Effect of norathyriol,isolated from Tripterospermum lanceolatum,on A 23 187-induced pleurisy and analgesia in mice

A 23 187-induced pleurisy in the mouse was demonstrated in this study. The protein leakage, leukocyte accumulation, LTB₄ and PGE₂ production in the pleural cavity of mice were increased by A 23 187 in a dose-dependent manner. At 7.5 nmole A 23 187 intrapleural injection, the protein level peaked at 0.5–2 h, PMN leukocytes accumulation peaked at 3–4 h, and LTB₄ and PGE₂ production peaked at 0.5–1 h. In this in vivo model we investigated the anti-inflammatory effect of norathyriol, isolated from Tripterospermum lanceolatum. A 23 187-induced protein leakage was reduced by norathyriol (ID₅₀ was about 30.6 mg/kg i.p.), indomethacin and BW 755 C. A 23 187-induced PMN leukocytes accumulation was suppressed by norathyriol (ID₅₀ was about 16.8 mg/kg, i.p.) and BW 755 C, while enhanced by indomethacin. Like BW 755 C, norathyriol reduced both LTB₄ and PGE₂ production (ID₅₀ was about 18.6and 29.1 mg/kg i.p., respectively), while indomethacin reduced PGE₂ but not LTB₄ generation. We also demonstrated the analgesic effect of norathyriol on the acetic acid-induced writhing response. Acetic acid-induced writhing response was depressed by norathyriol (ID₅₀ was about 27.9 mg/kg i.p.), indomethacin and ibuprofen. These results suggest that norathyriol, like BW 755 C, might be a dual, yet weak, cyclooxygenase and lipoxygenase pathway blocker. The inhibitory effect of norathyriol on the A 23 187-induced pleurisy and acetic acid-induced writhing response in mice is proposed to be dependent on the reduction of eicosanoids mediators formation in the inflammatory site. Correspondence to: J.-P. Wang at the above address     

Anti-inflammatory and analgesic effects of magnolol

Summary Magnolol, isolated from Magnolia officinalis, inhibited mouse hind-paw edema induced by carrageenan, compound 4880, polymyxin B and reversed passive Arthus reaction. Acetic acid-induced writhing response was depressed by magnolol, indomethacin and ibuprofen. The lethality of endotoxin challenge was reduced by pretreatment with magnolol, indomethacin and BW755C, a dual cyclo-oxygenase/lipoxygenase inhibitor. The recovered myeloperoxidase activity in edematous paw was significantly decreased in mice pretreated with magnolol and BW755C. Suppression of edema was demonstrated not only in normal mice but also in adrenalectomized animals. Magnolol was less potent on reducing PGD₂ formation in rat mast cell than that of indomethacin. Unlike dexamethasone, magnolol did not increase liver glycogen level. The results suggest that the anti-inflammatory effect of magnolol was neither mediated by glucocorticoid activity nor through releasing steroid hormones from adrenal gland. The action of magnolol is proposed to be dependent on reducing the level of eicosanoid mediators.Correspondence to J.-P. Wang at the above address     

Inhibition of LTB4 biosynthesis in situ by CGS 23885, a potent 5-lipoxygenase inhibitor, correlates with its pleural fluid concentrations in an experimentally induced rat pleurisy model

An intrapleural injection of carrageenan in rats induced LTB₄ and LTC₄/D₄/E₄ biosynthesis, exudate formation, and cellular influx in the pleural cavity. An injection of calcium ionophore (A23187, 100nmol) 16–18h after carrageenan injection augmented leukotriene biosynthesis and exudate formation, but not cellular influx. The carrageenan-induced pleurisy model modifid by A23187 administration was used to study the oral effect of CGS 23885 (N-hydroxy-N-[(6-phenoxy-2H-1-benzopyran-3-yl)-methyl]urea), a potent 5-lipoxygenase (5-LO) inhibitor, on inflammatory parameters. CGS 23885 dose-dependently (1 to 30mg/kg) inhibited the enhanced LTB₄ and LTC₄/D₄/E₄ (1 to 10mg/kg) biosynthesis, but had no effect on enhanced exudate formation. An inhibitory effect of CGS 23885 of small magnitude on cellular influx due to carrageenan stimulation was seen at 30mg/kg. The concentrations of CGS 23885 in the pleural fluid were dose-related, and a positive correlation (r ²=0.989) between pleural fluid concentration of LTB₄ and CGS 23885 was observed. The results confirm that CGS 23885 is a specific, orally active 5-LO inhibitor which can achieve concentrations in the pleural cavity sufficient to inhibit production of LTB₄ and LTC₄/D₄/E₄ in an ongoing inflammatory response. Received: 9 February 1995 / Accepted: 20 December 1996     

Induction of leukotriene B4 and prostaglandin E2 release from keratinocytes by protease-activated receptor-2-activating peptide in ICR mice

Protease-activated receptor-2 (PAR2) has been shown to play a key role in the pathophysiology of itch. However, the precise mechanism of PAR2-mediated itch remains largely unknown. In the present study, we investigated the effects of several agents on the scratching behavior induced by PAR2-activating peptide (SLIGRL-NH₂). Pretreatment of experimental animals with tacrolimus or the 5-lipoxygenase inhibitor zileuton significantly reduced SLIGRL-NH₂-induced scratching behavior, whereas histamine H₁ receptor antagonist cetirizine or the cyclooxygenase inhibitor indomethacin had little effect. Furthermore, intradermal injection of SLIGRL-NH₂ increased cutaneous levels of LTB₄ and PGE₂. In vitro, SLIGRL-NH₂ treatment enhanced LTB₄ and PGE₂ release from primary keratinocytes in a concentration-dependent manner. Preincubation of keratinocytes with zileuton resulted in a significant decrease of LTB₄ release and treatment of indomethacin led to a significant decrease of PGE₂ in response to SLIGRL-NH₂ stimulation. In addition, SLIGRL-NH₂-induced secretion of LTB₄ and PGE₂ was significantly inhibited by tacrolimus, whereas cetirizine had no effect. These results indicate that SLIGRL-NH₂ stimulates LTB₄ and PGE₂ release from mouse keratinocytes and that enhancement of LTB₄ and PGE₂ secretion contributes to SLIGRL-NH₂-induced scratching behavior in ICR mice.     

Comparison of the anti-inflammatory effects of dexamethasone,indomethacin and BW755C on carrageenin-induced pleurisy in rats

In rat carrageenin pleurisy, dexamethasone (0.25 mg/kg p.o.) inhibited exudate accumulation in the pleural cavity throughout the period of testing while the non-steroidal anti-inflammatory drugs indomethacin (10 mg/kg p.o.) and BW755C (100 mg/kg p.o.) inhibited it for 6 and 9 h respectively after the intrapleural injection of carrageenin but not thereafter. These observations were confirmed by the finding that, of the treatments 6 h after carrageenin, only that with dexamethasone reduced exudate volume at 15 h after carrageenin. The anti-exudative action of dexamethasone at 15 h after carrageenin may be at least in part mediated by endogenous substance(s) formed through gene expression, because it was prevented by actinomycin D. Dexamethasone and BW755C markedly inhibited cell accumulation in the pleural exudate throughout the period tested, while indomethacin inhibited it significantly between 9–24 h after carrageenin.     

Leukotriene B4 production and pharmacologic regulation of reverse passive Arthus pleurisy: importance of antigen dose

Immunoreactive leukotriene B4 (iLTB4), detected in the pleural cavity following induction of a reverse passive Arthus reaction (RPAR), was inhibited by the mixed lipoxygenase-cyclooxygenase inhibitors, phenidone and BW 755C, but not by cyclooxygenase inhibitors or by chlorpheniramine or methysergide. Both iLTB4 production and the subsequent pleural inflammation were dependent upon the dose of BSA antigen employed to elicit the RPAR pleurisy. However, inasmuch as BW 755C and phenidone were not distinguished from the cyclooxygenase inhibitors in their effects on fluid accumulation and cellular infiltration in RPAR pleurisy, it is doubtful that LTB4 plays a functional role in this inflammation model.     

In vivo and in vitro pharmacological activity of Aristolochia tagala (syn: Aristolochia acuminata) root extracts

Context: Aristolochia tagala Cham. (syn: Aristolochia acuminata Lam.) (Aristolochiaceae), known as Nallayishwari in Telugu, has been of interest to researchers because of its traditional uses for treating rheumatic pains and fever.

Objective: The anti-inflammatory activity of the petroleum ether, ethyl acetate, and ethanol extracts of A. tagala roots were investigated for the first time.

Materials and Methods: In vivo and in vitro anti-inflammatory effects were investigated employing the carrageenan-induced hind paw edema in rats and the macrophage cell line RAW264.7 stimulated with proinflammatory stimuli (lipopolysaccharide interferon γ or the calcium ionophore A23187) to determine PGE₂ or LTB₄ release, respectively.

Results: All the extracts exhibited anti-inflammatory effects which were found to be significant (p?<?0.001) at 200 and 400?mg/kg, p.o, in rats tested and the ethyl acetate extract inhibited the induction of PGE₂ with IC₅₀?=?39.1?mg mL^?1 and LTB₄ with IC₅₀?=?29.5?mg mL^?1.

Discussion and conclusion: These findings demonstrate that the A. tagala roots have excellent anti-inflammatory activity and validate the traditional indications of this plant in its origin country.     

Comparison of the effects of some compounds on human neutrophil degranulation and leukotriene B4 and thromboxane B2 synthesis

The effects of aspirin, indomethacin, phenylbutazone, eicosatetraynoic acid (ETYA), nordihydroguaiaretic acid (NDGA) and 3-amino-1-[3-(trifluoromethyl)-phenyl]-2-pyrazoline (BW755C) on human neutrophil degranulation induced by A23187 and F-Met-Leu-Phe (FMLP) have been studied. These effects have been compared with those on A23187 induced leukotriene B4 (LTB4) and thromboxane B2 (TXB2) synthesis by these cells to elucidate the relationship between LTB4 formation and degranulation. All compounds inhibited TXB2 synthesis by 50% at concentrations between 0.0016 and 50 microM. The synthesis of LTB4 was inhibited by 50% by ETYA (1.9 microM) and by NDGA (0.52 microM). Degranulation induced by A23187 and FMLP was inhibited by 50% by ETYA (16 and 11 microM respectively) and by NDGA (1.5 and 6.5 microM respectively). In the case of ETYA the concentrations required to inhibit degranulation were significantly higher than those required to inhibit LTB4 synthesis. In contrast, BW755C inhibited LTB4 synthesis by 50% at 2.8 microM but did not affect A23187-induced degranulation and was only a weak inhibitor of FMLP-induced degranulation (50% inhibition at 89 microM). The effects of the above compounds on the omega-oxidation of LTB4 by human neutrophils has also been studied to investigate the mechanism of action of these compounds. None of the above compounds affected the metabolism of LTB4 by these cells suggesting that their actions are not as non-specific anti-oxidants. These data indicate that human neutrophil degranulation induced by FMLP and A23187 is independent of LTB4 synthesis.     

Pharmacological modulation of responses of guinea-pig airways contracted with antigen and calcium ionophore A23187

Ovalbumin (OA) and calcium ionophore A23187 were used to induce contractions of sensitized guinea-pig tracheal and lung parenchymal preparations in the presence and absence of indomethacin. This model was used to examine the properties of a series of compounds reported to inhibit 5-lipoxygenase or to antagonize lipoxygenase products at the receptor level. FPL55712 and piriprost appeared to act as pharmacological antagonists because they rapidly reduced tracheal tone established by OA. The prolonged phase (i.e. greater than 10 min post-challenge) of airways contractions induced by OA is assumed to be lipoxygenase-dependent and was inhibited by nordihydroguaiaretic acid (NDGA), FPL55712, nafazatrom and benoxaprofen, in order of potency. Piriprost had similar inhibitory effects on the trachea, but not on lung parenchyma. The inhibitory effects of NDGA and FPL55712 were reduced, and those of nafazatrom increased by indomethacin. Indomethacin decreased the inhibitory effect of piriprost on the trachea, but facilitated inhibition by this agent on the parenchyma. A roughly similar pattern was seen on A23187-induced contractions, but FPL55712 did not modify these contractions and benoxaprofen enhanced the response of the trachea. BW755C enhanced the overall contractile response of OA- and A23187-induced tracheal contractions (but not parenchymal contractions) in a bell-shaped manner, an effect not seen in the presence of indomethacin. This indicated that BW755C could be acting as a cyclo-oxygenase inhibitor. The results suggested that, although inhibitors of the lipoxygenase pathway were partially effective in inhibiting the contractions of the airways induced by OA or A23187, other mediators in addition to those of the lipoxygenase pathway contribute to these contractions.     

Ca2+ as messenger of 5HT2-receptor stimulation in human blood platelets

Summary In blood platelets of man, both 5-hydroxytryptamine (5HT) and 80 nM of the Ca²⁺-ionophore A23187 led to rapid shape change reactions which were inhibited by prostaglandin E₁ (PGE₁), forskolin, 2-methyl-6-methoxy-8-nitroquinoline (quin2) and chlortetracycline. The IC₅₀-values of the inhibitors were similar in the 5HT- and the A23187-experiments. Higher amounts of A23187 abolished the inhibitory actions of PGE₁ and forskolin. Furthermore, 5HT and A23187 enhanced adrenaline-induced platelet aggregation their effects showing similar time dependence. Ketanserin, an antagonist of 5HT₂-receptors, and 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8), an intracellular Ca²⁺-antagonist, counteracted the effects of 5HT much more than those of A23187, whereas acetylsalicylate and indomethacin did not influence the actions of either 5HT or A23187. In addition, 5HT caused a concentration-dependent rise of intracellular free Ca²⁺ in platelets which was counteracted by ketanserin. PGE₁ and forskolin reduced the resting Ca²⁺-levels. 5HT did not affect either the basal or the PGE₁-stimulated activity of adenylate cyclase, whereas the Ca²⁺-ionophore A23187 slightly raised the basal activity of the enzyme. In conclusion, the functional effects of 5HT₂-receptor stimulation in human blood platelets (shape change reaction and enhancement of adrenaline aggregation) seem to be mediated by a rise of intracellular free Ca²⁺.This work was supported by the Swiss National Science Foundation as well as by the Alberto and Neni Bonizzi-Theler and the Emil Barell FoundationsPreliminary communications of some results presented here have been made at a satellite meeting (Shore Symposium) of the 5th International Catecholamine Symposium, Göteborg, 1983, and at the 3rd International Conference on Cyclic Nucleotides, Milano, 1983     

Effects of Two N-arylpiperazinylmethylpyrazolo [1,5-d][1,2,4]triazine Derivatives in Pain and Antidepressant Tests in Mice

The antinociceptive and antidepressant effects of two pyrazolotriazine derivatives, 2-phenyl-3,3α-dihydro-4-oxo-5-(4-phenylpiperazin-1-yl)methyl-pyrazolo[1,5-d][1,2,4]-triazine (SMI) and 2-phenyl-3,3α-dihydro-4-oxo-5-[4-(4-fluorophenyl)piperazin-1-yl]methylpyrazolo[1,5-d][1,2,4] triazine (SM3) have been investigated in mice using classical pharmacological tests. The intraperitoneal LD50 values of SMI and SM3 were 253.4 and 218.8 mg kg^? respectively. SMI and SM3 showed analgesic properties in the phenylbenzoquinone-induced abdominal constriction test (ED50 ? 10–15 mgkg^?, i.p.) and in the hot-plate test. The antinociceptive effects of the triazines were significantly reduced by administration of naloxone (1 and 3.2 mgkg^?, s.c.) and yohimbine (1 mgkg^?, p.o.). Acute intraperitoneal administration of both compounds (1 mgkg^? SMI or 1.5 mgkg^? SM3) potentiated morphine (0.15 mgkg^?, s.c.) analgesia in the phenylbenzoquinone test. Although this synergistic activity was not reversed by methysergide (0.5 mgkg^?, i.p.), the analgesic activity of both compounds was enhanced by administration of 5-hydroxytryptophan (50 mgkg^?, i.p.) in conjunction with carbidopa (25 mgkg^?, i.p.). Furthermore, neither compound (at 100 mgkg^?, i.p.) significantly reduced the duration of immobility of mice in the forced swimming test, and both (at 75 mgkg^?, i.p.) were ineffective at enhancing the toxic effects of yohimbine (30 mgkg^?, s.c). Only SM3 (ED50 = 74.5 mgkg^?, i.p.) significantly antagonized reserpine (2.5 mgkg^?, i.p.)-induced ptosis. Thus, the results suggest that SMI and SM3 have antinociceptive properties related to co-involvement of opioidergic and α₂-adrenoceptor mechanisms without associated antidepressant properties.     

Effects of Gabexate,a Protease Inhibitor,on Smooth Muscle of Guinea-Pig Stomach Fundus

Abstract: A protease inhibitor, gabexate (ethyl-p-6-guanidinohexanoyloxy benzoate), was found to have an antimuscarinic action in muscle strips of the guinea-pig gastric fundus. Gabexate reversibly inhibited carbachol-induced contractions in the presence of prostaglandin synthesis inhibitors (indomethacin or meclofenamate) with a pA₂ of 5.66 for the circular and 5.25 for the longitudinal muscle. The effect was not affected by tetrodotoxin. Gabexate also inhibited contractions produced by prostaglandin E₂ (PGE₂) (21.7 ± 7.3% with 30 μM, n = 12). The inhibition was markedly potentiated by anticholinesterase, diisopropyl fluorophosphate, but converted to contraction by atropine. In the absence of PGE₂, gabexate produced no mechanical response on its own even after atropine application. Treatment with hemicholinium, an acetylcholine synthesis inhibitor, also converted the relaxant effect of gabexate, applied during PGE₂-induced contraction, to contraction. Gabexate also inhibited contracture induced by 30 mM K⁺ weakly (13 ± 2% with 30 μM, n=5). This relaxation was abolished by atropine, without converting to contraction. PGE₂ and excess K⁺ are likely to release acetylcholine from nerve fibres. These results suggest that the inhibitory effect of gabexate is mainly due to the muscarinic receptor blocking action. In addition, gabexate has a potentiating action on the prostaglandin-induced contraction.     

Biphasic effect of cadmium ions on the secretion of leukotriene B4 in rabbit alveolar macrophages

 One major role of alveolar macrophages is the production of eicosanoids, which modulate immune and inflammatory processes in the lung. In this study, the effects were investigated of cadmium ions on the secretion of leukotriene (LT)B₄ and prostaglandin (PG)E₂, predominant products of lipoxygenase and cyclooxygenase, respectively. Cd²⁺ had an inhibitory effect on the secretion of LTB₄ and PGE₂ in response to A23187 stimulation at concentrations >3× 10^-5 M. This effect can be explained by the inhibition of arachidonic acid (20 : 4) liberation from membrane phospholipids by Cd²⁺, because Cd²⁺ inhibits both [³H]arachidonic acid (20 : 4) liberation from [³H]20 : 4-prelabeled macrophages and the cytosolic phospholipase A₂ activity. At concentrations <3×10^-5 M, Cd²⁺ had no effect on PGE₂ secretion but showed an augmentation of LTB₄ secretion. In vitro study using macrophage lysate showed enhanced LTB₄ synthesis from arachidonic acid by Cd²⁺, which could be responsible for the augmentation of LTB₄ secretion in cells. These results indicate that Cd²⁺ may increase inflammation by increasing LTB₄ production in lung. Received: 13 February 1996/Accepted: 23 April 1996     

Effects of NZ-107 on Airway Inflammation and Cell Activation in Guinea-pigs

Abstract— The effects of NZ-107 on some airway inflammation models and the generation of superoxide anion (O₂^?) were studied in guinea-pigs. Airway inflammation was caused by intra-tracheal injection of murine recombinant interleukin-5 (mrIL-5, 15 μg/animal), inhalation of platelet-activating factor (PAF, 0·003%) and intra-tracheal injection of leukotriene B₄ (LTB₄, 10 μg/animal). NZ-107 (4-bromo-5-(3-ethoxy-4-methoxybenzylamino)-3(2H)-pyridazinone) at a dose of 50 mg kg^?1, intraperitoneally reduced mrIL-5- and PAF-induced eosinophilia. This compound at a dose of 25 and 50 mg kg^?1 also suppressed LTB₄-induced eosinophilia and neutrophilia in bronchoalveolar lavage fluid (BALF). On the other hand, prednisolone at a dose of 20 mg kg^?1, i.p., prevented the increased number of macrophages, eosinophils and neutrophils induced by mrIL-5, the increased number of eosinophils induced by PAF and the increased number of eosinophils and neutrophils induced by LTB₄ in BALF. Furthermore, both drugs reduced mrIL-5- or PAF-induced increase in the number of airway epithelial cells in BALF. The generation of O₂^? was measured by the method of cytochrome C reduction. NZ-107 (10–100 μg mL^?1) attenuated PAF- and FMLP-induced O₂^? production from macrophages and reduced PAF-induced O₂^? generation by eosinophils but had no effect on that from neutrophils. These results indicate that NZ-107 prevents the increased number of pulmonary eosinophils and airway epithelial cells and the activation of macrophages and eosinophils, suggesting that NZ-107 may be useful as a remedy for airway inflammatory diseases such as bronchial asthma.     

Inhibition of the arachidonic acid cascade by norathyriol via blockade of cyclooxygenase and lipoxygenase activity in neutrophils

Recent studies have suggested that dual inhibitors of cyclooxygenase (COX) and lipoxygenase (LO) may be more beneficial in the treatment of inflammatory diseases in which platelet-leukocyte interaction dominates the underlying inflammatory process, than inhibitors of COX or LO alone. In this study, we examined oxygenated xanthones, shown previously to inhibit platelet and neutrophil activation, with respect to the potency of COX inhibition. 1,3,6,7-Tetrahydroxyxanthone (norathyriol) was the most potent. Norathyriol suppressed thromboxane B₂ (TXB₂) and leukotriene B₄ (LTB₄) formation in calcium ionophore (A23187)- and formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated rat neutrophils. Norathyriol was 3–4 times more active against LTB₄ formation than against TXB₂ formation (IC₅₀ about 2.8 vs. 10 µM, respectively). Norathyriol also inhibited prostaglandin D₂ (PGD₂) formation in A23187-stimulated rat mast cells (IC₅₀ 3.0±1.2 µM) and in arachidonic acid (AA)-activated mast cell lysate. Norathyriol was a more effective inhibitor of 5-LO activity than of COX, as shown also by analyses of enzyme activities in a cell-free system, of COX and 5-LO metabolic capacity in neutrophils and of ex vivo TXB₂ and LTB₄ formation in A23187-stimulated neutrophils. Moreover, norathyriol inhibited COX-2 and 12-LO with IC₅₀ values (19.6±1.5 and 1.2±0.1 µM, respectively) similar to those required for the inhibition of COX-1 and 5-LO (16.2±1.5 and 1.8±0.4 µM, respectively). Inhibition of 15-LO by norathyriol was slightly less active. Norathyriol had no effect on A23187-induced AA release from neutrophils and did not affect phospholipase A₂ (PLA₂) activity in a cell-free system. These results indicate that norathyriol inhibits the formation of PGs and LTs in neutrophils probably through direct blockade of COX and 5-LO activities. Norathyriol, a single molecule with multiple targets, might provide a potential therapeutic benefit in the treatment of inflammatory diseases.     

The antiinflammatory action of guanabenz is mediated through 5-lipoxygenase and cyclooxygenase inhibition

Guanabenz (2,6-dichlorobenzylidene amino guanidine acetate), an α₂-agonist, possesses antiinflammatory substances, the effect of guanabenz on LT and Since leukotrienes (LT) and prostaglandins(PG) are proinflammatory substances, the effect of guanabenz on LT and PG synthesis by inflammatory cells was investigated. Guanabenz, but not clonidine, B-HT 920 or B-HT 933 inhibited zymosan-induced LTC₄ (IC₅₀=13 μM) and PGE₂ (IC₅₀=10.9 μM) synthesis with no concomitant reduction in zymosan phagocytosis or cell viability. Similarlyguanabenz reduced LTB₄ (IC₅₀=37.4 μM) and PGE₂ (IC₅₀=13.8 μM) synthesis by A23187-stimulated rat glycogen elicited neutrophils. Furthermore, guanabenz did not inhibit platelet 12-lipoxygenase or phospholipase A₂. In vivo, guanabenz was orally active against rat carrageenan paw edema and adjuvant arthritis (ED_50^s=9 and 10 mg/kg, respectively). Topically applied guanabenz reduced arachidonic acid (AA)- or tetradecanoyl phorbol acetate (TPA)-induced ear inflammation (ED_50^s:AAA-induced ear edema, 1.4 mg/ear; PMA-induced ear edema, 0.013 mg/ear). Therefore, the antiinflammatory activity of guanabenz may be due to its ability to inhibit the formation of 5-lipoxygenase and cyclooxygenase products.     

Aluminofluoride- and Epidermal Growth Factor-Stimulated DNA Synthesis in MOB 3-4-F2 Cells

Abstract: In attempt to study the mechanism of F^?-induced, osteoblast-mediated bone formation, we tried to show the characteristics of Al-F complex-induced mitogenesis in osteoblastic cells. The MOB 3-4-F2 cell line, an osteoblast-like cell line derived from neonatal mouse calyaria, responded to F^? (1-2 mM) combined with Al³⁺ and epidermal growth factor (EGF, 0.01–10. ng/ml) with increased DNA synthesis. Of the several types of Al-F complexs, A1F₄^? is thought to act as a mitogenic factor. On the other hand, NaF at high concentrations (>2 mM) markedly decreased cell viability. The AlF₄^?-stimulated DNA synthesis at least with a delay of 48 hr, while EGF stimulated DNA synthesis within a few hours (4-6 hr). Both 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) and staurosporine, inhibitors of protein kinase C (PKC), further enhanced DNA synthesis in AlF₄^?-treated cells, whereas 12-O-tetradecanoyl-13-acetate (TPA), an activator of PKC, decreased the DNA synthesis. In EGF-treated cells, staurosporine and TPA, but not H-7, decreased DNA synthesis. In addition, indomethacin, an inhibitor of cyclooxygenase, partly inhibited the EGF-induced mitogenesis, which, however, was restored by addition of PGE₂. AlF₄^? as well as EGF, stimulated the release of arachidonic acid and its metabolites. Indomethacin failed to inhibit the AlF₄^?-induced mitogenesis. Thus, the mitogenic response of MOB 3-4-F2 cells to F^? in the presence of Al³⁺ had the following characteristics: (1) it was effective over a narrow range, (2) it had a slow onset, (3) included a PKC-sensitive mechanism and (4) a PG(E₂)-independent mechanism. In contrast, a wide range of EGF concentrations rapidly stimulated DNA synthesis by a PKC-sensitive, PG(E₂)-dependent mechanism in these cells.     

The modulation of peritoneal macrophage chemiluminescence by acute pleural inflammation, prostanoids and cyclo/lipoxygenase inhibitors

The chemiluminescent (CL) response of peritoneal macrophages was suppressed by induction 4 h earlier of an inflammatory reaction in the pleural cavity which was negated by prior administration of indomethacin, ketoprofen and BW 755C. These changes were accompanied by a concomitant rise in peritoneal PGI2 levels which was abolished by drug pretreatment. In vitro treatment of normal peritoneal macrophages with PGI2 inhibited their subsequent CL response. Indomethacin and ketoprofen produced elevated CL of macrophages obtained from untreated controls in vitro which was blocked by the lipoxygenase inhibitor NDGA. BW 755C and NDGA in vitro strongly inhibited macrophage CL and partially inhibited CL in a cell-free system. Use of these drugs in vivo demonstrated that indomethacin and ketoprofen augmented the CL response of peritoneal macrophages while BW 755C had no effect. These results suggest the inflammatory process per se can modulate the functions of macrophages in parts of the body remote from the inflammatory site. Moreover this modulation may be under the control of the prostanoid system.     

The antipyretic effect of dipyrone is unrelated to inhibition of PGE(2) synthesis in the hypothalamus

BACKGROUND AND PURPOSE

Bacterial lipopolysaccharide (LPS) induces fever through two parallel pathways; one, prostaglandin (PG)-dependent and the other, PG-independent and involving endothelin-1 (ET-1). For a better understanding of the mechanisms by which dipyrone exerts antipyresis, we have investigated its effects on fever and changes in PGE₂ content in plasma, CSF and hypothalamus induced by either LPS or ET-1.

EXPERIMENTAL APPROACH

Rats were given (i.p.) dipyrone (120 mg·kg⁻¹) or indomethacin (2 mg·kg⁻¹) 30 min before injection of LPS (5 µg·kg⁻¹, i.v.) or ET-1 (1 pmol, i.c.v.). Rectal temperature was measured by tele-thermometry. PGE₂ levels were determined in the plasma, CSF and hypothalamus by elisa.

KEY RESULTS

LPS or ET-1 induced fever and increased CSF and hypothalamic PGE₂ levels. Two hours after LPS, indomethacin reduced CSF and hypothalamic PGE₂ but did not inhibit fever, while at 3 h it reduced all three parameters. Three hours after ET-1, indomethacin inhibited the increase in CSF and hypothalamic PGE₂ levels but did not affect fever. Dipyrone abolished both the fever and the increased CSF PGE₂ levels induced by LPS or ET-1 but did not affect the increased hypothalamic PGE₂ levels. Dipyrone also reduced the increase in the venous plasma PGE₂ concentration induced by LPS.

CONCLUSIONS AND IMPLICATIONS

These findings confirm that PGE₂ does not play a relevant role in ET-1-induced fever. They also demonstrate for the first time that the antipyretic effect of dipyrone was not mechanistically linked to the inhibition of hypothalamic PGE₂ synthesis.