Rocastine (AHR-11325), a rapid acting,nonsedating antihistamine

Rocastine [AHR-11325, 2-[2-(dimethylamino)ethyl]-2,3-dihydro-4-methylpyrido-[3,2-f]-1,4-oxazepine-5(4H)-thione (E)-2-butenedioate)] is a rapid-acting, potent, nonsedating antihistamine. In guinea pigs challenged with a lethal dose of histamine, rocastine is as effective [based on 1 hr. oral, protective dose (PD₅₀s)] as brompheniramine, chlorpheniramine, pyrilamine, and promethazine and superior to astemizole, diphenhydramine, terfenadine, and oxaomide. Rocastine has a faster onset of action than does terfenadine; rocastine being as effective with a 15 min pretreatment time (PD₅₀=0.13 mg/kg) as it is with a 1 hr pretreatment time (PD₅₀=0.12 mg/kg), while the 15 min PD₅₀ of terfenadine (PD₅₀=44.0 mg/kg) is 22 times greater than the 1 hr PD₅₀ (PD₅₀=1.93 mg/kg). Against aerosolized histamine, rocastine was 7.12×, 2.63×, and equipotent to pyrilamine in preventing histamine-induced prostration at pretreatment times of 1, 3, and 6 hr, respectively. Rocastine protected guinea pigs from collapse induced by aerosolized antigen; rocastine was 36 × more potent (based on 1 hr PD₅₀) than diphenhydramine and as potent as oxatomide and terfenadine. Rocastine did not alter the EEG of cats at doses in vast excess (150×) of its antihistaminic dose nor did it potentiate yohimbine toxicity in mice. Further, rocastine possesses no anticholinergic, antiadrenergic, or antiserotonergic propertiesin vitro. Rocastine is a selective, nonsedating, H₁-antagonist with a rapid onset of action.     

Dermal inflammation in primates,mice, and guinea pigs: Attenuation by second-generation leukotriene B4 receptor antagonist,SC-53228

Granulocyte infiltration is a prominent feature of human psoriasis. Psoriatic lesional skin contains abnormally high amounts of immunoreactive leukotriene B₄ (LTB₄), a potent granulocyte chemotaxin in vivo and in vitro. SC-53228 [(+)-(S)-7-(3-{2-(cyclopropylmethyl)-3-methoxy-4-[(methylamino)carbonyl]phenoxy}propoxy)-3, 4-dihydro-8-propyl-2H-1-benzopyran-2-propanoic acid], a second-generation LTB₄ receptor antagonist, was tested topically and orally in phorbol ester-induced dermal inflammation in three species. Skin inflammation was induced by topical application of phorbol-12-myristate-13-acetate-(PMA/TPA) and assessed by ear thickness, levels of the neutrophil marker enzyme myeloperoxidase (MPO) and histological examination. In mice, SC-53228 inhibited inflammation with a topical ED₅₀ value of 200 ± 18 g. When applied to guinea pigs, SC-53228 (100 g) inhibited the MPO increase by 86%, while 1000 g abrogated inflammation in rhesus macaques with no plasma accumulation of the drug. A 1 % gel formulation was also efficacious in guinea pig PMA-induced epidermal inflammation. Furthermore, single oral dose administration to mice was efficacious (ED₅₀ < 2.5 mg/kg) as was multidose administration to rhesus macaques. PMA-induced skin inflammation possesses some of the attributes of human psoriasis and an agent such as SC-53228 may have utility in the medical management of this condition.     

Effects ofβ 2-adrenergic agonists on isolated guinea pig lung mast cells

The mast cell protective effects of the newly developed long-acting ₂-adrenergic salmeterol and formoterol were compared with those of conventionally used ₂-adrenergic, non-specific -agonists, disodium cromoglycate (DSCG) and theophylline. With the exception of DSCG, all the test agents inhibited ovalbumin-induced histamine release from enzymically dispersed guinea pig lung mast cells in a dose-dependent fashion. At the maximum concentration tested, theophylline produced the highest level of protection, inhibiting up to 90% of ovalbumin-induced histamine release whereas DSCG produced only 10% inhibition. The maximum inhibition produced by all the ₂-adrenergic tested was around 45%. While salmeterol was equipotent with salbutamol, formoterol was at least a 100-fold more potent. Hence the present study confirmed the previously reported mast cell stabilizing actions of conventional ₂-adrenergic and extended the observation to the newly developed long-acting analogues.     

Immunologische Untersuchungen bei Wegenerscher Granulomatose mit Nachweis von γ-Globulin-Antikörpern

Zusammenfassung Bei einem Fall von Wegenerscher Granulomatose fand sich neben einer Verschiebung des Proteinspektrums eine deutliche Heterogenität der-Globuline in Serum und Harn. Durch serologische Untersuchungen konnte ein Rheumafaktor sowie ein weiterer gegen-Globulin gerichteter Antikörper im Serum des Patienten nachgewiesen werden. Vermutlich handelt es sich hierbei um einen Antikörper gegen autologes-Globulin, welches bei dem Krankheitsprozeß zum Autoantigen wird. Verbindungen zur Periarteriitis nodosa und zur chronischen Polyarthritis werden aufgezeigt und diskutiert.

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Summary A case of Wegener's granulomatosis was characterised by a dysproteinaemia and a marked heterogenity of the-globulins in the serum and urine. By means of serological investigations a rheumatoid factor and another antibody to-globulin has been demonstrated in the serum of the patient. It is assumed that this is an antibody to autologous-globulin, which becomes autoantigenic in the pathogenesis of this disease. Relationships to periarteriitis nodosa and to rheumatoid arthritis have been discussed.

     

Eicosanoids and histamine mediate C5a-induced electrolyte secretion in guinea pig ileal mucosa

C5a is a biologically active polypeptide formed during the course of complement activation and is known to possess histamine-releasing and neutrophil chemotactic properties. In the present study, we have demonstrated that C5a can regulate electrolyte transport across guinea pig ileum, and we have investigated its mechanism of action. Segments of ileum stripped of longitudinal muscle were mounted in Ussing chambers (Krebs' buffer, 37°C, 95% O₂/5% CO₂) for monitoring short-circuit current (Isc). Serosal application of C5a evoked a transient increase in Isc with an EC₅₀ value of 5.0 nM indicating a potent effect. The C5a-induced increase in Isc was abolished by elimination of both Cl^– and HCO ₃ ^– from the Krebs' solution. Pretreatment with the cyclooxygenase inhibitor indomethacin (5M), the neurotoxin tetrodotoxin (0.5M) and the H₁ receptor antagonist pyrilamine (0.5M) reduced the effect of C5a, but the muscarinic antagonist atropine (0.5M) was without effect. C5a (100 nM) also evoked the release of histamine (measured by radioimmunoassay in the serosal bathing fluid) by 282% of the control value. In conclusion, in the guinea pig ileum C5a stimulates mucosal anion secretion by releasing histamine and cyclooxygenase products of arachidonic acid. The response is also mediated, in part, via non-chloinergic enteric nerves.     

Effect of BRL-35135 on LTB4-induced guinea pig eosinophil chemotaxis

The effect of an atypical -adrenoceptor agonist, BRL-35135 on leukotriene B₄-induced-guinea pig eosinophil chemotaxis was studied. BRL-35135 and SC-41930 (leukotriene B₄-antagonist) inhibited the chemotaxis in a concentration-dependent manner (IC₅₀=9.0×10^–6 and 2.6×10^–7 M, respectively). However, isoproterenol, fenoterol and another atypical -agonist, BRL-37344 had no effects. The inhibitory effect of BRL-35135 was not affected by (±)-propranolol (10^–4 M). In contrast, the nonselective -adrenoceptor antagonist, (–)-alprenolol (10^–4 M) dextrally shifted the inhibitory curve of BRL-35135. The response to BRL-35135 was antagonized in a competitive manner by (–)-alprenolol, with the slope of the Schild plot close to unity, and a pA ₂ value of 5.62. These findings suggest that guinea pig eosinophils possess an atypical receptor, which differs from either ₁, ₂ or atypical -adrenoceptor on guinea pig ileum, and through which eosinophil chemotaxis can be modulated by BRL-35135.     

The inhibition of 5-lipoxygenase by RG 6866

The generation of leukotrienes C₄, D₄ and E₄ from arachidonic acid is dependent upon the activity of 5-lipoxygenase (5-LOX). The effects of RG 6866 (N-methyl-4-benzyloxyphenylacetohydroxamic acid) on the activity of guinea pig 5-LOXin vitro andin vivo were determined in the present study. The generation of 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) from arachidonic acid by isolated guinea pig peritoneal polymorphonuclear (PMN) cells was inhibited by incubation with RG 6866 (IC₅₀=0.20 M). A similar effect (IC₅₀=0.23 M) was observed when 5-HETE production was measured in a supernatant fraction from PMNs. Additionally, the compound did not inhibit³H-LTD₄ binding to guinea pig membranes. In actively sensitized guinea pigs pretreated with indomethacin, propranolol and pyrilamine, RG 6866 inhibited antigen-induced systemic anaphylaxis and LTD₄-dependent bronchoconstriction in a dose-dependent manner following oral administration. In the pulmonary anaphylaxis model, significant (p<0.05) inhibition of the mortality was observed within 30 min and maintained through four hours after treatment with RG 6866 (50 mg/kg i.g.). Finally, orally administered RG 6866 inhibited the formation of LTC₄ in these animals with an ED₅₀=24.0 mg/kg. These findings indicate that RG 6866 is an inhibitor of 5-LOX bothin vitro andin vivo.Previously designated as REV-6866 in a preliminary communication.     

Pharmacological characterization of WAY-121,520: A potent anti-inflammatory indomethacin-based inhibitor of 5-lipoxygenase (5-LO)/phospholipase A2 (PLA2)

WAY-121,520 inhibited human synovial fluid PLA₂ (HSF-PLA₂) (IC₅₀=4 M) using arachidonic acid-labeledE. coli as substrate. Further biochemical characterization of WAY-121,520 demonstrated potent inhibition of 5-lipoxygenase (5-LO) activity in the murine macrophage (LTC₄, IC₅₀=4nM) and rat PMN (LTB₄, IC₅₀=10 nM) and an ability to antagonize LTD₄ binding to isolated guinea-pig trachea (pK _B=6.0).In vivo anti-inflammatory activity was noted in murine TPA-induced (ED₅₀=91 g/ear) and arachidonic acid-induced (66% inhibition at 400 g/ear) ear edema and in leukotriene-dependent antigen-induced bronchoconstriction in the guinea pig (73% inhibition at 50 mg/kg, p.o.). WAY-121,520 represents a novel series of indomethacin-based inhibitors of PLA₂ with anti-inflammatory activity resulting from a combination of biochemical activities (inhibition of 5-LO and PLA₂ and LTD₄ antagonism). This agent may provide added therapeutic efficacy over more selective inhibitors.     

Metoprolol in portal hypertension

Summary In a controlled trial, the effect of the ₁-selective blocking agent metoprolol on cirrhotic portal hypertension was investigated. A sustained reduction of portal pressure was observed in 60% of the treated patients after 1 and 2 months. No correlation between changes of portal pressure and cardiac output was established. This may indicate a direct action of-blocking substances on the splanchnic vascular system. The results suggest that treatment with metoprolol may be of value in patients with portal hypertension secondary to cirrhosis of the liver. However, to eliminate nonresponders the pressure has to be measured repeatedly.     

Effects of adenosine on guinea pig pulmonary eosinophils

Extracellular adenosine has pharmacological activity on a wide variety of cell types and may play an important role as an inflammatory modulator with both pro- and anti-inflammatory activities. These studies examine the effects of adenosine on guinea pig pulmonary eosinophils. Adenosine alone did not directly induce superoxide (O ₂ ^– ) production. Pretreatment with adenosine primed the O ₂ ^– response of guinea pig pulmonary eosinophils following the addition of 1 or 10M plateletactivating factor (PAF). Priming was seen at adenosine concentrations greater than 1 M and was maximal at 100M. At this maximal dose, adenosine priming increased the O ₂ ^– response to 1M and 10M PAF by 86% and 51%, respectively. Priming by adenosine was not seen when ionomycin or phorbol myristate acid (PMA) were used as agonists. In fura-2 loaded eosinophils, the addition of 100 M adenosine resulted in a small but significant rise in intracellular calcium of 54.4 ±9.2 nM above baseline. In contrast, similar adenosine concentrations had no effect on cytosolic calcium levels in guinea pig neutrophils. These data demonstrate a pro-inflammatory role for adenosine in elicited guinea pig pulmonary eosinophils.     

Antihistaminic/antiallergic activity of 2-dialkylaminoalkylthio(oxy)-1-substituted benzimidazoles: Evaluation “in vitro” and “in vivo”

A new series of 2-dialkylamino-alkylthio(oxy)-1-substituted benzimidazoles synthesized in our laboratories was found to have promising antihistaminic activity. The results of pharmacological screening (in vitro: radioreceptor binding and isolated organs; in vivo: protection against mortality induced by histamine or by compound 48/80, passive cutaneous anaphylaxis, and prolongation of barbiturate-induced sleeping-time) gave clear-cut structure-activity relationships. This series of products has a general selectivity towards H1 receptors, weak antiallergic properties and negligible central effects. DF 10967 (1-ethoxyethyl-2-dimethyl-aminoethylthiobenzimidazole) was the most interesting compound, being very potent both in vitro (Ki=3.2±0.8 nM) and in vivo (ID₅₀ 11 g/kg, i.p. and 8g/kg, i.p. against histamine- and 48/80-induced mortality), with no central effects. The last finding is probably due to poor penetration into the brain (as confirmed by in vivo binding test with [³H]-mepyramine) and to lack of interaction with other central receptors.     

Inhibitory effect of phloretin on histamine release from isolated rat mast cells

The ability of the flavonoid phloretin to inhibit histamine release from rat mast cells varied considerably with the releasing agent investigated. The response to the combination of the ionophore A23187 and the phorbol ester TPA and to suboptimal concentrations of the ionophore (0.5 M) was potently inhibited (IC₅₀ about 5 M), whereas phloretin was less potent against responses to the ionophore (1 M) IC₅₀ of 17 M), to antigen alone and in combination with TPA (IC₅₀ of 30–50 M), to TPA in the absence of calcium (IC₅₀ of 50 M) and to compound 48/80 in the absence and presence of calcium (IC₅₀ of 60–90 M). The inhibition by phloretin at concentrations above 10M was partly counteracted by glucose (5 mM) indicating effects on oxidative metabolism. The flavonoid quercetin was equally potent in inhibiting histamine release induced by antigen, the ionophore at different concentrations and in combination with TPA (IC₅₀ of 20M). Although not conclusive, the results are consistent with an inhibition of protein kinase C by phloretin at concentrations below 10 M. At higher concentrations unspecific actions become apparent and phloretin therefore seems to be of limited utility as a probe for signal-pathways in cell responses.     

Cytokine production by phytohemagglutinin-stimulated human blood cells: Effects of corticosteroids,T cell immunosuppressants and phosphodiesterase IV inhibitors

The ability of dexamethasone and prednisolone (corticosteroids), FK506 and cyclosporin A (T cell immunosuppressants), and of nitraquazone and rolipram (phosphodiesterase IV inhibitors) to inhibit cytokine production by stimulated human blood was investigated. Heparinized human blood obtained from normal healthy volunteers was stimulated with phytohemagglutinin (PHA) in the presence or absence of drug. After different incubation times, supernatant levels of interleukin (IL)-2, IL-5, granulocyte-macrophage colony stimulating factor (GM-CSF) and interferon (IFN-) were quantified by ELISA. Dexamethasone strongly inhibited the production of IL-5 (IC₅₀ = 0.004 µM), was less potent against IL-2 and IFN- (IC₅₀ = 0.02–0.05 µM) and showed a relatively weak effect against GM-CSF (IC₅₀ = 0.6 µM). Similarly prednisolone potently suppressed IL-5 generation (IC₅₀=0.05 µM), displayed a more modest activity on IL-2 and IFN- (IC₅₀ = 0.2–0.3 µM) and exerted only partial effects (43% inhibition at 1 µM) on GM-CSF. FK506 strongly suppressed the production of IL-2 (IC₅₀ = 0.01 µM) and GM-CSF (IC₅₀ = 0.03 µM), but was inactive (<30% inhibition at 1 µM) against IL-5 and IFN-. Similarly, cyclosporin A reduced the generation of IL-2 (IC₅₀ = 0.4 µM) and GM-CSF (IC₅₀ = 0.6 µM) while barely affecting the other two cytokines. Nitraquazone and rolipram were most active in reducing the production of IL-5 (IC₅₀ = 0.8 and 1.3 µM, respectively), while their potency against IL-2, GM-CSF and IFN- was 3–6 times lower, with IC₅₀'s between 2.4 and 8.0 µM. These data indicate that corticosteroids, T cell immunosuppressants and phosphodiesterase IV inhibitors affect cytokine production by PHA-stimulated human blood cells in a differential and pharmacotypical manner.     

Anti-inflammatory and antipyretic effects of boldine

Boldine, and antioxidant alkaloid isolated fromPeumus boldus, exhibits a dose-dependent anti-inflammatory activity in the carrageenan-induced guinea pig paw edema test with an oral ED₅₀ of 34 mg/kg. Boldine also reduces bacterial pyrogen-induced hyperthermia in rabbits to an extent which varied between 51% and 98% at a dose of 60 mg/kg p.o.In vitro studies carried out in rat aortal rings revealed that boldine is an effective inhibitor of prostaglandin biosynthesis, promoting 53% inhibition at 75 M. The latterin vitro effect may be mechanistically linked to the anti-inflammatory and antipyretic effects of boldine exertedin vivo.     

Modulation of bradykinin responses in airway smooth muscle by epithelial enzymes

We have studied the effect of epithelium removal on responses of guinea pig trachea to bradykinin (BK). BK (1 nM–10 M) gave a concentration-dependent relaxation when epithelium was present (E+: EC₅₀=10±3 nM). Epithelium removal resulted in a biphasic response to BK with relaxation at low concentrations (E–: EC₅₀=3.0±1.0 nM) and a recontraction to baseline at higher concentrations (EC₅₀=2.0±1 M). Phosphoramidon (10 M), an inhibitor of neutral endopeptidase (NEP), which cleaves BK into inactive peptides, potentiated relaxation (EC₅₀=1.0±0.9 nM and 0.1±0.1 nM in E+ and E respectively) and contraction in trachea with intact epithelium (EC₅₀=0.08±0.03 M). Inhibition of cyclooxygenase by indomethacin (5 M), inhibited relaxation to BK in E+ tracheal segments, resulting in a slight contraction (EC₅₀=1.0 M), whereas a potent contractile response was observed in E–segments (EC₅₀ 1.6 M, maximal contraction >1 g). In the presence of both indomethacin and phosphoramidon BK caused contraction, even in the presence of epithelium (EC₅₀=0.2±0.11 M), and the response in the absence of epithelium was similar to the response observed in trachea with intact epithelium (EC₅₀=0.25±0.1 M). The contractile effect of BK on airway smooth muscle may be inhibited by a protective role of epithelium, due to release of relaxant prostanoids and by degradation by epithelial NEP. In asthma, bronchoconstrictor responses to BK may be partly explained by loss of airway epithelium.     

Effects of Tebufelone (NE-11740), a new anti-inflammatory drug,on arachidonic acid metabolism

Tebufelone is a novel nonsteroidal anti-inflammatory drug (NSAID), of the di-tert-butylphenol (DTBP) class, which displays potent anti-inflammatory, analgesic and anti-pyretic properties in a variety of animal models. In this report, the effects of Tebufelone on arachidonic acid (AA) metabolism are reviewed. Tebufelone potently inhibits the formation of prostaglandins (PGE₂) a key mediator of pain and inflammation, in isolated enzyme preparations (IC₅₀=1.5 M,K _I=0.35 M), twoin vitro cellular systems: rat peritoneal macrophages (IC₅₀=0.02 M) and human whole blood (IC₅₀=0.08 M), andex vivo in man. In addition to PGE₂ inhibition, which is common to all NSAIDs, higher concentrations of Tebufelone block thein vitro formation of products of the lipoxygenase pathway [leukotrienes (LTB₄)] in rat macrophages (IC₅₀=20 M) and human whole blood (IC₅₀=22 M). Substrate incorporation studies (¹⁴C-AA) indicate that Tebufelone reversibly inhibits cyclooxygenase (CO) and 5-lipoxygenase (5-LO) enzymes rather than regulating the release of AA. Tebufelone was shown to be a more potent CO inhibitor than indomethacin and a less potent 5-LO inhibitor than RG-5901. Comparisons to structurally related compounds under development (E-5110, Esai; KME-4, Kanagafuchi), found Tebufelone to be the most potent CO inhibitorin vitro. All three DTBP compounds were equipotent 5-LO inhibitors. It is likely that Tebufelone's inhibitory effects on AA metabolism are, in part, responsible for itsin vivo efficacy and enhanced safety profile.     

Gastric and cardiovascular effects of histamine in the dog

The H-2 receptor stimulation of gastric acid secretion and of heart rate by histamine, a mixed H-1–H-2 agonist, given in 45-min successive step doses 2–150 g base/kg.h and 4(Me)histamine, (4(Me)H), 1.4 to 210 g base/kg.h, a specific H-2 agonist, in five conscious gastric fistula dogs showed no difference between the agonists in ED₅₀s or in maximal responses. The ED₅₀ for acid was lower (15–16 g/kg.h) than for cardiac chronotropism (25 to 27 g/kg.h). Both effects were competitively antagonized by the H-2 antagonist cimetidine, 0.5 to 1 mg/kg.h. Background infusions of diphenhydramine, 2 mg/kg.h, raised the maximum heart rate increase caused by histamine from +108 to +149 beats/min (p<0.05) but not that of 4(Me)H; acid outputs were not augmented. Diphenhydramine 2 mg/kg.h alone caused no significant change in heart rate or blood pressure. Histamine reduced systolic blood pressure (SBP) by 48 mmHg and with diphenhydramine background by 61 mmHg (p<0.05). 4(Me)H at a top dose of 210 g base/kg.h reduced SBP by 81 mmHg (p<0.05). To test whether the effects of added diphenhydramine could be interpreted as an H-1 receptor effect of histamine, the H-1 agonist 2-pyridylethylamine (PEA) was given alone (2–150 g/kg.h in 45-min steps) or as a 100 g/kg bolus during the infusion of 4(Me)H 50 g/kg.h. There was no effect of PEA on gastric acid, heart rate or blood pressure. Even though diphenhydramine augments the effect of histamine on heart rate and blood pressure, the lack of PEA effect would indicate that there is not a direct H-1 receptor mediated effect on gastric acid, heart rate or systolic blood pressure in the conscious dog. This contrasts with published data obtained in anesthetized animals. After a single dose of 4(Me)H, 50 g/kg.h had been infused i.v. for 45 min, acid output had reached 70% of the maximum seen at 90 min, heart rate had increased by 65% of its maximum response but SBP had not yet changed. Cimetidine blocked 4(Me)H-induced hypotension completely but blocked the heart rate increase only partially and competitively. We conclude that in the intact animal there is evidence for a direct H-2 mediated stimulation of heart rate in the conscious dog with kinetics similar to the H-2 stimulation of gastric acid secretion.Supported by Research Grant No. AM09260 from the National Institute of Arthritis, Metabolism and Digestive Diseases, National Institutes of Health and by the Medical Research Service of the Veterans Administration.     

Inhibitory effects ofγ-interferon on bradykinin-induced bone resorption and prostaglandin formation in cultured mouse calvarial bones

The effects of mouse recombinant-interferon (-IFN) and indomethacin on bone resorption stimulated by bradykinin, Lys-bradykinin, Met-Lys-bradykinin, des-Arg⁹-bradykinin and prostaglandin E₂ (PGE₂) have been studied using cultures of neonatal calvarial bones and analyzing the release of⁴⁵Ca from prelabelled bones as a paramenter of bone resorption. In addition, the effects of-IFN and indomethacin on formation of PGE₂ in bone cultures stimulated by bradykinin was analyzed. Indomethacin (1 mol/l) totally abolished bradykinin (1 mol/l) induced⁴⁵Ca release. The inhibitory effect of indomethacin could be fully reversed by addition of PGE₂ (1 mol/l).-IFN (1000 U/ml) almost totally inhibited⁴⁵Ca release stimulated by bradykinin (1 mol/l), but the inhibitory effect could only be partially overcome by PGE₂.-IFN and indomethacin also inhibited the stimulatory effects of Lys-bradykinin, Met-Lys-bradykinin and des-Arg⁹-bradykinin (1 mol/l) on⁴⁵Ca release. The stimulatory effects of PGE₂ (1 mol/l) on radioactive calcium mobilization was partially inhibited by-IFN (1000 U/ml), whereas indomethacin (1 mol/l) was without effect. The inhibitory effect of-IFN on⁴⁵Ca release stimulated by bradykinin and PGE₂ was dose-dependent with threshold for action at 3–30 U/ml. Comparative dose-response curves showed that-IFN was most potent as inhibitor of bradykinin induced⁴⁵Ca release. Bradykinin (1 mol/l) significantly stimulated PGE₂ formation by a mechanism that was completely inhibited by indomethacin (1 mol/l).-IFN (1000 U/ml) partially inhibited the stimulatory effect of bradykinin on PGE₂ formation. These data show that i)-IFN is a potent inhibitor of bone resorption induced by bradykinin and bradykinin analogues and ii) that the mechanism of action can be mainly explained by an inhibition of kinin induced prostaglandin biosynthesis. The results, however, also show that-IFN can inhibit bone resorption by mechanisms unrelated to prostaglandin formation.     

8-amino-9-substituted guanines: Potent purine nucleoside phosphorylase (PNP) inhibitors

A series of 8-amino-9-substituted guanines was synthesized and their activity evaluated against human purine nucleoside phosphorylase (PNP). All compounds were found to be potent inhibitors of human PNP (IC₅₀s: 0.17–126 M). They were also selectively cytotoxic to MOLT-4 lymphoblasts in the presence of a nontoxic amount (10 M) of the PNP substrate, 2-deoxyguanosine (GdR). The most potent of these analogs, 2,8-diamino-1,9-dihydro-9-(2-thienylmethyl)-6H-purin-6-one (8-amino-9-(2-thienyl-methyl)guanine; PD 119,229) has an IC₅₀ of 0.17 M (Ki=0.067 M), significantly more potent than the known standard, 8-aminoguanosine (IC₅₀=1.40 M). Thus it represents the most potent PNP inhibitor known to date when tested without limiting the concentration of inorganic phosphate.     

Antiinflammatory benzimidazole derivative with inhibitory effects on neutrophil function

5-Methyl-2,2,2-trifluoroethylsulfonyl-1H-benzimidazole (BI-L-45 XX) inhibits both neutrophil enzyme release and chemotaxisin vitro and also inhibits chemotaxisin vivo. BI-L-45 XX has an IC₅₀ between 16M and 25 M in inhibiting lysosomal enzyme release from human peripheral blood neutrophils. In a Boyden chamber experiment, BI-L-45 XX inhibited migration in response to fMLP with an IC₅₀ of 5 M. When given orally to passively sensitized rats at doses of 0.1 to 1.0 mg/kg, it inhibited migration of neutrophils to the pleural cavity in response to an antigen (ovalbumin) challenge. BI-L-45 XX also shows activity in the developing adjuvant arthritis model, with an ED₅₀ of 45 mg/kg, while exhibiting no significant inhibition of cyclooxygenase in a human platelet assay. This suggests the possibility that its antiinflammatory activity may be in part mediated by its effect on neutrophil function.