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Skeletal muscle tissue retains a remarkable regenerative capacity due to the activation of resident stem cells that in pathological conditions or after tissue damage proliferate and commit themselves into myoblasts. These immature myogenic cells undergo differentiation to generate new myofibers or repair the injured ones, giving a strong contribution to muscle regeneration. Cytokines and growth factors, potently released after tissue injury by leukocytes and macrophages, are not only responsible of the induction of the initial inflammatory response, but can also affect skeletal muscle regeneration. Growth factors exploit sphingosine kinase (SK), the enzyme that catalyzes the production of sphingosine 1-phosphate (S1P), to exert their biological effects in skeletal muscle. In this paper we show for the first time that bradykinin (BK), the leading member of kinin/kallikrein system, is able to induce myogenic differentiation in C2C12 myoblasts. Moreover, evidence is provided that SK1, the specific S1P-transporter spinster homolog 2 (Spns2) and S1P 2 receptor are involved in the action exerted by BK, since pharmacological inhibition/antagonism or specific down-regulation significantly alter BK-induced myogenic differentiation. Moreover, the molecular mechanism initiated by BK involves a rapid translocation of SK1 to plasma membrane, analyzed by time-lapse immunofluorescence analysis. The present study highlights the role of SK1/Spns2/S1P receptor 2 signaling axis in BK-induced myogenic differentiation, thus confirming the crucial involvement of this pathway in skeletal muscle cell biology. [ABSTRACT FROM AUTHOR]

Abstract: In a previous paper we showed that bradykinin (BK), interacting with its B2 receptor, inhibits proximal tubule Na+-ATPase activity but does not change (Na+ +K+)ATPase activity. The aim of this paper was to investigate the molecular mechanisms involved in B2-mediated modulation of proximal tubule Na+-ATPase by BK. To abolish B1 receptor-mediated effects, all experiments were carried out in the presence of (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Leu), des-Arg9-[Leu8]-BK (DALBK), a specific antagonist of B1 receptor. A dual effect on the Na+-ATPase activity through the B2 receptor was found: short incubation times (1–10 min) stimulate the enzyme activity; long incubation times (10–60 min) inhibit it. The stimulatory effect of BK is mediated by activation of phosphoinositide-specific phospholipase C β (PI-PLCβ)/protein kinase C (PKC); its inhibitory action is mediated by Ca2+-independent phospholipase A2 (iPLA2). Prior activation of the PI-PLCβ/PKC pathway is required to activate the iPLA2-mediated inhibitory phase. These results reveal a new mechanism by which BK can modulate renal sodium excretion: coupling between B2 receptor and activation of membrane-associated iPLA2. [Copyright &y& Elsevier]

In this paper, bradykinin (BK), an endogenous peptide hormone, which is involved in a number of physiological and pathophysiological processes was deposited onto the colloidal Au nanoparticles. The surface-enhanced Raman spectroscopy (SERS) was used to determine the adsorption mode of BK under different environmental conditions, including: excitation wavelengths (514.5 nm and 785.0 nm), pH of aqueous sol solutions (from pH = 3 to pH = 11), and size of the colloidal nanoparticles (10, 20, and 50 nm). The metal surface plasmon of the colloidal suspended Au nanoparticles was examined by ultraviolet-visible (UV–vis) spectroscopy. The results showed that the C -terminal part of BK plays a crucial role in the adsorption process onto the colloidal suspended Au particles. The Phe 5/8 and Arg 9 residues of BK mainly participate in the interactions with the colloidal Au nanoparticles. At acidic pH of the solution (pH = 3), the BK COO − terminal group through the both oxygen atoms strongly binds to the Au nanoparticles. The Phe 5 /Phe 8 rings adopt tilted orientation with respect to the colloidal Au nanoparticles with diameters of 10 and 20 nm. As the particle size increases to 50 nm, the flat orientation of the Phe ring(s) with respect to the Au nanoparticles is observed. [ABSTRACT FROM AUTHOR]

James Black believed that analysis of biological assays provides insights into the operation of physiological control systems. In this paper, we illustrate this point in three ‘cardiovascular’ assays. The first determined the half-life (t½) of ‘endothelium-derived relaxing factor’ (EDRF), using bradykinin to release EDRF, which produced concentration-related relaxations of a precontracted artery. With the introduction of time delays between the source of EDRF and the assay artery, there were rightward shifts in dose-response curves, which provided the basis of calculating t½. The second assay determined the roles of noradrenaline reuptake and prejunctional α2-adrenoceptor activity on transmitter concentration at sympathetic synapses with atria and resistance vessels. In the former, the reuptake role was paramount, whilst prejunctional receptor activity was dominant at vascular synapses, owing to anatomical differences. The third assay provided in vivo estimates of the enhancement of the total peripheral resistance responses to constrictor and dilator stimuli owing to the structural changes in hypertension. Major nonlinearities in the dose-response curve obscured this enhancement. Their effect was avoided by deriving extended dose-response curves from combined constrictor and dilator data, permitting calculation of the enhancement over the range between the nonlinearities. [ABSTRACT FROM AUTHOR]

Abstract: Bradykinin (BK) is involved in a wide variety of pathophysiological processes. Potent BK peptide antagonists can be developed introducing constrained unnatural amino acids, necessary to force the secondary structure of the molecule. In this paper, we report a structure–activity relationship study of two peptide analogues of the potent B2 antagonist HOE 140 by replacing the D-Tic-Oic dipeptide with conformationally constrained dipeptide mimetic β-turn inducers. [Copyright &y& Elsevier]

Abstract: The bradykinin 1 (B1) receptor is upregulated during times of inflammation and is important for maintaining inflamed and chronic pain states. Blocking this receptor has been shown to reverse and/or ameliorate pain and inflammation in animal models. In this report, we describe a new class of B1 receptor antagonists that contain the piperidine acetic acid tetralin core. A structure–activity relationship for these analogs is described in this paper. The most potent compounds from this class have IC50s<20nM in a B1 receptor functional assay. One of these compounds, 13g, shows modest oral bioavailability in rats. [Copyright &y& Elsevier]

Abstract: Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure–activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999–2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides. [Copyright &y& Elsevier]

Recently, we demonstrated that bradykinin (BK) counteracts the stimulatory effect of Ang-(1–7) on the Na+-ATPase activity from basolateral membrane of the proximal tubule through B2 receptor. In the present paper, the signaling pathway involved in the inhibitory response of the Na+-ATPase activity to BK was investigated. The following results indicate that the phospholipase A2 (PLA2)/COX/prostaglandin E (PGE2) pathway is implicated in this process: (1) The inhibitory effect of BK on Ang-(1–7)-stimulated enzyme is abolished in a dose-dependent manner by quinacrine (10−9;-10−6M), a nonspecific PLA2 inhibitor, and by PACOCF3 (10−7M), an inhibitor of a Ca2+-independent PLA2. However, AACOCF3 (2×10−4 M), an inhibitor of the cytosolic PLA2, does not modify the inhibitory effect of BK. (2) The inhibitory effect of BK on the Ang-(1–7)-stimulated enzyme is reversed by cyclooxygenase (COX) inhibitors diclofenac (10−12 M) and indomethacin (10−12 M). (3) PGE2 (10−12–10−5 M) inhibits the Na+-ATPase activity in a dose dependent manner. (4)The inhibitory effects of PGE2 and BK on the Na+-ATPase activity are not cumulative. (5) PGE2 (10−12–10−8 M) counteracts the stimulatory effect of Ang-(1–7) on the enzyme activity in a dose-dependent manner. [Copyright &y& Elsevier]

Recently, we demonstrated that angiotensin-(1–7) (Ang-(1–7)) stimulates the Na+-ATPase activity through a losartan-sensitive angiotensin receptor, whereas bradykinin inhibits the enzyme activity through the B2 receptor [Regul. Pept. 91 (2000) 45; Pharmacol. Rev. 32 (1980) 1]. In the present paper, the effect of bradykinin (BK) on Ang-(1–7)-stimulated Na+-ATPase activity was evaluated. Preincubation of Na+-ATPase with 10−9 M Ang-(1–7) increases enzyme activity from 7.9±0.9 to 14.1±1.5 nmol Pi mg−1 min−1, corresponding to an increase of 79% (p<0.05). This effect is reverted by bradykinin in a dose-dependent manner (10−14–10−8 M), reaching maximal inhibitory effect at 10−9 M. Des-Arg9 bradykinin (DABK), an agonist of B1 receptor, at the concentrations of 10−9–10−7 M, does not mimic the BK inhibitory effect, and des-Arg9-[Leu8]-BK (DALBK), a B1 receptor antagonist, at the concentrations of 10−10–10−7 M, does not prevent the inhibitory effect of BK on Ang-(1–7)-stimulated enzyme. On the other hand, HOE 140, an antagonist of B2 receptor, abolishes the inhibitory effect of BK on the Ang-(1–7)-stimulated enzyme in a dose-dependent manner, reaching maximal effect at 10−7 M. Taken together, these data indicate that stimulation of B2 receptors by BK can counteract the stimulatory effect of Ang-(1–7) on the proximal tubule Na+-ATPase activity. [Copyright &y& Elsevier]

In a previous paper, we have shown that bradykinin (Bk) and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulate arachidonic acid release from HEL-30 keratinocytes along a Bk-B2 receptor G-protein-coupled pathway or a protein kinase C-dependent mechanism, respectively. Here we show a cytosolic PLA2 (cPLA2) to be responsible for this effect. This enzyme exhibited a marked acyl-group specificity towards arachidonic acid. It was activated by Ca++ in micromolar concentrations and partially translocated from the cytoplasmic to the membrane fraction upon Ca++ treatment. Translocation was also observed upon treatment of cells with either Bk or TPA. However, only with Bk was a corresponding increase of the cytoplasmic Ca++ level observed, whereas TPA-induced translocation occurred at basal Ca++ concentrations. Indirect evidence for a G protein to be involved in Bk- but not TPA-dependent cPLA2 activation was provided using non-hydrolyzable GTP derivatives. It is concluded that keratinocyte cPLA2 plays a critical role in the initiation by exogenous and endogenous factors of the eicosanoid cascade in skin. [ABSTRACT FROM AUTHOR]

In order to evaluate the utility of copper surfaces as spray initiators for mass spectrometric ionization sources, it is necessary to establish how efficient and reproducible the methodology is. To do this, a superhydrophobic and bare copper surface were used to ionize the singly and doubly charged peptides, bradykinin and leucine-enkephalin spiked with substance P as an internal standard, respectively. Both treated and bare copper surfaces were cut to 90, 60, and 30° angles. Calibration curves were constructed for both peptides on a superhydrophobic surface using covalently bonded trichloro(1H, 1H, 2H, 2H-perflourooctyl)silane-treated copper, and bare copper surface. The highest sensitivity for all peptides was observed using a 30 or 60° tip with the silane-treated copper. Limits of detection and quantitation for the 60° silane-treated surface for bradykinin were 6.01 × 10−3 μM and 2.00 × 10−2 μM respectively, with a R2 of 0.9959. Limits of detection and quantitation for the 30° silane-treated surface for leucine-enkephalin were 3.28 × 10−2 μM and 1.09 × 10−1 μM respectively, with a R2 of 0.9993. Image 1 • Copper surfaces were used as spray initiators similar to paper spray ionization. • Surfaces are reusable, have fixed geometry, and can be functionalized, and require minimal solvent to initiate a spray event. • Metalspray ionization was used to test sensitivity between bare copper and modified copper surfaces. • Copper was functionalized with trichloro(1 H , 1 H , 2 H , 2 H -perflourooctyl)silane to create a superhydrophobic surface. • Superhydrophobic surface displayed greater sensitivity and lower limits of quantitation compared to bare copper surface. [ABSTRACT FROM AUTHOR]