Comparison between huperzine A, tacrine, and E2020 on cholinergic transmission at mouse neuromuscular junction in vitro. (1/663)

AIM: To compare the effects of huperzine A (Hup A), tacrine, and E2020 on cholinergic transmission at mouse neuromuscular junction in vitro. METHODS: The isolated mouse phrenic nerve-hemidiaphragm preparations were used with the conventional intracellular recording technique. The miniature end-plate potentials (MEPP), the mean quantal content of end-plate potentials (EPP), and the resting membrane potentials of muscle fiber were recorded. RESULTS: Hup A, tacrine, and E2020 at the concentration of 1.0 mumol.L-1 increased the amplitude, time-to-peak, and half-decay time of MEPP in the potencies of E2020 > Hup A > tacrine. Hup A did not significantly change the frequency of MEPP, the appearance of giant MEPP or slow MEPP, the resting membrane potentials, and the mean quantal content of EPP. CONCLUSION: Hup A is a selective and potent cholinesterase inhibitor, by which activity it facilitates the cholinergic transmission at mouse neuromuscular junction, and devoid of pre- and post-synaptic actions.  (+info)

Trigeminal nerve ganglion stimulation-induced neurovascular reflexes in the anaesthetized cat: role of endothelin(B) receptors in carotid vasodilatation. (2/663)

1. The effects of intravenous administration of endothelin (ET) receptor antagonists SB-209670 (0.001-10.0 mg kg(-1)), SB-217242, SB-234551 (0.01-10.0 mg kg(-1)) and BQ-788 (0.001-1.0 mg kg(-1)) were investigated on trigeminal nerve ganglion stimulation-induced neurovascular reflexes in the carotid vasculature of the anaesthetized cat. Comparisons were made with sumatriptan (0.003-3.0 mg kg(-1)) and alpha-CGRP8-37 (0.001-0.1 mg kg(-1)). 2. Trigeminal nerve ganglion stimulation produced frequency related increases in carotid blood flow, reductions in carotid vascular resistance and non-frequency related increases in blood pressure. Guanethidine (3 mg kg(-1), i.v.) blocked trigeminal nerve ganglion-induced increases in blood pressure but had no effect on changes in carotid flow or resistance. Maximal reductions in carotid vascular resistance was observed at 10 Hz, and this frequency was selected to investigate the effects of drugs on trigeminal nerve ganglion stimulation-induced responses in guanethidine treated cats. 3. Saline, alpha-CGRP8-37 SB-209670 and BQ-788 had little or no effect on resting haemodynamic parameters. SB-217242 (10 mg kg(-1), n=3) produced a 56% reduction in arterial blood pressure whereas SB-233451 (10 mg kg(-1), n=3) produced a 30% reduction in carotid vascular resistance. Sumatriptan produced dose-related reductions in resting carotid flow and increases (max. 104% at 0.3 mg kg(-1), n = 5) in vascular resistance. 4. SB-209670 (n=6-7), SB-217242 (n=3) and BQ-788 (n=3) produced inhibition of trigeminal nerve ganglion stimulation-induced reductions in carotid vascular resistance. Saline, SB-234551, alpha-CGRP8-37 and sumatriptan had no effect. 5. These data demonstrate ET(B) receptor blockade attenuates the vasodilator effects of trigeminal nerve ganglion stimulation in the carotid vascular bed of guanethidine pretreated anaesthetized cats.  (+info)

Microbiological degradation of bile acids. Nitrogenous hexahydroindane derivatives formed from cholic acid by Streptomyces rubescens. (3/663)

The metabolism of cholic acid (I) by Streptomyces rubescens was investigated. This organism effected ring A cleavage, side-chain shortening and amide bond formation and gave the following metabolites: (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1 beta-yl]valeric acid (IIa) and its mono-amide (valeramide) (IIb); and 2,3,4,6, 6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-1H-cyclopenta[f]quinoline-3,7 -dione(IIIe)and its homologues with the beta-oriented side chains, valeric acid, valeramide, butanone and propionic acid, in the place of the oxo group at C-7, i.e.compounds (IIIa), (IIIb), (IIIc) and (IIId) respectively. All the nitrogenous metabolites were new compounds, and their structures were established by partial synthesis except for the metabolite (IIIc). The mechanism of formation of these metabolites is considered. A degradative pathway of cholic acid (I) into the metabolites is also tentatively proposed.  (+info)

Polyamine biosynthesis inhibitors alter protein-protein interactions involving estrogen receptor in MCF-7 breast cancer cells. (4/663)

We investigated the effects of polyamine biosynthesis inhibition on the estrogenic signaling pathway of MCF-7 breast cancer cells using a protein-protein interaction system. Estrogen receptor (ER) linked to glutathione-S-transferase (GST) was used to examine the effects of two polyamine biosynthesis inhibitors, difluoromethylornithine (DFMO) and CGP 48664. ER was specifically associated with a 45 kDa protein in control cells. In cells treated with estradiol, nine proteins were associated with ER. Cells treated with polyamine biosynthesis inhibitors in the absence of estradiol retained the binding of their ER with a 45 kDa protein and the ER also showed low-affinity interactions with a number of cellular proteins; however, these associations were decreased by the presence of estradiol and the inhibitors. When samples from the estradiol+DFMO treatment group were incubated with spermidine prior to GST-ER pull down assay, an increased association of several proteins with ER was detected. The intensity of the ER-associated 45 kDa protein increased by 10-fold in the presence of 1000 microM spermidine. These results indicate a specific role for spermidine in ER association of proteins. Western blot analysis of samples eluted from GST-ER showed the presence of chicken ovalbumin upstream promoter-transcription factor, an orphan nuclear receptor, and the endogenous full-length ER. These results show that multiple proteins associate with ER and that the binding of some of these proteins is highly sensitive to intracellular polyamine concentrations. Overall, our results indicate the importance of the polyamine pathway in the gene regulatory function of estradiol in breast cancer cells.  (+info)

Interleukin-1alpha and tumour necrosis factor-alpha modulate airway smooth muscle DNA synthesis by induction of cyclo-oxygenase-2: inhibition by dexamethasone and fluticasone propionate. (5/663)

1. Previous studies have established that glucocorticoids inhibit airway smooth muscle DNA synthesis. The effects of a combination of the pro-inflammatory cytokines, interleukin-1alpha (IL-1alpha) and tumour necrosis factor-alpha (TNF-alpha) on the inhibition of DNA synthesis by glucocorticoids in human cultured airway smooth muscle have now been investigated, since these cytokines are chronically expressed in asthmatic airways. 2. Thrombin (0.3 u ml(-1)) and basic fibroblast growth factor (bFGF, 300 pM) stimulated increases in DNA synthesis which were concentration-dependently inhibited by dexamethasone (1-1000 nM). 3. The cytokine mixture, comprising IL-1alpha (0.01 and 0.1 pM) and TNF-alpha (3 and 30 pM), directly evoked increases in DNA synthesis which were attenuated by dexamethasone. However, the cytokine mixture prevented responses to bFGF or thrombin. 4. Paradoxically, in the presence of the cytokine mixture and bFGF, dexamethasone (1-1000 nM) concentration-dependently increased DNA synthesis. Furthermore, neither dexamethasone (100 nM) nor fluticasone propionate (1 nM) inhibited DNA synthesized in response to bFGF/cytokine mixture combination and dexamethasone was similarly inactive against the thrombin/cytokine mixture. 5. The levels of prostaglandin E2 (PGE2), an established inhibitor of airway smooth muscle DNA synthesis, remained below the limits of assay detection (0.05 nM) under basal conditions or following stimulation with either thrombin or bFGF. In contrast, the cytokine mixture alone, and in the presence of thrombin or bFGF, induced biologically active levels of PGE2. Dexamethasone (100 nM), the non-selective cyclo-oxygenase (COX) inhibitor indomethacin (3 microM) or the selective COX-2 inhibitor L-745,337 (0.3 microM) completely inhibited synthesis of PGE2. 6. Neither indomethacin (3 microM) nor L-745,337 (0.3 microM) influenced thrombin- or bFGF-induced DNA synthesis. However, each COX inhibitor enhanced DNA synthesis in cytokine-treated cells. 7. In unstimulated airway smooth muscle cells, COX-1, but not COX-2 protein was detectable by Western blotting. The induction of COX-2 protein by the cytokine mixture was attenuated by dexamethasone (100 nM), whereas the level of COX-1 protein was unaffected by either the cytokines or by dexamethasone. 8. Cytokine-induced, COX-2-dependent eicosanoid production inhibits DNA synthesis. The paradoxical increase in DNA synthesis observed in glucocorticoid treated airway smooth muscle stimulated by cytokine/bFGF combinations may be explained by the ability of glucocorticoids to repress COX-2 induction and prevent cytokine-induction of the DNA synthesis inhibitor, PGE2.  (+info)

Production of angiotensin II by homogeneous cultures of vascular smooth muscle cells from spontaneously hypertensive rats. (6/663)

Production of angiotensin II (Ang II) in spontaneously hypertensive rats (SHR)-derived vascular smooth muscle cells (VSMC) has now been investigated. A nonpeptide antagonist (CV-11974) of Ang II type 1 receptors inhibited basal DNA synthesis in VSMC from SHR, but it had no effect on cells from Wistar-Kyoto (WKY) rats. Ang II-like immunoreactivity, determined by radioimmunoassay after HPLC, was readily detected in conditioned medium and extracts of SHR-derived VSMC, whereas it was virtually undetectable in VSMC from WKY rats. Isoproterenol increased the amount of Ang II-like immunoreactivity in conditioned medium and extracts of SHR-derived VSMC, whereas the angiotensin-converting enzyme inhibitor delapril significantly reduced the amount of Ang II-like immunoreactivity in conditioned medium and extracts of these cells. Reverse transcription-polymerase chain reaction analysis revealed that the abundance of mRNAs encoding angiotensinogen, cathepsin D, and angiotensin-converting enzyme was greater in VSMC from SHR than in cells from WKY rats. The abundance of cathepsin D protein by Western blotting was greater in VSMC from SHR than in cells from WKY rats. Ang I-generating and acid protease activities were detected in VSMC from SHR, but not in cells from WKY rats. These results suggest that SHR-derived VSMC generate Ang II with increases in angiotensinogen, cathepsin D, and angiotensin-converting enzyme, which contribute to the basal growth. Production of Ang II by homogeneous cultures of VSMC is considered as a new mechanism of hypertensive vascular disease.  (+info)

Endothelin mediates renal vasodilation and hyperfiltration during pregnancy in chronically instrumented conscious rats. (7/663)

Profound vasodilation of the kidneys and other nonreproductive organs transpires during early pregnancy. Because nitric oxide (NO) was found to mediate renal vasodilation and hyperfiltration in conscious pregnant rats, and endogenous endothelin (ET) was suggested to be vasodilatory in the renal circulation of nonpregnant rats, we tested whether endothelin mediates the NO-dependent changes in the renal circulation during pregnancy. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured in conscious pregnant and virgin rats before and during infusion of 30 micrograms/min RES-701-1 (a selective ETB receptor subtype antagonist). Baseline GFR and ERPF were significantly increased by 35% in gravid rats relative to virgin controls. During infusion of RES-701-1, the pregnant rats responded more robustly, showing a greater decline in both GFR and ERPF such that renal function converged in the two groups of rats. ERPF also converged in pregnant and virgin rats during infusion of SB-209760, a nonselective ETA/B receptor subtype antagonist. Combined infusion of Nomega-nitro-L-arginine methyl ester [L-NAME, an NO synthase (NOS) inhibitor] and RES-701-1 reduced GFR and ERPF to levels comparable to those reached with either agent given alone, suggesting inhibition of a common vasodilatory pathway. RES-701-1 and SB-209670 significantly lowered the cGMP content of small renal arteries from gravid and virgin rats in vitro, strengthening the link between the renal endothelial ETB receptor subtype and NO. Importantly, we showed that RES-701-1 is not a direct inhibitor of NOS. We conclude that endothelin mediates the NO-dependent changes in the renal circulation of conscious rats during pregnancy.  (+info)

Isoprostanes and PGE2 production in human isolated pulmonary artery smooth muscle cells: concomitant and differential release. (8/663)

The isoprostanes are a group of biologically active arachidonic acid metabolites initially thought to be formed under conditions of oxidative stress and independently of cyclooxygenase. However, recent studies have demonstrated isoprostane production under conditions in which cyclooxygenase is intentionally activated/induced. Here we describe for the first time formation of isoprostanes by human vascular cells via independent pathways of oxidative stress and cyclooxygenase induction. We compared the release of the isoprostane with that of the traditional prostaglandin, prostaglandin E2. Cyclooxygenase-2 induction was confirmed by Western blot. When cells were stimulated with cytokines, the release of isoprostanes was inhibited by the cyclooxygenase-1 and -2 inhibitor indomethacin as well by as the cyclooxygenase-2 selective inhibitor L-745,337. However, treatment of cells with the superoxide-producing enzyme xanthine oxidase also resulted in isoprostane release, which was not affected by cyclooxygenase inhibition, unlike PGE2 release under the same condition. Thus, two independent pathways relating to oxidative stress and cyclooxygenase-2 induction form isoprostanes. These findings may have particular importance in diseases such as sepsis and ARDS in which oxidant stress occurs and cyclooxygenase is induced.  (+info)

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