C21 preserves endothelial function in the thoracic aorta from DIO mice: role for AT2, Mas and B2 receptors

Compound 21 (C21), a selective agonist of angiotensin type 2 receptor (AT2R), induces vasodilation through NO release. Since AT2R seems to be overexpressed in obesity, we hypothesize that C21 prevents the development of obesity-related vascular alterations. The main goal of this study was to assess the effect of C21on thoracic aorta endothelial function in a model of diet-induced obesity and to elucidate the potential crosstalk between AT2R, MasR and/or B2R in this response. 5-week-old male C57BL6J mice were fed a standard (CHOW) or a high-fat diet (HF) for 6 weeks and treated daily with C21 (1mg/Kg p.o) or vehicle, generating four groups: CHOW-C, CHOW-C21, HF-C, HF-C21. Vascular reactivity experiments were performed in thoracic aorta rings. Human endothelial cells (EA.hy926) were used to elucidate the signaling pathways, both at receptor and intracellular levels.Arteries from HF mice exhibited increased contractions to Ang II than CHOW mice, effect that was prevented by C21. PD123177, A779 and HOE-140 (AT2R, Mas and B2R antagonists) significantly enhanced Ang II-induced contractions in CHOW but not in HF-C rings, suggesting a lack of functionality of those receptors in obesity. C21 prevented those alterations and favoured the formation of AT2R/MasR and MasR/B2R heterodimers. HF mice also exhibited impaired relaxations to acetylcholine due to a reduced NO availability. C21 preserved NO release through PKA/p-eNOS and AKT/p-eNOS signaling pathways. In conclusion, C21 favours the interaction between AT2R, MasR and B2R and prevents the development of obesity-induced endothelial dysfunction by stimulating NO release through PKA/p-eNOS and AKT/p-eNOS signaling pathways.

Pharmacological Modulation of Blood–Brain Barrier Permeability by Kinin Analogs in Normal and Pathologic Conditions

The blood–brain barrier (BBB) is a major obstacle to the development of effective diagnostics and therapeutics for brain cancers and other central nervous system diseases. Peptide agonist analogs of kinin B1 and B2 receptors, acting as BBB permeabilizers, have been utilized to overcome this barrier. The purpose of the study was to provide new insights for the potential utility of kinin analogs as brain drug delivery adjuvants. In vivo imaging studies were conducted in various animal models (primary/secondary brain cancers, late radiation-induced brain injury) to quantify BBB permeability in response to kinin agonist administrations. Results showed that kinin B1 (B1R) and B2 receptors (B2R) agonists increase the BBB penetration of chemotherapeutic doxorubicin to glioma sites, with additive effects when applied in combination. B2R agonist also enabled extravasation of high-molecular-weight fluorescent dextrans (155 kDa and 2 MDa) in brains of normal mice. Moreover, a systemic single dose of B2R agonist did not increase the incidence of metastatic brain tumors originating from circulating breast cancer cells. Lastly, B2R agonist promoted the selective delivery of co-injected diagnostic MRI agent Magnevist in irradiated brain areas, depicting increased vascular B2R expression. Altogether, our findings suggest additional evidence for using kinin analogs to facilitate specific access of drugs to the brain.

A Systematic Review of Molecular Imaging Agents Targeting Bradykinin B1 and B2 Receptors

Kinins, bradykinin and kallidin are vasoactive peptides that signal through the bradykinin B1 and B2 receptors (B1R and B2R). B2R is constitutively expressed in healthy tissues and mediates responses such as vasodilation, fluid balance and retention, smooth muscle contraction, and algesia, while B1R is absent in normal tissues and is induced by tissue trauma or inflammation. B2R is activated by kinins, while B1R is activated by kinins that lack the C-terminal arginine residue. Perturbations of the kinin system have been implicated in inflammation, chronic pain, vasculopathy, neuropathy, obesity, diabetes, and cancer. In general, excess activation and signaling of the kinin system lead to a pro-inflammatory state. Depending on the disease context, agonism or antagonism of the bradykinin receptors have been considered as therapeutic options. In this review, we summarize molecular imaging agents targeting these G protein-coupled receptors, including optical and radioactive probes that have been used to interrogate B1R/B2R expression at the cellular and anatomical levels, respectively. Several of these preclinical agents, described herein, have the potential to guide therapeutic interventions for these receptors.

Participation of bradykinin, cannabinoid, and vanilloid receptors in the infarct-limiting effect of adaptation to normobaric hypoxia

Известно, что при хронической умеренной гипоксии формируется неспецифическая резистентность миокарда к повреждению при ишемии и следующей за ней реперфузии. Однако рецепторные механизмы формирования подобной устойчивости исследованы недостаточно. Цель исследования - изучение участия брадикининовых, каннабиноидных и ванилоидных рецепторов (TRPV1-каналов) в реализации инфаркт-лимитирующего эффекта хронической нормобарической гипоксии. Методика. Исследование выполнено на самцах крыс Вистар адаптированных к гипоксии, для чего животных подвергали непрерывной нормобарической гипоксии (ННГ) в течение 21 сут при 12% pO2, 0,3% pCO2. У крыс воспроизводили коронароокклюзию наложением лигатуры на левую нисходящую коронарную артерию в ее верхней трети на 45 мин. Реперфузию осуществляли путем освобождения лигатуры с визуальным контролем возобновления коронарного кровообращения по гиперемии ишемизированной области. Продолжительность реперфузии 2 ч. Для выявления зоны риска лигатуру вновь затягивали и в аорту вводили 5%-й раствор перманганата калия. Участок миокарда, не подвергшийся ишемии, окрашивался, неокрашенный участок являлся зоной риска. Срезы левого желудочка толщиной 2 мм окрашивали 1% раствором 2,3,5-трифенилтетразолия (37 °С, 30 мин). Размер зоны некроза и зоны риска определяли планиметрически с помощью программы Ellipse 2.02 (ViDiTo, Чешская республика). Для ингибирования каннабиноидных СВ1-рецепторов и СВ2-рецепторов использовали соответственно их селективные антагонисты римонабант (1 мг/кг) и AM630 (2,5 мг/кг); селективный антагонист HOE140 (50 мкг/кг) применяли для инактивации брадикининовых B2-рецепторов, капсазепин (3 мг/кг) - ванилоидных рецепторов (TRPV1-каналов). Все антагонисты вводили за 15 мин до коронароокклюзии. Результаты. Показано, что размер некротического повреждения миокарда у крыс адаптированных к гипоксии составляет 33% процента от размера зоны риска (53% у неадаптированных), что свидетельствует о выраженном инфаркт-лимитирующем эффекте. Этот эффект не проявлялся при ингибировании B2-брадикинировых рецепторов. Блокада каннабиноидных или ванилоидных рецепторов не влияла на инфаркт-лимитирующее действие ННГ. Следовательно, инфаркт-лимитирующий эффект ННГ зависит от активации брадикининовых B2-рецепторов, адаптационное повышение толерантности сердца к ишемии/реперфузии не зависит от каннабиноидных или ванилоидных рецепторов. Заключение. Брадикининовые рецепторы можно рассматривать в качестве одного из ключевых механизмов формирования инфаркт-лимитирующего действия ННГ. Учитывая данные о важной роли опиоидных рецепторов в кардиопротекции при ННГ, можно говорить о реализации инфаркт-лимитирующего эффекта хронической гипоксии через Gi/o-протеин-сопряженные опиоидные и брадикининовые рецепторы. Каннабиноидные рецепторы и TRPV1-каналы не участвуют в инфаркт-лимитирующем действии адаптации к нормобарической гипоксии. Aim. Chronic moderate hypoxia is known to induce nonspecific myocardial resistance to ischemia-reperfusion injury. However, receptor-mediated mechanisms of this resistance are understudied. The aim of this study was to investigate the involvement of bradykinin, cannabinoid, and vanilloid (TRPV1 channel) receptors in development of the infarction-limiting effect of chronic normobaric hypoxia (CNH). Methods. The study was performed on male Wistar rats exposed to CNH at 12% pO2 and 0.3% pCO2 for 21 days. Coronary occlusion was induced by ligation of the left descending coronary artery at the upper third of the artery for 45 min, which was followed by 2-h reperfusion produced by releasing the ligature under visual control of the recovery of coronary blood flow by hyperemia of the ischemic area. For detection of the area at risk, the ligature was tightened again, and 5% potassium permanganate solution was infused into the aorta to stain the nonischemic myocardial area. 2-mm sections of the left ventricle were stained with 1% solution of 2,3,4-triphenyl tetrazolium (37 oC, 30 min). Necrotic area and area at risk were measured planimetrically with the tEllipse 2.02 (ViDiTo, Czech Republic) software. Cannabinoid CB1 and CB2 receptors were inhibited with their respective antagonists, rimonabant (1 mg/kg) and AM630 (2.5 mg/kg); bradykinin B2 receptors were inactivated with the selective antagonist HOE140 (50 μg/kg); and vanilloid receptors (TRPV1 channels) were inhibited with capsazepine (3 mg/kg). All antagonists were administered 15 minutes prior to coronary occlusion. Results. The size of necrotic area was 33% of the area at risk in rats adapted to hypoxia vs. 53% in non-adapted rats. This infarct-limiting effect of adaptation to hypoxia was abolished by inhibition of B2-bradykinin receptors. Blockade of cannabinoid or vanilloid receptors did not change the infarct-limiting effect of CNH. Therefore, the infarction-limiting effect of CNH depends on activation of bradykinin B2 receptors but not of cannabinoid or vanilloid receptors. Conclusion. Activation of bradykinin receptors can be considered a key mechanism of the infarct-limiting effect of CNH. Since opioid receptors are known to play an important role in CNH cardioprotection, the infarct-limiting effect of CNH may be mediated by Gi/o-coupled opioid and bradykinin receptors. Cannabinoid receptors and TRV1-channels do not contribute to the infarct-limiting effect of adaptation to normobaric hypoxia.

Kinins and Cytokines in COVID-19: A Comprehensive Pathophysiological Approach

Most striking observations in COVID-19 patients are the hints on pulmonary edema (also seen on CT scans as ground glass opacities), dry cough, fluid restrictions to prevent more severe hypoxia, the huge PEEP that is needed while lungs are compliant, and the fact that anti-inflammatory therapies are not powerful enough to counter the severity of the disease. We propose that the severity of the disease and many deaths are due to a local vascular problem due to activation of B1 receptors on endothelial cells in the lungs. SARS-CoV-2 enters the cell via ACE2, a cell membrane bound molecule with enzymatic activity that next to its role in RAS is needed to inactivate des-Arg9 bradykinin, the potent ligand of the bradykinin receptor type 1 (B1). In contrast to bradykinin receptor 2 (B2), the B1 receptor on endothelial cells is upregulated by proinflammatory cytokines. Without ACE2 acting as a guardian to inactivate the ligands of B1, the lung environment is prone for local vascular leakage leading to angioedema. Angioedema is likely a feature already early in disease, and might explain the typical CT scans and the feeling of people that they drown. In some patients, this is followed by a clinical worsening of disease around day 9 due to the formation antibodies directed against the spike (S)-antigen of the corona-virus that binds to ACE2 that could contribute to disease by enhancement of local immune cell influx and proinflammatory cytokines leading to damage. In parallel, inflammation induces more B1 expression, and possibly via antibody-dependent enhancement of viral infection leading to continued ACE2 dysfunction in the lung because of persistence of the virus. In this viewpoint we propose that a bradykinin-dependent local lung angioedema via B1 and B2 receptors is an important feature of COVID-19, resulting in a very high number of ICU admissions. We propose that blocking the B1 and B2 receptors might have an ameliorating effect on disease caused by COVID-19. This kinin-dependent pulmonary edema is resistant to corticosteroids or adrenaline and should be targeted as long as the virus is present. In addition, this pathway might indirectly be responsive to anti-inflammatory agents or neutralizing strategies for the anti-S-antibody induced effects, but by itself is likely to be insufficient to reverse all the pulmonary edema. Moreover, we provide a suggestion of how to ventilate in the ICU in the context of this hypothesis.

Down-Expression of Kinin Receptors in Allergic Nasal Polyps Epithelia: An Immunohistochemistry Study

Objectives To investigate the expression of B1 and B2 receptors in patients with nasal polyps (NPs) compared to controls. Study Design Retrospective case series. Settings Single academic center. Subjects and Methods Nasal biopsies of patients with NPs were compared to inferior turbinates of control patients. Comparisons included basic demographics and comorbidities, intensity of inflammation, and immunohistochemical staining of B1 and B2 receptors measured by immunohistochemistry staining scores (ISSs). Results A total of 41 patients were enrolled, with 21 patients (51.2%) in the NP group and 20 patients as controls. No differences were found in the prevalence of allergic comorbidities and smoking between the groups. The NP group demonstrated significantly higher prevalence of moderate and severe mononuclear infiltrates compared to the control group (57.1% vs 5.3%, P < .001). The NP group had significantly lower B1 expression in smooth muscle compared to the control group (mean ISS 0.22 vs 1.56, P < .001, respectively) and significantly more B2 expression in epithelial cells (mean ISS 1.81 vs 0, P < .001, respectively). Conclusion Patients with NPs exhibit different expression patterns of B1 and B2 compared to control patients. This implies that bradykinin receptor regulation participates in the pathogenesis of NPs.