Biomedical subjects

Kenji Sakamoto

Publications and source records attributed to Kenji Sakamoto.

33 records · Page 2Linked to original sources

PubMed2003

Protease-activated receptor-2-mediated contraction of urinary bladder is enhanced in cyclophosphamide-treated rats.

Protease-activated receptor-2 (PAR-2) is activated by serine proteases, such as trypsin and mast cell tryptase. Recently, we have shown that activators of PAR-2 contract the rat urinary bladder mainly by stimulating release of prostaglandins (PGs) from the mucosal layer. In the present study, we investigated how the PAR-2-mediated responses are altered in rats with cyclophosphamide (CYP)-induced cystitis. The contractile responses to trypsin and PAR-2 activating peptide (PAR-2 AP; SLIGRL-NH2) in the urinary bladders were augmented by treatment of rats with CYP. The contractile effects of these PAR-2 activators on the smooth muscles of the urinary bladder were also potentiated after induction of cystitis by CYP. On the other hand, CYP-induced cystitis significantly attenuated contractions produced by PGE2 in the smooth muscles of the urinary bladder. The PAR-2-mediated contractions were significantly prevented by indomethacin or NS-398, an inhibitor of cyclooxygenase-2. Both trypsin and PAR-2 AP increased the release of PGE2 from the urinary bladder mucosa and smooth muscle. CYP-induced cystitis enhanced the PAR-2 activators-induced PGE2 releases from the urinary mucosa without affecting those from the smooth muscle of the urinary bladder. The PGE2 releases were prevented by indomethacin or NS-398. The mRNAs for PAR-2 in the urinary bladder mucosa and smooth muscle preparations were not altered in CYP-induced cystitis. These results suggest that PAR-2-mediated responses were enhanced in bladders from CYP-treated rats. The enhancement of PAR-2-mediated contraction might be ascribed to the increased production of PGs and the altered sensitivity of smooth muscle to PAR-2 activators.

Animals↗

PubMed2003

Relaxant effect of YM976, a novel phosphodiesterase 4 inhibitor, on bovine tracheal smooth muscle.

Effects of 4-(3-chlorophenyl)-1,7-diethylpyrido[2,3-d]pyrimidin-2(1H)-one (YM976), a novel and selective phosphodiesterase type 4 inhibitor, on tension and adenosine 3',5'-cyclic monophosphate (cAMP) content of bovine tracheal smooth muscle were compared with those of rolipram and theophylline. YM976, rolipram and theophylline relaxed the tracheal preparations contracted with histamine in a concentration-dependent manner. The relaxant effects of YM976 and rolipram were more potent than those of theophylline. These phosphodiesterase inhibitors-induced relaxations were dramatically diminished when tracheal smooth muscle was contracted with methacholine instead of histamine. Pretreatment of the tracheal preparations with YM976 (10 microM) or rolipram (10 microM), but not with theophylline (1 mM), shifted the concentration-response curves for contractile responses to histamine; however, the same procedure failed to affect concentration-response relationships for methacholine-induced contractions. At 1 and 10 microM, both YM976 and rolipram increased the tissues cAMP content. These results suggest that YM976 relaxes tracheal smooth muscle, probably through the cAMP-dependent mechanism.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2003

Lidocaine attenuates muscarinic receptor-mediated inhibition of adenylyl cyclase in airway smooth muscle.

We examined how lidocaine affects muscarinic receptor-mediated inhibition of adenylyl cyclase in bovine tracheal smooth muscles. Lidocaine (100 microM) augmented the relaxant responses to forskolin in the bovine tracheal smooth muscle contracted with methacholine (0.3 microM). On the other hand, lidocaine failed to affect the relaxant effects of forskolin on the histamine (100 microM)- and KCl (40 mM)-contracted preparations. Lidocaine (100 microM) enhanced both basal and forskolin-stimulated cAMP accumulation in the presence of methacholine (0.3 microM). However, in the absence of methacholine, neither basal nor forskolin-stimulated cAMP accumulation was affected by lidocaine. Similar phenomenon was observed when the bovine tracheal smooth muscles were treated with methoctramine (0.03 microM). In radioligand binding experiments, lidocaine inhibited [3H]N-methyl scopolamine binding to cloned human muscarinic receptors (M(1)-M(5)) expressed in Chinese hamster ovary cells. These results suggest that lidocaine prevents muscarinic receptor-mediated signaling pathway and thereby reverses inhibition of adenylyl cyclase by methacholine in bovine tracheal smooth muscle.

Adenylyl Cyclase Inhibitors↗

PubMed2003

Possible involvement of Ca2+-independent phospholipase A2 in protease-activated receptor-2-mediated contraction of rat urinary bladder.

Possible involvement of Ca(2+)-independent phospholipase A2 (iPLA2) was examined in protease-activated receptor-2 (PAR-2)-mediated contraction of the rat urinary bladder. Both PAR-2 activating peptide (PAR-2 AP; SLIGRL-NH2) and trypsin produced a concentration-dependent contractile response in the urinary bladder preparations. These contractions were significantly (p<0.01) attenuated by indomethacin (10 microM), an inhibitor of cyclooxygenase, or bromoenol lactone (BEL; 10 micro M), an inhibitor of iPLA2. On the other hand, the contractile responses to bradykinin were not significantly affected by BEL, although they were reduced by indomethacin. Arachidonyltrifluoromethyl ketone (AACOCF3; 30 microM), an inhibitor of cytosolic Ca(2+)-dependent phospholipase A2, did not affect the trypsin- and bradykinin-induced contractions. Both indomethacin and BEL had no inhibitory effect on the prostaglandin E2-induced contractions. These results suggest that PAR-2 activators and bradykinin stimulate the release of prostaglandins and thereby contract the rat urinary bladder smooth muscles. The release of prostaglandins by PAR-2 activators seems to be partly mediated by the iPLA2.

Animals↗

PubMed2003

The role of cholinesterases in rat urinary bladder contractility.

This study examines the effects of inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) on acetylcholine (ACh)-induced contraction in rat urinary bladder smooth muscle. Neostigmine, a non-selective ChE inhibitor, caused concentration-dependent contractions in rat urinary bladder strips, whereas tetraisopropylpyrophosphoramide (iso-OMPA; a BuChE inhibitor) failed to affect the resting tone of the preparations. Neostigmine (1 microM) markedly augmented the contractile responses to ACh. Although iso-OMPA (10 microM) also potentiated ACh-induced contraction, the effect was less than that evoked by neostigmine. The activities of AChE in rat urinary bladder strips were significantly (P<0.05) higher than those of BuChE. These results indicated that AChE, rather than BuChE, plays an important role in controlling ACh-induced contractions of rat urinary bladder.

Acetylcholinesterase↗

PubMed2003

Augmentation of rat urinary bladder relaxation mediated by beta1-adrenoceptors in experimental diabetes.

We examined how diabetes affects the beta-adrenoceptor subtypes mediating relaxation of rat urinary bladder smooth muscle contracted with carbachol. The relaxant responses to isoproterenol were larger in muscles from rats 8 to 10 weeks after induction of diabetes with streptozotocin (80 mg/kg, i.p.) as compared to the control muscles. In contrast, forskolin-induced relaxations did not differ significantly in the control and diabetes groups. Propranolol (1 microM) abolished the diabetes-induced augmentation of relaxant responses to isoproterenol. The relaxant responses to T-0509 ((-)-(R)-1-(3,4-dihydroxyphenyl)-2-[(3,4-dimethoxyphenethyl)-amino]ethanol hydrochloride), a beta(1)-adrenoceptor agonist, were small but significantly augmented by diabetes. On the other hand, diabetes did not change the relaxations produced by clenbuterol, a beta(2)-adrenoceptor agonist, and BRL37344 ((+/-)-(R*,R*)-(4-[2-([2-(3-chlorophenyl)-2-hydroxyethyl]amino)propyl]phenoxy)acetic acid), a beta(3)-adrenoceptor agonist. These results suggest that diabetes selectively augments the beta(1)-adrenoceptor-mediated relaxation of the rat urinary bladder smooth muscle.

Adrenergic beta-Agonists↗

PubMed2003

Expression of multidrug resistance protein 4 and 5 in the porcine coronary and pulmonary arteries.

Guanosine 3',5'-cyclic monophosphate (cGMP) has an important role in regulating vascular smooth muscle tone. We examined whether mRNA for multidrug resistance protein (MRP) 4 and MRP5, which were recently identified as ATP-dependent export pumps for cyclic nucleotides, is expressed in the porcine coronary and pulmonary arteries. The results showed that both arteries express mRNA for MRP4 and MRP5, and thus these proteins may be novel targets for the prevention and/or treatment of various cardiovascular diseases.

Animals↗

PubMed2003

Protease-activated receptor-2-mediated contraction in the rat urinary bladder: the role of urinary bladder mucosa.

The role of protease-activated receptor-2 (PAR-2) in the regulation of the rat urinary bladder contractility was investigated. Both trypsin and PAR-2 activating peptide (SLIGRL-NH(2)) produced a concentration-dependent contractile response in the urinary bladder preparations. These contractions were abolished by removal of the urinary bladder mucosa and were significantly reduced by indomethacin (10 microM). These results suggest that activation of PAR-2 stimulates release of prostaglandins from mucosal layer and thereby contracts rat urinary bladder smooth muscles.

Animals↗

PubMed2003

Production of monoclonal antibodies recognizing human hair follicle keratinocytes.

To raise new antibodies against the cells contained in human hair follicles, we immunized mice with a mixture of primary cultured human embryogenic keratinocytes thought to contain very immature keratinocytes, as antigen. Using a monoclonal antibody (MAb) producing technique, we obtained two MAbs, which recognize a specific portion of the hair follicle. MAb-8G2 was specific to the companion layer between the inner and outer root sheath of the follicle. This pattern of recognition was quite similar to the expression pattern of K6hf protein, a human hair follicle-specific type II cytokeratin. MAb-sDP showed unique recognition. Immunohistochemistry indicated that MAb-sDP specifically recognized the cells surrounding the dermal papilla (DP). These cells are possibly the germ line cells of hair matrix.

Animals↗

PubMed2002

Role of the M2 muscarinic receptor pathway in lidocaine-induced potentiation of the relaxant response to atrial natriuretic peptide in bovine tracheal smooth muscle.

We earlier reported that lidocaine augments the relaxation and accumulation of guanosine 3',5'-cyclic monophosphate produced by atrial natriuretic peptide (ANP) in bovine tracheal smooth muscle contracted with methacholine. However, the mechanism of that augmentation remains to be elucidated. In this study, we examined the role of muscarinic receptor-mediated signalling in the potentiation of ANP-induced relaxation by lidocaine. Lidocaine (100 micro M) augmented the relaxant responses to ANP in methacholine (0.3 microM)-contracted bovine tracheal smooth muscle but had no effect on the relaxant effects of ANP in preparations contracted with 100 micro M histamine. Treatment of tracheal preparations with methoctramine (0.03 microM), an M2 muscarinic receptor antagonist, enhanced ANP-induced relaxation and this treatment abolished the synergistic action of lidocaine on ANP. In radioligand-binding experiments, lidocaine concentration dependently displaced the specific binding of [3H]- N-methyl scopolamine to cloned human M2 and M3 muscarinic receptors expressed in Chinese hamster ovary cells. These results suggest that lidocaine acts as an M2 muscarinic receptor antagonist, thereby potentiating the relaxant responses to ANP in the bovine tracheal smooth muscle contracted with muscarinic receptor agonists.

Animals↗

PubMed2002

Stimulation of muscarinic M2 receptors inhibits atrial natriuretic peptide-mediated relaxation in bovine tracheal smooth muscle.

The influence of muscarinic M(2) receptors to modulate the relaxant effects of atrial natriuretic peptide (ANP) and sodium nitroprusside (SNP) was investigated in bovine tracheal smooth muscle. In bovine tracheal smooth muscles contracted with methacholine (0.3 micro M), methoctramine (0.03 micro M), a selective muscarinic M(2) receptor antagonist, augmented the relaxant responses to ANP without affecting the responses to SNP and 8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphate. Pertussis toxin (PTX; 200 ng/ml for 18 h) augmented the relaxation and accumulation of guanosine 3',5'-cyclic monophosphate produced by ANP. These results suggest that the stimulation of muscarinic M(2) receptors suppresses ANP-induced activation of particulate guanylyl cyclase via a PTX-sensitive G protein.

Animals↗

PubMed2002

Inhibitory mechanism of BRL37344 on muscarinic receptor-mediated contractions of the rat urinary bladder smooth muscle.

We examined the inhibitory mechanism of BRL37344, a beta-adrenoceptor agonist that is considered to be specific to beta(3)-subtype, on muscarinic receptor-mediated contraction of the rat urinary bladder smooth muscle. BRL37344 produced apparently biphasic concentration-relaxation curves in the urinary bladder smooth muscle contracted with carbachol (0.6 microM). The first and second phases had estimated p D(2) (-logEC(50)) values of 7.80+/-0.34 and 4.62+/-0.18, respectively ( n=6). The first component of the BRL37344 concentration-response curve was not affected by propranolol (1 microM), whereas it was inhibited by higher concentrations of the drug (10 microM or 30 microM). The second component was completely resistant to propranolol. On the other hand, BRL37344 produced monophasic concentration-relaxation of 30 mM KCl-precontracted urinary bladder smooth muscle with a p D(2) value of 8.34+/-0.18 ( n=6). Pretreatment of the urinary bladder smooth muscles with BRL37344 (30, 100 and 300 microM) significantly ( P<0.05) shifted the concentration-response curves for carbachol-induced contractions. In radioligand binding experiments, BRL37344 concentration-dependently displaced the specific binding of [(3)H] N-methyl scopolamine to muscarinic receptors on rat urinary bladder smooth muscle membranes. Additionally, BRL37344 inhibited [(3)H] N-methyl scopolamine binding to cloned human muscarinic receptors (M(1)-M(5)) expressed in Chinese hamster ovary cells. These results suggest that BRL37344 attenuates muscarinic receptor-mediated contractions through prevention of the agonists binding to their receptors, in addition to stimulation of beta(3)-adrenoceptors, in rat urinary bladder.

Adrenergic beta-Agonists↗

PubMed2002

Relaxation and potentiation of cGMP-mediated response by ibudilast in bovine tracheal smooth muscle.

The effects of ibudilast, an inhibitor of phosphodiesterases (PDEs), on tension, levels of guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP) were investigated in bovine tracheal smooth muscle. We especially examined the combined effect of ibudilast with the cGMP-elevating agents on these parameters. Ibudilast was equipotent to attenuate the precontractions induced by both 0.3 microM methacholine and 40 mM K(+). By contrast, the relaxant effects of sodium nitroprusside and salbutamol on 40 mM K(+)-contracted preparations were smaller than those on 0.3 microM methacholine-contracted ones. Neither N(omega)-nitro-L-arginine (100 microM), an inhibitor of nitric oxide synthase, nor ODQ (1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; 5 microM), an inhibitor of soluble guanylyl cyclase, affected the ibudilast-induced relaxation. The relaxations induced by ibudilast and diltiazem on 40 mM K(+)-contracted preparations were significantly attenuated when extracellular CaCl(2) was increased from 2.54 mM to 10 mM. Ibudilast (10 microM), which caused only minor effect by itself, significantly ( P<0.05) shifted the concentration-response curves for the relaxant responses to sodium nitroprusside (SNP), atrial natriuretic peptide (ANP) and salbutamol to the left. On the other hand, ibudilast did not change the relaxant responses to diltiazem. Unlike ibudilast, diltiazem (3 microM) failed to affect the SNP- and salbutamol-induced relaxations. Ibudilast significantly ( P<0.05) increased basal levels of cGMP and cAMP. Furthermore, ibudilast enhanced SNP (0.3 microM)- and ANP (0.3 microM)-induced cGMP accumulation and salbutamol (10 nM)-induced cAMP accumulation. Zaprinast (10 microM), a type 5 PDE inhibitor, enhanced both relaxation and cGMP accumulation induced by SNP and ANP without changing salbutamol-induced responses. These findings suggest that blockade of voltage-gated Ca(2+) channels is involved in the relaxing action of ibudilast in bovine tracheal smooth muscle. However, ibudilast potentiates relaxation responses to ANP and SNP by inhibition of PDE 5, not by blockade of Ca(2+) channels. The enhancement of cGMP-mediated response may contribute to the therapeutic effects of ibudilast.

Albuterol↗

PubMed2002

Differences in protective profiles of diltiazem isomers in ischemic and reperfused guinea pig hearts.

The effects of L-cis and D-cis diltiazem on the extracellular potassium concentration ([K(+)]e), pH and cardiac function were compared in ischemic guinea pig hearts. Before inducing ischemia, L-cis diltiazem (10 and 30 microM) reduced the left ventricular developed pressure (LVDP) with a marginal inhibition of heart rate (HR), whereas lower doses of the D-cis isomer decreased both LVDP and HR. L-cis Diltiazem only slightly inhibited the increase in [K(+)]e and the decrease in pH but significantly inhibited ischemic contractures in contrast to the marked inhibition of these parameters produced by even low doses of the D-cis isomer. Notably, at equipotent doses for the ischemic parameters, L-cis diltiazem restored the left ventricular end-diastolic pressure (LVEDP) and HR after reperfusion to a greater extent than the D-cis isomer. These results suggest that the L-cis isomer may specifically improve postischemic function, in addition to the modest action on [K(+)]e and pH, in guinea pig hearts.

Animals↗

PubMed2002

New triterpenoids from Tricholoma saponaceum.

Six new triterpenes, saponaceolides E (1), F (2), and G (3), and saponaceoic acids I (4), II (5), and III (6) were isolated from the fruiting body of the fungus Tricholoma saponaceum, and their structures were elucidated on the base of extensive NMR experiments. Compounds 1 and 2 exhibited inhibitor activity against B16 and L929 cells.

Basidiomycota↗