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The AT1 receptor for the vasopressor angiotensin II is one of the most important drug targets for the treatment of cardiovascular diseases. Sensitization of the AT1 receptor system is a common feature contributing to the pathogenesis of many cardiovascular disorders but underlying mechanisms are not fully understood. More than a decade ago, evidence was provided for control of AT1R activation by heterodimerization with the B2 receptor for the vasodepressor peptide, bradykinin, a physiological counterpart of the vasoconstrictor angiotensin II. AT1–B2 receptor heterodimerization was shown to enhance AT1R-stimulated signaling under pathophysiological conditions such as experimental and human pregnancy hypertension. Notably, AT1R signal sensitization of patients with preeclampsia hypertension was attributed to AT1R–B2R heterodimerization. Vice versa, transgenic mice lacking the AT1–B2 receptor heterodimer due to targeted deletion of the B2R gene showed a significantly reduced AT1R-stimulated vasopressor response compared to transgenic mice with abundant AT1R–B2R heterodimerization. Biophysical methods such as BRET and FRET confirmed those data by demonstrating efficient AT1–B2 receptor heterodimerization in transfected cells and transgenic mice. Recently, a study on AT1R-specific biased agonism directed the focus to the AT1–B2 receptor heterodimer again. The β-arrestin-biased [Sar1,Ile4,Ile8]-angiotensin II promoted not only the recruitment of β-arrestin to the AT1R but also stimulated the down-regulation of the AT1R-associated B2 receptor by co-internalization. Thereby specific targeting of the AT1R–B2R heterodimer became feasible and could open the way to a new class of drugs, which specifically interfere with pathological angiotensin II-AT1 receptor system activation., Biochemical pharmacology, 88 (3), ISSN:0006-2952, ISSN:1873-2968

Bradykinin drives normal lung fibroblasts into myofibroblasts, induces fibroblast proliferation and activates mitogen activated protein kinase pathways (MAPK) but its effects on bronchial fibroblasts from asthmatics (HBAFb) have not been yet studied. We studied bradykinin-induced fibroblast proliferation and differentiation and the related intracellular mechanisms in HBAFb compared to normal bronchial fibroblasts (HNBFb). Bradykinin-stimulated HBAFb and HNBFb were used to assess: bradykinin B 2 receptor expression by Western blot analysis; cell proliferation by [ 3 H] thymidine incorporation; α-smooth muscle actin (SMA) expression/polymerization by Western blot and immunofluorescence; epidermal growth factor (EGF) receptor, extracellular-regulated kinase (ERK) 1/2 and p38 MAPK activation by immunoprecipitation and Western blot, respectively. Constitutive bradykinin B 2 receptor and α-SMA expression was higher in HBAFb as compared to HNBFb. Bradykinin increased bradykinin B 2 receptor expression in HBAFb. Bradykinin, via bradykinin B 2 receptor, significantly increased fibroblast proliferation at lower concentration (10 −11 M) and α-SMA expression/polymerization at higher concentration (10 −6 M) in both cells. Bradykinin increased ERK1/2 and p38 phosphorylation via bradykinin B 2 receptor; EGF receptor inhibitor AG1478 and panmetalloproteinase inhibitor GM6001 blocked bradykinin-induced ERK1/2 activation but not p38 phosphorylation. Bradykinin, via bradykinin B 2 receptor, induced EGF receptor phosphorylation that was suppressed by AG1478. In HBAFb AG1478, GM6001, the ERK1/2-inhibitor U0126 and the p38 inhibitor SB203580 suppressed bradykinin-induced cell proliferation, but only SB203580 reduced myofibroblast differentiation. These data indicate that bradykinin is actively involved in asthmatic bronchial fibroblast proliferation and differentiation, through MAPK pathways and EGF receptor transactivation, by which bradykinin may contribute to airway remodeling in asthma, opening new horizons for potential therapeutic implications in asthmatic patients.

Bradykinin-potentiating peptides (BPPs) or proline-rich oligopeptides (PROs) isolated from the venom glands of Bothrops jararaca (Bj) were the first natural inhibitors of the angiotensin-converting enzyme (ACE) described. Bj-PRO-5a (

The syntheses of the potent, competitive bradykinin B2 receptor antagonists, 1–3, are described. These compounds represent the three structural classes of B2 receptor antagonists discovered in our program. Compounds 1–3 bind to the human IMR 90 fetal lung fibroblast bradykinin B2 receptor with affinity constants Ki = 3.4 μM, 0.77 μM, and 0.060 μM, respectively.

A series of non-peptide competitive antagonists of the human IMR 90 fetal lung fibroblast bradykinin B2 receptor have been designed and synthesized. Compound 15 binds with an affinity constant Ki = 60 nM. The SAR leading to the design of these non-peptide antagonists is described.

Substantial progress has been made recently in the field of kinin pharmacology with the identification of sensitive bioassay organs and the discovery of bradykinin B2 receptor antagonists. Data obtained with such compounds in various laboratories support the hypothesis that kinins act on multiple (at least two) receptor types. Domenico Regoli and colleagues review here the basic criteria of receptor characterization as they apply to kinins and present a critical analysis of the bioassay organs and B2 receptor antagonists currently used in kinin pharmacology.