Bradykinin receptors

Bradykinin actions in the central nervous system: historical overview and psychiatric implications

Bradykinin (BK), a well-studied mediator of physiological and pathological processes in the peripheral system, has garnered less attention regarding its function in the central nervous system, particularly in behavioural regulation. This review delves into the historical progression of research focused on the behavioural effects of BK and other drugs that act via similar mechanisms to provide new insights into the pathophysiology and pharmacotherapy of psychiatric disorders. Evidence from experiments with animal models indicates that BK modulates defensive reactions associated with panic symptoms and the response to acute stressors. The mechanisms are not entirely understood but point to complex interactions with other neurotransmitter systems, such as opioids, and intracellular signalling cascades. By addressing the existing research gaps in this field, we present new proposals for future research endeavours to foster a new era of investigation regarding BK's role in emotional regulation. Implications for psychiatry, chiefly for panic and depressive disorders are also discussed.

Dexamethasone targets actin cytoskeleton signaling and inflammatory mediators to reverse sulfur mustard-induced toxicity in rabbit corneas

PURPOSE

Sulfur mustard (SM), a bi-functional alkylating agent, was used during World War I and the Iran-Iraq war. SM toxicity is ten times higher in eyes than in other tissues. Cornea is exceptionally susceptible to SM-injuries due to its anterior positioning and mucous-aqueous interphase. Ocular SM exposure induces blepharitis, photosensitivity, dry eye, epithelial defects, limbal ischemia and stem cell deficiency, and mustard gas keratopathy leading to temporary or permanent vision impairments. We demonstrated that dexamethasone (Dex) is a potent therapeutic intervention against SM-induced corneal injuries; however, its mechanism of action is not well known. Investigations employing proteomic profiling (LC-MS/MS) to understand molecular mechanisms behind SM-induced corneal injury and Dex efficacy were performed in the rabbit cornea exposed to SM and then received Dex treatment. PEAKS studio was used to extract, search, and summarize peptide identity. Ingenuity Pathway Analysis was used for pathway identification. Validation was performed using immunofluorescence. One-Way ANOVA (FDR < 0.05; p < 0.005) and Student's t-test (p < 0.05) were utilized for analyzing proteomics and IF data, respectively. Proteomic analysis revealed that SM-exposure upregulated tissue repair pathways, particularly actin cytoskeleton signaling and inflammation. Prominently dysregulated proteins included lipocalin2, coronin1A, actin-related protein2, actin-related protein2/3 complex subunit2, actin-related protein2/3 complex subunit4, cell division cycle42, ezrin, bradykinin/kininogen1, moesin, and profilin. Upregulated actin cytoskeleton signaling increases F-actin formation, dysregulating cell shape and motility. Dex reversed SM-induced increases in the aforementioned proteins levels to near control expression profiles. Dex aids corneal wound healing and improves corneal integrity via actin cytoskeletal signaling and anti-inflammatory effects following SM-induced injuries.

Tilapia Fish Skin Treatment of Third-Degree Skin Burns in Murine Model

This study explored the feasibility of using fish skin bandages as a therapeutic option for third-degree skin burns. Following the California wildfires, clinical observations of animals with third-degree skin burns demonstrated increased comfort levels and reduced pain when treated with tilapia fish skin. Despite the promises of this therapy, there are few studies explaining the healing mechanisms behind the application of tilapia fish skin. In this study, mice with third-degree burns were treated with either a hydrocolloid adhesive bandage (control) (n = 16) or fish skin (n = 16) 7 days post-burn. Mice were subjected to histologic, hematologic, molecular, and gross evaluation at days 7, 16, and 28 post-burn. The fish skin offered no benefit to overall wound closure compared to hydrocolloids. Additionally, we detected no difference between fish skin and control treatments in regard to hypermetabolism or hematologic values. However, the fish skin groups exhibited 2 times more vascularization and 2 times higher expression of antimicrobial defensin peptide in comparison to controls. Proteomic analysis of the fish skin revealed the presence of antimicrobial peptides. Collectively, these data suggest that fish skin can serve as an innovative and cost-effective therapeutic alternative for burn victims to facilitate vascularization and reduce bacterial infection.

Cooperation of Complement MASP-1 with Other Proinflammatory Factors to Enhance the Activation of Endothelial Cells

Endothelial cells play an important role in sensing danger signals and regulating inflammation. Several factors are capable of inducing a proinflammatory response (e.g., LPS, histamine, IFNγ, and bradykinin), and these factors act simultaneously during the natural course of the inflammatory reaction. We have previously shown that the complement protein mannan-binding lectin-associated serine protease-1 (MASP-1) also induces a proinflammatory activation of the endothelial cells. Our aim was to investigate the possible cooperation between MASP-1 and other proinflammatory mediators when they are present in low doses. We used HUVECs and measured Ca²⁺ mobilization, IL-8, E-selectin, VCAM-1 expression, endothelial permeability, and mRNA levels of specific receptors. LPS pretreatment increased the expression of PAR2, a MASP-1 receptor, and furthermore, MASP-1 and LPS enhanced each other's effects in regulating IL-8, E-selectin, Ca²⁺ mobilization, and changes in permeability in a variety of ways. Cotreatment of MASP-1 and IFNγ increased the IL-8 expression of HUVECs. MASP-1 induced bradykinin and histamine receptor expression, and consequently, increased Ca²⁺ mobilization was found. Pretreatment with IFNγ enhanced MASP-1-induced Ca²⁺ mobilization. Our findings highlight that well-known proinflammatory mediators and MASP-1, even at low effective doses, can strongly synergize to enhance the inflammatory response of endothelial cells.

The relationship between clinical phenotype and kallikrein-kinin bioregulation in different forms of arthritis

OBJECTIVE

Patients with rheumatoid arthritis (RA) have shown increased levels of neutrophils generating kallikrein-kinin peptides in blood which are potent mediators of inflammation. This study investigated the association between the bioregulation of kinin-mediated inflammation with the clinical, quality of life, and imaging characteristics (e.g. ultrasonography) of different arthritides.

METHODS

Patients with osteoarthritis (OA, n = 29), gout (n = 10) and RA (n = 8) were recruited and screened for clinical symptoms, quality of life, and ultrasonographical assessment of arthritis. Blood neutrophils were assessed for the expression of bradykinin receptors (B1R and B2R), kininogens and kallikreins by immunocytochemistry with visualization by bright field microscopy. Levels of plasma biomarkers were measured by ELISA and cytometric bead array.

RESULTS

Quality of life (SF-36 domains and summary scores; including pain; and, HAQ) was similar across OA, gout and RA patients; with the exception of worse physical functioning scores between OA and gout patients. Synovial hypertrophy (on ultrasound) differed between groups (p = 0.001), and the dichotomised Power Doppler (PD) score of greater than or equal to 2 (PD-GE2) was marginally significant (p = 0.09). Plasma IL-8 were highest in patients with gout followed by RA and OA (both, P < 0.05). Patients with RA had higher plasma levels of sTNFR1, IL-1β, IL-12p70, TNF and IL-6, compared to OA and gout patients (all, P < 0.05). Patients with OA had higher expression of K1B and KLK1 on blood neutrophils followed by RA and gout patients (both, P < 0.05). Bodily pain correlated with B1R expression on blood neutrophils (r = 0.334, p = 0.05), and inversely with plasma levels of CRP (r = -0.55), sTNFR1 (r = -0.352) and IL-6 (r = -0.422), all P < 0.05. Expression of B1R on blood neutrophils also correlated with Knee PD (r = 0.403) and PD-GE2 (r = 0.480), both P < 0.05.

CONCLUSIONS

Pain levels and quality of life were similar between patients with OA, RA and gout with knee arthritis. Plasma inflammatory biomarkers and B1R expression on blood neutrophils correlated with pain. Targeting B1R to modulate the kinin-kallikrein system may pose as a new therapeutic target in the treatment of arthritis.

Impact of Vitamin D Status Correction on Serum Lipid Profile, Carboxypeptidase N and Nitric Oxide Levels in Saudi Adults

This study aimed to determine the impact on the lipid profile, carboxypeptidase N (CPN) and nitric oxide (NOx) associated with vitamin D (VD) status correction among Saudi adults with VD deficiency. A total 111 VD deficient (25(OH)D < 50 nmol/L)) adult Saudis aged 18-50 years old (57 females and 54 males) were enrolled in this 6-month interventional study. They were given 50,000 IU VD weekly for the first 2 months and then twice a month for the next 2 months, followed by 1000 IU daily for the last 2 months. The fasting lipid profile and the blood glucose, VD, NOx and CPN concentrations were measured at baseline and after intervention. Post-supplementation, the median VD was significantly higher (p < 0.001) in females [58.3 (50.6-71.2)] and males [57.8 (51.0-71.8)]. HDL cholesterol significantly increased (p = 0.05) and NOx significantly decreased (p = 0.02) in males post-supplementation. Triglycerides were positively associated with NOx in all subjects before (r = 0.44, p = 0.01) and after (r = 0.37, p = 0.01) VD status correction. There was a significant increase in serum levels of CPN2 (p = 0.02) in all subjects. Furthermore, CPN was inversely correlated with NOx (r = -0.35, p = 0.05) in males post-supplementation. In conclusion, VD status correction reduced serum NOx, particularly in males. The inhibition of NOx synthesis may be responsible for the anti-inflammatory effects of VD supplementation. An inverse association was found between NOx and CPN2.

Baculovirus Display of Peptides and Proteins for Medical Applications

Baculoviridae is a large family of arthropod-infective viruses. Recombinant baculoviruses have many applications, the best known is as a system for large scale protein production in combination with insect cell cultures. More recently recombinant baculoviruses have been utilized for the display of proteins of interest with applications in medicine. In the present review we analyze the different strategies for the display of proteins and peptides on the surface of recombinant baculoviruses and provide some examples of the different proteins displayed. We analyze briefly the commercially available systems for recombinant baculovirus production and display and discuss the future of this emerging and powerful technology.

Non-canonical androgen signaling pathways and implications in prostate cancer

Androgen signaling is a critical determinant of timely and proper development of all male organs including the prostate. Maturation of prostate and its neoplastic transformation is intricately associated with accurate androgen signaling. Ablation of androgen has therefore been the primary treatment mechanism of Prostate cancer (PCa) patients for several decades. Upon removal, the tumor recedes for a while, yet it reappears soon, in an androgen independent state, untreatable by current therapeutic regimens. Studies reveal that apart from the classical androgen signaling pathway known and targeted for almost a century, there exist several non-canonical pathways, with marked impact on classical androgen signaling and PCa growth. These include non-genomic signaling by androgens via alternate membrane GPCRs, signaling by non-androgens that ultimately impact the androgen signaling pathway, or an integration of non-genomic and genomic response as seen in case of protein kinase A activation. Accurate understanding of these various non-canonical androgen signaling pathways and their influence on the typical androgen signaling pathway can help design important interventions for PCa patients. This review analyses in detail the various non-classical androgen signaling pathways and their impact, if any, on classical mode of androgen action and PCa.

Drug delivery across the blood-brain barrier for the treatment of pediatric brain tumors - An update

Even though the last decade has seen a surge in the identification of molecular targets and targeted therapies in pediatric brain tumors, the blood brain barrier (BBB) remains a significant challenge in systemic drug delivery. This continues to undermine therapeutic efficacy. Recent efforts have identified several strategies that can facilitate enhanced drug delivery into pediatric brain tumors. These include invasive methods such as intra-arterial, intrathecal, and convection enhanced delivery and non-invasive technologies that allow for transient access across the BBB, including focused ultrasound and nanotechnology. This review discusses current strategies that are being used to enhance delivery of different therapies across the BBB to the tumor site - a major unmet need in pediatric neuro-oncology.

Bradykinin induces peripheral antinociception in PGE2-induced hyperalgesia in mice

BACKGROUND

Bradykinin (BK) is an endogenous peptide involved in vascular permeability and inflammation. It has opposite effects (inducing hyperalgesia or antinociception) when administered directly in the central nervous system. The aim of this study was to evaluate whether BK may also present this dual effect when injected peripherally in a PGE₂-induced nociceptive pain model, as well as to investigate the possible mechanisms of action involved in this event in mice.

METHODS

Male Swiss and C57BL/6 knockout mice for B₁ or B₂ bradykinin receptors were submitted to a mechanical paw pressure test and hyperalgesia was induced by intraplantar prostaglandin E₂ (2 µg/paw) injection.

RESULTS

Bradykinin (20, 40 and 80 ng/paw) produced dose-dependent peripheral antinociception against PGE₂-induced hyperalgesia. This effect was antagonized by bradyzide (8, 16 and 32 μg/paw), naloxone (12.5, 25 and 50 μg/paw), nor-binaltorphimine (50, 100 and 200 μg/paw) and AM251 (20, 40 and 80 μg/paw). Bestatin (400 µg/paw), MAFP (0.5 µg/paw) and VDM11 (2.5 µg/paw) potentiated the antinociception of a lower 20 ng BK dose. The knockout of B₁ or B₂ bradykinin receptors partially abolished the antinociceptive action of BK (80 ng/paw), bremazocine (1 μg/paw) and anandamide (40 ng/paw) when compared with wild-type animals, which show complete antinociception with the same dose of each drug.

CONCLUSION

The present study is the first to demonstrate BK-induced antinociception in peripheral tissues against PGE₂-induced nociception in mice and the involvement of κ-opioid and CB₁ cannabinoid receptors in this effect.

Plasmin-mediated cleavage of high-molecular-weight kininogen contributes to acetaminophen-induced acute liver failure

Acetaminophen (APAP)-induced liver injury is associated with activation of coagulation and fibrinolysis. In mice, both tissue factor-dependent thrombin generation and plasmin activity have been shown to promote liver injury after APAP overdose. However, the contribution of the contact and intrinsic coagulation pathways has not been investigated in this model. Mice deficient in individual factors of the contact (factor XII [FXII] and prekallikrein) or intrinsic coagulation (FXI) pathway were administered a hepatotoxic dose of 400 mg/kg of APAP. Neither FXII, FXI, nor prekallikrein deficiency mitigated coagulation activation or hepatocellular injury. Interestingly, despite the lack of significant changes to APAP-induced coagulation activation, markers of liver injury and inflammation were significantly reduced in APAP-challenged high-molecular-weight kininogen-deficient (HK-/-) mice. Protective effects of HK deficiency were not reproduced by inhibition of bradykinin-mediated signaling, whereas reconstitution of circulating levels of HK in HK-/- mice restored hepatotoxicity. Fibrinolysis activation was observed in mice after APAP administration. Western blotting, enzyme-linked immunosorbent assay, and mass spectrometry analysis showed that plasmin efficiently cleaves HK into multiple fragments in buffer or plasma. Importantly, plasminogen deficiency attenuated APAP-induced liver injury and prevented HK cleavage in the injured liver. Finally, enhanced plasmin generation and HK cleavage, in the absence of contact pathway activation, were observed in plasma of patients with acute liver failure due to APAP overdose. In summary, extrinsic but not intrinsic pathway activation drives the thromboinflammatory pathology associated with APAP-induced liver injury in mice. Furthermore, plasmin-mediated cleavage of HK contributes to hepatotoxicity in APAP-challenged mice independently of thrombin generation or bradykinin signaling.

Blood-Brain Barrier Modulation to Improve Glioma Drug Delivery

The blood-brain barrier (BBB) is formed by brain microvascular endothelial cells that are sealed by tight junctions, making it a significant obstacle for most brain therapeutics. The poor BBB penetration of newly developed therapeutics has therefore played a major role in limiting their clinical success. A particularly challenging therapeutic target is glioma, which is the most frequently occurring malignant brain tumor. Thus, to enhance therapeutic uptake in tumors, researchers have been developing strategies to modulate BBB permeability. However, most conventional BBB opening strategies are difficult to apply in the clinical setting due to their broad, non-specific modulation of the BBB, which can result in damage to normal brain tissue. In this review, we have summarized strategies that could potentially be used to selectively and efficiently modulate the tumor BBB for more effective glioma treatment.

Large Mammal Diversity and Endemism at Geremba Mountain Fragment, Southern Ethiopia

Outside protected areas in Ethiopia, there is a lack of information concerning mammalian diversity and ecology. Consequently, the findings of the research on large mammals at Geremba Mountain constitute one of the steps towards a continuing effort to document the diversity and distribution of Ethiopian mammals. The survey was conducted to investigate the species composition, relative abundance, and population structure of large mammals at Geremba Mountain fragment from August 2017 to February 2018, covering both dry and wet seasons. Direct (sighting) and indirect (scat) survey techniques were employed using systematically established transect lines and sampling plots, respectively. Transects and plots were established across three dominant habitat types (modified dry ever green Afromontane forest, alpine bamboo forest, and Erica scrubland). A total of 10 large mammal species were recorded including two endemic mammals, namely, Chlorocebus djamdjamensis and Tragelaphus scriptus meneliki. There was a statistically significant difference in the abundance of species among habitat types at Geremba Mountain. The highest diversity index was recorded in the alpine bamboo forest habitat (D = 7.142, H′ = 2.052), and the Erica scrubland had the lowest. Papio anubis was the most abundant species while Felis serval was the least abundant species. The populations of most of the species were characterized by more adult and more female individuals. However, promising young individuals of the endemic mammals (C. djamdjamensis and T. s. meneliki) and Papio anubis were recorded. The mountain fragment is an isolated island that is totally disconnected with other fragments in the region, so attempts should be made to connect the fragment with other fragments using wildlife corridors.

Mechanisms for Reducing Neuropathic Pain

Injury typically results in the development of neuropathic pain, but the pain normally decreases and disappears in paralleled with wound healing. The pain results from cells resident at, and recruited to, the injury site releasing pro-inflammatory cytokines and other mediators leading to the development of pro-inflammatory environment and causing nociceptive neurons to develop chronic ectopic electrical activity, which underlies neuropathic pain. The pain decreases as some of the cells that induce pro-inflammation, changing their phenotype leading to the blocking the release of pro-inflammatory mediators while releasing anti-inflammatory mediators, and blocking nociceptive neuron chronic spontaneous electrical activity. Often, despite apparent wound healing, the neuropathic pain becomes chronic. This raises the question of how chronic pain can be eliminated. While many of the cells and mediators contributing to the development and maintenance of neuropathic pain are known, a better understanding is required of how the injury site environment can be controlled to permanently eliminate the pro-inflammatory environment and silence the chronically electrically active nociceptive neurons. This paper examines how methods that can promote the transition of the pro-inflammatory injury site to an anti-inflammatory state, by changing the composition of local cell types, modifying the activity of pro- and anti-inflammatory receptors, inducing the release of anti-inflammatory mediators, and silencing the chronically electrically active nociceptive neurons. It also examines the hypothesis that factors released from platelet-rich plasma applied to chronic pain sites can permanently eliminate chronic inflammation and its associated chronic pain.

Renin-angiotensin inhibitors reprogram tumor immune microenvironment: A comprehensive view of the influences on anti-tumor immunity

Renin-angiotensin system inhibitors (RASi) have shown potential anti-tumor effects that may have a significant impact in cancer therapy. The components of the renin-angiotensin system (RAS) including both, conventional and alternative axis, appear to have contradictory effects on tumor biology. The mechanisms by which RASi impair tumor growth extend beyond their function of modulating tumor vasculature. The major focus of this review is to analyze other mechanisms by which RASi reprogram the tumor immune microenvironment. These involve impairing hypoxia and acidosis within the tumor stroma, regulating inflammatory signaling pathways and oxidative stress, modulating the function of the non-cellular components and immune cells, and regulating the cross-talk between kalli krein kinin system and RAS.

Increased phosphorylation of eNOS in nasal polyps of chronic rhinosinusitis patients can be diminished by 1,8-cineol

INTRODUCTION

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a significant health problem, but the pathogenesis remains unclear to date. Nitric oxide (NO) has known airway modulating functions. Therefore, we investigated nitric oxide production to determine the role of eNOS in nasal polyps, with additional analysis of the effect of the monoterpene oxide 1,8-cineol on the possible regulation of eNOS signaling and thus NO production.

METHODS

We determined eNOS expression, as well as regulatory and effector proteins like NOSTRIN and CASP8, using whole genome microarray, immunohistochemistry and western blot. To evaluate the influence of 1,8-cineol on eNOS signaling, we examined tissue samples of nasal polyps of patients with CRSwNP incubated with 100 μM 1,8-cineol using quantitative real-time PCR, western blot and phosphorylation arrays.

RESULTS

Microarray analysis revealed an increased gene expression of eNOS (1.40-fold) as well as a decreased gene expression of NOSTRIN (0.53-fold) and CASP8 (0.44-fold) in nasal polyps. At the protein level, we detected 2.3-fold higher protein expression of eNOS and significant higher phosphorylation levels of eNOS in nasal polyps (19.7-fold, p ≤ 0.001) compared to inferior turbinates. Additionally, 1,8-cineol did not influence NOSTRIN and CASP8, but decreased the eNOS phosphorylation significantly (p ≤ 0.05).

DISCUSSION

Our study demonstrated for the first time that nasal polyps exhibit an increased phosphorylation of eNOS, which could be important for vascular permeability and the associated edema and elevated inflammation. Additionally, we detected that 1,8-cineol affects the eNOS phosphorylation significantly and thus its activation. This could be important to handle the elevated inflammation and edema formation by regulating the vascular permeability.

Implication of the Kallikrein-Kinin system in neurological disorders: Quest for potential biomarkers and mechanisms

Neurological disorders represent major health concerns in terms of comorbidity and mortality worldwide. Despite a tremendous increase in our understanding of the pathophysiological processes involved in disease progression and prevention, the accumulated knowledge so far resulted in relatively moderate translational benefits in terms of therapeutic interventions and enhanced clinical outcomes. Aiming at specific neural molecular pathways, different strategies have been geared to target the development and progression of such disorders. The kallikrein-kinin system (KKS) is among the most delineated candidate systems due to its ubiquitous roles mediating several of the pathophysiological features of these neurological disorders as well as being implicated in regulating various brain functions. Several experimental KKS models revealed that the inhibition or stimulation of the two receptors of the KKS system (B1R and B2R) can exhibit neuroprotective and/or adverse pathological outcomes. This updated review provides background details of the KKS components and their functions in different neurological disorders including temporal lobe epilepsy, traumatic brain injury, stroke, spinal cord injury, Alzheimer's disease, multiple sclerosis and glioma. Finally, this work will highlight the putative roles of the KKS components as potential neurotherapeutic targets and provide future perspectives on the possibility of translating these findings into potential clinical biomarkers in neurological disease.

Exploring gene expression biomarker candidates for neurobehavioral impairment from total sleep deprivation

Background

Although sleep deprivation is associated with neurobehavioral impairment that may underlie significant risks to performance and safety, there is no reliable biomarker test to detect dangerous levels of impairment from sleep loss in humans. This study employs microarrays and bioinformatics analyses to explore candidate gene expression biomarkers associated with total sleep deprivation (TSD), and more specifically, the phenotype of neurobehavioral impairment from TSD. Healthy adult volunteers were recruited to a sleep laboratory for seven consecutive days (six nights). After two Baseline nights of 10 h time in bed, 11 subjects underwent an Experimental phase of 62 h of continuous wakefulness, followed by two Recovery nights of 10 h time in bed. Another six subjects underwent a well-rested Control condition of 10 h time in bed for all six nights. Blood was drawn for measuring gene expression on days two, four, and six at 4 h intervals from 08:00 to 20:00 h, corresponding to 12 timepoints across one Baseline, one Experimental, and one Recovery day.

Results

Altogether 212 genes changed expression in response to the TSD Treatment, with most genes exhibiting down-regulation during TSD. Also, 28 genes were associated with neurobehavioral impairment as measured by the Psychomotor Vigilance Test. The results support previous findings associating TSD with the immune response and ion signaling, and reveal novel candidate biomarkers such as the Speedy/RINGO family of cell cycle regulators.

Conclusions

This study serves as an important step toward understanding gene expression changes during sleep deprivation. In addition to exploring potential biomarkers for TSD, this report presents novel candidate biomarkers associated with lapses of attention during TSD. Although further work is required for biomarker validation, analysis of these genes may aid fundamental understanding of the impact of TSD on neurobehavioral performance.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4664-3) contains supplementary material, which is available to authorized users.

Bradykinin regulates cell growth and migration in cultured human cardiac c-Kit+ progenitor cells

Bradykinin is a well-known endogenous vasoactive peptide. The present study investigated the bradykinin receptor expression in human cardiac c-Kit⁺ progenitor cells and the potential role of bradykinin in regulating cell cycling progression and mobility. It was found that mRNA and protein of bradykinin type 2 receptors, but not bradykinin type 1 receptors, were abundant in cultured human cardiac c-Kit⁺ progenitor cells. Bradykinin (1-10 nM) stimulated cell growth and migration in a concentration-dependent manner. The increase of cell proliferation was related to promoting G0/G1 transition into G2/M and S phase. Western blots revealed that bradykinin significantly increased pAkt and pERK1/2 as well as cyclin D1, which were countered by HOE140 (an antagonist of bradykinin type 2 receptors) or by silencing bradykinin type 2 receptors. The increase of pAkt, pERK1/2 and cyclin D1 by bradykinin was prevented by the PI3K inhibitor Ly294002, the PLC inhibitors U73122 and neomycin, and/or the PKC inhibitor chelerythrine and the MAPK inhibitor PD98059. Our results demonstrate the novel information that bradykinin promotes cell cycling progression and migration in human cardiac c-Kit⁺ progenitor cells via activating PI3K, PLC, PKC, cyclin D1, pERK1/2, and pAkt.

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.

Differential effect of intranasally administrated kinin B1 and B2 receptor antagonists in Alzheimer’s disease mice

An Increasing body of evidence supports a critical role of brain inflammation in the pathogenesis of Alzheimer’s disease. A principal aspect of the brain immune response to inflammation is the activation of microglia. It has been shown that the kinin system is activated during brain inflammation and previously we demonstrated that bradykinin B1 receptor agonist reduced microglial activation in vitro. The aim of the present study was to investigate the effects of bradykinin B1 or B2 receptor antagonists on microglial release of pro-inflammatory factors in BV2 microglia. In vivo, we focused on the effects of intranasally given kinin antagonists on amyloid burden and microglia/macrophage marker expression in brains of 5X familial Alzheimer’s disease mice. The present data show that pharmacological antagonism of B1 receptor (R-715) but not B2 receptor (HOE-140) markedly increased nitric oxide and tumor necrosis factor alpha release from BV2 microglial cells. We also showed that intranasal treatment with R-715 but not HOE-140 of Alzheimer’s mice enhanced amyloid beta burden and microglia/macrophages activation. Taken together, our data reveal a possible role for the bradykinin B1 receptor in neuroinflammation and in the control of Abeta accumulation in transgenic mice, possibly through regulation of glial cell responses.

Vascular nitric oxide: Beyond eNOS

As the first discovered gaseous signaling molecule, nitric oxide (NO) affects a number of cellular processes, including those involving vascular cells. This brief review summarizes the contribution of NO to the regulation of vascular tone and its sources in the blood vessel wall. NO regulates the degree of contraction of vascular smooth muscle cells mainly by stimulating soluble guanylyl cyclase (sGC) to produce cyclic guanosine monophosphate (cGMP), although cGMP-independent signaling [S-nitrosylation of target proteins, activation of sarco/endoplasmic reticulum calcium ATPase (SERCA) or production of cyclic inosine monophosphate (cIMP)] also can be involved. In the blood vessel wall, NO is produced mainly from l-arginine by the enzyme endothelial nitric oxide synthase (eNOS) but it can also be released non-enzymatically from S-nitrosothiols or from nitrate/nitrite. Dysfunction in the production and/or the bioavailability of NO characterizes endothelial dysfunction, which is associated with cardiovascular diseases such as hypertension and atherosclerosis.

Alcohol potentiates postburn remote organ damage through shifts in fluid compartments mediated by bradykinin

Of the 450,000 burn patients each year, 50% have a positive blood alcohol content, and this predisposes them to worsened clinical outcomes. Despite high prevalence and established consequences, the mechanisms responsible for alcohol-mediated complications of postburn remote organ damage are currently unknown. To this end, mice received a single dose of alcohol (1.12 g/kg) or water by oral gavage and were subjected to a 15% total body surface area burn. Animals with a burn alone lost ∼5% of their body weight in 24 h, whereas intoxicated and burned mice lost only 1% body weight (P < 0.05) despite a 17% increase in hematocrit (P < 0.05) and a 57% increase in serum creatinine (P < 0.05) over burn injury alone. This retention of water weight despite increased dehydration suggests that intoxication at the time of a burn causes a shift in fluid compartments that may exacerbate end-organ ischemia and damage as evidenced by a 3-fold increase in intestinal bacterial translocation (P < 0.05), a 30% increase (P < 0.05) in liver weight-to-body weight ratio, and an increase in alveolar wall thickness over a burn alone. Furthermore, administration of the bradykinin antagonist HOE140 30 min after intoxication and burn restored fluid balance and alleviated end-organ damage. These findings suggest that alcohol potentiates postburn remote organ damage through shifts in fluid compartments mediated by bradykinin.

Functional expression of bradykinin B1 and B2 receptors in neonatal rat trigeminal ganglion neurons

Bradykinin (BK) and its receptors (B₁ and B₂ receptors) play important roles in inflammatory nociception. However, the patterns of expression and physiological/pathological functions of B₁ and B₂ receptors in trigeminal ganglion (TG) neurons remain to be fully elucidated. We investigated the functional expression of BK receptors in rat TG neurons. We observed intense immunoreactivity of B₂ receptors in TG neurons, while B₁ receptors showed weak immunoreactivity. Expression of the B₂ receptor colocalized with immunoreactivities against the pan-neuronal marker, neurofilament H, substance P, isolectin B4, and tropomyosin receptor kinase A antibodies. Both in the presence and absence of extracellular Ca²⁺ ([Ca²⁺]_o), BK application increased the concentration of intracellular free Ca²⁺ ([Ca²⁺]_i). The amplitudes of BK-induced [Ca²⁺]_i increase in the absence of [Ca²⁺]_o were significantly smaller than those in the presence of Ca²⁺. In the absence of [Ca²⁺]_o, BK-induced [Ca²⁺]_i increases were sensitive to B₂ receptor antagonists, but not to a B₁ receptor antagonist. However, B₁ receptor agonist, Lys-[Des-Arg⁹]BK, transiently increased [Ca²⁺]_i in primary cultured TG neurons, and these increases were sensitive to a B₁ receptor antagonist in the presence of [Ca²⁺]_o. These results indicated that B₂ receptors were constitutively expressed and their activation induced the mobilization of [Ca²⁺]_i from intracellular stores with partial Ca²⁺ influx by BK. Although constitutive B₁ receptor expression could not be clearly observed immunohistochemically in the TG cryosection, cultured TG neurons functionally expressed B₁ receptors, suggesting that both B₁ and B₂ receptors involve pathological and physiological nociceptive functions.

Elevation of soluble guanylate cyclase suppresses proliferation and survival of human breast cancer cells

Nitric oxide (NO) is an essential signaling molecule in biological systems. Soluble guanylate cyclase (sGC), composing of α1 and β1 subunit, is the receptor for NO. Using radioimmunoassay, we discovered that activation of sGC by treatment with bradykinin or sodium nitroprusside (SNP) is impaired in MCF-7 and MDA-MB-231 breast cancer cells as compared to normal breast epithelial 184A1 cells. The 184A1 cells expressed both sGC α1 and sGCβ1 mRNAs. However, levels of sGCβ1 mRNAs were relatively lower in MCF-7 cells while both mRNA of sGC subunits were absent in MDA-MB-231 cells. Treatment with DNA methyltransferase inhibitor 5-aza-2’-deoxycytidine (5-aza-dC) increased mRNA levels of both sGCα1 and sGCβ1 in MDA-MB-231 cells but only sGCβ1 mRNAs in MCF-7 cells. The 5-aza-dC treatment increased the SNP-induced cGMP production in MCF-7 and MDA-MB-231, but not in 184A1 cells. Bisulfite sequencing revealed that the promoter of sGCα1 in MDA-MB-231 cells and promoter of sGCβ1 in MCF-7 cells were methylated. Promoter hypermethylation of sGCα1 and sGCβ1 was found in 1 out of 10 breast cancer patients. Over-expression of both sGC subunits in MDA-MB-231 cells induced apoptosis and growth inhibition in vitro as well as reduced tumor incidence and tumor growth rate of MDA-MB-231 xenografts in nude mice. Elevation of sGC reduced protein abundance of Bcl-2, Bcl-xL, Cdc2, Cdc25A, Cyclin B1, Cyclin D1, Cdk6, c-Myc, and Skp2 while increased protein expression of p53. Our study demonstrated that down-regulation of sGC, partially due to promoter methylation, provides growth and survival advantage in human breast cancer cells.

Control of ENaC-mediated sodium reabsorption in the distal nephron by Bradykinin

Kinins, such as Bradykinin (BK), are peptide hormones of the kallikrein-kinin system. Apart from being a vasodilator, BK also increases urinary sodium excretion to reduce systemic blood pressure. It is becoming appreciated that BK modulates function of the epithelial Na(+) channel in the distal part of the renal nephron to affect tubular sodium reabsorption. In this chapter, we outline the molecular details, as well as discuss the physiological relevance of this regulation for the whole organism sodium homeostasis and setting chronic blood pressure.

A review on bradykinin-related peptides isolated from amphibian skin secretion

Amphibian skin secretion has great potential for drug discovery and contributes hundreds of bioactive peptides including bradykinin-related peptides (BRPs). More than 50 BRPs have been reported in the last two decades arising from the skin secretion of amphibian species. They belong to the families Ascaphidae (1 species), Bombinatoridae (3 species), Hylidae (9 speices) and Ranidae (25 species). This paper presents the diversity of structural characteristics of BRPs with N-terminal, C-terminal extension and amino acid substitution. The further comparison of cDNA-encoded prepropeptides between the different species and families demonstrated that there are various forms of kininogen precursors to release BRPs and they constitute important evidence in amphibian evolution. The pharmacological activities of isolated BRPs exhibited unclear structure–function relationships, and therefore the scope for drug discovery and development is limited. However, their diversity shows new insights into biotechnological applications and, as a result, comprehensive and systematic studies of the physiological and pharmacological activities of BRPs from amphibian skin secretion are needed in the future.

Preparation and structural analysis of (±)-cis-ethyl 2-sulfanylidenedecahydro-1,6-naphthyridine-6-carboxylate and (±)-trans-ethyl 2-oxooctahydro-1H-pyrrolo[3,2-c]pyridine-5-carboxylate

Bicycle ring closure on a mixture of (4aS,8aR)- and (4aR,8aS)-ethyl 2-oxodecahydro-1,6-naphthyridine-6-carboxylate, followed by conversion of the separatedcisandtransisomers to the corresponding thioamide derivatives, gave (4aSR,8aRS)-ethyl 2-sulfanylidenedecahydro-1,6-naphthyridine-6-carboxylate, C11H18N2O2S. Structural analysis of this thioamide revealed a structure with two crystallographically independent conformers per asymmetric unit (Z′ = 2). The reciprocal bicycle ring closure on (3aRS,7aRS)-ethyl 2-oxooctahydro-1H-pyrrolo[3,2-c]pyridine-5-carboxylate, C10H16N2O3, was also accomplished in good overall yield. Here the five-membered ring is disordered over two positions, so that both enantiomers are represented in the asymmetric unit. The compounds act as key intermediates towards the synthesis of potential new polycyclic medicinal chemical structures.

Direct regulation of ENaC by bradykinin in the distal nephron. Implications for renal sodium handling

PURPOSE OF REVIEW

Locally produced peptide hormones kinins, such as bradykinin, are thought to oppose many of the prohypertensive actions of the renin-angiotensin-aldosterone system. In the kidney, bradykinin, via stimulation of B2 receptors (B2R), favors natriuresis mostly due to the inhibition of tubular Na reabsorption. Recent experimental evidence identifies the epithelial Na channel (ENaC) as a key end effector of bradykinin actions in the distal tubular segments. The focus of this review is the physiological relevance and molecular details of the bradykinin signal to ENaC.

RECENT FINDINGS

The recent epidemiological GenSalt study demonstrated that genetic variants of the gene encoding B2R show significant associations with the salt sensitivity of blood pressure. Bradykinin was shown to have an inhibitory effect on the distal nephron sodium transport via stimulation of B2 receptor-phospholipase C (B2R-PLC) cascade to decrease ENaC open probability. Genetic ablation of bradykinin receptors in mice led to an augmented ENaC function, particularly during elevated sodium intake, likely contributing to the salt-sensitive hypertensive phenotype. Furthermore, augmentation of bradykinin signaling in the distal nephron was demonstrated to be an important component of the natriuretic and antihypertensive effects of angiotensin converting enzyme inhibition.

SUMMARY

Salt-sensitive inhibition of ENaC activity by bradykinin greatly advances our understanding of the molecular mechanisms that are responsible for shutting down distal tubule sodium reabsorption during volume expanded conditions to avoid salt-sensitive hypertension.

Bradykinin-related peptides (BRPs) from skin secretions of three genera of phyllomedusine leaf frogs and their comparative pharmacological effects on mammalian smooth muscles

While bradykinin has been identified in the skin secretions from several species of amphibian, bradykinin-related peptides (BRPs) are more common constituents. These peptides display a plethora of primary structural variations from the type peptide which include single or multiple amino acid substitutions, N- and/or C-terminal extensions and post-translational modifications such as proline hydroxylation and tyrosine sulfation. Such modified peptides have been reported in species from many families, including Bombinatoridae, Hylidae and Ranidae. The spectrum of these peptides in a given species is thought to be reflective of its predator profile from different vertebrate taxa. Here we report the isolation of BRPs and parallel molecular cloning of their respective biosynthetic precursor-encoding cDNAs from the skin secretions of the Mexican leaf frog (Pachymedusa dacnicolor), the Central American red-eyed leaf frog (Agalychnis callidryas) and the South American orange-legged leaf frog (Phyllomedusa hypochondrialis). Additionally, the eight different BRPs identified were chemically synthesized and screened for bioactivity using four different mammalian smooth muscle preparations and their effects and rank potencies were found to be radically different in these with some acting preferentially through bradykinin B1-type receptors and others through B(2)-type receptors.

Bradykinin promotes vascular endothelial growth factor expression and increases angiogenesis in human prostate cancer cells

Prostate cancer is the most commonly diagnosed malignancy in men and shows a tendency for metastasis to distant organs. Angiogenesis is required for metastasis. Bradykinin (BK) is an inflammatory mediator involved in tumor growth and metastasis, but its role in vascular endothelial growth factor (VEGF) expression and angiogenesis in human prostate cancer remains unknown. The aim of this study was to examine whether BK promotes prostate cancer angiogenesis via VEGF expression. We found that exogenous BK increased VEGF expression in prostate cancer cells and further promoted tube formation in endothelial progenitor cells and human umbilical vein endothelial cells. Pretreatment of prostate cancer with B2 receptor antagonist or small interfering RNA (siRNA) reduced BK-mediated VEGF production. The Akt and mammalian target of rapamycin (mTOR) pathways were activated after BK treatment, and BK-induced VEGF expression was abolished by the specific inhibitor and siRNA of the Akt and mTOR cascades. BK also promoted nuclear factor-κB (NF-κB) and activator protein 1 (AP-1) activity. Importantly, BK knockdown reduced VEGF expression and abolished prostate cancer cell conditional medium-mediated angiogenesis. Taken together, these results indicate that BK operates through the B2 receptor, Akt, and mTOR, which in turn activate NF-κB and AP-1, activating VEGF expression and contributing to angiogenesis in human prostate cancer cells.

Involvement of intercellular adhesion molecule-1 up-regulation in bradykinin promotes cell motility in human prostate cancers

Prostate cancer is the most commonly diagnosed malignancy in men and shows a predilection for metastasis to distant organs. Bradykinin (BK) is an inflammatory mediator and has recently been shown to mediate tumor growth and metastasis. The adhesion molecule intercellular adhesion molecule-1 (ICAM-1) plays a critical role during tumor metastasis. The aim of this study was to examine whether BK promotes prostate cancer cell migration via ICAM-1 expression. The motility of cancer cells was increased following BK treatment. Stimulation of prostate cancer cells with BK induced mRNA and protein expression of ICAM-1. Transfection of cells with ICAM-1 small interfering RNA reduced BK-increased cell migration. Pretreatment of prostate cancer cells with B2 receptor, phosphatidylinositol 3-kinase (PI3K), Akt, and activator protein 1 (AP-1) inhibitors or mutants abolished BK-promoted migration and ICAM-1 expression. In addition, treatment with a B2 receptor, PI3K, or Akt inhibitor also reduced BK-mediated AP-1 activation. Our results indicate that BK enhances the migration of prostate cancer cells by increasing ICAM-1 expression through a signal transduction pathway that involves the B2 receptor, PI3K, Akt, and AP-1. Thus, BK represents a promising new target for treating prostate cancer metastasis.

Prospective and management: acute nonimmunologic inhalation injuries

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Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

Bradykinin enhances cell migration in human prostate cancer cells through B2 receptor/PKCδ/c-Src dependent signaling pathway

BACKGROUND

Prostate cancer is the most commonly diagnosed malignancy in men and shows a predilection for metastasis to the bone. Bradykinin (BK) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. The aim of this study was to investigate whether Bradykinin is associated with migration of prostate cancer cells.

METHODS

Cancer cells migration activity was examined using the Transwell assay. The c-Src and PKCδ phosphorylation was examined by using Western blot method. The qPCR was used to examine the mRNA expression of metalloproteinase. A transient transfection protocol was used to examine NF-κB activity.

RESULTS

We found that bradykinin increased the chemomigration and the expression of MMP-9 of human prostate cancer cells. Bradykinin-mediated chemomigration and metalloproteinase expression was attenuated by PKCδ inhibitor (rottlerin), PKCδ siRNA, c-Src inhibitor (PP2) and c-Src mutant. Activations of PKCδ, c-Src and NF-κB pathways after bradykinin treatment was demonstrated, and bradykinin-induced expression of metalloproteinase and chemomigration activity was inhibited by the specific inhibitor and mutant of PKCδ, c-Src, and NF-κB cascades.

CONCLUSIONS

This study showed for the first time that the bradykinin mediates migration of human prostate cancer cells. One of the mechanisms underlying bradykinin directed migration was transcriptional up-regulation of MMP-9 and activation of B2 receptor, PKCδ, c-Src, and NF-κB pathways.

Expression patterns of kinin-dependent genes in endometrial cancer

OBJECTIVE

The present study has focused on the identification of the differences between expression patterns of kinin-dependent genes in endometrial cancer with the use of real-time quantitative reverse transcription polymerase chain reaction and oligonucleotide microarray.

MATERIALS AND METHODS

The study group consisted of 50 endometrium samples collected from women with endometrial cancer. Gene expression of kinin receptors BR1 and BR2 was evaluated with real-time quantitative reverse transcription polymerase chain reaction. The analysis of the expression profile of genes related to the kinin mitogenic signal transduction pathway was performed using HG-U133A oligonucleotide microarrays.

RESULTS

The transcriptional activity of the B1 receptor for kinins increased in patients with grade 1 (G1) and grade 2 (G2) endometrial cancer when compared to the control group, whereas it decreased in patients with grade 3 (G3) endometrial cancer. The expression of the B2 receptor showed a growing trend reaching the peak in the G2, whereas G3 was characterized by a decrease in the gene transcriptional activity. Significant differential gene expression was recorded for GNB1, PRKAR1A, KRAS, MAP2K2, GNG5, MAPK1, ADCY9, GNG11, JUN, PRKCA, PRKACB, FOS, PLCB4, ADCY8, and GNG12.

CONCLUSION

The expression changes in kinin-dependent genes might cause disturbance in the underlying biological processes, which could be important for the pathogenesis of endometrial cancer. This will eventually help to improve treatment strategies for patients with endometrial cancer in the future.

Salt-dependent inhibition of epithelial Na+ channel-mediated sodium reabsorption in the aldosterone-sensitive distal nephron by bradykinin

We have documented recently that bradykinin (BK) directly inhibits activity of the epithelial Na(+) channel (ENaC) via the bradykinin B2 receptor (B2R)-G(q/11)-phospholipase C pathway. In this study, we took advantage of mice genetically engineered to lack bradykinin receptors (B1R, B2R(-/-)) to probe a physiological role of BK cascade in regulation of ENaC in native tissue, aldosterone-sensitive distal nephron. Under normal sodium intake (0.32% Na(+)), ENaC open probability (P(o)) was modestly elevated in B1R, B2R(-/-) mice compared with wild-type mice. This difference is augmented during elevated Na(+) intake (2.00% Na(+)) and negated during Na(+) restriction (<0.01% Na(+)). Saturation of systemic mineralocorticoid status with deoxycorticosterone acetate similarly increased ENaC activity in both mouse strains, suggesting that the effect of BK on ENaC is independent of aldosterone. It is accepted that angiotensin-converting enzyme represents the major pathway of BK degradation. Systemic inhibition of angiotensin-converting enzyme with captopril (30 mg/kg of body weight for 7 days) significantly decreases ENaC activity and P(o) in wild-type mice, but this effect is diminished in B1R, B2R(-/-) mice. At the cellular level, acute captopril (100 μmol/L) treatment sensitized BK signaling cascade and greatly potentiated the inhibitory effect of 100 nmol/L of BK on ENaC. We concluded that BK cascade has its own specific role in blunting ENaC activity, particularly under conditions of elevated sodium intake. Augmentation of BK signaling in the aldosterone-sensitive distal nephron inhibits ENaC-mediated Na(+) reabsorption, contributing to the natriuretic and antihypertensive effects of angiotensin-converting enzyme inhibition.

The role of inflammation and COX-derived prostanoids in the effects of bradykinin on isolated rat aorta and urinary bladder

Bradykinin, a vasoactive peptide, increases during inflammation and induces the formation of prostaglandins through specific receptor activation. Two types of receptors mediate the biological effects of bradykinin, B(1) and B(2) receptors. Although B(2) receptors are present in most tissues, B(1) receptors are expressed after inflammatory stimuli or tissue injury. Bradykinin has a high affinity for B(2) and a low affinity for B(1) receptors, whereas the opposite occurs for des-Arg(9)-bradykinin. Recently, it has been reported that nonsteroidal anti-inflammatory drugs have different inhibitory activities on cyclooxygenase isozymes, COX-1, COX-2, and COX-3. In the present study, we have investigated the contributions of different COX isozyme inhibitions and inflammation on bradykinin-induced effects of isolated rat aorta and urinary bladder smooth muscle contractions. Male Sprague-Dawley rats weighing 200-250 g were used in the study. The vasodilatory responses to bradykinin (1 nM-1 μM) were studied on isolated rat aorta rings contracted with norepinephrine (0.1 μM) following incubation with dipyrone (100, 700, and 2,000 μM). The relaxant responses of dipyrone (100, 700, and 2,000 μM) were also compared on the isolated rat urinary bladder contracted with bradykinin (n = 8). A bacterial lipopolysaccharide was used for the induction of inflammation (n = 8). The levels of PGE(2), PGF(1α), TXB(2), nitric oxide synthase (NOS), IL-10, and TNF-α were all determined in both the plasma and the perfusate of the aorta preparations (n = 5). The vasodilatory activities of bradykinin and des-Arg9-bradykinin were significantly increased upon the inhibition of COX-3 (dipyrone at 100 μM). These effects disappeared in the inflamed group. PGE(2), PGF1α, and TXB(2) were significantly high, but NOS activity was low in the aorta perfusate after the inhibition of COX-3. Dipyrone showed the relaxant activity of the urinary bladder contracted with bradykinin. The vasodilatory activity of des-Arg(9)-bradykinin was in the inflamed group but not in the non-inflamed group. Bradykinin did not contract urinary bladder in inflamed group. The results suggest that COX-induced products may play an important role in the bradykinin-induced rat aortic smooth muscle relaxations.

Bradykinin-induced leukocyte- and platelet-endothelium interactions in the cerebral microcirculation

Bradykinin is known for its pathophysiological role as mediator of inflammation. Following cerebral ischemia, bradykinin promotes the secondary brain damage through an increase of vascular permeability and brain edema formation, again hallmarks of inflammation. It is not clear, whether bradykinin also activates inflammatory cells and regulates microcirculatory blood flow in the brain. The purpose of the study is to investigate the reaction of bradykinin upon cerebral leukocyte- and thrombocyte-endothelium interactions as well as microvascular perfusion. Intravital fluorescence microscopy of pial blood vessels was performed in gerbils. Intracarotid injection of bradykinin resulted in increased numbers of rolling and adherent leukocytes as well as rolling platelets at the venular endothelium. This was reversed by administration of a bradykinin B2 receptor antagonist. In contrast, after additional administration of a B1 receptor antagonist, microvascular blood-flow and capillary density was decreased. We conclude that bradykinin initiates leukocyte- and platelet-endothelium interactions in the cerebral microcirculation via activation of B2 receptors. Activation of B1 receptors ensures regular cerebral perfusion. Thus, to attenuate secondary brain damage, inhibition of B2 but not B1 receptors might be of therapeutical benefit.

Cardiovascular and vasoconstrictive actions of skate bradykinin in the little skate, Leucoraja erinacea (Elasmobranchii)

The vasoconstrictive and cardiovascular actions of a recently identified bradykinin (BK)-related peptide (Gly-Ile-Thr-Ser-Trp-Leu-Pro-Phe) from the little skate, Leucoraja erinacea were examined in the unanesthetised little skate. Intra-arterial administration of a skate BK (0.1-1 nmolkg(-1)) produced a hypertensive response with a rise in blood pressure reaching a maximum elevation of 28.7±4.8% over baseline (P<0.05, n=8) that was sustained for at least 12 min following administration of a 1 and 0.3 nmolkg(-1) dose of skate BK. Further, in vivo administration of 1 nmolkg(-1) skate BK induced a significant delayed increase in stroke volume (reaching a maximum of 54.4±14.7% above baseline) without significant effect on either cardiac output or heart rate. In vitro, skate BK constricted the 1st branchial, mesenteric (EC(50) 2.7×10(-9)M) and coeliac (EC(50) 3.1×10(-9)M) arterial preparations of the skate. In contrast, skate [Arg(9)]BK, the mammalian B(1) receptor agonist des-[Arg(9)]BK, and the mammalian B(2) receptor antagonist HOE-140 failed to induce vasoconstriction in these isolated arterial preparations. The vasoconstrictor actions of skate BK in the isolated mesenteric, coeliac and branchial arterial preparations were significantly inhibited when co-administrated with esculetin and phentolamine. Indomethacin also inhibited the vasoconstrictor actions of skate BK in the isolated branchial artery. We conclude that, as in mammals and teleost fish, multiple pathways involving at least the alpha adrenergic and leukotriene synthesis pathway are involved in mediating the vasoconstrictive actions of BK in vascular smooth muscle of the little skate.

Up-regulation of bradykinin B2 receptor by Pseudomonas aeruginosa via the NF-κB pathway

As the first line of host defense, inflammatory responses in response to bacterial infection are initiated by the production of a range of mediators. Infection of Pseudomonas aeruginosa has been shown to stimulate the production of bradykinin (BK), which is known as a universal mediator for the induction of inflammatory reaction via the predominant interaction with the bradykinin B2 receptor (B2R). Thus, the interaction between BK and B2R represents an important host innate response against invading P. aeruginosa. However, the contribution of P. aeruginosa to the up-regulation of B2R expression remains unclear. Here, we report that P. aeruginosa is potent in inducing the expression of B2R at the mRNA and protein levels in a dose- and time-dependent manner. Components produced and secreted from P. aeruginosa could play an essential role in inducing B2R expression, and the secreted components are not under the control of Type III secretion system or quorum sensing. B2R expression in response to P. aeruginosa is mediated by the induction of cellular signaling that leads to the activation of transcription factor NF-κB. Thus, this study demonstrates that P. aeruginosa is able to up-regulate the expression of B2R during infection via the NF-κB signaling pathway.

Nociceptive tolerance is improved by bradykinin receptor B1 antagonism and joint morphology is protected by both endothelin type A and bradykinin receptor B1 antagonism in a surgical model of osteoarthritis

Introduction

Endothelin-1, a vasoconstrictor peptide, influences cartilage metabolism mainly via endothelin receptor type A (ETA). Along with the inflammatory nonapeptide vasodilator bradykinin (BK), which acts via bradykinin receptor B1 (BKB1) in chronic inflammatory conditions, these vasoactive factors potentiate joint pain and inflammation. We describe a preclinical study of the efficacy of treatment of surgically induced osteoarthritis with ETA and/or BKB1 specific peptide antagonists. We hypothesize that antagonism of both receptors will diminish osteoarthritis progress and articular nociception in a synergistic manner.

Methods

Osteoarthritis was surgically induced in male rats by transection of the right anterior cruciate ligament. Animals were subsequently treated with weekly intra-articular injections of specific peptide antagonists of ETA and/or BKB1. Hind limb nociception was measured by static weight bearing biweekly for two months post-operatively. Post-mortem, right knee joints were analyzed radiologically by X-ray and magnetic resonance, and histologically by the OARSI histopathology assessment system.

Results

Single local BKB1 antagonist treatment diminished overall hind limb nociception, and accelerated post-operative recovery after disease induction. Both ETA and/or BKB1 antagonist treatments protected joint radiomorphology and histomorphology. Dual ETA/BKB1 antagonism was slightly more protective, as measured by radiology and histology.

Conclusions

BKB1 antagonism improves nociceptive tolerance, and both ETA and/or BKB1 antagonism prevents joint cartilage degradation in a surgical model of osteoarthritis. Therefore, they represent a novel therapeutic strategy: specific receptor antagonism may prove beneficial in disease management.

Bradykinin acutely inhibits activity of the epithelial Na+ channel in mammalian aldosterone-sensitive distal nephron

Activation of the renal kallikrein-kinin system results in natriuresis and diuresis, suggesting its possible role in renal tubular sodium transport regulation. Here, we used patch-clamp electrophysiology to directly assess the effects of bradykinin (BK) on the epithelial Na(+) channel (ENaC) activity in freshly isolated split-opened murine aldosterone-sensitive distal nephrons (ASDNs). BK acutely inhibits ENaC activity by reducing channel open probability (P(o)) in a dose-dependent and reversible manner. Inhibition of B2 receptors with icatibant (HOE-140) abolished BK actions on ENaC. In contrast, activation of B1 receptors with the selective agonist Lys-des-Arg(9)-BK failed to reproduce BK actions on ENaC. This is consistent with B2 receptors playing a critical role in mediating BK signaling to ENaC. BK has little effect on ENaC P(o) when G(q/11) was inhibited with Gp antagonist 2A. Moreover, inhibition of phospholipase C (PLC) with U73122, but not saturation of cellular cAMP levels with the membrane-permeable nonhydrolysable cAMP analog 8-cpt-cAMP, prevents BK actions on ENaC activity. This argues that BK stimulates B2 receptors with subsequent activation of G(q/11)-PLC signaling cascade to acutely inhibit ENaC activity. Activation of BK signaling acutely depletes apical PI(4,5)P(2) levels. However, inhibition of Ca(2+) pump SERCA of the endoplasmic reticulum with thapsigargin does not prevent BK signaling to ENaC. Furthermore, caffeine, while producing a similar rise in [Ca(2+)](i) as in response to BK stimulation, fails to recapitulate BK actions on ENaC. Therefore, we concluded that BK acutely inhibits ENaC P(o) in mammalian ASDN via stimulation of B2 receptors and following depletion of PI(4,5)P(2), but not increases in [Ca(2+)](i).

Bradykinin enhances cell migration in human chondrosarcoma cells through BK receptor signaling pathways

Bradykinin (BK) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. BK has recently been shown to be involved in carcinogenesis and cancer progression. In this study, we found that BK increased the migration and the expression of alpha2beta1 integrin in human chondrosarcoma cells. We also found that human chondrosarcoma tissues had significantly higher expression of the B1 and B2 receptors comparing to normal cartilage. BK-mediated migration and integrin up-regulation was attenuated by B1 and B2 BK receptor siRNA or antagonist. Activations of phospholipase C (PLC), protein kinase Cdelta (PKCdelta), and NF-kappaB pathways after BK treatment was demonstrated, and BK-induced integrin expression and migration activity was inhibited by the specific inhibitor of PLC, PKCdelta, and NF-kappaB cascades. Taken together, our results indicated that BK enhances the migration of chondrosarcoma cells by increasing alpha2beta1 integrin expression through the BK receptors/PLC/PKCdelta/NF-kappaB signal transduction pathway.