Pharmacological and functional characterization of bradykinin receptors in canine cultured tracheal epithelial cells

Bradykinin-stimulated cyclooxygenase activity stimulates vas deferens epithelial anion secretion in vitro in swine and humans

Epithelia lining the male reproductive duct modulate fertility by altering the luminal environment to which sperm are exposed. Although vas deferens epithelial cells reportedly express high levels of cyclooxygenases (Ptgs), and activation of bradykinin (BK) receptors can lead to upregulation of PTGS activity in epididymal epithelia, it remains unknown whether BKs and/or PTGSs have any role in modulating epithelial ion transport across vas deferens epithelia. Porcine and human vas deferens epithelial cell primary cultures and the PVD9902 cell line responded to lysylbradykinin with an increase in short circuit current (I SC; indicating net anion secretion), an effect that was 60%-93% reduced by indomethacin. The BK effect was inhibited by the B2 receptor subtype (BDKRB2) antagonist HOE140, whereas the B1 receptor subtype agonist des-Arg9-BK had no effect. BDKRB2 immunoreactivity was documented in most epithelial cells composing the native epithelium and on Western blots derived from cultured cells. Gene expression analysis revealed that the PTGS2 transcript is 20 times more abundant than its PTGS1 counterpart in cultured porcine vas deferens epithelia and that BDKRB2 mRNA is likewise highly expressed. Subsequent experiments revealed that prostaglandin E2, 1-OH prostaglandin E1 (prostaglandin E receptor 4 [PTGER4] agonist) and butaprost (PTGER2 agonist) increase I SC in a concentration-dependent manner, whereas sulprostone (mixed PTGER1 and PTGER3 agonist) produced no change in I SC. These results demonstrate that autacoids can affect epithelial cells to acutely modulate the luminal environment to which sperm are exposed in the vas deferens by enhancing PTGS activity, leading to the production of prostaglandins that act at PTGER4 and/or PTGER2 to induce or enhance anion secretion.

Resonant waveguide grating biosensor for living cell sensing

This article presents theoretical analysis and experimental data for the use of resonant waveguide grating (RWG) biosensors to characterize stimulation-mediated cell responses including signaling. The biosensor is capable of detecting redistribution of cellular contents in both directions that are perpendicular and parallel to the sensor surface. This capability relies on online monitoring cell responses with multiple optical output parameters, including the changes in incident angle and the shape of the resonant peaks. Although the changes in peak shape are mainly contributed to stimulation-modulated inhomogeneous redistribution of cellular contents parallel to the sensor surface, the shift in incident angle primarily reflects the stimulation-triggered dynamic mass redistribution (DMR) perpendicular to the sensor surface. The optical signatures are obtained and used to characterize several cellular processes including cell adhesion and spreading, detachment and signaling by trypsinization, and signaling through either epidermal growth factor receptor or bradykinin B2 receptor. A mathematical model is developed to link the bradykinin-mediated DMR signals to the dynamic relocation of intracellular proteins and the receptor internalization during B2 receptor signaling cycle. This model takes the form of a set of nonlinear, ordinary differential equations that describe the changes in four different states of B2 receptors, diffusion of proteins and receptor-protein complexes, and the DMR responses. Classical analysis shows that the system converges to a unique optical signature, whose dynamics (amplitudes, transition time, and kinetics) is dependent on the bradykinin signal input, and consistent with those observed using the RWG biosensors. This study provides fundamentals for probing living cells with the RWG biosensors, in general, optical biosensors.

Characterization of bradykinin receptors in canine cultured corneal epithelial cells: pharmacological and functional studies

The pharmacological properties of bradykinin (BK) receptors were characterized in canine cultured corneal epithelial cells (CECs) using [(3)H]-BK as a radioligand. Analysis of binding isotherms gave an apparent equilibrium dissociation constant of 0.34 +/- 0.07 nM and a maximum receptor density of 179 +/- 23 fmol/mg protein. Neither a B(1) receptor-selective agonist (des-Arg(9)-BK) nor antagonist ([Leu(8), des-Arg(9)]-BK) significantly inhibited [(3)H]-BK binding to CECs, thus excluding the presence of B(1) receptors in canine CECs. The specific binding of [(3)H]-BK to CECs was inhibited by B(2) receptor-selective agonists (BK and kallidin) and antagonists (Hoe 140 and [D-Arg(0), Hyp(3), Thi(5,8), D-Phe(7)]-BK), with a best fit using a one-binding-site model. The order of potency for the inhibition of [(3)H]-BK binding was BK = Hoe 140 > kallidin > [D-Arg(0), Hyp(3), Thi(5,8), D-Phe(7)]-BK. Stimulation of CECs by BK produced a concentration-dependent accumulation of inositol phosphates (IP) and an initial transient peak of intracellular Ca(2+). B(2) receptor-selective antagonist ([D-Arg(0), Hyp(3), Thi(5,8), D-Phe(7)]-BK) significantly antagonized the BK-induced responses with dissociation constants of 6.0-6.1. Pretreatment of CECs with pertussis toxin (PTX) or cholera toxin did not alter the BK-induced IP accumulation. Incubation of CECs in the absence of external Ca(2+) led to a significant attenuation of the IP accumulation induced by BK. These results demonstrate that BK directly stimulates phospholipase C-mediated signal transduction through BK B(2) receptors via a PTX-insensitive G protein in canine CECs. This effect may function as the transducing mechanism for BK-mediated cellular responses.

Mechanisms of bradykinin-mediated Ca(2+) signalling in canine cultured corneal epithelial cells

Experiments were designed to differentiate the mechanisms of bradykinin receptors mediating the changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) in canine cultured corneal epithelial cells (CECs). Bradykinin and Lys-bradykinin caused an initial transient peak of [Ca(2+)](i) in a concentration-dependent manner, with half-maximal stimulation (pEC(50)) obtained at 6.9 and 7.1, respectively. Pretreatment of CECs with pertussis toxin (PTX) or cholera toxin (CTX) for 24 h did not affect the bradykinin-induced [Ca(2+)](i) changes. Application of Ca(2+) channel blockers, diltiazem and Ni(2+), inhibited the bradykinin-induced Ca(2+) mobilization, indicating that Ca(2+) influx was required for the bradykinin-induced responses. Addition of thapsigargin (TG), which is known to deplete intracellular Ca(2+) stores, transiently increased [Ca(2+)](i) in Ca(2+)-free buffer, and subsequently induced Ca(2+) influx when Ca(2+) was readded to this buffer. Pretreatment of CECs with TG completely abolished bradykinin-induced initial transient [Ca(2+)](i), but had slight effect on bradykinin-induced Ca(2+) influx. Pretreatment of CECs with 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF96365) and 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122) inhibited the bradykinin-induced Ca(2+) release and Ca(2+) influx, consistent with the inhibition of receptor-gated Ca(2+) channels and phospholipase C (PLC) in CECs, respectively. These results demonstrate that bradykinin directly stimulates B(2) receptors and subsequently Ca(2+) mobilization via a PTX-insensitive G protein in canine CECs. These results suggest that bradykinin-induced Ca(2+) influx into the cells is not due to depletion of these Ca(2+) stores, as prior depletion of these pools by TG has no effect on the bradykinin-induced Ca(2+) influx that is dependent on extracellular Ca(2+) in CECs.

Pharmacological and functional characterization of bradykinin receptors in rat cultured vascular smooth muscle cells

The pharmacological properties of bradykinin receptors were characterized in rat cultured vascular smooth muscle cells (VSMCs) using [3H]-bradykinin as a ligand. Analysis of binding isotherms gave an apparent equilibrium dissociation constant (K(D)) of 1.2 +/- 0.2 nM and a maximum receptor density (Bmax) of 47.3 +/- 4.4 fmol/mg protein. The specific binding of [3H]-bradykinin to VSMCs was inhibited by the B2 receptor-selective agonists (bradykinin and kallidin) and antagonists ([D-Arg0, Hyp3, Thi5, D-Tic7, Oic8]-bradykinin (Hoe 140) and [D-Arg0, Hyp3, Thi(5,8), D-Phe7]-bradykinin) with an order of potency as kallidin = bradykinin = Hoe 140 > [D-Arg0, Hyp3, Thi(5,8), D-Phe7]-bradykinin, but not by a B1 receptor-selective agonist (des-Arg9-bradykinin) and antagonist ([Leu8, des-Arg9]-bradykinin). Stimulation of VSMCs by bradykinin produced a concentration-dependent inositol phosphate (IP) accumulation, and initial transient peak of [Ca2+]i with half-maximal responses (pEC50) were 7.53 and 7.69, respectively. B2 receptor-selective antagonists (Hoe 140 and [D-Arg0, Hyp3, Thi(5,8), D-Phe7]-bradykinin) significantly antagonized the bradykinin-induced responses with pK(B) values of 8.3-8.7 and 7.2-7.9, respectively. Pretreatment of VSMCs with pertussis toxin (100 ng/ml, 24 h) did not alter the bradykinin-induced inositol phosphate accumulation and [Ca2+]i changes in VSMCs. Removal of external Ca2+ led to a significant attenuation of responses induced by bradykinin. Influx of external Ca2+ was required for the bradykinin-induced responses, since Ca2+-channel blockers, nifedipine, verapamil, and Ni2+, partially inhibited the bradykinin-induced IP accumulation and Ca2+ mobilization. These results demonstrate that bradykinin stimulates phosphoinositide hydrolysis and Ca2+ mobilization via a pertussis toxin-insensitive G-protein in rat VSMCs. Bradykinin B2 receptors may be predominantly mediating IP accumulation and subsequently induction of Ca2+ mobilization may function as the transducing mechanism for bradykinin-stimulated contraction of vascular smooth muscle.

Bradykinin-induced phosphoinositide hydrolysis and Ca2+ mobilization in canine cultured tracheal epithelial cells

1. Experiments were designed to differentiate the mechanisms and subtype of kinin receptors mediating the changes in intracellular Ca2+ concentration ([Ca2+]i) induced by bradykinin (BK) in canine cultured tracheal epithelial cells (TECs). 2. BK and Lys-BK caused an initial transient peak of [Ca2+]i in a concentration-dependent manner, with half-maximal stimulation (pEC50) obtained at 7.70 and 7.23, respectively. 3. Kinin B2 antagonists Hoe 140 (10 nM) and [D-Arg0, Hyp3, Thi5,8, D-Phe7]-BK (1 microM) had high affinity in antagonizing BK-induced Ca2+ response with pKB values of 8.90 and 6.99, respectively. 4. Pretreatment of TECs with pertussis toxin (100 ng ml(-1)) or cholera toxin (10 microg ml(-1)) for 24 h did not affect the BK-induced IP accumulation and [Ca2+]i changes in TECs. 5. Removal of Ca2+ by the addition of EGTA or application of Ca2+-channel blockers, verapamil, diltiazem, and Ni2+, inhibited the BK-induced IP accumulation and Ca2+ mobilization, indicating that Ca2+ influx was required for the BK-induced responses. 6. Addition of thapsigargin (TG), which is known to deplete intracellular Ca2+ stores, transiently increased [Ca2+]i in Ca2+-free buffer and subsequently induced Ca2+ influx when Ca2+ was re-added to this buffer. Pretreatment of TECs with TG completely abolished BK-induced initial transient [Ca2+]i, but had slight effect on BK-induced Ca2+ influx. 7. Pretreatment of TECs with SKF96365 and U73122 inhibited the BK-induced Ca2+ influx and Ca2+ release, consistent with the inhibition of receptor-gated Ca2+-channels and phospholipase C in TECs, respectively. 8. These results demonstrate that BK directly stimulates kinin B2 receptors and subsequently phospholipase C-mediated IP accumulation and Ca2+ mobilization via a pertussis toxin-insensitive G protein in canine TECs. These results also suggest that BK-induced Ca2+ influx into the cells is not due to depletion of these Ca2+ stores, as prior depletion of these pools by TG has no effect on the BK-induced Ca2+ influx that is dependent on extracellular Ca2+ in TECs.

Uncoupling of bradykinin-induced phosphoinositide hydrolysis and Ca2+ mobilization by phorbol ester in canine cultured tracheal epithelial cells

1. Regulation of the increase in inositol phosphates (IPs) production and intracellular Ca2+ concentration ([Ca2+]i by protein kinase C (PKC) was investigated in canine cultured tracheal epithelial cells (TECs). Stimulation of TECs by bradykinin (BK) led to IPs formation and caused an initial transient [Ca2+]i peak in a concentration-dependent manner. 2. Pretreatment of TECs with phorbol 12-myristate 13-acetate (PMA, 1 microM) for 30 min attenuated the BK-induced IPs formation and Ca2+ mobilization. The maximal inhibition occurred after incubating the cells with PMA for 2 h. 3. The concentrations of PMA that gave half-maximal (pEC50) inhibition of BK-induced IPs accumulation and an increase in [Ca2+]i were 7.07 M and 7.11 M, respectively. Inactive phorbol ester, 4alpha-phorbol 12,13-didecanoate at 1 microM, did not inhibit these responses. Prior treatment of TECs with staurosporine (1 microM), a PKC inhibitor, inhibited the ability of PMA to attenuate BK-induced responses, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. 4. In parallel with the effect of PMA on the BK-induced IPs formation and Ca2+ mobilization, the translocation and down-regulation of PKC isozymes were determined. Analysis of cell extracts by Western blotting with antibodies against different PKC isozymes revealed that TECs expressed PKC-alpha, betaI, betaII, gamma, delta, epsilon, theta and zeta. With PMA treatment of the cells for various times, translocation of PKC-alpha, betaI, betaII, gamma, delta, epsilon and theta from cytosol to the membrane was seen after 5 min, 30 min, 2 h, and 4 h treatment. However, 6 h treatment caused a partial down-regulation of these PKC isozymes. PKC-zeta was not significantly translocated and down-regulated at any of the times tested. 5. Treatment of TECs with 1 microM PMA for either 30 min or 6 h did not significantly change the KD, and Bmax receptor for BK binding (control: KD=1.7+/-0.3 nM; Bmax=50.5+/-4.9 fmol/mg protein), indicating that BK receptors are not a site for the inhibitory effect of PMA on BK-induced responses. 6. In conclusion, these results suggest that activation of PKC may inhibit the phosphoinositide hydrolysis and consequently attenuate the [Ca2+]i increase or inhibit independently both responses to BK. The translocation of pKC-alpha, betaI, betaII, delta, epsilon, gamma, and theta induced by PMA caused an attenuation of BK-induced IPs accumulation and Ca2+ mobilization in TECs.