bluuebunny/crossref_metadata_2025_split huggingface dataset:
Histamine H2 receptors mediate the inhibitory effect of histamine on human eosinophil degranulation
Authors: Ezeamuzie Charles I , Philips Elizabeth 
Published: January 2005

The effect of histamine on human eosinophil degranulation and the receptor mediating such effect were studied in vitro using the complement C5a‐mediated eosinophil peroxidase (EPO) release model.
Following pre‐treatment with 5 μg ml−1 cytochalasin B(CB), C5a induced a concentration‐dependent release of EPO from eosinophils isolated from healthy donors.
Histamine (0.1–50 μM), but not L‐histidine, inhibited concentration‐dependently C5a‐induced EPO release with IC50 (95% CI) of 0.6 μM (0.3–1.2 μM) and maximal inhibition of ∼60%.
A similar effect was seen with the selective H2 agonists dimaprit (IC50 (95% CI)=6.9 μM (3.2–10.6 μM)) and amthamine (IC50 (95% CI)=0.4 μM (0.2–0.7 μM)). Neither the selective H1 agonist 6‐(2‐(4‐imidazolyl)ethylamino)‐N‐(4‐trifluoromethylphenyl) heptanecarboxamide(HTMT), nor the selective H3 agonists imetit (up to 100 μM) had any significant effect.
The inhibition by histamine was reversed by cimetidine (0.1–30 μM) and other H2 antagonists, but not the H1 antagonist mepyramine (1.0–100 μM), nor the H3 antagonist thioperamide (1.0–100 μM). Cimetidine (1–30 μM) shifted to the right the dimaprit log dose‐response curve, producing a pA2 value of 5.9 and Schild's plot slope of 0.98, thus confirming simple competitive antagonism.
Histamine (10–100 μM) increased intracellular level of adenosine 3′,5′‐cyclic monophosphate, which was completely abolished by cimetidine (30 μM), but not mepyramine or thioperamide. The cyclic AMP analogue – dibutyryl cyclic AMP – also inhibited degranulation (IC50 ∼300 μM). The cyclic AMP phosphodiesterase(PDE) IV inhibitor rolipram (10 μM) synergistically enhanced the inhibition of EPO release by histamine.
These results suggest that histamine, via stimulation of H2 receptors and a consequent elevation of intracellular levels of cyclic AMP, inhibits human eosinophil degranulation.

British Journal of Pharmacology (2000) 131, 482–488; doi:10.1038/sj.bjp.0703556
Effect of saikosaponin, a triterpene saponin, on apoptosis in lymphocytes: association with c‐myc, p53, and bcl‐2 mRNA
Authors: Hsu Ming‐Jen , Cheng Jur‐Shan , Huang Huei‐Chen 
Published: January 2005

The mechanisms involved in the apoptotic effect of saikosaponin‐d, a triterpene saponin from Bupleurum falcatum L., were studied in human CEM lymphocytes and compared with those of dexamethasone (3×10−7 M).
Saikosaponin‐d (10−8 to 10−5 M) inhibited the serum‐stimulated [3H]‐thymidine incorporation in a concentration‐dependent manner. Dexamethasone also inhibited serum‐stimulated [3H]‐thymidine incorporation.
Cell viability was unaffected by saikosaponin‐d until 10−5–10−4 M. Dexamethasone significantly reduced the number of viable cells.
Following saikosaponin‐d (10−5–10−4 M) treatment, flow cytometry analysis of propidium iodide‐stained cells showed a significant increase in the percentage of cells in the apoptotic region. Dexamethasone also significantly increased the percentage of apoptotic cells. The supravital exposure to propidium iodide and annexin V labelling demonstrated that saikosaponin‐d (10−5–10−4 M) induced apoptosis as well as necrosis.
The apoptotic effect of saikosaponin‐d (3×10−6–10−4 M) was also demonstrated by TUNEL analysis and DNA laddering. The percentage of apoptotic cells induced by saikosaponin‐d (3×10−6–10−5 M) was unaffected by the presence of Z‐VAD‐FMK, indicating that saikosaponin‐d‐induced apoptosis may not be mediated by caspase activity. However, the percentage of apoptotic cells induced by dexamethasone was significantly reduced by the presence of Z‐VAD‐FMK.
Levels of c‐myc, p53, and bcl‐2 mRNA were analysed by the reverse transcription‐polymerase chain reaction. Levels of c‐myc and p53 mRNA were significantly increased, while the level of bcl‐2 mRNA was decreased, by saikosaponin‐d (10−5 M) treatment. Dexamethasone did not significantly change the expression of these genes.
It is suggested that the apoptotic effect of saikosaponin‐d may be partly mediated by increases in c‐myc and p53 mRNA levels accompanied by a decrease in bcl‐2 mRNA level.

British Journal of Pharmacology (2000) 131, 1285–1293; doi:10.1038/sj.bjp.0703559
Anticonvulsant and proconvulsant effects of tramadol, its enantiomers and its M1 metabolite in the rat kindling model of epilepsy
Authors: Potschka Heidrun , Friderichs Elmar , Löscher Wolfgang 
Published: January 2005

The centrally acting analgesic tramadol has recently been reported to cause seizures at re‐commended dosages in patients, whereas animal experiments had indicated that seizures only occur in high, toxic doses. Tramadol has a dual mechanism of action that includes weak agonistic effects at the mu‐opioid receptor as well as inhibition of monoamine (serotonin, norepinephrine) re‐uptake. Its major (M1) metabolite mono‐O‐desmethyltramadol, which is rapidly formed in vivo, has a markedly higher affinity for mu receptors and may thus contribute to the effects of the parent compound. Furthermore, the pharmacological effects of tramadol appear to be related to the different, but complementary and interactive pharmacologies of its enantiomers. In the present study, we evaluated (±)‐tramadol, its enantiomers, and its M1 metabolite ((+)‐enantiomer) in the amygdala kindling model of epilepsy in rats. Adverse effects determined in kindled rats were compared to those in nonkindled rats.
At doses within the analgesic range, (±)‐tramadol and its enantiomers induced anticonvulsant effects in kindled rats. However, at only slightly higher doses seizures occurred. With (±)‐tramadol, generalized seizures were observed at 30 mg kg−1 in most kindled but not in nonkindled rats. The (−)‐enantiomer induced myoclonic seizures at 30 mg kg−1 in most kindled but not in nonkindled rats, although myoclonic seizure activity was observed in some nonkindled rats at 10 or 20 mg kg−1. Seizures were also observed after the (+)‐enantiomer and the (+)‐enantiomer of the M1 metabolite, but experiments with higher doses of these compounds were limited by marked respiratory depression.
The data demonstrate that kindling enhances the susceptibility of rats to convulsant adverse effects of tramadol and its enantiomers, indicating that a preexisting lowered seizure threshold increases the risk of tramadol‐induced seizures.

British Journal of Pharmacology (2000) 131, 203–212; doi:10.1038/sj.bjp.0703562
Extracellular ATP‐dependent activation of plasma membrane Ca2+ pump in HEK‐293 cells
Authors: Qi Z , Murase K , Obata S , Sokabe M 
Published: January 2005

It is well known that extracellular ATP (ATPo) elevates the intracellular Ca2+ concentration ([Ca2+]i) by inducing Ca2+ influx or mobilizing Ca2+ from internal stores via activation of purinoceptors in the plasma membrane. This study shows that ATPo also activates the plasma membrane Ca2+ pumps (PMCPs) to bring the elevated [Ca2+]i back to the resting level in human embryonic kidney‐293 (HEK‐293) cells.
The duration of ATPo‐induced intracellular Ca2+ transients was significantly increased by PMCP blockers, La3+ or orthovanadate. In contrast, replacement of extracellular Na+ with NMDG+, a membrane‐impermeable cation, had no significant effect on duration, thus suggesting that Na+/Ca2+ exchangers do not participate in the ATPo‐induced Ca2+ transient.
A rapid and significant decrease in [Ca2+]i, which was not dependent on extracellular Na+, was induced by ATPo in cells pretreated with thapsigargin (TG). This decrease was blocked by orthovanadate, indicating that it was caused by PMCPs rather than sarco/endoplasmic reticulum Ca2+ pumps (SERCPs).
UTP and ATPγS also caused a decrease in [Ca2+]i in cells pretreated with TG, although they were less effective than ATP. The effect of UTP implies the involvement of both P2Y1 and P2Y2 receptors, while the effect of ATPγS implies no significant role of ectophosphorylation and agonist hydrolysis in the agonist‐induced [Ca2+]i decreases.
These results point to a role of PMCPs in shaping the Ca2+ signal and in restoring the resting [Ca2+]i level to maintain intracellular Ca2+ homeostasis after agonist stimulation.

British Journal of Pharmacology (2000) 131, 370–374; doi:10.1038/sj.bjp.0703563
Effects of halothane on the transient outward K+ current in rat ventricular myocytes
Authors: Davies Lucinda A , Hopkins Philip M , Boyett Mark R , Harrison Simon M 
Published: January 2005

Halothane has been shown to affect several membrane currents in cardiac tissue including the L‐type calcium current (ICa), sodium current and a variety of potassium currents. However, little is known about the effects of halothane on the transient outward K+ current (Ito).
Single ventricular myocytes from rat hearts were voltage clamped using the whole cell patch configuration and an EGTA‐containing pipette solution to record the Ca2+‐independent, 4‐aminopyridine sensitive component of Ito. 300 μM Cd2+ or 10 μM nifedipine was used to block ICa.
At +80 mV, Ito (peak current minus current at the end of the pulse) was 1.8±0.2 nA under control conditions which was reduced to 1.3±0.2 nA by 1 mM halothane (P<0.001, mean±s.e.mean, n=9). The inhibition of Ito by halothane was concentration‐dependent (K0.5, 1.1±0.2 mM). One mM halothane led to a 16 mV shift in the steady‐state inactivation curve towards negative membrane potentials (P=0.005, n=8) but had no significant effect on the activation‐voltage relationship (P=0.724).
One mM halothane also increased the rate of inactivation of Ito; the dominant time constant of inactivation was reduced from 14±1 to 9±1 ms (P=0.017, mean±s.e.mean, n=6).
These data show that halothane reduced Ito; 0.3 mM, close to the MAC50 value for halothane, inhibited the current by 15% and as such, the inhibition of Ito will be relevant to the clinical situation. Halothane induced a shift in the steady‐state inactivation curve and accelerated the inactivation process of Ito which could be responsible for its inhibitory effect.
Due to the differential transmural expression of Ito in ventricular tissue, inhibition of Ito would reduce the transmural dispersion of refractoriness which could contribute to the arrhythmogenic properties of halothane.

British Journal of Pharmacology (2000) 131, 223–230; doi:10.1038/sj.bjp.0703565
Effect of MEN 10755, a new disaccharide analogue of doxorubicin, on sarcoplasmic reticulum Ca2+ handling and contractile function in rat heart
Authors: Zucchi Riccardo , Yu Gongyuan , Ghelardoni Sandra , Ronca Francesca , Ronca‐Testoni Simonetta 
Published: January 2005

The use of anthraquinone antineoplastic agents is limited by their cardiac toxicity, which is largely due to activation of the sarcoplasmic reticulum (SR) Ca2+ release channel (ryanodine receptor). MEN 10755 is a new disaccharide analogue of doxorubicin. We have evaluated its effects on SR function and its toxicity in isolated working rat hearts.
In rat SR vesicles, doxorubicin stimulated [3H]‐ryanodine binding by increasing its Ca2+‐sensitivity. At 1 μM Ca2+, ryanodine binding increased by 15.3±2.5 fold, with EC50=20.6 μM. Epirubicin produced a similar effect, i.e. 9.7±0.6 fold stimulation with EC50=11.1 μM. MEN 10755 increased ryanodine binding by 1.9±0.3 fold (P<0.01 vs doxorubicin and epirubicin), with EC50=38.9 μM.
Ca2+‐induced Ca2+ release experiments were performed by quick filtration technique, after SR loading with 45Ca2+. At 2 μM Ca2+, doxorubicin (50 μM) increased the rate constant of Ca2+ release to 82±5 s−1 vs a control value of 22±2 s−1 (P<0.01), whereas 50 μM MEN 10755 did not produce any significant effect (24±3 s−1).
Ca2+‐ATPase activity and 45Ca2+‐uptake were not significantly affected by doxorubicin, its 13‐dihydro‐derivative, epirubicin, MEN 10755 and the 13‐dihydro‐derivative of MEN 10755, at concentrations 100 μM.
In isolated heart experiments, administration of 30 μM doxorubicin or epirubicin caused serious contractile impairment, whereas 30 μM MEN 10755 produced only minor effects.
In conclusion, in acute experiments MEN 10755 was much less cardiotoxic than equimolar doxorubicin or epirubicin. This result might be accounted for by reduced activation of SR Ca2+ release.

British Journal of Pharmacology (2000) 131, 342–348; doi:10.1038/sj.bjp.0703575
Amphotericin B severely affects expression and activity of the endothelial constitutive nitric oxide synthase involving altered mRNA stability
Authors: Suschek Christoph Viktor , Bonmann Eckhard , Kleinert Hartmut , Wenzel Michael , Mahotka Csaba , Kolb Hubert , Förstermann Ulrich , Gerharz Claus‐Dieter , Kolb‐Bachofen Victoria 
Published: January 2005

The therapeutic use of the antifungal drug amphotericin B (AmB) is limited due to severe side effects like glomerular vasoconstriction and risk of renal failure during AmB administration. As nitric oxide (NO) has substantial functions in renal autoregulation, we have determined the effects of AmB on endothelial constitutive NO synthase (ecNOS) expression and activity in human and rat endothelial cell cultures.
AmB used at concentrations of 0.6 to 1.25 μg ml−1 led to increases in ecNOS mRNA and protein expression as well as NO production. This was the result of an increased ecNOS mRNA half‐life. In contrast, incubation of cells with higher albeit subtoxic concentrations of AmB (2.5–5.0 μg ml−1) resulted in a decrease or respectively in completely abolished ecNOS mRNA and protein expression with a strongly reduced or inhibited ecNOS activity, due to a decrease of ecNOS mRNA half‐life. None of the AmB concentrations affected promoter activity as found with a reporter gene construct stably transfected into ECV304 cells.
Thus, our experiments show a concentration‐dependent biphasic effect of AmB on expression and activity of ecNOS, an effect best explained by AmB influencing ecNOS mRNA stability. In view of the known renal accumulation of this drug the results reported here could help to elucidate its renal toxicity.

British Journal of Pharmacology (2000) 131, 473–481; doi:10.1038/sj.bjp.0703576
Curcumin inhibition of bleomycin‐induced pulmonary fibrosis in rats
Authors: Punithavathi Durairaj , Venkatesan Narayanan , Babu Mary 
Published: January 2005

Curcumin, an anti‐inflammatory, antioxidant, was evaluated for its ability to suppress bleomycin (BLM)‐induced pulmonary fibrosis in rats. A single intratracheal instillation of BLM (0.75 U 100−1 g, sacrificed 3, 5, 7, 14 and 28 days post‐BLM) resulted in significant increases in total cell numbers, total protein, and angiotensin‐converting enzyme (ACE), and alkaline phosphatase (AKP) activities in bronchoalveolar lavage fluid. Animals with fibrosis had a significant increase in lung hydroxyproline content. Alveolar macrophages from BLM‐administered rats elaborated significant increases in tumour necrosis factor (TNF)‐α release, and superoxide and nitric oxide production in culture medium. Interestingly, oral administration of curcumin (300 mg kg−1 10 days before and daily thereafter throughout the experimental time period) inhibited BLM‐induced increases in total cell counts and biomarkers of inflammatory responses in BALF. In addition, curcumin significantly reduced the total lung hydroxyproline in BLM rats. Furthermore, curcumin remarkably suppressed the BLM‐induced alveolar macrophage production of TNF‐α, superoxide and nitric oxide. These findings suggest curcumin as a potent anti‐inflammatory and anti‐fibrotic agent against BLM‐induced pulmonary fibrosis in rats.British Journal of Pharmacology (2000) 131, 169–172; doi:10.1038/sj.bjp.0703578
Advantages of heterologous expression of human D2long dopamine receptors in human neuroblastoma SH‐SY5Y over human embryonic kidney 293 cells
Authors: Alberts Glen L , Pregenzer Jeffrey F , Im Wha Bin 
Published: January 2005

The human D2long dopamine receptor when expressed heterologously in a human neuronal cell line, SH‐SY5Y, produced more robust functional signals than when expressed in a human embryonic kidney cell line, HEK293. Quinpirole (agonist)‐induced GTPγ35S binding and high affinity sites were 3–4 fold greater in SH‐SY5Y than in HEK293 cells.
N‐type Ca2+ channel currents present in SH‐SY5Y cells, but not HEK293 cells, were inhibited potently by quinpirole with a half‐maximal inhibitory concentration of 0.15±0.03 nM. Inhibition of adenylyl cyclases by agonists, on the other hand, was of similar potency and efficacy in the two cell lines.
GTPγ35S‐Bound Gα subunits from quinpirole‐activated and solubilized membranes were monitored upon immobilization with various Gα‐specific antibodies. Gαi and Gαo subunits were highly labelled with GTPγ35S in SH‐SY5Y cells, but only Gαi subunits were labelled in HEK293 cells. The additional Go coupling in SH‐SY5Y cells could arise, at least in part, from the presence of Go coupled‐effectors, such as the N‐type Ca2+ channel, and may contribute to robust agonist‐induced GTPγ35S binding, which is a reliable means for measuring ligand intrinsic efficacy.
It appears that expression of neuronal G protein‐coupled receptors in neuronal environments could reveal additional functional characteristics that are absent in non‐neuronal cell lines. This appears to be due to, at least in part, to the presence of neuron‐specific effectors. These findings underscore the importance of the cellular environment in which drug actions are examined, particularly in the face of intensive efforts to develop drugs for G protein‐coupled receptors of various origins.

British Journal of Pharmacology (2000) 131, 514–520; doi:10.1038/sj.bjp.0703580
Differential regulation of P2Y11 receptor‐mediated signalling to phospholipase C and adenylyl cyclase by protein kinase C in HL‐60 promyelocytes
Authors: Suh Byung‐Chang , Kim Tae‐Don , Lee Ihn‐Soon , Kim Kyong‐Tai 
Published: January 2005

The regulatory mode of the P2Y11 purinoceptor‐mediated signalling cascades towards phospholipase C and adenylyl cyclase was studied in HL‐60 promyelocytes.
Treatment with the potent P2Y11 receptor activator dATP evoked an elevated intracellular Ca2+ concentration ([Ca2+]i) and inositol 1,4,5‐trisphosphate (IP3) production that was sustained for longer than 30 min. However, the dATP‐induced responses were significantly inhibited by the activation of protein kinase C after a short exposure to phorbol 12‐myristate 13‐acetate (PMA).
dATP also potently stimulated cyclic AMP production with half maximum effect seen at 23±7 μM dATP. In addition, a 5‐min pretreatment with PMA enhanced the dATP‐stimulated cyclic AMP accumulation.
PMA potentiated the cyclic AMP production when adenylyl cyclase was activated directly by forskolin or indirectly by G protein activation after cholera toxin treatment. dATP also enhanced the forskolin‐mediated cyclic AMP generation.
Treatment of the cells with 10 μM U‐73122, which almost completely blocked the dATP‐stimulated IP3 production and [Ca2+]i rise, had no effect on cyclic AMP accumulation, while 10 μM 9‐(tetrahydro‐2‐furyl)adenine (SQ 22536), which inhibited the adenylyl cyclase activation, did not effect the dATP‐stimulated phosphoinositide turnover.
Taken together, the results indicate that P2Y11 receptor‐mediated activation of phospholipase C and adenylyl cyclase occurs through independent pathways and is differentially regulated by protein kinase C in HL‐60 cells.

British Journal of Pharmacology (2000) 131, 489–497; doi:10.1038/sj.bjp.0703581
Characterization of the ORL1 receptor on adrenergic nerves in the rat anococcygeus muscle
Authors: Ho M , Corbett A D , McKnight A T 
Published: January 2005

Nociceptin, the endogenous ORL1 receptor agonist inhibited the motor response to electrical‐field stimulation in the rat anococcygeus muscle. This effect was characterized using the peptide ligands acetyl‐Arg‐Tyr‐Tyr‐Arg‐Trp‐Lys‐NH2 (Ac‐RYYRWK‐NH2), acetyl‐Arg‐Tyr‐Tyr‐Arg‐Ile‐Lys‐NH2 (Ac‐RYYRIK‐NH2) and [Phe1ψ(CH2‐NH)Gly2]nociceptin(1‐13)NH2 ([F/G]NC(1‐13)NH2), and the non‐selective opioid antagonist naloxone benzoylhydrazone (NalBzOH).
Nociceptin produced a concentration‐dependent inhibition of the adrenergic motor response to electrical‐field stimulation (EC50 19 nM, pEC50 7.7±0.1, n=8), but the response to exogenous noradrenaline (0.2–1 μM) was unaffected. The inhibitory nerve response was not affected by up to 1 μM nociceptin.
After inhibition of nitric oxide synthase (Nω‐nitro‐L‐arginine 100 μM), and in the presence of peptidase inhibitors, nociceptin produced full inhibition of the pure adrenergic motor response (EC50 4 nM; pEC50 8.4±0.1, Emax 98.3±1.2%, n=12). Ac‐RYYRWK‐NH2 was a potent partial‐agonist (pEC50 9.0±0.1, Emax 66.4±5.2; n=11) but the efficacy of Ac‐RYYRIK‐NH2 (pEC50 8.0±0.2, Emax 36.7±3.5; n=12) was lower and the peptide could be tested as an antagonist (pA2 9.01).
[F/G]NC(1‐13)NH2 and NalBzOH had little or no efficacy and were competitive antagonists with pKB values of 7.4 (95% c.l. 7.1, 7.7) and 6.9 (95% c.l. 6.7, 7.1) respectively. Both increased the response to field stimulation at high concentrations, suggesting the release of an endogenous agonist for the ORL1 receptor during stimulation.
Rat nocistatin did not affect the response to electrical‐field stimulation, nor did it modify the inhibitory action of nociceptin.
Our findings suggest there is a significant endowment of ORL1 receptors on sympathetic terminals of the rat anococcygeus, where nociceptin mediates a powerful inhibitory effect on adrenergic neuromuscular transmission.

British Journal of Pharmacology (2000) 131, 349–355; doi:10.1038/sj.bjp.0703583
Inverse agonism and neutral antagonism at a constitutively active alpha‐1a adrenoceptor
Authors: Zhu Jun , Taniguchi Takanobu , Takauji Rumiko , Suzuki Fumiko , Tanaka Takashi , Muramatsu Ikunobu 
Published: January 2005

We have studied the antagonist action of prazosin and KMD‐3213 in a constitutively active mutant of the human alpha‐1a adrenoceptor in which Ala271 was substituted to Thr and was expressed in CHO cells. Inverse agonism was characterized by up‐regulation of receptor density, a decrease in basal GTPγS binding, and a reduction in basal inositol‐1,4,5‐trisphosphate (IP3) level.
According to the above criteria, prazosin acted as an inverse agonist, whilst KMD‐3213 behaved as a neutral antagonist.
Compared with the wild‐type receptor, mutant receptor exhibited single affinity sites for [3H]‐prazosin, [3H]‐KMD and the non‐radioactive ligands tested, and displayed significantly higher affinities for several agonists but not for the two antagonists.
Administration of KMD‐3213 to prazosin‐treated CHO cells expressing the mutant receptor reversed the inverse agonism of prazosin resulting in rapid increases in cellular IP3, in intracellular [Ca2+] and in the rate of extracellular acidification.
These results indicated that a neutral antagonist can reverse the action of an inverse agonist at the receptor site. The distinct properties of inverse agonist and neutral antagonist in affecting receptor function may be important for the clinical use of such antagonists.

British Journal of Pharmacology (2000) 131, 546–552; doi:10.1038/sj.bjp.0703584