Induction of B(1)-kinin receptors in vascular smooth muscle cells: cellular mechanisms of map kinase activation

Angiotensin-converting enzyme 2, the complement system, the kallikrein-kinin system, type-2 diabetes, interleukin-6, and their interactions regarding the complex COVID-19 pathophysiological crossroads

Because of the current COVID-19-pandemic, the world is currently being held hostage in various lockdowns. ACE2 facilitates SARS-CoV-2 cell-entry, and is at the very center of several pathophysiological pathways regarding the RAAS, CS, KKS, T2DM, and IL-6. Their interactions with severe COVID-19 complications (e.g. ARDS and thrombosis), and potential therapeutic targets for pharmacological intervention, will be reviewed.

Peptidoglycan induces bradykinin receptor 1 expression through Toll-like receptor 2 and NF-κB signaling pathway in human nasal mucosa-derived fibroblasts of chronic rhinosinusitis patients

Numerous studies have demonstrated that Gram-positive microbiomes play an important role in the pathogenesis and in the way of treatment of chronic rhinosinusitis (CRS). Kinins are inflammatory mediators and one of their receptors, namely bradykinin receptor 1 (BKR1 or B1R), is believed to be induced and involved in inflammation in pathophysiological conditions. In the present study, we investigated the effect of peptidoglycan (PGN), a major cell wall component of G(+) bacteria, on BKR expression and its signaling pathway in nasal fibroblasts from CRS without nasal polyp (CRSsNP). The PGN induced increases in B1R mRNA and protein production. The induction was abolished by the NF-κB and protein kinase A inhibitor. In parallel, the PGN treatment directly activated IκB/NF-κB signaling and CREB phosphorylation. Interestingly, a further analysis suggested no involvement of cAMP/PKA/CREB pathway in this induction. The B1R expression and IκB/NF-κB signaling pathway could be attenuated by Toll-like receptor-2 (TLR2) blocking/neutralizing Ab. In a functional assay, the addition of B1R selective agonist (Des-Arg¹⁰ -kallidin) to the fibroblasts after PGN stimulation led to an increase in CXCL8 release and p38 MAPK and ERK1/2 phosphorylation, which could be inhibited by the B1R antagonist. Taken together, our results revealed for the first time that PGN can increase B1R expression in human nasal mucosa-derived fibroblasts through TLR2 activation and NF-κB signaling pathway. This induction functionally leads to MAPKs activation and CXCL8 release upon B1R stimulation. Our results also suggest that a major component of G(+) bacteria can participate in B1R upregulation in nasal mucosa during CRSsNP progression.

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.

Urolinin: The First Linear Peptidic Urotensin-II Receptor Agonist

This study investigated the role of individual U-II amino acid positions and side chain characteristics important for U-IIR activation. A complete permutation library of 209 U-II variants was studied in an activity screen that contained single substitution variants of each position with one of the other 19 proteinogenic amino acids. Receptor activation was measured using a cell-based high-throughput fluorescence calcium mobilization assay. We generated the first complete U-II substitution map for U-II receptor activation, resulting in a detailed view into the structural features required for receptor activation, accompanied by complementary information from receptor modeling and ligand docking studies. On the basis of the systematic SAR study of U-II, we created 33 further short and linear U-II variants from eight to three amino acids in length, including d- and other non-natural amino acids. We identified the first high-potency linear U-II analogues. Urolinin, a linear U-II agonist (nWWK-Tyr(3-NO₂)-Abu), shows low nanomolar potency as well as improved metabolic stability.

Predictive value of serum bradykinin and desArg9-bradykinin levels for chemotherapeutic responses in active tuberculosis patients: A retrospective case series

BACKGROUND

There is an urgent need for methods that can rapidly and accurately assess therapeutic responses in patients with active tuberculosis (TB) in order to predict treatment outcomes. Exposure to bacterial pathogens can rapidly activate the plasma contact system, triggering the release of bradykinin (BK) and its metabolite desArg⁹-bradykinin (DABK) to induce inflammation and innate immune responses. We hypothesized that serum BK and DABK levels might act as sensitive immune response signatures for changes in Mycobacterium tuberculosis (Mtb) burden, and therefore examined how serum levels of these markers corresponded with anti-TB therapy in a small cohort of active TB cases.

METHODS

Nanotrap Mass-Spectrometry (MS) was used to analyze serial blood specimens from 13 HIV-negative adults with microbiologically confirmed active TB who were treated with first-line anti-TB chemotherapy. MS signal for BK (m/z 1060.5) and DABK (m/z 904.5) serum peptides were evaluated at multiple time-points (before, during, and after treatment) to evaluate how BK and DABK levels corresponded with disease status.

RESULTS

Serum BK levels declined from pretreatment baseline levels during the early stage anti-TB therapy (induction phase) and tended to remain below baseline levels during extended treatment (consolidation phase) and after therapy completion. BK levels were consistent with induction phase sputum culture conversions indicative of decreased Mtb burden reflecting good treatment responses. Serum DABK levels tended to increase during the induction phase and decrease at consolidation and post-therapy time points, which may indicate a shift from active disease to chronic inflammation to a disease free state. Elevated BK and DABK levels after treatment completion in one patient may be related to the subsequent recurrent TB disease.

CONCLUSIONS

Our pilot data suggests that changes in the circulating BK and DABK levels in adult TB patients can be used as potential surrogate markers of the host response both early and late in anti-TB treatment for both pulmonary and extrapulmonary TB patients. We will further exploit these host-response signatures in the future as biomarkers in combination with other clinical and microbiologic tools which may improve treatment efficacy and facilitate the development of host-directed therapy.

An interaction of renin-angiotensin and kallikrein-kinin systems contributes to vascular hypertrophy in angiotensin II-induced hypertension: in vivo and in vitro studies

The kallikrein-kinin and renin-angiotensin systems interact at multiple levels. In the present study, we tested the hypothesis that the B1 kinin receptor (B1R) contributes to vascular hypertrophy in angiotensin II (ANG II)-induced hypertension, through a mechanism involving reactive oxygen species (ROS) generation and extracellular signal-regulated kinase (ERK1/2) activation. Male Wistar rats were infused with vehicle (control rats), 400 ng/Kg/min ANG II (ANG II rats) or 400 ng/Kg/min ANG II plus B1 receptor antagonist, 350 ng/Kg/min des-Arg(9)-Leu(8)-bradykinin (ANGII+DAL rats), via osmotic mini-pumps (14 days) or received ANG II plus losartan (10 mg/Kg, 14 days, gavage - ANG II+LOS rats). After 14 days, ANG II rats exhibited increased systolic arterial pressure [(mmHg) 184 ± 5.9 vs 115 ± 2.3], aortic hypertrophy; increased ROS generation [2-hydroxyethidium/dihydroethidium (EOH/DHE): 21.8 ± 2.7 vs 6.0 ± 1.8] and ERK1/2 phosphorylation (% of control: 218.3 ± 29.4 vs 100 ± 0.25]. B1R expression was increased in aortas from ANG II and ANG II+DAL rats than in aortas from the ANG II+LOS and control groups. B1R antagonism reduced aorta hypertrophy, prevented ROS generation (EOH/DHE: 9.17 ± 3.1) and ERK1/2 phosphorylation (137 ± 20.7%) in ANG II rats. Cultured aortic vascular smooth muscle cells (VSMC) stimulated with low concentrations (0.1 nM) of ANG II plus B1R agonist exhibited increased ROS generation, ERK1/2 phosphorylation, proliferating-cell nuclear antigen expression and [H3]leucine incorporation. At this concentration, neither ANG II nor the B1R agonist produced any effects when tested individually. The ANG II/B1R agonist synergism was inhibited by losartan (AT1 blocker, 10 µM), B1R antagonist (10 µM) and Tiron (superoxide anion scavenger, 10 mM). These data suggest that B1R activation contributes to ANG II-induced aortic hypertrophy. This is associated with activation of redox-regulated ERK1/2 pathway that controls aortic smooth muscle cells growth. Our findings highlight an important cross-talk between the DABK and ANG II in the vascular system and contribute to a better understanding of the mechanisms involved in vascular remodeling in hypertension.

Ischemic stroke and traumatic brain injury: the role of the kallikrein-kinin system

Acute ischemic stroke and traumatic brain injury are a major cause of mortality and morbidity. Due to the paucity of therapies, there is a pressing clinical demand for new treatment options. Successful therapeutic strategies for these conditions must target multiple pathophysiological mechanisms occurring at different stages of brain injury. In this respect, the kallikrein-kinin system is an ideal target linking key pathological hallmarks of ischemic and traumatic brain damage such as edema formation, inflammation, and thrombosis. In particular, the kinin receptors, plasma kallikrein, and coagulation factor XIIa are highly attractive candidates for pharmacological development, as kinin receptor antagonists or inhibitors of plasma kallikrein and coagulation factor XIIa are neuroprotective in animal models of stroke and traumatic brain injury. Nevertheless, conflicting preclinical evaluation as well as limited and inconclusive data from clinical trials suggest caution when transferring observations made in animals into the human situation. This review summarizes current evidence on the pathological significance of the kallikrein-kinin system during ischemic and traumatic brain damage, with a particular focus on experimental data derived from animal models. Experimental findings are also compared with human data if available, and potential therapeutic implications are discussed.

Endothelium dependent expression and underlying mechanisms of des-Arg⁹-bradykinin-induced B₁R-mediated vasoconstriction in rat portal vein

Endothelial dysfunction has been implicated in portal vein obstruction, a condition responsible for major complications in chronic portal hypertension. Increased vascular tone due to disruption of endothelial function has been associated with an imbalance in the equilibrium between endothelium-derived relaxing and contracting factors. Herein, we assessed underlying mechanisms by which expression of bradykinin B(1) receptor (B(1)R) is induced in the endothelium and how its stimulation triggers vasoconstriction in the rat portal vein. Prolonged in vitro incubation of portal vein resulted in time- and endothelium-dependent expression of B(1)R and cyclooxygenase-2 (COX-2). Inhibition of protein kinase C (PKC) or phosphatidylinositol 3-kinase (PI3K) significantly reduced expression of B(1)R through the regulation of transcription factors, activator protein-1 (AP-1) and cAMP response element-binding protein (CREB). Moreover, pharmacological studies showed that B(1)R-mediated portal vein contraction was reduced by COX-2, but not COX-1, inhibitors. Notably, activation of endothelial B(1)R increased phospholipase A(2)/COX-2-derived thromboxane A(2) (TXA(2)) levels, which in turn mediated portal vein contraction through binding to TXA(2) receptors expressed in vascular smooth muscle cells. These results provide novel molecular mechanisms involved in the regulation of B(1)R expression and identify a critical role for the endothelial B(1)R in the modulation of portal vein vascular tone. Our study suggests a potential role for B(1)R antagonists as therapeutic tools for diseases where portal hypertension may be involved.

Kinin B1 receptor upregulation by angiotensin II and endothelin-1 in rat vascular smooth muscle cells: receptors and mechanisms

Oxidative stress upregulates the kinin B1 receptor (B1R) in diabetes and hypertension. Since angiotensin II (ANG II) and endothelin-1 (ET-1) are increased in these disorders, this study aims at determining the role of these two prooxidative peptides in B1R expression in rat vascular smooth muscle cells (VSMC). In the A10 cell line and aortic VSMC, ANG II enhanced B1R protein expression in a concentration- and time-dependent manner (maximal at 1 μM and 6 h). In A10 cells, ANG II (1 μM) also increased B1R mRNA expression at 3 h and the activation of induced B1R with the agonist [Sar-d-Phe8]-des-Arg9-BK (10 nM, 5 min) significantly enhanced mitogen -activated protein kinase (MAPK1/2) phosphorylation. The enhancing effect of ANG II on B1R protein expression in A10 cells was normalized by the AT1 (losartan) but not by the AT2 (PD123319) receptor antagonist. Furthermore, it was inhibited by inhibitors of phosphatidylinositol 3-kinase (wortmannin) and NF-κB (MG132) but not of MAPK (PD098059). Whereas the ETB receptor antagonist (BQ788) had no effect, the ETA receptor antagonist (BQ123) blocked the effect of ANG II at 6–8 h but not at an early time point. BQ123 and BQ788 also blocked the increasing effect of ET-1 on B1R protein expression. Antioxidants ( N-acetyl-l-cysteine and diphenyleneiodonium) abolished ANG II- and ET-1-increased B1R protein expression. In conclusion, B1R induction is linked to oxidative stress and activation of phosphatidylinositol 3-kinase and NF-κB. The newly synthesized B1R is functional and can activate MAPK signaling in VSMC. The effect of ANG II is mediated by the AT1 receptor and the subsequent activation of ETA through ET-1 release.

Differential regulation of inducible and endothelial nitric oxide synthase by kinin B1 and B2 receptors

Kinins are vasoactive peptides that play important roles in cardiovascular homeostasis, pain and inflammation. After release from their precursor kininogens, kinins or their C-terminal des-Arg metabolites activate two distinct G protein-coupled receptors (GPCR), called B2 (B2R) or B1 (B1R). The B2R is expressed constitutively with a wide tissue distribution. In contrast, the B1R is not expressed under normal conditions but is upregulated by tissue insult or inflammatory mediators. The B2R is considered to mediate many of the acute effects of kinins while the B1R is more responsible for chronic responses in inflammation. Both receptors can couple to Galphai and Galphaq families of G proteins to release mediators such as nitric oxide (NO), arachidonic acid, prostaglandins, leukotrienes and endothelium-derived hyperpolarizing factor and can induce the release of other inflammatory agents. The focus of this review is on the different transduction events that take place upon B2R and B1R activation in human endothelial cells that leads to generation of NO via activation of different NOS isoforms. Importantly, B2R-mediated eNOS activation leads to a transient ( approximately 5min) output of NO in control endothelial cells whereas in cytokine-treated endothelial cells, B1R activation leads to very high and prolonged ( approximately 90min) NO production that is mediated by a novel signal transduction pathway leading to post-translational activation of iNOS.

The kinin B(1) receptor and inflammation: new therapeutic target for cardiovascular disease

The kinin B(1) receptor plays an important role in mediating the inflammatory effects of the kallikrein-kinin pathway. The recent development of orally available non-peptidic antagonists and genetically modified mice deficient in B(1) receptor expression have demonstrated that the receptor plays a pivotal role in the cellular, particularly neutrophil, recruitment associated with an acute inflammatory response. These tools have also enabled elucidation of the pathways involved in mediating this effect and have highlighted a major role for chemokines, particularly CXCL5 and CCL2. Neutrophil recruitment is involved in the pathogenesis of renal disease and has very recently been implicated in the early stages of atherosclerosis. In this review we discuss the most recent evidence linking the B(1) receptor with the pathogenesis of these two inflammatory cardiovascular diseases and highlight the therapeutic potential of the kinin B(1) receptor in these disease states.

High glucose increases B1-kinin receptor expression and signaling in endothelial cells

The loss of endothelial function is the initiating factor in the development of diabetic vascular disease. Kinins control endothelial function by the activation of two receptors: the B2 which is constitutively expressed, and the B1 which is highly induced in pathological conditions. In the present study, we observed that the levels of B1-receptor mRNA and protein are induced in endothelial cells incubated in high glucose. An increase in B1-receptor was also observed in the endothelial layer of aortas, from 4-week diabetic rats. When cells were grown in high glucose, the B1 agonist des-Arg9-BK increased nitrite levels, whereas in normal glucose nitrite levels were unchanged. Nitrite increase was blocked by L-NAME and 1400W indicating the participation of the inducible Nitric Oxide Synthase (iNOS). iNOS protein levels were also increased in high glucose. These results demonstrate the participation of the B1 receptor in the signaling pathways mediated by kinins in high glucose.

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.

Research progress of vasculopathy in portal hypertension

Portal hypertension, one of the vascular diseases, not only has lesions in liver, but also changes in vascular structures and functions of extrahepatic portal system, systemic system and pulmonary circulation. The pathological changes of vasculopathy in portal hypertension include remodeling of arterialized visceral veins, intimal injury of visceral veins and destruction of contractile structure in visceral arterial wall. The mechanisms of vasculopathy in portal hypertension may be attributed to the changes of hemodynamics in portal system, immune response, gene modulation, vasoactive substances, and intrahepatic blood flow resistance. Portal hypertension can cause visceral hyperdynamic circulation, and the development and progression of visceral vasculopathy, while visceral vasculopathy can promote the development and progression of portal hypertension and visceral hyperdynamic circulation in turn. The aforementioned three factors interact in the pathogenesis of hepatic cirrhosis-induced portal hypertension and are involved in hemorrhage due to varicose vein rupture.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Kinin B1 receptors stimulate nitric oxide production in endothelial cells: signaling pathways activated by angiotensin I-converting enzyme inhibitors and peptide ligands

We reported previously a novel mode of action of angiotensin I-converting enzyme (kininase II; ACE) inhibitors mediated through the direct activation of bradykinin B(1) receptor, independent of endogenous kinins or ACE (J Biol Chem 277:16847-16852, 2002). We aimed to further clarify the mechanism of activation of B(1) receptor, which leads to prolonged nitric oxide (NO) release. The ACE inhibitor enalaprilat and the peptide ligand desArg(10)-kallidin (in nanomolar concentrations) release NO by activating endothelial NO synthase (eNOS) in bovine and inducible NO synthase (iNOS) in stimulated human endothelial cells. The peptide and the ACE inhibitor ligands activate eNOS by facilitating different signaling pathways. DesArg(10)-kallidin enhances inositol-phosphate generation and elevates [Ca(2+)](i) by first augmenting intracellular release and then the influx of extracellular Ca(2+). In contrast, enalaprilat stimulates only the influx of extracellular Ca(2+) through rare earth-sensitive channels, and its effect is blocked by cholera toxin or protein kinase C inhibitors. In addition, unlike desArg(10)-kallidin, enalaprilat can also release NO independent of Ca(2+) in bovine endothelial cells. The inflammatory cytokines interleukin-1beta and interferon-gamma induce both B(1) receptor and iNOS in human endothelial cells. In contrast to eNOS, B(1) ligands activate iNOS similarly. Both desArg(10)-kallidin and ACE inhibitors enhance arginine uptake and release NO independent of [Ca(2+)](i) elevation. This is the first report on the direct activation of B(1) receptor by ACE inhibitors in human endothelial cells. This interaction leads to prolonged NO release and possibly contributes to the documented benefits of the use of ACE inhibitors.