(1)R antagonist also significantly inhibited the increased production of superoxide anion in diabetic retinae.

CONCLUSION

B(1)R displays a pathological role in the early stage of diabetes by increasing oxidative stress and pro-inflammatory mediators involved in retinal vascular alterations. Hence, topical application of kinin B(1)R antagonist appears a highly promising novel approach for the treatment of diabetic retinopathy.

Antidiabetic efficacy of bradykinin antagonist R-954 on glucose tolerance test in diabetic type 1 mice

Insulin-dependent diabetes mellitus (type 1 diabetes) is an inflammatory autoimmune disease associated with many complications including nephropathy, retinopathy, neuropathy and hyperalgesia. Experimental evidence has shown that the bradykinin B1 receptor (BKB1-R) is involved in the development of type 1 diabetes and found to be upregulated alongside the disease. In the present study the effects of the selective BKB1-R antagonist the R-954 (Ac-Orn-[Oic(2), alpha-MePhe(5), D-beta Nal(7), Ile(8) ]des-Arg(9)-BK and the BKB1-R agonist des Arg(9)-BK (DBK) were studied on diabetic hyperglycemia. Diabetic type 1 was induced in C57 BL/KsJ mdb male mice by five consecutives doses of STZ (45mg/kg i.p.). A glucose tolerance test (GTT) was performed by an intraperitoneal administration of glucose, 8, 12 and 18days after the diabetes induction. The induction of type 1 diabetes provoked a significant hyperglycemia levels in diabetic mice at 12 and 18days after STZ. The administration of R-954 (400microg/kg i.p.) at 12 and 18days after STZ returned the glycemia levels of this animals to normal values. In addition the administration of DKB (300microg/kg i.p.) significantly potentiated the diabetes-induced hyperglycemia; this effect that was totally reversed by R-954. These results provide further evidence for the implication of BKB1-R in the type 1 diabetes mellitus (insulitis).

Histone deacetylase inhibition reduces myocardial ischemia-reperfusion injury in mice

Limitation of infarct size is a major goal of therapy for acute coronary syndromes, and research has focused on achieving rapid patency of infarct-related vessels. However, new understandings of epigenetic modifications during ischemia suggest additional targeted approaches that have not been extensively explored. Here, we show that ischemia induces histone deacetylase (HDAC) activity in the heart with deacetylation of histones H3/4 in vitro and in vivo. We show, utilizing a standard murine model of ischemia-reperfusion, that chemical HDAC inhibitors significantly reduce infarct area, even when delivered 1 h after the ischemic insult. We demonstrate that HDAC inhibitors prevent ischemia-induced activation of gene programs that include hypoxia inducible factor-1alpha, cell death, and vascular permeability in vivo and in vitro, thus providing potential mechanisms to explain reduced vascular leak and myocardial injury. In vitro, siRNA knockdown experiments implicate HDAC4 as a mediator of the effects in ischemic cardiac myocytes. These results demonstrate that HDAC inhibitors alter the response to ischemic injury in the heart and reduce infarct size, suggesting novel therapeutic approaches for acute coronary syndromes.

Retinal plasma extravasation in streptozotocin-diabetic rats mediated by kinin B(1) and B(2) receptors

BACKGROUND AND PURPOSE

We investigated whether or not kinin receptors play a role in diabetic blood-retinal barrier breakdown, which is a leading cause of vision loss.

EXPERIMENTAL APPROACH

Blood-retinal barrier breakdown was quantified using Evans blue, and expression of kinin B(1) receptor mRNA was measured using quantitative reverse transcrition-PCR. Diabetic rats (streptozotocin (STZ), 65 mg kg(-1)) received a single intraocular injection of bradykinin (BK) or des-Arg(9)-BK, alone, or in combination with antagonists for B(1) (des-Arg(10)-Hoe140, R-715) and/or B(2) (Hoe140) receptors, given intraocularly or intravenously (i.v.).

KEY RESULTS

In control rats, BK (0.1-10 nmol) dose-dependently increased plasma extravasation, which was inhibited by Hoe140 (0.2 nmol), whereas des-Arg(9)-BK (0.1 and 1 nmol) was without effect. B(1) receptor mRNA was markedly increased in retinas of diabetic rats, and this was prevented by N-acetyl-L-cysteine (1 g kg(-1) day(-1) for 7 days). Plasma extravasation in retinas of STZ-diabetic rats was higher than in controls and enhanced by des-Arg(9)-BK. Response to des-Arg(9)-BK was inhibited by intraocular or i.v. injection of B(1) receptor antagonists. Diabetes-induced plasma extravasation was inhibited only by a combination of des-Arg(10)-Hoe140 and Hoe 140 (100 nmol kg(-1), i.v. 15 min earlier) or by R-715 (1 micromol kg(-1), i.v.) injected daily for 7 days.

CONCLUSIONS AND IMPLICATIONS

Kinin B(1) receptors are upregulated in retinas of STZ-diabetic rats through a mechanism involving oxidative stress. Both kinin B(1) and B(2) receptors contribute to increased plasma extravasation in diabetic retinopathy. Chronic inhibition of both kinin receptors, possibly with antioxidant adjuvants, may be a novel therapeutic strategy for diabetic retinopathy.

Involvement of kinin B1 receptor and oxidative stress in sensory abnormalities and arterial hypertension in an experimental rat model of insulin resistance

Diabetes Mellitus leads to pain neuropathy and cardiovascular complications which remain resistant to current therapies involving the control of glycaemia. This study aims at defining the contribution of kinin B(1) receptor (B(1)R) and the oxidative stress on sensory abnormalities and arterial hypertension in a rat model of insulin resistance. Rats were fed with 10% d-glucose for a chronic period of 12-14 weeks and the impact of a diet supplemented with alpha-lipoic acid, a potent antioxidant, was determined on tactile and cold allodynia, arterial hypertension and the expression of kinin B(1)R (real-time PCR and autoradiography) in several tissues. Acute effects of brain penetrant (LF22-0542) and peripherally acting (R-715) B(1)R antagonists were also assessed. Glucose-fed rats exhibited tactile and cold allodynia along with increases in systolic blood pressure between 4 and 12 weeks; these alterations were alleviated by alpha-lipoic acid. The latter regimen also decreased significantly increased plasma levels of insulin and glucose and insulin resistance (HOMA index) at 14 weeks. B(1)R mRNA was virtually absent in liver, aorta, lung, kidney and spinal cord isolated from control rats, yet B(1)R mRNA was markedly increased in all tissues in glucose-fed rats. Up-regulated B(1)R mRNA and B(1)R binding sites (spinal cord) were significantly reduced by alpha-lipoic acid in glucose-fed rats. LF22-0542 reduced tactile and cold allodynia (3h) and reversed arterial hypertension (3-48h) in glucose-fed rats. R-715 abolished tactile and cold allodynia but had not effect on blood pressure. Data suggest that the oxidative stress contributes to the induction and up-regulation of B(1)R in the model of insulin resistance induced by glucose feeding. The over expressed B(1)R contributes centrally to arterial hypertension and in the periphery to sensory abnormalities.

The kinin B1 receptor antagonist SSR240612 reverses tactile and cold allodynia in an experimental rat model of insulin resistance

BACKGROUND AND PURPOSE

Diabetes causes sensory polyneuropathy with associated pain in the form of tactile allodynia and thermal hyperalgesia which are often intractable and resistant to current therapy. This study tested the beneficial effects of the non-peptide and orally active kinin B(1) receptor antagonist SSR240612 against tactile and cold allodynia in a rat model of insulin resistance.

EXPERIMENTAL APPROACH

Rats were fed with 10% D-glucose for 12 weeks and effects of orally administered SSR240612 (0.3-30 mg kg(-1)) were determined on the development of tactile and cold allodynia. Possible interference of SSR240612 with vascular oxidative stress and pancreatic function was also addressed.

KEY RESULTS

Glucose-fed rats exhibited tactile and cold allodynia, increases in systolic blood pressure and higher plasma levels of insulin and glucose, at 12 weeks. SSR240612 blocked tactile and cold allodynia at 3 h (ID(50)=5.5 and 7.1 mg kg(-1), respectively) in glucose-fed rats but had no effect in control rats. The antagonist (10 mg kg(-1)) had no effect on plasma glucose and insulin, insulin resistance (HOMA index) and aortic superoxide anion production in glucose-fed rats.

CONCLUSIONS AND IMPLICATIONS

We provide the first evidence that the B(1) receptors are involved in allodynia in an experimental rat model of insulin resistance. Allodynia was alleviated by SSR240612 most likely through a direct inhibition of B(1) receptors affecting spinal cord and/or sensory nerve excitation. Thus, orally active non-peptide B(1) receptor antagonists should have clinical therapeutic potential in the treatment of sensory polyneuropathy.

Role of the kinin B1 receptor in insulin homeostasis and pancreatic islet function

Kinins are potent vasoactive peptides generated in blood and tissues by the kallikrein serine proteases. Two distinct kinin receptors have been described, one constitutive (subtype B2) and one inducible (subtype B1), and many physiological functions have been attributed to these receptors, including glucose homeostasis and control of vascular permeability. In this study we show that mice lacking the kinin B1 receptor (B1 -/- mice) have lower fasting plasma glucose concentrations but exhibit higher glycemia after feeding when compared to wild-type mice. B1 -/- mice also present pancreas abnormalities, characterized by fewer pancreatic islets and lower insulin content, which leads to hypoinsulinemia and reduced insulin release after a glucose load. Nevertheless, an insulin tolerance test indicated higher sensitivity in B1 -/- mice. In line with this phenotype, pancreatic vascular permeability was shown to be reduced in B1 receptor-ablated mice. The B1 agonist desArg9bradykinin injected intravenously can induce the release of insulin into serum, and this effect was not observed in the B1 -/- mice or in isolated islets. Our data demonstrate the importance of the kinin B1 receptor in the control of pancreatic vascular homeostasis and insulin release, highlighting a new role for this receptor in the pathogenesis of diabetes and related diseases.

The kinin system mediates hyperalgesia through the inducible bradykinin B1 receptor subtype: evidence in various experimental animal models of type 1 and type 2 diabetic neuropathy

Both insulin-dependent (type 1) and insulin-independent (type 2) diabetes are complex disorders characterized by symptomatic glucose intolerance due to either defective insulin secretion, insulin action or both. Unchecked hyperglycemia leads to a series of complications among which is painful diabetic neuropathy, for which the kinin system has been implicated. Here, we review and compare the profile of several experimental models of type 1 and 2 diabetes (chemically induced versus gene-prone) and the incidence of diabetic neuropathy upon aging. We discuss the efficacy of selective antagonists of the inducible bradykinin B1 receptor (BKB1-R) subtype against hyperalgesia assessed by various nociceptive tests. In either gene-prone models of type 1 and 2 diabetes, the incidence of hyperalgesia mostly precedes the development of hyperglycemia. The administration of insulin, achieving euglycemia, does not reverse hyperalgesia. Treatment with a selective BKB1-R antagonist does not affect basal nociception in most normal control rats, whereas it induces a significant time- and dose-dependent attenuation of hyperalgesia, or even restores nociceptive responses, in experimental diabetic neuropathy models. Diabetic hyperalgesia is absent in streptozotocin-induced type 1 diabetic BKB1-R knockout mice. Thus, selective antagonism of the inducible BKB1-R subtype may constitute a novel and potential therapeutic approach for the treatment of painful diabetic neuropathy.

Inhibition of Type 1 Diabetic Hyperalgesia in Streptozotocin-Induced Wistar versus Spontaneous Gene-Prone BB/Worchester Rats: Efficacy of a Selective Bradykinin B1Receptor Antagonist

Insulin-dependent type 1 diabetes (T1D) is linked to a series of complications, including painful diabetic neuropathy (PDN). Several neurovascular systems are activated in T1D, including the inducible bradykinin (BK) B1 receptor (BKB1-R) subtype. We assessed and compared the efficacy profile of a selective BKB1-R antagonist on hyperalgesia in 2 models of T1D: streptozotocin (STZ) chemically induced diabetic Wistar rats and spontaneous BioBreeding/Worchester diabetic-prone (BB/Wor-DP) rats. Nociception was measured using the hot plate test to determine thermal hyperalgesia. STZ diabetic rats developed maximal hyperalgesia (35% decrease in their hot plate reaction time) within a week and remained in such condition and degree for up to 4 weeks postinjection. BB/Wor-DP rats also developed hyperalgesia over time that preceded hyperglycemia, starting at the age of 6 weeks (9% decrease in the hot plate reaction time) and stabilizing over the age of 16 to 24 weeks to a maximum (60% decrease in the hot plate reaction time). Single, acute subcutaneous administration of the selective BKB1-R antagonist induced significant time- and dose-dependent attenuation of hyperalgesia in both STZ diabetic and BB/Wor-DP rats. Thus, selective antagonism of the inducible BKB1-R subtype may constitute a novel and potential therapeutic approach for the treatment of PDN.

Increases of spinal kinin receptor binding sites in two rat models of insulin resistance

An autoradiographic study was conducted to determine whether kinin receptors are altered in the rat spinal cord in two experimental models of chronic hyperglycemia and insulin resistance. Sprague-Dawley rats were given 10% d-glucose in their drinking water alone or with insulin (9 mU/kg/min with osmotic pumps) for 4 weeks. Both groups and control rats were treated either with a normal chow diet or with an alpha-lipoic acid-supplemented diet as antioxidant therapy. After 4 weeks of treatment, glycemia, insulinemia, blood pressure, insulin resistance index, the production of superoxide anion in the aorta and the density of B2 receptor binding sites in the dorsal horn were significantly increased in the two models. These effects were prevented or attenuated by alpha-lipoic acid. In contrast, B2 receptor binding sites of most spinal cord laminae were increased in the glucose group only and were not affected by alpha-lipoic acid. Results show that chronic hyperglycemia associated with insulin resistance increases B1 and B2 receptor binding sites in the rat spinal cord through distinct mechanisms, including the oxidative stress for the B1 receptor.

Expression and distribution of kinin B1 receptor in the rat brain and alterations induced by diabetes in the model of streptozotocin

A role for kinin B1 receptors was suggested in the spinal cord and peripheral organs of streptozotocin (STZ)-diabetic rats. The present study aims at determining whether B1 receptors are also induced and over-expressed in the brain of STZ-rats at 2, 7, and 21 days post-treatment. This was addressed by in situ hybridization using the [35S]-UTPalphaS-labeled riboprobe and by in vitro autoradiography with the radioligand [125I]-HPP-des-Arg10-Hoe 140. In control rats, B1 receptor mRNA was found widely distributed in many brain regions. Low mRNA levels were found in thalamus and hypothalamus (7-12 nCi/g) while high mRNA signals were detected in cortical regions and hippocampus (18-29 nCi/g). In diabetic rats, B1 receptor mRNA was markedly increased in hippocampus, temporal/parietal cortices and amygdala at 2 and 7 days (+88 to +150%). Low densities of B1 receptor binding sites were detected in all analyzed regions in control rats (0.18-0.37 fmol/mg tissue). In diabetic rats, B1 receptor binding sites were significantly increased in hippocampus, amygdala, temporal/parietal, and perhinal/piriform cortices (+ 55 to + 165 %) at 7 days only. Results highlight an early but transient and reversible up-regulation of B1 receptors in specific brain regions of STZ-diabetic rats. This may offer the advantage of reducing putative central side effects with B1 receptor antagonists if used for the treatment of diabetic complications in the periphery.

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.

Hyperalgesia in non-obese diabetic (NOD) mice: A role for the inducible bradykinin B1 receptor

Most studies performed to investigate the role of the inducible bradykinin B(1) receptor in the pathology and complications of type 1 diabetes have been carried out using the model of streptozotocin (STZ)-induced diabetes. The model of spontaneous autoimmune diabetes in non-obese diabetic (NOD) mice involves a long-term inflammatory process that closely resembles the human type 1 diabetes. In the present study, we aimed at establishing the correlation between the progress of diabetic hyperalgesia and the incidence of diabetes, as a function of age, in NOD mice. We also evaluated the implication of the bradykinin B(1) receptor, a receptor up-regulated during the inflammatory progress of diabetes, in the development of diabetic hyperalgesia in NOD mice. Female NOD mice were followed up from the 4th to the 32nd week of age for the incidence of diabetes. Only NOD mice with plasma glucose concentration >20 mmol/l were considered diabetic. The nociception was assessed using the hot plate and the tail immersion pain tests and the effect of acute and chronic administration of the selective bradykinin B(1) receptor agonist, desArg(9)bradykinin and its selective antagonists, R-715 (Ac-Lys-[D-beta Nal(7), Ile(8)]desArg(9)bradykinin) and R-954 (Ac-Orn-[Oic(2), alpha-MePhe(5), D-beta Nal(7), Ile(8)]desArg(9)bradykinin), on the development of diabetic hyperalgesia was studied. Diabetic NOD mice developed a significant time-dependent hyperalgesia, as measured in both tests, starting from the 8th week of age with the maximum effect observed over 16 to 20 weeks, whereas the incidence of diabetes in the tested NOD mice was only 40.16% at the age of 16 weeks and reached a maximum of 73.23% at the age 24 weeks. Both acute and chronic administration of desArg(9)bradykinin (400 microg/kg) markedly increased the hyperalgesic activity in diabetic NOD mice in the hot plate and tail immersion nociceptive tests. The selective bradykinin B(1) receptor antagonist R-715 (400 microg/kg) and its more potent and long acting analogue R-954 (200 microg/kg), administered in acute or chronic manner, significantly attenuated diabetic hyperalgesia in NOD mice in both thermal pain tests and restored nociceptive responses to values observed in control non-diabetic siblings. Our results bring the first evidence that the development of hyperalgesia in NOD mice, a model of spontaneous type 1 diabetes, precedes the occurrence of hyperglycemia and is mediated by the bradykinin B(1) receptor. It is suggested that bradykinin B(1) receptor antagonism could become a novel therapeutic approach to the treatment of diabetic neuropathic complications.

Effects of a selective bradykinin B1 receptor antagonist on increased plasma extravasation in streptozotocin-induced diabetic rats: Distinct vasculopathic profile of major key organs

Diffuse vasculopathy is a common feature of the morbidity and increased mortality associated with insulino-dependent type 1 diabetes. Increased vascular permeability leading to plasma extravasation occurs in surrounding tissues following endothelial dysfunction. Such micro- and macro-vascular complications develop over time and lead to oedema, hypertension, cardiomyopathy, renal failure (nephropathy) and other complications (neuropathy, retinopathy). In the present investigation, we studied the effect of a selective bradykinin B(1) receptor antagonist, R-954, on the enhanced vascular permeability in streptozotocin (STZ)-induced diabetic Wistar rats compared with age-matched controls. Plasma extravasation was determined using Evans blue dye in selected target tissues (left and right heart atria, ventricles, lung, abdominal and thoracic aortas, liver, spleen, renal cortex and medulla), at 1 and 4 weeks following STZ administration. The vascular permeability was significantly increased in the aortas, cortex, medulla, and spleen in 1-week STZ rats and remained elevated at 4 weeks of diabetes. Both atria showed an increased vascular permeability only after 4-week STZ-administration. R-954 (2 mg/kg, bolus, s.c.), given 2 h prior to Evans blue dye, to 1- and 4-week diabetic rats significantly inhibited (by 48-100%) plasma leakage in most tested tissues affected by diabetes with no effect in healthy rats. These results showed that the inducible bradykinin B(1) receptor subtype participates in the modulation of the vascular permeability in diabetic rats and suggest that selective bradykinin B(1) receptor antagonism could have a beneficial role in reducing diabetic vascular complications.

Absence of diabetic hyperalgesia in bradykinin B1 receptor-knockout mice

Experimental evidence has shown that the inducible bradykinin (BK) B1 receptor (BKB1-R) subtype is involved in the development of hyperalgesia associated with type 1 diabetes. Selective BKB1-R antagonists inhibited, whereas selective agonists increased the hyperalgesic activity in diabetic mice in thermal nociceptive tests. Here we evaluate the development of diabetic hyperalgesia in a BKB1-R-knockout (KO) genotype compared to wild-type (WT) mice. The BKB1-R-KO mice were backcrossed for 10 generations to C57BL/6 genetic background before use in the experiments. Diabetes was induced by streptozotocin (STZ) and thermal nociception was assessed by the hot plate and tail immersion tests. The hyperalgesia observed in wild type mice was totally absent in the BKB1-R-KO mice. Furthermore, the selective BKB1-R agonist, desArg9BK, significantly increased the hyperalgesic activity in diabetic WT mice but had no effect on nociceptive responses in diabetic BKB1-R-KO mice. Taken together, the results confirm the crucial role of the BKB1-R, upregulated alongside inflammatory diabetes, in the development of diabetes-induced hyperalgesia.

Expression of kinin B1 receptors in the spinal cord of streptozotocin-diabetic rat

Previous studies have reported cardiovascular and nociceptive responses after intrathecal injection of kinin B1 receptor (B1R) agonists in the model of streptozotocin (STZ)-diabetic rat (diabetic). The aim of this study was to measure the early up-regulation of B1R binding sites and mRNA in the thoracic spinal cord of diabetic and control rats. Data show significant increases of specific B1R binding sites in the dorsal horn of diabetic rats 2 days (+315%), 7 days (+303%) and 21 days (+181%) after STZ treatment. Levels of mRNA were significantly increased (+68%) at 2 and 7 days but not at 21 days. These data bring the first molecular evidence for an early up-regulation of B1R in the spinal cord of diabetic rat.

Bradykinin stimulates MMP-2 production in guinea pig tracheal smooth muscle cells

The implication of bradykinin (BK) receptors in the release of the matrix metalloproteinase-2 (MMP-2; gelatinase A) was studied in guinea pig tracheal smooth muscle cells (GP-TSMC). Bradykinin (10(-8)-10(-4) M) induced a time- and concentration-dependent upregulation of MMP-2 production from cultured GP-TSMC. Pretreatment of the GP-TSMC with the bradykinin B2 receptor (BKB2-R) antagonist Hpp-HOE-140 (Hpp-D-Arg0-Hyp3-Thi5-D-Tic7-Oic8-BK; 10(-8)-10(-4) M) significantly inhibited the BK-stimulated upregulation of MMP-2 in GP-TSMC in a concentration-related manner. Conversely, GP-TSMC pretreated with the selective bradykinin B1 receptor (BKB1-R) antagonist R-954 (Ac-Om[Oic2, alpha-MePhe5, D-betaNal7, Ile8]desArg9BK; 10(-8)-10(-4) M) did not show any change in the response to BK. Moreover, the selective BKB2-R agonist Lys0BK (kallidin; 10(-8)-10(-4) M) stimulated whereas the selective BKB1-R agonist desArg9BK (DBK; 10(-8)-10(-4) M) had no effect on MMP-2 release from GP-TSMC. Further, the nonselective cyclooxygenase (COX) enzyme inhibitor indomethacin (IND; 10(-5) M), the glucocorticosteroid dexamethasone (DEX; 1 ng/mL) and the protein synthesis inhibitors, cycloheximide (CHX; 10(-6) M) and actinomycin D (ACT-D; 10(-8) M) also inhibited BK-induced MMP-2 release from GP-TSMC. These results provide the first evidence for the involvement of BK in the release of MMP-2 from airway smooth muscle cells through activation of the BKB2-R. Such response is mostly mediated by the induction of COX and the subsequent production of endogenous prostaglandins (PGs). It could therefore be suggested that MMP-2 might play a role in the process of airway remodeling.

Enhanced dermal and retinal vascular permeability in streptozotocin-induced type 1 diabetes in Wistar rats: blockade with a selective bradykinin B1 receptor antagonist

The vascular complications associated with type 1 diabetes are to some extent related to the dysfunction of the endothelium leading to an increased vascular permeability and plasma extravasation in the surrounding tissues. The various micro- and macro-vascular complications of diabetes develop over time, leading to nephropathy, retinopathy and neuropathy and cardiomyopathy. In the present study, the effect of a novel selective bradykinin B1 receptor (BKB1-R) antagonist, R-954, was investigated on the changes of vascular permeability in the skin and retina of streptozotocin (STZ)-induced type 1 diabetic rats. Plasma extravasation increased in the skin and retina of STZ-diabetic rats after 1 week and persisted over 4 weeks following STZ injection. Acute treatment with R-954 (2 mg/kg, bolus s.c.) highly reduced the elevated vascular permeability in both 1- and 4-week STZ-diabetic rats. These results showed that the inducible BKB1-R subtype modulates the vascular permeability of the skin and retina of type 1 diabetic rats and suggests that BKB1-R antagonists could have a beneficial role in diabetic neuropathy and retinopathy.

Autoradiographic distribution and alterations of kinin B2 receptors in the brain and spinal cord of streptozotocin-diabetic rats

This study investigates whether bradykinin (BK) B(2) receptor binding sites are increased in the brain and thoracic spinal cord of streptozotocin (STZ)-diabetic rats at 2, 7, and 21 days posttreatment by in vitro autoradiography with the radioligand [(125)I]HPP-Hoe 140. In control and diabetic rats, specific binding sites for B(2) receptors were detected in the brain and in various laminae of the spinal cord, predominantly in superficial laminae (K(d)=34 pM). In diabetic rats, B(2) receptor densities were significantly increased in lamina l of the dorsal horn (+35% at 7 and 21 days), spinal trigeminal nucleus (+70% at 7 and 21 days) and nucleus tractus solitarius (+100% at 2 and 7 days). B(2) receptor analogues D-Arg[Hyp(3),Thi(5),D-Tic(7),Oic(8)]-BK (Hoe 140), 3-(4 hydroxyphenyl)propionyl-Hoe 140 (HPP-Hoe 140), LF16-0687 mesylate ((2-Pyrrolidinecarboxamide, N-[3-[[4-aminoiminomethyl)benzoyl]amino]propyl]-1-[[2,4-dichoro-3-[[(2,4-dimethyl-8-quinolinyl)oxy]methyl]phenyl]sulfonyl]-(2S)-(9Cl)), and BK decreased binding of [(125)I]-HPP-Hoe 140 in the spinal dorsal horn, with K(i) values of 0.5, 1.5, 3.2, and 3.7 nM, respectively. These values were not significantly different in diabetic rats at 7 days (0.5 (Hoe 140), 0.7 (HPP-Hoe 140), 1.2 (BK), and 1.7 (LF16-0687) nM). While des-Arg(10)-Hoe 140 was three orders of magnitude less potent than Hoe 140, B(1) receptor agonist (des-Arg(9)-BK) and antagonist (AcLys[D-betaNal(7),Ile(8)]des-Arg(9)-BK, R-715) did not affect [(125)I]-HPP-Hoe 140 binding at 1 microM concentration. Data suggest a very discrete and temporal increase of B(2) receptor density (without affinity changes) in the spinal cord and hindbrain of STZ-diabetic rats. This contrasts with the early induction and over-expression of B(1) receptors reported in the brain and spinal cord of STZ-diabetic rats.

Des-Arg9-bradykinin increases intracellular Ca2+ in bronchoalveolar eosinophils from ovalbumin-sensitized and -challenged mice

The effects of the selective bradykinin B1 receptor agonist, des-Arg9-bradykinin and the bradykinin B2 receptor agonist, bradykinin were studied on the intracellular free Ca2+ concentration ([Ca2+]i) in murine bronchoalveolar lavage cells from control and ovalbumin-sensitized mice using fura-2 microfluorimetry. The bronchoalveolar lavage cells of control mice, which were predominantly alveolar macrophages, showed an increase in [Ca2+]i in response to bradykinin (1 microM) but not to des-Arg9-bradykinin (1 microM), indicating the presence of functional bradykinin B2 receptors and the absence of B1 receptors. Such elevation in [Ca2+]i induced by bradykinin was totally inhibited by the selective bradykinin B2 receptor antagonist, D-Arg0-Hyp3-Thi5-D-Tic7-Oic8-bradykinin (HOE-140; 10 microM). In contrast, bronchoalveolar lavage cells from ovalbumin-sensitized and -challenged mice significantly responded to both bradykinin and des-Arg9-bradykinin, indicating the presence of both functional bradykinin B1 and B2 receptors. Eosinophils exhibited higher response to des-Arg9-bradykinin (1 microM; 485% increase in [Ca2+]i) compared to bradykinin (1 microM; 163% increase in [Ca2+]i). This des-Arg9-bradykinin-induced [Ca2+]i increase was markedly inhibited by the selective bradykinin B1 receptor antagonist, Ac-Lys-[D-betaNal7, Ile8]des-Arg9-bradykinin (R-715; 10 microM). Des-Arg9-bradykinin neither modified the basal [Ca2+]i in lymphocytes nor in mononuclear cells from ovalbumin-sensitized and challenged mice, while bradykinin produced a [Ca2+]i increase in both cell types. Our results further support the implication of the inducible bradykinin B1 receptors in airway inflammatory response in ovalbumin-sensitized and challenged mice.

Beneficial effect of chronic treatment with the selective bradykinin B1 receptor antagonists, R-715 and R-954, in attenuating streptozotocin-diabetic thermal hyperalgesia in mice

Kinins are important mediators of cardiovascular homeostasis, inflammation and nociception. Bradykinin (BK) B(1) receptors (BKB1-R) are over-expressed in pathological conditions including diabetes, and were reported to play a role in hyperglycemia, renal abnormalities, and altered vascular permeability associated with type 1 diabetes. Recent studies from our laboratory demonstrated that BKB1-R are implicated in streptozotocin (STZ)-diabetes-mediated hyperalgesia, since acute administration of the selective BKB1-R antagonists significantly and dose-dependently inhibited such hyperalgesic activity. In the present study, we examined the effect of chronic treatment of STZ-diabetic mice with the selective BKB1-R agonist desArg9bradykinin (DBK) and two specific antagonists R-715 and R-954, on diabetic hyperalgesia. Diabetes was induced in male CD-1 mice by injecting a single high dose of STZ (200mg/kg, i.p.) and nociception was assessed using the hot plate, plantar stimulation, tail immersion and tail flick tests. Drugs were injected i.p. twice daily for 7 days, starting 4 days after STZ. We showed that chronically administered R-715 (400 micrograms/kg) and R-954 (200 micrograms/kg), significantly attenuated the hyperalgesic effect developed in STZ-diabetic mice as measured by the four thermal nociceptive tests. Further, chronic treatment with DBK (400 micrograms/kg) produced a marked potentiation of the hyperalgesic activity, an effect that was reversed by both R-715 and R-954. The results from this chronic study confirm a pivotal role of the BKB1-R in the development of STZ-diabetic hyperalgesia and suggest a novel approach to the treatment of this short-term diabetic complication using BKB1-R antagonists.

Role of bradykinin B(1) receptors in diabetes-induced hyperalgesia in streptozotocin-treated mice

Insulin-dependent diabetes mellitus (type-1 diabetes) is an inflammatory autoimmune disease associated with vascular permeability changes leading to many complications including nephropathy, retinopathy, hypertension, hyperalgesia and neuropathy. The bradykinin B(1) receptor was recently found to be upregulated during the development of the diabetes and to be involved in its complications. Kinins are known to be important mediators of a variety of biological effects including cardiovascular homeostasis, inflammation and nociception. In the present study, we studied the effect of the selective B(1) receptor agonist, des-Arg(9)-bradykinin, and its specific antagonists, Ac-Lys-[D-beta Nal(7), Ile(8)]des-Arg(9)-bradykinin (R-715) and Ac-Orn-[Oic(2), alphaMe Phe(5), D-beta Nal(7), Ile(8)]des-Arg(9)-bradykinin (R-954), on diabetic hyperalgesia. Diabetes was induced in male CD-1 mice by injecting a single high dose of streptozotocin (200 mg kg(-1), i.p.) and the nociception was assessed using the hot plate and the tail flick tests, 1 week following the injection of streptozotocin. Our results showed that induction of diabetes by streptozotocin provoked a marked hyperalgesia in diabetic mice expressed as about 11% decrease in hot plate reaction time and 26% decrease in tail flick reaction time. Following acute administration of R-715 (200-800 microg kg(-1), i.p.) and R-954 (50-600 microg kg(-1), i.p.), this hyperalgesic activity was blocked and the hot plate and tail flick latencies of diabetic mice returned to normal values observed in control healthy mice. In addition, the acute administration of des-Arg(9)-bradykinin (200-600 microg kg(-1), i.p.) significantly potentiated diabetes-induced hyperalgesia, an effect that was totally reversed by R-715 (1.6-2.4 mg kg(-1), i.p.) and R-954 (0.8-1.6 mg kg(-1), i.p.). These results provide a major evidence for the implication of the bradykinin B(1) receptors in the development of hyperalgesia associated with diabetes and suggest a novel approach to the treatment of this diabetic complication using the bradykinin B(1) receptor antagonists.